Controlling DC-DC Converters in Portable Devices: A Dynamic FPGA Based Pulse Shift Modulation Technique

Abstract

In portable devices, conventional modulation techniques, such as Pulse Width Modulation (PWM) and Pulse Frequency Modulation (PFM), have been proposed and used to control switches in DC-DC converters. These techniques are not efficient at wide load ranges and lead to converters that suffer from high conduction losses, switching losses, and ripple voltages. This paper proposes a novel modulation technique that increases the efficiency of DC-DC converters by reducing these losses and ripple voltages. The technique, Pulse Shift Modulation (PSM), dynamically changes the duty cycle and the switching frequency of the control signal with any change in load conditions. The proposed modulation technique produces lower losses and ripple voltages compared to those found in converters controlled by conventional techniques. Further, the proposed technique is implemented in a Field Programmable Gate Array (FPGA) device, which is faster and cheaper and consumes less power than processor-based implementations do.