High Power Factor Soft Switched Synchronous Buck with GaN SiP and Advanced HPF QR Controller

This paper presents the design and implementation of a 100W Synchronous Inverse Buck (SIB) converter for LED drivers, with a wide input voltage range, High Power Factor (HPF) and high efficiency. The proposed converter is based on a High Voltage (HV) Gallium Nitride (GaN) High Electron Mobility Transistors (HEMT) System in Package (SiP) and a novel advanced Quasi-Resonant (QR) analog controller with Power Factor Correction (PFC) control. The SIB is controlled to achieve Zero Voltage Switching (ZVS) for both the power switches. The analog controller includes a “THD Optimizer” block, which ensures low input current harmonic distortion (ITHD), a crucial factor for offline LED drivers. In the SIB, the High-Side (HS) switch always switches under ZVS, but the Low-Side (LS) switch operates in hard switching. The solution shown in this paper exploits the zero current detection and power device turn-on delay feature of the dedicated analog controller to add ZVS for the LS GaN transistor. The GaN SiP technology enables high-efficiency and high switching frequencies, while maintaining a small form factor.