Improvement of one-comparator counter-based PFM control for DC-DC converter

In this paper, counter-based pulse-width-modulated (PFM) control according to the output voltage ripple using a one-comparator scheme without any analogue-to-digital converter (ADC) used is presented herein, which is realized based on the field programmable gate arrays (FPGA) and applied to DC-DC converters. However, too small or distorted output ripple limits its performance. Consequently, a positive-sloped ramp wave injection method is used to overcome this problem and enhance its application capability significantly. In the paper, the details of this positive-sloped ramp wave injection method are illustrated. And, some experimental results are provided to verify the effectiveness of the proposed control strategy.