A quick braking circuit and a dental hollow cup brushless motor

Abstract

The utility model discloses a kind of quick braking circuit and dental hollow cup brushless motor, including the six-arm full-bridge drive circuit of adaptation three-phase brushless motor;Schottky diode is respectively connected in parallel between the input end and output end of three high-side bridge arms, and the conduction direction is opposite with the conduction direction of the high-side bridge arm;Discharge resistance, one end is connected with the input common end of three low-side bridge arms, the other end connects the cathode common end of three schottky diodes.The utility model significantly reduces the energy loss of braking current path, reduces the heat on the discharge path, improves circuit reliability;Discharge resistance concentrates and dissipates motor kinetic energy, avoids overheating problem caused by energy dispersion on bridge arm device, greatly shortens motor stop time, especially suitable for high-speed dental motor, can be reduced from 3-5 seconds to sub-second level;Without changing original drive logic, only by adding new device to realize quick braking, strong adaptability.

Description

Technical Field

[0001] This utility model relates to the field of dental medical equipment technology, and in particular to a fast braking circuit and a brushless motor for dental hollow cups. Background Technology

[0002] In high-speed dental brushless motors (such as coreless brushless motors), a six-arm full-bridge drive is commonly used for commutation control. Position information is typically obtained through Hall effect sensors to achieve closed-loop speed regulation and stable control. In applications such as dental implant equipment, the motor speed can reach 40,000 rpm, placing extremely high demands on the response speed and precision of motor start-stop. When the operator lifts the foot switch to stop the rotation immediately, the traditional method is to directly cut off the voltage to the drive bridge arm. After cutting off the drive bridge arm voltage using this method, the motor loses its electromagnetic driving force, but the rotor continues to rotate due to inertia. At this point, the windings only generate weak damping, resulting in extremely weak braking effect. Due to the motor's significant rotational inertia, it will continue to rotate for several seconds after the voltage is cut off. For example, at 40,000 rpm, it may take 3-5 seconds or even longer to completely stop after power failure. This poses serious safety hazards and operational delays, such as accidental injury to the operator or patient, and affects the efficiency and safety of the medical process.

[0003] To address this issue, some existing technologies attempt to short-circuit the motor coils after power failure or achieve dynamic braking through bridge arm control. However, these existing solutions generally suffer from the following significant problems: 1. Low braking efficiency and heat generation: When discharging back EMF energy through the body diode of the MOSFET, the high forward voltage drop of the body diode, typically between 0.7V and 1.2V or even higher, leads to low current path efficiency. A large amount of back EMF energy is dissipated as heat in the body diode, easily causing MOSFET overheating or even permanent damage, severely affecting the long-term reliability and stability of the circuit, especially during high-speed, high-current braking. 2. Slow braking response: The response speed of existing braking paths cannot meet the braking requirements of high-speed dental applications. The inherent characteristics of the body diode limit the current discharge speed, making it impossible to effectively shorten the motor stop time. Third, lack of safety redundancy and electromagnetic interference: The existing solution lacks an effective safety redundancy protection mechanism, which can easily cause circuit abnormalities under extreme operating conditions, such as overcurrent, overvoltage spikes, etc., and may even induce electromagnetic interference (EMI), affecting the normal operation of other precision medical equipment. Utility Model Content

[0004] The purpose of this invention is to provide a fast braking circuit and a brushless motor for dental hollow cups, so as to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0006] This utility model provides a fast braking circuit, including a six-arm full-bridge drive circuit adapted to a three-phase brushless motor, which has three high-side bridge arms and three low-side bridge arms. The fast braking circuit also includes:

[0007] Schottky diodes are connected in parallel between the input and output terminals of the three high-side bridge arms, respectively, and their conduction direction is opposite to that of the high-side bridge arms.

[0008] The discharge resistor has one end connected to the common input terminal of the three low-side bridge arms, and the other end connected to the common cathode terminal of the three Schottky diodes.

[0009] After the driving voltage of the motor is disconnected, the back electromotive force generated by the rotation of the motor is turned on by the Schottky diode with a low on-state voltage drop, and the kinetic energy of the motor is efficiently consumed in the discharge resistor.

[0010] Compared to traditional full-bridge circuits without added Schottky diodes, the body diode of the original MOSFET itself constitutes a potential back EMF discharge channel. When the motor generates back EMF, current can form a loop through the body diode of the higher-side bridge arm. Due to the high forward voltage drop of the body diode, the discharge efficiency is low, heat generation is severe, and the response speed is slow, failing to meet the requirements of rapid braking. This technical solution replaces the traditional MOSFET body diode with the low forward voltage drop of the Schottky diode, significantly reducing energy loss in the braking current path, reducing heat generation in the discharge path, and improving circuit reliability. The discharge resistor centrally dissipates the motor's kinetic energy, avoiding overheating caused by energy dispersion on the bridge arm devices, and greatly shortens the motor's stop time, especially suitable for 40,000 rpm high-speed dental motors, reducing it from 3-5 seconds to sub-seconds. The circuit structure is compatible with six-arm full-bridge circuits, requiring no changes to the original drive logic; rapid braking is achieved only through the addition of components, demonstrating strong adaptability.

[0011] As an extension of the above scheme, the anode of the Schottky diode is connected to the drain of the high-side bridge arm, and the cathode of the Schottky diode is connected to the source of the high-side bridge arm, so that each Schottky diode is connected in parallel and in reverse with the corresponding high-side bridge arm.

[0012] When this extended solution is working normally, i.e., when the high-side bridge arm is on or off, the Schottky diode is in a reverse bias state, which does not interfere with the main circuit current and avoids shunting that would affect the normal operation of the motor. During braking, the back electromotive force of the motor causes the Schottky diode to conduct in the forward direction, directly forming a low-resistance path from the output terminal of the high-side bridge arm or the three-phase winding side of the motor to the input terminal or VCC side, thereby improving the rapid flow of braking current and enhancing the response speed.

[0013] As an extension of the above solution, the Schottky diode has a withstand voltage greater than 60V, can withstand back EMF spikes, avoid diode breakdown damage, and improve braking reliability under terminal operating conditions.

[0014] As an extension of the above solution, the peak current of the Schottky diode is greater than 5A, which can prevent the diode from burning out under short-term high current, provide continuous and effective braking performance, and avoid braking interruption due to device failure.

[0015] As an extension of the above solution, the Schottky diode's forward voltage drop is less than 0.5V under rated braking current. This extension reduces losses, lowers heat generation, prevents MOSFET or diode damage due to overheating, and the low voltage drop allows for a larger braking current, enhancing braking torque and further shortening the stall time.

[0016] As an extension of the above solution, the discharge resistor is a wire-wound resistor or a ceramic-shell resistor that supports high-power pulse discharge, with a resistance value of 10Ω-30Ω. The wire-wound resistor or ceramic-shell resistor has high power tolerance and can withstand hundreds of watts of instantaneous power, adapting to the short-term high current dissipation during braking, avoiding overheating and burnout of the resistor, and the resistance value range of 10Ω-30Ω balances the braking current and power consumption.

[0017] As an extension of the above solution, the six-arm full-bridge drive circuit includes:

[0018] The three high-side bridge arms have their input terminals connected to the positive terminal of the DC power supply, and their output terminals connected to the A-phase, B-phase, and C-phase terminals of the three-phase windings of the motor, respectively.

[0019] The three low-side bridge arms have their output terminals connected to phase A, phase B, and phase C respectively, and their input terminals are all connected to one end of a current sampling resistor, the other end of which is grounded.

[0020] The drive and control unit controls the on and / or off states of the six bridge arms through drive signals, and combines the position signals from the Hall sensors to achieve motor commutation speed regulation.

[0021] In the extended design, the current sampling resistor can monitor the braking current in real time, working in conjunction with the drive and control unit to achieve overcurrent protection and improve circuit safety. The drive and control unit, combined with Hall sensor signals, can collaboratively control the arm state during braking, ensuring that the braking current matches the rotor position and avoiding reverse torque fluctuations.

[0022] As an extension of the above scheme, the Schottky diode includes Schottky diode D1, Schottky diode D2, and Schottky diode D3, and the high-side bridge arm includes high-side bridge arm Q1, high-side bridge arm Q2, and high-side bridge arm Q3.

[0023] The anode of the Schottky diode D1 is connected to the A-phase terminal or the output terminal of the high-side bridge arm Q1, and the cathode is connected to the positive terminal of the DC power supply or the input terminal of the high-side bridge arm Q1.

[0024] The anode of the Schottky diode D2 is connected to the B-phase terminal or the output terminal of the high-side bridge arm Q2, and the cathode is connected to the positive terminal of the DC power supply or the input terminal of the high-side bridge arm Q2.

[0025] The anode of the Schottky diode D3 is connected to the C-phase terminal or the output terminal of the high-side bridge arm Q3, and the cathode is connected to the positive terminal of the DC power supply or the input terminal of the high-side bridge arm Q3.

[0026] In the extended scheme, the back electromotive force energy of each phase can be quickly discharged through the corresponding Schottky diode, avoiding braking imbalance caused by energy accumulation in a certain phase.

[0027] As an extension of the above solution, the Schottky diode includes either a STPS10L60 Schottky diode or an MBR1060 Schottky diode. The STPS10L60 Schottky diode features low forward voltage drop, negligible switching losses, low thermal resistance, and specified avalanche capability; the MBR1060 Schottky diode features low power consumption, high efficiency, high forward surge current withstand capability, and low stored charge.

[0028] On the other hand, this utility model also provides a dental hollow cup brushless motor, including a fast braking circuit as described above.

[0029] Compared with existing technologies, this invention meets the stringent requirements of dental equipment for high-speed operation and instantaneous braking, shortens operation interruption time, improves treatment efficiency, reduces heat generation and electromagnetic interference during braking, meets the safety and electromagnetic compatibility requirements of medical equipment, avoids interference with other precision medical instruments, reduces the risk of accidental instrument contact during rapid braking, and improves the safety of patients and operators. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0031] Figure 1 This is a schematic diagram of the circuit structure of the rapid braking circuit in an embodiment;

[0032] Figure 2 This is a schematic diagram of the circuit structure of a conventional six-arm full-bridge drive circuit in an embodiment.

[0033] In the attached diagram: A, B, and C are the A-phase, B-phase, and C-phase terminals of the three-phase winding of the motor, respectively; Q1, Q2, and Q3 are the three high-side bridge arms, and Q4, Q5, and Q6 are the three low-side bridge arms, respectively; VCC is the positive terminal of the DC power supply; R1 is the discharge resistor; and R2 is the current sampling resistor. Detailed Implementation

[0034] This section will describe in detail the specific embodiments of the present utility model. The preferred embodiments of the present utility model are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present utility model, but they should not be construed as limiting the scope of protection of the present utility model.

[0035] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and 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. Therefore, they should not be construed as limitations on this utility model.

[0036] In the description of this utility model, if there are words such as "several", they mean one or more, "multiple" means two or more, "greater than", "less than", "exceeding" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself.

[0037] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0038] Reference Figures 1 to 2 The following are several embodiments of a fast braking circuit and a brushless motor for a dental hollow cup according to this utility model.

[0039] In some embodiments, such as Figure 2 As shown, this utility model provides a fast braking circuit, including a six-arm full-bridge drive circuit adapted to a three-phase brushless motor, which has three high-side bridge arms (Q1, Q2, Q3) and three low-side bridge arms (Q4, Q5, Q6). Both the high-side bridge arms and the low-side bridge arms are composed of power semiconductor switching devices, preferably MOSFETs.

[0040] In this circuit, the input terminal of the high-side bridge arm is the drain of the MOSFET, connected to the positive terminal VCC of the DC power supply. The output terminal of the high-side bridge arm is the source of the MOSFET, connected to the motor phase terminals (A, B, C), i.e., the three-phase windings of the motor. The input terminal of the low-side bridge arm is the source of the MOSFET, connected to a current sampling resistor and then grounded. The output terminal is the drain of the MOSFET, connected to the motor phase terminals (A, B, C), i.e., the three-phase windings of the motor. It should be noted that the electrical connections of the high-side bridge arms (Q1, Q2, Q3) and the low-side bridge arms (Q4, Q5, Q6) to the motor phase terminals (A, B, C) are made using a conventional six-arm full-bridge drive circuit. Figure 2 As shown, the circuit principles and components not described are implemented using existing technologies, and will not be elaborated upon here.

[0041] like Figure 1 As shown, the rapid braking circuit further includes:

[0042] Schottky diodes (D1, D2, D3) are connected in parallel between the input and output terminals of the three high-side bridge arms, respectively, and their conduction directions are opposite to those of the high-side bridge arms.

[0043] The discharge resistor R1 is connected at one end to the common input terminal of the three low-side bridge arms, and at the other end to the common cathode terminal of the three Schottky diodes.

[0044] After the driving voltage of the motor is disconnected, the back electromotive force generated by the rotation of the motor is turned on by the Schottky diodes (D1, D2, D3) with a low on-state voltage drop, and the kinetic energy of the motor is efficiently consumed in the discharge resistor R1.

[0045] Specifically, "motor disconnect drive voltage" means that the drive and control unit stops outputting conduction signals to the high-side and low-side bridge arms (i.e., all bridge arms are in the off state). At this time, the three-phase windings of the motor are only subjected to back electromotive force, and there is no external drive voltage input. When the drive and control unit determines that the user has lifted the foot switch (or received a stop command), it immediately executes the braking process. The drive and control unit quickly shuts off all full-bridge drive outputs, so that the motor drive signal is completely cut off, such as the gate drive signals (PWM) of all high-side and low-side MOSFETs being immediately pulled low.

[0046] In this embodiment, when braking is triggered, the motor's drive voltage is disconnected. If the foot switch is released, the drive unit stops outputting the bridge arm drive signal. The rotor continues to rotate due to inertia, cutting magnetic field lines and generating a back electromotive force (EMF) in the opposite direction to the original EMF. This back EMF causes the voltage of the corresponding phase winding to be higher than the input terminal or VCC of the higher-side bridge arm. At this time, the back EMF current (when the voltage of a phase coil is higher than ground potential) flows rapidly to the discharge resistor via the Schottky diode connected in parallel with its corresponding higher-side bridge arm. The kinetic energy of the motor rotation is efficiently and quickly converted into heat energy, dissipated in the discharge resistor, thus achieving rapid attenuation of the motor's kinetic energy and forcing the motor to stop rotating in a very short time. When current flows through the discharge resistor, the motor's kinetic energy is converted into resistive heat energy. Simultaneously, the current in the three-phase windings of the motor generates a braking torque in the opposite direction to the rotor's rotation, counteracting inertia until the rotor stops rotating.

[0047] Compared to the traditional approach, in the original full-bridge circuit (such as...) without the addition of Schottky diodes... Figure 2 In the conventional six-arm full-bridge drive circuit shown, the body diode of the original MOSFET itself constitutes a potential back EMF discharge channel. When the motor generates back EMF, current can form a loop through the body diode of the higher-side bridge arm. Due to the high on-state voltage drop of the body diode (0.7-1.2V), the discharge efficiency is low, heat generation is severe, and the response speed is slow, which cannot meet the requirements of rapid braking. This embodiment uses a Schottky diode to replace the discharge function of the body diode of the original bridge arm MOSFET. With a lower on-state voltage drop (≤0.5V) and a faster response speed, it provides a more efficient energy discharge path during braking, while avoiding damage to the body diode due to overheating.

[0048] This embodiment replaces the traditional MOSFET body diode (0.7-1.2V) with a Schottky diode's low forward voltage drop (≤0.5V), significantly reducing energy loss in the braking current path, reducing heat generation in the discharge path, and improving circuit reliability. The discharge resistor centrally dissipates motor kinetic energy, avoiding overheating caused by energy dispersion on the bridge arm devices, and greatly shortens motor downtime, especially suitable for 40,000rpm high-speed dental motors, reducing it from 3-5 seconds to sub-seconds. The circuit structure is compatible with the six-arm full-bridge design, requiring no changes to the original drive logic, and achieving rapid braking only by adding new devices, making it highly adaptable.

[0049] This embodiment significantly shortens the stopping time, reducing the time for the motor to come to a complete stop from several seconds (e.g., 3-5 seconds) using traditional methods to within 1 second, or even less than 0.5 seconds, achieving "second-level braking" or "sub-second-level braking." This is crucial for medical devices such as dental implant machines that require precise control and rapid response, greatly improving operational efficiency and safety. Furthermore, the additional circuit structure is simple, requiring only a Schottky diode connected in reverse parallel and a discharge resistor in series with the existing full-bridge drive. No complex additional logic control circuits or software algorithms are needed, making it easy to implement and integrate. This also reduces potential failure points caused by complex control, improving the overall reliability of the system. The rapid braking capability effectively reduces safety risks during operation, avoiding accidental injuries that may be caused by the motor's inertial rotation. Controlled energy dissipation also reduces the possibility of circuit abnormalities and electromagnetic interference, meeting the stringent electromagnetic compatibility (EMC) requirements for medical devices.

[0050] In some embodiments, the anode of the Schottky diode is connected to the drain of the high-side bridge arm, and the cathode of the Schottky diode is connected to the source of the high-side bridge arm, such that each Schottky diode is connected in parallel and in reverse with the corresponding high-side bridge arm.

[0051] In this embodiment, when the high-side bridge arm is on or off, the Schottky diode is in a reverse bias state, which does not interfere with the main circuit current and avoids shunting that could affect the normal operation of the motor. During braking, the back electromotive force of the motor causes the Schottky diode to conduct in the forward direction, directly forming a low-resistance path from the output terminal of the high-side bridge arm or the three-phase winding side of the motor to the input terminal or VCC side, thereby improving the rapid flow of braking current and enhancing the response speed.

[0052] In some embodiments, the Schottky diode has a withstand voltage greater than 60V. When a high-speed motor brakes, such as a dental brushless motor, the peak back electromotive force can exceed the operating voltage of 24-48V. This embodiment uses a withstand voltage of 60V or higher to withstand the back electromotive force spikes, preventing diode breakdown and improving braking reliability under extreme conditions.

[0053] In some embodiments, the peak current of the Schottky diode is greater than 5A. During high-speed braking, the instantaneous current driven by the back electromotive force is large. A peak current greater than 5A can prevent the diode from burning out under short-term high current, providing continuous and effective braking performance and avoiding braking interruption due to device failure.

[0054] Those skilled in the art will understand that in the six-arm full-bridge drive circuit adapted for a three-phase brushless motor of this invention, the positive terminal VCC of the DC power supply should be equipped with an energy storage capacitor (not shown in the figure). Under the filtering effect of the energy storage capacitor, even if current flows back to VCC during operation, it will not cause fluctuations. In practical applications, the motor is an inductive load and a high-power load, and there will be a large energy storage capacitor at VCC, such as 4700uF. Since this invention aims at rapid braking, the energy storage capacitor is not described or limited; it is a bridge between VCC and GND. When there is a sudden change in load or extreme operating conditions, there may be a scenario where the voltage on the motor side is higher than that on the VCC side due to the fluctuation of the motor load (the probability of this is very small), and there will not be a large voltage difference. A small voltage difference means a small forward current. The Schottky diode used in this embodiment has a forward current tolerance of more than 5A, which far exceeds the fluctuation current. The Schottky diode is not at risk of damage even when facing sudden changes in load or extreme operating conditions.

[0055] In some embodiments, the Schottky diode has a forward voltage drop of less than 0.5V under rated braking current. The forward voltage drop directly determines energy loss. A voltage drop below 0.5V, compared to 0.7-1.2V for a body diode, can reduce losses by more than 40%, reduce heat generation, and prevent MOSFETs or diodes from being damaged by overheating. Furthermore, the low voltage drop allows for a larger braking current, enhances braking torque, and further shortens the stop time.

[0056] In some embodiments, the discharge resistor is a wire-wound resistor or a ceramic-shell resistor that supports high-power pulse discharge, with a resistance value of 10Ω-30Ω. The wire-wound resistor or ceramic-shell resistor has high power tolerance, capable of withstanding hundreds of watts of instantaneous power, adapting to short-term high current dissipation during braking, preventing the resistor from overheating and burning out. The resistance range of 10Ω-30Ω balances braking current and power consumption. If the resistance is too small (less than 10Ω), the current will be too large; if the resistance is too large (greater than 30Ω), the braking speed will be reduced, thus balancing rapid braking and controllable power.

[0057] In some embodiments, such as Figure 1 As shown, the six-arm full-bridge drive circuit includes:

[0058] The three high-side bridge arms (Q1, Q2, Q3) have their input terminals connected to the positive terminal VCC of the DC power supply, and their output terminals connected to the A-phase, B-phase, and C-phase terminals of the three-phase windings of the motor, respectively.

[0059] The three low-side bridge arms (Q4, Q5, Q6) have their output terminals connected to phase A, phase B, and phase C respectively, and their input terminals are all connected to one end of the current sampling resistor R2, with the other end of the current sampling resistor R2 grounded.

[0060] The drive and control unit controls the on and / or off states of the six bridge arms through drive signals, and combines the position signals from the Hall sensors to achieve motor commutation speed regulation.

[0061] In this embodiment, the current sampling resistor can monitor the braking current in real time, working with the drive and control unit to achieve overcurrent protection and improve circuit safety. The drive and control unit, combined with Hall sensor signals, can collaboratively control the bridge arm state during braking, ensuring the braking current matches the rotor position and avoiding reverse torque fluctuations. In some preferred embodiments, during braking, the drive and control unit obtains the rotor position in real time via the Hall sensor, maintaining the braking path unobstructed only when the back EMF direction matches the Schottky conduction direction (without actively controlling bridge arm conduction), avoiding reverse current conflicts. Simultaneously, by monitoring the braking current through the current sampling resistor, when the current exceeds a threshold (e.g., 10A), the discharge resistor path can be briefly cut off (e.g., the series switch is turned off), achieving overcurrent protection.

[0062] In some embodiments, such as Figure 1 As shown, the Schottky diodes include Schottky diode D1, Schottky diode D2, and Schottky diode D3, and the high-side bridge arm includes high-side bridge arm Q1, high-side bridge arm Q2, and high-side bridge arm Q3. High-side bridge arm Q1 is a MOSFET connected to the high-side bridge arm of phase A, high-side bridge arm Q2 is a MOSFET connected to the high-side bridge arm of phase B, and high-side bridge arm Q3 is a MOSFET connected to the high-side bridge arm of phase C.

[0063] The anode of the Schottky diode D1 is connected to the A-phase terminal or the output terminal of the high-side bridge arm Q1, and the cathode is connected to the positive terminal of the DC power supply or the input terminal of the high-side bridge arm Q1.

[0064] The anode of the Schottky diode D2 is connected to the B-phase terminal or the output terminal of the high-side bridge arm Q2, and the cathode is connected to the positive terminal of the DC power supply or the input terminal of the high-side bridge arm Q2.

[0065] The anode of the Schottky diode D3 is connected to the C-phase terminal or the output terminal of the high-side bridge arm Q3, and the cathode is connected to the positive terminal of the DC power supply or the input terminal of the high-side bridge arm Q3.

[0066] In this embodiment, the back electromotive force energy of each phase can be quickly discharged through the corresponding Schottky diode, avoiding braking imbalance caused by energy accumulation in a certain phase.

[0067] In some embodiments, the Schottky diode includes a Schottky diode of model STPS10L60 or a Schottky diode of model MBR1060. The basic parameters of the Schottky diode of model STPS10L60 include: a reverse repetitive peak voltage of 60V, an average forward current of 10A, a maximum forward voltage of 600mV, a forward surge current of 220A, and a maximum operating temperature of 150°C. It features low forward voltage drop, negligible switching losses, low thermal resistance, and specified avalanche capability, enabling it to play a role in high-efficiency power conversion and reduce energy loss. The basic parameters of the Schottky diode of model MBR1060 include: a DC reverse withstand voltage of 60V, an average rectified current of 10A, and a forward voltage drop of 800mV at 10A. It features low power consumption, high efficiency, high forward surge current withstand capability, and low stored charge.

[0068] On the other hand, this utility model also provides a dental hollow cup brushless motor, including a fast braking circuit as described above.

[0069] This invention meets the stringent requirements of dental equipment for high-speed operation and instantaneous braking, shortens operation interruption time, improves treatment efficiency, reduces heat generation and electromagnetic interference during braking, meets the safety and electromagnetic compatibility requirements of medical equipment, avoids interference with other precision medical instruments, and reduces the risk of accidental instrument contact by rapid braking, thereby improving the safety of patients and operators.

[0070] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A fast braking circuit, comprising a six-arm full-bridge drive circuit adapted to a three-phase brushless motor, having three high-side bridge arms and three low-side bridge arms, characterized in that, The rapid braking circuit also includes: Schottky diodes are connected in parallel between the input and output terminals of the three high-side bridge arms, respectively, and their conduction direction is opposite to that of the high-side bridge arms. The discharge resistor has one end connected to the common input terminal of the three low-side bridge arms, and the other end connected to the common cathode terminal of the three Schottky diodes. After the driving voltage of the motor is disconnected, the back electromotive force generated by the rotation of the motor is turned on by the Schottky diode with a low on-state voltage drop, and the kinetic energy of the motor is efficiently consumed in the discharge resistor.

2. The rapid braking circuit according to claim 1, characterized in that: The anode of the Schottky diode is connected to the drain of the high-side bridge arm, and the cathode of the Schottky diode is connected to the source of the high-side bridge arm, so that each Schottky diode is connected in parallel and in reverse with the corresponding high-side bridge arm.

3. The rapid braking circuit according to claim 1, characterized in that: The Schottky diode has a withstand voltage greater than 60V.

4. The rapid braking circuit according to claim 1, characterized in that: The peak current of the Schottky diode is greater than 5A.

5. A fast braking circuit according to claim 1, characterized in that: The Schottky diode has a forward voltage drop of less than 0.5V under rated braking current.

6. A fast braking circuit according to claim 1, characterized in that: The discharge resistor is a wire-wound resistor or a ceramic-cased resistor that supports high-power pulse discharge, with a resistance value of 10Ω-30Ω.

7. A fast braking circuit according to claim 1, characterized in that: The six-arm full-bridge drive circuit includes: The three high-side bridge arms have their input terminals connected to the positive terminal of the DC power supply, and their output terminals connected to the A-phase, B-phase, and C-phase terminals of the three-phase windings of the motor, respectively. The three low-side bridge arms have their output terminals connected to phase A, phase B, and phase C respectively, and their input terminals are all connected to one end of a current sampling resistor, the other end of which is grounded. The drive and control unit controls the on and / or off states of the six bridge arms through drive signals, and combines the position signals from the Hall sensors to achieve motor commutation speed regulation.

8. A fast braking circuit according to claim 7, characterized in that: The Schottky diodes include Schottky diode D1, Schottky diode D2, and Schottky diode D3, and the high-side bridge arms include high-side bridge arms Q1, Q2, and Q3. The anode of the Schottky diode D1 is connected to the A-phase terminal or the output terminal of the high-side bridge arm Q1, and the cathode is connected to the positive terminal of the DC power supply or the input terminal of the high-side bridge arm Q1. The anode of the Schottky diode D2 is connected to the B-phase terminal or the output terminal of the high-side bridge arm Q2, and the cathode is connected to the positive terminal of the DC power supply or the input terminal of the high-side bridge arm Q2. The anode of the Schottky diode D3 is connected to the C-phase terminal or the output terminal of the high-side bridge arm Q3, and the cathode is connected to the positive terminal of the DC power supply or the input terminal of the high-side bridge arm Q3.

9. A fast braking circuit according to claim 1, characterized in that: The Schottky diode includes either the STPS10L60 or the MBR1060 Schottky diode.

10. A brushless motor for dental hollow cups, characterized in that: Includes a fast braking circuit as described in any one of claims 1-9.

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