20 W isolated flyback with 800 V avalanche-rugged MOSFET
The STMicroelectronics VIPER37LDTR is an offline flyback switching regulator from the VIPer™ plus family, integrating an 800 V avalanche-rugged power MOSFET and PWM controller in a 16-SOIC package. It delivers up to 20 W of continuous output power in an isolated flyback topology, switching at 60 kHz. The controller includes built-in fault protection — current limiting, over-temperature shutdown, and over-voltage protection — reducing external component count for a compact PSU design.
Breakdown voltage and switching frequency — sizing the transformer
The 800 V breakdown rating on the integrated MOSFET handles reflected voltage and leakage inductance spikes in universal AC input flyback designs. At 60 kHz, the switching frequency is a practical compromise between transformer size and switching losses — the core volume can be kept moderate while staying below the EMI quasi-peak limit without heavy filtering. The 80 % maximum duty cycle supports a wide input-voltage range and keeps secondary-side voltage stress manageable in a standard flyback.
Junction temperature and supply range — where it runs
The 150°C TJ max allows the part to run at full 20 W output without forced cooling in many sealed PSUs. The Vcc supply range of 8.5 V to 23.5 V gives the auxiliary winding plenty of headroom, and the 14 V start-up threshold ensures clean turn-on even with a slow-rising bulk capacitor.