Overvoltage and / or undervoltage testing

Abstract

To provide a method for checking the functionality of a voltage monitor of a circuit (11).SOLUTION: The method includes a computing unit (19) sending a test signal to a voltage source (13), which causes a change in the voltage of the voltage source (13). A comparison unit (17) compares the voltage at the output of a voltage source (24) with a reference voltage and sends a shutdown signal to a switch (15) if the voltage at the output of the voltage source (13) is outside a predetermined tolerance range. The switch (15) interrupts the flow of current upon receiving a shutdown signal, causing the voltage after the switch (15) to drop. According to the invention, the computing unit (19) measures the voltage after the switch (15) and draws conclusions about the functionality of the voltage monitor based on this voltage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for checking the function of a voltage monitor of a circuit according to claim 1 and a circuit according to the general terms of claim 11.

Background Art

[0002] Typical application areas of the method and circuit in the sense of the present invention are the automation industry. Automation technology is a branch of plant engineering and engineering science that deals with the automation of technical processes in complex machines and plants. The electrical circuit in the sense of the present invention relates in particular to a circuit for monitoring the system voltage and interrupting the voltage transmission if the voltage is outside the defined limits. (Often simply also referred to as "voltage monitor") Such a circuit for monitoring and interrupting the voltage is used, for example, when an overvoltage leads to a critical system state for safety and a currentless state represents a safe system state. For example, such an electrical circuit serves in particular to monitor the system voltage in various operating modes. If such a circuit fails, the monitoring and interruption of the system voltage ("voltage monitor") is no longer guaranteed, which can have significant consequences. Since the functions of the circuit are diverse, it is very important to ensure that the circuit functions reliably in order to avoid dangerous situations. Since it is often not easy or not fully achievable to guarantee error-free operation, the usual approach is to use redundant circuits. For example, the redundancy in which redundant circuits for monitoring and interrupting the voltage are arranged in series improves the robustness of the "monitoring and interruption" function. However, the disadvantage of such an arrangement is that the circuit is not tested during operation. For example, the reliable function or operability of the voltage monitor of the circuit is guaranteed by the redundancy of two elements arranged in series. These elements may include switches with an integrated shutdown mechanism that become active when a voltage outside the permitted system voltage range occurs. The advantage is that these voltage monitor elements are redundant within the circuit and even if one voltage monitor element fails, the second element can take over its task. However, once the circuit starts operating, the functionality of the voltage monitor is not continuously checked during operation. Therefore, in this arrangement, malfunctions are likely to occur gradually in both voltage monitors or due to a common cause of failure. Since there is no control of the voltage monitor, i.e., no functional control of the circuit for monitoring and interrupting the voltage, there is no information about the functionality of the circuit at any point in time.

[0003] Furthermore, manufacturing and installing two elements (two circuits) for the voltage monitor approximately doubles the material cost and installation volume compared to manufacturing and installing one element (one circuit).

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to demonstrate a method for checking the functionality of a voltage monitor (a circuit for monitoring system voltage with integrated voltage cutoff) that enables cost-effective and space-saving circuit implementation.

[0005] Furthermore, it is necessary to demonstrate a circuit for a voltage monitor that is as cost-effective and space-saving as possible.

Means for Solving the Problems

[0006] This problem is solved by using a method having the features of claim 1. The present invention relates to a method for checking the functionality of a voltage monitor of a circuit. The method according to the present invention and the circuit according to the present invention, described below, for checking the functionality of a voltage monitor are particularly used in the automation industry.

[0007] In a first step, a calculation unit transmits a test signal to a voltage source and changes the voltage of the voltage source. A comparison unit compares the voltage at the output of the power supply with a reference voltage and, if the voltage at the output of the power supply is outside the allowable range, transmits a shutdown signal to a switch (provided to cut off the current flow as part of the voltage monitor). When the switch receives the shutdown signal, it cuts off the current flow and drops the voltage downstream of the switch. The method according to the present invention is characterized by the fact that the calculation unit measures the voltage after the switch and derives a conclusion about the functionality of the voltage monitor based on this voltage.

[0008] By the method according to the present invention, it becomes possible to check the functionality of the voltage monitor by using a test signal from a computing unit. The test signal generates a voltage outside the allowable range of the operating voltage and is used to cut off the switch. The cutting off of the switch is triggered by a shutdown signal from a comparison unit, which is transmitted when the comparison unit determines that the voltage at the output of the voltage source is outside the allowable range. This is to check whether the switch-off mechanism is functioning and whether the voltage monitor is guaranteed in the circuit. This method can be used to guarantee the functionality of the voltage monitor in the circuit, and for this purpose, the circuit does not need to have redundant elements. By avoiding redundancy, that is, by using a single version of elements in the circuit, the circuit improves the cost efficiency for manufacturing and also saves space in terms of size.

[0009] Preferably, the test signal increases or decreases the voltage of the voltage source. The test signal can increase or decrease the voltage of the voltage source, thereby changing the voltage at the output of the voltage source accordingly. The system voltage has an allowable range with an upper limit and a lower limit. For this reason, the voltage monitor can check its functionality by decreasing or increasing the voltage.

[0010] The computing unit preferably transmits the test signal at regular time intervals. The functionality of the voltage monitor is checked by transmitting a test signal from the computing unit. The computing unit can be set to transmit a test signal to the voltage source at specific predefined time intervals. Thereby, the functionality of the voltage monitor can be checked periodically.

[0011] The operating voltage of the above circuit is preferably from 4.5 V to 5.5 V, more preferably from 4.85 V to 5.15 V, and the operating voltage range defines the range within which the functions of the system are guaranteed. This also determines the application range of the circuit.

[0012] The voltage changed by the test signal is preferably within a specified voltage range that is outside the operating voltage range and within which no overload of the system occurs. The role of the test pulse is to bring the voltage outside the operating voltage range. Preferably, the voltage is within the specified voltage range so that the elements of the circuit do not receive a high voltage difference that could potentially cause damage and, as a result, shorten the life of the circuit. A voltage of 6V can be provided as the upper limit of this voltage range.

[0013] In a further embodiment, the operating voltage range of the circuit is from 3.0 to 3.6V, preferably from 3.2 to 3.4V, and the operating voltage range defines the range within which the functions of the system are guaranteed. Again, the voltage changed by the test signal is preferably outside the operating voltage range and within the specified voltage range, and a voltage of 4V can be provided as the upper limit of this voltage range.

[0014] Preferably, the power supply circuit reduces the supply voltage as the input voltage to the system voltage. In this case, the voltage source functions as a voltage converter. The supply voltage can be any voltage provided. As long as the voltage source reduces the voltage to the system voltage, the circuit functions.

[0015] In another preferred embodiment, the supply voltage is from 10V to 50V, preferably from 18V to 30V. Thus, the supply voltage covers the range used in automation devices.

[0016] Preferably, during the transmission of the test signal and while there is a possibility of switching off the switch by the second voltage source, the operation of the circuit is maintained. The second voltage source ensures that the voltage at the output of the circuit does not drop to zero and, thus, guarantees that the circuit continues to operate.

[0017] The second voltage source preferably includes a capacitor. Since the capacitor can store electrical energy, it can function as a voltage source when checking the functionality of the voltage monitor in the circuit. During normal operation, the capacitor can be charged and discharged as needed to supply power to the circuit.

[0018] Another aspect of the present invention relates to a circuit for checking the functionality of a voltage monitor. This circuit includes a voltage source that provides an adjustable output voltage and a switch that blocks the flow of current. Further, 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 switch-off signal to the switch based on the result of the comparison. The calculation unit measures the voltage at the output of the switch. The calculation unit aims to send a test signal to the voltage source to change the voltage of the voltage source and check the functionality of the voltage monitor with the voltage at the output of the switch.

[0019] Preferably, the voltage at the output of the voltage source has an allowable range, and the comparison unit sends a shutdown signal to the switch when the measured voltage at the output of the voltage source is outside this allowable range.

[0020] Advantageously, a second voltage source, particularly a capacitor, is provided to supply current to the output of the circuit and ensure the continuous functionality of the circuit when the flow of current through the switch is blocked.

[0021] Preferably, a protection device is arranged between the second voltage source and the switch to prevent current from flowing from the second voltage source to the switch and to ensure that the measurement of the calculation unit by the second voltage source is not affected. Preferably, the protection device for feedback is formed by a semiconductor circuit, particularly a diode.

[0022] The optional features mentioned can be implemented in any combination as long as they are not mutually exclusive. In particular, when a preferred range is given, a more preferred range is obtained from the combination of the minimum and maximum values mentioned in the range.

[0023] Further advantages and features of the present invention will become apparent from the following description of exemplary embodiments of the present invention with reference to the schematic drawings.

Advantages of the Invention

[0024] Here, schematic diagrams that are not to exact scale are illustrated.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0026] The same reference numerals below represent the same or functionally identical elements in different figures. Additional apostrophes are for distinguishing elements that are similar, or functionally equivalent, or functionally similar in further embodiments.

[0027] Figure 1 shows a circuit diagram of circuit 11 according to the present invention with a switch-off function in the event of an overvoltage or undervoltage event. The supply voltage is applied to a variable voltage source 13. The voltage source 13 converts the supply voltage to a lower system voltage, which is monitored by a subsequent circuit 11 with a switch 15. The voltage source 13 has the ability to vary the system voltage. The system voltage can be varied 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 measures the actual voltage at the output of the voltage source sent to the comparison unit 17 by a first voltage feedback unit 16 and compares this actual voltage with a reference voltage from a reference voltage source 18. If the deviation exceeds the tolerance range, there is an overvoltage or undervoltage, and the comparison unit 17 sends a shutdown signal to the switch 15. In circuit 11, a calculation unit 19 and a diode 21 follow the switch 15. The diode 21 is designed to send the current from the switch 15 to one of the outputs of the circuit. The calculation unit 19 receives a voltage at the output of the switch by a second voltage feedback unit 20. From the voltage at the switch output, the calculation unit 19 can determine whether the voltage monitor of circuit 11 is functioning. At the same time, the calculation unit 19 is connected to the voltage source 13. The calculation unit 19 starts a test for the voltage monitor, sends a test signal to the voltage source 13, which varies the voltage of the voltage source. If the voltage exceeds or falls below the tolerance range of the system voltage, the comparison unit 17 generates a switch-off signal for the switch 15, and the switch 15 interrupts the current flow. Since the diode 21 prevents access of the current from the circuit output to the switch, the voltage across the switch drops rapidly. After the diode 21, another voltage source 23 in the form of a capacitor is attached. The current in this second voltage source 23 starts to flow when the voltage before and after the diode 21 drops. Thus, the second voltage source 23 ensures a stable voltage state at the circuit output after the diode 21, which usually means that the continuous function of circuit 11 is not interrupted during the execution of the test.Since the diode 21 has the characteristic of allowing current to flow only in one direction, the voltage in the switch output measured by the calculation unit 19 is not affected by the second voltage source 23.

[0028] FIG. 2 illustrates the voltages at four different points (V0, V1, V2, and V3) within the circuit over time, and the figures are presented one above the other such that the horizontal axes form the same time axis in all figures. The first figure illustrates the voltage over time at the connection between the computing unit 19 and the first voltage source 13, detected by the first voltage feedback unit 16. The second figure illustrates the voltage curve between the first voltage source 13 and the switch 15. The voltage at the output of the switch 15, detected by the second voltage feedback unit 20, is illustrated in the third figure. The fourth figure illustrates the voltage curve at the output of the circuit 11. At time t0, the computing unit 19 triggers a test for the voltage monitor by sending a signal to the first voltage source 13. In this case, the signal causes the voltage at the output of the voltage source 13 to increase. This voltage is continuously monitored and controlled by the comparison unit 17. As a result of the increase in the voltage at the output of the voltage source, the voltage after the switch also increases. At time t1, the voltage at the output of the power supply circuit reaches a value outside 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 the switch 15 cuts off the current flow. The voltage after the switch drops to zero within a very short time. The computing unit 19, which triggered the test and caused the voltage increase, measures the voltage that dropped at the output of the switch and recognizes that the test was successful. After the computing unit 19 detects the expected voltage drop, the comparison unit 17 stops sending the test signal to the first voltage source 13 at time t2. When the test signal ceases to exist, the voltage at the voltage source 13 drops again. Despite the switch being blocked, the voltage drop across the switch, which had been increasing until time t2, decreases after the test signal is removed. When the voltage before the switch, continuously monitored by the comparison unit 17, falls below a specific value and returns within the tolerance range of the operating voltage, the comparison unit 17 sends a signal to the switch 15 to release the current cutoff at time t3.Since the voltage before the switch is always at a high level, after the interruption is released, the voltage at the output of the switch also rises rapidly, and the voltage at the output of the switch reaches the same level as before the interruption within a short time after t3. In contrast to the state before the interruption, the voltage at the input of the switch, and thus at the output, also decreases and approaches the system voltage. The voltage at the output of the circuit is illustrated in its progression in the fourth figure and rises after the test signal is sent (t0) until the switch is interrupted (t1). In contrast 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 decrease in voltage is that the second voltage source 23 is in the form of a capacitor, which is located at the output of the circuit and ensures a constant current supply at the output of the circuit when the current passing through the switch 15 is interrupted. Since there is a diode between the output of the circuit and the switch, the current of the second voltage source 23 does not affect the voltage at the output of the switch. The capacitor discharges until time t3, after which the current can flow through the switch again. Although it takes a relatively long time for the voltage at the output of the circuit 11 to reach approximately the system voltage, this is because the capacitor is charged simultaneously and part of the current is used for charging.

[0029] Although the present invention has been described above with reference to specific embodiments, it is obvious that changes, modifications, variations, and combinations can be made without departing from the spirit of the present invention.

Explanation of Reference Numerals

[0030] 11 Circuit 13 First voltage source 15 Switch 16 First voltage feedback unit 17 Comparison unit 18 Reference voltage source 19 Calculation unit 20 Second voltage feedback unit 21 Diode 23 Second voltage source

Claims

1. A method for checking the functionality of the voltage monitor of circuit 11, comprising: a step in which the calculation unit 19 transmits a test signal to the voltage source 13 to change the voltage of the voltage source 13; a step in which the comparison unit 17 compares the voltage at the output of the voltage source 13 with a reference voltage, and if the voltage at the output of the voltage source 13 is outside the allowable range, transmits a shutdown signal to the switch 15; a step in which when the switch 15 receives the shutdown signal, it cuts off the current flow and reduces the voltage after the switch 15; and a step in which the calculation unit 19 measures the voltage after the switch 15 and derives a conclusion about the functionality of the voltage monitor based on this voltage.

2. The method according to claim 1, wherein the test signal increases or decreases the voltage of the voltage source 13.

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

4. The operating voltage range of the circuit is from 4.5 V to 5.5 V, preferably from 4.85 V to 5.15 V, or from 3.0 V to 3.6 V, preferably from 3.2 V to 3.4 V, and the operating voltage range defines the range within which the functions of the system are guaranteed. The method according to claim 1.

5. The method according to claim 1, wherein the voltage changed by the test signal is within a specified voltage range outside the operating voltage range and does not cause an overload of the system.

6. The method according to claim 1, wherein the maximum voltage for guaranteeing the function of the voltage monitor is from about 5.5 V to 6 V, or from 3.6 V to 4 V.

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

8. The method according to claim 1, wherein the supply voltage is from 10 V to 50 V, preferably from 18 V to 30 V.

9. The method according to claim 1, wherein the operation of the circuit 11 is maintained during the transmission of the test signal and during the possible switching off of the switch 15 by the second voltage source 23.

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

11. A circuit 11 for checking the functionality of a voltage monitor, a voltage source 13 that provides an adjustable output voltage, a switch 15 for interrupting the flow of current, a comparison unit 17 that compares the voltage at the output of the voltage source 13 with a reference voltage and can transmit a switch-off signal to the switch 15 based on the comparison result, and a calculation unit 19 that measures the voltage at the output of the switch 15, wherein the calculation unit 19 is provided to transmit a test signal to the voltage source 13 in order to vary the voltage of the voltage source 13 and check the operability of the voltage monitor with the voltage at the output of the switch 15. Circuit 11 is characterized by this.

12. The voltage at the output of the voltage source 13 has an allowable range, and the comparison unit 17 transmits a switch-off signal to the switch 15 when the voltage measured at the output of the voltage source 13 is outside this allowable range. The circuit according to claim 11 is characterized by this.

13. A second voltage source 23, particularly a capacitor, is provided, and when the flow of current passing through the switch 15 is interrupted, it supplies current to the output of the circuit to ensure the continuous function of the circuit 11. The circuit according to claim 11 is characterized by this.

14. A protection device for feedback is arranged between the second voltage source 23 and the switch 15 so that the measurement of the calculation unit by the second voltage source is not affected without current flowing from the second voltage source to the switch 15. The circuit according to claim 11 is characterized by this.

15. The protection device for feedback is formed by a semiconductor circuit, particularly a diode 21. The circuit according to claim 11 is characterized by this.

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