Vertical Output Circuit; Vertical Output Operation - Panasonic GP 31 Technical Manual

5.2

Vertical Output Circuit

Outline
1. The main function of this circuit is to produce a sawtooth deflection current and
amplify the vertical sawtooth waveform to the vertical deflection coil for vertical
scanning.
2. IC451 is a vertical IC that provides output deflection current to the vertical coil of the
deflection yoke.
3. The vertical sync. pulse output from pin 16 and 17 of IC601 is fed into pin 1 and 7 of
IC451. The sawtooth waveform is compared with the V
pin 7 IC451. Then, sawtooth waveform will be amplified and output through pin 5
IC451 to the vertical deflection coil.
4. The Pump Up circuit in IC451 works along with the external components C406 and
D402 to boost the vertical sawtooth waveform peak value.

Vertical Output Operation

1. To drive the vertical output stage a drive pulse is fed from IC601 to the vertical
output IC451 pin 1 & 7.
2. This vertical output IC IC451 consists of an operational amplifier to which the
vertical pulse in the form of a sawtooth is passed (pin 1), the results of which are
output via pin 5.
3. IC451 also contain a pump-up circuit which is used to provide a switching voltage for
the vertical flyback period. This is required as the energy requirement of the vertical
output stage is highest during flyback, as the electron beam has to be passed rapidly
from the bottom right hand corner of the screen, to the top left corner of the screen.
4. This brief additional energy requirement is met by increasing the supply voltage
available to the output stage to almost 2 times the supply.
5. During vertical sweep, the bootstrap capacitor C406 is charged up to almost supply
voltage via D402.
6. As a result of the DC displacement at the negative pole of capacitor C406 (rising to
the supply voltage), build up of the supply voltage for the output stage at pin 5 rises to
almost 2 times the supply voltage. At the same time, D402 is reverse-biased and thus
preventing discharge of C406 into supply line.
from non-inverting input at
ref
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