Detection of asymmetries in bidirectional semiconductor devices

Abstract

To provide a system for testing symmetry of a bidirectional semiconductor device in a circuit.SOLUTION: A system includes a signal generator, configured to pass a generated signal, which has two different generated frequencies, through a circuit including a bidirectional semiconductor device. The system further includes a processor, configured to identify, while the generated signal is passed through the circuit, a derived frequency, which is derived from the generated frequencies, on the circuit, and to generate, in response to identifying the derived frequency, output indicating that a property of the bidirectional semiconductor device is asymmetric. Other embodiments are also described.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application is related to another application entitled "TESTING ELECTRODE QUALITY" (Attorney Docket No. 1002-2170.1|ID-1790.1|BIO6343USNP2), filed on even date herewith, the disclosure of which is incorporated herein by reference.

[0002] FIELD OF THE INVENTION The present invention relates to the field of electronic circuits, especially for medical applications. [Background technology]

[0003] In many applications, symmetrical bidirectional semiconductor devices control the flow of electrical current through a circuit.

[0004] Patent Document 1 describes a measuring device and a measuring method having an impedance measuring function, and an electronic device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-066000 A Summary of the Invention [Means for solving the problem]

[0006] According to some embodiments of the present invention, there is provided a system including a signal generator configured to pass a generated signal having two different generated frequencies through a circuit including a bidirectional semiconductor device, the system further including a processor configured to identify a derived frequency derived from the generated frequency on the circuit while the generated signal is passing through the circuit, the processor further configured to generate an output in response to identifying the derived frequency indicative of an asymmetric characteristic of the bidirectional semiconductor device.

[0007] In some embodiments, the processor is configured to identify frequencies derived via electrophysiological channels that belong to the circuit.

[0008] In some embodiments, the derived frequency is within the bandwidth of the electrophysiological signal carried across the electrophysiological channel.

[0009] In some embodiments, each of the generated frequencies is outside the bandwidth.

[0010] In some embodiments, the characteristic includes impedance.

[0011] In some embodiments, the derived frequency is the difference between the generated frequencies.

[0012] In some embodiments, the processor is further configured to disable a power source connected to the circuit in response to detecting the derived frequency.

[0013] In some embodiments, the power source is selected from the group of power sources consisting of a cardiac defibrillator, a cardiac pacer, and an ablation generator.

[0014] In some embodiments, the bidirectional semiconductor device belongs to a voltage suppression device.

[0015] In some embodiments, the bidirectional semiconductor device belongs to a semiconductor switch.

[0016] According to some embodiments of the present invention, there is further provided a method including passing generated signals having two different generated frequencies through a circuit including a bidirectional semiconductor device, the method further including identifying a derived frequency derived from the generated frequencies on the circuit while passing the two generated signals through the circuit, and generating an output in response to identifying the derived frequency that indicates an asymmetric characteristic of the bidirectional semiconductor device.

[0017] According to some embodiments of the present invention, there is further provided a system including a signal generator configured to pass a generated signal having two different generated frequencies through a circuit including an intrabody electrode, the system further including a processor configured to identify a derived frequency derived from the generated frequency on the circuit while the generated signal is passing through the circuit, the processor further configured to generate an output indicative of a defect in the electrode in response to identifying the derived frequency.

[0018] In some embodiments, the derived frequency is the difference between the generated frequencies.

[0019] In some embodiments, each of the generated frequencies is less than 100 Hz.

[0020] In some embodiments, the amplitude of the generated signal is less than 50 μA.

[0021] In some embodiments, the signal generator is configured to pass the generated signal through the circuit while the electrodes are immersed in the electrolyte.

[0022] In some embodiments, the electrolyte comprises saline.

[0023] In some embodiments, the electrodes belong to an intracellular probe.

[0024] In some embodiments, the system further comprises a kit, the kit comprising: a signal generator; and and an electrical interface configured to connect the kit to the probe, thereby connecting the electrodes to the signal generator.

[0025] In some embodiments, the kit further includes a communications interface, and the processor is configured to identify the derived frequency by processing an output signal received from the kit via the communications interface.

[0026] In some embodiments, the electrode is one of a plurality of electrodes belonging to a probe, and the kit further comprises a multiplexer configured to selectively connect the electrode to the signal generator.

[0027] According to some embodiments of the present invention, there is further provided a method including passing generated signals having two different generated frequencies through a circuit including an intrabody electrode, the method further including identifying a derived frequency derived from the generated frequency on the circuit while passing the generated signals through the circuit, and generating an output indicative of a defect in the electrode in response to detecting the derived frequency. [Brief explanation of the drawings]

[0028] The invention is more fully understood from the following detailed description taken in conjunction with the drawings, in which: [Figure 1] 1 is a schematic, illustrative illustration of an electrophysiology system, according to some exemplary embodiments of the present invention; [Figure 2] 1 is a schematic, illustrative diagram of a circuit, according to some exemplary embodiments of the present invention; [Figure 3] 1 is a schematic, illustrative diagram of a system for testing electrode quality, according to some exemplary embodiments of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0029] Glossary In the context of this application, including the claims, the term "bidirectional semiconductor device" may refer to any semiconductor device configured to conduct both the positive and negative portions of an alternating current (AC) signal. If the characteristics (e.g., impedance) of a bidirectional semiconductor device are the same for both portions of the signal, the characteristics (or the device itself) are said to be "symmetrical," and if not, the characteristics (or the device itself) are said to be "asymmetrical."

[0030] Overview In many cases, it is desirable for bidirectional semiconductor devices in a circuit to have symmetrical characteristics so that alternating current (AC) passing through the device does not generate any direct current (DC) voltage. For circuits connected to intracorporeal probes, such as electrophysiological probes disposed within a subject's body, this symmetry is particularly important because any DC voltage generated from, for example, ablation radiofrequency (RF) current flowing through the bidirectional semiconductor device is likely to be dangerous to the subject. Therefore, there is a need for fast and efficient detection of any asymmetry in bidirectional semiconductor devices.

[0031] To address this need, an exemplary embodiment of the present invention provides a system for testing the symmetry of a bidirectional semiconductor device in a circuit. The system includes a signal generator connected to the circuit and configured to generate signals having two different frequencies. If the bidirectional semiconductor device is symmetric, the bidirectional semiconductor device behaves as a linear device and therefore does not generate any additional frequencies. However, if the bidirectional semiconductor device is asymmetric (e.g., by having asymmetric impedance), the device behaves nonlinearly and therefore causes other "derived" frequencies to be carried on the circuit that are derived from the frequency of the generated signal. Therefore, asymmetry can be detected by identifying one of these derived frequencies, such as the difference between the frequencies of the generated signals.

[0032] Advantageously, in electrophysiological applications, the symmetry tests described herein can be detected via existing electrophysiological channels so that no additional hardware is required. To facilitate this, the frequencies of the generated signals can be selected so that the difference between the frequencies falls within the bandwidth of the electrophysiological signals carried across the channel. Nevertheless, the frequencies themselves can be selected to fall outside this bandwidth so that the generated signals do not interfere with the detection of the electrophysiological signals.

[0033] An exemplary embodiment of the present invention further provides a test kit for testing electrode quality while the electrode is immersed in an electrolyte. The kit, which includes the aforementioned signal generator, is connected to the electrode so that the generated signal flows through the electrode. In the case of defects in the surface of the electrode (e.g., if the surface is rough or dirty), the nonlinearity of the interface between the electrode and the electrolyte increases, and as a result, the amplitude at which the derived frequencies are generated also increases. Therefore, by identifying one of the derived frequencies, the defect can be detected.

[0034] It is emphasized that although this specification relates primarily to electrophysiological applications, embodiments of the present invention may be used to test the symmetry of any bidirectional semiconductor device and to test any electrode quality.

[0035] System Description Reference is first made to FIG. 1, which is a schematic, illustrative illustration of an electrophysiology system 20, in accordance with some exemplary embodiments of the present invention.

[0036] System 20 includes an intracorporeal probe 26 having one or more intracorporeal electrodes 28 disposed at a distal end of intracorporeal probe 26. Using probe 26 and electrodes 28, physician 30 can acquire electrophysiological signals from subject 22, such as electrogram signals from heart 24 of subject 22. Alternatively or additionally, physician 30 can use probe 26 and electrodes 28 to pace or defibrillate heart 24 or to ablate tissue in heart 24.

[0037] Probe 26 is proximally connected to circuitry 34, which is typically housed within console 32. System 20 typically also includes a processor 38 and a monitor 36. In response to output from circuitry 34, processor 38 may display associated output on monitor 36, as further described below with reference to FIG.

[0038] In general, processor 38 may be embodied as a single processor or as a set of cooperatively networked or clustered processors. In some exemplary embodiments, the functionality of processor 38 described herein is implemented solely in hardware, e.g., using one or more application-specific integrated circuits (ASICs) or field-programmable gate arrays (FPGAs). In other exemplary embodiments, the functionality of processor 38 is implemented at least partially in software. For example, in some exemplary embodiments, processor 38 is embodied as a programmed digital computing device comprising at least a central processing unit (CPU) and random-access memory (RAM). Program code and / or data, including software programs, are loaded into the RAM for execution and processing by the CPU. The program code and / or data may be downloaded to the processor in electronic form, e.g., over a network. Alternatively or additionally, the program code and / or data may be provided and / or stored on a non-transitory tangible medium, such as magnetic, optical, or electronic memory. Such program code and / or data, when provided to a processor, results in a machine or special purpose computer configured to perform the tasks described herein.

[0039] Reference is now made to FIG. 2, which is a schematic, illustrative diagram of circuitry 34 shown in FIG. 1, in accordance with some exemplary embodiments of the present invention.

[0040] Circuitry 34 includes at least one digitizer 40 configured to digitize electrophysiological signals from electrodes 28 and output digitized signals 66 to processor 38 (FIG. 1) via a wired or wireless connection. Digitizer 40 may include any suitable filter for filtering the signals before digitization.

[0041] Typically, circuitry 34 further includes at least one power source configured to provide power to the electrodes. For example, circuitry 34 may include a cardiac pacer 42, a cardiac defibrillator, and / or an ablation generator. Typically, circuitry further includes at least one voltage suppression device 48 that suppresses the voltage provided by the power source.

[0042] In exemplary embodiments in which the probe includes multiple electrodes, the circuitry typically includes a different respective electrophysiology channel for each electrode. Each channel typically includes a separate digitizer 40 and voltage suppression device 48 connected in parallel with each other and to the electrode via a resistor 64. The circuitry 34 may further include a multiplexer 52 including a plurality of semiconductor switches 46 and a multiplexer controller 44. The multiplexer controller 44 is configured to control the switches 46 to selectively connect the channels to a power source.

[0043] In general, a circuit may include any number of electrodes, and therefore any number of channels. By way of example, Figure 2 shows an embodiment in which the probe includes two electrodes, designated in the figure as "Electrode 1" and "Electrode 2," and the circuit 34 correspondingly includes two channels, designated in the figure as "Channel 1" and "Channel 2."

[0044] The circuit 34 comprises at least one bidirectional semiconductor device.

[0045] For example, each switch 46 may comprise a bidirectional semiconductor device. As a particular example, each switch 46 may comprise a light-emitting diode (LED) 58 along with a pair of phototransistors 54 connected to each other and to a pair of parasitic diodes 56. In response to a control signal from the multiplexer controller 44, the LED 58 may emit light toward the phototransistor 54, causing the phototransistor to become conductive. Current (e.g., from the pacer 42) may then flow through the switch.

[0046] Alternatively or additionally, each voltage suppression device 48 may comprise a bidirectional semiconductor device. For example, each voltage suppression device 48 may comprise a pair of diodes 60 or thyristors connected in series or parallel with each other in opposing orientations. The diodes 60 may include, for example, avalanche diodes or Zener diodes.

[0047] Advantageously, circuit 34 is configured to test the symmetry of any of the bidirectional semiconductor devices belonging to the circuit. To facilitate this testing, the circuit includes at least one signal generator 50 configured to generate a signal having a first frequency f1 and a second frequency f2. Typically, the amplitude of the generated signal is relatively low, such as less than 10 μA, so as not to pose a risk to the subject. If the impedance or another characteristic (e.g., cutoff voltage) of one of the bidirectional semiconductor devices is asymmetric, the device will behave nonlinearly and thus generate other frequencies derived from f1 and f2, such as a frequency that is a linear combination of f1 and f2. The processor may detect the asymmetry by identifying one of these other frequencies in digitized signal 66, such as the beating frequency |f1-f2|, f1+f2, 2f1+f2, or |2f1-f2|.

[0048] In some exemplary embodiments, signal generator 50 comprises a voltage source. In such exemplary embodiments, as shown in FIG. 2, the signal generator may be modeled as a first voltage source 50a configured to generate a first signal having a first frequency f1 and a second voltage source 50b configured to generate a second signal having a second frequency f2, each of the voltage sources connected in series with a respective resistor 62. In other exemplary embodiments, signal generator 50 comprises a current source.

[0049] In some exemplary embodiments, circuitry 34 includes a different respective signal generator for each channel, while in other exemplary embodiments a single signal generator is connected to all of the channels via a multiplexer.

[0050] Typically, f1 and f2 are outside the bandwidth of (i.e., outside the range of frequencies exhibited by) the electrophysiological signal carried across the channel so that the generated signals do not interfere with the processing of the electrophysiological signal. For example, in applications in which an electrogram signal is carried across the channel, each of the generated frequencies may be greater than 500 Hz, such as greater than 1000 Hz. Nevertheless, at least one derived frequency, such as the difference between f1 and f2, typically lies within the aforementioned bandwidth, such that the sampling rate of the digitizer, which generally corresponds to the highest frequency within the bandwidth, is sufficient to capture the derived frequency. For example, in electrogram applications, the derived frequency may be less than 500 Hz, such as 400-500 Hz. Thus, the derived frequency may advantageously be identified in signal 66, i.e., the regular digitized electrophysiological signal received from digitizer 40.

[0051] In response to identifying the derived frequency (e.g., in response to identifying a component of signal 66 having the derived frequency and an amplitude above a predetermined threshold), the processor may generate an output indicating that the impedance of the bidirectional semiconductor device is asymmetric, for example, by displaying a suitable warning on monitor 36 (FIG. 1). Alternatively or additionally, in response to identifying the derived frequency, the processor may disable the power supply.

[0052] Electrode quality testing Reference is now made to FIG. 3, which is a schematic, illustrative illustration of a system 67 for testing the quality of electrodes 28 prior to use of probe 26, according to some exemplary embodiments of the present invention.

[0053] The system 67 includes a signal generator 50, as described above with respect to FIG. 2, which may be modeled as a first voltage source 50a configured to generate a first signal having a first frequency f1 and a second voltage source 50b configured to generate a second signal having a second frequency f2, each connected in series with a respective resistor 62 and a digitizer 40 configured to communicate with a processor 82 via a wired or wireless connection. To test each electrode, a signal generated from the signal generator passes through a circuit including the electrode. While the generated signal passes through the circuit, the processor 82 monitors the circuit for a derived frequency, such as |f1-f2|, by processing the digitized signal 66 as described above with reference to FIG. 2. In response to identifying the derived frequency (e.g., in response to identifying a component of the signal 66 having the derived frequency and an amplitude above a predetermined threshold), the processor 82 generates an output indicative of a defect in the electrode.

[0054] Typically, the signal generator and digitizer reside in a test kit 76 configured to connect to the probe 26, e.g., at its proximal end. Typically, the test kit 76 also includes a multiplexer 52 (which may comprise any type of switch) and a multiplexer controller 44. Each switch in the multiplexer 52 is configured to connect to a different respective electrode at the distal end of the probe 26 via a different respective wire. The wires may be contained in a cable 86 that may be connected to the probe 26 via a suitable interface in the handle 74 of the probe 26. In response to control signals 80 from the processor 82, the multiplexer controller 44 controls the multiplexer 52 such that the multiplexer selectively connects the electrodes for testing to the signal generator.

[0055] In general, processor 82 may be embodied as a single processor or as a set of cooperatively networked or clustered processors. In some exemplary embodiments, the functions of processor 82 described herein are implemented solely in hardware, for example, using one or more application-specific integrated circuits (ASICs) or field-programmable gate arrays (FPGAs). In other exemplary embodiments, the functions of processor 82 are implemented at least partially in software, as described above with respect to processor 38 (FIG. 1). Processor 82 may reside in test kit 76 or, as alluded to in FIG. 3, may reside in an external computer. In response to identifying the derived frequency, processor 82 may generate another output, such as by displaying a suitable warning on a computer monitor, outputting an audible alert, and / or activating a warning light associated with the test kit.

[0056] Typically, electrodes 28 are tested while immersed in an electrolyte solution 70, such as saline, that simulates the body's internal environment. The nonlinearity of the impedance at the interface between each electrode and solution 70, and therefore the amplitude of any derived frequency components of signal 66, increases with the degree of imperfections, e.g., roughness or dirt, on the electrode's surface. Thus, defects can be detected in response to identifying derived frequencies within signal 66, as described above.

[0057] A return electrode 72, typically disposed at the bottom of a container 68 containing the solution 70, is connected to the test kit via a wire 84. The wire 84 may be contained within a cable. Thus, the test circuit through which the generated signal passes includes the solution 70, the return electrode 72, and the wire 84.

[0058] Generally, the test kit may include a case made of any suitable material, such as plastic, configured to hold the various components of the kit described herein. The test kit may include any suitable electrical interface, such as a port or socket, for connecting the kit to a probe such that the electrode 28 is connected to a signal generator. Similarly, the test kit may include any suitable electrical interface for connecting the kit to a return electrode 72. Alternatively or additionally, the test kit may include any suitable wired or wireless communication interface (e.g., a universal serial bus (USB) port) for communicating with a processor 82, such that the processor can receive signals 66 from the kit and / or the kit may receive control signals 80 from the processor via the communication interface.

[0059] Typically, frequencies f1 and f2 are relatively small, such as less than 100 Hz, so as to amplify any nonlinear response of the electrodes, and the amplitude of each of the generated signals is also typically relatively small, such as less than 50 μA, to minimize any undesirable effects on the electrode surface.

[0060] It will be understood by those skilled in the art that the present invention is not limited to what has been particularly shown and described herein. Rather, the scope of the embodiments of the present invention includes both combinations and subcombinations of the various features described herein, as well as variations and modifications of features that are not present in the prior art, which would occur to one skilled in the art upon reading the above description. Documents incorporated by reference into this patent application are deemed to be part of this application, except that if any term is defined in these incorporated documents in a way that contradicts the definition given herein, either expressly or impliedly, then only the definition given herein shall be considered.

[0061] [Embodiment] (1) A system for testing the symmetry of a bidirectional semiconductor device in a circuit, comprising: a signal generator configured to pass generated signals having two different generated frequencies through a circuit including a bidirectional semiconductor device; 1. A processor, comprising: identifying a derived frequency derived from the generated frequency on the circuit while the generated signal passes through the circuit; a processor configured to generate an output in response to identifying the derived frequency, the output indicating that a characteristic of the bi-directional semiconductor device is asymmetric. (2) The system of embodiment 1, wherein the processor is configured to identify the derived frequency via an electrophysiological channel belonging to the circuit. (3) The system of embodiment 2, wherein the derived frequency is within the bandwidth of the electrophysiological signal carried across the electrophysiological channel. (4) The system of embodiment 3, wherein each of the generated frequencies is outside the bandwidth. (5) The system of embodiment 1, wherein the characteristic includes impedance.

[0062] (6) The system of embodiment 1, wherein the derived frequency is the difference between the generated frequencies. (7) The system of embodiment 1, wherein the processor is further configured to disable a power source connected to the circuit in response to detecting the derived frequency. (8) The system of embodiment 7, wherein the power source is selected from the group of power sources consisting of a cardiac defibrillator, a cardiac pacer, and an ablation generator. (9) The system of embodiment 1, wherein the bidirectional semiconductor device belongs to a voltage suppression device. (10) The system of embodiment 1, wherein the bidirectional semiconductor device belongs to a semiconductor switch.

[0063] (11) A method for testing the symmetry of a bidirectional semiconductor device in a circuit, comprising: passing the generated signals having two different generated frequencies through a circuit including a bidirectional semiconductor device; identifying a derived frequency derived from the generated frequency on the circuit while passing the two generated signals through the circuit; and generating an output in response to identifying the derived frequency, the output indicating that a characteristic of the bi-directional semiconductor device is asymmetric. (12) The method of embodiment 11, wherein identifying the derived frequency includes identifying the derived frequency via an electrophysiological channel belonging to the circuit. (13) The method of embodiment 12, wherein the derived frequency is within the bandwidth of an electrophysiological signal carried across the electrophysiological channel. (14) The method of embodiment 13, wherein each of the generated frequencies is outside the bandwidth. (15) The method of claim 11, wherein the characteristic comprises impedance.

[0064] (16) The method of embodiment 11, wherein the derived frequency is the difference between the generated frequencies. (17) The method of claim 11, further comprising disabling a power source connected to the circuit in response to detecting the derived frequency. (18) The method of embodiment 17, wherein the power source is selected from the group of power sources consisting of a cardiac defibrillator, a cardiac pacer, and an ablation generator. (19) The method of claim 11, wherein the bidirectional semiconductor device belongs to a voltage suppression device. (20) The method of embodiment 11, wherein the bidirectional semiconductor device belongs to a semiconductor switch.

Claims

1. 1. A system for testing the symmetry of a bidirectional semiconductor device in a circuit, comprising: an electrode configured to acquire electrophysiological signals from the heart; a power source configured to provide power to the electrodes; a circuit including a bidirectional semiconductor device configured to control power supplied from the power source to the electrode; a digitizer configured to digitize and output the electrophysiological signals obtained from the electrodes; a signal generator configured to provide generated signals on power supply lines from the power source to the electrodes having two different generated frequencies that are outside a bandwidth of the electrophysiological signal and whose difference is within the bandwidth; 1. A processor, comprising: calculating a derived frequency based on an output from the digitizer in response to the application of generated signals having the two different generated frequencies, the derived frequency being a difference in frequency; a processor configured to detect that the bidirectional semiconductor device is asymmetric based on the derived frequency.

2. The system of claim 1 , wherein the processor is further configured to disable the power supply if the processor detects that the bidirectional semiconductor device is asymmetric.

3. 3. The system of claim 2, wherein the power source is selected from the group of power sources consisting of a cardiac defibrillator, a cardiac pacer, and an ablation generator.

4. 2. The system of claim 1, wherein the circuit including the bidirectional semiconductor device is a voltage suppression device connected on a power supply line from the power source to the electrode.

5. The system of claim 1 , wherein the circuit including the bidirectional semiconductor device is a semiconductor switch that switches the power supply from the power source to the electrode.

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