CN107643449A - Detection circuit and detection method of the high pressure to the insulaion resistance of low pressure - Google Patents

Abstract

A kind of detection circuit of high pressure to the insulaion resistance of low pressure, including：With the first detection circuit, the in parallel with the second insulaion resistance second detection circuit and acquisition module that the first insulaion resistance is connected in parallel, the first detection circuit includes：First circuit resistor bridge group, the first sampling resistor, the second detection circuit include：Second circuit resistor bridge group, the second sampling resistor, the first sampling resistor access low-pressure end, the relative other end access low-pressure end being connected with second circuit resistor bridge group of the second sampling resistor with respect to the other end of the first circuit resistor bridge group；First circuit resistor bridge group or variable resistor group that second circuit resistor bridge group is resistance value changeable terminals or first, second resistance group are variable resistor group；Detection circuit and detection method of the above-mentioned high pressure to the insulaion resistance of low pressure, directly just detect that reality is total just over the ground, total negative actual resistance over the ground, detection is segmented independent of pattern, Standard resistance range has continuity, is more nearly with the situation of reality.

Description

High voltage to low voltage insulation resistance detection circuit and detection method

technical field

The invention relates to a detection circuit, in particular to a detection circuit and a detection method for detecting the resistance value of insulation resistance between high voltage and low voltage.

Background technique

Most of the existing insulation resistance tests use a sampling module with isolation to sample the insulation resistance. During the isolation process, the EMI caused by the isolation device has a greater impact. Some use low-precision AD sampling chips to sample them, which will result in low detection accuracy; The stability of the result is poor, and it is easy to be interfered by external signals; or the method of sampling and testing is adopted assuming insulation failure, which will cause the detected resistance range to be limited and discontinuous.

Contents of the invention

Based on this, it is necessary to provide a detection circuit for high-voltage to low-voltage insulation resistance that can improve the detection accuracy of the insulation resistance to be measured.

At the same time, a method for detecting the insulation resistance of high voltage to low voltage that can improve the detection accuracy of the insulation resistance to be measured is provided.

A detection circuit for high-voltage to low-voltage insulation resistance, comprising: a first detection circuit connected in parallel with the first insulation resistance between the positive pole of the high-voltage power supply and the low-voltage terminal, and a second insulation resistance between the negative pole of the high-voltage power supply and the low-voltage terminal A second detection circuit and an acquisition module connected in parallel, the first detection circuit includes: a first circuit bridge resistance group, and a circuit that is connected in series with or disconnected from the first circuit bridge resistance group and collects its voltage by the acquisition module The first sampling resistor, the second detection circuit includes: a second circuit bridge resistor group, and a second sampling resistor connected in series with or disconnected from the second circuit bridge resistor group and whose voltage is collected by the acquisition module, so The other end of the first sampling resistor connected to the first circuit bridge resistance group is connected to the low voltage end, and the second sampling resistor is connected to the low voltage end relative to the other end connected to the second circuit bridge resistance group; the second sampling resistor is connected to the low voltage end; The first circuit bridge resistance group or the second circuit bridge resistance group is a variable resistance group with variable resistance, or the first and second resistance groups are variable resistance groups.

In a preferred embodiment, the first circuit bridge resistor group or the second circuit bridge resistor group is a variable resistor group that changes the access resistance value by setting the switch to be closed or opened to change the resistance of the access detection circuit.

In a preferred embodiment, the first circuit bridge resistor group or the second circuit bridge resistor group includes: a fixed access resistor, and an adjustable resistor that can be connected in or disconnected according to needs.

In a preferred embodiment, the low-voltage terminal is a ground terminal, and the first circuit bridge resistor group includes: one or more first fixed access resistors, one or more first adjustable resistors, and The two ends of the first adjustment resistor and the first test switch that is closed or disconnected as required; the second circuit bridge resistance group includes: one or more second fixed access resistors, one or more second adjustment resistors, And a second test switch connected in parallel to both ends of the second adjusting resistor and closed or opened as required.

In a preferred embodiment, the first fixed access resistance is set to the same resistance value as the second fixed access resistance, the first adjustment resistance is set to the same resistance value as the second adjustment resistance, and the first sampling resistance is set to the same value as the second adjustment resistance. The resistance value of the second sampling resistor is set to be the same.

In a preferred embodiment, the acquisition module is provided with two differential analog data acquisition channels that use differential signals to respectively transmit the first sampling resistor and the second sampling resistor to collect and transmit data, and the current of the detection circuit is equal to or less than 3mA, The first fixed access resistor is a resistor R1, the first adjustable resistor is a resistor R2, the second fixed access resistor is a resistor R3, the second adjustable resistor is a resistor R4, and the R1=R2, R3=R4.

In a preferred embodiment, a high and low voltage isolating switch is provided between the first circuit bridge resistor group and the first sampling resistor, or between the second circuit bridge resistor group and the second sampling resistor.

A method for detecting insulation resistance between high voltage and low voltage, comprising:

Obtain the current of the first detection circuit: turn on the detection circuit, collect the voltage of the first sampling resistor, and calculate the current of the first sampling resistor according to the voltage and resistance of the first sampling resistor, thereby obtaining the first sampling resistor and the first circuit bridge resistance The current of the first detection circuit formed by the series connection of the groups;

The current representation of the first insulation resistance: calculate the voltage of the first detection circuit according to the resistance and current of the first detection circuit, so as to obtain the standby voltage connected in parallel with the first detection circuit and connected between the positive pole and the low voltage terminal of the high voltage power supply Measure the voltage of the first insulation resistance, and express the current of the first insulation resistance according to the voltage and resistance value formula of the first insulation resistance;

Obtain the current of the second detection circuit: collect the voltage of the second sampling resistor, and calculate the current of the second sampling resistor according to the voltage and resistance of the second sampling resistor, so as to obtain the series connection between the second sampling resistor and the second circuit bridge resistor group The current of the second detection circuit;

The current representation of the second insulation resistance: calculate the voltage of the second detection circuit according to the resistance and current of the second detection circuit, so as to obtain the standby voltage connected in parallel with the second detection circuit and connected between the negative pole of the high-voltage power supply and the low-voltage terminal. Measure the voltage of the second insulation resistance, and express the current of the second insulation resistance according to the voltage and resistance value formula of the second insulation resistance;

List the expression: According to the sum of the current of the first detection circuit and the current of the first insulation resistance is equal to the sum of the current of the second detection circuit and the current of the second insulation resistance, list the currents including the first insulation resistance and the second insulation resistance solve the equation;

Change the resistance value of the detection circuit: change the resistance value of the first circuit bridge resistance group or the resistance value of the second circuit bridge resistance group,

Perform the following steps according to the detection circuit that changes the resistance value:

The step of obtaining the current of the first detection circuit, the step of representing the current of the first insulation resistance, the step of obtaining the current of the second detection circuit, the step of representing the current of the second insulation resistance, and the step of listing expressions;

Simultaneous equation solution: According to the different detection values obtained before and after changing the resistance value of the detection circuit, and the sum of the current of the first detection circuit and the current of the first insulation resistance is equal to the sum of the current of the second detection circuit and the current of the second insulation resistance Two different solution equation expressions obtained by the equations including the first insulation resistance and the second insulation resistance are obtained simultaneously to obtain the first equation group to solve the resistance values of the first insulation resistance and the second insulation resistance to be measured.

In a preferred embodiment, it also includes: changing the resistance value of the detection circuit again: changing the resistance value of the first circuit bridge resistance group or the second circuit bridge resistance group resistance value, or changing the first and second circuit bridge resistance group resistance values ,

According to the detection circuit that changes the resistance value again, perform the following steps:

Obtain the current of the first detection circuit, the current representation of the first insulation resistance, obtain the current of the second detection circuit, and the current representation of the second insulation resistance,

then execute

List the expression: According to the sum of the current of the first detection circuit obtained after changing the resistance value of the detection circuit again and the current of the first insulation resistance obtained after changing the resistance value of the detection circuit again, it is equal to the current obtained after changing the resistance value of the detection circuit again The sum of the current of the second detection circuit obtained and the current of the second insulation resistance obtained after changing the resistance value of the detection circuit again, and a solution equation including the first insulation resistance and the second insulation resistance are listed;

Simultaneous equation solving: combine the solution equation formed after changing the resistance value of the detection circuit again, which includes the first insulation resistance and the second insulation resistance, with the solution equation formed after changing the resistance value of the detection circuit, or with the solution equation formed by the initial detection circuit Obtain the second equation group immediately, and solve the resistance values of the first insulation resistance and the second insulation resistance to be measured,

Error judgment: If the difference or difference ratio between the resistance value of the first insulation resistance to be measured obtained by solving the first equation set and the resistance value of the first insulation resistance to be measured obtained by solving the second equation set is within the error range, the first equation If the difference between the resistance value of the second insulation resistance obtained by solving the group and the resistance value or difference ratio of the second insulation resistance obtained by solving the second equation group is within the error range, then it is judged that the detection is passed,

If the judgment is passed, then

Obtain the resistance value of insulation resistance: solve the first equation set to obtain the first insulation resistance to be measured and solve the second equation set to obtain the first insulation resistance to be measured, take the average value or weighted average to obtain the resistance value of the first insulation resistance, and use the first equation The resistance value of the second insulation resistance obtained by solving the set of equations and the resistance value of the second insulation resistance obtained by solving the second equation set are averaged or weighted averaged to obtain the resistance value of the second insulation resistance.

In a preferred embodiment, it also includes: result optimization: repeating the operation or changing the resistance simultaneous equations of the detection circuit, the resistance value of the first insulation resistance obtained in the steps of obtaining the resistance value of the insulation resistance for multiple times, the resistance value of the second insulation resistance The average value calculation or weighted average calculation of the resistance values is carried out to optimize the calculation results, and the optimized first insulation resistance resistance value and the second insulation resistance resistance value are obtained;

In the error judgment step: if the difference or difference ratio between the resistance value of the first insulation resistance to be measured obtained by solving the first equation set and the resistance value of the first insulation resistance to be measured obtained by solving the second equation set is not within the error range Then discard; or if the resistance value of the second insulation resistance obtained by solving the first equation group and the resistance value or difference ratio of the second insulation resistance obtained by solving the second equation group are not within the error range, then discard;

If the solution value of the resistance value of the first insulation resistance and the solution value of the second insulation resistance are discarded,

Then execute the step of obtaining the current of the first detection circuit;

The first circuit bridge resistor group includes: one or more first fixed access resistors, one or more first adjustment resistors, and a circuit that is connected in parallel at both ends of the first adjustment resistor and is closed or disconnected as required. The first test switch; the second circuit bridge resistance group includes: one or more second fixed access resistors, one or more second adjustment resistors, and connected in parallel at both ends of the second adjustment resistance and performed as required a closed or open second test switch;

The step of changing the resistance value of the detection circuit or the step of changing the resistance value of the detection circuit again changes the resistance value of the first circuit bridge resistance group by changing the access or the number of access of the first adjustment resistor, or by changing the connection of the second adjustment resistor. The resistance value of the second circuit bridge resistance group is changed by entering or the number of accesses; the low-voltage terminal is a ground terminal.

The above-mentioned high-voltage to low-voltage insulation resistance detection circuit and detection method can directly detect the actual total positive-to-ground and total negative-to-ground actual resistance values, which do not depend on the mode segment detection, and the resistance range has continuity. The actual situation is closer; the calculation method and calculation formula used make the calculation amount less, and the calculation process does not need to open the square root, and it takes up less resources for the operation.

Description of drawings

Fig. 1 is the schematic diagram of the detection circuit of the insulation resistance of high voltage to low voltage of an embodiment of the present invention;

Fig. 2 is the schematic diagram of the acquisition module of an embodiment of the present invention;

3 is a flowchart of a method for detecting insulation resistance of high voltage to low voltage according to an embodiment of the present invention;

Fig. 4 is the flowchart of the detection method of the insulation resistance of high voltage to low voltage of a preferred embodiment of the present invention;

FIG. 5 is a flowchart of a method for detecting insulation resistance between high voltage and low voltage according to another preferred embodiment of the present invention.

detailed description

As shown in FIG. 1 , a detection circuit 100 of high-voltage to low-voltage insulation resistance according to an embodiment of the present invention includes: a first detection circuit 20 connected in parallel with the first resistance to be measured between the positive pole of the high-voltage power supply and the low-voltage terminal , a second detection circuit 40 connected in parallel with the second resistance to be measured connected between the negative pole of the high-voltage power supply and the low-voltage terminal, and the acquisition module U1. The high-voltage power supply in this embodiment is a relatively high-voltage power supply compared to the low-voltage terminal voltage. Preferably, the high-voltage power supply in this embodiment is mainly a relatively unsafe voltage power supply, the AC power is greater than or equal to 36V power supply, and the DC power supply is greater than or equal to 60V power supply. The high-voltage power supply can be a power supply, a battery pack, an energy storage power supply, a high-voltage cable, and other devices or systems that can provide power functions. In this embodiment, the low-voltage end is lower than the high-voltage power supply end voltage relative to the high-voltage power supply end voltage. The low-voltage end in this embodiment is preferably the low-voltage ground end.

In this embodiment, the first resistance to be measured is the insulation resistance Rp; the second resistance to be measured is the insulation resistance Rn.

The first detection circuit includes: a first circuit bridge resistor group, and a first sampling resistor Rx connected in series or disconnected with the first circuit bridge resistor group and whose voltage is collected by the collection module U1.

The first circuit bridge resistor group may be one resistor, or may be composed of multiple resistors. The first circuit bridge resistor group can be composed of multiple resistors connected in parallel or in series as required. Preferably, the first circuit bridge resistor group can adjust the first circuit bridge resistor group by changing the connection mode between the resistors, or connecting different resistors in series, or connecting different resistors in parallel, or connecting different resistors, or changing the number of connected resistors as required. resistance value.

The second detection circuit includes: a second circuit bridge resistor group, and a second sampling resistor Ry connected in series or disconnected with the second circuit bridge resistor group and whose voltage is collected by the acquisition module. The first circuit bridge resistor group or the second circuit bridge resistor group is a variable resistor group with variable resistance. Any one of the first circuit bridge resistance group and the second circuit bridge resistance group may be selected as a variable resistance group, or both may be variable resistance groups.

The second circuit bridge resistor group may be one resistor, or may be composed of multiple resistors. The second circuit bridge resistor group can be composed of multiple resistors connected in parallel or in series as required. Preferably, the second circuit bridge resistor group can adjust the second circuit bridge resistor group by changing the connection mode between the resistors, or connecting different resistors in series, or connecting different resistors in parallel, or connecting different resistors, or changing the number of connected resistors as required. resistance value.

Preferably, at least one of the first circuit bridge resistor group and the second circuit bridge resistor group is composed of multiple resistors, or at least one of them is composed of a variable resistor with a measurable resistance value or known variable resistance value.

Further, the first circuit bridge resistor group or the second circuit bridge resistor group in this embodiment includes: fixed access resistors, and adjustable resistors that can be connected in or disconnected according to needs.

Further, the first circuit bridge resistor group or the second circuit bridge resistor group in this embodiment is a variable resistor group that changes the resistance of the access detection circuit by setting the switch to be closed or opened, thereby changing the access resistance value.

Further, the first circuit bridge resistor group or the second circuit bridge resistor group in this embodiment includes: fixed access resistors, and adjustable resistors that can be connected in or disconnected according to needs. There may be one or more fixed access resistors in this embodiment. One or more adjusting resistors can also be set as required.

Further, the low voltage end of this embodiment is the ground end.

According to the setting of the first circuit bridge resistance group, the first circuit bridge resistance group of the present embodiment includes: one or more first fixed access resistors, one or more first adjustment resistors, and one or more first adjustment resistors connected in parallel Terminal and the first test switch that is closed or opened as required.

The first test switch is opened and closed to control whether the first adjustment resistor is connected to the first detection circuit to work, thereby changing the resistance value of the first circuit bridge resistor group.

Multiple first adjusting resistors can be provided, and a first test switch can be connected in parallel to each first adjusting resistor, or a first testing switch can be connected in parallel to multiple first adjusting resistors. Multiple first adjusting resistors can be connected in parallel, in series, or in any combination. A plurality of first adjusting resistors are selected to be connected in parallel with a first test switch, and the number of the first adjusting resistors is selected according to the requirement, and it only needs to not affect the test.

According to the setting of the second circuit bridge resistance group, the second circuit bridge resistance group of the present embodiment includes: one or more second fixed access resistors, one or more second adjustment resistors, and one or more second adjustment resistors connected in parallel terminal and a second test switch that is closed or opened as required.

The second test switch is opened and closed to control whether the second adjustment resistor is connected to the second detection circuit to work, thereby changing the resistance value of the second circuit bridge resistor group.

Multiple second adjusting resistors can be provided, and a second test switch can be connected in parallel to each second adjusting resistor, or a second testing switch can be connected in parallel to multiple second adjusting resistors. Multiple second adjusting resistors can be connected in parallel, in series, or in any combination. A second test switch is connected in parallel to multiple second adjusting resistors, and the number of the second adjusting resistors is selected according to the requirement, and it is sufficient that the test is not affected.

Further, for the convenience of detection, the first fixed access resistance and the second fixed access resistance of the preferred embodiment are set to be the same, the first adjustment resistance and the second adjustment resistance are set to be the same, and the first sampling resistance Rx The resistance setting of the second sampling resistor Ry is the same, that is, Rx=Ry.

Further, in order to facilitate the design and layout, and at the same time to facilitate measurement and reduce errors, the detection circuit of this embodiment adopts a symmetrical design layout, the first fixed access resistor is connected in series with the first adjustment resistor, and the first test resistor is connected in parallel at both ends of the first adjustment resistor. Switch S1, the other end of the first fixed access resistor is connected to the first resistance to be measured, the other end of the first adjusting resistor is connected to the first sampling resistor Rx; the second fixed access resistor is connected in series with the second adjusting resistor, and the second A second test switch S3 is connected in parallel at both ends of the adjusting resistor, the other end of the second fixed access resistor is connected to the second resistance to be tested, and the other end of the second adjusting resistor is connected to the second sampling resistor Ry. Further, in order to further facilitate design and layout, and to facilitate detection and calculation, in this preferred embodiment, the first fixed access resistor is resistor R1, the first adjustment resistor is resistor R2, the second fixed access resistor is resistor R3, and the first fixed access resistor is resistor R3. The second adjustment resistor is resistor R4. The resistor R1 and the resistor R2 are connected in series, the other end of the resistor R1 is connected to the high voltage end of the insulation resistance Rp, that is, the positive end of the power supply, the other end of the resistor R2 is connected to the first sampling resistor Rx, and the other end of the first sampling resistor Rx is connected to the low voltage ground end and It is connected to the low-voltage end of the insulation resistance Rp, and the first test switch S1 is connected in parallel at both ends of the resistance R2, and the two ends of the first sampling resistance Rx are also connected to the acquisition module U1; the resistance R3 and the resistance R4 are connected in series, and the other end of the resistance R3 It is connected to the high voltage end of the insulation resistor Rn, that is, the negative end of the power supply, and the other end of the resistor R4 is connected to the second sampling resistor Ry. A second test switch S3 is also connected in parallel at the end, and both ends of the second sampling resistor Ry are also connected to the acquisition module U1.

In order to further facilitate detection and calculation, the first fixed access resistance and the second fixed access resistance in this embodiment are set to be the same, and the first adjustment resistor and the second adjustment resistance are set to be the same; that is, R1=R2, R3 = R4.

As shown in FIG. 2 , further, preferably, the acquisition module U1 of this embodiment is provided with a differential analog data acquisition channel that uses differential signals to respectively transmit the first sampling resistor Rx and the second sampling resistor Ry to collect and transmit data.

Preferably, the acquisition module U1 of this embodiment is a 24-bit high-precision sampling chip, which has a wide magnification and low-noise input analog voltage sampling characteristics, two fully differential analog voltage sampling channels and four pseudo-differential sampling channels, ensuring The accuracy and stability of the sampled data during the analog voltage sampling process are improved. The fully differential analog voltage sampling channels of the acquisition module U1 are respectively connected to the first sampling resistor Rx and the second sampling resistor Ry. The first sampling resistor Rx, the second sampling resistor Ry and the differential signal lines respectively connected to the fully differential analog voltage sampling channels of the acquisition module U1 are provided with low-pass filter circuits to ensure the stability of signal transmission.

As shown in FIG. 2 , when the 10-pin AINCOM of the acquisition module U1 is configured as a pseudo-differential working mode, the analog inputs AIN1 to AIN4 are based on this input.

The 11-pin AIN1 of the acquisition module U1 is an analog input. When used in combination with AIN2, it can be configured as the positive input of the full differential input pair; when used in combination with AINCOM, it can be configured as a pseudo-differential input.

The 12-pin AIN2 of the acquisition module U1 is an analog input. When used in combination with AIN1, it can be configured as the negative input of the full differential input pair; when used in combination with AINCOM, it can be configured as a pseudo-differential input.

The 13-pin AIN3 of the acquisition module U1 is an analog input. When used in combination with AIN4, it can be configured as the positive input of the full differential input pair; when used in combination with AINCOM, it can be configured as a pseudo-differential input.

The 14-pin AIN4 of the acquisition module U1 is an analog input. When used in combination with AIN3, it can be configured as the negative input of the full differential input pair; when used in combination with AINCOM, it can be configured as a pseudo-differential input.

Pin 15 REFIN1 (+) of the acquisition module U1 is the positive reference input.

The 16-pin REFIN1 (-) of the acquisition module U1 is the negative reference input.

The 17-pin BPDSW of the acquisition module U1 is a bridge shutdown switch, which is connected to AGND.

The 18-pin AGND of the acquisition module U1 is the analog ground reference point.

The 19-pin DGND of the acquisition module U1 is the digital ground reference point.

Pin 23 of the acquisition module U1 is the serial data output/data ready output.

At the same time, the first sampling resistor Rx and the second sampling resistor Ry use differential wiring to transmit the analog voltage to the two differential analog data sampling channels of the acquisition module U1, which reduces the impact on the analog sampling data during line transmission. external interference.

The first sampling resistor Rx and the second sampling resistor Ry in this embodiment are high-precision sampling resistors, and their accuracy is guaranteed to be within 1%, which ensures that the sampling voltage accuracy can be higher.

Further, in this embodiment, a high and low voltage isolating switch is provided between the first circuit bridge resistor group and the first sampling resistor, or between the second circuit bridge resistor group and the second sampling resistor. The high and low voltage isolating switch in this embodiment includes: a first isolating switch S2 and a second isolating switch S4.

In this embodiment, a first isolating switch S2 is arranged between the first circuit bridge resistor group and the first sampling resistor; a second isolating switch S4 is arranged between the second circuit bridge resistor group and the second sampling resistor.

Further, a first isolating switch S2 is set between the first adjusting resistor of this embodiment, that is, the resistor R2, and the first sampling resistor Rx; Isolation switch S4.

Since the safe current of the human body is 10 mA, the current of the detection circuit in this embodiment is equal to or less than 10 mA. In order to ensure safety, preferably, the current of the detection circuit in this embodiment is equal to or less than 3mA. When designing, when Rp and Rn are not connected, only R1, R2, R3 and R4 are connected to the loop, that is, only the detection circuit is connected to the loop (including turning on or off the first test switch S1, the second test switch In the case of any one or more of S3), the maximum flowing current in the entire circuit is less than or equal to 3mA. Thus the full scale of the acquisition module U1 is: Ux ≤ Rx×3mA; Uy ≤ Ry×3mA. The power requirements of each resistor in the detection circuit: P≥ (3mA)×(3mA)×R; according to the fixed current limit, and considering the cost design, according to Uz=R×I, the larger the Uz, the greater its The larger the resistance requirement, the higher the power requirement of the resistor itself; according to Ohm's law, the resistor circuit is matched according to the power supply voltage to ensure that the leakage current between the high voltage and the ground voltage is kept within 3mA.

The acquisition module U1 of the present invention adopts a 24-bit high-precision sampling chip for sampling, and uses a differential signal form for signal transmission to prevent most of the common-mode interference; a low-pass filter circuit is implemented on each differential signal line to ensure signal transmission stability. In order to prevent the failure of the resistor, the selection of the rated power of the resistor requires P≥ (3mA)×(3mA)×R; at the same time, ensure that R1 and R3 are connected in series in the high-voltage circuit together. When the loop current I≤ 3mA, R≥Uz/I ; Resistors R1, R2, R3, and R4 are mainly used to build a bridge circuit for testing insulation resistance, and set it as a symmetrical circuit of R1=R3, R2=R4, Rx=Ry. When R1 and R3 are connected to the circuit, a set of equations can be obtained according to Kirchhoff’s node voltage theorem, and when R2 and R4 are connected, another set of equations can be obtained according to Kirchhoff’s node voltage theorem; Solving the problem immediately, the insulation resistance values Rp and Rn can be calculated according to the voltage value sampled by the sampling chip.

As shown in FIG. 3 , the method for detecting the insulation resistance of high voltage to low voltage using the above detection circuit according to an embodiment of the present invention includes:

Step S101, obtain the current of the first detection circuit: turn on the detection circuit, collect the voltage of the first sampling resistor, and calculate the current of the first sampling resistor according to the voltage and resistance of the first sampling resistor, thereby obtaining the first sampling resistor and the first The current of the first detection circuit formed by the series connection of the circuit bridge resistor groups;

Step S103, the current representation of the first insulation resistance: calculate the voltage of the first detection circuit according to the resistance and current of the first detection circuit, thereby obtaining The voltage of the first insulation resistance to be measured between the first insulation resistance, the current of the first insulation resistance is expressed according to the voltage and resistance value formula of the first insulation resistance;

Step S105, obtain the current of the second detection circuit: collect the voltage of the second sampling resistor, and calculate the current of the second sampling resistor according to the voltage and resistance of the second sampling resistor, so as to obtain the series connection between the second sampling resistor and the bridge resistor group of the second circuit connected to form the current of the second detection circuit,

Step S107, the current representation of the second insulation resistance: calculate the voltage of the second detection circuit according to the resistance and current of the second detection circuit, thereby obtaining The voltage of the second insulation resistance to be measured between is expressed according to the voltage and resistance value formula of the second insulation resistance to represent the current of the second insulation resistance;

Step S109, list the expression: according to the sum of the current of the first detection circuit and the current of the first insulation resistance is equal to the sum of the current of the second detection circuit and the current of the second insulation resistance, the list includes the first insulation resistance and the second The solution equation of insulation resistance;

Step S111, changing the resistance value of the detection circuit: changing the resistance value of the first circuit bridge resistance group or the second circuit bridge resistance group resistance value, or the first and first circuit bridge resistance group resistance values;

Repeat the above steps for detection according to the detection circuit after changing the resistance value:

Step S101, obtaining the current of the first detection circuit;

Step S103, the current representation of the first insulation resistance;

Step S105, obtaining the current of the second detection circuit;

Step S107, the current representation of the second insulation resistance;

Step S109, listing expressions;

Step S113, solving simultaneous equations: according to the different detection values obtained before and after changing the resistance value of the detection circuit, and the sum of the current of the first detection circuit and the current of the first insulation resistance is equal to the current of the second detection circuit and the current of the second insulation resistance The current sum equation obtains two different solution equation expressions including the first insulation resistance and the second insulation resistance, and simultaneously obtains the first equation group to solve the resistance values of the first insulation resistance and the second insulation resistance to be measured.

The current representation of the first insulation resistance in step S103 is derived according to the current of the first detection circuit obtained in step S101, so that step S103 is relatively set after step S101, which only means that step S103 can be placed after step S101, and does not mean that it is imminent sequence relationship.

The current of the second insulation resistance in step S107 is derived and expressed according to the current of the second detection circuit obtained in step S105, and step S107 can be relatively set after step S105, and does not mean that it is performed sequentially.

Step S101, obtaining the current of the first detection circuit and step S105, obtaining the current of the second detection circuit are in no particular order.

In step S109, the list of expressions can be placed after step S103 and step S107, and it does not mean sequential execution. Step S109 lists the expression steps as long as they are set after steps S103 and S107 and before solving the simultaneous equations in step S113, and it does not mean that they are performed sequentially.

As shown in Figure 4, further, preferably, the detection method of the high-voltage to low-voltage insulation resistance of this embodiment also includes: Step S115, changing the resistance value of the detection circuit again: changing the resistance value of the first circuit bridge resistance group or the second The resistance value of the circuit bridge resistor group,

According to the detection circuit after changing the resistance value again, perform the following steps:

Step S101, obtaining the current of the first detection circuit;

Step S103, the current representation of the first insulation resistance;

Step S105, obtaining the current of the second detection circuit;

Step S107, the current representation of the second insulation resistance;

Step S109, list the expression: the sum of the current of the first detection circuit obtained after changing the resistance value of the detection circuit again and the current of the first insulation resistance obtained after changing the resistance value of the detection circuit again is equal to changing the resistance value of the detection circuit again The sum of the current of the second detection circuit obtained after the value and the current of the second insulation resistance obtained after changing the resistance value of the detection circuit again lists the solution equation including the first insulation resistance and the second insulation resistance;

Step S117, solving simultaneous equations: combining the solution equation formed after changing the resistance value of the detection circuit again, which includes the first insulation resistance and the second insulation resistance, and the solution equation formed after changing the resistance value of the detection circuit, or the equation formed by the initial detection circuit Solve the equations to obtain the second equation group simultaneously, and solve the resistance values of the first insulation resistance and the second insulation resistance to be measured;

Step S119, error judgment: if the difference or difference ratio between the resistance value of the first insulation resistance to be measured obtained by solving the first equation set and the resistance value of the first insulation resistance to be measured obtained by solving the second equation set is within the error range, If the difference between the resistance value of the second insulation resistance obtained by solving the first equation group and the resistance value or difference ratio of the second insulation resistance obtained by solving the second equation group is within the error range, then it is judged that the detection is passed,

If the judgment is passed, then

Step S121, obtaining the insulation resistance value: solving the first equation set to obtain the first insulation resistance to be measured and solving the second equation set to obtain the first insulation resistance to be measured, taking the average or weighted average to obtain the resistance value of the first insulation resistance, and Solving the first set of equations to obtain the resistance value of the second insulation resistance and solving the second set of equations to obtain the resistance value of the second insulation resistance are averaged or weighted averaged to obtain the resistance value of the second insulation resistance.

Further, in step S117, in solving the simultaneous equations, the solution equation including the first insulation resistance and the second insulation resistance formed after changing the resistance value of the detection circuit again and the solution equation formed after changing the resistance value of the detection circuit, or the initial detection The solution equations formed by the circuit are combined to obtain the second equation group, and the resistance values of the first insulation resistance and the second insulation resistance to be measured are solved. Wherein, the detection circuit formed after changing the resistance value of the detection circuit again is different from the detection circuit formed after the resistance value of the detection circuit is changed or the initial detection circuit is formed and its simultaneous equation is solved.

Further, preferably, the detection method of the high-voltage to low-voltage insulation resistance of this embodiment also includes: step S123, result optimization: repeat the operation or change the detection circuit resistance value simultaneous equations, and obtain the insulation resistance value for multiple times. The resistance value of the first insulation resistance and the resistance value of the second insulation resistance are respectively averaged or weighted average to optimize the calculation results, and the optimized first insulation resistance and the second insulation resistance are obtained.

Further, step S119, in the error judging step: if the difference or difference ratio between the resistance value of the first insulation resistance to be measured obtained by solving the first equation set and the resistance value of the first insulation resistance to be measured obtained by solving the second equation set is not If it is within the error range, it will be discarded; or if the difference between the resistance value of the second insulation resistance obtained by solving the first equation set and the resistance value or difference ratio of the second insulation resistance obtained by solving the second equation set is not within the error range, it will be discarded;

If the calculated value of the resistance value of the first insulation resistance and the calculated value of the second insulation resistance are discarded, retest; execute:

Step S101, obtain the current of the first detection circuit: collect the voltage of the first sampling resistor, and calculate the current of the first sampling resistor according to the voltage and resistance of the first sampling resistor, so as to obtain the series connection between the first sampling resistor and the first circuit bridge resistor group connected to form the current of the first detection circuit;

Step S103, the current representation of the first insulation resistance: calculate the voltage of the first detection circuit according to the resistance and current of the first detection circuit, thereby obtaining The voltage of the first insulation resistance to be measured between the first insulation resistance and the resistance value formula represent the current of the first insulation resistance;

Step S105, obtain the current of the second detection circuit: collect the voltage of the second sampling resistor, and calculate the current of the second sampling resistor according to the voltage and resistance of the second sampling resistor, so as to obtain the series connection between the second sampling resistor and the bridge resistor group of the second circuit connected to form the current of the second detection circuit,

Step S107, the current representation of the second insulation resistance: calculate the voltage of the second detection circuit according to the resistance and current of the second detection circuit, thereby obtaining The voltage of the second insulation resistance to be measured between is expressed according to the voltage and resistance value formula of the second insulation resistance to represent the current of the second insulation resistance;

Step S109, list the expression: according to the sum of the current of the first detection circuit and the current of the first insulation resistance is equal to the sum of the current of the second detection circuit and the current of the second insulation resistance, the list includes the first insulation resistance and the second The solution equation of insulation resistance;

Step S111, changing the resistance value of the detection circuit: changing the resistance value of the first circuit bridge resistance group or the resistance value of the second circuit bridge resistance group,

Repeat the above steps for detection according to the detection circuit after changing the resistance value:

Step S101, obtaining the current of the first detection circuit;

Step S103, the current representation of the first insulation resistance;

Step S105, obtaining the current of the second detection circuit;

Step S107, the current representation of the second insulation resistance;

Step S109, listing expressions;

Step S113, solving simultaneous equations: according to the different detection values obtained before and after changing the resistance value of the detection circuit, and the sum of the current of the first detection circuit and the current of the first insulation resistance is equal to the current of the second detection circuit and the current of the second insulation resistance The current sum equation obtains two different solution equation expressions including the first insulation resistance and the second insulation resistance, and simultaneously obtains the first equation group to solve the resistance values of the first insulation resistance and the second insulation resistance to be measured.

Continue to change the resistance value of the detection circuit for detection; execute: step S115, change the resistance value of the detection circuit again: change the resistance value of the first circuit bridge resistance group or the resistance value of the second circuit bridge resistance group,

According to the detection circuit after changing the resistance value again, perform the following steps:

Step S101, obtaining the current of the first detection circuit;

Step S103, the current representation of the first insulation resistance;

Step S105, obtaining the current of the second detection circuit;

Step S107, the current representation of the second insulation resistance;

Step S109, list the expression: the sum of the current of the first detection circuit obtained after changing the resistance value of the detection circuit again and the current of the first insulation resistance obtained after changing the resistance value of the detection circuit again is equal to changing the resistance value of the detection circuit again The sum of the current of the second detection circuit obtained after the value and the current of the second insulation resistance obtained after changing the resistance value of the detection circuit again lists the solution equation including the first insulation resistance and the second insulation resistance;

Step S117, solving simultaneous equations: combine the solution equation formed after changing the resistance value of the detection circuit again, which includes the first insulation resistance and the second insulation resistance, and the solution equation formed after changing the resistance value of the detection circuit, or the previous or initial detection The solution equations formed by the circuit are combined to obtain the second equation group, and the resistance values of the first insulation resistance and the second insulation resistance to be measured are solved.

Further, the first circuit bridge resistor group in this embodiment includes: one or more first fixed access resistors, one or more first adjustment resistors, and a resistor connected in parallel to both ends of the first adjustment resistor and closed as required. or open the first test switch. The second circuit bridge resistance group includes: one or more second fixed access resistors, one or more second adjustment resistors, and a second test switch connected in parallel at both ends of the second adjustment resistance and closed or disconnected as required .

Step S111, change the resistance value of the detection circuit, or step S115, change the resistance value of the detection circuit again. 2. Adjusting the connection or number of connected resistors to change the resistance value of the second circuit bridge resistor group.

In this embodiment, the preferred choice is to change the access of the first adjustment resistor, that is, the first adjustment resistor is connected or not connected to the first detection circuit to change the resistance value of the first circuit bridge resistance group; The connection means that the second adjustment resistor is connected or not connected to the second detection circuit to change the resistance value of the second circuit bridge resistance group.

Further, the low voltage end of this embodiment is the ground end.

As shown in Figure 1 and Figure 5, the method for detecting the insulation resistance of high voltage to low voltage using the above-mentioned detection circuit in a preferred embodiment of the present invention includes as follows:

Step S301, closing the first isolating switch S2 and the second isolating switch S4, and turning on the detection circuit;

Step S303, the acquisition module U1 collects the voltage Ux1 of the first sampling resistor and the voltage Uy1 of the second sampling resistor through differential signal transmission;

Step S305, calculate the current of the first sampling resistor according to I1.1=Ux1/Rx, so as to obtain the current of the first detection circuit,

Calculate the current of the second sampling resistor according to I4.1 = Uy1/Ry, so as to obtain the current of the second detection circuit,

Step S307, calculate the voltage of the first detection circuit according to Up.1=(R1+R2+Rx)×I1.1, so as to obtain the first resistance to be measured in parallel with the first detection circuit, that is, the voltage across the insulation resistance Rp,

Calculate the voltage of the second detection circuit according to Un.1=(R3+R4+Ry)×I4.1, thereby obtain the second resistance to be measured in parallel with the second detection circuit, that is, the voltage at both ends of the insulation resistance Rn;

Step S309, according to the formula I2.1=Up.1/Rp, that is, according to the voltage at both ends of the first resistance to be measured, that is, the insulation resistance Rp and its resistance value formula to express the current of the first resistance to be measured, that is, the insulation resistance Rp ,

According to I3.1 = Un .1/ Rn, that is, according to the voltage at both ends of the second resistance to be measured, that is, the insulation resistance Rn and its resistance value formula to represent the current of the second resistance to be measured, that is, the insulation resistance Rn;

Step S311, according to the formula I1.1+I2.1=I3.1+I4.1, list the solution equation including the first insulation resistance and the second insulation resistance;

Step S501, closing the first isolation switch S2, the second isolation switch S4, and the first test switch S1, and turning on the detection circuit;

Step S503, collecting the voltage Ux2 of the first sampling resistor and the voltage Uy2 of the second sampling resistor;

Step S505, calculate the current of the first sampling resistor according to I1.2=Ux2/Rx, so as to obtain the current of the first detection circuit,

Calculate the current of the second sampling resistor according to I4.2=Uy2/Ry, so as to obtain the current of the second detection circuit;

Step S507, calculate the voltage of the first detection circuit according to Up.2=(R1+Rx)×I1.2, so as to obtain the voltage across the first resistance to be measured, that is, the insulation resistance Rp connected in parallel with the first detection circuit,

Calculate the voltage of the second detection circuit according to Un.2=(R3+R4+Ry)×I4.2, thereby obtain the second resistance to be measured in parallel with the second detection circuit, that is, the voltage at both ends of the insulation resistance Rn;

Step S509, according to the formula I2.2=Up.2/Rp, that is, according to the voltage at both ends of the first resistance to be measured, that is, the insulation resistance Rp and its resistance value formula to express the current of the first resistance to be measured, that is, the insulation resistance Rp ,

According to I3.2=Un .2/Rn, that is, according to the voltage at both ends of the second resistance to be measured, namely the insulation resistance Rn, and its resistance value formula to be sought, the second resistance to be measured is the current of the insulation resistance Rn;

Step S511, according to the formula I1.2+I2.2=I3.2+I4.2, list the solution equation including the first insulation resistance and the second insulation resistance;

Step S701, closing the first isolation switch S2, the second isolation switch S4, the first test switch S1, and the second test switch S3, and turning on the detection circuit;

Step S703, collecting the voltage Ux3 of the first sampling resistor and the voltage Uy3 of the second sampling resistor;

Step S705, calculate the current of the first sampling resistor according to I1.3=Ux3/Rx, so as to obtain the current of the first detection circuit,

Calculate the current of the second sampling resistor according to I4.3=Uy3/Ry, so as to obtain the current of the second detection circuit;

Step S707, calculate the voltage of the first detection circuit according to Up.3=(R1+Rx)×I1.3, so as to obtain the first resistance to be measured in parallel with the first detection circuit, that is, the voltage across the insulation resistance Rp,

Calculate the voltage of the second detection circuit according to Un.2=(R3+Ry)×I4.3, thereby obtain the second resistance to be measured in parallel with the second detection circuit, that is, the voltage at both ends of the insulation resistance Rn;

Step S709, according to the formula I2.3=Up.3/Rp, that is, according to the voltage at both ends of the first resistance to be measured, that is, the insulation resistance Rp, and the resistance value formula to represent the current of the first resistance to be measured, that is, the insulation resistance Rp ,

According to I3.3=Un.3/Rn, that is, according to the voltage at both ends of the second resistance to be measured, that is, the insulation resistance Rn, and its resistance value formula to represent the current of the second resistance to be measured, that is, the insulation resistance Rn;

Step S711, according to the formula I1.3+I2.3=I3.3+I4.3, list the solution equation including the first insulation resistance and the second insulation resistance;

Of course, you can also choose to close the first isolation switch S2, the second isolation switch S4, and the second test switch S3, and turn on the detection circuit; then collect the voltage Ux4 of the first sampling resistor and the voltage Uy4 of the second sampling resistor; and then calculate, It is similar to the above and will not be repeated here.

In I1.x + I2. x = I3.x + I4.x list the solution equations including the first insulation resistance and the second insulation resistance, choose two simultaneous equations to solve the equations to form the first equations, and solve The resistance values of the first insulation resistance and the second insulation resistance;

Then arbitrarily select two solving equations to combine the second equation group except the first equation group, which is different from the first equation group, and solve the resistance values of the first insulation resistance and the second insulation resistance.

In this embodiment, I1.1+I2.1=I3.1+I4.1 and I1.2+I2.2=I3.2+I4.2 are selected to be combined with the first equations for illustration. Select I1.3+ I2.3 = I3.3 + I4.3 and I1.1 + I2.1 = I3.1 + I4.1 simultaneous second equations for illustration. The simultaneous manner is only for the convenience of explanation, and is not limited to the above-mentioned simultaneous manner.

In step S901, I1.1+I2.1=I3.1+I4.1 and I1.2+I2.2=I3.2+I4.2 are combined to form the first equation group, and the first resistance to be measured is calculated as the insulation resistance Rp, and the resistance value of the second resistance to be measured, that is, the insulation resistance Rn,

Rp=[(R1+R2+Rx)×(R3+R4+Ry)×(Ux1×Uy2-Ux2×Uy1)] /[(R3+R4+Ry)×(Uy1×Uy2+Uy1×Ux2)-( R3+R4+Ry) ×(Uy1×Uy2+Uy2×Ux1)];

Rn =[(R1+R2+Rx)×(R1+Rx)×(Ux1×Uy3-Ux3×Uy1)] /[(R1+Rx)×(Uy1×Uy3+Uy1×Ux3)-(R1+R2+ Rx) ×(Uy1×Uy3+Uy3×Ux1)];

Step S903, simultaneously I1.3+I2.3=I3.3+I4.3 and I1.1+I2.1=I3.1+I4.1 form the second equation group, and calculate the first resistance to be measured that is insulation resistance Rp, and the resistance value of the second resistance to be measured, that is, the insulation resistance Rn,

Rp=[(R1+R2+Rx)×(R3+Ry)×(Ux1×Uy3-Ux3×Uy1)] /[(R3+Ry)×(Uy1×Uy3+Uy1×Ux3)-(R3+R4+ Ry) ×(Uy1×Uy3+Uy3×Ux1)],

Rn =[(R1+R2+Rx)×(R1+Rx)×(Ux1×Uy3-Ux3×Uy1)] /[(R1+Rx)×(Uy1×Uy3+Uy1×Ux3)-(R1+R2+ Rx) ×(Uy1×Uy3+Uy3×Ux1)];

Step S905, comparing the resistance values of Rp and Rn solved according to the first set of equations with the resistance values of Rp and Rn solved according to the second set of equations, whether they are within the set error range; if the error is within the set range, the test is passed ,

If it exceeds the set error, it will be filtered out and re-tested;

If the test passes, execute:

Step S907, the resistance values of Rp and Rn solved by the first equation group and the resistance values of Rp and Rn solved according to the second equation group are respectively weighted averaged or averaged to obtain the Rp and Rn measured for the first time Resistance.

Repeat the above steps according to the set number of times, for example, set the operation 10 times and so on.

In step S909 , weighted average or mean value is performed on the resistance values of Rp and Rn obtained each time to obtain the final resistance values of Rp and Rn.

Preferably, in step S905, the error between the resistance value of Rp and Rn solved according to the first equation group and the resistance value of Rp and Rn solved according to the second equation group is controlled within 5%, that is, the Rp obtained by the two equation groups , The difference of the resistance value of Rn is controlled within 5% relative to the resistance value.

The invention is mainly applied to the detection of the insulation resistance of low-voltage electricity relative to high-voltage electricity, including the insulation resistance detection of high-voltage cables to low-voltage lines, and the insulation resistance detection of the total positive and negative of automobile power battery packs to low-voltage systems. , Energy storage total positive and negative for the insulation resistance detection of the low-voltage power supply system and all high-voltage insulation resistance detection for the low-voltage system.

The high-voltage to low-voltage insulation resistance detection circuit and detection method of the present invention occupy less resources for microcomputer calculations, and the calculation process does not need to open the square root; the calculation is used for comparison of results to ensure the accuracy of the calculation results; multiple times are used to calculate the average value, This ensures the further accuracy and stability of the data.

The 24-bit precision AD chip used in the acquisition module U1 of the present invention has high acquisition accuracy; compared with the existing detection schemes, it is all based on mode judgment and detection, and its high-voltage always positive to low-voltage ground insulation resistance is the smallest, and high-voltage total negative to low-voltage The insulation resistance of the ground is the smallest, and when the total positive and negative resistances are equal to the low-voltage ground, the error of the detection result is very large; and the resistance range detected by the high-voltage to low-voltage insulation resistance detection circuit and detection method of the present invention has Continuity, does not depend on the mode segmentation detection, directly detects the actual total positive to ground, total negative to ground actual resistance, which is closer to the actual situation.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (10)

1. A detection circuit of high voltage to low voltage insulation resistance, characterized in that, comprising: a first detection circuit connected in parallel with the first insulation resistance between the positive pole of the high voltage power supply and the low voltage terminal, and the connection between the negative pole of the high voltage power supply and the low voltage terminal The second detection circuit connected in parallel with the second insulation resistance between them, and an acquisition module, the first detection circuit includes: a first circuit bridge resistance group, and a series connection or disconnection with the first circuit bridge resistance group and is determined by the first circuit bridge resistance group The acquisition module collects the first sampling resistor of its voltage, and the second detection circuit includes: a second circuit bridge resistor group, and a resistor connected in series or disconnected with the second circuit bridge resistor group and whose voltage is collected by the acquisition module The second sampling resistor, the other end of the first sampling resistor connected to the first circuit bridge resistor group is connected to the low voltage end, and the second sampling resistor is connected to the other end connected to the second circuit bridge resistor group Low-voltage end: the first circuit bridge resistance group or the second circuit bridge resistance group is a variable resistance group with variable resistance, or the first and second resistance groups are variable resistance groups. 2. The detection circuit of high voltage to low voltage insulation resistance according to claim 1, characterized in that: the first circuit bridge resistance group or the second circuit bridge resistance group is to change the access by setting the switch on or off A variable resistor group that detects circuit resistance and changes the access resistance value. 3. The detection circuit of high voltage to low voltage insulation resistance according to claim 1, characterized in that: the first circuit bridge resistor group or the second circuit bridge resistor group comprises: fixed access resistors, and variable access resistors Or adjust the resistance connected or disconnected according to the needs. 4. The detection circuit of high-voltage to low-voltage insulation resistance according to any one of claims 1 to 3, characterized in that: the low-voltage terminal is a ground terminal, and the first circuit bridge resistance group includes: one or more The first fixed access resistance, one or more first adjustment resistances, and the first test switch connected in parallel at both ends of the first adjustment resistance and closed or disconnected as required; the second circuit bridge resistance group includes : one or more second fixed access resistors, one or more second adjustment resistors, and a second test switch connected in parallel to both ends of the second adjustment resistors and closed or disconnected as required. 5. The detection circuit of high voltage to low voltage insulation resistance according to claim 4, characterized in that: the first fixed access resistance is set to the same resistance value as the second fixed access resistance, and the first adjustment resistance and the second fixed access resistance are set to be the same. The resistance value of the second adjusting resistor is set to be the same, and the resistance value of the first sampling resistor is set to be the same as that of the second sampling resistor. 6. The detection circuit of high voltage to low voltage insulation resistance according to claim 4, characterized in that: the acquisition module is provided with two differential signals that transmit the first sampling resistor and the second sampling resistor to collect and transmit data respectively. An analog data acquisition channel, the current of the detection circuit is equal to or less than 3mA, the first fixed access resistance is a resistor R1, the first adjustment resistor is a resistor R2, and the second fixed access resistance is a resistor R3, The second adjusting resistor is a resistor R4, and the R1=R2, R3=R4. 7. The detection circuit of high-voltage to low-voltage insulation resistance according to any one of claims 1 to 3, characterized in that: between the first circuit bridge resistance group and the first sampling resistor, or between the second circuit A high and low voltage isolating switch is arranged between the bridge resistor group and the second sampling resistor. 8. A method for detecting insulation resistance of high voltage to low voltage, characterized in that it comprises: Obtain the current of the first detection circuit: turn on the detection circuit, collect the voltage of the first sampling resistor, and calculate the current of the first sampling resistor according to the voltage and resistance of the first sampling resistor, thereby obtaining the first sampling resistor and the first circuit bridge resistance The current of the first detection circuit formed by the series connection of the groups; The current representation of the first insulation resistance: calculate the voltage of the first detection circuit according to the resistance and current of the first detection circuit, so as to obtain the standby voltage connected in parallel with the first detection circuit and connected between the positive pole and the low voltage terminal of the high voltage power supply Measure the voltage of the first insulation resistance, and express the current of the first insulation resistance according to the voltage and resistance value formula of the first insulation resistance; Obtain the current of the second detection circuit: collect the voltage of the second sampling resistor, and calculate the current of the second sampling resistor according to the voltage and resistance of the second sampling resistor, so as to obtain the series connection between the second sampling resistor and the second circuit bridge resistor group The current of the second detection circuit; The current representation of the second insulation resistance: calculate the voltage of the second detection circuit according to the resistance and current of the second detection circuit, so as to obtain the standby voltage connected in parallel with the second detection circuit and connected between the negative pole of the high-voltage power supply and the low-voltage terminal. Measure the voltage of the second insulation resistance, and express the current of the second insulation resistance according to the voltage and resistance value formula of the second insulation resistance; List the expression: According to the sum of the current of the first detection circuit and the current of the first insulation resistance is equal to the sum of the current of the second detection circuit and the current of the second insulation resistance, list the currents including the first insulation resistance and the second insulation resistance solve the equation; Change the resistance value of the detection circuit: change the resistance value of the first circuit bridge resistance group or the resistance value of the second circuit bridge resistance group, Perform the following steps according to the detection circuit that changes the resistance value: The step of obtaining the current of the first detection circuit, the step of representing the current of the first insulation resistance, the step of obtaining the current of the second detection circuit, the step of representing the current of the second insulation resistance, and the step of listing expressions; then execute Simultaneous equation solution: According to the different detection values obtained before and after changing the resistance value of the detection circuit, and the sum of the current of the first detection circuit and the current of the first insulation resistance is equal to the sum of the current of the second detection circuit and the current of the second insulation resistance Two different solution equation expressions obtained by the equations including the first insulation resistance and the second insulation resistance are obtained simultaneously to obtain the first equation group to solve the resistance values of the first insulation resistance and the second insulation resistance to be measured. 9. The detection method of high voltage to low voltage insulation resistance according to claim 8, further comprising: changing the resistance value of the detection circuit again: changing the resistance value of the first circuit bridge resistance group or the second circuit bridge resistance group Resistance value, or changing the resistance value of the first and second circuit bridge resistance groups, According to the detection circuit that changes the resistance value again, perform the following steps: The step of obtaining the current of the first detection circuit, the step of representing the current of the first insulation resistance, the step of obtaining the current of the second detection circuit, and the step of representing the current of the second insulation resistance, List the expression: According to the sum of the current of the first detection circuit obtained after changing the resistance value of the detection circuit again and the current of the first insulation resistance obtained after changing the resistance value of the detection circuit again, it is equal to the current obtained after changing the resistance value of the detection circuit again The sum of the current of the second detection circuit obtained and the current of the second insulation resistance obtained after changing the resistance value of the detection circuit again, and a solution equation including the first insulation resistance and the second insulation resistance are listed; Simultaneous equation solving: combine the solution equation formed after changing the resistance value of the detection circuit again, which includes the first insulation resistance and the second insulation resistance, with the solution equation formed after changing the resistance value of the detection circuit, or with the solution equation formed by the initial detection circuit Obtain the second equation group immediately, and solve the resistance values of the first insulation resistance and the second insulation resistance to be measured; Error judgment: If the difference or difference ratio between the resistance value of the first insulation resistance to be measured obtained by solving the first equation set and the resistance value of the first insulation resistance to be measured obtained by solving the second equation set is within the error range, the first equation If the difference between the resistance value of the second insulation resistance obtained by solving the group and the resistance value or difference ratio of the second insulation resistance obtained by solving the second equation group is within the error range, then it is judged that the detection is passed, If the judgment is passed, then Obtain the resistance value of insulation resistance: solve the first equation set to obtain the first insulation resistance to be measured and solve the second equation set to obtain the first insulation resistance to be measured, take the average value or weighted average to obtain the resistance value of the first insulation resistance, and use the first equation The resistance value of the second insulation resistance obtained by solving the set of equations and the resistance value of the second insulation resistance obtained by solving the second equation set are averaged or weighted averaged to obtain the resistance value of the second insulation resistance. 10. The detection method of high voltage to low voltage insulation resistance according to claim 9, is characterized in that, also comprises: Result optimization: repeat operation or change detection circuit resistance value simultaneous equation group, obtain insulation resistance resistance value for many times The resistance value of the first insulation resistance and the resistance value of the second insulation resistance obtained in the step are respectively carried out mean value calculation or weighted average calculation to optimize the calculation results, and obtain the optimized first insulation resistance resistance value and the second insulation resistance resistance value; In the error judgment step: if the difference or difference ratio between the resistance value of the first insulation resistance to be measured obtained by solving the first equation set and the resistance value of the first insulation resistance to be measured obtained by solving the second equation set is not within the error range Then discard; or if the resistance value of the second insulation resistance obtained by solving the first equation group and the resistance value or difference ratio of the second insulation resistance obtained by solving the second equation group are not within the error range, then discard; If the calculated value of the resistance value of the first insulation resistance and the calculated value of the second insulation resistance are discarded, retest; The first circuit bridge resistor group includes: one or more first fixed access resistors, one or more first adjustment resistors, and a circuit that is connected in parallel at both ends of the first adjustment resistor and is closed or disconnected as required. The first test switch; the second circuit bridge resistance group includes: one or more second fixed access resistors, one or more second adjustment resistors, and connected in parallel at both ends of the second adjustment resistance and performed as required a closed or open second test switch; The step of changing the resistance value of the detection circuit or the step of changing the resistance value of the detection circuit again changes the resistance value of the first circuit bridge resistance group by changing the access or the number of access of the first adjustment resistor, or by changing the connection of the second adjustment resistor. Change the resistance value of the second circuit bridge resistance group by entering or accessing the number; The low voltage end is a ground end.