Two-phase interleaved buck converter with a new Digital Self-Oscillating Modulator

Abstract

This paper presents a new digital self-oscillating modulator (DiSOM) for DC/DC converters. The DiSOM modulator allows the digital control algorithm to sample the output voltage at a sampling frequency higher than the converter switching frequency. This enables higher control loop bandwidth than for traditional digital PWM modulators given a certain switching frequency. A synchronised version of the DiSOM modulator is derived for interleaved converters. A prototype interleaved buck converter for point of load applications has been designed and built to test the performance of DiSOM modulator. The DiSOM modulator and a digital control algorithm have been implemented in an FPGA. Experimental results show that the converter has a very fast transient response when a loadstep is applied to the output. For a loadstep of 50% of nominal output current the output voltage overshoot is less than 2.5% of the nominal output voltage and the settling time is just 8 switching periods.