FA5590N 데이터 시트보기 (PDF) - Fuji Electric

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FA5590N

Power Supply Control IC(Power Factor Correction)

Fuji Electric 

FA5590N,FA5591N

9. Outline of circuit operation

This IC is a power-factor correction converter

utilizing a boosting chopper, operating in critical

mode. Hereinafter is outline of the operation

consisting of switching operation and power-factor

correction operation using the circuit diagram

shown in Fig. 1.

(1) Switching operation

This IC performs the switching operation in the

critical mode applying self-oscillation without using

an oscillator. Fig. 2 shows the outline of waveforms

of the switching operation in steady state. The

operation is as follows.

t1. Q1 turns on, the current through inductor (L1)

rises from zero. At the timing of Q1 on,

Vramp; output of ramp generator states to

rise.

t2. Vramp and Vcomp; output of the error

amplifier are compared by the PWM

comparator, and when Vramp>Vcomp, Q1

turns off and the output of the ramp generator

drops.

When Q1 turns off, the voltage across L1

inverts and the current through L1 decreases

while the current is supplied to the output side

through D1.

t3. The current through L1 is detected by Is

terminal, and when the current becomes zero,

the output of the current detection comparator

becomes High to turn on Q1 after delay given

by the delay circuit, thus moving to the next

switching cycle (t1).

Iin

IL1

AC

C1

By repeating the operations of t1 ~ t3, the switching

in critical mode is continued.

With the power-factor correction circuit in the

critical mode, the switching frequency is always

changing due to instantaneous values of the AC

input voltage. The switching frequency also

changes when the input voltage or load changes.

OUT

(Q1 gate)

Q1

Vds

IL1

Vcomp

Vramp

PWM.comp.

output

(reset)

ZCD.comp.

output

(set)

t1

t2

t3 t1

Fig. 2 Switching Operation, Waveforms

L1

D1

Vo

Q1

Vds

Rs

IS

5

OCP.comp

ZCD.comp

-10mV

RTZC

4

Delay

-0.6V

Restart

RAMP

OSC

PWM.comp

RT

3

FA5590/91

COMP

2

OUT

7

R

Q

UVLO

S

OVP

SP

TIMER

ERRAMP

Restart

FB

1

2.5V

Fuji Electric Co., Ltd.

AN-016E Rev.1.2

April-2011

Fig.1 Block diagram of operating circuit

11

http://www.fujielectric.co.jp/products/semiconductor/

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