STMicroelectronics STEVAL-VP318L2F

Overview

STEVAL-VP318L2F from STMicroelectronics is an evaluation board implementing a 15 V/1.2 A, 18 W isolated flyback converter using primary-side regulation (PSR), based on the VIPER318LDTR high-voltage offline controller with integrated 800 V avalanche-rugged MOSFET, 60 kHz fixed-frequency jittering PWM, and burst-mode light-load management. It targets general-purpose AC/DC power conversion in compact, low-BOM industrial and consumer systems.

For engineers reviewing the STEVAL-VP318L2F datasheet, STEVAL-VP318L2F pinout, STEVAL-VP318L2F application, or STEVAL-VP318L2F equivalent, this board enables rapid validation of PSR flyback topologies with tight line/load regulation (< ±3%), >83% average efficiency, IEC55022 Class B EMI compliance using minimal filter components, and configurable OVP/UVP thresholds.

Technical Context

The board implements a transformer-isolated, primary-side regulated flyback architecture eliminating optocoupler and secondary-side feedback circuitry. Control is executed by the VIPER318LDTR IC, which integrates a 800 V power MOSFET, current-mode PWM controller, and dedicated pins for OVP, UVP, and FB sensing - enabling precise output voltage regulation without secondary sensing.

Frequency jittering spreads the switching spectrum to reduce peak EMI emissions, while burst mode operation minimizes standby power consumption below ~10% load. Input protection includes independently settable overvoltage and undervoltage lockout thresholds via external resistor dividers on OVP and UVP pins.

Key Specifications

Availability

STEVAL-VP318L2F is available at Aetrix Electronics and suitable for AC/DC reference design validation, PSR flyback prototyping, and energy-efficient off-line power supply qualification requiring stable component supply, traceable sourcing, and lifecycle continuity.

Supply support for STEVAL-VP318L2F 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 devices, and silicon solutions for industrial, automotive, and consumer applications.

This evaluation board belongs to ST's STEVAL series of application-specific reference designs, developed to accelerate adoption of VIPerPlus offline converters in cost-sensitive, space-constrained AC/DC power supplies.

FAQ

What is the purpose of the OVP and UVP pins on STEVAL-VP318L2F?

The OVP (Overvoltage Protection) and UVP (Undervoltage Protection) pins are dedicated terminals on the VIPER318LDTR IC that accept external resistor dividers to set independent trip thresholds. OVP disables switching if reflected auxiliary winding voltage exceeds the programmed level, protecting downstream loads; UVP halts operation when input-derived auxiliary voltage falls below threshold, preventing unstable startup or brownout operation.

Does STEVAL-VP318L2F require an optocoupler for regulation?

No. STEVAL-VP318L2F uses primary-side regulation (PSR) implemented by the VIPER318LDTR, which derives output voltage information from the transformer auxiliary winding. This eliminates the need for an optocoupler, TL431, or secondary-side feedback network - reducing BOM count, cost, and board area while maintaining ±3% regulation accuracy.

Can STEVAL-VP318L2F be modified for different output voltages?

Yes. Output voltage is set by the turns ratio of the custom flyback transformer (T1) and the feedback divider connected to the FB pin. To change output voltage, the transformer auxiliary winding turns and/or the FB resistor divider must be recalculated and replaced. Reference design files and transformer specifications are provided in DB4436 for adaptation.

What is the role of frequency jittering in EMI reduction on this board?

Frequency jittering modulates the 60 kHz switching frequency by ±4 kHz around its center value, spreading energy across a wider spectral band. This lowers peak conducted EMI amplitudes, enabling compliance with IEC55022 Class B limits using only a minimal two-stage EMI filter (C1, C5, Laux, D6), reducing component count and board footprint versus fixed-frequency designs.