Current detection circuit capable of eliminating offset voltage of operational amplifier

Abstract

The present invention relates to a detection circuit, in particular, a current detection circuit capable of eliminating the offset voltage of an operational amplifier. The current detection circuit comprises a sampling resistor, a multiple magnification circuit, band-gap reference, an offset voltage selection circuit, a decoding control circuit and an analog-to-digital converter; the sampling resistor is connected in series to a current loop requiring current detection; three paths of the output of the band-gap reference and the output of the decoding control circuit are connected with the offset voltage selection circuit; the output of the offset voltage selection circuit is connected with the multiple magnification circuit; the input of the multiple magnification circuit is connected with two ends of the sampling resistor; and the output of the multiple magnification circuit is connected with the input of the analog-to-digital converter. With the current detection circuit of the invention adopted, the offset voltage of the input end of a rail-to-rail operational amplifier can be effectively offset, and therefore, design difficulty can be reduced, the circuit can be better integrated in a chip, and the design cost of a system can be reduced.

Description

technical field [0001] The invention relates to a detection circuit, in particular to a current detection circuit for eliminating the offset voltage of an operational amplifier. Background technique [0002] In the wireless charging sending circuit, it is necessary to detect the current of the sending coil to determine whether there is a receiving end or a foreign object on the coil. If there is a receiving end on the coil, it is necessary to detect the current of the sending coil to determine the power provided by the sending system. Through the communication control between the sending end and the receiving end, the power provided by the sending end is dynamically adjusted. [0003] A common current detection circuit connects a small sampling resistor (precision resistor) in series to the current loop that needs to measure the current, and then amplifies the voltage at both ends of the sampling resistor, and the amplified voltage undergoes analog-to-digital conversion to o...

AI Technical Summary

Problems solved by technology

The existing current detection circuit is the voltage obtained by amplifying the voltage at both ends of the current sampling resistor. However, due to the influence of the input offset voltage of the operational amplifier (referred to as "op amp"), it may cause , the output voltage of the amplified op amp is still zero

In order to overcome this problem, the first solution is to make the current detection circuit outside the chip and realize it by purchasing a high-performance operational amplifier (OP), which increases the cost of the system; the second solution needs to be designed in the chip An op amp with very small offset voltage, which will increase the chip area and design difficulty

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