Large-Power ZVZCS Full-Bridge Three-Level DC–DC Converter With Wide Operation Range and Its Application in Sapphire Crystal Furnace Power Supply

A novel zero-voltage and zero-current switching (ZVZCS) full-bridge (FB) three-level (TL) dc-dc converter is proposed, which can satisfy most requirements of wide operation range high-input dc-dc industrial applications. OFF-voltage on the primary switches can be maintained to V
_in
/2 by the input capacitors, and no extra primary clamping device is needed. The primary switches can obtain zero-voltage switching (ZVS) or zero-current switching (ZCS) easily. Furthermore, the operation mode can be altered under different output and input conditions, which ensures high efficiency over a wide operation range. The extra MOSFETs have low ON-state resistance and cause less switching loss; thus, the power loss caused by these MOSFETs can be omitted. Furthermore, these components are not inserted into the circuit loop of the input capacitors and primary switches, which may reduce the voltage spike on the primary switches at turn-off instants. The VA rating of the primary switches and input capacitors is identical to that of conventional FB TL dc-dc converters, and the utilization of the dc-link voltage is close to 100%. To evaluate the proposed converter, an industrial application example and some experimental results are also provided.