Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2002-11-19
2004-09-14
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06791239
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a piezoelectric transformation driving apparatus and particularly an apparatus that uses a single pulse-width modulation (PWM) control unit to drive synchronously a plurality of driving units, transformation units, piezoelectric units and loads.
BACKGROUND OF THE INVENTION
The light source of liquid crystal display (LCD) screens that are now being commonly used on desktop and notebook computers, PDAs, and Webpads is generated by a cold cathode fluorescent lamp (CCFL) actuated by a driving unit under a high voltage that projects light to a back panel so that displaying pictures become visible to users.
The LCD TV or LCD screen with a membrane touch screen requires a greater illumination to compensate visual requirements. The general driving device for actuating the CCFL as shown in
FIG. 1
usually uses one PWM control unit to drive one driving unit, then the driving unit drives the transformer and load (CCFL). The CCFL is ignited by a high voltage. A greater current will generate a greater illumination.
When the illumination and evenness of the back light is not sufficient, a plurality of lamps are needed. To meet this requirement, the number of the PWM control unit for driving the ignition, driving unit, and transformer also increases. As a result, the size of the circuit board becomes larger, and manufacturing is more difficult and the cost increases.
SUMMARY OF THE INVENTION
Therefore the primary object of the invention is to resolve the aforesaid disadvantages. The invention employs a single PWM control unit to drive a plurality of driving units, transformation units, piezoelectric units and loads to reduce the number of elements, shrink the circuit board, and simplify the manufacturing process and reduce the cost.
In order to achieve the foregoing object, the piezoelectric transformation driving apparatus of the invention includes a PWM control unit, a plurality of driving units, transformation units, piezoelectric units and loads. The PWM control unit outputs driving signals of the same phase and same frequency to synchronously drive the driving units, transformation units, piezoelectric units and loads to operate simultaneously.
REFERENCES:
patent: 6075325 (2000-06-01), Kouno et al.
patent: 6184631 (2001-02-01), Noma et al.
patent: 2001/0035698 (2001-11-01), Nakatsuka et al.
patent: 2001-85759 (2001-03-01), None
Cheng Eddie
Chou Chin-Wen
Birch & Stewart Kolasch & Birch, LLP
Shin Jiuh Corp.
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