Texas Instruments UCC28742DBVT

The UCC28742 off-line flyback controller is a highly integrated, 6-pin secondary-sideregulated PWM controller for efficient AC-to-DC power supplies. It is an isolated-flybackpower-supply controller that provides Constant-Voltage (CV) using an optical coupler to improvetransient response to large-load steps. This device processes information from opto-coupledfeedback and an auxiliary flyback winding for high-performance control of output voltage andcurrent.

The UCC28742 employs advanced control algorithms to achieve high operating efficiency andperformance. The drive output interfaces to a MOSFET power switch. Discontinuous conduction mode(DCM) with valley-switching reduces switching losses. Modulation of switching frequency and primarycurrent-peak amplitude (FM and AM) keeps the conversion efficiency high across the entire load andline ranges.

The controller has a maximum switching frequency of 80 kHz and always maintains controlof the peak-primary current in the transformer. A minimum switching frequency of 200 Hz facilitatesthe achievement of low no-load input power.