Battery equalization circuit and portable power tool

Abstract

A battery equalization circuit and a portable power tool are provided that can reduce implementation costs compared to the prior art. [Solution] A battery equalization circuit includes a plurality of single-unit equalization modules corresponding one-to-one to a plurality of batteries. Each single-unit equalization module includes a PMOS transistor, a power dissipation resistor, and a functional resistor. The PMOS transistor has a source connected to the positive electrode of the battery and a drain connected to the negative electrode of the battery via the power dissipation resistor. The functional resistor has a first end connected to the source of the PMOS transistor and a second end connected to a first pin of a BMS controller and a gate of the PMOS transistor, respectively. The negative electrode of the battery is further connected to a second pin of the BMS controller, the first pin and the second pin being two adjacent pins. When the first pin outputs a high level, the PMOS transistor is turned off, and when the first pin outputs a low level, the PMOS transistor is turned on.

Description

[Technical Field]

[0001] This application relates to the technical field of power tools, and more particularly to battery equalization circuits and portable power tools. [Background technology]

[0002] Lithium batteries have the advantages of high energy density, light weight, environmental friendliness, and non-pollution, and have a wide range of applications, including portable power tools such as electric drills, electric saws, lawn mowers, etc. Portable power tools typically employ a single cell pack, and due to their portability, the single cell pack typically includes a number of series-connected individual cells, for example, four, six, or eight 4.2V lithium batteries.

[0003] Lithium batteries typically require battery equalization during use. Conventional battery equalization techniques are primarily divided into active and passive equalization. Active equalization transfers energy from high-power elements to low-power elements through energy storage devices such as inductors, transformers, and capacitors. Active equalization offers advantages such as high energy utilization, fast equalization speed, and minimal heat generation. However, its drawbacks include complex circuitry, high cost, and difficult control, making it unsuitable for portable power tools. Passive equalization dissipates excess energy from high-power elements in the form of heat through energy-dissipating devices such as resistors. While passive equalization's drawbacks include wasted energy and significant heat generation, its advantages, such as simple circuitry, low cost, and high reliability, make it highly applicable to portable power tools.

[0004] In the passive equalization technology adopted by some conventional portable power tools, each battery is typically provided with a sampling resistor for collecting the voltage of the battery, a switching transistor and its associated components (such as a bias resistor), and a power consumption resistor, and a dedicated equalization controller is also provided to control the on / off of each switching transistor, making the implementation cost of this method somewhat high. Summary of the Invention [Problem to be solved by the invention]

[0005] To solve the above technical problems, the present application provides a battery equalization circuit and a portable power tool to reduce implementation costs. [Means for solving the problem]

[0006] According to a first aspect, a battery equalization circuit according to the present application is used in a portable power tool including a plurality of batteries connected in series in sequence, the battery equalization circuit is disposed on a BMS circuit board in the portable power tool and includes a plurality of individual equalization modules corresponding one-to-one to the plurality of batteries; The single-unit equalization module includes a PMOS transistor, a power dissipation resistor, and a functional resistor, wherein the source of the PMOS transistor is connected to the positive electrode of the battery, and the drain is connected to the negative electrode of the battery via the power dissipation resistor, the first end of the functional resistor is connected to the source of the PMOS transistor, and the second end is respectively connected to a first pin of a BMS controller and a gate of the PMOS transistor, the negative electrode of the battery is further connected to a second pin of the BMS controller, the first pin and the second pin are two adjacent pins, when the first pin outputs a high level, the PMOS transistor is turned off, the functional resistor is a sampling resistor, and when the first pin outputs a low level, the functional resistor is a bias resistor of the PMOS transistor, and the PMOS transistor is conductive.

[0007] Furthermore, a filter capacitor is connected between the first pin and the second pin.

[0008] Furthermore, the first pin of the unit equalization module is the second pin of the adjacent unit equalization module, and the second pin of the unit equalization module is the first pin of the adjacent unit equalization module.

[0009] Furthermore, the power dissipation resistors in each of the single equalization modules are arranged on the BMS circuit board in sequence according to the series connection order of the batteries; The first and second pins of the single equalization module output a low level at most once at the same time.

[0010] Additionally, the power dissipation resistor in each of the unitary equalization modules is located on the BMS circuit board in an area away from the battery.

[0011] According to a second aspect, a portable power tool according to the present application includes a plurality of batteries connected in series in sequence, and a plurality of standalone equalization modules disposed on a BMS circuit board of the portable power tool and corresponding to the plurality of batteries in a one-to-one relationship; The single-unit equalization module includes a PMOS transistor, a power dissipation resistor, and a functional resistor, wherein the source of the PMOS transistor is connected to the positive electrode of the battery, and the drain is connected to the negative electrode of the battery via the power dissipation resistor, the first end of the functional resistor is connected to the source of the PMOS transistor, and the second end is respectively connected to a first pin of a BMS controller and a gate of the PMOS transistor, the negative electrode of the battery is further connected to a second pin of the BMS controller, the first pin and the second pin are two adjacent pins, when the first pin outputs a high level, the PMOS transistor is turned off, the functional resistor is a sampling resistor, and when the first pin outputs a low level, the functional resistor is a bias resistor of the PMOS transistor, and the PMOS transistor is conductive.

[0012] Furthermore, a filter capacitor is connected between the first pin and the second pin.

[0013] Furthermore, the first pin of the unit equalization module is the second pin of the adjacent unit equalization module, and the second pin of the unit equalization module is the first pin of the adjacent unit equalization module.

[0014] Furthermore, the power dissipation resistors in each of the single equalization modules are arranged on the BMS circuit board in sequence according to the series connection order of the batteries; The first and second pins of the single equalization module output a low level at most once at the same time.

[0015] Additionally, the power dissipation resistor in each of the unitary equalization modules is located on the BMS circuit board in an area away from the battery. [Effects of the Invention]

[0016] As can be seen from the above technical solution, in the present application, different functional resistors have different functions, so the use of some components can be reduced compared to the prior art, such as the use of bias resistors, thereby reducing implementation costs. Furthermore, by reducing some components, the present application can place the battery equalization circuit on the BMS circuit board, so that a BMS controller can be used instead of a dedicated equalization controller compared to the prior art, further reducing implementation costs.

[0017] In order to more clearly explain the technical solutions in the embodiments of the present application or the prior art, the following will briefly describe the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some of the embodiments of the present application, not all of the embodiments. For those skilled in the art, other drawings obtained based on these drawings belong to the protection scope of the present application without paying creative labor. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a circuit structure schematic diagram of a battery equalization circuit in an embodiment of the present application; [Figure 2] This is a circuit diagram showing a state in which the first pin of the single equalization module outputs a low level. [Figure 3] FIG. 10 is another schematic circuit structure diagram of a single equalization module in an embodiment of the present application. [Figure 4] 1 is a structural schematic diagram of a power dissipation resistor in an embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0019] In order to more clearly understand the objectives, technical solutions and advantages of the present application, the present application will be described in more detail below in conjunction with the drawings and specific examples. It should be understood that the specific examples described herein are for the purpose of illustrating the present application, and are not intended to limit the present application.

[0020] The battery equalization circuit according to the embodiment of the present application can be used in a portable power tool. For example, the portable power tool may include a handheld power tool, such as an electric drill, an electric saw, or a lawn mower. As shown in FIG. 1 , the portable power tool may include a plurality of batteries 200 connected in series. For example, the number of the plurality of batteries 200 connected in series may be four, six, or eight, and the output voltage of the batteries may be 4.2 V. In the embodiment of the present application, the portable power tool may further include a circuit board on which a battery management system (BMS) is disposed, which is referred to as a BMS circuit board in the embodiment of the present application. As can be understood, a BMS controller 300 for managing the batteries is typically disposed on the BMS circuit board.

[0021] In the prior art, some portable power tools have passive equalization-related components arranged on a single circuit board, which affects the internal space utilization of the portable power tool. However, the embodiments of the present application can reduce the use of components compared to the prior art, so that the battery equalization circuit of the embodiments of the present application can be arranged on the BMS circuit board, eliminating the need for an additional circuit board and improving the internal space utilization of the portable power tool.

[0022] As shown in FIG. 1, the battery equalization circuit includes a plurality of single equalization modules 100 corresponding one-to-one to a plurality of batteries 200, that is, one single equalization module 100 is provided for one battery 200.

[0023] The single-unit equalization module 100 includes a PMOS transistor, a power dissipation resistor Rf, and a functional resistor Rj. Specifically, the source S of the PMOS transistor is connected to the positive electrode of the battery 200, and the drain D is connected to the negative electrode of the battery 200 via the power dissipation resistor Rf. A first end of the functional resistor Rj is connected to the source S of the PMOS transistor, and a second end of the functional resistor Rj is connected to a first pin of the BMS controller 300 and a gate G of the PMOS transistor, respectively. The negative electrode of the battery 200 is further connected to a second pin of the BMS controller 300, the first pin and the second pin being two adjacent pins.

[0024] Before introducing the working principle of the single-piece equalization module 100, it should be mentioned that in chip design, there is usually an equivalent internal impedance between two adjacent pins because the chip's internal physical structure, material properties, and circuit design are the same. Therefore, in the embodiment of this application, the internal impedance between two adjacent pins, the first pin and the second pin, is represented by an equivalent resistor Ra.

[0025] Based on this, the operating principle of the single equalization module 100 is as follows.

[0026] When pin 1 outputs a high level, the voltage at pin 1 is close to the voltage at the positive pole of the battery 200. Therefore, the voltage difference across the functional resistor Rj cannot satisfy the on-condition of the PMOS transistor, so the PMOS transistor is turned off. Therefore, the functional resistor Rj serves as a sampling resistor. That is, when pin 1 outputs a high level, the magnitude of the output voltage of the battery 200 can be determined by sampling the functional resistor Rj to determine whether the battery needs to be equalized.

[0027] When it is determined that the batteries need to be equalized, pin 1 outputs a low level. As shown in FIG. 2, the circuit consisting of battery 200, functional resistor Rj, and equivalent resistor Ra is conductive. The voltage difference across functional resistor Rj satisfies the on-condition of the PMOS transistor, turning the PMOS transistor conductive. That is, functional resistor Rj serves as the bias resistor for the PMOS transistor. Therefore, battery 200 and dissipative resistor Rf form a conductive circuit, and battery 200 dissipates power energy through dissipative resistor Rf to perform equalization. As can be seen, when equalization is complete, pin 1 simply outputs a high level. The equalization time, etc., can be reasonably set according to actual circumstances.

[0028] As can be seen from the above, in the embodiments of the present application, different functional resistors Rj have different functions, which allows the use of some components to be reduced compared to the prior art, such as reducing the use of bias resistors, thereby reducing implementation costs. Furthermore, by reducing some components, the embodiments of the present application allow the battery equalization circuit to be placed on the BMS circuit board, which allows a BMS controller to be used instead of a dedicated equalization controller compared to the prior art, further reducing implementation costs. Furthermore, while equalization in the prior art mainly occurs during battery charging periods, the embodiments of the present application can also perform equalization during rest periods (i.e., non-charging periods) as well as charging periods.

[0029] In some embodiments, as shown in FIG. 3, a filter capacitor C may be connected between the first and second pins of the single equalization module 100. As can be seen, the filtering effect of the filter capacitor C can make the control more stable, thereby improving the reliability of the embodiments of the present application.

[0030] In some embodiments, a first pin on a single equalization module 100 may be a second pin on an adjacent single equalization module 100, and a second pin on a single equalization module 100 may be a first pin on an adjacent single equalization module 100.

[0031] In the monolithic equalization module 100, the PMOS transistor is controlled primarily by the first pin, and thus the second pin can be multiplexed. Illustratively, as shown in FIG. 1 , from top to bottom, the first pin of the second monolithic equalization module 100 is also the second pin of the first monolithic equalization module 100. Similarly, the second pin of the second monolithic equalization module 100 is also the first pin of the third monolithic equalization module 100 (not shown). As can be seen, in the embodiment of the present application, multiplexing the second pin can save pin resources of the BMS controller 300.

[0032] In some embodiments, the power dissipation resistors Rf in each single equalization module 100 are arranged on the BMS circuit board in sequence according to the series connection order of the batteries. Illustratively, the number of batteries 200 in FIG. 1 is six, and the power dissipation resistors Rf from top to bottom are resistors Rf1 to Rf6, and the six power dissipation resistors Rf are arranged from left to right, as shown in FIG. 4.

[0033] Based on this, the first and second pins of each standalone equalization module 100 output a maximum of one low level at the same time. That is, at the same time, two adjacent standalone equalization modules 100 equalize at most one module, and therefore at the same time, two adjacent power dissipation resistors Rf consume at most one battery energy. When a power dissipation resistor Rf consumes battery energy, it generates heat and its temperature rises. Therefore, this pin control method in the embodiment of the present application prevents two adjacent power dissipation resistors Rf from generating heat at the same time, preventing local temperatures on the BMS circuit board from becoming too high and improving safety.

[0034] For example, from top to bottom, when the first pin of the first elementary equalization module 100 outputs a high level, the power dissipation resistor Rf1 does not operate and does not generate heat. In the embodiment of the present application, the second pin of the first elementary equalization module 100 outputs a low level, i.e., the first pin of the second elementary equalization module 100 outputs a low level, at this time, the power dissipation resistor Rf2 consumes power energy and generates heat. According to the embodiment of the present application, when the second pin of the second elementary equalization module 100 outputs a high level, i.e., the first pin of the third elementary equalization module 100 outputs a high level, the power dissipation resistor Rf3 does not operate and does not generate heat. Therefore, in the embodiment of the present application, two adjacent power dissipation resistors Rf do not generate heat at the same time.

[0035] 4, the power dissipation resistor Rf in each unit equalization module 100 is disposed on the BMS circuit board in an area away from the battery 200. Typically, the BMS circuit board and the battery pack are very close to each other, almost adjacent to each other. Therefore, in order to reduce the impact of heat generation from the power dissipation resistor Rf on the battery 200, in the embodiments of the present application, the power dissipation resistor Rf is disposed away from the battery 200, thereby reducing the impact on the temperature of the battery 200 during heat generation from the power dissipation resistor Rf and improving safety.

[0036] An embodiment of the present application further provides a portable power tool, including a plurality of batteries connected in series in sequence, and a plurality of standalone equalization modules disposed on a BMS circuit board in the portable power tool, corresponding one-to-one to the plurality of batteries.

[0037] The single-unit equalization module includes a PMOS transistor, a power dissipation resistor, and a functional resistor. The source of the PMOS transistor is connected to the positive terminal of the battery, and the drain is connected to the negative terminal of the battery via the power dissipation resistor. The functional resistor has a first end connected to the source of the PMOS transistor and a second end connected to a first pin of the BMS controller and a gate of the PMOS transistor, respectively. The negative terminal of the battery is further connected to a second pin of the BMS controller, the first pin and the second pin being two adjacent pins.

[0038] When the first pin outputs a high level, the PMOS transistor is turned off and the functional resistor is the sampling resistor; when the first pin outputs a low level, the functional resistor is the bias resistor of the PMOS transistor and the PMOS transistor is turned on.

[0039] In some embodiments, the single equalization module has a filter capacitor connected between the first and second pins.

[0040] In some embodiments, a first pin on a unitary equalization module is a second pin on an adjacent unitary equalization module, and a second pin on a unitary equalization module is a first pin on an adjacent unitary equalization module.

[0041] In some embodiments, the power dissipation resistors in each single equalization module are arranged on the BMS circuit board in sequence according to the series connection order of the batteries, and the first and second pins of each single equalization module output a low level at most once at the same time.

[0042] In some embodiments, the power dissipation resistors in each unitary equalization module are located on the BMS circuit board in an area away from the battery.

[0043] The specific implementation of the above embodiment, referring to the implementation of the battery equalization circuit described above, will not be further described here.

[0044] The above examples are merely preferred embodiments of the present application, and although the descriptions are more specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make some modifications and improvements without departing from the spirit of the present application, and these fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application should be governed by the appended claims.

Claims

1. A battery equalization circuit for use in a portable power tool including a plurality of batteries connected in series, the battery equalization circuit is disposed on a BMS circuit board in the portable power tool and includes a plurality of individual equalization modules corresponding one-to-one to the plurality of batteries; the PMOS transistor has a source connected to a positive electrode of a battery and a drain connected to a negative electrode of the battery via the power dissipation resistor; the functional resistor has a first end connected to the source of the PMOS transistor and a second end connected to a first pin of a BMS controller and a gate of the PMOS transistor, respectively; the negative electrode of the battery is further connected to a second pin of the BMS controller; the first pin and the second pin are two adjacent pins; when the first pin outputs a high level, the PMOS transistor is turned off; the functional resistor is a sampling resistor; and when the first pin outputs a low level, the functional resistor is a bias resistor of the PMOS transistor, and the PMOS transistor is made conductive.

2. 2. The battery equalization circuit of claim 1, further comprising a filter capacitor connected between said first pin and said second pin.

3. 3. The battery equalization circuit of claim 1, wherein a first pin on the single equalization module is a second pin on an adjacent single equalization module, and a second pin on the single equalization module is a first pin on an adjacent single equalization module.

4. The power dissipation resistors in each of the single equalization modules are arranged on the BMS circuit board in sequence according to the series connection order of the batteries; 4. The battery equalization circuit of claim 3, wherein the first pin and the second pin of the single equalization module output a maximum of one low level at the same time.

5. 5. The battery equalization circuit of claim 4, wherein a power dissipation resistor in each of the single equalization modules is located on the BMS circuit board in an area away from the batteries.

6. A portable power tool including: a plurality of batteries connected in series; and a plurality of stand-alone equalization modules disposed on a BMS circuit board of the portable power tool and corresponding to the plurality of batteries in a one-to-one relationship; the single-unit equalization module includes a PMOS transistor, a power dissipation resistor, and a functional resistor, the PMOS transistor having a source connected to a positive electrode of a battery and a drain connected to a negative electrode of the battery via the power dissipation resistor, the functional resistor having a first end connected to the source of the PMOS transistor and a second end connected to a first pin of a BMS controller and a gate of the PMOS transistor, respectively, the negative electrode of the battery being further connected to a second pin of the BMS controller, the first pin and the second pin being two adjacent pins, the PMOS transistor being turned off when the first pin outputs a high level, the functional resistor being a sampling resistor, and the PMOS transistor being turned on when the first pin outputs a low level.

7. 7. The portable power tool according to claim 6, wherein a filter capacitor is connected between the first pin and the second pin.

8. 8. A portable power tool as described in claim 6 or 7, characterized in that the first pin of the single equalization module is the second pin of an adjacent single equalization module, and the second pin of the single equalization module is the first pin of an adjacent single equalization module.

9. The power dissipation resistors in each of the single equalization modules are arranged on the BMS circuit board in sequence according to the series connection order of the batteries; 9. The portable power tool according to claim 8, wherein the first pin and the second pin of the single equalization module output a low level at most once at the same time.

10. 10. The portable power tool of claim 9, wherein the power dissipation resistor in each of the unitary equalization modules is located on the BMS circuit board in an area away from the battery.

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