Constant-voltage, constant-current controller with primary-side regulation for bipolar power devices


Product details


Control method Primary-side regulation Duty cycle (Max) (%) 99 Frequency (Max) (kHz) 80 UVLO thresholds on/off (V) 21/7.7 Features PSR, DCM, HV Start-up, Current Limiting, Green Mode, HV Start-up, Input Line Monitor, Leading Edge Blanking, Light Load Efficiency, Low Power, Soft Start Operating temperature range (C) -40 to 125 Rating Catalog open-in-new Find other Flyback controllers

Package | Pins | Size

SOIC (D) 7 29 mm² 4.9 x 6 open-in-new Find other Flyback controllers


  • < 10-mW No-Load Power
  • Primary-Side Regulation (PSR) Eliminates Opto-
  • ±5% Voltage and Current Regulation Across Line
    and Load
  • 700-V Start-Up Switch
  • 80-kHz Maximum Switching Frequency Enables
    High-Power Density Charger Designs
  • Quasi-Resonant Valley-Switching Operation for
    Highest Overall Efficiency
  • Wide VDD Range Allows Small Bias Capacitor
  • Dynamic BJT Drive
  • Overvoltage, Low-Line, and Overcurrent
    Protection Functions
  • Programmable Cable Compensation
  • SOIC-7 Package
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The UCC28720 flyback power supply controller provides isolated-output Constant-Voltage (CV) and Constant-Current (CC) output regulation without the use of an optical coupler. The devices process information from the primary power switch and an auxiliary flyback winding for precise control of output voltage and current.

An internal 700-V start-up switch, dynamically-controlled operating states and a tailored modulation profile support ultra-low standby power without sacrificing start-up time or output transient response.

Control algorithms in the UCC28720 allow operating efficiencies to meet or exceed applicable standards. The output drive interfaces to a bipolar transistor 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. Protection features help keep primary and secondary component stresses in check. The UCC28720 allows compensation for voltage drop in the cable to be programmed with an external resistor.

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Technical documentation

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Type Title Date
* Data sheet UCC28720 Constant-Voltage, Constant-Current Controller With Primary-Side Regulation datasheet (Rev. B) Sep. 30, 2015
Application note Minimize Standby Consumption for UCC287XX Family Aug. 01, 2019
Application note Maximum Output Power and Thermal Considerations for UCC28720 and UCC28722 Dec. 06, 2017
Application note Troubleshooting TI PSR controllers Oct. 03, 2016
Technical article Slim down your flyback; lose that excess snubber Feb. 15, 2016
White paper Control Challenges for Low Power AC/DC Converters Oct. 02, 2015
White paper Control Challenges for Low Power AC/DC Converters (PPT) Oct. 02, 2015
Technical article Designing multiple output converters with primary side sensing Aug. 04, 2015
Application note 5-W USB Flyback Design Example Using the UCC28722 Jan. 08, 2014
Technical article Isolated power supplies – Is analog dead? Sep. 24, 2013
User guide Using the UCC28720EVM-212 (Rev. A) Sep. 20, 2013

Design & development

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Hardware development

document-generic User guide
The UCC28720EVM-212 is a 5W evaluation module for evaluating an off line adapter for USB applications. It is intended for evaluation purposes and is not intended to be an end product. The UCC28720EVM-212 converters 100V to 240V RMS input voltage down to 5V DC, with a 1A current limit for USB adapter (...)
  • <10mW no load power
  • Primary Side Regulation (PSR) eliminates opto-coupler
  • +/- 5% Voltage & Current Regulation
  • Quasi-resonant valley switching operation for highest overall efficiency
  • Wide VDD range (35V) allows small bias capacitor
  • Drive Output for low cost Bipolar
  • Protection Functions: Over Voltage, Low (...)

Design tools & simulation

SLUC528A.ZIP (2330 KB)
SLUC529.ZIP (44 KB)

Reference designs

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SOIC (D) 7 View options

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