L6565 Quasi-Resonant Primary Controller IC | Current-Mode ZVS Flyback Controller

The L6565 primary-side controller IC enables designers to build highly-efficient quasi-resonant (QR) zero-voltage-switching (ZVS) flyback power supplies, ensuring lower switching loss and improved thermal performance. Using transformer demagnetization sensing, the controller automatically triggers MOSFET turn-on at the optimal point, helping maintain soft-switching operation across varying loads.

To stabilize output performance under AC mains variation, the device integrates line-voltage feed-forward, allowing consistent power delivery even when the supply fluctuates. For light-load efficiency, the L6565 reduces operating frequency while still staying close to ZVS behavior—ideal for modern designs seeking Blue Angel, Energy Star, and low-standby compliance.

This controller IC also includes onboard current-sense filtering, a high-precision 1% reference voltage, built-in error amplifier for primary-side regulation, and robust over-current protection in both pulse-by-pulse and hiccup fault modes. With start-up current < 70 μA and quiescent current < 3.5 mA, it enables extremely low standby power—critical for consumer power supplies.

The result is a compact, efficient and protected control solution for AC-DC adapters, SMPS supplies, office equipment, displays, and digital consumer electronics.

Recommended Industrial & Commercial Uses

Industrial & Commercial Uses

TV & Monitor SMPS power supply

Digital consumer electronics power stages

AC-DC chargers and universal adapters

Printer, fax, copier & scanner supplies

Office electronics power systems

Low-standby designs requiring eco-certification

Energy-efficient flyback topologies

Why Engineers Use L6565

✔ High-efficiency flyback control

✔ Reduced switching losses (ZVS turn-on)

✔ Ultra-low standby energy draw

✔ Wide mains handling with feed-forward

✔ Robust gate drive capability

✔ Complete protection suite

✔ Ideal for modern eco-rated power supplies