100V synchronous forward controller regulates without optocoupler

August 22, 2014 // By Graham Prophet
LT8310 is a primary-side synchronous forward controller that operates over an input voltage range of 6V to 100V, is targeted for power levels up to 200W, and provides a drive signal for secondary-side synchronous rectification to improve efficiency.

Output voltage regulation of ±8% can be attained without the use of an opto-coupler. When an opto-coupler is used, ±1.5% regulation can be realised. A programmable volt-second clamp provides a safeguard for transformer reset that prevents saturation and protects the MOSFET. This function optimises the transformer and MOSFET, reducing solution size.

The LT8310 computes the duty cycle required to create a constant VOUT in open loop applications, thereby simplifying the design. In closed loop applications, the LT8310 limits maximum VOUT if the opto-coupler path breaks open.

Features include programmable overcurrent protection, adjustable input undervoltage, overvoltage lockout and built-in thermal shutdown. The LT8310 has a programmable 100 kHz to 500 kHz operating switching frequency and can be synchronised to an external clock, enabling the use of a wide range of output inductor values and transformer sizes.

It comes in a TSSOP-20 package with several pins removed for high voltage spacing, in E- and I-grade (-40°C to 125°C junction temperature), H grade (-40°C to 150°C) and MP grade (-55°C to 150°C). Pricing starts at $2.99 (1000).

Linear Technology; www.linear.com/product/LT8310