NCP1237: Controller, Fixed Frequency, Current Mode, for Flyback Converters

Datasheet: Fixed Frequency Current Mode Controller for Flyback Converters
Rev. 4 (274.0kB)
Product Overview
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The NCP1237 is a new generation of the NCP12xx fixed-frequency current-mode controllers featuring Dynamic Self-Supply (DSS), pin to pin compatible with the previous generation. The DSS function greatly simplifies the design of the auxiliary supply and the VCC capacitor by activating the internal start-up current source to supply the controller during transients. Due to its proprietary Soft-Skip™ mode combined with frequency foldback, the controller exhibits excellent efficiency in light load condition while still achieving very low standby power consumption. This Soft-Skip feature also dramatically reduces the risk of acoustic noise, which enables the use of inexpensive transformers and capacitors in the clamping network. The NCP1237 features a dual-level timer-based fault detection that controls the amount of transient peak power that the controller can deliver for a limited time. Internal frequency jittering, ramp compensation, and a versatile latch input make this controller an excellent candidate for converters where ruggedness and components cost are the key constraints. In addition, the controller includes a new high voltage circuitry that combines a startup current source and a brown-out / line OVP detector able to sense the input voltage either from the rectified ac line or the dc filtered bulk voltage. Finally, due to a careful design, the precision of critical parameters is well controlled over the entire temperature range (-40°C to +125°C), enabling easier design and increased safety (e.g. ±5% for the peak current limit, ±7% for the oscillator).
Features   Benefits
  • Timer-Based Transient Power and Overload Protections with AutoRecovery (Option B) or Latched (Option A) Operation
  • Overload protection independent of the auxiliary winding
  • Frequency Jittering
  • Reduced EMI signature
  • Frequency Foldback transitioning into Soft-Skip
  • Improved Performance in Standby
  • High-Voltage Current Source with DSS with Built-in Brown-out and Line Overvoltage Protections
  • Fixed-Frequency Current-Mode Operation with Built-in Ramp Compensation
  • Adjustable Overpower Compensation
  • Latch-off Input for Severe Fault Conditions, with Direct Connection of an NTC for Overtemperature Protection (OTP)
  • Protection Against Winding Short-Circuit
  • 65 kHz Oscillator (100 kHz and 133 kHz Versions Available Upon Request)
  • VCC Operation up to 28 V
  • Increased Precision on Critical Parameters
  • ±1.0 A Peak Current Drive Capability
  • 4.0 ms Soft-Start
  • Internal Thermal Shutdown with Hysteresis
  • These Devices are Pb-Free, Halogen free/BFR free and are ROHS compliant
  • Ac-dc Adapters for Notebooks, LCD, and Printers
  • Offline Battery Chargers
  • Consumer Electronic Power Supplies
  • Auxiliary/Housekeeping Power Supplies
Budgetary Price/Unit
Case Outline
NCP1237AD65R2G Obsolete
Halide free
NCP1237 SOIC-7 751U 1 260 Tape and Reel 2500  
NCP1237BD65R2G Obsolete
Halide free
NCP1237 SOIC-7 751U 1 260 Tape and Reel 2500  
Market Leadtime (weeks) : Contact Factory
Market Leadtime (weeks) : Contact Factory
Case Outlines
NCP1237: Controller, Fixed Frequency, Current Mode, for Flyback Converters
NCP1237: Controller, Fixed Frequency, Current Mode, for Flyback Converters
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