Closed-Loop Current Control of a Buck Converter via Sensing of Optical Emission from a GaN PN Freewheeling Diode

This paper demonstrates the closed-loop control of a buck converter circuit using EL signals generated in a GaN PN diode, used as the freewheeling diode. A method of calibration of the EL signal based on utilizing the known duty cycle of the current drive waveform and the current amplitude is introduced to predict the rea- time current. A double-PI control architecture is used to implement closed-loop output voltage control with the EL signal. The closed-loop response shows good agreement and stable control with less than 6% error in steady-state. During step responses in load and setpoint, large settling times are observed and explained by limitations in the hardware used for signal detection and current estimation via the EL signal. A discussion is presented for improving the response time and accuracy of EL based current estimation for better converter control performance.