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

  • Over 84% efficiency at full load
  • Over 70% efficiency at 10% load
  • Provides 12V and 3.3V outputs
  • Works continuously up to 440Vac input and survives 1KVpeak surge

See the Important Notice and Disclaimer covering reference designs and other TI resources.


Schematic/Block Diagram

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Test Data

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Design Files

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(Output Voltage 1)
(Output Voltage 2)
Vin (Min) (V)185185
Vin (Max) (V)700700
Vout (Nom) (V)3.312
Iout (Max) (A).11
Output Power (W).3312
Input TypeDCDC
TopologyBuck- Integrated SwitchFlyback- Quasi Resonant

TI Devices (2)

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Part Number Name Product Family Sample & Buy Design Kits & Evaluation Modules
TPS560200  17V Input, 500mA Synchronous Step-Down Regulator in SOT-23 with Advanced Eco-Mode™  Step-down (buck) regulators  Sample & Buy View Design Kits & Evaluation Modules
UCC28720  Constant-voltage, constant-current controller with primary-side regulation for bipolar power devices  Offline & isolated DC/DC controllers & converters  Sample & Buy View Design Kits & Evaluation Modules

CAD/CAE symbols

Part # Package | Pins CAD File (.bxl) STEP Model (.stp)
TPS560200 Download Download
UCC28720 Download Download

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Technical documentation

See the Important Notice and Disclaimer covering reference designs and other TI resources.

User guide (1)
Title Type Size (KB) Date
PDF 822 20 Oct 2014
Design files (3)
Title Type Size (KB) Date
ZIP 52 20 Oct 2014
PDF 36 20 Oct 2014
PDF 192 20 Oct 2014

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