BD7690FJ-E2 Просмотр технического описания (PDF) - ROHM Semiconductor
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BD7690FJ-E2 Datasheet PDF : 26 Pages
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BD7690FJ
(3) About ErrAMP
(3-1) gmAMP
The VS pin monitors a divided voltage of the output voltage. The ripple voltage of AC frequency (50Hz/60Hz) overlaps with VS
pin. gmAMP removes this ripple voltage. gmAMP compares VAMP (2.5V typ.) with the divided voltage of the output voltage,
gmAMP controls the EO voltage by this gap. When EO pin voltage rises, ON width of the OUT pin becomes wide. When the EO
voltage less than about 0.7V, the IC stops switching. Therefore it can stop switching operation when EO pin connects to the
GND.
External parts value of EO pin should be set that the ripple voltage of AC frequency does not conduct to EO pin. And, please
confirm it by real board.
PFC Output
VS
-
+
2.50V
EO_ VSEO
Figure 6. gmAMP block diagram
(3-2) VS short protection
VS pin has a short protection function.
A state of PFC output voltage < VSHORT (0.3V typ.) continues more than TVS_SH (150us typ.), it stops switching.
It shows operation in Figure 7.
PFC
output Vout
VS
V SHORT
OUT
T VS_SH
Switching stop
Figure 7. 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. VS pin voltage becomes lower than VGUP (2.25V typ.) (equivalent to -10% of output voltage), the error
amplifier increases a gain. By this operation, ON width of OUT increases and prevents a long-term drop of the output voltage.
When VS pin voltage rises from VGUP(2.25V typ.), this operation stops.
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TSZ02201-0F2F0A200280-1-2
27. Mar. 2017 Rev.002
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