CN-115425850-B - Flyback switching power supply absorption circuit, transformer leakage inductance absorption method and chip

CN115425850BCN 115425850 BCN115425850 BCN 115425850BCN-115425850-B

Abstract

The invention relates to the technical field of electricity, in particular to a flyback switching power supply absorption circuit, a transformer leakage inductance absorption method and a chip, comprising a transformer, a first-side coil NP and a second-side coil NS, wherein the transformer comprises a primary-side coil NP and a secondary-side coil NS; the primary side sub-circuit comprises an energy storage branch connected with the primary side coil NP and an absorption branch connected with the primary side coil NP, when the energy storage branch is conducted, the primary side coil NP stores energy, when the absorption branch is conducted, leakage inductance energy of a transformer is absorbed, and the secondary side sub-circuit is connected with the secondary side coil NS, and when the secondary side coil NS is conducted, an output voltage VOUT is provided for a load connected with the secondary side coil NS. The problem of low power conversion efficiency can be solved. The leakage inductance energy is absorbed through the absorption branch circuit so as to be used by a load connected with the secondary side sub-circuit, and the power supply conversion efficiency can be improved.

Inventors

LIN XINCHUN
ZHANG JIE
ZHENG LINGBO

Assignees

深圳市力生美半导体股份有限公司
启东力生美集成电路有限公司

Dates

Publication Date: 20260505
Application Date: 20221011

Claims (12)

1. A flyback switching power supply sink circuit, the flyback switching power supply sink circuit comprising: A transformer comprising a primary winding NP and a secondary winding NS; The primary side sub-circuit comprises an energy storage branch circuit connected with the primary side coil NP and an absorption branch circuit connected with the primary side coil NP, when the energy storage branch circuit is conducted, the primary side coil NP stores energy, and when the absorption branch circuit is conducted, leakage inductance energy of the transformer is absorbed; The secondary side sub-circuit is connected with the secondary side coil NS, and provides an output voltage VOUT for a load connected with the secondary side coil NS when the secondary side coil NS is conducted; The energy storage branch comprises a first switching tube Q1, wherein the first switching tube Q1 is connected with the primary coil NP in series, the absorption branch comprises a second switching tube Q2, an absorption module, an absorption capacitor C3 and a power capacitor C5, and the second switching tube Q2 and the absorption capacitor C3 are connected in series and then connected with the primary coil NP in parallel; The absorption module comprises a sampling VS end, a sampling capacitor C3 and a second switching tube Q2, wherein the sampling VS end is connected between the absorption capacitor C3 and the second switching tube Q2; the control GATE end is connected to the control end of the second switching tube Q2 and used for controlling the on and off of the second switching tube Q2, the grounding GND end is connected with the primary coil NP and the first switching tube Q1; The absorption module is used for acquiring a voltage signal VS of the sampling VS end and a GND voltage signal of the grounding GND end under the condition that the first switching tube Q1 is disconnected, namely an energy storage branch is disconnected, and controlling the second switching tube Q2 to be conducted under the condition that the voltage signal VS is smaller than a preset voltage threshold of the GND voltage signal, so that the absorption capacitor C3 absorbs leakage inductance energy of a transformer, and supplying power to a load connected with the output end of the secondary side sub-circuit after the absorption capacitor C3 finishes absorbing the leakage inductance energy.
2. The flyback switching power supply absorption circuit according to claim 1, wherein the energy storage branch and the absorption branch do not operate simultaneously.
3. The flyback switching power supply sink circuit according to claim 1, wherein the sink module comprises a power sub-module, an analog comparator CMP, a delay module TD, an AND circuit AND, a driving sub-module DRV, wherein the power sub-module comprises a power unit, a single-phase on diode D1 AND the power capacitor C5; one end of the power supply sub-module is connected with a sampling VS end of the absorption module to sample a voltage signal VS for the absorption module; The inverting input end of the analog comparator CMP is connected with the sampling VS end, and the non-inverting input end of the analog comparator CMP is connected with the reference voltage Vref; the output end of the analog comparator CMP is connected with the first input end of the AND gate circuit AND; One end of the delay module TD is connected with the output end of the analog comparator CMP, AND the other end of the delay module TD is connected with the second input end of the AND gate circuit AND; the output end of the AND gate circuit AND is connected with the driving sub-module DRV; The output end of the driving sub-module DRV is connected with the control GATE end of the absorption module.
4. The flyback switching power supply absorption circuit according to claim 3, wherein, In response to the received voltage signal VS, the analog comparator CMP is configured to output a first high-level signal to the delay module TD AND the AND circuit AND if the voltage signal VS is smaller than the reference voltage Vref by a preset voltage threshold; in response to the received first high level signal, the delay module TD is configured to output a second high level signal to the AND gate AND; In response to the received first high level signal AND second high level signal, the AND circuit AND is configured to output a third high level signal to the driving sub-module DRV; In response to the received third high-level signal, the driving submodule DRV is configured to output a driving signal to a control GATE end of the absorption module, so that the second switching tube Q2 connected to the control GATE end is turned on after receiving the driving signal as a high level; The reference voltage Vref is the GND voltage signal, and the preset voltage threshold of the reference voltage Vref is the preset voltage threshold of the GND voltage signal.
5. The flyback switching power supply absorption circuit according to claim 4, wherein the delay module TD further comprises a timer; the timer is used for starting counting down based on a preset duration and outputting an end signal St when counting down is ended in response to the first high-level signal received by the delay module TD; the delay module TD is further configured to output a first low level signal to the AND circuit AND in response to the end signal St.
6. The flyback switching power supply absorption circuit of claim 5, wherein, The AND gate circuit AND is also used for outputting a second low level signal in response to the received first low level signal; In response to the received second low level signal, the driving submodule DRV is further configured to output a third low level signal to the control GATE terminal, so that the second switching tube Q2 connected to the control GATE terminal is turned off after receiving the third low level signal.
7. The flyback switching power supply absorption circuit according to claim 5, wherein the preset duration is shorter than the discharge duration of the secondary winding NS.
8. A transformer leakage inductance absorption method based on the flyback switching power supply absorption circuit according to any one of claims 1 to 7, characterized in that the method comprises: Under the condition that the first switching tube Q1 is disconnected, namely an energy storage branch is disconnected, a voltage signal VS of a sampling VS end of an absorption module in the absorption branch and a GND voltage signal of a grounding GND end of the absorption module are obtained; When the voltage signal VS is smaller than the GND voltage signal preset voltage threshold, controlling, by the absorption module, the second switching tube Q2 connected to the control GATE end of the absorption module to be turned on; And under the condition that the second switching tube Q2 is conducted, absorbing leakage inductance energy of the transformer through an absorption capacitor C3 in the absorption branch, and supplying power to a load connected with the output end of the secondary side subcircuit after the absorption capacitor C3 finishes absorbing the leakage inductance energy.
9. An absorption chip of a flyback switching power supply, characterized in that it comprises the absorption module of the flyback switching power supply absorption circuit according to any one of claims 1-7.
10. The snubber chip of claim 9, wherein the snubber chip includes a sampling VS terminal, a control GATE terminal, a ground GND terminal, and a power supply VDD terminal.
11. The snubber chip of claim 9, further comprising a second switching transistor Q2.
12. The absorbing chip of flyback switching power supply of claim 11 comprising a sampling VS terminal, a ground GND terminal and a power supply VDD terminal.

Description

Flyback switching power supply absorption circuit, transformer leakage inductance absorption method and chip Technical Field The invention relates to the technical field of electricity, in particular to a flyback switching power supply absorption circuit, a transformer leakage inductance absorption method and a chip. Background In flyback switching power supplies, due to the existence of leakage inductance of a transformer, the flyback switching power supply can generate large peak voltage at the moment of switching tube turn-off, the peak voltage can be coupled to sense a secondary side and is supplied to a load, so that the secondary side and the switching tube bear higher voltage stress, the load or the switching tube can be damaged when serious, the operation stability and safety of the whole system are affected, and the problem of electromagnetic interference is solved, therefore, the peak voltage needs to be restrained by adopting modes such as clamping absorption and the like. Conventional methods of absorbing spike voltages include clamping the voltage through diodes and capacitors of the RCD (Residual Current Device ) absorption circuit to slow down the spike voltage while discharging the absorbed energy using energy consuming elements (e.g., resistors). However, although the conventional RCD snubber circuit can improve the withstand voltage problem and optimize the electromagnetic interference characteristic, the energy absorbed by the capacitor is only released in a thermal form, so that the power conversion efficiency is difficult to be improved, and the problem of low power conversion efficiency exists. Disclosure of Invention The application provides a flyback switching power supply absorption circuit, a transformer leakage inductance absorption method and a chip, which can solve the problem of low power supply conversion efficiency. The application provides the following technical scheme: in a first aspect, the application provides an absorption circuit of an electric flyback switching power supply, which comprises a transformer, a first power supply and a second power supply, wherein the transformer comprises a primary coil NP and a secondary coil NS; The primary side sub-circuit comprises an energy storage branch circuit connected with the primary side coil NP and an absorption branch circuit connected with the primary side coil NP, when the energy storage branch circuit is conducted, the primary side coil NP stores energy, and when the absorption branch circuit is conducted, leakage inductance energy of the transformer is absorbed; And the secondary side sub-circuit is connected with the secondary side coil NS, and provides an output voltage VOUT for a load connected with the secondary side coil NS when the secondary side coil NS is conducted. Optionally, the energy storage branch circuit includes a first switching tube Q1, and the first switching tube Q1 is connected in series with the primary coil NP; The absorption branch circuit comprises a second switching tube Q2, an absorption module, an absorption capacitor C3 and a power capacitor C5, wherein the second switching tube Q2 and the absorption capacitor C3 are connected in series and then connected with the primary coil NP in parallel. Optionally, the absorption module includes: the sampling VS end is connected between the absorption capacitor C3 and the second switching tube Q2; The control GATE end is connected to the control end of the second switching tube Q2 and used for controlling the on and off of the second switching tube Q2; the grounding GND end is connected with the primary coil NP and the first switching tube Q1; The power supply VDD end is grounded after being connected with the power supply capacitor C5, and when the energy storage branch is conducted, the power supply VDD voltage for the absorption module to work normally is obtained; The absorption module is used for acquiring a voltage signal VS of the sampling VS end and a GND voltage signal of the grounding GND end under the condition that the first switching tube Q1 is disconnected, namely an energy storage branch is disconnected, and controlling the second switching tube Q2 to be conducted under the condition that the voltage signal VS is smaller than a preset voltage threshold of the GND voltage signal, so that the absorption capacitor C3 absorbs leakage inductance energy of a transformer, and supplying power to a load connected with the output end of the secondary side sub-circuit after the absorption capacitor C3 finishes absorbing the leakage inductance energy. Optionally, the energy storage branch and the absorption branch do not operate simultaneously. Optionally, the absorption module comprises a power sub-module, an analog comparator CMP, a delay module TD, an AND circuit AND, AND a driving sub-module DRV, wherein the power sub-module comprises a power unit, a single-phase conducting diode D1 AND the power capacitor C5; one end of the power supply sub-mod