This evaluation board is a system solution for a bridgeless totem-pole power factor corrector (PFC) with bidirectional power capability. The EVAL_3K3W_TP_PFC_SIC is enabled by Infineon‘s CoolSiC™ (silicon carbide) and CoolMOS™ Superjunction power MOSFETs as well as isolated drivers and an XMC™ microcontroller.
This bridgeless totem-pole PFC board is intended for applications that require high efficiency (≈99%) and high power density (72W/in3) such as high-end server and telecom. In addition, the bidirectional power flow capability allows this design to be used in battery chargers or battery formation applications.
The totem-pole implemented in this evaluation board operates in continuous-conduction mode (CCM) in both rectifier (PFC) and inverter mode which also implements digital control on Infineon XMC™ 1000 series microcontroller.
The figure above shows the placement of the different sections of this bridgeless totem-pole bi-directional PFC design. The board is 208mm long, with a width of 89mm and a height of 40mm (1U), for a power density of 73 W/in3.
Inmediately after the ac input connector, a two-stage EMI filter is placed as well as a fuse and NTC in-rush current limiter, together with the input relay. The dc output connector is placed on the same side of the board as the ac connector. Close to the output connector, a single-stage filter (with differential and common mode paths) is placed to guarantee proper aquisition of the output variables in efficiency measurements.
On the other side of the board, two daughter cards are introduced. They are the bias board and the control card. The bias board uses a QR CoolSET™ controller and 950V P7 CoolMOS™ switch to generate the required voltages for the control card, driving, relay and fan supply. The control card implements the required current, voltage and polarity sensing. The full digital control is implemented in the Infineon XMC™ microcontroller, which is in charge of the proper operation of the bridgeless totem-pole topology.
The rest of the board is occupied by the bridgeless totem-pole itself, which comprises the PFC choke, the bulk capacitor and a bridge with 650V CoolSiC™ MOSFET and 600V C7 CoolMOS™. The bulk capacitance is designed to provide a hold-up time of 10ms at 100% load and 20ms at 50% load when operating with an input voltage of 230Vrms, 50 Hz. The semiconductors in TO-247 package are mounted on a heatsink with attached fan, which blows air toward the PFC choke. The choke is designed with high-flux material in EQ shape in order to comply with the height requirement, high efficiency performance and high power density.
Summary of Features
- High efficiency bridgeless totem-pole PFC
- High power density
- Enabled by CoolSiC™ MOSFET 650V
- Digitally controlled with XMC1404
- Bidirectional capability (DC-AC operation)
- Efficiency close to 99%
- Compact form factor (72W/in3)
- Low component count
- Bidirectional operation (digital control)