System and method for driving an ultrasonic handpiece with a linear amplifier

Patent metadata

Field	Value
Publication number	US-10449570-B2
Application number	US-201715805849-A
Country	US
Kind code	B2
Filing date	Nov 7, 2017
Priority date	May 11, 2015
Publication date	Oct 22, 2019
Grant date	Oct 22, 2019

Abstract

A control console for a powered surgical tool. The console includes a transformer that supplies the drive signal to the surgical tool. A linear amplifier with active resistors selectively ties the ends of the transformer primary winding between ground and the open circuit state. Feedback voltages from the transformer windings regulate the resistances of the active resistors.

First claim

What is claimed is:

1. An AC signal generator for an ultrasonic handpiece including a driver and a tip coupled to the at least one driver that vibrates upon actuation of the driver, the AC signal generator comprising:
a transformer including a primary winding with opposed ends and a center tap to which a DC voltage is applied; and a secondary winding across which an AC drive signal is induced for actuating the driver of the handpiece; and
a linear amplifier including:
first and second transistors that function as first and second active resistors respectively that are each connected to a separate end of the opposed ends of said primary winding of said transformer and ground, wherein said linear transformer is configured to set the resistances of said first and second active resistors implemented by the first and second transistors to set the voltage at each opposed end of the primary winding between a ground state voltage and an open state voltage that so as to causes an AC voltage to develop across the primary winding that causes the AC drive signal to develop across said secondary winding;
a differential amplifier to which the voltages present at the opposed ends of the transformer primary winding are applied and that produces as a feedback signal a signal based on the differences between the voltages present at the opposed ends of the transformer primary winding for causing, responsive to receipt of an external control signal, a substantially linear response of the AC voltage developed across the primary winding that causes desired vibrations of the tip of the handpiece upon actuation of the driver by the AC drive signal developed across the secondary winding according to the external control signal; and
a control circuit that receives the feedback signal and the external control signal and that, based on the feedback signal and the external control signal, sets the resistances of said first and second active resistors implemented by said first and second transistors for generating the substantially linear response.

2. The AC signal generator of claim 1 , wherein said control circuit of said linear amplifier is configured to combine the feedback signal from said differential amplifier with the external control signal to produce a combined signal that regulates the resistances of said first and second active resistors implemented by said first and second transistors.

3. The AC signal generator of claim 2 , wherein said linear amplifier control circuit includes a rectifier and splitter to which the combined signal is applied, said rectifier and splitter being configured to split the combined signal into positive and negative components wherein the negative component of the combined signal is used to set the resistance of said first active resistor implemented by said first transistor and the positive component of the combined signal is used to set the resistance of said second active resistor implemented by said second transistor.

4. The AC signal generator of claim 1 , wherein said control circuit of said linear amplifier includes a first voltage controlled current source and a second voltage controlled current source that, based on the feedback signal from said differential amplifier and the external control signal, produce a current that sets the resistance of said first active resistor implemented by said first transistor and a current that sets the resistance of said second active resistor implemented by said second transistor respectively.

5. The AC signal generator of claim 4 , wherein said control circuit of said linear amplifier:
is configured to combine the feedback signal from said differential amplifier with the external control signal to produce a feedback adjusted external control signal, the feedback adjusted external control signal having both positive and negative components; and
said control circuit includes a rectifier and splitter that receives the feedback adjusted external control signal and that provides a negative component of the feedback adjusted external control signal as a control signal to said first voltage controlled current source and a positive component of the feedback adjusted external control signal as a control signal to said second voltage controlled current source.

6. The AC signal generator of claim 1 , further comprising:
a power supply for supplying a variable DC voltage to the center tap of said transformer primary winding;
a headroom monitor that monitors the voltage across said first and second transistors and that produces a signal representative of the voltage across said first and second transistors; and
a power supply controller that receives from said headroom monitor the signal representative of the voltage across said first transistor and the voltage across said second transistor, that is connected to said power supply for regulating the DC voltage supplied by said power supply, and that is configured to, based on the voltage across said first and second transistors indicated by said headroom monitor, set the level of the DC voltage said power supply supplies to the transformer primary winding.

7. The AC signal generator of claim 6 , wherein said headroom monitor is configured to receive as inputs, if said first and second transistors are FETs, the voltages present at the drains and sources of the FETs and, if said first and second transistors are bipolar transistors, the voltages present at the collectors and emitters of the bipolar transistors.

8. The AC signal generator of claim 6 , wherein said DC power supply includes a constant DC voltage supply and a boost converter to which DC voltage from said constant DC voltage supply is applied and that is configured to, in response to a control signal from said power supply controller, apply a varying DC voltage to the center tap of said transformer primary winding.

9. The AC signal generator of claim 1 , wherein said first and second transistors of said linear amplifier that function as said first and second active resistors respectively are MOSFETs.

10. The AC signal generator of claim 1 , wherein said linear amplifier is configured to, independent of the feedback signal and the external control signal, apply a signal to each of said first and second transistors so each of said first and second transistors is continually in a saturation mode.

11. An ultrasonic surgical tool system comprising:
an AC signal generator including:
a transformer with: a primary winding with opposed ends and a center tap to which a DC voltage is applied; and a secondary winding across which an AC drive signal is induced for application to a power generating unit of a surgical tool; and
a linear amplifier, said linear amplifier including:
first and second transistors that function as first and second active resistors respectively that are each connected to a separate end of the opposed ends of said primary winding of said transformer and ground, wherein said linear transformer is configured to set the resistances of said first and second active resistors to set the voltage at each opposed end of the primary winding between a ground state voltage and an open state voltage that causes an AC voltage to develop across the primary winding that causes the AC drive signal to develop across said secondary winding;
a differential amplifier to which the voltages present at the opposed ends of the transformer primary winding are applied and that said differential amplifier produces as a feedback signal a signal based on the differences between the voltages present at the opposed ends of the transformer primary winding; and
a control circuit that receives the feedback signal and an external control signal and that, based on the feedb

Assignees

• Stryker Corp

Inventors

• Downey Adam D
• Butler Neal R
• Rhodes Scott A

Classifications

• A61B2017/0003

  of parts of the instruments · CPC title

• A61B2217/007

  with irrigation system · CPC title

• H03F1/0216

  Continuous control · CPC title

• A61B17/320068

  using mechanical vibrations, e.g. ultrasonic (A61B17/22012 takes precedence; dental tooth drilling devices operated by vibration A61C3/03; removing intra-ocular material using mechanical vibrations A61F9/00745) · CPC title

• A61B2017/320069

  for ablating tissue · CPC title