STMicroelectronics STEVAL-ISA029V1

Overview

STEVAL-ISA029V1 from STMicroelectronics is an isolated triple-output flyback demonstration board based on the VIPer53-E smart power IC, delivering +12 V/1 A, +3.3 V/100 mA, and −24 V/40 mA from 85–300 VAC input. It implements optocoupler-based closed-loop regulation on the 12 V rail, post-regulation via LK112M33TR for 3.3 V, and discrete Zener-PNP linear regulation for the negative output-targeted at DVD and set-top box auxiliary power supply evaluation.

For engineers reviewing the STEVAL-ISA029V1 datasheet, STEVAL-ISA029V1 pinout, STEVAL-ISA029V1 application, or STEVAL-ISA029V1 equivalent, this board serves as a validated reference design for wide-input AC/DC flyback converters with mixed positive/negative regulated outputs and EN60950/EN55022-B compliance verification.

Technical Context

The board implements a primary-side controlled flyback topology using the VIPer53-E, which integrates a current-mode PWM controller and 700 V MDmesh™ MOSFET. Regulation is achieved via optocoupler feedback to the COMP pin, with switching frequency fixed at 60 kHz by external RC network on the OSC pin.

The +12 V output is the main regulated rail; +3.3 V is derived via a low-dropout linear regulator (LK112M33TR); −24 V uses a discrete Zener-diode-biased PNP transistor stage (BD140) with passive filtering. Safety isolation and EMI filtering meet industrial-grade requirements per EN60950 and EN55022-B Class B.

Key Specifications

Availability

STEVAL-ISA029V1 is available at Aetrix Electronics and suitable for DVD player power subsystem validation, set-top box auxiliary supply prototyping, and wide-input AC/DC flyback reference design development requiring stable component supply and documented safety/EMI compliance.

Supply support for STEVAL-ISA029V1 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing microcontrollers, power ICs, analog devices, and silicon solutions for industrial, automotive, and consumer applications.

This board belongs to ST's STEVAL (ST Evaluation) series-engineered to accelerate power supply design validation, provide ready-to-run schematics and layout guidance, and demonstrate integrated smart-power ICs like VIPer in real-world AC/DC topologies.

FAQ

What is the primary control IC used on the STEVAL-ISA029V1 board?

The board uses the VIPer53-E smart power IC, which integrates a current-mode PWM controller and a 700 V MDmesh™ MOSFET in one package. It operates at 60 kHz, accepts direct rectified AC input up to 300 VAC, and provides built-in overvoltage, overcurrent, and thermal protection-enabling compact, self-contained flyback designs without external gate drivers or controllers.

How is output regulation implemented across the three voltage rails?

Regulation is hierarchical: the +12 V rail is tightly regulated via optocoupler feedback to the VIPer53-E COMP pin; the +3.3 V rail uses the LK112M33TR low-dropout linear regulator for ±2% accuracy; the −24 V rail employs a discrete Zener diode (D8), resistor (R13), and PNP transistor (Q1) to generate a stable negative bias without secondary-side control circuitry.

Does STEVAL-ISA029V1 support safety certification testing out of the box?

Yes-the board is designed to meet EN60950-1 for safety and EN55022-B for conducted EMI. It includes reinforced isolation between primary and secondary sides, certified Y-capacitors (C17), properly rated X-capacitors (C1, C2, C4), and creepage/clearance-compliant PCB layout per IEC 60950, enabling direct use in pre-compliance lab testing for consumer power supplies.

Can the −24 V output be modified for different negative voltages?

Yes-the −24 V stage uses a discrete Zener-PNP regulator (D8, Q1, R13), so changing the Zener voltage (e.g., to −15 V or −12 V) and adjusting base bias resistors allows reconfiguration. However, output current remains limited to ~40 mA due to thermal constraints of the BD140 transistor and lack of active current limiting in this linear stage.