Extending the operational limits of the push-pull converter with SiC devices and an active energy recovery clamp circuit

This paper presents a push-pull converter as a promising alternative to more complex and more costly isolated dc-dc converters for cost-sensitive, high-performance applications. The push-pull converter utilizes silicon carbide (SiC) power devices along with an active energy recovery clamp (AERC) circuit to extend the conventional operational limits of the topology. The SiC devices provide higher voltage blocking capability while maintaining low on-resistance as well as low switching energy. The AERC allows for nearly all of the energy stored in the leakage inductance of the transformer to be transferred back to the input capacitors without adding any control complexity to the system. The use of SiC devices along with the AERC allows for the push-pull converter to operate at a higher voltage, higher current, and higher switching frequency while maintaining high efficiency. In this work a prototype is developed to be operated with an input voltage of 400 V, a switching frequency of 200 kHz, and an output power greater than 5 kW. The performance of this prototype is compared to the same push-pull converter using an RCD clamp and significant improvements in efficiency are seen. The push-pull converter with AERC also shows higher efficiency across a wide range of output power conditions when compared to a soft-switching phase-shifted full-bridge (PSFB) converter with similar design specifications. Overall a maximum efficiency of 96.5% was measured at an output power of 3.7 kW for the push-pull converter with AERC.