Novel MOS tube drive circuit for switch power supply

Abstract

The invention relates to a novel MOS tube drive circuit for a switch power supply, which comprises a MOS switch tube Q2 and a driving signal input terminal. The MOS tube drive circuit is characterized in that: a drive circuit (1) is arranged at the joint of a control input terminal of the MOS switch tube Q2 and the driving signal input terminal; the drive circuit (1) is formed by connecting a quick turn-off access (11), a discharging access (12) and a surging impact prevention access (13); the quick turn-off access (11) is connected in parallel with the surging impact prevention access (13) and then spans between the control input terminal of the MOS switch tube Q2 and the driving signal input terminal; and the discharging access (12) spans between a grid and an earth terminal of the MOS switch tube Q2. The MOS tube drive circuit can accelerate the turn-off of the MOS tube, control the ascending speed of driving current of the MOS tube effectively and improve the EMC characteristic ofthe integral switch power supply, and has the advantages of simple circuit, stable and reliable performance, easy realization and low cost.

Description

Technical field [0001] The present invention relates to the technical field of switching power supply drive circuits, in particular to a novel MOS tube drive circuit of a switching power supply. It belongs to the technical field of electronic switching power supplies. Background technique [0002] At present, most switching power supply circuits use MOS transistor drive circuits. A drive signal with an adjustable duty cycle is applied to the gate of the MOS transistor, and the output of the switching power supply is realized by controlling the on and off time of the MOS transistor. Effective control of voltage. The MOS drive circuit in the prior art generally adopts the following method: the control signal output from the control chip or generated by the oscillation circuit is connected to the gate of the MOS transistor through a drive resistor to realize on-off control of the MOS transistor. This method has the following problems: 1. Due to the existence of the gate-source jun...

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Problems solved by technology

This method has the following problems: 1. Due to the existence of the gate-source junction capacitance of the MOS transistor, the MOS transistor cannot be turned off quickly, and the MOS transistor will temporarily enter the linear region, and the conduction internal resistance of the MOS transistor entering the linear region is very large. It will cause low efficiency of the MOS tube, increased switching loss, and severe heat generation; 2. Since the driving current provided by the control signal to the MOS tube rises rapidly (rising edge), it will cause a high turn-on surge, resulting in damage to the MOS tube , to a certain extent, it will also affect the EMC characteristics of the entire switching power supply

[0003] For problem 1, some people have made some improvements in the circuit, that is, a high-frequency diode is connected in antiparallel to the driving resistor to quickly discharge the gate charge and accelerate the turn-off of the MOS tube, but the improvement effect is not obvious; for problem 2, Some people directly solve this problem by adding a dedicated driver chip, but due to the high price of the chip, the cost will increase a lot, and there is a defect of high cost

The MOS tube drive circuit has the following disadvantages: 1. The MOS tube cannot be turned off quickly, the efficiency of the MOS tube is low, and the switching loss is large; 2. The overall circuit structure is complex and the cost is high

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