TWI498046B - A led driving circuit and a secondary side controller thereof - Google Patents

Description

Light-emitting diode driving circuit and secondary side controller thereof

The invention relates to a light-emitting diode driving circuit with dimming function and a secondary side controller thereof, in particular to a dimming process, which can control the driving voltage of the light-emitting diode to a first driving voltage and a first A two-drive voltage LED driving circuit and a secondary side controller thereof.

As shown in the first figure, it is a conventional buck LED driving circuit. When the transistor switch Q2 is turned on (TURN ON), the power source V4 supplies current through the transistor switch Q2 to charge and store the inductor L1 and the capacitor C4 and simultaneously supplies energy to the LEDs D2 and D5 to emit light. When the transistor switch Q2 is turned off (TURN OFF), the energy is released by the inductor L1 and the capacitor C4, so that the light-emitting diodes D2 and D5 continue to emit light. The current flowing through the LEDs D2 and D5 generates a voltage drop across the resistor R7 to generate a current detection signal. The negative input terminal of the error amplifier U4 receives the current detection signal, and the positive input terminal receives a voltage reference signal Vref, and accordingly outputs an error amplification signal at the output end. Pulse Width Modulated (PWM) comparator U5 receives the error amplification signal and a triangular wave signal, compares the two signals and outputs a PWM signal to determine the on-time of the transistor switch Q2 at each cycle. Control power supply V4 provides energy to the buck LED driver circuit. Basically, the on-time of the transistor switch Q2 is controlled by the feedback voltage to allow the circuit to output sufficient voltage and current, so that the sense current of the resistor R7 is equal to a preset value. If the output current is too much or too little, the resistor R7 The voltage at both ends will change, and thus the on-time of the transistor switch Q2 will be changed, so that the voltage across the resistor R7 will be held at a constant value to achieve a steady current flow.

Please refer to the first figure again, and use a NAND gate U7A to simultaneously receive a dimming signal DIM and the PWM signal to achieve the dimming function. When the input dimming signal is at the low level (LOW LEVEL), the output of the anti-gate U7A is turned to the high level to stop the power transistor switch Q2 from being turned on. Although the inductor L1 and the capacitor C4 will release the energy through the diode D8 to maintain the LEDs D2 and D5 after the transistor switch Q2 is turned off, the inductor L1 and the capacitor C4 will release energy to the output voltage due to the long period of the dimming signal. (When the contact voltage of the inductor L1 and the capacitor C4 is lower than the threshold voltage of the light-emitting diodes D2 and D5, the light-emitting diodes D2 and D5 no longer emit light. However, due to the existence of some leakage paths, the output voltage will continue to drop until the energy storage of the inductor L1 and the capacitor C4 is completely released. When the input dimming signal turns to the high level (HIGH LEVEL), the output of the anti-gate U7A is controlled by the PWM signal, and the feedback control as described above is restored to achieve stable illumination. Thus, by controlling the change of the pulse width of the signal, the ratio of the LED lighting and the darkening time is controlled to obtain an average brightness.

This conventional dimming mode will generate an excessive transient voltage because it acts at both the on and off limits. The operating voltage and current waveforms are as shown in the second figure, and the voltage changes from zero volts to N*VF, where N is The number of LEDs connected in series, VF is the voltage across the predetermined current flowing through the LED. If there are dozens of LEDs in series, the voltage across them will vary by hundreds of volts. And N*VFmin refers to the cross caused by the light-emitting diode at the critical voltage. When the output voltage drops from N*VF to N*VFmin, the light-emitting diode stops emitting light almost. As shown in the second figure, the release rate of the capacitor energy storage will become slow until it is completely released. Since the re-conduction of the light-emitting diode requires an on-time, when the voltage supplied in an instant is too large, there will be a voltage stress in the plurality of series-connected LEDs that will be subjected to a voltage greater than a specification due to the different conduction, so that the light-emitting diode is burned. The situation occurs, so a voltage ramp control circuit must be provided. Although the above problem can be solved by adding a voltage ramp control circuit, this not only increases the cost of the LED driving circuit, but also increases the transient time of the voltage rise and fall of the dimming process and affects the dimming control. Accuracy.

In view of the above, the present invention provides a basic voltage that can be maintained at both ends of the LED module when the LED module is turned off, so that it can ensure input at both ends of the LED module. There is a small voltage change, so that the design of the LED driving circuit can eliminate the risk of damage of the LED component by considering the output voltage rise time and the additional output current limiting circuit. The body drive circuit costs and simplifies the layout of the PCB board.

To achieve the above objective, the present invention provides a light emitting diode driving circuit including a conversion circuit, a light emitting diode module, a current detector, and a control module. The conversion circuit converts an input voltage into an output voltage according to a control signal. The LED module is coupled to the conversion circuit and emits light according to the output voltage. The current detector is coupled to the current detector

The LED module generates a current detection signal according to a current flowing through the LED module. The control module generates the control signal according to the current detection signal and a dimming signal, so that the output voltage is controlled to a first driving voltage or a second driving voltage. Wherein, when the output voltage is at the first driving voltage, the LED module is in a stable illumination state; and when the output voltage is at the second driving voltage, the output voltage is approximately close to the LED mode. A threshold voltage of the group causes the LED module to emit almost no light.

The invention also provides another LED driving circuit, comprising a conversion circuit, a light emitting diode module, a current detector, a voltage detector and a control module. The conversion circuit converts an input voltage into an output voltage according to a control signal. The LED module is coupled to the conversion circuit and emits light according to the output voltage. The current detector is coupled to the LED module to generate a current detection signal according to a current flowing through the LED module. The voltage detector is coupled to the LED module to generate a voltage detection signal according to a voltage applied to the LED module. The control module generates the control signal according to the current detection signal, the voltage detection signal and a dimming signal, so that the output voltage is controlled to a first driving voltage or a second driving voltage. Wherein, when the output voltage is at the first driving voltage, the LED module is in a stable illumination state; and when the output voltage is at the second driving voltage, the output voltage is approximately close to the LED mode. A threshold voltage of the group causes the LED module to emit almost no light.

The invention also provides a secondary side control circuit applied to a luminescence a diode driving circuit, wherein the LED driving circuit includes a primary side control circuit, a conversion circuit, and at least one detector coupled to the conversion circuit, the secondary side control circuit coupling the at least one A detector. The secondary side control circuit described above may include a signal processor and a signal selection circuit. The signal processor is coupled to the at least one detector and generates at least one corresponding processing signal according to the at least one detection signal generated by the at least one detector; the signal selection circuit coupled to the signal processing And selecting one of the at least one processing signal according to a dimming signal. In addition, the secondary side control circuit may also include a signal selection circuit and a signal processor. The signal selection circuit is coupled to the at least one detector and selectively outputs one of the received signals according to a dimming signal. The signal processor is coupled to the signal selection circuit and selects a signal output generated by the signal according to the signal selection circuit. A processing signal.

The spirit of the present invention is that in the dimming control process, the output voltage of the LED driving circuit is controlled to a first driving voltage or a second driving voltage. When the output voltage is at the first driving voltage, the LED module is in current feedback control, so it is in a stable lighting state; and when the output voltage is in the second driving voltage, it is voltage feedback control, so the output voltage Approximate to the threshold voltage of the LED module (but greater than zero volts), so that the LED module is hardly illuminated, preferably slightly smaller than the threshold voltage of the LED module to ensure the LED The module does not emit light. Thus, during the dimming process, the voltage applied to the LED module is less than the conventional one. The pressure change can avoid the problem that the light-emitting diode is subjected to excessive voltage stress or inaccurate dimming control in the prior art.

In order to achieve the above control, it can be implemented by means of constant current, constant voltage switching or constant current and minimum duty cycle switching. Hereinafter, some preferred embodiments of the present invention will be described.

The third A is a circuit diagram of the LED driving circuit for constant current/constant voltage switching according to the present invention. As shown in FIG. 3A, the LED driving circuit includes a conversion circuit 10, a control module, a light-emitting diode module 30, a current detector 32, and a voltage detector 34. The control module includes a primary side control unit 12, a secondary side control unit 20a, and an isolation unit 36. The conversion circuit 10 converts an input voltage VIN into an output voltage VO according to a control signal of the primary side control unit 12 for driving the LED module 30. The voltage detector 34 detects the voltage of the LED module 30 to output a voltage detection signal; the current detector 32 is connected in series with the LED module 30 to detect the flow through the LED module. The current of 30 is used to generate a current detection signal. The secondary side control unit 20a receives the voltage detection signal, the current detection signal and a dimming signal, and generates a secondary side control signal accordingly, and transmits the signal to the primary side control unit 12 via the isolation unit 36, and is isolated. Unit 36 is an optocoupler in this embodiment and may be a transformer or other isolation element in practical use. The primary side control unit 12 may be a conventional PWM controller that generates the above control signal according to the secondary side control signal to control the conversion circuit 10 to convert the input voltage into the output voltage VO. In this embodiment, the conversion circuit 10 is illustrated by taking a flyback DC-to-DC conversion circuit as an example, and the actual application may be smooth. Conversion circuits such as directional, half-bridge, and full-bridge are not limited.

The secondary side control unit 20a includes a voltage detection signal processor 24a, a current detection signal processor 26a, and a signal selection circuit 28a. The voltage detection signal processor 24a receives the voltage detection signal and the dimming signal, and generates a voltage processing signal accordingly. The current detection signal processor 26a receives the current detection signal to generate a current processing signal. The signal selection circuit 28a receives the voltage processing signal and the current processing signal, and selects one of the outputs according to the magnitude of the two signals. In this embodiment, the dimming signal is a pulse signal and is input to the voltage detecting signal processor 24a to adjust the voltage processing signal output by the voltage detecting signal processor 24a.

The voltage detection signal processor 24a includes a signal selector 241a and an error amplifier 242a. The signal selector 241a selects to output a higher first reference voltage Vref1 or a lower second reference voltage Vref2 according to the dimming signal. The non-inverting input terminal of the error amplifier 242a receives the first reference voltage Vref1 or the second reference voltage Vref2 outputted by the signal selector 241a, and the inverting input terminal receives the voltage detecting signal of the voltage detector 34, and outputs the voltage accordingly. Processing the signal. The current detecting signal processor 26a is an error amplifier, and receives a third reference voltage Vref1 at the non-inverting input terminal, and the inverting input terminal receives the current detecting signal of the current detector 32, and outputs a current processing signal according to the current detecting signal. The signal selection circuit 28a includes two diodes, and the negative ends of the diodes are respectively coupled to the voltage detection signal processor 24a and the current detection signal processor 26a, and the positive ends are coupled to the isolation unit 36, and Select the lower level of the output voltage processing signal and current processing signal. In this embodiment, when the dimming signal level is the first level signal representing "OFF", the signal selection The selector 241a outputs a lower second reference voltage Vref2, causing the voltage detecting signal processor 24a to lower the level of the output voltage processing signal. At this time, the level of the voltage processing signal is lower than the level of the current processing signal, and the signal selection circuit 28a selects the output voltage processing signal. Therefore, the LED driving circuit operates in a constant voltage mode, so that the output voltage is reduced to the vicinity of the threshold voltage of the LED module, and the LED module emits almost no light. When the dimming signal level is the second level signal representing "ON", the signal selector 241a outputs a higher first reference voltage Vref1, so that the voltage detecting signal processor 24a increases the output voltage processing signal. Bit. At this time, the signal selection circuit 28a selects the output current processing signal. Therefore, the LED driving circuit operates in a constant current mode, and the output voltage rises to stabilize the current of the LED module to a predetermined current value, and the LED module is stably illuminated. In this way, the output voltage of the LED driving circuit is at the first driving voltage (constant current mode, the current is stabilized at a predetermined current value) or the second driving voltage (the constant voltage mode, the voltage is stabilized at a predetermined voltage value), and the two driving The difference in voltage is small to avoid the problems in the prior art. In addition, if the circuit is open, the current detection signal level returned by the current detector 32 is low, and the output voltage VO will continuously rise until the voltage detection signal of the voltage detector 34 reaches the first reference voltage Vref1. At this time, the voltage detecting signal processor 24a again obtains the feedback control master control, and limits the maximum value of the output voltage VO to achieve the overvoltage protection function.

Of course, the dimming signal can also be the inverting input of the control voltage detecting signal processor 24a, except that the input signal of the non-inverting input terminal of the controllable voltage detecting signal processor 24a reaches the level of the control output signal. End The function of the input signal or the direct control of the output of the voltage detecting signal processor 24a to achieve the above functions, or even to control any input signal or output signal of the current detecting signal processor 26a. To achieve the aforementioned functions. Referring to the third B diagram, a schematic diagram of the LED driving circuit for controlling the input signal level of the inverting input terminal of the error amplifier 242a. In this embodiment, the voltage detector 34 includes a first voltage dividing portion 34a and a second voltage dividing portion 34b, and the signal selector 241a switches the voltage dividing ratio of the voltage detector 34 to switch the LED driving. The function of the circuit in constant current mode or constant voltage mode.

In addition, in practical applications, the dimming signal can be DC dimming, pulse signal or clock dimming (that is, calculating the number of clock signals in a predetermined length of time, and converting to a duty cycle of dimming), etc., without limitation. Hereinafter, another preferred embodiment is illustrated by direct current dimming.

FIG. 3C is a schematic diagram of a light-emitting diode driving circuit according to an embodiment of the present invention for direct current dimming (ie, the level of the dimming signal represents the amplitude of the dimming). The secondary side control unit 20b includes a signal processor 24b and a signal selection circuit 28b. The signal selection circuit 28b receives the DC dimming signal, the voltage detection signal and the current detection signal, and selects one of the output voltage detection signal and the current detection signal to the signal processor 24b based on the DC dimming signal, and the signal processor 24b is configured according to the signal processor 24b. The received voltage detection signal or current detection signal outputs a signal to the primary side control unit 12, so that the primary side control unit 12 controls the conversion circuit 10 accordingly. Compared with the embodiment shown in FIG. 3A, in addition to the dimming signal being a direct current signal, the signal selection circuit is also pre-positioned to save the number of signal processors.

The signal selection circuit 28b includes a continuous flow pulse converter 281b, a level adjuster 282b, and a signal selector 283b. The DC-to-pulse converter 281b can be a comparator. The non-inverting input terminal receives the DC dimming signal, the inverting input terminal receives a triangular wave signal, and outputs a pulse signal accordingly. The level adjuster 282b adjusts the received current detection signal level so that the level of the current detection signal is adjusted to be in the same range as the level of the voltage detection signal. The signal selector 283b receives the current detection signal output by the level adjuster 282b and the voltage detection signal output by the voltage detector 34, and selects an output current detection signal according to the pulse signal output by the DC pulse converter 281b. Voltage detection signal. The signal processor 24b is an error amplifying circuit. The non-inverting input terminal receives a reference voltage Vref, and the inverting input terminal receives the signal output by the signal selector 283b, and outputs the secondary side control signal to the isolation unit 36 accordingly. The isolation unit 36 is coupled to a Zener diode as an output overvoltage protection to clamp the output voltage VO to a maximum output voltage value when the output voltage VO rises abnormally due to a circuit abnormality.

In this embodiment, when the pulse signal level outputted by the DC-to-pulse converter 281b is the first level signal representing "OFF", the signal selector 283b outputs a voltage detection signal. Therefore, the LED driving circuit operates in a constant voltage mode, so that the output voltage is reduced to the vicinity of the threshold voltage of the LED module, and the LED module emits almost no light. When the DC pulse converter 281b selects the output pulse signal level to be the second level signal representing "ON", the signal selector 283b selects the output current detection signal. Therefore, the LED driving circuit operates in the constant current mode and the output voltage The current of the light-emitting diode module is stabilized at a predetermined current value, and the light-emitting diode module stably emits light.

As described above, the present invention can also be implemented in a manner that regulates current and minimum duty cycle switching. Please refer to the third D diagram for a circuit diagram of a preferred embodiment of constant current and minimum duty cycle switching in accordance with the present invention. The secondary side control unit 20c includes a signal processor 24c, a minimum duty cycle signal generator 29c, and a signal selector 28c. The signal processor 24c is an error amplifier that outputs a current processing signal according to the current detection signal generated by the current detector 32 and a reference voltage. The minimum duty cycle signal generator 29c can externally set the minimum duty cycle to adjust for different application environments, such as external resistors as shown in the embodiment, or by capacitance or other means. The signal selector 28c receives the current processing signal and a minimum duty cycle signal generated by the minimum duty cycle signal generator 29c, and selects an output according to the dimming signal DIM. The primary side control unit 12c receives the signal output from the secondary side control unit 20c transmitted through the isolation unit 36, and controls the conversion circuit 10 accordingly.

In this embodiment, when the level of the dimming signal DIM is the first level signal representing "OFF", the signal selector 28c selects to output the minimum duty cycle signal. By appropriately setting the minimum duty cycle, the primary side control unit 12c has a very small duty cycle of the control signal outputted according to the minimum duty cycle signal, so that the energy transmitted to the secondary side via the conversion circuit 10 can approximately maintain the LED module 30. Basic loss of circuit components other than those. That is to say, when the driving voltage drops to the vicinity of the threshold voltage of the LED module 30, the voltage is stopped and maintained at a voltage value, and the LED module is hardly emitted. Light. When the level of the dimming signal DIM is the second level signal representing "ON", the signal selector 28c selects the output current detecting signal. Therefore, the LED driving circuit operates in a constant current mode, and the output voltage rises to stabilize the current of the LED module to a predetermined current value, and the LED module is stably illuminated.

Please refer to the fourth figure, which is a schematic diagram of driving voltages and driving current waveforms of the LED modules according to the embodiments of the present invention. When the dimming signal DIM is at the level of "ON", the driving voltage of the LED module is maintained near the first driving voltage N*VF. At this time, the LED module driving current is stably and stably Controlled at I; when the dimming signal DIM is at the level of "OFF", the driving voltage of the LED module is maintained near the second driving voltage N*VFmin, and the driving current of the LED module is Zero (or close to zero). In this way, the dimming function can still be achieved when the driving voltage of the light-emitting diode changes less than the driving voltage change of the prior art.

As described above, the present invention fully complies with the three requirements of the patent: novelty, advancement, and industrial applicability. The invention has been described above in terms of the preferred embodiments, and it should be understood by those skilled in the art that the present invention is not intended to limit the scope of the invention. It should be noted that variations and permutations equivalent to those of the embodiments are intended to be included within the scope of the present invention. Therefore, the scope of the invention is defined by the scope of the following claims.

10‧‧‧Transition circuit

12‧‧‧primary side control unit

12c‧‧‧primary side control unit

20a‧‧‧secondary control unit

20b‧‧‧secondary control unit

24a‧‧‧Signal Processor

24b‧‧‧Signal Processor

24c‧‧‧Signal Processor

242a‧‧‧Error amplifier

241a‧‧‧Signal selector

26a‧‧‧Signal Processor

28a‧‧‧Signal selection circuit

28b‧‧‧Signal Processor

28c‧‧‧Signal selector

281b‧‧‧DC to pulse converter

282b‧‧ ‧ level adjuster

283b‧‧‧Signal selector

29c‧‧‧Minimum duty cycle signal generator

30‧‧‧Lighting diode module

32‧‧‧ Current Detector

34‧‧‧Voltage Detector

34a‧‧‧First partial pressure department

34b‧‧‧Second voltage division

36‧‧‧Isolation unit

C4‧‧‧ capacitor

D2‧‧‧Lighting diode

D5‧‧‧Light Emitting Diode

D8‧‧‧ diode

DIM‧‧‧ dimming signal

EA‧‧Amplifier

L1‧‧‧Inductance

Q2‧‧‧Chip switch

R7‧‧‧ resistance

U‧‧‧ comparator

U4‧‧‧Error Amplifier

U7A‧‧‧Anti-gate

V4‧‧‧ power supply

VIN‧‧‧ input voltage

Vref‧‧‧reference voltage

Vref1‧‧‧ first reference voltage

Vref2‧‧‧second reference voltage

Vref3‧‧‧ third reference voltage

The first figure is a conventional buck LED driving circuit; 2 is a schematic diagram of a driving voltage and a driving current waveform of a conventional LED driving circuit; FIGS. 3A to 3D are circuit diagrams of a driving diode driving circuit according to the present invention; and a fourth diagram The waveforms of the driving voltage and the driving current of the LED module according to the embodiments of the present invention are shown.

10‧‧‧Transition circuit

12‧‧‧primary side control unit

20a‧‧‧secondary control unit

24a‧‧‧Signal Processor

241a‧‧‧Signal selector

242a‧‧‧Error amplifier

26a‧‧‧Signal Processor

28a‧‧‧Signal selection circuit

30‧‧‧Lighting diode module

32‧‧‧ Current Detector

34‧‧‧Voltage Detector

36‧‧‧Isolation unit

EA‧‧Amplifier

VO‧‧‧ output voltage

VIN‧‧‧ input voltage

Vref1‧‧‧reference voltage

Vref2‧‧‧ reference voltage

Vref3‧‧‧ reference voltage

Claims (15)

An LED driving circuit includes: a conversion circuit for converting an input voltage into an output voltage according to a control signal; a light emitting diode module coupled to the conversion circuit and emitting light according to the output voltage; a current detector is coupled to the LED module for generating a current detection signal according to a current flowing through the LED module; and a control module for detecting the signal according to the current a dimming signal, the control signal is generated, and the output voltage is controlled to a first driving voltage or a second driving voltage, wherein the control module comprises: a secondary side control unit coupled to the current detector Receiving the current detection signal and generating a current processing signal according to the second side control unit, and outputting the current processing signal or a minimum duty cycle signal according to the dimming signal; an isolation unit coupled to the second a side control unit, the isolation unit receives the signal output by the secondary side control unit, and generates a secondary side signal according to the same; and a primary side control unit coupled to the isolation unit, According to the secondary side signal to generate the control signal; wherein when the first output voltage is the driving voltage, the The light emitting diode module is in a stable light emitting state; and when the output voltage is at the second driving voltage, the output voltage is close to a threshold voltage of the light emitting diode module, so that the light emitting diode module is almost Does not shine. The illuminating diode driving circuit of claim 1, wherein the secondary side control unit comprises: a signal processor, receiving the current detecting signal, and generating the current processing signal accordingly; a periodic signal generator for generating a minimum duty cycle signal; and a signal selector coupled to the signal processor and the minimum duty cycle signal generator, and selectively outputting the current processing signal and the minimum according to the dimming signal One of the work cycle signals. The illuminating diode driving circuit of claim 2, wherein the signal processor comprises an error amplifier, and the error amplifier receives the current detecting signal and a reference voltage to generate the current processing signal. An LED driving circuit includes: a conversion circuit for converting an input voltage into an output voltage according to a control signal; a light emitting diode module coupled to the conversion circuit and emitting light according to the output voltage; a current detector is coupled to the LED module to generate a current detection signal according to a current flowing through the LED module; a voltage detector coupled to the LED a module for generating a voltage detection signal according to a voltage applied to one of the LED modules; and a control module for generating the signal according to the current detection signal, the voltage detection signal and a dimming signal Controlling the signal so that the output voltage is controlled by a first driving voltage or a second driving voltage, wherein the control module comprises: a secondary side control unit coupled to the current detector and the voltage detector The secondary side control unit receives the current detection signal and the voltage detection signal and generates a current processing signal and a voltage processing signal respectively, and outputs the current processing signal or the voltage processing signal according to the dimming signal. An isolation unit coupled to the secondary side control unit, the isolation unit receives the signal output by the secondary side control unit, and generates a secondary side signal accordingly; and a primary side control unit coupled The From the unit, to generate the control signal based on the secondary-side signal; wherein when the first output voltage is the driving voltage, the light emitting diode module in a stable emitting state; when the output voltage When the second driving voltage is located, the output voltage is close to a threshold voltage of the LED module, so that the LED module emits almost no light. The illuminating diode driving circuit of claim 4, wherein the secondary side control unit comprises: a current signal processor, receiving the current detecting signal, and generating the current processing signal according to the voltage; The signal processor receives the voltage detection signal and the dimming signal, and generates the voltage processing signal accordingly; and a signal selector coupled to the current signal processor and the voltage signal processor and processed according to the current The signal and the voltage processing signal output one of them. The illuminating diode driving circuit of claim 5, wherein the current signal processor comprises a first error amplifier, the first error amplifier receiving the current detecting signal and a first reference voltage to generate This current processes the signal. The illuminating diode driving circuit of claim 5, wherein the voltage signal processor comprises a second error amplifier, the second error amplifier receiving the voltage detecting signal and a second reference voltage to generate This voltage processes the signal. The illuminating diode driving circuit of claim 7, wherein the second reference voltage and one of the voltage detecting signals are The level is adjusted according to the dimming signal. The illuminating diode driving circuit of claim 4, wherein the secondary side control unit comprises: a current signal processor, receiving the current detecting signal and the dimming signal, and generating the current according to the current signal Processing a signal; a voltage signal processor receives the voltage detection signal and generates the voltage processing signal accordingly; and a signal selector coupled to the current signal processor and the voltage signal processor and processed according to the current The signal and the voltage processing signal output one of them. The illuminating diode driving circuit of claim 9, wherein the current signal processor comprises a first error amplifier, the first error amplifier receiving the current detecting signal and a first reference voltage to generate This current processes the signal. The illuminating diode driving circuit of claim 10, wherein the first reference voltage and the level of one of the current detecting signals are adjusted according to the dimming signal. The illuminating diode driving circuit of claim 9, wherein the voltage signal processor comprises a second error amplifier, and the second error amplifier receives the voltage detecting signal and a second reference voltage to generate This voltage processes the signal. Light-emitting diode driving electric power as described in claim 4 The secondary side control unit includes: a signal selection circuit coupled to the voltage detector and the current detector, and selectively outputting the voltage detection signal and the current detection signal according to the dimming signal And a signal processor coupled to the signal selection circuit and outputting the secondary signal according to the signal output by the signal selection circuit. The illuminating diode driving circuit of the ninth aspect of the invention, wherein the signal selecting circuit comprises: a level adjuster coupled to the current detector for adjusting the level of the current detecting signal; And a signal selector coupled to the level adjuster and the voltage detector, and outputting the adjusted current detecting signal and the voltage detecting signal according to the dimming signal. The illuminating diode driving circuit of claim 14, wherein the signal selecting circuit further comprises a continuous pulse signal converter, wherein the dimming signal is a direct current dimming signal, and the dc pulse signal converter Converted into a pulse signal to control the signal selector.