Insulation resistance detection circuit and detection device

Abstract

The utility model belongs to the field of integrated circuits, and discloses an insulation resistance detection circuit and a detection device, which comprise a first current-limiting resistor R1, a second current-limiting resistor R2, a first switch SP, a second switch SN, a divider resistor Rin, an isolation operational amplifier U1, a first analog-to-digital converter ADC1, an isolation communication device, a digital-to-analog converter DAC and a second analog-to-digital converter ADC2. A first current-limiting resistor R1 and a second current-limiting resistor R2 are arranged for current limiting, a divider resistor Rin is arranged as a voltage detection resistor, and input voltage which is scaled down is provided for an isolation operational amplifier U1. The collected voltage of the divider resistor is converted into a digital signal through the first analog-to-digital converter ADC1, the digital signal is transmitted to the digital-to-analog converter DAC through the isolation communication device in an isolation communication mode, then the digital signal is restored into an analog signal through the digital-to-analog converter DAC, and finally the analog signal is converted into the digital signal through the second analog-to-digital converter ADC2. And the detection of the insulation resistance is realized.

Description

Technical Field

[0001] The utility model belongs to the field of integrated circuits and relates to an insulation resistance detection circuit and a detection device. Background Art

[0002] In recent years, with the rapid market adoption of electric vehicles and the popularization of new energy designs, designers have increasingly demanded safe energy transmission. Currently, electric vehicles use high-voltage (HV) batteries around 400V for energy storage, with a strong trend toward higher voltage batteries to shorten charging times. DC fast chargers bypass the onboard battery charger to power the battery management system in electric vehicles. This means that the current in the HV DC line flows directly from the EV supply equipment to the vehicle. In solar string inverters, the HV DC line from the photovoltaic string panels can reach voltages of up to 1kV. Providing stable and efficient user protection mechanisms is crucial in this type of power distribution system.

[0003] To ensure system safety in high-voltage environments, all battery components are isolated from ground (GND) via high-resistance insulation resistors. This insulation limits the maximum leakage current, preventing personal injury from touching the system during normal operation. However, there is currently a lack of methods to detect the effectiveness of insulation resistance, making it impossible to promptly detect insufficient insulation resistance, which can lead to safety risks. Utility Model Content

[0004] The purpose of the utility model is to overcome the shortcomings of the prior art and provide an insulation resistance detection circuit and a detection device.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides an insulation resistance detection circuit, including a first current limiting resistor R1, a second current limiting resistor R2, a first switch SP, a second switch SN, a voltage divider resistor Rin, an isolation operational amplifier U1, a first analog-to-digital converter ADC1, an isolation communication device, a digital-to-analog converter DAC, and a second analog-to-digital converter ADC2; one end of the first current limiting resistor R1 is used to connect to the power supply end of the positive side insulation resistor RP, and the other end is connected to one end of the first switch SP; one end of the second current limiting resistor R2 is used to connect to the power supply end of the negative side insulation resistor RN, and the other end is connected to one end of the second switch SN; the other end of the first switch SP is connected to the other end of the second switch SN; the positive input end of the isolation operational amplifier U1 is connected to one end of the voltage divider resistor Rin and the connecting line between the first switch SP and the second switch SN, the negative input end is grounded, and the output end is connected to the first analog-to-digital converter ADC1, the isolation communication device, the digital-to-analog converter DAC, and the second analog-to-digital converter ADC2 in sequence.

[0007] Optionally, the first current limiting resistor R1 and the second current limiting resistor R2 are megohm resistors.

[0008] Optionally, the voltage-dividing resistor Rin is a kilo-ohm resistor.

[0009] Optionally, it also includes a power supply; the power supply is connected to the first analog-to-digital converter ADC1.

[0010] Optionally, the first analog-to-digital converter ADC1 and the second analog-to-digital converter ADC2 are analog-to-digital converters of model AS7606.

[0011] Optionally, the isolation operational amplifier U1 adopts an isolation operational amplifier of model SMC1301.

[0012] Optionally, both the first switch SP and the second switch SN are solid-state relays or bipolar transistors.

[0013] Optionally, the isolated communication device uses an isolation chip model NSI1312D-Q1.

[0014] Optionally, the first analog-to-digital converter ADC1 and the second analog-to-digital converter ADC2 are analog-to-digital converters of the same model.

[0015] In a second aspect, the present invention provides an insulation resistance detection device, wherein the insulation resistance detection circuit mentioned above is encapsulated inside the insulation resistance detection device.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention's insulation resistance detection circuit provides current limiting by providing a first current-limiting resistor R1 and a second current-limiting resistor R2, and a voltage-dividing resistor Rin as a voltage detection resistor to provide a proportionally scaled input voltage for an isolation operational amplifier U1. The collected voltage across the voltage-dividing resistor is then converted into a digital signal by a first analog-to-digital converter ADC1 and transmitted to a digital-to-analog converter DAC via an isolation communication device. The digital signal is then restored to an analog signal by the digital-to-analog converter DAC, and finally, the analog signal is converted to a digital signal by a second analog-to-digital converter ADC2, thereby detecting the insulation resistance. During measurement, the two resistance branches cannot be connected simultaneously. The current Iiso on the isolation barrier is proportional to the bus voltage, the isolation resistance, and the connected resistance branch. Therefore, the above-described configuration allows detection of the insulation resistance. Under normal circumstances, the insulation resistance RP between DC+ and ground, and the insulation resistance RN between DC- and ground are both in the megohm range. Therefore, the current on the isolation barrier will be very small, and thus the op amp will have a very small input signal. If the isolation barrier performance degrades, the current on the isolation barrier will increase, thereby causing the op amp input signal to increase. Therefore, the digital signal of the second analog-to-digital converter ADC2 can be used to effectively monitor the insulation resistance status. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a state topology diagram of the insulation resistance detection circuit of the utility model. DETAILED DESCRIPTION

[0019] In order to help those skilled in the art better understand the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0021] The present invention is described in further detail below with reference to the accompanying drawings:

[0022] See also Figure 1 In one embodiment of the present invention, an insulation resistance detection circuit is provided, including a first current limiting resistor R1, a second current limiting resistor R2, a first switch SP, a second switch SN, a voltage divider resistor Rin, an isolation operational amplifier U1, a first analog-to-digital converter ADC1, an isolation communication device, a digital-to-analog converter DAC, and a second analog-to-digital converter ADC2; one end of the first current limiting resistor R1 is used to connect to the power supply end of the positive side insulation resistor RP, and the other end is connected to one end of the first switch SP; one end of the second current limiting resistor R2 is used to connect to the power supply end of the negative side insulation resistor RN, and the other end is connected to one end of the second switch SN; the other end of the first switch SP is connected to the other end of the second switch SN; the positive input end of the isolation operational amplifier U1 is connected to one end of the voltage divider resistor Rin and the connecting line between the first switch SP and the second switch SN, the negative input end is grounded, and the output end is connected to the first analog-to-digital converter ADC1, the isolation communication device, the digital-to-analog converter DAC, and the second analog-to-digital converter ADC2 in sequence.

[0023] The present invention's insulation resistance detection circuit provides current limiting by providing a first current-limiting resistor R1 and a second current-limiting resistor R2, and a voltage-dividing resistor Rin as a voltage detection resistor to provide a proportionally scaled input voltage for an isolation operational amplifier U1. The collected voltage across the voltage-dividing resistor is then converted into a digital signal by a first analog-to-digital converter ADC1 and transmitted to a digital-to-analog converter DAC via an isolation communication device. The digital signal is then restored to an analog signal by the digital-to-analog converter DAC, and finally, the analog signal is converted to a digital signal by a second analog-to-digital converter ADC2, thereby detecting the insulation resistance. During measurement, the two resistance branches cannot be connected simultaneously. The current Iiso on the isolation barrier is proportional to the bus voltage, the isolation resistance, and the connected resistance branch. Therefore, the above-described configuration allows detection of the insulation resistance. Under normal circumstances, the insulation resistance RP between DC+ and ground, and the insulation resistance RN between DC- and ground, are both in the megohm range. Therefore, the current across the isolation barrier is very small, resulting in a small input signal to the op amp. If the isolation barrier performance degrades, the current across the isolation barrier increases, causing the op amp input signal to increase. Therefore, the digital signal from the second analog-to-digital converter ADC2 can effectively monitor the insulation resistance status. This design can adjust the voltage up to 1000V by modifying the resistor network of the connected resistor branch.

[0024] In a possible implementation, the first current limiting resistor R1 and the second current limiting resistor R2 are megohm resistors.

[0025] Specifically, megohm resistors, as current-limiting resistors, significantly limit the current flowing through a circuit due to their high resistance, thereby protecting the insulation resistance from excessive current. This is particularly important for monitoring insulation resistance over extended periods of time, ensuring the stability and safety of the circuit during long-term operation. Furthermore, megohm resistors can effectively reduce power consumption within the circuit, improving overall energy efficiency.

[0026] In a possible implementation, the voltage-dividing resistor Rin is a kilo-ohm resistor.

[0027] Specifically, the kilo-ohm resistors used as voltage dividers have a moderate resistance value, scaling down the input voltage to a range suitable for the isolated op amp U1. This not only improves measurement accuracy but also prevents excessive input voltages from saturating or damaging the op amp. Furthermore, the kilo-ohm resistors provide a certain current limiting effect, protecting the circuit from abnormal conditions such as short circuits.

[0028] In a possible implementation, a power supply is further included; the power supply is connected to the first analog-to-digital converter ADC1.

[0029] Specifically, by providing an independent power supply, electrical influences on the front-end circuit can be avoided.

[0030] In a possible implementation manner, the first analog-to-digital converter ADC1 and the second analog-to-digital converter ADC2 are analog-to-digital converters of model AS7606.

[0031] Specifically, the AS7606 analog-to-digital converter features high precision, high resolution, low power consumption, and high-speed conversion. Its high precision and high resolution ensure accurate conversion of analog signals into digital signals, thereby improving the accuracy of insulation resistance testing. Furthermore, its low power consumption and high-speed conversion characteristics help reduce overall circuit power consumption and improve system response speed.

[0032] In a possible implementation manner, the isolation operational amplifier U1 is an isolation operational amplifier of model SMC1301.

[0033] Specifically, the SMC1301 isolated op amp offers advantages such as high-performance isolation, low noise, wide bandwidth, and low power consumption. Its high-performance isolation effectively isolates input and output signals, preventing interference and crosstalk between circuits, thereby improving measurement stability and accuracy. Its low noise and wide bandwidth help reduce signal distortion and noise interference, improving the signal-to-noise ratio. Its low power consumption helps reduce overall circuit power consumption, extending system life.

[0034] In a possible implementation manner, both the first switch SP and the second switch SN are solid-state relays or bipolar transistors.

[0035] Specifically, solid-state relays or bipolar transistors, as switching elements, offer advantages such as fast response, high reliability, long life, compact size, and light weight. Their rapid response ensures that circuits can be quickly connected or disconnected when needed, thereby improving system responsiveness and flexibility. Their high reliability and long life help ensure the stability and reliability of circuits over extended periods of operation. Furthermore, their small size and light weight facilitate integration and installation.

[0036] In a possible implementation, the isolated communication device uses an NSI1312D-Q1 isolation chip.

[0037] Specifically, using appropriate isolation communication devices can achieve isolated transmission of digital signals, preventing signals from being interfered with and damaged during transmission. This not only improves signal integrity and accuracy, but also ensures the independence and security of circuits.

[0038] In a possible implementation manner, the first analog-to-digital converter ADC1 and the second analog-to-digital converter ADC2 are analog-to-digital converters of the same model.

[0039] Specifically, using the same model of ADC ensures that both converters have identical performance and characteristics, simplifying circuit design and debugging. This not only reduces design and production costs but also improves system maintainability and scalability. Furthermore, using the same model of ADC ensures compatibility and consistency between the two converters, thereby improving measurement accuracy and reliability.

[0040] The working process and principle of this utility model are as follows:

[0041] The calculation formulas for the positive side isolation voltage and the negative side isolation voltage are deduced as follows:

[0042] 1. Positive side isolation voltage VP. Open the second switch SN and close the first switch SP. Based on Iiso × RN − VDC + VP = 0, we can deduce Vp = VDC − Iiso × RN; where Iiso is the current in the isolation barrier. Substituting the isolation barrier leakage current calculation formula Iiso = VP / (RP || (R1 + Rin)) into the equation, we can deduce , and then it can be deduced that Vp=Vinp*(R1+Rin) / Rin; where Vinp is the collected positive terminal voltage; the voltage of Rin when the first switch SP is closed is collected by the first analog-to-digital converter ADC1, and is communicated and converted through the isolation communication device, the digital-to-analog converter DAC, and the second analog-to-digital converter ADC2.

[0043] 2. Negative isolation voltage VN. Open the first switch SP and close the second switch SN. Based on Iiso×RP+VDC+VN=0, we can deduce VN=-VDC−Iiso×RP. Substituting the isolation barrier leakage current formula Iiso=VN / (RN||(R2+Rin)) into the equation, we can deduce , it can be deduced that VN=VinN*(R2+Rin) / Rin, where VinN is the collected negative terminal voltage. The voltage of Rin when the second switch SN is closed is collected by the first analog-to-digital converter ADC1, and is communicated and converted through the isolation communication device, the digital-to-analog converter DAC, and the second analog-to-digital converter ADC2.

[0044] The formulas for the positive side insulation resistance RP and the negative side insulation resistance RN can be derived from the positive side isolation voltage VP and the negative side isolation voltage VN: Positive side insulation resistance RP = (-(Rin + R1) * (VDC + VN - VP)) / VN, where VDC is the total insulation voltage; Negative side insulation resistance RN = ((Rin + R2) * (VDC + VN - VP)) / VP.

[0045] In another embodiment of the present invention, an insulation resistance detection device is provided, wherein the insulation resistance detection circuit is encapsulated therein.

[0046] Provided is an efficient and stable insulation resistance detection device for detecting the state of insulation resistance under high voltage transmission state, thereby providing protection for users.

[0047] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An insulation resistance detection circuit, characterized in that: It includes a first current limiting resistor R1, a second current limiting resistor R2, a first switch SP, a second switch SN, a voltage divider resistor Rin, an isolation operational amplifier U1, a first analog-to-digital converter ADC1, an isolation communication device, a digital-to-analog converter DAC, and a second analog-to-digital converter ADC2; One end of the first current-limiting resistor R1 is used to connect to the power supply terminal of the positive side insulation resistor RP, and the other end is connected to one end of the first switch SP; one end of the second current-limiting resistor R2 is used to connect to the power supply terminal of the negative side insulation resistor RN, and the other end is connected to one end of the second switch SN; the other end of the first switch SP is connected to the other end of the second switch SN; The positive input terminal of the isolation operational amplifier U1 is connected to one end of the voltage divider resistor Rin and the connection line between the first switch SP and the second switch SN, the negative input terminal is grounded, and the output terminal is connected to the first analog-to-digital converter ADC1, the isolation communication device, the digital-to-analog converter DAC and the second analog-to-digital converter ADC2 in sequence.

2. The insulation resistance detection circuit according to claim 1, wherein: The first current limiting resistor R1 and the second current limiting resistor R2 are megohm-level resistors.

3. The insulation resistance detection circuit according to claim 1, wherein: The voltage dividing resistor Rin is a kilo-ohm resistor.

4. The insulation resistance detection circuit according to claim 1, wherein: It also includes a power supply; the power supply is connected to the first analog-to-digital converter ADC1.

5. The insulation resistance detection circuit according to claim 1, wherein: The first analog-to-digital converter ADC1 and the second analog-to-digital converter ADC2 are analog-to-digital converters of model AS7606.

6. The insulation resistance detection circuit according to claim 1, wherein: The isolation operational amplifier U1 is an isolation operational amplifier of model SMC1301.

7. The insulation resistance detection circuit according to claim 1, wherein: The first switch SP and the second switch SN are both solid-state relays or bipolar transistors.

8. The insulation resistance detection circuit according to claim 1, wherein: The isolated communication device uses an isolation chip model NSI1312D-Q1.

9. The insulation resistance detection circuit according to claim 1, wherein: The first analog-to-digital converter ADC1 and the second analog-to-digital converter ADC2 are analog-to-digital converters of the same model.

10. An insulation resistance detection device, characterized in that: The insulation resistance detection device encapsulates the insulation resistance detection circuit according to any one of claims 1 to 9.

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