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Figure 3.5.20.1 2501 outside drawing
3.5.14 Function introduction to TL431A
TL431 is a 2.5V comparator, shown as the figure 3.5.21.1. Compared the inputted voltage of R end with 2.5V,
when voltage of R end is more than 2.5V, KA end is on and photoelectric coupler starts to send out photocurrent;
when voltage of R end is less than 2.5V, KA end is cutoff and photoelectric coupler does not send out
photocurrent. CPU+3.3V in power board circuit must be kept in 3.3V, for the function of comparator. No matter
more than or less than 3.3V, through on and off status of comparator, it will control the on state of the output
end of photoelectric coupler TL431 to adjust the output space occupation ratio of switch module to control the
output voltage of transformer and masthead the power.
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Figure 3.5.21.1 TL431 outside drawing
3.5.15 function introduction to KA1M0880BTU
1. DESCRIPTION
The Fairchild Power Switch(FPS) product family is specially designed for an off-line SMPS with minimal
external components. The Fairchild Power Switch(FPS) consist of high voltage power SenseFET and current
mode PWM IC. Included PWM controller features integrated fixed frequency oscillator, under voltage lock-out,
leading edge blanking, optimized gate turn-on/turn-off driver, thermal shutdown protection, over voltage
protection, and temperature compensated precision current sources for loopcompensation and fault
protection circuitry. Compared to discrete MOSFET and PWM controller or RCC solution, a Fairchild Power
Switch(FPS) can reduce total component count, design size, weight and at the same time increase efficiency,
productivity, and system reliability. It has a basic platform well suited for cost effective design in either a
flyback converter or a forward converter.
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