A control circuit for a lithium battery-powered lawnmower brake stop

Abstract

The application discloses a kind of lithium electric mower brake parking control circuit, overcome the problem of lower reliability when existing technology is utilized to realize mower brake parking by software control, and there is certain security risk, including: parking control loop, for brake parking when motor is powered off;Energy storage loop, for storing electric energy when motor is working, and providing electric energy for parking control loop when motor is powered off;Power-off circuit, for making working loop or parking control loop in power-off state under different conditions;Working loop, for executing normal work of mower.No software access is required, to ensure brake parking when motor is powered off, with higher reliability.

Description

Technical Field

[0001] This invention relates to the field of automatic control technology, and in particular to a control circuit for braking and stopping a lithium-ion battery lawnmower. Background Technology

[0002] A lawnmower is a widely used outdoor tool that uses mechanical force to level lawns. The lawnmower's brake power-off device is crucial for its operation. If the power to the lawnmower's drive circuit is not cut off in time during braking, the motor will remain energized and rotating. This will cause a sharp increase in motor load and damage the battery plates.

[0003] Existing technologies typically employ software control, where a controller directs the motor via program commands to stop it. However, software-controlled motors, because they operate through program commands, require absolutely correct program input in actual production; otherwise, the motor may continue running indefinitely. This method has low reliability for stopping the motor and poses certain safety hazards. Furthermore, software-based stopping requires software evaluation for certification, and the program cannot be modified. This means that pre-existing program flaws cannot be addressed. It also presents significant disadvantages for product upgrades and replacements.

[0004] The existing hardware shutdown circuit for lawnmowers also has a significant flaw: it requires the brushless motor's back electromotive force (EMF) to be considered during the motor parameter setting process. This is because the motor's three-phase short circuit is achieved by switching the MOSFET on and off. When the input voltage is disconnected, the circuit loses power, and the back EMF generated by the motor needs to provide voltage to the MOSFET to ensure its smooth conduction. However, if the back EMF generated by the motor is too small, it will not reach the MOSFET's gate voltage, preventing the MOSFET from turning on, thus disabling the hardware shutdown function and preventing the motor from stopping. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of low reliability and certain safety hazards in the existing technology of using software control to stop a lawnmower by braking. It provides a control circuit for stopping a lithium-ion lawnmower by braking, which does not require software access and ensures that the lawnmower stops by braking when the motor is powered off, with high reliability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution, including:

[0007] The shutdown control circuit is used to brake and stop the motor when the power is cut off.

[0008] The energy storage circuit is used to store electrical energy when the motor is running and to provide power to the shutdown control circuit when the motor is powered off.

[0009] A power-off circuit is used to de-energize the working circuit or the shutdown control circuit under different circumstances.

[0010] The working circuit is used to perform the normal operation of the lawnmower.

[0011] When the motor is working, the working circuit performs various functions, the energy storage circuit stores energy, and the power-off circuit keeps the shutdown control circuit in a de-energized state. When the motor stops, the working circuit stops working, the energy storage circuit discharges, the power-off circuit keeps the working circuit in a de-energized state, and the electrical energy released by the energy storage circuit turns on the shutdown control circuit, causing the motor to stop.

[0012] This lithium-ion battery-powered lawnmower's brake and stop control circuit employs hardware logic to ensure braking and stopping simultaneously with motor power loss. This stopping method eliminates the need for software intervention, effectively avoiding software evaluation and allowing for controller upgrades within the certificate's validity period, ensuring a superior user experience.

[0013] Preferably, the shutdown control circuit includes a diode group and a MOSFET, wherein the positive terminal of the diode group is connected to the motor and the negative terminal is connected to the drain of the MOSFET.

[0014] When the motor is running, capacitor C43 is in a charging state; when the main circuit is disconnected and the motor loses power, capacitor C43 discharges to provide the gate voltage for the MOSFET, thereby turning on the MOSFET, ensuring the path of the shutdown control circuit, and smoothly executing the shutdown operation.

[0015] Preferably, the diode group includes three diode pairs, each of which is connected to one of the three phases U, V, and W of the motor.

[0016] Preferably, the diode pair includes a first diode and a second diode, wherein the positive terminal of the first diode is connected to the upper path of the phase and the negative terminal is connected to the drain of the MOSFET; the positive terminal of the second diode is connected to the lower path of the phase and the negative terminal is connected to the drain of the MOSFET.

[0017] Six diodes are located in the upper and lower circuits of the motor's three phases (U, V, and W), with their cathodes all connected to the drain of the same MOSFET. When the motor is running, the MOSFET is in an open-circuit state, and the circuit is not conductive. When the motor needs to be stopped, the upper or lower MOSFETs of these six diodes are turned on to short-circuit the three phases of the motor, thus stopping the motor. In this invention, all six diodes are Schottky diodes. This invention employs a method to simultaneously apply six control signals as braking signals. It is not limited to six diodes + one MOSFET (this is the lowest-cost solution); six independent diodes + one MOSFET can also be used, or six MOSFETs can be used (without diodes), or a dedicated driver chip can be used. When using six diodes + one MOSFET, it is not limited to Schottky diodes; ordinary diodes can also be used. Ultimately, an energy storage capacitor is used to simultaneously turn on three lower-arm large MOSFETs or three upper-arm large MOSFETs.

[0018] Preferably, the energy storage circuit includes a capacitor, one end of which is connected to the working circuit and the other end to the shutdown control circuit. The capacitor has a limited capacity, which can serve as a power source for a short period, successfully turning on the MOSFET and stopping the motor.

[0019] Preferably, the working circuit includes: a power supply circuit, and a tilt switch, a power disconnect module, a pull rod release module, and a communication module, all connected to the power supply circuit. The communication module is used for communication between the PLC in the switch box and the MCU in the main circuit.

[0020] Preferably, the power-off circuit includes:

[0021] The first power-off circuit is used to keep the working circuit in an open state when the motor stops;

[0022] The second power-off circuit is used to keep the shutdown control circuit in an open state when the motor is running.

[0023] At the moment of shutdown, the working circuit disconnects, meaning the circuit above the energy storage circuit is broken, and the energy storage circuit discharges. Because the first power-off circuit exists, the electrical energy released by the energy storage circuit cannot enter the working circuit; it can only provide power to the shutdown control circuit. As the energy storage circuit discharges, the shutdown control circuit becomes conductive, initiating the shutdown process. This provides a certain delay before the output is completely de-energized.

[0024] Preferably, the first power-off circuit includes a first Zener diode, with its anode connected to the working circuit and its cathode connected to the energy storage circuit. The circuit is broken by utilizing the unidirectional conductivity of the Zener diode.

[0025] Preferably, the second power-off circuit includes a second Zener diode and a transistor. The negative terminal of the second Zener diode is connected to one end of the energy storage circuit, the positive terminal of the second Zener diode is connected to the base of the transistor, the emitter of the transistor is grounded, and the collector of the transistor is connected to the input terminal of the shutdown control circuit. The circuit is broken by utilizing the unidirectional conductivity of the Zener diode.

[0026] Preferably, a first resistor is connected between the negative terminal of the Zener diode and the other end of the energy storage circuit, a second resistor is connected between the base of the transistor and the other end of the energy storage circuit, and a third resistor is connected between the emitter of the transistor and the input terminal of the shutdown control circuit. This ensures circuit safety.

[0027] Therefore, the present invention has the following beneficial effects: 1. The control circuit uses pure hardware logic and does not require software program intervention for control, which effectively avoids problems such as inability to stop the machine and program conflicts that may be caused by software logic errors. It also avoids a series of disadvantages such as the inability to update the program due to software evaluation; 2. It also provides a wider range of choices in motor selection and solves the problem that the motor itself cannot be stopped by hardware circuit due to its small back electromotive force. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the system structure of the present invention.

[0029] Figure 2 This is a partial circuit diagram of the working circuit of the present invention.

[0030] Figure 3 This is a circuit diagram of the communication module of the present invention.

[0031] Figure 4 This is a circuit diagram of the power-off circuit, energy storage circuit, and shutdown control circuit of the present invention.

[0032] In the diagram: 1. Working circuit; 2. Energy storage circuit; 3. Power failure circuit; 4. Shutdown control circuit; 5. External power supply; 6. Motor. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0034] This embodiment describes a control circuit for braking and stopping a lithium-ion battery-powered lawnmower, such as... Figure 1As shown, the system includes a working circuit 1, an energy storage circuit 2, a power-off circuit 3, and a stop control circuit 4 connected in sequence. The working circuit is connected to an external power supply 5, and the stop control circuit is also connected to the lawnmower motor 6. The working circuit is used to perform normal operation of the lawnmower, such as anti-tipping, power disconnection, lever extension, wire disconnection, and communication with the main circuit. The energy storage circuit is used to store electrical energy when the motor is working and to provide power to the stop control circuit when the motor is powered off. The power-off circuit is used to de-energize the working circuit or the stop control circuit under different conditions. The stop control circuit is used to brake and stop the machine when the motor is powered off.

[0035] This lithium-ion lawnmower brake stop control circuit not only effectively avoids the impact of software control circuits on stopping the machine, but also fully considers the influence of motor parameters. In the scheme of short-circuiting the motor three-phase through the stop control circuit, the traditional method of using the motor back EMF as the gate voltage of the stop control circuit is abandoned. Instead, an energy storage circuit is added to the hardware circuit to store electrical energy while the motor is running.

[0036] Its workflow is as follows:

[0037] When the motor is working, the working circuit performs various functions, the energy storage circuit stores energy, and the power-off circuit keeps the shutdown control circuit in a de-energized state. When the motor stops, the working circuit stops working, the energy storage circuit discharges, the power-off circuit keeps the working circuit in a de-energized state, and the electrical energy released by the energy storage circuit turns on the shutdown control circuit, causing the motor to stop.

[0038] Specifically:

[0039] like Figure 2 As shown, the working circuit includes a power supply circuit and a tilt switch, a power disconnect module, and a pull rod release module, which are respectively connected to the power supply circuit.

[0040] like Figure 3 As shown, the working circuit also includes a communication module, which includes U3, used to enable communication between the PLC in the switch box and the MCU in the main circuit. In this embodiment, U3 uses the HT7463 chip.

[0041] The specific circuit diagrams for the power-off circuit, energy storage circuit, and shutdown control circuit are as follows: Figure 4 As shown:

[0042] The power-off circuit includes diode D42, resistor R98, Zener diode D43, resistor R97, resistor R99, and transistor Q20; the energy storage circuit includes capacitor C43; and the shutdown control circuit includes resistor R965, resistor R96, MOSFET Q19, diode D35, diode D70, diode D40, diode D71, diode D41, and diode D72.

[0043] The anode of diode D42 is connected to the working circuit, and the cathode of diode D42 is connected to one end of capacitor C43, with the other end of capacitor C43 grounded. One end of resistor R98 is connected to one end of capacitor C43 and the cathode of Zener diode D43, with the other end of resistor R98 grounded. The anode of Zener diode D43 is connected to one end of resistor R97, and the other end of resistor R97 is connected to one end of resistor R99 and the base of transistor Q20. The other end of resistor R99 and the emitter of transistor Q20 are grounded, and the collector of transistor Q20 is connected to one end of resistor R95, one end of resistor R96, and the gate of MOSFET Q19. The other end of resistor R95 is connected to 12 The power supply is connected to V, and the other end of resistor R96 is grounded; the emitter of MOSFET Q19 is grounded, and the drain of MOSFET Q19 is connected to the cathodes of diodes D35, D70, D40, D71, D41, and D72 respectively; the anode of diode D35 is connected to the upper circuit of electrode W, the anode of diode D70 is connected to the upper circuit of electrode V, and the anode of diode D40 is connected to the upper circuit of electrode U; the anode of diode D71 is connected to the lower circuit of electrode W; the anode of diode D41 is connected to the lower circuit of electrode V, and the anode of diode D72 is connected to the lower circuit of electrode U.

[0044] A comparator can also be added between the power-off circuit and the shutdown control circuit to achieve accurate power-off delay.

[0045] The specific workflow is as follows:

[0046] When the motor is running, capacitor C43 is in a charging state; when the main circuit is disconnected and the motor loses power, capacitor C43 discharges to provide the gate voltage for the MOSFET, thereby turning on the MOSFET, ensuring the path of the shutdown control circuit, and smoothly executing the shutdown operation.

[0047] Six diodes are located in the upper and lower circuits of the motor's three phases (U, V, and W), respectively, with their cathodes all connected to the drain of the same MOSFET. When the motor is running, the MOSFET is in an open-circuit state, and the circuit is not conductive. When the motor needs to be stopped, the upper or lower MOSFET of these six diodes needs to be turned on to short-circuit the three phases of the motor, thereby stopping the motor. In this embodiment, all six diodes are Schottky diodes.

[0048] This invention employs a method to simultaneously apply six control signals as braking signals. It is not limited to the six diodes + one MOSFET in this embodiment (which is the lowest-cost solution). Alternatively, six independent diodes + one MOSFET can be used, or six MOSFETs can be used (without diodes). A dedicated driver chip can also be employed. When using six diodes + one MOSFET, it is not limited to the Schottky diodes used in this embodiment; ordinary diodes can also be used. Ultimately, an energy storage capacitor is used to simultaneously activate either three lower-arm large MOSFETs or three upper-arm large MOSFETs.

[0049] Figure 2 , Figure 3 , Figure 4 In this context, identical symbols indicate the connection relationships between circuit diagrams, such as... Figure 2 Point B and Figure 4 Connect at point B. Figure 2 A is in Figure 3 Connect at point A.

[0050] This application uses a capacitor C43 connected in parallel, which charges during power-on. Upon power-off, the power supply circuit is disconnected (i.e.,...). Figure 4 As shown, the circuit above C43 is open, and capacitor C43 discharges. Due to the presence of Zener diode D42, it cannot enter the upper main circuit and can only provide current to the lower branch, i.e., the shutdown control circuit. Capacitor C43 discharges, and the shutdown control circuit is turned on (i.e., the lower branch starts to stop). This provides a certain delay before the output is completely de-energized (because the capacitor's capacity is limited and serves as a power source for a certain short time), successfully turning on the MOSFET and causing the motor to stop.

[0051] This application adds an energy storage component to the control circuit, replacing the original method of the motor using its own back electromotive force to generate electrical energy, thus enabling the shutdown circuit to execute smoothly. During the shutdown process, the discharge of the energy storage component acts as a circuit delay, ensuring that even when the input is completely de-energized, the output can still smoothly execute the hardware logic requirements, achieving complete motor shutdown until the machine is completely de-energized.

[0052] In this embodiment, a capacitor is used as the energy storage component. However, this does not mean that this application can only use capacitors as the energy storage component. Similar solutions can be implemented by replacing capacitors or other energy storage components to replace the circuit. Similarly, relays or other components can be used to replace MOSFETs as switches.

[0053] The control circuit of this application uses pure hardware logic, eliminating the need for software intervention and effectively avoiding problems such as inability to stop the machine or program conflicts caused by software logic errors. It also avoids the drawbacks of software evaluation, such as the inability to update or upgrade the program. Furthermore, it provides a wider range of choices in motor selection, resolving the issue of motors with low back electromotive force preventing the use of hardware circuits for stopping the machine.

[0054] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A control circuit for braking and stopping a lithium-ion battery-powered lawnmower, characterized in that, include: The shutdown control circuit is used to brake and stop the motor when the power is cut off. It includes 6 diodes, which are located in the upper and lower circuits of the U, V and W phases of the motor respectively. The negative terminals of the diodes are all connected to the drain of the same MOSFET. During operation, the MOSFET is in an open circuit state. When the power is cut off, the energy storage circuit discharges to provide the gate voltage of the MOSFET and execute the shutdown operation. The energy storage circuit is used to store electrical energy when the motor is running and to provide power to the shutdown control circuit when the motor is powered off. A power-off circuit is used to de-energize the working circuit or the shutdown control circuit under different conditions. The power-off circuit includes a first power-off circuit that de-energizes the working circuit when the motor stops and a second power-off circuit that de-energizes the shutdown control circuit when the motor is running. The first power-off circuit includes a first Zener diode, with its anode connected to the working circuit and its cathode connected to the energy storage circuit. The second power-off circuit includes a second Zener diode and a transistor, with the cathode connected to one end of the energy storage circuit, the anode connected to the base of the transistor, the emitter grounded, and the collector connected to the input terminal of the shutdown control circuit. The working circuit, used to perform normal operation of the lawnmower, includes a power supply circuit and a tilt switch, a power disconnect module, and a lever release module, which are respectively connected to the power supply circuit. A comparator is set between the power-off circuit and the shutdown control circuit to achieve power-off delay.

2. The control circuit for braking and stopping a lithium-ion battery-powered lawnmower according to claim 1, characterized in that, The shutdown control circuit includes a diode group and a MOSFET. The positive terminal of the diode group is connected to the motor, and the negative terminal is connected to the drain of the MOSFET.

3. The control circuit for braking and stopping a lithium-ion battery-powered lawnmower according to claim 2, characterized in that, The diode group includes three diode pairs, each of which is connected to one of the three phases of the motor, namely U, V, and W.

4. The control circuit for braking and stopping a lithium-ion battery lawnmower according to claim 3, characterized in that, The diode pair includes a first diode and a second diode. The positive terminal of the first diode is connected to the upper path of the phase, and the negative terminal is connected to the drain of the MOSFET. The positive terminal of the second diode is connected to the lower path of the phase, and the negative terminal is connected to the drain of the MOSFET.

5. The control circuit for braking and stopping a lithium-ion battery-powered lawnmower according to claim 1, characterized in that, The energy storage circuit includes a capacitor, one end of which is connected to the working circuit and the other end of which is connected to the shutdown control circuit.

6. A control circuit for braking and stopping a lithium-ion battery-powered lawnmower according to claim 1 or 2, characterized in that, The working circuit includes a communication module connected to the power supply circuit.

7. The control circuit for braking and stopping a lithium-ion battery-powered lawnmower according to claim 1, characterized in that, A first resistor is connected between the negative terminal of the Zener diode and the other end of the energy storage circuit. A second resistor is also connected between the base of the transistor and the other end of the energy storage circuit. A third resistor is connected between the emitter of the transistor and the input terminal of the shutdown control circuit.

8. The control circuit for braking and stopping a lithium-ion battery lawnmower according to claim 6, characterized in that, The communication module includes a chip U3, which is model HT7463.

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