the power supply circuit sustains the off state as long as current of 500 m inimum flows to Vin terminal
from a start up resistor.
In order to prevent a malfunction to be caused by a noise and so on, delay tim e is provided by C1
incorporated in the IC and, therefore, the latch circuit operates when the OVP or TSD circuit is in operation,
or an external signal input is provided for about 10
or longer.
In addition, even after the latch circuit start operating, the constant voltage regulator circuit is in operation
and the circuit current is at high level.
As a result, Vin term inal voltage rapidly decreases.
W hen Vin terminal voltage becomes lower than the shutdown voltage, VIN(OFF) (4.9V typical), it starts
increasing as the circuit current is below 500 .
W hen it reaches the ON-state voltage, VIN(ON) (8V typical), Vin term inal voltage starts decreasing because
the circuit current increases again.
W hen the latch circuit is on, Vin terminal voltage increases and decreases within the range from 4.9V typical
to 8V typical and is prevented from abnormally rising.
Calibration of the latch is done by decreasing Vin term inal voltage below 3.3V.
The power supply can be restarted after disconnecting an AC input to the power supply once.
7. Thermal shutdown circuit
It is a circuit to trigger the latch circuit when the frame tem perature of the IC exceeds 150 (typical).
Although the temperature is actually sensed at the control chip, it works against overheating of the
power transistor as the power transistor and the control IC are mounted on the sam e lead frame.
8. Over-voltage protection circuit
It is a circuit to trigger the latch circuit when Vin terminal voltage exceeds 11V(typical).
Althrough it basically functions as protections as protection of Vin terminal against over-voltage,
since Vin term inal is usually supplied from the drive winding of the transformer and the voltage is propor
ational to the output voltage, it also functions against the over-voltage of secondary output which causes
when the control circuit opens or in some other events.
7-15. Stand-by Mode TOP210
This IC(TOP210) is used for low-power concumption when receiver is operating in stand-by mode.
1. DRAIN PIN (pin5)
Output MOSFET drain connection. Provides internal bias current during start-up operation via an internal
switched high voltage current source. Internal current sense point.
2. CONTRO L PIN (pin4)
Error am plifier and feedback current input pin for duty cycle control.
Internal bias current during normal operation.
It is also used as the supply bypass and auto-restart/compensation capacitor connection point.
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ACEC
