FA5546 Datasheet, PDF (21/27 Pages) Fuji Electric – Switching Power Supply Control IC

FA5546/47
(11) Output circuit
The push/pull structure output circuit drives the MOSFET
directly. The peak output current of the OUT terminal is
0.5A (source) and 1.0A (sink) in the maximum absolute
ratings.
In a state in which the IC is stopped in the undervoltage
lockout circuit or operation is suspended in the latch mode,
or in an auto reset wait state by overload protection function,
the OUT terminal is brought into the Low level, and the
MOSFET is interrupted.
(12) Brown out (low AC input voltage
protection)
This IC integrates a brown out function that stops the output
pulse of the OUT terminal when the AC input voltage
decreases to protect the circuit.
Integration of a high withstand voltage resistor eliminates
the need of external parts.
Switching is started when the peak of the AC input voltage
to the VH terminal reaches the brown in threshold voltage
(104V typ). (See Fig.19)
When the input voltage decreases down to brown out
threshold voltage (99V typ) or lower, the output is stopped
after 50ms (typ) of delay time. (See Fig.20)
The brown out function is actuated after the UVLO is reset.
While switching operation is suspended by the brown out
function, the startup circuit is subjected to ON/OFF control
to maintain the VCC voltage within the 15.5V to 18V (typ)
range.
Fig. 19 Brown in and brown out detection circuit
Brown IN
Diod brige
Half wave
Secondary
Vo
MOS gate
Brown-IN Vth
0
Rating Vo
0
0
Brown OUT
Diod brige
Half wave
Secondary
Vo
50ms Delay time
Brown-OUT Vth
0
Rating Vo
0
MOS gate
0
Fig. 20 Conceptual diagram of brown in and brown
out operations
Fuji Electric Co., Ltd.
AN-027E Rev.0.4
April -2011
21
http://www.fujielectric.co.jp/products/semiconductor/