CN109980303A - A kind of battery pack and electric tool combination suitable for electric tool - Google Patents

Abstract

The invention discloses a battery pack suitable for electric tools, comprising: a battery pack and a battery management system; the battery management system includes a voltage conversion circuit and a voltage acquisition circuit, and the input end of the voltage acquisition circuit is electrically connected with the output end of the voltage conversion circuit The voltage conversion circuit includes a differential amplifier circuit and a proportional amplifier circuit, the input end of the proportional amplifier circuit is electrically connected with the output end of the differential amplifier circuit, and the output end of the proportional amplifier circuit is used for outputting the converted voltage. The invention also discloses a power tool combination comprising the above battery pack. The battery pack suitable for electric tools of the present invention improves the sampling accuracy and sampling range of the voltage of a single cell, and can also be used in the case that the number of single cells in the battery pack is large and the voltage is relatively high, and is not subject to a single cell in series. The influence of the number of cells and the magnitude of the power supply voltage of the proportional amplifier circuit.

Description

A battery pack suitable for power tools and power tool combination

technical field

The present invention relates to a battery pack suitable for electric tools and an electric tool combination.

Background technique

Due to the convenience of use of power tools, its application range is getting wider and wider, and the output power requirements are getting higher and higher. Therefore, the output current requirements of battery packs that provide electrical energy for power tools are also increasing. The number of single-cell batteries also increases. In order to manage and monitor the battery pack, a battery management system (BATTERY MANAGEMENT SYSTEM, BMS) is used. In BMS, it is often necessary to sample the voltage of a single-cell battery for battery protection judgment, balance, Estimation of State of Charge (SOC) and State of Health (SOH), the voltage of a single cell is the most basic input data for battery management by BMS.

The acquisition of single-cell battery voltage is generally completed by the single-chip microcomputer in the BMS, and the analog signal input port of the single-cell battery voltage acquisition by the single-cell battery has a limit on the amplitude of the input voltage. , 3.3V, etc.). When the positive voltage of the single-cell battery exceeds the voltage amplitude limit of the analog signal input port of the microcontroller, a sampling circuit needs to be designed to convert the voltage of the single-cell battery to the voltage amplitude limit of the analog signal input port of the microcontroller.

In the prior art, when a plurality of single-cell batteries are connected in series to form a battery pack and the number of series-connected batteries is relatively large (for example, n is greater than 8), the single-cell battery with a higher series position (such as the 6th or above) The positive and negative voltages (such as Vbn, where n is generally greater than 6) added to the forward or reverse input of the operational amplifier in the differential circuit will exceed the supply voltage of the operational amplifier (commonly 5V, 12V or 15V), so It will cause the operational amplifier to not work properly and affect the voltage sampling. Moreover, when the battery is not used, the sampling circuit of the prior art will form a discharge loop to discharge the battery, which affects the service life of the battery.

SUMMARY OF THE INVENTION

The invention provides a battery pack suitable for electric tools, which can improve the sampling accuracy and sampling range of the voltage of a single cell.

In order to achieve above-mentioned goal, the present invention adopts following technical scheme:

A battery pack suitable for a power tool, the battery pack comprising: a housing; an adapter part for connecting the power tool to supply power to the power tool; a battery pack accommodated in the housing, the The battery pack includes a plurality of single-cell batteries; a battery management system, the battery management system includes a voltage conversion circuit and a voltage acquisition circuit, the input end of the voltage acquisition circuit is electrically connected with the output end of the voltage conversion circuit; the voltage The conversion circuit includes: a differential amplifier circuit, including two differential input terminals and one output terminal, the two differential input terminals are used to input the voltage to be sampled; the two differential input terminals are respectively connected to two ends of a single-cell battery. connected, or electrically connected to both ends of a series circuit formed by at least two single-cell batteries connected in series; a proportional amplifier circuit, including an input end and an output end, the input end of the proportional amplifier circuit and the output of the differential amplifier circuit The output terminal of the proportional amplifier circuit is electrically connected to the input terminal of the voltage acquisition circuit, and the output terminal of the proportional amplifier circuit is used for outputting the converted voltage.

Specifically, the differential amplifier circuit includes a first operational amplifier, a first resistance unit, a second resistance unit, a third resistance unit and a fourth resistance unit; the inverting input end of the first operational amplifier is connected to the first operational amplifier. The first end of the resistance unit is electrically connected, the second end of the first resistance unit is used as one of the two differential input ends; the forward input end of the first operational amplifier is connected to the second end of the resistance unit. The first end is electrically connected, and the second end of the second resistance unit is used as the other of the two differential input ends; the inverting input end of the first operational amplifier is connected with the third resistance unit through the third resistance unit. The output end of the first operational amplifier is electrically connected to the input end of the proportional amplifier circuit, and the forward input end of the first operational amplifier is grounded through the fourth resistance unit.

Specifically, the first resistance unit, the second resistance unit, the third resistance unit, and the fourth resistance unit are respectively composed of one or more resistances in series and parallel connection.

Specifically, the resistance value of the first resistance unit is equal to the resistance value of the second resistance unit; the resistance value of the third resistance unit is equal to the resistance value of the fourth resistance unit.

Specifically, the first operational amplifier further includes a power input terminal; the voltage of the forward input terminal or the reverse input terminal of the first operational amplifier is lower than the voltage input from the power input terminal.

Specifically, the proportional amplifier circuit includes a second operational amplifier, a fifth resistance unit, a sixth resistance unit and a seventh resistance unit; the inverting input end of the second operational amplifier communicates with the fifth resistance unit through the fifth resistance unit. The output end of the differential amplifier circuit is electrically connected, the reverse input end of the second operational amplifier is electrically connected with the output end of the second operational amplifier through the sixth resistance unit; the forward input end of the second operational amplifier is electrically connected through The seventh resistance unit is grounded.

Specifically, the fifth resistance unit, the sixth resistance unit, and the seventh resistance unit are respectively composed of one or more resistances in series and parallel.

Specifically, the product of the amplification factor of the differential amplification circuit and the amplification factor of the proportional amplification circuit is equal to the target amplification factor.

Specifically, the battery pack further includes a first switch, one end of the first switch is electrically connected to the ground wire in the battery pack, and the other end is electrically connected to the ground wire of the voltage conversion circuit; the first switch is electrically connected to the ground wire of the battery pack. The switch is configured to be turned on during operation of the battery pack and turned off when the battery pack is at rest.

Specifically, the output voltage of the output terminal of the voltage conversion circuit is less than or equal to the limit range of the input voltage of the voltage acquisition circuit.

Specifically, the number of single cells connected in series in the battery pack is greater than or equal to six.

Specifically, the single-cell battery is composed of at least one or more batteries connected in parallel.

A power tool combination, comprising a power tool and a battery pack as described above, the battery pack can be installed to the power tool to provide electrical energy for the power tool, the power tool comprises: a housing; a tool accessory for The functions of the power tool are realized; an output shaft supports the tool accessories; a motor is accommodated in the housing and is used for outputting a driving force to drive the output shaft to rotate; the motor is operably connected to the output shaft connection; the battery pack joint part is used for connecting the battery pack.

The present invention further provides a battery management system, the battery management system includes a battery pack, a voltage acquisition circuit and the voltage conversion circuit provided in any one of the embodiments, the battery pack includes a plurality of single-cell batteries; The input terminal is electrically connected to the output terminal of the voltage conversion circuit;

The two differential input terminals of the voltage conversion circuit are respectively electrically connected to both ends of a single-cell battery, or are respectively electrically connected to both ends of a series circuit formed by at least two single-cell batteries connected in series.

Specifically, the battery management system further includes:

a first switch, one end of the first switch is electrically connected to the ground wire in the battery pack, and the other end of the first switch is electrically connected to the ground wires of the differential amplifier circuit and the voltage conversion circuit;

The first switch is configured to be turned on during the operation of the battery pack and turned off when the battery pack is at rest.

Specifically, the first switch is a mechanical switch or a semiconductor switch.

Specifically, the output voltage of the output terminal of the voltage conversion circuit is less than or equal to the limit range of the input voltage of the voltage acquisition circuit.

Beneficial effects: the battery pack suitable for electric tools of the present invention improves the sampling accuracy and sampling range of the voltage of a single cell, and can also be used when the number of single cells in the battery pack is large and the voltage is relatively high. The cell voltage sampling result is not affected by the number of single cells connected in series and the magnitude of the power supply voltage of the proportional amplifier circuit.

Description of drawings

1 is a schematic diagram of the appearance structure of a battery pack as an embodiment;

2 is a schematic diagram of the appearance structure of a battery pack as another embodiment;

3 is a schematic structural diagram of a voltage conversion circuit provided by the prior art;

4 is a schematic structural diagram of another voltage conversion circuit provided by the prior art;

5 is a schematic structural diagram of a voltage conversion circuit provided by an embodiment of the present invention;

6 is a schematic structural diagram of another voltage conversion circuit provided by an embodiment of the present invention;

7 is a schematic structural diagram of another voltage conversion circuit provided by an embodiment of the present invention;

8 is a schematic structural diagram of another voltage conversion circuit provided by an embodiment of the present invention;

9 is a schematic structural diagram of a battery management system provided by an embodiment of the present invention;

10 is a schematic structural diagram of another battery management system provided by an embodiment of the present invention;

Figure 11 is a power tool combination as an embodiment;

FIG. 12 is a power tool combination as another embodiment.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, the drawings only show some but not all structures related to the present invention.

The battery pack of the present invention can be various types of battery packs. The battery pack 10 includes but is not limited to: a housing 11; an adapter part 12 for connecting a power tool to supply power to the power tool; a battery pack 13, which is accommodated in Inside the casing, the battery pack includes a plurality of single-cell batteries 131 .

1, as an embodiment of the battery pack 10, the battery pack 10 includes but is not limited to: a housing 11; an adapter 12 for connecting to a power tool to supply power to the power tool; a battery pack 13, accommodated in Inside the casing 11 , the battery pack 13 includes a plurality of single-cell batteries 131 , and each of the single-cell batteries 131 is connected in series or in parallel through a connection assembly 132 .

The battery pack 13 is an electrical energy container that stores electrical energy in the battery pack 10, which can store or output electrical energy through mutual conversion of electrical energy and chemical energy. The conversion realizes the storage and output of electrical energy. The battery pack 13 stores electrical energy when charged, and the battery pack 13 is capable of supplying its stored electrical energy to an electrical appliance when connected to an electrical appliance such as a power tool.

The battery pack 13 includes a plurality of single-cell batteries 131. Each single-cell battery 131 can provide a certain amount of electrical energy and has a positive and negative electrode that can be physically connected. connected in parallel. The single-cell battery 131 can be a cylindrical lithium battery as shown in FIG. 1 , whose nominal voltage is 4V, and the battery pack 10 shown in FIG. 1 can output a voltage of 56V, so it has at least 14 battery cells connected in series. The battery pack 10 can be applied to electric tools such as lawn mowers and snow blowers that require high output power. The battery pack 10 also includes a circuit board (not shown) on which circuit components, such as circuit components constituting a battery management system, are disposed.

Referring to FIG. 2 , as another embodiment of a battery pack 20 , the battery pack 20 is a wearable battery pack, including a battery pack body 21 and a wearable device 22 . The battery pack body 21 is used to provide a power source for the power tool, and the wearable device 22 is worn by the user, so that the user can carry the battery pack body 21 on the back of the user through the wearable device 22 . The battery pack body 21 has an adapter portion 23 , a battery pack 24 , and a casing 211 for accommodating the battery pack 24 .

The case 211 is generally in the shape of a box, and the battery pack 24 is accommodated in the case 211 . The wearable battery pack 20 has a large electric capacity, and the battery pack 24 includes a plurality of single-cell batteries 241, and the plurality of single-cell batteries 241 are connected in series or in parallel through connecting components (not shown), so that the wearable battery pack 24 can be connected in series or in parallel. The battery pack 20 can output relatively large electric power. Specifically, the output voltage of the battery pack 20 is at least 56V, and the single-cell battery can use the cylindrical rechargeable lithium battery shown in FIG. 2, and its nominal voltage is 4V. The number of batteries is considerably more than 6.

The battery pack body 21 further includes an adapter portion 23 for connecting the power tool to supply power to the power tool. As an embodiment, the adapting part 23 has a structure as shown in FIG. 2 , and includes a connecting cable 231 . One end of the connecting cable 231 is electrically connected to the circuit board 25 , and the other end is an external power supply that can be connected to. interface 232. The connection cable 231 extends along the upper part of the housing 211 , and the interface 232 of the connection cable 231 for external power supply is electrically connected to the power tool, and the electrical energy stored in the battery pack 24 is output to supply power to the power tool.

The battery pack 20 further includes a circuit board 25 on which circuit components, such as circuit components constituting a battery management system, are disposed. The circuit board 25 includes a circuit board positive terminal connected to the positive electrode of the battery pack 24 and a circuit board negative terminal connected to the negative electrode of the battery pack 24 .

The operation of the battery pack in the above embodiments also depends on the battery management system. The battery management system is accommodated in the casing of the battery pack. Specifically, at least some components of the battery management system are arranged on the circuit board in the battery pack. In BMS, it is often necessary to sample the voltage of a single cell for battery protection judgment, balance, state of charge (State of Charge, SOC) and state of health (State of Health, SOH) estimation. The most basic input data for battery management.

The acquisition of single-cell battery voltage is generally completed by the single-chip microcomputer in the BMS, and the analog signal input port of the single-cell battery voltage acquisition by the single-cell battery has a limit on the amplitude of the input voltage. , 3.3V, etc.). When the positive voltage of the single-cell battery exceeds the voltage amplitude limit of the analog signal input port of the microcontroller, a sampling circuit needs to be designed to convert the voltage of the single-cell battery to the voltage amplitude limit of the analog signal input port of the microcontroller.

Referring to FIG. 3 , a commonly used sampling circuit at present divides the voltage of a single-cell battery by using a voltage-dividing resistor. FIG. 3 is a schematic structural diagram of a voltage conversion circuit in the prior art. After the voltage is multiplied by the voltage division coefficient ( ) to get the real voltage value of a single-cell battery, and then subtract the next voltage (eg Vb2-Vb1) to get the current single-cell battery 300 (Vb2) voltage. Although this method is simple, the accuracy is too low, especially when multiple single-cell batteries are connected in series to form a battery pack and the number of series-connected batteries is relatively large, the accuracy will be greatly reduced and cannot meet the needs of BMS.

Referring to Figure 4, another sampling circuit uses a differential circuit to directly sample the voltage of a single cell. This sampling circuit can effectively suppress common-mode interference and has high sampling accuracy, but this circuit also has shortcomings. When the single-cell batteries 300 are connected in series to form a battery pack and the number of series-connected batteries is relatively large (for example, n is greater than 6), the positive and negative voltages (for example, Vbn, Where n is generally greater than 6) The voltage applied to the forward or reverse input of the operational amplifier in the differential circuit will exceed the power supply voltage of the operational amplifier (commonly 5V, 12V or 15V), which will cause the operational amplifier to fail to work normally and Affects voltage sampling.

The battery pack of the present invention is suitable for electric tools. Due to the convenience of use of electric tools, its application range is wider and wider, and the output power requirements are higher and higher. The output current of the battery pack that provides electric power for electric tools also varies Therefore, the number of single cells connected in series in the battery pack in the battery pack increases accordingly, and the number n of single cells is larger (for example, n is greater than 6). For a battery pack with a large number of single-cell batteries connected in series, during the single-cell voltage acquisition process using the above-mentioned prior art, the positive and negative voltages of the single-cell batteries with higher series positions (such as the 6th or above) are The voltage of the forward or reverse input of the operational amplifier added to the differential circuit will exceed the power supply voltage of the operational amplifier (commonly 5V, 12V or 15V), which will cause the operational amplifier to not work properly and affect the voltage sampling. Moreover, when the battery is not used, the sampling circuit of the prior art will form a discharge loop to discharge the battery, which affects the service life of the battery. Therefore, the voltage collection of a single-cell battery in the prior art cannot meet the voltage collection of a single-cell battery of the battery pack in this embodiment. Moreover, when the battery pack is not used, the above two sampling circuits will form a discharge loop to discharge the battery, which affects the service life of the battery.

Referring to FIG. 5 , in order to solve the above problems, the present invention provides a battery pack suitable for electric tools. The battery management system includes a voltage conversion circuit and a voltage acquisition circuit 330. The input terminal of the voltage acquisition circuit 330 is connected to the voltage conversion circuit. The output end of the circuit is electrically connected; wherein, the voltage conversion circuit includes a differential amplifier circuit 310 and a proportional amplifier circuit 320 .

The differential amplifier circuit 310 includes two differential input terminals in1, in2 and an output terminal out1. The two differential input terminals in1 and in2 are used to input the voltage to be sampled; the two differential input terminals in1 and in2 are respectively connected to Both ends of a single-cell battery 300 are electrically connected, or are respectively electrically connected to both ends of a series circuit formed by at least two single-cell batteries 300 connected in series;

The proportional amplifier circuit 320 includes an input terminal in3 and an output terminal out. The input terminal in3 of the proportional amplifier circuit 320 is electrically connected to the output terminal out1 of the differential amplifier circuit 310. The output terminal out of the proportional amplifier circuit 320 is used to output the converted voltage. The output terminal out of the proportional amplifier circuit 320 is electrically connected to the input terminal of the voltage acquisition circuit 330, and the output terminal of the proportional amplifier circuit 320 is used for outputting the converted voltage.

The voltage conversion circuit includes two stages, and the first stage uses a differential amplifier circuit 310 to differentially amplify the voltage to be sampled. When the voltage value of the voltage to be sampled is relatively high, the amplification factor of the differential amplifying circuit 310 adopts a relatively small value, so that the input voltages of the input terminals in1 and in2 of the differential amplifying circuit 310 are lower than the power supply voltage of the operational amplifier, thereby enabling differential amplification The circuit 310 is working normally. At this time, the amplification factor of the differential amplifier circuit 310 is relatively small, and the output voltage of the output terminal out1 is relatively small, which can not reach the target amplification factor of the voltage conversion circuit, and the output converted voltage is not easy to measure. Therefore, the second stage uses the proportional amplifier circuit 320 to amplify the voltage output by the differential amplifier circuit 310 to compensate the amplification factor of the first stage differential amplifier circuit 310, so that the voltage conversion circuit reaches the target amplification factor, and the output terminal of the proportional amplifier circuit 320 outputs the output The converted voltage is easy to measure.

Exemplarily, when the voltage value of the voltage to be sampled is relatively high and the normal operating voltage range of the differential amplifying circuit 310 is relatively small, the voltage value of the sampled voltage exceeds the normal operating voltage range of the differential amplifying circuit 310 . Therefore, in order to make the differential amplifier circuit 310 work normally, the amplification factor of the differential amplifier circuit 310 is designed so that the amplification factor of the differential amplifier circuit 310 is designed to be low, so that the differential amplifier circuit can work normally. When the amplification factor of the differential amplifier circuit 310 is relatively low, the target amplification factor cannot be reached, and the voltage value output by the output terminal out1 of the differential amplifier circuit 310 is also relatively low. Therefore, the proportional amplifier circuit 320 is used to proportionally amplify the voltage output by the output terminal out1 of the differential amplifier circuit 310 to compensate the amplification factor of the differential amplifier circuit 310, so that the converted voltage output by the output terminal out of the proportional amplifier circuit 320 is relatively large and easy to detect.

In the technical solution of this embodiment, by using a differential amplifier circuit with a low amplification factor, when the common-mode voltage at both ends of the differential amplifier circuit is relatively large, the differential amplifier circuit can work normally. It effectively suppresses the interference of the working mode and has high sampling accuracy, and uses a proportional amplifier circuit to amplify and output the voltage output by the differential amplifier circuit, and compensate the amplification factor of the differential amplifier circuit so that the voltage converted by the voltage conversion circuit meets the requirements.

On the basis of the above technical solution, referring to FIG. 3 , the product of the amplification factor of the differential amplifier circuit 310 and the amplification factor of the proportional amplifier circuit 320 is equal to the target amplification factor.

The target amplification factor A0 is the multiple of the converted voltage output by the output terminal out of the proportional amplification circuit 320 and the voltage to be sampled when the voltage conversion circuit is designed, which is equal to the amplification factor A1 of the differential amplification circuit 310 and the amplification factor A2 of the proportional amplification circuit 320 product of . For example, when designing the conversion circuit, A0 needs to be equal to 0.66, so the product of the amplification factor A1 of the differential amplifier circuit 310 and the amplification factor A2 of the proportional amplifier circuit 320 is equal to 0.66. In general, the amplification factor A1 of the differential amplifier circuit 310 is relatively small, for example, 0.2, and the amplification factor A2 of the proportional amplifier circuit 320 is 0.66/0.2=3.3.

FIG. 6 is a schematic structural diagram of another voltage conversion circuit provided by an embodiment of the present invention. As shown in FIG. 6 , on the basis of the foregoing embodiments, the differential amplifier circuit 310 in this embodiment includes a first operational amplifier N1, a first Resistor R1, second resistor R2, third resistor R3 and fourth resistor R4. Of course, the first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4 can also be the first resistor unit, the second resistor unit, the third resistor unit and the fourth resistor unit, and each resistor unit is composed of One or more resistors are connected in series and parallel.

The reverse input terminal of the first operational amplifier N1 is electrically connected to the first terminal of the first resistor R1, the second terminal of the first resistor R1 is used as one of the two differential input terminals in1, and the forward input of the first operational amplifier N1 The terminal is electrically connected to the first terminal of the second resistor R2, and the second terminal of the second resistor R2 serves as the other in2 of the two differential input terminals.

The inverting input terminal of the first operational amplifier N1 is electrically connected to the input terminal in3 of the proportional amplifier circuit 320 through the third resistor R3, and the forward input terminal of the first operational amplifier N1 is grounded through the fourth resistor R4.

As shown in FIG. 6 , without loss of generality, when the resistance of the first resistor R1 is equal to the resistance of the second resistor R2, and the resistance of the third resistor R3 is equal to the resistance of the fourth resistor R4, the third The ratio of the resistor R3 to the first resistor R1 is equal to the ratio of the fourth resistor R4 to the second resistor R2, and the amplification factor A1 of the differential amplifier circuit 310 is the ratio of the third resistor R3 to the first resistor R1, that is, the fourth resistor R4 Ratio to the second resistor R2. Assuming that the input voltage of a differential input terminal in2 of the differential amplifier circuit 310 is V1, after voltage division, the voltage at the forward input terminal of the first operational amplifier N1 is V2=V1·R4/(R2+R4)=V1/(1+ R2/R4), it can be seen that the larger the R2/R4, the smaller the V2. In order to make V2 smaller and meet the requirements of the first operational amplifier N1, R2/R4 is designed with a larger value, and the amplification factor A1=R4/R2 of the differential amplifier circuit will be smaller, which will not meet the requirements of the voltage conversion circuit. The relatively low amplification factor of the differential amplification circuit 310 is compensated by the proportional amplification circuit 320 of the second stage, so that the amplification factor of the entire amplification circuit meets the requirements of the voltage conversion circuit. It can be seen that when the ratio between the third resistor R3 and the first resistor R1 or the ratio between the fourth resistor R4 and the second resistor R2 is relatively small, that is, the amplification factor A1 of the differential amplifier circuit 310 is relatively small, the positive value of the first operational amplifier N1 The voltage value obtained by inputting the voltage division to the input terminal and the reverse input terminal is relatively low, so the first operational amplifier N1 is within the normal operating voltage range. When the amplification factor A1 of the differential amplifier circuit 310 is relatively low, the target amplification factor A0 cannot be achieved. Therefore, the proportional amplification circuit 320 is set to compensate the relatively low amplification factor of the differential amplification circuit 310, so that the voltage conversion circuit can reach the target amplification factor A0. For example, the target amplification factor A0 of the voltage conversion circuit is 0.66. When the voltage (eg V1) output by the two ends of in1 and in2 of the voltage to be sampled is relatively large, in order to make the forward and reverse inputs of the first operational amplifier N1 The input voltage (eg V2) of the terminal is within the normal working voltage range of the first operational amplifier N1, and the differential amplification factor A1 is set to 0.2. At this time, the differential amplification factor A1 cannot reach the target amplification factor A0, so the proportional amplification circuit 320 is set to compensate The amplification factor A1 of the differential amplifying circuit 310 is set to be the amplification factor A2 of the proportional amplification circuit 320 divided by the target amplification factor A0 divided by the amplification factor A1 of the differential amplifying circuit 310, that is, 0.66/0.2=3.3.

In the technical solution of this embodiment, the amplification factor of the first operational amplifier is adjusted by adjusting the ratio between the third resistor R3 and the first resistor R1, so that when the voltage value of the voltage to be sampled changes, the difference between the two differential input terminals of the differential amplifier circuit is guaranteed. The input voltage is within the range that enables the differential amplifier circuit to work normally, thereby improving the sampling precision and sampling range of the voltage to be sampled.

On the basis of the above embodiments, as shown in FIG. 6 , the first operational amplifier N1 further includes a power supply input terminal VCC; the voltage of the forward input terminal or the reverse input terminal of the first operational amplifier N1 is lower than the voltage input by the power supply input terminal VCC Voltage.

In order to ensure the normal operation of the first operational amplifier N1, the voltage of the forward input terminal or the reverse input terminal of the first operational amplifier N1 is lower than the voltage input by the power input terminal VCC, so the resistance values of the third resistor R3 and the fourth resistor R4 are set. It is smaller than the resistance value of the first resistor R1 and the second resistor R2, so that the voltage division value of the third resistor R3 and the fourth resistor R4 is relatively small, so that the voltage of the forward input terminal or the reverse input terminal of the first operational amplifier N1 is compared. Small.

7 is a schematic structural diagram of another voltage conversion circuit provided by an embodiment of the present invention. The proportional amplifier circuit 320 includes a second operational amplifier N2, a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7. Certainly, the fifth resistor R5 , the sixth resistor R6 and the seventh resistor R7 may also be a fifth resistor unit, a sixth resistor unit and a seventh resistor unit, and each resistor unit is respectively composed of one or more resistors in series and parallel.

The inverting input terminal of the second operational amplifier N2 is electrically connected to the output terminal out1 of the differential amplifier circuit 310 through the fifth resistor R5, and the inverting input terminal of the second operational amplifier N2 is electrically connected to the output terminal of the second operational amplifier N2 through the sixth resistor R6 The terminal out is electrically connected.

The positive input terminal of the second operational amplifier N2 is grounded through the seventh resistor R7.

The amplification factor A2 of the second operational amplifier N2 is the ratio between the sixth resistor R6 and the fifth resistor R5. Because the amplification factor A2 of the second operational amplifier N2 is relatively large, generally greater than 1, such as 3.3, the sixth resistor The resistance value of R6 is generally greater than the resistance value of the fifth resistor R5.

In the technical solution of this embodiment, the output voltage of the differential amplifier circuit is proportionally amplified by sampling the second operational amplifier N2 with a relatively large amplification factor, and the converted voltage with a relatively large voltage value is output, which makes it easier to measure the converted voltage. Measurement.

FIG. 8 is a schematic structural diagram of another voltage conversion circuit provided by an embodiment of the present invention. As shown in FIG. 8 , the first operational amplifier N1 and the second operational amplifier N2 can be simultaneously applied in the voltage conversion circuit, that is, the differential amplifier circuit 310 Including a first operational amplifier N1, the proportional amplifier circuit 320 includes a second operational amplifier N2, and its specific connection mode is the same as the connection mode of the first operational amplifier N1 and the second operational amplifier N2 in FIG. 6 and FIG. 7, and the beneficial effect is achieved. It is also the same, and will not be repeated here.

FIG. 9 is a schematic structural diagram of a battery management system suitable for a battery pack of a power tool according to the present invention. The battery management system is used to manage a battery pack. The battery pack includes a plurality of single-cell batteries 300. The battery management system It includes a voltage acquisition circuit 330 and a voltage conversion circuit. The input terminal of the voltage acquisition circuit 330 is electrically connected to the output terminal out of the voltage conversion circuit.

The two differential input terminals in1 and in2 of the voltage conversion circuit are respectively electrically connected to both ends of a single-cell battery 300 , or are respectively electrically connected to both ends of a series circuit formed by at least two single-cell batteries connected in series.

As shown in FIG. 9 , the battery pack includes n single-cell batteries 300 , where n is a positive integer greater than one. N single-cell batteries 300 are connected in series, and one of the two single-cell batteries 300 at both ends of the series-connected single-cell battery 300 is the first single-cell battery 300 , and the other is the n-th single-cell battery 300 , the first single-cell battery 300 . 300 negative ground wire GndBat. The two differential input terminals in1 and in2 of the differential amplifier circuit 310 in the voltage conversion circuit are respectively connected to two ends of a single cell battery 300 , so the voltage value of the voltage to be sampled is the voltage value of the single cell battery 300 .

As shown in FIG. 9 , when measuring the voltage of the i-th (for example, i is greater than 6) single-cell battery 300 when the negative ground wire GndBat of the first single-cell battery 300 is connected to the two ends of the i-th single-cell battery 300 The voltage value of the two differential input terminals in1 and in2 that are electrically connected is very large, which is the sum of the voltages of the 1st to i-1th single-cell batteries. The voltage value of the two differential input terminals in1 and in2 will exceed The voltage range in which the differential amplifier circuit 310 works normally affects the sampling of the voltage. At this time, the values of the third resistor R3 and the first resistor R1 are adjusted, and the amplification factor A1 of the differential amplifier circuit 310 is set to a relatively low level, so that the voltage values of the two differential input terminals of the differential amplifier circuit 310 are within the normal operation of the differential amplifier circuit 310. within the range. When the amplification factor A1 of the differential amplifier circuit 310 is relatively low, the target amplification factor cannot be achieved. Therefore, the proportional amplification circuit 320 is set to compensate the lower amplification factor of the differential amplifier circuit 310 so that the voltage conversion circuit can reach the target amplification factor.

The input terminal of the voltage acquisition circuit 330 is electrically connected to the output terminal out of the proportional amplifier circuit 320 , and the voltage acquisition circuit 330 acquires the converted voltage output by the output terminal out of the proportional amplifier circuit 320 in the voltage conversion circuit, and collects the voltage through the voltage acquisition circuit 330 The value of the converted voltage of , calculates the voltage across the single cell 300 according to the target magnification A0.

In the above embodiment, the number of single-cell batteries 300 is greater than or equal to six.

In the technical solution of this embodiment, the voltage of a single cell in the battery pack is sampled by the voltage conversion circuit in the above embodiment, and the converted voltage is calculated by the voltage acquisition circuit to obtain the voltage value of the single cell, which improves the measurement performance. The sampling accuracy and sampling range of the voltage of a single cell can also be used when the number of single cells in series in the battery pack is large and the voltage is relatively high, regardless of the number of single cells in series and the amplitude of the power supply voltage of the proportional amplifier circuit Impact. Therefore, the above technical solution is suitable for the battery pack of the present invention with a large number of single-cell batteries connected in series and a relatively high voltage, and improves the sampling accuracy and sampling range when measuring the voltage of a single-cell battery.

On the basis of the above embodiment, the output voltage of the output terminal out of the voltage conversion circuit is less than or equal to the limit range of the input voltage of the voltage acquisition circuit 330 .

Exemplarily, when the voltage acquisition circuit 330 is a single-chip microcomputer, that is, the converted voltage output by the output terminal out of the proportional amplifier circuit 320 is collected by the single-chip microcomputer. Because the analog signal input interface of the single-chip microcomputer has a voltage limit, the lowest is generally 0V, and the highest is not. exceeds the power supply voltage of the single-chip microcomputer (for example, 5V, 3.3V, etc.), at this time, the output voltage of the output terminal out of the proportional amplifier circuit 320 is less than or equal to the limit range of the input voltage of the voltage acquisition circuit 330, so that the single-chip microcomputer can normally receive the proportional amplifier circuit. The converted voltage output by the 320 output terminal out.

FIG. 10 is a schematic structural diagram of another battery management system suitable for an electric tool provided by an embodiment of the present invention. On the basis of the above-mentioned embodiment, this embodiment also includes:

The first switch SW, one end of the first switch SW is electrically connected to the ground line GndBat in the battery pack, and the other end of the first switch SW is electrically connected to the ground line GndSmp of the voltage conversion circuit.

As shown in FIG. 10 , in the voltage conversion circuit, there are many places connected to the ground line GndSmp, for example, one power input terminal VCC of the first operational amplifier N1 in the differential amplifier circuit 310 inputs a positive voltage, and the other power input terminal is grounded , one end of the fourth resistor R4 that is not electrically connected to the second resistor R2 is grounded, one power input terminal VCC of the second operational amplifier N2 in the proportional amplifier circuit 320 inputs a positive voltage, the other power input terminal is grounded, and the seventh resistor R7 One end is grounded, both are grounded through the ground wire GndSmp, that is, electrically connected to the ground wire GndSmp.

The first switch SW is used to be turned on during the operation of the battery pack, and turned off when the battery pack is at rest.

When the battery pack is not in use, the voltage conversion circuit will discharge the single-cell battery 300 in the battery pack through the ground wire GndSmp in the voltage conversion circuit and the ground wire GndBat in the battery pack to form a discharge loop. Therefore, the first switch SW is set. When the battery pack is at rest, it is turned off, and the discharge circuit formed by the voltage conversion circuit, the battery pack and the ground wire is disconnected, so as to avoid the discharge of the battery pack when the battery pack is at rest, and improve the service life of the battery pack. When the battery pack is charged and discharged, the first switch SW is closed, the voltage conversion circuit, the battery pack and the ground wire form a loop, the voltage conversion circuit works normally, and the voltage of the single cell 300 in the battery pack is sampled and converted.

On the basis of the above embodiments, the first switch SW is a mechanical switch or a semiconductor switch.

The first switch SW may be any switch, as long as the switch function is satisfied. For example, the first switch SW may be a mechanical switch. There are many kinds of mechanical switches, and an example here can be a knife, and the closing and opening of the knife is manually controlled. When the battery pack is at rest, manually disconnect the knife, and when the battery pack is charged and discharged, manually close the knife. It can also be a relay by way of example, and the relay is controlled by a control signal. The first switch SW may also be a semiconductor switch, for example, a transistor, and the function of the first switch SW is realized by controlling the disconnection and conduction of the transistor by a control signal.

The present invention also provides a power tool combination, the power tool combination includes the power tool and the above-mentioned battery pack, the battery pack can be installed to the power tool to provide electrical energy to the power tool, and the power tool includes : housing; tool accessories for realizing the function of the power tool; output shaft, supporting the tool accessories; motor, accommodated in the housing, for outputting driving force to drive the output shaft to rotate; the A motor is operably connected with the output shaft; and a battery pack joint is used for connecting the battery pack.

11 , as an embodiment of the power tool combination, the power tool is a lawn mower 111 , and the battery pack 112 is suitable for the lawn mower 111 . Since the output power of the lawn mower 111 is relatively large, the required output voltage and/or output current of the battery pack 112 is also large, so as to provide enough energy for the lawn mower. For the battery pack 112, since the voltage value provided by each battery cell is relatively fixed, in order to achieve a larger output voltage and/or output current for the battery pack 112, the battery pack must contain a considerable number of batteries unit, in this embodiment, the battery pack 112 can output a voltage of 56V, and the nominal voltage of each battery unit is 4V, so at least 14 battery units connected in series are required, and the number of battery units in series is relatively large. Therefore, the battery pack 112 in the power tool set can use the above-mentioned battery pack, which can improve the sampling accuracy and sampling range when measuring the voltage of a single-cell battery, and is not affected by the number of single-cell batteries connected in series and the power supply voltage of the proportional amplifier circuit the effect of the magnitude.

Of course, the battery packs in the present invention can be various types of battery packs, not limited to the battery packs in the above-mentioned embodiments, and can also be battery packs suitable for other electric tools, for example, as shown in FIG. Battery pack 122 for screwdriver 121 .

The battery pack suitable for electric tools of the present invention can ensure the sampling accuracy and sampling range of the voltage of the single-cell battery under the condition that the number of single-cell batteries in the battery pack is large and the voltage is relatively high, and is not affected by the single-cell battery connected in series. The effect of the number and magnitude of the supply voltage of the proportional amplifier circuit. Moreover, by arranging the first switch in the battery pack, the discharge of the battery pack when the battery pack is not used can be avoided, and the service life of the battery pack is improved.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention. The scope is determined by the scope of the appended claims.

Claims (10)

1. A battery pack suitable for a power tool, the battery pack comprising: case; an adapter part for connecting the electric tool to supply power to the electric tool; a battery pack, accommodated in the casing, the battery pack including a plurality of single-cell batteries; a battery management system, accommodated in the casing, the battery management system includes a voltage conversion circuit and a voltage acquisition circuit, the input end of the voltage acquisition circuit is electrically connected with the output end of the voltage conversion circuit; the voltage conversion circuit include: A differential amplifier circuit includes two differential input terminals and one output terminal, the two differential input terminals are used to input the voltage to be sampled; the two differential input terminals are respectively electrically connected to two ends of a single-cell battery, or respectively be electrically connected to both ends of a series circuit formed by at least two single-cell batteries connected in series; A proportional amplifier circuit, including an input terminal and an output terminal, the input terminal of the proportional amplifier circuit is electrically connected to the output terminal of the differential amplifier circuit, and the output terminal of the proportional amplifier circuit is electrically connected to the input terminal of the voltage acquisition circuit , the output terminal of the proportional amplifier circuit is used to output the converted voltage. 2. The battery pack according to claim 1, wherein the differential amplifier circuit comprises a first operational amplifier, a first resistance unit, a second resistance unit, a third resistance unit and a fourth resistance unit; The inverting input end of the first operational amplifier is electrically connected to the first end of the first resistance unit, and the second end of the first resistance unit serves as one of the two differential input ends; the first The forward input end of an operational amplifier is electrically connected to the first end of the second resistance unit, and the second end of the second resistance unit serves as the other of the two differential input ends; The reverse input terminal of the first operational amplifier is electrically connected to the output terminal of the first operational amplifier and the input terminal of the proportional amplifier circuit through the third resistance unit, and the forward input terminal of the first operational amplifier is electrically connected The terminal is grounded through the fourth resistance unit. 3 . The battery pack according to claim 2 , wherein: the first operational amplifier further comprises a power input terminal; the voltage of the forward input terminal or the reverse input terminal of the first operational amplifier is smaller than that of the power supply input terminal. 4 . input voltage. 4. The battery pack according to claim 1, wherein the proportional amplifier circuit comprises a second operational amplifier, a fifth resistance unit, a sixth resistance unit and a seventh resistance unit; The inverting input terminal of the second operational amplifier is electrically connected to the output terminal of the differential amplifier circuit through the fifth resistance unit, and the inverting input terminal of the second operational amplifier is electrically connected to the first operational amplifier through the sixth resistance unit. The output terminals of the two operational amplifiers are electrically connected; The forward input terminal of the second operational amplifier is grounded through the seventh resistor unit. 5 . The battery pack according to claim 1 , wherein the product of the amplification factor of the differential amplifier circuit and the amplification factor of the proportional amplifier circuit is equal to the target amplification factor. 6 . 6 . The battery pack according to claim 1 , wherein the battery pack further comprises a first switch, one end of the first switch is electrically connected to the ground wire in the battery pack, and the other end is connected to the ground wire in the battery pack. 7 . The ground wire of the voltage conversion circuit is electrically connected; the first switch is configured to be turned on during the operation of the battery pack, and turned off when the battery pack is at rest. 7 . The battery pack according to claim 1 , wherein the output voltage of the output terminal of the voltage conversion circuit is less than or equal to the limit range of the input voltage of the voltage acquisition circuit. 8 . 8 . The battery pack according to claim 1 , wherein the number of single cells connected in series in the battery pack is greater than or equal to 6. 9 . 9 . The battery pack according to claim 1 , wherein the single-cell battery is composed of at least one or more batteries connected in parallel. 10 . 10. A power tool combination comprising a power tool and a battery pack as claimed in any one of claims 1 to 9, the battery pack being mountable to the power tool to provide power to the power tool, the power tool include: case; Tool accessories for realizing the function of the power tool; an output shaft supporting the tool attachment; a motor, accommodated in the housing, for outputting a driving force to drive the output shaft to rotate; the motor is operably connected to the output shaft; The battery pack joint part is used for connecting the battery pack.