Optocoupler-Less Synchronous Forward Controller Still Regulates Output Voltage
Targeted for power levels up to 200 W, Linear Tech’s LT8310 primary-side synchronous forward controller provides a drive signal for secondary-side synchronous rectification to improve efficiency. The device operates over an input voltage range of 6 to 100 V. Meanwhile, output voltage regulation of ±8% is attainable without an optocoupler; when using an optocoupler, ±1.5% regulation is possible. A programmable volt-second clamp safeguards against saturation for transformer reset and protects the MOSFET. The controller computes the duty cycle required to create a constant VOUT in open-loop applications. For closed-loop apps, it limits maximum VOUT if the optocoupler path breaks open. Operating switching frequency is programmable from 100 to 500 kHz. Synchronization to an external clock enable makes possible the use of multiple output inductor values and transformer sizes. Other features include programmable overcurrent protection, adjustable input undervoltage, overvoltage lockout, and built-in thermal shutdown. The LT8310 comes in a TSSOP-20 package.