STMicroelectronics EVL6566B-65W-QR

Overview

EVL6566B-65W-QR from STMicroelectronics is a 65 W quasi-resonant flyback adapter evaluation board designed for high-end portable computer power supplies, delivering 19 V at 3.42 A continuous output, achieving >89% average efficiency without synchronous rectification, and consuming <100 mW standby power at 230 Vac.

For engineers reviewing the EVL6566B-65W-QR datasheet, EVL6566B-65W-QR application, EVL6566B-65W-QR design reference, or EVL6566B-65W-QR component selection for AC/DC adapter development, this board provides validated implementation of the L6566B QR controller with EN61000-3-2 Class-D compliance, EN55022 Class-B EMI performance, and EN60950 safety certification.

Technical Context

The board implements a discontinuous conduction mode (DCM) quasi-resonant flyback topology using the L6566B current-mode controller, which detects transformer demagnetization via ZCD pin and enforces valley-switching even under light loads via valley-skipping. Maximum switching frequency is set to ~165 kHz by an external resistor on the OSC pin.

Power stage uses an STF7NM80 800 V TO-220FP MOSFET with minimal heatsinking, an EER28L ferrite transformer with ~150 V reflected voltage, and parallel STPS20H100CFP Schottky rectifiers in TO-220FP packages. Output filtering includes a discrete LC stage to suppress high-frequency ripple and diode-induced spikes.

Key Specifications

Availability

EVL6566B-65W-QR is available at Aetrix Electronics and suitable for notebook adapter design, energy-efficient AC/DC reference development, and Class-D harmonic-compliant power supply qualification requiring stable component supply and documented thermal/mechanical layout.

Supply support for EVL6566B-65W-QR 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, analog ICs, power devices, and silicon solutions for industrial, automotive, and consumer applications.

This board belongs to ST's Power Supply Evaluation Kit product line, engineered to accelerate time-to-market for high-efficiency, standards-compliant offline SMPS designs targeting portable computing and energy-sensitive end equipment.

FAQ

What is the primary function of the L6566B controller on this board?

The L6566B operates as a current-mode quasi-resonant flyback controller that senses transformer demagnetization via the ZCD pin and enables valley-switching across all load conditions-including DCM-using its valley-skipping feature. It sets maximum frequency (~165 kHz) via an external OSC resistor and delivers tight regulation while minimizing switching losses without requiring auxiliary winding sensing.

Can this board be modified for 12 V or 24 V output?

Yes, output voltage can be adjusted by modifying the feedback divider network (R10/R11) and verifying loop stability, but transformer turns ratio, rectifier ratings, and snubber components must be re-evaluated. The EER28L core and STPS20H100CFP diodes are optimized for 19 V; changing output significantly requires redesign of magnetic components and thermal validation per EN60950.

Does the board include synchronous rectification?

No, the EVL6566B-65W-QR uses dual parallel STPS20H100CFP Schottky diodes for output rectification and achieves >89% efficiency without synchronous rectification. The design intentionally omits SR to demonstrate high efficiency using passive rectification, leveraging L6566B's valley-skipping to reduce MOSFET switching losses and minimize BOM cost and complexity.

Is the PCB layout suitable for EMC pre-compliance testing?

Yes, the single-sided CEM-1 PCB (58 × 121 mm) follows ST's recommended layout practices for quasi-resonant flyback converters, including minimized high-di/dt loops, grounded thermal pads for power devices, and integrated EMI filtering. It has been verified to meet EN55022 Class-B limits in standard lab setups, making it suitable for pre-compliance validation prior to formal certification.