Light emitting diode driving circuit

Abstract

An LED driving circuit includes a power source, a first voltage stepping-down module, a constant current driving module, a second voltage stepping-down module, a DIP switch module, a control module and a loading module. The power source provides a source voltage. The first voltage stepping-down module reduces the source voltage's voltage level and correspondingly generates a first buck voltage. The second voltage stepping-down module reduces the first buck voltage's voltage level to generate a second buck voltage. The DIP switch module generates a maximal current indicating signal according to the second bulk voltage. The control module generates a PWM signal based on the second buck voltage and the maximal current indicating signal. The constant current driving module generates a drive current according to the first buck voltage and the PWM signal, and drives the loading module using the drive current.

Claims

1. A light emitting diode (LED) driving circuit, comprising: a power source, configured to provide a source voltage; a first voltage stepping-down module, electrically coupled to the power source, and configured to reduce the source voltage and correspondingly generate a first buck voltage; a constant current driving module, electrically coupled to the first voltage stepping-down module; a second voltage stepping-down module, electrically coupled to the first voltage stepping-down module, and configured to reduce the first buck voltage to generate a second buck voltage; a dual-in-line package (DIP) switch module, electrically coupled to the second voltage stepping-down module, and configured to generate a maximal current indicating signal according to the second bulk voltage; a control module, electrically coupled to the second voltage stepping-down module, the DIP switch module and the constant current driving module, and configured to generate a pulse-width modulation (PWM) signal based on the second buck voltage and the maximal current indicating signal; and a loading module, electrically coupled to the control module and the constant current driving module; wherein the constant current driving module is configured to generate a drive current according to the first buck voltage and the PWM signal, and configured to drive the loading module using the drive current.

2. The LED driving circuit of claim 1, wherein the first voltage stepping-down module comprises: a voltage stepping-down chip, having an input terminal electrically coupled to the power source, having an output terminal electrically coupled to the constant current driving module, and having a ground terminal coupled to ground.

3. The LED driving circuit of claim 1, wherein the constant current driving module comprises: a driving chip, having an input terminal electrically coupled to the first voltage stepping-down module for receiving the first buck voltage, and having a control terminal electrically coupled to the control module for receiving the PWM signal; and a switch, having a control terminal electrically coupled to a drive terminal of the driving chip, having an input terminal electrically coupled to ground and an output terminal of the driving chip, electrically coupled to the loading module.

4. The LED driving circuit of claim 3, wherein the constant current driving module further comprising: a resistor, having a first terminal electrically coupled to the input terminal of the switch and the output terminal of the driving chip, and having a second terminal electrically coupled to ground.

5. The LED driving circuit of claim 3, wherein the switch comprises a metal-oxide semiconductor field effect transistor (MOSFET), the control terminal of the switch comprises a gate of the MOSFET, the input terminal of the switch comprises a drain of the MOSFET, and the output terminal of the switch comprises a source of the MOSFET.

6. The LED driving circuit of claim 3, wherein the switch comprises a bipolar junction transistor (BJT), the control terminal of the switch comprises a base of the BJT, the input terminal of the switch comprises a collector of the BJT, and the output terminal of the switch comprises an emitter of the BJT.

7. The LED driving circuit of claim 1, wherein the second voltage stepping-down module comprises: a voltage stepping-down chip, having an input terminal electrically coupled to the first voltage stepping-down module for receiving the first buck voltage, having an output terminal electrically coupled to the DIP switch module for relaying the second buck voltage, and having a ground terminal electrically coupled to ground.

8. The LED driving circuit of claim 1, wherein the DIP switch module comprises: a first resistor, having a first terminal electrically coupled to the second voltage stepping-down module for receiving the second buck voltage; at least one DIP switch, each of which having an input terminal electrically coupled to a second terminal of the first resistor and the control module; and at least one second resistor having a one-by-one correspondence with the at least one DIP switch; wherein each of the at least one second resistor has a first terminal electrically coupled to an output terminal of a corresponding DIP switch, and has a second terminal electrically coupled to ground.

9. The LED driving circuit of claim 8, wherein resistances of the at least one second resistor are entirely different.

10. The LED driving circuit of claim 8, wherein resistances of the at least one second resistor are partially different.

11. The LED driving circuit of claim 8, wherein the at least one second resistor shares a same resistance.

12. The LED driving circuit of claim 1, wherein the control module comprises: a master control chip, having an input terminal electrically coupled to the second voltage stepping-down module for receiving the second buck voltage, having a receiving terminal for receiving the maximal current indicating signal, having a control terminal electrically coupled to the constant current driving module for relaying the PWM signal, and having a ground terminal electrically coupled to ground.

13. The LED driving circuit of claim 1, further comprising: a voltage transformer, electrically coupled to the first voltage stepping-down module, the constant current driving module, and the loading module.

14. The LED driving circuit of claim 13, wherein the voltage transformer comprises: a primary winding, having a first terminal electrically coupled to the first voltage stepping-down module, and having a second terminal electrically coupled to the constant current driving module; and a secondary winding, electrically coupled to the loading module.

15. The LED driving circuit of claim 1, wherein the source voltage is a direct-current (DC) voltage.

16. The LED driving circuit of claim 15, wherein the DC voltage is generated by rectifying an alternative-current (AC) voltage.

17. The LED driving circuit of claim 1, wherein the source voltage is an alternative-current (AC) voltage.

18. The LED driving circuit of claim 1, wherein the loading module comprises: a LED unit.

19. The LED driving circuit of claim 18, wherein the loading module further comprises: a diode, having a positive terminal electrically coupled to the constant current driving module; and a common mode inductor, having a first input terminal electrically coupled to a negative terminal of the diode, having a second input terminal electrically coupled to ground, and having a first output terminal and second output terminal both electrically coupled to the LED unit.

20. The LED driving circuit of claim 19, wherein the loading module further comprises: a capacitor, having a first terminal electrically coupled to the first input terminal of the common mode inductor, and having a second terminal electrically coupled to ground.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a schematic diagram of a LED driving circuit according to one embodiment of the present invention.

(2) FIG. 2 illustrates a detailed circuit diagram of part of the LED driving circuit shown in FIG. 1.

(3) FIG. 3 illustrates an exemplary detailed diagram of the second voltage stepping-down module shown in FIG. 1.

(4) FIG. 4 illustrates an exemplary detailed diagram of the DIP switch module shown in FIG. 1.

(5) FIG. 5 illustrates an exemplary detailed diagram of the control module shown in FIG. 1.

DETAILED DESCRIPTION

(6) As mentioned above, the present disclosure discloses a LED driving circuit capable of adjusting its output current. Such that the disclosed LED driving circuit can be used for driving various types of LED units of different current amplitudes.

(7) FIG. 1 illustrates a schematic diagram of a LED driving circuit 100 according to one embodiment of the present invention. The LED driving circuit 100 includes a power source 101, a first voltage stepping-down module 102, a constant current driving module 103, a second voltage stepping-down module 105, a dual-in-line package (DIP) switch module 106, a control module 107, and a loading module 104.

(8) The power source 101 provides a source voltage VBUS.

(9) The first voltage stepping-down module 102 is electrically coupled to the power source 101. And the first voltage stepping-down module 102 reduces the source voltage VBUS's voltage level, so as to generate a first buck voltage V1.

(10) The constant current driving module 103 is electrically coupled to the first voltage stepping-down module 102.

(11) The second voltage stepping-down module 105 is electrically coupled to the first voltage stepping-down module 102. In addition, the second voltage stepping-down module 105 reduces the first buck voltage V1's voltage level, so as to generate a second buck voltage V2.

(12) The DIP switch module 106 is electrically coupled to the second voltage stepping-down module 105. Moreover, the DIP switch module 106 generates a maximal current indicating signal Imax according to the second bulk voltage V2.

(13) The control module 107 is electrically coupled to the second voltage stepping-down module 105, the DIP switch module 106 and the constant current driving module 103. Additionally, the control module 107 generates a pulse-width modulation (PWM) signal PWMC based on the second buck voltage V2 and the maximal current indicating signal Imax.

(14) The loading module 104 is electrically coupled to the control module 107 and the constant current driving module 103. Last, the constant current driving module 103 generates a drive current Idrive according to the first buck voltage V1 and the PWM signal PWMC. Also, the constant current driving module 103 drives the loading module 104 using the drive current Idrive.

(15) Specifically, in some examples, the DIP module 106 determines the maximal current indicating signal Imax for determining an upper-bound drive current of the LED driving circuit 100. Then, the control module 107 may determine an intermediate current amplitude that is smaller than the upper-bound drive current. In turn, the control module 107 generates the PWM signal for prompting the constant current driving module 103 to apply the intermediate current amplitude in the drive current Idrive. Therefore, the LED driving circuit 100 is capable of driving the loading module 104 via various amplitudes of drive currents. Such that the loading module 104 may also include various types of LED units. Furthermore, in some examples, the control module 107 determines the intermediate current amplitude by receiving a remote command, under the condition that the control module 107 has an additional RF module for receiving said remote command.

(16) In some examples, the source voltage VBUS may be a direct-current (DC) voltage or an alternative-current (AC) voltage. The DC voltage can even be generated by rectifying an AC voltage.

(17) FIG. 2 illustrates a detailed circuit diagram of part of the LED driving circuit 100 shown in FIG. 1.

(18) In one example, the LED driving circuit 100 further includes a voltage transformer T1. And the voltage transformer T1 is electrically coupled to the first voltage stepping-down module 102, the constant current driving module 103, and the loading module 104.

(19) In one example, the voltage transformer T1 includes a primary winding and a secondary winding. The primary winding's first terminal is electrically coupled to the first voltage stepping-down module 102. Also, the primary winding's second terminal is electrically coupled to the constant current driving module 103. The secondary winding is electrically coupled to the loading module 104.

(20) In one example, the first voltage stepping-down module 102 includes a voltage stepping-down chip U2. The voltage stepping-down chip 102's input terminal Vin is electrically coupled to the power source 101. Also, the voltage stepping-down chip 102's output terminal Vout is electrically coupled to the constant current driving module 103. Last, the voltage stepping-down chip 103's ground terminal GND is coupled to ground.

(21) In one example, the constant current driving module 103 includes a driving chip U1 and a switch Q1. The driving chip U1's input terminal Vin is electrically coupled to the first voltage stepping-down module 102 for receiving the first buck voltage V1. In addition, the driving chip U1's control terminal PWM is electrically coupled to the control module 107 for receiving the PWM signal PWMC.

(22) The switch Q1's control terminal is electrically coupled to a drive terminal Drive of the driving chip U1. Second, the switch Q1's input terminal is electrically coupled to ground and an output terminal Isense of the driving chip U1. Third, the switch Q1's output terminal is electrically coupled to the loading module 104.

(23) In one example, the constant current driving module 103 further includes a resistor R1. The resistor R1's first terminal is electrically coupled to the input terminal of the switch Q1 and the output terminal Isense of the driving chip U1. Also, the resistor R1's second terminal is electrically coupled to ground.

(24) In one example, the switch Q1 is implemented using a metal-oxide semiconductor field effect transistor (MOSFET). Therefore, first, the switch Q1's control terminal is the gate of the MOSFET. Second, the switch Q1's input terminal is the drain of the MOSFET. Third, the switch Q1's output terminal is the source of the MOSFET.

(25) In another example, the switch Q1 is implemented using a bipolar junction transistor (BJT). Therefore, first, the switch Q1's control terminal is the base of the BJT. Second, the switch Q1's input terminal is the collector of the BJT. Third, the switch Q1's output terminal is the emitter of the BJT.

(26) FIG. 3 illustrates an exemplary detailed diagram of the second voltage stepping-down module 105 shown in FIG. 1. In one example, the second voltage stepping-down module 105 includes a voltage stepping-down chip U3. The voltage stepping-down chip U3's input terminal Vin is electrically coupled to the first voltage stepping-down module 102 for receiving the first buck voltage V1. Also, the voltage stepping-down chip U3's output terminal Vout is electrically coupled to the DIP switch module 106 for relaying the second buck voltage V2. Moreover, the voltage stepping-down chip U3's ground terminal is electrically coupled to ground.

(27) FIG. 4 illustrates an exemplary detailed diagram of the DIP switch module 106 shown in FIG. 1. In one example, the DIP switch module 106 includes a first resistor R2, at least one DIP switch and at least one second resistor. For example, there are three DIP switches WJ1, WJ2 and WJ3 and three corresponding resistors R3, R4 and R5.

(28) The first resistor R2's first terminal is electrically coupled to the second voltage stepping-down module 105 for receiving the second buck voltage V2. Each of the at least one DIP switch WJ1, WJ2 and WJ3's input terminal is electrically coupled to a second terminal of the first resistor R2 and the control module 107. The at least one second resistor R3, R4 and R5 has a one-by-one correspondence with the at least one DIP switch WJ1, WJ2 and WJ3. Each of the at least one second resistor R3, R4 and R5's first terminal is electrically coupled to an output terminal of a corresponding DIP switch WJ1, WJ2 and WJ3. And each of the at least one second resistor R3, R4 and R5's second terminal is electrically coupled to ground.

(29) In some examples, resistances of the at least one second resistor R3, R4 and R5 are entirely different, partially different, or all the same. Such that the DIP switch module 106 is capable of controlling the upper-bound current indicating signal Imax's corresponding upper-bound current amplitude by switching on appropriate DIP switch(es) and correspondingly retrieve a desired total resistance and in turn a desired upper-bound current amplitude.

(30) FIG. 5 illustrates an exemplary detailed diagram of the control module 107 shown in FIG. 1. In one example, the control module 107 includes a master control chip U4. The master chip U4's input terminal Vin is electrically coupled to the second voltage stepping-down module 105 for receiving the second buck voltage V2. In addition, the master chip U4's receiving terminal ADC is used for receiving the maximal current indicating signal Imax. And the master chip U4's control terminal PWM is electrically coupled to the constant current driving module 103 for relaying the PWM signal PWMC. Last, the master chip U4's ground terminal GND is electrically coupled to ground.

(31) As shown in FIG. 2, and in some examples, the loading module 104 may include a LED unit that has a positive terminal LED+ and a negative terminal LED−.

(32) Also, in one example, the loading module 104 includes a diode D1 and a common mode inductor LF1. The diode D1's positive terminal is electrically coupled to the constant current driving module 103 for receiving the driving current Idrive.

(33) The common mode inductor LF1's first input terminal is electrically coupled to a negative terminal of the diode D1. Second, the common mode inductor LF1's second input terminal is electrically coupled to ground. Third, the common mode inductor LF1's first output terminal and second output terminal both electrically coupled to the LED unit via the positive terminal LED+ and the negative terminal LED− respectively.

(34) In one example, the loading module 104 additionally includes a capacitor C1. The capacitor C1's first terminal is electrically coupled to the first input terminal of the common mode inductor LF1. And the capacitor C1's second terminal is electrically coupled to ground.

(35) How the LED driving unit 100 works is summarized in the following paragraphs by referencing FIGS. 1-5. First, the first voltage-stepping down module 102 bucks the source voltage VBUS to generate the first buck voltage V1. Then the constant current driving module 103 initially uses the first buck voltage V1 to drive the loading module 104. Simultaneously, the second voltage stepping-down module 105 bucks the first buck voltage V1 to generate the second buck voltage V2. And both the control module 107 and the DIP switch module 106 are stably powered via the second buck voltage V2.

(36) The DIP switch module 106 determines an upper-bound output current amplitude for the drive current Idrive, with the aid of different configurations of the DIP switch module 106, e.g., different number of activated DIP switches and/or different resistances of applied resistors.

(37) The control module 107 receives the maximal current indicating signal Imax. Also, with the aid of the control module 107's microprocessor, the control module 107 performs a modulus transformation on the maximal current indicating signal Imax. Such that the control module 107 perceives the upper-bound of the LED driving circuit 100's drive current. In some examples, the control module 107 also receives an external RF signal for calculating a desired output current amplitude based on the perceived upper-bound drive current via its microprocessor. In addition, the control module 107's microprocessor calculates the PWM signal PWMC for prompting the constant current driving module 103 to output the desired output current amplitude, i.e., the drive current Idrive.

(38) In this fashion, the LED driving circuit 100 is capable of adapting to different types of LED units using drive currents of different corresponding amplitudes.

(39) Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.