Zero-crossing detection circuit and switching power supply including the circuit

Abstract

The invention relates to a zero-crossing detection circuit.The zero-crossing detection circuit comprises a sampling circuit unit, a feedforward access circuit unit and a comparison circuit unit.The sampling circuit unit receives a reference signal and a zero-crossing signal, outputs a first output signal according to the reference signal and outputs a second output signal according to the zero-crossing signal; the feedforward access circuit unit receives the first output signal and the second output signal, outputs a third output signal according to the first output signal and outputs a fourth output signal according to the second output signal; the comparison circuit unit outputs a first voltage signal according to the second output signal and the third output signal, outputs a second voltage signal according to the first output signal and the fourth output signal and outputs a zero-crossing detection control signal according to the first voltage signal and the second voltage signal.The first output signal and the second output signal are transmitted to the comparison circuit unit in a reverse superposition mode, an input of the comparison circuit unit is increased, and therefore transconductance of the comparison circuit unit is improved, and a transient response of the zero-crossing detection circuit is accelerated.

Description

technical field [0001] The invention relates to the field of electronics, in particular to a zero-crossing detection circuit and a switching power supply including the circuit. Background technique [0002] The zero-crossing detection circuit will delay the zero-crossing judgment due to the influence of response time and input offset voltage. For a common zero-crossing detection circuit, its response time will be tens of nanoseconds or even longer, and the offset voltage will be above ten millivolts. Usually, the method of adding advance in the zero-crossing detection circuit is used to try to offset the influence of the response time. However, due to the deviation of the process, the advance cannot completely offset the influence of the response time, so the fast transient response can accurately solve this problem. [0003] figure 1 It is a schematic diagram of the application environment of the zero-crossing detection circuit, that is, a synchronous rectification step-d...

AI Technical Summary

Problems solved by technology

At the same time, it solves the problem of inductive current backflow in the switching power supply circuit

Images