描述 Description

The NCP1238 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. 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).

特性 Features

? Timer-Based Overload Protection with AutoRecovery (Option B) or Latched (Option A) Operation
? Overload protection independent of the auxiliary voltage
? Frequency Jittering
? Reduced EMI Signature
? Frequency Foldback transitioning into Soft-Skip
? Improved Performance in Standby
? High-Voltage Current Source with DSSwith 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

應用 Application

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

簡介

NCP1238屬于集成電路（IC）的ACDC轉換器離線開關。由制造生產的NCP1238AC DC 轉換器，離線開關該系列是元器件級控制產品，用于構建將交流市電轉換為直流電（通常電壓大幅降低）的設備。集成和未集成系統(tǒng)主要開關元件的器件均包括在內。由于高輸入輸出電壓比，以及此類系統(tǒng)中通常需要隔離，這些器件通常與外部變壓器配合使用。盡管通常使用定制變壓器來實現(xiàn)此用途，但也有許多專門用于此用途的庫存產品，請參見“開關轉換器，SMPS 變壓器”標題。