MODELLING OF OPERATION MODES AND ELECTROMAGNETIC INTERFERENCES OF GaN-TRANSISTOR CONVERTERS

Abstract

Goal. To analyze the efficiency and EMI of a half-bridge converter built on GaN transistors at different switching frequencies and to issue recommendations for its application. Methodology. An EPC9035 development board from Efficient Power Conversion was selected for research. This board is a half-bridge converter built on the EPC2022 eGaN® transistors and contains a driver for controlling these transistors. To simplify the assessment of the conversion efficiency, it is suggested to use a computer model of the development board and LISN, which simulates the active load with the LC filter. Results. Simulation results of the converter efficiency with the nominal values of the elements according to the EPC9035 manual showed significant deviations from the calculated values at frequencies above 50 kHz. This is explained by the presence of inrush current through transistors. The inrush current depends on the «dead time» between the intervals when the transistors are open and the delays specified in the SPICE model of LM5113 driver. To reduce the amplitude of inrush current and, accordingly, to increase the duration of the «dead time» interval, it is proposed to double the capacitors responsible for the formation of this interval. Simulation of the converter efficiency with the doubled values of the circuit elements showed that the results almost coincide with the calculated values of the efficiency in the range from 0.05 MHz to 5 MHz. The converter on the EPC2022 transistors has the highest efficiency at 50 kHz which decreases by 0.03-0.04 at 500 kHz. Therefore, it is recommended that the operating frequency should be set close to 500 kHz. Simulation of EMI levels resulted that the difference in the duration of the «dead time» does not have a significant effect on the levels of simulated EMI. The largest difference between the simulation results and the experiment is observed at frequencies about 30 MHz and is 3-6 dB. Originality. For the first time, the computer model was used to calculate the efficiency of a half-bridge converter on GaN transistors at different frequencies. Practical significance. Considering the high output current, high operating voltage and short switching times, GaN transistors are promising for use in pulse generators, power supplies with operating frequencies exceeding 500 kHz, and in powerful Class D hi-fi amplifiers with small dimensions, such as automotive ones.

Keywords

• gan transistors
• computer simulation
• electromagnetics interferences
• energy efficiency