Electric toothbrush control circuit

Abstract

The utility model relates to a control circuit of an electric toothbrush, which is low in cost, small in size and light in weight and has the functions of quick charging and current backflow prevention. The control circuit is composed of a circuit board, a battery, a motor and connecting pieces among the circuit board, the battery and the motor. The circuit board is composed of a power interface module, a battery management module, a motor driving module, a central controller and a man-machine interaction module, the battery management module and the motor driving module are both main loops formed by discrete components and necessary auxiliary circuits, and the work of the battery management module and the motor driving module is controlled by the central controller. And the battery management module is an STEP-DOWN type switching power supply circuit provided with a battery voltage feedback circuit and a charging current feedback circuit. The STEP-DOWN type switching power supply circuit is composed of an input energy storage capacitor, a main transistor, a driving circuit of the main transistor, a fly-wheel diode, an inductor and an output energy storage capacitor. And the control electrode of the main transistor is directly connected to the central controller or is connected to the central controller through a charging driving circuit.

Description

Technical Field

[0001] The utility model relates to a control circuit for an electric toothbrush, and more specifically, to a control circuit for an electric toothbrush with low cost, miniaturization, light weight, fast charging and anti-current backflow functions. Background Art

[0002] As an upgraded product of traditional toothbrushes, the annual global consumption of electric toothbrushes reaches hundreds of millions. Its basic characteristics are consumables, handheld and electric, that is, ① the toothbrush head is driven by electricity to generate rubbing actions; ② miniaturization, light weight, and built-in power supply to meet the handheld requirements; ③ the pursuit of low cost to conform to its consumable nature.

[0003] Through research on the increasingly mature industry demands and actual measurement and research on user experience, the following technical requirements are defined:

[0004] 1) The toothbrush is an appliance used in the washroom and has frequent contact with water. Therefore, as an electric tool, it is a necessary requirement for the toothbrush to be waterproof and prevent "accidental" electrical connections caused by water.

[0005] 2) The functions of an electric toothbrush determine that its miniaturization and light weight have more practical significance. Therefore, small-sized batteries and small-sized circuit boards can better meet the actual needs of users.

[0006] 3) The household electric toothbrush can be used for multiple purposes, that is, one main unit can be equipped with multiple brush heads, and multiple members in a family can take turns using it by replacing the brush heads. Since the washing time of all members in the same family is generally relatively tight, and the requirements for miniaturization and light weight of the electric toothbrush determine that its built-in battery is as small as possible and its capacity is limited, there is a contradiction between the two. Therefore, quickly replenishing electrical energy for the battery during the rotation interval becomes the optimal way to solve this contradiction, that is: the fast charging function is preferred for this type of product.

[0007] In traditional technologies, battery charging is realized by using a dedicated battery management chip, which is divided into linear charging and switching charging technologies. Among them: the linear charging chip for civilian low-cost products supports a maximum instantaneous charging current of no more than 1A, and a large area of heat dissipation copper foil (that is, it needs to occupy a large area of the circuit board) is required to maintain a large current for a long time. Under the pressure of low cost, the performance and quality of low-cost linear charging chips vary greatly, which greatly increases the inspection and verification costs of each batch of quality and also greatly increases the quality risk of the whole machine; the cost of the switching charging chip for civilian low-cost products is very high, occupying a large proportion of the whole machine, restricting the low-cost expectation of the whole machine.

[0008] 4) Since electric toothbrushes are rapidly becoming popular, consumer groups at different levels have different cost requirements, but a large proportion of consumers are relatively sensitive to costs. Therefore, the waterproof requirement and the low-cost requirement also pose a contradiction. To achieve waterproofing in traditional technologies, wireless charging technology is adopted. Wireless charging technology has the following problems in such products: ① high cost; ② under the requirement of fast charging, the cost investment of wireless charging is even higher; ③ wireless charging inevitably requires implanting a receiving coil in the toothbrush, which greatly restricts the miniaturization requirement. Especially under the requirement of fast charging, the receiving coil needs a larger volume.

[0009] Based on the above research results and aiming at the above problems, this application is proposed. Summary of the Invention

[0010] The purpose of the present utility model is to design a control circuit for a miniaturized and lightweight electric toothbrush with fast charging function, anti-reverse charging function and battery protection function according to the research on the background technology and actual needs.

[0011] The technical solution adopted by the present utility model to solve its technical problems is to provide a control circuit for an electric toothbrush, which is composed of a circuit board, a battery, a motor, and connectors between the above three. The characteristics are that the circuit board is composed of 5 major functional modules: a power interface module, a battery management module, a motor drive module, a central controller, and human-computer interaction. Moreover, both the battery management module and the motor drive module are composed of a main circuit formed by discrete components and necessary auxiliary circuits, and their operations are controlled by the central controller.

[0012] The difference between this solution and the traditional technology is that this solution abandons the technical route of using a dedicated battery management chip and a dedicated motor drive circuit in the traditional technology. Instead, the conditional judgment and action instructions in battery charging and discharging and motor driving are delivered to the central controller for control, and only a main circuit formed by discrete components and necessary auxiliary circuits controlled by the central controller are adopted to achieve the purpose of low cost, miniaturization and lightweight.

[0013] As a further preferred solution, the power interface module is composed of a Type-C USB connector and a protocol circuit, and provides two nodes: a power positive terminal and a power negative terminal for the subsequent stage; the protocol circuit is a resistor connected between the CC1 and GND pins of the Type-C USB connector and between the CC2 and GND pins.

[0014] This solution selects the currently most widely used Type-C connector as the power input port. It not only abandons the traditional, high-cost, and large-volume wireless charging solution and selects a wired charging solution, but also enables this electric toothbrush to not require a dedicated power adapter, making it more flexible to use and with lower costs. The protocol circuit can ensure that when the user selects a power adapter with a fast charging function, the output voltage of the power adapter is limited to 5V, which can ensure that the control circuit of this electric toothbrush only needs to be applicable to a single 5V power supply, without the need to be compatible with a wide range of input voltages. With a single operating point, it can reduce costs and improve performance.

[0015] As a further preferred solution, the battery management module is a BUCK switching power supply circuit provided with a battery voltage feedback circuit and a charging current feedback circuit, where:

[0016] The BUCK switching power supply circuit is composed of an input energy storage capacitor, a main transistor (including but not limited to P-type MOSFET, PNP-type triode, etc.) and its drive circuit, a freewheeling diode, an inductor, and an output energy storage capacitor;

[0017] The battery voltage feedback circuit is a three-terminal sampling network composed of series resistors, which is connected in parallel across the battery, and the middle tap is used as the battery voltage sampling signal output terminal to connect to the central processor;

[0018] The charging current feedback circuit is composed of a charging current detection resistor in series with the battery and a first resistor-capacitor filtering network. The first resistor-capacitor filtering network is a three-terminal network with a resistor and a capacitor in series, which is connected in parallel across the charging current detection resistor, and the middle tap is used as the charging current sampling signal output terminal to connect to the central processor;

[0019] The control electrode of the main transistor is directly connected to the central controller or connected to the central controller through a charging drive circuit.

[0020] This solution uses a STEP-DOWN switching power supply circuit to deliver current to the battery. Compared with the traditional dedicated linear charging chip solution, this solution can provide a larger and controllable constant current charging current, which is more suitable for the requirements of fast charging.

[0021] As a further preferred solution, the motor drive module is composed of a switching transistor, a motor current feedback circuit, and a motor back-peak absorption network, where:

[0022] The motor current feedback circuit is composed of a motor current detection resistor and a second resistor-capacitor filtering network; the motor current detection resistor is in series with the switching transistor; the second resistor-capacitor filtering network is a three-terminal network with a resistor and a capacitor in series, which is connected in parallel across the motor current detection resistor, and the middle tap is used as the motor current sampling signal output terminal to connect to the central processor;

[0023] The motor back-peak absorption network is a diode connected in anti-parallel across the motor terminals, and / or an absorption capacitor connected in parallel across the motor terminals.

[0024] This solution adopts a resistive current detection scheme, and uses the voltage drop signal of the measured current on the current detection resistor as the current acquisition signal to be sent to the central processor. Compared with technical solutions such as current transformers, this solution has the lowest cost and the smallest volume.

[0025] As a further preferred solution, the power interface module further includes an anti-current backflow circuit, which is connected in series between the positive power supply terminal of the power interface module and the battery management module, and is a diode or a P-type field effect transistor (MOSFET).

[0026] In this solution, an anti-current backflow circuit is connected in series between the power input connector and the battery management module to prevent the battery current from flowing back reversely to the power input connector. An electric toothbrush is a toiletry and is frequently in contact with water. Even if the power input connector is provided with a sealing device, there may be situations of improper operation or sealing failure. Once the power input connector comes into contact with water, the electrical energy of the built-in battery can be reversely discharged through the water between the terminals of the power input connector, which not only affects the service life of the battery, but also causes insufficient battery storage and affects the user experience.

[0027] In this solution, the addition of the anti-current backflow circuit can effectively solve the above problems.

[0028] As a further preferred solution, the switching transistor is an N-type MOSFET, or multiple N-type MOSFETs connected in parallel with each other.

[0029] In the motor drive module circuit of this solution, an N-type MOSFET is selected as the main switch for starting / stopping the motor. Compared with a triode, in high-current applications, the MOSFET can be directly driven by the IO of the central controller, is easier to drive, has a lower cost, and a smaller volume.

[0030] As a further preferred solution, the charging current detection resistor is a positive temperature coefficient thermistor (PTC), or a one-time fuse, or a circuit in which a resistor is connected in series with a one-time fuse.

[0031] In this solution, a positive temperature coefficient thermistor (PTC) or a one-time fuse is used as the charging current detection resistor. When the charging current is too large, the resistance value of the PTC increases rapidly to reduce the charging current, or the one-time fuse blows to block the charging current. A second layer of protection is added to meet the requirement of limiting the charging current, further improving the protection function for the battery. Compared with the technical route using an ordinary current detection resistor, although when using an ordinary current detection resistor, by selecting a resistor with a suitable package and rated power, the current detection resistor can also be burned out due to overheating during overcurrent, which also plays the role of a second layer of protection, but in this solution, the protection action is faster and the protection function is more reliable.

[0032] As a further preferred solution, the motor current detection resistor is a positive temperature coefficient thermistor (PTC), or a one-time fuse, or a circuit in which a resistor is connected in series with a one-time fuse.

[0033] Similar to the previous solution, after this solution is implemented, a second layer of protection can be added to the motor circuit, further improving the protection functions for the motor and the battery.

[0034] As a further preferred solution, the human-machine interaction module is composed of a charging status indicator light, an operation indicator light, and buttons; where:

[0035] The charging status indicator light includes a red indicator light and a green indicator light, which are connected to the central processing unit through current-limiting resistors and are lit respectively during the charging process and when the battery is fully charged;

[0036] There are multiple operation indicator lights, which are connected to the central processing unit through current-limiting resistors, providing a running light effect in a way of lighting up in turn, or providing multiple status indications in a way of distributed lighting.

[0037] As a further preferred solution, for the human-machine interaction module, there are multiple buttons. After being respectively connected in series with resistors of different resistance values, they are connected in parallel to the same node and then connected to a pin of the central processing unit, that is, the central processing unit identifies the statuses of multiple buttons through one pin.

[0038] In this solution, the central processing unit identifies the statuses of multiple buttons by detecting the resistance value to the ground on the pin connected to the button. It can use a central processing unit with fewer pins to realize the status identification of multiple buttons, which can not only reduce the cost of the central processing unit, but also adopt a smaller package of the central processing unit, reducing the area occupied on the PCB, and overall realizing miniaturization and light weight.

[0039] In summary, after the implementation of the present utility model, functions such as fast charging, anti-backflow, double-layer protection for the battery, and double-layer protection for the motor can be realized with lower cost and smaller PCB area, meeting the requirements of miniaturization, light weight, and low cost of the electric toothbrush. Brief Description of the Drawings

[0040] The present utility model will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0041] Figure 1 is the schematic diagram of the toothbrush control circuit with basic functions;

[0042] Figure 2 is the schematic diagram of the power interface module, battery management module, and central controller function module of the toothbrush control circuit with the function of preventing current backflow;

[0043] Figure 3 is the schematic diagram of the power interface module, battery management module, and central controller function module of the toothbrush control circuit with a PWM drive circuit and a current backflow prevention circuit;

[0044] Figure 4 is the schematic diagram of the motor drive module circuit for enhancing the driving ability;

[0045] Figure 5 is the schematic diagram of the current backflow prevention circuit with a gate drive circuit. Detailed Embodiment

[0046] In order to make the purpose, technical solutions, and advantages of the present utility model clearer, the embodiments of the present utility model will be further described in detail below in conjunction with the drawings.

[0047] Embodiment 1: Toothbrush Control Circuit with Basic Functions

[0048] As Figure 1 shown, the circuit is composed of five major parts: a power interface module, a battery management module, a motor drive module, a central controller, and a human-computer interaction. Among them:

[0049] The power interface module part is composed of a Type-C USB connector USB1 and a protocol circuit composed of resistors R1 and R2. Resistors R1 and R2 pull down the PIN3 and PIN4 pins (i.e., CC1 and CC2 pins) of the connector USB1 to the power ground. Its function is to ensure that the power adapter connected to the connector USB1 delivers a power supply with a voltage of DC5V to this circuit through the connector USB1. According to the unified protocol, whether it is an ordinary USB power adapter or a USB power adapter with a fast charging function, when the CC1 and CC2 pins of the USB connector are connected to pull-down resistors to the power ground, the output voltage of the USB power adapter is 5V. The interface part defines that the input power received by this circuit is a fixed and single-range DC5V. The subsequent circuits only need to work within a single power range, reducing the design difficulty and cost.

[0050] The battery management module is partially composed of a charging power detection circuit, a BUCK switching power supply circuit, a charging power detection circuit, etc. Among them:

[0051] The charging power detection circuit is composed of a resistive voltage division network formed by R3 and R4. When the USB adapter supplies power to this circuit through the connector USB1, the voltage at the node VCC is 5V. After being divided by R3 and R4, a high level is provided to the central controller U2 through the node DC5V, which is recognized as "charging power connected" by the central controller U2; when the 5V power supply of the USB adapter is removed, the voltage at the VCC node of this circuit is 0V. After being divided by R3 and R4, a low level is provided to the central controller U2 through the node DC5V, which is recognized as "charging power not connected" by the central controller U2;

[0052] The main circuit of the BUCK switching power supply circuit is composed of an input energy storage capacitor C1, a main transistor Q3, a freewheeling diode D3, an inductor L1, and an output energy storage capacitor C2. Through the high-speed switching of the main transistor Q3, electrical energy is transferred from the input energy storage capacitor C1 to the output energy storage capacitor C2, and then the battery BT1 is charged through the short-circuit breaker JP1 and the charging current detection resistor R7. The main transistor Q3 is a P-type MOSFET, and its switching action is controlled by the PIN1 pin (PWM node) of the central controller U2. That is, a PWM signal is sent from the PIN1 pin of the central controller U2 to the gate of the main transistor Q3 to control the switching timing of the main transistor Q3, thereby controlling the output voltage of the BUCK switching power supply circuit and achieving the purpose of controlling the charging current. The positive electrode of the battery (BAT node) is connected to the PIN5 pin (BAT node) of the central controller U2, serving as the input terminal for U2 to sample the battery voltage, used to detect the battery voltage in real time, so that U2 can adjust the charging current according to the battery voltage and judge the state of charge of the battery (undercharged, fully charged, not fully charged, etc.). R5 is the gate bias resistor of Q3, providing a bias voltage for the gate of Q3.

[0053] The charging power detection circuit is composed of the charging current detection resistor R7 and a resistive-capacitive filter network formed by the resistor R8 and the capacitor C3. The charging current detection resistor R7 is connected in series in the main battery charging circuit. The voltage drop of the charging current on R7 is proportional to the charging current and can accurately represent the value of the charging current. After being filtered by R8 and C3, this voltage drop is input to the PIN6 pin (one of the input pins of the ADC inside U2) of the central controller U2 through the CS node. U2 can obtain the real-time charging current value after ADC conversion.

[0054] The motor drive module is partially composed of a switching transistor Q1, a motor current feedback circuit, and a motor flyback absorption network. Among them:

[0055] The switching transistor Q1 is an N-type MOSFET, whose gate is connected to PIN16 of the central processing unit U2. R6 is the bias resistor of the gate of Q1, which is used to ensure that Q1 is in the off state even when the state of PIN16 may be uncertain.

[0056] The motor current feedback circuit consists of the motor current detection resistor R13 and the RC filter network composed of the resistor R12 and the capacitor C8. R13 is connected in series on the main motor circuit. The voltage drop of the current flowing through the motor on R13 is proportional to the motor current and can accurately represent the value of the motor current. After being filtered by R2 and C8, this voltage drop is input to PIN10 of the central controller U2 (one of the input pins of the ADC inside U2) through the I_DET node. U2 can obtain the real-time motor current value after ADC conversion.

[0057] The motor back-peak absorption network is composed of the diode D4 connected in reverse. During the process when the switching transistor Q1 is turned on and the motor is powered on, D4 is reverse-biased and non-conductive. When the switching transistor Q1 is turned off instantaneously, a relatively high back electromotive force will be generated in the motor winding, which not only may break down Q1 and cause its damage, but also will cause instantaneous electromagnetic radiation. After D4 is connected, the back electromotive force of the motor winding can be short-circuited to avoid the above damages.

[0058] C6 is an energy storage capacitor, which is installed near the motor connection terminal and is used to slow down the voltage drop of the VCC node at the moment when the motor starts.

[0059] The human-machine interaction consists of the buttons SWI and SW2, the indicator lights LED1~LED6, the current-limiting resistors R9, R10, R11, and the button ID resistor R17. Among them:

[0060] LED1~LED4 are the operation status indicator lights. Their cathodes are respectively connected to PIN11, PIN12, PIN13, and PIN9 of the central processing unit U2, and their anodes are connected in parallel to the same node and connected to the VCC positive power supply node through the current-limiting resistor R9. During the operation of the motor, U2 can achieve the running light effect by alternately turning on or off LED1~LED4, or make different status indications by turning on different LEDs.

[0061] LED5 and LED6 are charging status indicator lights. When LED5 is lit, it emits red light, and when LED6 is lit, it emits green light. After U2 detects the connection of the charging power supply through the charging power supply detection circuit, it judges the state of charge of the battery through the PIN5 pin, and correspondingly controls the duty cycle of the PWM node to control the charging current of the battery. During the charging process, the LED6 node is at a low level and the LED5 node is at a high level, turning on LED6 (green light), indicating that it is charging; in the fully charged state, the PWM node maintains a high level, prohibits Q3 from conducting, stops charging, and makes the LED6 node at a high level and the LED5 node at a low level, turning on LED5 (red light), indicating that it is fully charged.

[0062] One end of each of the buttons SWI and SW2 is connected to the power ground; the other end of SW2 is connected to the same node SW after being connected in series with the button ID resistor R17, and is connected to the PIN8 pin (SW) of U2. Since the resistance value to the ground of the button SWI and SW2 circuits (when the button is pressed) is different at the SW node, U2 can enable the built-in pull-up resistor through the PIN8 pin, so that when the buttons SWI and SW2 are pressed separately, the voltage value of the PIN8 pin is different. By detecting the voltage value of the PIN8 pin in real time, U2 can judge whether the button connected to the PIN8 pin is pressed, and correspondingly judge which one of SWI and SW2 is pressed.

[0063] R9, C4, and C5 form a resistor-capacitor filter, which is connected between the VCC node and the VDD node. The VDD node is connected to the positive power supply pin PIN2 of the central processing unit U2, which is the positive extreme of the power supply for U2. Among C4 and C5, one is a storage capacitor of uF level, which is used to ensure the stability of the VDD power supply voltage during the operation of U2, and the other is a decoupling capacitor with high-frequency characteristics, which is used to filter out high-frequency noise in the VDD power supply. R9 is connected across the VCC node and the VDD node. When there is a voltage difference between the VCC node and the VDD node, current flows between the VCC node and the VDD node through the resistor R9 to achieve voltage balance between the two. That is, the resistor-capacitor filter composed of R9, C4, and C5 makes the voltage fluctuation amplitude on the VDD node much smaller than the voltage fluctuation amplitude on the VCC node when the voltage of the VCC node fluctuates.

[0064] During operation, during the charging process, U2 provides a PWM signal to the gate of the main transistor Q3 through the PIN1 pin, detects the charging current through the PIN6 pin, and can control the charging current to be at a set value by adjusting the duty cycle of the PWM signal in a closed loop. That is, U2 can achieve constant large-current charging - fast charging by adjusting the duty cycle of the PWM signal in a closed loop.

[0065] In extreme cases, when the charging current is too large, it may cause battery damage. However, when U2 fails to adjust the charging current in a timely manner, or when the charging current adjustment fails, the charging current detection resistor burns out due to overheating, providing a second layer of protection for the battery.

[0066] During the charging process, U2 detects the battery voltage in real time through the PIN5 pin. When the battery voltage approaches the full charge voltage, U2 reduces the duty cycle of the PWM signal, reducing the charging current to the trickle value. Until full charge, the PIN5 pin is set to high level or high impedance state, turning off Q3. After Q3 is turned off, when the charging power supply continues to be connected, the charging power supply provides power for the VCC node, and at the same time provides power for the central controller U2 through R9; when the charging power supply is removed, the body diode inside Q3 is forward biased, and the battery provides power for the VCC and VDD nodes through the body diode inside Q3.

[0067] During the operation of the motor, U2 detects the battery voltage in real time through the PIN5 pin and detects the motor current in real time through the PIN10 pin. If the motor current exceeds the set value, and / or the battery voltage is lower than the set low voltage protection value, then U2 turns off Q1 through the PIN16 pin.

[0068] In extreme cases, if the motor is overcurrent and U2 adjustment fails (such as Q1 failure), the motor current detection resistor R13 will overheat and burn out, providing a second layer of protection for the motor and the battery.

[0069] Looking at this embodiment overall, ① this circuit does not use the dedicated linear charging chip and dedicated switching charging chip in the traditional technology, but only samples the necessary discrete components to build the BUCK main circuit. The functions of current control and battery charging state detection during the charging process are all delivered to the central controller U2, enabling the charging to form a current closed-loop control. ② This circuit does not use the dedicated motor drive chip in the traditional technology, but only uses a switching transistor as the motor drive switch and uses a motor current detection resistor as the current sensor to transmit the motor current information to the central controller U2, thereby forming a control closed-loop. When the motor is overcurrent, U2 turns off the switching transistor in a timely manner to prevent the motor from overcurrent. Compared with the traditional technology, the circuit of this embodiment has the characteristics of low cost and small PCB area occupation (no need to consider the heat dissipation problem of the linear charging chip) in addition to all the functions, and can achieve the goals of low cost, miniaturization, and light weight.

[0070] Embodiment 2: Toothbrush control circuit with anti-current backflow function

[0071] As Figure 2 shown, compared with the circuit of Embodiment 1, in this embodiment, an anti-current backflow circuit is inserted between the positive power supply terminal of the power interface module and the VCC node. The other parts are the same as those of Embodiment 1, not shown and will not be elaborated again.

[0072] The anti-current backflow circuit is composed of Q5 and R16. Among them, Q5 is a P-type MOSFET, whose drain is connected to the positive power supply terminal of the power supply interface module, and the source is connected to the VCC node. A resistor R16 is connected across the source and the gate. At the same time, the gate of Q5 is connected to PIN7 (STBY node) of the central processor U2, and the state of Q5 is controlled by PIN7 of U2.

[0073] When U2 detects the access of the charging power supply through the charging power supply detection circuit (formed by R3 and R4), U2 sets PIN7 to a low level, and Q5 is in the conducting state. Q5 is a MOSFET with a on-resistance in the order of dozens of milliohms. The voltage drop of the charging current on Q5 is very small, which basically does not affect the charging efficiency and the charging current. When the charging power supply is removed or the battery is fully charged, U2 sets PIN7 to a high level or a high impedance state, and Q5 turns off. The body diode inside Q5 has its anode connected to the drain and the cathode connected to the source. Therefore, after Q5 turns off, the battery loses the connection loop with the positive power supply terminal of the charging power supply interface module and cannot discharge through the charging power supply detection circuit (formed by R3 and R4) and the charging power supply interface module, playing a role in preventing current backflow. Even if the charging power supply interface module is flooded, it will not cause battery current leakage. At the same time, since the discharge path through the charging power supply detection circuit (formed by R3 and R4) is cut off, the standby current of the electric toothbrush can also be reduced, which is beneficial to extending the standby time of the electric toothbrush and the service life of the battery.

[0074] Embodiment 3: A charging circuit with a PWM drive circuit

[0075] As Figure 3 shown, compared with Embodiments 1 and 2, in this embodiment, a gate drive circuit is added at the gate of the main transistor Q3 of the BUCK circuit. The other parts are the same as those in Embodiment 2 and are not shown and will not be elaborated.

[0076] The added gate drive circuit is composed of a MOEFET transistor Q4 and a bias resistor R6, which is used to quickly charge and discharge the gate of Q3, making the conduction and cut-off of Q3 more complete. ① It can greatly increase the switching frequency of Q3 and reduce the volume of the inductor L1, thus ensuring the miniaturization and light weight of the positive electrode; ② It shortens the time of Q3 in the linear region during the switching process, reduces the power consumption of Q3, reduces the heat generation of Q3, reduces the junction temperature, improves the service life of Q3, and improves the efficiency of the entire BUCK circuit.

[0077] Embodiment 4: A motor drive module with enhanced driving ability

[0078] As Figure 4 shown, the difference between this embodiment and Embodiments 1, 2, and 3 is that the switching transistor of the motor drive module is composed of two N-type MOSFETs in parallel. Therefore, the other parts of the circuit are not shown and will not be elaborated.

[0079] Figure 4 Among them, the switching transistor of the motor drive module is composed of Q1 and Q2 in parallel, which can expand the driving ability, reduce the voltage drop when the switching transistor is turned on, increase the service life of the switching transistor, and improve the reliability of the whole machine.

[0080] Embodiment 5: Anti-current backflow circuit with a gate drive circuit

[0081] As Figure 5 shown, the difference between this embodiment and other embodiments is that a drive circuit composed of a field effect transistor Q6 and its gate bias resistor R14 is added to the gate of Q5 in the anti-current backflow circuit to perform level matching on the gate voltage of Q5, ensuring that Q5 works in the switching state throughout and will not work in the linear region, thus ensuring the anti-current backflow effect.

[0082] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent circuit or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. An electric toothbrush control circuit, consisting of a circuit board, a battery, a motor, and a connector between the three, characterized in that: The circuit board is composed of a power interface module, a battery management module, a motor drive module, a central controller, and a human-computer interaction module. In addition, the battery management module and the motor drive module are main circuits and necessary auxiliary circuits built with discrete components, and their operations are controlled by the central controller.

2. An electric toothbrush control circuit according to claim 1, characterized in that: The power interface module is composed of a Type-C USB connector and a protocol circuit, and provides two nodes, the positive power terminal and the negative power terminal, for the subsequent stage; the protocol circuit is a resistor connected between the CC1 and GND pins of the Type-C USB connector, and between the CC2 and GND pins.

3. The electric toothbrush control circuit according to claim 1, characterized in that: The battery management module is a BUCK-type switching power supply circuit provided with a battery voltage feedback circuit and a charging current feedback circuit, wherein: The BUCK type switching power supply circuit is composed of an input energy storage capacitor, a main transistor and its driving circuit, a freewheeling diode, an inductor, and an output energy storage capacitor; The battery voltage feedback circuit is a three-terminal sampling network composed of series resistors, connected in parallel to the two ends of the battery, and the middle tap is connected to the central processor as the battery voltage sampling signal output terminal; The charging current feedback circuit is composed of a charging current detection resistor connected in series with the battery, and a first resistor-capacitor filter network, wherein the first resistor-capacitor filter network is a three-terminal network in which a resistor and a capacitor are connected in series, connected in parallel to both ends of the charging current detection resistor, and the middle tap is connected to the central processor as a charging current sampling signal output terminal; The control electrode of the main transistor is directly connected to the central controller, or is connected to the central controller through a charging drive circuit.

4. The electric toothbrush control circuit according to claim 1, characterized in that: The motor drive module is composed of a switching transistor, a motor current feedback circuit and a motor reverse peak absorption network, wherein: The motor current feedback circuit is composed of a motor current detection resistor and a second resistor-capacitor filter network; wherein the motor current detection resistor is connected in series with the switch transistor; the second resistor-capacitor filter network is a three-terminal network in which a resistor and a capacitor are connected in series, connected in parallel to both ends of the motor current detection resistor, and the middle tap is connected to the central processor as the motor current sampling signal output end; The motor reverse peak absorption network is a diode connected in anti-parallel to both ends of the motor, and / or an absorption capacitor connected in parallel to both ends of the motor.

5. An electric toothbrush control circuit according to claims 1 and 2, characterized in that: The power interface module also includes an anti-current backflow circuit, which is connected in series between the positive power terminal of the power interface module and the battery management module and is a diode or a P-type MOSFET.

6. An electric toothbrush control circuit according to claim 4, characterized in that: The switch transistor is an N-type MOSFET, or a plurality of N-type MOSFETs connected in parallel.

7. The electric toothbrush control circuit according to claim 3, characterized in that: The charging current detection resistor is a positive temperature coefficient thermistor (PTC), or a one-time fuse, or a circuit in which a resistor and a one-time fuse are connected in series.

8. The electric toothbrush control circuit according to claim 4, characterized in that: The motor current detection resistor is a positive temperature coefficient thermistor (PTC), or a one-time fuse, or a circuit in which a resistor and a one-time fuse are connected in series.

9. The electric toothbrush control circuit according to claim 1, characterized in that: The human-computer interaction module is composed of a charging status indicator light, an operation indicator light and a button; wherein: The charging status indicator light includes a red indicator light and a green indicator light, which are connected to the central processor through a current limiting resistor and light up when charging is in progress and when the battery is fully charged, respectively; There are multiple operating indicator lights, which are connected to the central processing unit through current limiting resistors, and are lit in turn to provide a marquee effect, or are lit in a distributed manner to provide multiple status indications.

10. The electric toothbrush control circuit according to claim 9, characterized in that: The human-computer interaction module has multiple buttons, which are connected in series with resistors of different resistance values ​​and then connected in parallel to the same node and connected to a pin of the central processing unit. That is, the central processing unit identifies the status of multiple buttons through one pin.

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