CN-122001203-A - Switching power supply starting control circuit and switching power supply

CN122001203ACN 122001203 ACN122001203 ACN 122001203ACN-122001203-A

Abstract

The application discloses a switching power supply starting control circuit and a switching power supply, wherein the switching power supply starting control circuit comprises an open-loop delay module and a delay interruption module which are connected with each other before acting on open-loop protection response of the switching power supply, the open-loop delay module is connected with a voltage feedback pin of a power supply control chip in the switching power supply, the open-loop delay module is configured to enable the power supply control chip to enter a closed-loop control state when the output voltage of the switching power supply is larger than a first preset voltage threshold value, and the delay interruption module is configured to interrupt control of the voltage feedback pin voltage by the open-loop delay module when the output voltage of the switching power supply is larger than a second preset voltage threshold value so that the power supply control chip exits the closed-loop control state, wherein the second preset voltage threshold value is larger than the first preset voltage threshold value. The problem of power-on failure of the switching power supply caused by the fact that the response time of the open-loop protection of the chip is short can be solved.

Inventors

LI ANG
LI WEN

Assignees

普联技术有限公司

Dates

Publication Date: 20260508
Application Date: 20260316

Claims (10)

1. The switching power supply starting control circuit is characterized by comprising an open-loop delay module and a delay interruption module which are connected with each other before an open-loop protection response of a switching power supply is acted; the open loop time delay module is connected with a voltage feedback pin of a power supply control chip in the switching power supply, and is configured to send a first control signal to the voltage feedback pin when the output voltage of the switching power supply is greater than a first preset voltage threshold value so that the power supply control chip enters a closed loop control state; The delay interruption module is configured to send a second control signal to the voltage feedback pin when the output voltage of the switching power supply is greater than a second preset voltage threshold value, and interrupt the control of the open-loop delay module on the voltage feedback pin so that the power supply control chip exits from a closed-loop control state; Wherein the second preset voltage threshold is greater than the first preset voltage threshold.
2. The switching power supply start-up control circuit of claim 1, wherein the open loop delay module comprises an isolation coupler and a delay control unit; one end of a receiving side device of the isolation coupler is connected with the voltage feedback pin, the other end of the receiving side device is grounded, a transmitting side device of the isolation coupler is connected with the delay control unit in series, and the delay interruption module is connected with the transmitting side device in parallel; When the output voltage of the switching power supply is greater than a first preset voltage threshold, the delay control unit is configured to drive the transmitting side device to be conducted so that the receiving side device is conducted in response to the conducting action of the transmitting side device, and a first control signal is sent to the voltage feedback pin so that the power supply control chip enters a closed-loop control state; The delay interrupt module is configured to be conducted when the output voltage of the switching power supply is larger than a second preset voltage threshold value so as to bypass the transmitting side device, enable the receiving side device not to respond to the transmitting side device any more, and send a second control signal to the voltage feedback pin so that the power supply control chip exits from a closed-loop control state.
3. The switching power supply start control circuit according to claim 2, wherein the delay control unit includes a delay voltage detection sub-circuit and a delay control sub-circuit which are connected to each other, the delay voltage detection sub-circuit and the delay control sub-circuit are respectively connected to an output terminal of the switching power supply, and the delay control sub-circuit is further connected to the transmitting side device; The delay voltage detection subcircuit is configured to output a delay conduction signal to the delay control subcircuit when the output voltage of the switching power supply is greater than a first preset voltage threshold; The delay control subcircuit is configured to conduct a path between an output end of the switching power supply and the transmitting side device when the delay conducting signal is received, so that the output voltage of the switching power supply supplies power to the transmitting side device and conducts the transmitting side device.
4. A switching power supply start-up control circuit according to claim 3, wherein the delay control sub-circuit comprises a first transistor, and the delay voltage detection sub-circuit comprises a second transistor and a first zener diode; One non-control end of the first transistor is connected with one end of the transmitting side device, the other non-control end of the first transistor is connected with the output end of the switching power supply, the other end of the transmitting side device is grounded, the control end of the first transistor is connected with one non-control end of the second transistor, the other non-control end of the second transistor is grounded, the control end of the second transistor is connected with the anode of the first zener diode, and the cathode of the first zener diode is connected with the output end of the switching power supply.
5. The switching power supply start-up control circuit according to claim 1, wherein the delay interrupt module comprises an interrupt voltage detection sub-circuit and an interrupt control sub-circuit which are connected with each other, the interrupt voltage detection sub-circuit is connected with an output end of the switching power supply, and the interrupt control sub-circuit is connected with the open loop delay module; The interrupt voltage detection sub-circuit is configured to output a delay interrupt signal to the interrupt control sub-circuit when the output voltage of the switching power supply is greater than a second preset voltage threshold; The interrupt control sub-circuit is configured to be conducted after receiving the delay interrupt signal, and sends a second control signal to the voltage feedback pin, and the open-loop delay module interrupts the control of the voltage feedback pin, so that the power supply control chip exits from a closed-loop control state.
6. The switching power supply start-up control circuit of claim 5, wherein the interrupt voltage detection subcircuit includes a second zener diode, and wherein the interrupt control subcircuit includes a third transistor; The two non-control ends of the third transistor are respectively connected with the open-loop delay module, the control end of the third transistor is connected with the anode of the second zener diode, and the cathode of the second zener diode is connected with the output end of the switching power supply.
7. The switching power supply start-up control circuit according to claim 1, further comprising an additional freewheel module, wherein the switching power supply includes a closed-loop control circuit including a loop control isolation coupler including a loop receiving side device and a loop transmitting side device, one end of the loop receiving side device being connected to a voltage feedback pin of the power supply control chip, the other end of the loop receiving side device being grounded, one end of the loop transmitting side device being connected to an output end of the switching power supply, the other end of the loop transmitting side device being connected to the additional freewheel module; The additional freewheel module is configured to drive the loop transmitting side device to conduct when the switching power supply output voltage is larger than a third preset voltage threshold value, so that the loop receiving side device is conducted in response to the conducting action of the loop transmitting side device, and a first control signal is sent to the voltage feedback pin, so that the power supply control chip enters a closed-loop control state.
8. The switching power supply start-up control circuit according to claim 7, wherein the additional freewheel module includes a freewheel control sub-circuit and an on-off control sub-circuit connected to each other, the freewheel control sub-circuit being connected in series with the loop transmitting side device, the on-off control sub-circuit being connected to an output terminal of the switching power supply; The on-off control sub-circuit is configured to output a follow current conduction signal to the follow current control sub-circuit when the output voltage of the switching power supply is greater than the third preset voltage threshold; The follow current control sub-circuit is configured to conduct a path between the loop transmitting side device and the output end of the switching power supply after receiving the follow current conducting signal, so that the loop transmitting side device is conducted under the action of the output voltage of the switching power supply.
9. The switching power supply start-up control circuit of claim 8, wherein the freewheel control subcircuit includes a fourth transistor, and the on-off control subcircuit includes a third zener diode; one non-control end of the fourth transistor is connected with the loop transmitting side device, the other non-control end of the fourth transistor is grounded, the control end of the fourth transistor is connected with the anode of the third zener diode, and the cathode of the third zener diode is connected with the output end of the switching power supply.
10. A switching power supply comprising the switching power supply start-up control circuit of any one of claims 1 to 9.

Description

Switching power supply starting control circuit and switching power supply Technical Field The application relates to the technical field of power supplies, in particular to a switching power supply starting control circuit and a switching power supply. Background In order to improve the reliability of the switching power supply, a power supply control chip in the switching power supply is internally provided with various protection logics, such as overcurrent protection, overvoltage protection, open loop protection and the like, wherein the open loop protection is realized in a way that the voltage feedback pin potential of the power supply control chip is not pulled down within a period of time (for example, 60 ms) after power supply is established, and the power supply control chip judges that the switching power supply enters a fault state and stops working, so that the switching power supply cannot be normally electrified due to the open loop protection. The conventional solution to the problem is to adjust the loop response speed and accelerate the establishment of output voltage, so that the voltage feedback pin potential of the power supply control chip is pulled down early. However, the scheme for modifying the loop has great influence on the overall performance of the switching power supply (such as ripple, dynamic load and the like), increases the debugging difficulty of the whole power supply, and solves the problem of power supply power failure by the method when other performances of the power supply are considered. Therefore, a solution to the problem of power failure caused by a short response time of the open-loop protection of the chip of the switching power supply is needed without affecting the overall performance of the switching power supply. Disclosure of Invention In view of the above-mentioned drawbacks of the prior art, the present application aims to provide a switching power supply start control circuit and a switching power supply, so as to solve the problem of power failure caused by too short response time of open loop protection of a chip of the switching power supply, and overcome the defect that the existing solution has a larger influence on the overall performance of the switching power supply. The first aspect of the embodiment of the application provides a switching power supply starting control circuit, which is applied to the open loop protection response of a switching power supply and comprises an open loop delay module and a delay interruption module which are connected with each other; the open loop time delay module is connected with a voltage feedback pin of a power supply control chip in the switching power supply, and is configured to send a first control signal to the voltage feedback pin when the output voltage of the switching power supply is greater than a first preset voltage threshold value so that the power supply control chip enters a closed loop control state; The delay interruption module is configured to send a second control signal to the voltage feedback pin when the output voltage of the switching power supply is greater than a second preset voltage threshold value, and interrupt the control of the open-loop delay module on the voltage feedback pin so that the power supply control chip exits from a closed-loop control state; Wherein the second preset voltage threshold is greater than the first preset voltage threshold. In some embodiments of the present application, the open loop delay module includes an isolation coupler and a delay control unit; one end of a receiving side device of the isolation coupler is connected with the voltage feedback pin, the other end of the receiving side device is grounded, a transmitting side device of the isolation coupler is connected with the delay control unit in series, and the delay interruption module is connected with the transmitting side device in parallel; When the output voltage of the switching power supply is greater than a first preset voltage threshold, the delay control unit is configured to drive the transmitting side device to be conducted so that the receiving side device is conducted in response to the conducting action of the transmitting side device, and a first control signal is sent to the voltage feedback pin so that the power supply control chip enters a closed-loop control state; The delay interrupt module is configured to be conducted when the output voltage of the switching power supply is larger than a second preset voltage threshold value so as to bypass the transmitting side device, enable the receiving side device not to respond to the transmitting side device any more, and send a second control signal to the voltage feedback pin so that the power supply control chip exits from a closed-loop control state. In some embodiments of the present application, the delay control unit includes a delay voltage detection sub-circuit and a delay control sub-circuit that are connected to each o