Secondary Side Average Current Mode Controller

The UCC3839 provides the control functions for secondary side average current mode control in isolated power supplies. Start up, pulse width modulation and MOSFET drive must be accomplished independently on the primary side. Communication from secondary to primary side is anticipated through an opto-isolator.
Accordingly, the UCC3839 contains a fixed gain Current Sense Amplifier voltage and current error Amplifiers and a Gm type Buffer driver Amplifier for the opto-isolator. Additional housekeeping functions include a precision 5V reference and a bias supply Regulator
Power for the UCC3839 CAN be generated by peak rectifying the voltage of the secondary winding of the isolation transformer. From this unregulated voltage, the UCC3839?s bias supply Regulator will generate its own 7.5V bias supply using an external, N-channel, depletion mode FET
The UCC3839 CAN be configured for traditional average current mode control where the output of the voltage error Amplifier commands the current error Amplifier It CAN also be configured for output voltage regulation with average current mode short circuit current limiting, employing two parallel control loops regulating the output voltage and output current independently.
By Texas Instruments