Driving method and driving circuit of piezoelectric transformers
First Claim
1. A method of supplying power to a discharge tube such that the discharge tube has a constant luminance throughout its length, said method comprising steps of:
- driving a first piezoelectric transformer at a frequency voltage;
driving a second piezoelectric transformer at a same frequency voltage as said first piezoelectric transformer and 180 degrees out of phase;
applying an output of said first piezoelectric transformer to a first input terminal at a first end of said discharge tube; and
applying an output of said second piezoelectric transformer to a second input terminal at an opposite end of said discharge tube to turn on said discharge tube.
1 Assignment
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Accused Products
Abstract
A driving circuit of the present invention includes first and second piezoelectric transformers 12, 14 for outputting a voltage at a secondary terminal which is input from a primary terminal utilizing a piezoelectric effect, frequency control means 21 for outputting a frequency signal for operating the first piezoelectric transformer 12 at a required frequency voltage, phase reversing means 16 for reversing a phase of the frequency signal by 180 degrees, driving circuits 13, 15 for applying a frequency voltage to each of the piezoelectric transformers 12, 14 based on these frequency signals of which phases are different from each other by 180 degrees, a discharge tube 11 in which an output of the first piezoelectric transformer 12 is applied to a first input terminal and an output of the second piezoelectric transformer 14 is applied to a second input terminal, a circuit 20 for controlling a voltage of the first piezoelectric transformer 12 so that a current flowing in this discharge tube becomes to be constant, and circuits 22, 17 for controlling a voltage input to the second piezoelectric transformer 14 so that output voltages of the first and second piezoelectric transformers become to be the same voltages.
47 Citations
14 Claims
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1. A method of supplying power to a discharge tube such that the discharge tube has a constant luminance throughout its length, said method comprising steps of:
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driving a first piezoelectric transformer at a frequency voltage; driving a second piezoelectric transformer at a same frequency voltage as said first piezoelectric transformer and 180 degrees out of phase; applying an output of said first piezoelectric transformer to a first input terminal at a first end of said discharge tube; and applying an output of said second piezoelectric transformer to a second input terminal at an opposite end of said discharge tube to turn on said discharge tube. - View Dependent Claims (2, 3)
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4. A driving circuit for piezoelectric transformers supplying power to a discharge tube having a constant luminance throughout its length, comprising:
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first and second piezoelectric transformers; frequency control means for outputting a frequency signal for operating said first piezoelectric transformer at a required frequency voltage; phase reversing means for reversing a phase of the frequency signal by 180 degrees for outputting a reversed frequency signal; first driving circuit means for driving said first piezoelectric transformer with said frequency signal and second driving circuit means for driving said second piezoelectric transformer with said reversed frequency signal, wherein outputs of said first and second piezoelectric transformers are applied to opposite input terminals of a discharge tube, respectively. - View Dependent Claims (5)
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6. A piezoelectric transformer driving circuit for powering a discharge tube having a constant luminance value along it length, comprising:
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first and second piezoelectric transformers; frequency control means for outputting a frequency signal for operating said first piezoelectric transformer at a frequency voltage; phase reversing means for reversing a phase of the frequency signal by 180 degrees to output a reversed frequency signal; first driving means for driving said first piezoelectric transformer with said frequency signal; second driving means for driving said second piezoelectric transformer with said reversed frequency signal; a discharge tube comprising first and second power input terminals at opposite ends thereof, said first piezoelectric transformer supplying power to said first input terminal and said second piezoelectric transformer supplying power to said second power terminal; means for controlling a voltage of said first piezoelectric transformer so that a current flowing in said discharge tube is constant; and means for controlling a voltage input to said second piezoelectric transformer so that output voltages of said first and second piezoelectric transformers become are the same voltages. - View Dependent Claims (7, 8)
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9. A piezoelectric transformer driving circuit for powering a discharge tube having a constant luminance value along it length, comprising:
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first and second two piezoelectric transformers; frequency control means for outputting a frequency signal for operating said first piezoelectric transformer at a required frequency voltage; phase reversing means for reversing a phase of the frequency signal by 180 degrees to output a reversed frequency signal; first driving circuit means for driving said first piezoelectric transformer with said frequency signal; second driving means for driving said second piezoelectric transformer with said reversed frequency signal; a discharge tube in which an output of said first piezoelectric transformer is applied to a first input terminal at a first end of said discharge tube, and an output of said second piezoelectric transformer is applied to a second input terminal at a second end of said discharge tube; means for controlling a drive frequency of said first piezoelectric transformer so that luminance of said discharge tube is constant; and means for controlling a voltage input to said second piezoelectric transformer so that output voltages of said first and second piezoelectric transformers are the same voltages. - View Dependent Claims (10, 11)
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12. A circuit for illuminating a discharge tube with a constant luminance throughout its length, comprising:
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a discharge tube having a first input terminal at first end and a second input terminal at a second end, opposite said first end; first piezoelectric transformer connected to supply power to said first input terminal; second piezoelectric transformer connected to supply power to said second input terminal; first and second driving circuits respectively connecting said first and second piezoelectric transformers to a power supply; voltage comparison circuit for comparing the voltage supplied to the discharge tube by the first and second piezoelectric transformers and outputting a comparison signal; switch means for connecting and disconnecting said second drive circuit from said power supply in response to said comparison signal such that output voltage of said second piezoelectric transformer matches output voltage of the first piezoelectric transformer; frequency control means for driving said first and said second drive circuits with a frequency signal 180°
out of phase with each other; andone of a current detection circuit for detecting the current through said discharge tube and a luminance detector for detecting a luminance value from said discharge tube, for controlling said frequency driving said first and said second drive circuits, whereby said discharge tube has a constant luminance throughout its length. - View Dependent Claims (13)
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14. A method for illuminating a discharge tube with a constant luminance throughout its length, comprising the steps of:
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providing a discharge tube having a first input terminal at a first end and a second input terminal at a second end, opposite said first end; supplying power to said first input terminal with a first transformer operating at a first frequency; and supplying power to said second input terminal with a second transformer operating at a second frequency, said second frequency being 180°
out of phase to said first frequency.
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Specification