Full-Wave Sense-FET-Based Inductor-Current Sensor With Wide Dynamic Range for Buck Converters

This brief presents a full-wave inductor current sensor with wide dynamic range for buck converters. To extend the effective sensing range to zero or even negative current, an offset current is superimposed on the sensed inductor current. Besides, the adaptive-bias generator is applied to the proposed sensor with the aim to further suppress the variations of bandwidth and phase margin across the wide dynamic sensing range. Moreover, the seamless current sensing approach is introduced to achieve the smooth sensing waveform through the whole switching cycle. A buck converter with the proposed current sensor has been fabricated in a 0.18- $\mu \text{m}$ standard CMOS process. Compared with the fixed-biased counterpart, the loop bandwidth variation of the proposed sensor is merely 3.3 MHz across the current range from −200 mA to 1.2 A. Measurement results show that the response time is less than 20 ns for various loads and no glitches appear at the sensed current.