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BD7692FJ

Power Factor Correction Controller IC

ROHM Semiconductor 

BD7692FJ

Description of Blocks - continued

3 About ErrAMP

3.1 GmAMP

The VS pin monitors a divided point for resistance of the output voltage. The ripple voltage of AC frequency (50 Hz/60

Hz) overlaps with the VS pin. GmAMP removes this ripple voltage. GmAMP compares VAMP (2.500 V Typ) with the

removed voltage, GmAMP controls the EO voltage by this gap. When the EO pin voltage rises, ON width of the OUT pin

becomes wide. When the EO voltage less than VOFF_TH (0.30 V Typ), the IC stops switching. Therefore, it can stop

switching operation when the EO pin connects to the GND.

Please set the external parts number of the error amplifier so that AC frequency does not overlap in EO pin. And, please

confirm it by an actual board.

PFC Output

VS

-

+

2.500 V

EO

Figure 3. GmAMP Block Diagram

3.2 VS Short Protection

The VS pin has a short protection function.

A state of VS pin voltage < VSHORT (0.300 V Typ) continues tVS_SH (150 µs Typ) or more, it stops switching.

Figure 4 shows the operation.

PFC

Output

VOUT

VS

VSHORT

OUT

tVS_SH

Switching Stop

Figure 4. Operation of VS Short Protection

3.3 VS Low Voltage Gain Increase Function

When output voltage decreases by output load sudden changes, an output voltage drop period becomes long because

a voltage control loop is slow. The VS pin voltage becomes lower than VGUP (2.250 V Typ) (equivalent to -10 % of output

voltage), the error amplifier increases the speed of the voltage control loop. ON width of OUT increases and prevents a

long-term drop of the output voltage. When the VS pin voltage rises from VGUP (2.250 V Typ), this operation stops.

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TSZ22111 • 15 • 001

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TSZ02201-0F2F0A200320-1-2

04.Oct.2018 Rev.001

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