A method for realizing a fast response time for the output current change of a MOS current-mode buck DC-DC converter which utilizes a quadratic and vin-dependent compensation slope

Abstract

In this study, a fast response time of less than 10 us has been realized for the sudden output current change between 220 mA and 20 mA of a MOS current-mode buck DC-DC converter which utilizes a quadratic and input-voltage-dependent compensation slope. By using a quadratic and input-voltage-dependent compensation slope, the frequency characteristics of the current feedback loop become constant, and the converter's overall frequency characteristics come to be determined by just adjusting the frequency characteristics in the voltage feedback loop. By changing the time constant in an error amplifier to manipulate the phase margin, the converter's output voltage change becomes small and its response time becomes fast. The test chip of a MOS current-mode buck DC-DC converter using a 0.35-um CMOS process and a 5 MHz clock realized a 40.8 mV output voltage change and a 7.2 us of the response time.