A high-voltage level shifter with sub-nano-second propagation delay for switching power converters

Abstract

A level-shifting circuit with sub-nano-second propagation delay for high input voltage switched-mode power converters is presented. The proposed circuit uses isolated low-voltage NMOS transistors and capacitive coupling to shift the control signal of the high-side power switch from a low-voltage logic domain (VLogic ~ 5V) up to a high-voltage power domain (VIN ~ 65V) with less than 115ps propagation delay. As a result, the non-overlap time inserted between the control signals of the high-side and low-side power switches can be minimized, leading to higher efficiency. Moreover, the control signal is shifted to the high-voltage power domain without reducing its voltage swing, which helps minimizing the on-resistance of the switch and further improves efficiency. The proposed circuit is fully integrated in a 0.18μm technology with no off-chip components. It occupies less than 0.75mm2 and provides built-in protection for the low-voltage devices with no additional protection circuitry. Transistor level simulations demonstrate the circuit's functionality and performance.