Monolithically integrated voltage level shifter for Wide Bandgap Devices-based converters

Abstract

Power converters based on Wide Bandgap Devices (WBD) are able to operate at high-frequency and high-voltage. In such synchronous converters a very short dead-time is advised because a lot of WBD do no have a parasitic body diode to conduct current in reverse. Into a high-voltage inverter, isolators generate isolated floating gate signals from logic level input signals. Mismatch between high-side and low-side signal propagation delays involves setting a long secure dead-time. To overcome this matching issue in order to guarantee the dead-time duration and time location, we propose other input signal propagation paths. Both input signals pass through a single lowside 2-channel digital isolator and one isolated signal is translated to the high-side gate driver by a high-speed monolithically integrated level-shifter. The proposed voltage level translator structure has been implemented with a high-voltage diode-less SiC vertical JFET and low voltage MOSFETs. At 240V power supply voltage and 100 kHz switching frequency, the level-shifter propagation delay is only 10 ns with a 1.85 mA supply current. Moreover an effective built-in current regulator prevents the circuit from any current spikes, overvoltage and overconsumption. Such topology allows to safely set a very short 23 ns dead-time and improves WBD-based converter operations while reducing size and price.