Synchronous rectification driving module, synchronous rectification driving circuit and BUCK type voltage reduction circuit

Abstract

The invention provides a synchronous rectification driving module, a synchronous rectification driving circuit and a BUCK type voltage reduction circuit. A PMOS power tube is used as an upper tube ofthe synchronous rectification circuit, an NMOS power tube is used as a lower tube, and a PMOS power tube driving circuit and an NMOS power tube driving circuit are improved; wherein the PMOS driving circuit is powered by adopting a direct VCCGND; according to the PMOS drive circuit, the voltage of the grid drive end of the PMOS power tube is limited by adopting a method of limiting the voltage ofan M18 grid and enabling M18 and M19 to be matched for discharging, so the circuit structure is simplified while the drive capability is ensured; the NMOS driving circuit stabilizes the voltage of a grid driving end of the NMOS power tube by limiting the voltage of the base of the triode Q1, and ensures that the grid driving end of the NMOS power tube has enough drive capability by amplifying thecurrent flowing out of the M24 through the Q1 and Q2.

Description

technical field [0001] The invention relates to the field of synchronous rectification circuits, in particular to a synchronous rectification drive module, a synchronous rectification drive circuit and a buck-type step-down circuit. Background technique [0002] The power transistors in the step-down circuit include power triodes and power MOS transistors. The power MOS transistors are further divided into PMOS power transistors and NMOS power transistors. For the step-down (BUCK) circuit, the conventional buck-type step-down circuit is divided into asynchronous Rectifier circuit and synchronous rectifier circuit. Although the asynchronous rectifier circuit has low cost, its freewheeling diode has a large freewheeling loss. In order to solve this problem, people have introduced a synchronous rectifier circuit, using a special-purpose The power MOSFET replaces the Schottky freewheeling diode used in the traditional asynchronous rectification circuit. The change of the freewhe...

AI Technical Summary

Problems solved by technology

When NMOS is selected as the lower tube, although the power supply voltage generated by the internal LDO (LDO is a low dropout regulator, a low-dropout linear regulator) can be used to drive the NMOS power tube, considering that the NMOS power tube requires a large current when it is turned on , the chip cannot integrate a large-capacity capacitor, and the instantaneous large current will affect the stability of the internal working voltage of the chip. People often use a separate power supply for the NMOS power tube drive circuit in practical applications, and some application products will also use external capacitors. The way to stabilize the power supply voltage of the NMOS power tube built-in drive circuit

The structure of the traditional driving circuit is relatively complex, resulting in large wafer area, high chip cost, and external capacitors lead to many peripheral components of the system, increasing system cost and reducing product competitiveness

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