An Accurate Secondary-Side Controller with GaN-8ased CGS Isolated Driver Achieving Sub-1% Error On-Chip Sensing

LLC resonant converters are commonly used as front-end converters in servers and electric vehicle chargers due to their soft-switching capabilities, including zero-voltage switching (ZVS) and zero-current switching (ZCS) [1]–[5]. Conventional synchronous rectifiers (SR) use power switches to increase efficiency by replacing diodes [6]–[8] to handle root-mean-square (RMS) currents up to 11 A. However, due to the high on-resistance $(\mathrm{R}_{\text{on}})$ of hig h -voltage Bipolar-CMOS-DMOS (BCD) power switches, the efficiency gain is only 1.8%. $\text{In}$ contrast, a Gallium Nitride (GaN)-based SR can further reduce power loss to $2.0\%$, but the lack of a body diode increases losses during dead time (Fig. 32.3.1 top left) [9], [10]. Additionally, GaN-based rectifiers are typically made larger to reduce $\mathrm{R}_{\text{on}}$ and prevent current collapse. Therefore, a driver with strong driving capability, zero delay, and precise sensing for SR on/off timing is essential.