CCM mode requires commutation of boost diode at the trough of the current ripple waveform. At low line diode current is very high resulting in high Qrr in bipolar diodes. For a PN diode, Qrr increases with both operating temperature and dI/dt, resulting in the possibility of thermal runaway from switching losses. For this reason, high performance CCM PFC converters require using the fastest available diodes such as very high performance Silicon tandem diodes or Silicon Carbide diodes for no Qrr.