Synchronous rectification drive module, synchronous rectification drive circuit and buck type step-down circuit

Abstract

The invention provides a synchronous rectification driving module, a synchronous rectification driving circuit and a buck-type step-down circuit, which adopts a PMOS power tube as the upper tube of the synchronous rectification circuit, and an NMOS power tube as the lower tube, and improves the PMOS power tube driving circuit and the NMOS power tube. tube drive circuit; the PMOS drive circuit uses direct VCC‑GND power supply; the PMOS drive circuit uses the method of limiting the gate voltage of M18 and making M18 and M19 discharge together to limit the voltage of the gate drive terminal of the PMOS power tube, so as to ensure the driving ability. At the same time, the circuit structure is simplified; the NMOS drive circuit stabilizes the voltage of the gate drive terminal of the NMOS power tube by limiting the base voltage of the transistor Q1, and ensures the gate drive terminal of the NMOS power tube by amplifying the current flowing out of M24 through Q1 and Q2. There is enough driving capacity.

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 tube in the step-down circuit has two kinds of power triode and power MOS tube. The power MOS tube is divided into PMOS power tube and NMOS power tube. For the buck (BUCK) circuit, the conventional BUCK type step-down circuit is divided into asynchronous Rectification type circuit and synchronous rectification type circuit, although the asynchronous rectification type circuit is low in cost, its freewheeling diode has a large freewheeling loss. The power MOSFET replaces the Schottky freewheeling diode used in the traditional asynchronous rectification circuit. The change of the freewheeling device requires the corresponding drive circuit to be redesigned. Compared with the drive circuit of the asynchronous ...

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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