Two-level LED security light with motion sensor

Abstract

An LED security light includes a light emitting unit, at least one sensing unit, a loading and power control unit and a power supply unit configured with a first power source and a second power source, wherein a power level detector and a power switching circuitry are installed to select and connect at least one of the first power source and the second power source to the light emitting unit. The light emitting unit is activated at dusk and is deactivated at dawn. When the first power source is used, the LED security light generates a first level illumination. When the second power source is used, the LED security light generates a second level illumination. The first power source is a solar power while the second power source is a backup battery.

Claims

1. A two-level LED security light, comprising: a light emitting unit configured with an LED load; a photo sensor unit; a motion sensor unit; a loading and power control unit configured with at least a controller and an unidirectional semiconductor switching device, for managing an electrical power transmission to the light emitting unit; a power supply unit configured with a first power source and a second power source, for supplying an electrical power to the light emitting unit; and at least one external control unit; wherein the controller is electrically coupled with the unidirectional semiconductor switching device, the photo sensor unit, the motion sensor unit and the at least one external control unit; wherein the controller operates in conjunction with a power switching circuitry to select and connect at least one of the first power source and the second power source to the light emitting unit; wherein when the first power source is connected to the light emitting unit, the controller operates to output a first pulse width modulation signal to control a conduction state or a cutoff state of the unidirectional semiconductor switching device to deliver a first average electric current to the LED load to perform a first illumination mode according to signals received from the photo sensor unit and the motion sensor unit; wherein when an ambient light detected by the photo sensor unit is lower than a first predetermined value, the LED load is switched on; wherein when the ambient light detected by the photo sensor unit is higher than a second predetermined value, the LED load is switched off; wherein when a motion intrusion is detected by the motion sensor unit, the loading and power control unit manages to conduct the unidirectional semiconductor switching device to deliver a first average electric current to the LED load for generating a first level illumination for a first predetermined time duration before resuming to a turned off state; wherein when the second power source is connected to the light emitting unit, the controller operates to output a second pulse width modulation signal to control the conduction state or the cutoff state of the unidirectional semiconductor switching device to deliver a second average electric current to the LED load for generating a second illumination mode according to signals received from the photo sensor unit and the motion sensor unit; wherein when the ambient light detected by photo sensor unit is lower than the first predetermined value, the LED load is switched on; wherein when the ambient light detected by the photo sensor unit is higher than the second predetermined value, the LED load is switched off; wherein when the motion intrusion is detected by the motion sensor unit, the loading and power control unit manage to conduct the unidirectional semiconductor switching device to deliver a second average electric current to the LED load for generating a second level illumination for a second predetermined time duration before resuming back to the turned off state; wherein the at least one external control unit is usable for adjusting and setting at least one operating parameter including at least a time length of the first predetermined time duration, the time length of the second predetermined time duration, a light intensity of the first level illumination and a light intensity of the second level illumination.

2. The two-level LED security light according to claim 1, wherein the light intensity of the first level illumination is higher than the light intensity of the second level illumination.

3. The two-level LED security light according to claim 1, wherein the first power source is a solar power module configured with a solar panel for converting solar light into electrical energy, a charging circuit and a power storage unit for storing the electrical energy.

4. The two-level LED security light according to claim 3, wherein the power switching circuitry comprises a power detector for detecting a power level remaining in the power storage unit of the first power source during an operating period of the LED security light; wherein when the power level of the first power source detected by the power detector is equal to or greater than a predetermined threshold level, the controller manages to operate the power switching circuitry for outputting an electric power from the first power source to the light emitting unit.

5. The two-level LED security light according to claim 4, wherein when the power level of the first power source detected by the power detector of the power switching circuitry is lower than the predetermined threshold level, the controller manages to operate the power switching circuitry to connect the second power source to the light emitting unit.

6. The two-level LED security light according to claim 5, wherein the power switching circuitry includes a first power switching element installed between the second power source and the light emitting unit, wherein when the power switching circuitry is operated to connect the second power source to the light emitting unit, the controller manages to conduct the first power switching element.

7. The two-level LED security light according to claim 6, wherein the first power switching element is a transistor.

8. The two-level LED security light according to claim 6, wherein the first power switching element is a relay.

9. The two-level LED security light according to claim 4, wherein when the power switching circuitry operates to connect the second power source to the light emitting unit, the controller manages to continuously connect the first power source to the light emitting unit.

10. The two-level LED security light according to claim 3, wherein the second power source is a rechargeable battery unit.

11. The two-level LED security light according to claim 10, wherein when the solar power module is in a charging state operated by the charging circuit, the power switching circuitry utilizes a power level detector to detect the power level remaining in the power storage unit of the first power source being equal to a maximum power level designed for the first power source indicating the first power source is fully charged, the controller manages the charging circuit to connect to the second power source, wherein when the power level of the second power source becomes equal to a second maximum voltage level designed for the second power source indicating the second power source is fully charged, the controller further manages the charging circuit to reconnect with the first power source.

12. The two-level LED security light according to claim 1, the second power source is a non-rechargeable battery unit.

13. The two-level LED security light according to claim 1, wherein a first external control unit is installed to be electrically coupled with the controller for adjusting and setting the light intensity of the first level illumination.

14. The two-level LED security light according to claim 1, wherein a second external control unit is installed to be electrically coupled with the controller for adjusting and setting the light intensity of the second level illumination.

15. The two-level LED security light according to claim 1, wherein the controller is a microcontroller programmable for outputting a control signal to control a conduction period and a cutoff period of the unidirectional semiconductor switching device during each power operating cycle.

16. The two-level LED security light according to claim 1, wherein the controller is an application specific integrated circuit (ASIC) customized for outputting a control signal to control a conduction period and a cutoff period in each power operating cycle.

17. A two-level LED security light, comprising: a light emitting unit configured with an LED load; a photo sensor unit; a loading and power control unit configured with at least a controller and an unidirectional semiconductor switching device, for managing an electrical power transmission to the light emitting unit; a power supply unit configured with a first power source and a second power source, for supplying an electrical power to the light emitting unit; and at least one external control unit; wherein the controller is electrically coupled with at least the unidirectional semiconductor switching device, the photo sensor unit and the time setting unit; wherein the controller operates in conjunction with a power switching circuitry to select and connect at least one of the first power source and the second power source to the light emitting unit; wherein when the first power source is connected to the light emitting unit, the controller operates to output a first pulse width modulation signal to control a conduction state or a cutoff state of the unidirectional semiconductor switching device to deliver a first average electric current to the LED load to perform a first illumination mode according to a signal received from the photo sensor unit; wherein when an ambient light detected by the photo sensor unit is lower than a first predetermined value, the LED load is switched on and the loading and power control unit manages to turn on the light emitting unit to perform the first illumination mode generating a first level illumination; wherein when the ambient light detected by the photo sensor unit is higher than a second predetermined value, the LED load is switched off and the loading and power control unit manages to turn off the light emitting unit; wherein when the second power source is connected to the light emitting unit, the controller operates to output a second pulse width modulation signal to control the conduction state or the cutoff state of the unidirectional semiconductor switching device to deliver a second average electric current to the LED load for generating a second illumination mode according to the signal received from the photo sensor unit; wherein when the ambient light detected by photo sensor unit is lower than the first predetermined value, the LED load is switched on and the loading and power control unit manages to turn on the light emitting unit to perform the second illumination mode generating a second level illumination; wherein when the ambient light detected by the photo sensor unit is higher than the second predetermined value, the LED load is switched off and the loading and power control unit manages to turn off the light emitting unit; wherein the at least one external control unit is usable for adjusting and setting at least one operating parameter including a light intensity of the first level illumination and a light intensity of the second level illumination.

18. The two-level LED security light according to claim 17, wherein the light intensity of the first level illumination is higher than the light intensity of the second level illumination.

19. The two-level LED security light according to claim 17, wherein the first power source is a solar power module configured with a solar panel for converting solar light into electrical energy, a charging circuit and a power storage unit for storing the electrical energy.

20. The two-level LED security light according to claim 19, wherein the power switching circuitry comprises a power detector for detecting a power level remaining in the power storage unit of the first power source during an operating period of the LED security light; wherein when the power level of the first power source detected by the power detector is equal to or greater than a predetermined threshold level, the controller manages to operate the power switching circuitry for outputting an electric power from the first power source to the light emitting unit.

21. The two-level LED security light according to claim 20, wherein when the power level of the first power source detected by the power detector of the power switching circuitry is lower than the predetermined threshold level, the controller manages to operate the power switching circuitry to connect the second power source to the light emitting unit.

22. The two-level LED security light according to claim 21, wherein the power switching circuitry includes a first power switching element installed between the second power source and the light emitting unit, wherein when the power switching circuitry is operated to connect the second power source to the light emitting unit, the controller manages to conduct the first power switching element.

23. The two-level LED security light according to claim 22, wherein the first power switching element is a transistor.

24. The two-level LED security light according to claim 22, wherein the first power switching element is a relay.

25. The two-level LED security light according to claim 20, wherein when the power switching circuitry operates to connect the second power source to the light emitting unit, the controller manages to continuously connect the first power source to the light emitting unit.

26. The two-level LED security light according to claim 19, wherein the second power source is a rechargeable battery unit.

27. The two-level LED security light according to claim 26, wherein when the solar power module is in a charging state operated by the charging circuit, the power switching circuitry utilizes a power level detector to detect the power level remaining in the power storage unit of the first power source being equal to a maximum power level designed for the first power source indicating the first power source is fully charged, the controller manages the charging circuit to connect to the second power source, wherein when the power level of the second power source becomes equal to a second maximum voltage level designed for the second power source indicating the second power source is fully charged, the controller further manages the charging circuit to reconnect with the first power source.

28. The two-level LED security light according to claim 17, the second power source is a non-rechargeable battery unit.

29. The two-level LED security light according to claim 17, wherein a first external control unit is installed to be electrically coupled with the controller for adjusting and setting the light intensity of the first level illumination.

30. The two-level LED security light according to claim 17, wherein a second external control unit is installed to be electrically coupled with the controller for adjusting and setting the light intensity of the second level illumination.

31. The two-level LED security light according to claim 17, wherein the controller is a microcontroller programmable for outputting a control signal to control a conduction period and a cutoff period of the unidirectional semiconductor switching device during each power operating cycle.

32. The two-level LED security light according to claim 17, wherein the controller is an application specific integrated circuit (ASIC) customized for outputting a control signal to control a conduction period and a cutoff period in each power operating cycle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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.

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

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

(4) 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.

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

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

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

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

(9) FIG. 5 illustrates a schematic diagram of a two-level LED security light in accordance to the third exemplary embodiment of the present disclosure.

(10) FIG. 6 illustrates a schematic diagram of a two-level LED security light in accordance to the fourth exemplary embodiment of the present disclosure.

(11) 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

(12) 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

(13) 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.

(14) The loading and power control unit 140 which is coupled to the light-emitting unit 150 may be implemented by a microcontroller. 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 and switching components. The loading and power control unit 140 may control the light-emitting unit 150 to generate at least two levels of illumination variations.

(15) When the light sensing control unit 120 detects that the 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. 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 flow through the light-emitting unit 150, to generate the 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.

(16) 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. The light-emitting unit 250 includes three series-connected LEDs L1˜L3. The LEDs L1˜L3 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 L1˜L3 and a ground GND. The loading and power control unit 140 implemented by the microcontroller 240 may output a pulse width modulation (PWM) signal to the gate of transistor Q1 to control the average electric current. 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.

(17) 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.

(18) 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.

(19) In addition, the microcontroller 240 is coupled to a time setting unit 260, wherein the time setting unit 260 may allow the user to configure the predetermined duration associated with the high level illumination in the PC mode, however the present disclosure is not limited thereto.

Second Exemplary Embodiment

(20) 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.

(21) 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 L1˜L3 and NMOS transistors Q1 and Q2. The LEDs L1˜L3 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 L1˜L3 are operated in constant-current mode.

(22) 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 L1˜L3 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 L1˜L3. 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.

(23) When light sensor 220 detects that the 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 L1˜L3 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 L1˜L3 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.

(24) 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.

(25) 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 L1˜L3 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.

(26) 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 include 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

(27) Refer back to FIG. 1, wherein the light-emitting unit 150 may include a phase controller and one or more parallel-connected alternating current (AC) LEDs. The 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.

(28) 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 includes 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.

(29) 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.

(30) 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<½f−t.sub.o for a light-source load with a cut-in voltage V.sub.t, wherein t.sub.o=(½πf)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 (½f)=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.

(31) 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.

(32) 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, and a phase controller 551. 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 ACLEDs and more than one bi-directional switching devices. Furthermore, the color temperatures of the ACLED1 and the ACLED2 may be selected to be different.

(33) 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

(34) 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 ACLED1˜3 having identical luminous power as well as 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).

(35) 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 ACLED1˜3 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.

(36) 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

(37) 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.

(38) The pin PS of the microcontroller 240 synchronously controls the operations of switches 752 and 753. If the three ACLED1˜3 have identical luminous power, then in the PC mode, the pin PC and pin PS of the microcontroller 240 synchronously close the switches 751˜753 to render ACLED1˜3 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.

(39) 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.

(40) 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.

(41) 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.