Controller, Fixed Frequency, Current Mode, for Flyback Converters

Obsolete

Overview

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).

  • Ac-dc Adapters for Notebooks, LCD, and Printers
  • Offline Battery Chargers
  • Consumer Electronic Power Supplies
  • Auxiliary/Housekeeping Power Supplies

  • Timer-Based Transient Power and Overload Protections with AutoRecovery (Option B) or Latched (Option A) Operation
  • 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
  • Frequency Jittering
  • 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
  • Frequency Foldback transitioning into Soft-Skip
  • 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

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CAD Models

Compliance

Package Type

Case Outline

MSL Type

MSL Temp (°C)

Container Type

Container Qty.

Topology

Control Mode

fsw Typ (kHz)

Stand-by Mode

UVLO (V)

Short Circuit Protection

Latch

Soft Start

VCC Max (V)

Drive Cap. (mA)

Reference Price

NCP1237AD65R2G

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Obsolete

CAD Model

Pb

A

H

P

SOIC-7

1

260

REEL

2500

Flyback

Current Mode

65

Yes

9.5

Yes

Yes

Yes

28

1000 / 1000

Price N/A

More Details

NCP1237BD65R2G

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Obsolete

CAD Model

Pb

A

H

P

SOIC-7

1

260

REEL

2500

Flyback

Current Mode

65

Yes

9.5

Yes

Yes

Yes

28

1000 / 1000

Price N/A

More Details

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