阅读说明：本技术 一种温度检测电路、温度检测方法及电动工具 (Temperature detection circuit, temperature detection method and electric tool ) 是由 聂明刚 郑玉 于 2020-11-17 设计创作，主要内容包括：本发明适用于电动工具领域,提供一种温度检测电路、温度检测方法及电动工具,该温度检测电路包括：热敏电阻器、第一分压电阻、第二分压电阻、控制模块以及第一开关单元；所述第一开关单元与所述第一分压电阻串联后,连接在供电模块与所述热敏电阻器第一端之间,且所述第一开关单元的控制端连接所述控制模块；所述第一开关单元与所述第一分压电阻串联后与所述第二分压电阻并联；所述热敏电阻器第二端接地；所述控制模块电压采集端连接到所述热敏电阻器第一端,采集所述热敏电阻器第一端的分压值。本发明能保证电动工具大电流工作时温度值检测准确。(The invention is suitable for the field of electric tools, and provides a temperature detection circuit, a temperature detection method and an electric tool, wherein the temperature detection circuit comprises: the circuit comprises a thermistor, a first voltage-dividing resistor, a second voltage-dividing resistor, a control module and a first switch unit; the first switch unit is connected between a power supply module and the first end of the thermistor after being connected with the first voltage dividing resistor in series, and the control end of the first switch unit is connected with the control module; the first switch unit is connected with the first voltage dividing resistor in series and then connected with the second voltage dividing resistor in parallel; the second end of the thermistor is grounded; the voltage acquisition end of the control module is connected to the first end of the thermistor and acquires a voltage division value of the first end of the thermistor. The invention can ensure the temperature value detection accuracy of the electric tool during heavy current work.)

1. A temperature detection circuit is characterized by comprising a thermistor, a first voltage-dividing resistor, a second voltage-dividing resistor, a control module and a first switch unit;

the first switch unit is connected between a power supply module and the first end of the thermistor after being connected with the first voltage dividing resistor in series, and the control end of the first switch unit is connected with the control module;

the first switch unit is connected with the first voltage dividing resistor in series and then connected with the second voltage dividing resistor in parallel;

the second end of the thermistor is grounded;

the voltage acquisition end of the control module is connected to the first end of the thermistor and acquires a voltage division value of the first end of the thermistor.

2. The temperature detection circuit of claim 1, wherein the temperature detection circuit further comprises a filtering unit, the filtering unit comprising:

one end of the first current limiting resistor is connected with the voltage acquisition end of the control module, and the other end of the first current limiting resistor is connected with the first end of the thermistor;

and one end of the filter capacitor is connected with the voltage acquisition end of the control module, and the other end of the filter capacitor is grounded.

3. The temperature detection circuit according to claim 1, wherein the first switching unit includes:

the input end of the first switching tube is connected with a power supply module, and the output end of the first switching tube is connected with the first divider resistor;

one end of the second current limiting resistor is connected with the control end of the first switching tube, and the other end of the second current limiting resistor is connected with the first output end of the control module;

and one end of the first pull-down resistor is respectively connected with the control end of the first switching tube and one end of the second current-limiting resistor, and the other end of the first pull-down resistor is grounded.

4. The temperature detection circuit according to claim 1, wherein when the first switch unit is turned on, the first voltage dividing resistor is connected in parallel with the second voltage dividing resistor and then connected in series with the thermistor, and the control module voltage acquisition terminal acquires a voltage dividing value of the first voltage dividing resistor and the second voltage dividing resistor after being connected in parallel with each other and then connected with the thermistor; when the first switch unit is turned off, the second voltage-dividing resistor is connected with the thermistor in series, and the voltage-dividing value of the second voltage-dividing resistor and the thermistor is acquired by the voltage acquisition end of the control module.

5. The temperature detection circuit according to any one of claims 1 to 4, further comprising a second switching unit connected in series with the second voltage-dividing resistor, and a control terminal of the second switching unit is connected to the control module.

6. The temperature detection circuit according to claim 5, wherein the second switching unit includes:

the input end of the second switching tube is connected with the power supply module, and the output end of the second switching tube is connected with the second voltage-dividing resistor;

one end of the third current limiting resistor is connected with the control end of the second switching tube, and the other end of the third current limiting resistor is connected with the second output end of the control module;

and one end of the second pull-down resistor is connected with the control end of the second switch tube, and the other end of the second pull-down resistor is grounded.

7. The temperature detection circuit according to claim 5, wherein when the first switch unit is turned on and the second switch unit is turned off, the first voltage dividing resistor is connected in series with the thermistor, and the control module voltage acquisition terminal acquires voltage dividing values of the first voltage dividing resistor and the thermistor; when the first switch unit is turned off and the second switch unit is turned on, the second voltage-dividing resistor is connected in series with the thermistor, and the voltage-dividing value of the second voltage-dividing resistor and the thermistor is acquired by the voltage acquisition end of the control module.

8. An electric power tool comprising a battery pack module, a main controller, and the temperature detection circuit according to any one of claims 1 to 7, wherein the thermistor is provided in the battery pack module, and the battery pack module and the main controller are connected by a power supply line.

9. A temperature detection method for use in the temperature detection circuit of any one of claims 1-4, the method comprising:

the first switch unit is switched off, and the voltage division value V of the second voltage division resistor and the thermistor is acquired_{AD_BATNTC1}；

A first switch unit is conducted, and after the first voltage division resistor and the second voltage division resistor are connected in parallel, the voltage division value V of the first voltage division resistor and the voltage division value V of the second voltage division resistor are acquired_{AD_BATNTC2}；

According to the collected partial pressure value V_{AD_BATNTC1}And a partial pressure value V_{AD_BATNTC2}Calculating the voltage drop voltage of the ground wire and the resistance value of the thermistor;

and obtaining a corresponding temperature value according to the calculated resistance value of the thermistor.

10. A temperature detection method for use in the temperature detection circuit of any one of claims 5-7, the method comprising:

switching off the first switch unit, switching on the second switch unit, and collecting the voltage division value V of the second voltage division resistor and the thermistor_{AD_BATNTC1}；

Switching on the first switch unit, switching off the second switch unit, and collecting the voltage division value V of the first voltage division resistor and the thermistor_{AD_BATNTC3}；

According to the collected partial pressure value V_{AD_BATNTC1}And a partial pressure value V_{AD_BATNTC3}Calculating the voltage drop voltage of the ground wire and the resistance of the thermistor;

and obtaining a corresponding temperature value according to the calculated resistance value of the thermistor.

Technical Field

The invention belongs to the field of electric tools, and particularly relates to a temperature detection circuit, a temperature detection method and an electric tool.

Background

In the prior art, there are many types of electric tools, and a battery pack is connected to a control board through a power supply module line to drive a load (electric tool) to work. Under the condition that the electric tool works at a large current, because the power supply module line is long enough and has internal resistance, potential difference can be formed between the battery pack and two sides of the control board, and the voltage of the power supply module line acquired by the control board is unequal to the actual voltage of the battery pack. And the existence of the potential difference can also cause the sampling accuracy rate of the temperature of the battery pack to be influenced. Therefore, when the electric tool works at a large current, the voltage sampling is inaccurate, and the measured resistance value of the thermistor and the temperature value detected according to the resistance value of the thermistor are also inaccurate.

Disclosure of Invention

The embodiment of the invention provides a temperature detection circuit, aiming at solving the problem that the temperature value detected by an electric tool during heavy-current work is inaccurate in the prior art.

The embodiment of the invention provides a temperature detection circuit, which comprises a thermistor, a first voltage-dividing resistor, a second voltage-dividing resistor, a control module and a first switch unit, wherein the thermistor is connected with the first voltage-dividing resistor;

the first switch unit is connected between a power supply module and the first end of the thermistor after being connected with the first voltage dividing resistor in series, and the control end of the first switch unit is connected with the control module;

the first switch unit is connected with the first voltage dividing resistor in series and then connected with the second voltage dividing resistor in parallel;

the second end of the thermistor is grounded;

the voltage acquisition end of the control module is connected to the first end of the thermistor and acquires a voltage division value of the first end of the thermistor.

Still further, the temperature detection circuit further includes a filter unit, and the filter unit includes:

one end of the first current limiting resistor is connected with the voltage acquisition end of the control module, and the other end of the first current limiting resistor is connected with the first end of the thermistor;

and one end of the filter capacitor is connected with the voltage acquisition end of the control module, and the other end of the filter capacitor is grounded.

Still further, the first switching unit includes:

the input end of the first switching tube is connected with a power supply module, and the output end of the first switching tube is connected with the first divider resistor;

one end of the second current limiting resistor is connected with the control end of the first switching tube, and the other end of the second current limiting resistor is connected with the first output end of the control module;

and one end of the first pull-down resistor is respectively connected with the control end of the first switching tube and one end of the second current-limiting resistor, and the other end of the first pull-down resistor is grounded.

Furthermore, when the first switch unit is turned on, the first voltage dividing resistor is connected in parallel with the second voltage dividing resistor and then connected in series with the thermistor, and the control module voltage acquisition end acquires a voltage dividing value of the thermistor after the first voltage dividing resistor is connected in parallel with the second voltage dividing resistor; when the first switch unit is turned off, the second voltage-dividing resistor is connected with the thermistor in series, and the voltage-dividing value of the second voltage-dividing resistor and the thermistor is acquired by the voltage acquisition end of the control module.

Furthermore, the voltage regulator further comprises a second switch unit connected with the second voltage-dividing resistor in series, and the control end of the second switch unit is connected with the control module.

Still further, the second switching unit includes:

the input end of the second switching tube is connected with the power supply module, and the output end of the second switching tube is connected with the second voltage-dividing resistor;

one end of the third current limiting resistor is connected with the control end of the second switching tube, and the other end of the third current limiting resistor is connected with the second output end of the control module;

and one end of the second pull-down resistor is connected with the control end of the second switch tube, and the other end of the second pull-down resistor is grounded.

Furthermore, when the first switch unit is turned on and the second switch unit is turned off, the first voltage dividing resistor is connected in series with the thermistor, and the control module voltage acquisition end acquires voltage dividing values of the first voltage dividing resistor and the thermistor; when the first switch unit is turned off and the second switch unit is turned on, the second voltage-dividing resistor is connected in series with the thermistor, and the voltage-dividing value of the second voltage-dividing resistor and the thermistor is acquired by the voltage acquisition end of the control module.

The invention also provides an electric tool, which comprises a battery pack module, a main controller and the temperature detection circuit, wherein the thermistor is arranged in the battery pack module, and the battery pack module is connected with the main controller through a power line.

The invention also provides a temperature detection method for the temperature detection circuit, which comprises the following steps:

the first switch unit is switched off, and the voltage division value V of the second voltage division resistor and the thermistor is acquired_{AD_BATNTC1}；

A first switch unit is conducted, and after the first voltage division resistor and the second voltage division resistor are connected in parallel, the voltage division value V of the first voltage division resistor and the voltage division value V of the second voltage division resistor are acquired_{AD_BATNTC2}；

According to the collected partial pressure value V_{AD_BATNTC1}And a partial pressure value V_{AD_BATNTC2}Calculating the voltage drop voltage of the ground wire and the resistance value of the thermistor;

and obtaining a corresponding temperature value according to the calculated resistance value of the thermistor.

The invention also provides a temperature detection method for the temperature detection circuit, which comprises the following steps:

switching off the first switch unit, switching on the second switch unit, and collecting the voltage division value V of the second voltage division resistor and the thermistor_{AD_BATNTC1}；

Switching on the first switch unit, switching off the second switch unit, and collecting the voltage division value V of the first voltage division resistor and the thermistor_{AD_BATNTC3}；

According to the collected partial pressure value V_{AD_BATNTC1}And a partial pressure value V_{AD_BATNTC3}Calculating the voltage drop voltage of the ground wire and the resistance of the thermistor;

and obtaining a corresponding temperature value according to the calculated resistance value of the thermistor.

The embodiment of the invention sets a first divider resistor and a second divider resistor which are connected in parallel and then connected in series with a thermistor, and a first switch unit is connected in series on the first divider resistor, the on-off of the first divider resistor is controlled under the condition that a power supply module provides voltage through the level signal output by a control module, so as to acquire the voltage division value obtained by voltage division of the first divider resistor and the second divider resistor after being connected in parallel and the thermistor and the voltage division value obtained by voltage division of the second divider resistor and the thermistor, and based on two voltage division values acquired twice and the parameters of each known divider resistor, the accurate resistance value of the thermistor and the voltage drop voltage generated on the ground wire of the power supply module can be obtained through calculation, and the resistance value of the thermistor can be checked to obtain the corresponding temperature value so as to obtain the accurate temperature value for controlling the running state of the electric tool, protecting the controller and the battery. The voltage drop value generated on the ground wire of the power supply module can be used for compensating the battery voltage acquisition error caused by the large-current work, so that the battery voltage value read by the controller is more accurate, the control is more accurate, the operation is more stable, and the battery life is favorably protected.

Drawings

Fig. 1 is a circuit diagram of a temperature detection circuit according to an embodiment of the present invention;

FIG. 2 is a circuit diagram of another temperature sensing circuit provided by an embodiment of the present invention;

FIG. 3 is a circuit diagram of another temperature sensing circuit provided by an embodiment of the present invention;

FIG. 4 is a circuit diagram of another temperature sensing circuit provided by an embodiment of the present invention;

FIG. 5 is a flow chart of a method for detecting temperature according to an embodiment of the present invention;

FIG. 6 is a flow chart of another temperature detection method provided by an embodiment of the invention;

fig. 7 is a schematic view of an electric tool according to an embodiment of the present invention.

Wherein, 1, a thermistor; r1, a first divider resistor; r2 and a second divider resistor; 2. a control module; 3. a first switch unit; q1, a first switch tube; r4 and a second current limiting resistor; r5, a first pull-down resistor; r3, a first current limiting resistor; c1, a filter capacitor; 4. a second switching unit; q2, second switch tube; r6 and a third current limiting resistor; r7, a second pull-down resistor; 5. a battery pack module; 6. and a main controller.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The first switch unit of the circuit is connected between a power supply module and the first end of the thermistor after being connected with the first voltage dividing resistor in series, the control end of the first switch unit is connected with the control module, the first switch unit is connected with the first voltage dividing resistor in series and then connected with the second voltage dividing resistor in parallel, the second end of the thermistor is grounded, and the voltage acquisition end of the control module is connected to the first end of the thermistor to acquire the voltage dividing value of the first end of the thermistor. The invention sets a first divider resistor and a second divider resistor which are connected in parallel and then connected in series with a thermistor, and a first switch unit is connected in series on the first divider resistor, the on-off of the first divider resistor is controlled under the condition that a power supply module provides voltage through the level signal output by a control module, so as to acquire the divided voltage value obtained by dividing the first divider resistor and the second divider resistor with the thermistor after being connected in parallel and the divided voltage value obtained by dividing the second divider resistor and the thermistor, and the accurate resistance value of the thermistor and the voltage drop voltage generated on the ground wire of the power supply module can be obtained through calculation based on two divided voltage values acquired twice and the parameters of each known divider resistor, and the resistance value of the thermistor can be checked to obtain the corresponding temperature value so as to obtain the accurate temperature value for controlling the running state of the electric tool, protecting the controller and the battery. The voltage drop value generated on the ground wire of the power supply module can be used for compensating the battery voltage acquisition error caused by the large-current work, so that the battery voltage value read by the controller is more accurate, the control is more accurate, the operation is more stable, and the battery life is favorably protected.

Example one

Referring to fig. 1, an embodiment of the present invention provides a temperature detection circuit, including a thermistor 1, a power supply module, a first voltage dividing resistor R1, a second voltage dividing resistor R2, a control module 2, and a first switch unit 3;

the first switch unit 3 is connected in series with the first voltage dividing resistor R1 and then connected between a power supply module and the first end of the thermistor 1, and the control end of the first switch unit 3 is connected with the control module 2;

the first switch unit 3 is connected in series with the first voltage-dividing resistor R1 and then connected in parallel with the second voltage-dividing resistor R2;

the second end of the thermistor 1 is grounded;

the voltage acquisition end of the control module 2 is connected to the first end of the thermistor 1 and acquires a voltage division value of the first end of the thermistor 1.

The power supply module can be an AC/DC power supply, a storage battery, a dry battery and the like.

In the invention, the first switch unit 3 is connected in series with the first voltage dividing resistor R1, then connected in parallel with the second voltage dividing resistor R2, and then connected between the power supply module and the first end of the thermistor 1.

As shown in fig. 1, the output end of the first switch unit 3 is connected to one end of the first voltage-dividing resistor R1, the control end of the first switch unit 3 is connected to the control module 2, the input end of the first switch unit 3 and one end of the second voltage-dividing resistor R2 are simultaneously connected to the power supply module, and the other end of the first voltage-dividing resistor R1 and the other end of the second voltage-dividing resistor R2 are simultaneously connected to the first end of the thermistor 1; of course, the positions of the first switch unit 3 and the first voltage-dividing resistor R1 may be interchanged, specifically, the input end of the first switch unit 3 is connected to one end of the first voltage-dividing resistor R1, the control end of the first switch unit 3 is connected to the control module 2, the output end of the first switch unit 3 and one end of the second voltage-dividing resistor R2 are simultaneously connected to the first end of the thermistor 1, and the other end of the first voltage-dividing resistor R1 and the other end of the second voltage-dividing resistor R2 are simultaneously connected to the power supply module.

In the embodiment of the present invention, as shown in fig. 1, the thermistor 1 may be an NTC (Negative Temperature Coefficient thermistor 1) or a PTC (Positive Temperature Coefficient thermistor 1), and the resistance value of the Negative Temperature Coefficient thermistor 1 is lower as the Temperature is higher. When the thermistor 1 is in a normal state, the existence of the internal resistance of the ground wire of the battery connecting wire can generate potential difference in the circuit, and the temperature detection circuit provided by the invention can obtain the accurate resistance value of the thermistor 1 and the voltage drop voltage generated on the ground wire of the power supply module, and can compensate the potential difference in the working process according to the voltage drop voltage. The resistance value of the thermistor 1 has a fixed corresponding relation with the temperature, and the temperature value can be obtained by looking up the resistance/temperature corresponding table of the thermistor 1.

The power supply module provides working voltage for the circuit, when the first switch unit 3 is turned on, the first switch unit 3 is connected in series with the first voltage dividing resistor R1 and then connected in parallel with the second voltage dividing resistor R2, and after the parallel connection, one end of the power supply module is connected to the 3.3V power supply module, and the other end of the power supply module is connected to the thermistor 1. The IO port of the control module 2 is connected to the control end of the first switch unit 3, and can provide a level signal to the first switch unit 3 for controlling the on/off state of the branch, that is, whether the power supply module voltage can flow through the first voltage dividing resistor R1. When the first switch unit 3 is turned on, the power module voltage is simultaneously supplied to the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, so that the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 simultaneously divide the voltage of the thermistor 1; when the first switch unit 3 is turned off, the power supply module voltage is divided into the second voltage dividing resistor R2 and the thermistor 1. The voltage acquisition end of the control module 2 is connected with one end of the thermistor 1, and then the voltage acquisition end can acquire the voltage division values corresponding to two different voltage divisions.

Referring to fig. 1, the control module 2 may be a single chip, and is provided with a first output end and a voltage collecting end. The first output end of the control module 2 may refer to a pin IO1 shown in fig. 1, the pin IO1 is connected to the control end of the first switch unit 3, and the control module 2 controls the pin IO1 to output a low level signal/a high level signal to control the on/off state of the first switch unit 3, so that after the circuit is powered on, the first voltage dividing resistor R1 and the second voltage dividing resistor R2 divide voltage with the thermistor 1, for example: the power supply module 3.3V voltage supply circuit is connected to the thermistor 1 through the second voltage dividing resistor R2, and controls the IO1 port of the control module 2 to output a high level signal, if the control end of the first switch unit 3 is cut off under the high level signal, the voltage of the power supply module does not pass through the first voltage dividing resistor R1, and at this time, the voltage collecting end of the control module 2 can collect the voltage dividing values of the second voltage dividing resistor R2 and the thermistor 1.

In the embodiment of the invention, a first divider resistor R1 and a second divider resistor R2 which are connected in parallel and then connected in series with a thermistor 1 are arranged, a first switch unit 3 is connected in series with the first divider resistor R1, the on-off of the first divider resistor R1 is controlled under the condition that a power supply module supplies voltage through the level signal output by a control module 2, and then the divided voltage value obtained by dividing the voltage of the thermistor 1 after the first divider resistor R1 and the second divider resistor R2 are connected in parallel and the divided voltage value obtained by dividing the voltage of the second divider resistor R2 and the thermistor 1 are collected, based on two collected divided voltage values and the parameters of known divider resistors, the accurate resistance value of the thermistor 1 and the voltage drop voltage generated on the ground wire of the power supply module can be obtained through calculation, the resistance value of the thermistor 1 can be checked to obtain the corresponding temperature value, and then the accurate temperature value can be obtained, the controller is used for controlling the running state of the electric tool and protecting the controller and the battery. The voltage drop value generated on the ground wire of the power supply module can be used for compensating the battery voltage acquisition error caused by the large-current work, so that the battery voltage value read by the controller is more accurate, the control is more accurate, the operation is more stable, and the battery life is favorably protected.

Example two

Referring to fig. 2, in the embodiment of the present invention, based on the first embodiment, the apparatus further includes a filtering unit, where the filtering unit includes:

one end of the first current limiting resistor R3 is connected with the voltage acquisition end of the control module 2, and the other end of the first current limiting resistor R3 is connected with the first end of the thermistor 1;

and one end of the filter capacitor C1 is connected with the voltage acquisition end of the control module 2, and the other end of the filter capacitor C1 is grounded.

The filtering unit comprises a first current limiting resistor R3 and a filtering capacitor C1, the first current limiting resistor R3 is connected between the voltage acquisition end of the control module 2 and the thermistor 1 in series, one end of the filtering capacitor C1 is connected with the voltage acquisition end of the control module 2, and the other end of the filtering capacitor C1 is grounded to filter the voltage division values of the switch unit and the thermistor 1.

The filtering unit can filter out interference signals in the circuit. The first current limiting resistor R3 is used for current limiting, so that the circuit components can be prevented from being burnt by large current; the filter capacitor C1 may perform a filtering function. One end of the first current limiting resistor R3 is connected to the thermistor 1, the first switch unit 3 and the second switch unit 4, and the voltage collecting end of the control module 2 is connected between the first current limiting resistor R3 and the filter capacitor C1, and is used for collecting the voltage dividing values of the first voltage dividing resistor R1, the second voltage dividing resistor R2 and the thermistor 1 after the filter unit performs voltage stabilizing filtering.

Referring to FIG. 2, the first current limiting resistor R3 may be 0402/100R/50V. The model of the filter capacitor C1 can be 0402/103/50V. One end of the first current limiting resistor R3 is connected to the thermistor 1, the other end of the first current limiting resistor R3 is connected to one end of the filter capacitor C1 and the voltage collecting end of the control module 2, and the other end of the filter capacitor C1 is grounded. Therefore, after the voltage of the power supply module is output to the thermistor 1 through the first switch unit 3, the second switch unit 4, the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, a filtering unit is added in the circuit, so that the output voltage can be filtered, and the stable output voltage can be conveniently collected at the voltage collecting end.

EXAMPLE III

In an embodiment of the present invention, based on the first embodiment, the first switch unit 3 includes:

a first switch tube Q1, an input end of the first switch tube Q1 is connected to a power supply module, and an output end of the first switch tube Q1 is connected to the first voltage dividing resistor R1;

one end of the second current limiting resistor R4 is connected to the control end of the first switching tube Q1, and the other end of the second current limiting resistor R4 is connected to the first output end of the control module 2;

and one end of the first pull-down resistor R5 is connected to the control end of the first switch tube Q1 and one end of the second current-limiting resistor, and the other end of the first pull-down resistor R5 is grounded.

Referring to fig. 1, the first switch Q1 may be a P-MOS transistor, model 40P05Y, and is used as a switch in the embodiment of the present invention. The model of the first divider resistor R1 is 0402/5K/50V; the model of the second current limiting resistor R4 is 0402/330R/50V; the first pull-down resistor R5 is 0402/10K/50V.

The input terminal of the first switch Q1 is a source (S pole), the output terminal of the first switch Q1 is a drain (D pole), and the control terminal of the first switch Q1 is a gate (G pole).

Specifically, the S pole of Q1 is connected to the 3.3V power supply module, the G pole is connected to the second current limiting resistor R4 and one end of the first pull-down resistor R5, and the D pole is connected to one end of the first voltage dividing resistor R1 and then connected to the thermistor 1. The other end of the second current limiting resistor R4 is connected to the first output terminal (pin IO1) of the control module 2, and the other end of the first pull-down resistor R5 is grounded. The second current limiting resistor R4 and the first pull-down resistor R5 can be used to limit the current flowing through the circuit of the first switch unit 3, and thus, the circuit can be protected.

When the first switch unit 3 is turned on, the first voltage dividing resistor R1 is connected in parallel with the second voltage dividing resistor R2 and then connected in series with the thermistor 1, and the voltage collecting end of the control module 2 collects the voltage dividing value of the first voltage dividing resistor R1 and the second voltage dividing resistor R2 connected in parallel and then connected with the thermistor 1; when the first switch unit 3 is turned off, the second voltage dividing resistor R2 is connected in series with the thermistor 1, and the voltage collecting terminal of the control module 2 collects the voltage dividing values of the second voltage dividing resistor R2 and the thermistor 1.

Analysis of the working principle of the present embodiment:

when the IO1 pin of the control module 2 is at a high level, the Q1 is not turned on, and the power supply module voltage is directly divided by the second voltage dividing resistor R2 and the thermistor 1, the calculation formula is as follows:

VAD _ BATNTC1 is the voltage division value between the second voltage-dividing resistor R2 and the thermistor 1, R2 is the resistance value of the second voltage-dividing resistor R2, VBAT _ GND is the voltage drop of the ground, and R8 is the resistance value of the thermistor 1.

Further, when the second output terminal of the control module 2 is at a low level, Q1 is turned on, the power supply module supplies power, and the second voltage dividing resistor R2 is connected in parallel with the first voltage dividing resistor R1 and then connected in series with the thermistor 1 for voltage division, which has the following calculation formula:

the VAD _ battnc 2 is a voltage division value between the first voltage division resistor R1 and the second voltage division resistor R2 after being connected in parallel and the thermistor 1, and R1 is a resistance value of the first voltage division resistor R1.

As shown in fig. 5, the specific method of temperature detection includes:

the first switch unit 3 is switched off, and the voltage division value VAD _ BATNTC1 of the second voltage division resistor R2 and the thermistor 1 is acquired;

turning on the first switch unit 3, and acquiring a voltage division value VAD _ BATNTC2 of the thermistor 1 after the first voltage division resistor R1 and the second voltage division resistor R2 are connected in parallel;

calculating the voltage drop voltage of the ground wire and the resistance value of the thermistor 1 according to the collected partial voltage value VAD _ BATNTC1 and the partial voltage value VAD _ BATNTC 2;

and obtaining a corresponding temperature value according to the calculated resistance value of the thermistor 1.

When VAD _ BATNTC1, VAD _ BATNTC2, R2 and R1 are known, R8 and VBAT _ GND can be calculated by combining the above equations (1) and (2). For convenience of calculation, the relationship of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 in the circuit may be R2 — 2R 1. Of course, R1 and R2 may have other relationships, and are not limited in the embodiments of the present invention. The resistance/temperature correspondence table of the thermistor 1 is checked based on the calculated resistance value of the thermistor 1, and a corresponding temperature value can be obtained.

Optionally, as another possible embodiment, referring to fig. 3, a second switch unit 4 connected in series with the second voltage-dividing resistor R2 is further included, and a control end of the second switch unit 4 is connected to the control module 2.

As shown in fig. 3, the output end of the second switch unit 4 is connected to one end of the second voltage-dividing resistor R2, the control end of the second switch unit 4 is connected to the control module 2, the input end of the second switch unit 4 and one end of the first voltage-dividing resistor R1 or the input end of the first switch unit 3 are simultaneously connected to the power supply module, and the other end of the second voltage-dividing resistor R2 and the other end of the first voltage-dividing resistor R1 or the output end of the first switch unit 3 are simultaneously connected to the first end of the thermistor 1; of course, the positions of the second switch unit 4 and the second voltage-dividing resistor R2 may be interchanged, specifically, the input end of the second switch unit 4 is connected to one end of the second voltage-dividing resistor R2, the control end of the second switch unit 4 is connected to the control module 2, the output end of the second switch unit 4 and one end of the first voltage-dividing resistor R1 or the output end of the first switch unit 3 are simultaneously connected to the first end of the thermistor 1, and the other end of the second voltage-dividing resistor R2 and the other end of the first voltage-dividing resistor R1 or the input end of the first switch unit 3 are simultaneously connected to the power supply module.

The control module 2 further includes a second output terminal of the control module 2, such as a pin IO2 shown in fig. 3. The pin IO2 is connected to the input terminal of the second switch unit 4, and outputs a low level signal/a high level signal through the control pin IO2, so as to control the on/off state of the second switch unit 4.

Wherein the second switching unit 4 includes:

the input end of the second switching tube Q2 is connected with a power supply module, and the output end of the second switching tube Q2 is connected with the second voltage-dividing resistor R2;

one end of the third current limiting resistor R6 is connected to the control end of the second switching tube Q2, and the other end of the third current limiting resistor R6 is connected to the second output end of the control module 2;

and one end of the second pull-down resistor R7 is connected with the control end of the second switching tube Q2, and the other end of the second pull-down resistor R7 is grounded.

Specifically, with continued reference to fig. 3, the second switch Q2 may be a P-MOS transistor, model 40P05Y, and is used as a switch in the embodiment of the present invention. The model of the second voltage-dividing resistor R2 is 0402/10K/50V; the model of the third current limiting resistor R6 is 0402/330R/50V; the second pull-down resistor R7 is 0402/10K/50V.

The input terminal of the second switch Q2 is a source (S pole), the output terminal of the second switch Q2 is a drain (D pole), and the control terminal of the second switch Q2 is a gate (G pole).

More specifically, the S pole of Q2 is connected to the 3.3V power supply module, the G pole is connected to the third current limiting resistor R6 and one end of the second pull-down resistor R7, and the D pole is connected to one end of the second voltage dividing resistor R2 and then connected between the thermistor 1 and the second current limiting resistor R4. The other end of the second current limiting resistor R4 is connected to the second output terminal of the control module 2, and the other end of the third current limiting resistor R6 is grounded. The third current limiting resistor R6 and the second pull-down resistor R7 may be used to limit the magnitude of the current flowing through the circuit of the second switch unit 4, and thus function as a protection circuit.

When the first switch unit 3 is turned on and the second switch unit 4 is turned off, the first voltage dividing resistor R1 is connected in series with the thermistor 1, and the voltage collecting terminal of the control module 2 collects the voltage dividing values of the first voltage dividing resistor R1 and the thermistor 1; when the first switch unit 3 is turned off and the second switch unit 4 is turned on, the second voltage dividing resistor R2 is connected in series with the thermistor 1, and the voltage collecting terminal of the control module 2 collects the voltage dividing values of the second voltage dividing resistor R2 and the thermistor 1.

When the first switching unit 3 and the second switching unit 4 have a circuit at the same time, the operating principle is analyzed as follows: when the first switch unit 3 and the second switch unit 4 have circuits at the same time, the IO1 pin of the control module 2 is set to be low, the IO2 pin is set to be high, the Q1 is turned on, and the Q2 is turned off. The voltage of the power supply module flows from the S pole to the D pole of the Q1, then flows through the thermistor 1 through the first voltage dividing resistor R1, and finally can acquire a voltage dividing value obtained by serial voltage division of the first voltage dividing resistor R1 and the thermistor 1 at a voltage acquisition end of the control module 2 connected with the thermistor 1. I.e., the voltage drop voltage generated on the ground line in the circuit by the thermistor 1 in the case where the first switching unit 3 is turned on, corresponds to the following formula (3),

the VAD _ battnc 3 is the voltage division value between the first voltage division resistor R1 and the thermistor 1.

As shown in fig. 6, the specific method of temperature detection includes:

turning off the first switch unit 3, turning on the second switch unit 4, and collecting a voltage division value VAD _ BATNTC1 of the second voltage division resistor R2 and the thermistor 1;

turning on the first switch unit 3, turning off the second switch unit 4, and collecting a voltage division value VAD _ BATNTC3 of the first voltage division resistor R1 and the thermistor 1;

calculating the voltage drop voltage of the ground wire and the resistance of the thermistor 1 according to the collected partial voltage value VAD _ BATNTC1 and the partial voltage value VAD _ BATNTC 3;

and obtaining a corresponding temperature value according to the calculated resistance value of the thermistor 1.

Further, when the IO1 pin of the control module 2 is set to a high level and the IO2 pin is set to a low level 1, Q1 is turned off, Q2 is turned on, the voltage of the power supply module flows from the S pole to the D pole of Q2, then flows through the thermistor 1 via the second voltage dividing resistor R2, and finally, the voltage dividing value of the thermistor 1 after voltage division by the second voltage dividing resistor R2 and the thermistor 1 in series can be collected at the voltage collecting end of the control module 2 connected with the thermistor 1. In this way, by adding the thermistor 1 to the circuit, voltage division is performed with the second voltage-dividing resistor R2, so that the voltage drop generated on the ground line in the circuit when Q1 is turned off and Q2 is turned on can be calculated, and the specific formula is as shown in fig. 1. After the VAD _ battntc 1 and VAD _ battntc 3 are collected, the resistance value of the thermistor 1 and the voltage drop of the ground wire can be calculated according to the formula (1) and the formula (3) in combination with known information.

As another possible embodiment, as shown with reference to fig. 1, the first switching unit 3 may be replaced to the second switching unit 4. Thus, when the pin I02 is set to low level, the second switch unit 4 is turned on, and the power module voltage flows through the first divider resistor R1, the second divider resistor R2 and the thermistor 1 at the same time, so as to obtain the above formula (2). When the pin IO2 is set to a high level, the voltage of the power supply module passes through the first voltage divider resistor R1 and the thermistor 1 to obtain a formula (3), and according to the formula (3) and the formula (2), the resistance of the thermistor 1 and the voltage drop of the ground line can be calculated as well.

As another possible embodiment, after the resistance value of the thermistor 1 is calculated, whether the battery is over-temperature can be determined according to the resistance value of the thermistor 1. In the embodiment of the present invention, if the thermistor 1 is a negative temperature coefficient thermistor 1, the resistance value is lower as the temperature is higher, for example: the preset over-temperature protection resistance threshold is 20 Ω, and when the thermistor 1 is 20 Ω, it indicates that over-temperature protection is needed. The over-temperature protection mode can be that prompt information is sent to prompt that over-temperature protection is needed, and can be that a circuit switch is disconnected to avoid burning out components due to over-temperature, and the like. In the embodiment of the present invention, the manner of the over-temperature protection is not limited.

In the embodiment of the invention, a first divider resistor R1 and a second divider resistor R2 which are connected in parallel and then connected in series with a thermistor 1 are arranged, a first switch unit 3 is connected in series with the first divider resistor R1, the on-off of the first divider resistor R1 is controlled under the condition that a power supply module supplies voltage through the level signal output by a control module 2, and then the divided voltage value obtained by dividing the voltage of the thermistor 1 after the first divider resistor R1 and the second divider resistor R2 are connected in parallel and the divided voltage value obtained by dividing the voltage of the second divider resistor R2 and the thermistor 1 are collected, based on two collected divided voltage values and the parameters of known divider resistors, the accurate resistance value of the thermistor 1 and the voltage drop voltage generated on the ground wire of the power supply module can be obtained through calculation, the resistance value of the thermistor 1 can be checked to obtain the corresponding temperature value, and then the accurate temperature value can be obtained, the controller is used for controlling the running state of the electric tool and protecting the controller and the battery. The voltage drop value generated on the ground wire of the power supply module can be used for compensating the battery voltage acquisition error caused by the large-current work, so that the battery voltage value read by the controller is more accurate, the control is more accurate, the operation is more stable, and the battery life is favorably protected.

Example four

Referring to fig. 7, fig. 7 shows an electric tool provided by the present invention, the electric tool includes a battery pack module 5, a main controller 6 and a temperature detection circuit provided in any one of the above embodiments, and the thermistor 1 is disposed in the battery pack module 5, and the battery pack module 5 and the main controller 6 are connected by a power line.

As shown in fig. 7, the battery pack module 5 may be a lithium battery pack, or may be another type of battery pack. The lithium battery pack refers to the assembly and production of lithium batteries and is also called a lithium battery pack. And the thermistor 1 described above is provided in the battery pack module 5. The main controller 6 may be a part that controls the switching of the circuit. The temperature detection circuit is provided in the main controller 6 (the first switch unit 3, the second switch unit 4, the control module 2, and the filter unit) except for the thermistor 1 provided in the battery pack module 5. The battery pack module 5 is connected to the main controller 6 via a power line and a ground line.

Through adding thermistor 1 in battery package module 5, after having heavy current to flow in the power module line, control module 2 can control the level height of first output, second output to control first switch unit 3 to switch on/off, gather the partial pressure value of first divider resistance R1 and the circuit after thermistor 1 divides voltage in battery package module 5 at control module 2 voltage acquisition end, and gather the partial pressure value of the circuit after second divider resistance R2 and the voltage division of thermistor 1 in battery package module 5. The thermistor 1 resistance value and the ground drop voltage can be calculated in combination with known information. The resistance value of the thermistor 1 can be looked up to obtain a corresponding temperature value, and then an accurate temperature value is obtained, so that the operation state of the electric tool is controlled, and the controller and the battery are protected. The voltage loss of the circuit is compensated by adding the thermistor 1 into the circuit and calculating the voltage drop voltage of the ground wire, so that the electric tool can perform stable voltage sampling when working at a large current, and the electric tool with the voltage compensation circuit can accurately detect the battery voltage when working at a high power, timely control the running state of the electric tool, protect the battery or accurately display the battery power, and enable a user to know the battery state in time.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.