A Digital Dithering Phase Shift Modulator for Enhanced Resolution

This article proposes a digital dithering phase shift modulator to control power electronic converters. The presented modulator allows a higher resolution for digitally generated phase-shift signals without the need for fine time steps using very high-frequency or high-resolution timers. To achieve this, two coarse, counter-based phase-shift signals that differ in their phase shift values by one bit are used, and a total phase-shift output signal is derived by periodically switching between these two. The result is a dithered phase-shift control signal with an increased switching frequency or resolution. A prototype circuit for the control signal generation for a dual-active half-bridge converter is presented. Using only a 48 MHz digital clock signal, a control signal with a switching frequency of 188 kHz and a resolution of 12 bits is achieved. The modulation concept is described, and its application is verified using simulations and experimental tests.