an8038 Panasonic Corporation of North America, an8038 Datasheet - Page 16

• Manufacturer Part Number: an8038
• Description: Ac-dc Switching Power Supply Control Ic With Rcc Local Resonance Circuit For Improved Conformance With Energy Conservation Laws
• Manufacturer: Panasonic Corporation of North America

AN8038, AN8038S
16
[2] Operation descriptions (continued)
discharges the soft
when the IC stops.
4. Power supply output control system (IFB: feedback)
start capacitance
Application Notes (continued)
This transistor
power MOSFET. On- and off-periods are controlled as follows: a feedback current responding to the output of
output-voltage detection circuit formed at secondary output side is input to IFB pin through a photocoupler
connected to IFB pin (pin 14), and is converted to V
current from IFB pin increases. This makes V
becomes longer). Furthermore cancellation ability is about 250 A for the dark current of photocoupler.
Constant-voltage control of the power supply output is conducted by changing the on- and off-periods of the
The more AC input voltage becomes higher and/or the more the load current decreases, the more the flowout
5
4
3
2
1
0
0
Dark current
5 : 1
Figure 7. Feedback current vs.
Figure 6. Power supply output control system
PC
0.2
20 k
0.4
FB
250 A typ.
voltage higher and on-period shorter (at the standby, off-period
Primary side
V
I
IFB
FB
FB
0.6
(mA)
voltage. (See figure 6.)
7 V
V
FB
0.8
characteristics
Secondary side
AN1431T/M
PC
1.0
Voltage Regulators
1.2
Secondary side
power supply output
required (to bias the
At least 1 mA is
AN1431T/M.)