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An ultrasonic power supply for driving a piezoelectric transducer at its parallel resonant frequency includes a clamped-mode resonant converter for converting direct current to alternating current and a demodulator, a loop filter and a voltage controlled oscillator in a phase locked loop configurati

An ultrasonic power supply for driving a piezoelectric transducer at its parallel resonant frequency includes a clamped-mode resonant converter for converting direct current to alternating current and a demodulator, a loop filter and a voltage controlled oscillator in a phase locked loop configuration. The power supply also includes a control circuit for adjustably setting and controlling the amplitude of vibration of the transducer, and providing during start-up a ramp start. The power supply, further, includes a control circuit for limiting the maximum permissible current flow to the transducer and the reverse current flow from the transducer resulting from stored mechanical energy. Both control circuits provide feedback signals which control the pulse width modulated operation of the clamped-mode resonant converter and thereby control the voltage amplitude of the alternating current output from the converter. The phase locked loop circuit causes the frequency of the alternating current output from the converter to track the parallel resonant frequency of the transducer.

대표청구항 ▼

A power supply for operating a piezoelectric transducer comprising: a direct current supply; a clamped-mode resonant converter coupled for receiving direct current from said direct current supply and providing an alternating current output for operating a piezoelectric transducer at its parallel res

A power supply for operating a piezoelectric transducer comprising: a direct current supply; a clamped-mode resonant converter coupled for receiving direct current from said direct current supply and providing an alternating current output for operating a piezoelectric transducer at its parallel resonant frequency; an output network coupled to said converter for receiving the alternating current output from said converter and providing an alternating current output of suitable magnitude for operating the piezoelectric transducer at said resonant frequency, and including means for providing a first alternating current signal commensurate with the current flowing between said output network and the transducer; a current filter coupled to said network for receiving said first alternating current signal and providing a second signal commensurate with the amplitude and phase of the fundamental frequency of the current flowing between said converter and the transducer; a demodulator coupled for receiving said second signal and receiving also a digital signal commensurate with the fundamental frequency of the current flowing between said converter and transducer but phase shifted by ninety degrees, and providing a third signal commensurate with the value of the imaginary current component of the fundamental frequency of the current flowing between said converter and the transducer; a loop filter coupled to said modulator for receiving said third signal and including means for producing a fourth signal having a direct current amplitude commensurate with the amplitude of said imaginary current component; a voltage controlled oscillator adapted to operate at a predetermined frequency coupled for receiving said fourth signal as a control signal for causing said oscillator to change its frequency commensurate with the amplitude of said fourth signal, providing said digital signal to said demodulator, and providing further output signals responsive to the operating frequency of said oscillator, and a modulator and driver circuit coupled for receiving said further output signals from said oscillator and providing control signals to said converter for causing said converter to produce said alternating current output at a frequency which causes the transducer to operate at its parallel resonant frequency.