CN215910570U

CN215910570U - Adjustable capacitance detection circuit

Info

Publication number: CN215910570U
Application number: CN202121742153.5U
Authority: CN
Inventors: 严世宝; 李茂�; 魏永峰; 严岩
Original assignee: Hefei Tongzhi Electrical Control Technology Co ltd
Current assignee: Hefei Tongzhi Electrical Control Technology Co ltd
Priority date: 2021-07-27
Filing date: 2021-07-27
Publication date: 2022-02-25
Anticipated expiration: 2031-07-27

Abstract

The utility model discloses an adjustable capacitance detection circuit in the field of capacitance detection, which comprises a processor, a sampling circuit, a group of excitation power supplies, a diode V1, a resistor R0, a switch S1, a switch S2, a switch S3, a switch S4 and an adjustable constant current circuit, wherein the anode of the diode V1 is connected with the anode of the excitation power supply, the cathode of the diode V1 is connected with the first end of the resistor R0, the second end of the resistor R0 is connected with the first end of the adjustable constant current circuit and the first end of the switch S1, the second end of the switch S1 is connected with the first ends of the switches S2 and S3, and distributed capacitance is arranged between the second end of the switch S1 and the excitation power supply ground; the second end of the switch S2 is connected with the second end of the adjustable constant current circuit, the second end of the switch S3 is connected with the sampling circuit, the sampling circuit is connected with the processor, and the adjustable constant current circuit is further connected with the excitation power ground. The utility model can obtain the value change of the distributed capacitor during charging and discharging by switching the state of the switch conversion circuit, thereby completing the calculation of the capacitance value of the distributed capacitor.

Description

Adjustable capacitance detection circuit

Technical Field

The utility model relates to the field of capacitance detection, in particular to an adjustable capacitance detection circuit.

Background

In an electrical network of any voltage class, the phenomenon of distributed capacitance is prevalent, and the effect of distributed capacitance on the control system, particularly the high frequency circuits, is significant. Particularly, in a high-voltage system, the leakage current, the leakage voltage and the like of the distributed capacitor are one of direct factors causing personal and equipment safety hazards. Meanwhile, the large distributed capacitance is also a negative factor which is easy to cause instantaneous disturbance to the power grid. Therefore, how to detect the value of the distributed capacitance is particularly important to send out warning in time, and the applicant provides a solution for detecting the distributed capacitance.

SUMMERY OF THE UTILITY MODEL

The present invention is directed to an adjustable capacitance detection circuit to solve the above problems.

In order to achieve the purpose, the utility model provides the following technical scheme:

an adjustable capacitance detection circuit comprises a processor, a sampling circuit, a group of excitation power supplies, a diode V1, a resistor R0, a switch S1, a switch S2, a switch S3, a switch S4 and an adjustable constant current circuit, wherein the anode of the diode V1 is connected with the anode of the excitation power supply, the cathode of the diode V1 is connected with the first end of the resistor R0, the second end of the resistor R0 is connected with the first end of the adjustable constant current circuit and the first end of the switch S1, the second end of the switch S1 is connected with the first ends of the switches S2 and S3, and a distributed capacitor is arranged between the second end of the switch S1 and the excitation power supply ground; the second end of the switch S2 is connected with the second end of the adjustable constant current circuit, the second end of the switch S3 is connected with the sampling circuit, the sampling circuit is connected with the processor, and the adjustable constant current circuit is further connected with the excitation power ground.

As an improved scheme of the present invention, the adjustable constant current circuit includes an adjustable resistor Rk, a constant resistor R1, and a constant current transistor VTH, wherein a first end of the adjustable resistor Rk is connected to a first end of the switch S1, a second end of the adjustable resistor Rk is connected to a first end of the resistor R1, a second end of the resistor R1 is connected to a control electrode of the constant current transistor VTH, an anode of the constant current transistor VTH is connected to a second end of the switch S2, and a cathode of the constant current transistor VTH is connected to an excitation power ground.

As a modified scheme of the utility model, the second end of the switch S1 is connected with the second end of the switch S4, the first end of the switch S4 is connected with the positive pole or the negative pole of the high-voltage bus through an external circuit, and the distributed capacitance is distributed capacitance of the positive pole or the negative pole of the high-voltage bus to the excitation power ground.

As a modified scheme of the utility model, the switches S1, S2, S3 and S4 are all electronic switch tubes.

As an improved scheme of the utility model, the sampling circuit comprises a filter circuit, an isolation circuit, a differential amplification circuit and an AD acquisition circuit which are sequentially connected.

Has the advantages that: according to the utility model, the distributed capacitor can be charged and discharged by switching the switch, so that the numerical value change of the distributed capacitor during charging and discharging is obtained, and the calculation of the capacitance value of the distributed capacitor is completed. The detection of distributed capacitance and fixed capacitance of different voltage buses can be met, warning can be provided for the influence of the distributed capacitance of the high-frequency control circuit, necessary safety warning and rectification verification can be provided for leakage current and leakage voltage faults caused by the distributed capacitance of a high-voltage electric network, and the requirements of personal and equipment safety use are met.

Drawings

FIG. 1 is a general schematic diagram of the detection circuit of the present invention;

fig. 2 is a schematic diagram of the implementation of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

An adjustable capacitance detection circuit is shown in fig. 1-2, and comprises a diode V1, a resistor R0, a switch S1, a switch S2, a switch S3, a switch S4, an adjustable constant current circuit, a processor, a sampling circuit, and a group of excitation power supplies consisting of +24V, P _ GND.

The anode of the diode V1 is connected with +24V, the cathode is connected with the first end of the resistor R0, and the diode V1 plays a role in preventing reverse connection. The second end of the resistor R0 is connected to the first end of the adjustable constant current circuit and the first end of the switch S1, and the resistor R0 is a current-limiting resistor. The second end of the switch S1 is connected with the first ends of the switches S2 and S3, and the detection capacitor is arranged between the second end of the switch S1 and the excitation power ground; the second end of the switch S2 is connected with the second end of the adjustable constant current circuit, the second end of the switch S3 is connected with the sampling circuit, the sampling circuit is connected with the processor, and the adjustable constant current circuit is further connected with the P _ GND.

The embodiment mainly utilizes the constant current discharge principle of the capacitor to detect the capacitor. The detection capacitor can be a fixed capacitor or a distributed capacitor formed between the high-voltage direct-current bus and the excitation power ground. The sampling circuit comprises a filter circuit, an isolation circuit, a differential amplification circuit and an AD acquisition circuit which are sequentially connected, and the composition of the sampling circuit is mature technology, so that the sampling circuit can be directly selected and purchased in the market, and is not repeated herein.

The adjustable constant current circuit comprises an adjustable resistor Rk, a constant resistor R1 and a constant current triode VTH, wherein the first end of the adjustable resistor Rk is connected with the first end of a switch S1, the second end of the adjustable resistor Rk is connected with the first end of a resistor R1, the second end of the resistor R1 is connected with the control electrode of the constant current triode VTH, the anode of the constant current triode VTH is connected with the second end of the switch S2, and the cathode of the constant current triode VTH is connected with an excitation power ground.

When the second end of the switch S1 is also connected with the second end of the switch S4, and the first end of the switch S4 is connected with the positive pole or the negative pole of the high-voltage bus through an external circuit, the detection capacitor is a distributed capacitor C between the positive pole or the negative pole of the high-voltage bus and the excitation power ground₀. At this time, the first terminal of the switch S4 is set to Vtest point, the distributed capacitance C in FIG. 2₀Is the equivalent capacitance in the electrical system, and the physical capacitance is not present in the embodiments. Distributed capacitance C₀Switched in by a fourth switch S4 via the Vtest point, C₀In addition toOne terminal is connected to P _ GND.

The working principle is as follows:

first, the switch S1, the switch S3, and the switch S4 are closed. The Vtest point is connected to the high voltage bus through an external circuit. The Vtest point can be connected to the positive or negative pole of the high-voltage bus through an external circuit, so that the distributed capacitance between the positive or negative pole of the bus and the excitation power ground before the bus voltage is electrified is detected.

After the switches S1, S3 and S4 are switched on, the distributed capacitor C is pressurized by the excitation power supply +24V1₀Charging takes place via a resistor R0, while a capacitor C is distributed₀The voltage at the two ends of the voltage transformer is processed by a sampling circuit and is collected and processed by a processor. When distributing capacitance C₀After the charging is saturated, the voltages at two ends are stable, and the processor reads the distributed capacitor C through the sampling of the AD chip₀First voltage U at both ends₁. The processor can be selected as a single chip microcomputer or other data processors.

Distributed capacitance C₀After the voltages at the two ends are stable, the switch S1 and the switch S4 are opened, the switch S2 and the switch S3 are closed, and the distributed capacitor C is connected with the switch S3526₀And discharging with a constant current triode VTH, wherein the discharging current I of the constant current triode VTH is regulated by the sum of an adjustable resistor Rk and a fixed resistor R1.

The switches S1, S2, S3 and S4 are four groups of electronic switches and have the advantages of high stability and easiness in control. The processor reads the distributed capacitance C through the sampling circuit after the processor sends an instruction for turning on the switch S2₀When the voltage across them is equal to C₀When the voltage between the two ends is discharged to U2, the processor gives an instruction for opening the switch S2, stops timing, and calculates the accumulated time T from the time when the switch S2 is turned on to the time when the switch S2 is turned off. The value of U2 is related to the minimum operating voltage of the constant current discharge transistor VTH to maintain its constant current discharge.

The adjustable resistor Rk can be set as fixed resistors at several gears, and the whole constant current triode VTH can perform constant current discharge at a fixed gear by switching among several gears. Theoretically, the adjustable resistor Rk can also be used as an adjustable potentiometer, so that the constant current transistor VTH realizes stepless adjustment of the discharge current, but the discharge current is required to be used as a known parameter to participate in calculation, and the current real-time current value after stepless adjustment cannot be accurately obtained in practical application, so that the adjustable resistor Rk is not preferable in specific application. When the sum of the adjustable resistor Rk and the resistor R1 is zero, the constant current discharge triode is equivalent to a diode with the maximum constant current value of the diode.

Because the distributed capacitance adopts a constant current discharge principle, only time is a variable in the whole integration process, and convenience is brought to calculation of the distributed capacitance.

Capacitor voltage U_cThe relationship with the discharge current I is:

let I_oConstant value, then there are:

C₀＝Q/U_c＝(I*T)/U_c＝(I*T)/(U₁-U₂)

the distributed capacitance C can be calculated by calculating the formula in the detection principle of the distributed capacitance₀The capacitance value of (2) is detected, and then S1-S4 are cut off.

When the switch S1 is not connected to the switch S4, i.e., not connected to the high voltage bus bar electrode, the detection capacitor can be a fixed capacitor, and the detection principle is the same as described above.

According to the utility model, the distributed capacitor can be charged and discharged by switching the switch, so that the numerical value change of the distributed capacitor during charging and discharging is obtained, and the calculation of the capacitance value of the distributed capacitor is completed. The detection of distributed capacitance and fixed capacitance of different voltage buses can be met, warning can be provided for the influence of the distributed capacitance of the high-frequency control circuit, necessary safety warning and rectification verification can be provided for leakage current and leakage voltage faults caused by the distributed capacitance of a high-voltage electric network, and the requirements of personal and equipment safety use are met. The detection circuit provided by the utility model is simple, free of maintenance, clear in logic and easy to realize.

Although the present description is described in terms of embodiments, not every embodiment includes only a single embodiment, and such description is for clarity only, and those skilled in the art should be able to integrate the description as a whole, and the embodiments can be appropriately combined to form other embodiments as will be understood by those skilled in the art.

Therefore, the above description is only a preferred embodiment of the present application, and is not intended to limit the scope of the present application; all changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

1. An adjustable capacitance detection circuit comprises a processor, a sampling circuit and a group of excitation power supplies, and is characterized by further comprising a diode V1, a resistor R0, a switch S1, a switch S2, a switch S3, a switch S4 and an adjustable constant current circuit, wherein the anode of the diode V1 is connected with the anode of the excitation power supply, the cathode of the diode V1 is connected with the first end of the resistor R0, the second end of the resistor R0 is connected with the first end of the adjustable constant current circuit and the first end of the switch S1, the second end of the switch S1 is connected with the first ends of the switches S2 and S3, and a detection capacitor is arranged between the second end of the switch S1 and the excitation power supply ground; the second end of the switch S2 is connected with the second end of the adjustable constant current circuit, the second end of the switch S3 is connected with the sampling circuit, the sampling circuit is connected with the processor, and the adjustable constant current circuit is further connected with the excitation power ground.

2. The adjustable capacitance detection circuit according to claim 1, wherein the adjustable constant current circuit comprises an adjustable resistor Rk, a constant resistor R1 and a constant current transistor VTH, wherein a first end of the adjustable resistor Rk is connected to a first end of the switch S1, a second end of the adjustable resistor Rk is connected to a first end of the resistor R1, a second end of the resistor R1 is connected to a control electrode of the constant current transistor VTH, an anode of the constant current transistor VTH is connected to a second end of the switch S2, and a cathode of the constant current transistor VTH is connected to the excitation power ground.

3. The adjustable capacitance detection circuit according to claim 2, wherein the second terminal of the switch S1 is connected to the second terminal of the switch S4, the first terminal of the switch S4 is connected to the positive or negative terminal of the high voltage bus through an external circuit, and the detection capacitor is a distributed capacitor of the positive or negative terminal of the high voltage bus to the excitation power ground.

4. The adjustable capacitance detection circuit according to claim 2, wherein the detection capacitor is a fixed capacitor.

5. The adjustable capacitor detection circuit as claimed in claim 3, wherein the switches S1, S2, S3 and S4 are electronic switches.

6. The adjustable capacitance detection circuit according to claim 4, wherein the sampling circuit comprises a filter circuit, an isolation circuit, a differential amplification circuit and an AD acquisition circuit which are connected in sequence.