Stepping motor drive system and tubing occluder system

Abstract

To provide a stepping motor drive system used for driving a stepping motor of an occluder device in relation to a heart-lung machine.SOLUTION: The stepping motor drive system includes a tube clamping device, a stepping motor, a first winding output port, a first winding input port, a second winding output port, a second winding input port, a first snubber circuit, and a drive system including a second snubber circuit.SELECTED DRAWING: Figure 5

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims priority to and the benefit of U.S. patent application Ser. No. 16 / 777,533, filed Jan. 30, 2020, which is incorporated by reference in its entirety. [Technical field]

[0002] This document relates to a stepper motor drive system that may be used, for example, to drive a stepper motor of an occluder device in association with a heart-lung machine. [Background technology]

[0003] Hollow fiber oxygenators are utilized in extracorporeal circuits to meet the gas exchange needs of patients during medical procedures such as cardiopulmonary bypass surgery. Blood from the patient is either gravity drained or VAVD is used to obtain the flow rate necessary to maintain sufficient volume in the reservoir. Sometimes a pump, such as a peristaltic or centrifugal pump coupled with a magnetic drive system, is used in the main line of the circuit to pump blood from the reservoir, through the oxygenator, and finally back to the patient. Flow through such a line can be controlled by adjustably restricting the line, such as by manually pinching the line or through the use of mechanisms such as occluders. Some occluders are driven by stepper motors.

[0004] A stepper motor is generally a brushless direct current (DC) motor that includes a collection of electromagnetic coils. These coils can be energized and de-energized to rotate the motor's rotor in equal subdivisions of revolution, or "steps." The coils are energized and de-energized by a controller or external driver circuit. To rotate the motor shaft, power is applied to the coils, which magnetically attract the rotor. Once the rotor is aligned with a first electromagnet, the next coil is turned on, the first coil is turned off, and the rotor rotates slightly to align with the next coil. This process can then be repeated to control and rotate the rotor to a selected position or rotational distance at a selected speed. Summary of the Invention

[0005] This document describes a stepper motor drive system that may be used, for example, to drive a stepper motor of an occluder device in connection with a heart-lung machine. The stepper motor drive system described herein may also be beneficially used in many other contexts in which stepper motors are used.

[0006] In one aspect, the present disclosure is directed to a tube occluder system including a tube clamping device configured to releasably receive a tube; a stepper motor having a first winding and a second winding and positioned to adjust an amount of compression applied to the tube by the tube clamping device; and a drive system electrically coupled to the stepper motor and including a first winding output port configured to electrically connect to a first winding input of the first winding, a first winding input port configured to electrically connect to a first winding output of the first winding, a second winding output port configured to electrically connect to a second winding input of the second winding, a second winding input port configured to electrically connect to a second winding output of the second winding, a first snubber circuit in electrical communication between the first winding input port and the second winding output port, and a second snubber circuit in electrical communication between the second winding input port and the first winding output port.

[0007] In some embodiments, the system may include some, all, or none of the following features: The first snubber circuit may include a first resistor and a first diode in series electrical connection with the first resistor, the first diode configured to pass current from the first winding input port to the second winding output port and prevent current flow from the second winding output port to the first winding input port. The second snubber circuit may include a second resistor and a second diode in series electrical connection with the second resistor, the second diode configured to pass current from the second winding input port to the first winding output port and prevent current flow from the first winding output port to the second winding input port. The tube occluder system may also include a power bus, a first diode configured to pass current from the power bus to the first winding output port, and a second diode configured to pass current from the power bus to the second winding output port. The tube occluder system may also include a low potential power bus, a first switch configured to controllably connect the first winding input port to the low potential power bus, a second switch configured to controllably connect the second winding input port to the low potential power bus, and at least one resistor configured to limit current flow from the first winding input port to the low potential power bus and to limit current flow from the second winding input port to the low potential power bus.

[0008] In another aspect, a method of recirculating energy in a stepper motor may include providing power to a first output and a second output on a power bus; flowing power to a first electrical load electrically connected to the first output; switching a first switch to block the flow of power from the first electrical load to a low potential bus; switching a second switch to allow power from the power bus to flow from the second output, through a second electrical load electrically connected to the second output, to the low potential bus; directing the flow of power from the first electrical load to the second output with a first snubber circuit; switching the second switch to block the flow of power from the second electrical load to the low potential bus; switching the first switch to allow power from the power bus to flow from the first output, through the first electrical load to the low potential bus; and directing the flow of power from the second electrical load to the first output with a second snubber circuit. The method may also include preventing reverse current flow from the first snubber circuit to the power bus and preventing reverse current flow from the second snubber circuit to the power bus. The first snubber circuit may include a first resistor and a first diode in series electrical connection with the first resistor, where directing power flow from the first electrical load to the second output by the first snubber circuit may include allowing power flow from the first electrical load at the first input to the second output by the first diode and preventing power flow from the second output to the first input by the first diode. The second snubber circuit may include a second resistor and a second diode in series electrical connection with the second resistor, wherein directing the flow of power from the second electrical load to the first output by the second snubber circuit may include allowing the flow of power from the second electrical load at the second input to the first output by the second diode, and preventing the flow of power from the first output to the second input by the second diode.The first electrical load may include a first inductive electrical load, and the second electrical load may include a second inductive electrical load, and switching the first switch may include energizing the first inductive electrical load to permit power from the power bus to flow from the first output, through the first electrical load, to the low potential bus, and switching the second switch may include energizing the second inductive electrical load to permit power from the power bus to flow from the second output, through a second electrical load electrically connected to the second output, to the low potential bus. The flow of power from the first electrical load to the first output may include at least in part a current flow caused by an inductance of the first inductive electrical load, and the flow of power from the second electrical load to the second output may include at least in part a current flow caused by an inductance of the second inductive electrical load. The first electrical load may include a first winding of a stepper motor, and the second electrical load may include a second winding of the stepper motor. Switching the first switch may include energizing the first winding to permit power from the power bus to flow from the first output, through a first electrical load, to the low potential bus, and switching the second switch may include energizing the second winding to permit power from the power bus to flow from the second output, through a second electrical load electrically connected to the second output, to the low potential bus. The method may also include controllably switching the first switch and the second switch to urge rotation of the stepper motor in a first direction, actuating, by the stepper motor, a tube clamping device configured to releasably receive the tube, and adjusting an amount of compression applied to the tube by the tube clamping device based on the actuation.

[0009] In another aspect, an electric drive system includes a first power output port configured to electrically connect to a first load input of a first electrical load, a first power input port configured to electrically connect to a first load output of the first electrical load, a second power output port configured to electrically connect to a second load input of a second electrical load, a second power input port configured to electrically connect to a second load output of the second electrical load, a first snubber circuit in electrical communication between the first load input port and the second load output port, and a second snubber circuit in electrical communication between the second load input port and the first load output port.

[0010] Various embodiments may include some, all, or none of the following features: The first snubber circuit may include a first resistor and a first diode in series electrical connection with the first resistor, the first diode configured to pass current from the first load input port to the second load output port and prevent current flow from the second load output port to the first load input port, and the second snubber circuit may include a second resistor and a second diode in series electrical connection with the second resistor, the second diode configured to pass current from the second load input port to the first load output port and prevent current flow from the first load output port to the second load input port. The system may also include a power bus, a first diode configured to pass current from the power bus to the first load output port, and a second diode configured to pass current from the power bus to the second load output port. The system may also include a low-potential power bus, a first switch configured to controllably connect a first load input port to the low-potential power bus, a second switch configured to controllably connect a second load input port to the low-potential power bus, and at least one resistor configured to limit a flow of current from the first load input port to the low-potential power bus and to limit a flow of current from the second load input port to the low-potential power bus. At least one of the first electrical load and the second electrical load may be an inductive electrical load. The first electrical load may be a first winding of a stepper motor and the second electrical load may be a second winding of the stepper motor.

[0011] The techniques described herein may be used to provide one or more benefits. For example, compared to current systems, a stepper motor drive system described herein causes a stepper motor to exhibit faster response, such as when accelerating to a full speed. For example, in some cases, the time required for a stepper motor to reach full speed may be about 10 times faster using a stepper motor drive system described herein compared to current systems.

[0012] Additionally, the stepper motor drive systems described herein are more energy efficient than current systems, in other words, they use less electrical energy and dissipate less energy as heat than current systems.

[0013] Additionally, the stepper motor drive system described herein is less noisy electrically and mechanically than current systems, in other words, it produces less current ripple, less torque ripple, has lower required operating voltages and currents, and has improved electromagnetic compatibility.

[0014] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. Although methods and materials similar or equivalent to those described herein can be used to practice the present invention, suitable methods and materials are described herein. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be limiting.

[0015] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description herein. Other features, objects, and advantages of the invention will become apparent from the description and drawings, and from the claims. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic illustration of a patient undergoing open heart surgery while being supported using an extracorporeal circulation circuit according to certain embodiments provided herein. [Diagram 2] FIG. 2 illustrates a portion of a heart-lung machine and tube occluder device, according to some embodiments. [Diagram 3] FIG. 3 is a schematic diagram of a prior art stepper motor. [Figure 4] FIG. 4 is a schematic diagram of a prior art motor driver circuit. [Diagram 5] FIG. 5 is a schematic diagram of an example motor driver circuit, according to some embodiments. [Figure 6] FIG. 6 is a chart of example motor driver electrical waveforms according to some embodiments. [Figure 7] FIG. 7 is a chart of example motor driver electrical waveforms according to some embodiments. [Figure 8] FIG. 8 is a chart of example motor driver electrical waveforms according to some embodiments. [Figure 9] FIG. 9 is a flow diagram of an example process according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Like numbers refer to corresponding parts throughout.

[0018] This document describes a stepper motor drive system that may be used to drive stepper motors in tube occluder systems and devices, for example, in connection with heart-lung machines. The stepper motor drive system described herein may also be beneficially used in many other contexts in which stepper motors are used.

[0019] As shown in FIG. 1, various types of medical procedures may be performed on the patient 10 while the patient 10 is connected to a life-supporting cardiopulmonary bypass machine system 100. In this example, the patient 10 is undergoing open-heart surgery, during which the patient's 10 heart 12 and lungs are purposefully stopped functioning temporarily. However, the patient's 10 body continues to have a metabolic need to be supplied with circulating oxygenated blood during the medical procedure, and the cardiopulmonary bypass machine system 100 performs such a function. That is, as will be explained further below, the cardiopulmonary bypass machine system 100 is connected to the patient 10 and performs the functions of the patient's 10 heart 12 and lungs so that the patient 10 remains alive and healthy during the open-heart surgery. The cardiopulmonary bypass machine system 100 may be used for many different types of medical procedures. For example, medical procedures in which the cardiopulmonary bypass machine system 100 may be used include, but are not limited to, coronary artery bypass grafting, heart valve repair, heart valve replacement, heart transplants, lung transplants, ablation procedures, septal defect repair, congenital heart defect repair, aneurysm repair, pulmonary endarterectomy, pulmonary thrombectomy, and the like.

[0020] In the illustrated example, cardiopulmonary bypass machine system 100 includes components and subsystems such as a heart-lung machine 110, an extracorporeal circuit 120, one or more temperature control systems 130, a blood monitoring system 140, a perfusion data management system 150, and a regional oximetry system 160. Some types of procedures using cardiopulmonary bypass machine system 100 may not require all of the components and subsystems shown. Some types of procedures using cardiopulmonary bypass machine system 100 may require additional components and / or subsystems that are not shown.

[0021] The extracorporeal circuit 120 is connected to the patient 10 and to the heart-lung machine 110. Other systems, such as a temperature control system 130, a blood monitoring system 140, and a perfusion data management system 150, may also be arranged to interface with the extracorporeal circuit 120. The extracorporeal circuit 120 is connected to the patient 10 at the patient's heart 12. Oxygen-depleted blood (venous blood) from the patient 10 is extracted from the patient 10 at the patient's heart 12 using a venous catheter 121. As will be explained further below, the blood is circulated through the extracorporeal circuit 120 to receive oxygen and remove carbon dioxide. The oxygenated blood is then returned through the extracorporeal circuit 120 to the patient's heart 12 via an aortic cannula 129.

[0022] The extracorporeal circuit 120 may include at least a venous tubing 122 coupled to a venous catheter 121, a blood reservoir 123, a centrifugal pump 124, an oxygenator 125, an arterial filter 126, one or more air bubble detectors 128, and an arterial tubing 127 coupled to an aortic cannula 129. The venous catheter 121 and the venous tubing 122 are in fluid communication with the venous side of the circulatory system of the patient 10. The venous tubing 122 is also in fluid communication with an inlet to the reservoir 123. An outlet from the reservoir 123 is connected by tubing to an inlet of the pump 124. An outlet of the pump 124 is connected by tubing to an inlet of the oxygenator 125. An outlet of the oxygenator 125 is connected by tubing to an inlet of the arterial filter 126. An outlet of the arterial filter 126 is connected to the arterial tubing 127. One or more pressure transducers may be positioned along the arterial tubing 127 to detect the heart / lung machine (HLM) system line pressure of the blood in the arterial tubing 127, which is measured by the heart / lung machine 110 and monitored by a perfusionist. The arterial tubing 127 is connected to an aortic cannula 129, which is in physical contact with the heart 12 and in fluid communication with the arterial side of the circulatory system of the patient 10.

[0023] Briefly, the extracorporeal circuit 120 operates by withdrawing venous oxygen-depleted blood from the patient 10 via the venous catheter 121 and depositing the venous blood in the reservoir 123 via the venous tube 122. In some cases, gravity is used to cause the blood to flow or drain from the patient 10 to the reservoir 123. In some cases, a vacuum is used to assist the blood to flow from the patient 10 to the reservoir 123. It is intended that at least some amount of blood is maintained in the reservoir 123 at all times during the surgical procedure. Otherwise, if the reservoir 123 empties, air may be pumped into the extracorporeal circuit 120 and potentially into the vasculature of the patient 10. Such an outcome could be fatal to the patient 10. Thus, the perfusionist is tasked with visually monitoring the level of blood in the reservoir 123. Additionally, a level detector may be included with the reservoir 123 to generate an alarm in response to detection of a low level condition in the reservoir 123. Additionally, one or more air bubble detectors 128 may be located at various sites along the extracorporeal circuit 120. Blood from the reservoir 123 is drawn from the reservoir 123 by a pump 124. The illustrated embodiment includes a single-use centrifugal pump as the pump 124, although in some cases a peristaltic pump from the heart-lung machine 110 is used instead. The pressure generated by the pump 124 propels the blood through an oxygenator 125. The perfusionist will adjust the pump 124 to operate as desired while avoiding operational issues such as negative cavitation that may result in micro-air particles in the blood of the extracorporeal circuit 120. In the oxygenator 125, the venous blood is enriched with oxygen and carbon dioxide is removed from the blood. The oxygen-rich arterial blood now exits the oxygenator 125, travels through an arterial filter 126 to remove emboli, and passes through an arterial tubing 127 before being infused into the patient's heart 12 via an aortic cannula 129.The extracorporeal circuit 120 may also include tubing and other components to facilitate functions such as, but not limited to, draining blood accumulating in the heart of the patient 10, providing surgical suction to maintain visibility of the surgical field, delivering cardioplegia fluid to the heart 12 of the patient 10 during the procedure, measuring blood parameters, removing air from the blood, hemoconcentrating, adding medication, taking blood samples, heating and cooling the blood, and the like.

[0024] The cardiopulmonary bypass machine system 100 also includes a heart-lung machine 110. The heart-lung machine 110 is a complex system including multiple pumps, monitors, controls, user interfaces, alarms, safety devices, etc., all of which are monitored and operated / adjusted by a perfusionist during a surgical procedure. For example, the illustrated heart-lung machine 110 includes an arterial pump 111 (which may be a drive system for a disposable centrifugal pump 124 or a peristaltic pump as shown), an aspiration pump 112, an exhaust / drainage pump 113, a cardioplegia fluid pump 114, and a cardioplegia fluid delivery pump 115. The heart-lung machine 110 may also include or be interfaced with devices such as tubing occluders, gas mixers, etc. Parameters of the heart-lung machine 110, such as the rotational speeds and other parameters of each of the pumps, are set and adjusted by the perfusionist. For example, the speed of the arterial pump 111 is adjusted to maintain a desired level of blood in the reservoir 123 and provide the necessary level of blood circulation within the patient 10.

[0025] The cardiopulmonary bypass machine system 100 also includes one or more temperature control systems 130. In a first embodiment, the temperature control system 130 is used to heat and cool the patient's blood in the oxygenator 125 via a heat exchanger. Additionally, the temperature control system 130 is used to heat and cool the cardioplegia fluid being delivered to the heart 12 of the patient 10. Typically, the temperature control system 130 is used in a cooling mode during the procedure (to reduce metabolic demand) and then used to warm the blood and / or cardioplegia fluid as the surgical procedure nears its end. A perfusionist is tasked with monitoring and adjusting the temperature control system 130 as needed during the surgical procedure.

[0026] The cardiopulmonary bypass machine system 100 also includes a blood monitoring system 140, as shown. The blood monitoring system 140 is used to monitor the extracorporeal blood of the patient 10 during the surgical procedure. Parameters monitored may include, but are not limited to, pH, pCO2, pO2, K+, temperature, SO2, hematocrit, hemoglobin, base excess, bicarbonate, oxygen consumption, and oxygen delivery.

[0027] The cardiopulmonary bypass machine system 100 also includes a perfusion data management system 150 and a regional oximetry system 160, as shown. These systems may also be used by a perfusionist to monitor the condition of the patient 10 and / or the condition of the cardiopulmonary bypass machine system 100 during the surgical procedure.

[0028] The cardiopulmonary bypass machine system 100 also includes an occluder device 170 (e.g., a tube occluder system) as shown. In the illustrated example arrangement, the occluder device 170 is located along the venous tubing 122. Alternatively or additionally, the occluder device 170 may be located along the arterial tubing 127 or any other tube of the cardiopulmonary bypass machine system 100. The occluder device 170 applies an external clamping force to the outer diameter of the tube to regulate the flow of fluid through the tube. In some cases, the occluder device 170 is used as a blocking device that can be actuated to completely occlude the tube, thereby preventing all fluid flow through the tube.

[0029] 2, in this example, an occluder device 170 is shown attached to the heart-lung machine 110. The occluder device 170 includes an occluder housing 172, a drive system housing 174, and a user interface 176.

[0030] Occluder housing 172 is configured to releasably receive a tube (in this example, the tube is IV tubing 122). Within occluder housing 172 is a clamping mechanism (not shown) that compresses the outer diameter of tubing 122, and a stepper motor (not shown) that drives the clamping mechanism. The stepper motor can be operated to adjust a controlled amount of compression applied to tubing 122 to regulate fluid flow therethrough.

[0031] Within the drive system housing 174 is a stepper motor drive system (not shown) that is electrically coupled to the stepper motor. The stepper motor drive system is described further below.

[0032] The occluder device 170 also includes a user interface 176. A user (e.g., a perfusionist) can adjust the flow rate of fluid within the tube 122 via the user interface 176.

[0033] Referring to FIG. 3, a schematic diagram of an example stepper motor 300 is shown. Stepper motor 300 includes rotor 310, phase 320a, and phase 320b. In the illustrated example, stepper motor 300 is an eight-wire unipolar stepper motor, where phase 320a includes winding 322a and winding 324a, and phase 320b includes winding 322b and winding 324b. Each of coils 322a, 322b, 324a, and 324b has a coil input and a coil output. In some embodiments, a unipolar stepper motor has one winding per phase, each with a center tap, and each section of the winding can be energized for each direction of the magnetic field. Typically, for a given phase, the center tap of each winding is made common, which results in three leads per phase, resulting in six leads in total (e.g., for a two-phase motor). In some embodiments, the two center taps may be internally joined resulting in a five-wire configuration. In some embodiments, the stepper motor 300 may be a bipolar stepper motor with a single coil per phase.

[0034] In use, the windings 322a, 322b, 324a and 324b of phases 320a and 320b may be controllably energized and de-energized (e.g., under the control of a motor controller) to encourage rotation of rotor 310. When energized, electrical coils such as each of windings 322a, 322b, 324a and 324b do not instantaneously conduct current. Rather, current flow begins relatively slowly and increases to its maximum flow as the magnetic fields generated by the current flow through the coils build to their maximum. Conversely, current flow through a coil does not instantaneously stop when the coil is de-energized. The collapsing magnetic field will continue to encourage current flow until it reduces to zero.

[0035] 4, a schematic diagram of a prior art motor driver circuit 400 is shown. The circuit 400 is configured to drive windings 401a and 401b of a stepper motor. In some implementations, windings 401a and 401b may be all or a portion of example phases 320a or 320b of example stepper motor 300 of FIG.

[0036] Winding 401a includes a coil 402a and a resistor 403a. In some embodiments, coil 402a may model the inductance of winding 401a. In some embodiments, resistor 403a may model the inherent DC resistance of winding 401a. Winding 401b includes a coil 402b and a resistor 403b. In some embodiments, coil 402b may model the inductance of winding 401b. In some embodiments, resistor 403b may model the inherent DC resistance of winding 401b. Coil 402a is part of an electromagnet that drives a winding of a stepper motor, and coil 402b is part of an electromagnet that drives another winding of the stepper motor. The winding inductance is typically specified in the stepper motor data sheet, so the designer has some idea of ​​how long it will take to store energy in the winding, which can be approximated by a first order differential equation: tau=L / R, where L is the winding inductance and R is the winding resistance (DCR) (e.g., winding_current(time)=(Vsupply / DCR)*(1-e -t / tau )).

[0037] A power supply 410 provides power to a power bus 412. The power bus 412 provides power to winding 401a and winding 401b. Current flow from the power bus 412 through winding 401a to a low potential bus 420 (e.g., ground, neutral, negative) is controllably blocked and allowed by switch 430a based on a control signal provided to a switch input 432a. Current flow from the power bus 412 through winding 401b to the low potential bus 420 is controllably blocked and allowed by switch 430b. In the illustrated example, switches 430a and 430b are MOSFET devices.

[0038] By controllably alternating the flow of power through switches 430a and 430b, windings 401a and 401b can be energized and de-energized to encourage rotation of the stepper motor. As discussed above, the current flow through the coils does not stop instantaneously when power is switched off. Instead, there is a residual current flow induced by the collapsing magnetic field around the coils. In the illustrated example, such currents can cause voltage spikes across switches 430a and 430b that could damage switches 430a and 430b (e.g., by electrical arcing) if not accounted for by snubber circuit 450.

[0039] In the example of FIG. 4, snubber circuit 450 is a known snubber circuit configuration. When switch 430a is disconnected, residual current from winding 401a is prevented from flowing to the low potential bus 420. Residual current in winding 401a is allowed to flow from winding 401a through diode 452a and current dissipation resistor 454 back to power bus 412. Diode 452a prevents current from power bus 412 from bypassing winding 401a. When switch 430b is disconnected, residual current from winding 401b is prevented from flowing to the low potential bus 420. Residual current in winding 401b is allowed to flow from winding 401b through diode 452b and current dissipation resistor 454 back to power bus 412. Diode 452b prevents current from power bus 412 from bypassing winding 401b.

[0040] Generally, the residual energy flowing through the snubber circuit 450 is dissipated (e.g., turned into heat) by the current dissipation resistor 454. In the example circuit 400, the residual energy is lost through dissipation and may have undesirable effects such as heat generation. In the example circuit 400, the speed of the coils 402a, 402b is proportional to the amount of power available on the power bus 412. For example, if the coils 402a, 402b need to be energized more quickly (e.g., to create less current ripple and / or torque ripple, to better ensure that the stepper motor 300 does not stall), the output of the power supply 410 needs to be increased (e.g., resulting in increased size, cost, weight of the circuit 400), and as the amount of power being switched by the switches 430a, 430b increases, the amount of electromagnetic interference (EMI) (e.g., switching noise) may increase and may need to be addressed depending on the application (e.g., further increasing the size, cost, and complexity of the circuit 400).

[0041] 5, a schematic diagram of an example motor driver circuit 500 is shown, according to some embodiments disclosed herein. The circuit 500 is configured to drive windings 501a and 501b of a stepper motor. In some implementations, windings 501a and 501b may resemble any two of example windings 322a, 322b, 324a, and 324b of example stepper motor 300 of FIG.

[0042] Winding 501a includes a coil 502a and a resistor 503a. In some embodiments, coil 502a may model the inductance of winding 501a. In some embodiments, resistor 503a may model the inherent DC resistance of winding 501a. Winding 501b includes a coil 502b and a resistor 503b. In some embodiments, coil 502b models the inductance of winding 501b. In some embodiments, resistor 503b may model the inherent DC resistance of winding 501b. Coil 502a is part of an electromagnet that drives a motor winding of a stepper motor (e.g., example stepper motor 300), and coil 502b is part of an electromagnet that drives another motor winding of the same or different phase of the stepper motor.

[0043] The load input port 504a is configured to accept power into the winding 501a and the load output port 506a is configured to allow power to flow out of the winding 501a. In the illustrated example, the load input port 504a is a stepper motor winding input port or input lead and the load output port 506a is a stepper motor winding output port or output lead.

[0044] The power supply 510 provides power to a power bus 512. The power bus 512 provides power to a load output port 514a and a load output port 514b. The load output port 514a is configured to electrically connect to the load input port 504a, and the load output port 514b is configured to electrically connect to the load input port 504b. The load input port 516a is configured to electrically connect to the load output port 506a to receive power flowing out from the winding 501a. The load input port 516b is configured to electrically connect to the load output port 506b to receive power flowing out from the winding 501b. The reverse flow of current to the power bus 512 is blocked by a diode 518a disposed between the load output port 514a and the power bus 512. The reverse flow of current from the winding 501a to the power bus 512 is blocked by a diode 518a disposed between the load output port 514a and the power bus 512. Reverse flow of current from winding 501b to power bus 512 is blocked by diode 518b disposed between load output port 514b and power bus 512. In some embodiments, diodes 518a, 518b may be omitted, for example, when power supply 510 is a unidirectional power supply. In some embodiments, diodes 518a and 518b may be replaced by a single diode, for example, in the case of a six-lead stepper motor where the power supply is bidirectional. In some embodiments, diodes 518a and 518b may be removed, for example, in the case of a six-lead stepper motor where the power supply is unidirectional. In some embodiments where an eight-lead stepper motor is used, both diodes 518a and 518b may be used regardless of whether power supply 410 is unidirectional and / or bidirectional.

[0045] Circuit 500 includes a low potential bus 520. In the illustrated example, low potential bus 520 is a ground bus, but in some embodiments low potential bus 520 may include a neutral conductor, a negative conductor (e.g., a return conductor), or may be any suitable voltage lower than the voltage of power bus 512.

[0046] Current flow from the power bus 512 through winding 501a to the low potential bus 520 is controllably blocked and allowed by switch 530a based on a control signal provided to switch input 532a. Current flow from the power bus 512 through winding 501b to the low potential bus 520 is controllably blocked and allowed by switch 530b. In the illustrated example, switches 530a and 530b are MOSFET devices, but in some embodiments switches 530a and 530b may be any suitable form of controllable switch (e.g., FET, IGBT, BJT, or other form of transistor, relay) that can control the flow of current through windings 501a and 501b. A current limiting resistor 522 limits the flow of current to the low potential bus.

[0047] By controllably alternating the flow of power through the switches 530a and 530b, the windings 501a and 501b can be energized and de-energized to encourage rotation of the stepper motor. As mentioned above, the current flow through the coils does not stop instantly when the power is switched off, and there is a residual current flow induced by the collapsing magnetic field around the coils 502a, 502b. In the illustrated example, such currents that could otherwise cause voltage spikes across the switches 530a and 530b (and potentially damage the switches 530a and 530b, e.g., by electrical arcing) are accounted for by the snubber circuit 550.

[0048] The snubber circuit includes a branch 551a and a branch 551b. The branch 551a provides electrical communication between the load input port 516a and the load output port 514b. The branch 551a includes a diode 552a connected in series with a current limiting resistor 554a. The diode 552a is configured to allow current flow from the load input port 516a to the load output port 514b and prevent current flow from the load output port 514b to the load input port 516a. The branch 551b provides electrical communication between the load input port 516b to the load output port 514a. The branch 551b includes a diode 552b connected in series with a current limiting resistor 554b. The diode 552b is configured to allow current flow from the load input port 516b to the load output port 514a and prevent current flow from the load output port 514a to the load input port 516b.

[0049] In use, switch 530a is turned on, causing winding 501a to be energized while switch 530b is off. Switch 530a is then turned off. Residual current will be pushed out of coil 502a. The reverse flow of this residual current is blocked by diode 518a and diode 552b. The forward flow of this residual current is blocked by switch 530a, leaving branch 551a as the only electrical path through which the residual current can flow. As coil 502a becomes de-energized, the residual current flows through branch 551a to load output port 514b. Since diode 518b prevents current from flowing back to power bus 512, current flows into winding 501b and to coil 502b. In the illustrated example, the residual current resulting as coil 502a becomes de-energized is used to energize coil 502b to at least a partial extent. In some implementations, the snubber circuit 550 may recover energy in the coil 502a (e.g., rather than dissipating it) and use the recovered energy, along with power from the power bus 512, to energize the coil 502b more quickly than it could be energized based solely on power from the power bus 512.

[0050] Continuing with the previous example, in use, switch 530b is turned on, causing winding 501b to be energized, and switch 530a is turned off. Switch 530b is then turned off. Residual current will be pushed out of coil 502b. The reverse flow of this residual current is blocked by diode 518b and diode 552a. The forward flow of this residual current is blocked by switch 530b, leaving branch 551b as the only electrical path through which the residual current can flow. As coil 502b becomes de-energized, the residual current flows through branch 551b to load output port 514a. Because diode 518a prevents current from flowing back to power bus 512, current flows into winding 501a and to coil 502a. In the illustrated example, the residual current resulting as coil 502b becomes de-energized is used to energize coil 502a to at least a partial extent. In some implementations, the snubber circuit 550 may recover energy in the coil 502b (e.g., rather than dissipating it) and use the recovered energy, along with power from the power bus 512, to energize the coil 502a more quickly than it could be energized based solely on power from the power bus 512.

[0051] In some implementations, energy efficiency may be increased by redirecting residual energy from the coils 502a, 502b back to their mating coils, e.g., at least a portion of the residual coil energy may be reused instead of being completely dissipated.

[0052] In some implementations, by redirecting residual energy from coils 502a, 502b to their mating coils, temperature and / or thermal management needs may be reduced. For example, circuit 500 does not implement a current dissipation resistor, such as current dissipation resistor 454 of FIG. 4, that dissipates residual coil energy as heat. Because circuit 500 substantially recycles coil energy rather than substantially dissipating it as heat, thermal management associated with such heat generation is substantially reduced.

[0053] In some implementations, by redirecting the residual energy from the coils 502a, 502b to their paired coils, the circuit 500 may be implemented efficiently (e.g., more efficiently than the example circuit 400). For example, in the example circuit 400, to increase the speed at which the coils 402a, 402b are energized, the capacity of the power source 410 and / or the power bus 412 must be increased, which may increase the size, weight, cost, and / or complexity of the circuit 400. Unlike the circuit 400, the circuit 500 is configured to use the residual energy from one of the coils 502a, 502b, in addition to power from the power bus 512, to energize the other of the coils 502a, 502b. Thus, the performance of the coils 502a, 502b may be increased (e.g., to produce less current ripple and / or torque ripple, to be more certain that the stepper motor will not stall) without the size, weight, cost, and / or complexity that may be associated with achieving a similar performance increase by increasing the capacity of the power supply 510 and / or power bus 512.

[0054] In some implementations, electromagnetic interference (EMI) and / or EMI management needs may be reduced by redirecting residual energy from the coils 502a, 502b to their mating coils. For example, residual energy in the coils 502a, 502b may be redirected relatively more quickly away from the switches 530a, 530b than in circuit 400, resulting in a relatively lower voltage across the switches 530a, 530b. The relatively lower voltage provided by the snubber circuit 550 may result in a relatively lower amount of EMI (e.g., switching noise) caused by switching the switches 530a, 530b as compared to circuit 400.

[0055] 6-8 are charts of example motor driver electrical waveforms.

[0056] Figure 6 is a chart 600 illustrating an example of a current waveform 610 that may be generated by the example circuit 500 of Figure 5. Figure 6 also illustrates an example of a current waveform 620 that may be generated by a known circuit, such as circuit 400 of Figure 4.

[0057] It can be observed that both waveforms 610 and 620 have approximately the same start-up behavior since there is no energy stored yet in their respective motor coils. After the first coil stores energy, the effect of energy recirculation can be observed, with waveform 610 rising faster and having less ripple than waveform 620. In the illustrated example, both cases had the same 24v supply voltage. The faster rise time of waveform 610 is due to the energy stored in the coil being transferred quickly to the complementary coil during the switching edge, allowing these coils (or windings or inductances) to have more initial energy and therefore less ripple in the primary 1-e -t / tau This will fit the curve better and therefore exhibit less current ripple.

[0058] 7 is a chart 700 illustrating another example of a current waveform 710 that may be generated by the example circuit 500 of FIG. 5. FIG. 7 also illustrates an example of a current waveform 720 that may be generated by a known circuit, such as the circuit 400 of FIG. 4. The chart 700 illustrates an example of a ripple current after a supply voltage (e.g., of the power buses 412 and 512) is adjusted to match a peak current value (e.g., at the end of an on-time cycle) as represented by line 730. The waveform 710 has a ripple of about 141 mA as measured between an initial current value represented by line 732 and a peak current value 730. In contrast, the waveform 720 has a ripple of about 1.57 A between an initial current value represented by line 734 and a peak current value 730. The ripple of the example circuit 500 exhibits a ripple that is about 11 times smaller than the ripple exhibited by the known circuit 400. In implementations in which the power supply is regulated to achieve an equivalent average current instead of a peak current, the factor of ripple reduction provided by circuit 500 may be even greater.

[0059] FIG. 8 is a chart 800 illustrating another example of a current waveform pair 810 that may be generated by the example circuit 500 of FIG. 5. FIG. 8 also illustrates an example of a current waveform pair 820 that may be generated by a known circuit, such as the circuit 400 of FIG. 4. The current waveform pair 810 includes a waveform 812a and a waveform 812b. In some implementations, the waveforms 812a and 812b may represent example currents in windings in a motor phase (e.g., for purposes of more clearly illustrating the reduced ripple provided by the circuit 500). In some implementations, the waveform 812a may be an example of a current waveform across the example winding 501a, and the waveform 812b may be an example of a current waveform across the example winding 501b. The current waveform pair 820 includes a waveform 822a and a waveform 822b. In some implementations, waveform 822a may be an example of a current waveform across example winding 401a, and waveform 822b may be an example of a current waveform across example winding 401b. Generally, chart 800 illustrates an example of the improvement in ripple and energy transfer provided by circuit 500 as compared to circuit 400.

[0060] 9 is a flow diagram of an example process 900 according to some embodiments. In some implementations, the process 900 may be performed by the example circuit 500 of FIG.

[0061] At 910, power is provided on a power bus to a first output and a second output. For example, power may be provided by power supply 510 on power bus 512 to load output port 514a and load output port 514b.

[0062] At 920, a first switch is switched to interrupt the flow of power from the first electrical load to the low potential bus. For example, switch 530a may be switched off to stop power flowing from winding 501a to the low potential bus 520.

[0063] At 930, a second switch is switched to allow power from the power bus to flow from the second output, through a second electrical load electrically connected to the second output, and to the low potential bus. For example, switch 530b may be switched on to allow power from power bus 512 to flow through winding 501b to the low potential bus 520.

[0064] At 940, a first snubber circuit directs the flow of power from a first electrical load to a second output. For example, branch 551a of snubber circuit 550 conducts the residual energy that entered through load input port 516a and was blocked by switch 530a to load output port 514b.

[0065] In some implementations, the first snubber circuit may include a resistor and a diode in series electrical connection with the resistor. For example, branch 551a includes diode 552a and current-limiting resistor 554a. In some implementations, directing the flow of power from the first electrical load to the second output by the first snubber circuit may include allowing the flow of power from the first electrical load at the first input to the second output by the diode, and preventing the flow of power from the second output to the first input by the diode. For example, diode 552a may allow a unidirectional flow of current from load input port 516a to load output port 514b.

[0066] At 950, a second switch is switched to block the flow of power from the second electrical load to the low-potential bus. For example, switch 530b may be switched to block power coming in through load input port 516b from flowing to the low-potential bus 520.

[0067] At 960, a first switch is switched to allow power from the power bus to flow from the first output, through the first electrical load, and to the low potential bus. For example, switch 530a is switched to allow power to flow from load input port 516a to the low potential bus 520.

[0068] At 970, the second snubber circuit directs the flow of power from the second electrical load to the first output. For example, branch 551b of snubber circuit 550 conducts the residual energy flowing through load input port 516b and interrupted by switch 530b to load output port 514a. In some implementations, the flow of power from the first electrical load to the first output may be a current flow caused at least in part by the inductance of the first inductive electrical load, and the flow of power from the second electrical load to the second output may be a current flow caused at least in part by the inductance of the second inductive electrical load.

[0069] In some implementations disclosed herein, the second snubber circuit may include a resistor and a diode in series electrical connection with the resistor. For example, branch 551b includes diode 552b and current-limiting resistor 554b. In some implementations, directing the flow of power from the second electrical load to the first output by the second snubber circuit may include allowing the flow of power from the second electrical load at the second input to the first output by the diode, and preventing the flow of power from the first output to the second input by the diode. For example, diode 552b may allow a unidirectional current flow from load input port 516b to load output port 514a.

[0070] In some implementations disclosed herein, the process 900 may also include preventing a reverse flow of current from the first snubber circuit to the power bus and preventing a reverse flow of current from the second snubber circuit to the power bus. For example, diodes 518a and 518b may prevent a reverse flow of power from the snubber circuit 550 to the power bus 512.

[0071] In some implementations disclosed herein, the first electrical load may be a first inductive electrical load, and the second electrical load may be a second inductive electrical load. For example, the winding 501a is an electrical load including a coil 502a that is an inductive electrical load, and the winding 501b is an electrical load including a coil 502b that is another inductive electrical load. In some implementations, switching the first switch may include energizing the first inductive electrical load to allow power from the power bus to flow from the first output, through the first electrical load electrically connected to the first output, to the low potential bus. For example, when current flows through the winding 501a, the coil 502a may be in an energized state. In some implementations, switching the second switch may include energizing the second inductive electrical load to allow power from the power bus to flow from the second output, through the second electrical load electrically connected to the second output, to the low potential bus. For example, when current flows through winding 501b, coil 502b may be in an energized state.

[0072] In some embodiments disclosed herein, the first electrical load may be a first winding of a stepper motor, and the second electrical load may be a second winding of a stepper motor. For example, winding 501a may be all or a portion of winding 320a of stepper motor 300, and winding 501b may be all or a portion of winding 320b. In some implementations, switching the first switch to allow power from the power bus to flow from the first output, through the first electrical load, to the low potential bus may include energizing the first winding, and switching the second switch to allow power from the power bus to flow from the second output, through a second electrical load electrically connected to the second output, to the low potential bus may include energizing the second winding. For example, switches 530a and 530b may be switched to energize windings 501a and 501b, which may be windings 320a and 320b.

[0073] In some implementations disclosed herein, the process 900 may also include controllably switching a first switch and a second switch to prompt rotation of the stepper motor in a first direction, actuating, by the stepper motor, a tube clamping device configured to releasably receive the tube, and adjusting an amount of compression applied to the tube by the tube clamping device based on the actuation. For example, the example circuit 500 may be used to actuate the example stepper motor 300 of FIG. 3, which may be configured to actuate the example occluder device 170 of FIGS. 1 and 2. The stepper motor 300 may be operated to control the amount of compression applied to the tube 122, thereby regulating the flow of fluid through the tube 122.

[0074] Although the examples provided herein generally discuss the concept of recirculating energy from one winding of a motor phase to another winding of the same motor phase, other embodiments exist. For example, the processes and systems described herein may be modified to recirculate energy from a winding of a motor phase to another winding of another motor phase. In another example, the processes and systems described herein may be modified to recirculate energy from any suitable energy storage device (e.g., an inductor, an inductive load, a capacitor, a capacitive load) to any other suitable energy storage device.

[0075] Although the present specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or what may be claimed, but rather as descriptions of features that may be specific to a particular embodiment of a particular invention. Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, even if features are described herein as functioning in a particular combination and are initially claimed as such, one or more features from the claimed combination may, in some cases, be deleted from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0076] Similarly, although operations are illustrated in the figures in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown, or in sequential order, or that all of the illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system modules and components in the embodiments described herein should not be understood as requiring such separation in all embodiments, and it should be understood that the program components and systems described may generally be integrated into a single product or packaged into multiple products.

[0077] Specific embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims may be performed in a different order and still achieve desirable results. As an example, the processes illustrated in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous. The following is a summary of the claims as originally filed: [1] A tube occluder system comprising: a tube clamping device configured to releasably receive a tube; a stepper motor having a first winding and a second winding and arranged to adjust the amount of compression applied to the tube by the tube clamping device; a drive system electrically coupled to the stepper motor, a first winding output port configured to electrically connect to a first winding input of the first winding; a first winding input port configured to electrically connect to a first winding output of the first winding; a second winding output port configured to electrically connect to a second winding input of the second winding; a second winding input port configured to electrically connect to a second winding output of the second winding; a first snubber circuit in electrical communication between the first winding input port and the second winding output port; a second snubber circuit in electrical communication between the second winding input port and the first winding output port; A drive system comprising: A tube occluder system comprising: [2] The tube occluder system of [1], wherein the first snubber circuit comprises a first resistor and a first diode in series electrical connection with the first resistor, the first diode configured to pass current from the first winding input port to the second winding output port and prevent current flow from the second winding output port to the first winding input port. [3] The tube occluder system of [2], wherein the second snubber circuit comprises a second resistor and a second diode in series electrical connection with the second resistor, the second diode configured to pass current from the second winding input port to the first winding output port and prevent current flow from the first winding output port to the second winding input port. [4] The tube occluder system of any one of [1] to [3], further comprising: a power bus; a first diode configured to pass current from the power bus to the first winding output port; and a second diode configured to pass current from the power bus to the second winding output port. [5] The tube occluder system of any one of [1] to [4], further comprising: a low potential power bus; a first switch configured to controllably connect the first winding input port to the low potential power bus; a second switch configured to controllably connect the second winding input port to the low potential power bus; and at least one resistor configured to limit current flow from the first winding input port to the low potential power bus and to limit current flow from the second winding input port to the low potential power bus. [6] A method for recycling energy in a stepper motor, the method comprising: providing power to a first output and a second output on a power bus; applying power to a first electrical load electrically connected to the first output; switching a first switch to interrupt the flow of power from the first electrical load to a low potential bus; switching a second switch to permit power from the power bus to flow from the second output, through a second electrical load electrically connected to the second output, and to the low potential bus; directing power flow from the first electrical load to the second output with a first snubber circuit; switching the second switch to interrupt the flow of power from the second electrical load to the low potential bus; switching the first switch to allow power from the power bus to flow from the first output, through the first electrical load, and to the low potential bus; directing power flow from the second electrical load to the first output with a second snubber circuit; A method comprising: [7] preventing a reverse flow of current from the first snubber circuit to the power bus; and preventing a backflow of current from the second snubber circuit to the power bus; and The method of [6], further comprising: [8] The first snubber circuit includes a first resistor and a first diode in series electrical connection with the first resistor, and directing the flow of power from the first electrical load to the second output by the first snubber circuit is permitting a flow of power from the first electrical load at a first input to the second output through the first diode; preventing a flow of power from the second output to the first input by the first diode; The method according to [6], comprising: [9] The second snubber circuit includes a second resistor and a second diode in series electrical connection with the second resistor, and directing the flow of power from the second electrical load to the first output by the second snubber circuit is permitting a flow of power from the second electrical load at the second input to the first output by the second diode; preventing a flow of power from the first output to the second input by the second diode; The method according to [8], comprising:

[10] The first electrical load comprises a first inductive electrical load; the second electrical load comprises a second inductive electrical load; switching the first switch to permit power from the power bus to flow from the first output, through the first electrical load, and to the low potential bus comprises energizing the first inductive electrical load; The method of any one of [6] to [9], wherein switching the second switch comprises energizing the second inductive electrical load so as to allow power from the power bus to flow from the second output, through the second electrical load electrically connected to the second output, and to the low potential bus.

[11] The method of

[10] , wherein the flow of power from the first electrical load to the first output comprises, at least in part, a current flow caused by an inductance of the first inductive electrical load, and the flow of power from the second electrical load to the second output comprises, at least in part, a current flow caused by an inductance of the second inductive electrical load.

[12] The first electrical load comprises a first winding of a stepping motor; The method according to any one of [6] to

[11] , wherein the second electrical load comprises a second winding of the stepping motor.

[13] Switching the first switch to permit power from the power bus to flow from the first output, through the first electrical load, and to the low potential bus comprises energizing the first winding;

[12] The method of claim 12, wherein switching the second switch comprises energizing the second winding to allow power from the power bus to flow from the second output, through the second electrical load electrically connected to the second output, and to the low potential bus.

[14] controllably switching the first switch and the second switch to urge rotation of the stepper motor in a first direction; actuating, by the stepper motor, a tube clamping device configured to releasably receive a tube; adjusting an amount of compression applied to the tube by the tube clamping device based on the actuation; and The method of claim 13, further comprising:

[15] An electric drive system comprising: a first power output port configured to electrically connect to a first load input of a first electrical load; a first power input port configured to electrically connect to a first load output of the first electrical load; a second power output port configured to electrically connect to a second load input of a second electrical load; a second power input port configured to electrically connect to a second load output of the second electrical load; and a first snubber circuit in electrical communication between the first load input port and the second load output port; a second snubber circuit in electrical communication between the second load input port and the first load output port; An electric drive system comprising:

[16] The first snubber circuit comprises a first resistor and a first diode in series electrical connection with the first resistor, the first diode configured to pass current from the first load input port to the second load output port and to prevent current flow from the second load output port to the first load input port;

[15] . The electric drive system of claim 15, wherein the second snubber circuit comprises a second resistor and a second diode in series electrical connection with the second resistor, the second diode configured to pass current from the second load input port to the first load output port and prevent current flow from the first load output port to the second load input port.

[17] The electric drive system of

[15] or

[16] , further comprising: a power bus; a first diode configured to pass current from the power bus to the first load output port; and a second diode configured to pass current from the power bus to the second load output port.

[18] The electric drive system of any one of

[15] to

[17] , further comprising: a low potential power bus; a first switch configured to controllably connect the first load input port to the low potential power bus; a second switch configured to controllably connect the second load input port to the low potential power bus; and at least one resistor configured to limit current flow from the first load input port to the low potential power bus and to limit current flow from the second load input port to the low potential power bus.

[19] The electric drive system according to any one of

[15] to

[18] , wherein at least one of the first electric load and the second electric load is an inductive electric load.

[20] An electric drive system according to any one of

[15] to

[19] , wherein the first electrical load is a first winding of a stepping motor, and the second electrical load is a second winding of the stepping motor.

Claims

1. 1. An electric drive system comprising: a first power output port configured to electrically connect to a first load input of a first electrical load; a first power input port configured to electrically connect to a first load output of the first electrical load; a second power output port configured to electrically connect to a second load input of a second electrical load; a second power input port configured to electrically connect to a second load output of the second electrical load; a first snubber circuit in electrical communication between the first power input port and the second power output port; a second snubber circuit in electrical communication between the second power input port and the first power output port; the first snubber circuit comprises a first resistor and a first diode in series electrical connection with the first resistor, the first diode configured to pass current from the first power input port to the second power output port and to prevent current flow from the second power output port to the first power input port; the second snubber circuit comprises a second resistor and a second diode in series electrical connection with the second resistor, the second diode configured to pass current from the second power input port to the first power output port and prevent current flow from the first power output port to the second power input port.

2. An electric drive system, a first power output port configured to electrically connect to a first load input of a first electrical load; a first power input port configured to electrically connect to a first load output of the first electrical load; a second power output port configured to electrically connect to a second load input of a second electrical load; a second power input port configured to electrically connect to a second load output of the second electrical load; a first snubber circuit in electrical communication between the first power input port and the second power output port; a second snubber circuit in electrical communication between the second power input port and the first power output port; 11. The electric drive system, further comprising: a power bus; a first diode configured to pass current from the power bus to the first power output port; and a second diode configured to pass current from the power bus to the second power output port.

3. The electric drive system of claim 1 or 2, wherein at least one of the first electrical load and the second electrical load is an inductive electrical load.

4. 4. The electric drive system of claim 1, wherein the first electrical load is a first winding of a stepper motor and the second electrical load is a second winding of the stepper motor.

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