Motor current sampling circuit and motor driver

Abstract

The utility model relates to a motor current sampling circuit and a motor driver, the motor current sampling circuit comprises at least two phase current sampling units, each phase current sampling unit is connected with a phase line of a motor and is used for sampling current of at least two phase lines of the motor; the at least two current detection amplification units are connected with the at least two phase current sampling units in a one-to-one correspondence manner and are used for acquiring sampling signals of the phase current sampling units and amplifying the sampling signals according to a set proportion; the at least two differential units are connected with the current detection amplification units in a one-to-one correspondence manner and are used for transmitting the sampling signals amplified by the current detection amplification units in a differential signal form; the precision of motor current sampling and the accuracy of data transmission are high, and the control precision of the motor is improved.

Description

Technical Field

[0001] The utility model relates to the field of motor control, in particular to a motor current sampling circuit and a motor driver. Background Art

[0002] Motor current sampling is an important part of the motor control process. It can monitor the operating status of the motor, ensure the safe operation of the motor, and is also an effective basis for adjusting the operating parameters of the motor. In the related art, current sampling is performed in the lower bridge arm of the inverter circuit, that is, close to the ground side of the motor winding. However, the accuracy of current sampling and the accuracy of the sampled data are still problems that plague technicians. Therefore, how to improve the accuracy of motor current sampling and the accuracy of data is an urgent problem to be solved in motor applications. Utility Model Content

[0003] In view of the deficiencies of the above-mentioned related technologies, the purpose of the present application is to provide a motor current sampling circuit and a motor driver, aiming to solve the problems of low precision of motor current sampling and low data accuracy.

[0004] A motor current sampling circuit, comprising:

[0005] At least two phase current sampling units, each of which is connected to a phase line of the motor and is used to sample currents of at least two phase lines of the motor;

[0006] At least two current detection amplifying units are connected to the at least two phase current sampling units in a one-to-one correspondence, and are used to obtain sampling signals of the phase current sampling units and amplify the sampling signals according to a set ratio;

[0007] At least two differential units are connected to the current detection amplifying units in a one-to-one correspondence, and are used to transmit the sampling signals amplified by the current detection amplifying units in the form of differential signals.

[0008] Optionally, the at least two phase current sampling units include a first phase current sampling unit and a second phase current sampling unit, the first phase current sampling unit is connected to a first phase line in the inverter circuit, and the second phase current sampling unit is connected to a second phase line in the inverter circuit.

[0009] Optionally, the at least two phase current sampling units further include a third phase current sampling unit, and the third phase current sampling unit is connected to a third phase line in the inverter circuit.

[0010] Optionally, each of the phase current sampling units includes a sampling resistor, and the sampling resistor is arranged on a phase line of the inverter circuit.

[0011] Optionally, the current detection amplification unit includes a bidirectional current detection amplifier;

[0012] The bidirectional current detection amplifier includes a first input terminal, a second input terminal, a reference voltage input terminal and an output terminal; the first input terminal and the second input terminal of the bidirectional current detection amplifier are respectively connected to the two ends of the sampling resistor to obtain the sampling signal of the phase line where the sampling resistor is located; the reference voltage input terminal of the bidirectional current detection amplifier is connected to the reference voltage; the output terminal of the bidirectional current detection amplifier is used to output the amplified sampling signal.

[0013] Optionally, the differential unit includes an inverter, which includes an input terminal, a reference voltage input terminal and an output terminal; the input terminal of the inverter receives the amplified sampling signal; the reference voltage input terminal of the inverter is connected to the reference voltage; the output terminal of the inverter is used to output the opposite signal of the amplified sampling signal; the output terminal of the differential unit outputs a group of differential signals consisting of the amplified sampling signal and its opposite signal.

[0014] Optionally, the differential unit also includes a voltage follower, which includes an input terminal, a reference voltage input terminal and an output terminal; the input terminal of the voltage follower is connected to the bidirectional current detection amplifier to obtain the amplified sampling signal; the reference voltage input terminal of the voltage follower is connected to the reference voltage; the output terminal of the voltage follower is connected to the input terminal of the inverter to transmit the amplified sampling signal to the inverter.

[0015] Optionally, the differential unit includes a first output terminal and a second output terminal; the first output terminal is provided with a first filtering unit, and the first output terminal is connected to the output terminal of the voltage follower through the first filtering unit; the second output terminal is provided with a second filtering unit, and the second output terminal is connected to the output terminal of the inverter through the second filtering unit; the first output terminal and the second output terminal are used to output the differential signal formed by the voltage follower and the inverter to the outside.

[0016] On the other hand, the present application also provides a motor driver, comprising the above-mentioned motor current sampling circuit.

[0017] Optionally, it also includes:

[0018] an analog-to-digital conversion unit connected to the differential unit in the motor current sampling circuit, used to obtain a differential signal transmitted by the differential unit, and obtain a digital signal of the amplified sampling signal according to the differential signal;

[0019] The processing unit connected to the analog-to-digital conversion unit is used to obtain a digital signal of the amplified sampling signal.

[0020] The motor current sampling circuit detects the phase current and amplifies it through the current detection amplifier unit, which can realize continuous sampling and effectively improve the accuracy of current sampling. In addition, the motor current sampling circuit amplifies the current through the current detection amplifier unit and uses the differential unit to convert the differential signal. It has a wider common mode range to improve the sampling performance, and also makes the sampling signal more anti-interference, ensuring the accuracy of data transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of current sampling of an inverter circuit in the related art;

[0022] Figure 2 A schematic block diagram of a motor current sampling circuit provided by an embodiment of the utility model;

[0023] Figure 3 A schematic diagram of a partial circuit of a motor current sampling circuit provided by an embodiment of the utility model;

[0024] Figure 4 A circuit diagram of a differential unit provided in an embodiment of the utility model;

[0025] Description of reference numerals:

[0026] 100-inverter circuit; 10-phase current sampling unit; 11-first phase current sampling unit; 12-second phase current sampling unit; 20-current detection amplifier unit; 21-first current detection amplifier unit; 22-second current detection amplifier unit; 201-first input end of bidirectional current detection amplifier; 202-second input end of bidirectional current detection amplifier; 203-reference voltage input end of bidirectional current detection amplifier; 204-output end of bidirectional current detection amplifier; 30-differential unit; 31-first differential unit; 32-second differential unit; 310-voltage follower; 311- Input terminal of voltage follower; 312-reference voltage input terminal of voltage follower; 313-output terminal of voltage follower; 320-inverter; 321-input terminal of inverter; 322-reference voltage input terminal of inverter; 323-output terminal of inverter; 331-first output terminal of differential unit; 332-second output terminal of differential unit; 3311-first filtering unit; 3312-second filtering unit; R-sampling resistor; R1-first sampling resistor; R2-second sampling resistor; R3-first resistor; C1-filter capacitor; U-first phase line; V-second phase line; W-third phase line. DETAILED DESCRIPTION

[0027] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly and comprehensively understood.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0029] Example:

[0030] In order to achieve more accurate sampling of the motor current, this embodiment provides a motor current sampling circuit, which includes at least two phase current sampling units 10 , at least two current detection amplification units 20 and at least two differential units 30 .

[0031] The phase current sampling unit 10 is a unit that can obtain relevant parameters of the current. By measuring the electrical characteristics of the phase current sampling unit 10, the current situation on the line it samples can be reflected. A single phase current sampling unit 10 is connected to one phase line of the motor, and at least two phase current sampling units 10 are used to sample the current on at least two phase lines of the motor. For example, when there are two phase current sampling units 10, each phase current sampling unit 10 is connected to one of the phase lines to sample the current of the two phase lines respectively.

[0032] The current detection amplifier unit 20 is connected to the phase current sampling unit 10 in a one-to-one correspondence, that is, each phase current sampling unit 10 is provided with a corresponding current detection amplifier unit 20. The current detection amplifier unit 20 is used to obtain the sampling signal of the phase current sampling unit 10 and amplify the sampling signal according to a set ratio. Amplifying the signal sampled by the phase current sampling unit 10 (i.e., the sampling signal) can facilitate more accurate measurement in subsequent processes.

[0033] The differential unit 30 is connected to the current detection amplifier unit 20 in a one-to-one correspondence, and is used to transmit the sampling signal amplified by the current detection amplifier unit 20 in the form of a differential signal. That is to say, in the motor current sampling circuit of this embodiment, the sampling signal is amplified and then transmitted in the form of a differential signal. It can be understood that the transmission object of the sampling signal can be a circuit or device used to perform further processing on the sampling signal. For example, if the sampling signal is to be converted from digital to analog, the sampling signal will be transmitted to the analog-to-digital conversion unit. In other examples, the differential unit 30 can also be connected to other circuits or devices to transmit the sampling signal to subsequent circuits.

[0034] It should be noted that the differential signal form refers to forming the sampling signal amplified by the current detection amplifier unit 20 into two signals (referred to as positive and negative signals) with the same reference potential, the same amplitude and opposite directions. Since the influence of external interference on the positive and negative signals is the same, the external interference can be subtracted by subtracting the positive and negative signals at the receiving end.

[0035] See also Figure 1 In the related art, a sampling resistor R is set in the lower bridge arm of the inverter circuit 100 for sampling, and it must be ensured that there is enough lower tube conduction time in each PWM (Pulse-Width Modulation) cycle to obtain effective current sampling; under high-speed PWM modulation, the effective sampling window is small, which affects the accuracy. The sampling signal obtained by sampling is directly transmitted to the ADC (Analog-to-Digital Converter). This embodiment can achieve continuous sampling and greatly improve the sampling accuracy by sampling the current on the phase line; and the amplified sampling signal is formed into a differential signal for transmission, which can increase the anti-interference ability of signal transmission, common-mode noise can be completely eliminated, and electromagnetic interference can be effectively suppressed.

[0036] See also Figure 2 , which shows a block diagram of the motor current sampling circuit. For sampling of the current on a single phase line, at least one phase current sampling unit 10, one current detection amplifier unit 20 and one differential unit 30 may be used for sampling, amplification and transmission. Figure 2 The illustrated structure can be regarded as a sampling module, which reflects the most basic part of the motor current sampling circuit of this embodiment for sampling the current on a single phase line. The motor current sampling circuit in this embodiment is capable of sampling the current on at least two phase lines. In practical applications, there may be at least two of the above-mentioned sampling modules, each sampling module corresponding to a phase line. Among them, the sampling modules on different phase lines can be exactly the same, and in other examples, they can also be different.

[0037] It should be noted that the phase line referred to in this embodiment is a phase line in a two-phase inverter circuit or a three-phase inverter circuit of a motor; taking a three-phase inverter circuit as an example, its three phases are usually called U phase, V phase and W phase. That is, the motor current sampling circuit of this embodiment will be connected to the inverter circuit 100.

[0038] In some embodiments, the at least two phase current sampling units 10 include a first phase current sampling unit 11 and a second phase current sampling unit 12. The first phase current sampling unit 11 is connected to the first phase line U in the inverter circuit 100, and the second phase current sampling unit 12 is connected to the second phase line V in the inverter circuit 100. The inverter circuit 100 can be a two-phase inverter circuit or a three-phase inverter circuit. Figure 3 , corresponding to the first phase current sampling unit 11, the current detection amplifying unit 20 and the differential unit 30 connected thereto can be referred to as the first current detection amplifying unit 21 and the first differential unit 31; similarly, the current detection amplifying unit 20 and the differential unit 30 connected to the second phase current sampling unit 12 can be referred to as the second current detection amplifying unit 22 and the second differential unit 32.

[0039] like Figure 3 As shown, for a three-phase inverter circuit, current sampling can be performed on only two phases. The sampling signal of the other phase can be calculated by calculating that the sum of the three-phase current vectors is zero. In some embodiments, for a three-phase inverter circuit, current sampling can also be performed directly on all three phases, and then at least two phase current sampling units 10 also include a third phase current sampling unit 10, which is connected to the third phase line W in the inverter circuit 100.

[0040] The phase current sampling unit 10 may include a sampling resistor R, and the sampling resistor R is arranged on the phase line of the inverter circuit 100 . Figure 3 A specific circuit implementation of the motor current sampling circuit is illustrated. Taking the current sampling of two phases of the three-phase inverter circuit as an example, a first sampling resistor R1 is provided on the first phase line U, and the first sampling resistor R1 is connected in series to the first phase line U. The potential difference across the first sampling resistor R1 will be able to reflect the current flowing through the first sampling resistor R1 (that is, the current on the first phase line U). Similarly, a second sampling resistor R2 is provided on the second phase line V, and the specifications of the second sampling resistor R2 can be exactly the same as those of the first sampling resistor R1. In other embodiments, the phase current sampling unit 10 can also use other devices that can reflect the current size, such as Hall devices.

[0041] The current detection amplifier unit 20 includes a bidirectional current detection amplifier, which can amplify the input current and output a larger current. Compared with the conventional technology of using a power amplifier to amplify the signal, the bidirectional current detection amplifier can have a wider common mode range and better precision in some implementations.

[0042] The bidirectional current detection amplifier includes a first input terminal 201, a second input terminal 202, a reference voltage input terminal 203 and an output terminal 204. The first input terminal 201 of the bidirectional current detection amplifier is connected to one end of the sampling resistor R, and the second input terminal 202 of the bidirectional current detection amplifier is connected to the other end of the sampling resistor R, that is, the input terminals of the bidirectional current detection amplifier are respectively connected to the two ends of the sampling resistor R to obtain the sampling signal of the phase line where the sampling resistor R is located (that is, the potential difference between the two ends of the sampling resistor R). The reference voltage input terminal 203 of the bidirectional current detection amplifier is connected to the reference voltage REF, which is usually provided by a stable and known voltage source as a standard value for reference to other voltages in the circuit. The output terminal 204 of the bidirectional current detection amplifier will be used to output the amplified sampling signal, and the specific amplification factor can be preset by the developer. The signal of the output terminal 204 of the bidirectional current detection amplifier can be the difference between the voltages at the two ends of the sampling resistor R, thereby reflecting the current on the phase line where the sampling resistor R is located. In this embodiment, the output terminal 204 of the bidirectional current detection amplifier will be connected to the differential unit 30, and a differential signal will be formed through the differential unit 30.

[0043] In some embodiments, Figure 4 As shown, the differential unit 30 includes an inverter 320, and the inverter 320 is used to invert the input signal to form a differential signal. The inverter 320 includes an input terminal 321, a reference voltage input terminal 322 and an output terminal 323. The input terminal 321 of the inverter 320 receives the amplified sampling signal, that is, it is directly or indirectly connected to the output terminal 204 of the bidirectional current detection amplifier. The reference voltage input terminal 322 of the inverter 320 is also connected to the reference voltage, which is the same voltage as the reference voltage connected to the bidirectional current detection amplifier and can be provided by the same voltage source. The output terminal 323 of the inverter 320 is used to output the opposite signal of the amplified sampling signal. The amplified sampling signal and the opposite signal have the same amplitude and opposite phase, forming a set of differential signals (also called differential signals).

[0044] exist Figure 4In the example, the differential unit 30 also includes a voltage follower 310, which is used to keep the output voltage the same as the input voltage, and can also be understood as an amplifier with a voltage amplification factor of 1. By providing the voltage follower 310 in the differential unit 30, the output resistance can be effectively reduced, and the interference of the front and rear stage circuits can be isolated, the stability of the sampling signal amplified by the current detection amplifier unit 20 can be improved, and the motor current sampling circuit of this embodiment can have a better sampling range. The voltage follower 310 includes an input terminal 311, a reference voltage input terminal 312 and an output terminal 313. The input terminal 311 of the voltage follower 310 is connected to the bidirectional current detection amplifier to obtain the amplified sampling signal. The reference voltage input terminal 312 of the voltage follower 310 is connected to the reference voltage, and the reference voltage can also be provided by the same voltage source. The output terminal 313 of the voltage follower 310 is connected to the input terminal 321 of the inverter 320 to transmit the amplified sampling signal to the inverter 320; it should be understood that at this time, the voltage follower 310 outputs a signal that is the same or substantially the same as the amplified sampling signal (that is, the voltage amplification factor is 1 or very close to 1), and for ease of description, it is still referred to as the amplified sampling signal in this application. In this example, the differential signal formed by the differential unit 30 is the reverse signal output by the inverter 320 and the amplified sampling signal output by the voltage follower 310.

[0045] The differential unit 30 includes a first output terminal 331 and a second output terminal 332. The first output terminal 331 of the differential unit 30 is provided with a first filter unit 3311, and the first output terminal of the differential unit 30 is connected to the output terminal of the voltage follower 310 through the first filter unit 3311. The second output terminal 332 of the differential unit 30 is provided with a second filter unit 3321, and the second output terminal 332 of the differential unit 30 is connected to the output terminal of the inverter 320 through the second filter unit 3321. The first filter unit 3311 and the second filter unit 3321 are circuits or devices that can be used to filter signals, which can ensure the stability of the signal during transmission and remove noise. The first output terminal 331 and the second output terminal 332 of the differential unit 30 are used to output the differential signal to the outside. In actual applications, the first output terminal 331 and the second output terminal 332 of the differential unit 30 will be connected to subsequent circuits or devices, and the subsequent circuits or devices receive the differential signal and obtain the result of current sampling based on the differential signal.

[0046] The first filter unit 3311 and the second filter unit 3312 may be the same or different. As an example, the first filter unit 3311 and the second filter unit 3312 may be an RC filter circuit, which includes a first resistor R3 and a filter capacitor C. The first resistor R3 is connected in series to the signal transmission line, one end of the filter capacitor C is connected to one side of the output end of the first resistor R3, and the other end is grounded.

[0047] The present embodiment also provides a motor driver, which includes the motor current sampling circuit of the above example. The motor driver of the present embodiment can sample the phase current of the motor, realize continuous sampling, and allow the current sampling to perform PWM cycle averaging operation in some implementation processes, which greatly improves the sampling accuracy. In addition, the amplified sampling signal is transmitted in the form of a differential signal, has strong anti-infection ability, external common mode noise can be effectively removed, and can suppress electromagnetic interference. It can be seen that the current sampling performance of the motor driver of the present embodiment is good, which is conducive to more precise control of the motor.

[0048] In some embodiments, the motor driver further includes an analog-to-digital conversion unit connected to the differential unit 30 in the motor current sampling circuit. The analog-to-digital conversion unit is used to obtain the differential signal transmitted by the differential unit 30, and obtain a digital signal of the amplified sampling signal according to the differential signal. The amplified sampling signal is an analog signal, which can be converted into a digital signal by the analog-to-digital conversion unit for processing by the processing unit. It is understandable that in some examples, the analog-to-digital conversion unit may include a differential-to-single-ended circuit, which, after receiving the differential signal, restores it to a single-ended signal to simplify subsequent processing operations.

[0049] The motor driver also includes a processing unit connected to the analog-to-digital conversion unit. The processing unit can be a module or device with processing capabilities such as an MCU (Microcontroller Unit) chip, a single-chip microcomputer, etc. Exemplarily, the processing unit can be a main controller of the motor driver. The processing unit obtains a digital signal of the amplified sampling signal, through which the current on the corresponding phase line can be determined. Of course, the processing unit can perform corresponding processing or control according to the current obtained by sampling, and this embodiment does not limit this.

[0050] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made according to the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A motor current sampling circuit, characterized in that: include: At least two phase current sampling units, each of which is connected to a phase line of the motor and is used to sample currents of at least two phase lines of the motor; At least two current detection amplifying units are connected to the at least two phase current sampling units in a one-to-one correspondence, and are used to obtain sampling signals of the phase current sampling units and amplify the sampling signals according to a set ratio; At least two differential units are connected to the current detection amplifying units in a one-to-one correspondence, and are used to transmit the sampling signals amplified by the current detection amplifying units in the form of differential signals.

2. The motor current sampling circuit according to claim 1, characterized in that: The at least two phase current sampling units include a first phase current sampling unit and a second phase current sampling unit, the first phase current sampling unit is connected to a first phase line in the inverter circuit, and the second phase current sampling unit is connected to a second phase line in the inverter circuit.

3. The motor current sampling circuit as claimed in claim 2, characterized in that: The at least two phase current sampling units further include a third phase current sampling unit, and the third phase current sampling unit is connected to a third phase line in the inverter circuit.

4. The motor current sampling circuit according to claim 2 or 3, characterized in that: Each of the phase current sampling units includes a sampling resistor, and the sampling resistor is arranged on the phase line of the inverter circuit.

5. The motor current sampling circuit as claimed in claim 4, characterized in that: The current detection amplification unit includes a bidirectional current detection amplifier; The bidirectional current detection amplifier includes a first input terminal, a second input terminal, a reference voltage input terminal and an output terminal; the first input terminal and the second input terminal of the bidirectional current detection amplifier are respectively connected to the two ends of the sampling resistor to obtain the sampling signal of the phase line where the sampling resistor is located; the reference voltage input terminal of the bidirectional current detection amplifier is connected to the reference voltage; the output terminal of the bidirectional current detection amplifier is used to output the amplified sampling signal.

6. The motor current sampling circuit as claimed in claim 5, characterized in that: The differential unit comprises an inverter, and the inverter comprises an input terminal, a reference voltage input terminal and an output terminal; the input terminal of the inverter receives the amplified sampling signal; The reference voltage input terminal of the inverter is connected to the reference voltage; The output end of the inverter is used to output the opposite signal of the amplified sampling signal; the output end of the differential unit outputs a group of differential signals consisting of the amplified sampling signal and its opposite signal.

7. The motor current sampling circuit as claimed in claim 6, characterized in that: The differential unit further includes a voltage follower, which includes an input terminal, a reference voltage input terminal and an output terminal; the input terminal of the voltage follower is connected to the bidirectional current detection amplifier to obtain the amplified sampling signal; the reference voltage input terminal of the voltage follower is connected to the reference voltage; The output end of the voltage follower is connected to the input end of the inverter to transmit the amplified sampling signal to the inverter.

8. The motor current sampling circuit as claimed in claim 7, characterized in that: The differential unit includes a first output end and a second output end; the first output end is provided with a first filtering unit, and the first output end is connected to the output end of the voltage follower through the first filtering unit; the second output end is provided with a second filtering unit, and the second output end is connected to the output end of the inverter through the second filtering unit; the first output end and the second output end are used to output the differential signal formed by the voltage follower and the inverter to the outside.

9. A motor driver, characterized in that: The motor current sampling circuit comprises the motor current sampling circuit as described in any one of claims 1 to 8.

10. The motor driver according to claim 9, characterized in that: Also includes: an analog-to-digital conversion unit connected to the differential unit in the motor current sampling circuit, used to obtain a differential signal transmitted by the differential unit, and obtain a digital signal of the amplified sampling signal according to the differential signal; The processing unit connected to the analog-to-digital conversion unit is used to obtain a digital signal of the amplified sampling signal.

Images