Computer graphics processing and selective visual display system – Display driving control circuitry – Display power source
Reexamination Certificate
2001-08-02
2004-03-23
Chang, Kent (Department: 2673)
Computer graphics processing and selective visual display system
Display driving control circuitry
Display power source
C345S076000, C345S212000, C315S169300, C363S059000
Reexamination Certificate
active
06710773
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to integrated circuits, and more specifically, to an integrated circuit for implementing a inductorless electroluminescent panel driver.
2. Background of the Invention
Electroluminescent (EL) panels are in common use as backlights for keyboards and displays. Recent uses of EL panels include wrist watches, cellular telephone displays and keyboards, notebook computers and personal digital assistants (PDAs). In order to produce illumination from an EL panel, an alternating high voltage power supply is required. An EL panel driver includes a high voltage power supply, and a mechanism for switching the high voltage power supply output to produce a high voltage output of alternating polarity for connection to the EL panel.
Traditionally, an integrated circuit controlled for implementing an EL panel driver circuit contains an oscillator, a high voltage power supply and a switching circuit coupled to the oscillator and the high voltage power supply for creating the alternating high voltage output for connection to the EL panel.
The high voltage power supply in an integrated circuit EL panel driver typically includes connections for either an inductor or a transformer to convert a low voltage input power supply to a high voltage that is then coupled to one or more terminals of the integrated circuit, which include a flyback switch transistor terminal and a terminal for coupling the high voltage DC output to the switching circuit that alternates the voltage supplied to the EL panel.
With the high density integration requirements present in devices such as cellular telephones and notebook computers, and in devices having very small packages such as wristwatches, it is desirable to produce a single integrated circuit solution with a minimum of external components and terminals. However, it is impractical to incorporate inductors or transformers within an integrated circuit package.
Therefore, it would be desirable to provide a inductorless apparatus and method for driving EL panels that may be incorporated within a single integrated circuit package.
SUMMARY OF THE INVENTION
The above objective of providing a inductorless apparatus and method for driving EL panels is accomplished in an integrated circuit including a high voltage power supply and a switching circuit for producing an alternating high voltage output from the high voltage power supply. The high voltage power supply includes a plurality of charge pump circuits for generating the high voltage power supply output. The high voltage power supply may also include a multi-stage charge pump to reduce voltage loss associated with driving charge pump circuits from a low voltage power supply, which results in a lesser number of overall charge pumps required to achieve a the voltage level required to drive the EL panel.
The foregoing and other objectives, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiment of the invention, as illustrated in the accompanying drawings.
REFERENCES:
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patent: 4496977 (1985-01-01), Ikeda
patent: 4769753 (1988-09-01), Knudson et al.
patent: 5491623 (1996-02-01), Jansen
patent: 5861719 (1999-01-01), Koskowich et al.
patent: 6043610 (2000-03-01), Buell
patent: 6232964 (2001-05-01), Lee
Jenkins James Michael Oliver
Lei Jimes
Chang Kent
Harris Andrew M.
Moy Jeffrey D.
Sheng Tom
Supertex Inc.
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