FA5538N 데이터 시트보기 (PDF) - Fuji Electric

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FA5538N

(FA5526 thru FA5538 Series) Fuji Switching Power Control IC

Fuji Electric 

FA5526/5527/5528/5536/5537/5538

9. Description of block circuits

(1) Start-up circuit

The FA5526/27/28/36/37/38 has built-in start-up

circuits with maximum rated voltage of 500V.

Wiring is shown in Figs.1 to 3.

When power is turned on, a current is supplied to the

VCC pin from the start-up circuit, charging the capacitor,

C2, connected to the VCC pin, increasing its voltage,

activating the IC, and the power supply starts operation.

The current supplied to the VCC pin from the VH pin is

approximately 6.8mA at Vcc=0V, decreases as Vcc

increases and becomes approximately 6.1mA at the

start-up voltage. A resistor is connected in series to the

VH pin to prevent the IC from being damaged due to

surge in AC and other lines.

Fig.1 shows the commonest wiring, connecting the VH

pin to half-wave rectified AC input voltage and taking the

longest start-up time of the three ways of wiring. When

AC input voltage is turned off after the circuit changed to

a latch mode due to overload or overvoltage protection,

the latch mode can be reset in a relatively short time of

several seconds because a current is not supplied from

the VH pin.

In Fig.2, the VH pin is connected to full-wave rectified

AC input voltage, reducing start-up time to approximately

half as compared to half-wave rectification circuit shown

in Fig.1. The latch mode can be reset in a short time

same as in Fig.1 because AC input voltage is cut off.

In Fig.3, the VH pin is connected to rectified and

smoothed AC input voltage, resulting in the shortest

start-up time of the three ways of wiring. In this way of

wiring, it takes time for the latch mode to be reset

because charged C1 voltage is applied to the VH pin

even if the IC have changed to the latch mode.

Depending on usage conditions, in general it takes

several minutes.

When VCC pin voltage exceeds ON threshold voltage

of the low-voltage malfunction-protective circuit and the

IC is activated, the start-up circuit is cut off and VH pin

input current becomes 25uA (typ.).

protection.” ).

Fig.1 Start-up circuit 1 (half wave)

Fig.2 Start-up circuit 2 (full wave)

When IC enters to the latch mode due to any

abnormal condition, the start-up circuit is activated

again, the latch condition is maintained and Vcc voltage

is held at approximately 23V. Here, FA5526/27/28

enters to the latch mode by overload or over-voltage,

but FA5536/37/38 does not enter to the latch mode

without an additional external circuit (See “9.-(8)/(9)

Overload protection,” “9.-(10)/(11) Over-voltage

Fuji Electric Co., Ltd.

AN-087E Rev.1.0

15

April-2011

Fig.3 Start-up circuit 3 (DC)

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

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