High Voltage Capacitor Charger for Photo-Flash Using LT3751

  • Rajkumar Sharma
  • moderate
  • Tested
  • SKU: EL69594
  • Quote Now

This project is built for professional photo flash systems. The circuit generates high voltage from a low voltage battery to operate a photo-flash tube. The project can also be used in other applications like high voltage capacitor chargers, emergency strobe, high voltage power supply, security, detonators, etc. LT3751 is the heart of the project.

The LT3751 is a high voltage input flyback controller designed to rapidly charge a large capacitor to a user-adjustable high target voltage set by the transformer turns ratio and three external resistors. Optionally, a feedback pin can be used to provide a low noise high voltage regulated output. The LT3751 has an integrated rail-to-rail MOSFET gate driver that allows for efficient operation down to 4.75V. A low 106mV differential current sense threshold voltage accurately limits the peak switch current. Added protection is provided via user-selectable overvoltage and under-voltage lockouts for both VCC and VTRANS. This project can charge a 220μF capacitor to 300V in less than one second. The CHARGE pin is used to initiate a new charge cycle and provides ON/OFF control. The DONE pin indicates when the capacitor has reached its programmed value and the part has stopped charging. The FAULT pin indicates when the LT3751 has shut down due to either VCC or VTRANS voltage exceeding the user-programmed supply tolerances. CN1 supply input, CN2 output, CN3 have no use.


  • Supply 24V DC
  • Output 300V DC
  • Charging time less than a second

Note: Output voltage adjustment is possible with few changes in resistor’s value, refer table below table. High voltage is present on output, please take appropriate precautions.


Parts List

Output voltage


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Sharon Boyd

Thank you for such a wonderful project. I have a question.
What modifications do i need to make to get the output of atleast 700V from this controller?
I mean, what is limiting the output?

Wagaba Allan Scofield

How many amps does it pull from 12v battery to charge 300v 220uf capacitor in less than a second

Hakan Basar

Do you have any other type of schematic with input voltage 5v ? I wanted to use it via battery pack . Thanks.


how to stop charging lt3751 and how to crate limit for output voltage??????
please answer me

Paul Butler

What is the full load amps for this unit? Is the unit for sale or just a description of project?


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