High-precision current detection circuit working in sub-threshold region

Abstract

A high-precision current detection circuit working in a sub-threshold region belongs to the technical field of analog simulated circuits. The circuit comprises a sampling unit, a detection unit and adynamic bias unit, the sampling unit is used to sample a current to be detected, the current to be detected passes a second PMOS to cause change of the drain-end voltage of the second PMOS, the detection unit copies the current of the second PMOS via a first PMOS, the current to be detected is responded to the voltage between the two ends of a first resistor to realize current detection, and the dynamic bias unit transmits the current to be detected to the detection unit without loss. Voltage feedback and current feedback are introduced to ensure that voltage of the point A changes dynamicallywith voltage of the point B, the MOS is controlled to work in the sub-threshold region, power consumption is reduced, current loss is reduced, and the detection precision is improved.

Description

technical field [0001] The invention belongs to the technical field of analog integrated circuits, and in particular relates to a high-precision current detection circuit, which is mainly used for detecting the current of a power chip. Background technique [0002] How to simply, accurately and quickly detect the current of the power supply chip is related to the performance of the entire switching power supply chip. At present, the current detection methods commonly used in the chip include series resistance detection, power tube R DS Detection technology, filter detection method, SenseFET current detection technology, etc. Using an external resistor or an internal integrated resistor to detect the inductor current, if the resistance is too large, it will increase the power consumption and reduce the efficiency of the converter. Suitable; by detecting the on-resistance R of the power tube DS The method of voltage at both ends, although the additional power loss is elimina...

AI Technical Summary

Problems solved by technology

The limitations of this circuit are:

[0008] (1) When the detected current changes, V B will change when V A Unable to follow in time, resulting in inconsistent voltages at A and B points;

[0009] (2) At the same time, although I PM1 >>I PM3 But there is still an error, and when the detected current decreases, the error will increase

The limitation of this circuit is that although the currents of PM11 and PM6 are guaranteed to be consistent in theory, in practice, especially when the detected current is small, the current consistency cannot be guaranteed, and when the detected current is small, the lost current ratio The current flowing through PM9 is much larger, so the error is still large

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