Dual-mode synchronous rectification control circuit for DCM and CCM

Abstract

The invention provides a dual-mode synchronous rectification control circuit for a DCM and a CCM, belonging to the technical field of power management. The structure of the circuit is simple, the rectification conduction loss can be effectively reduced, and high efficiency of synchronous rectification is realized. Minimum dead time control is realized by a second negative level detector. A turn-off time shielding module prevents the wrong turn-on of a synchronous rectifier tube M2, and a turn-on time shielding module prevents the wrong turn-off of the synchronous rectifier tube M2. Drain electrodes of LDMOS and DEMOS high voltage devices are used by a first sampling end to bear high voltage, the clamping of a drain end VD of the synchronous rectifier tube M2 by a Zener is avoided, and the current leakage to the ground by the drain end VD of the synchronous rectifier tube M2 is prevented. The high efficiency of synchronous rectification is realized by the above measures together. In addition, a synchronous control module is introduced, and the synchronous rectification in a current continuous mode CCM is realized.

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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