The simplified circuit diagram of the EVAL_2K4W_ACT_BRD_S7 demo board from Infineon Technologies is shown above. The ac-dc converter is a 2400W standard boost PFC working in CCM with two added features:
- Active-bridge line rectification for efficiency improvement
- Replacement of the Electro-Magnetic (EM) relay with a solid-state relay for power density increase
The active-line rectification is realized with a plug-in daughter card, named as KIT_ACT_BRD_60R0xxS7 in the above block diagram, based on the 600V CoolMOS™ S7 in a TOLL package.
The classic bulky EM relay is replaced with a 600V CoolMOS S7 (also in a TOLL package) in series with the bulk capacitor and parallelized with a NTC resistor for inrush current limitation.
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The PFC stage is operated at both low-line (90Vrms minimum, 120Vrms nominal) and high-line (230Vrms nominal, 265Vrms maximum) in CCM with a 65kHz fixed switching frequency. The bulk capacitance is designed to comply with typical hold-up time of 20ms. The PFC controls the input ac current to a sinusoidal shape and the output dc voltage to a fixed dc value (around 390V) by means of an easy-to-use analog controller.
The other daughter card, named as KIT_6W_12V_P7_950V, is employed to derive the 12V power supply for the PFC controller, for the driving stage of the PFC switch and the solid-state relay. Finally, it is also used to supply the active-bridge daughter card.
The power supply has been designed to comply with the requirements of a data center server PFC stage targeting 80 PLUS Titanium efficiency and exceeding 80 W/in3 of power density.