Low offset current comparator

Abstract

The invention relates to a low offset current comparator, comprising a first triode and a second triode, wherein bases of the first triode and the second triode are connected with an emitter of a third triode; a collector of the first triode and the base of the third triode are interconnected with a drain of a fifth MOS (Metal Oxide Semiconductor) tube; the collector of the third triode is connected with the drains of a fourth MOS tube to a seventh MOS tube; the drain of a sixth MOS tube is connected with the collector of the second triode; a grid of the sixth MOS tube is connected with the drain thereof and simultaneously connected with the grid of the seventh MOS tube; the drain of the seventh MOS tube is connected with the drain of a third MOS tube; sources of the third MOS tube, a second MOS tube and a first MOS tube are grounded; the grid of the third MOS tube is interconnected with the second MOS tube and the first MOS tube; and the drain of the second MOS tube is connected with the drain of the fourth MOS tube. The low offset current comparator of the invention has simple structure and high detection precision, ensures steady operation of a convertor, improves conversion efficiency of the convertor, and can be safe and reliable.

Description

technical field [0001] The present invention relates to a circuit structure, especially a low offset current comparator, specifically a circuit structure for detecting the reverse current of a freewheeling switch tube of a synchronous rectification DC-DC converter, which belongs to the synchronous rectification DC -Technical field of DC converters. Background technique [0002] DC-DC converters can be divided into asynchronous rectification and synchronous rectification according to the different freewheeling methods adopted. Among them, asynchronous rectification is a common basic rectification method in switching power supplies, which uses rectifier diodes as freewheeling devices. The loss of the switching power supply is mainly composed of three parts: the loss of the power switch tube, the loss of the high-frequency transformer, and the loss of the output rectifier tube. In recent years, with the development of electronic technology, in order to reduce the overall powe...

AI Technical Summary

Problems solved by technology

For a synchronous rectification converter, when it works in Discontinuous Conduction Mode, a circuit is generally required to detect the node where the freewheeling power transistor is connected to the external inductor L ( SW) voltage, when the voltage reaches the set threshold value, the freewheeling power tube is turned off through the logic circuit, preventing the filter capacitor Cout from consuming energy through the external inductor L discharging to the ground, and reducing the efficiency of the converter

However, since the on-resistance of general freewheeling power tubes is very small (on the order of tens of mΩ), the SW threshold can be as small as tens of microvolts (μV), which will place high requirements on the sensitivity of the detection circuit

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