CN113054887B - Overvoltage protection circuit and method for electric tools and electric tools - Google Patents
Overvoltage protection circuit and method for electric tools and electric tools Download PDFInfo
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- CN113054887B CN113054887B CN201911383371.1A CN201911383371A CN113054887B CN 113054887 B CN113054887 B CN 113054887B CN 201911383371 A CN201911383371 A CN 201911383371A CN 113054887 B CN113054887 B CN 113054887B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/02—Providing protection against overload without automatic interruption of supply
- H02P29/024—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
- H02P29/0241—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load the fault being an overvoltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
- H02H7/09—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against over-voltage; against reduction of voltage; against phase interruption
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- Power Engineering (AREA)
- Control Of Ac Motors In General (AREA)
Abstract
本发明实施例公开了一种电动工具的过压保护电路、方法以及电动工具，该电动工具的过压保护电路包括：整流电路、第一电容支路、第二电容支路、驱动电路和控制电路；整流电路与驱动电路电连接，驱动电路与无刷电机电连接，整流电路和驱动电路连接的线路上并联有第一电容支路和第二电容支路；第一电容支路包括第一电容，第二电容支路包括串联连接的第一开关和第二电容，第二电容的容值大于第一电容的容值；控制电路分别与第一开关和驱动电路电连接，控制电路用于在电动工具关机阶段控制第一开关导通。本发明实施例提供的技术方案通过控制第一开关的通断，减少电解电容的充放电时间，有利于延长电解电容的使用寿命。
Embodiments of the present invention disclose an overvoltage protection circuit and method for an electric tool, as well as an electric tool. The overvoltage protection circuit of the electric tool includes: a rectifier circuit, a first capacitor branch, a second capacitor branch, a drive circuit and a control circuit; the rectifier circuit is electrically connected to the drive circuit, the drive circuit is electrically connected to the brushless motor, a first capacitor branch and a second capacitor branch are connected in parallel on the line connecting the rectifier circuit and the drive circuit; the first capacitor branch includes a first capacitor, the second capacitor branch includes a first switch and a second capacitor connected in series, the capacitance of the second capacitor is greater than the capacitance of the first capacitor; the control circuit is electrically connected to the first switch and the drive circuit respectively, and the control circuit is used to The first switch is controlled to be turned on during the power tool shutdown phase. The technical solution provided by the embodiment of the present invention reduces the charging and discharging time of the electrolytic capacitor by controlling the on-off of the first switch, which is beneficial to extending the service life of the electrolytic capacitor.
Description
Technical Field
The embodiment of the invention relates to the technical field of electronics, in particular to an overvoltage protection circuit and method of an electric tool and the electric tool.
Background
The high-voltage brushless motor adopts a semiconductor switching device to realize electronic commutation, namely the electronic switching device is used for replacing the traditional contact type commutator and the brush. The device has the advantages of high reliability, no reversing spark, low mechanical noise and the like, and is widely applied to various electric tools.
When the armature of the brushless motor rotates, the electromotive force induced in the armature winding is called back electromotive force because of the opposite direction of the current; due to the existence of back electromotive force, the brushless motor has freewheels on the bus at the shutdown stage, so that voltage spikes are generated. In the prior art, an electrolytic capacitor is generally adopted to stabilize input voltage, but when the brushless motor works, the electrolytic capacitor is continuously charged and discharged to cause large heating value, so that the service life of the electrolytic capacitor is short.
Disclosure of Invention
The embodiment of the invention provides an overvoltage protection circuit and method of an electric tool and the electric tool, so as to prolong the service life of an electrolytic capacitor.
In a first aspect, an embodiment of the present invention provides an overvoltage protection circuit for an electric tool, including: the device comprises a rectifying circuit, a first capacitance branch, a second capacitance branch, a driving circuit and a control circuit;
the rectification circuit is used for converting the accessed alternating current into direct current and outputting the direct current; the rectifying circuit is electrically connected with the driving circuit, the driving circuit is electrically connected with the motor, and a first capacitance branch and a second capacitance branch are connected in parallel on a circuit connected with the rectifying circuit and the driving circuit;
the first capacitor branch circuit comprises a first capacitor, and is electrically connected with the rectifying circuit to filter direct current output by the rectifying circuit; the second capacitor branch comprises a first switch and a second capacitor which are connected in series, and the capacitance value of the second capacitor is larger than that of the first capacitor; the control circuit is respectively and electrically connected with the first switch and the driving circuit, and is used for outputting a conduction signal to the first switch to control the conduction of the first switch in the power-off stage of the electric tool.
In a second aspect, an embodiment of the present invention further provides an overvoltage protection method for an electric tool, where the overvoltage protection method for an electric tool is performed by the overvoltage protection circuit for an electric tool provided by the embodiment of the present invention;
the overvoltage protection method of the electric tool comprises the following steps:
when the control circuit detects a shutdown signal of the electric tool, a conduction signal is output to the first switch, the first switch is controlled to be conducted, and the second capacitor is connected to the bus.
In a third aspect, the embodiment of the invention further provides an electric tool, which comprises the overvoltage protection circuit and the motor of the electric tool provided by the embodiment of the invention; the power tool also includes a housing.
According to the embodiment of the invention, the first capacitance branch circuit and the second capacitance branch circuit are connected in parallel on a circuit connected with the rectifying circuit and the driving circuit. The first capacitor branch circuit comprises a first capacitor and is used for filtering the voltage output by the rectifying circuit; the second capacitor branch comprises a first switch and a second capacitor, when the electric tool is in a shutdown stage, the control circuit controls the first switch to be conducted, and the second capacitor is connected into the bus to absorb voltage peaks on the bus. According to the technical scheme provided by the embodiment of the invention, the second capacitor is connected in the shutdown stage of the electric tool to absorb the voltage peak generated on the bus by the follow current of the brushless motor, and the second capacitor is connected in the bus only when the electric tool is shut down, so that the service life of the second capacitor is prolonged.
Drawings
Fig. 1 is a block diagram of an overvoltage protection circuit of an electric tool according to an embodiment of the present invention;
FIG. 2 is a block diagram illustrating an overvoltage protection circuit of another power tool according to an embodiment of the present invention;
FIG. 3 is a block diagram illustrating an exemplary embodiment of an overvoltage protection circuit for an electric tool;
FIG. 4 is a block diagram illustrating an exemplary embodiment of an overvoltage protection circuit for an electric tool;
FIG. 5 is a block diagram illustrating an exemplary embodiment of an overvoltage protection circuit for an electric tool;
fig. 6 is a schematic structural diagram of an electric tool according to an embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.
Fig. 1 is a block diagram of an overvoltage protection circuit of an electric tool according to an embodiment of the present invention. Referring to fig. 1, the overvoltage protection circuit of the electric tool includes: the rectifying circuit 10, the first capacitive branch 20, the second capacitive branch 30, the driving circuit 40 and the control circuit 50;
the rectifying circuit 10 is used for converting the accessed alternating current into direct current and outputting the direct current; the rectifying circuit 10 is electrically connected with the driving circuit 40, the driving circuit 40 is electrically connected with the brushless motor 70, and a first capacitor branch 20 and a second capacitor branch 30 are connected in parallel on a circuit connecting the rectifying circuit 10 and the driving circuit 40;
the first capacitor branch 20 comprises a first capacitor C1, and the first capacitor branch 20 is electrically connected with the rectifying circuit 10 to filter direct current output by the rectifying circuit 10; the second capacitor branch 30 includes a first switch K1 and a second capacitor C2 connected in series, where the capacitance value of the second capacitor C2 is greater than that of the first capacitor C1; the control circuit 50 is electrically connected to the first switch K1 and the driving circuit 40, respectively, and the control circuit 50 is configured to output a conducting signal to the first switch K1 to control the first switch K1 to be turned on during a power-off stage of the electric tool.
Specifically, the power supply 60 is an ac power supply, the rectifying circuit 10 converts ac power output by the power supply 60 into dc power to provide an operating voltage for the driving circuit 40, the first capacitor branch 20 includes a first capacitor C1, and the first capacitor C1 can be used to filter the dc power output by the rectifying circuit 10. Because the first capacitor C1 is a filter capacitor, if the first capacitor C1 adopts an electrolytic capacitor, the first capacitor C1 is continuously charged and discharged when the electric tool works, so that a large amount of heat is generated by the first capacitor C1, and the service life of the first capacitor C1 is shortened. Thus, in some embodiments, the first capacitor C1 is a thin film capacitor, which is not easily damaged by heat. The control circuit 50 outputs a PWM signal to the driving circuit 40, and the driving circuit 40 controls the motor 70 to rotate according to the received PWM signal. The motor 70 may be a brushless motor in which a counter electromotive force is generated in an armature winding in a direction opposite to a current direction when an armature of the brushless motor rotates. When the power tool is turned off (i.e., the motor 70 is turned off), a voltage spike is formed on the bus bar due to the counter-electromotive force of the motor 70, which causes a freewheel between the armature windings.
In the embodiment of the invention, the second capacitor branch 30 is connected in parallel to the circuit connecting the rectifying circuit 10 and the driving circuit 40 to absorb the voltage spike generated by the electric tool in the shutdown stage. When the electric tool is in the shutdown phase, the control circuit 50 generates a conducting signal of the first switch K1 according to the shutdown signal, the first switch K1 is closed, the second capacitor C2 is connected into the bus, and the voltage spike on the bus is absorbed by the second capacitor C2. When the electric tool normally works, the first switch K1 is in an off state, the second capacitor C2 does not participate in work, and the service life of the second capacitor C2 can be prolonged. In an exemplary embodiment, the capacitance of the second capacitor C2 is larger than that of the first capacitor C1, and the capacitance of the second capacitor C2 is larger, so that when the bus voltage suddenly changes, the second capacitor C2 can absorb the energy of the sudden change wave through the larger charge, so that the energy is smooth, and the absorption of the voltage spike on the bus is more favorable.
According to the embodiment of the invention, the first capacitance branch circuit and the second capacitance branch circuit are connected in parallel on a circuit connected with the rectifying circuit and the driving circuit. The first capacitor branch circuit comprises a first capacitor and is used for filtering direct current output by the rectifying circuit; the second capacitor branch comprises a first switch and a second capacitor, when the electric tool is in a shutdown stage, the control circuit controls the first switch to be conducted, and the second capacitor is connected into the bus to absorb voltage peaks on the bus. According to the technical scheme provided by the embodiment of the invention, the second capacitor is connected in the shutdown stage of the electric tool to absorb the voltage peak generated on the bus by the follow current of the brushless motor, and the second capacitor is connected in the bus only when the electric tool is shut down, so that the service life of the second capacitor is prolonged.
Optionally, based on the above embodiment, the first capacitor C1 is a thin film capacitor, and the second capacitor C2 is an electrolytic capacitor.
Specifically, the first capacitor C1 may be a thin film capacitor, and is configured to filter the direct current output by the rectifying circuit 10, and the capacitance value of the thin film capacitor is smaller than that of the electrolytic capacitor, so that the voltage spike cannot be absorbed. The second capacitor C2 may be an electrolytic capacitor, and is configured to absorb an overvoltage on the bus in a shutdown stage of the electric tool, where the electrolytic capacitor has a larger capacitance, and when the overvoltage occurs on the bus, the electrolytic capacitor absorbs the surge energy generated by a voltage spike of the overvoltage through a large charge, so that the voltage on the bus is stable. And the second capacitor C2 is connected to the bus only in the shutdown stage of the electric tool, so that the heating value of the electrolytic capacitor can be reduced, and the service life of the second capacitor C2 can be prolonged.
Optionally, fig. 2 is a block diagram of an overvoltage protection circuit of another electric tool according to an embodiment of the present invention. On the basis of the above embodiment, referring to fig. 2, the first switch K1 includes a transistor T, and the rectifying circuit 10 includes a first output terminal A1 and a second output terminal A2; the first end of the transistor T is electrically connected to the first output terminal A1 of the rectifying circuit 10, the second end of the transistor T is electrically connected to the first end of the second capacitor C2, the second end of the second capacitor C2 is electrically connected to the second output terminal A2 of the rectifying circuit 10, the third end of the transistor T is electrically connected to the second output terminal D2 of the control circuit 50, and the first output terminal D1 of the control circuit 50 is electrically connected to the control terminal B3 of the driving circuit 40.
Specifically, the transistor T may be an IGBT with a higher switching frequency, and may be turned on quickly during the power-off phase of the electric tool, so as to connect the second capacitor C2 to the bus line quickly. The power-off stage of the electric tool may be understood as a period from when the power switch is turned off to when the motor 70 stops rotating, or a period from when the electric tool detects a power-off signal to when the motor 70 stops rotating. For example, when the power tool detects a shutdown signal through a software program, the control circuit 50 sends a turn-on signal of the transistor T, and the transistor T turns on according to the turn-on signal, and connects the second capacitor C2 into the bus line to absorb the voltage spike in the bus.
Optionally, the transistor T is turned on during the power-off phase of the electric tool, and the second capacitor C2 is connected to the bus. The advantage of the arrangement is that as the second capacitor C2 is an electrolytic capacitor, in the working process, the electrolytic capacitor has the problem that the service life of the electrolytic capacitor is reduced due to easy heating, so that the transistor T is conducted only in the shutdown stage of the electric tool, and the second capacitor C2 is connected into a bus to absorb voltage spikes; when the electric tool is in normal operation, the transistor T is turned off, the second capacitor C2 is withdrawn from operation, and the operation time of the second capacitor C2 is reduced, so that the service life of the second capacitor C2 can be prolonged.
Optionally, fig. 3 is a block diagram of an overvoltage protection circuit of another electric tool according to an embodiment of the present invention. On the basis of the above embodiment, referring to fig. 3, the control circuit 50 includes a controller 51 and a driving chip 52, and the driving chip 52 includes a control terminal F1 and an output terminal F2;
the controller 51 includes a first output end E1 and a second output end E2, the first output end E1 of the controller 51 is electrically connected to the control end F1 of the driving chip 52, the second output end E2 of the controller 51 is electrically connected to the third end of the transistor T, and the output end F2 of the driving chip 52 outputs a driving signal to the driving circuit 40.
Specifically, the driving circuit 40 may be a bridge structure, and is formed by three groups of electronic switches, and the driving chip 52 is used for controlling on or off of the electronic switches in the driving circuit 40. The driving chip 52 is connected in series between the controller 51 and the driving circuit 40, receives a control signal output by the controller 51, and controls on or off of an electronic switch in the driving circuit 40 according to the control signal. For example, the control signal output by the controller 51 may be a PWM control signal. In embodiments of the present invention, the driver chip 52 is shown separate from the controller 51, and in other embodiments, the driver chip 52 and the controller 51 may be integrated into one piece.
Optionally, with continued reference to fig. 3 based on the above embodiment, the overvoltage protection circuit of the electric tool further includes a power conversion circuit 80 and a second switch K2, and the driving chip 52 further includes a power terminal F3;
the second switch K2 is used to turn on or off the motor 70; the power conversion circuit 80 includes a first input end G1, a second input end G2, and an output end G3, the first input end G1 of the power conversion circuit 80 is electrically connected to the first output end A1 of the rectifying circuit 10, the second input end G2 of the power conversion circuit 80 is electrically connected to the second output end A2 of the rectifying circuit 10, and the output end G3 of the power conversion circuit 80 is electrically connected to the power end F3 of the driving chip 52 or the controller 51 through the second switch K2; the controller 51 is configured to output a turn-on signal to the first switch K1 to control the first switch K1 to turn on when the second switch K2 is turned off; the second switch K2 is an electronic switch or a mechanical switch.
Specifically, the power conversion circuit 80 may be a DC/DC circuit for converting the rectified direct current voltage into the operating voltage required by the driving chip 52. The second switch K2 may be a start switch of the electric tool for starting or shutting down the motor 70, and the shutdown phase of the electric tool may be a period of time after the second switch is turned off. The second switch K2 may be an electronic switch or a mechanical switch, and when the second switch K2 is closed, the driving chip 52 and/or the controller 51 receives an electrical signal from the power conversion circuit 80, and the motor 70 is powered on; when the second switch K2 is turned off, the electrical connection between the driving chip 52 and/or the controller 51 and the power conversion circuit 80 is cut off, and the motor 70 is powered off. Illustratively, closing the second switch K2, the power conversion circuit 80 converts the dc voltage output by the rectifying circuit 10 into the working voltage required by the driving chip 52 or the controller 51, and the driving chip 52 and the controller 51 are started; the controller 51 outputs a PWM control signal to the driving chip 52, and the driving chip 52 controls the electronic switch in the driving circuit 40 to be turned on according to the PWM control signal output from the controller 51, so as to drive the motor 70 to rotate. When the second switch K2 is turned off, the controller 51 outputs a turn-on signal of the transistor T, and the transistor T turns on and then connects the second capacitor C2 to the bus to absorb a voltage spike generated on the bus due to freewheeling when the motor 70 is turned off. When the electric tool is turned on again, the controller 51 controls the transistor T to be turned off, and the second capacitor C2 is turned off, so as to reduce the heat productivity of the second capacitor C2, which is beneficial to delay the service life of the second capacitor C2.
Optionally, fig. 4 is a block diagram of an overvoltage protection circuit of another electric tool according to an embodiment of the present invention. On the basis of the above embodiment, referring to fig. 4, the overvoltage protection circuit of the electric tool according to the embodiment of the present invention further includes a voltage detection circuit 90, and the controller 51 further includes an input end E3;
the voltage detection circuit 90 includes an input terminal H1 and an output terminal H2, the input terminal H1 of the voltage detection circuit 90 is electrically connected to the three-phase winding of the motor 70, and the output terminal H2 of the voltage detection circuit 90 is electrically connected to the input terminal E3 of the controller 51.
Specifically, the voltage detection circuit 90 is configured to detect a phase voltage of the motor 70. The power tool also includes a current detection circuit (not shown) for detecting the current applied to the stator windings. A rotor position calculation unit (not shown in the figures) is configured to estimate the rotor position of the brushless motor based at least on the phase voltages of the brushless motor and the currents of the stator windings. For example, the inductance value of the stator winding is estimated according to the phase voltage of the motor 70 and the current of the stator winding, and a one-to-one matching relationship between the inductance value and the rotor position is established (a matching relationship is established by a table look-up method or a formula modeling method, etc.), so as to obtain the position of the rotor. The controller 51 outputs a PWM control signal to the driving circuit 40 according to the rotor position obtained by the rotor position calculating unit to make the motor 70 generate a continuous torque, and the motor 70 rotates under the action of the torque.
Of course, when the voltage detection circuit 90 detects that the motor 70 is over-voltage during normal operation of the electric tool, the controller 51 outputs the on signal of the transistor T, and absorbs the voltage spike of the over-voltage through the second capacitor C2.
Optionally, fig. 5 is a block diagram of an overvoltage protection circuit of another electric tool according to an embodiment of the present invention. On the basis of the above embodiment, referring to fig. 5, a specific working principle of the overvoltage protection circuit of the electric tool provided by the embodiment of the invention is as follows:
the power supply 60 provides an ac voltage, the rectifying circuit 10 converts the ac voltage output from the power supply 60 into a dc voltage, and the first capacitor C1 filters the dc voltage output from the rectifying circuit 10. The switch K2 is closed, the power supply conversion circuit 80 converts the direct-current voltage output by the rectifying circuit 10 into the voltage required by the driving chip 52, the working voltage is provided for the driving chip 52, and the driving chip is started; the controller 51 outputs a PWM control signal to the driving chip 52, and the driving chip 52 controls the electronic switches Q1 to Q6 in the driving circuit 40 to be turned on according to the PWM control signal output from the controller 51. The voltage detection circuit 90 detects a phase voltage of the motor 70, and the power tool further includes a current detection circuit (not shown) for detecting a current applied to the stator winding. A rotor position calculation unit (not shown in the figures) is configured to estimate the rotor position of the motor based at least on the phase voltages of the brushless motor and the currents of the stator windings. For example, the inductance value of the stator winding is estimated according to the phase voltage of the motor 70 and the current of the stator winding, and a one-to-one matching relationship between the inductance value and the rotor position is established (a matching relationship is established by a table look-up method or a formula modeling method, etc.), so as to obtain the position of the rotor. The controller 51 adjusts the output PWM control signal to the driving circuit 40 according to the rotor position obtained by the rotor position calculating unit to make the motor 70 generate a continuous torque, and the motor 70 rotates under the action of the torque.
When the second switch K2 is turned off, the electrical connection between the driving chip 52 and/or the controller 51 and the power conversion circuit 80 is cut off, the motor 70 is powered off, the controller 51 outputs a conducting signal of the transistor T, and the transistor T is turned on and then connects the second capacitor C2 to the bus to absorb a voltage spike generated on the bus due to freewheeling when the motor 70 is turned off. When the electric tool is turned on again, the controller 51 controls the transistor T to be turned off, and the second capacitor C2 is turned off, so as to reduce the heat productivity of the second capacitor C2, which is beneficial to delay the service life of the second capacitor C2. During the normal operation of the electric tool, when the voltage detection circuit 90 detects that the motor 70 is over-voltage, the controller 51 outputs a conducting signal of the transistor T, and absorbs a voltage spike of the over-voltage through the second capacitor C2, so as to further protect the safety and reliability of the electric tool.
Optionally, an embodiment of the present invention further provides an overvoltage protection method for an electric tool, with reference to fig. 5, where the method is performed by an overvoltage protection circuit for an electric tool provided by the embodiment of the present invention, and the overvoltage protection method for an electric tool includes:
when the control circuit 50 detects a shutdown signal of the electric tool, it outputs a conduction signal to the first switch K1, controls the first switch K1 to be turned on, and connects the second capacitor C2 to the bus.
Specifically, the shutdown signal may be a signal that the second switch K2 is triggered to shut down the brushless motor, or may be an abnormal protection shutdown signal, such as an overcurrent shutdown, where the brushless motor shutdown includes a brushless motor braking and a brushless motor stopping driving to stop freely. When the second switch K2 is turned off, the controller 51 outputs a turn-on signal of the transistor T, and the transistor T turns on and then connects the second capacitor C2 to the bus to absorb a voltage spike generated on the bus due to freewheeling when the motor 70 is turned off. When the electric tool is turned on again, the controller 51 controls the transistor T to be turned off, and the second capacitor C2 is turned off, so as to reduce the heat productivity of the second capacitor C2, which is beneficial to delay the service life of the second capacitor C2.
Optionally, with continued reference to fig. 5, the over-voltage protection method of the electric tool further includes: in the normal operation process, if the voltage detection circuit 90 detects an overvoltage, an overvoltage signal is output, the control circuit 50 outputs a conducting signal according to the overvoltage signal, the first switch K1 is turned on, and the second capacitor C2 is connected to the bus.
Specifically, during the normal operation of the electric tool, when the voltage detection circuit 90 detects that the motor 70 has overvoltage, the controller 51 outputs the on signal of the first switch K1, and absorbs the voltage spike of the overvoltage through the second capacitor C2, so as to further protect the safety and reliability of the electric tool.
According to the embodiment of the invention, the first capacitance branch circuit and the second capacitance branch circuit are connected in parallel on a circuit connected with the rectifying circuit and the driving circuit. The first capacitor branch circuit comprises a first capacitor and is used for filtering the voltage output by the rectifying circuit; the second capacitor branch comprises a first switch and a second capacitor, when the electric tool is in a shutdown stage, the control circuit controls the first switch to be conducted, and the second capacitor is connected into the bus to absorb voltage peaks on the bus. According to the technical scheme provided by the embodiment of the invention, the second capacitor is connected in the shutdown stage of the electric tool to absorb the voltage peak generated on the bus by the follow current of the brushless motor, and the second capacitor is connected in the bus only when the electric tool is shut down, so that the service life of the second capacitor is prolonged.
Optionally, fig. 6 is a schematic structural diagram of an electric tool according to an embodiment of the present invention, where the electric tool includes an overvoltage protection circuit and a brushless motor of the electric tool according to the foregoing embodiments, and the electric tool further includes a housing. . While the present embodiment is directed to a sander, it should be understood that the present invention is not limited to the disclosed embodiments, but is applicable to other types of power tools including, but not limited to, angle grinders, electric drills, electric wrenches, electric saws.
The electric tool provided by the embodiment of the invention comprises the overvoltage protection circuit of the electric tool in the embodiment, so that the electric tool provided by the embodiment of the invention also has the beneficial effects described in the embodiment, and the description is omitted herein.
Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.
Claims (10)
1. An overvoltage protection circuit for an electric tool, comprising: the device comprises a rectifying circuit, a first capacitance branch, a second capacitance branch, a driving circuit, a control circuit, a power conversion circuit and a second switch;
the rectification circuit is used for converting the accessed alternating current into direct current and outputting the direct current;
the rectifying circuit is electrically connected with the driving circuit, the driving circuit is electrically connected with the motor, and a first capacitance branch and a second capacitance branch are connected in parallel on a circuit connected with the rectifying circuit and the driving circuit;
the first capacitor branch circuit comprises a first capacitor, and is electrically connected with the rectifying circuit to filter direct current output by the rectifying circuit;
the second capacitor branch comprises a first switch and a second capacitor which are connected in series, and the capacitance value of the second capacitor is larger than that of the first capacitor; the control circuit is respectively and electrically connected with the first switch and the driving circuit, and is used for outputting a conduction signal to the first switch to control the first switch to be conducted in the power-off stage of the electric tool;
the input end of the power conversion circuit is electrically connected with the rectifying circuit, and the output end of the power conversion circuit is electrically connected with the driving chip or the controller through the second switch;
the second switch is used for starting or closing the motor; the controller is used for outputting a conduction signal to the first switch to control the first switch to be conducted when the second switch is disconnected.
2. The overvoltage protection circuit of a power tool of claim 1, wherein the first capacitor is a thin film capacitor and the second capacitor is an electrolytic capacitor.
3. The overvoltage protection circuit of a power tool of claim 1, wherein the first switch comprises a transistor and the rectifying circuit comprises a first output and a second output; the first end of the transistor is electrically connected with the first output end of the rectifying circuit, the second end of the transistor is electrically connected with the first end of the second capacitor, the second end of the second capacitor is electrically connected with the second output end of the rectifying circuit, the third end of the transistor is electrically connected with the second output end of the control circuit, and the first output end of the control circuit is electrically connected with the control end of the driving circuit.
4. The overvoltage protection circuit of claim 3, wherein said transistor is turned on during a shutdown phase of said power tool to connect said second capacitor to a bus.
5. The overvoltage protection circuit of a power tool of claim 3, wherein the control circuit comprises a controller and a driver chip, the driver chip comprising a control terminal and an output terminal;
the controller comprises a first output end and a second output end, the first output end of the controller is electrically connected with the control end of the driving chip, the second output end of the controller is electrically connected with the third end of the transistor, and the output end of the driving chip outputs a driving signal to the driving circuit.
6. The overvoltage protection circuit of a power tool of claim 5, wherein the driver chip further comprises a power supply terminal;
the power conversion circuit comprises a first input end, a second input end and an output end, wherein the first input end of the power conversion circuit is electrically connected with the first output end of the rectifying circuit, the second input end of the power conversion circuit is electrically connected with the second output end of the rectifying circuit, and the output end of the power conversion circuit is electrically connected with the power end or the controller of the driving chip through the second switch;
the second switch is an electronic switch or a mechanical switch.
7. The over-voltage protection circuit of the power tool of claim 5, further comprising a voltage detection circuit, the controller further comprising an input;
the voltage detection circuit comprises an input end and an output end, wherein the input end of the voltage detection circuit is respectively and electrically connected with the three-phase winding of the motor, and the output end of the voltage detection circuit is electrically connected with the input end of the controller.
8. An overvoltage protection method of an electric tool, characterized in that the overvoltage protection method of an electric tool is performed by the overvoltage protection circuit of an electric tool according to any one of claims 1 to 7;
the overvoltage protection method of the electric tool comprises the following steps:
when the control circuit detects a shutdown signal of the electric tool, a conduction signal is output to the first switch, the first switch is controlled to be conducted, and the second capacitor is connected to the bus.
9. The method of overvoltage protection for a power tool of claim 8, further comprising: in the normal operation process, if the voltage detection circuit detects the overvoltage of the three-phase winding, a three-phase winding overvoltage signal is output, the control circuit outputs a conducting signal according to the three-phase winding overvoltage signal, the first switch is conducted, and the second capacitor is connected to the bus.
10. A power tool comprising the overvoltage protection circuit of the power tool of any one of claims 1-7 and a motor;
the power tool also includes a housing.
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| CN112981860A (en) * | 2021-03-15 | 2021-06-18 | 广东威灵电机制造有限公司 | Control device and clothes treatment device |
| WO2022193574A1 (en) * | 2021-03-15 | 2022-09-22 | 广东威灵电机制造有限公司 | Control apparatus and laundry treating apparatus |
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