STMicroelectronics STEVAL-ISA117V1

Overview

STEVAL-ISA117V1 from STMicroelectronics is a fully assembled, CE-compliant demonstration board implementing a 12 V / 0.35 A (4.2 W) isolated flyback power supply using the VIPER16LN off-line PWM controller. It operates across universal AC input (90–264 VAC, 45–65 Hz), achieves >75% average efficiency, delivers ±5% output regulation, and maintains <30 mW standby consumption at 230 VAC with auxiliary biasing - targeting low-power industrial and consumer auxiliary supply applications.

For engineers reviewing the STEVAL-ISA117V1 datasheet, STEVAL-ISA117V1 schematic, STEVAL-ISA117V1 transformer winding ratio, or STEVAL-ISA117V1 application notes, this board serves as a validated reference design for VIPER16LN-based 4 W isolated flyback converters requiring EMI compliance (EN55022 Class B), thermal fault protection, and no-auxiliary-winding operation capability.

Technical Context

The board implements a primary-side regulated, discontinuous conduction mode (DCM) flyback topology with integrated 800 V avalanche-rugged power section and fixed 60 kHz switching frequency with jittering to reduce EMI peaks. Feedback is closed via PC817 optocoupler and TS431 shunt regulator, enabling precise output voltage control without secondary-side sensing circuitry.

VIPER16LN supplies itself via internal current generator (eliminating auxiliary winding), but supports external biasing through transformer pin 1–2 (turn ratio 7.33:1) to achieve ultra-low standby power. Protection features include thermal shutdown with hysteresis, delayed overload response, and open-loop failure detection - active only when externally biased.

Key Specifications

Availability

STEVAL-ISA117V1 is available at Aetrix Electronics and suitable for industrial control auxiliary supplies, smart meter power rails, IoT gateway standby rails, and white goods control board power conversion requiring stable component supply, pre-validated safety isolation, and regulatory-ready EMI performance.

Supply support for STEVAL-ISA117V1 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, Switzerland, designing and manufacturing microcontrollers, power ICs, analog chips, and MEMS sensors for industrial, automotive, and consumer markets.

This evaluation board belongs to ST's STEVAL (ST Evaluation) series - purpose-built reference designs that demonstrate real-world implementation of ST's high-voltage AC-DC converters, emphasizing rapid prototyping, safety certification readiness, and layout best practices for isolated power stages.

FAQ

What is the maximum continuous output power and under what conditions?

The STEVAL-ISA117V1 delivers 4.2 W continuously (12 V × 0.35 A) at ambient temperatures ≤60 °C with natural convection cooling. Output derating begins above 60 °C ambient, and full power is maintained across 90–264 VAC input with line regulation better than ±5% and load regulation within ±5% from 0–100% load.

How does the board achieve <30 mW standby consumption?

Standby power <30 mW at 230 VAC is achieved only when jumper J is installed to enable external biasing from the transformer auxiliary winding (pins 1–2). In self-biased mode (J removed), standby rises to ~50 mW due to internal current generator operation - both modes are validated per EN50564 test procedures.

Can this board be modified for 5 V or 24 V output?

Yes - output voltage is set by the TS431/PC817 feedback divider (R11a/R11b/R12a/R12b). To change to 5 V, replace R11a with 22 kΩ and R12a with 10 kΩ; for 24 V, use R11a = 47 kΩ and R12a = 10 kΩ. Transformer turns ratio remains valid, but output diode (D2) and output capacitor (C9) must be re-rated accordingly.

Is the board certified for safety or EMC out-of-the-box?

No - STEVAL-ISA117V1 is a demonstration board, not a certified end-product. It meets EN55022 Class B radiated/conducted EMI limits in standard lab setups and incorporates reinforced isolation (≥4 kV RMS) per IEC 60747-5-5, but final system-level safety certification (IEC 62368-1, UL 62368-1) requires integration into an approved enclosure with proper creepage/clearance validation.