an8027 Panasonic Corporation of North America, an8027 Datasheet - Page 20

• Manufacturer Part Number: an8027
• Description: Ac-dc Switching Power Supply Control Ic With Standby Mode
• Manufacturer: Panasonic Corporation of North America

AN8027, AN8037
20
[1] Operation descriptions (continued)
11. Timer latch (continued)
12. Setting the timer period
Application Notes (continued)
Power MOSFET
called timer period) needs to be longer than the rise time of the power supply. Since at operation start the IC is in
the same condition as the overload or output short-circuit condition, if the timer period is shorter, the power
supply works latch and can not start.
to the SD pin. Make sure, however, that the capacitor is not too high, otherwise the power supply may be damaged.
SD pin voltage
output voltage
Power supply
The period between the detection of the erroneous power output and the moment OVP is triggered (hereinafter
Therefore, the IC has a design making it possible to adjust the timer period with the external capacitor connected
Out pin voltage
SD pin charge current
CF pin voltage
OCP pin voltage
V
(R
OCP
OCP
current
V
V
I
2.2 V typ.
22 k )
DS
SD
O
0
0
0
V
FB
Off
Cycle T
Figure 17. Basic timer latch operation
On
Figure 18
I
SD
Input voltage is detected from the flow of current from the TR pin.
Charge current is provided from the SD pin within
a period when the voltage on the CF pin satisfies the
following condition during the on-period.
Timer period input voltage correction
V
V
OCP
TH1 SD
I
SD
E
I
V
SD
IN
CF
n
; large
; large
3.8 V typ.
V
I
TR
FB
70 A, n 8.4
Power supply
Power supply
Power supply
Voltage Regulators
SD
stop
stop
stop
Time
Time
Time