STMicroelectronics STEVAL-ISA196V1

Overview

STEVAL-ISA196V1 from STMicroelectronics is a non-isolated 5 V / 1.2 A flyback evaluation board based on the VIPer114LS high-voltage PWM controller with integrated 800 V MOSFET, delivering 6 W output power, <10 mW no-load input power at 230 VAC, and >78% active-mode efficiency for universal AC input (85–265 VAC) applications.

For engineers reviewing the STEVAL-ISA196V1 datasheet, STEVAL-ISA196V1 schematic, STEVAL-ISA196V1 application notes, or STEVAL-ISA196V1 bill of materials, this board serves as a validated reference design for compact, low-BOM, single-layer offline flyback converters targeting industrial power supplies, smart home sensors, and auxiliary power rails in embedded systems.

Technical Context

The board implements a primary-side regulated, current-mode controlled flyback topology without optocoupler feedback or auxiliary winding, relying on the VIPer114LS's internal sensing and adaptive cycle-by-cycle current limiting. It operates in discontinuous conduction mode (DCM) across full load and line range.

Key design constraints include fixed 65 kHz switching frequency, integrated high-voltage startup circuitry, built-in thermal shutdown and overcurrent protection, and compliance with EN55022 Class B conducted EMI limits without external filtering beyond the specified X/Y capacitors and common-mode choke.

Key Specifications

Availability

STEVAL-ISA196V1 is available at Aetrix Electronics and suitable for industrial sensor nodes, smart meter auxiliary supplies, IoT gateway standby rails, and low-power AC/DC adapter development requiring stable component supply and pre-validated safety-compliant topologies.

Supply support for STEVAL-ISA196V1 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 chips, and MEMS sensors for automotive, industrial, and consumer markets.

This board belongs to ST's STEVAL (ST Evaluation) series-engineered to accelerate prototyping of ST's proprietary power conversion ICs like the VIPerPlus family, specifically targeting cost-sensitive, space-constrained offline SMPS designs.

FAQ

What is the purpose of the NTC thermistor (RV) on STEVAL-ISA196V1?

The NTC thermistor (RV, 16 Ω) is placed in series with the input fuse (F1) to limit inrush current during cold-start conditions, preventing fuse blowout and reducing stress on the bulk capacitor C1 and bridge rectifier BR. Its resistance drops with temperature, enabling normal operation after initial surge suppression.

Does STEVAL-ISA196V1 support output short-circuit protection?

Yes-the VIPer114LS IC provides cycle-by-cycle current limiting and automatic restart after fault clearance. During sustained short-circuit, the board enters hiccup mode: it shuts down for ~1 s, then attempts soft restart. This behavior is confirmed in the VIPer114LS datasheet and verified on the board under test conditions.

Can the output voltage be adjusted to 3.3 V or 12 V?

No-output voltage is fixed at 5 V by the internal reference and primary-side regulation algorithm of the VIPer114LS. Changing output requires redesigning the transformer turns ratio, feedback network, and rectifier/filter components; no onboard resistor divider or jumper enables adjustment.

Is an auxiliary winding required for V_CC supply on this board?

No-the VIPer114LS uses high-voltage startup via an internal current source drawing from the drain pin, eliminating need for an auxiliary winding. V_CC is maintained during operation by energy recovered from the transformer's leakage inductance through D2 and C10, as shown in the schematic.