Conducted Emissions for Different Conversion Ratios of GaN-Based Synchronous Buck Converter

Large voltage conversion ratios of the switching DC-DC converters are difficult to achieve at high switching frequencies due to the short pulses of the control signals for the FET switches. To overcome this, multiple stages of the DC-DC converters with smaller conversion ratios can be used. A synchronous buck converter based on the gallium-nitride FET switches is designed to analyze the impact of the different voltage conversion ratios on the power efficiency and differential-mode conducted EMI at the input of the converter. The conducted EMI and power efficiency are measured for duty ratios of 10% to 50% and for switching frequencies up to 5 MHz. The input and output voltage and power levels are set to reproduce the operating conditions of the front-end and load converter in the multi-stage step-down switching DC-DC converter topology.