Protection circuit and electric power tool, charger

Abstract

The utility model relates to a kind of protection circuit, electric tool and charger, to realize the voltage protection of electric tool, charging equipment and power grid sensitive load.The protection circuit provided by the present application is based on the hardware structure of circuit control between multiple modules is innovated: the innovative combination of hardware architecture between power processing module, reference comparison module and power control module, the protection of circuit is realized by voltage sampling, voltage comparison and on-off control.The protection circuit can automatically cut off the power supply of rear-end equipment when detecting that power grid voltage is too low, prevent working under undervoltage state, so as to protect equipment and prolong its service life.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of power electronic protection, especially to a protection circuit and electric tool, charger. BACKGROUND

[0002] Current high-voltage electric tools generally adopt AC / DC rectification power supply or AC motor direct drive mode, and the motor control system has strict requirements on grid voltage stability. The prior art usually monitors the grid voltage through a voltage detection circuit, and drives a switch control circuit to cut off the power supply loop when detecting that the voltage is lower than a safety threshold. However, such a scheme has the following defects: the threshold is fixed, the protection trigger point cannot be flexibly adjusted according to the actual grid environment, and the cost is high, thereby causing the device to be easily damaged in the voltage fluctuation frequent area and poor adaptability. SUMMARY

[0003] The main purpose of the utility model is to provide a protection circuit, which aims to realize voltage protection of electric tools, charging devices and grid sensitive loads.

[0004] In order to achieve the above purpose, the first aspect of the embodiment of the application provides a protection circuit applied to a charger or an electric tool, which comprises:

[0005] a power supply processing module, a reference comparison module, a power control module and a driving module,

[0006] The input end of the power supply processing module is connected with a power supply, and the output end is connected with the reference comparison module. The power supply processing module is used for dividing and processing an electrical signal input by the power supply to generate a target voltage signal.

[0007] The reference end of the reference comparison module receives the target voltage signal, and the output end generates a control signal.

[0008] The input end of the power control module is connected with the reference comparison module and receives the control signal. The output end generates a driving level.

[0009] The driving module is controlled by the driving level and opens and closes the path of the power supply to the load.

[0010] The power supply processing module comprises a threshold adjustment circuit, and the threshold adjustment circuit comprises a plurality of resistors. The range of the voltage threshold in the voltage dividing and processing is adjusted by the resistance value of the resistor.

[0011] Optionally, the power supply processing module in the protection circuit provided by the application further comprises a rectifier bridge circuit and a filter circuit.

[0012] The alternating current input end of the rectifier bridge circuit is connected with an alternating current power supply. The direct current output end is grounded through the filter circuit to generate the direct current bus voltage.

[0013] Optionally, the threshold adjustment circuit in the power processing module of the protection circuit comprises: at least two resistors, the at least two resistors form a voltage dividing circuit,

[0014] a voltage dividing point in the voltage dividing circuit is connected with an input end of the reference comparison module.

[0015] Optionally, the reference comparison module of the protection circuit comprises a reference voltage source and a comparator.

[0016] One end of an input end of the comparator is connected with the reference voltage source, and the other end is connected with the power processing module.

[0017] An output end of the comparator is connected with the driving module.

[0018] The comparator is configured to detect a difference between the target voltage signal and the preset voltage threshold.

[0019] and generate a control signal according to a detection result, so as to control on-off of a loop between the power control module and the load.

[0020] Optionally, the reference comparison module of the protection circuit further comprises an isolator.

[0021] An input end of the isolator is connected with the comparator, and an output end of the isolator is connected with the power control module.

[0022] Optionally, the power control module of the protection circuit comprises a first switch module and a second switch module.

[0023] An input end of the first switch module is connected with the reference comparison module, and an output end of the first switch module is connected with the second switch module.

[0024] The second switch is connected with the driving module.

[0025] The first switch module is configured to, in response to the control signal, turn off the second switch module or turn on the second switch module.

[0026] Optionally, the first switch module of the protection circuit comprises a triode switch.

[0027] An emitter of the triode is grounded, a base of the triode is connected with the reference comparison module.

[0028] and a collector of the triode is connected with a power voltage through a pull-up resistor.

[0029] If the triode switch is turned on, a level signal for driving the second switch module is output.

[0030] Optionally, the second switch module in the protection circuit provided in the application comprises a MOS switch.

[0031] The gate of the MOS switch is connected to the first switch module.

[0032] The source of the MOS switch is connected to the DC bus voltage output by the power supply processing module, and the drain is connected to a load.

[0033] The protection circuit provided in the application is based on the innovative combination of the hardware architecture of multiple modules, and realizes the protection of the circuit through voltage comparison and on-off control. In the circuit, the process of signal transmission between multiple modules includes: an AC power input voltage signal is converted to generate a DC bus through a voltage processing module, and then a target voltage signal is generated through voltage sampling and division, and is transmitted to a reference comparison module to determine whether the target voltage signal exceeds a threshold value, and a control signal is generated according to the determination result, and the control signal is isolated through a switch to drive a switch module, thereby controlling the conduction or cutoff of the switch module.

[0034] The protection circuit can automatically cut off the power supply of the rear-end device when detecting that the grid voltage is too low, thereby preventing the device from working in an under-voltage state, and prolonging the service life of the device.

[0035] At the same time, the protection circuit can also effectively prevent the device from running in an over-current, over-heat, and motor locked-rotor state caused by an over-low voltage, thereby significantly prolonging the service life of the electric tool, the motor, and the energy storage power supply.

[0036] At the same time, the protection circuit can also flexibly set the protection voltage point through resistance voltage division, and adapt to different grid environments and device requirements.

[0037] In order to achieve the above purpose, a second aspect of the embodiment of the application provides an electric tool, which comprises a control circuit, a motor, and a work component,

[0038] The control circuit at least comprises the protection circuit described in the above embodiment.

[0039] The control circuit and the motor are connected, and the motor is used to drive the work component.

[0040] The electric tool provided in the application can immediately cut off the power supply when detecting an under-voltage through the protection circuit, thereby preventing the motor from being burned out due to locked-rotor, and prolonging the service life of the motor.

[0041] In order to achieve the above purpose, a third aspect of the embodiment of the application provides a charger, which comprises a control circuit,

[0042] The control circuit at least comprises the protection circuit described in the above embodiments.

[0043] The charger provided by the application can also perform battery protection when discharging, so as to avoid reverse discharging of the lithium battery at low voltage. BRIEF DESCRIPTION OF DRAWINGS

[0044] The specific embodiments of the utility model will be further described in detail below with reference to the drawings:

[0045] Figure 1 The circuit schematic diagram adopted by the prior art in the embodiments of the application is shown in the following figure:

[0046] Figure 2 The circuit block diagram adopted by the embodiments of the application is shown in the following figure:

[0047] Figure 3 The circuit schematic diagram adopted by the embodiments of the application is shown in the following figure: Figure 1

[0048] Figure 4 The circuit schematic diagram adopted by the embodiments of the application is shown in the following figure: Figure 2 .

[0049] In the following figures, the marks in the figures are explained as follows: Figure 1

[0050] The protection circuit 20, the power supply processing module 201, the reference comparison module 202, the power control module 203 and the driving module 204. DETAILED DESCRIPTION

[0051] The scheme provided by the embodiments of the application provides a protection circuit, a power tool and a charger, which can detect voltage fluctuation of a power grid, cut off power supply protection under unstable power grid, and delay service life and use range of the power tool and the charger.

[0052] In the prior art, the current market power tool, in the process of motor driving, the power supply AC is rectified to DC motor or AC power is directly supplied to the motor to drive the working part to work, in this mode, the working environment of the power tool requires very high stability of the power grid, and too high or too low fluctuation of the power grid will cause damage to the power tool, however, the voltage protection sampled by the power tool is relatively basic or not strong in adaptability,

[0053] For example:

[0054] Mechanical relay scheme: dependent on electromagnetic coil on-off, slow response speed, frequent action easy to cause contact ablation, insufficient service life;

[0055] Pure comparator scheme: requires independent reference source (such as LM336), increases system cost and wiring complexity, and has poor anti-power grid noise ability;​

[0056] Fixed threshold scheme: The protection threshold is not adjustable, which cannot adapt to the power grid fluctuation range in different regions (such as 170V-250V), resulting in malfunction or protection failure.

[0057] For example, in the prior art, the entire voltage protection circuit uses a voltage sensor to collect electrical signals and transmit them to a detection module. The ADC value of the voltage change is used to determine the fluctuation of the mains voltage, thereby protecting the circuit from damage. This method has very high accuracy; however, the disadvantages are that the sensor is expensive and easily damaged.

[0058] For example, please refer to the appendix. Figure 2 The circuit diagram shown uses a voltage divider circuit in the series resistors of the entire control loop to directly transmit the electrical signal to the detection module. The ADC value of the voltage change inside the module is used to determine the fluctuation of the mains voltage, thereby realizing the protection circuit and avoiding damage caused by voltage. However, this circuit can be damaged by some voltage spikes in the mains, and the cost is relatively high.

[0059] Correspondingly, when a charger is connected to an AC power source to power a battery pack or power tool, it will also face fluctuations in the power grid, and therefore voltage protection is also required.

[0060] Based on the above technical pain points, there is an urgent need for a low-cost, adjustable threshold, and fast-response voltage protection solution. Therefore, this application provides a comparator-based voltage-adjustable low-voltage protection circuit that dynamically sets the protection threshold through a resistor network to achieve millisecond-level fast power-off protection.

[0061] Please refer to the attached document. Figure 3 The circuit diagram shown illustrates a protection circuit 20 provided in this embodiment of the application. The protection circuit 20 includes:

[0062] The power processing module 201, the reference comparison module 202, the power control module 203, and the drive module 204;

[0063] The input terminal of the power processing module 201 is connected to the power supply, and the output terminal is connected to the reference comparison module. The power processing module is used to divide and process the electrical signal input to the power supply module to generate the target voltage signal.

[0064] The reference terminal of the reference comparison module 202 receives the target voltage signal, and the output terminal generates a control signal;

[0065] The power control module 203 is connected to the reference comparison module at its input terminal to receive the control signal and generates a drive level at its output terminal.

[0066] The drive module 204, controlled by the drive level, switches the power supply path to the load.

[0067] The power processing module includes a threshold adjustment circuit, which includes multiple resistors to adjust the range of the preset voltage threshold in the reference comparison module by adjusting the resistance value of the resistors.

[0068] The reference terminal of the aforementioned reference comparison module receives the target voltage signal.

[0069] A control signal is generated based on the comparison result between the target voltage signal and the preset voltage threshold.

[0070] If the comparison result indicates that the target voltage signal is greater than a preset threshold, the comparator generates a first control signal;

[0071] If the comparison result indicates that the target voltage signal is less than or equal to a preset threshold, a second control signal is generated.

[0072] The power control module sends a first control signal or a second control signal to the power control module through the output of the reference comparison module.

[0073] The protection circuit provided in this application embodiment is based on an innovative hardware structure for circuit control between multiple modules: an innovative combination of hardware architectures between the power processing module, the reference comparison module, and the power control module, which achieves circuit protection through voltage sampling, voltage comparison, and on / off control.

[0074] The protection circuit provided in this application embodiment also includes an innovation in the hardware device construction and connection method, realizing electrical signal processing and transmission. The process of electrical signal transmission between multiple modules in this circuit includes: the AC power input voltage signal is converted into a DC bus by the voltage processing module, and then sampled by voltage division to generate a target voltage signal, which is transmitted to the reference comparison module to determine whether the target voltage signal exceeds the threshold. Based on the determination result, a control signal is generated, and then the control signal is isolated by a switch to drive the switch module, thereby controlling the switch module to be turned on or off.

[0075] In an optional embodiment, the protection circuit provided in this application includes a power processing module comprising: an AC-to-DC converter.

[0076] The AC / DC conversion module includes: a rectifier bridge circuit and a filter circuit;

[0077] The AC input terminal of the rectifier bridge circuit is connected to an AC power supply, and the DC output terminal is grounded through the filter circuit to generate the DC bus voltage.

[0078] The protection circuit provided in this application embodiment can filter out instantaneous fluctuations in the power grid (such as glitches in the signal waveform) by adding an appropriate filter circuit at the detection point, preventing the circuit from malfunctioning during short-term voltage drops. This is equivalent to providing a certain "anti-jitter" time, avoiding frequent switching. If a true delayed start is required, an additional RC delay circuit or a dedicated delay chip is usually needed.

[0079] In an optional embodiment, the protection circuit provided in this application, the threshold adjustment circuit in the power processing module, includes: at least two resistors, wherein the at least two resistors form a voltage divider circuit.

[0080] The voltage divider circuit is connected to the reference comparison module through a voltage divider point, and the voltage divider point is connected to the reference ground through a resistor.

[0081] For example, a threshold adjustment circuit is connected to the reference comparison module through the voltage divider point in the voltage divider circuit, so that the range of the preset voltage threshold can be adjusted by the resistance value of the resistor.

[0082] The voltage divider detection module consists of a first resistor (R1), a second resistor (R2), and an adjustable resistor (R3) connected in series;

[0083] The voltage divider sampling signal is taken from the connection node between the second resistor (R2) and the adjustable resistor (R3);

[0084] Adjusting the resistance value of the adjustable resistor (R3) changes the voltage threshold range of the voltage divider sampling signal.

[0085] In an optional embodiment, the protection circuit provided in this application further includes a protection threshold adjustment. By setting different voltage values, the minimum grid voltage that triggers the power outage is determined, thereby determining the protection threshold of the trigger circuit. For example, the protection threshold of the circuit is set by the ratio of the voltage divider resistors R1, R2, and R3. When the grid voltage drops to the set protection threshold, the voltage value V_sample at the voltage divider point can trigger the reference comparison module to turn on. For example, the protection threshold at the voltage divider point is set to the reference voltage of TL431, 2.5V.

[0086] Optionally, the voltage division ratio can be changed by altering the resistance value of any of the resistors R1, R2, and R3. For example:

[0087] In the circuit, by increasing the resistance of R1 or decreasing the resistance of R2 / R3 (relative to other resistors), V_sample can be reduced under the same mains voltage. This means that a higher mains voltage is required to make V_sample > 2.5V (i.e., the protection point voltage is increased, the preset voltage threshold), thus making it suitable for situations where the mains voltage itself is too high or earlier protection is required.

[0088] In a circuit, decreasing R1 or increasing R2 / R3 (relative to other resistors) will increase V_sample under the same mains voltage. This means that a lower mains voltage is required for V_sample to be less than 2.5V (i.e., the protection point voltage is reduced), thus making it suitable for applications with low mains voltage or where the device needs to operate at a lower voltage.

[0089] The protection circuit provided in this application allows for flexible setting of the protection voltage point through resistor voltage division, adapting to different power grid environments and equipment requirements.

[0090] In an optional embodiment, the protection circuit provided in this application includes a reference comparison module comprising a reference voltage source and a comparator.

[0091] One end of the comparator input is connected to the reference voltage source, and the other end is connected to the power processing module;

[0092] The output of the comparator is connected to the driver module;

[0093] The comparator is used to detect the difference between the target voltage signal and the preset voltage threshold.

[0094] And generate control signals based on the detection results;

[0095] If the detection result indicates that the target voltage signal is greater than a preset threshold, the comparator generates a first control signal.

[0096] If the detection result indicates that the target voltage signal is less than or equal to a preset threshold, a second control signal is generated.

[0097] The first control signal turns on the power control module; the second control signal turns off the power control module.

[0098] For example, the reference voltage source and comparator included in the reference comparison module can be integrated into a single chip, thereby further improving circuit control efficiency and saving board size.

[0099] The reference comparison module may also include a feedback control device, that is, voltage detection and feedback control are achieved through an external resistor network.

[0100] In an optional embodiment, the feedback control device described above can be a TL431. The TL431 module consists of a 2.5V precision reference voltage source, a voltage comparator, and an output switch. The output voltage of the reference terminal is compared with the precision reference voltage source. The reference terminal (Ref) of the device is connected to the voltage divider sampling signal, and the anode is grounded. When the voltage divider sampling signal is >2.5V, the cathode outputs a low-level control signal; when the voltage divider sampling signal is <2.5V, the cathode outputs a high-impedance control signal.

[0101] In an optional embodiment, the protection circuit provided in this application further includes an isolator in the reference comparison module.

[0102] The input terminal of the isolator is connected to the output terminal of the comparator, and the output terminal of the isolator is connected to the signal input terminal of the power control module.

[0103] The isolator is used to receive the control signal transmitted by the comparator and provide electrical isolation.

[0104] If the isolator receives the first control signal, its output terminal generates a corresponding conduction signal, driving the power control module to enter the conduction working state.

[0105] If the isolator receives the second control signal, its output terminal generates a corresponding conduction signal, driving the power control module to enter the cut-off working state.

[0106] For example, the isolator described above may include an opto-isolator, which will be referred to as an optocoupler in the following description.

[0107] After receiving the control signal transmitted by the comparator, the aforementioned optocoupler generates a corresponding conduction signal at its output terminal to indicate the output behavior of the optocoupler, such as conducting between the CE terminals on the output side to generate a voltage or current signal.

[0108] If the optocoupler receives the first control signal, the light-emitting diode on its input side will light up, thereby turning on the phototransistor on the output side, which in turn provides a low-impedance conduction path (or a low-level signal) for the power control module, thus turning on the power control module.

[0109] If the optocoupler receives the second control signal, the light-emitting diode on its input side will turn off, thereby causing the phototransistor on the output side to be cut off, thus providing a high-impedance cutoff path (or a high-level signal) for the power control module, causing the power control module to turn off.

[0110] The protection circuit provided in this application, by adding an isolation device to the reference comparison module, can establish an electrical isolation barrier between two circuits, thereby preventing current, ground loops, surges and noise from flowing directly between the two circuits, while allowing signal or power transmission, thus improving the stability of signal transmission.

[0111] In an optional embodiment, the protection circuit provided in this application includes a power control module comprising: a first switch module and a second switch module;

[0112] The input terminal of the first switch module is connected to the output terminal of the reference comparison module, and the output terminal is connected to the second switch module;

[0113] The second switch is connected to the drive module;

[0114] The first switch module responds to the control signal by either disconnecting or connecting the second switch module.

[0115] Both the first and second switching modules can select any type of switching device, such as a diode, transistor, or MOSFET.

[0116] In an optional embodiment, the protection circuit provided in this application, the first switching module, includes: a transistor switch;

[0117] Its emitter is grounded, and its base is connected to the emitter of the switching module;

[0118] Its collector is connected to the power supply voltage via a pull-up resistor and outputs the drive level.

[0119] For example, when determining the control signal, a pull-up resistor is used to ensure that the gate of the second switch is at a high level when the first switch is turned off, thus preventing the MOSFET from being mistakenly turned on due to floating.

[0120] For example, if the current voltage is detected to exceed a preset voltage threshold, a rapid shutdown can be achieved through the first switch, such as directly pulling down the gate voltage of the second switch Q2 when the first switch Q1 is saturated and turned on.

[0121] The second switch Q2 power unit and its drive circuit can reduce conduction losses, improve efficiency and reliability.

[0122] In an alternative embodiment, high-voltage side isolation can be achieved, such as placing the sampling point on the high-voltage DC bus side and using optocouplers to isolate and transmit the control signal to the low-voltage control side, thereby improving safety and anti-interference capabilities.

[0123] In an optional embodiment, the protection circuit provided in this application, the second switching module, includes: a MOS switch, the gate of which is connected to the first switching module;

[0124] Its source is connected to the DC bus voltage output by the power processing module, and its drain is connected to the load.

[0125] For example, when the drive level output by the first switch module is low, the second switch module is turned on; correspondingly, when the drive level is high, the second switch module is turned off.

[0126] For example: the second switching module is a P-channel field-effect transistor; the source of the P-channel field-effect transistor is the input terminal of the second switching module; the drain of the P-channel field-effect transistor is the output terminal of the second switching module; and the gate of the P-channel field-effect transistor is the control terminal of the second switching module.

[0127] The power consumption of the on-resistance of the MOS switch in the protection circuit provided in this application embodiment is lower than that of the relay, thus achieving low conduction loss; at the same time, the solid-state switch supports tens of thousands of switching cycles, resulting in low maintenance costs.

[0128] Please refer to the attached document. Figure 4 The circuit diagram shown illustrates the control logic of the protection circuit in this application:

[0129] The power processing module in this circuit diagram includes a half-wave rectifier bridge composed of diodes D1, D2, and D3. The AC power is connected to the input terminal of diode D1 and then output through diode D3, converting the AC power into pulsating DC power.

[0130] Furthermore, one end of resistor R1 in the power processing module is connected to the power supply, and the other end is connected to R2, thereby limiting the current on the high-voltage side of the power supply, avoiding the impact of large current, and also reducing the voltage divider network in the subsequent stage.

[0131] Furthermore, resistors R1, R2, and R3 in the power processing module form a voltage divider network to regulate the voltage. Among them, R2, as the core resistor of the voltage divider network, is connected at one end to R1 and at the other end to resistor R3 and feedback regulation device.

[0132] Furthermore, in conjunction with different application scenarios, this paper further elaborates on how the reference comparison unit controls whether the power control module is turned on or off.

[0133] Example 1: The mains voltage is normal / too high (e.g., the voltage sample value at the voltage divider point V_sample>2.5V).

[0134] When the power processing module detects that the mains voltage is normal or too high, the switch U1 in the reference comparison module will be turned on (the K terminal is pulled low) and output a low-level signal. This low-level signal causes the base voltage of the switch Q1 in the power control module to be pulled low, at which point Q1 is turned off (closed).

[0135] When Q1 is turned off, its collector voltage is pulled high (VCC) by the pull-up resistor.

[0136] A high-level signal drives the power switch Q2 to conduct.

[0137] After the Q2 switch is turned on, the power control module connects the grid voltage (or the rectified DC bus voltage) to the load so that the load can work normally.

[0138] Example 2: The mains voltage is too low (e.g., the sampled voltage value at the voltage divider point, V_sample < 2.5V).

[0139] When the power processing module detects that the mains voltage is normal or too high, the switch U1 in the reference comparison module is turned off (K-terminal high resistance state). At this time, the VCC power supply is applied to the base of the switch Q1 in the power control module through resistor R4, diode D4 and Zener diode ZD1. The diode D4 is used to isolate or prevent reverse polarity, and the Zener diode ZD1 is used to limit the voltage and protect the base of Q1.

[0140] After receiving the voltage signal, switch Q1 obtains sufficient base current and turns on.

[0141] After switch Q1 is turned on, its collector (i.e., the base or gate of Q2) is pulled low to near ground potential, and this low level causes power switch Q2 to turn off.

[0142] When the low level turns off Q2, the power control module disconnects the load from the power grid / DC bus, and the load stops working and is protected.

[0143] The protection circuit provided in this application embodiment achieves effective monitoring of the mains voltage and low-voltage protection function by using the reference voltage and switching characteristics of the feedback device, combined with a simple resistor voltage divider and switching circuit. It is especially practical in areas with unstable power grids.

[0144] Please refer to the attached document. ​ The circuit diagram shown illustrates the control logic of the protection circuit in this application:

[0145] The core of the protection circuit shown in the figure is a voltage comparator (i.e., U1 in the figure), which compares the real-time sampled grid voltage with an accurate fixed reference voltage, outputs a high or low level signal according to the comparison result, thereby controlling the turn-on and turn-off of the subsequent power switching transistor, and finally implements the undervoltage protection function. Specifically:

[0146] After the grid alternating current is rectified by D1, D2, D3 and filtered by capacitor C, a pulsating direct current voltage VDD is obtained. The level of VDD directly reflects the effective value of the grid voltage. VDD is divided by a voltage divider network composed of resistors R1, R2 and R3, and a sampling voltage V_sample is generated at the connection point (or similar node) of R2 and R3.

[0147] A stable reference voltage V_ref is obtained by a voltage regulator diode (ZD1) or voltage division of a stable power supply through resistors (e.g., R6, R7). For example, the cathode of ZD1 is connected to VCC and the anode is grounded, so a stable negative reference (e.g., 3.3V or 5.6V) is provided at its anode. This V_ref value is the critical threshold for protection action, and the corresponding grid voltage value is the protection point. The protection point voltage can be changed by adjusting the resistance values of R1, R2 and R3.

[0148] After sampling is completed, the sampling voltage V_sample is sent to the inverting input terminal (-) of the comparator U1, and the reference voltage V_ref is sent to its non-inverting input terminal (+).

[0149] When the grid voltage is normal (high): the voltage value of V_sample > the voltage value of V_ref. At this time, the comparator U1 outputs a low level.

[0150] When the grid voltage is too low (undervoltage): V_sample < V_ref. At this time, the comparator U1 flips and outputs a high level.

[0151] The output of the comparator U1 drives the base of the first-stage switching transistor Q1 (usually an NPN-type triode).

[0152] When undervoltage is detected, U1 outputs a high level (during undervoltage): Q1 obtains base current and is saturated and conducts. After Q1 conducts, its collector voltage is pulled down to near ground potential.

[0153] When the voltage is normal, U1 outputs a low level: Q1 is cut off. Its collector voltage is pulled up to VDD or another power supply VCC by a pull-up resistor (e.g., R4).

[0154] The collector of Q1 controls the state of the second-stage switching transistor Q2, and Q2 then directly controls the gate of the power switching transistor Q3 (P-MOSFET).

[0155] The protection circuit provided in this application embodiment has a comparator-based scheme with extremely fast response speed (depending on the comparator's slew rate), high accuracy (more stable reference voltage), and prevents frequent circuit jumps when the grid voltage fluctuates at the critical point by reasonably designing the reference circuit and feedback.

[0156] In an optional embodiment, this application provides a power tool, which includes a control circuit, a motor, and a working component, wherein the control circuit includes at least the protection circuit described in the above embodiments.

[0157] In this control circuit, an external power supply is connected to a protection circuit, which is used to detect fluctuations in the external power supply.

[0158] The control circuit is connected to the motor, which is used to drive the working component.

[0159] For example, the control circuit may further include: a controller:

[0160] The controller can be connected to the output of the reference comparison module in the protection circuit to receive signals of voltage abnormalities in a timely manner.

[0161] For example, the circuit structure in the power tool includes: a reference comparison module connected to a fault diagnosis pin in the controller via an optocoupler isolation circuit, thereby receiving the control signal output by the reference comparison module.

[0162] The controller can also generate fault handling strategies based on abnormal voltage signals.

[0163] For example, the circuit structure in a power tool includes: the output terminal of the switching device in the power control module is connected to the relay drive coil, and after receiving a control signal of abnormal voltage, the relay promptly closes the port circuit to protect the power tool.

[0164] Correspondingly, if the power supply voltage is within the normal range, the drive module establishes a closed loop with the power supply module and controls the motor operation according to the controller's commands.

[0165] The power tool provided in this application uses a protection circuit to immediately cut off power when undervoltage is detected, preventing the motor from stalling and burning out, thereby extending the motor's lifespan.

[0166] In an optional embodiment, this application provides a charger that includes a control circuit, wherein the control circuit includes at least the protection circuit described in the above embodiments.

[0167] The control circuit controls the connection and disconnection of the charging circuit between the power input terminal and the power output terminal through the protection circuit. If an abnormal fluctuation in the input power voltage signal is detected, the charging circuit will be disconnected in time.

[0168] For example, the control circuit may further include: a controller:

[0169] The controller can be connected to the output of the reference comparison module in the protection circuit to receive voltage fault signals in a timely manner and generate fault handling strategies.

[0170] The charger provided in this application can provide voltage protection when discharging based on the above-mentioned protection circuit, so as to prevent the lithium battery from being reverse discharged at low voltage.

[0171] This invention uses terms such as "first" and "second" to describe various types of information, but such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another; for example, without departing from the scope of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information.

[0172] In this utility model, unless otherwise explicitly specified and limited, terms such as "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meanings of the above-mentioned terms in this utility model according to the specific circumstances.

[0173] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0174] The above description is merely a preferred embodiment of this utility model and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of this utility model is not limited to the specific combination of the above-described technical features, but should also cover other technical solutions formed by any combination of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this utility model.

Claims

1. A protection circuit, characterized in that, The protection circuit, applied to power tools or chargers, includes: The power processing module, reference comparison module, power control module, and drive module are included. The input terminal of the power processing module is connected to the power supply, and the output terminal is connected to the reference comparison module. The power processing module is used to divide and process the electrical signal input by the power supply to generate the target voltage signal. The reference terminal of the reference comparison module receives the target voltage signal, and the output terminal generates a control signal; The input terminal of the power control module is connected to the reference comparison module to receive the control signal, and the output terminal generates the drive level. The drive module, controlled by the drive level, switches the power supply path to the load. The power processing module includes a threshold adjustment circuit, which includes multiple resistors to adjust the range of the voltage threshold in the voltage divider process by adjusting the resistance values ​​of the resistors.

2. The protection circuit according to claim 1, characterized in that, The power processing module includes a rectifier bridge circuit and a filter circuit. The AC input terminal of the rectifier bridge circuit is connected to an AC power supply, and the DC output terminal is grounded through the filter circuit to generate a DC bus voltage.

3. The protection circuit according to claim 1, characterized in that, The threshold adjustment circuit in the power processing module includes at least two resistors, which form a voltage divider circuit. The voltage divider point in the voltage divider circuit is connected to the input terminal of the reference comparison module.

4. The protection circuit according to claim 1, characterized in that, The reference comparison module in the protection circuit includes: Reference voltage source and comparator; One end of the comparator input is connected to the reference voltage source, and the other end of the input is connected to the power processing module; The output of the comparator is connected to the driver module; The comparator is used to detect the difference between the target voltage signal and the preset voltage threshold. It generates control signals based on the detection results to control the connection and disconnection of the circuit between the power control module and the load.

5. The protection circuit according to claim 4, characterized in that, The benchmark comparison module also includes: an isolator. The input terminal of the isolator is connected to the comparator, and the output terminal is connected to the power control module.

6. The protection circuit according to claim 1, characterized in that, The power control module in the protection circuit includes: a first switch module and a second switch module; The input terminal of the first switch module is connected to the reference comparison module, and the output terminal is connected to the second switch module; The second switch is connected to the drive module; The first switch module responds to the control signal by either disconnecting or connecting the second switch module.

7. The protection circuit according to claim 6, characterized in that, The first switching module includes: a transistor switch; The emitter of the transistor is grounded, and the base is connected to the reference comparison module; Furthermore, the collector is connected to the power supply voltage via a pull-up resistor; If the transistor switch is turned on, a level signal is output to drive the second switch module.

8. The protection circuit according to claim 6, characterized in that, The second switching module includes: a MOS switch; The gate of the MOS switch is connected to the first switch module; Its source is connected to the DC bus voltage output by the power processing module, and its drain is connected to the load.

9. A power tool, characterized in that... The power tool includes a control circuit, a motor, and a working part, wherein the control circuit includes at least the protection circuit described in any one of claims 1 to 8; The control circuit is connected to the motor, which is used to drive the working component.

10. A charger, characterized in that... The charger includes a control circuit, which includes at least the protection circuit as described in any one of claims 1 to 8.

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