Offline switching regulator with integrated 800 V MOSFET
The STMicroelectronics VIPER013BLSTR is an offline switching regulator from the VIPER™ series that integrates a power MOSFET with an 800 V breakdown voltage, enabling direct connection to rectified mains in universal-input AC-DC converters. It supports buck, buck-boost, and flyback topologies with a fixed switching frequency of 60 kHz, and delivers up to 8 W of output power without an external power switch. The device includes control features such as enable and soft start, and provides fault protection including current limiting, over-load, over-voltage, and short-circuit protection.
60 kHz switching — transformer sizing and EMI
The 60 kHz switching frequency is a design anchor for the power transformer and output filter components — at this frequency a ferrite core with moderate cross-section handles the volt-second product for an 8 W flyback, keeping the transformer physically small. The 80 % maximum duty cycle gives headroom for low-line operation in a buck or flyback configuration, allowing the controller to maintain regulation down to the valley of the rectified AC waveform.