GaN power switch: the crucial technology enabling the ultra-efficient bridgeless totem pole topology
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 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.
The bridgeless totem pole PFC topology offers various advantages compared to other approaches, including:
- Fewer components
- Lowest conduction losses
- Highest efficiency
Conventional silicon super-junction MOSFETs are unsuitable for use in the hard-switched half-bridge arrangement in a bridgeless totem-pole topology, which calls instead for the superior characteristics – including low output capacitance and zero reverse recovery – of GaN High Electron-Mobility Transistor (HEMT) switches.
In the GaNdalf II system, CoolGaN™ devices from Infineon offer outstanding performance when operating in continuous conduction mode, helping the PFC stage to achieve efficiency of 99.0%.
Key components of the GaNdalf II power system
- Infineon CoolGaN™ transistors and isolated driver
- Microchip dsPIC33CH dual core 16-bit digital signal controller
- Microchip signal chain and power management devices
- Myrra custom inductor
- Murata isolated DC-DC converter module
- Infineon 17mΩ MOSFET for synchronous rectification
Key features of the GaNdalf II PFC circuit
- Input-voltage range: 85V to 265V AC
- Output voltage: 400V DC
- Supports loads up to 2kW
- <10% total harmonic distortion
- >0.99 power factor
- Digitally controlled: eases overall control (zero crossing, GaN and synchronous rectification drive)
