High-precision insulation detection circuit system and method

Abstract

The invention discloses a high-precision insulation detection circuit system and method.The circuit system comprises a first resistor network R1, a second resistor network R2, a third resistor network R3, an optocoupler control switch K1 and an optocoupler control switch K2, one end of the first resistor network R1 is connected with the total positive phase of a battery, and the other end of the first resistor network R1 is connected with the front end of the optocoupler control switch K1 in series; the tail end of the optocoupler control switch K1 is connected with a second resistor network R2 in series, the other end of the second resistor network R2 is connected with an optocoupler control switch K2 in series, the tail end of the optocoupler control switch K2 is connected with a third resistor network R3 in series, and the tail end of the third resistor network R3 is connected with the total negative phase of the battery. According to the scheme, bridge arms and optocoupler switches thereof are reduced, the insulation detection principle is realized by using a simpler scheme, the PCB layout is more facilitated, the circuit is simple and reliable, and the manufacturing cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of battery insulation detection, and particularly to a high-precision insulation detection circuit system and method. Background Art

[0002] With the development of lithium batteries, lithium batteries are increasingly widely used as power batteries or energy storage batteries, and the voltage platform and charge and discharge current are getting higher and higher. However, if there is a leakage problem in the power battery, it may seriously lead to personal safety problems or major property loss problems. From the perspective of electrical safety, the battery insulation detection function has become one of the core functions of the battery management system. It is necessary to detect the insulation impedance of the positive and negative poles of the battery pack and the load high-voltage bus to the ground (chassis) to ensure that the battery system works more safely and reliably, and provide a basis for the safety management of the battery system. The most commonly used method for existing battery insulation detection is the balanced bridge method. A standard resistor is connected in parallel between the positive and negative high-voltage buses and the vehicle body ground. By switching the switch, the voltage division ratio of the positive and negative buses to the vehicle body ground is changed, and then the insulation resistance of the battery is calculated. To achieve this, multiple high-voltage optocouplers are required to control the corresponding bridge arms, and the circuit is relatively complex. On the other hand, two additional high-voltage side voltage samplings need to be added and sent to the MCU for sampling through isolation amplifiers, resulting in a complex circuit, low reliability, and high cost. For the unbalanced bridge, although it solves the problems of complex circuit and a large number of high-voltage optocouplers, when the insulation resistance value is small, the accuracy deviation is relatively large. Summary of the Invention

[0003] In view of the above technical problems, the present invention provides a high-precision insulation detection circuit system and method.

[0004] The present invention is implemented by the following technical solutions: A high-precision insulation detection circuit system includes a first resistor network R1, a second resistor network R2, and a third resistor network R3, as well as two optocoupler control switches K1 and K2. One end of the first resistor network R1 is connected to the total positive of the battery, and the other end is connected in series with the front end of the optocoupler control switch K1. The end of the optocoupler control switch K1 is connected in series with the second resistor network R2. The other end of the second resistor network R2 is connected in series with the optocoupler control switch K2. The end of the optocoupler control switch K2 is connected in series with the third resistor network R3. The end of the third resistor network R3 is connected to the total negative of the battery.

[0005] Specifically, the node where the end of the optocoupler control switch K1 is connected in series with the second resistor network R2 is grounded.

[0006] Specifically, it further includes differential operational amplifiers U1 and U2, a precision voltage regulator U3, and an analog front end U4. The input end of the operational amplifier U1 is connected to the acquisition point P1, and a resistor R6 is connected in series at the output end. A resistor R7 is connected in series at the output end of the operational amplifier U2. The resistor R6 and the resistor R7 are connected in parallel and connected to the input end of the precision voltage regulator U3. The output end of the precision voltage regulator U3 is connected to the acquisition port of the analog front end U4.

[0007] Specifically, the operational amplifiers U1 and U2, and the precision voltage regulator U3 are powered by the analog front end U4.

[0008] Specifically, the operational amplifiers U1 and U2 are differential operational amplifiers. The precision voltage regulator U3 provides a level with a reference of 0.5V for the operational amplifiers. The analog front end U4 is an integrated high-voltage acquisition device.

[0009] Specifically, it further includes system insulation equivalent resistors RN and RP. The insulation equivalent resistor RN is equivalent to the resistance value between the connection end of the first resistor network R1 and the positive terminal of the battery total and the grounding end of the optocoupler control switch K1. The insulation equivalent resistor RP is equivalent to the resistance value between the grounding end of the second resistor network R2 and the connection end of the third resistor network R3 to the negative terminal of the battery total.

[0010] Specifically, the first resistor network R1 and the second resistor network R2 are both composed of 4 539K resistors connected in series. The third resistor network R3 is composed of 2 15K resistors connected in parallel.

[0011] A high-precision insulation detection method is implemented based on the described high-precision insulation detection circuit system, including the following steps: Step S1: After the system is powered on, the optocoupler control switches K1 and K2 are both in the off state. At this time, the control switch K2 is closed to form a first acquisition loop. In this state, the switch K1 is open and the switch K2 is closed, which is equivalent to the first resistor network R1 not being connected to the loop. For the insulation positive, there is only the equivalent resistor RP. For the insulation negative loop, it is the sum of RN in parallel with the second resistor network R2 and the third resistor network R3. At this time, a voltage sample V1 is acquired once, and the U+ and U- voltage values are calculated based on the V1 sample voltage and the first acquisition loop. Step S2: The optocoupler control switches K1 and K2 are closed to form a second acquisition loop. In this state, the switch K1 is closed and the switch K2 is closed, which is equivalent to the insulation positive being composed of RP in parallel with the first resistor network R1. For the insulation negative loop, it is the sum of RN in parallel with the second resistor network R2 and the third resistor network R3. At this time, a secondary sample voltage V2 is acquired, and the U+' and U-' voltage values are calculated based on the V2 sample voltage and the second sample loop. Step S3: Combine the voltage values ​​U+ and U- calculated in step S1 and the voltage values ​​U+' and U-' calculated in step S2 to solve the insulation positive equivalent resistance RP and the insulation negative equivalent resistance RN; Step S4: Disconnect K1 and K2 to complete an insulation detection state.

[0012] Specifically, step S1 calculates the voltage values ​​of U+ and U- according to the V1 sampling voltage and the first acquisition circuit. The specific calculation formula is: U-=(V1-0.5V)*((R2+R3) / R3); U+=Ub - U-; According to the calculated U+ and U-, we can get: ; Among them, V1 is the primary sampling voltage of the system; U+ is the positive equivalent voltage of the primary insulation of the system; U- is the negative equivalent voltage of the primary insulation of the system.

[0013] Specifically, the voltage values ​​U+' and U-' are calculated based on the V2 sampling voltage and the second sampling loop, and the specific calculation formula is: U-'=(V2-0.5V)*((R2+R3) / R3); U+'=Ub - U-'; According to the calculated U+' and U-', we can get: ; Among them, V2 is the system secondary sampling voltage; U+' is the system secondary insulation positive equivalent voltage; U-' is the system secondary insulation negative equivalent voltage.

[0014] The beneficial effects of the present invention are as follows: the present invention uses an unbalanced bridge type to realize insulation detection, simplifies the insulation detection steps, is a safer and more reliable circuit, increases the insulation detection accuracy, detects the insulation state in real time, and ensures the safety of equipment and personnel; compared with a full-bridge insulation detection circuit, the bridge arm and its optical coupling switch are reduced, and a simpler solution is used to realize the insulation detection principle, which is more conducive to PCB layout, the circuit is simple and reliable, the manufacturing cost is low, the detection result is accurate, and the implementation is convenient. The front-end acquisition sampling integrated chip has higher reliability and safety than the distributed circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0016] Figure 1 This is the architecture diagram of the insulation detection circuit system in the embodiment of the present invention; Figure 2 This is the schematic diagram of the closure of switch K2 in the insulation detection circuit system in the embodiment of the present invention; Figure 3 This is the equivalent circuit diagram of the closure of switch K2 in the insulation detection circuit system in the embodiment of the present invention; Figure 4 This is the schematic diagram of the closure of switches K1 and K2 in the insulation detection circuit system in the embodiment of the present invention; Figure 5 This is the equivalent circuit diagram of the closure of switches K1 and K2 in the insulation detection circuit system in the embodiment of the present invention. Detailed implementation manners

[0017] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0018] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0019] The following combines the attached Figures 1 - 5 , and details some implementation manners of the present invention. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0020] The present invention provides a high-precision insulation detection circuit system. In a preferred embodiment, the system circuit includes a first resistor network R1, a second resistor network R2, and a third resistor network R3, as well as two optocoupler control switches K1 and K2. One end of the first resistor network R1 is connected to the total positive of the battery, and the other end is connected in series with the front end of the optocoupler control switch K1. The end of the optocoupler control switch K1 is connected in series with the second resistor network R2. The other end of the second resistor network R2 is connected in series with the optocoupler control switch K2. The end of the optocoupler control switch K2 is connected in series with the third resistor network R3. The end of the third resistor network R3 is connected to the total negative of the battery; the node where the end of the optocoupler control switch K1 is connected in series with the second resistor network R2 is grounded.

[0021] In one embodiment, it also includes differential operational amplifiers U1 and U2, a precision voltage regulator U3 and an analog front end U4, wherein the input end of the operational amplifier U1 is connected to the acquisition point P1, and the output end is connected in series with a resistor R6; the output end of the operational amplifier U2 is connected in series with a resistor R7, the resistor R6 and the resistor R7 are connected in parallel and connected to the input end of the precision voltage regulator U3, and the output end of the precision voltage regulator U3 is connected to the acquisition port of the analog front end U4.

[0022] In this embodiment, the operational amplifiers U1 and U2, and the precision voltage regulator U3 are powered by the analog front end U4; the operational amplifiers U1 and U2 are differential operational amplifiers, the precision voltage regulator U3 provides a reference level of 0.5V for the operational amplifiers, and the analog front end U4 is an integrated high-voltage acquisition device.

[0023] In one embodiment, the system also includes insulation equivalent resistances RN and RP, wherein the insulation equivalent resistance RN is equivalent to the resistance between the first resistance network R1 and the total positive phase connection terminal of the battery and the ground terminal of the optocoupler control switch K1, and the insulation equivalent resistance RP is equivalent to the resistance between the ground terminal of the second resistance network R2 and the total negative phase terminal of the battery connected to the third resistance network R3. The first resistance network R1 and the second resistance network R2 are both composed of four 539K resistors in series, and the third resistance network R3 is composed of two 15K resistors in parallel.

[0024] The present invention also proposes a high-precision insulation detection method, which is implemented based on the high-precision insulation detection circuit system, and includes the following steps: Step S1: After the system is powered on, the optocoupler control switches K1 and K2 are both in the disconnected state, and the control switch K2 is closed to form a first acquisition loop; in this state, switch K1 is disconnected and switch K2 is closed, which is equivalent to the first resistor network R1 not being connected to the loop, and the insulated positive circuit only has an equivalent resistor RP, and the insulated negative circuit is connected by RN and the sum of the second resistor network R2 and the third resistor network R3. At this time, a voltage sample V1 is collected, and the U+ and U- voltage values ​​are calculated based on the V1 sample voltage and the first acquisition loop; Step S2: close the optical coupler control switches K1 and K2 to form a second acquisition loop; in this state, switch K1 is closed, switch K2 is closed, the equivalent insulation positive loop is composed of RP and the first resistor network R1, and the insulation negative loop is composed of RN and the sum of the second resistor network R2 and the third resistor network R3. At this time, the secondary sampling voltage V2 is collected, and the U+' and U-' voltage values ​​are calculated according to the V2 sampling voltage and the second sampling loop; Step S3: Combine the voltage values ​​U+ and U- calculated in step S1 and the voltage values ​​U+' and U-' calculated in step S2 to solve the insulation positive equivalent resistance RP and the insulation negative equivalent resistance RN; Step S4: Disconnect K1 and K2 to complete an insulation detection state.

[0025] In this embodiment, in step S1, the U+ and U- voltage values are calculated based on the V1 sampling voltage and the first acquisition circuit. The specific calculation formula is as follows: U- = (V1 - 0.5V) * ((R2 + R3) / R3); U+ = Ub - U-; Based on the calculated U+ and U-, it can be obtained that: ; where V1 is the system primary sampling voltage; U+ is the system primary insulation positive equivalent voltage; U- is the system primary insulation negative equivalent voltage.

[0026] In this embodiment, the U+' and U-' voltage values are calculated based on the V2 sampling voltage and the second sampling circuit. The specific calculation formula is as follows: U-' = (V2 - 0.5V) * ((R2 + R3) / R3); U+' = Ub - U-'; Based on the calculated U+' and U-', it can be obtained that: ; where V2 is the system secondary sampling voltage; U+' is the system secondary insulation positive equivalent voltage; U-' is the system secondary insulation negative equivalent voltage.

[0027] In a specific embodiment, the object of the present invention is to provide a method for detecting the insulation of the positive and negative busbars of a battery, and a specific circuit system is proposed, as Figure 1 shown, which includes a first resistor network R1, a second resistor network R2, a third resistor network R3, opto-coupler control switches K1 and K2, operational amplifiers U1 and U2, a precision voltage regulator U3, and an analog front end AFE U4.

[0028] In this embodiment, the first resistor network R1 is composed of 4 539K resistors connected in series; the second resistor network R2 is composed of 4 539K resistors connected in series; the third resistor network R3 is composed of 2 15K resistors connected in parallel; the operational amplifiers U1 and U2 are differential operational amplifiers; the precision voltage regulator U3 provides a reference 0.5V level for the operational amplifier; the front end AFE U4 is an integrated high-voltage acquisition device; K1 and K2 are high-voltage isolation opto-couplers AQV258HAXC88; Ub is the system total voltage, directly acquired by the AFE; V1 is the system primary sampling voltage; U+ is the system primary insulation positive equivalent voltage; U- is the system primary insulation negative equivalent voltage; V2 is the system secondary sampling voltage; U+' is the system secondary insulation positive equivalent voltage; U-' is the system secondary insulation negative equivalent voltage.

[0029] In this embodiment, the circuit system is as Figure 1As shown in the figure, one end of the first resistor network R1 is connected to the total positive of the battery, the other end is connected in series with the switch K1, the end of K1 is connected in series with the second resistor network R2, the end of the second resistor network R2 is connected in series with K2, and this node is the access reference point for the system ground (chassis). The end of K2 is connected in series with the third resistor network R3, and the end of the third resistor network R3 is connected to the total negative of the battery. The input end of the operational amplifier U1 is connected to the acquisition point P1, the output end of the operational amplifier U1 is connected in series with R6, the output end of the precision voltage regulator U2 is connected in series with R7, the other end of R6 and the other end of R7 are connected in parallel to the input end of U3, and the output of U3 is connected to the acquisition port of U4. The power supply of U1, U2, and U3 is provided by U4. RN and RP are the equivalent resistances of the system insulation.

[0030] Specific implementation process: The first step (refer to Figure 2 、 Figure 3 ): After the system is powered on, both switches K1 and K2 are in the off state. At this time, control switch K2 is closed to form the first acquisition loop. In this state, K1 is off and K2 is on, which is equivalent to R1 not being connected to the loop. For the positive insulation, there is only the equivalent resistance RP. For the negative insulation loop, it is composed of RN in parallel with the sum of R2 and R3. The equivalent circuit is as shown in Figure 3 . At this time, sample the voltage V1 once. According to the V1 sampling voltage and the first acquisition loop, calculate the voltage values of U+ and U-. The specific formulas are as follows; Equation 1: U- = (V1 - 0.5V) * ((R2 + R3) / R3) Equation 2: U+ = Ub - U-; Based on the calculated U+ and U-, obtain Equation 3: Equation 3: .

[0031] The second step (refer to Figure 4 、 Figure 5 ): Close switches K1 and K2 to form the second acquisition loop. In this state, K1 is on and K2 is on. The equivalent positive insulation is composed of RP in parallel with R1, and the negative insulation loop is composed of RN in parallel with the sum of R2 and R3. The equivalent circuit is as shown in Figure 5. At this time, sample the secondary sampling voltage V2. According to the V2 sampling voltage and the second sampling loop, calculate U+' and U-'. The specific formulas are as follows Equation 4: U-' = (V2 - 0.5V) * ((R2 + R3) / R3); Equation 5: U+' = Ub - U-'; Based on the calculated U+' and U-', obtain Equation 6: Equation 6: ; Simultaneously solve Equation 3 and Equation 6 to obtain the equivalent resistance RP of the positive insulation and the equivalent resistance RN of the negative insulation.

[0032] Step 3: Disconnect K1 and K2, and at this time, one insulation detection state is completed.

[0033] For the foregoing embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that this application is not limited by the described action sequence, because according to this application, some steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification belong to preferred embodiments, and the actions involved are not necessarily essential to this application.

[0034] In the above embodiments, the basic principles, main features and advantages of the present invention are described. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, any changes and modifications made by those skilled in the art should fall within the protection scope of the appended claims of the present invention.

Claims

1. A high-precision insulation detection circuit system, characterized in that: It includes a first resistor network R1, a second resistor network R2 and a third resistor network R3, and two optocoupler controlled switches K1 and K2, wherein one end of the first resistor network R1 is connected to the total positive phase of the battery, and the other end is connected in series with the front end of the optocoupler controlled switch K1, the end of the optocoupler controlled switch K1 is connected in series with the second resistor network R2, the other end of the second resistor network R2 is connected in series with the optocoupler controlled switch K2, the end of the optocoupler controlled switch K2 is connected in series with the third resistor network R3, and the end of the third resistor network R3 is connected to the total negative phase of the battery.

2. A high-precision insulation detection circuit system as claimed in claim 1, characterized in that: The end of the optocoupler control switch K1 and the second resistor network R2 are connected in series and are grounded.

3. A high-precision insulation detection circuit system as claimed in claim 1, characterized in that: It also includes differential operational amplifiers U1 and U2, a precision voltage regulator U3 and an analog front end U4. The input end of the operational amplifier U1 is connected to the acquisition point P1, and the output end is connected in series with a resistor R6; the output end of the operational amplifier U2 is connected in series with a resistor R7, the resistor R6 and the resistor R7 are connected in parallel and connected to the input end of the precision voltage regulator U3, and the output end of the precision voltage regulator U3 is connected to the acquisition port of the analog front end U4.

4. A high-precision insulation detection circuit system as claimed in claim 3, characterized in that: The operational amplifiers U1 and U2, and the precision voltage regulator U3 are powered by the analog front end U4.

5. A high-precision insulation detection circuit system as claimed in claim 3, characterized in that: The operational amplifiers U1 and U2 are differential operational amplifiers, the precision voltage regulator U3 provides a reference level of 0.5V for the operational amplifiers, and the analog front end U4 is an integrated high-voltage acquisition device.

6. A high-precision insulation detection circuit system as claimed in claim 1, characterized in that: It also includes system insulation equivalent resistances RN and RP, wherein the insulation equivalent resistance RN is equivalent to the resistance between the first resistance network R1 and the total positive phase connection terminal of the battery and the ground terminal of the optocoupler control switch K1, and the insulation equivalent resistance RP is equivalent to the resistance between the ground terminal of the second resistance network R2 and the total negative phase terminal of the battery connected to the third resistance network R3.

7. A high-precision insulation detection circuit system as claimed in claim 1, characterized in that: The first resistor network R1 and the second resistor network R2 are both composed of four 539K resistors connected in series, and the third resistor network R3 is composed of two 15K resistors connected in parallel.

8. A high-precision insulation detection method, implemented based on a high-precision insulation detection circuit system according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step S1: After the system is powered on, the optocoupler control switches K1 and K2 are both in the disconnected state, and the control switch K2 is closed to form a first acquisition loop; in this state, switch K1 is disconnected and switch K2 is closed, which is equivalent to the first resistor network R1 not being connected to the loop, and the insulated positive circuit only has an equivalent resistor RP, and the insulated negative circuit is connected by RN and the sum of the second resistor network R2 and the third resistor network R3. At this time, a voltage sample V1 is collected, and the U+ and U- voltage values ​​are calculated based on the V1 sample voltage and the first acquisition loop; Step S2: close the optical coupler control switches K1 and K2 to form a second acquisition loop; in this state, switch K1 is closed, switch K2 is closed, the equivalent insulation positive loop is composed of RP and the first resistor network R1, and the insulation negative loop is composed of RN and the sum of the second resistor network R2 and the third resistor network R3. At this time, the secondary sampling voltage V2 is collected, and the U+' and U-' voltage values ​​are calculated according to the V2 sampling voltage and the second sampling loop; Step S3: Combine the voltage values ​​U+ and U- calculated in step S1 and the voltage values ​​U+' and U-' calculated in step S2 to solve the insulation positive equivalent resistance RP and the insulation negative equivalent resistance RN; Step S4: Disconnect K1 and K2 to complete an insulation detection state.

9. A high-precision insulation detection method as claimed in claim 8, characterized in that: The step S1 calculates the voltage values ​​of U+ and U- according to the V1 sampling voltage and the first acquisition circuit. The specific calculation formula is: U-=(V1-0.5V)*((R2+R3) / R3); U+=Ub - U-; According to the calculated U+ and U-, we can get: ； Among them, V1 is the primary sampling voltage of the system; U+ is the positive equivalent voltage of the primary insulation of the system; U- is the negative equivalent voltage of the primary insulation of the system.

10. A high-precision insulation detection method according to claim 8, characterized in that: The voltage values ​​U+' and U-' are calculated based on the V2 sampling voltage and the second sampling loop. The specific calculation formula is: U-'=(V2-0.5V)*((R2+R3) / R3); U+'=Ub - U-'; According to the calculated U+' and U-', we can get: ； Among them, V2 is the system secondary sampling voltage; U+' is the system secondary insulation positive equivalent voltage; U-' is the system secondary insulation negative equivalent voltage.

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