Digitally-Controlled GaN-Based 1.5kW Bridgeless Totem Pole PFC Reference Design

March 21, 2019 by Paul Shepard

At this weeks' IEEE Applied Power Electronics Conference in Anaheim, California, GaN Systems and Solantro Semiconductor were highlighting the performance and benefits of a 1.5kW Bridgeless Totem Pole PFC controlled by advanced digital control methods coupled with 650V GaN enhancement mode HEMTs (E‑HEMT). This design solution achieves 80 PLUS® Titanium standards for data centers and computing applications.

It has high power density, reliable start-up, reduced heat sinking, improved cooling and low EMI.  The topology is bi-directional and can be easily scaled and incorporated as a front-end of ac-dc converters for EV on-board chargers and industrial power supply applications.

The latest Solantro® SA4041 32-bit, 50MHz digital power processor facilitates solutions which leverage the performance benefits of GaN Systems' 650V E-HEMT family. The SA4041 integrates high-speed analog peripherals, digital accelerators, event driven timers, and digital processing. Industrial, automotive, and renewable energy applications can benefit from the enhanced performance and reduced component count the SA4041-based solutions offer.

GaN Systems' GS66508B 650V E-HEMTs are implemented with the patented Island Technology® cell layout for reduction of the device size and cost, while delivering substantially higher current and better performance than other GaN devices.  GaNPX® packaging enables low inductance and thermal resistance in a small package.

The GS66508B is a bottom-side cooled transistor that is easy to drive. It has exceptionally low total gate charge, QG, and output capacitance, Coss, resulting in low switching losses and therefore providing very high efficiency.

(click on efficiency curves to enlarge)


  • Universal AC line input voltage (85Vac- 264Vac)
  • 400Vdc regulated bus output voltage
  • 5kW continuous output power
  • Full load efficiency >99%, PF >0.99
  • Low THD (<2.5%)
  • Variable frequency control

Solution Overview:

SA4041 Digital Power Processor

  • 32-bit RISC CPU with 64 KB RAM and 256 KB internal flash memory
  • A highly integrated mixed-signal IC with the industry's most complete set of analog and digital power peripherals. Enables designs with low parts count, high power density and low eBOM cost.
  • Patented digital hardware accelerators eliminate CPU burden associated with high-frequency switching control of GaN devices and increase available CPU processing bandwidth for auxiliary system and housekeeping functions.
  • Gate control with cross-conduction protection
  • High-performance digital PLL for reliable grid synchronization and start-up
  • Variable frequency control minimizes EMI/RFI vs competitive fixed frequency control ICs
  • Optimizes efficiency at all power levels by using different control modes: burst, continuous-conduction and transition
  • Communication via SPI and UART ports

GS66508B 650V E-HEMTs

  • Easy gate drive requirements (0 V- 6 V)
  • Transient tolerant gate drive (-20 V / +10 V)
  • Very high switching frequency (> 10 MHz)
  • Fast and controllable fall and rise times
  • Reverse current capability
  • Zero reverse recovery loss
  • GaNPX® packaging enables low inductance & thermal resistance in high power density applications.