A children's vehicle motor drive circuit

Abstract

This invention belongs to the field of drive circuit technology, and particularly relates to a drive circuit for a children's stroller motor, comprising: a main control module for outputting forward control signals, reverse control signals, and brake control signals; a drive control unit, whose input terminal is electrically connected to the output terminal of the main control module, for processing the received forward control signals and reverse control signals to output electronic switch drive signals; and a logic control unit, whose input terminal is electrically connected to the output terminal of the main control module. This application designs the two upper arms of the H-bridge actuator as normally open power switch units, physically disconnecting the stroller motor from the power supply when no valid power switch control signal is received. This completely solves the major safety hazard of the existing H-bridge upper MOSFET being constantly energized and spontaneously combusting due to quality defects or electrostatic damage, thus eliminating the risk of fire when the stroller is stationary.

Description

Technical Field

[0001] This invention belongs to the field of drive circuit technology, and in particular relates to a drive circuit for a children's vehicle motor. Background Technology

[0002] As a common children's entertainment product, the core power system of electric children's vehicles consists of a DC motor and a matching drive circuit. Currently, the industry generally adopts a full NMOS H-bridge circuit composed of four NMOS field-effect transistors as the mainstream drive solution for children's vehicle motors. This solution can realize the forward and backward functions of the children's vehicle by controlling the conduction and turn-off timing of the four MOSFETs, and can achieve continuous adjustment of motor speed by applying a PWM (pulse width modulation) signal to the lower MOSFET. It has the advantages of relatively simple circuit structure and low cost.

[0003] However, the aforementioned existing technical solutions have two fatal flaws that are difficult to overcome in practical applications:

[0004] First, there are serious safety hazards. The instantaneous maximum current during the start-up and stalling of a stroller motor can reach over 60A, which conventional mechanical power switches cannot withstand. Therefore, the power switch in the existing circuit is only used to cut off the power supply to the control circuit, and does not physically shut off the main power supply circuit of the MOSFETs on the H-bridge, resulting in the two MOSFETs on the H-bridge always being energized. When the stroller is left idle in a warehouse, garage, or similar environment for a long time, if the MOSFETs themselves have manufacturing defects, or are damaged by electrostatic discharge or surge voltage, causing a short circuit, the motor will directly connect to the power supply and run uncontrollably, leading to overheating or even spontaneous combustion. Currently, there have been many cases of fires caused by accidental damage to MOSFETs when strollers are idle, resulting in serious property damage and safety threats.

[0005] Secondly, the circuit suffers from low reliability and a high MOSFET failure rate. Because the source voltages of the two upper MOSFETs in the all-NMOSH bridge dynamically change with the motor's operating state, an additional bootstrap circuit must be used to provide a drive signal to the upper MOSFET's gate that is higher than the power supply voltage to ensure reliable conduction. Due to the limitations of the bootstrap circuit's operating principle, the maximum duty cycle of the PWM signal driving the motor cannot reach 100%, typically remaining between 95% and 98%. This means that the upper MOSFET will continuously generate high-frequency switching losses in high-speed operation, leading to increased junction temperature, accelerated device aging, further increasing the probability of MOSFET failure, and shortening the overall lifespan of the drive circuit.

[0006] Currently, no effective solutions have been proposed in the industry to address the aforementioned issues. Existing improvements mainly focus on increasing the voltage rating of the MOSFETs or adding heat dissipation structures, but these cannot fundamentally solve the safety hazards of the H-bridge transistors being constantly energized or the switching losses caused by the limited duty cycle of the PWM circuit. Therefore, developing a children's vehicle motor drive circuit that can simultaneously eliminate the risk of spontaneous combustion and improve circuit reliability is of significant practical importance. Summary of the Invention

[0007] The purpose of this invention is to address the aforementioned technical problems by providing a children's vehicle motor drive circuit.

[0008] In view of this, the present invention provides a children's vehicle motor drive circuit, comprising:

[0009] The main control module is used to output forward control signals, reverse control signals, and braking control signals;

[0010] The drive control unit, whose input terminal is electrically connected to the output terminal of the main control module, is used to process the received forward control signal and backward control signal to output the electronic switch drive signal;

[0011] The logic control unit, whose input terminal is electrically connected to the output terminal of the main control module, is used to output power switch control signals according to the received forward control signals, reverse control signals and braking control signals;

[0012] The H-bridge actuator has its input terminals connected to the output terminals of the drive control unit and the logic control unit, respectively. It is used to receive the electronic switch drive signal and the power switch control signal, and control the forward rotation, reverse rotation and stop of the children's vehicle motor according to the received signals.

[0013] The two upper arms of the H-bridge actuator are normally open power switch units, which physically disconnect the stroller motor from the power supply when no valid power switch control signal is received.

[0014] Furthermore, the H-bridge execution unit includes a first power switch, a second power switch, a first electronic switch, and a second electronic switch; the first power switch and the second power switch constitute the two upper arms of the H-bridge, and the first electronic switch and the second electronic switch constitute the two lower arms of the H-bridge.

[0015] Furthermore, both the first power switch and the second power switch are normally open relays; one end of the normally open contact of the first power switch is connected to the power supply, and the other end is connected to the first terminal of the stroller motor; one end of the normally open contact of the second power switch is connected to the power supply, and the other end is connected to the second terminal of the stroller motor.

[0016] Furthermore, both the first electronic switch and the second electronic switch are NMOS field-effect transistors; the drain of the first electronic switch is connected to the first terminal of the stroller motor, and the source is grounded; the drain of the second electronic switch is connected to the second terminal of the stroller motor, and the source is grounded.

[0017] Furthermore, the gates of the first electronic switch and the second electronic switch are electrically connected to the first electronic switch driving terminal and the second electronic switch driving terminal of the drive control unit through current-limiting resistors, respectively.

[0018] Furthermore, the drive control unit and the logic control unit are implemented by two identical drive chips; each drive chip integrates one electronic switch drive channel and two power switch drive channels.

[0019] Furthermore, it also includes a first freewheeling unit and a second freewheeling unit; the first freewheeling unit is connected in reverse parallel between the drain and source of the first electronic switch, and the second freewheeling unit is connected in reverse parallel between the drain and source of the second electronic switch.

[0020] Furthermore, both the first freewheeling unit and the second freewheeling unit are Schottky diodes.

[0021] Furthermore, it also includes a braking unit; the two terminals of the braking unit are respectively connected to the first terminal and the second terminal of the stroller motor, and the control terminal is connected to the brake signal output terminal of the logic control unit; when the logic control unit does not receive a forward control signal and a reverse control signal, it controls the braking unit to engage and conduct, thereby short-circuiting the first terminal and the second terminal of the stroller motor.

[0022] Furthermore, the braking unit is a normally open relay.

[0023] The beneficial effects of this invention are:

[0024] This application designs the two upper arms of the H-bridge actuator as normally open power switch units, which physically disconnects the connection between the stroller motor and the power supply when no valid power switch control signal is received. This completely solves the major safety hazard of the MOSFET on the upper part of the H-bridge being energized for a long time and spontaneously combusting due to quality defects or electrostatic damage in the prior art, thus eliminating the risk of fire when the stroller is stationary. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a children's vehicle motor drive circuit proposed in this invention. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0027] In the description of this application, it should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0028] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0029] It should be noted that in the description of this application, the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0030] It should be noted that, in this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0031] Reference Figure 1 A children's stroller motor drive circuit, characterized in that it includes:

[0032] The main control module is used to output forward control signals, reverse control signals, and braking control signals;

[0033] The drive control unit, whose input terminal is electrically connected to the output terminal of the main control module, is used to process the received forward control signal and backward control signal to output the electronic switch drive signal;

[0034] The logic control unit, whose input terminal is electrically connected to the output terminal of the main control module, is used to output power switch control signals according to the received forward control signals, reverse control signals and braking control signals;

[0035] The H-bridge actuator has its input terminals connected to the output terminals of the drive control unit and the logic control unit, respectively. It is used to receive the electronic switch drive signal and the power switch control signal, and control the forward rotation, reverse rotation and stop of the children's vehicle motor according to the received signals.

[0036] The two upper arms of the H-bridge actuator are normally open power switch units, which physically disconnect the stroller motor from the power supply when no valid power switch control signal is received.

[0037] This application designs the two upper arms of the H-bridge actuator as normally open power switch units, which physically disconnects the connection between the stroller motor and the power supply when no valid power switch control signal is received. This completely solves the major safety hazard of the MOSFET on the upper part of the H-bridge being energized for a long time and spontaneously combusting due to quality defects or electrostatic damage in the prior art, thus eliminating the risk of fire when the stroller is stationary.

[0038] The boost drive circuit required for the upper NMOS transistor in existing technologies has been eliminated, allowing the PWM speed control signal duty cycle of the lower transistor electronic switch to reach 100%, completely eliminating the switching losses of the MOS transistor, significantly reducing the heat generation and damage probability of the MOS transistor, and extending the service life of the drive circuit.

[0039] The circuit adopts a modular architecture design consisting of a main control module, a drive control unit, a logic control unit, and an H-bridge execution unit. The circuit logic is clear and the functions are well-defined, which facilitates subsequent debugging, maintenance, and functional expansion, while also improving the circuit's anti-interference capability.

[0040] In the example of this application, the H-bridge execution unit includes a first power switch, a second power switch, a first electronic switch, and a second electronic switch; the first power switch and the second power switch constitute the two upper arms of the H-bridge, and the first electronic switch and the second electronic switch constitute the two lower arms of the H-bridge.

[0041] This structure adopts the classic H-bridge architecture with power switches and electronic switches on separate upper and lower arms, which can reliably realize the three basic working states of motor forward rotation, reverse rotation and stop, in accordance with the basic principles of motor drive.

[0042] By separating the power switching and high-speed speed regulation functions of the H-bridge, the upper arm is responsible for the physical switching of the power supply, while the lower arm is responsible for PWM speed regulation. This balances the high current carrying capacity and high-precision speed regulation requirements, and can adapt to the high current surge during the start-up of the children's vehicle motor and the speed regulation requirements during operation.

[0043] In the example of this application, both the first power switch and the second power switch are normally open relays; one end of the normally open contact of the first power switch is connected to the power supply, and the other end is connected to the first terminal of the stroller motor; one end of the normally open contact of the second power switch is connected to the power supply, and the other end is connected to the second terminal of the stroller motor.

[0044] Normally open relays are used as the upper arm power switches of the H-bridge. By utilizing their inherent characteristics of disconnection when there is no power and activation when there is power, the relay contacts are naturally disconnected when the power switch is off or when the main control module fails and there is no output, thus achieving physical isolation of the power supply. The safety and reliability are far higher than those of semiconductor switches.

[0045] The relay contacts have a strong current-carrying capacity and can easily withstand the instantaneous large current of more than 60A when the children's vehicle motor starts, which solves the problem that the power switch and MOSFET in the existing technology cannot withstand the impact of large current and improves the overload capacity of the circuit.

[0046] In the example of this application, both the first electronic switch and the second electronic switch are NMOS field-effect transistors; the drain of the first electronic switch is connected to the first terminal of the stroller motor, and the source is grounded; the drain of the second electronic switch is connected to the second terminal of the stroller motor, and the source is grounded.

[0047] Using NMOS field-effect transistors as the lower arm electronic switches of the H-bridge, and taking advantage of their low on-resistance, fast switching speed and low cost, efficient PWM speed regulation of the motor is achieved, ensuring the smoothness of the stroller's ride.

[0048] The source of an NMOS transistor is directly grounded, eliminating the need for a boost drive circuit. This further simplifies the circuit structure, reduces circuit complexity and failure rate, and improves drive efficiency.

[0049] In the example of this application, the gates of the first electronic switch and the second electronic switch are electrically connected to the first electronic switch driving terminal and the second electronic switch driving terminal of the drive control unit through current-limiting resistors, respectively.

[0050] By connecting a current-limiting resistor in series with the gate of the NMOS transistor, the charging and discharging current of the gate is effectively limited, preventing the gate of the NMOS transistor from being damaged due to excessive drive current. At the same time, the oscillation of the gate signal is suppressed, and the stability of the switching action is improved.

[0051] Current-limiting resistors can reduce the output load of the driver chip, protect the driver chip from being burned out by overcurrent, and improve the reliability and shock resistance of the entire driver circuit.

[0052] The sources of both the first and second electronic switches are grounded through a current sampling resistor with a resistance of 0.006Ω and a 2512 package. This current sampling resistor is used to detect the motor's operating current in real time. When the detected current exceeds a set threshold, the main control module can cut off the control signal to achieve overcurrent protection, further improving circuit safety.

[0053] In the example of this application, the drive control unit and the logic control unit are implemented by two identical drive chips; each drive chip integrates one electronic switch drive channel and two power switch drive channels.

[0054] Two identical driver chips are used to implement the drive control and logic control functions respectively. Each chip integrates one electronic switch drive channel and two power switch drive channels, which accurately matches the drive requirements of this circuit. No additional discrete components are needed to build the drive circuit, which greatly simplifies the PCB layout.

[0055] The two chips have clearly defined functions and do not interfere with each other, which improves the fault tolerance of the circuit. The failure of a single chip will not cause the entire drive circuit to fail completely. At the same time, standardized chip selection reduces production and procurement costs.

[0056] In the example of this application, a first freewheeling unit and a second freewheeling unit are also included; the first freewheeling unit is connected in reverse parallel between the drain and source of the first electronic switch, and the second freewheeling unit is connected in reverse parallel between the drain and source of the second electronic switch.

[0057] By connecting a freewheeling unit in reverse parallel across the two ends of the electronic switch, the induced reverse electromotive force generated when the motor winding is de-energized can be quickly absorbed, preventing high voltage spikes from breaking down the NMOS transistor and protecting the electronic switch from damage.

[0058] The freewheeling unit provides a freewheeling circuit for the motor windings, avoiding electromagnetic interference caused by sudden changes in motor current and improving the electromagnetic compatibility (EMC) of the circuit.

[0059] In the example of this application, both the first freewheeling unit and the second freewheeling unit are Schottky diodes.

[0060] Schottky diodes are used as freewheeling units. Taking advantage of their extremely short reverse recovery time and low forward voltage drop, they are particularly suitable for high-frequency PWM speed control scenarios. They can significantly reduce power loss during freewheeling and improve the overall efficiency of the circuit.

[0061] Schottky diodes have small package size and good heat dissipation performance, making them suitable for the miniaturization design requirements of children's vehicle drive circuits. At the same time, their high current carrying capacity can meet the motor's freewheeling requirements.

[0062] In the example of this application, a braking unit is also included; the two terminals of the braking unit are respectively connected to the first terminal and the second terminal of the stroller motor, and the control terminal is connected to the brake signal output terminal of the logic control unit; when the logic control unit does not receive a forward control signal and a reverse control signal, it controls the braking unit to engage and conduct, thereby short-circuiting the first terminal and the second terminal of the stroller motor.

[0063] An independent braking unit is added, which achieves energy-efficient braking by short-circuiting both ends of the motor. This allows the stroller to stop quickly when there is no forward / backward signal, improving the stroller's driving safety and preventing rollover accidents.

[0064] The braking action is directly controlled by the logic control unit and interlocked with the motor drive logic to ensure that the brake is only triggered when the motor stops, thus avoiding short circuits and component damage caused by the simultaneous operation of the brake and drive.

[0065] In the example of this application, the braking unit is a normally open relay.

[0066] Normally open relays are used as the braking unit. By utilizing the high current carrying capacity of their contacts, they can safely withstand the instantaneous high current during short-circuit braking of the motor, resulting in reliable braking performance and a long service life.

[0067] The normally open relay design ensures that the braking unit is in the open state when the circuit is de-energized or the main control fails, thus avoiding safety accidents caused by accidental braking. At the same time, in conjunction with the active control of the logic control unit, a safe and reliable braking function is achieved.

[0068] In this application, the driving chip is model MX3212; the normally open relay is model SRG-S-112DM-F; the NMOS field-effect transistor is model HY4008; the Schottky diode is model MBR20100; and the brake relay is model SRG-S-124D.

[0069] The main control module, drive control unit and logic control unit are powered by +12V, and the main power supply of the H-bridge execution unit is the stroller battery power supply VBAT.

[0070] The specific working process of this circuit is as follows: When the main control module receives a forward command, it outputs a forward control signal to the drive control unit and the logic control unit. The logic control unit drives the first power switch to engage, connecting the first terminal of the stroller motor to the VBAT power supply. At the same time, the drive control unit outputs a PWM signal to the gate of the first electronic switch, controlling the first electronic switch to conduct. The second terminal of the stroller motor is grounded, and the motor rotates forward to achieve forward movement of the stroller. When the main control module receives a reverse command, the logic control unit drives the second power switch to engage, connecting the second terminal of the stroller motor to the VBAT power supply. At the same time, the drive control unit outputs a PWM signal to the gate of the second electronic switch, controlling the second electronic switch to conduct. The first terminal of the stroller motor is grounded, and the motor rotates backward to achieve reverse movement of the stroller. When the main control module does not receive a forward or reverse command, both the first and second power switches are disconnected, physically cutting off the connection between the motor and the VBAT power supply. At the same time, the logic control unit drives the brake unit to engage, short-circuiting the two ends of the motor to achieve energy-saving braking.

[0071] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A drive circuit for a motor of a child's vehicle, characterized in that include: The main control module is used to output forward control signals, reverse control signals, and braking control signals; The drive control unit, whose input terminal is electrically connected to the output terminal of the main control module, is used to process the received forward control signal and backward control signal to output the electronic switch drive signal; The logic control unit, whose input terminal is electrically connected to the output terminal of the main control module, is used to output power switch control signals according to the received forward control signals, reverse control signals and braking control signals; The H-bridge actuator has its input terminals connected to the output terminals of the drive control unit and the logic control unit, respectively. It is used to receive the electronic switch drive signal and the power switch control signal, and control the forward rotation, reverse rotation and stop of the children's vehicle motor according to the received signals. The two upper arms of the H-bridge actuator are normally open power switch units, which physically disconnect the stroller motor from the power supply when no valid power switch control signal is received.

2. The stroller motor drive circuit of claim 1, wherein, The H-bridge execution unit includes a first power switch, a second power switch, a first electronic switch, and a second electronic switch; the first power switch and the second power switch constitute the two upper arms of the H-bridge, and the first electronic switch and the second electronic switch constitute the two lower arms of the H-bridge.

3. The stroller motor drive circuit of claim 2, wherein, Both the first power switch and the second power switch are normally open relays; one end of the normally open contact of the first power switch is connected to the power supply, and the other end is connected to the first terminal of the stroller motor; one end of the normally open contact of the second power switch is connected to the power supply, and the other end is connected to the second terminal of the stroller motor.

4. The stroller motor drive circuit of claim 2, wherein, Both the first electronic switch and the second electronic switch are NMOS field-effect transistors; the drain of the first electronic switch is connected to the first terminal of the stroller motor, and the source is grounded; the drain of the second electronic switch is connected to the second terminal of the stroller motor, and the source is grounded.

5. The stroller motor drive circuit of claim 4, wherein, The gates of the first electronic switch and the second electronic switch are electrically connected to the first electronic switch driving terminal and the second electronic switch driving terminal of the drive control unit through current-limiting resistors, respectively.

6. The stroller motor drive circuit of claim 1, wherein, The drive control unit and logic control unit are implemented by two identical drive chips; each drive chip integrates one electronic switch drive channel and two power switch drive channels.

7. The stroller motor drive circuit of claim 1, wherein, It also includes a first freewheeling unit and a second freewheeling unit; the first freewheeling unit is connected in reverse parallel between the drain and source of the first electronic switch, and the second freewheeling unit is connected in reverse parallel between the drain and source of the second electronic switch.

8. The stroller motor drive circuit of claim 7, wherein, Both the first freewheeling unit and the second freewheeling unit are Schottky diodes.

9. The stroller motor drive circuit of claim 1, wherein, It also includes a braking unit; the two terminals of the braking unit are respectively connected to the first terminal and the second terminal of the stroller motor, and the control terminal is connected to the brake signal output terminal of the logic control unit; when the logic control unit does not receive a forward control signal and a reverse control signal, it controls the braking unit to engage and conduct, so that the first terminal and the second terminal of the stroller motor are short-circuited.

10. The stroller motor drive circuit of claim 8, wherein, The braking unit is a normally open relay.

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