12V / 6A Universal-Input Isolated Flyback Design

January 17, 2017 by Jeff Shepard

STMicroelectronics now offers the STEVAL-ISA180V1 evaluation board which implements a wide mains range flyback isolated converter (with an output of 12V at 0.6A), developed for general-purpose applications. This high-voltage converter intelligently integrates an 800V rugged power MOSFET with pwm current-mode control. The core of the design is the new VIPer0P off-line high voltage converter from VIPerPlus family with zero power features.

The evaluation board features a small size and minimal BOM, high efficiency, low standby consumption and high reliability due to these protections: pulse skip mode to avoid flux-runaway, delayed overload protection (OLP), max duty cycle counter, VCC clamp and thermal shutdown.

Key features include: Universal ac main input voltage range of 85- to 265-Vac; Rated output power of 7.2W; Input power in standby at 230Vac is less than 18mW; Active mode efficiency is over 80%; EMI meets EN55022-Class-B; and RoHS compliant.

These performance levels are achieved due to the following VIPer0P characteristics: 800V avalanche rugged Power MOSFET; Embedded HV start-up; 60kHz fixed switching frequency with jittering; Pulse frequency modulation and ultra-low stand-by consumption of the internal circuitry under light load condition; Current-mode pwm controller with drain current limit protection for easy compensation; and soft-start.

These features facilitate building a complete system design with a minimum component count. In addition, enhanced system reliability is ensured by: pulse skip mode to avoid flux-runaway; Delayed overload protection (OLP); Maximum duty cycle counter; VCC clamp; and Thermal shutdown.