GaNdalf 1kW Bridgeless Totem Pole PFC Reference Board with Digital Control

January 30, 2019 by Paul Shepard

The GaNdalf reference design board from Future Electronics takes advantage of the low output capacitance and zero reverse recovery of the latest X-Gan HEMT power switches from Panasonic, which are fabricated from wide bandgap GaN semiconductor material.

Operating from a universal mains input range of 85- to 265-Vac, the GaNdalf board achieves a power factor of >0.98 and efficiency in the PFC stage of better than 99.0%.

Power factor correction is widely used in ac-dc power supplies with an input power greater than 75W. The PFC circuit controls the input current to synchronize it with the input voltage and to minimize reactive power losses. Power-system designers are under more pressure than ever to achieve high efficiency across the whole ac-dc converter circuit.

In the PFC stage, the drive for efficiency has led designers to evaluate various bridgeless PFC circuit topologies, which remove the rectifying diode bridge and its associated power losses from the input of the PFC stage.

GaNdalf board

In the GaNdalf board design, Future Electronics has implemented a bridgeless totem pole PFC topology which offers very high efficiency and a low component count. Conventional silicon superjunction MOSFETs perform poorly in this hard-switched topology, so Future Electronics has based its PFC circuit on two Panasonic PGA2E07BA X-Gan switches.

To implement digital control, the preferred control method for the bridgeless totem pole PFC topology, the GaNdalf board uses Microchip's dsPIC33H dual-core digital signal controller. This is an excellent platform for digital control, and provides spare processing capacity for additional functions such as system monitoring and communication.

Providing an output voltage of up to 400Vdc, the GaNdalf board may be used to supply loads up to 1kW. Total harmonic distortion is <10%.

Features and specifications:

  • Input-voltage range: 85- to 265-Vac
  • Output voltage: 400Vdc
  • Supports loads up to 1kW
  • <10% total harmonic distortion
  • >0.98 power factor
  • Digitally controlled: eases overall control (zero crossing, GaN and synchronous rectification drive)
  • Panasonic's GaN High Electron-Mobility Transistors (HEMTs).
    • These devices benefit from the superior electrical and thermal properties of the wide bandgap gallium nitride material to provide far better switching and conduction performance than equivalent silicon-based FETs
  • Microchip's most recent dual-core 16-bit Digital Signal Controller (DSC)