L6565 Quasi-Resonant SMPS

The L6565 designed as a current-mode primary controller IC, explicitly  to build offline Quasi-resonant ZVS (Zero Voltage Switching at switch turn-on) fly- back converters. The quasi-resonant operation achieved using a transformer demagnetization sensing input that triggers MOSFET’s turn-on.

In this device, the converter’s power capability variations with the mains voltage compensated via line voltage feedforward. Under the light load condition,  the device features a special function that automatically lowers the operating frequency. But still maintaining the operation as close to ZVS as possible. In addition to very low start-up and quiescent currents, this feature helps keep low the consumption from the mains at light load.  And also Blue Angel and Energy Star compliant.

The IC includes also a disable function, an on-chip filter on current sense, an error amplifier with a precise reference voltage for primary regulation and an effective two-level overcurrent protection. Basically, in ZVS converters the power switch  dynamically connected in parallel to the tank circuit. The superposition of the resonant voltage across the tank circuit (and the switch, while it is in off state) on the DC input voltage generates the zero-voltage condition for the switch to turn on.

APPLICATIONS

• Tv/monitor SMPS
• Ac-dc adapters/chargers
• Digital consumer
• Printers, fax machines,
• Photocopiers and scanners