Electronic circuit for monitoring state of voltage-dependent resistive component

Abstract

The invention relates to an electronic circuit for monitoring the state of a voltage-dependent resistive component by means of a current sink, in which a change in the state of the voltage VN of the voltage-dependent resistive component is monitored, comprising: one or more voltage-dependent resistive components; one or more voltage sources, wherein at least one first voltage source has a known voltage; one or more operational amplifiers, wherein the one or more operational amplifiers are connected with the transistor; one or more supply voltages, wherein at least one first supply voltage feeds the operational amplifier; one or more sensors for measuring a voltage difference between the voltage VN and a second voltage; one or more resistors wherein the drain resistor limits the current to a maximum value when the voltage-related resistive component is in a short-circuit state; one or more current conductors, wherein the current conductor comprises an adjustable current IMOV; one or more transistors; one or more ground lines; and one or more analog-to-digital converters.

Description

Technical Field

[0001] The invention relates to an electronic circuit for monitoring the condition of a voltage-dependent resistor component, wherein the electronic circuit is designed with a precise current sink. The invention also relates to a method for monitoring the condition of a voltage-dependent resistor component. Background Art

[0002] Voltage-dependent resistor components such as varistors are used as overvoltage protection in various applications. They age due to external influences, in particular after being exposed to high-energy pulses. The threshold voltage and therefore the leakage current can change due to the exposure to high-energy pulses, the continuous application of excessive voltages, temperature, humidity and vibrations. In order to measure the threshold voltage on a voltage-dependent resistor component, a certain level of current is applied during the manufacturing process. This allows statements to be made about the threshold voltage of the voltage-dependent resistor component.

[0003] US10714241 B2 relates to an overvoltage protection device, comprising: a metal oxide varistor (MOV) having a first surface and a second surface; a semiconductor substrate having a first outer surface and a second outer surface, and having a semiconductor arc extinguishing device, the semiconductor arc extinguishing device comprising a plurality of semiconductor layers arranged in electrical series with each other, wherein the semiconductor substrate is arranged on a first side of the metal oxide varistor; a conductive region arranged between the second surface of the MOV and the first outer surface of the semiconductor substrate; a first electrical contact arranged on the first surface of the MOV; and a second electrical contact arranged on the second outer surface of the semiconductor substrate.

[0004] US10746808 B2 relates to a device for identifying a leakage current, which uses a center point grounding method, wherein an identification current flowing in a resistor and the sensitivity to the identification current are kept low. Summary of the invention

[0005] According to the present invention, an electronic circuit is provided for monitoring the state of a voltage-dependent resistor component, such as a varistor, via a precise current sink, wherein a state change of a voltage V_N of the resistor component is monitored, the electronic circuit comprising:

[0006] a) one or more voltage-dependent resistive components,

[0007] b) one or more voltage sources, wherein at least one first voltage source has a known voltage,

[0008] c) one or more operational amplifiers, wherein the one or more operational amplifiers are connected to the transistors,

[0009] d) one or more supply voltages, at least one first supply voltage feeding the operational amplifier,

[0010] e) one or more sensors for measuring a voltage difference between the first voltage and the voltage V_Lim,

[0011] f) one or more resistors, wherein a first resistor limits the current to a maximum value when the voltage-dependent resistance element is in a short-circuit state,

[0012] g) one or more current conductors, wherein a first current conductor comprises an adjustable current I_MOV,

[0013] h) one or more transistors,

[0014] i) one or more ground wires and

[0015] j) One or more analog-to-digital converters.

[0016] A precise current sink is an electronic circuit for state monitoring of voltage-dependent resistive components such as varistors, which has a dedicated electronic circuit for monitoring current and for detecting information about system status and / or function. A precise current sink also includes the ability to analyze current and identify deviations from a target value or a determined threshold voltage. A precise current sink for state monitoring can, for example, determine whether the current is within a specific range or a specific threshold, whether there is a current peak or sag, or whether the current has a specific behavior pattern and / or fluctuation. In order to evaluate the system status, a precise current sink can also detect information about resistance, voltage or other electrical parameters.

[0017] The voltage-dependent resistor component according to the invention comprises an electronic component, such as a varistor, which absorbs the voltage peaks that occur and protects sensitive electronic components, such as household appliances, inverters or fuel cells, from overvoltage. Varistors are, for example, ceramic or metal oxide semiconductor materials that usually have nonlinear resistance properties. This makes the resistance of the varistor largely dependent on the applied voltage. At low voltages, the varistor behaves like a high-resistance insulator. When a certain threshold voltage, which is related to the breakdown voltage or the varistor voltage, is exceeded, the component resistance changes suddenly and becomes conductive.

[0018] The voltage difference according to the features corresponds to a value obtained by calculating the voltage V_N by subtracting a previously calculated voltage V_Lim from the voltage of a first voltage source, for example a battery, the voltage of which is known.

[0019] The voltage V_N is, for example, a threshold voltage in the sense of the solution according to the invention, a specific voltage at which a specific behavior or a specific response occurs in an electrical component or system. It indicates the threshold value above which the behavior or characteristics of the component change. For example, voltage-dependent resistor components such as varistors are electronic components that are primarily used to stabilize voltages and to protect electronic devices from overvoltages.

[0020] The maximum value according to the invention corresponds to a known voltage value of a first voltage source, wherein the voltage source is, for example, a battery.

[0021] A transistor in the sense of the solution proposed according to the invention is an electronic component that amplifies or switches electrical signals. The transistor can be, for example, a metal oxide semiconductor field effect transistor (MOSFET). MOSFET is a special type of transistor based on the field effect principle. For a MOSFET, the current between the drain and source terminals is controlled by changing the voltage of the gate electrode. Applying a positive voltage at the gate terminal generates an electric field in the semiconductor material that influences the movement of charge carriers.

[0022] In another advantageous embodiment of the electronic circuit according to the present invention, the electronic circuit comprises at least two voltage-dependent resistance elements.

[0023] In an electronic circuit comprising a plurality of voltage-dependent resistor elements, the electronic circuit according to the invention makes it possible, for example, to monitor the state of individual components of the voltage-dependent resistor elements and thus save costs. By virtue of the transistor position dependency, for example, a current can be directed in a targeted manner through one of the voltage-dependent resistor elements and monitored. In this case, the transistor position and / or the number of transistors can vary depending on the number of voltage-dependent resistor elements.

[0024] In another advantageous embodiment of the electronic circuit proposed according to the invention, an analog-to-digital converter is included, which has a capacitor C2 connected in parallel with the analog-to-digital converter and optionally a diode connected in series.

[0025] By the additional use proposed according to the invention of a capacitor C2 connected in parallel with the analog-to-digital converter and optionally a diode connected in series, the voltage V_Lim is measured, wherein the voltage V_Lim is measured via a transistor and / or a measuring resistor (source resistor).

[0026] In another advantageous embodiment of the electronic circuit according to the present invention, the at least one resistor element connected to the operational amplifier comprises a filtering function and / or a current limiting function.

[0027] According to a further advantageous embodiment of the electronic circuit proposed according to the invention, the at least one capacitor C_filter connected to the operational amplifier comprises a filter function.

[0028] In a further advantageous embodiment of the electronic circuit proposed according to the invention, a fault in at least one voltage-dependent resistance element is determined if the voltage difference exceeds or falls below a predefined threshold value.

[0029] The predefined threshold value of the electronic circuit according to the invention refers to a determined value or tolerance range used as a reference point or tolerance value, for example to determine a decision or a state. According to the invention, the predefined threshold value comprises a specific voltage value tolerance within which the voltage-dependent resistor component is considered to be functioning normally.

[0030] By means of the electronic circuit implemented according to the invention for condition monitoring of one or more voltage-dependent resistor components, it is possible, for example, to diagnose whether the voltage-dependent resistor component is faulty or aging when a predetermined threshold value is exceeded or fallen below, thereby enabling corresponding measures to be taken to maintain or replace the faulty voltage-dependent resistor component. Thus, for example, the voltage-dependent resistor component can be replaced before it is thermally damaged or is no longer energetically capable of absorbing energy pulses.

[0031] According to the present invention, a method for controlling an electronic circuit is provided, wherein the electronic circuit performs a state monitoring of one or more voltage-dependent resistor components, wherein the following steps are performed:

[0032] I. Providing an electronic circuit according to the present invention,

[0033] II. Providing a current I_MOV, wherein the current I_MOV can be adjusted,

[0034] III. Calculate or measure the voltage V_Lim,

[0035] IV. Calculate the voltage V_N, and

[0036] V. Determine the state of the voltage-dependent resistor component.

[0037] The current I_MOV is provided by regulation, wherein the regulation is calculated from the quotient of a freely selectable reference voltage and a freely selectable measuring resistor. For example, precise regulation can be performed depending on the tolerance values ​​of the reference voltage and the measuring resistor, wherein the smaller the tolerance of the two values, the more precise the regulation. Typically, a current I_MOV corresponding to 1 mA is provided.

[0038] The voltage V_Lim can be calculated according to the following formula:

[0039] Voltage VLim =I MOV (Measurement resistance + drain resistance + RDS)

[0040] Here, the drain resistance (channel resistance) RDS is calculated, for example, by means of the gate voltage read back from the MOSFET model via an analog-to-digital converter. The calculation of the channel resistance (or model) has certain errors, which are related to temperature, aging and components, for example. The calculation of the voltage V_N includes a difference result, where the minuend includes the voltage of the first voltage source, such as a battery, and the subtrahend includes the previously calculated or measured voltage V_Lim.

[0041] According to the final step proposed by the method according to the invention, the state of the voltage-dependent resistor element is determined, wherein, for example, a short circuit of the voltage-dependent resistor element is detected when the calculated voltage V_N is 0 V. In the event of a complete interruption of the current, when the calculated voltage V_Lim is 0 V, the voltage-dependent resistor element is classified as defective.

[0042] In an advantageous development of the method according to the invention, the voltage-dependent resistor element is state-monitored in an operating state and / or once in an initial phase, wherein a series of measurements of the state of the voltage-dependent resistor element is generated and an initial error of the voltage-dependent resistor element is then calculated therefrom.

[0043] Thus, for example, deviations or sudden changes of the voltage V_N between the measured values ​​can be identified based on the generated measurement series. By generating a measurement series, for example a measurement series of the voltage V_N, it is additionally possible to visualize the measured voltage values ​​of the voltage V_N over a period of time in order to obtain an overview of deviations and sudden changes. Furthermore, the measurement series can be used to check, for example, time-related analyses during a change of the voltage V_N over time, wherein patterns and periodic changes are identified. Furthermore, further checks such as trend analysis, event analysis and correlation analysis can be performed based on the generated measurement series.

[0044] For example, during operation, condition monitoring can be performed by continuously determining the condition of the voltage-dependent resistance element, wherein, for example, a gradient determination of the aging of the voltage-dependent resistance element over time can be evaluated.

[0045] In an advantageous development of the method according to the invention, the current I_MOV can be set in such a way that the current I_MOV reaches a current range of 100 μA to 15 mA, preferably 700 μA to 1.3 mA, 1 mA being particularly preferred.

[0046] In an advantageous development of the method according to the invention, the voltage V_Lim can be measured at the external circuit or the analog-to-digital converter.

[0047] Advantages of the present invention:

[0048] According to the proposed solution, data detected by accurate current sink is used for status monitoring to detect and diagnose faults or improve system performance. This enables a quick response to abnormal or irregular phenomena in the voltage V_N, which can timely eliminate faults or optimize the system.

[0049] In the solution according to the invention, a voltage-dependent resistor component, such as a varistor, can be state-monitored.

[0050] In the solution proposed according to the present invention, the protection function can be ensured by monitoring the state of voltage-related resistance components such as varistors. In addition, the component function can be ensured, and the protection function can be ensured when voltage peaks occur.

[0051] In addition, early identification of malfunctions and / or failures allows problems to be eliminated before damage occurs to the components to be protected. By monitoring voltage-dependent resistor components and identifying problems in good time, they can be prevented from affecting other parts of the system. In this way, the service life of the entire system can be extended.

[0052] Regular monitoring of voltage-dependent resistor components and early identification of problems allow targeted maintenance or replacement of components. This prevents costly system failures and thus reduces operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The embodiments of the present invention are described in detail according to the accompanying drawings and the following description.

[0054] Figure 1 A schematic diagram of an electronic circuit for monitoring the state of a voltage-dependent resistor component is shown;

[0055] Figure 2 A schematic diagram of an electronic circuit for monitoring the state of a voltage-dependent resistance component is shown, the electronic circuit comprising a diode and a second capacitor;

[0056] Figure 3 A schematic diagram of a control method of an electronic circuit for monitoring the state of a voltage-dependent resistor component is shown. DETAILED DESCRIPTION

[0057] In the following description of embodiments of the present invention, identical or similar elements are denoted by the same reference numerals, wherein a repeated description of these elements is omitted in individual cases. The figures merely schematically illustrate the subject matter of the present invention.

[0058] Figure 1 The schematic diagram of an electronic circuit 100 for state monitoring of a voltage-dependent resistor element 102 is shown, the electronic circuit comprising a varistor, an operational amplifier 106, wherein the operational amplifier 106 is fed by a supply voltage 108, wherein the operational amplifier 106 has a non-inverting input 106.1, an inverting input 106.2, an output 106.3, a reference voltage 122 at the non-inverting input 106.1, three resistor elements 112, wherein the resistor element 112, a feedback resistor 112.1 is located between the inverting input 106.2 and the output 106.3 and is additionally connected in series with a capacitor C_filter 110.1, wherein a further resistor element 112 is connected as a load resistor 112.2 at the output 106.3 of the operational amplifier 106. In addition, Figure 1 The device comprises a voltage source 104, a first voltage source 104.1 connected in series with a varistor, wherein a first voltage 126 of the first voltage source 104.1 is known and / or calculable, and a current I_MOV 118 flows from the first voltage source 104.1 to the voltage-dependent resistor element 102. The first voltage source 104.1 can comprise a battery, for example.

[0059] Figure 1 A transistor 114 is also included, wherein the transistor 114 corresponds to Figure 1 MOSFET 114.1, wherein two wires 116.1 and 116.2 are brought together at gate interface 114.2, wherein one wire 116.1 of the wires is led out from output terminal 106.3 of operational amplifier 106 and the other wire 116.2 is led out from non-inverting input terminal 106.1 of operational amplifier 106. In addition, a source resistor 112.3 is connected in series at source interface 114.3, wherein a fourth wire 116.4 of non-inverting input terminal 106.1 of operational amplifier 106 is connected between source resistor 112.3 and MOSFET 114.1. In addition, according to Figure 1 , a drain resistor 112.4 is connected in series at the drain interface 114.4 of the MOSFET 114.1.

[0060] Operational amplifier 106 is used as control and regulating element, for example. Drain resistor 112.4 is connected in series with drain interface 114.4 of MOSFET 114.1. Current is thus limited and MOSFET 114.1 is therefore protected. The maximum output current of MOSFET 114.1 can be controlled by appropriately dimensioning the resistor. Source resistor 112.3 can be connected in series with source interface 114.3 of MOSFET 114.1, for example, so that the voltage drop on MOSFET 114.1 can be measured and used as the feedback path of operational amplifier 106. Operational amplifier 106 can monitor the output voltage of MOSFET 114.1 and make corresponding adjustments to maintain the desired current. For example, feedback resistor 112.1 and capacitor C_filter110.1 form a feedback loop from the output of operational amplifier 106 to gate interface 114.2 of MOSFET 114.1. With the help of this feedback loop, for example, the stability of the system can be ensured and undesired vibration or instability can be avoided.

[0061] also, Figure 1 The external circuit 100.2 includes an analog-to-digital converter 124, a switch 136 and two resistor elements 112. The external circuit 100.2 can be used to measure the voltage V_Lim 130, for example. Figure 1 An optional sensor 100 . 3 is included, which detects data, such as the temperature. The measured data are evaluated, for example, in a microcontroller, which can be part of an analog-to-digital converter 124 , for example.

[0062] Thus, for example, changes in voltage-dependent resistance elements 102 , such as varistors, can be detected by comparing threshold voltages during the service life and preventive measures can be taken.

[0063] Figure 2 The schematic diagram of an electronic circuit 200 for state monitoring of a voltage-dependent resistor element 102 is shown, the electronic circuit comprising a varistor, an operational amplifier 106, wherein the operational amplifier 106 is fed by a first supply voltage 108.1, wherein the operational amplifier 106 has a non-inverting input 106.1, an inverting input 106.2, an output 106.3, a reference voltage 122 at the non-inverting input 106.1, three resistor elements 112, wherein the resistor element 112, a feedback resistor 112.1 are located between the inverting input 106.2 and the output 106.3 and a capacitor C_filter 110.1 is additionally connected in series, wherein a further resistor element 112 is connected as a load resistor 112.2 at the output 106.3 of the operational amplifier 106. In addition, Figure 1The invention comprises a voltage source 104 , a first voltage source 104 . 1 connected in series with a varistor, wherein a first voltage 126 of the first voltage source 104 . 1 is known and / or calculable, wherein a current I_MOV 118 flows from the first voltage source 104 . 1 to the voltage-dependent resistor element 102 .

[0064] also, Figure 2 The transistor 114 is included, wherein the transistor 114 corresponds to Figure 2 MOSFET 114.1, wherein two wires 116.1 and 116.2 are brought together at gate interface 114.2, wherein wire 116.1 is led out from output terminal 106.3 of operational amplifier 106, and another second wire 116.2 is led out from non-inverting input terminal 106.1 of operational amplifier 106. In addition, resistance element 112 and source resistor 112.3 are connected in series at source interface 114.3, wherein wire 116.4 of non-inverting input terminal 106.1 of operational amplifier 106 is connected between source resistor 112.3 and MOSFET 114.1. In addition, according to Figure 2 , a drain resistor 112.4 is connected in series at the drain interface 114.4 of the MOSFET 114.1.

[0065] Figure 2 The external circuit 100.2 is also included, wherein the external circuit 100.2 includes an analog-to-digital converter 124, a switch 136, a capacitor 202, a diode 201 and two resistors 112. The capacitor 202 is connected in parallel with the resistor 112 and the analog-to-digital converter 124, wherein the diode 201 is connected in series with the resistor element 112. Figure 2 As shown, diode 201 can be optionally omitted, for example. External circuit 100 . 2 is used, for example, to measure voltage V_Lim 130 .

[0066] like Figure 2 As shown, the voltage V_Lim 130 can be measured when the switch 136 is closed, wherein the switch 136 must be opened before closing so that a constant current flows through the variable resistor, which discharges the capacitor 202 to a certain pressure level before the capacitor 202 is discharged. For example, the voltage V_Lim 130 can be extrapolated from the variation curve of the discharge voltage at the measuring resistor of the analog-to-digital converter 124. For example, a diode 201 can be used to prevent backflow. In addition, Figure 2 A sensor 100 . 3 is included, which detects data, such as the temperature. The measured data are evaluated, for example, in a microcontroller, which can be part of an analog-to-digital converter 124 , for example.

[0067] exist Figure 1 and Figure 2In the figure, protection circuits, such as a Zener diode for MOSFET 114.1, are omitted for better illustration.

[0068] like Figure 3 As shown, the embodiment of the method 300 according to the invention shown comprises, for example, the control of an electronic circuit 100, 200 for state monitoring of one or more voltage-dependent resistor components 102. A first step comprises providing 302 an electronic circuit 100, 200 according to the solution according to the invention. A second step comprises providing 304 a current I_MOV 118, wherein the current I_MOV can be regulated, for example. The regulation of the current I_MOV 118 can be realized, for example, by dividing the reference voltage 122 by the source resistance 112.3. A third step comprises determining 306 a voltage V_Lim 130, wherein the voltage V_Lim 130 can be either calculated and / or measured. In a fourth step of the method 300 according to the invention, the voltage V_N 128 is calculated. The calculation 308 of the voltage V_N 128 is realized, for example, by subtracting the battery voltage (first voltage 126) from the voltage V_Lim 130. In a final step, a fifth method step, the state of the voltage-dependent resistor component 102, for example the state of a varistor, is determined 310.

[0069] When determining 310 the state of the varistor, it can be determined, for example, whether the varistor is still functional, wherein a fault is determined when a threshold voltage is undershot or exceeded. This is, for example, the case where the threshold value V_N deviates from the data table value by more than + / -5% or 10%. In addition, a series of measurements can be generated. With the aid of the memory, deviations of 1% to 5% from the previous value can then lead to errors, since this initial error of the varistor is not taken into account. In addition, a fault of the varistor can be determined if the current is completely interrupted, wherein 0 volts are detected when calculating 306 the voltage V_Lim 130. If the voltage V_Lim 130 is equal to the first voltage source 104.1, the varistor is short-circuited.

[0070] The invention is not limited to the embodiments described herein and the aspects emphasized therein. On the contrary, numerous modifications are possible within the scope of the art within the scope indicated by the claims.

Claims

1. An electronic circuit (100) for monitoring the state of a voltage-dependent resistor component (102), such as a varistor, via a current sink, wherein: The electronic circuit monitors the state change of the voltage V_N (128) of the voltage-dependent resistor component (102), the electronic circuit comprising: a. one or more voltage-dependent resistor components (102), b. one or more voltage sources (104), wherein at least one first voltage source (104.1) has a known voltage, c. one or more operational amplifiers (106), wherein the one or more operational amplifiers are connected to the transistor (114), d. one or more supply voltages (108), wherein at least one first supply voltage (108.1) feeds the operational amplifier (106), e. one or more sensors (100.3) for measuring a voltage difference between the first voltage (126) and the voltage V_Lim (130), f. one or more resistor components (112), wherein when the voltage-dependent resistor component (102) is in a short-circuit state, the drain resistor (112.4) limits the current to a maximum value, g. one or more current conductors (116), wherein a first current conductor (116.1) comprises an adjustable current I_MOV (118), h. one or more transistors (114), i. One or more ground wires (134) and j. One or more analog-to-digital converters (124).

2. The electronic circuit (100) according to claim 1, wherein the electronic circuit (100) comprises at least two voltage-dependent resistance components (102).

3. The electronic circuit (100) according to any of the preceding claims, wherein the electronic circuit (100) comprises an analog-to-digital converter (124) having a capacitor (202) connected in parallel with the analog-to-digital converter (124) and a diode (201) optionally connected in series.

4. The electronic circuit (100) according to any one of the preceding claims, wherein At least one resistor element (112) connected to the operational amplifier (106) includes a filtering function and / or a current limiting function.

5. The electronic circuit (100) according to any one of the preceding claims, wherein At least one capacitor C_filter (110.1) connected to the operational amplifier (106) comprises a filtering function.

6. The electronic circuit (100) according to any one of the preceding claims, wherein: If the voltage difference exceeds or falls below a predefined threshold, it is determined that at least one voltage-dependent resistor element (102) is faulty.

7. A method (300) for controlling an electronic circuit (100), wherein: Electronic Circuits (100) Condition monitoring of one or more voltage-dependent resistor components (102) is performed according to claims 1 to 6, and the method comprises at least the following steps: I. Providing (302) an electronic circuit (100) according to any one of claims 1 to 7, II. providing (304) a current I_MOV (118), wherein the current I_MOV (118) is adjustable, III. Calculating (306) or measuring the voltage V_Lim (130), IV. Calculate (308) the voltage V_N (128) and V. Determining (310) the state of the voltage-dependent resistor element (102).

8. A method (300) for controlling an electronic circuit (100) according to claim 7, wherein the state of the voltage-dependent resistor element (102) is monitored in an operating state and / or once in an initial phase, wherein a measurement series of the state of the voltage-dependent resistor element (102) is generated and an initial error of the voltage-dependent resistor element (102) is calculated therefrom.

9. A method (300) for controlling an electronic circuit (100) according to claims 7 to 8, wherein the current I_MOV (118) is regulated so that the current I_MOV (118) reaches a current range of 100 μA to 15 mA, preferably 700 μA to 1.3 mA, with 1 mA being particularly preferred.

10. The method (300) for controlling an electronic circuit (100) according to claims 8 to 10, wherein the voltage V_Lim (130) is measured at an external circuit (100.2, 200.2) or an analog-to-digital converter (124).

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