Parallel superposition output circuit of step-down switching power supply

Abstract

The invention discloses a step-down switching power supply parallel superposition output circuit. A voltage terminal; the positive electrode of the light-emitting end of the optical coupler OP1 receives a starting signal, the negative electrode of the optical coupler OP1 is grounded, the emitting electrode of the optical coupler OP1 is connected with the voltage end, and the collecting electrode of the optical coupler OP1 is connected with the control end of the switching tube Q3; one end of the conduction end of the switching tube Q3 is connected with the switching power supply circuit, and the other end of the conduction end of the switching tube Q3 is connected with the control end of the switching tube Q4; one end of the conduction end of the switching tube Q4 is connected with the voltage end, and the other end of the conduction end of the switching tube Q4 is connected with the input end. According to the invention, multiple groups of switching power supplies are superposed, and conduction control is carried out by using the switching tube Q4, so that the BUCK circuit can work safely, and output currents of all paths can be superposed to supply power to a load.

Description

Technical Field

[0001] This invention relates to the field of LED power supplies, and more particularly to a parallel superimposed output circuit for a step-down switching power supply. Background Technology

[0002] Due to the demands of the LED driver power supply industry, a single power supply may contain two or more BUCK constant current power supplies. Their outputs share a common positive terminal (V+ in the diagram), with 1V- marked as the first negative output and 2V- marked as the second negative output. The typical usage scenario is that V+ and 1V-, or V+ and 2V-, serve as independent outputs to two sets of LED lights. Before this circuit was added, connecting 1V- and 2V- together as a single output could potentially cause mutual interference, leading to the failure of BUCK switching devices (such as MOSFETs) or output instability. Summary of the Invention

[0003] To address the aforementioned issues, this technical solution provides a step-down switching power supply parallel superposition output circuit.

[0004] To achieve the above objectives, the technical solution is as follows: A step-down switching power supply parallel superposition output circuit includes: Voltage terminal; Optocoupler OP1, the positive terminal of the light-emitting terminal of the optocoupler OP1 receives the start signal, the negative terminal is grounded, the emitter is connected to the voltage terminal, and the collector is connected to the control terminal of the switching transistor Q3; One end of the conducting terminal of the switching transistor Q3 is connected to the switching power supply circuit, and the other end of the conducting terminal is connected to the control terminal of the switching transistor Q4. One end of the conducting terminal of the switching transistor Q4 is connected to the voltage terminal, and the other end is connected to the input terminal.

[0005] In some embodiments, the switching power supply circuit includes; Transformer T22C, one end of which is connected to the voltage terminal, and the other end of which is connected to diode D4; The diode D4 is connected to the voltage terminal through the electrolytic capacitor EC4; The diode D4 is also connected to a power supply unit U10, and the output terminal of the power supply unit U10 is connected to the switching transistor Q3.

[0006] In some embodiments, a resistor R20 is connected between the power supply unit U10 and the control terminal of the switching transistor Q3.

[0007] In some embodiments, a resistor R21 is connected between the optocoupler OP1 and the switching transistor Q3.

[0008] In some embodiments, the positive terminal of the light-emitting end of the optocoupler OP1 is connected to a resistor R22.

[0009] In some embodiments, the switching transistors Q3 and Q4 are transistors or MOSFETs.

[0010] In some embodiments, the switching transistor Q4 is a diode.

[0011] The beneficial effects of this application are: This application uses multiple sets of switching power supplies superimposed and utilizes the conduction control of the switching transistor Q4 to ensure the safe operation of the BUCK circuit, and the output current of each circuit will be superimposed to supply power to the load. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0013] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention; Figure 2 This is a schematic diagram of the overall circuit structure of an embodiment of the present invention. Detailed Implementation

[0014] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0015] Please refer to Figure 1-2 As shown, a parallel superimposed output circuit for a step-down switching power supply includes: Voltage terminal; Optocoupler OP1, the positive terminal of the light-emitting terminal of the optocoupler OP1 receives the start signal, the negative terminal is grounded, the emitter is connected to the voltage terminal, and the collector is connected to the control terminal of the switching transistor Q3; One end of the conducting terminal of the switching transistor Q3 is connected to the switching power supply circuit, and the other end of the conducting terminal is connected to the control terminal of the switching transistor Q4. One end of the conducting terminal of the switching transistor Q4 is connected to the voltage terminal, and the other end is connected to the input terminal.

[0016] Specifically, the switching power supply circuit includes; Transformer T22C, one end of which is connected to the voltage terminal, and the other end of which is connected to diode D4; The diode D4 is connected to the voltage terminal through the electrolytic capacitor EC4; The diode D4 is also connected to a power supply unit U10, and the output terminal of the power supply unit U10 is connected to the switching transistor Q3.

[0017] Specifically, a resistor R20 is connected between the power supply unit U10 and the control terminal of the switching transistor Q3.

[0018] Specifically, a resistor R21 is connected between the optocoupler OP1 and the switching transistor Q3.

[0019] Specifically, the positive terminal of the light-emitting end of the optocoupler OP1 is connected to a resistor R22.

[0020] Specifically, the switching transistors Q3 and Q4 are either transistors or MOSFETs.

[0021] Specifically, the switching transistor Q4 is a diode.

[0022] This application connects a MOSFET Q4 in series with the negative output terminal of the BUCK circuit, along with power supply components T22C, D4, EC4, and U10; control components Q3, R20, R21, OP1, and R22; and MCU_IO, which controls the high and low levels of the microcontroller. When two or more channels operate independently, the MCU_IO outputs a high level, and pins 1 and 2 of the optocoupler diodes light up, while pins 4 and 3 of the transistor conduct. After Q3 receives base current, its emitter-collector junction conducts. The voltage across EC4, regulated by the three-terminal U10, is applied between the gate and source of MOSFET Q4 to obtain the VGS drive voltage. The drain and source then exhibit low resistance, and Q4 provides only a low-loss path under this condition. When two or more channels operate in parallel, the MCU_IO output is low, and pins 1 and 2 of the optocoupler diode do not emit light. Pins 4 and 3 of the transistor are cut off. The emitter-collector junction of Q3 is also cut off. There is no VGS drive voltage between the gate and source of MOSFET Q4, and the drain and source present high resistance. The current loop will flow through the body diode from the source to the drain of the MOSFET. The external interference of the BUCK switching device (such as the MOSFET) is shielded by the body diode from the source to the drain of the MOSFET, and the BUCK circuit will operate safely. The output current of each channel will be superimposed to power the load. If the loss when the BUCK circuit operates independently is not considered, a diode D5 can be directly connected in series to replace MOSFET Q4 at the negative output terminal.

[0023] The above description is only a preferred embodiment of this application and is not intended to limit the scope of implementation of this application. Any other embodiments whose principles and basic structures are the same as or similar to those of this application are within the protection scope of this application.

Claims

1. A parallel superimposed output circuit for a step-down switching power supply, characterized in that, include; Voltage terminal; Optocoupler OP1, the positive terminal of the light-emitting terminal of the optocoupler OP1 receives the start signal, the negative terminal is grounded, the emitter is connected to the voltage terminal, and the collector is connected to the control terminal of the switching transistor Q3; One end of the conducting terminal of the switching transistor Q3 is connected to the switching power supply circuit, and the other end of the conducting terminal is connected to the control terminal of the switching transistor Q4. One end of the conducting terminal of the switching transistor Q4 is connected to the voltage terminal, and the other end is connected to the input terminal.

2. The parallel superimposed output circuit of a step-down switching power supply according to claim 1, characterized in that: The switching power supply circuit includes: Transformer T22C, one end of which is connected to the voltage terminal, and the other end of which is connected to diode D4; The diode D4 is connected to the voltage terminal through the electrolytic capacitor EC4; The diode D4 is also connected to a power supply unit U10, and the output terminal of the power supply unit U10 is connected to the switching transistor Q3.

3. The parallel superimposed output circuit of a step-down switching power supply according to claim 2, characterized in that: A resistor R20 is connected between the power supply unit U10 and the control terminal of the switching transistor Q3.

4. The parallel superimposed output circuit of a step-down switching power supply according to claim 1, characterized in that: A resistor R21 is connected between the optocoupler OP1 and the switching transistor Q3.

5. The parallel superimposed output circuit of a step-down switching power supply according to claim 1, characterized in that: The positive terminal of the light-emitting end of the optocoupler OP1 is connected to a resistor R22.

6. The parallel superimposed output circuit of a step-down switching power supply according to claim 1, characterized in that: The switching transistors Q3 and Q4 are either transistors or MOSFETs.

7. The parallel superimposed output circuit of a step-down switching power supply according to claim 1, characterized in that: The switching transistor Q4 is a diode.

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