EP0424685A2
Expired / Lapsed
EP
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Method for driving an ultrasonic transducer
Assignee: Bausch and Lomb Inc
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Filing: 1990-09-28
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Granted: —
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Expires: 2010-09-28
Abstract
Abstract An electronic control system for determining the resonant frequency of and driving ultrasonic transducers in a phacoemulsification probe used for ophthalmic surgery. The control system includes a voltage control led oscillator, power amplifier, power monitor, and automatic gain control circuit operating under the direction of command signals received from a microprocessor-based control console. The control system operates in a constant apparent power, direct drive mode with closed loop feedback maintaining the electrical power provided to the primary of a RLC transformer at the constant level requested by the command signals from the console. The frequency of the drive signal is held at the dominant resonant frequency of the ultrasonic transducer which is being driven by the control system. This resonant frequency is determined via a calibration procedure performed when the probe is first attached to the control system. During this procedure a constant voltage drive signal is swept through a range of frequencies and the electrical power consumed by the transducer is measured and stored at selected intervals such as 100 Hertz increments. The resonant frequency is also determined in part by looking for the frequency at which maximum power is consumed by the probe. The stored data is also subjected to other tests to cheok that the peak is indeed a resonant frequency and that the probe has selected output power characteristics about this resonant frequency thus helping to ensure that the probe is capable of operating satisfactorily when driven by the control system.
Inventors
- 👤 Daniel L Williams, Jr.
- 👤 Kevin P. Kepley
- 👤 John A. Painter
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 12:22
CPC Classifications
B; B06; B06B; B06B1/00; B06B1/02; B06B1/0207; B06B1/0223; B06B1/0238; B06B1/0246; B06B1/0253; A; A61; A61F; A61F9/00; A61F9/007; A61F9/00736; A61F9/00745; A61B; A61B17/00; A61B2017/00681; A61B2017/00725; A61B2017/00973; B06B2201/00; B06B2201/40; B06B2201/70; B06B2201/76
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
131 words
A method for driving an ultrasonic transducer of a ophthalmic surgical instrument at its dominant resonant frequency by holding the electrical power consumed by the transducer substantially constant at a desired level of power consumption by use of closed loop feedback control, comprising: (a) generating an electrical signal oscillating at a desired ultrasonic frequency; (b) amplifying the oscillating electrical signal; (c) applying the amplified electrical signal to an ultrasonic transducer; (d) monitoring how much electrical power of the amplified electrical signal is consumed by the ultrasonic transducer; (e) comparing how much electrical power of the amplified electrical signal is being consumed against the desired level of power consumption; and (f) automatically adjusting the power level of amplified signal to maintain the consumed electrical power substantially equal to the desired power level.
Claim 2
Independent Claim
131 words
A method for driving an ultrasonic transducer of a ophthalmic surgical instrument at its dominant resonant frequency by holding the electrical power consumed by the transducer substantially constant at a desired level of power consumption by use of closed loop feedback control, comprising: (a) generating an electrical signal oscillating at a desired ultrasonic frequency; (b) amplifying the oscillating electrical signal; (c) applying the amplified electrical signal to an ultrasonic transducer; (d) monitoring how much electrical power of the amplified electrical signal is consumed by the ultrasonic transducer; (e) comparing how much electrical power of the amplified electrical signal is being consumed against the desired level of power consumption; and (f) automatically adjusting the power level of amplified signal to maintain the consumed electrical power substantially equal to the desired power level.
Claim 3
Dependent Claim
180 words
A method of claim 1 for automatically determining the resonant frequency of a surgical instrument powered by an ultrasonic transducer, comprising the steps of; (a) providing an alternating current electric driving signal having a substantially constant voltage level to drive the ultrasonic transducer at any desired one of a number of frequencies within a given range of frequencies; (b) monitoring the electrical power consumed by the probe at different frequencies within the range of frequencies; (c) selecting an apparent resonant frequency within the range of frequencies by determining which frequency, out of those frequencies which were monitored, had the greatest electrical power from the driving signal consumed by the probe; (d) comparing the amount of power consumed at the apparent resonant frequency with amounts of power consumed by the probe at a first frequency below the apparent resonant frequency, and at a second frequency above the apparent resonant frequency; and (e) deciding whether the apparent resonant frequency is the dominant resonant frequency of the probe at least in part based upon the results of the comparisons performed in step (d).
Claim 4
Dependent Claim
27 words
A method as in claim 2 further comprising the step of: (f) sweeping the driving signal through at least the given range of frequencies during step (b).
Claim 5
Dependent Claim
98 words
A method as in claim 2 wherein: step (d) further includes comparing the amount of power consumed at the apparent resonant frequency with amounts of power consumed by the probe at third and fourth frequencies below the apparent resonant frequency and at fifth and sixth frequencies above the apparent resonant frequency; and step (e) includes requiring that the power consumed at each of the first through sixth frequencies to be at least a predetermined amount below the power consumed at the apparent resonant frequency in order to decide that the apparent resonant frequency is the dominant resonant frequency.
Claim 6
Dependent Claim
105 words
A method as in claim 4, wherein: step (d) further includes comparing the power consumed by the probe at the apparent resonant frequency against the power consumed by the probe at a plurality of frequencies below and a plurality of frequencies above a band of predetermined size in Hertz centered about the apparent resonant frequency, and step (e) includes requiring that the power consumed at each of the pluralities of frequencies below and above the band be at least a predetermined amount below the power consumed at the apparent resonant frequency in order to decide that the apparent resonant frequency is the dominant resonant frequency.
Claim 7
Dependent Claim
43 words
A method as in claim 2, wherein: the given range of frequencies is within a band of frequencies from about 26 KHz to about 32 KHz; and the first and second frequencies are at least about 100 HZ from the apparent resonant frequency.
Claim 8
Dependent Claim
56 words
The method of claim 1, further comprising the step of: (g) providing transformer means for stepping up voltage and having an input side and output side connected to the ultrasonic transducer, and wherein step (c) is performed by at least in part by applying the amplified electrical signal to the input side of the transformer means.
Claim 9
Dependent Claim
66 words
The method of claim 1 wherein step (a) is performed at least in part by applying a frequency command signal to a voltage controlled oscillator, and the method further comprises the step of: (g) selecting the frequency represented by the frequency command signal to be substantially equal to a dominant resonant frequency of the uitrasonic transducer within the ophthalmic surgical instrument under a predetermined test condition.
Claim 10
Dependent Claim
79 words
The method of claim 1 wherein: step (e) includes producing an error signal representative of the difference between the desired level of power consumption by the transducer and the actual level of power consumption of the transducer as determined in step (d); and step (f) is performec at least in part by altering an amplitude characteristic of the electrical signal generated in step (a) prior to performing step (b) in accordance with the error signal produced in step (e).
Claim 11
Dependent Claim
25 words
The method of claim 9 wherein the altering of the amplitude characteristic is achieved by attenuating the amplitude of electrical signal generated in step (a).
References Cited (Backward Citations)
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