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Constant-Voltage, Constant-Current Flyback Controller Using Opto-Coupler Feedback

Availability: 5,990


Package | PIN: SOIC (D) | 7
Temp: Q (-40 to 125)
Carrier: Partial Tube
Qty Price
1-9 $1.19
10-24 $1.07
25-99 $1.00
100-249 $0.87
250-499 $0.80
500-749 $0.67
750-999 $0.55
1000+ $0.50


  • Less than 10-mW No-Load Power Capability
  • Optocoupled Feedback for CV, and
    Primary-Side Regulation (PSR) for CC
  • Enables ±1% Voltage Regulation and ±5% Current Regulation Across Line and Load
  • 700-V Startup Switch
  • 100-kHz Maximum Switching Frequency Enables High-Power-Density Charger Designs
  • Resonant-Ring Valley-Switching Operation for Highest Overall Efficiency
  • Frequency Dithering to Ease EMI Compliance
  • Clamped Gate-Drive Output for MOSFET
  • Overvoltage, Low-Line, and Overcurrent Protection Functions
  • SOIC-7 Package
  • Create a Custom Design Using the UCC28740 With the WEBENCH® Power Designer

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Texas Instruments  UCC28740D

The UCC28740 isolated-flyback power-supply controller provides Constant-Voltage (CV)using an optical coupler to improve transient response to large-load steps. Constant-Current (CC)regulation is accomplished through Primary-Side Regulation (PSR) techniques. This device processesinformation from opto-coupled feedback and an auxiliary flyback winding for precisehigh-performance control of output voltage and current.

An internal 700-V startup switch, dynamically controlled operating states, and a tailoredmodulation profile support ultra-low standby power without sacrificing startup time or outputtransient response.

Control algorithms in the UCC28740 allow operating efficiencies to meet or exceedapplicable standards. The drive output interfaces to a MOSFET power switch. Discontinuousconduction mode (DCM) with valley-switching reduces switching losses. Modulation of switchingfrequency and primary current-peak amplitude (FM and AM) keeps the conversion efficiency highacross the entire load and line ranges.

The controller has a maximum switching frequency of 100 kHz and always maintains controlof the peak-primary current in the transformer. Protection features keep primary and secondarycomponent stresses in check. A minimum switching frequency of 170 Hz facilitates the achievement ofless than 10-mW no-load power.