CN-224233561-U - Switching conversion circuit

CN224233561UCN 224233561 UCN224233561 UCN 224233561UCN-224233561-U

Abstract

The utility model provides a switching conversion circuit. The switch conversion circuit comprises a primary side circuit and a secondary side circuit. The primary circuit includes a primary winding and the secondary circuit includes a first output circuit and a second output circuit. The first output circuit comprises a secondary side switching tube, a first secondary side winding coupled with the primary side winding, a sampling circuit, a comparison circuit and a trigger circuit. The sampling circuit is used for obtaining a sampling signal representing the output voltage of the first output circuit. The first input end of the comparison circuit is coupled with the sampling circuit, and the second input end of the comparison circuit is coupled with the constant voltage reference signal end. The trigger circuit is coupled with the comparison circuit, and the output end of the trigger circuit is coupled with the control end of the secondary side switching tube. The second output circuit includes a second secondary winding coupled to the primary winding. The primary side circuit is coupled to the second output circuit to obtain a feedback signal representing an output current of the second output circuit. The switching conversion circuit provided by the utility model has the advantages of higher system loop speed and better dynamic response.

Inventors

LIU BAIREN
YAN WEIWEI

Assignees

深圳市必易微电子股份有限公司

Dates

Publication Date: 20260512
Application Date: 20250528

Claims (10)

1. A switching converter circuit comprising a primary circuit and a secondary circuit, the primary circuit comprising a primary winding, the secondary circuit comprising: A first output circuit including a secondary switch tube, a first secondary winding coupled to the primary winding, a sampling circuit for obtaining a sampling signal representing the output voltage of the first output circuit, a first input terminal coupled to the sampling circuit, a second input terminal coupled to the constant voltage reference signal terminal, a trigger circuit coupled to the comparison circuit, an output terminal coupled to the control terminal of the secondary switch tube, and a trigger circuit coupled to the control terminal of the secondary switch tube A second output circuit including a second secondary winding coupled to the primary winding; the primary side circuit is coupled to the second output circuit to obtain a feedback signal representing an output current of the second output circuit.
2. The switching converter circuit of claim 1 wherein said first output circuit comprises a constant voltage output circuit comprising a secondary side switching tube and said second output circuit comprises a constant current output circuit.
3. The switching converter circuit of claim 1 wherein the sampling circuit comprises a first sampling resistor and a second sampling resistor, the first terminal of the first sampling resistor being coupled to the first terminal of the first capacitor, the first terminal of the second sampling resistor being coupled to the second terminal of the first sampling resistor, the second terminal of the second sampling resistor being coupled to the second terminal of the first capacitor, the first capacitor being an output capacitor of the first output circuit.
4. The switching converter circuit of claim 3 wherein the comparison circuit comprises a first comparator having a non-inverting input coupled to the first terminal of the second sampling resistor and an inverting input coupled to the constant voltage reference signal terminal for receiving the constant voltage reference signal.
5. The switching converter circuit of claim 1 wherein the trigger circuit comprises an RS flip-flop having a set terminal coupled to the primary side drive signal terminal for obtaining the primary side drive signal, a reset terminal coupled to the output terminal of the comparator circuit, and an output terminal coupled to the secondary side switching tube.
6. The switching converter circuit of claim 1 wherein the second output circuit comprises a transconductance amplifier circuit and a compensation capacitor, wherein a first input terminal of the transconductance amplifier circuit is coupled to the constant current reference signal, a second input terminal of the transconductance amplifier circuit is coupled to a load in the second output circuit, an output terminal of the transconductance amplifier circuit is coupled to a first terminal of the compensation capacitor, and a second terminal of the compensation capacitor is coupled to ground.
7. The switching converter circuit of claim 6 wherein the second output circuit further comprises a third sampling resistor, a first terminal of the third sampling resistor being coupled to a load in the second output circuit, a second terminal of the third sampling resistor being coupled to ground.
8. The switching converter circuit of claim 6 wherein said primary side circuit further comprises a primary side drive signal generation circuit for generating a primary side drive signal based on the compensation signal.
9. The switching converter circuit of claim 8 wherein the primary drive signal generation circuit comprises a second comparator having a first input for receiving the primary current sample signal, a second input for receiving the current reference signal, and an output coupled to the primary switching tube.
10. The switching converter circuit of claim 1 wherein the secondary side circuit further comprises a ramp signal generating circuit coupled to the comparator circuit, the ramp signal generating circuit for generating the constant voltage reference signal.

Description

Switching conversion circuit Technical Field The utility model belongs to the field of power electronics, relates to a switching conversion technology, and in particular relates to a switching conversion circuit. Background The switch power supply is widely applied due to the advantages of high efficiency, energy saving, small volume, light weight, stable output, multiple protection functions, wide input voltage range and the like. The advantages enable the switching power supply to perform well in various application scenes, and meet the requirements of modern electronic equipment on power supplies. In the application of a single-stage architecture constant-voltage constant-current LED backlight, flyback topology Flyback is a common application topology, and the secondary side of a Flyback switching circuit can be designed with two windings, wherein one winding is used for constant-voltage output, and the other winding is used for constant-current output. One prior art implementation is shown in fig. 1, where the flyback switching circuit includes a primary side circuit a and a secondary side circuit. The secondary side circuit includes a constant current output circuit b and a constant voltage output circuit c. The constant current output circuit b and the constant voltage output circuit c are controlled by COMP compensation loops. The constant voltage output circuit c adopts CV constant voltage loop control, and the output voltage of the constant voltage output circuit c or the partial pressure of the output voltage is sampled as feedback to control the primary side output energy, so that the output voltage is constant. And the constant current output circuit b adopts CC constant current loop control, and generates a secondary side compensation signal COMP_CC to control the conduction time of the secondary side switching tube Q1 by taking the sampled output current IFB as feedback and comparing with an internal constant current reference signal VREF_CC, thereby controlling the output current to be kept constant. In a single primary switching period, when the primary switching tube MOSFET is turned on, the secondary switching tube Q1 is turned on, the RAMP RAMP voltage gradually rises, after the primary switching tube MOSFET is turned off, the secondary circuit first carries out follow current through the winding of the transformer S1, energy is transmitted to the constant current output circuit b, when the RAMP RAMP voltage is higher than the secondary compensation signal COMP_CC, the secondary driving signal gate_cc becomes low, and the secondary switching tube Q1 is turned off. The secondary side circuit continuously flows through a winding of the transformer S2, energy is transmitted to the constant voltage output circuit c, the divided voltage VFB of the sampled output voltage is used as a voltage feedback signal, and the voltage feedback signal is compared with an internal constant voltage reference signal VREF_CV to generate a compensation signal COMP which is fed back to the primary side circuit, so that the energy output by the primary side circuit is regulated. The existing control mode is limited by the bandwidth difference of the outer ring and the inner ring, has relatively poor dynamic response and relatively complex control. In view of the above, there is a need to provide a new structure for solving at least some of the above problems. Disclosure of utility model The present utility model is directed to a switching converter circuit that addresses one or more of the problems of the prior art. According to one aspect of the present utility model, a switching converter circuit is disclosed, the switching converter circuit comprising a primary circuit and a secondary circuit, the primary circuit comprising a primary winding, the secondary circuit comprising: A first output circuit including a secondary switch tube, a first secondary winding coupled to the primary winding, a sampling circuit for obtaining a sampling signal representing the output voltage of the first output circuit, a first input terminal coupled to the sampling circuit, a second input terminal coupled to the constant voltage reference signal terminal, a trigger circuit coupled to the comparison circuit, an output terminal coupled to the control terminal of the secondary switch tube, and a trigger circuit coupled to the control terminal of the secondary switch tube A second output circuit including a second secondary winding coupled to the primary winding; the primary side circuit is coupled to the second output circuit to obtain a feedback signal representing an output current of the second output circuit. In one embodiment, the first output circuit comprises a constant voltage output circuit comprising a secondary side switching tube, and the second output circuit comprises a constant current output circuit. In an embodiment, the sampling circuit includes a first sampling resistor and a second sampling resistor, the first en