TWO-LEVEL LED SECURITY LIGHT WITH MOTION SENSOR

Abstract

A two-level LED security light within it has a light-emitting unit including an LED load which may be turned on or turned off by a loading and power control unit activated by a light sensing control unit and a motion sensing unit. When the motion sensing unit detects a motion signal, the light-emitting unit is switched to a high level illumination for a predetermined time length adjustable by a time setting unit, and then the loading and power control unit manages to turn off the light-emitting unit thru a soft off process. The LED load is configured with a plurality of LEDs accommodating to the power supply unit wherein a voltage V across each LED is confined in a range V.sub.th<V<V.sub.max, with V.sub.th being a minimum voltage to turn on the LED and V.sub.max a maximum voltage to avoid damaging the LED.

Claims

1. An LED security light, comprising: a power supply unit; a light-emitting unit, including an LED load; a loading and power control unit; a light sensing control unit; a motion sensing unit, including at least one motion sensor; and a time setting unit; wherein the loading and power control unit comprises a controller and a switching circuitry, and the controller is electrically coupled with the switching circuitry; wherein the switching circuitry is electrically coupled with a power source of the power supply unit and the light-emitting unit, and the power source is a DC power source configured in the power supply unit; wherein the switching circuitry comprises at least one unidirectional semiconductor switching device; wherein the controller outputs pulse width modulation (PWM) signals to control average conduction rates of the switching circuitry for delivering different average electric currents from the power supply unit to drive the LED load of the light-emitting unit such that the light-emitting unit respectively generates illuminations of different light intensities for performing different illumination modes activated by the light sensing control unit, the motion sensing unit and the time setting unit; wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the light-emitting unit is turned on by the loading and power control unit activated by the light sensing control unit to perform a first illumination mode with the motion sensing unit in a deactivated state, and the first illumination mode continues for a first predetermined time duration; wherein upon a maturity of the first predetermined time duration the loading and power control unit manages to decrease the average electric current delivered to the LED load of the light-emitting unit to perform a second illumination mode for a second predetermined time duration, and at the same time the motion sensing unit is activated; wherein when a motion signal is detected by the motion sensing unit, the loading and power control unit manages to increase the average electric current delivered to the LED load of the light-emitting unit to perform a third illumination mode for a third predetermined time duration before being switched back to the second illumination mode; wherein at dawn when the ambient light detected by the light sensing control unit is higher than a second predetermined value, and the loading and power control unit manages to switch off the light-emitting unit; wherein the light intensity of the third illumination mode is higher than the light intensity of the second illumination mode; wherein the time setting unit is used for adjusting and setting at least a time length of at least one of the first predetermined time duration, the second predetermined time duration and the third predetermined time duration; wherein the LED load in conjunction with the DC power source is designed with an adequate combination of in series and in parallel connections such that an electric current passing through each LED of the LED load remains at an adequate level, and a voltage V across each LED complies with a constraint of V.sub.th<V<V.sub.max featuring electrical characteristics of the LED; wherein V.sub.th is a minimum threshold voltage required to trigger the LED to start emitting light and V.sub.max is a maximum operating voltage across the LED to avoid a thermal damage to LED construction; and wherein the controller comprises at least a programmable integrated circuit device or an application specific integrated circuit.

2. The LED security light according to claim 1, wherein the value of V.sub.th is equal or greater than 2.5 volts, and the value of V.sub.max is in a range between 3.5 volts and 20 volts depending on a packaging specification of the LED.

3. The LED security light according to claim 2, wherein the value of the voltage V across the LED is confined to be in an operating range from 2.5 volts to 20 volts.

4. The LED security light according to claim 1, wherein the first predetermined time duration is programmable by the time setting unit.

5. The LED security light according to claim 1, wherein the light intensity of the first illumination mode is adjustable by an external control unit.

6. The LED security light according to claim 1, wherein the time length of the second predetermined duration is set to end at dawn activated by the light sensing control unit.

7. The LED security light according to claim 1, wherein the second predetermined duration is programmable by the time setting unit.

8. The LED security light according to claim 1, wherein the light intensity of the second illumination mode is adjustable by an external control unit.

9. The LED security light according to claim 1, wherein the motion sensor is a passive infrared sensor.

10. The LED security light according to claim 1, wherein the motion sensor is a microwave motion sensor or an ultrasonic motion sensor.

11. An LED security light, comprising: a power supply unit; a light-emitting unit, including an LED load; a loading and power control unit; a light sensing control unit; a motion sensing unit, including at least one motion sensor; and a time setting unit; wherein the loading and power control unit comprises a controller and a switching circuitry, and the controller is electrically coupled with the switching circuitry; wherein the switching circuitry is electrically coupled with a power source of the power supply unit and the light-emitting unit, and the power source is a DC power source configured in the power supply unit; wherein the switching circuitry comprises at least one unidirectional semiconductor switching device; wherein the controller outputs pulse width modulation (PWM) signals to control average conduction rates of the switching circuitry for delivering different average electric currents from the power supply unit to drive the LED load of the light-emitting unit such that the light-emitting unit respectively generates illuminations of different light intensities for performing different illumination modes activated by the light sensing control unit, the motion sensing unit and the time setting unit; wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the light-emitting unit is turned on by the loading and power control unit activated by the light sensing control unit to perform a first illumination mode with a first level illumination and with the motion sensing unit being in a deactivated state, and the first illumination mode continues for a first predetermined time duration; wherein upon a maturity of the first predetermined time duration the loading and power control unit manages to cutoff the average electric current delivered to the LED load of the light-emitting unit and at the same time the motion sensing unit is activated; wherein when a motion signal is detected by the motion sensing unit, the loading and power control unit manages to deliver an average electric current to the LED load of the light-emitting unit to perform a second illumination mode with a second level illumination for a second predetermined time duration before being switched back to the turned off state; wherein at dawn when the ambient light detected by the light sensing control unit is higher than a second predetermined value, the light-emitting unit is switched off by the loading and power control unit; wherein the time setting unit is used for adjusting and setting at least a time length of at least one of the first predetermined time duration and the second predetermined time duration; wherein the LED load in conjunction with the DC power source is designed with an adequate combination of in series and in parallel connections such that an electric current passing through each LED of the LED load remains at an adequate level, and a working voltage V across each LED complies with a constraint of V.sub.th<V<V.sub.max featuring electrical characteristics of the LED; wherein V.sub.th is a minimum threshold voltage required to trigger the LED to start emitting light and V.sub.max is a maximum operating voltage across the LED to avoid a thermal damage to LED construction; and wherein the controller comprises at least a programmable integrated circuit device or an application specific integrated circuit.

12. The LED security light according to claim 11, wherein the value of V.sub.th is equal or greater than 2.5 volts, and the value of V.sub.max is in a range between 3.5 volts and 20 volts depending on a packaging specification of the LED.

13. The LED security light according to claim 12, wherein the value of the voltage V across the LED is confined to be in an operating range from 2.5 volts to 20 volts.

14. The LED security light according to claim 11, wherein the time length of the first predetermined time duration is programmable by the time setting unit.

15. The LED security light according to claim 11, wherein the light intensity of the first illumination mode is adjustable by an external control unit.

16. The LED security light according to claim 11, wherein the time length of the second predetermined time duration is programmable by the time setting unit.

17. The LED security light according to claim 11, wherein the light intensity of the second illumination mode is adjustable by an external control unit.

18. The LED security light according to claim 11, wherein the motion sensor is a passive infrared sensor.

19. The LED security light according to claim 11, wherein the motion sensor is a microwave motion sensor or an ultrasonic motion sensor.

20. An LED security light, comprising: a power supply unit; a light-emitting unit, including an LED load; a loading and power control unit; a light sensing control unit; a motion sensing unit, including at least one motion sensor; and a time setting unit; wherein the loading and power control unit comprises a controller and a switching circuitry, and the controller is electrically coupled with the switching circuitry; wherein the switching circuitry is electrically coupled with a power source of the power supply unit and the light-emitting unit, and the power source is a DC power source configured in the power supply unit; wherein the switching circuitry comprises at least one unidirectional semiconductor switching device; wherein the controller outputs pulse width modulation (PWM) signals to control average conduction rates of the switching circuitry for delivering different average electric currents from the power supply unit to drive the LED load of the light-emitting unit such that the light-emitting unit respectively generates illuminations of different light intensities for performing different illumination modes activated by the light sensing control unit, the motion sensing unit and the time setting unit; wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the loading and power control unit operates to turn on the light emitting unit to perform a low level illumination mode comprising at least a first level illumination for a first predetermined time duration; wherein when a motion signal is detected by the motion sensing unit, the loading and power control unit operates to increase the average electric current delivered to the LED load of the light-emitting unit to perform a high level illumination mode for a preset time period before being switched back to the low level illumination mode; wherein the light intensity of the high level illumination mode is higher than the light intensity of the low level illumination mode; wherein at dawn when the ambient light detected by the light sensing control unit is higher than a second predetermined value, the light-emitting unit is switched off by the loading and power control unit; wherein the time setting unit is used for adjusting and setting at least a time length of at least one of the first predetermined time duration of the low level illumination mode and the preset time period of the high level illumination mode; wherein the LED load in conjunction with the DC power source is designed with an adequate combination of in series and in parallel connections such that an electric current passing through each LED of the LED load remains at an adequate level, and a working voltage V across each LED of the LED load complies with a constraint of V.sub.th<V<V.sub.max featuring electrical characteristics of the LED; wherein V.sub.th is a minimum threshold voltage required to trigger the LED to start emitting light and V.sub.max is a maximum operating voltage across the LED to avoid a thermal damage to LED construction; and wherein the controller comprises at least a programmable integrated circuit device or an application specific integrated circuit.

21. The LED security light according to claim 20, wherein the low level illumination mode further comprises a second level illumination; wherein upon a maturity of the first predetermined time duration, the loading and power control unit operates to further reduce the light intensity of the low level illumination mode to perform the second level illumination to end at dawn activated by the light sensing control unit.

22. The LED security light according to claim 21, wherein the light intensity of the second level illumination is set at zero.

23. The LED security light according to claim 21, wherein the maturity of the first predetermined time duration is set to end at a midnight time point.

24. The LED security light according to claim 20, wherein the value of V.sub.th is equal or greater than 2.5 volts, and the value of V.sub.max is in a range between 3.5 volts and 20 volts depending on a packaging specification of the LED.

25. The LED security light according to claim 20, wherein the value of the voltage V across each LED is confined to be in an operating range from 2.5 volts to 20 volts.

26. The LED security light according to claim 20, wherein the motion sensor is a passive infrared sensor.

27. The LED security light according to claim 20, wherein the motion sensor is a microwave motion sensor or an ultrasonic motion sensor.

28. The LED security light according to claim 20, wherein the time length of the low level illumination mode is set to end at dawn activated by the light sensing control unit.

29. The LED security light according to claim 20, wherein the first predetermined duration is programmable by the time setting unit.

30. The LED security light according to claim 20, wherein the time length of the preset time period is programmable by the time setting unit.

31. An LED security light, comprising: a power supply unit; a light-emitting unit, including an LED load; a loading and power control unit; a light sensing control unit; a motion sensing unit, including at least one motion sensor; and a time setting unit; wherein the loading and power control unit comprises a controller and a switching circuitry, and the controller is electrically coupled with the switching circuitry; wherein the switching circuitry is electrically coupled with a power source of the power supply unit and the light-emitting unit, and the power source is a DC power source configured in the power supply unit; wherein the switching circuitry comprises at least one unidirectional semiconductor switching device; wherein the controller outputs pulse width modulation (PWM) signals to control average conduction rates of the switching circuitry for delivering different average electric currents from the power supply unit to drive the LED load of the light-emitting unit such that the light-emitting unit respectively generates illuminations of different light intensities for performing different illumination modes for respective predetermined time durations activated by the light sensing control unit, the motion sensing unit and the time setting unit; wherein the time setting unit is used for adjusting and setting at least a time length of the predetermined time durations; wherein the power supply unit is a structure of DC power sources comprising an AC/DC power converter to convert AC power into DC powers required for operating the LED security light; wherein the LED load in conjunction with the DC power source is designed with an adequate combination of in series and in parallel connections such that an electric current passing through each LED of the LED load remains at an adequate level, and a working voltage V across each LED complies with a constraint of V.sub.th<V<V.sub.max featuring electrical characteristics of the LED; wherein V.sub.th is a minimum threshold voltage required to trigger the LED to start emitting light and V.sub.max is a maximum operating voltage across the LED to avoid a thermal damage to LED construction; and wherein the controller comprises at least a programmable integrated circuit device or an application specific integrated circuit.

32. The LED security light according to claim 31, wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the loading and power control unit operates to switch on the light-emitting unit; wherein when a motion signal is detected by the motion sensing unit, the loading and power control unit manages to turn on the light-emitting unit thru a soft on process, wherein the controller successively outputs a series of PWM signals to gradually increase the average electric current to drive the LED load of the light-emitting unit to generate a high level illumination, and the high level illumination continues for a predetermined time duration; wherein when the ambient light detected by the light sensing control unit is higher than a second predetermined value, the light-emitting unit is turned off by the controller.

33. The LED security light according to claim 31, wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the loading and power control unit operates to switch on the light-emitting unit; wherein when a motion signal is detected by the motion sensing unit, the loading and power control unit manages to turn on the light-emitting unit to generate a high level illumination, the high level illumination continues for a predetermined time duration before the loading and power control unit manages to reduce illumination intensity of the light-emitting unit thru a soft off process, wherein the controller successively outputs a series of PWM signals to gradually decrease the average electric current to drive the LED load of the light-emitting unit such that the illumination intensity of the light-emitting unit is gradually reduced.

34. The LED security light according to claim 31, wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the light-emitting unit is switched on by the loading and power control unit; wherein when a motion signal is detected by the motion sensing unit, the loading and power control unit manages to turn on the light-emitting unit to perform a high level illumination for a predetermined time duration, wherein upon a maturity of the predetermined time duration the loading and power control unit manages to turn off the light-emitting unit thru a soft off process, wherein the soft off process is designed with a two stage approach; wherein for the first stage of the soft off process, the loading and power control unit manages to instantly reduce the illumination level of the light-emitting unit to a low level illumination and continues the low level illumination for a first short time interval, wherein for the second stage of the soft off process the loading and power control unit operates to turn off the light-emitting unit.

35. The LED security light according to claim 34, wherein for the second stage of the soft off process the loading and power control unit operates to gradually turn off the illumination of the light-emitting unit over a second short time interval.

36. The LED security light according to claim 34, wherein during the soft off process if a new motion signal is further detected by the motion sensing unit indicating an occupant remaining in the detection area, the loading and power control unit instantly operates to restart a new cycle of the high level illumination for a new predetermined time duration; wherein during the soft off a process if no further motion signal is received indicating the detection area is unoccupied, the light-emitting unit is thereby successfully turned off

37. The LED security light according to claim 36, wherein the new predetermined time duration is equal to the predetermined time duration used prior to restarting the new cycle of the high level illumination.

38. The LED security light according to claim 36, wherein the new predetermined time duration is programmed to be longer than the predetermined time duration used prior to restarting the new cycle of the high level illumination according to a programmed combination of increasing delay times.

39. The LED security light according to claim 31, wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the light-emitting unit is switched on by the loading and power control unit; wherein when a motion signal is detected by the motion sensing unit, the loading and power control unit manages to turn on the light-emitting unit to perform a high level illumination for a predetermined time duration, and upon a maturity of the predetermined time duration the loading and power control unit manages to turn off the light-emitting unit with a two stage shutoff process; wherein for the first stage of the shutoff process, the loading and power control unit manages to perform a sudden disruption of illumination for a short moment and resume instantly back to the high level illumination to continue for a first short time interval, wherein for the second stage of the shutoff process the loading and power control unit operates to gradually turn off the light-emitting unit over a second short time interval.

40. The LED security light according to claim 39, wherein during the two stage shutoff process if a new motion signal is further detected by the motion sensing unit indicating an occupant remaining in the detection area, the loading and power control unit instantly manages to resume the high level illumination and restarts a new cycle of the high level illumination for a new predetermined time duration; wherein during the two stage shutoff process if no further motion signal is received indicating the detection area is unoccupied, the light-emitting unit is thereby successfully turned off

41. The LED security light according to claim 40, wherein the time length of the new predetermined time duration is equal to the time length of the predetermined time duration.

42. The LED security light according to claim 40, wherein the time length of the new predetermined time duration is longer than the time length of the predetermined time duration according to a programmed combination of increasing delay times.

43. The LED security light according to claim 31, wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the light-emitting unit is switched on by the loading and power control unit to generate a low level illumination; wherein when a motion signal is detected by the motion sensing unit, the loading and power control unit manages to increase the average electric current from the power source to the LED load of the light-emitting unit to generate a high level illumination for a predetermined time duration, wherein upon a maturity of the predetermined time duration the loading and power control unit manages the light-emitting unit to resume the low level illumination, wherein if a new motion signal is further detected by the motion sensing unit within a short predetermined time interval after the light-emitting unit being switched back to the low level illumination, the loading and power control unit instantly manages to resume the high level illumination and restart a new cycle of illumination for a new predetermined time duration, wherein the time length of the new predetermined time duration is longer than the time length of the predetermined time duration according to a programmed combination of increasing delay times.

44. The LED security light according to claim 31, wherein the value of V.sub.th is equal or greater than 2.5 volts, and the value of V.sub.max is in a range between 3.5 volts and 20 volts depending on a packaging specification of the LED.

45. The security light according to claim 44, wherein the value of the voltage V across each LED is confined to be in an operating range from 2.5 volts to 20 volts

46. The LED security light according to claim 31, wherein the motion sensor is a passive infrared sensor.

47. The LED security light according to claim 31, wherein the motion sensor is a microwave motion sensor or an ultrasonic motion sensor.

48. An LED security light, comprising: a power supply unit; a light-emitting unit, including an LED load; a loading and power control unit; a light sensing and control unit; and a time setting unit; wherein the loading and power control unit comprises a controller and a switching circuitry, the controller is electrically coupled with the switching circuitry, the switching circuitry is electrically coupled between a power source and the light-emitting unit, and the power source is a DC power source configured in the power supply unit; wherein with the switching circuitry the light-emitting unit is turned on or turned off by the loading and power control unit, and the switching circuitry comprises at least one unidirectional semiconductor switching device; wherein the controller outputs pulse width modulation (PWM) signals to control average conduction rates of the switching circuitry for delivering different average electric currents from the power supply unit to drive the LED load of the light-emitting unit such that the light-emitting unit respectively generates illuminations of different light intensities for performing different illumination modes activated by the light sensing control unit and the time setting unit; wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the light-emitting unit is turned on by the loading and power control unit to perform a first illumination mode for a predetermined time duration set by the time setting unit, and then the controller manages to change the lighting performance of the LED security light from the first illumination mode to a second illumination mode; wherein the light intensity of the second illumination mode is lower than the light intensity of the first illumination mode; wherein at dawn when the ambient light detected by the light sensing control unit is higher than a second predetermined value, the light-emitting unit is turned off by the controller; wherein the time setting unit is used for adjusting and setting a time length of the predetermined time duration; wherein the LED load in conjunction with the DC power source is designed with an adequate combination of in series and in parallel connections such that an electric current passing through each LED of the LED load remains at an adequate level, and a working voltage V across each LED complies with a constraint of V.sub.th<V<V.sub.max featuring electrical characteristics of the LED; wherein V.sub.th is a minimum threshold voltage required to trigger the LED to start emitting light and V.sub.max is a maximum operating voltage across the LED to avoid a thermal damage to LED construction; and wherein the controller comprises at least a programmable integrated circuit device or an application specific integrated circuit.

49. The LED security light according to claim 48, wherein the value of V.sub.th is equal or greater than 2.5 volts, and the value of V.sub.max is in a range between 3.5 volts and 20 volts depending on a packaging specification of the LED.

50. The LED security light according to claim 49, wherein the value of the working voltage V across each LED is confined to be in an operating range from 2.5 volts to 20 volts.

51. An LED security light, comprising: a power supply unit; a light-emitting unit, including an LED load; a loading and power control unit; and a light sensing control unit; wherein the loading and power control unit comprises a controller and a switching circuitry, the controller is electrically coupled with the switching circuitry, the switching circuitry is electrically coupled between a power source and the LED load of the light-emitting unit, and the power source is a DC power source configured in the power supply unit; wherein with the switching circuitry the light-emitting unit is turned on or turned off by the loading and power control unit, and the switching circuitry comprises at least one unidirectional semiconductor switching device; wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the controller of the loading and power control unit outputs a control signal to conduct the switching circuitry to deliver an average electric current to the LED load such that to turn on the light-emitting unit for generating an illumination; wherein at dawn when the ambient light detected by the light sensing control unit is higher than a second predetermined value, the controller of the loading and power control unit outputs a control signal to cutoff the switching circuitry to turn off the light-emitting unit; wherein the LED load in conjunction with the DC power source is designed with a configuration of in series or in parallel connections such that an electric current passing through each LED of the LED load remains at an adequate level, and a working voltage V across each LED of the LED load complies with a constraint of V.sub.th<V<V.sub.max featuring electrical characteristics of the LED; wherein V.sub.th is a minimum threshold voltage required to trigger the LED to start emitting light and V.sub.max is a maximum operating voltage across the LED to avoid a thermal damage to LED construction; and wherein the controller comprises at least an integrated circuit device programmable for generating the control signals or an application specific integrated circuit customized for generating the control signals.

52. The LED security light according to claim 51, wherein the value of V.sub.th is equal or greater than 2.5 volts, and the value of V.sub.max is in a range between 3.5 volts and 20 volts depending on a packaging specification of the LED.

53. The LED security light according to claim 52, wherein the value of the working voltage V across each LED is confined to be in an operating range from 2.5 volts to 20 volts.

54. An LED security light, comprising: a power supply unit; a light-emitting unit, including an LED load; a loading and power control unit; a light sensing control unit; and an external control unit; wherein the loading and power control unit comprises a controller and a switching circuitry, the controller is electrically coupled with the switching circuitry, the switching circuitry is electrically coupled between a power source and the LED load of the light-emitting unit, and the power source is a DC power source configured in the power supply unit; wherein with the switching circuitry the light-emitting unit is turned on or turned off by the loading and power control unit, and the switching circuitry comprises at least one unidirectional semiconductor switching device, wherein the controller outputs control signals to control average conduction rates of the switching circuitry for delivering different average electric currents from the power supply unit to drive the LED load of the light-emitting unit such that the light-emitting unit respectively generates illuminations of different light intensities for performing at least a first illumination mode and a second illumination mode activated by the light sensing control unit and the external control unit; wherein the external control unit is a power interruption detection circuitry electrically coupled to the controller for detecting a short power interruption signal, wherein the controller controls the switching circuitry in response to the short power interruption signal detected to alternately switch the light-emitting unit between performing a first illumination mode and performing a second illumination mode, wherein the light intensity of the first illumination mode is higher than the light intensity of the second illumination mode; wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the light-emitting unit is turned on by the loading and power control unit to perform the first illumination mode; wherein whenever the short power interruption signal is detected by the external control unit, the controller operates to alternately switch the light-emitting unit between performing the first illumination mode and performing the second illumination mode; wherein at dawn when the ambient light detected by the light sensing control unit is higher than a second predetermined value, the controller of the loading and power control unit operates to cutoff the switching circuitry to turn off the light emitting unit. wherein the LED load in conjunction with the DC power source is designed with a configuration of in series or in parallel connections such that an electric current passing through each LED of the LED load remains at an adequate level, and a working voltage V across each LED of the LED load complies with a constraint of V.sub.th<V<V.sub.max featuring electrical characteristics of the LED; wherein V.sub.th is a minimum threshold voltage required to trigger the LED to start emitting light and V.sub.max is a maximum operating voltage across the LED to avoid a thermal damage to LED construction; and wherein the controller comprises at least an integrated circuit device programmable for generating the control signals or an application specific integrated circuit customized for generating the control signals.

55. The LED security light according to claim 54, wherein the value of V.sub.th is equal or greater than 2.5 volts, and the value of V.sub.max is in a range between 3.5 volts and 20 volts depending on a packaging specification of the LED.

56. The LED security light according to claim 55, wherein the value of the working voltage V across each LED is confined to be in an operating range from 2.5 volts to 20 volts.

57. An LED motion sensing security light, comprising: a power supply unit; a light-emitting unit, including an LED load; a loading and power control unit; a light sensing control unit; a motion sensing unit, including at least one motion sensor; and a time setting unit; wherein the loading and power control unit comprises a controller and a switching circuitry, and the controller is electrically coupled with the switching circuitry; wherein the switching circuitry is electrically coupled with a power source of the power supply unit and the light-emitting unit, and the power source is a DC power source configured in the power supply unit; wherein the switching circuitry comprises at least one unidirectional semiconductor switching device; wherein the controller outputs a pulse width modulation (PWM) signal to control a conduction rate of the switching circuitry for transmitting an average electric current from the power source to drive the LED load of the light-emitting unit to generate an illumination activated by the motion sensing unit for performing a motion sensing illumination mode; wherein the time setting unit is used for adjusting and setting at least a time length of the predetermined time durations; wherein the power supply unit is a structure of DC power sources comprising an AC/DC power converter to convert AC power into DC powers required for operating the LED security light; wherein the LED load in conjunction with the DC power source is designed with an adequate combination of in series and in parallel connections such that an electric current passing through each LED of the LED load remains at an adequate level, and a working voltage V across each LED complies with a constraint of V.sub.th<V<V.sub.max featuring electrical characteristics of the LED; wherein V.sub.th is a minimum threshold voltage required to trigger the LED to start emitting light and V.sub.max is a maximum operating voltage across the LED to avoid a thermal damage to LED construction; wherein at dusk when an ambient light detected by the light sensing control unit is lower than a first predetermined value, the loading and power control unit operates to switch on the light-emitting unit; wherein when a motion signal is detected by the motion sensing unit, the loading and power control unit manages to conduct the switching circuitry to deliver the average electric current to drive the LED load for generating the illumination for a predetermined time duration preset by the time setting unit; wherein when the ambient light detected by the light sensing control unit is higher than a second predetermined value, the light-emitting unit is turned off by the controller.

58. The LED motion sensing security light according to claim 57, wherein the value of V.sub.th is equal or greater than 2.5 volts, and the value of V.sub.max is in a range between 3.5 volts and 20 volts depending on a packaging specification of the LED.

59. The LED motion sensing security light according to claim 58, wherein the value of the working voltage V across each LED is confined to be in an operating range from 2.5 volts to 20 volts.

60. The LED motion sensing security light according to claim 57, wherein an external control unit is further installed and electrically coupled with the controller to receive and convert an external control signal into a message signal interpretable by the controller, wherein upon receiving the message signal the controller operates to activate a switching process to alternately perform among a high level non-motion sensing illumination mode, a low level non-motion sensing illumination mode and the motion sensing illumination mode.

61. The LED motion sensing security light according to claim 60, wherein the external control unit is a short power interruption detection circuitry and the external control signal is an short power interruption signal, wherein when a first short power interruption signal is detected, the controller operates to change the performance of the light emitting unit from the motion sensing illumination mode to the high level non-motion sensing illumination mode, wherein when a second short power interruption signal is furthered detected, the controller operates to change the performance of the light emitting unit from the high level non-sensing illumination mode to the low level non-sensing illumination mode, wherein when a third short power interruption signal is further detected, the controller manages to change the performance of the light emitting unit back to the motion sensing illumination mode to complete a cycle of the switching process.

62. The LED motion sensing security light according to claim 57, wherein an external control unit is further installed and electrically coupled with the controller to receive and convert an external control signal into a message signal interpretable by the controller, wherein upon receiving the message signal the controller operates to activate a switching process to alternately perform between a low level non-motion sensing illumination mode and the motion sensing illumination mode.

63. The LED motion sensing security light according to claim 62, wherein the external control unit is a short power interruption detection circuitry and the external control signal is a short power interruption signal, wherein when a first short power interruption signal is detected, the controller operates to change the performance of the light emitting unit from the motion sensing illumination mode to the low level non-motion sensing illumination mode, wherein when a second short power interruption signal is furthered detected, the controller operates to change the performance of the light emitting unit from the low level non-sensing illumination mode back to the motion sensing illumination mode to complete a cycle of the switching process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0014] FIG. 1 schematically illustrates a block diagram of a two-level LED security light in accordance with an exemplary embodiment of the present disclosure.

[0015] FIG. 2A illustrates a schematic diagram of a two-level LED security light in accordance to the first exemplary embodiment of the present disclosure.

[0016] FIG. 2B graphically illustrates a timing waveform of a pulse width modulation (PWM) signal in accordance to the first exemplary embodiment of the present disclosure.

[0017] FIG. 3A illustrates a schematic diagram of a two-level LED security light in accordance to the second exemplary embodiment of the present disclosure.

[0018] FIG. 3B illustrates a schematic diagram of a two-level LED security light in accordance to the second exemplary embodiment of the present disclosure.

[0019] FIG. 4A illustrates a schematic diagram of a two-level LED security light in accordance to the third exemplary embodiment of the present disclosure.

[0020] FIG. 4B illustrates a timing waveform of two-level LED security light in accordance to the third exemplary embodiment of the present disclosure.

[0021] FIG. 5 illustrates a schematic diagram of a two-level LED security light in accordance to the third exemplary embodiment of the present disclosure.

[0022] FIG. 6 illustrates a schematic diagram of a two-level LED security light in accordance to the fourth exemplary embodiment of the present disclosure.

[0023] FIG. 7 illustrates a schematic diagram of a two-level LED security light in accordance to the fifth exemplary embodiment of the present disclosure.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0024] Reference is made in detail to the exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or alike parts.

First Exemplary Embodiment

[0025] Refer to FIG. 1, which schematically illustrates a block diagram of a two-level LED security light in accordance to the first exemplary embodiment of the present disclosure. A two-level LED security light (herein as the lighting apparatus) 100 includes a power supply unit 110, a light sensing control unit 120, a motion sensing unit 130, a loading and power control unit 140, and a light-emitting unit 150. The power supply unit 110 is used for supplying power required to operate the system, wherein the associated structure includes the known AC/DC voltage converter. The light sensing control unit 120 may be a photoresistor, which may be coupled to the loading and power control unit 140 for determining daytime or nighttime in accordance to the ambient light. The motion sensing unit 130 may be a passive infrared sensor (PIR), which is coupled to the loading and power control unit 140 and is used to detect intrusions. When a person is entering a predetermined detection zone of the motion sensing unit 130, a sensing signal thereof may be transmitted to the loading and power control unit 140.

[0026] The loading and power control unit 140 which is coupled to the light-emitting unit 150 may be implemented by a microcontroller electrically coupled with a switching circuitry electrically connected between the light emitting unit 150 and the power supply unit 110. The switching circuitry may comprise a plurality of semiconductor switching components. The loading and power control unit 140 may control the illumination levels of the light-emitting unit 150 in accordance to the sensing signal outputted by the light sensing control unit 120 and the motion sensing unit 130. The light-emitting unit 150 may include a plurality of LEDs. The loading and power control unit 140 may control the light-emitting unit 150 to generate at least two levels of illumination variations.

[0027] When the light sensing control unit 120 detects that an ambient light is lower than a predetermined value (i.e., nighttime), the loading and power control unit 140 executes the Photo-Control (PC) mode by turning on the light-emitting unit 150 to generate a high level illumination for a predetermined duration then return to a low level illumination for Power-Saving (PS) mode or it may alternatively generate the low level illumination to perform the power saving mode. When the light sensing control unit 120 detects that the ambient light is higher than a predetermined value (i.e., dawn), the loading and power control unit 140 turns off the light-emitting unit 150. In the PS mode, when the motion sensing unit 130 detects a human motion, the loading and power control unit 140 may increase the electric current which flows through the light-emitting unit 150, to generate another high level illumination for a short predetermined duration. After the short predetermined duration, the loading and power control unit 140 may automatically lower the electric current that flow through the light-emitting unit 150 thus have the light-emitting unit 150 return to low level illumination for saving energy.

[0028] Refer to 2A, which illustrates a schematic diagram of a two-level LED security light in accordance to the first exemplary embodiment of the present disclosure. The light sensing control unit 120 may be implemented by a light sensor 220; the motion sensing unit 130 may be implemented by a motion sensor 230; the loading and power control unit 140 may be implemented by a microcontroller 240 electrically coupled to a switching circuitry Q1. The light-emitting unit 250 includes three series-connected LEDs L1L3. The LEDs L1L3 is connected between a DC source and a transistor Q1, wherein the DC source may be provided by the power supply unit 110. The transistor Q1 may be an N-channel metal-oxide-semiconductor field-effect-transistor (NMOS). The transistor Q1 is connected between the three series-connected LEDs L1L3 and a ground GND. The loading and power control unit 140 implemented by the microcontroller 240 may output a control signal like a pulse width modulation (PWM) signal to control an average electric current delivered to the light emitting unit 250. It is worth to note that the electric components depicted in FIG. 2A only serves as an illustration for the exemplary embodiment of the present disclose and hence the present disclosure is not limited thereto.

[0029] Refer to FIG. 2B concurrently, which graphically illustrates a timing waveform of a pulse width modulation (PWM) signal in accordance to the first exemplary embodiment of the present disclosure. In the PC mode, the PWM signal may be used to configure the transistor Q1 to have the conduction period T.sub.on being longer than the cut-off period T.sub.off. On the other hand in the PS mode, the PWM signal may configure the transistor Q1 to have the conduction period T.sub.on being shorter than the cut-off period T.sub.off. In comparison of the illumination levels between the PC and PS modes, as the conduction period T.sub.on of transistor Q1 being longer under the PC mode, therefore have higher average electric current driving the light-emitting unit 250 thereby generate high illumination, which may be classified as the high level illumination; whereas as the conduction period T.sub.on of transistor Q1 is shorter in the PS mode, therefore have lower average electric current driving the light-emitting unit 250 thereby generate low illumination, which may be classified as the low level illumination.

[0030] The microcontroller 240 turns off the light-emitting unit 250 during the day and activates the PC mode at night by turning on the light-emitting unit 250 to generate the high level illumination for a short predetermined duration then return to the low level illumination thereby entering the PS mode. When the motion sensor 230 detects a human motion in the PS mode, the light-emitting unit 250 may switch to the high level illumination for illumination or warning application. The light-emitting unit 250 may return to the low level illumination after maintaining at the high level illumination for a short predetermined duration to save energy.

[0031] In addition, the microcontroller 240 is coupled to a time setting unit 260, wherein the time setting unit 260 may allow a user to configure the predetermined duration associated with the high level illumination in the PC mode, however the present disclosure is not limited thereto. The time setting unit 260 may also be used for setting a predetermined time duration associated with the low level illumination as well as a predetermined time duration associated with a motion activated high level illumination. The time setting unit 260 is typically configured with an analogue circuitry comprising a resister and a capacitor for setting a time length. However, if precision of time length is crucial or much preferred, a digital circuitry may be employed, wherein a voltage divider with a variable resister coupled to the microcontroller designed with a time setting subroutine or a push button device coupled with a grounding pin of the microcontroller designed with the time setting subroutine for more precisely setting a time length for performing an illumination mode.

Second Exemplary Embodiment

[0032] Refer again to FIG. 1, wherein the illumination variations of the light-emitting unit 150 may be implemented through the number of light-source loads being turned on to generate more than two levels of illumination. The lighting apparatus 100 in the instant exemplary embodiment may be through turning on a portion of LEDs or all the LEDs to generate a low and a high level of illuminations.

[0033] Refer to FIG. 3A concurrently, which illustrates a schematic diagram of a two-level LED security light 100 in accordance to the second exemplary embodiment of the present disclosure. The main difference between FIG. 3A and FIG. 2A is in the light-emitting unit 350, having three series-connected LEDs L1L3 and NMOS transistors Q1 and Q2. The LEDs L1L3 are series connected to the transistor Q1 at same time connected between the DC source and a constant electric current control circuit 310. Moreover, transistor Q2 is parallel connected to the two ends associated with LEDs L2 and L3. The gates of the transistors Q1 and Q2 are connected respectively to a pin PC and a pin PS of the microcontroller 240. The constant electric current control circuit 310 in the instant exemplary embodiment maintains the electric current in the activated LED at a constant value, namely, the LEDs L1L3 are operated in constant-current mode.

[0034] Refer to FIG. 3A, the pin PC of the microcontroller 240 controls the switching operations of the transistor Q1; when the voltage level of pin PC being either a high voltage or a low voltage, the transistor Q1 may conduct or cut-off, respectively, to turn the LEDs L1L3 on or off. The pin PS of the microcontroller 240 controls the switch operations of the transistor Q2, to form two current paths 351 and 352 on the light-emitting unit 350. When the voltage at the pin PS of the microcontroller 240 is high, the transistor Q2 conducts, thereby forming the current path 351 passing through the LED L1 and the transistor Q2; when the voltage at the pin PS being low, the transistor Q2 cuts-off, thereby forming the current path 352 passing through all the LEDs L1L3. The microcontroller 240 may then control the switching operation of the transistor Q2 to turn on the desired number of LEDs so as to generate a high or a low level illumination.

[0035] When light sensor 220 determines that an ambient light is higher than a predetermined value, the microcontroller 240 through the pin PC outputs a low voltage, which causes the transistor Q1 to cut-off and turns off all the LEDs L1L3 in the light-emitting unit 350. Conversely, when the light sensor 220 detects that the ambient light is lower than the predetermined value, the microcontroller 240 activates the PC mode, i.e., outputting a high voltage from pin PC and a low voltage from pin PS, to activate the transistor Q1 while cut-off the transistor Q2, thereby forming the current path 352, to turn on the three LEDs L1L3 in the light-emitting unit 350 so as to generate the high level illumination for a predetermined duration. After the predetermined duration, the microcontroller 240 may switch to the PS mode by having the pin PC continue outputting a high voltage and the pin PS outputting a high voltage, to have the transistor Q2 conducts, thereby forming the current path 351. Consequently, only the LED L1 is turned on and the low level illumination is generated.

[0036] When the motion sensor detects a human motion in the PS mode, the pin PS of the microcontroller 240 temporarily switches from the high voltage to a low voltage, to have the transistor Q2 temporarily cuts-off thus forming the current path 352 to activate all the LEDs in the light-emitting unit 350, thereby temporarily generates the high level illumination. The light-emitting unit 350 is driven by a constant electric current, therefore the illumination level generated thereof is directly proportional to the number of LEDs activated. FIG. 3B illustrates another implementation for FIG. 3A, wherein the relays J1 and J2 are used in place of NMOS transistors to serve as switches. The microcontroller 240 may control the relays J2 and J1 through regulating the switching operations of the NPN bipolar junction transistors Q4 and Q5. Moreover, resistors R16 and R17 are current-limiting resistors.

[0037] In the PC mode, the relay J1 being pull-in while the relay J2 bounce off to have constant electric current driving all the LEDs L1L3 to generate the high level illumination; in PS mode, the relays J1 and J2 both pull-in to have constant electric current only driving the LED L1 thus the low level illumination may be thereby generated. Furthermore, when the motion sensor 230 detects a human motion, the pin PS of the microcontroller 240 may temporarily switch from high voltage to low voltage, forcing the relay J2 to temporarily bounce off and the relay J1 pull-in so as to temporarily generate the high level illumination.

[0038] The LED L1 may adopt a LED having color temperature of 2700K while the LEDs L2 and L3 may adopt LEDs having color temperature of 5000K in order to increase the contrast between the high level and the low level illuminations. The number of LEDs included in the light-emitting unit 350 may be more than three, for example five or six LEDs. The transistor Q2 may be relatively parallel to the two ends associated with a plurality of LEDs to adjust the illumination difference between the high and the low illumination levels. Additionally, the light-emitting unit 350 may be connected to a plurality of transistors Q2, which are respectively coupled to the two ends associated with each LED to provide more lighting variation selections. The microcontroller 240 may decide the number of LEDs to turn on in accordance to design needs at different conditions. Based on the explanation of the aforementioned exemplary embodiment, those skills in the art should be able to deduce other implementation and further descriptions are therefore omitted.

Third Exemplary Embodiment

[0039] Refer back to FIG. 1, wherein the light-emitting unit 150 may include one or more parallel-connected alternating current (AC) LEDs. A phase controller is coupled between the described one or more parallel-connected ACLEDs and AC power source. The loading and power controller 140 in the instant exemplary embodiment may through the phase controller adjust the average power of the light-emitting unit 150 so as to generate variations in the low level and the high level illuminations.

[0040] Refer to FIG. 4A, which illustrates a schematic diagram of a two-level LED security light 100 in accordance to the third exemplary embodiment of the present disclosure. The main difference between FIG. 4A and FIG. 3 is in that the light-source load is an ACLED, which is coupled to the AC power source, and further the light-emitting unit 450 is connected to a phase controller 451. The phase controller 451 includes a bi-directional switching device 452, here, a triac, a zero-crossing detection circuit 453, and a resistor R. The microcontroller 240 turns off the light-emitting unit 450 when the light sensor 220 detects that the ambient light is higher than a predetermined value. Conversely, when the light sensor 220 detects that the ambient light is lower than the predetermined value, the microcontroller 240 activates the PC mode by turning on the light-emitting unit 450. In the PC mode, the microcontroller 240 may select a control pin for outputting a pulse signal which through a resistor R triggers the triac 452 to have a large conduction angle. The large conduction angle configures the light-emitting unit 450 to generate a high level illumination for a predetermined duration. Then the microcontroller 240 outputs the pulse signal for PS mode through the same control pin to trigger the triac 452 to have a small conduction angle for switching the light-emitting unit 450 from the high level illumination to the low level illumination of the PS mode. Moreover, when the motion sensor 230 (also called motion sensing unit) detects a human motion in the PS mode, the microcontroller 240 temporarily outputs the PC-mode pulse signal through the same control pin to have the light-emitting unit 450 generated the high level illumination for a short predetermined duration. After the short predetermined duration, the light-emitting unit 450 returns to the low level illumination.

[0041] In the illumination control of the ACLED, the microcontroller 240 may utilize the detected zero-crossing time (e.g., the zero-crossing time of an AC voltage waveform) outputted from the zero-crossing detection circuit 453 to send an AC synchronized pulse signal thereof which may trigger the triac 452 of the phase controller 451 thereby to change the average power input to the light-emitting unit 450. As the ACLED has a cut-in voltage V.sub.t for start conducting, thus if the pulse signal inaccurately in time triggers the conduction of the triac 452, then the instantaneous value of AC voltage may be lower than the cut-in voltage V.sub.t of ACLED at the trigger pulse. Consequently, the ACLED may result in the phenomenon of either flashing or not turning on. Therefore, the pulse signal generated by the microcontroller 240 must fall in a proper time gap behind the zero-crossing point associated with the AC sinusoidal voltage waveform.

[0042] Supposing an AC power source having a voltage amplitude V.sub.m and frequency f, then the zero-crossing time gap t.sub.D of the trigger pulse outputted by the microcontroller 240 should be limited according to t.sub.o<t.sub.D<.sub.ft.sub.o for a light-source load with a cut-in voltage V.sub.t, wherein t.sub.o=(f)sin.sup.1(V.sub.t/V.sub.m). The described criterion is applicable to all types of ACLEDs to assure that the triac 452 can be stably triggered in both positive and negative half cycle of the AC power source. Take ACLED with V.sub.t(rms)=80V as an example, and supposing the V.sub.m(rms)=110V and f=60 Hz, then t.sub.o=2.2 ms and (f)=8.3 ms may be obtained. Consequently, the proper zero-crossing time gap t.sub.D associated with the phase modulation pulse outputted by the microcontroller 240 which lagged the AC sinusoidal voltage waveform should be designed in the range of 2.2 ms<t.sub.D, <6.1 ms.

[0043] Refer to FIG. 4B, which illustrates a timing waveform of the two-level LED security light in accordance to the third exemplary embodiment of the present disclosure. Waveforms (a)(d) of FIG. 4B respectively represent the AC power source, the output of the zero-crossing detection circuit 453, the zero-crossing delay pulse at the control pin of the microcontroller 240, and the voltage waveform across the two ends of the ACLED in the light-emitting unit 450. The zero-crossing detection circuit 453 converts the AC voltage sinusoidal waveform associated with the AC power source to a symmetric square waveform having a low and a high voltage levels as shown in FIG. 4B(b). At the zero-crossing point of the AC voltage sinusoidal wave, the symmetric square waveform may transit either from the low voltage level to the high voltage level or from the high voltage level to the low voltage level. Or equivalently, the edge of the symmetric square waveform in the time domain corresponds to the zero-crossing point of the AC voltage sinusoidal waveform. As shown in FIG. 4B(c), the microcontroller 240 outputs a zero-crossing delay pulse in correspondence to the zero-crossing point of the AC sinusoidal waveform in accordance to the output waveform of the zero-crossing detection circuit 453. The zero-crossing delay pulse is relative to an edge of symmetric square waveform behind a time gap t.sub.D in the time domain. The t.sub.D should fall in a valid range, as described previously, to assure that the triac 452 can be stably triggered thereby to turn on the ACLED. FIG. 4B(d) illustrates a voltage waveform applied across the two ends associated with the ACLED. The illumination level of the light-emitting unit 450 is related to the conduction period t.sub.on of the ACLED, or equivalently, the length t.sub.on is directly proportional to the average power inputted to the ACLED. The difference between the PC mode and the PS mode being that in the PC mode, the ACLED has longer conduction period, thereby generates the high level illumination; whereas in the PS mode, the ACLED conduction period is shorter, hence generates the low level illumination.

[0044] Refer to FIG. 5, which illustrates a schematic diagram of a two-level LED security light 100 in accordance to the third exemplary embodiment of the present disclosure. The light-emitting unit 550 of the lighting apparatus 100 includes an ACLED1, an ACLED2. The phase controller 551 includes triacs 552 and 553, the zero-crossing detection circuit 554 as well as resistors R1 and R2. The light-emitting unit 550 of FIG. 5 is different from the light-emitting unit 450 of FIG. 4 in that the light-emitting unit 550 has more than one ACLED and more than one bi-directional switching device. Furthermore, the color temperatures of the ACLED1 and the ACLED2 may be selected to be different.

[0045] In the exemplary embodiment of FIG. 5, the ACLED1 has a high color temperature, and the ACLED2 has a low color temperature. In the PC mode, the microcontroller 240 uses the phase controller 551 to trigger both ACLED1 and ACLED2 to conduct for a long period, thereby to generate the high level illumination as well as illumination of mix color temperature. In the PS mode, the microcontroller 240 uses the phase controller 551 to trigger only the ACLED2 to conduct for a short period, thereby generates the low level illumination as well as illumination of low color temperature. Moreover, in the PS mode, when the motion sensor 230 detects a human motion, the microcontroller 240 may through the phase controller 551 trigger the ACLED1 and ACLED2 to conduct for a long period. Thereby, it may render the light-emitting unit 450 to generate the high level illumination of high color temperature and to produce high contrast in illumination and hue, for a short predetermined duration to warn the intruder. Consequently, the lighting apparatus may generate the high level or the low level illumination of different hue. The rest of operation theories associated with the light-emitting unit 550 are essentially the same as the light-emitting unit 450 and further descriptions are therefore omitted.

Fourth Exemplary Embodiment

[0046] Refer to FIG. 6, which illustrates a schematic diagram of a two-level LED security light 100 in accordance to the fourth exemplary embodiment of the present disclosure. The light-emitting unit 150 of FIG. 1 may be implemented by the light-emitting unit 650, wherein the light-emitting unit 650 includes three ACLED13 having identical luminous power electrically connected to switches 651 and 652. In which, switches 651 and 652 may be relays. The parallel-connected ACLED1 and ACLED2 are series-connected to the switch 652 to produce double luminous power, and of which the ACLED3 is parallel connected to, to generate triple luminous power, and of which an AC power source is further coupled to through the switch 651. Moreover, the microcontroller 240 implements the loading and power control unit 140 of FIG. 1. The pin PC and pin PS are respectively connected to switches 651 and 652 for outputting voltage signals to control the operations of switches 651 and 652 (i.e., open or close).

[0047] In the PC mode, the pin PC and pin PS of the microcontroller 240 control the switches 651 and 652 to be closed at same time. Consequently, the ACLED13 are coupled to the AC power source and the light-emitting unit 650 may generate a high level illumination of triple luminous power. After a short predetermined duration, the microcontroller 240 returns to PS mode. In which the switch 651 is closed while the pin PS controls the switch 652 to be opened, consequently, only the ACLED3 is connected to AC power source, and the light-emitting unit 650 may thus generate the low level illumination of one luminous power. In the PS mode, when the motion sensor 230 detects a human motion, the microcontroller 240 temporarily closes the switch 652 to generate high level illumination with triple luminous power for a predetermined duration. After the predetermined duration, the switch 652 returns to open status thereby to generate the low level illumination of one luminous power. The lighting apparatus of FIG. 6 may therefore through controlling switches 651 and 652 generate two level illuminations with illumination contrast of at least 3 to 1.

[0048] The ACLED1 and ACLED2 of FIG. 6 may be high power lighting sources having color temperature of 5000K. The ACLED3 may be a low power lighting source having color temperature of 2700K. Consequently, the ACLED may generate two levels of illuminations with high illumination and hue contrast without using a zero-crossing detection circuit.

Fifth Exemplary Embodiment

[0049] Refer to FIG. 7, which illustrates a schematic diagram of a two-level LED security light in accordance to the fifth exemplary embodiment of the present disclosure. The light-emitting unit 750 of FIG. 7 is different from the light-emitting unit 640 of FIG. 6 in that the ACLED3 is series-connected to a circuit with a rectified diode D and a switch 753 parallel-connected together, and of which is further coupled through a switch 751 to AC power source. When the switch 753 closes, the AC electric current that passes through the ACLED3 may be a full sinusoidal waveform. When the switch 753 opens, the rectified diode rectifies the AC power, thus only one half cycle of the AC electric current may pass through the ACLED, consequently the luminous power of ALCED3 is cut to be half.

[0050] The pin PS of the microcontroller 240 synchronously controls the operations of switches 752 and 753. If the three ACLED13 have identical luminous power, then in the PC mode, the pin PC and pin PS of the microcontroller 240 synchronously close the switches 751753 to render ACLED13 illuminating, thus the light-emitting unit 750 generates a high level illumination which is three-times higher than the luminous power of a single ACLED. When in the PS mode, the microcontroller 240 closes the switch 751 while opens switches 752 and 753. At this moment, only the ACLED3 illuminates and as the AC power source is rectified by the rectified diode D, thus the luminous power of ACLED3 is half of the AC power source prior to the rectification. The luminous power ratio between the high level and the low level illuminations is therefore 6 to 1. Consequently, strong illumination contrast may be generated to effectively warn the intruder.

[0051] It should be noted that the light-emitting unit in the fifth exemplary embodiment is not limited to utilizing ACLEDs. In other words, the light-emitting unit may include any AC lighting sources such as ACLEDs, incandescent lamps, or fluorescent lamps.

[0052] In respect to the LED load of the light emitting unit 150, the cut-in voltage V.sub.t of ACLEDs or a plurality of LEDs is attributable to unique electrical characteristics of a light emitting diode, which are completely different from the conventional incandescent light bulb. The light emitting diode is made with a semiconductor material characterized with three unique electrical features, the first feature is one way conduction, the second feature is a minimum threshold voltage V.sub.th to trigger each light emitting diode to start emitting light and the third feature is a maximum working voltage V.sub.max allowed to impose on each light emitting diode to avoid a thermal damage or burning out the semiconductor construction of the light emitting diode. The described cut-in voltage V.sub.t refers to a total threshold voltage of the light emitting unit 150 while the minimum threshold voltage V.sub.th and the maximum working voltage V.sub.max are related to individual light emitting diode. For each light emitting diode of the light emitting unit 150, regardless the light-source load being configured with an AC LED module or a DC LED module, the working voltage of each light emitting diode is confined to operate in a domain established by the minimum threshold V.sub.th and the maximum working voltage V.sub.max. It is required that the configuration of the light emitting unit and the power source is designed with a configuration of in series and/or in parallel connections such that the electric current passing through each LED of the light emitting unit remains at an adequate level and thus a voltage V across each LED of the LED lamp complies with an operating constraint of V.sub.th<V<V.sub.max featuring electrical characteristics of the LED, wherein V.sub.th is a minimum threshold voltage required to trigger each LED to start emitting light and V.sub.max is a maximum operating voltage across each LED to avoid a thermal damage or burning out a semiconductor structure of the LED construction. The voltage operating domain characterized by V.sub.th<V<V.sub.max is in practice restricted in a range between 2.5 volts and 20 volts. Such narrow operating range therefore posts an engineering challenge for a circuit designer to successfully design a reliable circuitry configured with an adequate combination of in series connection and in parallel connection for operating a higher power LED security light.

[0053] A lighting apparatus may be implemented by integrating a plurality of LEDs with a microcontroller and various types of sensor components in the controlling circuit in accordance to the above described five exemplary embodiments. This lighting apparatus may automatically generate high level illumination when the ambient light detected is insufficient and time-switch to the low level illumination. In addition, when a person is entering the predetermined detection zone, the lighting apparatus may switch from the low level illumination to the high level illumination, to provide the person with sufficient illumination or to generate strong illumination and hue contrast for monitoring the intruder.

[0054] The above-mentioned descriptions represent merely the exemplary embodiment of the present disclosure, without any intention to limit the scope of the present disclosure thereto. Various equivalent changes, alternations or modifications based on the claims of present disclosure are all consequently viewed as being embraced by the scope of the present disclosure.