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Fairchild |
KA7525B
Power Factor Correction Controller
www.fairchildsemi.com
Features
• Internal Start-up Timer
• Internal Current Sense Blanking Which Eliminates the
Need for an External R/C filter
• Overvoltage Comparator Eliminates Runaway Output
Voltage
• Zero Current Detector
• One Quadrant Multiplier
• Trimmed 1.5% Internal Bandgap Reference
• Under Voltage Lock Out with 2.1V of Hysteresis
• Totem Pole Output with High State Clamp
• Low Start-up and Operating Current
• 8-Pin DIP or 8-Pin SOP.
Applications
• Electronic Ballast
• SMPS
Description
The KA7525B provides simple and high performance active
power factor correction. KA7525B is optimized for
electronic ballast and low power, high density power
supplies requiring a minimum board area, reduced
component count and low power dissipation. Addition of
internal current sense blanking (Internal R,C) eliminates the
need for an external R/C filter. Internal clamping of the error
amplifier and multiplier outputs improves turn on overshoot
characteristics and current limiting. Special circuitry has also
been added to prevent no load runaway conditions. Output
drive clamps limiting power MOSFET gate drive
independent of supply voltage greatly enhance the products
practical application.
8-DIP
1
8-SOP
1
©2002 Fairchild Semiconductor Corporation
Rev.1.0.1
KA7525B
Pin Assignments
INV 1
EA OUT 2
MULT 3
CS 4
(Top View)
8 Vcc
7 OUT
6 GND
5 Idet
Pin Definitions
Pin Number
Pin Name
1 INV
2 EA_OUT
3 MULT
4 CS
5 Idet
6 GND
7 OUT
8 Vcc
Pin Function Description
Inverting input of the error amplifier. The output of the Boost converter
should be resistively divided to 2.5V and connected to this pin.
The output of the error amplifier. A feedback compensation network is
placed between this pin and the INV pin.
Input of the multiplier stage. The full-wave rectified AC is divided to less
than 2V and is connected to this pin.
Input of the PWM comparator. Current is sensed in the Boost stage
MOSFET by a resistor in the source lead. An internal leading edge
blanking circuitry has been included to reject any high frequency noise
present on the current waveform.
The zero current detector senses the inductor current by monitoring
when the Boost inductor auxiliary winding voltage falls below 1.8V.
The ground potential of all the pins.
The output of a high current power driver capable of driving the gate of a
power MOSFET.
The logic and control power supply connection.
2
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