10 W flyback with an 800 V avalanche MOSFET — the offline power stage
The STMicroelectronics VIPER15HN is a monolithic offline flyback switching regulator from the VIPer™ plus series, integrating a 800 V avalanche-rugged power MOSFET with a PWM controller in a 7-lead DIP package. It delivers up to 10 W of isolated output power, switching at 225 kHz to shrink the transformer footprint. The device includes built-in fault protection — current limiting, over-temperature, and over-voltage — so the primary-side bill of materials stays lean.
For new designs, ST's current VIPer™ plus portfolio offers functionally similar devices, but pin-compatibility is not guaranteed.
Supply range and start-up sequencing
The Vcc supply range is 8.5 V to 23.5 V, with a 14 V start-up threshold. This start-up voltage is typical for offline converters that charge the Vcc capacitor from the rectified DC bus through a start-up resistor; once the auxiliary winding takes over, the supply drops into the normal operating window. The 225 kHz fixed switching frequency sets the transformer design — plan the core and turns ratio for that frequency to avoid saturation at full load.
Thermal budget — 150 °C junction limit
The 800 V breakdown MOSFET provides good derating margin for universal AC input, but switching losses at 225 kHz add to the thermal budget.