Circuit arrangement for accurately and effectively driving an ultrasonic transducer
First Claim
1. A method for driving an ultrasonic transducer, intended for use in atomization of liquids, at a selected one of its resonance frequencies, comprising:
- parallely tuning out, at the selected resonance frequency, an intrinsic capacitance of said ultrasonic transducer by shunting said transducer by a tuning impedance by connecting said tuning impedance in parallel with said transducer;
applying a driving voltage signal to the transducer;
sensing a resulting current signal through the transducer;
comparing the phases of the driving voltage and the resulting current signals;
and changing the frequency of the driving voltage signal until said driving voltage and resulting current signals are in phase.
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Accused Products
Abstract
A method for driving an ultrasonic transducer, intended for use in atomization of liquids, at one of its selected resonance frequencies, by tuning out the capacitance of the ultrasonic transducer by means of an inductor, by sensing the transducer current, by comparing the phases of the transducer driving voltage and the transducer current and by controlling a voltage controlled oscillator for driving the ultrasonic transducer, by means of a phase error signal such that the ultrasonic transducer is driven with a frequency at which the transducer driving voltage and the transducer current are in phase, whereby the transducer driving circuit is locked to a natural resonance frequency of the ultrasonic transducer.
102 Citations
35 Claims
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1. A method for driving an ultrasonic transducer, intended for use in atomization of liquids, at a selected one of its resonance frequencies, comprising:
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parallely tuning out, at the selected resonance frequency, an intrinsic capacitance of said ultrasonic transducer by shunting said transducer by a tuning impedance by connecting said tuning impedance in parallel with said transducer; applying a driving voltage signal to the transducer; sensing a resulting current signal through the transducer; comparing the phases of the driving voltage and the resulting current signals; and changing the frequency of the driving voltage signal until said driving voltage and resulting current signals are in phase. - View Dependent Claims (2, 3, 4, 5)
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6. A circuit arrangement for driving an ultrasonic transducer adapted to be used for atomization of liquids, at a selected one of its resonance frequencies comprising:
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a parallel connected tuning means, including a tuning impedance, connected in parallel with said transducer so as to shunt said transducer, for tuning out, at a selected resonance frequency, an intrinsic capacitance of said ultrasonic transducer so that at the selected resonance frequency a transducer driving voltage and a transducer current are in phase; voltage controlled oscillator means having an oscillator input and an oscillator output coupled for driving said ultrasonic transducer with said transducer driving voltage; current sensor means for sensing said transducer current; phase comparator means, having two comparator inputs and a comparator output, for comparing the phases of said transducer driving voltage and said transducer current, a first one of said two comparator inputs being coupled to receive a voltage signal being proportional in phase to said transducer driving voltage and the other one of said two comparator inputs being coupled to receive a current signal from said current sensor means, the current signal being proportional in phase to said transducer current; an output signal of said phase comparator means being coupled to cause said voltage controlled oscillator means to output a frequency at which the transducer driving voltage and the transducer current are in phase, whereby said circuit arrangement is locked to said selected resonance frequency. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A circuit arrangement for driving an ultrasonic transducer adapted to be used for atomization of liquids, at a selected one of its resonance frequencies, comprising:
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tuning means for tuning out, at a selected resonance frequency, an intrinsic capacitance of said ultrasonic transducer so that at the selected resonance frequency a transducer driving voltage and a transducer current are in phase; voltage controlled oscillator means having an oscillator input and an oscillator output coupled for driving said ultrasonic transducer with said transducer driving voltage; current sensor means for sensing said transducer current; phase comparator means, having two comparator inputs and a comparator output, for comparing the phases of said transducer driving voltage and said transducer current, a first one of said two comparator inputs being coupled to receive a voltage signal being proportional in phase to said transducer driving voltage and the other one of said two comparator inputs being coupled to receive a current signal from said current sensor means, the current signal being proportional in phase to said transducer current; an output signal of said phase comparator means being coupled to cause said voltage controlled oscillator means to output a frequency at which the transducer driving voltage and the transducer current are in phase, whereby said circuit arrangement is locked to said selected resonance frequency; first controllable switch means having a first switch control input and being coupled between said voltage controlled oscillator means and said ultrasonic transducer, for intermittently connecting said ultrasonic transducer to said oscillator output; and pulse width modulator means coupled between said first switch control input and said current sensor means, for outputting switch control pulses, the duty cycle of which is a function of an actual level of an output signal from said current sensor means such that the width of said switch control pulses is larger the smaller is the level of said output signal from said current sensor means. - View Dependent Claims (26, 27, 28)
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29. A circuit arrangement for driving an ultrasonic transducer adapted to be used for atomization of liquids, at a selected one of its resonance frequencies, comprising:
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tuning means for tuning out, at a selected resonance frequency, an intrinsic capacitance of said ultrasonic transducer so that at the selected resonance frequency a transducer driving voltage and a transducer current are in phase; voltage controlled oscillator means having an oscillator input and an oscillator output coupled for driving said ultrasonic transducer with said transducer driving voltage; current sensor means for sensing said transducer current; phase comparator means, having two comparator inputs and a comparator output, for comparing the phases of said transducer driving voltage and said transducer current, a first one of said two comparator inputs being coupled to receive a voltage signal being proportional in phase to said transducer driving voltage and the other one of said two comparator inputs being coupled to receive a current signal from said current sensor means, the current signal being proportional in phase to said transducer current; an output signal of said phase comparator means being coupled to cause said voltage controlled oscillator means to output a frequency at which the transducer driving voltage and the transducer current are in phase, whereby said circuit arrangement is locked to said selected resonance frequency; a sweep generator having a generator input and a generator output and being coupled to control said voltage controlled oscillator means to sweep its frequency between the limits of its predetermined frequency range; a controllable sweep switching means having a sweep switch control input and being coupled between said sweep generator and said oscillator input; an auxiliary phase comparator means for outputting a sweep switch control signal, and having two auxiliary phase comparator inputs and an auxiliary phase comparator output; a first one of said two auxiliary phase comparator inputs being coupled to receive said voltage signal being phase-proportional to said transducer driving voltage and a second one of said two auxiliary phase comparator inputs being coupled to receive said current signal being phase-proportional to said transducer current; the auxiliary phase comparator output being coupled to said sweep switch control input for connecting the sweep generator output to said oscillator input when a difference of the phases of the signals at said two auxiliary phase comparator inputs reaches a predetermined threshold. - View Dependent Claims (30, 31, 32, 33, 34, 35)
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Specification