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IC manufacturers ADI Power by Linear

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ADI Power by Linear LT3748 | Demoboard DC1745A

100V Isolated Flyback Converter


TopologyFlyback Converter
Input voltage100-400 V
Output 115 V / 3 A
IC revision2


Demonstration circuit 1745A is an isolated flyback converter featuring the LT3748 controller for high input voltage applications. It is designed for a 15V output at up to 3A from a 100V to 400V DC input. The part senses the isolated output voltage from the third winding of the flybacktransformer during the off time of the power switch. No opto-coupler or signal transformer is required for regulation.

A minimum load of approximately 150mA is required on the output of the circuit to maintain regulation. Optionally, the demo circuit can be powered from a universal offline input (85V~265V, 50/60Hz) using the ACinput terminals. Provisions for an EMI filter and surge protection are provided in the demo circuit. The EMI filter is designed to meet the EN55022 Class B standard. The table below summarizes the performance.

The demo circuit can be easily modified for applications requiring different output voltages/currents from either an AC or DC input. Some pre-designed EFD25, EF16, and EF25 transformers from vendors such as WürthElectronics, Sumida, Pulse Engineering and Coilcraft can be assembled on the board. Some of these transformers are listed in Table 1.

The LT3748 is a high input voltage isolated flyback controller that eliminates the need for an optocoupler and secondary-side reference voltage, all while maintaining isolation between the primary and secondary-side withonly one part, the transformer, having to cross the isolation barrier. The LT3748 is well suited for a wide variety of industrial, automotive, medical, telecom, datacom applications, where regulated isolated output is required.The LT3748 datasheet gives a complete description of the part, operation and application information. The datasheet should be read in conjunction with this quick start guide for Demonstration Circuit 1745A before powering the demo circuit.


Remarks:Table 1. Pre-Designed Transformers for High Voltage Applications with LT3748Refer page no.2