Datasheet LT1249 (Linear Technology)

LT1249 Power Factor Controller
U FEATURES DESCRIPTIO
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Standard 8-Pin Packages
The 8-pin LT®1249 provides active power factor correc- ■
High Power Factor Over Wide Load Range
tion for universal offline power systems with very few
with Line Current Averaging
external parts. By using fixed high frequency PWM current ■ International Operation Without Switches averaging without the need for slope compensation, the ■ Instantaneous Overvoltage Protection LT1249 achieves far lower line current distortion, with a ■ Minimal Line Current Dead Zone smaller magnetic element than systems that use either peak ■ Typical 250µA Start-Up Supply Current current detection or zero current switching approach, in ■ Rejects Line Switching Noise both continuous and discontinuous modes of operation. ■ Synchronization Capability The LT1249 uses a multiplier containing a square gain ■ Low Quiescent Current: 9mA function from the voltage amplifier to reduce the AC gain ■ Fast 1.5A Peak Current Gate Driver at light output load and thus maintains low line current distortion and high system stability. The LT1249 also
U
provides filtering capability to reject line switching noise
APPLICATIO S
which can cause instability when fed into the multiplier. ■ Universal Power Factor Corrected Power Supplies Line current dead zone is minimized with low bias voltage ■ Preregulators up to 1500W at the current input to the multiplier. The LT1249 provides many protection features including peak current limiting and overvoltage protection. The switching frequency is internally set at 100kHz. While the LT1249 simplifies PFC design with minimal parts count, the LT1248 provides flexibilities in switching , LTC and LT are registered trademarks of Linear Technology Corporation. frequency, overvoltage and current limit.
W BLOCK DIAGRA
VAOUT MOUT CAOUT GND VCC 5 3 2 1 7.5V 7 VREF R + 7.5V MOUT VSENSE 4k V + EA CC RUN 6 – IA 250µA MAX 16V/10V – MULTIPLIER IM IAC 32k I 2 I + IB I A B M = 4 200µA2 CA – – R Q + GTDR 15µA + S gm = 1/3k RUN 8 1V + 0.7V M1 – + OSC SYNC 4k – 44µA 16V 20µA 22µA 35pF 1249 BD 1