STEVAL-ISA010V1: 12V & 5V @ 150mA Total, 85 ~ 500VAC

This document describes the STEVAL-ISA010V1 demonstration board, which is designed as an example of a simple non-isolated auxiliary power supply for a range of input voltages from 85 VAC to 500 VAC.

There is an ever-increasing demand for small power supplies capable of working without voltage range limitations, even at nominal levels of 400 VAC and 415 VAC, respectively. The real voltage levels can reach 500 VAC (415 V + 20%). The major markets for this type of SMPS are home appliances and metering.

The new STMicroelectronics™ family of monolithic converters is well-suited for this range of input voltages, thanks to the 800 V avalanche-rugged MOSFET integrated within the same package with the control chip. This application note describes a low power SMPS with a buck topology using STMicroelectronics’ VIPer16 fixed-frequency off-line converter as a main circuit. The VIPer16 device includes an 800 V rugged power switch, a PWM controller, programmable overcurrent, overvoltage, overload, a hysteretic thermal protection, soft-start and safe auto-restart after any fault condition removal.

Burst mode operation at light load combined with the very low consumption of the device helps to meet standby energy-saving regulations. The significant benefit of this new chip derives from the jitter of the switching frequency and the possibility to supply the chip directly from the DC HV bus, so auxiliary supply is not mandatory. The VIPer16 is suitable for flyback or buck topologies, and thanks to an internal self-supply circuit it does not require an auxiliary supply.