Switch detection circuit and power tool

Abstract

This application discloses a switch detection circuit and a power tool. The switch detection circuit includes a switch, an overvoltage protection branch, a unidirectional conduction branch, a pull-up branch, a current-limiting branch, and a controller. The overvoltage protection branch reduces its impedance when the voltage at the second terminal of the switch exceeds a first voltage threshold. The unidirectional conduction branch is cut off when the voltage at the second terminal of the switch is greater than or equal to the voltage at the first node, and conducts when the voltage at the second terminal of the switch is less than the voltage at the first node. When the unidirectional conduction branch is conducting, if the switch is closed, the voltage level at the second node is pulled down; if the switch is open, the voltage level at the second node is pulled up by the branch. The controller determines the switch state based on the voltage level at the second node. This method enables the detection of the switch state while reducing the risk of controller damage, improving the reliability of the power tool and extending its service life.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a switch detection circuit and a power tool. Background Technology

[0002] Most power tools have a hardware switch for controlling the motor's start and stop. Therefore, during circuit design, the MCU (Microcontroller Unit) typically detects the on / off state of this hardware switch to control the motor's operation. However, power tools such as angle grinders and electric drills often operate in harsh environments, making them susceptible to external interference, which can cause the MCU to malfunction, leading to damage to the power tool or creating safety hazards. Utility Model Content

[0003] This application provides a switch detection circuit and a power tool, which can detect the state of the switch while reducing the risk of damage to the controller, improving the reliability of the power tool, and extending its service life.

[0004] In a first aspect, embodiments of this application provide a switch detection circuit, comprising: a switch, the first terminal of which is grounded; an overvoltage protection branch electrically connected between the second terminal of the switch and ground, configured to reduce its impedance when the voltage at the second terminal of the switch exceeds a first voltage threshold, thereby discharging energy from the second terminal of the switch to ground; a unidirectional conductive branch, a pull-up branch, a current-limiting branch, a clamping branch, and a controller, wherein the unidirectional conductive branch is electrically connected to the pull-up branch and the current-limiting branch at a first node, the current-limiting branch is electrically connected to the clamping branch and the controller at a second node, the pull-up branch, the clamping branch, and the controller are all electrically connected to a power supply, and the clamping branch is also grounded; the unidirectional conductive branch is configured to reduce its impedance when the voltage at the second terminal of the switch exceeds a first voltage threshold, thereby discharging energy from the second terminal of the switch to ground; a unidirectional conductive branch, a pull-up branch, a current-limiting branch, a clamping branch, and the controller are all electrically connected to a power supply, and the clamping branch is also grounded; the unidirectional conductive branch is configured to... The switch is cut off when the voltage at the second terminal is greater than or equal to the voltage at the first node, and turned on when the voltage at the second terminal is less than the voltage at the first node. When the unidirectional conductive branch is on, if the switch is closed, the voltage level of the second node is pulled down to a first level; if the switch is open, the voltage level of the second node is pulled up to a second level by the pull-up branch. The current-limiting branch is configured to limit the current input to the second node. The clamping branch is configured to clamp the voltage of the second node within a preset voltage range based on the power supply and ground. The controller is configured to determine the state of the switch based on the voltage level of the second node, wherein the state of the switch includes a closed state and an open state.

[0005] In one or more embodiments, the switch detection circuit further includes a filter branch; the filter branch is electrically connected between the second node and ground, and the filter branch is configured to filter the voltage of the second node.

[0006] In one or more embodiments, the overvoltage protection branch includes a transient voltage suppression diode; the transient voltage suppression diode is electrically connected between the second terminal of the switch and ground.

[0007] In one or more embodiments, the unidirectional conductive branch includes a first diode; the anode of the first diode is electrically connected to the first node, and the cathode of the first diode is electrically connected to the second terminal of the switch.

[0008] In one or more embodiments, the pull-up branch includes a first resistor; the first resistor is electrically connected between the power supply and the first node.

[0009] In one or more embodiments, the current-limiting branch includes a second resistor; the second resistor is electrically connected between the first node and the second node.

[0010] In one or more embodiments, the clamping branch includes a second diode and a third diode; the anode of the second diode and the cathode of the third diode are both electrically connected to the second node, the cathode of the second diode is electrically connected to the power supply, and the anode of the third diode is grounded.

[0011] In one or more embodiments, the filtering branch includes a first capacitor; the first capacitor is electrically connected between the second node and ground.

[0012] Secondly, embodiments of this application provide an electric tool, including the switch detection circuit described above. Attached Figure Description

[0013] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, which are not intended to limit the embodiments, and elements having the same reference numerals in the drawings are designated as similar elements.

[0014] Figure 1 This is a schematic diagram of the block diagram of the switch detection circuit provided in the embodiments of this application. Figure 1 ;

[0015] Figure 2 This is a schematic diagram of the block diagram of the switch detection circuit provided in the embodiments of this application. Figure 2 ;

[0016] Figure 3 Is with Figure 2 The circuit structure diagram corresponding to the block diagram shown is shown. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and thoroughly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0018] It should be noted that when an element is described as "connected" to another element, it can be directly connected to the other element, or there can be one or more intermediate elements between them.

[0019] Furthermore, the technical features involved in the various embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0020] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the block diagram of the switch detection circuit provided in an embodiment of this application. Figure 1 As shown, the switch detection circuit 100 includes a switch K1, an overvoltage protection branch 10, a unidirectional conductive branch 20, a pull-up branch 30, a current limiting branch 40, a clamping branch 50, and a controller 60.

[0021] Among them, the first terminal of switch K1 is grounded to GND, the overvoltage protection branch 10 is electrically connected between the second terminal of switch K1 and ground GND, the unidirectional conductive branch 20, the pull-up branch 30 and the current limiting branch 40 are connected to the first node P1, the current limiting branch 40, the clamping branch 50 and the controller 60 are electrically connected to the second node P2, the pull-up branch 30, the clamping branch 50 and the controller 60 are all electrically connected to the power supply VCC, and the clamping branch 50 is also grounded to GND.

[0022] Specifically, switch K1 is configured to be closed or open. Overvoltage protection branch 10 is configured to reduce its impedance when the voltage at the second terminal of switch K1 exceeds a first voltage threshold, thereby discharging energy from the second terminal of switch K1 to ground (GND). The first voltage threshold is determined by the characteristics of the devices in overvoltage protection branch 10. Unidirectional conduction branch 20 is configured to be cut off when the voltage at the second terminal of switch K1 is greater than or equal to the voltage at the first node P1, and to be turned on when the voltage at the second terminal of switch K1 is less than the voltage at the first node P1. When unidirectional conduction branch 20 is on, if switch K1 is closed, the level of the second node P1 is pulled down to the first level; if switch K1 is open, the level of the second node P2 is pulled up to the second level by pull-up branch 30. Current limiting branch 40 is configured to limit the current input to the second node P2. Clamping branch 50 is configured to clamp the voltage of the second node P2 within a preset voltage range based on power supply VCC and ground GND, wherein the preset voltage range is determined by the characteristics of the devices in clamping branch 50. Controller 60 is configured to determine the state of switch K1 based on the level of the second node P2, wherein the state of switch K1 includes a closed state and an open state.

[0023] In this way, when the voltage at the second terminal of switch K1 is undisturbed, the voltage at the second terminal of switch K1 is less than or equal to the voltage at the first node P1, and the unidirectional conduction branch 20 is activated. If switch K1 is closed, the level of the second node P2 is pulled down to the first level; if switch K1 is open, the level of the second node P2 is pulled up to the second level by the pull-up branch 30. Subsequently, the controller 60 can determine whether the state of switch K1 is closed or open based on the first and second levels, thus realizing the detection of the state of switch K1. Secondly, overvoltage protection is achieved through the overvoltage protection branch 10, the current input to the second node P1 is limited through the current limiting branch 40, and the voltage of the second node P2 is clamped within a preset voltage range through the clamping branch 50. This can prevent abnormal situations where the current and voltage input to the controller 60 are too large, thereby reducing the risk of damage to the controller 60, improving the reliability of the power tool, and extending its service life.

[0024] In some embodiments, such as Figure 2 As shown, the switch detection circuit 100 also includes a filter branch 70.

[0025] The filter branch 70 is electrically connected between the second node P2 and ground GND, and is configured to filter the voltage of the second node P2. This filters out spike pulses to prevent excessive voltage input to the controller 60.

[0026] Please refer to Figure 3 , Figure 3 An example is shown with Figure 2The block diagram shown corresponds to one type of circuit structure. For example... Figure 3 As shown, the overvoltage protection branch 10 includes a transient voltage suppression diode DW1.

[0027] Transient voltage suppressor diode DW1 is electrically connected between the second terminal of switch K1 and ground (GND). Transient voltage suppressor diode DW1 effectively absorbs interference and ESD (Electrostatic Discharge), thus protecting downstream circuitry from damage. The first voltage threshold is the breakdown voltage of transient voltage suppressor diode DW1. When a voltage transient occurs, causing the voltage at the second terminal of switch K1 to exceed the first voltage threshold, transient voltage suppressor diode DW1 can quickly switch from a high-resistance state to a low-resistance state, clamping the excessive voltage to a safe level, thereby protecting downstream circuitry.

[0028] In some embodiments, the unidirectional conductive branch 20 includes a first diode D1.

[0029] The anode of the first diode D1 is electrically connected to the first node P1, and the cathode of the first diode D1 is electrically connected to the second terminal of the switch K1.

[0030] When the second terminal of switch K1 is not disturbed, the voltage at the second terminal of switch K1 is less than the voltage at the first node P1, and the first diode D1 is turned on. When the second terminal of switch K1 is disturbed, causing its voltage to increase, if the voltage at the second terminal of switch K1 is still less than the voltage at the first node P1, then the first diode D1 is turned on; if the voltage at the second terminal of switch K1 is greater than or equal to the voltage at the first node P1, then as long as the voltage at the second terminal of switch K1 does not exceed the reverse breakdown voltage of the first diode D1, due to the unidirectional conductivity of the first diode D1, the first diode D1 remains off, thereby preventing excessively high voltage input to the controller 60.

[0031] In some embodiments, the pull-up branch 30 includes a first resistor R1.

[0032] The first resistor R1 is electrically connected between the power supply VCC and the first node P1. The first resistor R1 is a pull-up resistor.

[0033] In some embodiments, the current-limiting branch 40 includes a second resistor R2.

[0034] The second resistor R2 is electrically connected between the first node P1 and the second node P2. The second resistor R2 is a current-limiting resistor.

[0035] In some embodiments, the clamping branch 50 includes a second diode D2 and a third diode D3.

[0036] The anode of the second diode D2 and the cathode of the third diode D3 are both electrically connected to the second node P2. The cathode of the second diode D2 is electrically connected to the power supply VCC, and the anode of the third diode D3 is grounded to GND.

[0037] Specifically, the second diode D2 is used to clamp the voltage at the second node P2 to a maximum of VCC + VD2, where VD2 is the forward voltage drop of the second diode D2. The third diode D3 is used to clamp the voltage at the second node P2 to a minimum of -VD3, where VD3 is the forward voltage drop of the third diode D3. Therefore, the preset voltage range is [-VD3, VCC + VD2].

[0038] In some embodiments, the filter branch 70 includes a first capacitor C1.

[0039] The first capacitor C1 is electrically connected between the second node P2 and ground GND.

[0040] exist Figure 3 In the circuit, when the voltage at the second terminal of switch K1 is undisturbed, the voltage at the second terminal of switch K1 is less than or equal to the voltage at the first node P1, and the first diode D1 is turned on. If switch K1 is closed, the second node P2 is grounded to GND through the second resistor R2, the first diode D1, and switch K1, and the voltage level of the second node P2 is pulled down to the first voltage level (low level). If switch K1 is open, the second node P2 is connected to the power supply VCC through the second resistor R2 and the first resistor R1, and the voltage level of the second node P2 is pulled up to the second voltage level (high level). Subsequently, the controller 60 can determine whether the state of switch K1 is closed or open based on the first and second voltage levels, thus realizing the detection of the state of switch K1. Secondly, overvoltage protection is achieved through transient voltage suppression diode DW1 and first diode D1, current is limited by second resistor R2 to the input to second node P1, and voltage at second node P2 is clamped within a preset voltage range by second diode D2 and third diode D3. This can prevent abnormal situations where the current and voltage input to controller 60 are too large, thereby reducing the risk of controller 60 being damaged, improving the reliability of power tools and extending their service life.

[0041] This application also provides an electric tool, which includes the switch detection circuit 100 in any embodiment of this application.

[0042] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

[0043] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A switch detection circuit, characterized in that, include: A switch, wherein the first terminal of the switch is grounded; An overvoltage protection branch, electrically connected between the second terminal of the switch and ground, is configured to reduce its impedance when the voltage at the second terminal of the switch is greater than a first voltage threshold, so as to discharge the energy at the second terminal of the switch to ground. The system includes a unidirectional conductive branch, a pull-up branch, a current-limiting branch, and a controller. The unidirectional conductive branch, the pull-up branch, and the current-limiting branch are electrically connected to a first node. The current-limiting branch and the controller are electrically connected to a second node. Both the pull-up branch and the controller are electrically connected to a power supply. The unidirectional conduction branch is configured to be cut off when the voltage at the second terminal of the switch is greater than or equal to the voltage at the first node, and to be turned on when the voltage at the second terminal of the switch is less than the voltage at the first node. When the unidirectional conduction branch is turned on, if the switch is closed, the level of the second node is pulled down to a first level; if the switch is open, the level of the second node is pulled up to a second level by the pull-up branch. The current-limiting branch is configured to limit the current input to the second node; The controller is configured to determine the state of the switch based on the level of the second node, wherein the state of the switch includes a closed state and an open state.

2. The switch detection circuit according to claim 1, characterized in that, The switch detection circuit also includes a clamping branch; The clamping branch is electrically connected to the current limiting branch and the controller at the second node, and the clamping branch is also connected to the power supply and ground respectively. The clamping branch is configured to clamp the voltage of the second node within a preset voltage range based on the power supply and ground.

3. The switch detection circuit according to claim 1, characterized in that, The switch detection circuit also includes a filter branch; The filter branch is electrically connected between the second node and ground, and the filter branch is configured to filter the voltage of the second node.

4. The switch detection circuit according to any one of claims 1-3, characterized in that, The overvoltage protection branch includes a transient voltage suppression diode; The transient voltage suppression diode is electrically connected between the second terminal of the switch and ground.

5. The switch detection circuit according to any one of claims 1-3, characterized in that, The unidirectional conductive branch includes a first diode; The anode of the first diode is electrically connected to the first node, and the cathode of the first diode is electrically connected to the second terminal of the switch.

6. The switch detection circuit according to any one of claims 1-3, characterized in that, The pull-up branch includes a first resistor; The first resistor is electrically connected between the power source and the first node.

7. The switch detection circuit according to any one of claims 1-3, characterized in that, The current-limiting branch includes a second resistor; The second resistor is electrically connected between the first node and the second node.

8. The switch detection circuit according to claim 2, characterized in that, The clamping branch includes a second diode and a third diode; The anode of the second diode and the cathode of the third diode are both electrically connected to the second node. The cathode of the second diode is electrically connected to the power supply, and the anode of the third diode is grounded.

9. The switch detection circuit according to claim 3, characterized in that, The filter branch includes a first capacitor; The first capacitor is electrically connected between the second node and ground.

10. A power tool, characterized in that, Includes the switch detection circuit as described in any one of claims 1-9.

Images