Automobile windscreen wiper intelligent protection circuit based on PPTC resettable fuse

Abstract

The utility model relates to the technical field of electronic parts, in particular to an intelligent protection circuit for an automobile windscreen wiper based on a PPTC (Polymeric Positive Temperature Coefficient) resettable fuse. Comprising a wiper motor control circuit, a wiper motor, a gear switch and a protection circuit, the wiper motor control circuit controls the wiper motor through the gear switch, and the protection circuit is connected with the wiper motor control circuit, the wiper motor and the gear switch. The protection circuit comprises a PPTC resettable fuse overcurrent protection circuit, an RV voltage dependent resistor overvoltage protection circuit, isolation filter inductors L1 and L2, a capacitor C1 and a capacitor C2. According to the utility model, the number of components is small, the occupied volume is small, the cost is lower, the reliability is higher, related potential safety hazards or problems can be well solved, the repair and maintenance become simpler, and the market competitive advantage can be obviously improved.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic components, in particular to an automobile wiper intelligent protection circuit based on a PPTC resettable fuse. Background Art

[0002] The existing automobile wiper protection circuit uses semiconductor contactless circuits such as thyristors and transistors to replace the previous mechanical control circuit. Its installation space and volume are greatly reduced, and the reliability, stability and life of the circuit are greatly improved without mechanical contacts. However, transistors and thyristor circuits are also easily broken down and short-circuited by the reverse electromotive force pulse current and voltage during the forward and reverse conversion process of the motor. The continuous high current caused by motor stalling can also cause transistors and thyristors to heat up and burn out.

[0003] Later, a separate protection circuit was designed for the MCU system circuit. This required designing a series of circuit systems, including sampling circuits, sampling signal amplification circuits, MCU signal analysis and processing circuits, MCU control signal output and amplification, and control execution circuits. Furthermore, the high-speed and low-speed circuits had to be controlled separately, so two sets of protection circuit systems were required to ensure the proper operation of the MCU and DSP control system circuits. As can be seen from the above, this protection circuit is very complex and uses a large number of components, each of which is susceptible to damage due to quality issues or poor production. Utility Model Content

[0004] The purpose of this utility model is to provide an intelligent protection circuit for automobile wipers based on a PPTC resettable fuse, which uses a small number of components, has high reliability, is not easily damaged, has overvoltage and overcurrent protection, and can effectively extend the life of the wiper motor system equipment, so as to achieve an ideal solution and control circuit.

[0005] In order to achieve the above-mentioned purpose, the utility model adopts the following technical solution: an intelligent protection circuit for automobile wipers based on a PPTC resettable fuse, comprising a wiper motor control circuit, a wiper motor, a gear switch and a protection circuit, wherein the wiper motor control circuit controls the wiper motor through the gear switch, and the protection circuit connects the wiper motor control circuit, the wiper motor and the gear switch, and the protection circuit comprises a PPTC resettable fuse overcurrent protection circuit, an RV varistor overvoltage protection circuit, isolation filter inductors L1 and L2, and capacitors C1 and C2.

[0006] Furthermore, the PPTC resettable fuse overcurrent protection circuit includes a first resettable fuse PPTC1, a second resettable fuse PPTC2, a third resettable fuse PPTC3 and a fourth resettable fuse PPTC4. One end of the first resettable fuse PPTC1 is connected to the source of the MOS tube Q1, and the other end is connected to the node of the capacitor C2 and the isolation filter inductor L2. One end of the second resettable fuse PPTC2 is connected to the source of the MOS tube Q2, and the other end is connected to the node of the capacitor C1 and the isolation filter inductor L1. One end of the third resettable fuse PPTC3 is connected to the power supply, and the other end is connected to the gear switch. One end of the fourth resettable fuse PPTC4 is connected to the positive pole of the input end, and the other end is connected to the wiper motor control circuit.

[0007] Furthermore, the RV varistor overvoltage protection circuit includes a first RV varistor and a second RV varistor, one end of the first RV varistor is connected to the isolation filter inductor L1, and the other end is grounded; one end of the second RV varistor is connected to the isolation filter inductor L2, and the other end is grounded.

[0008] Furthermore, the wiper motor control circuit is also connected to a return sensor G1.

[0009] Furthermore, the wiper motor is also connected to a temperature control switch, one end of the temperature control switch is electrically connected to the wiper motor, and the other end is electrically connected to the gear switch.

[0010] Furthermore, the drain of the MOS transistor Q1 is connected to the gear switch, and the gate is connected to the wiper motor control circuit; the drain of the MOS transistor Q2 is connected to the gear switch, and the gate is connected to the wiper motor control circuit.

[0011] Furthermore, the power source is a vehicle-mounted DC12V lead-acid battery.

[0012] Furthermore, the temperature control switch adopts a highly sensitive bimetallic temperature control switch.

[0013] The utility model uses PPTC in conjunction with inductor L and varistor RV to form a wiper protection circuit, so as to achieve the function of protecting the wiper motor with a minimum of components. It not only has a small number of components, occupies a small volume, has lower cost and higher reliability, but also can well solve the above-mentioned hidden dangers or problems, and makes repair and maintenance simpler, significantly improves market competitiveness, and will also change the relevant design ideas of engineers. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a circuit topology diagram of the utility model. DETAILED DESCRIPTION

[0015] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be provided below with reference to the accompanying drawings. The drawings illustrate preferred embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to facilitate a more thorough and comprehensive understanding of the disclosure of the present invention.

[0016] It should be noted that when an element is referred to as being “fixed to” another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or there may be an intermediate element.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0018] See also Figure 1 This utility model provides an intelligent protection circuit for automotive wipers based on a PPTC resettable fuse. This intelligent protection circuit primarily drives the wiper motor. The forward and reverse rotation of the wiper motor drives the wipers back and forth, scraping rain off the front and rear windshields. Because the wiper motor rotates periodically in forward and reverse directions during operation, this process generates high-voltage reverse electromotive force and high current that require suppression and overcurrent control. Furthermore, the motor needs protection in the event of a jam or stall. Without this protection, the motor could burn out or cause catastrophic fires, potentially leading to burnout. Therefore, this circuit utilizes a PPTC resettable fuse and an RV varistor in conjunction with isolation filter inductors L1 and L2 and capacitors C1 and C2 to provide overcurrent and overvoltage protection. This design and application significantly improves the reliability, safety, and stability of the wiper motor control circuit system, effectively extending the life of the wiper system circuit. Furthermore, a highly sensitive bimetallic temperature switch is designed to be placed in close proximity to the motor, effectively disconnecting the power supply when the motor heats above the designed high temperature, ensuring motor damage and system safety.

[0019] like Figure 1As shown, here the return principle switch K1 is particularly shown. When the wipers are wiping normally, positions 1 and 2 are connected. When the driver turns off the wiper function, the wiper motor is not immediately disconnected from the power supply, because the driver does not know the wiper position after turning off the wiper switch. After the driver turns off the wiper switch, regardless of the wiper position, the controller will connect positions 1 and 3 of the return switch. At this time, the wiper motor will continue to be energized and move back to the designed stop position before it can be truly completely powered off. If the wipers are wiping from right to left and the driver turns off the wipers, and the wipers need to reverse to the right to return to the designed stop position, the process of the wiper motor suddenly changing from forward to reverse will generate a reverse electromotive force of up to 150V to 200V. If not controlled, this high voltage will be transmitted back to the MOS tube of the control circuit or damage a series of other related circuits, which may cause catastrophic problems.

[0020] like Figure 1 As shown in the figure, the temperature control switch TQ1 is adhered to the outer surface of the wiper motor M with thermal grease. It will only disconnect when the motor becomes abnormally hot and will not disconnect under normal conditions. It is because of this TQ1 that the control system is in an absolutely safe state and there are no safety concerns. The first self-resettable fuse PPTC1 and the second self-resettable fuse PPTC2 complete the suppression of large current surges between the forward and reverse rotation of the motor without completely limiting the current. However, the third self-resettable fuse PPTC3 is used after the wiper operation is turned off. The wipers may still be in an intermediate position during the wiping process. Therefore, although the driver has turned off the wipers, they will not stop immediately but will continue to operate to the set stop position. During the circuit conversion and operation of the wiper returning to the position, a pulse width of 1mS to 2.5mS and a reverse electromotive force of 150V to 200V are generated. The wiper may also suddenly become stuck. At this time, the third self-resettable fuse PPTC3 provides current limiting protection.

[0021] As can be seen from the above, when using this solution, regardless of accidental, inevitable, or unintentional human factors, the PPTC resettable fuse proactively controls current limiting, ensuring timely current limiting and protection for the system circuit. The use of all surface-mount devices and a compact design not only reduces the number of components but also significantly improves product safety and reliability, significantly reduces costs, and significantly reduces PCB area and space. It also facilitates design by engineers and allows for automated, large-scale production.

[0022] The key features of this new intelligent windshield wiper protection circuit based on PPTC resettable fuses are: 1. The wipers may need to be used in rainless conditions. In these conditions, wiper friction is greater than in rainy conditions, and the motor's operating current is also relatively high. In this case, the resistance of the first resettable fuse PPTC1 or the second resettable fuse PPTC2 will increase slightly, but this will not affect motor operation. While the motor temperature may rise, due to the absence of rain, it will not be used for extended periods, which will not affect the disconnection of the temperature control switch TQ1. However, due to the high resistance, the forward and reverse rotation of the motor will generate high voltage. In this case, RV1 or RV2 will be periodically turned on to reduce the risk of high voltage damage to the MOS transistor. 2. The transfer switch K1 is actually a MOS transistor circuit; a simplified diagram is shown here for clarity and clarity to illustrate the principle. 3. When the driver switches the wiper position to off, K1 automatically switches to positions 1 and 3, conducting. Regardless of the wiper's position, the wiper returns to its designated stop position. This generates a potential high voltage of 150V to 200V in the motor. VR1 or VR2, L1 or L2, and the second resettable fuse PPTC2 mitigate this back-EMF from damaging the MOSFETs. The third resettable fuse PPTC3, in particular, is particularly effective. The high current flowing through it can cause a motor stall if the wipers freeze in icy or snowy conditions. A driver might switch the wipers on, only to find they don't move, and then switch them off. During this process, the motor may have cycled forward and reverse several times, potentially drawing high current. This could result in the motor failing to rotate when switched off, effectively stalling the motor. However, the third resettable fuse PPTC3 protects the motor from damage, the MOSFETs, or the control circuitry. This prevents potential problems, particularly catastrophic fires. This innovative design uses fewer components, achieves more functions, and boasts a simple circuit, precise control, high safety, and high reliability. It effectively extends product life, reduces production and maintenance costs, and significantly reduces PCB area and space. This makes automated, large-scale production more feasible and operable, significantly improving engineers' design and production efficiency.

[0023] like Figure 1The figure shows the topology and composition of the intelligent protection circuit for automobile wipers based on PPTC resettable fuses of the present invention. The topology of the system is composed of a drive control circuit and a protection circuit with the wiper motor as the core. The drive circuit completes the forward and reverse rotation and high-speed and low-speed conversion of the motor to drive the wipers to complete the wiping operation in a reciprocating manner; the protection circuit includes RV overvoltage protection and PPTC overcurrent protection circuits, as well as L1 and L2 filtering and high-frequency high-voltage isolation circuits. The above-mentioned overvoltage protection is aimed at the peak high-voltage pulse reverse electromotive force generated by the motor at the moment of stopping when it changes from forward to reverse. If it is not suppressed, it will be reversed to the control circuit and break down and damage the G pole of the MOS tube. Therefore, RV1 and RV2 are designed to complete this function; the above-mentioned wiper is suddenly connected to bits 1 and 2 at the moment the driver turns off the wiper, and then bits 1 and 3 are suddenly connected. The wiper may be moving to the left, and will immediately turn to the right at the moment of stopping. The stop at this time is too sudden and the power is quickly lost and the reversal is started. The motor coil will generate a reverse pulse high voltage of 150V to 200V. At the same time, the superimposed reverse power supply voltage and the large current generated are passed through the third self-resetting fuse PPTC3. Therefore, the importance of designing the third self-resetting fuse PPTC3 for overcurrent limiting protection is self-evident. In this topology, the overvoltage conduction of RV generates a very large current through the third resettable fuse PPTC3. Therefore, the current limiting protection of the third resettable fuse PPTC3 greatly improves the safety and reliability of the system circuit. In addition, the third resettable fuse PPTC3 is equally important in protecting the wiper motor M from short circuits, overloads, and motor stalls.

[0024] Special Note: The connection and disconnection principles and connection position conversion process for K1, points 1, 2, and 3 in this circuit diagram are presented for simplicity and intuitiveness. The actual circuit is a contactless circuit using high-power MOS transistors. Only by designing a contactless circuit can the reliability and service life of the system product be ensured.

[0025] The utility model is based on the working principle of the automobile wiper intelligent protection circuit of the PPTC self-resetting fuse. The power supply of the vehicle DC12V lead-acid battery is added to the wiper motor control circuit through the fourth self-resetting fuse PPTC4, providing a stable working power supply for the wiper system. The wiper motor drive control circuit outputs a corresponding switch signal to the MOS tube Q1 or MOS tube Q2 under the driver's operation control command. After the MOS tube Q1 or MOS tube Q2 is turned on, the current passes through the first self-resetting fuse PPTC1 or the second self-resetting fuse PPTC2 and L1 or L2 to power the wiper motor M, so that the motor The rotation drives the wiper to complete the normal work of wiping back and forth in a 90-degree fan-shaped service area. At this time, bits 1 and 2 of K1 are in the waiting state and the working state. Only after the driver turns off the wiper, the wiper control circuit will receive the shutdown signal and K1 will immediately switch to bits 1 and 3 to be connected, forcing the wiper drive circuit to jump immediately and start the wiper return circuit. At this time, no matter where the wiper is and in what direction the wiping movement is, it will immediately switch to the return mode, that is, continue to work immediately to make the wiper return to the designed stop position and be detected by the G1 sensor to stop when the power is cut off. At this time, the wiper system will completely stop working.

[0026] During windshield wiper operation, when there's water on the glass, the wiper friction is low, the wiper motor resistance is low, and the corresponding current is also relatively low. However, when the wiper is needed to remove dust from the glass surface, there's no water on the glass. In this state, the wiper friction is high, the wiper motor resistance is also high, and the corresponding wiper motor current is also relatively high. At this time, the resistance of the first resettable fuse PPTC1 or the second resettable fuse PPTC2 increases slightly to achieve the purpose of current limiting. However, this resistance increase does not occur immediately because the motor current is not a continuous high current. Therefore, the resistance of the first resettable fuse PPTC1 or the second resettable fuse PPTC2 increases slightly, but then decreases again when the current decreases. This is a cyclical change process. During this process, the third resettable fuse PPTC3 circuit is not working, so no current flows through the third resettable fuse PPTC3. During the above-mentioned wiper operation, the wiper always moves back and forth within a 90-degree angle and within a service area with a fixed angle as shown below to complete the function of wiping water or dust.

[0027] During this back-and-forth motion, the wiper motor changes in a forward and reverse cycle. During this change, the motor always rotates in one direction and needs to stop for a designed time before rotating in the opposite direction. During this process, the motor will generate a relatively high voltage reverse electromotive force. At this time, RV1 or RV2 is triggered to short-circuit the high voltage to the ground, and the isolation of L1 or L2 together completes the overvoltage protection, so that this high voltage will not be reversed and damage the MOS tube of the previous control circuit. When RV1 or VR2 is turned on and shorted to the ground, the power supply will also be short-circuited to the ground. Due to the resistance value of the first self-resettable fuse PPTC1 or the second self-resettable fuse PPTC2, a complete short circuit will not be formed. Moreover, because its resistance value will increase under high current and limit the current, it plays a role in protecting the MOS tube and the control circuit. However, this high current time is far from the time it takes for the MOS tube to heat up and burn out, so the protection effect is obvious.

[0028] If the wiper is frozen by ice and snow before the above work, or the motor shaft is rusted and blocked, the motor cannot rotate when the operator turns on the wiper. At this time, the motor will generate a large current several times the operating current, and the coil has no effect on DC current. If it is not limited, the switch MOS tube and other devices in the control circuit will be quickly burned. The operator has to wait for a long time because of not knowing. The first self-resetting fuse PPTC1 or the second self-resetting fuse PPTC2 is designed here. It will become larger under this large current to achieve the purpose of current limiting, and after the power is turned off, the first self-resetting fuse PPTC1 or the second self-resetting fuse PPTC2 will automatically return to the initial low resistance state without affecting the operation of the wiper.

[0029] Furthermore, as mentioned above, after the driver turns off the wipers, the wiper control circuit loses power, forcing the wiper drive circuit to jump immediately and start the wiper return circuit. That is, K1 in the figure will immediately switch to position 1 and 3 to be connected. At this time, no matter where the wipers are and in which direction the wiping movement is made, they will immediately switch to the return mode, forcing the wipers to immediately return to the designed stop position before they can stop. At this time, the wiper system will completely stop working. During the wiper's operation, there may be a situation where there's no waiting time for switching (because the control circuit is powered off), resulting in a high voltage of 150V to 200V and a wide pulse of 1.5mS to 2.5mS. This also generates a proportionally large current in the circuit. If this current is reversed, it could burn out the MOSFET in the control circuit, or the insulation varnish in the motor coil could break down and spark, or the motor could be accidentally stuck or forced to stall, generating even greater current. Under this high current, the third resettable fuse PPTC3 designed here quickly switches to a high resistance state, thus providing current limiting protection. Similarly, the fourth resettable fuse PPTC4 provides current limiting protection in the event of an overcurrent or short circuit in the control circuit. Like PPTC1 to PPTC4, once in protection mode, they simultaneously provide current limiting protection for the entire system. By selecting slightly higher currents for the first and second resettable fuses PPTC1 and PPTC2, they prevent the wiper from entering deep protection mode during normal operation, ensuring proper wiper operation.

[0030] PPTC1-PPTC4 are overcurrent protection thermistors. When high current flows through a PPTC, its internal temperature rises, causing its resistance to vary within a set temperature range. The combined effects of internal heat and external temperatures cause the PPTC to expand, disconnecting most of the conductive links within the PPTC and causing its resistance to suddenly increase. When the power is disconnected, the PPTC cools, causing it to contract when cooled, reconnecting the conductive links and returning to their original state. Therefore, PPTCs are also called resettable fuses. This demonstrates that using a PPTC provides overcurrent protection with a single component. This compares favorably to the vast array of circuits and components required for MCU control, including sampling, amplification, comparison, output, and execution, which consume significantly more PCB area, volume, space, procurement costs, production costs, management costs, and testing costs. PPTCs offer significantly higher reliability and safety, as it's impossible for every component in an MCU system to be 100% reliable and long-lasting. Therefore, the use of PPTC overcurrent protection components in conjunction with RV overvoltage protection resolves the aforementioned safety issues and addresses reliability and longevity concerns. It's an indisputable fact that fewer components improve reliability and safety. Furthermore, the use of PPTC overcurrent protection in this design fully utilizes the properties of PPTC materials. Besides resolving the aforementioned known issues, it also protects against both intentional and unintentional short circuits during the production and installation process. This prevents short circuits in the circuit system from burning out due to component damage, and even prevents serious fires.

[0031] This ingenious unit circuit or modular design not only provides current-limiting protection against component damage and short circuits, but also provides both artificial and unintentional short-circuit protection for the wiper motor circuit system, preventing short-circuit damage and serious fires. It also solves design challenges for related equipment manufacturers and engineers, using minimal components, occupying less space, reducing costs, and increasing reliability, making the product safer. Without changing the overall design of related equipment, the wiper system provides true safety assurance, directly enhancing manufacturers' market competitiveness.

[0032] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the present utility model patent shall be determined by the appended claims.

Claims

1. The intelligent protection circuit for automobile wipers based on PPTC resettable fuse is characterized by: It includes a wiper motor control circuit, a wiper motor, a gear switch and a protection circuit. The wiper motor control circuit controls the wiper motor through the gear switch. The protection circuit is connected to the wiper motor control circuit, the wiper motor and the gear switch. The protection circuit includes a PPTC self-resettable fuse overcurrent protection circuit, an RV varistor overvoltage protection circuit, isolation filter inductors L1 and L2, and capacitors C1 and C2.

2. The intelligent protection circuit for automobile wipers based on a PPTC resettable fuse according to claim 1 is characterized in that: The PPTC resettable fuse overcurrent protection circuit includes a first resettable fuse PPTC1, a second resettable fuse PPTC2, a third resettable fuse PPTC3 and a fourth resettable fuse PPTC4. One end of the first resettable fuse PPTC1 is connected to the source of the MOS tube Q1, and the other end is connected to the node of the capacitor C2 and the isolation filter inductor L2. One end of the second resettable fuse PPTC2 is connected to the source of the MOS tube Q2, and the other end is connected to the node of the capacitor C1 and the isolation filter inductor L1. One end of the third resettable fuse PPTC3 is connected to the power supply, and the other end is connected to the gear switch. One end of the fourth resettable fuse PPTC4 is connected to the positive pole of the input end, and the other end is connected to the wiper motor control circuit.

3. The intelligent protection circuit for automobile wipers based on a PPTC resettable fuse according to claim 1, characterized in that: The RV varistor overvoltage protection circuit includes a first RV varistor and a second RV varistor, one end of the first RV varistor is connected to the isolation filter inductor L1, and the other end is grounded; one end of the second RV varistor is connected to the isolation filter inductor L2, and the other end is grounded.

4. The automobile wiper intelligent protection circuit based on a PPTC resettable fuse according to claim 1 is characterized in that: The wiper motor control circuit is also connected to a return sensor G1.

5. The intelligent protection circuit for automobile wipers based on a PPTC resettable fuse according to claim 1, characterized in that: The wiper motor is further connected to a temperature control switch, one end of the temperature control switch is electrically connected to the wiper motor, and the other end is electrically connected to the gear switch.

6. The intelligent protection circuit for automobile wipers based on a PPTC resettable fuse according to claim 2, characterized in that: The drain of the MOS transistor Q1 is connected to the gear switch, and the gate is connected to the wiper motor control circuit. The drain of the MOS transistor Q2 is connected to the gear switch, and the gate is connected to the wiper motor control circuit.

7. The intelligent protection circuit for automobile wipers based on a PPTC resettable fuse according to claim 2, characterized in that: The power source is a vehicle-mounted DC12V lead-acid battery.

8. The automobile wiper intelligent protection circuit based on a PPTC resettable fuse according to claim 5, characterized in that: The temperature control switch adopts a highly sensitive bimetallic temperature control switch.

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