STMicroelectronics STEVAL-ISA171V1

Overview

STEVAL-ISA171V1 from STMicroelectronics is a 15 W, 12 V/1.25 A evaluation board implementing a quasi-resonant flyback AC-DC converter using the VIPER35HD high-voltage offline controller. It accepts universal AC input (90–264 VAC), achieves >82% active-mode efficiency, consumes <30 mW at 230 VAC standby, and meets EN55022 Class-B EMI pre-compliance for industrial power supply design.

For engineers reviewing the STEVAL-ISA171V1 datasheet, STEVAL-ISA171V1 schematic, STEVAL-ISA171V1 application notes, or STEVAL-ISA171V1 alternative evaluation boards, this reference design provides validated layout, BOM, and performance data for rapid prototyping of compact, low-standby, quasi-resonant flyback converters targeting IoT edge nodes and industrial auxiliary supplies.

Technical Context

The board implements a primary-side regulated quasi-resonant flyback topology centered on the VIPER35HD - an integrated 800 V MOSFET + current-mode PWM controller with burst-mode operation for ultra-low no-load consumption. Control loop stability is maintained via optocoupler feedback (SFH610A-2) and TL432-based shunt regulator.

Quasi-resonant switching reduces EMI by zero-voltage turn-on and minimizes switching losses across line/load conditions. The transformer (T1) features 3.3 µH primary inductance and is optimized for 100 kHz nominal switching frequency with valley-switching detection.

Key Specifications

Availability

STEVAL-ISA171V1 is available at Aetrix Electronics and suitable for industrial auxiliary power, smart sensor node power, and PLC I/O module design requiring stable component supply and fast-turn evaluation support.

Supply support for STEVAL-ISA171V1 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, delivering microcontrollers, power ICs, analog devices, and silicon solutions for automotive, industrial, and consumer applications.

The STEVAL-ISA171V1 belongs to ST's ST EVAL series of application-specific evaluation kits, designed to accelerate validation of VIPerPLUS offline controllers in cost-sensitive, space-constrained AC-DC power designs.

FAQ

What is the primary controller IC used on the STEVAL-ISA171V1?

The board uses the VIPER35HD - an integrated 800 V high-voltage MOSFET and current-mode PWM controller from ST's VIPerPLUS family. It enables quasi-resonant operation, burst-mode standby control, and primary-side regulation without auxiliary winding sensing.

Does the STEVAL-ISA171V1 include safety-certified isolation?

Yes - it incorporates reinforced isolation between primary and secondary sides per IEC 60747-5-2, verified by creepage/clearance distances ≥8 mm and reinforced insulation on the SFH610A-2 optocoupler and transformer T1, meeting basic safety requirements for Class II applications.

Can the output voltage be adjusted, and how?

Yes - output voltage is set by the resistor divider (R10, R11) feeding the TL432 shunt regulator. Adjusting R10/R11 ratio changes the feedback reference, enabling precise 12 V tuning or reconfiguration to other values (e.g., 5 V or 15 V) within the VIPER35HD's regulation capability.

Is a bill of materials (BOM) provided with the STEVAL-ISA171V1?

Yes - the official DB2744 data brief includes a complete, manufacturer-validated BOM listing all components (including transformer T1, optocoupler SFH610A-2, TL432, and VIPER35HD), along with part numbers, manufacturers, and footprint references for direct replication or modification.