Experimental investigation on reverse recovery characteristics of high-performance high-frequency diodes

Isolated DC-DC conversion with high power density is widely achieved by DC to high-frequency AC conversion, followed by isolation and high frequency rectification. Selection of high-performance diodes for such high-frequency rectification is challenging as a trade-off is often required among numerous conflicting parameters. Three high performance diodes, namely, an ultra-fast silicon diode, a super barrier diode and a silicon carbide Schottky diode, are compared experimentally for their relative performances for high frequency rectification. The experimental cases include rectification of sinusoidal, square and quasi-square wave alternating waveforms as these are commonly encountered in compact power supplies. At first, the diodes are compared for their forward voltage drops and their reverse recovery times with low-amplitude, high-frequency alternating waveforms generated using a waveform generator. Later the diodes are tested with sinusoidal excitation of much higher amplitude, generated using a power amplifier and the above said waveform generator. It is seen that the results of the comparative study at lower amplitude hold good at higher amplitude as well. A unique experimental condition is applied for enhancing and estimating the case-to-ambient thermal resistance of the diode under study. Later, from the practically obtained thermal resistance and the measured temperature rise of each of the diode, the power loss incurred in each diode is obtained. The experiments clearly demonstrate that the SiC diode, though having the highest forward voltage drop, has the lowest temperature rise and power dissipation on account of superior reverse recovery characteristics.