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High-Efficiency Flyback Controller With Optocoupler Feedback


Package | PIN: SOT-23 (DBV) | 6
Temp: Q (-40 to 125)
Carrier: Cut Tape
Qty Price
1-9 $0.76
10-24 $0.68
25-99 $0.63
100-249 $0.53
250-499 $0.49
500-749 $0.40
750-999 $0.32
1000+ $0.29


  • Opto-Coupled Feedback Enables up to 1% Regulation
  • Accurate Current Limit with Overload Timeout Protection and Delayed Hiccup Response
  • Resonant-Ring Valley-Switching Operation for Highest Overall Efficiency
  • 80-kHz Maximum Switching Frequency
  • Frequency Dithering to Ease EMI Compliance
  • Clamped Gate-Drive Output for MOSFET
  • Ultra-Low Start-Up Current and Large VDD Hysteresis
    • High Value Start-Up Resistor
    • Low Bias Capacitance
  • Fault Protections
    • Input Low Line
    • Output Over-Voltage
    • Over-Current
    • Short-Circuit
  • SOT23-6 Package
  • Create a Custom Design Using the UCC28742 with the WEBENCH® Power Designer

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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.