Overvoltage and / or undervoltage inspection

Abstract

The invention relates to a method for checking the functional capability of voltage monitoring of a circuit (11). The method comprises sending a test signal to a voltage source (13) by a computing unit (19), the test signal causing a change in the voltage of the voltage source (13). A comparison unit (17) compares the voltage at the output of the voltage source (13) with a reference voltage and sends a turn-off signal to the switch (15) if the voltage at the output of the voltage source (13) is outside a predetermined tolerance range. When a turn-off signal is obtained, the switch (15) interrupts the flow of current, whereby the voltage after the switch (15) drops. According to the invention, a computing unit (19) measures the voltage following the switch (15) and deduces the functionality of the voltage monitoring on the basis of the voltage.

Description

Field of the Invention

[0001] The present invention relates to a method for checking the functional ability of a voltage monitoring for a circuit according to claim 1 and a circuit according to the preamble of claim 11. Background Art

[0002] Typical application areas for the method and the circuit in the sense of the present invention are the automation industry. Automation technology is a subfield of plant engineering and engineering science and relates to the automation of technical processes in complex machines and plants. The circuit in the sense of the present invention particularly relates to a circuit for monitoring a system voltage and interrupting the forwarding of the voltage if the system voltage lies outside a defined limit. For example, such a circuit for monitoring and interrupting the voltage (often only referred to as "voltage monitoring") is used where an overvoltage leads to a safety-critical system state and a currentless state represents a safe system state. For example, such a circuit is particularly responsible for monitoring the system voltage in different operating modes. Since the monitoring and interruption of the system voltage ("voltage monitoring") will no longer be ensured, the consequences of a malfunction of such a circuit can have a significant impact. Due to this broad effect of the circuit function, it is crucial to ensure the reliable function of the circuit in order to be able to avoid dangerous situations. Since ensuring an error-free function is often not trivial or cannot be carried out in its full scope, a redundant circuit design is usually provided. The robustness of the function "monitoring and interruption" is increased due to the redundancy, in which case redundant circuits for monitoring and interrupting the voltage are arranged in series, for example. However, a disadvantage of such an arrangement is often that the circuit is not tested during operation. For example, in the prior art, the reliable function or functional ability of the voltage monitoring of a circuit is ensured by means of a redundancy of two elements arranged in series. Each of the elements can comprise a switch having an integrated shutdown mechanism that is activated when the voltage is outside the permitted system voltage range. In this case, the advantage is that these elements for carrying out the voltage monitoring are redundant in the circuit and, when one element for carrying out the voltage monitoring fails, the second element can continue the task. However, after a one-time commissioning, the voltage monitoring is not continuously checked with regard to its functional ability during operation. Therefore, such an arrangement is vulnerable to malfunctions that occur gradually or due to an error in a common cause in the two voltage monitorings. Due to the lack of control of the voltage monitoring, i.e., the lack of functional control of the circuit for monitoring and interrupting the voltage, there is no information about the functional ability of the circuit at any point in time.

[0003] Furthermore, the manufacture and installation of two elements (two circuits) for carrying out the voltage monitoring are associated with almost double material costs and installation volume compared to a single element (single circuit). Summary of the Invention

[0004] The object of the present invention is to show a method for testing the functional ability of a voltage monitoring (circuit for monitoring the system voltage with integrated voltage interruption), which enables the circuit to be implemented in a cost - low and space - saving manner.

[0005] Furthermore, a circuit for voltage monitoring that is as cost - low and space - saving as possible should be shown.

[0006] This object is solved by a method having the features of claim 1.

[0007] The present invention relates to a method for testing the functional ability of the voltage monitoring of a circuit. The circuit according to the invention and the method according to the invention for testing the functional ability of voltage monitoring described below are in particular applied in the automation industry.

[0008] In a first step, the computing unit sends a test signal to the voltage source, which causes a change in the voltage of the voltage source. The comparison unit compares the voltage at the output of the voltage source with a reference voltage and, if the voltage at the output of the voltage source is outside the tolerance range, sends a shutdown signal to the switch (the switch is arranged to interrupt the current flow in the range of voltage monitoring). When the shutdown signal is obtained, the switch interrupts the current flow, whereby the voltage drops after the switch. The method according to the invention is characterized in that the computing unit measures the voltage after the switch and infers the functional ability of the voltage monitoring based on this voltage.

[0009] The method according to the invention enables the functional ability of the voltage monitoring to be tested by using a test signal from the computing unit. The test signal is used to generate a voltage that is outside the tolerance range of the operating voltage and based on this induces the interruption of the switch. The interruption of the switch is triggered by the shutdown signal of the comparison unit, which is sent when the comparison unit determines that the voltage at the output of the voltage source is outside the tolerance range. Thereby, it is checked whether the shutdown mechanism works and whether the voltage monitoring in the circuit is ensured. By means of this method, the functional ability of the voltage monitoring can be ensured in the circuit, where the circuit does not have to have redundant components for this purpose. By dispensing with redundancy, i.e., by using components in a separate implementation in the circuit, the circuit becomes not only cost - low in terms of manufacturing but also space - saving in terms of size.

[0010] Preferably, the test signal causes an increase or a decrease in the voltage of the voltage source. The test signal can increase or decrease the voltage of the voltage source, thereby correspondingly changing the voltage at the output of the voltage source. The system voltage has a tolerance range that has a lower limit and an upper limit. For this reason, the functional ability of the voltage monitoring can be tested by using a decrease or an increase in the voltage.

[0011] The computing unit advantageously sends test signals at regular time intervals. The functional ability of the voltage monitoring is verified by sending test signals from the computing unit. The computing unit can be set such that the computing unit sends test signals to the voltage source at specific and predefined time intervals. This enables the regular verification of the functional ability of the voltage monitoring.

[0012] Preferably, the operating voltage range of the circuit is between 4.5–5.5 V, preferably between 4.85–5.15 V, where the operating voltage range defines the range in which the functionality of the system is guaranteed. Thereby, the usage range of the circuit is also determined simultaneously.

[0013] The voltage changed by the test signal is preferably outside the operating voltage range and within the defined voltage range in which no overload of the system occurs. The task of the test pulse is to bring the voltage outside the operating voltage range. Here, preferably the voltage is within the defined voltage range so that the components of the circuit do not suffer high voltage differences such that the components may be damaged, which in turn may reduce the service life of the circuit. A voltage of 6 V can be set as the upper limit for this voltage range.

[0014] In another embodiment, the operating voltage range of the circuit is between 3.0–3.6 V, preferably between 3.2–3.4 V, where the operating voltage range defines the range in which the functionality of the system is guaranteed. Here, the voltage changed by the test signal is also preferably outside the operating voltage range and within the defined voltage range, where a voltage of 4 V can be set as the upper limit for this voltage range.

[0015] Preferably, the voltage source reduces the supply voltage as the input voltage to the system voltage. In this case, the voltage source serves as a voltage converter. The supply voltage can be any provided voltage. As long as the voltage source reduces the voltage to the system voltage, the functional ability of the circuit is given.

[0016] In another preferred embodiment, the supply voltage is between 10 V and 50 V, preferably between 18 V and 30 V. Thus, the supply voltage covers the range used in automation in the case of the device.

[0017] Preferably, during the sending of the test signal and possibly the turning off of the switch, the operation of the circuit is maintained by a second voltage source. The second voltage source ensures that the voltage at the output of the circuit does not drop to zero and thus the circuit continues to remain in operation.

[0018] The second voltage source preferably includes a capacitor. The capacitor can be used as a voltage source during the functional ability test of the voltage monitoring in the test circuit, because the capacitor can store electrical energy. During normal operation, the capacitor is charged respectively, and when needed, current can be supplied to the circuit by discharging the capacitor.

[0019] Another aspect of the present invention relates to a circuit for testing the functional ability of voltage monitoring. The circuit includes a voltage source providing an adjustable output voltage and a switch for interrupting the current flow. In addition, the circuit includes a comparison unit that compares the voltage at the output of the voltage source with a reference voltage and can send a shutdown signal to the switch based on the comparison result. A calculation unit measures the voltage at the output of the switch. The calculation unit is arranged to send a test signal to the voltage source to change the voltage of the voltage source and to test the functional ability of voltage monitoring using the voltage at the output of the switch.

[0020] Preferably, the voltage at the output of the voltage source has a tolerance range, and if the measured voltage at the output of the voltage source is outside this tolerance range, the comparison unit sends a shutdown signal to the switch.

[0021] Advantageously, a second voltage source, in particular a capacitor, is provided, which supplies current to the output of the circuit when the current flow is interrupted by the switch and ensures the continued function of the circuit.

[0022] Preferably, an anti-feedback protection device is arranged between the second voltage source and the switch, such that current cannot flow from the second voltage source to the switch and the measurement of the calculation unit is not affected by the second voltage source. Preferably, the anti-feedback protection device is constituted by a semiconductor circuit, in particular a diode.

[0023] The optional features mentioned can be implemented in any combination, as long as the features are not mutually exclusive. In particular, where preferred ranges are described, other preferred ranges are obtained from the combination of the minimum and maximum values mentioned in the range.

[0024] Other advantages and features of the present invention are derived from the following description of embodiments of the present invention with reference to the schematic diagrams. Description of the Drawings

[0025] In a schematic diagram not to scale:

[0026] Figure 1 A circuit diagram showing the circuit according to the present invention;

[0027] Figure 2showing a graph with a time series of voltages at four points of the circuit when a test signal is sent; DETAILED DESCRIPTION

[0028] In the following, the same reference numerals in different figures represent the same or functionally identical elements. Additional primes may be used to distinguish similar or functionally identical or functionally similar elements in another implementation.

[0029] Figure 1 The circuit diagram of the circuit 11 according to the invention with a shutdown function in the event of overvoltage or undervoltage is shown. The supply voltage is applied to a variable voltage source 13. The voltage source 13 converts the supply voltage into a lower system voltage, which is monitored by the subsequent circuit 11 using a switch 15. In this case, the voltage source 13 has the property of being able to change the system voltage. The change in the system voltage can be triggered at pre-set intervals or by an external input. A comparison unit 17 is installed between the voltage source 13 and the switch 15. The comparison unit 17 compares the current voltage at the output of the voltage source, which is forwarded to the comparison unit 17 by means of a first voltage readback device 16, and compares the current voltage with a reference voltage from a reference voltage source 18. If the deviation is greater than the permissible tolerance, there is an overvoltage or undervoltage, and the comparison unit 17 sends a shutdown signal to the switch 15. In the circuit 11, after the switch 15, there is a calculation unit 19 and a diode 21. The diode 21 is provided for transmitting the current from the switch 15 to the output of the circuit on one side. The calculation unit 19 obtains the voltage at the outlet of the switch by means of the second voltage readback device 20. Based on the voltage at the outlet of the switch, the calculation unit 19 can determine whether the voltage monitoring of the circuit 11 is functional. At the same time, the calculation unit 19 is connected to the voltage source 13. The calculation unit 19 initiates a test for voltage monitoring and sends a test signal to the voltage source 13 for this purpose, whereby the voltage of the voltage source is changed. If the voltage is above or below the tolerance range of the system voltage, the comparison unit 17 generates a switch-off signal for the switch 15, whereupon the switch 15 interrupts the current flow. Since the diode 21 blocks the passage of the current from the circuit output to the switch, the voltage drops rapidly after the switch. After the diode 21, another voltage source 23 in the form of a capacitor is arranged. When the voltage before the diode 21 and thus also after the diode 21 is reduced, the current in the second voltage source 23 begins to flow. Therefore, the second voltage source 23 causes a stable state of the voltage after the diode 21 and at the output of the circuit, whereby the continued function of the circuit 11 is generally not interrupted when the test is performed. Due to the property of the diode 21 that current flows in only one direction, the voltage at the output of the switch measured by the calculation unit 19 remains unaffected by the second voltage source 23 .

[0030] exist Figure 2Shows the time series of voltages (V0, V1, V2, and V3) at four different points in the circuit, where the graphs are shown superimposed such that the horizontal axis constitutes the same time axis in all graphs. The first graph shows the time variation of the voltage at the connection between the computing unit 19 and the first voltage source 13, which voltage is detected by the first voltage feedback device 16. The variation of the voltage between the first voltage source 13 and the switch 15 is shown in the second graph. The voltage at the output of the switch 15 detected by the second voltage feedback device 20 is shown in the third graph. The fourth graph again shows the variation of the voltage at the output of the circuit 11. At time point t0, a test for voltage monitoring is triggered by the computing unit 19 by sending a signal to the first voltage source 13. In this case, the signal causes an increase in the voltage at the output of the voltage source 13. The voltage is continuously monitored and controlled by the comparison unit 17. Due to the increase in the voltage at the output of the voltage source, the voltage after the switch also increases. At time point t1, the voltage at the output of the voltage source reaches a value that is no longer within the tolerance range of the operating voltage and is detected by the comparison unit 17. Subsequently, the comparison unit 17 sends a shutdown signal to the switch 15, and immediately afterwards the switch 15 interrupts the current flow. In a very short time, the voltage after the switch drops to zero. The computing unit 19 that triggered the test and has caused the voltage increase measures the decreasing voltage at the output of the switch and notices that the test has thus been successful. After the expected voltage drop has been detected by the computing unit 19, the test signal sent by the computing unit 17 to the first voltage source 13 is stopped at time point t2. By canceling the test signal, the voltage at the voltage source 13 is reduced again. The voltage before the switch that has continued to increase despite the interrupted switch until time point t2 is reduced after canceling the test signal. If the voltage before the switch continuously controlled by the comparison unit 17 drops below a predetermined value and thus again falls within the tolerance range of the operating voltage, the comparison unit 17 sends a signal to the switch 15 at time point t3 to cancel the interruption of the current flow. Since the voltage before the switch always has an increasing value, the voltage at the output of the switch also rises rapidly after canceling the interruption, such that shortly after t3, the voltage at the output of the switch is at a level similar to that before the interruption. Compared to the state before the interruption, the voltage at the input of the switch and thus also at the output is reduced and approximately approaches the system voltage. The voltage at the output of the circuit (the variation of which is shown in the fourth graph) also rises after sending the test signal (t0) until the interruption of the switch (t1). Compared to the voltage after the switch, the voltage at the output of the circuit does not drop suddenly to zero after t1, but decreases slowly.The reason for the slow voltage decrease is the second voltage source 23 in the form of a capacitor, which is arranged at the output of the circuit and ensures a specific power supply at the output of the circuit when the current flow is interrupted by the switch 15. Due to the diode between the output of the circuit and the switch, the current of the second voltage source 23 cannot affect the voltage at the output of the switch. The capacitor discharges until the time point t3, after which the current can flow again via the switch. The voltage at the output of the circuit 11 reaches the system voltage approximately in the longest time because the capacitor is charged simultaneously and a part of the current is used for this purpose.

[0031] The present invention has been described above with reference to specific embodiments, and it is obvious that changes, modifications, variations, and combinations can be made without departing from the inventive concept.

[0032] List of reference numerals:

[0033] 11 Circuit

[0034] 13 First voltage source

[0035] 15 Switch

[0036] 16 First voltage feedback device

[0037] 17 Comparison unit

[0038] 18 Reference voltage source

[0039] 19 Calculation unit

[0040] 20 Second voltage feedback device

[0041] 21 Diode

[0042] 23 Second voltage source.

Claims

1. A method for testing the functional ability of voltage monitoring of a circuit 11, comprising the following steps: The calculation unit 19 sends a test signal to the first voltage source 13, and the test signal causes a change in the voltage of the voltage source 13. The comparison unit 17 compares the voltage at the output terminal of the voltage source 13 with a reference voltage, and if the voltage at the output terminal of the voltage source 13 is outside the tolerance range, it sends a shutdown signal to the switch 15. When the shutdown signal is obtained, the switch 15 interrupts the current flow, thereby causing the voltage to drop after the switch 15. It is characterized in that The calculation unit 19 measures the voltage after the switch 15 and infers the functional ability of the voltage monitoring based on this voltage.

2. The method according to claim 1, wherein The test signal causes the voltage of the voltage source 13 to increase or decrease.

3. The method according to claim 1, wherein The calculation unit 19 sends test signals at regular time intervals.

4. The method according to claim 1, wherein The operating voltage range of the circuit is between · 4.5–5.5 V, preferably between 4.85–5.15 V, or · 3.0–3.6 V, preferably between 3.2–3.4 V. Wherein the operating voltage range defines the range in which the function of the system is guaranteed.

5. The method according to claim 1, characterized in that The voltage changed by the test signal is outside the operating voltage range and within the defined voltage range where no overload of the system occurs.

6. The method according to claim 1, characterized in that, The maximum voltage for ensuring the function of the voltage monitoring is between approximately 5.5 - 6 V or between 3.6 - 4 V.

7. The method according to claim 1, characterized in that The voltage source 13 reduces the supply voltage as the input voltage to the system voltage.

8. The method according to claim 1, characterized in that The supply voltage is between 10 V and 50 V, preferably between 18 V and 30 V.

9. The method according to claim 1, characterized in that During the sending of the test signal and the possible shutdown of the switch 15, the operation of the circuit 11 is maintained by the second voltage source 23.

10. The method according to claim 1, wherein The second voltage source 23 includes a capacitor.

11. A circuit 11 for testing the functional ability of voltage monitoring, comprising A voltage source 13 that provides an adjustable output voltage. A switch 15 for interrupting the current flow. A comparison unit 17 that compares the voltage at the output terminal of the voltage source 13 with a reference voltage and is capable of sending a shutdown signal to the switch 15 based on the comparison result. A calculation unit 19 that measures the voltage at the output terminal of the switch 15. It is characterized in that The calculation unit 19 is arranged to send a test signal to the voltage source 13 to change the voltage of the voltage source 13 and to test the functional ability of the voltage monitoring using the voltage at the output terminal of the switch 15.

12. The circuit according to claim 11, wherein, The voltage at the output terminal of the voltage source 13 has a tolerance range, and if the measured voltage at the output terminal of the voltage source 13 is outside this tolerance range, the comparison unit 17 sends a shutdown signal to the switch 15.

13. The circuit according to claim 11, wherein A second voltage source 23, especially a capacitor, is provided. When the current flow is interrupted by the switch 15, the second voltage source 23 supplies current to the output terminal of the circuit and ensures the continued function of the circuit 11.

14. The circuit according to claim 11, wherein The protection device against feedback is arranged between the second voltage source 23 and the switch 15 such that current cannot flow from the second voltage source 23 to the switch 15, and the measurement of the calculation unit is not affected by the second voltage source 23.

15. The circuit according to claim 11, characterized in that, The protection device against feedback consists of a semiconductor circuit, in particular a diode 21.

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