A single path insulation detection circuit for an unbalanced bridge

Abstract

The utility model provides a kind of single-path insulation detection circuit of unbalance bridge, it is related to high voltage electrical system technical field, the circuit includes: first voltage division module, by first voltage division resistor network, the first end of first voltage division module connects bus positive pole;Second voltage division module, by second voltage division resistor network and detection voltage division resistor series connection, its first end connects the second end of first voltage division module, its second end connects bus negative pole;Casing disconnecting switch, between the connecting point between the second end of first voltage division module and the first end of second voltage division module and casing ground;First disturbance branch, containing the first switch and first disturbance resistor network in series, first disturbance branch is parallel with first voltage division module;Second disturbance branch, containing the second switch and second disturbance resistor network in series, second disturbance branch is parallel with second voltage division module;Voltage detection unit, one end is connected with the one end of detection voltage division resistor, the other end of voltage detection unit connects reference ground.

Description

Technical Field

[0001] This utility model relates to the field of high-voltage electrical system technology, specifically to a single-channel insulation detection circuit for an unbalanced bridge. Background Technology

[0002] In high-voltage electrical systems, insulation performance is one of the core technical indicators for ensuring safe system operation. Insulation failure can lead to serious safety accidents such as leakage, short circuits, and even fires. Therefore, real-time monitoring of the insulation status between the high-voltage circuit and the equipment casing (housing) and timely detection of potential insulation hazards are crucial for the safety protection of high-voltage electrical systems. Currently, the unbalanced bridge detection scheme is one of the most widely used solutions for insulation testing in high-voltage electrical systems. This scheme constructs an unbalanced bridge structure containing resistance networks of upper and lower bridge arms. By utilizing the difference in insulation resistance between the upper and lower bridge arms to ground and detecting voltage changes between bridge arm nodes, it monitors the insulation resistance between the positive and negative poles of the high-voltage busbar and the housing, effectively assessing the insulation status of the system.

[0003] However, in practical applications, existing unbalanced bridge insulation detection circuits often suffer from inadequate isolation between the bridge arm circuit and the chassis ground when the detection process ends and the circuit enters a non-detection state. A weak leakage current path may exist between the high-voltage bus circuit and the chassis, leading to increased leakage current. In some cases, charge accumulation may even cause the chassis to become energized, threatening the personal safety of maintenance personnel and the stable operation of the equipment. Furthermore, existing unbalanced bridge detection schemes typically employ dual independent voltage detection circuits to sample the voltage divider nodes of the upper and lower bridge arms separately. This dual-path detection method not only requires a large number of electronic components, increasing circuit complexity and hardware costs, but also involves redundant algorithms for synchronous acquisition and processing of dual signals, which is detrimental to the miniaturization design and efficiency improvement of the system. Utility Model Content

[0004] In view of the above problems, this utility model embodiment provides a single-channel insulation detection circuit for an unbalanced bridge. The single-channel insulation detection circuit for the unbalanced bridge includes: a first voltage divider module, which is composed of a first voltage divider resistor network, and the first end of the first voltage divider module is connected to the positive terminal of the bus.

[0005] The second voltage divider module is composed of a second voltage divider resistor network and a detection voltage divider resistor connected in series. The first end of the second voltage divider module is connected to the second end of the first voltage divider module, and the second end of the second voltage divider module is connected to the negative terminal of the bus.

[0006] A housing disconnect switch is connected between the connection point between the second end of the first voltage divider module and the first end of the second voltage divider module and the housing ground.

[0007] The first disturbance branch includes a first switch and a first disturbance resistor network connected in series, and the first disturbance branch is connected in parallel with the first voltage divider module;

[0008] The second disturbance branch includes a second switch and a second disturbance resistor network connected in series, and the second disturbance branch is connected in parallel with the second voltage divider module;

[0009] A voltage detection unit, one end of which is connected to one end of the detection voltage divider resistor, and the other end of which is connected to a reference ground.

[0010] In one possible implementation, the total resistance of the first voltage divider network is equal to the total resistance of the second voltage divider network.

[0011] In one possible implementation, both the first voltage divider resistor network and the second voltage divider resistor network are composed of multiple equal-value resistors connected in series.

[0012] In one possible implementation, the resistance of the detection voltage divider resistor is 1 / 500 to 1 / 1000 of the resistance of a single resistor in the second voltage divider resistor network.

[0013] In one possible implementation, both the first perturbation resistor network and the second perturbation resistor network are composed of multiple equivalent resistors connected in series.

[0014] In one possible implementation, the total resistance of the first perturbation resistor network is equal to the total resistance of the first voltage divider resistor network.

[0015] In one possible implementation, the total resistance of the second perturbation resistor network is equal to the total resistance of the second voltage divider resistor network.

[0016] In one possible implementation, the voltage detection unit includes:

[0017] An operational amplifier follower circuit, wherein the input terminal of the operational amplifier follower circuit is connected to one end of the detection voltage divider resistor;

[0018] An ADC conversion chip, wherein the input terminal of the ADC conversion chip is connected to the output terminal of an operational amplifier follower circuit;

[0019] A microcontroller, the input of which is connected to the output of an ADC converter chip to receive the digital output signal of the ADC converter chip.

[0020] In one possible implementation, the first switch, the second switch, and the housing disconnect switch may include any one of a coil relay, a reed relay, a high-voltage MOSFET, or a solid-state relay.

[0021] The above-described one or more technical solutions in the embodiments of this application have at least one or more of the following technical effects:

[0022] This utility model provides a single-channel insulation detection circuit for an unbalanced bridge. By setting a chassis isolating switch between the connection point of the first and second voltage divider modules and the chassis ground, the chassis can be completely isolated from the high-voltage circuit in the non-detection state, completely cutting off the potential leakage current path and avoiding the risk of the chassis becoming charged due to charge accumulation. This greatly ensures the safety of maintenance personnel and the stability of equipment operation. At the same time, by utilizing the structure of the first and second disturbance branches connected in parallel with the corresponding voltage divider modules, combined with the single-channel detection design of the detection voltage divider resistor and voltage detection unit, only one detection circuit is needed to complete the synchronous monitoring of the voltage changes of the upper and lower bridge arms. Compared with the traditional dual-channel detection scheme, this greatly reduces the number of components such as resistors and sampling units, simplifies the hardware architecture, reduces circuit complexity and cost, and avoids the cumbersome process of synchronous acquisition and redundant calculation of dual-channel signals, effectively improving detection efficiency and system integration.

[0023] The above description is merely an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this utility model more obvious and understandable, specific embodiments of this utility model are given below. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the module composition structure of the single-channel insulation detection circuit of the unbalanced bridge in this embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of the circuit principle of the single-channel insulation detection circuit of the unbalanced bridge in the embodiment of this utility model.

[0027] Explanation of reference numerals in the attached figures: 100, First voltage divider module; 110, First voltage divider resistor network; 200, Second voltage divider module; 210, Second voltage divider resistor network; 220, Detection voltage divider resistor; 300, Housing isolation switch; 400, First disturbance branch; 410, First switch; 420, First disturbance resistor network; 500, Second disturbance branch; 510, Second switch; 520, Second disturbance resistor network; 600, Voltage detection unit; 610, Operational amplifier follower circuit; 620, ADC conversion chip; 630, Microcontroller. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0029] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this invention as detailed in the appended claims.

[0030] The overall concept of the technical solution provided by this utility model is as follows:

[0031] Please see Figure 1 The single-channel insulation detection circuit of the unbalanced bridge includes:

[0032] The first voltage divider module 100 is composed of a first voltage divider resistor network 110. The first end of the first voltage divider module 100 is connected to the positive terminal of the bus. The first voltage divider module 100 is the front-end voltage divider unit of the entire insulation detection circuit. Its core function is to proportionally attenuate the high voltage of the positive terminal of the high voltage bus to generate an intermediate voltage signal suitable for subsequent detection circuit processing. The first voltage divider module 100 is composed of a first voltage divider resistor network 110, which is essentially a combination of voltage divider resistors. It usually adopts a series or series-parallel hybrid structure. The specific design needs to be determined according to the actual requirements.

[0033] The second voltage divider module 200 is composed of a second voltage divider resistor network 210 and a detection voltage divider resistor 220 connected in series. The first terminal of the second voltage divider module 200 is connected to the second terminal of the first voltage divider module 100, and the second terminal is connected to the negative terminal of the bus. Similar to the first voltage divider module 100, the second voltage divider module 200 typically consists of multiple high-resistance resistors connected in series or in parallel. 0 is used in conjunction with the first voltage divider module 100 to form the upper and lower bridge arm voltage divider structure of the unbalanced bridge, distributing the voltage difference of the high-voltage bus to the intermediate node and the detection voltage divider resistor 220 proportionally; the second voltage divider resistor network 210 is connected in series with the detection voltage divider resistor 220 to form a "high voltage-low voltage" voltage divider chain. The second voltage divider resistor network 210 is responsible for further attenuating the output voltage of the first voltage divider module 100, while the detection voltage divider resistor 220 is responsible for adjusting the output of the second voltage divider resistor network 210 to a voltage that can be collected by the voltage detection unit 600.

[0034] The housing disconnect switch 300 is connected between the connection point between the second terminal of the first voltage divider module 100 and the first terminal of the second voltage divider module 200 and the housing ground. The housing disconnect switch 300 is a key component in the balanced bridge single-circuit insulation detection circuit to ensure personal safety and stable equipment operation. Its core function is to control the connection and disconnection between the intermediate node (the connection point between the second terminal of the first voltage divider module 100 and the first terminal of the second voltage divider module 200) and the housing ground to achieve leakage current isolation in non-detection state and normal voltage division in detection state.

[0035] The first disturbance branch 400 includes a first switch 410 and a first disturbance resistor network 420 connected in series. The first disturbance branch 400 is connected in parallel with the first voltage divider module 100. The core function of the first disturbance branch 400 is to change the equivalent resistance of the first voltage divider module 100 by switching the on / off state of the first switch 410, thereby adjusting the potential of the intermediate node and ultimately affecting the voltage collected by the voltage detection unit 600.

[0036] The second disturbance branch 500 includes a second switch 510 and a second disturbance resistor network 520 connected in series. The second disturbance branch 500 is connected in parallel with the second voltage divider module 200. The core function of the second disturbance branch 500 is to change the equivalent resistance of the second voltage divider module 200 by switching the on / off state of the second switch 510, thereby adjusting the potential of the intermediate node and ultimately affecting the voltage collected by the voltage detection unit 600.

[0037] The voltage detection unit 600 has one end connected to one end of the detection voltage divider resistor 220, and the other end connected to reference ground. The detection voltage divider resistor 220 is the signal source for the voltage detection unit 600. The voltage across the detection voltage divider resistor 220 directly reflects the insulation status of the high-voltage busbar to the casing. The voltage detection unit 600 collects the voltage across the detection voltage divider resistor 220 and converts it into a digital quantity, providing raw data for subsequent insulation resistance calculations.

[0038] By setting a chassis isolating switch 300 between the connection point of the first voltage divider module 100 and the second voltage divider module 200 and the chassis ground, the chassis can be completely isolated from the high-voltage circuit in the non-detection state, completely cutting off the potential leakage current path and avoiding the risk of the chassis becoming charged due to charge accumulation, which greatly ensures the safety of maintenance personnel and the stability of equipment operation. At the same time, by utilizing the structure of the first and second disturbance branches 500 connected in parallel with the corresponding voltage divider modules, combined with the single-channel detection design of the detection voltage divider resistor 220 and the voltage detection unit 600, only one detection circuit is needed to complete the synchronous monitoring of the voltage changes of the upper and lower bridge arms. Compared with the traditional dual-channel detection scheme, the number of resistors, sampling units and other components is greatly reduced, simplifying the hardware architecture, reducing circuit complexity and cost, and avoiding the cumbersome process of synchronous acquisition and redundant calculation of dual-channel signals, effectively improving detection efficiency and system integration.

[0039] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0040] Furthermore, the total resistance of the first voltage divider network 110 is equal to the total resistance of the second voltage divider network 210. When the total resistance of the first voltage divider network equals the total resistance of the second voltage divider network, the unbalanced bridge insulation detection circuit exhibits symmetrical voltage division characteristics. The voltages at the output terminals of the first voltage divider network 110 and the second voltage divider network 210 are each divided into half of the total bus voltage. This design simplifies the calculation logic of insulation resistance and achieves linear voltage control through the adjustment of the disturbance branch.

[0041] Furthermore, both the first voltage divider resistor network 110 and the second voltage divider resistor network 210 are composed of multiple equivalent resistors connected in series. When both the first voltage divider resistor network 110 and the second voltage divider resistor network 210 are composed of multiple equivalent resistors connected in series, the voltage division characteristics of the circuit will exhibit uniform voltage division characteristics and high stability.

[0042] Preferably, the resistance value of the detection voltage divider resistor 220 is 1 / 500 to 1 / 1000 of the resistance value of a single resistor in the second voltage divider resistor network 210. As a safety attenuator in the insulation detection circuit, the detection voltage divider resistor 220 achieves safe attenuation and precise voltage division of the high-voltage signal by having a resistance value that is 1 / 500 to 1 / 1000 of the resistance value of a single resistor in the second voltage divider resistor network 210, which is much smaller than the resistance value of a single resistor in the voltage divider network.

[0043] Furthermore, both the first perturbation resistor network 420 and the second perturbation resistor network 520 are composed of multiple equivalent resistors connected in series.

[0044] Furthermore, the total resistance of the first disturbance resistor network 420 is equal to the total resistance of the first voltage divider resistor network 110.

[0045] Furthermore, the total resistance of the second disturbance resistor network 520 is equal to the total resistance of the second voltage divider resistor network 210.

[0046] Furthermore, the voltage detection unit 600 includes:

[0047] The op-amp follower circuit 610 has its input terminal connected to one end of the voltage divider resistor 220. The core function of the op-amp follower circuit 610 (voltage follower) is to isolate the front-end circuit from the back-end ADC converter chip 620, while providing high input impedance and stable voltage output.

[0048] The input terminal of the ADC converter chip 620 is connected to the output terminal of the op-amp follower circuit 610. The core function of the ADC converter chip 620 is to convert the analog voltage signal output by the op-amp into a digital code that can be recognized by the microcontroller 630.

[0049] Microcontroller 630 has its input connected to the output of ADC converter chip 620 to receive the digital output signal from ADC converter chip 620. Microcontroller 630 receives the digital signal from ADC converter chip 620, performs algorithm calculations (such as insulation resistance inverse calculation), and outputs the detection result.

[0050] Furthermore, the first switch 410, the second switch 510, and the housing disconnect switch 300 can include any one of a coil relay, a reed relay, a high-voltage MOSFET, or a solid-state relay. The selection of the first and second switches 510 and the housing disconnect switch 300 requires comprehensive consideration of electrical withstand voltage, voltage division accuracy, response speed, isolation requirements, cost, and size. Coil relays are suitable for high-voltage, high-current, low-frequency applications, but they are larger, have a shorter lifespan, and may experience contact sticking issues. Reed relays are suitable for high-frequency, low-current applications, have a longer lifespan, are less prone to contact sticking issues, but are also larger and more expensive. High-voltage MOSFETs are cheaper and smaller, but have poorer insulation performance, making them suitable for low-cost, small-size, high-frequency applications. Solid-state relays are cheaper and smaller. In practical applications, a trade-off must be made based on specific requirements. Solid-state relays are preferred for applications with lower electrical clearance requirements, while reed relays are preferred for applications with higher requirements.

[0051] Please see Figure 2 In one exemplary embodiment, the first voltage divider resistor network 110 is composed of multiple resistors R166-R170 of equal resistance connected in series, and its equivalent resistance is R1; the second voltage divider resistor network 210 is composed of multiple resistors R173-R177 of equal resistance connected in series, and its equivalent resistance is R2; the detection voltage divider resistor 220 is composed of a single resistor R178, and its equivalent resistance is R3; it is required that when the bus voltage is at the design maximum value, the current flowing through R1, R2, and R3 is less than 1mA.

[0052] The first disturbance branch 400 consists of a first switch 410SW1 and a first disturbance resistor network 420. The first disturbance resistor network 420 is composed of multiple resistors R189-R192 with equal resistance values ​​connected in series. Its equivalent resistance is R4, and the resistance value of R4 is the same as that of R1. The first switch 410SW1 controls whether R4 is connected in parallel with the first voltage divider module 100.

[0053] The first disturbance branch 400 consists of a second switch 510SW2 and a second disturbance resistor network 520. The second disturbance resistor network 520 is composed of multiple resistors R193-R197 with equal resistance values ​​connected in series. Its equivalent resistance is R5, and the resistance value of R5 is the same as that of R2. The second switch 510SW2 controls whether R5 is connected in parallel with the first voltage divider module 100.

[0054] The housing disconnect switch 300 consists of a disconnect switch SW3, which is used to disconnect the high-voltage side from the housing during the stop detection process.

[0055] The op-amp follower circuit 610 in the voltage detection unit 600 includes op-amp U40, which differentially amplifies the voltage across resistor R178 and then outputs it to ADC conversion chip 620.

[0056] Furthermore, the insulation impedance testing process includes the following steps:

[0057] First, disconnect the first switch SW1, the second switch SW2, and the isolating switch SW3. At this time, the voltage detection unit 600 collects the voltage V0 as follows:

[0058]

[0059] Therefore, Vbus can be obtained as:

[0060]

[0061] Then, first close the isolating switch SW3, then close the first switch SW1, keeping the second switch SW2 open. At this time, the voltage detection unit 600 collects the voltage V1 as follows:

[0062]

[0063] Where Vbus is the total DC bus voltage, Rx is the equivalent resistance to be measured between the positive bus and the chassis, and Ry is the equivalent resistance to be measured between the negative bus and the chassis.

[0064] Next, disconnect the first switch SW1, close the second switch SW2, and keep the isolating switch SW3 closed. At this time, the voltage V2 collected by the voltage detection unit 600 is:

[0065]

[0066] Finally, disconnect the first switch SW1, the second switch SW2, and the disconnecting switch SW3. Then, calculate the specific values ​​of Rx and Ry by solving the system of equations V1 and V2 simultaneously.

[0067] The formula for calculating Rx is as follows:

[0068]

[0069] The formula for calculating Ry is as follows:

[0070]

[0071] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0072] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this utility model without departing from the spirit and scope of the embodiments of this utility model. Therefore, if these modifications and variations to the embodiments of this utility model fall within the scope of the claims of this utility model and their equivalents, then this utility model also intends to include these modifications and variations.

Claims

1. A single-channel insulation detection circuit for an unbalanced bridge, characterized in that, include: The first voltage divider module is composed of a first voltage divider resistor network, and the first end of the first voltage divider module is connected to the positive terminal of the bus. The second voltage divider module is composed of a second voltage divider resistor network and a detection voltage divider resistor connected in series. The first end of the second voltage divider module is connected to the second end of the first voltage divider module, and the second end of the second voltage divider module is connected to the negative terminal of the bus. A housing disconnect switch is connected between the connection point between the second end of the first voltage divider module and the first end of the second voltage divider module and the housing ground. The first disturbance branch includes a first switch and a first disturbance resistor network connected in series, and the first disturbance branch is connected in parallel with the first voltage divider module; The second disturbance branch includes a second switch and a second disturbance resistor network connected in series, and the second disturbance branch is connected in parallel with the second voltage divider module; A voltage detection unit, one end of which is connected to one end of the detection voltage divider resistor, and the other end of which is connected to a reference ground.

2. The single-channel insulation detection circuit for an unbalanced bridge according to claim 1, characterized in that, The total resistance of the first voltage divider resistor network is equal to the total resistance of the second voltage divider resistor network.

3. The single-channel insulation detection circuit for an unbalanced bridge according to claim 1, characterized in that, Both the first voltage divider resistor network and the second voltage divider resistor network are composed of multiple resistors of equal value connected in series.

4. The single-channel insulation detection circuit for an unbalanced bridge according to claim 3, characterized in that, The resistance value of the detection voltage divider resistor is 1 / 500 to 1 / 1000 of the resistance value of a single resistor in the second voltage divider resistor network.

5. A single-channel insulation detection circuit for an unbalanced bridge according to claim 1, characterized in that, Both the first perturbation resistor network and the second perturbation resistor network are composed of multiple equivalent resistors connected in series.

6. The single-channel insulation detection circuit for an unbalanced bridge according to claim 1, characterized in that, The total resistance of the first disturbance resistor network is equal to the total resistance of the first voltage divider resistor network.

7. The single-channel insulation detection circuit for an unbalanced bridge according to claim 1, characterized in that, The total resistance of the second disturbance resistor network is equal to the total resistance of the second voltage divider resistor network.

8. The single-channel insulation detection circuit for an unbalanced bridge according to claim 1, characterized in that, The voltage detection unit includes: An operational amplifier follower circuit, wherein the input terminal of the operational amplifier follower circuit is connected to one end of the detection voltage divider resistor; An ADC conversion chip, wherein the input terminal of the ADC conversion chip is connected to the output terminal of an operational amplifier follower circuit; A microcontroller, the input of which is connected to the output of an ADC converter chip to receive the digital output signal of the ADC converter chip.

9. A single-channel insulation detection circuit for an unbalanced bridge according to claim 1, characterized in that, The first switch, the second switch, and the housing disconnect switch may include any one of a coil relay, a reed relay, a high-voltage MOSFET, or a solid-state relay.

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