TWI854385B - Power management device for power tools - Google Patents

Abstract

A power management device for an electric tool includes a pressure relief circuit, a voltage detection module and a control module, wherein the pressure relief circuit is connected in parallel with a motor drive module, the pressure relief circuit includes a power consumption element and a pressure relief switch element connected in series, and the pressure relief switch element can be controlled to be turned on or off; the voltage detection module detects the positive terminal and the The control module sets a threshold voltage according to the voltage detected by the voltage detection module, and when the voltage detected by the voltage detection module is less than the threshold voltage, the control module keeps the voltage relief switch element turned off, and when the voltage detected by the voltage detection module exceeds the threshold voltage, the control module controls the voltage relief switch element to be turned on. In this way, the threshold voltage of the voltage relief circuit can be actively set.

Description

Power management device for power tools

The present invention relates to power tools; in particular, to a power management device for power tools.

Power tools use the rotation of motors to drive workpieces, saving manpower. However, when the motor brakes instantly from a rotating state, a back electromotive force will be generated, and the back electromotive force will flow back from the motor to the circuit or power supply before the motor. The higher the speed of the motor, the greater the voltage of the back electromotive force generated when braking. Therefore, the back electromotive force may damage the circuit or power supply before the motor.

To solve the above problem, a common practice is to install a transient voltage suppressor (TVS) before the motor. The transient voltage suppressor will conduct when the voltage of the back EMF is greater than the breakdown voltage, forming a discharge path for the back EMF to prevent the back EMF from damaging the circuit or power supply before the motor.

However, transient voltage suppressors are passive components with a fixed breakdown voltage. Power tool manufacturers cannot change the breakdown voltage of transient voltage suppressors. Therefore, if the voltage of the back EMF to be suppressed needs to be changed, the only option is to replace the transient voltage suppressor with one that meets the required breakdown voltage.

In view of this, an object of the present invention is to provide a power management device for an electric tool, which can actively set the threshold voltage of the discharge path of the back electromotive force of the motor.

In order to achieve the above-mentioned purpose, the present invention provides a power management device for an electric tool, which is electrically connected between a power connection port of the electric tool and a motor drive module, wherein the power connection port has a positive terminal and a negative terminal, the positive terminal and the negative terminal are used to connect a power source, and the motor drive module is electrically connected to the positive terminal and the negative terminal; the power management device includes a pressure relief circuit, a voltage detection module and a control module, wherein the pressure relief circuit is connected in parallel with the motor drive module, and the pressure relief circuit includes a power consumption element connected in series. The invention relates to a device for controlling a voltage relief switch element and a voltage relief switch element, wherein the voltage relief switch element can be controlled to be turned on or off; the voltage detection module detects the voltage between the positive terminal and the negative terminal; the control module is electrically connected to the voltage relief switch element and the voltage detection module, and the control module sets a threshold voltage according to the voltage detected by the voltage detection module; when the voltage detected by the voltage detection module is less than the threshold voltage, the control module keeps the voltage relief switch element turned off, and when the voltage detected by the voltage detection module exceeds the threshold voltage, the control module controls the voltage relief switch element to be turned on.

The effect of the present invention is that the power management device can actively set the threshold voltage of the pressure relief circuit in response to the voltage of the power source connected to the power connection port, so that when the voltage of the back electromotive force generated when the motor brakes is greater than the threshold voltage, the pressure relief circuit is actively controlled to immediately form a discharge path of the back electromotive force.

In order to explain the present invention more clearly, a preferred embodiment is described in detail with reference to the drawings. Please refer to FIG1 , which shows a power management device 1 for a power tool according to a first preferred embodiment of the present invention. The power management device 1 is electrically connected between a power connection port 100 and a motor drive module 200 of the power tool.

The power connection port 100 has a positive terminal 100a and a negative terminal 100b, and the positive terminal and the negative terminal 100b are detachably connected to a power source. In this embodiment, the power source is a battery 300, such as a lithium battery, but it is not limited thereto. The power source can also be a DC power supply. The positive terminal 100a and the negative terminal 100b are respectively used to contact the positive electrode 300a and the negative electrode 300b of the battery 300. The two power input terminals 200a and 200b of the motor drive module 200 are electrically connected to the positive terminal 100a and the negative terminal 100b respectively to receive power from the battery 300, and the motor drive module 200 is connected to a motor 400 and a control device (not shown). The motor 400 can be a brushless motor, but is not limited thereto, and can also be a brushed motor. The control device is used to output a control signal to the motor drive module 200, so that the motor drive module 200 drives the motor 400 to rotate.

The power management device 1 includes a voltage relief circuit 10, a voltage detection module 16 and a control module 18.

The voltage relief circuit 10 is connected in parallel with the motor drive module 200 to provide a discharge path for the back electromotive force generated when the motor 400 brakes. The voltage relief circuit 10 includes a power consumption element 12 and a voltage relief switch element 14 connected in series. In this embodiment, the power consumption element 12 is a power resistor, one end of which is electrically connected to the positive terminal 100a and the power input terminal 200a. The voltage relief switch element 14 has a first end 142 and a second end 144. The first end 142 is electrically connected to the other end of the power consumption element 12, and the second end 144 is electrically connected to the negative terminal 100b and the power input terminal 200b. The voltage relief switch element 14 further has a third terminal 146, and the third terminal 146 is electrically connected to the control module 18. The voltage relief switch element 14 can be controlled by the control module 18 to turn on or off the first terminal and the second terminal. The voltage relief switch element 14 can be a transistor, such as FET, BJT, but not limited thereto, and can also be a controllable element such as a relay that can be turned on or off. When the voltage relief switch element 14 is turned on, the voltage relief circuit 10 forms a discharge path. In practice, the positions of the power consumption element 12 and the voltage relief switch element 14 can also be swapped, as long as they are maintained in series.

The voltage detection module 16 is used to detect the voltage between the positive terminal 100a and the negative terminal. In this embodiment, the voltage detection module 16 includes a voltage detection circuit 162. The voltage detection circuit 162 is electrically connected to the positive terminal 100a. The voltage detection circuit 162 can be, for example, a resistor divider circuit.

The control module 18 is electrically connected to the voltage relief switch element 14 and the voltage detection module 16, and sets a threshold voltage according to the voltage detected by the voltage detection module 16. The control module 18 may be, for example, a microcontroller. Preferably, when the battery 300 is installed to the power connection port 100 and the positive electrode 300a and the negative electrode 300b of the battery are connected to the positive terminal 100a and the negative terminal 100b, the control module 18 immediately detects the voltage of the battery 300 and sets the threshold voltage. In this embodiment, a predetermined voltage range corresponding to the battery is pre-set in the control module 18, and the predetermined voltage range has a lower limit voltage and an upper limit voltage. Taking a battery with a rated voltage specification of 40V as an example, the lower limit voltage of the predetermined voltage range is 30V and the upper limit voltage is 42V.

When the control module 18 detects that the voltage of the battery falls within the predetermined voltage range through the voltage detection module 16, the control module 18 sets the threshold voltage according to the predetermined voltage range, and sets the threshold voltage to be greater than the upper voltage limit. The control module 18 adds a voltage difference to the upper voltage limit as the threshold voltage, and the voltage difference between the threshold voltage and the upper voltage limit is greater than or equal to 5V. In this embodiment, the voltage difference is 6V. For example, for a battery with a rated voltage specification of 40V, the threshold voltage is 48V. In other words, when the control module determines that the battery voltage is in the range of 30V to 42V, the threshold voltage is set to 48V.

Alternatively, the control module 18 may also pre-store a correspondence table of a plurality of predetermined voltage ranges and a plurality of threshold voltages, as shown in Table 1 below. The control module 18 sets one of the predetermined voltage ranges as the predetermined voltage range applicable to the power tool, for example, 30V~42V is selected as the predetermined voltage range of the power tool of this embodiment. When the control module 18 measures the voltage of the battery through the voltage detection module 16, the predetermined voltage range set in the correspondence table can be compared with the voltage of the battery to obtain the corresponding threshold voltage.

Table 1 Correspondence between the preset voltage range and the threshold voltage Predetermined voltage range Threshold voltage 9V~12.6V 18.6V 15V~21V 27V 30V~42V 48V 45V~63V 70V

After setting the threshold voltage, the control module 18 keeps the voltage relief switch element 14 turned off when the voltage detected by the voltage detection module 16 is less than the threshold voltage, and controls the voltage relief switch element 14 to be turned on when the control module 18 determines that the voltage detected by the voltage detection module 16 exceeds the threshold voltage. In other words, when the control module 18 determines that no back electromotive force is generated or the generated back electromotive force is small, the voltage relief switch element 14 is not turned on; when the control module 18 determines that the back electromotive force is too large, the voltage relief switch element 14 is turned on to allow the power consumption element to consume the back electromotive force.

Thus, the control module 18 can actively set the threshold voltage of the voltage relief circuit 10 in response to the voltage applied to the power connection port 100, and actively monitor whether the motor 400 generates excessive back electromotive force when braking (i.e., the voltage applied to the power connection port 100 is greater than the threshold voltage), and provide a discharge path for the back electromotive force when the back electromotive force is too large to prevent the back electromotive force from reversely charging the battery and causing damage to the battery 300. In addition, when the power source is a DC power supply, it can also prevent the back electromotive force from flowing back to the DC power supply and causing damage to the DC power supply.

FIG2 shows a power management device 2 for an electric tool according to a second preferred embodiment of the present invention, which is based on the structure of the first embodiment and further includes a main switch element 20. The main switch element 20 has a first end 202 and a second end 204, wherein the first end 202 is electrically connected to the positive terminal 100a, and the second end 204 is electrically connected to the power input end 200a of the motor drive module 200, and the motor drive module 200 is electrically connected to the positive terminal 100a through the main switch element 20. The main switch element 20 further has a third end 206, wherein the third end 206 is electrically connected to the control module 18, and the main switch element 20 can be controlled by the control module 18 to make the first end 202 and the second end 204 conductive or inconductive. The main switch element 20 can be a transistor, such as FET, BJT, but is not limited thereto, and can also be a controllable element such as a relay that can be turned on or off.

The voltage detection circuit 162 of the voltage detection module 16 is electrically connected to the positive terminal 100 a and the first end 202 of the main switch element 20 .

In addition, in this embodiment, the power management device 2 further includes a warning module 22, and the warning module 22 is electrically connected to the control module 18. The warning module 22 can be a light-emitting element (such as an LED) and/or a sound-emitting element (such as a buzzer) for emitting light and/or sound warnings.

When the battery 300 is installed to the power connection port 100 and the positive pole 300a and the negative pole 300b of the battery 300 are connected to the positive terminal 100a and the negative terminal 100b, the control module 18 has not yet controlled the main switch element 20 to be turned on, and the main switch element 20 remains in the cut-off state. At this time, the control module 18 detects the voltage between the positive terminal 100a and the negative terminal 100b through the voltage detection module 16. When the voltage detected by the voltage detection module 16 falls within the corresponding predetermined voltage range, the control module 18 sets the threshold voltage according to the predetermined voltage range and controls the first end 202 and the second end 204 of the main switch element 20 to conduct. In this way, the power of the battery can be supplied to the motor drive module. The control module 18 sets the threshold voltage by adding the voltage difference to the upper limit voltage, or obtaining the threshold voltage from a corresponding table between the predetermined voltage range and the threshold voltage.

Before the control module 18 controls the main switch element 20 to conduct, when the control module 18 determines that the voltage detected by the voltage detection module 16 exceeds or is lower than the predetermined voltage range, it means that the voltage of the battery does not meet the voltage required by the power tool, and the first end and the second end of the main switch element 20 are cut off to avoid excessively high voltage causing damage to the motor drive module 200 and/or the motor 400, or too low voltage causing the motor drive module 200 and/or the motor 400 to fail to operate as expected. In addition, the control module 18 controls the warning module 22 to issue a warning to prompt the user.

After the control module 18 controls the main switch element 20 to be turned on, when the control module 18 determines that the voltage detected by the voltage detection module 16 is less than the threshold voltage, the voltage relief switch element 14 is kept turned off. When the control module 18 determines that the voltage detected by the voltage detection module 16 exceeds the threshold voltage, the voltage relief switch element 14 is controlled to be turned on to allow the power consumption element 12 to consume the back electromotive force.

FIG3 shows a power management device 3 for an electric tool according to a third preferred embodiment of the present invention, which is based on the structure of the second embodiment, except that the voltage detection module 24 includes another voltage detection circuit (hereinafter referred to as the second voltage detection circuit 244) in addition to the original voltage detection circuit (hereinafter referred to as the first voltage detection circuit 242). The second voltage detection circuit 244 is electrically connected between the second terminal 204 of the main switch element 20 and the power input terminal 200a of the motor drive module 200.

When the voltage detected by the first voltage detection circuit 242 falls within the corresponding predetermined voltage range, the control module 18 sets the threshold voltage according to the predetermined voltage range and controls the first end 202 and the second end 204 of the main switch element 20 to be connected. When the control module 18 determines that the voltage detected by the first voltage detection circuit 242 exceeds or is lower than the predetermined voltage range, the first end 202 and the second end 204 of the main switch element 20 are kept disconnected and the warning element is controlled to issue a warning.

In addition, before the control module 18 controls the first terminal 202 and the second terminal 204 of the main switch element 20 to conduct, the second voltage detection circuit 244 can be used to determine whether the main switch element 20 has excessive leakage current or short circuit. More specifically, in an ideal situation, when the main switch element 20 is turned off, no leakage current should be generated or the leakage current should be very small, so the voltage measured by the second voltage detection circuit 244 should be 0V or close to 0V. When the control module 18 determines that the voltage detected by the second voltage detection circuit 244 is greater than a predetermined voltage, the main switch element 20 is kept turned off and the warning module 22 is controlled to issue a warning to remind the user that the main switch element 20 is damaged. The predetermined voltage may be, for example, greater than 0.5V.

After the control module 18 controls the conduction between the first end 202 and the second end 204 of the main switch element 20, it compares the voltage detected by the second voltage detection circuit 244 with the threshold voltage to determine whether to control the voltage relief switch element 14 to be turned on. When the control module 18 determines that the voltage detected by the second voltage detection circuit 244 exceeds the threshold voltage, the voltage relief switch element 14 is controlled to be turned on to allow the power consumption element 12 to consume the back electromotive force.

The power management device 3 of this embodiment further includes a current detection circuit 26, which is electrically connected between the power connection port 100 and the motor drive module 200. In this embodiment, the current detection circuit 26 is connected between the negative terminal 100b of the power connection port 100 and the power input terminal 200b of the motor drive module 200. The control module 18 is electrically connected to the current detection circuit 26, and when the current detected by the current detection circuit 26 is greater than a predetermined current, the control module 18 controls the first terminal 202 and the second terminal 204 of the main switch element 20 to be cut off. The preset current can be set according to the specifications of the power tool to detect and protect against short circuits.

The power management device 3 of the present embodiment further includes a temperature detection module 28, which is electrically connected to the control module 18. The temperature detection module 28 has a plurality of temperature detectors 282, which are respectively disposed at the pressure relief switch element 14, the main switch element 20 and the motor drive module 200, and respectively detect the temperatures of the pressure relief switch element 14, the main switch element 20 and the motor drive module 200.

When the temperature of any one of the pressure relief switch element 14, the main switch element 20 and the motor drive module 200 detected by the temperature detection module 28 is greater than a predetermined temperature, the control module 18 controls the first end 202 and the second end 204 of the main switch element 20 to be cut off, and controls the warning module 22 to issue a warning to prompt the user. In this way, the power can be cut off immediately to prevent the pressure relief switch element 14, the main switch element 20 and the motor drive module 200 from being damaged due to excessive temperature.

As described above, the power management device of the power tool of the present invention can actively set the corresponding threshold voltage according to the voltage of the power source connected to the power connection port, so as to form a discharge path of the back electromotive force immediately when the back electromotive force generated when the motor brakes is too large, so as to prevent the excessive back electromotive force from flowing back to the power source and causing damage. And it can achieve the effect of accurately controlling the discharge timing of the back electromotive force.

The above description is only the preferred embodiment of the present invention. Any equivalent changes made by applying the present invention specification and the scope of patent application should be included in the patent scope of the present invention.

1,2,3: Power management device 10: Pressure relief circuit 12: Power consumption element 14: Pressure relief switch element 142: First end 144: Second end 146: Third end 16: Voltage detection module 162: Voltage detection circuit 18: Control module 20: Main switch element 202: First end 204: Second end 206: Third end 22: Warning module 24: Voltage detection module 242: First voltage detection circuit 244: Second voltage detection circuit 26: Current detection circuit 28: Temperature detection module 282: Temperature detector 100: Power connection port 100a: Positive terminal 100b: Negative terminal 200: Motor drive module 200a, 200b: Power input terminal 300: Battery 300a: Positive terminal 300b: Negative terminal 400: Motor

FIG. 1 is a schematic diagram of a power management device for an electric tool according to the first preferred embodiment of the present invention. FIG. 2 is a schematic diagram of a power management device for an electric tool according to the second preferred embodiment of the present invention. FIG. 3 is a schematic diagram of a power management device for an electric tool according to the third preferred embodiment of the present invention.

1: Power management device 10: Pressure relief circuit 12: Power consumption element 14: Pressure relief switch element 142: First terminal 144: Second terminal 146: Third terminal 16: Voltage detection module 162: Voltage detection circuit 18: Control module 100: Power connection port 100a: Positive terminal 100b: Negative terminal 200: Motor drive module 200a, 200b: Power input terminal 300: Battery 300a: Positive pole 300b: Negative pole 400: Motor

Claims (10)

A power management device for an electric tool is electrically connected between a power connection port of the electric tool and a motor drive module, wherein the power connection port has a positive terminal and a negative terminal, wherein the positive terminal and the negative terminal are used to connect a power source, and the motor drive module is electrically connected to the positive terminal and the negative terminal; the power management device comprises: a pressure relief circuit connected in parallel with the motor drive module, wherein the pressure relief circuit comprises a series connection a power consumption element and a pressure relief switch element, the pressure relief switch element can be controlled to be turned on or off; a voltage detection module, detecting the voltage between the positive terminal and the negative terminal; a control module, electrically connected to the pressure relief switch element and the voltage detection module, the control module sets a threshold voltage according to the voltage detected by the voltage detection module; the control module turns on when the voltage detected by the voltage detection module is less than the threshold voltage; When the voltage detected by the voltage detection module exceeds the threshold voltage, the pressure relief switch element is controlled to be turned on; and a main switch element having a first end and a second end, the first end being electrically connected to the positive terminal, the second end being electrically connected to the motor drive module, the motor drive module being electrically connected to the positive terminal through the main switch element; the main switch element can be controlled to The first end and the second end are turned on or off; the control module is electrically connected to the main switch element. When the voltage detected by the voltage detection module falls within a predetermined voltage range, the control module sets the threshold voltage according to the predetermined voltage range and controls the first end and the second end of the main switch element to be turned on, wherein the predetermined voltage range has an upper limit voltage, and the threshold voltage is greater than the upper limit voltage. The power management device of the electric tool as described in claim 1, wherein the control module detects the voltage between the positive terminal and the negative terminal through the voltage detection module when the main switch element is turned off. A power management device for an electric tool as described in claim 2, wherein the voltage difference between the threshold voltage and the upper limit voltage is greater than or equal to 5V. The power management device of the electric tool as described in claim 1, wherein the voltage detection module includes a first voltage detection circuit and a second voltage detection circuit, the first voltage detection circuit is electrically connected between the positive terminal and the first end of the main switch element; the second voltage detection circuit is electrically connected between the second end of the main switch element and the motor drive module; when the voltage detected by the first voltage detection circuit falls within the predetermined voltage range, the control module sets the threshold voltage according to the predetermined voltage range, and compares the voltage detected by the second voltage detection circuit with the threshold voltage to determine whether to control the voltage relief switch element to be turned on or not. As described in claim 4, before the control module controls the conduction between the first end and the second end of the main switch element, when it is determined that the voltage detected by the second voltage detection circuit is greater than a predetermined voltage, the main switch element is kept turned off. The power management device of the electric tool as described in claim 5 includes a warning module electrically connected to the control module, and the control module controls the warning module to issue a warning when the voltage detected by the second voltage detection circuit is greater than the predetermined voltage. The power management device of the power tool as described in claim 1 comprises a current detection circuit electrically connected between the power connection port and the motor drive module; the control module is electrically connected to the current detection circuit, and when the current detected by the current detection circuit is greater than a predetermined current, the first end and the second end of the main switch element are controlled to be cut off. The power management device of the electric tool as described in claim 1 includes a temperature detection module electrically connected to the control module, the temperature detection module detects the temperature of the pressure relief switch element; when the temperature detected by the temperature detection module is greater than a predetermined temperature, the control module controls the first end and the second end of the main switch element to be cut off. The power management device of the electric tool as described in claim 1 includes a temperature detection module electrically connected to the control module, the temperature detection module detects the temperature of the main switch element; when the temperature detected by the temperature detection module is greater than a predetermined temperature, the control module controls the first end and the second end of the main switch element to be cut off. The power management device of the electric tool as described in claim 8 or 9 includes a warning module electrically connected to the control module, and the control module controls the warning module to issue a warning when the temperature detected by the temperature detection module is greater than the predetermined temperature.

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