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Multi-mode controller for SMPS
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The L6566BH is an extremely versatile current-mode primary controller IC, specifically designed for high-performance offline flyback converters running off rectified 3-phase input lines. It is also suited to single-stage, single-switch, input-current-shaping converters (single-stage PFC) for applications that must comply with EN61000-3-2 or JEITA-MITI regulations.

Both fixed-frequency (FF) and quasi-resonant (QR) operation are supported. The user can choose either of the two depending on application needs. The device features an externally programmable oscillator: it defines the converter switching frequency in FF mode and the maximum allowed switching frequency in QR mode.

When FF operation is selected, the ICs work as a standard current-mode controller with a maximum duty cycle limited to 70% min. The oscillator frequency can be modulated to mitigate EMI emissions.

QR operation, when selected, occurs at heavy load and is achieved through a transformer demagnetization sensing input that triggers MOSFET turn-on. Under some conditions, ZVS (zero-voltage switching) can be achieved. The converter’s power capability rise with the mains voltage is compensated by line voltage feedforward. At medium and light load, as the QR operating frequency equals the oscillator frequency, a function (valley skipping) is activated to prevent further frequency rise and keep the operation as close to ZVS as possible.

With either FF or QR operation, at very light load the ICs enter a controlled burst-mode operation that, along with the built-in, non-dissipative, high-voltage startup circuit and the low quiescent current, helps keep the consumption from the mains low and meet energy saving recommendations.

An innovative adaptive UVLO helps minimize the issues related to the fluctuations of the self-supply voltage due to transformer parasites.

The protection functions included in this device are: not-latched input undervoltage (brownout), output OVP (auto-restart or latch-mode selectable), a first-level OCP with delayed shutdown to protect the system during overload or short-circuit conditions (auto-restart or latch-mode selectable), and a second-level OCP that is invoked when the transformer saturates or there is a short-circuit of the secondary diode. A latched disable input allows easy implementation of OTP with an external NTC, while an internal shutdown prevents IC overheating.

Programmable soft-start, leading-edge blanking on the current sense input for greater noise immunity, slope compensation (in FF mode only), and a shutdown function for externally controlled burst-mode operation or remote ON/OFF control complete the features of this device.

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Errata Sheet
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Key Features

  • Selectable multimode operation: fixed frequency or quasi-resonant
  • On-board 840 V high voltage startup
  • Advanced light load management
  • Low quiescent current (< 3 mA)
  • Adaptive UVLO
  • Line feedforward for constant power capability vs. mains voltage
  • Pulse-by-pulse OCP, shutdown on overload (latched or auto-restart)
  • Transformer saturation detection
  • Programmable frequency modulation for EMI reduction
  • Latched or auto-restart OVP
  • Brownout protection
  • -600/+800 mA totem pole gate driver with active pull-down during UVLO
  • SO16N package

Circuit Diagram

Design Resources


Technical Documentation

Product Specifications

Description Version Size
DS6580: Multimode controller for SMPS
2.0 1,259 KB

Presentations & Training Material


Description Version Size
Primary side regulation controllers portfolio
1,130 KB

Related Tools and Software

Related Tools and Software

Part Number Description
EVL6566B-40WSTB 40 W wide input range flyback converter using L6566BH Multimode controller for SMPS
EVL6566B-65W-SR 12 V - 65 W FF flyback adapter with synchronous rectification featuring L6566B, STSR30 and SEA05L
EVL6566B-65W-QR 19 V - 65 W quasi resonant flyback adapter board

Publications and Collaterals


Description Version Size
1.0.0 3,070 KB

Sample & Buy

Part Number Marketing StatusPackagePacking TypeAutomotive GradeOrder From STUnit Price (US$)*
@ 1000
Distributor AvailabilityRoHS Compliance GradeDownload
Material Declaration**
L6566BHActiveSO-16Tube_-.625Distributor reported inventory date: 2016-02-08
Distributor NameRegionStockMin. order
Farnell Element14Order NowEUROPE301
L6566BHTRActiveSO-16Tape And Reel_-.625Distributor reported inventory date: 2016-02-07
Distributor NameRegionStockMin. order
ARROWOrder NowAMERICA25002500

(*) Suggested Resale Price per unit (USD) for BUDGETARY USE ONLY. For quotes, prices in local currency, please contact your local ST Sales Office or our Distributors
(**) The Material Declaration forms available on may be generic documents based on the most commonly used package within a package family. For this reason, they may not be 100% accurate for a specific device. Please contact our sales support for information on specific devices.
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