Excitation circuit of rotary transformer
By introducing a detection resistor and a charging/discharging circuit into the rotary transformer excitation circuit, the problem of power supply damage caused by short circuit in the rotary transformer at high temperatures is solved, and self-recovery protection is achieved. This method is suitable for rotary transformer excitation circuits in high-temperature environments.
Patent Information
- Application Number
- CN202511096695.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-06
- Publication Date
- 2025-10-31
AI Technical Summary
Existing rotary transformer excitation circuits are prone to short circuits in high-temperature environments, leading to damage to the excitation power supply. Furthermore, self-resetting fuses have limited lifespan at high temperatures and cannot effectively protect the devices.
An excitation circuit is designed, which includes an operational amplifier, a drive amplifier circuit, a detection resistor, a conduction threshold device, and a charging and discharging circuit. Overcurrent protection is achieved by detecting the voltage change of the detection resistor, and the charging and discharging circuit is used to self-recover after the short circuit is removed.
It achieves overcurrent protection when the rotary transformer is short-circuited, protects the excitation circuit from damage, and automatically restores power supply after the short circuit is removed. It is suitable for effective protection in high-temperature environments.
Smart Images
Figure CN120879475A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of excitation power supply technology, specifically to an excitation circuit for a rotary transformer. Background Technology
[0002] A rotary transformer is a position sensor that requires an external power supply. The circuit that generates this power is called the excitation circuit. The output of the excitation circuit is a sine wave with a driving capability of 100mA, and it typically uses a push-pull circuit. During the use of a rotary transformer, short circuits are prone to occur, leading to damage to the excitation power supply. In practical applications, it has been found that rotary transformers have a higher probability of short-circuiting to the casing in high-temperature environments above 80°C.
[0003] In the industry, overcurrent protection circuits are typically added to the excitation circuits of rotary transformers, using only fuses for protection. However, this approach is limited in application due to its inability to self-reset and the potential for device damage. Alternatively, self-resetting fuses can be added to protect the excitation power supply, but their application is restricted because they have limited lifespan and are difficult to use in ambient temperatures above 80°C. Summary of the Invention
[0004] In view of this, this application provides an excitation circuit for a rotary transformer, which can realize overcurrent protection of the excitation circuit of the rotary transformer when the rotary transformer is short-circuited. The overcurrent protection time can be set, and the excitation circuit can automatically recover and continue to work after the short circuit is removed.
[0005] To solve the above problems, the technical solution provided in this application is as follows:
[0006] An excitation circuit for a rotary transformer includes: an operational amplifier, a drive amplifier circuit, a detection resistor, a turn-on threshold device, and a charging / discharging circuit;
[0007] The first input terminal of the operational amplifier is connected to a reference voltage, and the second input terminal of the operational amplifier is connected to an excitation power supply; the output terminal of the operational amplifier is connected to the input terminal of the driving amplifier circuit, and the output terminal of the driving amplifier circuit is used to connect to a rotary transformer.
[0008] The first power supply terminal of the drive amplifier circuit is connected to the operating power supply through the detection resistor; the second power supply terminal of the drive amplifier circuit is grounded.
[0009] The conduction threshold device is connected to the detection resistor. When the voltage of the detection resistor is greater than the threshold, the conduction threshold device is turned on, pulling the first input terminal of the operational amplifier low to ground.
[0010] The charging and discharging circuit includes a resistor and a capacitor. The first terminal of the charging and discharging circuit is connected to a preset voltage, the second terminal of the charging and discharging circuit is connected to the first input terminal of the operational amplifier, and the third terminal of the charging and discharging circuit is grounded.
[0011] Optionally, the conduction threshold device includes an optocoupler, the two input terminals of the optocoupler are connected to the two ends of the detection resistor, the first output terminal of the optocoupler is connected to the first input terminal of the operational amplifier, and the second output terminal of the optocoupler is grounded.
[0012] Optionally, the conduction threshold device includes a first PNP transistor, a second NPN transistor, and a fifth current-limiting resistor;
[0013] The emitter and base of the first PNP transistor are connected to the two ends of the detection resistor, the collector of the first PNP transistor is connected to the first end of the fifth current-limiting resistor, the second end of the fifth current-limiting resistor is connected to the base of the second NPN transistor, the collector of the second NPN transistor is connected to the first input terminal of the operational amplifier, and the emitter of the second NPN transistor is grounded.
[0014] Optionally, the charging and discharging circuit includes a first voltage divider resistor, a second voltage divider resistor, and a capacitor;
[0015] The first end of the first voltage divider resistor is connected to the reference voltage, the second end of the first voltage divider resistor is connected to the first end of the second voltage divider resistor, the second end of the second voltage divider resistor is grounded, and the capacitor is connected in parallel across the two ends of the second voltage divider resistor.
[0016] Optionally, the driving amplifier circuit includes a first resistor, a second resistor, a first push-pull circuit, and a second push-pull circuit;
[0017] The input terminal of the first push-pull circuit is connected to the output terminal of the operational amplifier, and the output terminal of the second push-pull circuit is used to connect to the rotary transformer;
[0018] The first end of the first push-pull circuit is connected to the first end of the second push-pull circuit through the first resistor, and the second end of the first push-pull circuit is connected to the second end of the second push-pull circuit through the second resistor. The bases of the corresponding transistors of the first push-pull circuit and the second push-pull circuit are connected together.
[0019] Optionally, the first push-pull circuit includes a first switching transistor, a second switching transistor, a first current-limiting resistor, and a second current-limiting resistor, and the second push-pull circuit includes a third switching transistor, a fourth switching transistor, a third current-limiting resistor, and a fourth current-limiting resistor.
[0020] The first terminal of the first switching transistor is connected to the first terminal of the first resistor, the second terminal of the first switching transistor is connected to the first terminal of the first current-limiting resistor, the second terminal of the first current-limiting resistor is connected to the first terminal of the second current-limiting resistor, the second terminal of the second current-limiting resistor is connected to the first terminal of the second switching transistor, and the second terminal of the second switching transistor is connected to the first terminal of the second resistor. The connection point between the first current-limiting resistor and the second current-limiting resistor is the input terminal of the first push-pull circuit.
[0021] The first terminal of the third switching transistor is connected to the second terminal of the first resistor, the second terminal of the third switching transistor is connected to the first terminal of the third current-limiting resistor, the second terminal of the third current-limiting resistor is connected to the first terminal of the fourth current-limiting resistor, the second terminal of the fourth current-limiting resistor is connected to the first terminal of the fourth switching transistor, the second terminal of the fourth switching transistor is connected to the second terminal of the second resistor, and the connection point of the third current-limiting resistor and the fourth current-limiting resistor is the output terminal of the second push-pull circuit.
[0022] Optionally, the first to fourth switching transistors are transistors or metal-oxide-semiconductor field-effect transistors.
[0023] Optional features also include: negative feedback circuits;
[0024] The negative feedback circuit is connected to the second input terminal of the operational amplifier and the output terminal of the drive amplifier circuit.
[0025] The negative feedback circuit is used to adjust the amplification factor of the operational amplifier.
[0026] Optionally, the negative feedback circuit includes a feedback resistor and a feedback capacitor; the second input terminal of the operational amplifier is connected to the excitation power supply through an input resistor;
[0027] The first end of the feedback resistor is connected to the second input terminal of the operational amplifier, the second end of the feedback resistor is connected to the output terminal of the driving amplifier circuit, and the feedback capacitor is connected in parallel across the feedback resistor.
[0028] Optionally, the waveform of the excitation power supply is a sine wave, the reference voltage is less than the preset voltage, and the preset voltage is less than the voltage of the working power supply.
[0029] This application achieves overcurrent protection for the excitation circuit of the rotary transformer when it is short-circuited by the above-mentioned scheme. When an overcurrent occurs, the power supply from the excitation circuit to the rotary transformer can be cut off. Moreover, by utilizing the charging and discharging time of the charging and discharging circuit, the excitation circuit can automatically recover and continue to work to provide excitation power to the rotary transformer after the short-circuit fault is cleared, without the need for manual power restoration. This achieves automatic and effective protection for the excitation circuit of the rotary transformer in high-temperature scenarios. Attached Figure Description
[0030] Figure 1 A schematic diagram of an excitation circuit for a rotary transformer provided in this application;
[0031] Figure 2 A circuit diagram of an excitation circuit for a rotary transformer provided in an embodiment of this application;
[0032] Figure 3 Another circuit diagram of an excitation circuit for a rotary transformer provided in an embodiment of this application. Detailed Implementation
[0033] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods. The described embodiments are only a part of the embodiments of this application, and not all of them. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be simply construed as limiting the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.
[0034] This application provides an excitation circuit for a rotary transformer with short-circuit protection, addressing the limitations of existing technologies that use self-resetting fuses for overcurrent protection due to device lifespan constraints and inability to operate under high-temperature conditions. The excitation circuit of the rotary transformer provided in this application is described in detail below with reference to the accompanying drawings.
[0035] See Figure 1 The figure is a schematic diagram of the excitation circuit of a rotary transformer provided in this application.
[0036] like Figure 1 As shown, the excitation circuit of the rotary transformer provided in this application includes a conduction threshold device 101, a charging and discharging circuit 102, a drive amplifier circuit 103, an operational amplifier U2A, and a detection resistor R1.
[0037] The threshold device 101 is connected to the detection resistor R1. When the voltage of the detection resistor R1 is greater than the threshold, the threshold device 101 is turned on, pulling the first input terminal of the operational amplifier U2A low to ground.
[0038] Specifically, for example, the two input terminals of the turn-on threshold device 101 are connected to the two ends of the detection resistor R1, the first output terminal of the turn-on threshold device 101 is connected to the first input terminal of the operational amplifier U2A, and the second output terminal of the turn-on threshold device 101 is grounded.
[0039] The first input terminal of the operational amplifier U2A is connected to the reference voltage Uref, and the second input terminal of the operational amplifier U2A is connected to the excitation power supply EXC+. The output terminal of the operational amplifier U2A is connected to the input terminal of the drive amplifier circuit 103, and the output terminal of the drive amplifier circuit 103 is connected to the rotary transformer to provide operating power to the rotary transformer.
[0040] The first terminal of the charging and discharging circuit 102 is connected to a preset voltage AVDD, the second terminal of the charging and discharging circuit 102 is connected to the first input terminal of the operational amplifier U2A, and the third terminal of the charging and discharging circuit 102 is grounded.
[0041] The first power supply terminal of the drive amplifier circuit 103 is connected to the operating power supply VCC through the detection resistor R1, and the second power supply terminal of the drive amplifier circuit 103 is grounded.
[0042] Under normal operating conditions of the rotary transformer, the operational amplifier U2A amplifies the excitation signal to the voltage value required by the rotary transformer, and the drive amplifier circuit 103 amplifies the signal output by the operational amplifier U2A and outputs the excitation signal to the rotary transformer.
[0043] When a short circuit occurs in the rotary transformer, the voltage across the sensing resistor R1 will increase. When the turn-on threshold device 101 detects the increase in voltage across the sensing resistor R1, it will reduce the input of the operational amplifier U2A to ground, causing the excitation circuit to shut down its output, i.e., it will stop supplying power to the rotary transformer.
[0044] The charging and discharging circuit 102 can be set with an overcurrent protection time to protect the circuit from damage. Once the short circuit is removed, the excitation circuit can automatically recover to its normal operating state. This application does not specifically limit the exact structure of the charging and discharging circuit 102, but it generally includes resistors and capacitors. The parameters of the resistors and capacitors can be set according to the required self-recovery time.
[0045] The excitation circuit provided in this application embodiment achieves overcurrent protection for the excitation circuit of the rotary transformer when a short circuit occurs. When an overcurrent occurs, the power supply from the excitation circuit to the rotary transformer can be cut off. Moreover, by utilizing the charging and discharging time of the charging and discharging circuit, the excitation circuit can automatically recover and continue to work to provide excitation power to the rotary transformer after the short circuit fault is removed, without the need for manual power restoration. This achieves automatic and effective protection for the excitation circuit of the rotary transformer in high-temperature scenarios.
[0046] The embodiments of this application do not specifically limit the specific structure of the conduction threshold device. It can be built by circuitry or implemented by integrated devices, such as optocouplers or transistors. Different implementation methods are described below with reference to the accompanying drawings.
[0047] See Figure 2The figure is a circuit diagram of an excitation circuit for a rotary transformer provided in an embodiment of this application.
[0048] The conduction threshold device in the excitation circuit provided in this application embodiment is described using an optocoupler as an example. Specifically, the excitation circuit includes: optocoupler U1, charging and discharging circuit, driving amplifier circuit, operational amplifier U2A, and detection resistor R1.
[0049] The two input terminals of optocoupler U1 are connected in parallel across the two ends of sensing resistor R1. The first output terminal of optocoupler U1 is connected to the first input terminal of amplifier U2A, and the second output terminal of optocoupler U1 is grounded.
[0050] The charging and discharging circuit includes: a first voltage divider resistor R3, a second voltage divider resistor R4, and a capacitor C1. The first terminal of the first voltage divider resistor R3 is connected to a preset voltage. In this embodiment, the preset voltage is 5V. The second terminal of the first voltage divider resistor R3 and the first terminal of the second voltage divider resistor R4 are both connected to the first input terminal of the operational amplifier U2A. The second terminal of the second voltage divider resistor R4 is grounded to GND. The capacitor C1 is connected in parallel across the two terminals of the second voltage divider resistor R4.
[0051] The excitation power supply EXC+ is connected to the second input terminal of the operational amplifier U2A via the input resistor R7.
[0052] The driving amplifier circuit 103 includes: a first resistor R2, a second resistor R11, a first push-pull circuit, and a second push-pull circuit. The first push-pull circuit includes a first transistor Q2, a second transistor Q3, a first current-limiting resistor R6, and a second current-limiting resistor R9. The second push-pull circuit includes a third transistor Q1, a fourth transistor Q4, a third current-limiting resistor R5, and a fourth current-limiting resistor R8.
[0053] The collector of the first transistor Q2 is connected to the collector of the third transistor Q1 through the first resistor R2. The base of the first transistor Q2 is connected to the base of the third transistor Q1. The emitter of the first transistor Q2 is connected to the emitter of the second transistor Q3 through the first current-limiting resistor R6 and the second current-limiting resistor R9.
[0054] The collector of the second transistor Q3 is connected to the collector of the fourth transistor Q4 through the second resistor R11, and the base of the second transistor Q3 is connected to the base of the fourth transistor Q4.
[0055] The collector of the third transistor Q1 is connected to the second end of the detection resistor R1, and the emitter of the third transistor Q1 is connected to the emitter of the fourth transistor Q4 through the third current-limiting resistor R5 and the fourth current-limiting resistor R8.
[0056] The collector of the fourth transistor Q4 is grounded.
[0057] Figure 2In this configuration, the reference voltage Uref can be 3.75V, and the operating power supply VCC can be 15V.
[0058] Under normal operating conditions of the excitation circuit, operational amplifier U2A adjusts the bias voltage of the excitation power supply EXC+ to the reference voltage Uref and amplifies the excitation signal to the voltage value required by the resolver. The first push-pull circuit amplifies the output signal of operational amplifier U2A and provides it to the second push-pull circuit. The function of the second push-pull circuit is to perform zero-crossing correction, making the power supply waveform provided to the resolver a relatively standard sine wave, improving the power quality of the resolver and facilitating its operational stability. The second push-pull circuit outputs the zero-crossing corrected excitation signal EX+ to the resolver.
[0059] When a short circuit fault occurs in the rotary transformer, the current flowing through the detection resistor R1 increases, which increases the voltage drop across the detection resistor R1. Since the optocoupler U1 has a conduction threshold, when the current flowing through the detection resistor R1 increases to the point where the voltage drop across the detection resistor R1 reaches the conduction threshold of the optocoupler U1, the optocoupler U1 conducts, causing the voltage at the second terminal of the charging and discharging circuit 102 to drop to ground.
[0060] At this time, capacitor C1 of charging and discharging circuit 102 discharges through the second voltage divider resistor R4, so that the first input terminal of operational amplifier U2A still has input. When capacitor C1 finishes discharging, the voltage of the first input terminal of operational amplifier U2A drops to ground, operational amplifier U2A stops outputting excitation signal, and the excitation circuit enters protection state.
[0061] After the short-circuit fault of the rotary transformer is cleared, the current flowing through the detection resistor R1 decreases. When the current flowing through the detection resistor R1 decreases to the point where the voltage across the detection resistor R1 drops below the conduction threshold of the optocoupler U1, the optocoupler U1 is turned off. At this time, the capacitor C1 of the charging and discharging circuit 102 is charged. When the capacitor C1 is fully charged, the voltage at the first input terminal of the operational amplifier U2A returns to the reference voltage Uref, and the excitation circuit resumes normal operation.
[0062] The overcurrent protection time can be adjusted by adjusting the values of the second voltage divider resistor R2 and capacitor C1.
[0063] A feedback resistor R10 is connected between the second input terminal of the operational amplifier U2A and the output terminal of the drive amplifier circuit 103. A feedback capacitor C2 is connected in parallel across the feedback resistor R10. The feedback resistor R10 and the feedback capacitor C2 form a negative feedback circuit, which is used to adjust the amplification factor of the operational amplifier U2A, that is, to adjust the gain.
[0064] The above embodiments use an optocoupler as an example to describe the conduction threshold device. The following describes a transistor as an example of the conduction threshold device.
[0065] See Figure 3 This figure is another circuit diagram of the excitation circuit of a rotary transformer provided in an embodiment of this application.
[0066] The excitation circuit provided in this application embodiment includes: a first PNP transistor Q5, a second NPN transistor Q6, a fifth current-limiting resistor R12, a charging and discharging circuit, a driving amplifier circuit, an operational amplifier U2A, and a detection resistor R1.
[0067] In this configuration, the emitter and base of the first PNP transistor Q5 are connected to the two ends of the detection resistor R1, the collector of the first PNP transistor Q5 is connected to the base of the second NPN transistor Q6 through the fifth current-limiting resistor R12, the collector of the second NPN transistor Q6 is connected to the first input terminal of the operational amplifier U2A, and the emitter of the second NPN transistor Q6 is grounded.
[0068] The connection methods of other parts and Figure 2 The implementation methods are the same and will not be repeated here.
[0069] When the excitation circuit is working normally, the operational amplifier U2A adjusts the bias voltage of the excitation power supply EXC+ to the reference voltage Uref, and amplifies the excitation signal to the voltage value required by the rotary transformer. The drive amplifier circuit outputs the excitation signal EX+, which has been amplified by the first push-pull circuit and zero-crossing corrected by the second push-pull circuit, to the rotary transformer.
[0070] When a short-circuit fault occurs in the rotary transformer, the current flowing through the detection resistor R1 increases, causing the voltage drop across the detection resistor R1 to increase. Since the first PNP transistor Q5 and the second NPN transistor Q6 have conduction thresholds, when the current flowing through the detection resistor R1 increases to the point where the voltage drop across the detection resistor R1 reaches the conduction threshold of the first PNP transistor Q5 and the second NPN transistor Q6, the first PNP transistor Q5 and the second NPN transistor Q6 conduct, causing the voltage at the second terminal of the charging and discharging circuit 102 to drop to ground.
[0071] At this time, capacitor C1 in the charging and discharging circuit discharges through the second voltage divider resistor R4, so that the first input terminal of operational amplifier U2A still has input. When capacitor C1 finishes discharging, the voltage at the first input terminal of operational amplifier U2A drops to ground, operational amplifier U2A stops outputting excitation signal, and the excitation circuit enters protection state.
[0072] After the short-circuit fault of the rotary transformer is cleared, the current flowing through the detection resistor R1 decreases. When the current flowing through the detection resistor R1 decreases to the point where the voltage across the detection resistor R1 drops below the conduction threshold of the first PNP transistor Q5 and the second NPN transistor Q6, the first PNP transistor Q5 and the second NPN transistor Q6 are turned off. At this time, the capacitor C1 of the charging and discharging circuit 102 is charged. When the capacitor C1 is fully charged, the voltage at the first input terminal of the operational amplifier U2A returns to the reference voltage Uref, and the excitation circuit resumes normal operation.
[0073] The overcurrent protection time can be adjusted by adjusting the values of the second voltage divider resistor R2 and capacitor C1.
[0074] A feedback resistor R10 is connected between the second input terminal of the operational amplifier U2A and the output terminal of the drive amplifier circuit. A feedback capacitor C2 is connected in parallel on both sides of the feedback resistor R10. The feedback resistor R10 and the feedback capacitor C2 form a negative feedback circuit, which is used to adjust the amplification factor of the operational amplifier U2A.
[0075] The excitation circuit of the rotary transformer with short-circuit protection provided in this application realizes overcurrent protection of the rotary transformer excitation circuit when the rotary transformer is short-circuited through the above principle. The overcurrent protection time can be set, and the excitation circuit can self-recover and continue to work after the short circuit is removed, thereby realizing effective protection of the rotary transformer excitation circuit in high-temperature scenarios.
[0076] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. An excitation circuit for a rotary transformer, characterized in that, include: Operational amplifier, driver amplifier circuit, detection resistor, on-threshold device, and charging / discharging circuit; The first input terminal of the operational amplifier is connected to a reference voltage, and the second input terminal of the operational amplifier is connected to an excitation power supply; the output terminal of the operational amplifier is connected to the input terminal of the driving amplifier circuit, and the output terminal of the driving amplifier circuit is used to connect to a rotary transformer. The first power supply terminal of the drive amplifier circuit is connected to the operating power supply through the detection resistor; the second power supply terminal of the drive amplifier circuit is grounded. The conduction threshold device is connected to the detection resistor. When the voltage of the detection resistor is greater than the threshold, the conduction threshold device is turned on, pulling the first input terminal of the operational amplifier low to ground. The charging and discharging circuit includes a resistor and a capacitor. The first terminal of the charging and discharging circuit is connected to a preset voltage, the second terminal of the charging and discharging circuit is connected to the first input terminal of the operational amplifier, and the third terminal of the charging and discharging circuit is grounded.
2. The excitation circuit according to claim 1, characterized in that, The conduction threshold device includes an optocoupler, the two input terminals of the optocoupler are connected to the two ends of the detection resistor, the first output terminal of the optocoupler is connected to the first input terminal of the operational amplifier, and the second output terminal of the optocoupler is grounded.
3. The excitation circuit according to claim 1, characterized in that, The conduction threshold device includes a first PNP transistor, a second NPN transistor, and a fifth current-limiting resistor; The emitter and base of the first PNP transistor are connected to the two ends of the detection resistor, the collector of the first PNP transistor is connected to the first end of the fifth current-limiting resistor, the second end of the fifth current-limiting resistor is connected to the base of the second NPN transistor, the collector of the second NPN transistor is connected to the first input terminal of the operational amplifier, and the emitter of the second NPN transistor is grounded.
4. The excitation circuit according to claim 1, characterized in that, The charging and discharging circuit includes a first voltage divider resistor, a second voltage divider resistor, and a capacitor; The first end of the first voltage divider resistor is connected to the reference voltage, the second end of the first voltage divider resistor is connected to the first end of the second voltage divider resistor, the second end of the second voltage divider resistor is grounded, and the capacitor is connected in parallel across the two ends of the second voltage divider resistor.
5. The excitation circuit according to any one of claims 1-4, characterized in that, The driving amplifier circuit includes a first resistor, a second resistor, a first push-pull circuit, and a second push-pull circuit. The input terminal of the first push-pull circuit is connected to the output terminal of the operational amplifier, and the output terminal of the second push-pull circuit is used to connect to the rotary transformer; The first end of the first push-pull circuit is connected to the first end of the second push-pull circuit through the first resistor, and the second end of the first push-pull circuit is connected to the second end of the second push-pull circuit through the second resistor. The bases of the corresponding transistors of the first push-pull circuit and the second push-pull circuit are connected together.
6. The excitation circuit according to claim 5, characterized in that, The first push-pull circuit includes a first switching transistor, a second switching transistor, a first current-limiting resistor, and a second current-limiting resistor; the second push-pull circuit includes a third switching transistor, a fourth switching transistor, a third current-limiting resistor, and a fourth current-limiting resistor. The first terminal of the first switching transistor is connected to the first terminal of the first resistor, the second terminal of the first switching transistor is connected to the first terminal of the first current-limiting resistor, the second terminal of the first current-limiting resistor is connected to the first terminal of the second current-limiting resistor, the second terminal of the second current-limiting resistor is connected to the first terminal of the second switching transistor, and the second terminal of the second switching transistor is connected to the first terminal of the second resistor. The connection point between the first current-limiting resistor and the second current-limiting resistor is the input terminal of the first push-pull circuit. The first terminal of the third switching transistor is connected to the second terminal of the first resistor, the second terminal of the third switching transistor is connected to the first terminal of the third current-limiting resistor, the second terminal of the third current-limiting resistor is connected to the first terminal of the fourth current-limiting resistor, the second terminal of the fourth current-limiting resistor is connected to the first terminal of the fourth switching transistor, the second terminal of the fourth switching transistor is connected to the second terminal of the second resistor, and the connection point of the third current-limiting resistor and the fourth current-limiting resistor is the output terminal of the second push-pull circuit.
7. The excitation circuit according to claim 6, characterized in that, The first to fourth switching transistors are bipolar transistors or metal-oxide-semiconductor field-effect transistors.
8. The excitation circuit according to any one of claims 1-4, characterized in that, Also includes: Negative feedback circuit; The negative feedback circuit is connected to the second input terminal of the operational amplifier and the output terminal of the drive amplifier circuit. The negative feedback circuit is used to adjust the amplification factor of the operational amplifier.
9. The excitation circuit according to claim 8, characterized in that, The negative feedback circuit includes a feedback resistor and a feedback capacitor; the second input terminal of the operational amplifier is connected to the excitation power supply through an input resistor. The first end of the feedback resistor is connected to the second input terminal of the operational amplifier, the second end of the feedback resistor is connected to the output terminal of the driving amplifier circuit, and the feedback capacitor is connected in parallel across the feedback resistor.
10. The excitation circuit according to any one of claims 1-4, characterized in that, The waveform of the excitation power supply is a sine wave, the reference voltage is less than the preset voltage, and the preset voltage is less than the voltage of the working power supply.