Secondary Side Controllers

Secondary side controllers replace the output rectifier diode in a flyback or forward topology switching regulators. By replacing the diode with a N-channel MOSFET, applications are no longer restricted by the heat constraints of the output diode. The IC replicates the behavior of a diode by sensing the drain-to-source voltage to determine when the current becomes negative.  Synchronous secondary side controllers enable higher efficiency solutions, allowing higher power levels and smaller solutions size.

Most prior solutions use a signal transformer driven from the primary-side to control the synchronous rectifier; however Linear Technology's solutions sense the drain-to-source voltage of the MOSFET for activation. This technique not only eliminates a transformer, but allows the secondary side controller to work with Linear Technology’s growing line of no-opto-coupler products required for output voltage feedback boundary conduction mode (BCM)/critical conduction mode (CrCM) flyback converters, making it highly versatile for many types of applications.