CN117665393A - Insulation resistance detection circuit - Google Patents
Insulation resistance detection circuit Download PDFInfo
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- CN117665393A CN117665393A CN202311667316.1A CN202311667316A CN117665393A CN 117665393 A CN117665393 A CN 117665393A CN 202311667316 A CN202311667316 A CN 202311667316A CN 117665393 A CN117665393 A CN 117665393A
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- 238000009413 insulation Methods 0.000 title claims abstract description 109
- 238000001514 detection method Methods 0.000 title claims abstract description 38
- 238000005259 measurement Methods 0.000 claims description 49
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- 239000003990 capacitor Substances 0.000 claims description 32
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/30—Structural combination of electric measuring instruments with basic electronic circuits, e.g. with amplifier
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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Abstract
The invention relates to an insulation resistance detection circuit, which designs a brand new detection circuit structure, and efficiently and accurately calculates the insulation resistance value of a system by measuring the voltage between a direct current bus and an electric chassis of an electric automobile.
Description
Technical Field
The invention relates to the technical field of resistance detection, in particular to an insulation resistance detection circuit.
Background
With the development of the electric automobile industry, the safety requirements of electric automobiles are continuously improved, and according to the international standard regulations of electric automobiles: the insulation resistance value is divided by the nominal voltage U of the direct current system of the electric automobile, and the result is larger than 100 omega/V, so that the safety requirement is met. For insulation resistance detection of an electric automobile power storage battery, a common insulation detection method, such as a relay detection method with low sensitivity, a balanced bridge method which cannot accurately and timely alarm when insulation of the positive electrode and the negative electrode is reduced, and an alternating current signal method, such as an alternating current signal method, are adopted, so that ripple waves of a direct current system are increased, power supply quality is affected, distributed capacitance of the system can directly influence a measurement result, and resolution is low. The voltage class of the direct current system of the electric automobile covers a wide range of 90V-500V, the voltage changes frequently in the running process, and the traditional common insulation detection method cannot meet the requirement of high-precision detection of the insulation resistance, so that a dynamic new measurement method is urgently needed.
Disclosure of Invention
Based on this, it is necessary to provide an insulation resistance detection circuit and an insulation resistance measurement method capable of efficiently performing high-precision detection of insulation resistance.
In order to achieve the above object, the embodiment of the present invention adopts the following technical scheme:
in one aspect, an insulation resistance detection circuit is provided, including an insulation resistance Rn to be detected, an insulation resistance Rp to be detected, a measurement resistance R01, a measurement resistance R02, resistors R1 to R24, a photo coupler U10, a photo coupler U11, a field effect transistor Q1, a field effect transistor Q2, operational amplifiers A1 to A7, capacitors C1 to C4, an isolation chip U12, and an isolation chip U13;
one end of the insulation resistor Rn to be tested is respectively connected with one end of the resistor R5 and a negative bus of the electric vehicle direct current system, the other end of the insulation resistor Rn to be tested is connected with one end of the insulation resistor Rp to be tested, the other end of the insulation resistor Rp to be tested is respectively connected with one end of the resistor R3 and a positive bus of the electric vehicle direct current system, and the other end of the resistor R3 is sequentially connected with the other end of the resistor R5 in series through a resistor R4, a resistor R10, a resistor R9, a measuring resistor R02, a measuring resistor R01, a resistor R8, a resistor R7 and a resistor R6;
one end of the resistor R1 is used for being connected with a first digital input terminal, the other end of the resistor R1 is connected with the grid electrode of the field effect tube Q2 through the photoelectric coupler U11, the source electrode of the field effect tube Q2 is connected between the resistor R7 and the resistor R6, and the drain electrode of the field effect tube Q2 is connected between the measuring resistor R01 and the resistor R8;
one end of the resistor R2 is used for being connected with a second digital input terminal, the other end of the resistor R2 is connected with the grid electrode of the field effect tube Q1 through the photoelectric coupler U10, the source electrode of the field effect tube Q1 is connected between the resistor R4 and the resistor R10, and the drain electrode of the field effect tube Q1 is connected between the measuring resistor R02 and the resistor R9;
one end of a resistor R11 is connected with the drain electrode of the field effect transistor Q2, the other end of the resistor R11 is respectively connected with one end of a resistor R14 and the inverting input end of an operational amplifier A3, the output end of the operational amplifier A3 is respectively connected with the other end of the resistor R14 and one end of a resistor R18, the non-inverting input end of the operational amplifier A3 is respectively connected with the other end of a resistor R12, one end of a resistor R13 and one end of a resistor R15, one end of the resistor R12 is connected between an insulation resistor Rn to be tested and an insulation resistor Rp to be tested, the other end of the resistor R13 is grounded, the other end of the resistor R15 is respectively connected with the inverting input end and the output end of the operational amplifier A1, the non-inverting input end of the operational amplifier A1 is respectively connected with one end of a resistor R16 and one end of a resistor R17, the other end of the resistor R16 is connected with a working power supply, and the other end of the resistor R17 is grounded;
the inverting input end of the operational amplifier A4 is respectively connected with the other end of the resistor R18, one end of the capacitor C1 and the pin 3 of the isolation chip U12, the non-inverting input end of the operational amplifier A4 is grounded, the output end of the operational amplifier A4 is respectively connected with the other end of the capacitor C1 and one end of the resistor R19, the other end of the resistor R19 is connected with the pin 1 of the isolation chip U12, the pin 6 of the isolation chip U12 is respectively connected with the inverting input end of the operational amplifier A5 and one end of the capacitor C2, the output end of the operational amplifier A5 is connected with the other end of the capacitor C2 and is used as a first output terminal, the non-inverting input end of the operational amplifier A5 is connected with the pin 5 of the isolation chip U12 in parallel connection with the capacitor C2 and is connected with a common ground;
one end of a resistor R21 is connected with the drain electrode of the field effect transistor Q1, the other end of the resistor R21 is connected with the non-inverting input end of the operational amplifier A2, the inverting input end of the operational amplifier A2 is connected with the output end of the operational amplifier A2, the output end of the operational amplifier A2 is connected with one end of the resistor R22, the inverting input end of the operational amplifier A6 is respectively connected with the other end of the resistor R22, one end of the capacitor C3 and the pin 3 of the isolation chip U132, the non-inverting input end of the operational amplifier A6 is respectively connected with the other end of the capacitor C3 and one end of the resistor R23, the other end of the resistor R23 is connected with the pin 1 of the isolation chip U13, the pin 6 of the isolation chip U13 is respectively connected with the inverting input end of the operational amplifier A7 and one end of the capacitor C4, the output end of the operational amplifier A7 is connected with the other end of the capacitor C4 and serves as a second output terminal, the resistor R24 is connected with the capacitor C4 in parallel, and the non-inverting input end of the operational amplifier A7 is connected with the pin 5 of the isolation chip U13 and is connected with a common ground.
In one embodiment, the insulation resistance detection circuit further comprises a single chip microcomputer, wherein the single chip microcomputer comprises a first digital input terminal and a second digital input terminal, a first measurement terminal and a second measurement terminal, the first measurement terminal is connected with the output end of the operational amplifier A5, and the second measurement terminal is connected with the output end of the operational amplifier A7;
the singlechip is used for outputting driving pulses through the first digital input terminal and the second digital input terminal and measuring output voltages through the first measuring terminal and the second measuring terminal.
In one embodiment, the singlechip sends an alarm signal when the measured value of the insulation resistance measured according to the output voltage is lower than a safety threshold value of the insulation resistance of the chassis by the positive bus and the negative bus of the preset electric vehicle direct current system.
In one embodiment, resistors R3 through R10 employ 0805 package resistors.
On the other hand, there is also provided an insulation resistance measuring method applied to the insulation resistance detecting circuit, the insulation resistance measuring method including the steps of:
setting the first digital input terminal and the second digital input terminal to a low level, and measuring and comparing output voltages of the first output terminal and the second output terminal;
setting the digital input terminal corresponding to the output terminal with small output voltage to be high level, and re-measuring the output voltages of the first output terminal and the second output terminal;
and calculating to obtain the resistance values of the insulation resistor Rn to be measured and the insulation resistor Rp to be measured according to the re-measured output voltages of the first output terminal and the second output terminal.
One of the above technical solutions has the following advantages and beneficial effects:
the insulation resistance detection circuit designs a brand-new detection circuit structure, and the insulation resistance value of the system is efficiently and accurately calculated by measuring the voltage between the direct current bus and the electric chassis of the electric automobile.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an equivalent circuit structure for insulation resistance detection in one embodiment;
FIG. 2 is a schematic diagram of an insulation resistance detection circuit according to an embodiment;
FIG. 3 is a schematic diagram of a measurement flow of an insulation resistance measurement method in one embodiment.
Detailed Description
In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the invention, whereby the invention is not limited to the specific embodiments disclosed below.
Embodiments of the present invention will be described in detail below with reference to the attached drawings in the drawings of the embodiments of the present invention.
In the research process of the application, the inventor researches and calculates the insulation resistance value of the power storage battery by measuring the voltage between the direct current bus and the electric chassis of the electric automobile. According to the related literature data, the insulation condition of the electric automobile is measured by the insulation resistance of the direct current positive and negative buses to the ground, namely, if the insulation resistance of the positive and negative buses to the ground can meet the safety requirement, the insulation resistance of the whole power storage battery can also meet the safety requirement.
Assuming that the voltage of a direct current system (namely the total voltage of a battery) of the electric automobile is U, insulation resistances between a direct current positive bus and a direct current negative bus to be tested and an electric chassis (EGND) are respectively R p 、R n The voltage between the direct current positive bus and the direct current negative bus and the electric chassis is U respectively p 、U n The equivalent model of the dc system under test can be shown as the left part of the switch S1 and the switch S2 in fig. 1.
Electric automobile insulation detection equivalent model shown in figure 1, R in figure 1 C1 And R is C2 For a standard resistance of known resistance value for measurement, the working principle of the insulation detection model is as follows: when the switch S1 and the switch S2 are all opened, the voltages between the positive bus and the negative bus and the electric chassis are measured to be U p0 And U n0 From the circuit law, it is possible to obtain:
when the switch S1 is closed and the switch S2 is open, thenAdding a standard bias resistor R between a positive bus and an electric chassis C1 The voltages between the positive bus, the negative bus and the electric chassis are measured to be U respectively pp And U np It is also possible to obtain:
similarly, a current relationship corresponding to insulation resistance in the following two cases can also be obtained: (1) switch S1 is open and switch S2 is closed; (2), switch S1 is open and switch S2 is closed.
Study of the influence of measured parameters on accuracy: the total error of the system has a direct relation with the ratio between the standard resistance value and the measured resistance. When R is C1 ＝R p The measurement error of the system is minimal. At this time, the error of the standard resistor is assumed to be negligible, all the voltage measurement errors are assumed to be equal, and if the total error gamma of the calculation result is required to be less than or equal to 5%, the error of the voltage measurement must meet gamma V ≤1.125％。
However, the insulation resistance of the system of the electric vehicle is changed during the actual long-term operation, and the resistance value R C1 It is impossible to make small (otherwise, the insulation condition of the electric vehicle is directly reduced), and the resistance value can be selected between 100 Ω/V and 500 Ω/V in static measurement, so that the actual error is larger. For example, for a nominal 500V electric vehicle DC system, R may be selected C1 If the insulation resistance is required to meet the measurement result error of less than 5% at the minimum value of 50kΩ, the error of the voltage measurement must be made less than 0.625%.
Study of the effects of battery voltage transients on power storage batteries: the insulation resistance of the electric automobile is generally a slowly varying parameter, and the measurement process is fast, so that the actual insulation resistance to be measured in the measurement process can be considered to be unchanged. This value can be treated as a constant value during the brief measurement process, but it is necessary to ensure that the voltage U is measured during the measurement process p0 And U n0 Sampling simultaneity and voltage U pp And U np Simultaneity of sampling otherwise destroys the above computationThe correct conditions for the process.
In summary, the system design and key parameter selection may be as follows: the standard bias resistor should be selected in accordance with the following principles: (1) the original insulation performance of the tested system is not affected basically; (2) taking the measurement accuracy requirement of the system into consideration; (3) Automatically configuring standard resistance values of different grades according to the system voltage grade; (4) high precision, low temperature drift coefficient.
As is clear from the above-described research analysis of the present application, in the case of the standard bias resistor determination, the accuracy of the voltage detection directly determines the accuracy of the final insulation resistance detection result. Generally, the nominal voltage of the electric automobile is between 90V and 500V, a certain fluctuation range exists in the battery voltage in the running process, and a certain variation range exists in the insulation resistance to be tested, so that the voltage measurement circuit of the universal detection system must ensure that the measurement with equal precision is realized in the whole range, and the measurement of the voltages of the positive bus and the negative bus to the ground must be completed simultaneously. In the application, the structure and parameters of the measuring circuit of the positive bus and the negative bus to the ground voltage are completely consistent, and the acquisition process can be controlled by the CPU to start conversion at the same time, so that the simultaneity of measuring parameters is satisfied.
In one embodiment, referring to fig. 2, an insulation resistance detection circuit 100 is provided, which includes an insulation resistance Rn to be detected, an insulation resistance Rp to be detected, a measurement resistance R01, a measurement resistance R02, resistors R1 to R24, a photo coupler U10, a photo coupler U11, a field effect transistor Q1, a field effect transistor Q2, operational amplifiers A1 to A7, capacitors C1 to C4, an isolation chip U12, and an isolation chip U13.
One end of the insulation resistor Rn to be tested is respectively connected with one end of the resistor R5 and a negative bus of an electric vehicle direct current system (such as BT 1), the other end of the insulation resistor Rn to be tested is connected with one end of the insulation resistor Rp to be tested, the other end of the insulation resistor Rp to be tested is respectively connected with one end of the resistor R3 and a positive bus of the electric vehicle direct current system, and the other end of the resistor R3 is sequentially connected with the other end of the resistor R5 in series through the resistor R4, the resistor R10, the resistor R9, the measuring resistor R02, the measuring resistor R01, the resistor R8, the resistor R7 and the resistor R6.
One end of the resistor R1 is used for being connected with the first digital input terminal, the other end of the resistor R1 is connected with the grid electrode of the field effect tube Q2 through the photoelectric coupler U11, the source electrode of the field effect tube Q2 is connected between the resistor R7 and the resistor R6, and the drain electrode of the field effect tube Q2 is connected between the measuring resistor R01 and the resistor R8.
One end of the resistor R2 is used for being connected with a second digital input terminal, the other end of the resistor R2 is connected with the grid electrode of the field effect tube Q1 through the photoelectric coupler U10, the source electrode of the field effect tube Q1 is connected between the resistor R4 and the resistor R10, and the drain electrode of the field effect tube Q1 is connected between the measuring resistor R02 and the resistor R9.
One end of the resistor R11 is connected with the drain electrode of the field effect transistor Q2, and the other end of the resistor R11 is respectively connected with one end of the resistor R14 and the inverting input end of the operational amplifier A3. The output end of the operational amplifier A3 is respectively connected with the other end of the resistor R14 and one end of the resistor R18, the non-inverting input end of the operational amplifier A3 is respectively connected with the other end of the resistor R12, one end of the resistor R13 and one end of the resistor R15, and one end of the resistor R12 is connected between the insulation resistor Rn to be tested and the insulation resistor Rp to be tested. The other end of the resistor R13 is grounded. The other end of the resistor R15 is respectively connected with the inverting input end and the output end of the operational amplifier A1. The noninverting input end of the operational amplifier A1 is respectively connected with one end of a resistor R16 and one end of a resistor R17, the other end of the resistor R16 is connected with a working power supply, and the other end of the resistor R17 is grounded.
The inverting input end of the operational amplifier A4 is respectively connected with the other end of the resistor R18, one end of the capacitor C1 and the pin 3 of the isolation chip U12, the non-inverting input end of the operational amplifier A4 is grounded, and the output end of the operational amplifier A4 is respectively connected with the other end of the capacitor C1 and one end of the resistor R19. The other end of the resistor R19 is connected with the pin 1 of the isolation chip U12. The pin 6 of the isolation chip U12 is respectively connected with the inverting input end of the operational amplifier A5 and one end of the capacitor C2, and the output end of the operational amplifier A5 is connected with the other end of the capacitor C2 and serves as a first output terminal. Resistor R20 is connected in parallel with capacitor C2. The noninverting input end of the operational amplifier A5 is connected with the pin 5 of the isolation chip U12 and is connected with the common ground end.
One end of a resistor R21 is connected with the drain electrode of the field effect transistor Q1, and the other end of the resistor R21 is connected with the non-inverting input end of the operational amplifier A2. The inverting input end of the operational amplifier A2 is connected with the output end, the output end of the operational amplifier A2 is connected with one end of the resistor R22, and the inverting input end of the operational amplifier A6 is respectively connected with the other end of the resistor R22, one end of the capacitor C3 and the pin 3 of the isolation chip U132. The non-inverting input end of the operational amplifier A6 is grounded, the output end of the operational amplifier A6 is respectively connected with the other end of the capacitor C3 and one end of the resistor R23, and the other end of the resistor R23 is connected with the pin 1 of the isolation chip U13. The pin 6 of the isolation chip U13 is respectively connected with the inverting input end of the operational amplifier A7 and one end of the capacitor C4, and the output end of the operational amplifier A7 is connected with the other end of the capacitor C4 and serves as a second output terminal. Resistor R24 is connected in parallel with capacitor C4. The noninverting input end of the operational amplifier A7 is connected with the pin 5 of the isolation chip U13 and is connected with the common ground end.
It can be understood that the first digital input terminal IN1 and the second digital input terminal IN2 are used as 2 input ends IN the TTL logic circuit of the present embodiment, and are used for receiving digital signal input provided by the outside, such as driving pulse, so as to control the on-off of the field effect transistor through the photocoupler, and cooperate to realize the measurement requirement of the later stage circuit. The optocoupler U10 and the optocoupler U11 can be existing OPTOISO optocouplers in the field, and the resistance value between the collector and the emitter of the phototriode is changed by controlling the luminous intensity of an internal light emitting diode, so that the current of the circuit where the phototriode is positioned is controlled, and the aims of isolation and drive control required by the circuit during operation are fulfilled. N-channel field effect transistors can be adopted for the field effect transistor Q1 and the field effect transistor Q2 so as to support efficient and reliable signal on-off control. The operational amplifiers A1 to A7 can adopt the existing LMV321 operational amplifier in the field, have high reliability and good economic benefit, and can effectively improve the reliability and the working efficiency of the circuit.
Specifically, in actual measurement, the power consumption of the parallel resistors is considered to be high, so that the voltage division mode of multistage series connection is adopted in the embodiment to reduce the power consumption of the resistors. For the sake of explanation, it can be assumed, but is not limited to, that the series resistance R s Series resistors such as resistor R3, resistor R4, resistor R5, resistor R6, resistor R7, resistor R8, resistor R9, and resistor R10 in fig. 2 are=100 kΩ. Can be, but is not limited to, measuring resistance r=1kΩ, for exampleSuch as resistor R01 and resistor R02 in fig. 2. The isolation chip U12 and the isolation chip U13 may be linear optocoupler isolators existing in the art, and the output plus one-stage follower is connected to the isolation chip U12 or the isolation chip U13, so that output control (giving a fixed square wave signal) is provided by the optocoupler, the amplification factor of the linear optocoupler isolator may be, but not limited to, 1 time (the specific multiple may be selected in an adapting manner according to the measurement requirement of the actual application scenario), and then the input and output of the linear optocoupler are the same (u1=uo1, u2=uo2,) and the insulation resistance value may be calculated. Wherein the uppercase letter designation with a subscript designates an electrical parameter value of the corresponding device, such as a resistance value, a voltage value, and the like.
When the level of the first digital input terminal IN1 is low:
when the level of the first digital input terminal IN1 is a high level:
when the level of the second digital input terminal IN2 is low:
when the level of the second digital input terminal IN2 is high:
the measurement procedure may be as follows:
the first step: the first digital input terminal IN1 level and the second digital input terminal IN2 level are both set to low levels, and the output U is measured o1 And U o2 Comparing the two values to find out the smaller voltage, and the smaller voltageThe one of (2) indicates that the insulation resistance of the one is small, assuming U o2 The voltage is small.
And a second step of: the second digital input terminal IN2 is set high, at which time the output voltage U 'is remeasured' o1 And U' o2 。
The combination of the previous expressions can be derived (||represents the parallel resistance value):
r can be calculated by combining the two expressions p And R is n 。
If U o1 Smaller, only the input level of the first digital input terminal IN1 is controlled, the measurement process is the same, the calculation method is the same, but the R of the measurement result is p And R is R n The result is just the expression swap.
The insulation resistance detection circuit 100 designs a brand-new detection circuit structure, and the insulation resistance value of the system is efficiently and accurately calculated by measuring the voltage between the direct current bus and the electric chassis of the electric automobile.
It should be noted that, the high-speed output unit of the singlechip is utilized to output pulse signals, so as to drive the photoelectric switch tube to change the resistance, the pulse speed is not required to be too high, and the acquisition time is as low as possible or at the center of high level because the signal near the change edge is unstable, so that the acquisition stability is ensured. The insulation resistance measurement only needs to measure the minimum insulation resistance, so that the insulation resistance of the positive electrode and the negative electrode is compared firstly after the first step, then the photoelectric switch on which side is opened is determined, if the insulation resistances of the positive electrode and the negative electrode are equal, any one light spot switch can be set according to a program to be opened, and then the second step of measurement is carried out.
In one embodiment, the insulation resistance detection circuit 100 further includes a single chip microcomputer. The singlechip comprises a first digital input terminal, a second digital input terminal, a first measurement terminal and a second measurement terminal. The first measuring terminal is connected with the output end of the operational amplifier A5, and the second measuring terminal is connected with the output end of the operational amplifier A7. The singlechip is used for outputting driving pulses through the first digital input terminal and the second digital input terminal and measuring output voltages through the first measuring terminal and the second measuring terminal.
It can be understood that in this embodiment, the single-chip microcomputer can be integrated onto the insulation resistance detection circuit 100, so as to improve the integration level of the circuit, and the single-chip microcomputer can provide convenient and quick on-site on-line driving control and measurement output, so as to achieve the technical effect of further improving the service efficiency of the circuit. The single chip microcomputer can adopt various existing single chip microcomputers as long as the single chip microcomputer can be used for providing required driving control and measurement calculation functions.
In one embodiment, the singlechip sends an alarm signal when the measured value of the insulation resistance measured according to the output voltage is lower than a safety threshold value of the insulation resistance of the chassis by the positive bus and the negative bus of the preset electric vehicle direct current system.
It can be understood that in this embodiment, since the safety threshold of the power supply positive and negative leads to the chassis insulation resistance is preset, when the measured value of the insulation resistance is lower than the safety threshold, the singlechip can also send an alarm signal to quickly indicate to the measurement user that the current chassis insulation resistance has poor safety requirements, thereby further improving the use efficiency of the circuit during measurement. In principle, it can be determined that the insulating property is poor at 100 Ω/V or less, the insulating property is excellent at 500 Ω/V, and the insulating property is good in the middle.
In one embodiment, resistors R3 through R10 employ 0805 package resistors. It can be understood that, due to the higher voltage, the resistors R3-R10 can be 0805 package resistors in the embodiment to better meet the power requirement, so as to further improve the reliability and environmental adaptability of the circuit.
In one embodiment, as shown in fig. 3, an insulation resistance measurement method is further provided and applied to the insulation resistance detection circuit 100, where the insulation resistance measurement method specifically includes the following steps:
s12, setting the first digital input terminal and the second digital input terminal to be low level, and measuring and comparing output voltages of the first output terminal and the second output terminal;
s14, setting a digital input terminal corresponding to an output terminal with small output voltage to be high level, and re-measuring the output voltages of the first output terminal and the second output terminal;
s16, calculating to obtain the resistance values of the insulation resistor Rn to be tested and the insulation resistor Rp to be tested according to the re-measured output voltages of the first output terminal and the second output terminal.
It will be appreciated that, regarding the explanation of the insulation resistance detection circuit 100 in this embodiment, the same explanation as that of the embodiments of the insulation resistance detection circuit 100 described above may be referred to, and the detailed description will not be repeated here.
The measurement procedure may be as follows:
the first step: the first digital input terminal IN1 level and the second digital input terminal IN2 level are both set to low levels, and the output U is measured o1 And U o2 Comparing the two values to find out the smaller voltage, the smaller voltage indicates the smaller insulation resistance of the side, and it is assumed that U o2 The voltage is small.
And a second step of: the second digital input terminal IN2 is set high, at which time the output voltage U 'is remeasured' o1 And U' o2 。
The combination of the previous expressions can be derived (||represents the parallel resistance value):
r can be calculated by combining the two expressions p And R is n 。
If U o1 Smaller, only the input level of the first digital input terminal IN1 is controlled, the measurement process is the same, the calculation method is the same, but the R of the measurement result is p And R is R n The result is just the expression swap.
According to the insulation resistance measuring method, based on the insulation resistance detecting circuit 100 with brand new design, the insulation resistance value of the system is efficiently and accurately calculated by measuring the voltage between the direct current bus and the electric chassis of the electric automobile, and the detecting circuit can be used for controlling the digital pulse input of the two digital input terminals in real time and flexibly and correspondingly measuring the output voltage of the output terminal, so that the insulation resistance value under each measuring scene is accurately calculated, the minimum value of the insulation resistance of the power storage battery can be detected, dynamic real-time measurement can be realized, and the technical effect of effectively completing high-precision detection of the insulation resistance is realized.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the present invention, unless explicitly specified and limited otherwise, the terms "connected" and the like are to be construed broadly, and may be, for example, mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
Claims (5)
1. The insulation resistance detection circuit is characterized by comprising an insulation resistance Rn to be detected, an insulation resistance Rp to be detected, a measurement resistance R01, a measurement resistance R02, resistors R1 to R24, a photoelectric coupler U10, a photoelectric coupler U11, a field effect tube Q1, a field effect tube Q2, operational amplifiers A1 to A7, capacitors C1 to C4, an isolation chip U12 and an isolation chip U13;
one end of the insulation resistor Rn to be tested is respectively connected with one end of the resistor R5 and a negative bus of the electric vehicle direct current system, the other end of the insulation resistor Rn to be tested is connected with one end of the insulation resistor Rp to be tested, the other end of the insulation resistor Rp to be tested is respectively connected with one end of the resistor R3 and a positive bus of the electric vehicle direct current system, and the other end of the resistor R3 is sequentially connected to the other end of the resistor R5 in series through the resistor R4, the resistor R10, the resistor R9, the measuring resistor R02, the measuring resistor R01, the resistor R8, the resistor R7 and the resistor R6;
one end of the resistor R1 is used for being connected with a first digital input terminal, the other end of the resistor R1 is connected with the grid electrode of the field effect tube Q2 through the photoelectric coupler U11, the source electrode of the field effect tube Q2 is connected between the resistor R7 and the resistor R6, and the drain electrode of the field effect tube Q2 is connected between the measuring resistor R01 and the resistor R8;
one end of the resistor R2 is used for being connected with a second digital input terminal, the other end of the resistor R2 is connected with the grid electrode of the field effect tube Q1 through the photoelectric coupler U10, the source electrode of the field effect tube Q1 is connected between the resistor R4 and the resistor R10, and the drain electrode of the field effect tube Q1 is connected between the measuring resistor R02 and the resistor R9;
one end of the resistor R11 is connected to the drain electrode of the field effect transistor Q2, the other end of the resistor R11 is connected to one end of the resistor R14 and an inverting input end of the operational amplifier A3, an output end of the operational amplifier A3 is connected to the other end of the resistor R14 and one end of the resistor R18, a non-inverting input end of the operational amplifier A3 is connected to the other end of the resistor R12, one end of the resistor R13 and one end of the resistor R15, one end of the resistor R12 is connected between the insulation resistor Rn to be tested and the insulation resistor Rp to be tested, the other end of the resistor R13 is grounded, the other end of the resistor R15 is connected to an inverting input end and an output end of the operational amplifier A1, a non-inverting input end of the operational amplifier A1 is connected to one end of the resistor R16 and one end of the resistor R17, the other end of the resistor R16 is connected to a working power supply, and the other end of the resistor R17 is grounded;
the inverting input end of the operational amplifier A4 is respectively connected with the other end of the resistor R18, one end of the capacitor C1 and the pin 3 of the isolation chip U12, the non-inverting input end of the operational amplifier A4 is grounded, the output end of the operational amplifier A4 is respectively connected with the other end of the capacitor C1 and one end of the resistor R19, the other end of the resistor R19 is connected with the pin 1 of the isolation chip U12, the pin 6 of the isolation chip U12 is respectively connected with the inverting input end of the operational amplifier A5 and one end of the capacitor C2, the output end of the operational amplifier A5 is connected with the other end of the capacitor C2 and is used as a first output terminal, the non-inverting input end of the operational amplifier A5 is connected with the pin 5 of the isolation chip U12 in parallel and is connected with a common ground;
one end of the resistor R21 is connected with the drain electrode of the field effect transistor Q1, the other end of the resistor R21 is connected with the non-inverting input end of the operational amplifier A2, the inverting input end and the output end of the operational amplifier A2 are connected, the output end of the operational amplifier A2 is connected with one end of the resistor R22, the inverting input end of the operational amplifier A6 is respectively connected with the other end of the resistor R22, one end of the capacitor C3 and the pin 3 of the isolation chip U132, the non-inverting input end of the operational amplifier A6 is grounded, the output end of the operational amplifier A6 is respectively connected with the other end of the capacitor C3 and one end of the resistor R23, the other end of the resistor R23 is connected with the pin 1 of the isolation chip U13, the pin 6 of the isolation chip U13 is respectively connected with the inverting input end of the operational amplifier A7 and one end of the capacitor C4, the output end of the operational amplifier A7 is connected with the other end of the capacitor C4 and serves as a second output terminal, and the non-inverting input end of the capacitor C24 is connected with the common pin 5 of the isolation chip U7.
2. The insulation resistance detection circuit according to claim 1, further comprising a single-chip microcomputer, wherein the single-chip microcomputer comprises a first digital input terminal, a second digital input terminal, a first measurement terminal and a second measurement terminal, the first measurement terminal is connected with the output end of the operational amplifier A5, and the second measurement terminal is connected with the output end of the operational amplifier A7;
the singlechip is used for outputting driving pulses through the first digital input terminal and the second digital input terminal and measuring output voltages through the first measuring terminal and the second measuring terminal.
3. The insulation resistance detection circuit according to claim 2, wherein the single chip microcomputer sends out an alarm signal when the insulation resistance measured value measured according to the output voltage is lower than a safety threshold value of a preset electric vehicle direct current system positive bus and a preset electric vehicle negative bus on insulation resistance of a chassis.
4. An insulation resistance detection circuit according to any one of claims 1 to 3, wherein said resistors R3 to R10 employ 0805 package resistances.
5. An insulation resistance measuring method applied to the insulation resistance detection circuit according to any one of claims 1 to 4, characterized by comprising the steps of:
setting the first digital input terminal and the second digital input terminal to a low level, and measuring and comparing output voltages of the first output terminal and the second output terminal;
setting a digital input terminal corresponding to an output terminal with small output voltage to be high level, and re-measuring the output voltages of the first output terminal and the second output terminal;
and calculating to obtain the resistance values of the insulation resistance Rn to be measured and the insulation resistance Rp to be measured according to the re-measured output voltages of the first output terminal and the second output terminal.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311667316.1A CN117665393A (en) | 2023-12-06 | 2023-12-06 | Insulation resistance detection circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311667316.1A CN117665393A (en) | 2023-12-06 | 2023-12-06 | Insulation resistance detection circuit |
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| CN117665393A true CN117665393A (en) | 2024-03-08 |
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| CN202311667316.1A Pending CN117665393A (en) | 2023-12-06 | 2023-12-06 | Insulation resistance detection circuit |
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| CN (1) | CN117665393A (en) |
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- 2023-12-06 CN CN202311667316.1A patent/CN117665393A/en active Pending
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