A 400 V Dual-Phase Series-Capacitor Buck Converter GaN IC With Integrated Closed-Loop Control

Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) offer a 13× better
$R_{\text{DS,on}}Q_{g}$
figure-of-merit than silicon laterally-diffused metal-oxide semiconductor (LDMOS) devices for power converters operating above 100 V. Recent GaN manufacturing advancements allow monolithic integration, merging sensing, protection, and control circuits with high-voltage GaN HEMTs. This article presents a fully monolithic closed-loop series-capacitor buck converter for 200-to-5 V and 400-to-12 V direct conversion. The presented design manages closed-loop control complexity, overcoming challenges in analog and digital GaN circuitry and reducing static power consumption. A unique switching sequence eliminates the need for a level shifter, addressing challenges associated with common-mode transient immunity and high
$dv/dt$
signals. Converter operation is experimentally validated up to 400 V. The on-chip closed-loop control regulates the 5 V output voltage to within 87 mV under a load step from 0.35 to 0.85 A. The design achieves a competitive power density of 2.17 W
$\mathrm{/}\text{cm}^{3}$
, delivering 13.7 W at 400-to-12 V and attains a peak efficiency of 80.2
$ \%$
for 200-to-5 V operation. This work represents the first demonstration of closed-loop control with an integrated multiphase half-bridge capable of operating at 400
$\, \text{V}$
.