# US 3,944,881 A · Vertical centering control circuit

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- Number: US 3,944,881 A
- Document ID: US3944881A
- Status: Granted
- Kind: A
- Application number: 05/469,010
- Filed: 1974-05-10
- Granted: 1976-03-16
- Earliest claimed: 1974-05-10
- Assignees: General Electric Company
- Inventors: David P. Lynch
- Web page: https://patentgrep.com/patent/US3944881A

## CPC

- H04N 3/227: Centering
- H03K 4/725: {Push-pull amplifier circuits}
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)

## Abstract

Utilization of a diode in the input of the vertical deflection drive amplifier serves to render the amplifier insensitive to power supply variation and shortens the response time of the amplifier to changes in the vertical centering circuit. In one embodiment the diode is connected in series with the variable terminal of the centering potentiometer in the input of the vertical drive amplifier. In a second embodiment, wherein the vertical deflection drive amplifier includes a differential amplifier, the diode is connected to one input of the amplifier and the centering circuit is connected to the second input of the amplifier. In both embodiments the diode forms part of a time constant circuit which controls the linearity of the sweep signal applied to the input of the amplifier and also controls the response time of the amplifier to DC voltage level change.

## Claims

### Claim 1

In a television receiver having a cathode ray tube and a deflection circuit including vertical deflection windings for deflecting the one or more electron beams of the cathode ray tube in a vertical direction, a vertical deflection drive circuit comprising:
a source of sweep signal varying at the desired vertical sweep rate,
an amplifier having an input and an output, said input being responsive to said sweep signal enabling said output to apply an amplified sweep signal to said vertical deflection windings,
a vertical centering control coupled to said input to apply a controllable DC voltage to said amplifier,
and time constant means coupled to said source and to said input, said time constant means including means having the characteristic of a diode to shorten the response time of said amplifier to vertical centering control adjustment and to provide a time constant for said sweep signal of sufficient duration to linearize the shape of the sweep portions thereof.

### Claim 2 (depends on 1)

The invention as recited in claim 1 wherein said input comprises first and second input terminals, and said means having the characteristic of a diode is a diode, said diode being connected to the first input terminal to clamp said first input terminal to a DC reference voltage.

### Claim 3 (depends on 2)

The invention recited in claim 2 wherein said diode couples said vertical centering control to said first input terminal to clamp said first input terminal to said controllable DC voltage.

### Claim 4 (depends on 2)

The invention recited in claim 2 wherein said vertical centering control is connected to said second input terminal and said diode clamps said first input terminal to a fixed DC reference voltage.