Low-cost rotary transformer excitation and protection circuit

Abstract

The utility model relates to the technical field of motor control, in particular to a low-cost rotary transformer excitation and protection circuit, which comprises a main control chip (MCU), a filter circuit, a differential operational amplifier circuit, a power amplification circuit, an overcurrent protection circuit, a blocking capacitor and a rotary transformer which are connected with one another, and the output end of the power amplification circuit is further connected with the main control chip (MCU). The circuit is used for monitoring an excitation output signal in the circuit. According to the scheme, the other end of the rotary transformer is directly grounded, a same conditioning circuit is omitted, the circuit structure is simpler, the cost is reduced, and it can still be guaranteed that the output rotary transformer excitation signal can drive the rotary transformer. Besides, excitation output signals in the circuit can be monitored, when the output signals are abnormal, excitation PWM output by the main control chip can be closed conveniently, and operation safety of the motor is guaranteed.

Description

Technical Field

[0001] The utility model relates to the technical field of motor control, in particular to a low-cost resolver excitation and protection circuit. Background Art

[0002] In the field of motor control related to new energy vehicles, the motor angle is usually detected by a resolver. The excitation and decoding of the resolver are very important parts for motor control. The decoding of the resolver can obtain the position and speed of the rotor. If the resolver signal (excitation signal and feedback signal) is abnormal during the motor control process, it will cause the motor to run in an erroneous state, which may seriously endanger personal safety.

[0003] The decoding of resolver is usually divided into hardware decoding and software decoding.

[0004] Hardware decoding uses hardware decoding chips and peripheral circuits to complete the output of excitation signals and the decoding of feedback signals, but the price of decoding chips is relatively expensive, the hardware circuit is relatively complex, and the hardware cost is high;

[0005] Software decoding usually uses the main control chip to output the resolver excitation signal, and obtains two differential excitation signals (positive excitation signal and negative excitation signal) through signal conditioning and amplification circuits and outputs them to the resolver. Compared with hardware decoding, the decoding chip cost is reduced, but the protection circuit usually uses current signal sampling circuits, comparison circuits, microcontrollers, etc. for overcurrent protection. The protection circuit has more components and a complex circuit structure. In addition, the two identical differential excitation signal conditioning and amplification circuits require a large number of components, and the hardware cost is still high.

[0006] Therefore, a new technical solution is urgently needed to solve the above technical problems. Utility Model Content

[0007] The purpose of the utility model is to overcome the above-mentioned problems of the prior art and provide a low-cost resolver excitation and protection circuit for solving the technical problems that the decoding chip of the resolver using hardware decoding in the traditional technology is expensive, the hardware circuit is relatively complex, the hardware cost is high, and the protection circuit using software decoding has more components and a complex circuit structure, and the two identical differential excitation signal conditioning and amplification circuits require a large number of components and the hardware cost is still high.

[0008] The above objectives are achieved through the following technical solutions:

[0009] A low-cost resolver excitation and protection circuit comprises a main control chip, a filter circuit, a differential operational amplifier circuit, a power amplifier circuit, an overcurrent protection circuit, a DC blocking capacitor and a resolver which are connected to each other. The output end of the power amplifier circuit is connected to the main control chip for monitoring the excitation output signal in the circuit.

[0010] Furthermore, the filtering circuit includes a primary filtering circuit and a secondary filtering circuit which are connected to each other, the primary filtering circuit is composed of a first resistor and a first capacitor, and the secondary filtering circuit is composed of a second resistor and a second capacitor.

[0011] Furthermore, the differential operational amplifier circuit includes an operational amplifier, a seventh resistor and a fourth capacitor, the reverse input terminal of the operational amplifier is connected to the output terminal of the secondary filtering circuit, the positive input terminal of the operational amplifier is connected to the power supply, and the output terminal of the operational amplifier is connected to the power amplifier circuit; a twelfth resistor, a thirteenth resistor and a seventh capacitor connected in sequence are arranged between the positive input terminal of the operational amplifier and the power supply.

[0012] Furthermore, a third capacitor is provided between the inverting input terminal of the operational amplifier and the output terminal of the secondary filtering circuit.

[0013] Further, the power amplifier circuit includes a first triode and a second triode, an eighth resistor and a ninth resistor are connected in series between the emitter of the first triode and the emitter of the second triode, a power supply, a third resistor, a fourth resistor, a first diode, a second diode, a fifth resistor and a sixth resistor are connected to the collector and base of the first triode and the second triode; and the cathode of the first diode and the anode of the second diode are connected to the output end of the operational amplifier.

[0014] Furthermore, the overcurrent protection circuit includes a first overcurrent protection circuit arranged at the base of the first transistor and the outer end of the eighth resistor, and a second overcurrent protection circuit arranged at the base of the second transistor and the outer end of the eighth resistor.

[0015] Furthermore, the first overcurrent protection circuit comprises a third diode, a fourth diode and a fifth diode connected in series in sequence, and the second overcurrent protection circuit comprises a sixth diode, a seventh diode and an eighth diode connected in series in sequence.

[0016] Furthermore, the DC blocking capacitor is a fifth capacitor.

[0017] Furthermore, a common mode inductor is provided between the fifth capacitor and the rotary transformer.

[0018] Furthermore, a voltage divider and protection circuit is provided between the output end of the overcurrent protection circuit and the main control chip, and the voltage divider and protection circuit includes a tenth resistor, an eleventh resistor, a sixth capacitor, a ninth diode and a tenth diode.

[0019] The utility model provides a low-cost resolver excitation and protection circuit. Compared with the traditional resolver excitation circuit with two differential excitation signals (positive excitation signal and negative excitation signal), the other end of the resolver in this solution is directly grounded, eliminating the same (negative differential excitation signal) conditioning circuit. Not only is the circuit structure more concise and the cost is reduced, but it can also ensure that the output resolver excitation signal can drive the resolver. In addition, the excitation output signal in the circuit can be monitored. When the output signal is abnormal, the excitation PWM output by the main control chip can be turned off to ensure the safe operation of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a module framework diagram of a low-cost resolver excitation and protection circuit described in the utility model;

[0021] Figure 2 The present invention is a circuit diagram of a low-cost resolver excitation and protection circuit. DETAILED DESCRIPTION

[0022] The utility model is further described in detail below based on the accompanying drawings and embodiments. The described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0023] like Figure 1 As shown, the present invention provides a low-cost resolver excitation and protection circuit, including an interconnected main control chip MCU, a filter circuit, a differential operational amplifier circuit, a power amplifier circuit, an overcurrent protection circuit, a DC blocking capacitor and a resolver. The output end of the power amplifier circuit is connected to the main control chip MCU to monitor the excitation output signal in the circuit. When the output signal is abnormal, the excitation PWM output by the main control chip is turned off.

[0024] Working principle:

[0025] The main control chip MCU outputs an excitation PWM signal, and filters the PWM signal into a smooth sine and cosine excitation signal through a filtering circuit. The sine and cosine signals are amplified to the amplitude signal required by the resolver through a differential operational amplifier circuit, and then the output capacity of the sine and cosine excitation signal is improved through a power amplifier circuit. The excitation signal is input to the resolver, and the other end of the resolver is directly grounded; and the excitation output signal in the circuit is monitored through excitation feedback sampling.

[0026] like Figure 2 As shown, the filtering circuit in this embodiment includes a primary filtering circuit and a secondary filtering circuit connected to each other. The primary filtering circuit is composed of a first resistor R1 and a first capacitor C1, and is used to filter the excitation PWM signal output by the main control chip MCU into a sine-cosine excitation signal; the secondary filtering circuit is composed of a second resistor R2 and a second capacitor C2, and is used to further filter out interference signals from the sine-cosine excitation signal to obtain a smooth sine-cosine excitation signal.

[0027] The differential operational amplifier circuit is used to amplify the smoothed sine and cosine excitation signal to the amplitude signal required by the rotary transformer, and includes an operational amplifier U1, a seventh resistor R7 and a fourth capacitor C4, wherein the seventh resistor R7 and the fourth capacitor C4 are respectively connected to the reverse input terminal of the operational amplifier U1, the reverse input terminal of the operational amplifier U1 is connected to the output terminal of the secondary filter circuit, the positive input terminal of the operational amplifier U1 is connected to the power supply VDD, and the output terminal of the operational amplifier U1 is connected to the power amplifier circuit;

[0028] A twelfth resistor R12, a thirteenth resistor R13 and a seventh capacitor C7 connected in sequence are provided between the positive input terminal of the operational amplifier U1 and the power supply VDD, for dividing and filtering the power supply VDD, and connected to the positive input terminal of the operational amplifier U1 to provide a DC bias voltage therefor.

[0029] A third capacitor C3 is also provided between the reverse input terminal of the operational amplifier U1 and the output terminal of the secondary filter circuit. In this embodiment, the third capacitor C3 is connected in series in the circuit, which can effectively isolate the DC voltage and protect the main control chip MCU.

[0030] The power amplifier circuit in this embodiment is used to improve the output capacity of the sine-cosine excitation signal, including a first transistor Q1 and a second transistor Q2, an eighth resistor R8 and a ninth resistor R9 are connected in series between the emitter of the first transistor Q1 and the emitter of the second transistor Q2, and the collector and base of the first transistor Q1 and the second transistor Q2 are connected to a power supply VDD, a third resistor R3, a fourth resistor R4, a first diode D1, a second diode D2, a fifth resistor R5 and a sixth resistor R6;

[0031] The cathode of the first diode D1 and the anode of the second diode D2 are connected to the output end of the operational amplifier U1;

[0032] The power supply VDD selects a suitable voltage to ultimately meet the amplitude required by the rotary transformer.

[0033] like Figure 2 As shown, the overcurrent protection circuit in this embodiment includes a first overcurrent protection circuit arranged at the base of the first transistor Q1 and the outer end of the eighth resistor R8, and a second overcurrent protection circuit arranged at the base of the second transistor Q2 and the outer end of the eighth resistor R9.

[0034] Among them, the first overcurrent protection circuit package includes a third diode D3, a fourth diode D4 and a fifth diode D5 connected in series in sequence, and the second overcurrent protection circuit package includes a sixth diode D6, a seventh diode D7 and an eighth diode D8 connected in series in sequence.

[0035] Specifically, when the voltage drop formed by the increased current on the eighth resistor R8 and the sum of the voltage drops of the base and emitter of the first transistor Q1 are greater than the sum of the voltage drops of the third diode D3, the fourth diode D4 and the fifth diode D5, the diode is clamped, and a certain current flows through the diode, limiting the current flowing through the eighth resistor R8 within a certain range, thereby preventing the first transistor Q1 from being damaged by overcurrent.

[0036] Similarly, when the voltage drop formed by the increased current on the ninth resistor R9 and the sum of the voltage drops of the base and emitter of the second transistor Q2 are greater than the sum of the voltage drops of the sixth diode D6, the seventh diode D7 and the eighth diode D8, the diode is clamped, and a certain current flows through the diode, limiting the current flowing through the ninth resistor R9 within a certain range, thereby preventing the second transistor Q2 from being damaged by overcurrent.

[0037] It should be noted that, in this solution, the overcurrent threshold can also be adjusted by adjusting the number of diodes connected in series or the resistance values ​​of the eighth resistor R8 and the ninth resistor R9.

[0038] The DC blocking capacitor in this embodiment is a fifth capacitor C5, which has two functions, including:

[0039] First, this solution adopts a single-ended excitation signal output solution, which requires filtering out the DC bias voltage. The fifth capacitor C5 plays the role of blocking DC and passing AC.

[0040] The second and fifth capacitors C5 can prevent the output port from being short-circuited to the power supply, which may cause reverse overvoltage damage to the first transistor Q1 and the second transistor Q2.

[0041] As an optimization of the solution, a common-mode inductor L1 is provided between the fifth capacitor C5 and the rotary transformer, which is used to filter out common-mode interference of the excitation sine and cosine signals and output them to the rotary transformer.

[0042] As a further optimization of this solution, a voltage divider and protection circuit is also arranged between the output end of the overcurrent protection circuit and the main control chip MCU, and the voltage divider and protection circuit includes a tenth resistor R10, an eleventh resistor R11, a sixth capacitor C6, a ninth diode D9 and a tenth diode D10, which are used to perform voltage protection on the main control chip MCU.

[0043] The above description is only for illustrating the implementation mode of the present invention and is not intended to limit the present invention. For those skilled in the art, any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-cost resolver excitation and protection circuit, characterized in that: It includes a main control chip (MCU), a filtering circuit, a differential operational amplifier circuit, a power amplifier circuit, an overcurrent protection circuit, a DC blocking capacitor and a rotary transformer which are interconnected. The output end of the power amplifier circuit is also connected to the main control chip (MCU) to monitor the excitation output signal in the circuit.

2. A low-cost resolver excitation and protection circuit according to claim 1, characterized in that: The filter circuit comprises a primary filter circuit and a secondary filter circuit which are connected to each other, wherein the primary filter circuit is composed of a first resistor (R1) and a first capacitor (C1), and the secondary filter circuit is composed of a second resistor (R2) and a second capacitor (C2).

3. A low-cost resolver excitation and protection circuit according to claim 2, characterized in that: The differential operational amplifier circuit comprises an operational amplifier (U1), a seventh resistor (R7) and a fourth capacitor (C4), the reverse input end of the operational amplifier (U1) is connected to the output end of the secondary filter circuit, the positive input end of the operational amplifier (U1) is connected to a power supply (VDD), and the output end of the operational amplifier (U1) is connected to the power amplifier circuit; A twelfth resistor (R12), a thirteenth resistor (R13) and a seventh capacitor (C7) which are connected in sequence are arranged between the positive input terminal of the operational amplifier (U1) and the power supply (VDD).

4. A low-cost resolver excitation and protection circuit according to claim 3, characterized in that: A third capacitor (C3) is also provided between the inverting input terminal of the operational amplifier (U1) and the output terminal of the secondary filter circuit.

5. A low-cost resolver excitation and protection circuit according to claim 3, characterized in that: The power amplifier circuit comprises a first triode (Q1) and a second triode (Q2), an eighth resistor (R8) and a ninth resistor (R9) are connected in series between the emitter of the first triode (Q1) and the emitter of the second triode (Q2), and a power supply (VDD), a third resistor (R3), a fourth resistor (R4), a first diode (D1), a second diode (D2), a fifth resistor (R5) and a sixth resistor (R6) are connected to the collector and base of the first triode (Q1) and the second triode (Q2); The cathode of the first diode (D1) and the anode of the second diode (D2) are connected to the output end of the operational amplifier (U1).

6. A low-cost resolver excitation and protection circuit according to claim 5, characterized in that: The overcurrent protection circuit comprises a first overcurrent protection circuit arranged at the base of the first transistor (Q1) and the outer end of the eighth resistor (R8), and a second overcurrent protection circuit arranged at the base of the second transistor (Q2) and the outer end of the eighth resistor (R9).

7. A low-cost resolver excitation and protection circuit according to claim 6, characterized in that: The first overcurrent protection circuit comprises a third diode (D3), a fourth diode (D4) and a fifth diode (D5) connected in series in sequence, and the second overcurrent protection circuit comprises a sixth diode (D6), a seventh diode (D7) and an eighth diode (D8) connected in series in sequence.

8. A low-cost resolver excitation and protection circuit according to claim 7, characterized in that: The DC blocking capacitor is a fifth capacitor (C5).

9. A low-cost resolver excitation and protection circuit according to claim 8, characterized in that: A common mode inductor (L1) is provided between the fifth capacitor (C5) and the rotary transformer.

10. A low-cost resolver excitation and protection circuit according to claim 2, characterized in that: A voltage divider and protection circuit is also provided between the output end of the overcurrent protection circuit and the main control chip (MCU), and the voltage divider and protection circuit comprises a tenth resistor (R10), an eleventh resistor (R11), a sixth capacitor (C6), a ninth diode (D9) and a tenth diode (D10).

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