Motor protection device, fan and vehicle-mounted air conditioner

Abstract

The invention discloses a protection device of a motor, a fan and a vehicle-mounted air conditioner. The protection device comprises a sampling unit, a control unit and a protection unit, wherein the sampling unit samples sampling voltage of an input power supply of the motor; the hysteresis comparison unit is used for creating a high-voltage protection threshold value and outputting a set first level signal under the condition that the sampling voltage is higher than the high-voltage protection threshold value, so that the switch unit is disconnected, the power supply end of the motor is powered off, and the motor is protected; and the hysteresis comparison unit also creates a low-voltage protection threshold value, and outputs a set second level signal under the condition that the sampling voltage is lower than the low-voltage protection threshold value, so that the switch unit is switched on, the power supply end of the motor is electrified, and the motor is recovered to run. According to the scheme, the hysteresis comparison unit is used for setting the high-voltage protection threshold value and the low-voltage protection threshold value and comparing the high-voltage protection threshold value and the low-voltage protection threshold value with the sampling voltage, frequent protection of the motor can be avoided, and the reliability of motor protection is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle air conditioners, and specifically relates to a motor protection device, a fan and a vehicle air conditioner, and more particularly to a motor overvoltage protection circuit, a fan and a vehicle air conditioner based on a comparator U2A. Background Art

[0002] The battery voltage of the car air conditioner is not stable. The battery voltage will fluctuate greatly when the car starts and stops, which can easily cause overvoltage or undervoltage in the car air conditioner, causing frequent motor protection and thus damaging the internal control components of the fan.

[0003] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0004] The object of the present invention is to provide a motor protection device, a fan and a vehicle air conditioner to solve the problem that the battery voltage fluctuation of the motor equipment (such as the vehicle air conditioner) easily causes overvoltage or undervoltage, resulting in frequent motor protection, thereby damaging the internal control components of the fan. By using a hysteresis comparison module to set a high voltage protection threshold and a low voltage protection threshold and compare them with the sampled voltage, frequent motor protection of the fan can be avoided, thereby improving the reliability of the fan protection.

[0005] The present invention provides a motor protection device, comprising: a sampling unit, a hysteresis comparison unit, and a switch unit; wherein the sampling unit is used to sample the voltage of the input power supply of the motor from the input power supply access terminal of the motor to obtain a sampled voltage; the hysteresis comparison unit is used to output a set high potential when the hysteresis comparison unit starts to work, so as to create a high voltage protection threshold; and output a set first level signal when the sampled voltage is higher than the high voltage protection threshold; the switch unit is used to disconnect the switch unit itself when receiving the first level signal output by the hysteresis comparison unit, so as to cut off the power supply terminal of the motor and realize the protection of the motor; the hysteresis comparison unit is also used to output a set low potential after the hysteresis comparison unit controls the switch unit itself to disconnect, so as to create a low voltage protection threshold; and output a set second level signal when the sampled voltage is lower than the low voltage protection threshold; the switch unit is also used to turn on the switch unit itself when receiving the second level signal output by the hysteresis comparison unit, so as to power the power supply terminal of the motor and resume the operation of the motor.

[0006] In some embodiments, the sampling unit includes: a first sampling resistor module and a second sampling resistor module; wherein the input power supply of the motor is grounded after passing through the first sampling resistor module and the second sampling resistor module; and the common end of the first sampling resistor module and the second sampling resistor module, as the output end of the sampling unit, is connected to the comparison input end of the hysteresis comparison unit.

[0007] In some embodiments, the hysteresis comparison unit includes: a comparison module and a threshold setting module; the inverting input terminal of the comparison module is used as the comparison input terminal of the hysteresis comparison unit; the non-inverting input terminal of the comparison module is used as the threshold input terminal of the hysteresis comparison unit; wherein the output terminal of the sampling unit is connected to the inverting input terminal of the comparison module; a preset DC power supply is connected to the non-inverting input terminal of the comparison module and the output terminal of the comparison module respectively after passing through the threshold setting module; the output terminal of the comparison module can be connected to the control terminal of the switch unit; wherein the comparison module is used to output a set high potential when the hysteresis comparison unit starts to work, so as to create a high voltage protection threshold through the threshold setting module; and compare the sampled voltage with the high voltage protection threshold, and output a set first level signal when the sampled voltage is higher than the high voltage protection threshold; the comparison module is also used to output a set low potential after the hysteresis comparison unit controls the switch unit to disconnect itself, so as to create a low voltage protection threshold through the threshold setting module; and compare the sampled voltage with the low voltage protection threshold, and output a set first level signal when the sampled voltage is lower than the low voltage protection threshold.

[0008] In some embodiments, the threshold setting module includes: a first voltage-dividing resistor module, a second voltage-dividing resistor module, a third voltage-dividing resistor module, a fourth voltage-dividing resistor module, a fifth voltage-dividing resistor module, and a sixth voltage-dividing resistor module; wherein a preset first DC power supply is grounded after passing through the first voltage-dividing resistor module and the second voltage-dividing resistor module; a common end of the first voltage-dividing resistor module and the second voltage-dividing resistor module is connected to the in-phase input end of the comparison module; the preset first DC power supply is also grounded after passing through the fourth voltage-dividing resistor module, the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module; a common end of the fourth voltage-dividing resistor module and the fifth voltage-dividing resistor module is connected to the output end of the comparison module; the third voltage-dividing resistor module is connected between the common end of the first voltage-dividing resistor module and the second voltage-dividing resistor module, and the common end of the fourth voltage-dividing resistor module and the fifth voltage-dividing resistor module; the common end of the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module, as the output end of the hysteresis comparison unit, is connected to the control end of the switch unit.

[0009] In some implementations, the hysteresis comparison unit further includes: a filtering module; wherein the filtering module is arranged between the non-inverting input terminal of the comparison module and ground.

[0010] In some implementations, the hysteresis comparison unit further includes: a filtering module; wherein the filtering module is connected in parallel with the second voltage-dividing resistor module.

[0011] In some embodiments, the hysteresis comparison unit further includes: a TVS tube module; wherein a cathode of the TVS module is connected to a common end of the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module; and an anode of the TVS module is grounded.

[0012] In some embodiments, the switching unit includes: a switching tube module; wherein the output end of the hysteresis comparison unit is connected to the control end of the switching tube module; the input power supply of the motor is connected to the first connection end of the switching tube module; and the second connection end of the switching tube module is grounded.

[0013] Matching the above device, the present invention further provides a fan, including: the above motor protection device.

[0014] Matching the above-mentioned device, the present invention further provides a vehicle-mounted air conditioner on the other hand, including: the above-mentioned motor protection device, or the above-mentioned fan.

[0015] Therefore, the scheme of the present invention sets a sampling module, a hysteresis comparison module and a switch module between the input power supply of the motor in the fan and the load, uses the sampling module to sample the voltage of the input power supply of the fan to obtain a sampling voltage, uses the hysteresis comparison module to set a high voltage protection threshold and a low voltage protection threshold and compares them with the sampling voltage, when the sampling voltage is higher than the high voltage protection threshold, the switch module is disconnected to cut off the power to the load, and when the sampling power is lower than the low voltage protection threshold, the switch module is turned on to enable the load to be powered and run; thus, by using the hysteresis comparison module to set the high voltage protection threshold and the low voltage protection threshold and compare them with the sampling voltage, frequent protection of the fan motor can be avoided, thereby improving the reliability of fan protection.

[0016] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention.

[0017] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of an embodiment of a motor protection device of the present invention;

[0019] Figure 2 The schematic diagram of the working process of the motor overvoltage protection circuit based on the comparator U2A;

[0020] Figure 3 It is a schematic diagram of the structure of the motor overvoltage protection circuit based on the comparator U2A;

[0021] Figure 4 It is a structural diagram of the threshold value calculation equivalent circuit 1;

[0022] Figure 5 It is a structural diagram of the threshold value calculation equivalent circuit 2;

[0023] Figure 6 It is a structural diagram of the threshold value calculation equivalent circuit 3;

[0024] Figure 7 This is a schematic diagram of the simulation results of the motor overvoltage protection circuit based on the comparator U2A. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] Considering that the battery voltage fluctuation of motor equipment (such as car air conditioners) can easily cause overvoltage or undervoltage, resulting in frequent motor protection, thus damaging the internal control components of the fan. In related solutions, the solution to this problem is to increase the withstand voltage of the internal control components of the fan, such as increasing the motor withstand voltage from 40V to 60V, but this method has some problems, such as: when the motor withstand voltage is adjusted from 40V to 60V, after-sales service will still receive feedback that the fan motor is overvoltage damaged and the motor needs to be replaced; and there are fewer power chips, power tubes, electrolytic capacitors and other devices with a withstand voltage of 60V or above, and the price is relatively high, and these conventional devices are relatively large in size and are not suitable for fans.

[0027] There are also some solutions that provide protection solutions based on comparator U2A and MCU, which only control the motor to stop running under high voltage. The motor does not leave the high-voltage environment, and the reaction is slow, with a high risk of damage. And only one comparison voltage is set. If the power supply voltage is near the protection point, it is easy to cause frequent protection.

[0028] Some other solutions are based on the voltage clamping characteristics of TVS tubes for protection, but they require high-power TVS tubes for use in 24V high-power power supply circuits, and the cost of high-power TVS tubes is relatively high. On the other hand, if the interference voltage is too high and the interference time is too long, it is easy to cause the front-stage fuse to short-circuit or the TVS tube to heat up severely.

[0029] Therefore, the solution of the present invention proposes a motor overvoltage protection circuit based on the comparator U2A, which adopts a pure hardware structure, forms a hysteresis comparison module based on the comparator U2A, and uses the hysteresis comparison module to set two voltage protection thresholds (i.e., a high voltage protection threshold and a low voltage protection threshold). A voltage protection range can be formed between the two voltage protection thresholds, which can avoid long-term fluctuations in the power supply voltage at a single voltage protection threshold, resulting in frequent protection of the motor, thereby improving the reliability of the fan overvoltage protection.

[0030] According to an embodiment of the present invention, a protection device for a motor is provided. Figure 1 The structural diagram of an embodiment of the device of the present invention is shown in FIG. The motor protection device may include: a sampling unit (such as Figure 2 Sampling module shown), hysteresis comparison unit (such as Figure 2 hysteresis comparison module shown), and a switch unit (such as Figure 2 The sampling unit, the hysteresis comparison unit and the switch unit are sequentially arranged between the input power access terminal of the motor and the power supply terminal of the motor.

[0031] Wherein, the sampling unit is used to sample the voltage of the input power supply of the motor from the input power supply access terminal of the motor to obtain a sampled voltage.

[0032] The hysteresis comparison unit is used to output a set high potential when the hysteresis comparison unit starts to work, so as to create a high voltage protection threshold; and, when the sampling voltage is higher than the high voltage protection threshold, output a set first level signal to control the switch unit to disconnect itself, so as to cut off the power supply end of the motor and protect the motor; the set first level signal is such as a low level signal.

[0033] The switch unit is used to disconnect the switch unit itself when receiving the first level signal output by the hysteresis comparison unit, so as to cut off the power supply end of the motor and protect the motor.

[0034] The hysteresis comparison unit is also used to output a set low potential after the hysteresis comparison unit controls the switch unit to disconnect itself, so as to create a low voltage protection threshold; and, when the sampling voltage is lower than the low voltage protection threshold, output a set second level signal to control the switch unit to turn on itself, so that the power supply end of the motor is energized and the motor resumes operation; the set second level signal is such as a high level signal.

[0035] The switch unit is further used to turn on the switch unit itself when receiving the second level signal output by the hysteresis comparison unit, so that the power supply end of the motor is powered and the motor resumes operation.

[0036] Figure 2 The following is a schematic diagram of the working process of the motor overvoltage protection circuit based on the comparator U2A. Figure 2 As shown, the motor overvoltage protection circuit based on the comparator U2A includes: a sampling module, a hysteresis comparison module, a switch module, and a fan module, which are connected in sequence. The hysteresis comparison module can create two voltage protection thresholds for comparison, such as a high voltage protection threshold and a low voltage protection threshold, and a voltage protection range can be formed between the two voltage protection thresholds.

[0037] Among them, the sampling module samples the voltage of the input power supply to obtain a sampled voltage, and provides the sampled voltage to the hysteresis comparison module. The hysteresis comparison module compares the sampled voltage. If the sampled voltage exceeds the set value (such as the highest voltage in the voltage protection range), the hysteresis comparison module outputs a low level, controls the switch module to close, and the fan load module is powered off and stops running; if the sampled voltage is lower than the set value (such as the lowest voltage in the voltage protection range), the hysteresis comparison module outputs a high level, controls the switch module to turn on, and the fan load module is powered on and runs.

[0038] The scheme of the present invention provides a motor overvoltage protection circuit based on a comparator U2A, which realizes overvoltage protection purely by hardware, uses an ordinary comparator U2A to form a hysteresis comparison module, and actively creates a high voltage protection threshold and a low voltage protection threshold as two voltage protection thresholds for comparison. A voltage protection range can be formed between the two voltage protection thresholds, which can avoid long-term fluctuations of the power supply voltage at a single voltage protection threshold, resulting in frequent protection of the motor, thereby improving the reliability of the fan overvoltage protection.

[0039] In some embodiments, the sampling unit includes: a first sampling resistor module (such as Figure 3 The resistor R9 shown), and the second sampling resistor module (such as Figure 3 Resistor R7 shown).

[0040] Wherein, the input power supply of the motor (such as Figure 3 The 24V DC power supply VCC shown in the figure is connected to ground after passing through the first sampling resistor module and the second sampling resistor module. The common end of the first sampling resistor module and the second sampling resistor module, as the output end of the sampling unit, is connected to the comparison input end of the hysteresis comparison unit (such as Figure 3 The inverting input of comparator U2A shown).

[0041] Figure 3 Figure 2 is a schematic diagram of the motor overvoltage protection circuit based on the comparator U2A. Figure 3 In the example shown, resistors R9 and R7 form a sampling module for the input power supply. In the sampling module, the calculation of the sampling resistor is as follows: resistors R9 and R7 form a sampling module for the input power supply, the sampling value is U-, and the protection voltage threshold should be calculated according to the high voltage protection threshold. If the protection voltage is set to 40V, and the resistance value of resistor R7 is 10kΩ, then: R9 = 40 / (9.93V / R7)-R7 = 30.28kΩ. According to the resistor selection, resistor R9 is selected to be 30kΩ; recalculate the protection voltage threshold Vb1 = 9.93V / 10kΩ×(30kΩ+10kΩ) = 39.72V. Then, the recovery voltage Vb2 = 8.57V / 10kΩ×(30kΩ+10kΩ) = 34.28V. The sampling point of the sampling module is point 10, and the sampling value name is set to U-, which means the sampling value provided to the inverting input terminal U- of the comparator U2A.

[0042] Among them, the recovery voltage Vb2 refers to the voltage threshold of the fan when exiting the protection state, that is, the low voltage threshold. The recovery voltage Vb2 is calculated by the low voltage threshold of the comparator U2A and the sampling resistor; that is to say, when the power supply voltage of the fan is lower than the low voltage threshold, it can exit the protection state. The function of the sampling resistor is to sample and divide the voltage of the fan power supply. The voltage of the fan power supply is relatively high, and the input pin of the comparator U2A cannot be directly connected, so two sampling resistors are required to divide the voltage to pull down the voltage of the fan power supply, and it must be lower than the power supply voltage of the comparator U2A.

[0043] In some embodiments, the hysteresis comparison unit includes: a comparison module and a threshold setting module, the comparison module is as follows: Figure 3 The comparator U2A shown in the figure has a threshold setting module such as Figure 3 The resistors R1, R2, R3, R4, R5 and R6 shown in the figure; the inverting input terminal of the comparison module serves as the comparison input terminal of the hysteresis comparison unit; the non-inverting input terminal of the comparison module serves as the threshold input terminal of the hysteresis comparison unit.

[0044] Wherein, the output end of the sampling unit is connected to the inverting input end of the comparison module; the preset DC power supply is connected to the non-inverting input end of the comparison module and the output end of the comparison module respectively after passing through the threshold setting module; the output end of the comparison module can be connected to the control end of the switch unit; wherein the comparison module is used to output a set high potential when the hysteresis comparison unit starts to work, so as to create a high voltage protection threshold through the threshold setting module; and, compare the sampled voltage with the high voltage protection threshold, and output a set first level signal when the sampled voltage is higher than the high voltage protection threshold; the comparison module is also used to output a set low potential after the hysteresis comparison unit controls the switch unit to disconnect itself, so as to create a low voltage protection threshold through the threshold setting module; and, compare the sampled voltage with the low voltage protection threshold, and when the sampled voltage is lower than the low voltage protection threshold (such as Figure 3 The gate of the switch tube Q1 shown).

[0045] See also Figure 2 and Figure 3 In the example shown, the sampling module samples the input power of the fan (specifically, the input power of the motor in the fan), obtains the sampled value through calculation, and outputs the sampled value to the inverting input terminal of the comparator U2A of the hysteresis comparison module, and the comparator U2A compares the sampled voltage.

[0046] The initial output potential of the hysteresis comparison module is a high potential. After equivalent calculation, it is concluded that the initial threshold of the positive input terminal of the comparator U2A is the high voltage protection threshold. When the sampled voltage exceeds the high voltage protection threshold, the comparator U2A outputs a low level, the switch module is disconnected, the fan module enters protection, and the output potential of the comparator U2A is a low potential. After equivalent calculation, it is concluded that the threshold of the positive input terminal at this time is the low voltage protection threshold; when the sampled voltage is lower than the low voltage protection threshold, the comparator U2A outputs a high level, the switch module is closed, the fan module exits protection, and the output potential of the comparator U2A is a high potential. After equivalent calculation, it is concluded that the threshold of the positive input terminal of the comparator U2A at this time is the high voltage protection threshold. This is repeated to form a hysteresis comparison.

[0047] The switch module is connected to the output end of the comparator U2A. When the output end of the comparator U2A is at a high level, the switch module is turned on. When the output end of the comparator U2A is at a low level, the switch module is turned off.

[0048] The fan module is the load in the circuit. When the switch module is turned on, the fan module is powered on and operates; when the switch module is turned off, the fan module is powered off for protection.

[0049] The car air conditioner uses a low-voltage 24V DC power supply. Due to cost pressure and device withstand voltage limit, the withstand voltage of the fan internal control device is usually 40V. When the car is started or stopped, the car battery power supply voltage will exceed 60V instantaneous high voltage, which will cause damage to the fan control device and greatly shorten its life. The protection measures taken in related schemes for this situation are either frequent protection or too costly, and the defects are obvious. The scheme of the present invention relies purely on hardware to achieve overvoltage protection. Under the premise of lower cost than switching 60V withstand voltage devices, a voltage protection range is created using comparator U2A to replace the single-point protection voltage threshold comparison to avoid frequent protection.

[0050] Preferably, when the hysteresis comparison unit includes a comparison module and a threshold setting module, the hysteresis comparison unit further includes: a filtering module (such as Figure 3 The capacitor C1 shown in the figure); wherein the filtering module is arranged between the in-phase input terminal of the comparison module and the ground. Figure 3 In the example shown, the capacitor C1 is a filter device for eliminating interference signals of the reference voltage of the hysteresis comparison unit.

[0051] In some implementations, the threshold setting module includes: a first voltage dividing resistor module (such as Figure 3 The resistor R2 shown in FIG. 1 ), the second voltage divider resistor module (such as Figure 3 The resistor R1 shown in FIG. 1 ), the third voltage-dividing resistor module (such as Figure 3 The resistor R5 shown in FIG. 1 ), the fourth voltage-dividing resistor module (such as Figure 3 The resistor R3 shown in FIG. 1 ), the fifth voltage-dividing resistor module (such as Figure 3 The resistor R4 shown), and the sixth voltage-dividing resistor module (such as Figure 3 Resistor R6 shown).

[0052] Wherein, the preset first DC power supply (such as Figure 3 The DC power supply Vd shown in the figure is grounded after passing through the first voltage-dividing resistor module and the second voltage-dividing resistor module; the common end of the first voltage-dividing resistor module and the second voltage-dividing resistor module is connected to the in-phase input end of the comparison module; the preset second DC power supply (such as Figure 3 The DC power supply Vc) shown is connected to the power supply end of the comparison module.

[0053] The preset first DC power supply (such as Figure 3 The DC power supply Vd) shown in the figure is also grounded after passing through the fourth voltage-dividing resistor module, the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module; the common end of the fourth voltage-dividing resistor module and the fifth voltage-dividing resistor module is connected to the output end of the comparison module.

[0054] The third voltage-dividing resistor module is connected between the common end of the first voltage-dividing resistor module and the second voltage-dividing resistor module, and between the common end of the fourth voltage-dividing resistor module and the fifth voltage-dividing resistor module; the common end of the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module serves as the output end of the hysteresis comparison unit and is connected to the control end of the switch unit.

[0055] exist Figure 3 In the example shown, the hysteresis comparison module composed of the comparator U2A, the resistor R1, the resistor R2, the resistor R3, the resistor R4, the resistor R5, and the resistor R6 has better anti-interference performance than the ordinary comparator U2A. The difference between the hysteresis comparison module and the ordinary comparison module is that the hysteresis comparison module creates the high and low voltage protection thresholds of the positive terminal 7 of the input comparator U2A through the high and low level outputs of the comparator U2A, so that a dual-threshold voltage protection range can be formed, avoiding the situation where the single threshold protection of the ordinary comparator U2A will cause the unstable sampling voltage at the inverting input terminal to cause the subsequent switch module to frequently switch protection. Therefore, the hysteresis comparison module set in the solution of the present invention can effectively protect the overall overvoltage protection circuit and improve the overall stability and anti-interference performance of the hardware circuit.

[0056] Preferably, when the hysteresis comparison unit includes a comparison module and a threshold setting module, and the threshold setting module includes a first voltage-dividing resistor module, a second voltage-dividing resistor module, a third voltage-dividing resistor module, a fourth voltage-dividing resistor module, a fifth voltage-dividing resistor module and a sixth voltage-dividing resistor module, the hysteresis comparison unit further includes: a filtering module (such as Figure 3 The capacitor C1 is shown. The filtering module is connected in parallel with the second voltage-dividing resistor module; that is, the filtering module is connected in parallel at both ends of the second voltage-dividing resistor module.

[0057] exist Figure 3 In the example shown, capacitor C1 is a filter device for eliminating interference signals of the reference voltage input to the non-inverting input terminal of the comparator U2A.

[0058] In some embodiments, the hysteresis comparison unit further includes: a TVS tube module (such as Figure 3 The TVS tube D2); wherein, the cathode of the TVS module is connected to the common end of the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module; the anode of the TVS module is grounded.

[0059] exist Figure 3 In the example shown, the switch module includes a switch tube Q1 (such as a MOS tube). A TVS tube (transient voltage suppression diode) D2 is a protection device for the switch tube Q1 to prevent the gate voltage of the switch tube Q1 from being too high and being damaged.

[0060] In some embodiments, the switch unit includes: a switch tube module (such as Figure 3 The switch tube Q1 shown in the figure); wherein the output end of the hysteresis comparison unit is connected to the control end of the switch tube module (such as the gate of the MOS tube); the input power supply of the motor is connected to the first connection end of the switch tube module (such as the drain of the MOS tube); the second connection end of the switch tube module (such as the source of the MOS tube) is grounded.

[0061] exist Figure 3 In the example shown, the sampling module includes: resistors R9 and R7. The hysteresis comparison module includes: comparator U2A, resistors R1, R2, R3, R4, R5, R6, and capacitor C1. The switch module includes: TVS tube D2, switch tube Q1 (such as MOS tube). Figure 3 In the example shown, resistors R9 and R7 form a sampling module, comparator U2A, resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, and resistor R6 form a hysteresis comparison module, switch tube Q1 (such as MOS tube) is a switch module, and load Rload is a fan module; capacitor C1 is a filter component for eliminating interference signals of the reference voltage. TVS tube D2 is a protection device for switch tube Q1 to prevent the gate voltage of switch tube Q1 from being damaged by excessively high voltage.

[0062] Among them, resistor R4 plays a current limiting role and is used to protect the switch module. At the same time, the resistance value of resistor R4 is also within the range of the equivalent resistance calculation value of the hysteresis comparison module, but because the resistance value of resistor R4 is relatively small, it can be ignored when calculating the equivalent resistance. Therefore, resistor R4 plays a role in both the hysteresis comparison module and the switch module, but relatively speaking, it plays a greater role in the switch module, so it can also be considered that resistor R4 belongs to the switch module. Since the resistance value of resistor R4 is negligible in the calculation, the remaining resistors R1, R2, R3, R5, and R6 form the following. Figure 4 The equivalent circuit shown in the figure, in this case, the potential of point 7 can be calculated by the value of the resistor. Point 7 is directly connected to the non-inverting input of the comparator U2A, which is used to determine the high voltage threshold. When the comparator outputs a low level, it is equivalent to the comparator being directly grounded, and the resistor R6 is equivalent to a short circuit. The resistors R1, R2, R3, and R5 form the following circuit: Figure 6 The equivalent circuit diagram shown, in this case the calculated potential at point 7, is used to determine the low voltage threshold.

[0063] In the solution of the present invention, the comparison threshold of the hysteresis comparison module is not a threshold point, but creates different rising thresholds and falling thresholds, so that the output of the hysteresis comparison module is always kept in a low or high state, which can effectively avoid the situation where the power supply voltage is near the protection voltage of the comparator U2A, resulting in frequent protection of the switch module. Figure 3 As shown, the U+ terminal of the comparator U2A is used as the comparison reference terminal, and the U- terminal of the comparator U2A is connected to the power sampling signal. When the input terminal U- of the comparator U2A is less than the input terminal U+ of the comparator U2A, the output terminal 1 of the comparator U2A outputs a high level, the switch tube Q1 is turned on, and the fan load is powered; when the input terminal U- of the comparator U2A is greater than the input terminal U+ of the comparator U2A, the output terminal 1 of the comparator U2A outputs a low level, the switch tube Q1 is turned off, and the fan load is powered off to protect the fan load.

[0064] Figure 4 This is the structural diagram of the threshold calculation equivalent circuit 1. Figure 5 This is the structural diagram of the threshold calculation equivalent circuit 2. Figure 6 This is a schematic diagram of the structure of the threshold calculation equivalent circuit 3. When performing equivalent calculations on the high and low voltage protection thresholds at the non-inverting input of the comparator U2A, you can refer to Figure 4 , Figure 5 and Figure 6 Example shown.

[0065] See also Figure 4 and Figure 5 In the example shown, the equivalent calculation of the high voltage protection threshold of the non-inverting input of the comparator U2A is as follows: When the inverting input U- of the comparator U2A is less than the non-inverting input U+ of the comparator U2A, the output terminal 1 of the comparator U2A outputs a high level. Since the resistance of the resistor R4 is much smaller than the resistance of the resistor R6, the resistors R1, R2, R3, R4, R5 and R6 can be simplified to Figure 4 Resistors R2, R3, and R5 form a △-type connection, which can be converted to a Y-type connection for easy calculation. The equivalent conversion circuit is as follows: Figure 5 According to the equivalent calculation formula of △-type connection and Y-type connection, the resistance values ​​of resistors R11, R22 and R33 can be calculated by the following formula:

[0066] R11=R2×R3 / (R2+R3+R5)≈367Ω;

[0067] R22=R2×R5 / (R2+R3+R5)≈1.361kΩ;

[0068] R33=R3×R5 / (R2+R3+R5)≈1.837kΩ; then, the voltage at the non-inverting input terminal U+ of the comparator U2A is:

[0069] U+=12V / [(R22+R1) / / (R33+R6)+R11]×[(R22+R1) / / (R33+R6)] / (R22+R1)×R1=9.93V, which is used to determine the high and low voltage thresholds of the non-inverting input terminal of the comparator U2A.

[0070] See also Figure 4 and Figure 6 In the example shown, the equivalent calculation of the low voltage protection threshold of the non-inverting input terminal of the comparator U2A is as follows: when the inverting input terminal U- of the comparator U2A is greater than the non-inverting input terminal U+ of the comparator U2A, the output terminal 1 of the comparator U2A outputs a low level, and the resistor R4 is equivalent to being short-circuited to the ground GND, then the resistors R1, R2, R3, R4, R5, and R6 can be simplified to Figure 6 , then the non-inverting input terminal U+ of comparator U2A ’ The voltage is: U+ ’ =12V / (R1 / / R5+R2)×(R1 / / R5)=8.57V. Among them, U+ ’ is the calculated low voltage threshold, and voltage U+ is the calculated high voltage threshold.

[0071] In the solution of the present invention, a comparator U2A is used to form a hysteresis comparison module, and two voltage protection thresholds for comparison are actively created by using the hysteresis comparison module. The power supply voltage (i.e., the sampling voltage of the input power supply) is obtained by detection. When the power supply voltage is higher than the highest voltage in the voltage protection range, protection will be performed; when the power supply voltage is lower than the lowest voltage in the voltage protection range, the protection state will be restored to normal, thus avoiding the situation where the motor is frequently protected. In addition, the devices selected in the solution of the present invention are relatively conventional, the solution is easy to implement, and has a wide range of applications.

[0072] Figure 7 Figure 1 is a schematic diagram of the simulation results of the motor overvoltage protection circuit based on the comparator U2A. Figure 7 In the figure, the vertical axis is voltage and the horizontal axis is time. The red vertical line on the left is the T1 timeline, and the blue vertical line on the right is the T2 timeline. The waveform of Channel_A is red, and the waveform of Channel_B is green. The overlapping part of the green waveform and the T1 timeline on the left is represented by blue, and the overlapping part of the green waveform and the T2 timeline on the right is represented by red. The waveform of Channel_A is the fan power input waveform, and the waveform of Channel_B is the fan voltage waveform after protection. The parameters at the bottom of the figure are as follows: the first line is the T1 sampling parameters, the second line is the T2 sampling parameters, the third line is the sampling value difference of T2-T1, the first column is the sampling timeline, the second column is the Channel_A sampling value, the third column is the Channel_B sampling value, Reverse is the inverting button, Save is the save button, and Ext.Trigger is the external trigger option. Figure 7In the simulation results of the motor overvoltage protection circuit based on comparator U2A shown in the figure, the red waveform is the power supply voltage waveform, and the green waveform is the voltage waveform of the load Rload. It can be seen from the simulation results that when the input voltage of comparator U2A is greater than 39.685V, comparator U2A is triggered to output a low level, and the switch tube Q1 is turned off, causing the load Rload to be powered off and protect the load; when the power supply voltage drops to 34.397V, comparator U2A outputs a high level, MOS tube Q1 is turned on, and the load Rload is powered. Considering the neglect of the input impedance of comparator U2A and the measurement error, the protection voltage and recovery voltage obtained by simulation measurement are close to the calculated values. The measurement results meet the design requirements and meet the fan overvoltage protection effect.

[0073] It should be noted that the voltage protection circuit solution proposed in the solution of the present invention can be used in other products, not limited to air conditioner fans, by adjusting the device parameters on the circuit.

[0074] According to the technical solution of the present invention, a sampling module, a hysteresis comparison module and a switch module are arranged between the input power supply of the motor in the fan and the load, the sampling module is used to sample the voltage of the input power supply of the fan to obtain a sampling voltage, a high voltage protection threshold and a low voltage protection threshold are set by the hysteresis comparison module and compared with the sampling voltage, when the sampling voltage is higher than the high voltage protection threshold, the switch module is disconnected to cut off the power supply to the load, and when the sampling power supply is lower than the low voltage protection threshold, the switch module is turned on to enable the load to be powered on and run; thus, by using the hysteresis comparison module to set the high voltage protection threshold and the low voltage protection threshold and compare with the sampling voltage, frequent protection of the fan motor can be avoided, thereby improving the reliability of the fan protection.

[0075] According to an embodiment of the present invention, a fan corresponding to the protection device of the motor is also provided. The fan may include: the protection device of the motor described above.

[0076] In the fan, the motor protection device may include: a sampling unit (such as Figure 2 Sampling module shown), hysteresis comparison unit (such as Figure 2 hysteresis comparison module shown), and a switch unit (such as Figure 2 The sampling unit, the hysteresis comparison unit and the switch unit are sequentially arranged between the input power access terminal of the motor and the power supply terminal of the motor.

[0077] Wherein, the sampling unit is used to sample the voltage of the input power supply of the motor from the input power supply access terminal of the motor to obtain a sampled voltage.

[0078] The hysteresis comparison unit is used to output a set high potential when the hysteresis comparison unit starts to work, so as to create a high voltage protection threshold; and, when the sampling voltage is higher than the high voltage protection threshold, output a set first level signal to control the switch unit to disconnect itself, so as to cut off the power supply end of the motor and protect the motor; the set first level signal is such as a low level signal.

[0079] The switch unit is used to disconnect the switch unit itself when receiving the first level signal output by the hysteresis comparison unit, so as to cut off the power supply end of the motor and protect the motor.

[0080] The hysteresis comparison unit is also used to output a set low potential after the hysteresis comparison unit controls the switch unit to disconnect itself, so as to create a low voltage protection threshold; and, when the sampling voltage is lower than the low voltage protection threshold, output a set second level signal to control the switch unit to turn on itself, so that the power supply end of the motor is energized and the motor resumes operation; the set second level signal is such as a high level signal.

[0081] The switch unit is further used to turn on the switch unit itself when receiving the second level signal output by the hysteresis comparison unit, so that the power supply end of the motor is powered and the motor resumes operation.

[0082] like Figure 2 As shown, the motor overvoltage protection circuit based on the comparator U2A includes: a sampling module, a hysteresis comparison module, a switch module, and a fan module, which are connected in sequence. The hysteresis comparison module can create two voltage protection thresholds for comparison, such as a high voltage protection threshold and a low voltage protection threshold, and a voltage protection range can be formed between the two voltage protection thresholds.

[0083] Among them, the sampling module samples the voltage of the input power supply to obtain a sampled voltage, and provides the sampled voltage to the hysteresis comparison module. The hysteresis comparison module compares the sampled voltage. If the sampled voltage exceeds the set value (such as the highest voltage in the voltage protection range), the hysteresis comparison module outputs a low level, controls the switch module to close, and the fan load module is powered off and stops running; if the sampled voltage is lower than the set value (such as the lowest voltage in the voltage protection range), the hysteresis comparison module outputs a high level, controls the switch module to turn on, and the fan load module is powered on and runs.

[0084] The scheme of the present invention provides a motor overvoltage protection circuit based on a comparator U2A, which realizes overvoltage protection purely by hardware, uses an ordinary comparator U2A to form a hysteresis comparison module, and actively creates a high voltage protection threshold and a low voltage protection threshold as two voltage protection thresholds for comparison. A voltage protection range can be formed between the two voltage protection thresholds, which can avoid long-term fluctuations of the power supply voltage at a single voltage protection threshold, resulting in frequent protection of the motor, thereby improving the reliability of the fan overvoltage protection.

[0085] In some embodiments, the sampling unit includes: a first sampling resistor module (such as Figure 3 The resistor R9 shown), and the second sampling resistor module (such as Figure 3 The resistor R7 shown in the figure). Wherein, the input power supply of the motor (such as Figure 3 The 24V DC power supply VCC shown in the figure is connected to ground after passing through the first sampling resistor module and the second sampling resistor module. The common end of the first sampling resistor module and the second sampling resistor module, as the output end of the sampling unit, is connected to the comparison input end of the hysteresis comparison unit (such as Figure 3 The inverting input of comparator U2A shown).

[0086] See Figure 3 In the example shown, resistors R9 and R7 form a sampling module for the input power supply. In the sampling module, the calculation of the sampling resistor is as follows: resistors R9 and R7 form a sampling module for the input power supply, the sampling value is U-, and the protection voltage threshold should be calculated according to the high voltage protection threshold. If the protection voltage is set to 40V, and the resistance value of resistor R7 is 10kΩ, then: R9 = 40 / (9.93V / R7)-R7 = 30.28kΩ. According to the resistor selection, resistor R9 is selected to be 30kΩ; recalculate the protection voltage threshold Vb1 = 9.93V / 10kΩ×(30kΩ+10kΩ) = 39.72V. Then, the recovery voltage Vb2 = 8.57V / 10kΩ×(30kΩ+10kΩ) = 34.28V. The sampling point of the sampling module is point 10, and the sampling value name is set to U-, which means the sampling value provided to the inverting input terminal U- of the comparator U2A.

[0087] In some embodiments, the hysteresis comparison unit includes: a comparison module and a threshold setting module, the comparison module is as follows: Figure 3 The comparator U2A shown in the figure has a threshold setting module such as Figure 3The resistors R1, R2, R3, R4, R5 and R6 shown in the figure; the inverting input terminal of the comparison module serves as the comparison input terminal of the hysteresis comparison unit; the non-inverting input terminal of the comparison module serves as the threshold input terminal of the hysteresis comparison unit. Wherein, the output end of the sampling unit is connected to the inverting input end of the comparison module; the preset DC power supply is connected to the non-inverting input end of the comparison module and the output end of the comparison module respectively after passing through the threshold setting module; the output end of the comparison module can be connected to the control end of the switch unit; wherein the comparison module is used to output a set high potential when the hysteresis comparison unit starts to work, so as to create a high voltage protection threshold through the threshold setting module; and, compare the sampled voltage with the high voltage protection threshold, and output a set first level signal when the sampled voltage is higher than the high voltage protection threshold; the comparison module is also used to output a set low potential after the hysteresis comparison unit controls the switch unit to disconnect itself, so as to create a low voltage protection threshold through the threshold setting module; and, compare the sampled voltage with the low voltage protection threshold, and when the sampled voltage is lower than the low voltage protection threshold (such as Figure 3 The gate of the switch tube Q1 shown).

[0088] See also Figure 2 and Figure 3 In the example shown, the sampling module samples the input power of the fan (specifically, the input power of the motor in the fan), obtains the sampled value through calculation, and outputs the sampled value to the inverting input terminal of the comparator U2A of the hysteresis comparison module, and the comparator U2A compares the sampled voltage.

[0089] The initial output potential of the hysteresis comparison module is a high potential. After equivalent calculation, it is concluded that the initial threshold of the positive input terminal of the comparator U2A is the high voltage protection threshold. When the sampled voltage exceeds the high voltage protection threshold, the comparator U2A outputs a low level, the switch module is disconnected, the fan module enters protection, and the output potential of the comparator U2A is a low potential. After equivalent calculation, it is concluded that the threshold of the positive input terminal at this time is the low voltage protection threshold; when the sampled voltage is lower than the low voltage protection threshold, the comparator U2A outputs a high level, the switch module is closed, the fan module exits protection, and the output potential of the comparator U2A is a high potential. After equivalent calculation, it is concluded that the threshold of the positive input terminal of the comparator U2A at this time is the high voltage protection threshold. This is repeated to form a hysteresis comparison.

[0090] The switch module is connected to the output end of the comparator U2A. When the output end of the comparator U2A is at a high level, the switch module is turned on. When the output end of the comparator U2A is at a low level, the switch module is turned off.

[0091] The fan module is the load in the circuit. When the switch module is turned on, the fan module is powered on and operates; when the switch module is turned off, the fan module is powered off for protection.

[0092] The car air conditioner uses a low-voltage 24V DC power supply. Due to cost pressure and device withstand voltage limit, the withstand voltage of the fan internal control device is usually 40V. When the car is started or stopped, the car battery power supply voltage will exceed 60V instantaneous high voltage, which will cause damage to the fan control device and greatly shorten its life. The protection measures taken in related schemes for this situation are either frequent protection or too costly, and the defects are obvious. The scheme of the present invention relies purely on hardware to achieve overvoltage protection. Under the premise of lower cost than switching 60V withstand voltage devices, a voltage protection range is created using comparator U2A to replace the single-point protection voltage threshold comparison to avoid frequent protection.

[0093] Preferably, when the hysteresis comparison unit includes a comparison module and a threshold setting module, the hysteresis comparison unit further includes: a filtering module (such as Figure 3 The capacitor C1 shown in the figure); wherein the filtering module is arranged between the in-phase input terminal of the comparison module and the ground. Figure 3 In the example shown, the capacitor C1 is a filter device for eliminating interference signals of the reference voltage of the hysteresis comparison unit.

[0094] In some implementations, the threshold setting module includes: a first voltage dividing resistor module (such as Figure 3 The resistor R2 shown in FIG. 1 ), the second voltage divider resistor module (such as Figure 3 The resistor R1 shown in FIG. 1 ), the third voltage-dividing resistor module (such as Figure 3 The resistor R5 shown in FIG. 1 ), the fourth voltage-dividing resistor module (such as Figure 3 The resistor R3 shown in FIG. 1 ), the fifth voltage-dividing resistor module (such as Figure 3 The resistor R4 shown), and the sixth voltage-dividing resistor module (such as Figure 3 Resistor R6 shown).

[0095] Wherein, the preset first DC power supply (such as Figure 3 The DC power supply Vd shown in the figure is grounded after passing through the first voltage-dividing resistor module and the second voltage-dividing resistor module; the common end of the first voltage-dividing resistor module and the second voltage-dividing resistor module is connected to the in-phase input end of the comparison module; the preset second DC power supply (such as Figure 3 The DC power supply Vc) shown is connected to the power supply end of the comparison module.

[0096] The preset first DC power supply (such as Figure 3The DC power supply Vd) shown in the figure is also grounded after passing through the fourth voltage-dividing resistor module, the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module; the common end of the fourth voltage-dividing resistor module and the fifth voltage-dividing resistor module is connected to the output end of the comparison module.

[0097] The third voltage-dividing resistor module is connected between the common end of the first voltage-dividing resistor module and the second voltage-dividing resistor module, and between the common end of the fourth voltage-dividing resistor module and the fifth voltage-dividing resistor module; the common end of the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module serves as the output end of the hysteresis comparison unit and is connected to the control end of the switch unit.

[0098] exist Figure 3 In the example shown, the hysteresis comparison module composed of the comparator U2A, the resistor R1, the resistor R2, the resistor R3, the resistor R4, the resistor R5, and the resistor R6 has better anti-interference performance than the ordinary comparator U2A. The difference between the hysteresis comparison module and the ordinary comparison module is that the hysteresis comparison module creates the high and low voltage protection thresholds of the positive terminal 7 of the input comparator U2A through the high and low level outputs of the comparator U2A, so that a dual-threshold voltage protection range can be formed, avoiding the situation where the single threshold protection of the ordinary comparator U2A will cause the unstable sampling voltage at the inverting input terminal to cause the subsequent switch module to frequently switch protection. Therefore, the hysteresis comparison module set in the solution of the present invention can effectively protect the overall overvoltage protection circuit and improve the overall stability and anti-interference performance of the hardware circuit.

[0099] Preferably, when the hysteresis comparison unit includes a comparison module and a threshold setting module, and the threshold setting module includes a first voltage-dividing resistor module, a second voltage-dividing resistor module, a third voltage-dividing resistor module, a fourth voltage-dividing resistor module, a fifth voltage-dividing resistor module and a sixth voltage-dividing resistor module, the hysteresis comparison unit further includes: a filtering module (such as Figure 3 The capacitor C1 is shown. The filtering module is connected in parallel with the second voltage-dividing resistor module; that is, the filtering module is connected in parallel at both ends of the second voltage-dividing resistor module.

[0100] exist Figure 3 In the example shown, capacitor C1 is a filter device for eliminating interference signals of the reference voltage input to the non-inverting input terminal of the comparator U2A.

[0101] In some embodiments, the hysteresis comparison unit further includes: a TVS tube module (such as Figure 3 The TVS tube D2); wherein, the cathode of the TVS module is connected to the common end of the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module; the anode of the TVS module is grounded.

[0102] exist Figure 3 In the example shown, the switch module includes a switch tube Q1 (such as a MOS tube). A TVS tube (transient voltage suppression diode) D2 is a protection device for the switch tube Q1 to prevent the gate voltage of the switch tube Q1 from being too high and being damaged.

[0103] In some embodiments, the switch unit includes: a switch tube module (such as Figure 3 The switch tube Q1 shown in the figure); wherein the output end of the hysteresis comparison unit is connected to the control end of the switch tube module (such as the gate of the MOS tube); the input power supply of the motor is connected to the first connection end of the switch tube module (such as the drain of the MOS tube); the second connection end of the switch tube module (such as the source of the MOS tube) is grounded.

[0104] exist Figure 3 In the example shown, the sampling module includes: resistors R9 and R7. The hysteresis comparison module includes: comparator U2A, resistors R1, R2, R3, R4, R5, R6, and capacitor C1. The switch module includes: TVS tube D2, switch tube Q1 (such as MOS tube). Figure 3 In the example shown, resistors R9 and R7 form a sampling module, comparator U2A, resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, and resistor R6 form a hysteresis comparison module, switch tube Q1 (such as MOS tube) is a switch module, and load Rload is a fan module; capacitor C1 is a filter component for eliminating interference signals of the reference voltage. TVS tube D2 is a protection device for switch tube Q1 to prevent the gate voltage of switch tube Q1 from being damaged by excessively high voltage.

[0105] In the solution of the present invention, the comparison threshold of the hysteresis comparison module is not a threshold point, but creates different rising thresholds and falling thresholds, so that the output of the hysteresis comparison module is always kept in a low or high state, which can effectively avoid the situation where the power supply voltage is near the protection voltage of the comparator U2A, resulting in frequent protection of the switch module. Figure 3 As shown, the U+ terminal of the comparator U2A is used as the comparison reference terminal, and the U- terminal of the comparator U2A is connected to the power sampling signal. When the input terminal U- of the comparator U2A is less than the input terminal U+ of the comparator U2A, the output terminal 1 of the comparator U2A outputs a high level, the switch tube Q1 is turned on, and the fan load is powered; when the input terminal U- of the comparator U2A is greater than the input terminal U+ of the comparator U2A, the output terminal 1 of the comparator U2A outputs a low level, the switch tube Q1 is turned off, and the fan load is powered off to protect the fan load.

[0106] In the solution of the present invention, a comparator U2A is used to form a hysteresis comparison module, and the hysteresis comparison module is used to actively create two voltage protection thresholds for comparison. The power supply voltage (i.e., the sampling voltage of the input power supply) is obtained by detection. When the power supply voltage is higher than the highest voltage in the voltage protection range, protection will be performed; when the power supply voltage is lower than the lowest voltage in the voltage protection range, the protection state will be restored to normal, thereby avoiding frequent protection of the motor.

[0107] Since the processing and functions implemented by the fan of this embodiment basically correspond to the embodiments, principles and examples of the device, for the details not described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0108] According to an embodiment of the present invention, a vehicle air conditioner corresponding to the motor protection device is also provided. The vehicle air conditioner may include: the motor protection device described above, or the fan described above.

[0109] Since the processing and functions implemented by the vehicle air conditioner of this embodiment basically correspond to the embodiments, principles and examples of the device, for the details not described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0110] In summary, it is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0111] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A motor protection device, characterized in that: include: A sampling unit, a hysteresis comparison unit, and a switch unit; wherein, The sampling unit is used to sample the voltage of the input power supply of the motor from the input power supply access terminal of the motor to obtain a sampled voltage; The hysteresis comparison unit is used to output a set high potential when the hysteresis comparison unit starts to work, so as to create a high voltage protection threshold; and output a set first level signal when the sampled voltage is higher than the high voltage protection threshold; The switch unit is used to disconnect the switch unit itself when receiving the first level signal output by the hysteresis comparison unit, so as to cut off the power supply end of the motor and protect the motor; The hysteresis comparison unit is further used to output a set low potential after the hysteresis comparison unit controls the switch unit to disconnect itself, so as to create a low voltage protection threshold; and output a set second level signal when the sampled voltage is lower than the low voltage protection threshold; The switch unit is further used to turn on the switch unit itself when receiving the second level signal output by the hysteresis comparison unit, so that the power supply end of the motor is powered and the motor resumes operation.

2. The motor protection device according to claim 1, characterized in that: The sampling unit includes: a first sampling resistor module and a second sampling resistor module; wherein, The input power supply of the motor is grounded after passing through the first sampling resistor module and the second sampling resistor module; The common end of the first sampling resistor module and the second sampling resistor module, as the output end of the sampling unit, is connected to the comparison input end of the hysteresis comparison unit.

3. The motor protection device according to claim 1 or 2, characterized in that: The hysteresis comparison unit includes: a comparison module and a threshold setting module; the inverting input terminal of the comparison module is used as the comparison input terminal of the hysteresis comparison unit; the non-inverting input terminal of the comparison module is used as the threshold input terminal of the hysteresis comparison unit; wherein, The output end of the sampling unit is connected to the inverting input end of the comparison module; the preset DC power supply is connected to the non-inverting input end of the comparison module and the output end of the comparison module respectively after passing through the threshold setting module; the output end of the comparison module can be connected to the control end of the switch unit; The comparison module is used to output a set high potential when the hysteresis comparison unit starts to work, so as to create a high voltage protection threshold through the threshold setting module; and compare the sampled voltage with the high voltage protection threshold, and output a set first level signal when the sampled voltage is higher than the high voltage protection threshold; The comparison module is also used to output a set low potential after the hysteresis comparison unit controls the switch unit to disconnect itself, so as to create a low voltage protection threshold through the threshold setting module; and compare the sampled voltage with the low voltage protection threshold when the sampled voltage is lower than the low voltage protection threshold.

4. The motor protection device according to claim 3, characterized in that: The threshold setting module includes: a first voltage-dividing resistor module, a second voltage-dividing resistor module, a third voltage-dividing resistor module, a fourth voltage-dividing resistor module, a fifth voltage-dividing resistor module, and a sixth voltage-dividing resistor module; wherein, A preset first DC power supply is grounded after passing through the first voltage-dividing resistor module and the second voltage-dividing resistor module; a common end of the first voltage-dividing resistor module and the second voltage-dividing resistor module is connected to the in-phase input end of the comparison module; The preset first DC power supply is also grounded after passing through the fourth voltage-dividing resistor module, the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module; the common end of the fourth voltage-dividing resistor module and the fifth voltage-dividing resistor module is connected to the output end of the comparison module; The third voltage-dividing resistor module is connected between the common end of the first voltage-dividing resistor module and the second voltage-dividing resistor module, and between the common end of the fourth voltage-dividing resistor module and the fifth voltage-dividing resistor module; the common end of the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module serves as the output end of the hysteresis comparison unit and is connected to the control end of the switch unit.

5. The motor protection device according to claim 3, characterized in that: The hysteresis comparison unit further includes: a filtering module; wherein, The filtering module is arranged between the in-phase input terminal of the comparing module and the ground.

6. The motor protection device according to claim 4, characterized in that: The hysteresis comparison unit further includes: a filtering module; wherein, The filtering module is connected in parallel with the second voltage-dividing resistor module.

7. The motor protection device according to claim 4, characterized in that: The hysteresis comparison unit further includes: a TVS tube module; wherein, The cathode of the TVS module is connected to the common end of the fifth voltage-dividing resistor module and the sixth voltage-dividing resistor module; the anode of the TVS module is grounded.

8. The motor protection device according to any one of claims 1 to 7, characterized in that: The switch unit comprises: a switch tube module; wherein, The output end of the hysteresis comparison unit is connected to the control end of the switch tube module; the input power supply of the motor is connected to the first connection end of the switch tube module; and the second connection end of the switch tube module is grounded.

9. A fan, characterized in that: include: A protective device for an electric motor as claimed in any one of claims 1 to 8.

10. A vehicle air conditioner, characterized in that: include: A protective device for a motor as claimed in any one of claims 1 to 8, or a fan as claimed in claim 9.

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