A control circuit and method for a direct current motor

Abstract

This invention provides a control circuit and method for a DC motor. By connecting the DC motor to a DC power supply, the control circuit includes a voltage monitoring unit for monitoring the output voltage of the DC power supply and a switching circuit for controlling the operation of the DC motor. The control circuit also includes a PWM signal output unit to output a PWM signal for controlling the switching circuit. The PWM signal output unit is configured to adjust the duty cycle of the output PWM signal based on the voltage monitoring unit's result. This allows motors with different resistance values ​​to continuously operate in a voltage-stabilized state. It also identifies when the motor or other loads are under heavy load or overload conditions and stops the motor from starting, preventing damage to the motor or other loads due to power supply voltage pull-down after prolonged operation. When the input power supply voltage is too high, it can adjust the magnitude of the input power supply voltage to prevent the motor's excitation current from increasing with the applied voltage, thereby preventing core loss.

Description

Technical Field

[0001] This invention relates to the field of intelligent control technology, and in particular to a control circuit and method for a DC motor. Background Technology

[0002] Because DC power supplies have limited load-carrying capacity, their output voltage will drop significantly under heavy or overload conditions, severely impacting the load. When the power supply voltage drops, the motor's rotational torque decreases considerably. If the load remains constant, the motor current must increase dramatically to produce the required torque. If the required torque exceeds the motor's limits, the motor may overload and be damaged. If the voltage remains consistently too low, the motor will overheat and burn out.

[0003] When a motor starts up, if the power supply voltage is lower than the motor's rated voltage, the induced magnetic field in the rotor will weaken, thus reducing the induced magnetic field, rotor winding current, and rotating magnetic field. This reduction in both aspects significantly decreases torque, and in severe cases, the motor may be difficult or unable to start. During normal operation, when the voltage drops, the motor speed decreases due to the reduced torque and constant load. This accelerates the cutting of the rotor winding magnetic lines of force, increasing the induced current and stator current. Sometimes this can cause overcurrent operation, leading to prolonged overheating or even burnout. When the power supply voltage is higher than the motor's rated voltage, the motor's excitation current increases with the applied voltage, increasing core losses, reducing the motor's power factor, and negatively impacting its operation.

[0004] Existing technologies for detecting the power supply voltage of DC motors have complex structures and high costs. They primarily collect power supply voltage for calculations of other voltages, thus lacking the function of voltage regulation and stabilization. Furthermore, they cannot solve the problem of motor damage caused by power supply voltage fluctuations during motor startup and operation.

[0005] Therefore, there is an urgent need to provide a DC motor control circuit and method that can adjust the power supply voltage so that the system is in a stable voltage state during operation, thus preventing damage to the motor during startup and operation. Summary of the Invention

[0006] To address the technical problems in existing DC motors, such as the lack of voltage regulation and stabilization in the power supply voltage, and the inability to prevent motor damage due to power supply voltage fluctuations during startup and operation, this invention proposes a control circuit and method for DC motors to solve the aforementioned technical problems.

[0007] In one aspect, the present invention provides a control circuit for a DC motor, comprising the following steps:

[0008] The DC motor is connected to a DC power supply. The control circuit includes a voltage monitoring unit for monitoring the output voltage of the DC power supply and a switching circuit for controlling the operation of the DC motor. The control circuit also includes a PWM signal output unit to output a PWM signal for controlling the switching circuit. The PWM signal output unit is configured to adjust the duty cycle of the output PWM signal based on the result of the voltage monitoring unit. The PWM signal output unit adjusts the output voltage of the DC power supply based on the value of the power supply voltage monitored by the voltage monitoring unit and stabilizes the output voltage of the DC power supply at a set voltage value.

[0009] Furthermore, it also includes a current monitoring unit for monitoring the output current of the DC power supply, and a PWM signal output unit configured to adjust the duty cycle of the output PWM signal based on the results of the voltage monitoring unit and the current monitoring unit. The PWM signal output unit adjusts the output voltage of the DC power supply based on the power supply voltage value monitored by the voltage monitoring unit, and stabilizes the output voltage of the DC power supply within a set voltage range. The current monitoring unit monitors in real time, and the PWM signal output unit determines the maximum output power of the motor based on the collected voltage and current values, ensuring that the motor is always operating in maximum power mode.

[0010] Furthermore, the switching circuit includes a transistor switch, and the PWM signal output by the PWM signal output unit is input to the control terminal of the transistor switch. The PWM signal output unit outputs a PWM signal, which controls the magnitude of the current and voltage in the circuit by controlling the turn-off frequency of the transistor switch.

[0011] Furthermore, the PWM signal output unit is configured to gradually increase the duty cycle of the PWM signal and simultaneously acquire the current value monitored by the current monitoring unit when the detected output voltage of the DC power supply is higher than the first set voltage; if the detected output voltage is equal to or lower than the first set voltage but higher than the second set voltage, the PWM output unit determines that the DC motor has started and saves the PWM value at this moment, and simultaneously acquires the current value monitored by the current monitoring unit, and then enters the maximum power control mode. By setting a voltage range, motors with different resistance values ​​within this voltage range can start. If a power supply voltage lower than this range is detected, it is determined to be an overload, causing the power supply voltage to drop significantly, and the motor is controlled to prevent it from starting, thus protecting the motor and other loads.

[0012] Furthermore, in the maximum power control mode, the duty cycle of the PWM signal output unit is adjusted in real time to keep the output voltage of the DC power supply constant at the third set voltage value. If the PWM signal output unit continuously detects that the output voltage of the DC power supply cannot be kept constant at the third set voltage value and is lower than the second set voltage value, it determines that the power supply's load-carrying capacity is insufficient, and at this time, the PWM signal output unit stops outputting signals. The PWM signal output unit calculates the third set voltage at maximum output power by collecting the voltage and current values ​​in the circuit, and makes the motor work at the third set voltage at maximum power.

[0013] Furthermore, the first set voltage is the difference between the static voltage and the voltage difference. The static voltage is the DC power supply voltage value collected and recorded in real time when the motor stops working, and the voltage difference ranges from 0.1V to 1V.

[0014] Furthermore, the first set voltage and the third set voltage are both greater than the second set voltage.

[0015] Furthermore, the voltage monitoring unit includes a voltage divider circuit and a first A / D sampling circuit. The voltage divider circuit has a test potential point, and the first A / D sampling circuit acquires the voltage value of the test potential point. The voltage value acquired by the first A / D sampling circuit is transmitted to the PWM signal output unit, which calculates the power supply voltage value by calculating the voltage at the test potential point.

[0016] Furthermore, the current monitoring unit includes a sampling resistor and a second A / D sampling circuit, which acquires the current value flowing through the sampling resistor. By acquiring the current value flowing through the sampling resistor, the current value in the loop is obtained.

[0017] According to a second aspect of the present invention, a control method for a DC motor is provided, the method comprising:

[0018] The operation of the DC motor is controlled using the control circuit for the DC motor proposed in the first aspect.

[0019] This invention proposes a control circuit and method for a DC motor. By connecting the DC motor to a DC power supply, the control circuit includes a voltage monitoring unit for monitoring the output voltage of the DC power supply and a switching circuit for controlling the operation of the DC motor. The control circuit also includes a PWM signal output unit to output a PWM signal for controlling the switching circuit. The PWM signal output unit is configured to adjust the duty cycle of the output PWM signal based on the voltage monitoring unit's result. This allows motors with different resistance values ​​to continuously operate in a voltage-stabilized state. It also identifies when the motor or other loads are under heavy load or overload conditions and stops the motor from starting, preventing damage to the motor or other loads due to power supply voltage pull-down after prolonged operation. When the input power supply voltage is too high, it can adjust the magnitude of the input power supply voltage to prevent the motor's excitation current from increasing with the applied voltage, thereby preventing core loss. Attached Figure Description

[0020] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of the invention. Other embodiments and many anticipated advantages of the embodiments will be readily recognized as they become better understood through reference to the following detailed description. Other features, objects, and advantages of this application will become more apparent from reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0021] Figure 1 This is a schematic diagram of the module connection of a control circuit for a DC motor according to the first embodiment of this application;

[0022] Figure 2 This is a schematic diagram of a control circuit for a DC motor according to the first embodiment of this application;

[0023] Figure 3 This is a schematic diagram of the module connection of a control circuit for a DC motor according to a second embodiment of this application;

[0024] Figure 4 This is a schematic diagram of a control circuit for a DC motor according to a second embodiment of this application. Reference numerals: 1-DC power supply; 2-DC motor; 21-Freewheeling diode; 3-Voltage monitoring unit; 31-First resistor; 32-Second resistor; 33-First A / D sampling circuit; 4-Switching circuit; 41-Sampling resistor; 42-Second A / D sampling circuit; 5-PWM signal output unit; 6-Current monitoring unit. Detailed Implementation

[0025] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0027] It should be understood that although the terms first, second, third, etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first information may also be referred to as second information without departing from the scope of this invention, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0028] Example 1

[0029] like Figure 1 As shown, the DC motor 2 is connected to the DC power supply 1. The control circuit includes a voltage monitoring unit 3 for monitoring the output voltage of the DC power supply 1 and a switching circuit 4 for controlling the operation of the DC motor 2. The control circuit also includes a PWM signal output unit 5 to output a PWM signal for controlling the switching circuit 4. The PWM signal output unit 5 is configured to adjust the duty cycle of the output PWM signal according to the result of the voltage monitoring unit 3. The PWM signal output unit 5 adjusts the output voltage of the DC power supply 1 according to the value of the power supply voltage monitored by the voltage monitoring unit 3, and stabilizes the output voltage of the DC power supply 1 at a set voltage value.

[0030] like Figure 2As shown, the switching circuit 4 includes a transistor switch, which can be a bipolar junction transistor (BJT). The PWM signal output from the PWM signal output unit 5 is input to the control terminal of the transistor switch. The PWM signal output unit 5 outputs a PWM signal, which controls the current and voltage in the circuit by controlling the turn-off frequency of the transistor switch. A freewheeling diode 21 is connected in parallel with the DC motor 2. The freewheeling diode 21 can be a fast recovery diode or a Schottky diode. It is used in the circuit to protect the motor from breakdown or burnout by induced voltage. The freewheeling diode 21 also eliminates reverse voltage protection caused by sudden changes in voltage and current across the inductive load in the DC circuit.

[0031] In a specific embodiment, the voltage monitoring unit 3 includes a voltage divider circuit and a first A / D sampling circuit 33. The voltage divider circuit includes a first resistor 31 and a second resistor 32, which form a complete loop with the power supply voltage. The voltage divider circuit is connected in parallel with the load loop. One end of the second resistor 32 is connected in series with the first resistor 31, and the other end of the second resistor 32 is connected to the signal reference ground. The potential point of the second resistor 32 relative to the signal reference ground can be selected as the test potential point. The voltage value collected by the first A / D sampling circuit 33 is transmitted to the PWM signal output unit 5. The PWM signal output unit 5 includes an MCU control chip, which calculates the power supply voltage value based on the voltage at the test potential point.

[0032] In a specific embodiment, the PWM signal output unit 5 is configured to gradually increase the duty cycle of the PWM signal if the output voltage of the DC power supply 1 is detected to be higher than a first set voltage; if the output voltage is detected to be equal to or lower than the first set voltage, the PWM output unit determines that the DC motor 2 has started and saves the PWM value at this moment. The PWM signal output unit 5 outputs the PWM signal in a way that digitally controls the analog circuit; a microcontroller with built-in PWM control can be selected. The voltage or current source is applied to the transistor switch in the switching circuit 4 as a repeating pulse sequence of on / off states. When on, the DC power supply is applied to the load; when off, the power supply is disconnected. Therefore, the duty cycle of the high level in the PWM wave within one cycle is used to control the turn-off of the transistor switch, thereby controlling the current and voltage of the control circuit.

[0033] Therefore, the principle behind the PWM signal output unit 5 controlling the circuit voltage in Example 1 to maintain a stable circuit voltage is as follows: First, a first preset voltage is established within the MCU. The motor starts with an initial duty cycle of N%, increasing by 1% every x ms until it reaches M%, while simultaneously monitoring the power supply voltage. If the power supply voltage is measured to be lower than the first preset voltage during startup, the duty cycle stops increasing, an overload point is confirmed, the current current value and power supply voltage value are recorded, and startup is complete. If the power supply voltage is measured to be higher than or equal to the first preset voltage during startup, when the duty cycle increases to M%, the current power supply voltage value is recorded, and startup is complete. Furthermore, the power supply voltage value is monitored in real time throughout the startup process to determine if the motor is stalled or short-circuited. If stalling or short-circuiting occurs, an abnormal code is output, and abnormal handling is initiated.

[0034] Example 2

[0035] The difference between Example 2 and Example 1 is that Example 2 adds a current monitoring unit 6. The PWM signal output unit 5 can calculate the maximum output power when the load is running based on the values ​​collected from the current monitoring unit 6 and the voltage monitoring unit 3. By adjusting the voltage and current in the circuit, the system can be kept in the maximum power working mode.

[0036] like Figure 3 As shown, in a specific embodiment, a current monitoring unit 6 is also included for monitoring the output current of the DC power supply 1. The PWM signal output unit 5 is configured to adjust the duty cycle of the output PWM signal based on the results of the voltage monitoring unit 3 and the current monitoring unit 6. The PWM signal output unit 5 adjusts the output voltage of the DC power supply 1 based on the power supply voltage value monitored by the voltage monitoring unit 3, and stabilizes the output voltage of the DC power supply 1 within a set voltage range. The current monitoring unit 6 monitors in real time, and the PWM signal output unit 5 determines the maximum output power of the motor based on the collected voltage and current values, so that the motor is always in the maximum power operating mode.

[0037] like Figure 4 As shown, in a specific embodiment, the current monitoring unit 6 includes a sampling resistor 41 and a second A / D sampling circuit 42. By acquiring the current value flowing through the sampling resistor 41, the current value in the circuit is obtained. The sampling resistor 41 can be obtained by the result of series and parallel connections of resistors. The voltage value across the sampling resistor 41 is measured, thereby calculating the current value in the circuit.

[0038] Therefore, in Embodiment 2, the principle of the PWM signal output unit 5 controlling the circuit voltage to keep the circuit voltage stable is as follows: the PWM signal output unit 5 is configured to gradually increase the duty cycle of the PWM signal when the output voltage of the DC power supply 1 is detected to be higher than the first set voltage; if the output voltage is detected to be equal to or lower than the first set voltage and simultaneously higher than the second set voltage, the PWM signal output unit 5 determines that the DC motor 2 has started and saves the PWM value at this moment.

[0039] In a specific embodiment, the duty cycle of the PWM signal of the PWM signal output unit 5 is adjusted in real time under maximum power control mode to keep the output voltage of the DC power supply 1 constant at a third set voltage value. If the PWM signal output unit 5 continuously monitors that the output voltage of the DC power supply 1 cannot be kept constant at the third set voltage value and is lower than the second set voltage value, it determines that the power supply has insufficient load-carrying capacity, and at this time, the PWM signal output unit 5 stops outputting signals. The PWM signal output unit 5 calculates the third set voltage at maximum output power by collecting the voltage and current values ​​in the circuit, and makes the motor work at the third set voltage at maximum power.

[0040] In a specific embodiment, the first set voltage is the difference between the static voltage and the voltage difference. The static voltage is the DC power supply voltage value recorded in real time when the motor stops working. In engineering applications, the preferred range of the voltage difference is 0.1V-1V, depending on the actual load conditions.

[0041] The current value is monitored in real time throughout the startup process to determine whether the motor is stalled or short-circuited. If stalling or short-circuiting occurs, an exception code is output and exception handling is initiated.

[0042] Maximum power output operating mode:

[0043] After the system starts up, it adjusts the duty cycle to stabilize the input voltage at the third set voltage according to different load conditions and power supply capabilities. The first and third set voltages are both greater than the second set voltage. At the same time, it monitors the load current to keep the system at maximum output power. It also monitors the continuous working time. If it works continuously for x minutes, it enters the exception handling stage and outputs an exception code.

[0044] Exception handling is as follows:

[0045] 1. If a motor stall or short circuit is detected, immediately clear the duty cycle and shut down the motor.

[0046] 2. If the motor is detected to be operating continuously for an extended period of time, immediately clear the duty cycle and shut down the motor.

[0047] 3. If insufficient power supply capacity is detected, immediately clear the duty cycle and shut down the motor.

[0048] The so-called voltage regulation state allows the voltage to fluctuate within a set allowable voltage range, also known as the safe voltage range. To ensure the system operates within this safe voltage range, the power supply voltage can be monitored and adjusted, or the loop current can be monitored and adjusted. Alternatively, the power supply voltage can be monitored simultaneously to first ensure the system operates within the set allowable voltage range. Then, by acquiring the loop current, the PWM signal output unit 5 calculates that within the set allowable voltage range, the current is adjusted using the PWM signal to operate the system in maximum power mode.

[0049] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A control circuit for a DC motor, characterized in that, The DC motor is connected to a DC power supply. The control circuit includes a voltage monitoring unit for monitoring the output voltage of the DC power supply, a current monitoring unit for monitoring the output current of the DC power supply, and a switching circuit for controlling the operation of the DC motor. The control circuit also includes a PWM signal output unit to output a PWM signal for controlling the switching circuit. The PWM signal output unit is configured to adjust the duty cycle of the output PWM signal based on the results of the voltage monitoring unit and the current monitoring unit. The PWM signal output unit is configured to gradually increase the duty cycle of the PWM signal and simultaneously acquire the current value monitored by the current monitoring unit if the output voltage of the DC power supply is detected to be higher than a first set voltage. If the output voltage is detected to be equal to or lower than the first set voltage but higher than a second set voltage, the PWM signal output unit determines that the DC motor has started and saves the PWM value at this moment, and simultaneously acquires the current value monitored by the current monitoring unit. Then, it enters the maximum power control mode. The PWM signal output unit is configured to maintain the system at maximum output power and monitor the continuous working time. If MIN is entered into exception handling, an exception code is output. In the maximum power control mode, the duty cycle of the PWM signal of the PWM signal output unit is adjusted in real time to keep the output voltage of the DC power supply constant at the third set voltage value. If the PWM signal output unit continuously detects that the output voltage of the DC power supply cannot be kept constant at the third set voltage value and is lower than the second set voltage value, it is determined that the power supply has insufficient load-carrying capacity. At this time, the PWM signal output unit stops outputting signals.

2. The control circuit for a DC motor according to claim 1, characterized in that, The switching circuit includes a transistor switch, and the PWM signal output by the PWM signal output unit is input to the control terminal of the transistor switch.

3. The control circuit for a DC motor according to claim 1, characterized in that, The first set voltage is the difference between the static voltage and the voltage difference. The static voltage is the DC power supply voltage value collected and recorded in real time when the motor stops working. The voltage difference ranges from 0.1V to 1V.

4. The control circuit for a DC motor according to claim 3, characterized in that, The first set voltage and the third set voltage are both greater than the second set voltage.

5. The control circuit for a DC motor according to claim 1, characterized in that, The voltage monitoring unit includes a voltage divider circuit and a first A / D sampling circuit. The voltage divider circuit is provided with a test potential point, and the first A / D sampling circuit acquires the voltage value of the test potential point.

6. The control circuit for a DC motor according to claim 1, characterized in that, The current monitoring unit includes a sampling resistor and a second A / D sampling circuit, the second A / D sampling circuit acquiring the current value flowing through the sampling resistor.

7. A control method for a DC motor, the method using a control circuit for a DC motor according to any one of claims 1-6 to control the operation of the DC motor.

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