# US 5,705,901 A · Microprocessor-controlled screen voltage generation circuit

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- Number: US 5,705,901 A
- Document ID: US5705901A
- Status: Granted
- Kind: A
- Application number: 08/822,913
- Filed: 1997-03-21
- Granted: 1998-01-06
- Earliest claimed: 1996-05-13
- Assignees: Acer Peripherals, Inc.
- Inventors: Chang-Fa Hsiesh
- Web page: https://patentgrep.com/patent/US5705901A

## CPC

- H04N 5/68: Circuit details for cathode-ray display tubes {(deviation circuits H04N3/16)}
- H04N 9/28: Arrangements for convergence or focusing
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A circuit for generating a screen voltage is provided. The circuit employs an operational amplifier and two NPN transistors and receives an analog control signal from a microprocessor. The analog control signal is input to the negative input terminal of the operational amplifier. The output screen voltage is taken at emitter of one NPN transistor. In one preferred embodiment, Vcc is taken at a primary side of a high voltage transformer within the display device and input to the collector of the one NPN transistor.

## Claims

### Claim 1

A circuit for generating a screen voltage, comprising:
an operational amplifier, the operational amplifier having a negative input terminal receiving an analog control signal, a positive input terminal and an output terminal;
a first NPN transistor having a base, a collector and an emitter, the collector is coupled to a Vcc voltage, the collector and base being coupled together via a first resistor, the screen voltage being generated at the emitter and coupled to the positive input terminal of the operational amplifier;
a second NPN transistor having a base, a collector and an emitter, the base being coupled to the output terminal of the operational amplifier, the collector being coupled to the base of the first NPN transistor.

### Claim 2

A display device, the display device including a high voltage transformer, comprising:
input means receiving an adjustment instruction;
microcontroller means, responsive to said adjustment instruction, generating an analog control signal;
memory means coupled to the microcontroller means for storing a program executed by the microcontroller means; and
electronic adjustment means, responsive to the analog control signal, for generating a screen voltage signal using a power supply from a primary side of the high voltage transformer.

### Claim 3 (depends on 2)

The display device as recited in claim 2, wherein the screen voltage generation means comprises:
an operational amplifier, the operational amplifier having a negative input terminal receiving said analog control signal, a positive input terminal and an output. terminal;
a first NPN transistor having a base, a collector and an emitter, the collector is coupled to a Vcc voltage, the collector and base being coupled together via a first resistor, the screen voltage being generated at the emitter and coupled to the positive input terminal of the operational amplifier;
a second NPN transistor having a base, a collector and an emitter, the base being coupled to the output terminal of the operational amplifier, the collector being coupled to the base of the first NPN transistor.