FA5604 Datasheet, PDF (22/31 Pages) Fuji Electric – FUJI Power Supply Control IC

FA5604/5605/5606
10. Design advice
(1)Deciding the startup circuit
The connection methods of the startup circuit are as follows: connecting the starting resistor R1 before rectification
(AC line) (Fig. 17); connecting the starting resistor R1 after rectification (DC line) (Fig. 18).
When connecting the starting resistor before rectification, if the latch operates, a current applied to the IC from the
starting resistor is stopped by stopping the AC input, and the latch can be reset in a significantly short time.
On the other hand, if connecting the starting resistor after rectification, because a current is applied to the IC from
the smoothing capacitor C1 of the main circuit through the starting resistor even if the AC input is stopped, it takes
time to reset the latch.
DB
AC INPUT
T1
C1
DB
AC INPUT
T1
C1
▼
R1
D1
VCC
C2
6
▽
FA5604/05/06
5
OUT
MOSFET
Rs
▼
Fig.17
▼
R1
D1
VCC
C2
6
▽
FA5604/05/06
5
OUT
MOSFET
Rs
▼
Fig.18
If it is necessary to set the startup and shutdown voltages, connect the resistor R2 between the VCC and the GND
as shown in Fig. 19.
When connecting only the starting resistor R1, if setting a relatively large value for the starting resistor R1, the
latch release voltage is more than the starting voltage. Under this condition, if the input voltage is reduced for some
reason when the latch is stopped, release of the latch and startup may be performed repeatedly.
It is recommended to insert the resistor R2 between the VCC and the GND in order to avoid this phenomenon.
V1
R1
D1
VCC
C2
6
FA5604/05/06 ^{R2 ▽}
4
GND
▽ _Fig.19
The following are the points for setting the starting resistance.
Because the consumption current of the IC is low due to adoption of the CMOS process, it is possible to set a large
value for the starting resistance. When determining the value of the starting resistance, the following three
conditions shall be satisfied:
(a) Start the IC when turning on the power.
(b) Supply the IC consumption current at latch operation to maintain the latch condition.
(c) Supply the IC consumption current during off-state of the on-off function to maintain the off-state.
Note that these are the minimum conditions for using this IC and it is necessary to determine the value considering
the starting time required for the setting.
Fuji Electric Co., Ltd.
AN-033E Rev.1.2
April-2011
22
http://www.fujielectric.co.jp/products/semiconductor/