A 2MHz 150-to-400V input isolated DC-DC bus converter with monolithic slope-sensing ZVS detection achieving 13ns turn-on delay and 1.6W power saving

The growing development of industrial power supplies demands DC-DC converters that are increasingly efficient and reliable. Industrial bus supplies that operate from a front-end PFC could experience fluctuations from 150V to 400V [1]. This requires isolated DC-DC converters to function over a wide range of the high-input condition. Zero-voltage switching (ZVS) with proper dead-time control is essential in these converters to remove the dominant switching power loss for achieving better power efficiency. Specifically, each power FET should be controlled to turn on right after its ZVS operation is complete. If the dead time is set too short, the power FET would be turned on with large drain-to-source voltage, resulting in large turn-on loss. The converter would also suffer from large reverse conduction loss of the power FETs due to excessive dead time [2,3]. Since the ideal dead time varies with different input voltages and load currents, the capability of generating adaptive dead time with minimal turn-on delay (tdon) in the ZVS converters is important, especially for high-frequency converter operation, but is challenging to realize. Previously, a valley switching scheme was reported to provide adaptive dead-time control under different conditions. However, it requires an off-chip auxiliary winding that complicates the magnetic design, and needs tdon of >100ns that limits the converter operation in the MHz range [4].