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Flyback controllers

UCC28720

ACTIVE

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

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Data sheet

UCC28720

ACTIVE
Data sheet Order now

Product details

Topology Buck, Flyback Control mode Primary-side regulation Duty cycle (max) (%) 99 Switching frequency (max) (kHz) 80 Features Current limiting, DCM, Green mode, High-voltage startup, Input line monitor, Leading edge blanking, Light-load efficiency, Low power, PSR, Soft start UVLO thresholds on/off (V) 21/7.7 Operating temperature range (°C) -40 to 125 Rating Catalog Gate drive (typ) (A) 0.037
Topology Buck, Flyback Control mode Primary-side regulation Duty cycle (max) (%) 99 Switching frequency (max) (kHz) 80 Features Current limiting, DCM, Green mode, High-voltage startup, Input line monitor, Leading edge blanking, Light-load efficiency, Low power, PSR, Soft start UVLO thresholds on/off (V) 21/7.7 Operating temperature range (°C) -40 to 125 Rating Catalog Gate drive (typ) (A) 0.037
SOIC (D) 7 29.4 mm² 4.9 x 6
  • < 10-mW No-Load Power
  • Primary-Side Regulation (PSR) Eliminates Opto-
    Coupler
  • ±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
  • < 10-mW No-Load Power
  • Primary-Side Regulation (PSR) Eliminates Opto-
    Coupler
  • ±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

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.

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) PDF | HTML 30 Sep 2015
More literature Flyback Aux Winding OVP and UVLO Fault Sensing Design and Troubleshooting Tips PDF | HTML 31 Aug 2021
More literature Minimize Standby Consumption for UCC287XX Family 01 Aug 2019
More literature Maximum Output Power and Thermal Considerations for UCC28720 and UCC28722 06 Dec 2017
More literature Troubleshooting TI PSR controllers 03 Oct 2016
Technical article Slim down your flyback; lose that excess snubber 15 Feb 2016
More literature Control Challenges for Low Power AC/DC Converters 02 Oct 2015
More literature Control Challenges for Low Power AC/DC Converters (PPT) 02 Oct 2015
Technical article Designing multiple output converters with primary side sensing 04 Aug 2015
More literature 5-W USB Flyback Design Example Using the UCC28722 08 Jan 2014
Technical article Isolated power supplies – Is analog dead? 24 Sep 2013
EVM User's guide Using the UCC28720EVM-212 (Rev. A) 20 Sep 2013

Design & development

For additional terms or required resources, click any title below to view the detail page where available.

Evaluation board

UCC28720EVM-212 — UCC28720EVM-212 5W Evaluation Module for USB off-line adapter

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 (...)
User guide: PDF
Not available on TI.com
Calculation tool

UCC28722 MathCad Design Tool (Rev. A)

SLUC528A.ZIP (2330 KB)
Download
Calculation tool

UCC28722 Excel Design Tool

SLUC529.ZIP (44 KB)
Download
Reference designs

PMP20744 — 85 to 265VAC Input 12V/3W Low Cost Flyback with BJT Reference Design

This 12V/3W reference design is optimized for very low cost and yet maintains good efficiency. Two key factors for minimizing cost are a BJT is used for the main power switch, and primary-side regulation (PSR) eliminates the need for an optocoupler. The UCC28720 quasi-resonant flyback controller (...)
Test report: PDF
Schematic: PDF
Reference designs

PMP8678 — High Voltage Input (184Vac…707Vac) to 12V@1A, 3.3V@100mA Non-isolated Flyback Reference Design

The UCC28720 is a quasi resonant controller and is specialized to drive high voltage BJTs. When the drain voltage is higher than 1KV, BJTs are the best choice for low to mid power flyback converters. In this case two voltages are supplied: 12V@1A and 3.3V@100mA.
Test report: PDF
Schematic: PDF
Reference designs

PMP9622 — 350W Constant Voltage - Constant Current (CVCC) Phase-Shifted Full Bridge reference design

This reference design uses the UCC3895 Phase-Shifted Full Bridge controller to implement a high efficiency, 120VAC input to 44Vdc up to 8A output.  The power supply is set up to be  constant voltage-constant current.  The voltage and current are set by fixed resistor values and could (...)
Test report: PDF
Schematic: PDF
Reference designs

PMP9649 — Reference Design - Universal Line Input AC-DC 3W High Side Buck Converter using UCC28720

The PMP9649 reference design is a simple, low-cost high side Buck converter to convert universal AC input voltage (85Vac to 265Vac) to a non-isolated 20V/150mA DC output with UCC28720 controller. BJT is applied as the buck switch for cost optimization, and simplicity is achieved with bulit-in (...)
Test report: PDF
Schematic: PDF
Reference designs

PMP9243 — Primary-Side Reg Flyback for Industrial AC Input Up to 583VAC w/Bipolar Transistor Reference Design

The PMP9243 reference design uses the UCC28720 primary-side regulated flyback controller to generate a 15V/0.25A output from an industrial AC input (up to 583VAC). A bipolar transistor is used as the switch on the primary side to minimize the circuit cost.
Test report: PDF
Reference designs

PMP9517 — Small Form Factor 10W Offline Flyback Power Supply Reference Design

The PMP9517 is a high density constant voltage / constant current power supply with an 85VAC-265VAC input range and 5V/10W outptut. The design features primary side regulation (PSR) of a low cost power transistor (BJT). With low component count and low cost, the design is suitable for USB type (...)
Test report: PDF
Schematic: PDF
Reference designs

PMP9135 — 85 to 265 VAC input 5V/10W low cost flyback with BJT reference design

Constant Voltage/Constant Current  power supply generates 5V at 2A output. The design features primary side regulation (PSR) of a power transistor (BJT). With a low component count and low cost, the design can be use in USB type power supplies for PDA's, tablets, cameras and cell phones.
Test report: PDF
Schematic: PDF
Reference designs

PMP9235 — 120VAC Input 5V/250mA Flyback Converter With BJT Switch Reference Design

This reference design creates a 5V at 250mA from a 120VAC Input. The UCC28720 primary side controller with a BJT power switch provides a low cost design. It is important to note the outputs are only functionally (not for safety) isolated from the input.
Test report: PDF
Reference designs

PMP9059 — 120VAC Input 5V/200mA Flyback Converter With BJT Switch Reference Design

This reference design creates a 5V at 200mA from a 120VAC Input. This supply is to designed to fit into a very small volume with approximately 10mm total height. The UCC28720 primary side controller with a BJT power switch provides a low cost design. A TPS71433 is also used to provide an (...)
Test report: PDF
Reference designs

PMP9044 — Primary-Side Regulated Flyback for Universal 3-phase AC Input w/Bipolar Transistor Reference Design

The PMP9044 reference design uses the UCC28720 primary-side regulated flyback controller to generate a 3.3V/0.5A output from a 3-phase univeral AC input. A bipolar transistor is used as the switch on the primary side to minimize the circuit cost.
Test report: PDF
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SOIC (D) 7 View options

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