11 W offline switcher with 730 V internal MOSFET
The STMicroelectronics VIPER122LSTR is a monolithic offline switching regulator that integrates a 730 V avalanche-rugged power MOSFET and a PWM controller in a single SSOP-10 package. It delivers up to 11 W across buck, buck-boost, or flyback topologies — one part covers isolated and non-isolated rails up to that power ceiling. Switching at a fixed 60 kHz, the internal oscillator sets the EMI signature and transformer magnetising inductance without external timing components. The 80 % duty cycle ceiling gives headroom for wide-input flyback designs at low line.
At 60 kHz the core volume and winding turns for a flyback transformer at 11 W are small enough to fit an RM8 or EP13 core — a known sweet spot for offline auxiliary supplies. The fixed frequency also simplifies conducted EMI filtering because the fundamental and its harmonics sit at predictable frequencies.