Cold-cathode driver and liquid crystal display

Details Cold-cathode driver and liquid crystal display Cold-cathode driver and liquid crystal display

2005-06-07

2005-06-07

Vannucci, James (Department: 2821)

Electric lamp and discharge devices: systems

Periodic switch in the supply circuit

Silicon controlled rectifier ignition

C310S316020

Reexamination Certificate

active

06903517

ABSTRACT:
A cold cathode tube driving device using a piezoelectric transformer in which an output voltage varies depending on a frequency of an input voltage, as a booster transformer for driving a cold cathode tube, includes: a frequency dividing means which generates a driving pulse of an average frequency corresponding to frequency data outputted from a frequency setting means at a distribution cycle which is a driving pulse N cyclic period; a controller which controls a control cycle so as to perform the same driving for predetermined number of times A (A≧2) at the average frequency; and a burst pulse generating means which generates a pulse having a duty width in accordance with a dimming level externally applied thereto and having a frequency outputted from the controller.A control cycle is A times (natural number) the distribution cycle and the driving is performed A times at the same average frequency, whereby a digital driving system using the frequency distribution of the driving pulse is achieved. Consequently, a space for the driving circuit can be saved and cost can be reduced. Further, a frequency distribution system is adopted, thereby obtaining frequency resolution required for satisfactory dimming performance and lighting performance. Moreover, a burst dimming system is adopted, thereby suppressing brightness flicker seen in a tube current control system. Additionally, there is no electric power loss seen in a system in which a power source is turned on or off and further a shield circuit is unnecessary because of a system in which the driving pulse is turned on or off. In particular, the control cycle is A times the distribution cycle and the burst dimming is performed in which the driving is executed A times at the same average frequency, whereby the brightness flicker can be prevented by controlling the tube current to be constant with high dimming resolution assured.

REFERENCES:
patent: 5854543 (1998-12-01), Satoh et al.
patent: 6075325 (2000-06-01), Kouno et al.
patent: 6153962 (2000-11-01), Noma et al.
patent: 6362798 (2002-03-01), Kimura et al.
patent: 1050954 (2000-11-01), None
patent: 2000-133485 (2000-05-01), None
patent: 2000-139081 (2000-05-01), None

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