Rotating speed detection circuit of brush motor

Abstract

The utility model relates to the technical field of rotating speed detection of electric equipment, in particular to a rotating speed detection circuit of a brush motor, which comprises a driving circuit, a signal sampling circuit, a signal filtering and amplifying circuit and a signal comparison circuit, the driving circuit is used for controlling the rotating speed of the brush motor, the input end of the driving circuit is connected with a voltage-stabilized source, the output end of the driving circuit is connected with the input end of the signal sampling circuit, the output end of the signal sampling circuit is connected with the input end of the signal filtering and amplifying circuit, and the signal sampling circuit is used for collecting actual working current of the driving circuit; the signal filtering and amplifying circuit is used for filtering and amplifying the sampling signals, the output end of the signal filtering and amplifying circuit is connected with the input end of the signal comparison circuit, and the signal comparison circuit is used for signal comparison. The problems that the cost is high and the calculation precision is limited by use scenes due to the fact that the real-time rotating speed of the motor is calculated through multiple sensors in an existing technical scheme are solved.

Description

Technical Field

[0001] This application relates to the field of rotational speed detection technology for electric equipment, and specifically to a speed detection circuit for a brushed motor. Background Technology

[0002] In the field of medical electric equipment, brushed motors are commonly used as the power source to achieve precise control of moving parts. For brushed motors that require speed regulation, incremental encoders are usually installed on the motor as speed acquisition sensors to calculate the real-time speed of the motor in order to monitor and adjust the speed in real time.

[0003] In existing technical solutions, a common approach is to use the I / O pins of a microcontroller chip to collect encoder logic signals for counting, and then convert the number of encoder logic signals collected per unit time into N revolutions per minute, thereby calculating the motor speed.

[0004] However, commonly used ABL encoders require two or more I / Os, which not only increases the burden on the microcontroller resources, but also requires additional encoders to be installed for brushed motors that are not equipped with ABL encoders, resulting in higher costs. Furthermore, incremental encoders need to be replaced after a certain number of years of use, which has high maintenance costs. In some harsh environments, such as magnetic field environments, the accuracy of the encoder may be affected, posing potential risks. Utility Model Content

[0005] This application addresses the problem that existing technologies rely on multiple sensors to calculate the real-time speed of a motor, resulting in high costs and limitations in calculation accuracy due to application scenarios. It provides a speed detection circuit for a brushed motor that uses a simple circuit to measure the real-time speed of the motor without the need for sensors, thus reducing costs.

[0006] To solve the above problems, the technical solution of this application is:

[0007] A speed detection circuit for a brushed motor includes a drive circuit, a signal sampling circuit, a signal filtering and amplification circuit, and a signal comparison circuit.

[0008] The drive circuit is used to control the speed of the brushed motor. The input terminal of the drive circuit is connected to a regulated power supply, and the output terminal of the drive circuit is connected to the input terminal of a signal sampling circuit. The output terminal of the signal sampling circuit is connected to the input terminal of a signal filtering and amplification circuit. The signal sampling circuit is used to collect the actual operating current of the drive circuit. The signal filtering and amplification circuit is used to filter and amplify the sampled signal. The output terminal of the signal filtering and amplification circuit is connected to the input terminal of a signal comparison circuit. The signal comparison circuit is used to perform signal comparison.

[0009] Optionally, the driving circuit includes a first MOSFET, a second MOSFET, a third MOSFET, and a fourth MOSFET;

[0010] The first MOSFET, the second MOSFET, the third MOSFET, and the fourth MOSFET are electrically connected to form an H-bridge circuit, and a PWM signal generator is connected to the input terminal of the H-bridge circuit.

[0011] The first MOSFET and the fourth MOSFET form a pair of diagonal terminals of the H-bridge circuit, and the second MOSFET and the third MOSFET form the other pair of diagonal terminals of the H-bridge circuit.

[0012] Optionally, the signal sampling circuit includes a sampling resistor, the output terminal of the driving circuit is grounded after passing through the sampling resistor, and the sampling resistor is also connected to the input terminal of the signal filtering and amplification circuit.

[0013] Optionally, the signal filtering and amplification circuit includes a second resistor, a third resistor, a first capacitor, and an amplifier. One side of the second resistor is connected to the signal sampling circuit, and the other side is connected to the non-inverting input terminal of the amplifier via an RC circuit composed of the third resistor and the first capacitor. The output terminal of the amplifier is connected to the signal comparison circuit, and the output terminal of the amplifier is also connected to the inverting input terminal of the amplifier.

[0014] Optionally, the signal comparison circuit includes a second capacitor, a sixth resistor, a seventh resistor, an eighth resistor, and a comparator.

[0015] The second capacitor is connected to a signal filtering and amplification circuit on one side and to the inverting input of a comparator on the other side. The non-inverting input of the comparator is connected to the regulated power supply via the sixth and seventh resistors. The comparator outputs through the eighth resistor.

[0016] Optionally, the first MOSFET, the second MOSFET, the third MOSFET, and the fourth MOSFET all include N-channel MOSFETs, and the N-channel MOSFETs include FR3710 type MOSFETs.

[0017] Optionally, the amplifier may include a TLC2272 type amplifier.

[0018] Optionally, the comparator includes an LM393AH type amplifier.

[0019] The beneficial effects of this application through the above technical solution are as follows:

[0020] The brushed motor speed detection circuit provided in this application includes a brushed motor, a drive circuit, a signal sampling circuit, a signal filtering and amplification circuit, and a signal comparison circuit. The drive circuit adopts an H-bridge circuit design, providing a flexible speed control method for the brushed motor. During the rotation of the brushed motor, the carbon brushes are triggered with each revolution. The spark interference from the carbon brush stroke is coupled into the motor current. First, the motor current of the brushed motor is sampled by the sampling resistor in the signal sampling circuit. Then, the sampled signal is filtered by the RC circuit composed of the third resistor and the first capacitor in the signal filtering and amplification circuit. The filtered current signal is amplified by the amplifier and then enters the signal comparison circuit. In the signal comparison circuit, the current signal is high-pass filtered by the second capacitor, finally obtaining the high-frequency interference signal coupled into the current by the motor carbon brushes. This signal is compared with a set voltage threshold by a comparator. If the high-frequency interference signal is greater than the voltage threshold, a high-level signal is output, indicating that the brushed motor has rotated one revolution. Furthermore, the non-inverting input of the signal comparison circuit is connected to a voltage divider circuit composed of the sixth and seventh resistors, and the sixth resistor is connected to a regulated power supply, ensuring the stability of the circuit operation and reducing the impact of power fluctuations. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a brushed motor speed detection circuit provided in an embodiment of this application;

[0022] Figure 2 This is a schematic diagram of a driving circuit and a signal sampling circuit provided in an embodiment of this application;

[0023] Figure 3 This is a schematic diagram of a signal filtering and amplification circuit provided in an embodiment of this application;

[0024] Figure 4 This is a schematic diagram of a signal comparison circuit provided in an embodiment of this application.

[0025] The following diagram is labeled as follows: 1 is the driving circuit, 2 is the signal sampling circuit, 3 is the signal filtering and amplification circuit, 4 is the comparator circuit, Q1 is the first MOSFET, Q2 is the second MOSFET, Q3 is the third MOSFET, Q4 is the fourth MOSFET, R1 is the sampling resistor, R2 is the second resistor, R3 is the third resistor, R4 is the fourth resistor, R5 is the fifth resistor, R6 is the sixth resistor, R7 is the seventh resistor, R8 is the eighth resistor, C1 is the first capacitor, C2 is the second capacitor, U1B is the amplifier, and U2B is the comparator. Detailed Implementation

[0026] The present application will be further described below with reference to the accompanying drawings and specific embodiments:

[0027] refer to Figure 1As shown, a speed detection circuit for a brushed motor includes a drive circuit 1, a signal sampling circuit 2, a signal filtering and amplification circuit 3, and a signal comparison circuit 4.

[0028] The drive circuit 1 is used to control the speed of the brushed motor. The input terminal of the drive circuit 1 is connected to a regulated power supply, and the output terminal of the drive circuit 1 is connected to the input terminal of the signal sampling circuit 2. The output terminal of the signal sampling circuit 2 is connected to the input terminal of the signal filtering and amplification circuit 3. The signal sampling circuit 2 is used to collect the actual operating current of the drive circuit 1. The signal filtering and amplification circuit 3 is used to filter and amplify the sampled signal. The output terminal of the signal filtering and amplification circuit 3 is connected to the input terminal of the signal comparison circuit 4. The signal comparison circuit 4 is used to perform signal comparison.

[0029] refer to Figure 2 As shown, in one possible implementation, the driving circuit 1 includes a first MOSFET Q1, a second MOSFET Q2, a third MOSFET Q3, and a fourth MOSFET Q4;

[0030] The first MOSFET Q1, the second MOSFET Q2, the third MOSFET Q3, and the fourth MOSFET Q4 are electrically connected to form an H-bridge circuit. The input terminal of the H-bridge circuit is connected to a PWM signal generator, and the PWM control duty cycle output is used to control the forward and reverse rotation and stop of the electric device.

[0031] Specifically, the drains of the first MOSFET Q1 and the third MOSFET Q3 are connected to the regulated power supply, the sources of the first MOSFET Q1 and the third MOSFET Q3 are connected to the drains of the second MOSFET Q2 and the fourth MOSFET Q4, the sources of the second MOSFET Q2 and the fourth MOSFET Q4 are grounded, and the gates of the first MOSFET Q1, the second MOSFET Q2, the third MOSFET Q3 and the fourth MOSFET Q4 are respectively connected to the PWM signal generator;

[0032] The first MOSFET Q1 and the fourth MOSFET Q4 form a pair of diagonal terminals of the H-bridge circuit, and the second MOSFET Q2 and the third MOSFET Q3 form the other pair of diagonal terminals of the H-bridge circuit.

[0033] In one possible implementation, the first MOSFET Q1, the second MOSFET Q2, the third MOSFET Q3, and the fourth MOSFET Q4 all include N-channel MOSFETs, wherein the N-channel MOSFETs are FR3710 type MOSFETs.

[0034] In one possible implementation, the signal sampling circuit 2 includes a sampling resistor R1, the output terminal of the driving circuit 1 is grounded through the sampling resistor R1, and the sampling resistor R1 is also connected to the input terminal of the signal filtering and amplification circuit 3.

[0035] refer to Figure 3 As shown, in one possible implementation, the signal filtering and amplification circuit 3 includes a second resistor R2, a third resistor R3, a first capacitor C1, a fourth resistor R4, a fifth resistor R5, and an amplifier U1B. One side of the second resistor R2 is connected to the signal sampling circuit 2, and the other side is connected to the non-inverting input terminal of the amplifier U1B via an RC circuit composed of the third resistor R3 and the first capacitor C1. The output terminal of the amplifier U1B is connected to the signal comparison circuit 4, and the output terminal of the amplifier U1B is also connected to the inverting input terminal of the amplifier U1B. Specifically, the inverting input terminal of the amplifier U1B is connected to ground after being connected to the fourth resistor R4, and is connected to the output terminal of the amplifier U1B after being connected to the fifth resistor R5.

[0036] In this embodiment, one end of the third resistor R3 is connected to a +5V regulated power supply, and one end of the first capacitor C1 is grounded.

[0037] As one possible implementation, the amplifier U1B is a TLC2272 type amplifier.

[0038] refer to Figure 4 As shown, in one possible implementation, the signal comparison circuit 4 includes a second capacitor C2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a comparator U2B. One side of the second capacitor C2 is connected to the signal filtering and amplification circuit 3, and the other side is connected to the inverting input terminal of the comparator U2B. The non-inverting input terminal of the comparator U2B is connected to the regulated power supply via the sixth resistor R6 and the seventh resistor R7. The comparator U2B outputs through the eighth resistor R8.

[0039] In this embodiment, the sixth resistor R6 is connected to a +5V regulated power supply, and one end of the seventh resistor R7 is grounded. The sixth resistor R6 and the seventh resistor R7 form a voltage divider circuit to provide a stable reference voltage for the comparator U2B.

[0040] As one possible implementation, the comparator U2B is an LM393AH type amplifier.

[0041] In this embodiment, during operation:

[0042] The PWM signal generator outputs a PWM signal to control the drive circuit 1 to work, and the drive circuit 1 drives the brushed motor to work. When the brushed motor is working, it will trigger the carbon brush with each rotation. The spark interference of the carbon brush stroke will be coupled into the motor current.

[0043] The motor current is collected by sampling resistor R1 and output to an RC circuit consisting of third resistor R3 and first capacitor C1 for filtering. The filtered current is amplified by amplifier U1B. The output of amplifier U1B is connected to signal comparison circuit 4. In signal comparison circuit 4, second capacitor C2 filters the signal to obtain the high-frequency interference signal coupled to the current by the motor carbon brush. The high-frequency interference signal enters comparator U2B and is compared with the threshold voltage signal.

[0044] When comparator U2B outputs a high-level signal, it indicates that there is a high-frequency interference signal output. The high-frequency interference signal originates from the spark interference of the carbon brush stroke. Therefore, when comparator U2B outputs a high-level signal, it indirectly indicates that the brushed motor has rotated one revolution. The speed of the brushed motor is obtained by recording the high-level signal output of comparator U2B within a unit time (60s).

[0045] The preferred embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Any equivalent or similar modifications or substitutions to the technical solutions of this application without departing from the spirit of this application or the scope of disclosure shall fall within the protection scope of this application.

Claims

1. A rotational speed detection circuit for a brush motor, characterized by comprising: The application relates to a signal sampling and comparison circuit for a brush motor, which comprises a driving circuit (1), a signal sampling circuit (2), a signal filter-amplifying circuit (3) and a signal comparison circuit (4). The driving circuit (1) is used for controlling the rotating speed of the brush motor, the input end of the driving circuit (1) is connected with a stabilized power supply, the output end of the driving circuit (1) is connected with the input end of the signal sampling circuit (2), the output end of the signal sampling circuit (2) is connected with the input end of the signal filter-amplifying circuit (3), the signal sampling circuit (2) is used for collecting the actual working current of the driving circuit (1), the signal filter-amplifying circuit (3) is used for filtering and amplifying the sampling signal, the output end of the signal filter-amplifying circuit (3) is connected with the input end of the signal comparison circuit (4), and the signal comparison circuit (4) is used for signal comparison. The signal sampling circuit (2) comprises a sampling resistor (R1), the output end of the driving circuit (1) is connected with the ground through the sampling resistor (R1), and the sampling resistor (R1) is also connected with the input end of the signal filter-amplifying circuit (3).

2. A rotational speed detection circuit for a brush motor according to claim 1, characterized in that, The driving circuit (1) comprises a first MOS tube (Q1), a second MOS tube (Q2), a third MOS tube (Q3) and a fourth MOS tube (Q4). The first MOS tube (Q1), the second MOS tube (Q2), the third MOS tube (Q3) and the fourth MOS tube (Q4) are electrically connected to form an H-bridge circuit, and the input end of the H-bridge circuit is connected with a PWM signal generator.

3. The rotational speed detection circuit of a brush motor according to claim 1, wherein The signal filter-amplifying circuit (3) comprises a second resistor (R2), a third resistor (R3), a first capacitor (C1) and an amplifier (U1B), one side of the second resistor (R2) is connected with the signal sampling circuit (2), the other side of the second resistor (R2) is connected with the non-inverting input end of the amplifier (U1B) through an RC circuit formed by the third resistor (R3) and the first capacitor (C1), and the output end of the amplifier (U1B) is connected with the signal comparison circuit (4) and also connected with the inverting input end of the amplifier (U1B).

4. The rotational speed detection circuit of a brush motor according to claim 1, wherein The signal comparison circuit (4) comprises a second capacitor (C2), a sixth resistor (R6), a seventh resistor (R7), an eighth resistor (R8) and a comparator (U2B), one side of the second capacitor (C2) is connected with the signal filter-amplifying circuit (3), the other side of the second capacitor (C2) is connected with the inverting input end of the comparator (U2B), the non-inverting input end of the comparator (U2B) is connected with the stabilized power supply through the sixth resistor (R6) and the seventh resistor (R7), and the comparator (U2B) outputs through the eighth resistor (R8).

5. The rotational speed detection circuit of a brush motor according to claim 2, wherein The first MOS tube (Q1), the second MOS tube (Q2), the third MOS tube (Q3) and the fourth MOS tube (Q4) all comprise N-channel MOS tubes, and the N-channel MOS tubes comprise FR3710 type MOS tubes.

6. A rotational speed detection circuit for a brush motor according to claim 3, wherein The amplifier (U1B) comprises a TLC2272 type amplifier.

7. A rotational speed detection circuit for a brush motor according to claim 4, wherein The comparator (U2B) comprises an LM393AH type amplifier.

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