Capacitance Detection Circuit and Device

Abstract

The capacitance detection circuit and device provided by the embodiments of the present application relate to the technical field of capacitance detection. The capacitance detection circuit is applied to a capacitance detection device including a single-chip microcomputer. The capacitance detection circuit includes: a first compensation unit, the first end of which is connected to the output end of the single-chip microcomputer; a first injection unit, the first end of which is connected to the second end of the first compensation unit, the second end of which is connected to the high-voltage negative electrode, and the third end of which is connected to the input end of the single-chip microcomputer; a capacitance to be measured, the first end of which is connected to the low-voltage negative electrode, and the second end of which is connected to the second end of the first injection unit; a second compensation unit, the first end of which is connected to the low-voltage negative electrode, and the second end of which is connected to the second end of the first injection unit; wherein, the output end of the single-chip microcomputer is used to send a square wave signal, and the input end is used to receive the voltage signal at the third end of the first injection unit. Through the above settings, the cost can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of capacitance detection, and in particular, to a capacitance detection circuit and device. Background Art

[0002] Electric vehicles are currently a hot topic of research and development in various countries. Compared with traditional fuel vehicles, the development of electric vehicles can effectively alleviate the pressure of fossil energy depletion, and at the same time help reduce the emissions of carbon dioxide and other sulfur-containing gases. China has introduced a large number of encouraging policies to support the development of the electric vehicle industry and included electric vehicles in the seven strategic emerging industries. Compared with traditional vehicles, the proportion of the electronic and electrical systems in electric vehicles has increased significantly, and the power system of electric vehicles is a high-voltage system that has never been used in vehicles before, with a voltage platform of several hundred volts. Therefore, electrical insulation is an important item for the high-voltage safety of electric vehicles.

[0003] However, in the current solutions for measuring the insulation resistance of electric vehicles, the measurement accuracy is affected by the Y capacitance between the vehicle's high-voltage system and low-voltage system, and it is necessary to measure the Y capacitance.

[0004] However, the inventors have found through research that in the prior art, the capacitance detection circuit is complex, resulting in a relatively high cost. Summary of the Invention

[0005] In view of this, the purpose of the present application is to provide a capacitance detection circuit and device to improve the problems existing in the prior art.

[0006] To achieve the above purpose, the embodiments of the present application adopt the following technical solutions:

[0007] A capacitance detection circuit is applied to a capacitance detection device including a single-chip microcomputer. The capacitance detection circuit includes:

[0008] A first compensation unit, the first end of which is connected to the output end of the single-chip microcomputer;

[0009] A first injection unit, the first end of which is connected to the second end of the first compensation unit, the second end is connected to the high-voltage negative pole, and the third end is connected to the input end of the single-chip microcomputer;

[0010] A capacitance to be measured, the first end of which is connected to the low-voltage negative pole, and the second end is connected to the second end of the first injection unit;

[0011] A second compensation unit, the first end of which is connected to the low-voltage negative pole, and the second end is connected to the second end of the first injection unit;

[0012] Among them, the output end of the single-chip microcomputer is used to send a square wave signal, and the input end is used to receive the voltage signal at the third end of the first injection unit.

[0013] In a preferred selection of the embodiment of the present application, the first compensation unit includes a first resistor, the first end of which is connected to the output end of the single-chip microcomputer, and the second end is connected to the first end of the first injection unit.

[0014] In a preferred selection of the embodiment of the present application, the first injection unit includes:

[0015] A second resistor, the first end of which is connected to the second end of the first compensation unit, and the second end is used as the third end of the first injection unit and is connected to the input end of the single-chip microcomputer;

[0016] A first capacitor, the first end of which is connected to the second end of the second resistor, and the second end is connected to the high-voltage negative electrode.

[0017] In a preferred selection of the embodiment of the present application, the second compensation unit includes a second capacitor, the first end of which is connected to the low-voltage negative electrode, and the second end is connected to the second end of the first injection unit.

[0018] In a preferred selection of the embodiment of the present application, the first compensation unit further includes a fourth capacitor, the first end of which is connected to the first end of the first resistor, and the second end is connected to the second end of the first resistor.

[0019] In a preferred selection of the embodiment of the present application, the capacitance detection circuit further includes a first insulation unit, the first end of which is connected to the low-voltage negative electrode, and the second end is connected to the high-voltage negative electrode.

[0020] In a preferred selection of the embodiment of the present application, the first insulation unit includes a third resistor, the first end of which is connected to the low-voltage negative electrode, and the second end is connected to the high-voltage negative electrode.

[0021] In a preferred selection of the embodiment of the present application, the resistance value of the first resistor R1 is 100Ω.

[0022] In a preferred selection of the embodiment of the present application, the resistance value of the second resistor R2 is 200kΩ.

[0023] The embodiment of the present application further provides a capacitance detection device, including:

[0024] A single-chip microcomputer;

[0025] The above capacitance detection circuit;

[0026] Among them, the input end and the output end of the single-chip microcomputer are respectively connected to the capacitance detection circuit. The output end of the single-chip microcomputer is used to send a square wave signal, and the input end is used to receive the voltage signal output by the capacitance detection circuit.

[0027] The capacitance detection circuit and device provided by the embodiments of the present application improve the problem of high cost caused by the complexity of the capacitance detection circuit in the prior art by setting a capacitance detection circuit including a first compensation unit, a first injection unit, a capacitance to be measured, and a second compensation unit. The input end of the single-chip microcomputer is used to receive the voltage signal at the third end of the first injection unit to calculate the capacitance value of the capacitance to be measured. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 It is a structural block diagram of the capacitance detection device provided by the embodiments of the present application.

[0030] Figure 2 It is a structural block diagram of the capacitance detection circuit provided by the embodiments of the present application.

[0031] Figure 3 It is another structural block diagram of the capacitance detection circuit provided by the embodiments of the present application.

[0032] Figure 4 It is a circuit schematic diagram of the capacitance detection circuit provided by the embodiments of the present application.

[0033] Reference numerals: 10 - capacitance detection device; 100 - capacitance detection circuit; 110 - first compensation unit; 120 - first injection unit; 130 - second compensation unit; 140 - first insulation unit; R1 - first resistor; R2 - second resistor; R3 - third resistor; C1 - first capacitor; C2 - second capacitor; C3 - capacitance to be measured; C4 - fourth capacitor; 200 - single-chip microcomputer. Detailed Embodiments

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. It should be understood that the accompanying drawings in this application only serve the purpose of illustration and description, and are not used to limit the protection scope of this application. The flowcharts used in this application illustrate the operations implemented according to some embodiments of this application. It should be understood that the operations in the flowchart may not be implemented in sequence, and steps without a logical context relationship may be reversed or implemented simultaneously. In addition, those skilled in the art can add one or more other operations to the flowchart or remove one or more operations from the flowchart under the guidance of the content of this application.

[0035] In addition, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. The components of the embodiments of this application usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of this application claimed, but only represents the selected embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of this application.

[0036] In order to enable those skilled in the art to use the content of this application, the following implementation manners are given. For those skilled in the art, without departing from the spirit and scope of this application, the general principles defined here can be applied to other embodiments and application scenarios.

[0037] It should be noted that the term "including" will be used in the embodiments of this application to indicate the existence of the features stated thereafter, but does not exclude the addition of other features.

[0038] The terms used in the following embodiments are only for the purpose of describing specific embodiments, and are not intended to be a limitation on this application. As used in the specification of this application, the singular forms "a", "an", "the", "above", "said", "this" are also intended to include expressions such as "one or more", unless there is a clear indication to the contrary in the context. It should also be understood that in the following embodiments of this application, "at least one", "one or more" means one, two, or more than two. The term "and / or" is used to describe the association relationship of associated objects and indicates that three relationships can exist; for example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone, where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0039] References to "one embodiment" or "some embodiments" or the like described in this specification mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the present application. Thus, statements such as "in one embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments", etc., which appear at different places in this specification, do not necessarily all refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized. The terms "comprising", "including", "having" and their variants all mean "including but not limited to", unless otherwise specifically emphasized.

[0040] As Figure 1 shown, an embodiment of the present application provides a capacitance detection device 10, which may include a capacitance detection circuit 100 and a single-chip microcomputer 200.

[0041] Specifically, the input end and the output end of the single-chip microcomputer 200 are respectively connected to the capacitance detection circuit 100. The output end of the single-chip microcomputer 200 is used to send a square wave signal, and the input end is used to receive the voltage signal output by the capacitance detection circuit 100, and calculate the capacitance value of the capacitance C3 to be measured according to the voltage output by the capacitance detection circuit 100.

[0042] Regarding the single-chip microcomputer 200, it should be noted that the single-chip microcomputer 200 is also called a single-chip microcomputer (SingleChip Microcomputer), or a microcontroller unit (Microcontroller Unit, MCU). It appropriately reduces the frequency and specifications of the central processing unit (Central Process Unit, CPU), and integrates peripherals such as memory, counter (Timer), USB, A / D conversion, UART, PLC, DMA, and even the LCD drive circuit on a single chip to form a chip-level computer for different combinations of control for different application scenarios.

[0043] Combined with Figure 2 , an embodiment of the present application also provides a capacitance detection circuit 100, which can be used in the above capacitance detection device 10. The capacitance detection circuit 100 may include a first compensation unit 110, a first injection unit 120, a second compensation unit 130, and a capacitance C3 to be measured.

[0044] Specifically, the first end of the first compensation unit 110 is connected to the output end of the single-chip microcomputer 200. The first end of the first injection unit 120 is connected to the second end of the first compensation unit 110, the second end is connected to the high-voltage negative electrode, and the third end is connected to the input end of the single-chip microcomputer 200. The first end of the capacitor C3 to be measured is connected to the low-voltage negative electrode, and the second end is connected to the second end of the first injection unit 120. The first end of the second compensation unit 130 is connected to the low-voltage negative electrode, and the second end is connected to the second end of the first injection unit 120.

[0045] Among them, the output end of the single-chip microcomputer 200 is used to send a square wave signal, and the input end is used to receive the voltage signal at the third end of the first injection unit 120.

[0046] Through the above settings, by setting the capacitance detection circuit 100 including the first compensation unit 110, the first injection unit 120, the capacitor C3 to be measured, and the second compensation unit 130, the input end of the single-chip microcomputer 200 is used to receive the voltage signal at the third end of the first injection unit 120 to calculate the capacitance value of the capacitor C3 to be measured, improving the problem of high cost caused by the complexity of the capacitance detection circuit 100 in the prior art.

[0047] Regarding the first compensation unit 110, it should be noted that the specific composition of the first compensation unit 110 is not limited and can be set according to actual application requirements.

[0048] For example, in an alternative example, the first compensation unit 110 may include a first resistor R1. The first end of the first resistor R1 is connected to the output end of the single-chip microcomputer 200, and the second end is connected to the first end of the first injection unit 120.

[0049] Among them, the specific resistance value of the first resistor R1 is not limited and can be set according to actual application requirements.

[0050] For example, in an alternative example, the resistance value of the first resistor R1 may be 100 Ω.

[0051] Further, the first compensation unit 110 may further include a fourth capacitor C4. The first end of the fourth capacitor C4 is connected to the first end of the first resistor R1, and the second end is connected to the second end of the first resistor R1.

[0052] Regarding the first injection unit 120, it should be noted that the specific composition of the first injection unit 120 is not limited and can be set according to actual application requirements.

[0053] For example, in an alternative example, the first injection unit 120 may include a second resistor R2 and a first capacitor C1.

[0054] Specifically, the first end of the second resistor R2 is connected to the second end of the first compensation unit 110, and the second end serves as the third end of the first injection unit 120 and is connected to the input end of the single-chip microcomputer 200. The first end of the first capacitor C1 is connected to the second end of the second resistor R2, and the second end is connected to the high-voltage negative electrode.

[0055] That is to say, the first end of the second resistor R2 is connected to the second end of the first resistor R1, and the second end serves as the third end of the first injection unit 120 and is connected to the input end of the single-chip microcomputer 200.

[0056] Among them, the specific resistance value of the second resistor R2 is not limited and can be set according to actual application requirements.

[0057] For example, in an alternative example, the specific resistance value of the second resistor R2 may be 200 kΩ.

[0058] Optionally, the specific capacitance value of the first capacitor C1 is not limited and can be set according to actual application requirements.

[0059] For example, in an alternative example, the specific capacitance value of the first capacitor C1 may be 2 μF.

[0060] Regarding the second compensation unit 130, it should be noted that the specific composition of the second compensation unit 130 is not limited and can be set according to actual application requirements.

[0061] For example, in an alternative example, the second compensation unit 130 may include a second capacitor C2. The first end of the second capacitor C2 is connected to the low-voltage negative electrode, and the second end is connected to the second end of the first injection unit 120. That is to say, the first end of the second capacitor C2 is connected to the low-voltage negative electrode, and the second end is connected to the high-voltage negative electrode.

[0062] Regarding the capacitor to be measured C3, it should be noted that the first end of the capacitor to be measured C3 is connected to the low-voltage negative electrode, and the second end is connected to the high-voltage negative electrode.

[0063] Combined Figure 3 and Figure 4 , the capacitance detection circuit 100 may further include a first insulation unit 140.

[0064] Specifically, the first end of the first insulation unit 140 is connected to the low-voltage negative electrode, and the second end is connected to the high-voltage negative electrode.

[0065] Regarding the first insulation unit 140, it should be noted that the specific composition of the first insulation unit 140 is not limited and can be set according to actual application requirements.

[0066] For example, in an alternative example, the first insulation unit 140 may include a third resistor R3. The first end of the third resistor R3 is connected to the low-voltage negative electrode, and the second end is connected to the high-voltage negative electrode.

[0067] It should be noted that the output end of the single-chip microcomputer 200 sends a 5V / 10HZ square wave signal V1, which is injected into the first capacitor C1 through the first resistor R1, the fourth capacitor C4, and the second resistor R2. Then, a loop is formed by the third resistor R3, the second capacitor C2, and the capacitor under test C3 between the high-voltage negative electrode and the low-voltage negative electrode. The input end of the single-chip microcomputer 200 receives the voltage signal V2 at the first end of the first capacitor C1 and calculates the loop current I:

[0068]

[0069] R1 << R2;

[0070]

[0071] Specifically, the measurement principle of the capacitor can be expressed as follows:

[0072]

[0073]

[0074]

[0075] Among them, C: capacitance value; Q: electric charge quantity; U: voltage difference across the capacitor; I: current value flowing through the capacitor; t - T: current flowing time (half cycle of the injected square wave). Substitute the above loop current I into formula (2). Since the injection frequency is 10HZ and the period is only 0.1S, the trapezoidal method can be used to calculate the integral of the current to calculate the integral of the current within the time of T / 2. Substitute the obtained integral result Q into formula (1) to calculate the capacitance value:

[0076] C = C1 / / (C3 + C2);

[0077] Therefore, the size of the capacitor under test C3 is:

[0078]

[0079] It should be noted that the insulation detection circuit in the prior art includes the first resistor R1, the second resistor R2, and the first capacitor C1. The capacitance detection circuit 100 provided in the embodiments of the present application adds the second capacitor C2 and the fourth capacitor C4. The first resistor R1 and the fourth capacitor C4 jointly compensate the circuit to avoid the influence of the third resistor R3 on the acquisition accuracy of the capacitor under test C3. The third resistor R3 simulates the insulation resistance, and the capacitor under test C3 simulates the coupling capacitor between the vehicle's high-voltage system (total positive / total negative) and the low-voltage ground.

[0080] In the prior art, the peak-to-peak value can be calculated from the peak voltage and valley voltage of V2, and by calibrating different peak-to-peak values corresponding to different insulation resistance values, the calibration values are organized into a software array table. When in use, the insulation resistance value can be reported by looking up the table. The capacitance detection circuit 100 provided in the embodiments of the present application, based on the original insulation detection circuit, does not need to add an additional measurement circuit. Only by adding two capacitors to the original circuit, the size of the Y capacitor can be calculated through corresponding calculation methods. By increasing the cost minimally, the existing insulation detection circuit can simultaneously have the function of measuring the Y capacitor. At the same time, the measurement accuracy is not affected by the size of the insulation resistance, that is, the Y capacitor value can be measured within the full range of the insulation resistance. This method has low cost and simple calculation method, and has a huge promoting effect on optimizing the insulation resistance measurement affected by the Y capacitor.

[0081] In summary, the capacitance detection circuit and device provided in the embodiments of the present application, by setting a capacitance detection circuit including a first compensation unit, a first injection unit, a capacitor under test, and a second compensation unit, the input end of the single-chip microcomputer is used to receive the voltage signal at the third end of the first injection unit to calculate the capacitance value of the capacitor under test, which improves the problem of high cost caused by the complexity of the capacitance detection circuit in the prior art.

[0082] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A capacitance detection circuit, characterized in that, Applied to a capacitance detection device including a microcontroller, the capacitance detection circuit includes: A first compensation unit, the first end of which is connected to the output end of the microcontroller; A first injection unit, the first end of which is connected to the second end of the first compensation unit, the second end is connected to the high-voltage negative electrode, and the third end is connected to the input end of the microcontroller; A capacitance to be measured, the first end of which is connected to the low-voltage negative electrode, and the second end is connected to the second end of the first injection unit; A second compensation unit, the first end of which is connected to the low-voltage negative electrode, and the second end is connected to the second end of the first injection unit; Wherein, the output end of the microcontroller is used to send a square wave signal, and the input end is used to receive the voltage signal at the third end of the first injection unit; The first compensation unit includes a first resistor, the first end of which is connected to the output end of the microcontroller, and the second end is connected to the first end of the first injection unit; The first injection unit includes: A second resistor, the first end of which is connected to the second end of the first compensation unit, and the second end is used as the third end of the first injection unit and is connected to the input end of the microcontroller; wherein, the resistance value of the second resistor is much larger than the resistance value of the first resistor; A first capacitor, the first end of which is connected to the second end of the second resistor, and the second end is connected to the high-voltage negative electrode; The second compensation unit includes a second capacitor, the first end of which is connected to the low-voltage negative electrode, and the second end is connected to the second end of the first injection unit.

2. The capacitance detection circuit according to claim 1, wherein The first compensation unit further includes a fourth capacitor, the first end of which is connected to the first end of the first resistor, and the second end is connected to the second end of the first resistor.

3. The capacitance detection circuit according to claim 1, wherein The capacitance detection circuit further includes a first insulation unit, the first end of which is connected to the low-voltage negative electrode, and the second end is connected to the high-voltage negative electrode.

4. The capacitance detection circuit according to claim 3, wherein The first insulation unit includes a third resistor, the first end of which is connected to the low-voltage negative electrode, and the second end is connected to the high-voltage negative electrode.

5. The capacitance detection circuit according to claim 1, characterized in that, The resistance value of the first resistor R1 is 100Ω.

6. The capacitance detection circuit according to claim 1, wherein The resistance value of the second resistor R2 is 200kΩ.

7. A capacitance detection device, characterized in that, Including: A microcontroller; The capacitance detection circuit according to any one of claims 1-6; Wherein, the input end and the output end of the microcontroller are respectively connected to the capacitance detection circuit, the output end of the microcontroller is used to send a square wave signal, and the input end is used to receive the voltage signal output by the capacitance detection circuit.

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