A 1–2-MHz 150–400-V GaN-Based Isolated DC–DC Bus Converter With Monolithic Slope-Sensing ZVS Detection

Abstract

This paper presents a wide-range high-voltage (HV) isolated phase-shifted full-bridge dc–dc bus converter with eGaN power FETs driven by an integrated synchronous CMOS gate driver. The monolithic slope-sensing zero-voltage switching detector (SS-ZVSD) is developed to automatically provide adaptive deadtime control with near-constant short turn-on delay for enabling ZVS of synchronous power transistors during switching transitions under different input voltages and load currents. This not only minimizes the switching loss and the reverse conduction loss but also supports high-frequency operation, leading to high-frequency high-efficiency converters. A HV-level shifter with differential-mode noise blanking scheme is also proposed in the gate driver to enhance the converter reliability in high input voltages. To verify the performances of the isolated converter using 650-V eGaN power FETs, the gate drivers were implemented in a 1.45- $\mu \text{m}$ 700-V BCD process. The converter supports the input voltage from 150 to 400 V and delivers a maximum output power of 250 W. The proposed SS-ZVSD achieves adaptive deadtime with about 13-ns turn-on delay over wide ranges of the input voltage and load current, thereby enabling the converter running up to 2 MHz with 1.6-W power saving. The proposed converter operates 14 $\times $ faster than the prior art with comparable power efficiency.