ROMJIST Volume 24, No. 2, 2021, pp. 161-181
Gabriel PETRASUC, Paul MIRESAN, Marius NEAG, Cosmin CHIRA A Novel Full-Wave Current Sensor for Automotive Synchronous Buck Converters
ABSTRACT: This paper presents a novel full-wave current sensor based on the Vds-sense technique, suitable for fully integrated complementary switching power stages such as those used in synchronous buck DC-DC converters. It is designed to operate over a wide range of input voltages required by automotive applications. Provisions have been made for both current- and voltage-output, as well as for trimming. The novel sensor was derived by addressing the main limitations of a solution published previously by the authors. Both the circuit topology and circuit implementation were improved in order to increase the sensor accuracy. The new topology is simpler and allows for the signal paths to be implemented by using low-voltage transistors; the main transconductors were implemented by using the common-gate topology, which provides large bandwidth for a relatively low power consumption. A design example is presented in some detail: a full-wave current sensor for synchronous buck DC-DC converter designed in a High-Voltage 180nm CMOS process. The converter provides a nominal 5V output and up to 500mA, while the input voltage varies between 6V and 45V. Simulation results shown that the current sensor presented here operates over the entire range of input voltages and resulting duty-cycle, between 10% and 80%. The relative error when the signals driving the power switches have a 50% duty-cycle is under 1.2%pkpk for inductor currents larger than 200mA and remains below 7.2%pkpk down to 50mA.KEYWORDS: Full-wave current sensor, Vds-sense, sense-FET, synchronous buck converter, Sample&Hold, common-gate amplifierRead full text (pdf)