Comparative Study on Practical Implications of Digital Peak Current and Hysteresis Current Controllers for MHz Frequency DC-DC Converters

Fast switching characteristics of gallium nitride (GaN) semiconductor devices have enabled power converters to operate in megahertz (MHz) scale switching frequencies. Practical implementation of this fast switching operation requires high-speed controllers, which is increasingly becoming difficult to be achieved using the digital microcontrollers due to the hardware limitations such as signal latency and sampling rates. The objective of this paper is to analyze the impact of the hardware limitations for implementing classical control techniques for fast switching power converters and to propose a viable alternative to meet control requirement without compromising on switching frequency. The adverse effects due to the hardware limitations of existing controllers for implementing digital peak current (DPC) control technique have been analyzed in this paper. An improved controller performance has been achieved by replacing the DPC control with digital hysteresis current (DHC) control technique, even with the same hardware limitations of the microcontroller. A 70 V to 48 V 2.4 kW 1.5 MHz GaN FET - based buck converter is designed and simulated to validate the performance of the DPC and DHC control techniques.