Process and apparatus for phase-regulated power and frequency control of an ultrasonic transducer
First Claim
1. A method of phase-controlled power and frequency regulation of an ultrasonic transducer for dispersion of a liquid under conditions wherein said transducer is loaded variably by said liquid, said method comprising the steps of:
- (a) driving said ultrasonic transducer with voltage pulses amplified by a driver stage from a variable-frequency oscillator of a phase-control circuit;
(b) initially varying a frequency of said oscillator by a wobbler to establish a series resonant frequency of said transducer and locking an output frequency of said oscillator at said series resonant frequency with said phase-control circuit;
(c) thereafter setting and maintaining a capacitive phase angle between current and voltage in said transducer so that said phase-control circuit reduces the output frequency of said oscillator so that it is reduced relative to said series resonant frequency; and
(d) automatically shifting said phase-angle output in a direction resulting in an increase in said output frequency, thereby shifting said output frequency more closely toward said series resonant frequency of the transducer in response to mechanical loading of said ultrasonic transducer by said liquid.
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Abstract
A phase-regulated power and frequency control of an ultrasonic transducer which is supplied by a variable frequency oscillator of a phase control circuit with a plurality of voltage pulses amplified by a driver. First the variable frequency oscillator is canned to find a resonance frequency of the ultrasonic transducer and the scanner is locked to the resonance frequency of the ultrasonic transducer after locking into the phase control circuit. After initial oscillation of the ultrasonic transducer in the vicinity of a series resonance frequency thereof a capacitive phase angle between voltage and current is introduced and is maintained operationally so that by phase control of the phase control circuit the operating frequency of the oscillator is reduced relative to the series resonance frequency of the transducer. A phase angle change as a result of mechanical loading of the transducer leads to an increase of the operating frequency of the oscillator and thus to a shift toward the series resonance frequency of the transducer.
51 Citations
20 Claims
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1. A method of phase-controlled power and frequency regulation of an ultrasonic transducer for dispersion of a liquid under conditions wherein said transducer is loaded variably by said liquid, said method comprising the steps of:
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(a) driving said ultrasonic transducer with voltage pulses amplified by a driver stage from a variable-frequency oscillator of a phase-control circuit; (b) initially varying a frequency of said oscillator by a wobbler to establish a series resonant frequency of said transducer and locking an output frequency of said oscillator at said series resonant frequency with said phase-control circuit; (c) thereafter setting and maintaining a capacitive phase angle between current and voltage in said transducer so that said phase-control circuit reduces the output frequency of said oscillator so that it is reduced relative to said series resonant frequency; and (d) automatically shifting said phase-angle output in a direction resulting in an increase in said output frequency, thereby shifting said output frequency more closely toward said series resonant frequency of the transducer in response to mechanical loading of said ultrasonic transducer by said liquid. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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- 10. In an apparatus for phase-regulated power and frequency control of an ultrasonic transducer in contact with a liquid to be dispersed thereby and variably loaded in said liquid, particularly a piezoelectric ultrasonic transducer, comprising a variable-frequency oscillator controlled by a phase control circuit for generation of voltage pulses, a driver connected to receive said voltage pulses for amplification and a transformer for transmission of excitation pulses for said transducer, a synchronization signal required for influencing said phase control circuit being detected in a coil of said transformer, and a wobbler which varied an output frequency of said oscillator to find a series resonance frequency of said transducer and said phase control circuit locks said output frequency to said resonance frequency, the improvement wherein an adjustable phase shift member is connected to said phase control circuit whose phase shift angle is adjusted so that with said phase control circuit locking to said series resonant frequency but lies below said series resonant frequency a capacitive phase angle between current and voltage is maintained in said transducer so that said phase angle is automatically shifted in a direction resulting in an increase in said output frequency, thereby shifting said output frequency more closely toward said series resonant frequency of said transducer.
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19. A process for phase-regulated power and frequency control of an ultrasonic transducer which is energized by a variable frequency oscillator of a phase control circuit with a plurality of voltage pulses amplified by a driver comprising:
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(a) scanning said variable-frequency oscillator to find a resonance frequency of said ultrasonic transducer with a wobbler; (b) locking in said phase control circuit; (c) locking said wobbler to said resonance frequency of said ultrasonic transducer; (d) after start-up of oscillation of said ultrasonic transducer near a series resonance frequency of said resonance frequencies introducing and maintaining operationally a capacitive phase angle of from -30°
to -85°
between voltage and current in said transducer;(e) controlling the phase of said phase control circuit to reduce an operating frequency of said oscillator relative to said series resonance frequency of said transducer so that a phase angle change as a result of mechanical loading of said transducer leads to an increase of said operating frequency of said oscillator and thus to a shift toward said series resonance frequency of said transducer; and (f) adjusting an additional impedance in a circuit associated with said transducer to set a phase gradient at low frequencies below said series resonance frequency. - View Dependent Claims (20)
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Specification