AN8037 Panasonic Semiconductor, AN8037 Datasheet - Page 21

• Manufacturer Part Number: AN8037
• Description: AC-DC switching power supply control IC with standby mode
• Manufacturer: Panasonic Semiconductor

Voltage Regulators
[1] Operation descriptions (continued)
12. Setting the timer period (continued)
Application Notes (continued)
Timer period (T
T
adjusted according to the overload level. Furthermore, in the application circuit, the timer period can be adjusted
in both standby and normal modes. To enable this, let the microcomputer on the secondary side detect the operat-
ing mode (i.e., either the standby or normal mode) of the IC to vary the value of the resistor connected to the OCP
pin with the photocoupler. Refer to figures 19 and 20.
The timer period is adjusted
by detecting the overload level
on the secondary side from I
TIM(S)
By detecting the overload level on the secondary side from I
{C
V
V
I
T
T
PC
SD(AVE)
SD
SD
TH1-SD
STB-SD
SD
I
FB
TIM
C
C
Timer period
(V
CF
CF
FB
) is obtained from the following formula.
TH1-SD
3.9 V typ.
1.6 V typ.
I
SD
(V
(V
OCP
OCP
20 k
T
FB
Current mirror
(s)
SD
I
SD
2
V
7
.
STB-SD
/T
1 : 5
V
V
Standby mode
Timer capacitor charging condition
FB
FB
I
Current mirror
The following condition must be
satisfied during on-period.
TR
)/I
)/I
V
)}/I
AN8027, AN8037
ON
ON
FB
70 A
V
SD(AVE)
OCP
V
C
V
V
I
T
T
C
V
V
I
FB
SD
ON
Figure 20
SD
SD
CF
40
TH1-SD
STB-SD
OCP
FB
I
Figure 19
SD
On
: Capacitor connected to SD pin
: Shutdown operating threshold voltage 3.9 V typ.
: Shutdown standby voltage 1.5 V typ.
: Timer latch charge current
: Timer latch charge period
: Cycle
: Capacitor connected to CF pin
: OCP pin voltage
: Voltage internally converted from feedback signal I
: On-period charge current
I
TR
I
I
100 A
FB
5
OCP
Normal operation mode
70
20 k
FB
TR
SD
OCP
GND
The operating mode (i.e., either the standby
or normal mode) is detected by
the microcomputer on the secondary side
and the timer period is adjusted.
V
and changing T
(Values are for an example circuit.)
CC
V
Load on secondary side (W)
BE
R
OCP
C
PC2
TIM
100 A typ.
SD
250 A typ.
AN8027, AN8037
, the timer period can be
D
B
I
TR
4
NB
FB
21