Systems and methods for controlling patient leakage current in surgical systems

Abstract

A console and method for supplying a drive signal to a surgical tool are provided. The console includes a transformer including primary and secondary windings. The primary winding receives an input signal from a power source and induces a drive signal in the secondary winding to supply the drive signal to a surgical tool. A first current source including a leakage control winding is coupled to the path of the drive signal. The primary winding induces a first cancellation current in the leakage control winding to be injected into the path of the drive signal to cancel the leakage current. A sensor coupled to the path of the drive signal outputs a sense signal to provide feedback related to the leakage current. The sensor may be connected to a second leakage current cancellation source and / or a fault detection stage. The power source may be variable and may also power the second current source.

Description

[0001] This application is a divisional application of the invention patent application with the application date of December 4, 2018, application number 201880086424.0, and invention name “System and method for controlling patient leakage current in a surgical system”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This patent application claims priority to and all benefits of U.S. Provisional Patent Application No. 62 / 595,235, filed on December 6, 2017, the entire disclosure of which is incorporated herein by reference. Technical Field

[0004] The present disclosure relates generally to consoles that supply drive signals to powered surgical tools, and more particularly, are designed to reduce patient leakage current to / from the drive signals. Background Art

[0005] Electric surgical tool systems can be considered to have three basic components. The console generates drive signals that have the characteristics necessary to actuate the second component of the system (generator). The generator converts the electrical energy of the drive signal into another form of energy. The types of energy converted from electrical energy include mechanical energy, thermal energy (heat) and photon (light) energy. The third component of the tool system is an energy applicator. The energy applicator receives the energy output by the generator and applies the energy to the target tissue to perform a specific treatment task. Some tool systems are designed to apply prepared electrical energy to the target tissue. In this type of system, the generator is essentially a conductor through which the drive signal is applied to the exposed electrode, through which the current is provided to the tissue. The electrode serves as an energy applicator. The electrode can be placed on the patient or integrated into the handpiece. Other tool systems are designed to provide mechanical energy. In this type of system, the generator converts electrical energy, such as an AC drive signal, into mechanical energy, such as vibration, which is applied to the patient through the handpiece.

[0006] An integral part of many surgical tool systems is a surgical tool, which may be a handpiece. At least, the handpiece is a physical component designed to be held by a physician, from which an energy applicator extends. A generator is typically included in the surgical tool. A surgical tool system designed in this way is an ultrasonic surgical tool system. The surgical tool of the system includes a generator, which includes one or more drivers. Each driver vibrates in response to the application of an AC signal. The horn is tightly mechanically connected to the driver. The tip used as an energy applicator extends distally from the horn. The vibration of the driver is generated as a vibration in the horn and (by extension) in the tip. The movement of the vibrating tip against the tissue causes ablation and removal of the tissue.

[0007] An inherent feature shared by many powered surgical tool systems and other powered components is the presence of parasitic capacitance between components of these systems. Parasitic capacitance is the capacitance that exists between two components that are at unequal voltages. As a result of the presence of this capacitance, a parasitic alternating current can flow through one of these components. For example, when the surgical tool includes a power generation unit to which an AC drive signal is applied, a parasitic current can flow through the metal structural components of the surgical tool due to the parasitic capacitance between the power generation components inside the surgical tool through which the current flows. This parasitic current can result in what is known as leakage current. In general, leakage current is an unintended current that flows through a system component to which current is applied for other purposes. More specifically, patient leakage current is an unintended current that flows through a patient.

[0008] During surgery, there is a possibility that the patient could be inadvertently grounded. If this event does occur, leakage current could flow from the surgical tool into the patient. To avoid danger to the patient, the electric surgical tool system should be designed to minimize leakage current flowing through the patient, such as in the case where the patient is grounded. If a surgical tool that may have leakage current is applied to the patient, the leakage current could theoretically flow through the patient to the ground. This current could adversely affect the function of the patient's organs and tissues.

[0009] For these reasons, surgical tool systems with surgical tools intended to be applied to a patient are designed to ensure that normal leakage current is less than 100 pAmps. If they are to be used in the United States, surgical tool systems with surgical tools intended to be applied to cardiac tissue must be designed to have normal leakage current less than 10 pAmps. These requirements are based on the IEC 60601 medical design standard. The IEC 60601 standard also describes the process of testing powered surgical tools to ensure that leakage current is below these maximum values.

[0010] It is further required that a tool applied to the patient cannot be used as a ground connection. Primarily, if for some reason a voltage from another source is applied to the patient, the tool should not be used as a ground connection, otherwise it will cause current to flow through the patient.

[0011] An electric surgical tool system may have an output that is isolated from ground to prevent current leakage. However, an isolated output circuit alone is not sufficient to reduce leakage to acceptable levels. Some electric surgical tool systems have been designed with the ability to detect an open circuit and be able to reduce their peak output voltage accordingly. This results in several performance issues. Reducing the peak output voltage to minimize leakage current may reduce the performance of the tool system because the peak output voltage may induce the spark required for proper coagulation. In addition, the amount of time required for the generator to sense an open circuit environment may result in a transient voltage spike, which may allow leakage current to occur.

[0012] One approach is to reduce parasitic capacitance to reduce parasitic current. If the tool is an ultrasonic surgical tool, parasitic capacitance can be reduced by providing electrically insulating impedance disks between the driver and the horn, the mechanical parts of the surgical tool being intended to be vibrated by the driver. One disadvantage associated with providing these disks is that they inhibit the transfer of vibrations from the driver to the horn and tip. This mechanical damping reduces the efficiency of the surgical tool.

[0013] Therefore, it is necessary to at least solve the above-mentioned technical deficiencies of the existing systems and methods. Summary of the invention

[0014] In one embodiment, a console for supplying a drive signal to a surgical tool and a method for operating the same are provided. The console includes a transformer including a primary winding and a secondary winding. The primary winding is configured to receive an input signal from a power supply and to induce a drive signal in the secondary winding to supply the drive signal to the surgical tool. The console also includes a first current source, the first current source including a leakage control winding coupled to a path of the drive signal, and the primary winding is configured to induce a first offset current in the leakage control winding to be injected into the path of the drive signal to offset the leakage current of the drive signal. The console also includes a sensor coupled to the path of the drive signal, wherein the sensor is configured to output a sensing signal to provide feedback related to the leakage current.

[0015] In another embodiment, a console for supplying a drive signal to a surgical tool and a method for operating the console are provided. The console includes a transformer including a primary winding and a secondary winding. The primary winding is configured to receive an input signal from a power supply and to induce a drive signal in the secondary winding to supply the drive signal to the surgical tool. The console also includes a first current source, the first current source including a leakage control winding coupled to a path of the drive signal, and the primary winding is configured to induce a first offset current in the leakage control winding to be injected into the path of the drive signal to offset the leakage current of the drive signal. The sensor is configured to sense the characteristics of the input signal and output a sensed signal related to the characteristics of the input signal. The second current source is coupled to the path of the drive signal. A variable gain device is coupled to the sensor and the second current source. The selection interface is coupled to the second current source and the variable gain device, and is configured to enable selection of one of a plurality of leakage current adjustment settings, and the selected leakage current adjustment setting is provided to the variable gain device. The variable gain device is configured to receive a sensed signal and modify the sensed signal based on the selected leakage current adjustment setting. The second current source is configured to generate a second cancellation current based on the modified sense signal from the variable gain device, and inject the second cancellation current into the path of the drive signal to cancel the leakage current of the drive signal.

[0016] In another embodiment, a console for supplying a drive signal to a surgical tool and a method for operating the console are provided. The console includes a variable power supply, a transformer, and a current source. The transformer includes a primary winding and a secondary winding. The primary winding is coupled to the variable power supply and is configured to receive an input signal from the variable power supply and induce a drive signal in the secondary winding to supply the drive signal to the surgical tool. The current source is coupled to a path of the drive signal and is coupled to the variable power supply. The variable power supply is configured to energize the current source. The current source is configured to generate a compensation current to be injected into the path of the drive signal to offset the leakage current of the drive signal.

[0017] These embodiments provide a variety of advantages, including enabling the console to maintain low leakage current without the use of cumbersome additional equipment that reduces the output power of the surgical tool, providing the ability to monitor the leakage current of the drive signal - which can achieve further leakage control and increase the level of fault detection, and / or simplifying the console by using a single power supply to power the drive signal and leakage control source. Other advantages of the console and method described herein and its embodiments will be understood with reference to the description provided herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Advantages of the present invention will become readily appreciated as the following detailed description is considered in conjunction with the accompanying drawings.

[0019] Figure 1 One embodiment of a powered surgical tool system including a surgical table and a surgical tool is depicted.

[0020] Figure 2 is a block diagram of the operation of a feedback loop for measuring and canceling leakage current according to one example.

[0021] Figure 3 is a schematic diagram of two sources for canceling leakage current of a powered surgical tool system according to one example.

[0022] Figure 4 is a schematic diagram of an embodiment of a powered surgical tool system including a console having two leakage current cancellation stages and current-based sensing of leakage current.

[0023] Figure 5 is a schematic diagram of another embodiment of a powered surgical tool system including a console having two leakage current cancellation stages and voltage-based sensing of a drive signal.

[0024] Figure 6 is a schematic diagram of an alternative embodiment to another embodiment of a powered surgical tool system including a console having two leakage current cancellation stages and techniques for adjusting leakage current settings.

[0025] Figure 7 is a schematic diagram of another embodiment of a powered surgical tool system including a console having two leakage current cancellation stages and a fault detection stage for leakage current.

[0026] Figure 8 is a schematic diagram of a circuit included in a fault detection stage according to one embodiment. DETAILED DESCRIPTION

[0027] Overview

[0028] Referring to the drawings, wherein like reference numerals designate like or corresponding parts throughout the several views, a powered surgical tool system 20 is provided having a console 22 configured to supply a drive signal 105 to a surgical tool 28 .

[0029] Reference will now be made to the embodiments shown in the accompanying drawings, and specific language will be used to describe them. By using specific language to describe the exemplary embodiments, it is not intended to limit the scope of the present disclosure. Any changes and further modifications to the inventive features shown herein that would normally occur to a person skilled in the relevant art and possessing the present disclosure, as well as any other application of the principles of the present disclosure shown herein, are considered to be within the scope of the disclosure claimed.

[0030] Reference now Figure 1 An electric surgical tool system 20 is generally described and is referred to as "system 20" hereinafter for simplicity. System 20 includes a surgical tool 28. Surgical tool 28 can be an ultrasonic surgical tool or a tool for applying RF or other types of electrosurgical energy. Surgical tool 28 may include a housing or body 30. Body 30 is the portion of surgical tool 28 that is actually held by a physician. Body 30 forms a proximal end 29 of the surgical tool. The term "proximal" is understood to mean closer to the physician holding the surgical tool and farther from a site 33 to which the surgical tool 28 is applied. A distal end 31 of surgical tool 28 is disposed opposite proximal end 29. The term "distal" is understood to mean farther from the physician and closer to a site 33 to which the surgical tool 28 is applied.

[0031] The console 22 is part of the system 20. The console 22 supplies a drive signal 105 (described below) via a cable 32 to which a surgical tool 28 is connected. In an embodiment where the surgical tool 28 is an ultrasonic surgical tool, it is desirable, but not necessary, to assemble the cable 32 and the surgical tool 28 into a single unit. The console 22 includes components that function as signal generators. These components generate a drive signal 105, such as an AC signal, which is applied to a generator 27 of the surgical tool 28. The generator 27, also referred to as a transducer, converts the AC signal into the type of surgical energy to be applied to the patient. For example, in an ultrasonic surgical tool 28, the generator 27 can be a piezoelectric stack that converts electrical energy into vibrations. Alternatively, in an RF surgical tool 28, since the electrical energy is applied directly to the patient through electrodes, the generator 27 may not be required. Figure 1 The surgical tool 28 shown is configured to apply ultrasonic or RF energy to the patient through the surgical tool tip at the distal end 31. The surgical energy may also be applied to the patient tissue 33 through electrodes or other surgical tools other than those described herein. Regardless of the type of energy applied, the console 22 is designed to minimize the possibility of electrical current leakage into the patient's body.

[0032] The control interface 24 is connected to the console 22. Figure 1 In FIG. 2 , the control interface 24 is a foot pedal. The state of the control interface 24 is monitored by a processor 35 within the console 22. The control interface 24 is a user-actuated control member that regulates activation and / or specific control of the surgical tool 28 through the console 22. Figure 1 , the control interface 24 is shown as part of a foot pedal assembly that includes several pedals. The additional pedals can be used to control devices such as irrigation pumps, suction pumps, or lights. The control interface 24 may include Figure 1 Configurations other than the footrests shown in .

[0033] The console 22 may also include a user interface 26, such as a graphical user interface or switches. Like the control interface 24, the user interface 26 is monitored by a processor 35 within the console 22. The user interface 26 is controlled by the physician to control the operating parameters of the surgical tool 28. In an ultrasonic embodiment, these operating parameters may include the amplitude of the amplitude of the vibration of the surgical tool 28.

[0034] The control interface 24 and the user interface 26 are understood to be general representations of means for inputting commands to the system 20. In some configurations of the system 20, a single control unit may perform both functions. For example, the system 20 may be configured such that when the joystick or foot pedal is initially first depressed, the system 20 subjects the tip of the surgical tool 28 to a relatively small amplitude vibration cycle. As a result of continued depression of the joystick or foot pedal, the console 22 resets the drive signal 105 applied to the surgical tool 28 to subject the tip to a larger amplitude vibration cycle.

[0035] The console 22 may include a display 34. The images on the display 34 may be generated by a processor 35 in conjunction with the console 22. The information depicted on the display 34 includes, but is not limited to, information related to the user interface 26, information identifying the surgical tool 28 and the tip, and any other information describing the operation, settings, or notifications of the system 20. The display 34 may be a touch screen display. In these forms, commands may be input into the processor 35 within the console 22 by pressing the image of a button presented on the display 34. Any suitable interface components may be provided between the display 34 and the processor 35 to facilitate the presentation of images on the display 34 and the input of commands into the processor 35. Additional details regarding processors that may be used with embodiments of the present disclosure are included in PCT Patent Application No. PCT / US2016 / 031651, the contents of which are included in WO2016 / 183084A1 / US Patent Publication No., the contents of which are incorporated herein by reference in their entirety.

[0036] The processor 35 regulates the output of the drive signal 105 from the console 22. The physician-controlled inputs on which the processor 35 sets the drive signal 105 may be based on the state of the control interface 24 and / or the user interface 26. Commands input through the display 34 may also be used to control the setting of the drive signal 105. The characteristics of the drive signal 105 may also be set based on data read from the surgical tool 28 memory. The characteristics of the drive signal 105 are also used by the console 22 as feedback signals to further assist in the setting of the drive signal 105. Based on these multiple inputs, the processor 35 outputs a signal that controls the drive signal 105.

[0037] Reference Figure 4-7 , the console 22 includes or is otherwise coupled to a power supply 82. The power supply 82 is configured to apply an input signal to a primary winding 84 of a transformer 90. The input signal from the power supply 82 is applied to a center tap of the primary winding 84 of the transformer 90. The transformer 90 electrically isolates the patient-side circuit from the power supply 82. The transformer 90 prevents any DC component of the signal in the primary winding 84 from being transmitted to the secondary winding 88, and can be designed with insulation to minimize capacitive coupling, such as Figure 4-7The insulation is shown as core 98.

[0038] Opposite taps of the primary winding 84 are coupled to linear amplifiers 86, respectively. Each amplifier 86 applies an AC signal of varying potential and frequency to a tap of the primary winding 84. The base signal applied to the amplifier 86 as a control signal adjusts the frequency and potential of the signal output by the amplifier 86. In an embodiment where the system 20 includes an ultrasonic surgical tool 28, the AC signal generated on the primary winding 84 may have a frequency between 10 kHz and 100 kHz. The signal may have a peak-to-peak voltage of at least 200 volts or more. For other applications such as RF therapy, the AC signal may have a frequency and voltage range different from that described herein.

[0039] The structure of the power supply 82 and the linear amplifier 86 are not limited to the specific embodiments shown herein, and may include different configurations for generating an AC signal on the primary winding 84. Further understanding of these subcomponents may be found in PCT Patent Application No. PCT / US2016 / 031651, the contents of which are included in WO 2016 / 183084A1 / US Patent Publication No., the contents of which are incorporated herein by reference in their entirety.

[0040] The AC signal generated on the primary winding 84 induces an AC signal on the secondary winding 88 of the transformer 90. This signal on the secondary winding 88 of the transformer 90 is a drive signal 105, which is applied to the generator 27 in the surgical tool 28 through the cable 32. The cable 32 contains a high voltage conductor 100 with a high potential current flowing toward the surgical tool 28 and a low voltage conductor 102 with a low potential current flowing away from the surgical tool 28. The path 104 of the drive signal (also referred to as a "drive path") is defined by these conductors 100, 102. The drive signal 105 is the current flowing through the drive path 104. In an embodiment where the drive signal 105 is used to actuate the ultrasonic driver, the drive signal has a voltage of at least 500VAC and can exceed 1000VAC.

[0041] The drive path 104 is surrounded by a shield 99. The shield 99 prevents parasitic capacitance between the high voltage conductor 100 and ground or any object near the drive path 104. In addition, the shield can be coupled to the low voltage conductor 102 within the surgical tool 28. In embodiments where this connection exists, the shield 99 also serves as a secondary path for return current and protects the patient when the low voltage conductor 102 is disconnected.

[0042] II. Leakage Current Detection and Cancellation Techniques

[0043] According to the techniques described herein, the system 20 can employ leakage cancellation techniques to cancel patient leakage current (also referred to as "leakage current"). Leakage current is generally current that flows through a patient connected to the surgical tool 28. Leakage current can flow from the console 22, to the surgical tool 28, through the patient to ground. Thus, leakage current is generally an unintended current that flows through the patient.

[0044] It will be understood from the examples described herein that the system 20 can employ leakage current cancellation using active control or using a combination of active and passive control. Active control techniques employ elements that are determined based on input or feedback signals. Passive control techniques employ elements that passively provide leakage current cancellation without active determination, such as transformers, resistors, capacitors, inductors, and the like. Active control techniques may include passive elements to supplement active devices. One or more of these active and passive leakage current cancellation systems may be included in the console 22.

[0045] exist Figure 3 In one embodiment shown, an equivalent circuit is provided that illustrates the operation of a first source 68' and a second source 74' for cancelling leakage current. The first source 68' is of a passive type and is described as an AC voltage source. The second source 74' is of an active type and is described as a variable AC voltage source. The first source 68' generates a first cancelling current 80' and the second source 74' generates a second cancelling current 122'. Thus, the first and second sources 68', 74' are current sources because these sources 68', 74' generate cancelling currents 80', 122', respectively, as Figure 3 Sources 68', 74' are referred to herein as current sources.

[0046] The power supply representation 56 (including the power supply 82 and the transformer) generates the drive signal 105 for the surgical tool 28. These sources 68', 74' inject a cancellation current 80', 122' into the drive signal 105 or the path 104 of the drive signal 105.

[0047] In this equivalent schematic, a first current source 68' is connected in series with capacitor 70, and a second current source 74' is connected in series with capacitor 76. Impedance 58 represents the known impedance of surgical tool 28, resistor 66 represents the variable impedance across surgical site 33, and capacitors 60 and 64 represent the capacitance of high-side and low-side voltage conductors 100, 102, respectively. These capacitances can be parasitic, resulting in the generation of leakage current 62'. In this example, leakage current 62' in drive signal 105 is passing through capacitor 60.

[0048] According to the IEC 60601 medical design standard, the leakage current of the powered surgical tool system 20 should be kept at 100 μAmps or less. If the powered surgical tool system 20 is designed to be used on or near cardiac tissue, the maximum leakage current is 10 pAmps.

[0049] In some embodiments, the first current source 68' is designed to cancel a majority (e.g., 50%-90%) of the leakage current 62'. The second current source 74' generates a second cancellation current 122' to cancel at least some of the residual leakage current 62' that remains after the first cancellation current 80' cancels. For example, this residual leakage current 62' can be 1-40% of the total leakage current 62'. In one example, the first current source 68 can be designed to cancel up to ±500pA of patient leakage current while leaving a small amount of residual leakage current, such as ±40pA of patient leakage current. In other examples, the second current source 74' can cancel most of the leakage current 62'.

[0050] In an ideal console 22, leakage current 62' of drive signal 105 will be equal to first cancellation current 80' plus second cancellation current 122'.Alternative embodiments may use a single active or passive current source, any combination of active and / or passive current injection sources, or any plurality of the above.

[0051] It will be appreciated from the embodiments described herein that the second (active) current source 74 may include other components in addition to those components that actually generate the second offset current 122. Such other components may, for example, help determine how or when to generate the second offset current 122. As such, the phrase "second current source" as described herein is not limited to only current generating components.

[0052] Reference now Figure 4-7 , other aspects of the first current source 68 and the second current source 74 are described. The first current source 68 may also be referred to as a matching current source. According to one embodiment, the first current source 68 includes a leakage control winding 92. The leakage control winding 92 may also be referred to as a tuning winding or a sensing winding. The leakage control winding 92 may be integrated with the transformer 90 so that the transformer 90 includes the leakage control winding 92. An example of how to make both the leakage control winding 92 and the capacitor 94 integral with the transformer 90 is described in PCT Application No. PCT / US2017 / 034437, the contents of which are disclosed in PCT Publication No.__, the contents of which are incorporated herein by reference in their entirety. The first current source 68 may also include a capacitor 94.

[0053] The primary winding 84 induces a current in the leakage control winding 92. The induction of this current helps to generate the first cancellation current 80 by the first current source 68. The first cancellation current 80 is injected into the low side voltage conductor 102 of the drive signal path 104. Although Figure 4 A first cancellation current 80 is shown injected into the low side voltage conductor 102, but a cancellation current of opposite polarity may be injected into the high side voltage conductor 100 to cancel the leakage current 62'. In embodiments where the console 22 includes a transformer 90 on which the drive signal 105 is generated, one or all of the components forming the first current source 68 may be constructed as a single unit with the transformer 90.

[0054] Additional details regarding the structure of the transformer 90 and the first current source 68 can be found in PCT Application No. PCT / US2017 / 034437, the contents of which are disclosed in PCT Publication No. __, the contents of which have been previously incorporated herein by reference in their entirety.

[0055] A. Closed-loop leakage current compensation control

[0056] Reference Figure 2 , 4 , 5 and 7, describe embodiments of a second current source 74 used by the console 22 to cancel at least some of the leakage current 62. In one example, the second current source 74 uses a feedback signal to cancel at least some of the leakage current 62, which can be a measure of the current or voltage of the drive signal 105.

[0057] exist Figure 2 The control loop shown is shown to cancel the leakage current 62 by using a feedback signal. One or more sensors 36 measure the characteristics of the drive signal 105 and output a sense signal 110' related to the leakage current 62. The sense signal 110' can be a current, a voltage, or any characteristic that has a known or determinable relationship with the leakage current 62. The target value 114' is set and can be 0 or any other positive or negative value. The target value 114' can be a target signal including a current amplitude or a voltage. The target value 42 can include both AC and DC components. The difference between the sense signal 110' and the target value 114' is determined to generate an error signal 44. In one embodiment, the error signal 44 is calculated by adding the positive target value 114' to the negative value (negative) of the sense signal 110' by the summing stage 40. Many other ways of determining the difference between the sense signal 110' and the target value 114' can replace the summing process.

[0058] The error signal 44 is multiplied by the gain device 46. The gain device 46 can increase, decrease or allow the error signal 44 to remain the same. The gain device 46 can be a circuit, software or a combination of both. The gain device 46 outputs a cancellation current 122' that is injected into the drive signal 105' to cancel the leakage current 62. The human body model 50 representing the surgical tool 28 being applied to the patient is powered by the drive signal 105, which includes the cancellation current 122'. The transfer function of the control loop can be expressed as: TF=G / (1+S*G). Where G represents the gain 46 and S represents the sensed signal 110'. Figure 2 The principle shown in Figure 4 , 5 and 7 are implemented in the embodiment of the surgical system 20 shown.

[0059] exist Figure 4-7 Components of the surgical system 20 associated with reducing or eliminating leakage current 62 are depicted in FIG. Figure 4 , 5 7 and 8 depict embodiments having passive (first) and active (second) leakage current cancellation sources 68, 74, respectively.

[0060] The second current source 74 receives two inputs, namely the sensed signal 110 and the target value 114. In one embodiment, Figure 4 As shown in , a transformer 106 is used to sense the residual leakage current 62 in the drive signal 105 and generate a sense signal 110. The transformer 106 includes a drive path 104 as a primary winding. In other words, the primary winding of the transformer 106 includes a high-side voltage conductor 100 and a low-side voltage conductor 102. The transformer 106 has a secondary winding that implements a sensor 108.

[0061] The sensor 108 senses the common mode current in the drive path 104 and outputs a sense signal 110 indicating the common mode current to the second current source 74. The common mode current provides some indication or relationship with the leakage current 62. Mainly, the high side voltage conductor 100 conducts current to the surgical device, while the low side voltage conductor 102 conducts current away from the surgical tool 28. Ideally, these currents 100 and 102 are equal in magnitude and opposite in polarity. When there is a leakage current 62, the magnitude of the current on the high side voltage conductor 100 will be different from the magnitude of the current on the low side voltage conductor 102. This current difference is the common mode current. The common mode current is a measure of the current flowing in a single direction. When there is a common mode current on the drive path 104, it generates a magnetic field that is sensed by the secondary winding, i.e., the sensor 108. In this embodiment, the common mode current is directly related to the leakage current 62 of the drive signal 105 because the common mode current only exists when a certain amount of current is lost between the high side voltage conductor 100 and the low side voltage conductor 102. If the leakage current 62 is not present, the high side voltage conductor 100 has a current that is equal and opposite to the current on the low side voltage conductor 102. In this case, the common mode current and the leakage current 62 in the electric surgical tool system are both zero or substantially zero.

[0062] exist Figure 5 , sensor 108 is replaced by sensor 126, which is shown as a capacitor. Sensor 126 senses the voltage on the low-side voltage conductor 102 of drive path 104. When there is no leakage current 62, the voltage on the low-side conductor will be 0 volts or approximately 0 volts relative to power supply 82.

[0063] In embodiments where the shield 99 is also electrically connected to the low voltage conductor 102 in the surgical tool 28 , the common mode current is the difference between the current in the high voltage conductor 100 and the current in the low voltage conductor 102 plus the shield 99 .

[0064] exist Figure 4 , 5 In Figures 1 and 7, the leakage current 62 is shown as a small current opposite to that portion of the drive signal 105 on the low voltage conductor 102 to represent the current that has escaped from the drive signal 105 and passed to the ground through another path. This leakage current 62 is the result of current that may be lost in a variety of ways and locations throughout the system, including capacitive coupling between components of the system 20 and / or current leakage through the patient. The leakage current 62 can be shown anywhere that unintended current flow occurs. In some cases, the first offset current 80 and the second offset current 122 can cause the leakage current 62 to flow in the opposite direction to the direction of the leakage current 62 shown in the figure.

[0065] The sensed signal 110 may be modified by one or more gain devices, such as Figure 4 ,5 7 and 7 are depicted as amplifier 112. The sense signal 110 is input to the second current source 74 to determine the second cancellation current 122.

[0066] The second input to the second current source 74 is the target value 114. Figure 4 , 5 The sense signal 110 and the target value 114 are fed into a summing amplifier 118 having an amplifier 120 to output a second cancellation current 122. Figure 4 and 7 In FIG. 1 , the target value 114 is a target current for comparison with the sense signal 110, which is used to determine the second offset current 122. In this example, the target current may be, for example, 0 amperes, representing an ideal situation where leakage current is eliminated. Figure 5 In the present invention, target value 114 is a target voltage, which may be set to 0 volts, for example, and also represents an ideal situation where leakage current is eliminated. Other target values ​​114 other than those described herein are also contemplated and may be utilized.

[0067] like Figure 4 , 5 7, a power source drives a second current source 74. In the example shown, this is the same power source 82 that powers the transformer 90. Other aspects of the power source 82 related to the second current source 74 are described below. Alternatively, the power source that powers the second current source 74 may be different from the power source 82. The target value 114 may have a certain amount of DC offset because the DC power source 82 is used to power the second cancellation current 122. The target value 114 may be modified by a gain device 116 and then used as an input to a summing amplifier 118 having an additional amplifier stage 120. The summing amplifier 118 having the amplifier stage 120 determines the difference between the target value 114 and the sense signal 110. The summing amplifier 118 having the amplifier stage 120 then outputs the second cancellation current 122.

[0068] Before injecting the second cancellation current into the drive path 104, a capacitor 124 may be used to block any DC component of the second cancellation current 122 from entering the drive path 104. In some embodiments, the capacitor 124 uses a low capacitance.

[0069] This second cancellation current 122 cancels at least some of the residual leakage current 62 that remains when the first leakage current cancellation 80 is injected. Regardless of the type of sensor 106, 126 used, the second cancellation current 122 will change the magnitude of the current on the low-side voltage conductor 102 to more closely match the magnitude of the current on the high-side voltage conductor 100 and bring the voltage relative to the power supply 82 closer to 0 volts.

[0070] exist Figure 4 , 5 Unpublished equivalents of the active current leakage cancellation techniques shown in and 7 are fully contemplated. Figure 4 , 5 The schematics shown in FIG. 7 may include other or different components than those specifically shown in the figures, but still produce appropriate cancellation currents (as expected).

[0071] B. Open loop control current offset control

[0072] Figure 6 Another embodiment of a second current source 74 for generating a second current cancellation current 122 is shown. In this embodiment, a measurement from the drive signal 105 is not utilized. Instead, a sensor 130 is included to measure the AC signal generated by the transformer 90. In one example, the AC signal is the voltage of the surgical tool 28 handpiece. The sensor 130 can be part of the transformer 90 or in addition to it. Figure 6 In the embodiment of FIG. 1 , the sensor 130 is a transformer winding.

[0073] Sensor 130 measures the AC signal generated across transformer 90 and sends the sensed signal to gain stage 132, which is configured to scale the AC signal from sensor 130. Variable gain device 132 may be part of second current source 74, or may be separate therefrom.

[0074] The selection interface 134 is coupled to the second current source 74 and the gain stage 132. The selection interface 134 is configured to enable selection of one of a plurality of leakage current adjustment settings. The leakage current adjustment settings provide a user-selectable fine-tuning offset of the leakage current 62. The leakage current adjustment settings may be stored in a lookup table in the console 22 memory.

[0075] exist Figure 6 In the example shown, the selection interface 134 is a potentiometer, which may be an adjustable circuit or a digital potentiometer controlled by software. The selection interface 134 may also be implemented by a user interface on the display 34 of the console 22. Other types of selection interfaces that enable selection of leakage current adjustment settings are contemplated.

[0076] Selection interface 134 enables easier adjustment of positive or negative leakage current. Adjustments may be made to enable console 22 to meet IEC 60601 or any other or different standard for leakage current.

[0077] The selection interface 134 is coupled to the sensor 130 through the first gain stage. The selection interface 134 receives a scaled version of the AC signal from the first gain stage 132. The selection interface 134 is coupled to a variable gain amplifier 138, which can adjust the gain from -1 to +1 based on the adjustment setting of the selection interface 134. In the case where the selection interface 134 is a potentiometer, the variable gain amplifier 138 includes an output 136 that interfaces with the potentiometer to variably operate the potentiometer.

[0078] In one embodiment, the selector interface 134 is adjusted as part of the manufacturing process. This allows for greater manufacturing tolerances and ensures that each console 22 meets the requirements for minimizing leakage current.

[0079] The output of amplifier 138 is then fed to power amplifier 140, which uses a power supply, such as power supply 82 that powers drive signal 105. In an alternative, a separate power supply may be used for second current source 74. Amplifier 140 outputs second cancellation current 122 into drive signal path 104. Second cancellation current 122 is DC blocked by capacitor 124 before being injected into drive signal path 104.

[0080] As discussed in the previous section on Figure 4 , 5 and 7 are the same as the embodiments described, in Figure 6 The second cancellation current 122 generated in the embodiment of can be used in combination with the first cancellation current 80 generated by the first current source 68 to provide fine tuning of the cancellation of the leakage current 62.

[0081] exist Figure 6 Unpublished equivalents of the active current leakage cancellation technique shown in are fully contemplated. Figure 6 The schematics shown in FIG. 1 may include additional or different components than those specifically shown in the figures, while still producing appropriate cancellation currents (as expected).

[0082] C. Variable power supply for the second current source

[0083] For the purposes described herein and Figure 4-7In any of the embodiments shown in the drawings, the power supply 82 coupled to the primary winding 84 of the transformer 90 can be a variable power supply. According to one example, the power supply 82 has a variable output DC voltage level that can be set. In one embodiment, the voltage is between 25 and 250 VDC. Other types of power supplies with or without variable voltage levels can also be used. The voltage of the signal from the power supply 82 is set based on a power control signal applied to the power supply 82. The power supply 82 can apply a DC input signal to the center tap of the primary winding 84 of the transformer 90. The DC input signal from the power supply 82 can have a varying potential. Specifically, the potential of the input signal can be set to vary as a function of the potential of the drive signal 105 to be applied to the generator 27 of the surgical tool 28.

[0084] The variable power supply 82 may be used to power, drive, or otherwise provide input to any second current source 74 shown in all figures. The second current source 74 may be coupled to the path of the drive signal 104 and to the variable power supply 82. The variable power supply 82 is configured to power the current source 74, and the current source 74 (powered by the variable power supply 82) is configured to generate a cancellation current 122 to be injected into the path 104 of the drive signal to cancel the leakage current of the drive signal.

[0085] Specifically, the DC input signal from the power supply 82 applied to the primary winding 84 may also be used as an input to one or more of the amplifiers 120 or 140 of the second current source 74, such as Figure 4 , 5 and 7. Specifically, the DC input signal can be used as a positive voltage to facilitate amplification of the signal generated by the second current source 74 to ensure that the signal is at the correct voltage. In these forms, the DC signal can also be applied as an input signal to the second current source 74, such as Figure 4 , 5 7, the power supply 82 feeds it into the stage that produces the target value 114. The second current source 74 includes a feedback subcircuit that adjusts the target value 114 from the variable power supply 82 so that the signal does not drift due to changes in the DC positive voltage applied to the one or more amplifiers. Figure 6 In the illustrated embodiment, the second current source 74 is powered by a variable power supply 82 that is connected to the amplifier 140 .

[0086] The variable power supply 82 drives the second cancellation current 122. In one embodiment, this is the same power supply 82 that powers the drive path 104 of the surgical tool 28. Using the same power supply 82 provides a benefit because the power required to drive the second cancellation current 122 varies in proportion to the power of the drive signal 105. Alternatively, a separate power supply may be used to drive the second leakage current source 74.

[0087] While it is advantageous to reuse the variable power supply 82 to power the leakage current cancellation source, embodiments may include a separate power supply to generate the second cancellation current 122 .

[0088] The variable power supply 82 may have configurations and capabilities other than those shown in the figures and described herein. In addition, the variable power supply 82 may be coupled to components of the console 22 other than those shown in the figures.

[0089] D. Leakage Current Fault Detection Technology

[0090] Figure 7 Shown with Figure 4 The same components are supplemented with a fault detection stage 144 which may be implemented by circuitry and / or software.

[0091] Fault detection stage 144 is coupled to sensor 106 or alternatively to Figure 5 The fault detection stage 144 is configured to receive the sensed signals 110 from the sensors 106 , 126 and generate a fault detection signal 158 to detect a fault condition associated with the leakage current 62 .

[0092] If the sense signal 110 indicates that the level of the leakage current 62 exceeds a specified threshold, it may be due to a fault in the system 20, such as a short circuit or a patient connection to ground. When the leakage current 62 is too large, the fault detection stage 144 triggers a fault detection signal 158 on the GPIO (general purpose input / output) line.

[0093] The controller 160 is coupled to the fault detection stage 144, for example on a GPIO line, and is configured to receive the fault detection signal 158 from the fault detection stage 144 and determine a fault condition related to the leakage current 62. The controller 160 may have one or more microprocessors for processing instructions or for processing algorithms stored in a memory to control the operation of the console 22. Additionally or alternatively, the controller 160 may include one or more microcontrollers, field programmable gate arrays, systems on a chip, discrete circuits, and / or other suitable hardware, software, or firmware capable of performing the functions described herein. The fault detection stage 144 and the controller 160 may be combined or separate elements.

[0094] The fault detection stage 144 is configured to sense the presence of the fault detection signal 158 for a predetermined period of time and, when the predetermined period of time is reached, send the fault detection signal 158 to the controller 160. The fault detection stage 144 may do this to ensure that permanent faults are detected and to avoid false alarms based on negligible or intermittent signal spikes.

[0095] The controller 160 receives the fault detection signal 158 from the GPIO line and is configured to compare the fault detection signal 158 with a target value to determine a fault condition. In response to determining a fault condition, the controller 160 may reduce or terminate power to the surgical tool 28. The controller 160 may trigger other responses to the console 22 or the surgical tool 28 other than those described herein.

[0096] Figure 8 An embodiment of a fault detection stage 144 is shown. In some embodiments, the fault detection stage 144 becomes active only when the sensed common-mode current or low-side voltage exceeds a specified level. The sense signal 110 can be modified by an amplifier 112. The amplifier 112 can be the same as the first gain stage used to generate the second offset current 122, or it can be a separate gain device. The sense signal 110 is then fed to a low-pass filter 146 and a rectifier 148. The low-pass filter 146 removes high-frequency signals that exceed a specified threshold. If the low-pass filter 146 is relatively close to the filter frequency, it can also attenuate the signal. The gain device depicted as an amplifier 148 can be used to change the amplitude of the sense signal 110 in response to any attenuation. During a fault condition, the sense signal 110 pulsates in each drive cycle (e.g., when the drive signal 105 is at maximum amplitude, the common-mode current sensed by the sensor 108 will be maximum, and when the drive signal 105 is minimum, the common-mode current will be close to 0). A filter including capacitor 150 and resistor 152 is put in place to keep the fault condition at a maximum level between pulses. The RC time constant of the filter is the capacitance of capacitor 150 multiplied by the resistance of resistor 152. The fault signal is then output to inverter 154, which inverts the applied signal to output a fault signal 158 to controller 160. Controller 160 monitors the signal, and when the fault condition exists for a specific period of time, controller 160 can take appropriate action on the system as needed. The actions taken by controller 160 include alerting the operator of surgical tool 28 via display 34, reducing the power output by power supply 82, and / or cutting off power to surgical tool 28.

[0097] The fault detection stage 144, controller 160, and components thereof may be different than described herein, but still implement the capabilities for detecting leakage current faults as described herein.

[0098] Several embodiments have been described in the foregoing description. However, the embodiments discussed herein are not intended to be exhaustive or to limit the invention to any particular form. The terms used are intended to be descriptive, rather than restrictive, in nature. In view of the above teachings, many modifications and variations are possible, and the invention may be practiced in a manner different from that specifically described.

[0099] From the above detailed description, many features and advantages of the present invention are apparent, therefore, the appended claims are intended to cover all such features and advantages of the present invention that fall within the true spirit and scope of the present invention. In addition, since many modifications and variations will readily occur to those skilled in the art, it is not desirable to limit the present invention to the exact construction and operation illustrated and described, therefore, all suitable modifications and equivalent forms that fall within the scope of the present invention may be resorted to.

Claims

1. A console for supplying a driving signal to a surgical tool, the console comprising: a transformer including a primary winding and a secondary winding, the primary winding being configured to receive an input signal from a power source and induce a drive signal in the secondary winding to supply the drive signal to the surgical tool; a first current source including a leakage control winding coupled to the path of the drive signal, the primary winding being configured to induce a first offset current in the leakage control winding to be injected into the path of the drive signal to offset the leakage current of the drive signal; as well as A sensor is coupled to the path of the drive signal, wherein the sensor is configured to output a sense signal to provide feedback related to the leakage current.

2. The console according to claim 1, wherein: The transformer and the first current source are integrated into a single package.

3. The console according to any one of claims 1 to 2, wherein: The first current source also includes a capacitor coupled in series with the leakage control winding.

4. The console according to any one of claims 1 to 3, wherein: The primary winding, the leakage control winding, and the secondary winding are configured to jointly generate a capacitance between the leakage control winding and the secondary winding.

5. The console according to any one of claims 1 to 4, wherein: The drive signal is configured to drive an ultrasonic surgical tool.

6. The console according to any one of claims 1 to 5, further comprising a second current source configured to cancel a leakage current, and the second current source is coupled to a path of the drive signal and the sensor.

7. The console according to claim 6, wherein: The second current source is powered by the power supply.

8. The console according to any one of claims 1 to 7, wherein: The sensor is configured to sense a common mode current of the drive signal and output the common mode current of the drive signal as a sense signal, wherein the common mode current is related to a leakage current of the drive signal.

9. The console according to claim 7, wherein: The path of the drive signal includes a high voltage conductor and a low voltage conductor, and the sensor is further defined as a transformer winding arranged around both the high voltage conductor and the low voltage conductor, wherein the transformer winding is configured to output a common mode current of the drive signal.

10. The console of any one of claims 1-9, further comprising a fault detection stage coupled to the sensor and configured to receive the sense signal to generate a fault detection signal for detecting a fault condition related to leakage current.

11. The console according to claim 10, wherein: The fault detection stage includes a low pass filter, a rectifier and a filter configured to transform the sense signal to generate the fault detection signal.

12. The console of claim 10, further comprising a controller coupled to the fault detection stage and configured to receive the fault detection signal from the fault detection stage and to determine a fault condition related to leakage current.

13. The console according to any one of claims 10 to 12, wherein: The fault detection stage is configured to sense the presence of the fault detection signal within a predetermined time period and send the fault detection signal to a controller when the predetermined time period is reached.

14. The console according to any one of claims 10 to 13, wherein: The controller is configured to compare the fault detection signal to a target value to determine a fault condition and to reduce or terminate power to the surgical tool in response to determination of a fault condition.

15. A console for supplying a driving signal to a surgical tool, the console comprising: Variable power supply; a transformer including a primary winding and a secondary winding, the primary winding being coupled to a variable power supply and configured to receive an input signal from the variable power supply and to induce a drive signal in the secondary winding to supply the drive signal to a surgical tool; and A current source is coupled to the path of the drive signal and to a variable power supply, wherein the variable power supply is configured to supply power to the current source, and wherein the current source is configured to generate a compensation current to be injected into the path of the drive signal to compensate for the leakage current of the drive signal.

16. The console of claim 15, further comprising a sensor coupled to a path of the drive signal, wherein: The sensor is configured to output a sense signal to provide feedback related to the leakage current.

17. The console of claim 16, wherein: The current source is coupled to the sensor.

18. The console of claim 17, wherein: The current source includes a gain device coupled to the sensor, wherein the gain device is configured to receive the sense signal and a target value as inputs and determine a difference between the sense signal and the target value, and determine a compensation current based on the difference.

19. The console according to any one of claims 15 to 18, further comprising: a sensor configured to sense a characteristic of the input signal and output a sensing signal related to the characteristic of the input signal; a variable gain device coupled to the sensor and the current source; a selection interface coupled to the current source and the variable gain device and configured to enable selection of one of a plurality of leakage current adjustment settings and to provide the selected leakage current adjustment setting to the variable gain device; wherein the variable gain device is configured to receive the sense signal and modify the sense signal based on the selected leakage current adjustment setting; and Wherein the current source is configured to generate a cancellation current based on a modified sense signal from a variable gain device.

20. A console according to any one of claims 15 to 19, wherein: The variable power supply is variable within a range defined from 25 VDC to 250 VDC.

21. The console of claim 18, wherein: The variable power supply energizes a source for the target value, and the variable power supply is configured to provide a DC offset to the target value in addition to the AC value.

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