An overcurrent protection circuit suitable for dual-channel unbalanced load output

Abstract

This invention discloses an overcurrent protection circuit suitable for dual-channel unbalanced load output, comprising a DC / DC converter unit. The DC / DC converter unit includes a single-ended forward dual-output circuit implemented via a transformer T1. The single-ended forward dual-output circuit includes a main output circuit and an auxiliary output circuit, each connected in series with inductors L1 and L2, respectively. The overcurrent protection circuit includes a main acquisition and operational amplifier circuit, an auxiliary acquisition and operational amplifier circuit, and a feedback control circuit. The input terminals of the main and auxiliary acquisition and operational amplifier circuits are connected to their respective output terminals. The feedback control circuit connects the output terminals of the main and auxiliary acquisition and operational amplifier circuits in parallel to a PWM controller after diode isolation. This invention solves the problem of independent current sampling for large and small output currents, and achieves accurate overcurrent protection for dual-channel unbalanced loads through parallel feedback of independent operational amplifier circuits.

Description

Technical Field

[0001] This invention relates to the field of overcurrent protection technology for switching power supplies, and specifically to an overcurrent protection circuit suitable for dual-path unbalanced load output. Background Technology

[0002] As a crucial power supply device for electronic products, switching power supplies, besides meeting electrical performance requirements, must also prioritize their own protection. The overcurrent protection circuit's function is to promptly adjust the PWM duty cycle and control the output voltage of the switching power supply when an overcurrent occurs on the output side, protecting itself and the output-side equipment from burnout. Existing switching power supply overcurrent protection methods often involve sampling and monitoring the primary current to indirectly monitor the current of each output channel. While this method is simple in structure, the overcurrent protection point is significantly affected by input voltage variations. Furthermore, for dual or multiple output power supplies with significantly different load currents, it is difficult to achieve precise overcurrent protection for each channel. Summary of the Invention

[0003] The purpose of this invention is to provide an overcurrent protection circuit suitable for dual-channel unbalanced load output, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] An overcurrent protection circuit suitable for dual-channel unbalanced load output includes a DC / DC converter unit. The DC / DC converter unit includes a single-ended forward dual-channel output circuit implemented through a transformer T1. The single-ended forward dual-channel output circuit includes a main output circuit and an auxiliary output circuit connected in series with inductors L1 and L2, respectively. The overcurrent protection circuit includes a main acquisition and operational amplifier circuit, an auxiliary acquisition and operational amplifier circuit, and a feedback control circuit. The input terminals of the main acquisition and operational amplifier circuit and the auxiliary acquisition and operational amplifier circuit are respectively connected to the output terminals of the main output circuit and the auxiliary output circuit. The feedback control circuit connects the output terminals of the main acquisition and operational amplifier circuit and the auxiliary acquisition and operational amplifier circuit in parallel to a PWM controller after isolation by diodes.

[0006] As a further aspect of the present invention: the transformer T1 includes a primary winding Np and two secondary windings Ns1 and Ns2, and the winding structure of the primary winding and the secondary winding of the transformer T1 are the same.

[0007] As a further aspect of the present invention: the main path acquisition and operational amplifier circuit includes a main path current sampling circuit and a main path operational amplifier circuit, wherein the output terminal of the main path current sampling circuit is connected to the input terminal of the main path operational amplifier circuit; the auxiliary path acquisition and operational amplifier circuit includes an auxiliary path current sampling circuit and an auxiliary path operational amplifier circuit, wherein the output terminal of the auxiliary path current sampling circuit is connected to the input terminal of the auxiliary path operational amplifier circuit.

[0008] As a further aspect of the present invention: the feedback control circuit connects the output terminals of the main operational amplifier circuit and the auxiliary operational amplifier circuit in parallel to the PWM controller after isolation by diodes.

[0009] As a further embodiment of the present invention: the main current sampling circuit includes a current transformer L3, a diode D5, resistors R3, R4, and R5, and a capacitor C3. The current transformer L3 is a through-type transformer. One end of the current transformer L3 in the input direction is connected to the anode of the diode D5, and one end of the current transformer L3 in the output direction is connected to the output ground. One end of the resistor R4 is connected to the cathode of the diode D5, and the other end is connected to the output ground. One end of the resistor R5 is connected to the anode of the diode D5, and the other end is connected to the output ground. One end of the capacitor C3 is connected to the output ground, and the other end is connected to the cathode of the diode D5 after passing through the resistor R3.

[0010] As a further embodiment of the present invention: the main operational amplifier circuit includes an operational amplifier N1, a Zener diode D6, resistors R6, R7, R8, R9, and R10, and a capacitor C4. The anode of the Zener diode D6 is grounded, and its cathode is connected to the supply voltage VCC of the operational amplifier N1 via resistor R7, and then connected to the non-inverting input terminal of the operational amplifier N1 after being divided by resistors R8 and R9. The inverting input terminal of the operational amplifier N1 is connected to R3 and C3 via resistor R10. The inverting input terminal of the operational amplifier N1 is connected to its output terminal via a series resistor R6 and capacitor C4.

[0011] As a further embodiment of the present invention: the auxiliary operational amplifier circuit includes an operational amplifier N2, a Zener diode D7, resistors R13, R14, R15, and capacitor C5. The cathode of the Zener diode D7 is connected to the non-inverting input terminal of the operational amplifier N2 after being divided by resistors R13 and R14. The inverting input terminal of the operational amplifier N2 is connected to its output terminal through a series resistor R15 and capacitor C5.

[0012] As a further aspect of the present invention: the auxiliary current sampling circuit includes a sampling resistor Rs, resistors R11, R12, and R16. One end of the resistor Rs is connected to one end of the inductor L2 and is connected to the inverting input terminal of the operational amplifier N2 through resistor R16. The other end of the resistor Rs is connected to the output ground. The anode of the Zener diode D7 is connected to the output ground, and its cathode is connected to the supply voltage VCC of the operational amplifier N2 through resistor R12 and is connected to the inverting input terminal of the operational amplifier N2 through resistor R11.

[0013] As a further aspect of the present invention: the feedback control circuit includes diodes D8 and D9, the cathode of diode D8 is connected to the output terminal of amplifier N1, the cathode of diode D9 is connected to the output terminal of amplifier N2, and the anodes of diodes D8 and D9 are connected in parallel and fed back to the PWM controller.

[0014] Compared with existing technologies, the advantages of this invention are as follows: The overcurrent protection circuit for dual-path unbalanced load output described in this invention utilizes the current transformer in the main current sampling circuit and the sampling resistor in the auxiliary current sampling circuit to employ different sampling circuits for the main power supply circuits with large and small output currents. This not only enables accurate sampling but also reduces power loss. The operational amplifiers of the main and auxiliary circuits are connected in parallel to compare and calculate the sampled output current signals. After isolation by diodes in the feedback control circuit, the signals are fed back to the PWM controller. This ensures that if an overcurrent occurs in any of the circuits, the circuit enters an overcurrent protection state. Once the overcurrent state is resolved, the circuit automatically returns to normal operation. This design is highly suitable for overcurrent protection of dual-path unbalanced load output circuits. Attached Figure Description

[0015] Figure 1 This is the circuit schematic diagram of the present invention.

[0016] In the diagram: 1-DC / DC converter unit, 2-main acquisition and operational amplifier circuit, 3-auxiliary acquisition and operational amplifier circuit, 4-feedback control circuit. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figure 1In this embodiment of the invention, an overcurrent protection circuit suitable for dual-path unbalanced load output includes a DC / DC converter unit 1. The DC / DC converter unit 1 includes a single-ended forward dual-path output circuit implemented through a transformer T1. The single-ended forward dual-path output circuit includes a main output circuit and an auxiliary output circuit connected in series with inductors L1 and L2, respectively. The overcurrent protection circuit includes a main acquisition and operational amplifier circuit 2, an auxiliary acquisition and operational amplifier circuit 3, and a feedback control circuit 4. The input terminals of the main acquisition and operational amplifier circuit 2 and the auxiliary acquisition and operational amplifier circuit 3 are respectively connected to the output terminals of the main output circuit and the auxiliary output circuit. The feedback control circuit 4 connects the output terminals of the main acquisition and operational amplifier circuit 2 and the auxiliary acquisition and operational amplifier circuit 3 in parallel to a PWM controller after isolation by diodes. The transformer T1 includes a primary winding Np and two secondary windings Ns1 and Ns2, and the winding structure of the primary winding and the secondary winding of the transformer T1 are identical. The main circuit acquisition and operational amplifier circuit 2 includes a main circuit current sampling circuit and a main circuit operational amplifier circuit, with the output terminal of the main circuit current sampling circuit connected to the input terminal of the main circuit operational amplifier circuit; the auxiliary circuit acquisition and operational amplifier circuit 3 includes an auxiliary circuit current sampling circuit and an auxiliary circuit operational amplifier circuit, with the output terminal of the auxiliary circuit current sampling circuit connected to the input terminal of the auxiliary circuit operational amplifier circuit.

[0019] The main current sampling circuit includes a current transformer L3, a diode D5, resistors R3, R4, and R5, and a capacitor C3. The current transformer L3 is a through-type transformer. One end of the current transformer L3 in the input direction is connected to the anode of diode D5, and the other end of the current transformer L3 in the output direction is connected to the output ground. One end of resistor R4 is connected to the cathode of diode D5, and the other end is connected to the output ground. One end of resistor R5 is connected to the anode of diode D5, and the other end is connected to the output ground. One end of capacitor C3 is connected to the output ground, and the other end passes through resistor R3 and then to the diode. The cathode of D5 is connected; the main operational amplifier circuit includes operational amplifier N1, Zener diode D6, resistors R6, R7, R8, R9, and R10, and capacitor C4. The anode of Zener diode D6 is grounded, and its cathode is connected to the supply voltage VCC of operational amplifier N1 via resistor R7, and then connected to the non-inverting input terminal of operational amplifier N1 after voltage division by resistors R8 and R9. The inverting input terminal of operational amplifier N1 is connected to R3 and C3 via resistor R10. The inverting input terminal of operational amplifier N1 is connected to its output terminal via resistor R6 and capacitor C4 connected in series.

[0020] The auxiliary operational amplifier circuit includes operational amplifier N2, Zener diode D7, resistors R13, R14, R15, and capacitor C5. The cathode of Zener diode D7 is connected to the non-inverting input of operational amplifier N2 after being divided by resistors R13 and R14. The inverting input of operational amplifier N2 is connected to its output via resistor R15 and capacitor C5 in series. The auxiliary current sampling circuit includes sampling resistor Rs, resistors R11, R12, and R16. One end of resistor Rs is connected to one end of inductor L2 and then to the inverting input of operational amplifier N2 via resistor R16. The other end of Rs is connected to the output ground. The anode of Zener diode D7 is connected to the output ground, and its cathode is connected to the supply voltage VCC of operational amplifier N2 via resistor R12 and then to the inverting input of operational amplifier N2 via resistor R11.

[0021] The feedback control circuit includes diodes D8 and D9. The cathode of diode D8 is connected to the output terminal of amplifier N1, and the cathode of diode D9 is connected to the output terminal of amplifier N2. The anodes of diodes D8 and D9 are connected in parallel and fed back to the PWM controller.

[0022] In cases where the main output circuit current is large, sampling with a sampling resistor would result in excessive power consumption across the resistor, reducing the overall efficiency of the switching power supply. Therefore, this invention employs a feedthrough current transformer L3 to sample the main output circuit current, converting the large current in the output AC circuit into a smaller current of a certain proportion. This smaller current is then converted into a voltage signal by diode D5 and resistor R4. After rectification and filtering by resistor R3 and capacitor C3, it is converted into a DC voltage signal and connected to the inverting input of operational amplifier N1. To prevent the magnetic core of current transformer L3 from saturating, resistor R5 is used for magnetic reset. Zener diode D6, after voltage division by resistors R8 and R9, serves as the reference voltage for main circuit overcurrent protection and is connected to the non-inverting input of operational amplifier N1. Resistor R6 and capacitor C4 form a compensation network to maintain the stability of operational amplifier N1. Under normal load conditions on the main circuit, the voltage at the inverting input terminal of operational amplifier N1 is less than that at the non-inverting input terminal, operational amplifier N1 outputs a high level, diode D8 is cut off, and the circuit operates normally. When the current of the main circuit output is overloaded, the voltage at the inverting input terminal of operational amplifier N1 is greater than that at the non-inverting input terminal, operational amplifier N1 outputs a low level, diode D8 is turned on, and the circuit enters overcurrent protection mode.

[0023] When the output current of the auxiliary output circuit is relatively small, a sampling resistor is used to sample the current of the auxiliary output circuit. This circuit has a simple structure and is easy to design. Therefore, in this invention, a resistor Rs is used to sample the current of the auxiliary output circuit. This sampled current, combined with the DC bias voltage formed by the Zener diode D7 and resistors R16 and R11, is then connected to the inverting input of operational amplifier N2. The voltage of diode D7, after being divided by resistors R13 and R14, serves as the reference voltage for the main circuit overcurrent protection and is connected to the non-inverting input of operational amplifier N2. Resistor R15 and capacitor C5 form a compensation network to maintain the stability of operational amplifier N2. Under normal operating conditions, the voltage at the inverting input of operational amplifier N2 is less than the voltage at the non-inverting input, operational amplifier N2 outputs a high level, diode D9 is cut off, and the circuit operates normally. When the auxiliary output current is overloaded, the voltage at the inverting input of operational amplifier N2 is greater than the voltage at the non-inverting input, operational amplifier N2 outputs a low level, diode D9 conducts, and the circuit enters the overcurrent protection state.

[0024] The operational amplifier circuits of the main and auxiliary circuits are connected in parallel to the PWM controller after isolation by diodes D8 and D9. This diode isolation ensures that the two protection circuits are isolated from each other and do not affect each other. When both circuits are operating under normal load, operational amplifiers N1 and N2 both output high levels, and the output signals are cut off by diodes D8 and D9, allowing the circuit to operate normally. When an overload occurs in either circuit, its operational amplifier outputs a low level, the corresponding diode conducts, and the output error signal is fed back to the PWM controller, achieving overcurrent protection. Once the overload is relieved, the circuit automatically returns to normal operating conditions.

[0025] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0026] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. An overcurrent protection circuit suitable for dual-path unbalanced load output, comprising a DC / DC converter unit (1), wherein the DC / DC converter unit (1) comprises a single-ended forward dual-path output circuit implemented by a transformer T1, wherein the single-ended forward dual-path output circuit comprises a main output circuit and an auxiliary output circuit respectively connected in series with inductors L1 and L2, characterized in that, The overcurrent protection circuit includes a main circuit acquisition and operational amplifier circuit (2), an auxiliary circuit acquisition and operational amplifier circuit (3), and a feedback control circuit (4). The input terminals of the main circuit acquisition and operational amplifier circuit (2) and the auxiliary circuit acquisition and operational amplifier circuit (3) are respectively connected to the output terminals of the main circuit output circuit and the auxiliary circuit output circuit. The feedback control circuit (4) connects the output terminals of the main circuit acquisition and operational amplifier circuit (2) and the auxiliary circuit acquisition and operational amplifier circuit (3) in parallel to the PWM controller after isolation by diodes. The transformer T1 includes a primary winding Np and two secondary windings Ns1 and Ns2, and the winding structure of the primary winding and the secondary winding of the transformer T1 are the same. The main circuit acquisition and operational amplifier circuit (2) includes a main circuit current sampling circuit and a main circuit operational amplifier circuit. The output terminal of the auxiliary current sampling circuit is connected to the input terminal of the main operational amplifier circuit; the auxiliary current sampling circuit (3) includes an auxiliary current sampling circuit and an auxiliary operational amplifier circuit, the output terminal of the auxiliary current sampling circuit is connected to the input terminal of the auxiliary operational amplifier circuit; the main current sampling circuit includes a current transformer L3, a diode D5, resistors R3, R4, R5, and a capacitor C3, the current transformer L3 is a through-hole type, one end of the current transformer L3 in the input direction is connected to the anode of the diode D5, one end of the current transformer L3 in the output direction is connected to the output ground, one end of the resistor R4 is connected to the cathode of the diode D5, and the other end is connected to the output ground, one end of the resistor R5 is connected to the anode of the diode D5, and the other end is connected to the output ground, one end of the capacitor C3 is connected to the output ground, and the other end is connected to the cathode of the diode D5 after passing through the resistor R3; The main operational amplifier circuit includes operational amplifier N1, Zener diode D6, resistors R6, R7, R8, R9, and R10, and capacitor C4. The anode of Zener diode D6 is grounded, and its cathode is connected to the supply voltage VCC of operational amplifier N1 via resistor R7, and then connected to the non-inverting input terminal of operational amplifier N1 after voltage division by resistors R8 and R9. The inverting input terminal of operational amplifier N1 is connected to R3 and C3 via resistor R10. The inverting input terminal of operational amplifier N1 is connected to its output terminal via a series resistor R6 and capacitor C4. The auxiliary operational amplifier circuit includes operational amplifier N2, Zener diode D7, resistors R13, R14, and R15, and capacitor C5. The cathode of the Zener diode D7 is connected to the non-inverting input of operational amplifier N2 after being divided by resistors R13 and R14. The inverting input of operational amplifier N2 is connected to its output via a series resistor R15 and capacitor C5. The auxiliary current sampling circuit includes a sampling resistor Rs, resistors R11, R12, and R16. One end of resistor Rs is connected to one end of inductor L2 and is connected to the inverting input of operational amplifier N2 via resistor R16. The other end of Rs is connected to the output ground. The anode of the Zener diode D7 is connected to the output ground, and its cathode is connected to the supply voltage VCC of operational amplifier N2 via resistor R12 and to the inverting input of operational amplifier N2 via resistor R11.

2. The overcurrent protection circuit for dual-channel unbalanced load output according to claim 1, characterized in that, The feedback control circuit (4) connects the output terminals of the main operational amplifier circuit and the auxiliary operational amplifier circuit in parallel to the PWM controller after isolation by diodes.

3. An overcurrent protection circuit suitable for dual-channel unbalanced load output according to any one of claims 1-2, characterized in that, The feedback control circuit includes diodes D8 and D9. The cathode of diode D8 is connected to the output terminal of amplifier N1, and the cathode of diode D9 is connected to the output terminal of amplifier N2. The anodes of diodes D8 and D9 are connected in parallel and fed back to the PWM controller.

Images