an8021l Panasonic Corporation of North America, an8021l Datasheet - Page 9

• Manufacturer Part Number: an8021l
• Description: Ac-dc Switching Power Supply Control Ic
• Manufacturer: Panasonic Corporation of North America

Voltage Regulators
[2] Operation descriptions (continued)
3. Overvoltage protection circuit (OVP)
Triangular wave oscillation
TIM/OVP terminal voltage
Application Notes (continued)
Internal reference voltage
1) When the voltage input to the OVP terminal exceeds the threshold voltage (6.0 V typical) as the result of power
2) The OVP is released (reset) under the following conditions:
supply to protect the load when the power supply output generates abnormal voltage higher than the normal
output voltage due to failure of the control system or an abnormal voltage applied from the outside (figure 2 and
figure 3).
is supplied from the transformer drive coil. Since this voltage is proportional to the secondary side output voltage,
it still operates even when the secondary side output has overvoltage.
OVP is an abbreviation of Over Voltage Protection. It refers to a self-diagnosis function, which stops the power
Basically, it is set to monitor the voltage of supply voltage V
supply output abnormality, the protective circuit shuts down the internal reference voltage of the IC to stop all
of the controls and keeps this stop condition.
• Decreasing the supply voltage (V
connected to the OVP terminal can be discharged with the constant current of 5 A (typical) for the next re-start.
The discharge circuit is incorporated so that the electric charge which is charged in the capacitor
V
V
th(OUT)
7
IC output
V
V
V
V
th(OUT)
th(OVP)
Z
th(OVP)
0 V
0 V
0 V
0 V
Secondary side output voltage under normal operation V
: Secondary side output overvoltage threshold
: OVP operation threshold
: Zener voltage (external parts of OVP terminal)
V
Z
V
CC
(to 7.1 V)
(to V
(to 5 V)
(to 2 V)
terminal voltage under normal operation
Figure
CC
CC
)
2. Explanation of OVP operation
8.4 V typical: OVP release supply voltage)
V
(to 6 V)
TH
OVP
CC
terminal of the IC. Normally, the V
(IC stop state)
(IC stop state)
(IC stop state)
OUT
AN8021L, AN8021SB
V
7
CC
voltage
Time
Time
Time
Time
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