Circuit for driving ultrasonic transducer
First Claim
1. A circuit for driving an ultrasonic transducer comprisingan oscillating means for generating a driving signal whose frequency is controlled in accordance with a frequency control signal;
- a first phase detecting means for detecting a phase of said driving signal to generate a first phase detection signal;
a second phase detecting means for detecting a phase of the vibration of the ultrasonic transducer to generate a second phase detection signal;
a reference signal generating means for generating a reference signal whose frequency is continuously changed; and
a frequency control means for selectively changing the operation of the driving circuit between a sweep control mode in which the frequency of the driving signal generated from said oscillating means is controlled to follow the frequency of said reference signal by comparing one of said first and second phase detection signals with said reference signal and a feedback control mode in which the frequency of the driving signal generated from said oscillating means is controlled to follow a resonance frequency of the ultrasonic transducer by comparing said first and second phase detection signals with each other.
1 Assignment
0 Petitions
Accused Products
Abstract
Circuit for use in a surgical operation including a phase lock loop having a voltage controlled oscillator, and a phase comparator for comparing a phase of a voltage of a driving signal and a phase of a signal representing the vibration phase of the ultrasonic transducer to derive a phase difference therebetween which is applied to the voltage controlled oscillator as a frequency control voltage such that the driving signal is phase-locked with a resonance frequency of the ultrasonic transducer, the improvement being characterized in that during a start period, a reference signal having a frequency which is increased monotonously is applied to the phase comparator such that the frequency of the driving signal is increased until the driving signal is phase-locked with the vibration phase of the ultrasonic transducer vibrating at the resonance frequency. After the phase-lock condition has been attained, the signal representing the vibration phase of the ultrasonic transducer is applied to the phase comparator instead of the reference signal.
-
Citations
41 Claims
-
1. A circuit for driving an ultrasonic transducer comprising
an oscillating means for generating a driving signal whose frequency is controlled in accordance with a frequency control signal; -
a first phase detecting means for detecting a phase of said driving signal to generate a first phase detection signal; a second phase detecting means for detecting a phase of the vibration of the ultrasonic transducer to generate a second phase detection signal; a reference signal generating means for generating a reference signal whose frequency is continuously changed; and a frequency control means for selectively changing the operation of the driving circuit between a sweep control mode in which the frequency of the driving signal generated from said oscillating means is controlled to follow the frequency of said reference signal by comparing one of said first and second phase detection signals with said reference signal and a feedback control mode in which the frequency of the driving signal generated from said oscillating means is controlled to follow a resonance frequency of the ultrasonic transducer by comparing said first and second phase detection signals with each other. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
-
- 15. A circuit for driving an ultrasonic transducer and including a driving signal generating means which has an open loop control mode in which the frequency of the driving signal is increased or decreased continuously and a feedback control mode in which the frequency of the driving signal is controlled in accordance with a phase difference between voltage and current of the driving signal such that the frequency of the driving signal follows a varying resonance frequency of the ultrasonic transducer, and a switching means for selectively driving said driving signal generating means between said open loop control mode and the feedback control mode by comparing the phases of the voltage and current of the driving signal, the improvement being characterized in that said switching means comprises an impedance detector for detecting an impedance of the ultrasonic transducer, a comparator for comparing the impedance of the ultrasonic transducer with a predetermined threshold value and generating a resonance point detecting signal when the impedance is decreased below said threshold value, and a switch for changing the open loop control mode into the feedback control mode in response to said resonance point detection signal.
-
21. A driving circuit for generating a driving signal for an ultrasonic transducer including
a frequency sweep means for effecting the frequency sweep over a predetermined frequency range; -
a means for operating the driving circuit under a sweep control mode in which the frequency of the driving signal is increased or decreased continuously within said predetermined frequency range with the aid of said frequency sweep means; a means for operating the driving circuit under a feedback control mode in which the frequency of the driving signal is controlled to follow a varying resonance frequency of the ultrasonic transducer; and a switching means for selectively driving said driving circuit between said sweep control mode and the feedback control mode by comparing the phases of the voltage and current of the driving signal, the improvement being characterized in that said switching means comprises an impedance detector for detecting an impedance of the ultrasonic transducer, a comparator for comparing the impedance of the ultrasonic transducer with a predetermined threshold value and generating a resonance point detection signal when the impedance is decreased below said threshold value, and a switching circuit for changing the sweep control mode into the feedback control mode in response to said resonance point detection signal. - View Dependent Claims (22, 23, 24, 25, 26, 27)
-
-
28. A driving circuit for generating a driving signal for an ultrasonic transducer comprising
a phase lock loop for adjusting a frequency of the driving signal to follow a resonance frequency of the ultrasonic transducer in accordance with a voltage phase detection signal representing a phase of a voltage of the driving signal and a current phase detection signal; -
a reference signal generating circuit for generating a reference signal having a frequency which is varied continuously; and a control means for selectively driving said phase lock loop between a first control mode in which during a start period, the frequency of the driving signal is controlled in accordance with a phase difference between the reference signal and the voltage phase detection signal until the driving signal is phase-locked with a resonance frequency of the ultrasonic transducer, and a second control mode in which after the driving signal has been phase-locked with the resonance frequency of the ultrasonic transducer, the frequency of the driving signal is controlled in accordance with a phase difference between the voltage phase detection signal and the current phase detection signal. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36)
-
-
37. A driving circuit for driving an ultrasonic transducer comprising
a frequency sweep means for effecting the frequency sweep over a predetermined frequency range; -
a means for operating the driving circuit under a sweep control mode in which the frequency of the driving signal is increased or decreased continuously within said predetermined frequency range with the aid of said frequency sweep means; a means for operating the driving circuit under a feedback control mode in which the frequency of the driving signal is controlled to follow a varying resonance frequency of the ultrasonic transducer; a switching means for selectively driving said driving circuit between said sweep control mode and the feedback control mode; a means for amplifying the driving signal with a variable amplification factor; and an amplification control means for controlling the amplification factor of said amplifying means such that the amplification factor is gradually increased from a lower value during the sweep control mode to a higher value during the feedback control mode. - View Dependent Claims (38, 39, 40, 41)
-
Specification