A flyback synchronous rectifier circuit

Abstract

The invention discloses a flyback synchronous rectification circuit, comprising: a first synchronous rectification module for generating a secondary side drive control signal complementary to a control signal of a primary side MOSFET; a second synchronous rectification module for The synchronous rectification control signal is generated by the drain level and the source level of the synchronous rectification signal; the synchronous rectification signal processing module is used to collect the secondary side drive control signal and the synchronous rectification control signal, and according to the rising edge of the secondary side drive control signal and all The falling edge of the driving control signal obtains the driving signal of the secondary side MOSFET; the secondary side driving module is used for driving the secondary side MOSFET by using the driving signal. The entire flyback synchronous rectifier circuit can improve the efficiency of the flyback circuit at the beginning of turn-on and turn-off, which can improve the efficiency at light load and heavy load; at the same time, it can suppress the voltage spike on the secondary side, Improve circuit reliability.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to a flyback synchronous rectifier circuit. Background technique [0002] Synchronous rectifier circuits are widely used and can significantly improve the conversion efficiency of power modules. When the synchronous rectifier circuit is under light load or no load, the inductor current is discontinuous. At this time, the synchronous rectification signal that is completely opposite to the input will cause a reverse current in the output, which will generate excess circulating current in the circuit and increase the light load and no load. In parallel, voltage spikes may also be generated on the secondary side, causing damage to the synchronous rectifier tube; and the synchronous rectification technology that detects the relationship between the output and the transformer level, due to sampling and signal delay, will cause synchronous rectification to appear befo...

AI Technical Summary

Problems solved by technology

The turn-on time of the circuit voltage is obtained by comparing the sampling circuit with the reference value, and the delay is relatively large, resulting in the body diode conduction loss of the synchronous rectification MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor, Metal-Oxide-Semiconductor Field-Effect Transistor) when turned on Larger, the detection of input current and output level is used when turning off, the time is longer, the turn-off time will be later than the actual zero current moment, and a small circulating current will be generated

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