GaN-enabled digital PFC reference design board achieves 99% efficiency

The GaNdalf development platform, which provides a blueprint for high-performance bridgeless Power Factor Correction (PFC) circuit designs for loads up to one kilowatt, and which benefits from the superior operating characteristics of gallium nitride (GaN) power components and digital control enabled by the latest dual-core digital signal controller from Microchip.

The GaNdalf reference design board 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 85V-265V AC, the GaNdalf board achieves a power factor of >0.98 and efficiency in the PFC stage of better than 99.0%. 

Power Factor Correction (PFC) is widely used in AC/DC power supplies with an input power greater than 75W. The PFC circuit controls the input current to synchronise it with the input voltage and to minimise 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. 

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 400V DC, the GaNdalf board may be used to supply loads up to one kilowatt. Total harmonic distortion is less than ten percent. 

Etienne Lanoy, Director of the Future Electronics Centres of Excellence, which produced the GaNdalf board, said: ‘“The relative performance advantages of GaN FETs over silicon MOSFETS signals a new paradigm for customers to add value to the latest power system designs, trading off higher efficiency, faster switching and smaller size. With GaNdalf, the Centre of Excellence engineering team demonstrates the value which GaN technology can bring to one area of power system design, namely PFC. 

“The excellent performance that GaN provides under high-voltage/hard-switching conditions enables the highest efficiency for a relatively low component count. But this is tricky to realise and much needs to be learned to gain the full benefits of GaN. The knowledge attained by Future Electronics through this project should be of significant value to customers and we stand ready to partner with customers and enable them to take advantage of this new technology.”

The GaNdalf board will be available to qualified customers of Future Electronics in Q1 2019.