Dual mode synchronous rectification control circuit for dcm and ccm

Abstract

A dual-mode synchronous rectification control circuit suitable for DCM and CCM belongs to the technical field of power management. The invention has a simple structure, can effectively reduce the conduction loss of rectification, and realize high efficiency of synchronous rectification. Among them, the second negative level detector realizes extremely small dead-time control; the off-time shielding module prevents the synchronous rectifier M2 from being turned on by mistake, and the on-time shielding module prevents the synchronous rectifier M2 from being turned off by mistake; the first sampling terminal The drains of high-voltage devices LDMOS and DEMOS are used to withstand high voltage, which avoids clamping the drain terminal VD of the synchronous rectifier M2 with a Zener tube, and prevents the drain terminal VD of the synchronous rectifier M2 from leaking current to the ground; the above measures work together The high efficiency of synchronous rectification is realized; in addition, a synchronous control module is introduced to realize synchronous rectification under continuous current mode CCM.

Description

technical field [0001] The invention belongs to the technical field of power management, and in particular relates to a dual-mode synchronous rectification control circuit suitable for DCM and CCM. Background technique [0002] As the size of modern high-speed VLSI continues to decrease, the power consumption continues to decrease, the required power supply voltage is also getting lower and lower, and the output current is getting higher and higher. In the low-voltage and high-current output environment, the conduction voltage drop of traditional rectifier diodes is high. Even if a low-drop Schottky diode is used, a voltage drop of more than 0.4V will occur, resulting in increased rectification losses and reduced power supply efficiency. Synchronous rectification technology can greatly reduce the power consumption of the rectification part by using MOSFETs with lower on-resistance, improve the performance of the converter, and achieve high efficiency of the power supply. ...

AI Technical Summary

Problems solved by technology

In addition, when the synchronous rectifier M2 is turned off, the drain (VD terminal) of the synchronous rectifier M2 will cause the VD voltage to ring due to LC oscillation, and the VD ringing voltage may cause 1) the synchronous rectifier is turned on by mistake, Reduce the rectification efficiency; 2) The internal devices of the rectifier chip are broken down by high voltage

For the former, a TON / TOFF signal is usually used to shield the false shutdown / turn-on, while for the latter, the traditional method is to clamp the VD sampling terminal with a Zener tube, and clamp the VD voltage when the Zener tube breaks down. It is at a safe level, but this scheme will cause the power supply to discharge current to the ground through the breakdown Zener tube, resulting in a reduction in rectification efficiency

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