TWI540933B - Light emitting diode drive circuit - Google Patents

Description

Light-emitting diode driving circuit

The invention relates to a driving circuit, in particular to a light emitting diode driving circuit with valley switching effect.

A light-emitting diode is a component that uses a low-voltage DC drive. Generally, in general lighting applications, a switching converter (Switching Converter) is often used as its driving circuit.

Referring to FIG. 1, FIG. 2 and FIG. 3, a general switching converter is shown in FIG. 1 as a buck converter (Buck Converter), and as shown in FIG. 2, a Buck-Boost Converter. And in the flyback converter shown in FIG. 3, the switching element 11 is switched to achieve the effect of adjusting the output voltage/current. However, at the moment when the switching element 11 is switched, switching loss occurs ( Switching Loss) and Electromagnetic Interference (EMI).

In recent years, in the study of reducing switching loss and electromagnetic interference, Quasi-Resonant and Valley Switching technologies have been widely studied and used. This technique uses the voltage across the switching element 11 to resonate due to parasitic elements. The characteristic is obtained by observing the voltage across the switching element 11 and switching when the voltage across the switching element 11 is at the valley of the resonance, Since the voltage across the switching element 11 is in the valley, it means that the voltage difference across the switching element 11 is a low voltage or even a zero voltage, so that the loss generated during switching can be reduced, and the voltage change rate (dv/dt) at the switching instant is also Smaller, so the signal strength of electromagnetic interference is also reduced.

In most of the quasi-resonant and valley switching techniques, in order to detect the voltage across the switching element 11, an auxiliary winding 12 and two voltage dividing resistors 13 must be added, and the voltage dividing resistors are measured by a control circuit 14. The observed voltage V _{AUX of the} 13 connection point is then compared with a predetermined voltage to know whether the voltage across the switching element 11 is in the valley.

Referring to FIG. 3 and FIG. 4, FIG. 4 is a schematic diagram showing switching waveforms of a positive voltage comparison method corresponding to the flyback converter circuit of FIG. 3, wherein V _{gs is} the gate-source voltage of the switching element 11, V. _{Ds is} the drain-source voltage of the switching element 11, V _ref is a predetermined voltage, Valley is the comparison output of the observed voltage V _AUX and the predetermined voltage V _ref , and Set is the positive edge trigger signal of the signal Valley for providing As a time for controlling the switching element 11 to be used, t _dis is the current of the inductance L connected in series with the switching element 11 from the peak discharge to zero, t _{on is the on-} time of the switching element 11, and t _{off is} the switching element 11 On time.

As can be seen from FIG. 4, since the position of the valley point of the observed voltage V _AUX is a variable, the predetermined predetermined voltage V _ref cannot follow the valley point of the observed voltage V _{AUX well} , but only in the second half of the resonance. Switching, you cannot achieve absolute valley switching.

Referring to FIG. 3 and FIG. 5, FIG. 5 is a schematic diagram showing switching waveforms of the negative voltage comparison method corresponding to the flyback converter circuit of FIG. 3. As can be seen from FIG. 5, the predetermined voltage V _ref still cannot follow the observation well. The valley point of the voltage V _AUX cannot achieve absolute valley switching.

Furthermore, as can be seen from FIG. 1 , FIG. 2 and FIG. 3 , in the prior art, the auxiliary winding 12 and the voltage dividing resistor 13 have to be added to detect the observed voltage V _AUX and are on the control circuit 14 . A corresponding pin is also added to receive the observed voltage V _AUX for subsequent comparisons, which increases the number of system circuit components and results in higher costs.

Accordingly, it is an object of the present invention to provide a light emitting diode driving circuit having a valley switching effect.

Therefore, the LED driving circuit of the present invention is suitable for driving a plurality of LEDs, and the LED driving circuit comprises a conversion circuit and a control circuit.

The conversion circuit receives a power signal to provide an output current to drive the light emitting diodes, and includes a switching element, a current detecting element, and an inductor.

The switching element has a first end, a second end, and a control end receiving a control signal, controlled by the control signal to switch between on and off.

The current detecting component is electrically connected to the switching component and outputs a resonant signal by detecting a resonant current related to a voltage across the switching component.

The inductor is electrically connected to the switching element.

The control circuit is electrically connected to the current detecting component and the control end of the switching component, and receives the resonant signal and determines according to the resonant signal The valley point of the voltage across the switching element, and the control signal is output according to the valley point of the voltage across the switching element to control the switching of the switching element.

The effect of the invention is: applying the principle that the phase difference between the resonant current and the voltage in the resonant circuit theory is 90 degrees, detecting the resonant current by setting the current detecting component and outputting the resonant signal for the control circuit to judge the switching component The valley point of the voltage at both ends controls the switching of the switching elements, and can achieve absolute valley switching and reduce the signal intensity of the loss and electromagnetic interference generated during switching.

2‧‧‧Power circuit

Vac‧‧‧AC power supply

201‧‧‧The first end of the AC power supply

202‧‧‧The second end of the AC power supply

21‧‧‧Electromagnetic interference filter module

Cf‧‧‧Electromagnetic interference filter capacitor

Lf‧‧‧electromagnetic interference filter inductor

22‧‧‧Bridge rectifier module

D1‧‧‧First Diode

D2‧‧‧ second diode

D3‧‧‧ third diode

D4‧‧‧ fourth diode

C1‧‧‧Filter Capacitor

3‧‧‧Transition circuit

Q1‧‧‧Switching elements

L‧‧‧Inductance

Do‧‧‧Flywheel diode

Co‧‧‧ output capacitor

Rcs‧‧‧ current detecting component

4‧‧‧Control circuit

CS‧‧‧Responding to the detection side

VSS‧‧‧Control circuit ground

VDD‧‧‧ power supply terminal

GATE‧‧ switch control terminal

COMP‧‧‧ phase compensation end

41‧‧‧ Valley Detection Module

411‧‧‧Amplifier

412‧‧‧ Comparator

413‧‧‧monostable flip-flop

42‧‧‧Switching control module

V _ref ‧‧‧predetermined voltage

Set‧‧‧ trigger signal

Valley‧‧‧Valley Signal

Vss‧‧‧Control circuit ground voltage

i _L ‧‧‧Inductor current

9‧‧‧Lighting diode

Other features and effects of the present invention will be apparent from the following description of the drawings. FIG. 1 is a circuit diagram illustrating a conventional LED driving circuit using a buck converter; 2 is a circuit diagram illustrating a conventional LED driving circuit using a step-down converter; FIG. 3 is a circuit diagram illustrating a conventional LED driving circuit using a flyback converter; 4 is a schematic diagram of a switching waveform of a conventional LED driving circuit using a flyback converter; FIG. 5 is another switching waveform diagram of a conventional LED driving circuit using a flyback converter; 6 is a schematic circuit diagram of a first preferred embodiment of the LED driving circuit of the present invention; FIG. 7 is a circuit diagram of a trough detecting module of the first preferred embodiment. Figure 8 is a schematic diagram of a switching waveform of the first preferred embodiment; Figure 9 is a circuit diagram of a second preferred embodiment of the LED driving circuit of the present invention; and Figure 10 is the second preferred embodiment. A schematic diagram of a switching waveform of an embodiment.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to FIG. 6 and FIG. 7 , the first preferred embodiment of the LED driving circuit of the present invention is suitable for driving a plurality of LEDs 9 , wherein the LED driving circuit comprises a power circuit 2 and a conversion circuit 3 . And a control circuit 4.

The power circuit 2 receives an AC power supply Vac to output a power signal. The AC power supply Vac has a first end 201 and a second end 202. The power circuit 2 includes an electromagnetic interference filter module 21 and a bridge rectifier module. 22, and a filter capacitor C1.

The electromagnetic interference filter module 21 is electrically connected between the AC power supply Vac and the bridge rectifier module 22, and includes an electromagnetic interference filter inductor Lf and two electromagnetic interference filter capacitors Cf.

The electromagnetic interference filter inductor Lf has a first end electrically connected to the first end 201 of the AC power source Vac, and a second end.

The electromagnetic interference filter capacitors Cf are electrically connected between the first end and the second end of the electromagnetic interference filter inductor Lf and the second end 202 of the AC power source Vac.

It is to be noted that, as the EMI filter module 21 has various implementations, those skilled in the art may also change accordingly. The circuit in this embodiment is for illustrative purposes only and is not limited thereto. .

The bridge rectifier module 22 has a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4.

The first diode D1 has an anode end electrically connected to the second end of the electromagnetic interference filter inductor Lf, and a cathode end electrically connected to the conversion circuit 3 and outputting the power signal.

The second diode D2 has an anode end electrically connected to a ground end, and a cathode end electrically connected to the second end of the electromagnetic interference filter inductor Lf.

The third diode D3 has an anode end electrically connected to the second end 202 of the AC power source Vac, and a cathode end electrically connected to the conversion circuit 3 and outputting the power signal.

The fourth diode D4 has an anode end electrically connected to the ground end, and a cathode end electrically connected to the second end 202 of the alternating current power source Vac.

The filter capacitor C1 has a first end for outputting the power signal and a second end electrically connected to the ground.

The conversion circuit 3 receives the power signal to provide an output current to drive the light-emitting diodes 9, and includes a switching element Q1, a current detecting element Rcs, an inductor L, a flywheel diode Do, and an output. Capacitance Co.

In this embodiment, a buck converter circuit using a floating grounding technique is used as an explanation, but the switching mode is used. Switching Converter can be used, not limited to the application of floating grounding technology or buck conversion circuit.

The switching element Q1 has a first end, a second end, and a control end receiving a control signal, and is controlled by the control signal to switch between on and off.

The current detecting component Rcs is a resistive component electrically connected to the second end of the switching component Q1 to detect a resonant current related to the voltage across the switching component Q1 and converted into a resonant signal output that is a voltage.

The flywheel diode Do has a grounded anode end and a cathode end electrically connected to the second end of the switching element Q1.

The output capacitor Co has a first end that provides the output current to drive the light emitting diodes 9, and a grounded second end.

The inductor L and the current detecting component Rcs are connected in series between the first end of the output capacitor Co and the cathode end of the flywheel diode Do, and the connection point of the inductor L and the current detecting component Rcs provides a floating ground voltage. Vss.

The control circuit 4 is electrically connected to the connection point of the switching element Q1 and the current detecting element Rcs, the connection point of the inductor L and the current detecting element Rcs, and the control end of the switching element Q1, and receives the floating ground voltage. Vss and the resonant signal outputted by the current detecting component Rcs, and determining a valley point of the voltage across the switching element Q1 according to the resonant signal, and outputting the control signal according to a valley point of the voltage across the switching element Q1 to control the switch The component Q1 is switched, and the control circuit 4 includes a power terminal VDD, a switch control terminal GATE, a feedback detection terminal CS, and a phase compensation terminal COMP. A control circuit ground VSS, a valley detecting module 41, and a switching control module 42.

The power terminal VDD is used to receive the power required by the control circuit 4.

The switch control terminal GATE is electrically connected to the control terminal of the switching element Q1 and outputs the control signal.

The feedback detection terminal CS is electrically connected to the connection point between the switching element Q1 and the current detecting component Rcs to receive the resonant signal and receive a feedback signal corresponding to the inductor L current and the output current.

The phase compensation terminal COMP is used to compensate the phase of the feedback signal to stabilize the system.

The control circuit ground VSS is electrically connected to the connection point of the inductor L and the current detecting component Rcs and receives a control circuit ground voltage Vss. In this embodiment, the grounding voltage Vss of the control circuit is Is the floating ground voltage in the circuit.

The valley detection module 41 is electrically connected to the feedback detection terminal CS, receives the resonance signal to determine a valley point of the voltage across the switching element Q1, and outputs a judgment about a voltage valley point across the switching element Q1. The valley detecting module 41 has an amplifier 411, a comparator 412 and a monostable flip-flop 413.

The amplifier 411 is electrically connected to the feedback detection terminal CS, receives the resonance signal, and outputs after amplification.

The comparator 412 is electrically connected to the amplifier 411 and a predetermined voltage V _ref , receives the amplified resonant signal and compares it with the predetermined voltage V _ref to determine a negative half-edge interval of the resonant signal below zero, and outputs a correlation. In the comparison of the results of the valley signal Valley.

The one-shot flip-flop 413 is electrically connected to the comparator 412, receives the valley signal Valley, and triggers the valley signal Valley to determine the zero-crossing point of the resonant signal, and outputs the determination signal set.

The switching control module 42 is electrically connected to the valley detecting module 41 and the switch control terminal GATE, receives the determining signal set and outputs the control signal according to the determining signal set.

Referring to FIG. 6, FIG. 7, and FIG. 8, since the buck conversion of the conversion circuit 3 is well known in the art, it will not be described herein.

8 is a schematic diagram of switching waveforms corresponding to the buck converter circuit of FIG. 6, wherein V _{gs is} the gate-source voltage of the switching element Q1, and V _{ds is} the drain-source of the switching element Q1. The voltage, the predetermined voltage V _ref is designed to be zero level in the embodiment, v _{cs is} the voltage across the current detecting element Rcs (ie, the feedback signal and the resonant signal), i _{L is} the inductor L current, The valley signal Valley is a comparison output of the amplified current detecting component Rcs across the voltage v _cs and the predetermined voltage V _ref , and the determining signal set is a negative edge triggering signal of the valley signal Valley and is used as a control for the switch. The component Q1 uses, t _dis is the time when the inductor L current i _{L is} discharged from the peak to zero, t _{on is the on-} time of the switching element Q1, and t _{off is} the non-conduction time of the switching element Q1, wherein the current detecting component Rcs in series with the inductor L, according to Ohm's law, the waveform of the voltage across the current detecting v _cs Rcs element of the inductor current i _L L quite waveform, i.e., the same phase of the two waveforms, the size was often several times, so in FIG. 8 Use the same waveform representation.

The invention mainly utilizes the principle that the phase difference between the resonant current and the voltage is 90 degrees in the resonance circuit theory. As can be seen from FIG. 8, the inductor L current i _L and the cross-over voltage of the switching element Q1 (dip-source) The pole voltage V _ds ) has the same oscillation frequency and the phase difference is 90 degrees. Therefore, the present invention can detect the change of the inductor L current i _L and determine the zero-crossing point of the inductor L current i _L . The valley point of the voltage across the V _ds across the switching element Q1 is indirectly detected.

, When the gate of the switching element Q1 as shown in FIG. 8 - source voltage V _gs is switched to the low level (i.e., the switching element Q1 is turned off by the control), both ends of the voltage across the switching element Q1 V _ds Rising, and starting to oscillate after the inductor L current i _{L is} discharged from the peak to the zero, the valley detecting module 41 detects the cross-voltage v _{cs of the} current detecting component Rcs (ie, is equivalent to detecting the inductor L current i _L And changing, by the comparator 412, the predetermined voltage V _ref (zero level in this embodiment) to determine a zero crossing point, and then triggering via the monostable flip-flop 413 as a negative edge, ie A determination signal set corresponding to a valley point across the voltage V _ds across the switching element Q1 may be output for the switching control module 42 to adjust the output of the control signal.

In this embodiment, the gate-source voltage V _{gs of} the switching element Q1 is switched back to a high level when the switching element Q1 crosses the voltage V _ds across the third trough, for the purpose of illustrating the present invention. Detecting and switching to any trough can be designed to switch between the first trough, the second trough, ... or other troughs according to actual needs, and is not limited to this.

Through the above description, the advantages of this embodiment can be summarized as follows:

First, the present embodiment is applied resonant circuit theory, the phase difference between current and voltage resonance is a schematic of 90 degrees, by detecting the voltage across the current detecting element v _cs Rcs that the inductance L _L of the waveform of the current i, And by determining the zero crossing point of the inductor L current i _L waveform, the valley point of the cross-over voltage V _ds of the switching element Q1 is indirectly known, as can be seen from FIG. 8 , compared with the prior art, In this embodiment, the valley point of the voltage across the V _ds across the switching element Q1 can be accurately detected, so that the absolute valley (low voltage or even zero voltage) can be switched to reduce the loss generated during the switching and reduce the electromagnetic interference signal. strength.

2. In this embodiment, the current detecting component Rcs is used to indirectly determine the valley point of the voltage across the switching element Q1, and the feedback terminal originally used as the feedback control protection on the control circuit 4 is used as the feedback detection. In the terminal CS, the auxiliary winding, the voltage dividing resistor, and the control circuit 4 are added in the prior art to increase the corresponding pin position. This embodiment can greatly reduce the component number and circuit cost of the overall circuit, and the embodiment can be applied to all The LED driver circuit based on the switching converter has a wide range of advantages in industrial utilization.

Referring to FIG. 7, FIG. 9, and FIG. 10, a second preferred embodiment of the LED driving circuit of the present invention is similar to the first preferred embodiment. The difference between the preferred embodiment and the first preferred embodiment is that in the present embodiment, a buck-boost converter using a floating grounding technique is used as an illustration, but the switching converter ( Switching Converter) is applicable, not limited to the application of floating grounding technology or step-down converter circuit.

The inductor L has a first end electrically connected to the second end of the switching element Q1 and a second end connected to the ground.

The output capacitor Co has a first end that provides an output current to drive the LEDs 9, and a second end that electrically connects the anode end of the flywheel diode Do.

The flywheel diode Do and the current detecting component Rcs are connected in series between the second end of the output capacitor Co and the first end of the inductor L, and the connection point of the current detecting component Rcs and the inductor L provides a floating ground Voltage Vss.

Since the step-down conversion of the conversion circuit 3 is well known in the art, it will not be described here.

10 is a schematic waveform diagram of switching corresponding to the step-down converter of FIG. 9, wherein i _{Do is} the flywheel diode Do current, because when the switching element Q1 is turned off, the inductor current i _L flows through the Flywheel diode Do, so i _L = i _Do at this time. Since the current detecting element Rcs the flywheel diode Do in series, according to Ohm's law, the current detecting element Rcs waveforms of the voltage across the v _cs flywheel diode Do and the current waveform i _{D o} rather, i.e. and the inductor current i _L of the waveform rather, the use of same waveform is shown in FIG. 10 is a waveform of the voltage across the current detecting v _cs Rcs element in the switching element Q1 is turned off.

As can be seen from FIG. 10, the flywheel diode Do current i _Do (corresponding to the inductor current i _L when the switching element Q1 is turned off) is the same as the oscillation frequency of the two ends of the switching element Q1 across the voltage V _ds and the phase difference is 90 degrees. Therefore, the present invention can indirectly detect the cross-over voltage V of the switching element Q1 by detecting the change of the flywheel diode Do current i _Do and determining the zero crossing point of the flywheel diode Do current i _Do . _Ds trough point.

, When the gate of the switching element Q1 as shown in FIG. 10 - source voltage V _gs is switched to the low level (i.e., the switching element Q1 is turned off by the control), both ends of the voltage across the switching element Q1 V _ds Ascending, and the flywheel diode Do current i _Do (corresponding to the inductor current i _L when the switching element Q1 is turned off) starts to oscillate from the peak discharge to zero, and the valley detecting module 41 detects the current detecting component Rcs The cross-voltage v _cs (that is, the detection of the flywheel diode Do current i _Do change) and determine the zero crossing point, the output signal corresponding to the valley point of the cross-voltage V _ds across the switching element Q1 can be outputted Set for the switching control module 42 to adjust the output of the control signal.

In this embodiment, the gate-source voltage V _{gs of} the switching element Q1 is switched back to a high level when the switching element Q1 crosses the voltage V _ds across the third trough, for the purpose of illustrating the present invention. Detecting and switching to any trough can be designed to switch between the first trough, the second trough, ... or other troughs according to actual needs, and is not limited to this.

Thus, the second preferred embodiment can achieve the same purpose and effect as the first preferred embodiment described above.

In summary, the present invention can not only achieve absolute valley switching, but also reduce the loss generated during switching, reduce the signal strength of electromagnetic interference, and can greatly reduce the component number and circuit cost of the whole circuit, and has the advantages of industrial utilization. It is indeed possible to achieve the object of the invention.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

2‧‧‧Power circuit

Vac‧‧‧AC power supply

201‧‧‧The first end of the AC power supply

202‧‧‧The second end of the AC power supply

21‧‧‧Electromagnetic interference filter module

Cf‧‧‧Electromagnetic interference filter capacitor

Lf‧‧‧electromagnetic interference filter inductor

22‧‧‧Bridge rectifier module

D1‧‧‧First Diode

D2‧‧‧ second diode

D3‧‧‧ third diode

D4‧‧‧ fourth diode

C1‧‧‧Filter Capacitor

3‧‧‧Transition circuit

Q1‧‧‧Switching elements

L‧‧‧Inductance

Do‧‧‧Flywheel diode

Co‧‧‧ output capacitor

Rcs‧‧‧ current detecting component

4‧‧‧Control circuit

CS‧‧‧Responding to the detection side

VSS‧‧‧Control circuit ground

VDD‧‧‧ power supply terminal

GATE‧‧ switch control terminal

COMP‧‧‧ phase compensation end

41‧‧‧ Valley Detection Module

42‧‧‧Switching control module

Vss‧‧‧Control circuit ground voltage

i _L ‧‧‧Inductor current

9‧‧‧Lighting diode

Claims (10)

An LED driving circuit is configured to drive a plurality of LEDs. The LED driving circuit includes: a conversion circuit that receives a power signal to provide an output current to drive the LEDs, and includes: a switching element having a first end, a second end, and a control end receiving a control signal, controlled by the control signal to switch between on and off, a current detecting component electrically connected to the switching component And electrically connecting the switching element by detecting a resonant current related to a voltage across the switching element to output a resonant signal, and an inductor; and a control circuit including a switch control end electrically connecting the switching element The control terminal outputs the control signal, and the feedback detection terminal electrically connects the connection point between the switching component and the current detecting component to receive the resonant signal and receive the current corresponding to the inductor and the output current a feedback signal, and a control circuit ground, electrically connecting a connection point between the inductor and the current detecting component, and receiving a control circuit ground voltage; wherein Analyzing valley point circuit voltage across the switching element based on the resonant signal, and outputs the control signal to control the switching element is switched according to the voltage across the valley point of the switching element. The illuminating diode driving circuit of claim 1, wherein: The current detecting component is a resistive component that detects the resonant current and converts it into a resonant signal output that is a voltage. The control circuit further includes: a valley detecting module electrically connected to the feedback detecting end to receive the resonant signal Determining a valley point of the voltage across the switching element, and outputting a determination signal related to a voltage valley point across the switching element, and a switching control module electrically connecting the valley detecting module and the switch control end, Receiving the determination signal and outputting the control signal according to the determination signal. The illuminating diode driving circuit of claim 2, wherein the valley detecting module has: a comparator electrically connected to the feedback detecting end and a predetermined voltage, receiving the resonant signal and the predetermined voltage Comparing to determine a negative half-edge interval of the resonant signal below zero, and outputting a valley signal related to the comparison result, and a monostable flip-flop, electrically connecting the comparator, receiving the valley signal and according to the The valley signal determines the zero crossing point of the resonant signal and outputs the determination signal. The illuminating diode driving circuit of claim 3, wherein the conversion circuit is a buck converter. The illuminating diode driving circuit of claim 4, wherein the converting circuit further comprises a flywheel diode and an output capacitor; the first end of the switching component receives the power signal, and the flywheel diode has a Grounded anode end, and an electrical connection a cathode end of the second end of the switching element, the output capacitor has a first end for providing the output current to drive the light emitting diodes, and a grounded second end, wherein the inductor and the current detecting component are connected in series The first end of the output capacitor and the cathode end of the flywheel diode. The illuminating diode driving circuit of claim 3, wherein the conversion circuit is a step-down converter. The illuminating diode driving circuit of claim 6, wherein the converting circuit further comprises a flywheel diode and an output capacitor; the first end of the switching component receives the power signal, and the inductor has an electrical connection a first end of the second end of the switching element, and a grounded second end, the output capacitor has a first end for providing the output current to drive the light emitting diodes, and an electrical connection to the anode end of the flywheel diode The second end of the flywheel diode and the current detecting component are serially connected between the second end of the output capacitor and the first end of the inductor. The LED driving circuit of claim 3, further comprising a power circuit for receiving an AC power source for outputting the power signal, the AC power source having a first end and a second end, the power circuit including a bridge rectifier module, the bridge rectifier module has: a first diode body having an anode end electrically connected to the first end of the AC power source, and a cathode end outputting the power signal, a second two a pole body having an anode end electrically connected to the ground, and a Electrically connecting the cathode end of the first end of the AC power source, a third diode body having an anode end electrically connected to the second end of the AC power source, and a cathode end outputting the power signal, and a fourth diode The body has an anode end electrically connected to the ground and a cathode end electrically connected to the second end of the alternating current power source. The illuminating diode driving circuit of claim 8, wherein the power circuit further comprises: a filter capacitor having a first end for outputting the power signal and a second end electrically connected to the ground. The illuminating diode driving circuit of claim 9, wherein the power circuit further comprises an electromagnetic interference filtering module electrically connected between the alternating current power source and the bridge rectifier module.