High-Efficiency Flyback Controller with 1% Output regulation accuracy


Product details


Control method Secondary-side regulation Duty cycle (Max) (%) 99 Frequency (Max) (kHz) 105 UVLO thresholds on/off (V) 22/7.7 Features SSR, DCM Operating temperature range (C) -40 to 125 Rating Catalog open-in-new Find other Flyback controllers

Package | Pins | Size

SOT-23 (DBV) 6 5 mm² 2.9 x 1.6 open-in-new Find other Flyback controllers


  • Opto-Coupled Feedback Enables up to 1% Regulation
  • Accurate Current Limit with Overload Timeout Protection and Delayed Hiccup Response
  • Resonant-Ring Valley-Switching Operation for Highest Overall Efficiency
  • 80-kHz Maximum Switching Frequency
  • Frequency Dithering to Ease EMI Compliance
  • Clamped Gate-Drive Output for MOSFET
  • Ultra-Low Start-Up Current and Large VDD Hysteresis
    • High Value Start-Up Resistor
    • Low Bias Capacitance
  • Fault Protections
    • Input Low Line
    • Output Over-Voltage
    • Over-Current
    • Short-Circuit
  • SOT23-6 Package
  • Create a Custom Design Using the UCC28742 with the WEBENCH® Power Designer

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The UCC28742 off-line flyback controller is a highly integrated, 6-pin secondary-side regulated PWM controller for efficient AC-to-DC power supplies. It is an isolated-flyback power-supply controller that provides Constant-Voltage (CV) using an optical coupler to improve transient response to large-load steps. This device processes information from opto-coupled feedback and an auxiliary flyback winding for high-performance control of output voltage and current.

The UCC28742 employs advanced control algorithms to achieve high operating efficiency and performance. The drive output interfaces to a MOSFET power switch. Discontinuous conduction mode (DCM) with valley-switching reduces switching losses. Modulation of switching frequency and primary current-peak amplitude (FM and AM) keeps the conversion efficiency high across the entire load and line ranges.

The controller has a maximum switching frequency of 80 kHz and always maintains control of the peak-primary current in the transformer. A minimum switching frequency of 200 Hz facilitates the achievement of low no-load input power.

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Technical documentation

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Type Title Date
* Data sheet UCC28742 High-Efficiency Flyback Controller with Optocoupler Feedback datasheet (Rev. A) May 08, 2018
More literature PCB layout guidelines to optimize power supply performance Mar. 23, 2021
Application note Minimize Standby Consumption for UCC287XX Family Aug. 01, 2019
Technical article Choosing the right flyback controller for your design Aug. 24, 2018
Application note Selecting Electrolitic Bus Capacitor for Universal Input Jul. 17, 2018
User guide Using the UCC28742EVM-001 (Rev. B) Jun. 06, 2018

Design & development

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Design tools & simulation

SLUJ001A.ZIP (840 KB) - SIMPLIS Model
SLUC652B.ZIP (301 KB)

Reference designs

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CAD/CAE symbols

Package Pins Download
SOT-23 (DBV) 6 View options

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