CN110798938A - LED driver - Google Patents

Abstract

The invention discloses an LED driver, comprising: a PFC main circuit, a drive control circuit, an isolation circuit, a voltage regulation circuit, a frequency control drive circuit, a current regulation circuit and a resonant DC-DC circuit, the PFC main circuit and the resonant DC-DC circuit connection, the resonant DC-DC circuit is respectively connected with the input end of the current regulation circuit and the input end of the voltage regulation circuit, the output end of the current regulation circuit is connected with the input end of the frequency control drive circuit, and the output end of the frequency control drive circuit is connected with the resonant DC The DC circuit is connected, the output end of the voltage regulation circuit is connected with the input end of the drive control circuit through the isolation circuit, and the output end of the drive control circuit is connected with the PFC main circuit. The invention realizes the multi-channel output of the LED driver through the different coupling coefficients of the two secondary windings of the transformer and the primary winding, and realizes that the multi-channel output of one LED has both constant voltage output and constant current through the voltage regulating circuit and the current regulating circuit. output.

Description

an LED driver

technical field

The present invention relates to the technical field of lighting equipment, and in particular, to an LED driver.

Background technique

LEDs are widely used in the field of lighting due to their advantages of energy saving, environmental protection, long life and high conversion efficiency. The LED driver converts the input voltage to DC and supplies the LED load. At present, there are two types of LED drivers, one is an LED driver that outputs constant current, and the other is an LED driver that outputs constant voltage. In some lighting situations, the same driver needs to drive two loads at the same time. The existing LED driver can output two or more channels, but the multiple outputs of the same driver are of the same type, that is, the same driver has multiple channels of constant current. The output may have multiple constant voltage outputs, but it cannot achieve both constant current output and constant voltage output in the multiple outputs of the same driver.

For example, a "constant voltage and constant current driver for high-power LED spotlights" disclosed in Chinese patent documents, its publication number CN201467519U, which was published on May 12, 2010, includes a power input end, which is connected to the power input end. The rectifier circuit, the switch transformer connected with the rectifier circuit, and the output terminal connected with the switch transformer for connecting the load LED, is characterized in that: it also includes a PFC circuit, a power drive constant voltage circuit and a constant current circuit, the PFC circuit It is set between the rectifier circuit and the switching transformer. The power drive constant voltage circuit includes a power drive circuit and a constant voltage control circuit. The power drive circuit is set between the PFC circuit and the switching transformer. The constant voltage control circuit collects the output signal of the switching transformer. A feedback signal is generated to the power drive circuit, and a constant current circuit is arranged between the switching transformer and the output end. The constant voltage and constant current output of the LED driver is realized through a constant current circuit and constant voltage current, but the LED driver of the invention can only realize constant voltage or constant current output, and cannot realize both constant current output and constant current output in the multiple outputs of the same driver. There is a constant voltage output.

SUMMARY OF THE INVENTION

The invention mainly solves the problem that the prior art LED driver cannot realize the simultaneous output of constant voltage and constant current by the same driver; and provides an LED driver, which can detect and control the constant voltage and constant current, so that the multiple outputs of the same driver have both There are constant current output and constant voltage output.

The above technical problems of the present invention are mainly solved by the following technical solutions: an LED driver, including a PFC main circuit, a drive control circuit, an isolation circuit, a voltage regulation circuit, a frequency control drive circuit, a current regulation circuit and a resonant DC- DC circuit, the input end of the PFC main circuit is used as the input end of the LED driver and used to connect the power supply, the output end of the PFC main circuit is connected with the input end of the resonant DC-DC circuit, the resonant DC -The output end of the DC circuit includes a constant voltage output end and a constant current output end, the input end of the current regulation circuit is connected to the constant current output end, and the output end of the current regulation circuit is connected to the frequency control drive circuit , the current adjustment circuit is used to detect the current output by the constant current output terminal and output the first feedback signal to the frequency control drive circuit, and the frequency control drive circuit outputs the first drive signal according to the magnitude of the first feedback signal For the resonant DC-DC circuit, the current output by the constant current output terminal is maintained constant through the operating frequency of the resonant DC-DC circuit, and the input terminal of the voltage regulation circuit is connected to the constant voltage output terminal, The output end of the voltage regulation circuit is connected to the drive control circuit through an isolation circuit, and the voltage regulation circuit is used to detect the voltage output by the constant voltage output end and output a second feedback signal to the drive control circuit through the isolation circuit circuit, the drive control circuit outputs a second drive signal to the PFC main circuit according to the magnitude of the second feedback signal to make the output voltage constant, thereby making the voltage of the constant voltage output terminal constant. The input terminal of the PFC main circuit is connected to the power supply, and the voltage is boosted by the PFC circuit and then output to the resonant DC-DC circuit. The resonant DC-DC circuit performs constant voltage and constant current output. The voltage is detected by constant voltage and the detection result is fed back to the drive control circuit. The output voltage of the PFC main circuit is adjusted by the drive control circuit to achieve constant voltage output. The detection result is fed back to the frequency control drive circuit, and the output current of the resonant DC-DC circuit is adjusted by the frequency control drive circuit to realize constant current output. Through one LED driver, both constant voltage output and constant current output are realized in multiple outputs.

Preferably, the PFC main circuit includes an inductance L, a switch tube S0, a diode D1 and a capacitor C0, one end of the inductance L is connected to the positive pole of the power supply, and the other end of the inductance L is respectively connected to one end of the switch tube S0 And the anode of the diode D1 is connected, the other end of the switch S0 is connected to one end of the capacitor C0 and the negative electrode of the power supply, the other end of the capacitor C0 is connected to the cathode of the diode D1, and the capacitor C0 The two ends of the PFC are also connected with the resonant DC-DC circuit as the output end of the PFC main circuit. The current passes through the inductor L to prevent the high-voltage interference signal from damaging the circuit. The voltage stored at both ends of the capacitor C0 is controlled by the switch S0 to control and adjust the output voltage Vbus of the PFC main circuit. The diode D1 prevents the current from flowing back into the switch S0.

Preferably, the resonant DC-DC circuit further includes a switch unit, a resonant capacitor Cr and a transformer, the transformer includes a primary winding N1, a secondary winding M1 and a secondary winding M2, the primary winding N1 and the The resonant capacitor Cr is connected in series and then connected to the switch unit, and the other end of the switch unit is used as the input end of the resonant DC-DC circuit; the secondary winding M1 is used as a constant voltage output through the first rectified output end after rectification terminal, the secondary winding M2 is used as a constant current output terminal through the second rectified output terminal after rectification. The secondary winding M1 and the secondary winding M2 are transformed through the transformer, so that the circuit generates two outputs.

Preferably, the coupling coefficient between the secondary winding M1 and the primary winding N1 is greater than the coupling coefficient between the secondary winding M2 and the primary winding N1. According to the different coupling coefficients of the secondary winding M1 and the secondary winding M2 and the primary winding N1, the resonant DC-DC circuit generates multiple different outputs.

Preferably, the switch unit in the resonant DC-DC circuit includes a switch tube S1 and a switch tube S2; the resonant DC-DC circuit further includes a diode D2, a diode D3, a diode D4, a diode D5, a capacitor C1, Capacitor C2 and resistor Rs, the first end of the switch S1 is used as the input positive end of the resonant DC-DC circuit, the second end of the switch S1 is respectively connected with the first end of the switch S2 and the original One end of the side winding N1 is connected, the second end of the switch tube S2 is used as the input negative end of the resonant DC-DC circuit and is connected to one end of the resonant capacitor Cr, and the other end of the resonant capacitor Cr is connected to the primary side winding. The other end of N1 is connected, the secondary winding M1 and the secondary winding M2 have tapped ends, the first end of the secondary winding M1 is connected to the anode of the diode D2, and the second end of the secondary winding M1 The diode D3 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the tap terminal of the secondary winding M1 to the capacitor C1, and the two ends of the capacitor C1 serve as the constant voltage output terminal. ; The first end of the secondary winding M2 is connected to the anode of the diode D4, the second end of the secondary winding M2 is connected to the anode of the diode D4 through the diode D5, and the cathode of the diode D4 is connected to the anode of the diode D4. The first end of the capacitor C2 is connected, the tap end of the secondary winding M2 is connected to the second end of the capacitor C2 and the first end of the resistor Rs, respectively, and the two ends of the capacitor C2 serve as the A constant current output terminal, the second terminal of the resistor Rs is connected to the current adjustment circuit. The switching tube S1, the switching tube S2, the resonant capacitor Cr, the diode D2, the diode D3, the diode D4, the diode D5 and the transformer form the LLC half-bridge resonant circuit, which converts the direct current output from the PFC main circuit into alternating current, and converts the voltage through the transformer. The coupling coefficients of the two secondary windings of the transformer and the primary winding are different, so that the voltage and current output by the resonant DC-DC circuit are different, and the output power of most outputs is different. The half-bridge rectifier composed of diode D4 and diode D5 converts the alternating current into direct current, and supplies power to the LED lamp after being stabilized by the capacitor C1 and the capacitor C2.

Preferably, the voltage adjustment circuit includes an operational amplifier U1, a resistor R1, a resistor R2, a resistor R3 and a capacitor C4, and the negative input terminal of the operational amplifier U1 is respectively connected with the first terminal of the capacitor C4, the resistor One end of R1 is connected to one end of the resistor R2, the other end of the resistor R1 is connected to the first end of the capacitor C1, the other end of the resistor R2 is connected to the second end of the capacitor C1, and the capacitor C4 The second terminal of the 2 is connected to the output terminal of the operational amplifier U1 through the resistor R3, and the non-inverting input terminal of the operational amplifier U1 inputs the voltage reference signal Vref1. The operational amplifier U1 compares the detected voltage signal with the voltage reference signal Vref1, and outputs a second feedback signal through the isolation circuit to the drive control circuit according to the comparison result. The capacitor C1, the resistor R3 and the operational amplifier form a negative feedback adjustment.

Preferably, the isolation circuit includes an optocoupler, the input end of the optocoupler is connected to the voltage regulation circuit, and the output end of the optocoupler is connected to the drive control circuit. The voltage regulation circuit and the drive control circuit are isolated by the optocoupler to prevent the high frequency signal from interfering with the circuit.

Preferably, the current adjustment circuit includes an operational amplifier U2, a capacitor C5 and a resistor R4, and the negative input terminal of the operational amplifier U2 is respectively connected to the first terminal of the capacitor C5 and the second terminal of the resistor Rs, so The second end of the capacitor C5 is connected to the output end of the operational amplifier U2 via the resistor R4, and the current reference signal Iref1 is input to the non-inverting input end of the operational amplifier. The detected current signal is compared with the current reference signal Iref1 through the operational amplifier U2, and the first feedback signal is output to the frequency control driving circuit according to the comparison result. The operational amplifier U2, capacitor C5 and resistor R4 constitute negative feedback adjustment.

Preferably, the frequency control drive circuit includes a resonance control chip, a voltage controlled oscillator and a drive circuit, the voltage controlled oscillator receives the first feedback signal transmitted by the current adjustment circuit and determines the The size of the frequency of the switch tube S1 and the switch tube S2 transmits the frequency signal to the resonance control chip, and the resonance control chip generates the drive signal through the drive circuit according to the frequency signal and outputs it to the switch tube S1 and the switch tube S2. . The resonance control chip receives the first feedback signal output by the current adjustment circuit, and controls the conduction and cut-off of the MOS transistor Q1 and the MOS transistor Q2 according to the first feedback signal, so as to stabilize the current output of the resonant DC-DC circuit and the current reference signal Iref1 to ensure The circuit realizes constant current output.

Preferably, the drive control circuit includes a PFC control chip, an operational amplifier U3, an operational amplifier U4 and an RS flip-flop A1, and the positive phase input terminal of the operational amplifier U3 and the negative phase input terminal of the operational amplifier U4 input all The second feedback signal transmitted by the voltage regulation circuit, the negative input terminal of the operational amplifier U3 inputs the voltage reference signal Vref2, the output terminal of the operational amplifier U3 is connected to the S terminal of the RS flip-flop A1, and the operational amplifier U3 is connected to the S terminal of the RS flip-flop A1. The non-inverting input terminal of the amplifier U4 inputs the voltage reference signal Vref3, the output terminal of the operational amplifier U4 is connected to the R terminal of the RS flip-flop A1, and the Q terminal and the Q non-terminal of the RS flip-flop A1 are both connected to the The PFC control chip is connected, and the PFC control chip is connected with the switch tube S0. The PFC control chip controls the switch tube S0 according to the output result of the RS flip-flop, so that the output voltage of the PFC main circuit is stabilized at the voltage reference signal Vref1, and the constant voltage output of the circuit is realized.

The beneficial effects of the invention are as follows: (1) multiple outputs of the LED driver are realized through different coupling coefficients between the two secondary windings of the transformer and the primary winding; (2) the voltage is detected by the voltage regulating circuit and the driving control circuit Adjust to realize the constant voltage output of the LED driver; (3) realize the constant current output of the LED driver through the current detection of the current regulating circuit and the adjustment of the frequency control driving circuit.

Description of drawings

FIG. 1 is a schematic structural diagram of the LED driver according to the first embodiment.

FIG. 2 is a schematic diagram of the LED driver circuit of the first embodiment.

FIG. 3 is a schematic diagram of the voltage regulation circuit of the first embodiment.

FIG. 4 is a schematic diagram of the current regulation circuit of the first embodiment.

In the figure 1. Power supply, 2. PFC main circuit, 3. Resonant DC-DC circuit, 4. Current regulating circuit, 5. Voltage regulating circuit, 6. Frequency control driving circuit, 7. Isolation circuit, 8. Driving control circuit.

Detailed ways

The technical solutions of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

Embodiment 1: An LED driver, as shown in FIG. 1, includes a PFC main circuit 2, a drive control circuit 8, an isolation circuit 7, a voltage adjustment circuit 5, a frequency control drive circuit 6, a current adjustment circuit 4 and a resonant DC-DC Circuit 3, the input end of the PFC main circuit 2 is used as the input end of the LED driver and used to connect the power supply 1, the output end of the PFC main circuit 2 is connected with the input end of the resonant DC-DC circuit 3, and the output end of the resonant DC-DC circuit 3 is connected. The terminals include a constant voltage output terminal and a constant current output terminal. The input terminal of the current adjustment circuit 4 is connected to the constant current output terminal of the resonant DC-DC circuit 3. The output terminal of the current adjustment circuit 4 is connected to the frequency control drive circuit 6. The current adjustment The circuit 4 is used to detect the current output by the constant current output terminal and output the first feedback signal to the frequency control drive circuit 6, and the frequency control drive circuit 6 outputs the first drive signal to the resonant DC-DC circuit 3 according to the magnitude of the first feedback signal, The operating frequency of the resonant DC-DC circuit 3 is used to maintain the constant current output from the constant current output terminal. The input terminal of the voltage regulating circuit 5 is connected to the constant voltage output terminal of the resonant DC-DC circuit 3. The output terminal of the voltage regulating circuit 5 The isolation circuit is connected to the drive control circuit 8, and the voltage adjustment circuit 5 is used to detect the voltage output by the constant voltage output terminal and output a second feedback signal to the drive control circuit 8 through the isolation circuit, and the drive control circuit 8 outputs according to the magnitude of the second feedback signal The second driving signal is given to the PFC main circuit 2 to make the output voltage constant, thereby making the voltage at the constant voltage output terminal constant.

As shown in Figure 2, the PFC main circuit 2 includes an inductor L, a switch S0, a diode D1 and a capacitor C0. One end of the inductor L is connected to the positive pole of the power supply 1, and the other end of the inductor L is connected to one end of the switch S0 and the diode D1 respectively. The anode is connected, and the other end of the switch tube S0 is connected to one end of the capacitor C0 and the negative electrode of the power supply 1 respectively. The other end of the capacitor C0 is connected to the cathode of the diode D1. - DC circuit 3 connection.

The resonant DC-DC circuit 3 includes a switching unit, a resonant capacitor Cr, a transformer, a diode D2, a diode D3, a diode D4, a diode D5, a capacitor C1, a capacitor C2 and a resistor Rs, and the transformer includes a primary winding N1, a secondary winding M1 and a secondary winding The side winding M2, the primary winding N1 and the resonant capacitor Cr are connected in series and then connected to the switch unit, and the other end of the switch unit is used as the input end of the resonant DC-DC circuit; the secondary side winding M1 passes through the first rectifier output after rectification as a constant voltage The output terminal, the secondary winding M2 is used as a constant current output terminal through the second rectified output terminal after rectification. The coupling coefficient between the secondary winding M1 and the primary winding N1 is greater than the coupling coefficient between the secondary winding M2 and the primary winding N1. The switching unit It includes a switch tube S1 and a switch tube S2, the first end of the switch tube S1 is used as the input positive end of the resonant DC-DC circuit, and the second end of the switch tube S1 is respectively connected with the first end of the switch tube S2 and the primary side winding N1. connected, the second end of the switch tube S2 is used as the input negative end of the resonant DC-DC circuit and is connected to one end of the resonant capacitor Cr, the other end of the resonant capacitor Cr is connected to the other end of the primary winding N1, the secondary winding M1 and the secondary side The winding M2 has a tap end, the first end of the secondary winding M1 is connected to the anode of the diode D2, the second end of the secondary winding M1 is connected to the anode of the diode D2 through the diode D3, and the cathode of the diode D2 is connected to the anode of the diode D2. The tap end of the secondary winding M1 is connected to the capacitor C1, and the two ends of the capacitor C1 are used as the constant voltage output end; the first end of the secondary winding M2 is connected to the anode of the diode D4, and the second end of the secondary winding M2 is connected to the diode D4 through the diode D5 and the diode D4. The anode of the diode D4 is connected to the first end of the capacitor C2, the tap end of the secondary winding M2 is connected to the second end of the capacitor C2 and the first end of the resistor Rs respectively, and the two ends of the capacitor C2 are used as constant current output terminal, the second terminal of the resistor Rs is connected to the current regulating circuit 4 .

The isolation circuit 7 includes a photocoupler, the input end of the photocoupler is connected to the voltage adjustment circuit 5 , and the output end of the photocoupler is connected to the driving control circuit 8 .

The frequency control driving circuit 6 includes a resonance control chip, a voltage-controlled oscillator and a driving circuit. The voltage-controlled oscillator receives the first feedback signal transmitted by the current adjustment circuit 4 and determines the switch tube S1 and the switch tube S2 according to the size of the first feedback signal. The size of the frequency, the frequency signal is transmitted to the resonance control chip, and the resonance control chip produces the drive signal through the drive circuit according to the frequency signal and outputs it to the switch tube S1 and the switch tube S2.

The drive control circuit 8 includes a PFC control chip, an operational amplifier U3, an operational amplifier U4 and an RS flip-flop A1, the positive input terminal of the operational amplifier U3 and the negative input terminal of the operational amplifier U4 input the second feedback signal transmitted by the voltage adjustment circuit 5 , the negative-phase input terminal of the operational amplifier U3 inputs the voltage reference signal Vref2, the output terminal of the operational amplifier U3 is connected to the S terminal of the RS flip-flop A1, the positive-phase input terminal of the operational amplifier U4 inputs the voltage reference signal Vref3, and the output of the operational amplifier U4 The terminal is connected to the R terminal of the RS flip-flop A1, the Q terminal and the Q non-terminal of the RS flip-flop A1 are both connected to the PFC control chip, and the PFC control chip is connected to the switch tube S0.

As shown in FIG. 3 , the voltage adjustment circuit 5 includes an operational amplifier U1, a resistor R1, a resistor R2, a resistor R3 and a capacitor C4. The negative input terminal of the operational amplifier U1 is respectively connected to the first terminal of the capacitor C4, one end of the resistor R1 and the resistor. One end of R2 is connected, the other end of resistor R1 is connected to the first end of capacitor C1, the other end of resistor R2 is connected to the second end of capacitor C1, and the second end of capacitor C4 is connected to the output end of operational amplifier U1 through resistor R3 , the non-inverting input terminal of the operational amplifier U1 inputs the voltage reference signal Vref1.

As shown in FIG. 4 , the current adjustment circuit 4 includes an operational amplifier U2, a capacitor C5 and a resistor R4. The negative input terminal of the operational amplifier U2 is respectively connected to the first terminal of the capacitor C5 and the second terminal of the resistor Rs. The two terminals are connected to the output terminal of the operational amplifier U2 through the resistor R4, and the current reference signal Iref1 is input to the non-inverting input terminal of the operational amplifier.

In the specific application, the 220V AC power is rectified by the rectifier circuit and then enters the PFC main circuit 2 through the power supply 1. The input voltage amplitude of the PFC main circuit 2 changes sinusoidally. The inductor L, the switch tube S0, and the diode D1 form a Boost circuit. Controlled by the control circuit, the input current of the Boost circuit is close to the input voltage, that is, close to a sine wave, which realizes the PFC function. The PFC main circuit 2 realized by the Boost circuit outputs the DC voltage Vbus under the control of the voltage regulation circuit 5 and the drive control circuit 8, and inputs the DC voltage Vbus with a relatively stable amplitude into the resonant DC-DC circuit 3, and the resonant DC-DC circuit 3 The switch tube S1, the switch tube S2, the resonant capacitor Cr, the diode D2, the diode D3, the diode D4, the diode D5 and the transformer form an LLC half-bridge resonant circuit, and the voltage output by the PFC main circuit 2 is DC-DC converted. The coupling coefficients of the two secondary windings and the primary winding are different, and the secondary winding M1 is closely coupled with the primary winding N1, so that the voltage output from the first channel has a high correlation with the primary winding N1 of the transformer of the resonant DC-DC circuit 3. The switch tube S0 of the PFC main circuit 2 is controlled by the voltage regulating circuit 5 and the drive control circuit 8, and the value of the output voltage Vbus of the PFC main circuit 2 is adjusted by controlling the switch tube S0, so that the value of the output voltage Vbus of the PFC main circuit 2 is Stable at the value set by the voltage reference signal Vref1, so that the output voltage of the first channel of the resonant DC-DC circuit 3 is stabilized at a certain value, so as to realize the constant voltage output of the LED driver, and the coupling degree between the secondary winding M2 and the primary winding N1 low, there is a large leakage inductance. The switch S1 and the switch S2 of the resonant DC-DC circuit 3 are controlled by the current adjustment circuit 4 and the frequency control drive circuit 6, so that the second output current is stable at the current reference signal Iref1 , so that the second output current of the resonant DC-DC circuit 3 is stabilized at a certain value to realize the constant current output of the LED driver, and further, when multiple outputs of the same LED driver are realized, there are both constant voltage output and constant current output.

The above-mentioned embodiment is only a preferred solution of the present invention, and does not limit the present invention in any form, and there are other variations and modifications under the premise of not exceeding the technical solution recorded in the claims.

Claims (10)

1. An LED driver, comprising:

the LED driving circuit comprises a PFC main circuit, a driving control circuit, an isolation circuit, a voltage regulating circuit, a frequency control driving circuit, a current regulating circuit and a resonant DC-DC circuit, wherein the input end of the PFC main circuit is used as the input end of the LED driver and is used for being connected with a power supply, the output end of the PFC main circuit is connected with the input end of the resonant DC-DC circuit, the output end of the resonant DC-DC circuit comprises a constant voltage output end and a constant current output end, the input end of the current regulating circuit is connected with the constant current output end, the output end of the current regulating circuit is connected with the frequency control driving circuit, the current regulating circuit is used for detecting the current output by the constant current output end and outputting a first feedback signal to the frequency control driving circuit, and the frequency control driving circuit outputs a first driving signal to the resonant DC-DC circuit according to the magnitude of the, the working frequency of the resonant DC-DC circuit is used for maintaining the constant current output by the constant current output end, the input end of the voltage regulating circuit is connected with the constant voltage output end, the output end of the voltage regulating circuit is connected with the drive control circuit through an isolation circuit, the voltage regulating circuit is used for detecting the voltage output by the constant voltage output end and outputting a second feedback signal to the drive control circuit through the isolation circuit, and the drive control circuit outputs a second drive signal to the PFC main circuit according to the magnitude of the second feedback signal to enable the output voltage of the PFC main circuit to be constant, so that the voltage of the constant voltage output end is constant.

2. The LED driver as claimed in claim 1, wherein the main PFC circuit comprises an inductor L, a switch tube S0, a diode D1 and a capacitor C0, one end of the inductor L is connected to a positive power supply terminal, the other end of the inductor L is connected to one end of the switch tube S0 and an anode of the diode D1, the other end of the switch tube S0 is connected to one end of the capacitor C0 and a negative power supply terminal, the other end of the capacitor C0 is connected to a cathode of the diode D1, and two ends of the capacitor C0 are connected to the resonant DC-DC circuit as an output terminal of the main PFC circuit.

3. The LED driver as claimed in claim 1, wherein the resonant DC-DC circuit further comprises a switching unit, a resonant capacitor Cr and a transformer, the transformer comprises a primary winding N1, a secondary winding M1 and a secondary winding M2, the primary winding N1 and the resonant capacitor Cr are connected in series and then connected to the switching unit, and the other two ends of the switching unit are used as input ends of the resonant DC-DC circuit; the secondary winding M1 is used as a constant voltage output end through a rectified first end rectification output end, and the secondary winding M2 is used as a constant current output end through a rectified second rectification output end.

4. The LED driver as claimed in claim 3, wherein the coupling coefficient of the secondary winding M1 to the primary winding N1 is greater than the coupling coefficient of the secondary winding M2 to the primary winding N1.

5. The LED driver of claim 3, wherein the switch unit in the resonant DC-DC circuit comprises a switch tube S1 and a switch tube S2; the resonant DC-DC circuit further includes a diode D2, a diode D3, a diode D4, a diode D5, a capacitor C1, a capacitor C2, and a resistor Rs, wherein a first end of the switching tube S1 is used as an input positive terminal of the resonant DC-DC circuit, a second end of the switching tube S1 is respectively connected to the first end of the switching tube S2 and one end of the primary winding N1, a second end of the switching tube 2 is used as an input negative terminal of the resonant DC-DC circuit and is connected to one end of the resonant capacitor Cr, the other end of the resonant capacitor Cr is connected to the other end of the primary winding N1, the secondary winding M1 and the secondary winding M2 have tap terminals, the first end of the secondary winding M1 is connected to the anode of the diode D2, the second end of the secondary winding M1 is connected to the anode of the diode D2 via the diode D3, the cathode of the diode D5 is connected to the tap terminal 1 of the secondary winding M1, two ends of the capacitor C1 are used as the constant voltage output end; a first end of the secondary winding M2 is connected to an anode of the diode D4, a second end of the secondary winding M2 is connected to an anode of the diode D4 through the diode D5, a cathode of the diode D4 is connected to a first end of the capacitor C2, a tap end of the secondary winding M2 is connected to a second end of the capacitor C2 and a first end of the resistor Rs, two ends of the capacitor C2 are used as the constant current output end, and a second end of the resistor Rs is connected to the current regulating circuit.

6. The LED driver as claimed in claim 5, wherein the voltage regulation circuit comprises an operational amplifier U1, a resistor R1, a resistor R2, a resistor R3 and a capacitor C4, wherein a negative phase input terminal of the operational amplifier U1 is connected to a first terminal of the capacitor C4, a first terminal of the resistor R1 and a first terminal of the resistor R2, the other terminal of the resistor R1 is connected to a first terminal of the capacitor C1, the other terminal of the resistor R2 is connected to a second terminal of the capacitor C1, a second terminal of the capacitor C4 is connected to an output terminal of the operational amplifier U1 via the resistor R3, and a positive phase input terminal of the operational amplifier U1 is inputted with a voltage reference signal Vref 1.

7. The LED driver as claimed in claim 1, wherein the isolation circuit comprises a photo coupler, an input terminal of the photo coupler is connected to the voltage regulating circuit, and an output terminal of the photo coupler is connected to the driving control circuit.

8. The LED driver as claimed in claim 5, wherein the current regulation circuit comprises an operational amplifier U2, a capacitor C5 and a resistor R4, wherein the negative phase input terminal of the operational amplifier U2 is connected to the first terminal of the capacitor C5 and the second terminal of the resistor Rs respectively, the second terminal of the capacitor C5 is connected to the output terminal of the operational amplifier U2 through a resistor R4, and the positive phase input terminal of the operational amplifier inputs the current reference signal Iref 1.

9. The LED driver as claimed in claim 5, wherein the frequency control driving circuit includes a resonant control chip, a voltage-controlled oscillator and a driving circuit, the voltage-controlled oscillator receives the first feedback signal from the current regulating circuit and determines the magnitudes of the frequencies of the switch tube S1 and the switch tube S2 according to the magnitude of the first feedback signal, and transmits a frequency signal to the resonant control chip, and the resonant control chip generates a driving signal according to the frequency signal by the driving circuit and outputs the driving signal to the switch tube S1 and the switch tube S2.

10. The LED driver as claimed in claim 2, wherein the driving control circuit comprises a PFC control chip, an operational amplifier U3, an operational amplifier U4 and an RS trigger A1, wherein the positive phase input terminal of the operational amplifier U3 and the negative phase input terminal of the operational amplifier U4 input the second feedback signal transmitted by the voltage regulation circuit, the negative phase input terminal of the operational amplifier U3 inputs a voltage reference signal Vref2, the output terminal of the operational amplifier U3 is connected to the S terminal of the RS trigger A1, the positive phase input terminal of the operational amplifier U4 inputs the voltage reference signal Vref3, the output terminal of the operational amplifier U4 is connected to the R terminal of the RS trigger A1, the Q terminal and the QNOT terminal of the RS trigger A1 are both connected to the PFC control chip, and the PFC control chip is connected to the switch tube S0.

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