Internal circuit offset auto compensation current sensor for wireless power systems

Abstract

This paper, we implemented a method to compensate the internal offset in the instrumentation amplifier structure. The proposed current sensor is used in a wireless power transmitter where the input voltage is changed. In order to lower the input voltage, resistor dividing is performed at the input terminal of the amplifier. When a voltage offset occurs in the circuit using this input voltage, the closed-loop circuit is changed to the open-loop and the open-loop output is confirmed in the calibration circuit to compensate the voltage offset generated in the circuit. We implemented the current sensor within +5 % error rate of the output occurring in the amplifier and resistor. The current sensor is designed with a 180 nm BCD process and it converts 0 ∼ 1.8 V voltage output by sensing 0 ∼ 3 A current.