1. Skip to navigation
  2. Skip to content
  3. Skip to sidebar

LT8310/LT1431 81W Isolated Forward Converter with Opto Feedback; VIN = 12V/24V, VOUT = 54V@1.5A

George Qian - Senior Applications Engineer
Gabino Alonso - Strategic Marketing Engineer
Jan 30th 2015

The LT8310 is a constant-frequency resonant reset forward converter controller with a low side N-channel MOSFET gate driver. The LT8310 has a wide input voltage range from 6V to 100V. Its switching frequency can be programed from 100kHz to 500kHz to optimize efficiency, performance or external component size. The LT8310's protection mechanisms end the normal switching cycle or force system shutdown to protect the application circuit. These protections include programmable overcurrent protection, adjustable input undervoltage, overvoltage lockout and built-in thermal shutdown.

The LT1431 is an adjustable shunt voltage regulator providing feedback to the primary side via an opto-coupler, it is used on the forward converter's secondary side to handle output voltage regulation.

8310_1431 Nonsync Forward with Opto 12/24VIN to 54Vout@1.5AFigure 1. LT8310/LT1431 Schematic Diagram

The LT8310+LT1431 nonsynchronous forward converter design features a simple schematic, and low components count. The circuit uses the LT8310 and LT1431 in a resonant reset forward topology to deliver 54V @ 1.5A output from 10.8V to 26.4V input. At 1.5A load the peak efficiency is 93% for 12VIN, and 91.2% for 24VIN. The efficiency vs. load current graph and the associated thermal images (12V and 24V) are shown below. 

Typical Efficiency CurveTypical Efficiency Curve


Thermal Image at 12Vin, 54V @ 1.5A Output, with No Forced AirThermal Image at 12Vin, 54V @ 1.5A Output, with No Forced Air


Thermal Image at 24Vin, 54V @ 1.5A Output, with No Forced AirThermal Image at 24Vin, 54V @ 1.5A Output, with No Forced Air




LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice

To launch a ready to run LTspice demonstration circuit for this part:

To explore other ready to run LTspice demonstration circuits, please visit our Demo Circuits Collection.