Multi-mode protection circuit of double-winding secondary side feedback switching power supply

Abstract

The invention relates to the field of switching power supplies, and discloses a multi-mode protection circuit of a double-winding secondary side feedback switching power supply. The circuit comprisesa demagnetization time detection circuit, a demagnetization time setting circuit and a logic judgment circuit, wherein the demagnetization time detection circuit is used for detecting voltage change of a drain end of a power switch tube at an initial winding side to detect the demagnetization time; the demagnetization time setting circuit comprises a CS peak value sampling and holding circuit andan adaptive demagnetization time comparison circuit, the CS peak value sampling and holding circuit samples and holds a CS peak value signal when PWM is started each time, and the adaptive demagnetization time comparison circuit outputs adaptive demagnetization threshold time according to the sampled CS peak value signal; and the logic judgment circuit is used for comparing the demagnetization time with the threshold time, and outputting a protection signal if the demagnetization time is less than the threshold time. By adopting the technical scheme of the invention, output voltage changes aredirectly reflected through the demagnetization time, so that protection measures under various abnormal conditions can be achieved, the abnormal working state of the system is reduced, and potentialsafety hazards are avoided.

Description

technical field [0001] The invention relates to the field of switching power supply design, in particular to a multi-mode protection circuit of a double-winding secondary side feedback switching power supply. Background technique [0002] With the strong demand for consumer electronic products and the upgrading of various electronic products, the requirements for power modules are also getting higher and higher. The power module usually provides constant voltage or constant current to the functional modules to ensure their stable operation. According to market demand and cost control, the current power module is getting smaller and smaller, and there are fewer and fewer components on the PCB board. It can not only be used for portable miniaturization applications, but also save terminal costs. The topology structure of omitting the auxiliary winding came into being. . The double winding omits the auxiliary winding, so there is no auxiliary winding to supply power to the VC...

AI Technical Summary

Problems solved by technology

[0006] The technical problem to be solved by the present invention is: in order to overcome the problems that the existing dual-winding secondary side feedback switching power supply topology cannot intuitively reflect the rise of the output voltage, cannot protect the FB pin of the feedback terminal from being suspended, and cannot protect the output diode terminal from being suspended in the air. A multi-mode protection circuit for dual-winding secondary-side feedback switching power supply

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