Panasonic EURO 4 Chassis Technical Manual page 13

8.3. Start Up Circuitry
The start-up circuit is used to start and stop
operations of the control IC IC801, by detecting the
voltage appearing at the Vcc terminal, pin 4.
At start-up, capacitor C816 is charged via the
start-up circuit consisting of resistors R805, R814
which applies 16V to pin 4 of IC801.
The voltage applied to pin 4 of
the start circuit, over-voltage monitor and latch
circuit which is used to control the oscillator and
drive stage. With pin 4 at 16V,
operate and drive the internal MOS-FET transistor
into conduction resulting in current flow via the
primary winding, pin 3 (drain terminal) and pin 2
(source terminal) of IC801.
IC801 is then fed to
IC801 begins to
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Once IC801 begins to operate the supply voltage at
pin 4 is supplied via the rectifying diode D803 and
smoothing capacitor C816 which is fed from the
drive winding of the switching transformer T801.
This supply voltage which is fed from the drive
winding B2 of T801 is initially unable to provide the
supply voltage demanded and so the voltage at pin 4
decreases.
The charge held by C816 however slows this
decreasing voltage at pin 4 long enough to prevent
the shut down voltage of 10V being reached, thus
allowing the drive winding voltage at B2 to become
established.
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