FA5640 Datasheet, PDF (23/35 Pages) Fuji Electric – Fuji Switching Power Supply Control IC

FA5640/41/42
(3) Operation under overload
Using the built-in timer, the duration of overload status of 200 ms or longer is detected, and switching is stopped forcibly.
If the switching is stopped, supply of current from the auxiliary winding is eliminated, and the VCC pin voltage reduces to 9
V or lower, the startup circuit is operated, and the VCC is maintained within the range from 9 V to 11 V. If overload status
continues for 200 ms or longer, the switching is stopped, and then after the elapse of 1400 ms, the switching is resumed.
At that time, if the overload status persists, start and stop switching are repeated. If the load returns to normal, normal
operation is resumed.
At the time of startup, it is necessary to increase the output voltage to the setting within the timer setting of 200 ms. Since
the operation is performed automatically using the built-in timer, even if external power is input directly to the VCC pin,
operation is reset automatically.
14V
11V
VCC pin
voltage ^9V
8V
Start up ^on
Circuit
On/Off
signal
off
FB pin
voltage
3.3V
active
OLP timer
operation
disabled
200ms
OLP timer
output
1600ms
200ms
200ms
1600ms
200ms
1600ms
Output pin
switching
pulse
Normal
load
Over
load
Fig.10 Operation under overload (Automatic reset type)
Normal
load
Fuji Electric Co., Ltd.
AN-064E Rev.1.1
April 2011
23
http://www.fujielectric.co.jp/products/semiconductor/