H-bridge push-pull excitation circuit for rotary transformer

Abstract

An excitation circuit for a transformer-based measurement device is provided, the transformer-based measurement device having an excitation coil. The excitation circuit comprises an H-bridge circuit and a compensation circuit. The H-bridge circuit is used for converting the single-pole square wave signal into a double-pole square wave signal so as to drive the magnet exciting coil. The H-bridge circuit includes push-pull amplifiers arranged in two branches. A compensation circuit is coupled between the two branches of the H-bridge circuit and compensates for any distortion in the bipolar square wave signal caused by an excitation coil that is an inductive load on the H-bridge circuit.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to position sensors, and in particular to position sensors including excitation circuits for transformer-based measurement devices. BACKGROUND

[0002] Many transformer-based measurement devices have been developed to detect the position of an object. One type of transformer-based measurement device is a rotary transformer used to detect the angular position of a rotating object, such as a motor shaft. Another type of transformer-based measurement device is a linear variable differential transformer used to detect a linear position.

[0003] In particular, a rotary transformer is an electrical device used to detect the angular position of a rotating object, such as a motor shaft. It is a rotary transformer that works by modulating the amplitude of a carrier waveform according to the angular position of the rotating object. The ability of a rotary transformer to measure angular position makes it ideal for various aerospace, automotive, industrial, medical, and military applications.

[0004] In aerospace, rotary transformers are used to detect the position of aircraft control surfaces, such as ailerons, flaps, rudders, and elevators. Rotary transformers can also be used to measure the position of engines, propellers, and other components. Rotary transformers are used in navigation and guidance systems for unmanned aerial vehicles (UAVs) and satellites.

[0005] In addition to the use of rotary transformers in aerospace, rotary transformers are used in many other industries. Rotary transformers are used in automotive applications to detect the position of steering wheels, brakes, and transmissions. In industrial applications, rotary transformers are used to measure the position of conveyor belts, cranes, and other industrial machinery. In medical applications, rotary transformers are used to measure the position of robotic arms used in surgical procedures.

[0006] Sensors including rotary transformers typically include an excitation circuit for driving an excitation coil of the rotary transformer, which excitation coil causes an output signal to be picked up by a sense coil, which output signal can be used to determine an angular position. Many conventional rotary transformer excitation circuits include operational amplifiers, such as an inverting amplifier and a non-inverting amplifier. But when the particular application of the sensor requires a square wave excitation, these excitation circuits can produce a bipolar signal with slightly different positive and negative amplitudes due to the different characteristics and tolerances of the inverting amplifier and the non-inverting amplifier. These conventional excitation circuits are also typically complex, including a large number of components that reduce the reliability of the conventional excitation circuits.

[0007] Therefore, it would be desirable to have a system and method that takes into account at least some of the issues discussed above, as well as possibly other issues. SUMMARY

[0008] Example implementations of the present disclosure relate to position sensors, and in particular to transformer-based measurement devices (e.g., a rotary transformer or a linear variable differential transformer, but not limited thereto) that include an H-bridge push-pull excitation circuit. In this regard, example implementations provide an excitation circuit having an H-bridge circuit that includes a push-pull amplifier arranged in two branches. Push-pull amplifiers are typically used for capacitive loads; however, in this excitation circuit of example implementations, the push-pull amplifier is used with the inductive load of the excitation coil of the rotary transformer. Accordingly, the excitation circuit can also include a compensation circuit for compensating for any distortion in the output signal of the excitation coil caused by the excitation coil as an inductive load on the H-bridge circuit.

[0009] The H-bridge circuit including the push-pull amplifier can reduce the complexity and number of components in the excitation circuit, which can increase the reliability of the excitation circuit. The H-bridge circuit can also enable the circuit to produce a bipolar output signal having equal (or substantially equal) positive and negative amplitudes.

[0010] The present disclosure thus includes, but is not limited to, the following example implementations.

[0011] Some example implementations provide a position sensor including a transformer-based measurement device connectable to a movable object, the transformer-based measurement device including an excitation coil and a plurality of sense coils; and an excitation circuit for converting a unipolar square wave signal to a bipolar square wave signal to drive the excitation coil to generate an alternating magnetic field and induce an output signal in the plurality of sense coils that varies according to a position of the object, the excitation circuit including: an H-bridge circuit including a push-pull amplifier arranged in two branches, the H-bridge circuit for converting the unipolar square wave signal to the bipolar square wave signal; and a compensation circuit coupled between the two branches of the H-bridge circuit, the compensation circuit for compensating for any distortion in the bipolar square wave signal caused by the excitation coil as an inductive load on the H-bridge circuit.

[0012] Some example implementations provide an excitation circuit including: an H-bridge circuit for converting a unipolar square wave signal to a bipolar square wave signal to drive an excitation coil of a transformer-based measurement device, the H-bridge circuit including a push-pull amplifier arranged in two branches; and a compensation circuit coupled between the two branches of the H-bridge circuit, the compensation circuit for compensating for any distortion in the bipolar square wave signal caused by the excitation coil as an inductive load on the H-bridge circuit.

[0013] Some example implementations provide an excitation circuit including a gate drive circuit to convert a unipolar square wave signal to a bipolar square wave signal to drive an excitation coil of a transformer-based measurement device, the gate drive circuit including a non-inverting gate driver and an inverting gate driver arranged in two legs to implement an H-bridge circuit, and a compensation circuit coupled between the two legs of the H-bridge circuit, the compensation circuit to compensate for any distortion in the bipolar square wave signal caused by the excitation coil as an inductive load on the H-bridge circuit.

[0014] Some example implementations provide a method including converting a unipolar square wave signal to a bipolar square wave signal to drive an excitation coil, converting the unipolar square wave signal including applying the unipolar square wave signal to an H-bridge circuit having a push-pull amplifier arranged in two legs, the H-bridge circuit converting the unipolar square wave signal to the bipolar square wave signal, and compensating for distortion in the bipolar square wave signal caused by the excitation coil as an inductive load on the H-bridge circuit.

[0015] These and other features, aspects, and advantages of the present disclosure will become evident to those skilled in the art from a reading of the following detailed description, together with the accompanying drawings. The present disclosure includes any combination of two, three, four, or more of the features or elements set forth in the present disclosure, whether or not explicitly set forth in a particular example implementation described herein. The present disclosure is intended to be construed broadly and to encompass any and all combinations of the features or elements set forth in the present disclosure, whether or not such combinations are explicitly described in the present disclosure. The present disclosure is intended to be read in its entirety and with the understanding that the disclosure is not limited to the specific examples described herein. The present disclosure is intended to encompass all modifications and variations within the scope of the present disclosure, whether or not such modifications and variations are described herein.

[0016] Accordingly, it will be appreciated that this Summary is provided merely for purposes of summarizing some example implementations so as to provide a basic understanding of the disclosure. Accordingly, it will be appreciated that the above-described example implementations are merely examples and should not be construed as limiting the scope or spirit of the disclosure in any way. Other example implementations, aspects, and advantages will become apparent from a reading of the following detailed description taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of some of the described example implementations. BRIEF DESCRIPTION OF DRAWINGS

[0017] Accordingly, having generally described the example implementations of the present disclosure, reference will now be made to the drawings, which are not necessarily drawn to scale, and wherein:

[0018] Figure 1Ais a block diagram of a position sensor according to some example implementations of the present disclosure, the position sensor comprising: an excitation circuit comprising an H-bridge circuit having a push-pull amplifier arranged in two legs; and a compensation circuit coupled between the two legs;

[0019] Figure 1B is a block diagram of a position sensor according to some example implementations, similar to the position sensor shown in Figure 1A and comprising a rotor coil.

[0020] Figure 1C is a block diagram of a position sensor according to some example implementations, similar to the position sensor shown in Figure 1A and comprising a processing circuit;

[0021] Figure 2 illustrates a unipolar square wave signal and a bipolar square wave signal according to some example implementations;

[0022] Figure 3 illustrates an excitation circuit according to some example implementations, which can correspond to the excitation circuit of Figure 1 ;

[0023] Figure 4 illustrates another implementation of the excitation circuit of Figure 3 with a compensation circuit according to some example implementations;

[0024] Figure 5 illustrates an excitation circuit according to some example implementations, which can correspond to the excitation circuit of Figure 1, wherein the H-bridge circuit is embodied by a gate drive circuit;

[0025] Figure 6 illustrates another implementation of the excitation circuit of Figure 5 with a compensation circuit according to some example implementations;

[0026] Figure 7 , Figure 8 , Figure 9 and Figure 10 illustrate excitation circuits according to some example implementations of Figure 3 , Figure 4 , Figure 5 and Figure 6 respectively, wherein the excitation circuit comprises a voltage follower circuit; and

[0027] Figure 11A and Figure 11B are flowcharts of methods according to various example implementations. DETAILED DESCRIPTION

[0028] Some embodiments of the disclosure will now be described, by way of example, with reference to the following drawings. In the drawings, like references may refer to similar elements throughout the several views. Like numbers refer to like elements throughout.

[0029] References to first, second, etc. should not be interpreted as implying particular order unless otherwise specified or clear from the context. A feature described as on top of another feature (unless otherwise specified or clear from the context) can instead be on the bottom, and vice versa; and similarly, a feature described as on the left of another feature can instead be on the right, and vice versa. Further, while reference may be made herein to quantitative measurements, values, geometric relationships, etc., any one or more of these quantitative measurements, values, geometric relationships, etc., if not all, can be approximate, to account for acceptable variations that may occur, such as due to engineering tolerances, etc., unless otherwise stated.

[0030] As used herein, unless otherwise specified or clear from the context, an "or" of a set of operands is an "inclusive or" and is true if one or more of the operands is true, as opposed to an "exclusive or," which is false if all of the operands are true. Thus, for example, "[A] or [B]" is true if [A] is true, or if [B] is true, or if both [A] and [B] are true. Also, unless otherwise specified or clearly directed to a singular form from the context, the article "a" means "one or more." Further, it should be understood that the terms "data," "content," "digital content," "information," and similar terms may be used interchangeably, unless otherwise specified.

[0031] Example embodiments of the present disclosure relate generally to position sensors, and in particular to position sensors including excitation circuits for transformer-based measurement devices.

[0032] Figure 1Ais a block diagram of a position sensor 100A for measuring a position of a movable object according to some example implementations of the present disclosure. As shown, the position sensor includes a transformer-based measurement device 102 and an excitation circuit 104. The transformer-based measurement device is connectable to an object 106. The transformer-based measurement device includes an excitation coil 108 and a plurality of sense coils 110. In some examples, the transformer-based measurement device is a rotary transformer that includes a rotor that is connectable to a rotatable shaft (object 106). In other examples, the transformer-based measurement device is a linear variable differential transformer (LVDT) that includes a core that is connectable to a linearly movable object 106.

[0033] The excitation circuit 104 can convert the unipolar square wave signal 112 to a bipolar square wave signal 114 to drive the excitation coil 108 of the transformer-based measurement device 102 to generate an alternating magnetic field and induce an output signal in the plurality of sense coils 110 that varies according to a position of the object 106. In the case of a rotary transformer, the output signal can vary according to an angular position of the rotor and, thus, an angular position of the object 106; and in the case of an LVDT, the output signal can vary according to a linear position of the core and, thus, a linear position of the object 106.

[0034] In some examples, the excitation circuit 104 includes an H-bridge circuit 116 having push-pull amplifiers 118A, 118B arranged in two branches. The H-bridge circuit can convert the unipolar square wave signal 112 to the bipolar square wave signal 114. As indicated in the SUMMARY section, the push-pull amplifiers 118A, 118B of the excitation circuit 104 are used with the inductive load of the excitation coil 108 of the transformer-based measurement device 102. Accordingly, the excitation circuit 104 can also include a compensation circuit 120 for compensating for any distortion in the bipolar square wave signal 114 caused by the excitation coil 108 as an inductive load on the H-bridge circuit 116. In this regard, the compensation circuit can compensate for an inductive lag of current in the push-pull amplifiers 118A, 118B. The lag of current results in distortion of the bipolar square wave signal 114 due to the interaction with the push-pull amplifiers 118A, 118B. In this regard, when the direction of current through the push-pull amplifiers 118A, 118B is reversed, the voltage drop across the push-pull amplifiers 118A, 118B is also reversed; and since the excitation coil 108 is inductive, the current lags the applied voltage. The compensation network can make the current in phase with the voltage and, thus, reduce, if not eliminate, the resulting distortion. In some examples, the compensation circuit can operate in resonance with the excitation coil; and in these examples, the compensation circuit can be referred to as a resonant compensation circuit.

[0035] One example of a suitable unipolar square wave signal 112 is a pulse width modulated (PWM) signal, which can be provided with a 50% duty cycle. Figure 2 Further examples illustrate a unipolar square wave signal 112 and a bipolar square wave signal 114, which can be amplified relative to the unipolar square wave signal 112. In some examples, the bipolar square wave signal 114 includes pulses that alternate in amplitude between the first supply rail and the second supply rail. Also as shown, in some examples, the bipolar square wave signal can be output as a differential signal pair 216A, 216B to input to respective ends of the excitation coil 108 of the transformer-based measurement device 102.

[0036] Returning to Figure 1A The excitation coil 108 can be driven to generate an alternating magnetic field, and an output signal that varies according to the position of the object 106 is induced in the plurality of sense coils 110. In this regard, the excitation coil 108 can be magnetically coupled to the sense coils 110. In some configurations of the transformer-based measurement device 102, such as in the case of an LVDT that includes a core, the core can be ferromagnetic, and the excitation coil can be magnetically coupled to the sense coils through the ferromagnetic core.

[0037] In some configurations of the transformer-based measurement device 102, such as in the case of a rotary transformer that includes a rotor, the excitation coil 108 can be located on the rotor, and the plurality of sense coils 110 can be stationary relative to the rotor that moves with the object 106 (e.g., for a rotary transformer, the plurality of sense coils 110 can be located on a stator in which the rotor rotates). In other configurations, as Figure 1B shown, for the position sensor 100B, the transformer-based measurement device 102 can include a rotor coil 122, and the excitation coil 108 and the plurality of sense coils 110 can both be stationary relative to the rotor coil 122 (e.g., located on a stator). The excitation coil 108 can be magnetically coupled to the sense coils 110 through the rotor coil 122. Thus, the alternating magnetic field generated by the excitation coil 108 can induce a current in the rotor coil 122, which current induces a secondary alternating magnetic field and an output signal in the plurality of sense coils 110.

[0038] Figure 1C is similar to Figure 1AA block diagram of the position sensor 100A shown and the position sensor 100C including the processing circuit 124. In some examples, the processing circuit 124 can process output signals from the plurality of sense coils 110 to determine a position of the object 106 to which the transformer-based measurement device 102 is capable of being connected. In various examples, the processing circuit 124 can include a demodulation circuit, a signal conditioning circuit, or an analog-to-digital converter (ADC), without limitation. The processing circuit 124 can also include a general purpose or special purpose processor, microprocessor, controller, or microcontroller, without limitation.

[0039] Figure 3 An excitation circuit 300 is illustrated that can correspond to the excitation circuit 104 of FIG. 1, in accordance with some example implementations. As shown, the unipolar square wave signal 112 can be a first unipolar square wave signal 302, and the excitation circuit 300 can include a polarity inverter 304 to convert the first unipolar square wave signal 302 to a second unipolar square wave signal 306 having a polarity opposite that of the first unipolar square wave signal 302. The excitation circuit 300 can also optionally include buffers at inputs of an H-bridge circuit 308 to match the timing, i.e., phase, between the first unipolar square wave signal 302 and the second unipolar square wave signal 306.

[0040] As also shown, the excitation circuit 300 includes the H-bridge circuit 308 to convert the first unipolar square wave signal 302 and the second unipolar square wave signal 306 to the bipolar square wave signal 114 to drive the excitation coil 108 (not shown) of the transformer-based measurement device 102. The H-bridge circuit 308 can include a first push-pull amplifier 310A and a second push-pull amplifier 310B arranged in two branches. The first push-pull amplifier 310A can be driven by the first unipolar square wave signal 302, and the second push-pull amplifier 310B can be driven by the second unipolar square wave signal 306. The excitation circuit 300 can also include a compensation circuit 312 coupled between the two branches of the H-bridge circuit 308. In this regard, the compensation circuit 312 can compensate for any distortion in the bipolar square wave 114 signal caused by the excitation coil 108 as an inductive load on the H-bridge circuit 308.

[0041] In some examples, respective ones of the first push-pull amplifier 310A and the second push-pull amplifier 310B include a complementary pair of transistors connected in a push-pull configuration. Gates of the complementary pair of transistors of the first push-pull amplifier 310A are driven by the first unipolar square wave signal 302, and gates of the complementary pair of transistors of the second push-pull amplifier 310B are driven by the second unipolar square wave signal 306. The first push-pull amplifier 310A and the second push-pull amplifier 310B can output respective signals of the differential signal pair 216A and 216B so as to form the bipolar square wave signal 114.

[0042] As shown in some more specific examples, the first push-pull amplifier 310A includes a complementary transistor pair M 31 M 32 Furthermore, the second push-pull amplifier 310B includes a complementary transistor pair M. 33 M 34 The complementary transistor pair for the respective push-pull amplifiers in the first push-pull amplifier 310A and the second push-pull amplifier 310B includes a pair for coupling the excitation coil to the first power supply rail V. CC The corresponding high-side transistor M 31 / M 33 and the corresponding low-side transistor M for coupling the excitation coil to the second power supply rail (denoted as ground). 32 / M 34 The complementary transistor pair can be any of a variety of different types of transistors. In the illustrated example, the transistors are metal-oxide-semiconductor field-effect transistors (MOSFETs). Specifically, the corresponding high-side transistor M... 31 / M 33 It is a p-type MOSFET, and the corresponding low-side transistor M 32 / M 34 It is an n-type MOSFET.

[0043] In some examples, the compensation circuitry includes a first compensation circuit R coupled to the output of the first push-pull amplifier 310A. 31 C 31 and the second compensation circuit R coupled to the output of the second push-pull amplifier 206B 32 C 32 In the non-limiting example shown, resistor R 31 The first end is coupled to the output of the first push-pull amplifier 310A, and the second end resistor R 31 Through capacitor C 31 Coupled to the second power supply rail (ground). Similarly, resistor R 32 The first end is coupled to the output of the second push-pull amplifier 310B, and the second end resistor R 32 Through capacitor C 32 Coupled to the second power supply rail (ground). Therefore, the first compensation circuit R 31 C 31 Second compensation circuit R 32 C 32 Coupled between the two branches of the H-bridge circuit 308 via a second power supply rail. In other examples, such as... Figure 4 As shown, the compensation circuit 408 includes R coupled between the output terminals of the first push-pull amplifier 310A and the second push-pull amplifier 310B. 41 C41 In Figure 4 In the non-limiting example shown, the resistor R 41 and the capacitor C 41 are coupled in series between the outputs of the first totem-pole amplifier 310A and the second totem-pole amplifier 310B. The compensation circuit 408 is shown as a resistor-capacitor (RC) circuit. However, it should be understood that the compensation circuit 408 can be implemented in a variety of different ways.

[0044] In some examples, the polarity inverter 304 and the H-bridge circuit 308 are embodied by a gate drive circuit that includes a non-inverting gate driver that includes the first totem-pole amplifier 310A and an inverting gate driver that includes the polarity inverter and the second totem-pole amplifier 310B. In some of these examples, the gate drive circuit can output the bipolar square wave signal 114 as a pair of differential signals 216A, 216B output by respective ones of the non-inverting gate driver and the inverting gate driver of the gate drive circuit.

[0045] Figure 5 and Figure 6 Examples are illustrated in which the field excitation circuit includes a gate drive circuit 504 having a non-inverting gate driver 506A and an inverting gate driver 506B that output respective ones of a pair of differential signals 216A, 216B. Some examples of suitable gate driver circuits are the following power MOSFET drivers from Microchip Technology Incorporated, Chandler, Arizona, all of which include a non-inverting gate driver and an inverting gate driver: TC4425A, TC4428A, MIC4425, MIC4128, MIC4428, MCP14E8, MCP14A0305, MCP14E5, MCP14E5, MCP14A0455, MCP1405A, and MCP4225. Other examples of suitable gate driver circuits include the TC1412N and MCP14A0152 power MOSFET drivers from Microchip Technology Incorporated that include a non-inverting gate driver, and the TC1412 and MCP14A0151 power MOSFET drivers from Microchip Technology Incorporated that include an inverting gate driver.

[0046] In some examples, the field excitation circuit 104 includes a voltage buffer, such as a voltage follower circuit, for transmitting the bipolar square wave signal 114 from the H-bridge circuit 116 to the compensation circuit 120. In Figure 7 andFigure 8 In some examples, for example, the excitation circuit includes a voltage follower circuit 720 for transmitting the bipolar square wave signal from the H-bridge circuit 308 to the compensation circuits 312, 408, respectively. Also in some examples, for example, the excitation circuit includes a voltage follower circuit 720 for transmitting the bipolar square wave signal from the gate drive circuit 504 to the compensation circuits 508, 608. Figure 9 and Figure 10 In some examples, for example, the excitation circuit includes a voltage follower circuit 720 for transmitting the bipolar square wave signal from the H-bridge circuit 308 to the compensation circuits 312, 408, respectively. Also in some examples, for example, the excitation circuit includes a voltage follower circuit 720 for transmitting the bipolar square wave signal from the gate drive circuit 504 to the compensation circuits 508, 608.

[0047] In some examples, for example, the excitation circuit includes a voltage follower circuit 720 for transmitting the bipolar square wave signal from the H-bridge circuit 308 to the compensation circuits 312, 408, respectively. Also in some examples, for example, the excitation circuit includes a voltage follower circuit 720 for transmitting the bipolar square wave signal from the gate drive circuit 504 to the compensation circuits 508, 608. Figures 7 to 10 In some examples, according to some examples, the voltage follower circuit 720 includes a pair of transistors and diodes for a respective one of the first push-pull amplifier 310A and the second push-pull amplifier 310B ( Figure 7 and Figure 8 ) or the non-inverting gate driver 506A and the inverting gate driver 506B ( Figure 9 and Figure 10 ). Specifically, the voltage follower circuit 720 includes transistors M 71 , M 72 and breakover diodes D 71 , D 72 for the first push-pull amplifier 310A / non-inverting gate driver 506A, and transistors M 73 , M 74 and breakover diodes D 73 , D 74 for the second push-pull amplifier 310B / non-inverting gate driver 506B. As shown, the transistors are implemented with bipolar junction transistors (BJTs). However, it should be noted that the voltage follower circuit can be implemented in a variety of different ways.

[0048] Figure 11A and Figure 11B is a flowchart of a method 1100 implemented in accordance with various examples. The method includes converting a unipolar square wave signal to a bipolar square wave signal to drive an excitation coil, as shown at block 1102. Figure 11A

[0049] Converting the unipolar square wave signal includes applying the unipolar square wave signal to an H-bridge circuit having a push-pull amplifier arranged in two legs, the H-bridge circuit converting the unipolar square wave signal to a bipolar square wave signal, as shown at block 1104. Converting the unipolar square wave signal also includes compensating for distortion in the bipolar square wave signal caused by the excitation coil as an inductive load on the H-bridge circuit, as shown at block 1106.

[0050] ​In some examples, the excitation coil belongs to a transformer-based measurement device connected to a moving object, and the excitation coil includes a plurality of sense coils. The bipolar square wave signal drives the excitation coil to generate an alternating magnetic field, and an output signal that varies according to a position of the object is induced in the plurality of sense coils. In some of these examples, the method 1100 includes processing the output signal to determine the position of the object, as shown at block 1108 of FIG. 11. Figure 11B

[0051] In some examples, the unipolar square wave signal is a first unipolar square wave signal, and converting the unipolar square wave signal at block 1102 includes converting the first unipolar square wave signal to a second unipolar square wave signal having an opposite polarity to the first unipolar square wave signal. In some of these examples, the push-pull amplifier includes a first push-pull amplifier driven by the first unipolar square wave signal and a second push-pull amplifier driven by the second unipolar square wave signal.

[0052] In some examples in which the push-pull amplifier includes the first push-pull amplifier and the second push-pull amplifier, the distortion is compensated at block 1106 using a first compensation circuit coupled to an output of the first push-pull amplifier and a second compensation circuit coupled to an output of the second push-pull amplifier.

[0053] In some examples in which the push-pull amplifier includes the first push-pull amplifier and the second push-pull amplifier, the distortion is compensated at block 1106 using a compensation circuit coupled between outputs of the first push-pull amplifier and the second push-pull amplifier.

[0054] In some examples, the distortion is compensated at block 1106 using a resistor-capacitor (RC) circuit.

[0055] As explained above and reiterated below, the present disclosure includes, but is not limited to, the following example implementations.

[0056] ​Clause 1. A position sensor comprising: a transformer-based measurement device connectable to a movable object, the transformer-based measurement device comprising an excitation coil and a plurality of sense coils; and an excitation circuit to convert a unipolar square wave signal to a bipolar square wave signal to drive the excitation coil to generate an alternating magnetic field and induce an output signal in the plurality of sense coils that varies according to a position of the object, the excitation circuit comprising: an H-bridge circuit comprising push-pull amplifiers arranged in two legs, the H-bridge circuit to convert the unipolar square wave signal to the bipolar square wave signal; and a compensation circuit coupled between the two legs of the H-bridge circuit, the compensation circuit to compensate for any distortion in the bipolar square wave signal caused by the excitation coil as an inductive load on the H-bridge circuit.

[0057] Clause 2. The position sensor of clause 1, wherein the position sensor comprises processing circuitry to process the output signal to determine the position of the object.

[0058] Clause 3. The position sensor of clause 1 or clause 2, wherein the transformer-based measurement device is a rotary transformer, the object to which the transformer-based measurement device is connectable is a rotatable shaft, and the output signal in the plurality of sense coils varies according to an angular position of the shaft.

[0059] Clause 4. The position sensor of any one of clauses 1-3, wherein the transformer-based measurement device is a linear variable differential transformer (LVDT), wherein the object to which the transformer-based measurement device is connectable is linearly movable, and the output signal in the plurality of sense coils varies according to a linear position of the object.

[0060] Clause 5. The position sensor of any one of clauses 1-4, wherein the bipolar square wave signal comprises pulses that alternate in amplitude between a first supply rail and a second supply rail.

[0061] Clause 6. The position sensor of any one of clauses 1-5, wherein a respective one of the push-pull amplifiers comprises a complementary pair of transistors connected in a push-pull configuration.

[0062] Clause 7. The position sensor of any one of clauses 1-6, wherein the unipolar square wave signal is a first unipolar square wave signal, and the excitation circuit includes a polarity inverter to convert the first unipolar square wave signal to a second unipolar square wave signal having a polarity opposite the first unipolar square wave signal, and wherein the push-pull amplifier includes a first push-pull amplifier driven by the first unipolar square wave signal and a second push-pull amplifier driven by the second unipolar square wave signal.

[0063] Clause 8. The position sensor of clause 7, wherein respective ones of the first push-pull amplifier and the second push-pull amplifier include a complementary pair of transistors connected in a push-pull configuration.

[0064] Clause 9. The position sensor of clause 8, wherein gates of the complementary pair of transistors of the first push-pull amplifier are driven by the first unipolar square wave signal, and gates of the complementary pair of transistors of the second push-pull amplifier are driven by the second unipolar square wave signal.

[0065] Clause 10. The position sensor of clause 8 or clause 9, wherein the complementary pair of transistors includes a high-side transistor to couple the excitation coil to a first supply rail and a low-side transistor to couple the excitation coil to a second supply rail.

[0066] Clause 11. The position sensor of any one of clauses 1-10, wherein the H-bridge circuit is to output the bipolar square wave signal as a differential signal pair to respective ends of the excitation coil.

[0067] Clause 12. The position sensor of clause 11, wherein the push-pull amplifier outputs respective ones of the differential signal pair.

[0068] Clause 13. The position sensor of any one of clauses 1-12, wherein the push-pull amplifier includes a first push-pull amplifier and a second push-pull amplifier, and wherein the compensation circuit includes a first compensation circuit coupled to an output of the first push-pull amplifier and a second compensation circuit coupled to an output of the second push-pull amplifier.

[0069] Clause 14. The position sensor of any one of clauses 1-13, wherein the push-pull amplifier includes a first push-pull amplifier and a second push-pull amplifier, and wherein the compensation circuit is coupled between outputs of the first push-pull amplifier and the second push-pull amplifier.

[0070] Clause 15. The position sensor of any one of clauses 1-14, wherein the excitation circuit includes a voltage buffer for transmitting the bipolar square wave signal from the H-bridge circuit to the compensation circuit.

[0071] Clause 16. The position sensor of clause 15, wherein the voltage buffer is a voltage follower circuit.

[0072] Clause 17. The position sensor of any one of clauses 1-16, wherein the push-pull amplifier includes a first push-pull amplifier and a second push-pull amplifier, and wherein the H-bridge circuit is embodied by a gate drive circuit including: a non-inverting gate driver including the first push-pull amplifier; and an inverting gate driver including the second push-pull amplifier.

[0073] Clause 18. The position sensor of clause 17, wherein the gate drive circuit is for outputting the bipolar square wave signal as a pair of differential signals output by respective ones of the non-inverting gate driver and the inverting gate driver.

[0074] Clause 19. The position sensor of any one of clauses 1-18, wherein the compensation circuit is a resistor-capacitor (RC) circuit.

[0075] Clause 20. An excitation circuit, comprising: an H-bridge circuit for converting a unipolar square wave signal into a bipolar square wave signal to drive an excitation coil of a transformer-based measurement device, the H-bridge circuit including a push-pull amplifier arranged in two legs; and a compensation circuit coupled between the two legs of the H-bridge circuit, the compensation circuit for compensating for any distortion in the bipolar square wave signal caused by the excitation coil as an inductive load on the H-bridge circuit.

[0076] Clause 21. The excitation circuit of clause 20, wherein the transformer-based measurement device is a rotary transformer.

[0077] Clause 22. The excitation circuit of clause 20 or clause 21, wherein the transformer-based measurement device is a linear variable differential transformer (LVDT).

[0078] Clause 23. The excitation circuit of any one of clauses 20-22, wherein the bipolar square wave signal includes pulses that alternate in amplitude between a first supply rail and a second supply rail.

[0079] Clause 24. The field circuit of any one of clauses 20-23, wherein respective ones of the push-pull amplifiers comprise a complementary pair of transistors connected in a push-pull configuration.

[0080] Clause 25. The field circuit of any one of clauses 20-24, wherein the unipolar square wave signal is a first unipolar square wave signal, and the field circuit comprises a polarity inverter for converting the first unipolar square wave signal to a second unipolar square wave signal having a polarity opposite the first unipolar square wave signal, and wherein the push-pull amplifiers comprise a first push-pull amplifier driven by the first unipolar square wave signal and a second push-pull amplifier driven by the second unipolar square wave signal.

[0081] Clause 26. The field circuit of clause 25, wherein respective ones of the first push-pull amplifier and the second push-pull amplifier comprise a complementary pair of transistors connected in a push-pull configuration.

[0082] Clause 27. The field circuit of clause 26, wherein gates of the complementary pair of transistors of the first push-pull amplifier are driven by the first unipolar square wave signal, and gates of the complementary pair of transistors of the second push-pull amplifier are driven by the second unipolar square wave signal.

[0083] Clause 28. The field circuit of clause 26 or clause 27, wherein the complementary pair of transistors comprises a high-side transistor for coupling the field coil to a first supply rail and a low-side transistor for coupling the field coil to a second supply rail.

[0084] Clause 29. The field circuit of any one of clauses 20-28, wherein the H-bridge circuit is for outputting the bipolar square wave signal as a differential signal pair for input to respective ends of the field coil.

[0085] Clause 30. The field circuit of clause 29, wherein the push-pull amplifiers output respective ones of the differential signal pair.

[0086] Clause 31. The field circuit of any one of clauses 20-30, wherein the push-pull amplifiers comprise a first push-pull amplifier and a second push-pull amplifier, and wherein the compensation circuit comprises a first compensation circuit coupled to an output of the first push-pull amplifier and a second compensation circuit coupled to an output of the second push-pull amplifier.

[0087] Clause 32. The excitation circuit of any one of clauses 20-31, wherein the push-pull amplifier comprises a first push-pull amplifier and a second push-pull amplifier, and wherein the compensation circuit is coupled between outputs of the first push-pull amplifier and the second push-pull amplifier.

[0088] Clause 33. The excitation circuit of any one of clauses 20-32, wherein the excitation circuit comprises a voltage buffer for transmitting the bipolar square wave signal from the H-bridge circuit to the compensation circuit.

[0089] Clause 34. The excitation circuit of clause 33, wherein the voltage buffer is a voltage follower circuit.

[0090] Clause 35. The excitation circuit of any one of clauses 20-34, wherein the push-pull amplifier comprises a first push-pull amplifier and a second push-pull amplifier, and wherein the H-bridge circuit is embodied by a gate drive circuit comprising: a non-inverting gate driver comprising the first push-pull amplifier; and an inverting gate driver comprising the second push-pull amplifier.

[0091] Clause 36. The excitation circuit of clause 35, wherein the gate drive circuit is for outputting the bipolar square wave signal as a pair of differential signals output by respective ones of the non-inverting gate driver and the inverting gate driver.

[0092] Clause 37. The excitation circuit of any one of clauses 20-36, wherein the compensation circuit is a resistor-capacitor (RC) circuit.

[0093] Clause 38. An excitation circuit, comprising: a gate drive circuit for converting a unipolar square wave signal to a bipolar square wave signal to drive an excitation coil of a transformer-based measurement device, the gate drive circuit comprising a non-inverting gate driver and an inverting gate driver arranged in two legs to implement an H-bridge circuit; and a compensation circuit coupled between the two legs of the H-bridge circuit, the compensation circuit for compensating for any distortion in the bipolar square wave signal caused by the excitation coil as an inductive load on the H-bridge circuit.

[0094] Clause 39. The excitation circuit of clause 38, wherein the bipolar square wave signal comprises pulses that alternate in amplitude between a first supply rail and a second supply rail.

[0095] Clause 40. The excitation circuit of clause 38 or clause 39, wherein the gate drive circuit is to output the bipolar square wave signal as a differential signal pair output by respective ones of the non-inverting gate driver and the inverting gate driver.

[0096] Clause 41. The excitation circuit of any one of clauses 38-40, wherein the non- inverting gate driver comprises a first push-pull amplifier, and the non-inverting gate driver comprises a polarity inverter and a second push-pull amplifier.

[0097] Clause 42. The excitation circuit of clause 41, wherein the unipolar square wave signal is a first unipolar square wave signal, and the polarity inverter is to convert the first unipolar square wave signal to a second unipolar square wave signal having a polarity opposite the first unipolar square wave signal, and wherein the first push-pull amplifier is driven by the first unipolar square wave signal, and the second push-pull amplifier is driven by the second unipolar square wave signal.

[0098] Clause 43. The excitation circuit of clause 41 or clause 42, wherein respective ones of the first push-pull amplifier and the second push-pull amplifier comprise a complementary transistor pair connected in a push-pull configuration.

[0099] Clause 44. The excitation circuit of clause 43, wherein gates of the complementary transistor pair of the first push-pull amplifier are driven by the first unipolar square wave signal, and gates of the complementary transistor pair of the second push-pull amplifier are driven by the second unipolar square wave signal.

[0100] Clause 45. The excitation circuit of clause 43 or clause 44, wherein the complementary transistor pair comprises a high-side transistor to couple the field coil to a first supply rail and a low-side transistor to couple the field coil to a second supply rail.

[0101] Clause 46. The excitation circuit of any one of clauses 38-45, wherein the H-bridge circuit is to output the bipolar square wave signal as a differential signal pair to input to respective ends of the field coil.

[0102] Clause 47. The excitation circuit of clause 46, wherein the non-inverting gate driver and the inverting gate driver are to output respective ones of the differential signal pair.

[0103] Clause 48. The excitation circuit of any one of clauses 38-47, wherein the compensation circuit comprises a first compensation circuit coupled to an output of the non- inverting gate driver and a second compensation circuit coupled to an output of the inverting gate driver.

[0104] Clause 49. The excitation circuit of any one of clauses 38-48, wherein the compensation circuit is coupled between outputs of the non-inverting gate driver and the inverting gate driver.

[0105] Clause 50. The excitation circuit of any one of clauses 38-49, wherein the excitation circuit includes a voltage buffer for transmitting the bipolar square wave signal from the H-bridge circuit to the compensation circuit.

[0106] Clause 51. The excitation circuit of clause 50, wherein the voltage buffer is a voltage follower circuit.

[0107] Clause 52. The excitation circuit of any one of clauses 38-51, wherein the compensation circuit is a resistor-capacitor (RC) circuit.

[0108] Clause 53. A method comprising: converting a unipolar square wave signal to a bipolar square wave signal to drive an excitation coil, converting the unipolar square wave signal including: applying the unipolar square wave signal to an H-bridge circuit having a push-pull amplifier arranged in two legs, the H-bridge circuit converting the unipolar square wave signal to the bipolar square wave signal; and compensating for distortion in the bipolar square wave signal caused by the excitation coil as an inductive load on the H-bridge circuit.

[0109] Clause 54. The method of clause 53, wherein the excitation coil belongs to a transformer-based measurement device connected to an object that is moving, and the excitation coil includes a plurality of sense coils, the bipolar square wave signal driving the excitation coil to generate an alternating magnetic field and induce output signals in the plurality of sense coils that vary according to a position of the object, and wherein the method includes: processing the output signals to determine the position of the object.

[0110] Clause 55. The method of clause 54, wherein the transformer-based measurement device is a rotary transformer, the object to which the transformer-based measurement device is connected is a shaft that is rotating, and the output signals in the plurality of sense coils vary according to an angular position of the shaft.

[0111] Clause 56. The method of clause 54 or clause 55, wherein the transformer-based measurement device is a linear variable differential transformer (LVDT), wherein the object to which the transformer-based measurement device is connected is moving linearly, and the output signals in the plurality of sense coils vary according to a linear position of the object.

[0112] Clause 57. The method of any of clauses 53-56, wherein the bipolar square wave signal comprises pulses that alternate in amplitude between a first supply rail and a second supply rail.

[0113] Clause 58. The method of any of clauses 53-57, wherein respective ones of the push-pull amplifiers comprise complementary pairs of transistors connected in a push-pull configuration.

[0114] Clause 59. The method of any of clauses 53-58, wherein the unipolar square wave signal is a first unipolar square wave signal, and converting the unipolar square wave signal comprises converting the first unipolar square wave signal to a second unipolar square wave signal of opposite polarity to the first unipolar square wave signal, and wherein the push-pull amplifiers comprise a first push-pull amplifier driven by the first unipolar square wave signal and a second push-pull amplifier driven by the second unipolar square wave signal.

[0115] Clause 60. The method of clause 59, wherein respective ones of the first push-pull amplifier and the second push-pull amplifier comprise complementary pairs of transistors connected in a push-pull configuration.

[0116] Clause 61. The method of clause 60, wherein gates of the complementary pairs of transistors of the first push-pull amplifier are driven by the first unipolar square wave signal, and gates of the complementary pairs of transistors of the second push-pull amplifier are driven by the second unipolar square wave signal.

[0117] Clause 62. The method of clause 60 or clause 61, wherein the complementary pairs of transistors comprise a high-side transistor for coupling the field coil to a first supply rail and a low-side transistor for coupling the field coil to a second supply rail.

[0118] Clause 63. The method of any of clauses 53-62, wherein the H-bridge circuit outputs the bipolar square wave signal as a pair of differential signals for input to respective ends of the field coil.

[0119] Clause 64. The method of clause 63, wherein the push-pull amplifiers output respective ones of the pair of differential signals.

[0120] Clause 65. The method of any of clauses 53-64, wherein the push-pull amplifiers comprise a first push-pull amplifier and a second push-pull amplifier, and wherein the distortion is compensated using a first compensation circuit coupled to an output of the first push-pull amplifier and a second compensation circuit coupled to an output of the second push-pull amplifier.

[0121] Clause 66. The method of any one of clauses 53-65, wherein the push-pull amplifier comprises a first push-pull amplifier and a second push-pull amplifier, and wherein the distortion is compensated using a compensation circuit coupled between outputs of the first push-pull amplifier and the second push-pull amplifier.

[0122] Clause 67. The method of any one of clauses 53-66, wherein the push-pull amplifier comprises a first push-pull amplifier and a second push-pull amplifier, and wherein the H-bridge circuit is embodied by a gate drive circuit comprising: a non-inverting gate driver comprising the first push-pull amplifier; and an inverting gate driver comprising the second push-pull amplifier.

[0123] Clause 68. The method of clause 67, wherein the gate drive circuit outputs the bipolar square wave signal as a pair of differential signals output by respective ones of the non-inverting gate driver and the inverting gate driver.

[0124] Clause 69. The method of any one of clauses 53-68, wherein the distortion is compensated using a resistor-capacitor (RC) circuit.

[0125] Many modifications and other embodiments of the present disclosure set forth herein will come to mind to one skilled in the art to which the present disclosure pertains having the benefit of the teachings presented in the foregoing description and the associated drawings. Therefore, it is to be understood that the present disclosure is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing description and the associated drawings set forth example embodiments in the context of certain example combinations of elements and / or functions, one of ordinary skill in the art will appreciate that other combinations of elements and / or functions are also possible and can provide the same or similar benefits, and that such other combinations are intended to be included within the scope of the appended claims. In this regard, for example, the different combinations set forth in some of the appended claims are also contemplated. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A position sensor comprising: a transformer-based measurement device connectable to a movable object, the transformer-based measurement device including an excitation coil and a plurality of sense coils; and an excitation circuit for converting a unipolar square wave signal to a bipolar square wave signal to drive the excitation coil to generate an alternating magnetic field and induce an output signal in the plurality of sense coils that varies according to a position of the object, the excitation circuit including: an H-bridge circuit including push-pull amplifiers arranged in two legs, the H-bridge circuit for converting the unipolar square wave signal to the bipolar square wave signal; and a compensation circuit coupled between the two legs of the H-bridge circuit, the compensation circuit for compensating for any distortion in the bipolar square wave signal caused by the excitation coil as an inductive load on the H-bridge circuit.

2. The position sensor of claim 1, wherein the position sensor includes a processing circuit for processing the output signal to determine the position of the object.

3. The position sensor of claim 1, wherein the unipolar square wave signal is a first unipolar square wave signal, and the excitation circuit includes a polarity inverter for converting the first unipolar square wave signal to a second unipolar square wave signal having a polarity opposite the first unipolar square wave signal, and wherein the push-pull amplifiers include a first push-pull amplifier driven by the first unipolar square wave signal and a second push-pull amplifier driven by the second unipolar square wave signal.

4. The position sensor of claim 3, wherein respective ones of the first and second push-pull amplifiers include complementary transistor pairs connected in a push-pull configuration.

5. The position sensor of claim 4, wherein gates of the complementary transistor pairs of the first push-pull amplifier are driven by the first unipolar square wave signal, and gates of the complementary transistor pairs of the second push-pull amplifier are driven by the second unipolar square wave signal.

6. The position sensor of claim 4, wherein the complementary transistor pairs include a high-side transistor for coupling the excitation coil to a first supply rail and a low-side transistor for coupling the excitation coil to a second supply rail.

7. The position sensor of claim 3, wherein the H-bridge circuit is embodied by a gate drive circuit, the gate drive circuit comprising: a non-inverting gate driver including the first push-pull amplifier; and an inverting gate driver including the second push-pull amplifier.

8. The position sensor of claim 7, wherein the gate drive circuit is for outputting the bipolar square wave signal as a differential signal pair output by respective ones of the non-inverting gate driver and the inverting gate driver.

9. The position sensor of claim 1, wherein the compensation circuit is a resistor-capacitor (RC) circuit.

10. An excitation circuit comprising: an H-bridge circuit for converting a unipolar square wave signal to a bipolar square wave signal to drive a field coil of a transformer-based measurement device, the H-bridge circuit comprising push-pull amplifiers arranged in two branches; and a compensation circuit coupled between the two branches of the H-bridge circuit, the compensation circuit for compensating for any distortion in the bipolar square wave signal caused by the field coil as an inductive load on the H-bridge circuit.

11. The field circuit of claim 10, wherein the bipolar square wave signal comprises pulses that alternate in amplitude between a first supply rail and a second supply rail.

12. The field circuit of claim 10, wherein respective ones of the push-pull amplifiers comprise complementary pairs of transistors connected in a push-pull configuration.

13. The field circuit of claim 10, wherein the unipolar square wave signal is a first unipolar square wave signal, and the field circuit comprises a polarity inverter for converting the first unipolar square wave signal to a second unipolar square wave signal of opposite polarity to the first unipolar square wave signal, and wherein the push-pull amplifiers comprise a first push-pull amplifier driven by the first unipolar square wave signal and a second push-pull amplifier driven by the second unipolar square wave signal.

14. The field circuit of claim 13, wherein respective ones of the first and second push-pull amplifiers comprise complementary pairs of transistors connected in a push-pull configuration.

15. The field circuit of claim 14, wherein gates of the complementary pairs of transistors of the first push-pull amplifier are driven by the first unipolar square wave signal, and gates of the complementary pairs of transistors of the second push-pull amplifier are driven by the second unipolar square wave signal.

16. The field circuit of claim 14, wherein the complementary pairs of transistors comprise a high-side transistor for coupling the field coil to a first supply rail and a low-side transistor for coupling the field coil to a second supply rail.

17. The field circuit of claim 10, wherein the H-bridge circuit is for outputting the bipolar square wave signal as a differential signal pair for input to respective ends of the field coil.

18. The field circuit of claim 17, wherein the push-pull amplifiers output respective ones of the differential signal pair.

19. The field circuit of claim 10, wherein the push-pull amplifiers comprise a first push-pull amplifier and a second push-pull amplifier, and wherein the compensation circuit comprises a first compensation circuit coupled to an output of the first push-pull amplifier and a second compensation circuit coupled to an output of the second push-pull amplifier.

20. The field circuit of claim 10, wherein the push-pull amplifiers comprise a first push-pull amplifier and a second push-pull amplifier, and wherein the compensation circuit is coupled between outputs of the first and second push-pull amplifiers.

21. The field circuit of claim 10, wherein the field circuit includes a voltage buffer for transmitting the bipolar square wave signal from the H-bridge circuit to the compensation circuit.

22. The field circuit of claim 10, wherein the push-pull amplifier includes a first push-pull amplifier and a second push-pull amplifier, and The H-bridge circuit is embodied by a gate drive circuit, and the gate drive circuit comprises: a non-inverting gate driver including the first push-pull amplifier; and an inverting gate driver including the second push-pull amplifier.

23. The field circuit of claim 22, wherein the gate drive circuit is for outputting the bipolar square wave signal as a pair of differential signals output by respective ones of the non-inverting gate driver and the inverting gate driver.

24. The field circuit of claim 10, wherein the compensation circuit is a resistor-capacitor (RC) circuit.

25. A method comprising: converting a unipolar square wave signal to a bipolar square wave signal to drive a field coil, converting the unipolar square wave signal including: applying the unipolar square wave signal to an H-bridge circuit having a push-pull amplifier arranged in two legs, the H-bridge circuit converting the unipolar square wave signal to the bipolar square wave signal; and compensating for distortion in the bipolar square wave signal caused by the field coil as an inductive load on the H-bridge circuit.

26. The method of claim 25, wherein the field coil belongs to a transformer-based measurement device connected to an object that is moving, and the field coil includes a plurality of sense coils, the bipolar square wave signal driving the field coil to generate an alternating magnetic field and induce an output signal in the plurality of sense coils that varies according to a position of the object, and wherein the method comprises: processing the output signal to determine the position of the object.

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