Active Gate Delay Time Control of Si/SiC Hybrid Switch for Junction Temperature Balance over a Wide Power Range

The optimal gate delay time control between the two internal devices to achieve the excellent electrical and thermal performance of the Si/SiC hybrid switch is considerably affected by several factors and requires careful adjustment to suit the different operation conditions of power converters. However, the conventional gate control solution for the hybrid switch applies a fixed delay time to achieve the minimum switching loss at a specific load current, resulting in disparities in junction temperature of internal devices over a wide load range. This effectively reduced the safe operating area by risking one internal switch subjected to overrated junction temperature in a wide range operation with regard to power handling condition. To avoid such a serious risk of reliability degradation or thermal breakdown, a novel active gate delay time control strategy based on the electro-thermal coupling loss model is proposed. The gate delay time was dynamically adjusted and optimized according to the operation conditions of power converters so that the operation junction temperature difference of the two internal devices can be minimized. Experimental results demonstrate that the junction temperature of the hybrid switch decreases by 20°C at 8kW load condition and its maximum power handling capability increases by 18% without compromising the power converter's efficiency in a 20 kHz Si/SiC hybrid switch based DC/DC buck converter compared with the conventional approach.