METHOD FOR DETECTING THE SWITCHING STATE OF A SWITCHING CONTACT OF AN ELECTROMETAL SWITCHING DEVICE HAVING AT LEAST ONE PAIR OF CONTACTS, AND A SWITCHING ARRANGEMENT FOR DETECTING THE SWITCHING STATE

Description

[0001] The present invention relates to a method for detecting the switching state of a switching contact of an electromechanical switching device having at least one contact pair, wherein during an operating phase for detecting the switching state, the switching contact is subjected to a switching current and the switching current is analyzed by means of an evaluation unit to determine whether the switching contact is in a closed switching state or in an open switching state.

[0002] DE 200 08 548 U1 discloses an arrangement for detecting the switching position of a mains switch for microprocessor-controlled devices with a switch-off delay. It describes a mains switch comprising two series-connected switches which can only be opened or closed together. One contact of one switch is connected to one of the two live or (neutral) conductors, and the other contact is connected to a first input of a sensor which, when voltage is applied and the mains switch is switched on, conducts a measuring current to the second input of the sensor, which is connected to the corresponding other of the two live or (neutral) conductors. The sensor transmits an output signal corresponding to the switching position of the mains switch to a microprocessor in the device.From DE 10 2018 114425 A1 a switching monitoring device is also known which provides information about the switching state of a relay switching contact, in particular depending on the relay control.

[0003] The invention is based on the object of providing a method for detecting the switching state of a switching contact of an electromechanical switching device and a circuit arrangement for detecting the switching state of a switching contact, wherein the circuit arrangement is optimized for reduced power loss, thereby also achieving better thermal management.

[0004] This object is achieved by a method for detecting the switching state of a switching contact of an electromechanical switching device having at least one contact pair. During an operating phase, the switching contact is subjected to a switching current to detect the switching state, and the switching current is analyzed by an evaluation unit to determine whether the switching contact is in a closed switching state or an open switching state. According to the invention, during the operating phase, the switching contact is subjected to a switching current that is designed as a clocked voltage or current signal to detect the switching state of the switching contact.In contrast to operating procedures in which the switching contacts are continuously subjected to a required minimum power during status detection, this has the advantage of reducing power losses during the operating phases in which the switching state of the switching contacts is detected, thus reducing heat input within the switching device. However, it is still necessary that the switching contacts be subjected to a prescribed minimum power to ensure reliable contact at all times. This reliably removes any contamination from the switching contacts. For 24 V relays with gold contacts, for example, a power of 24 V and 1 mA is required.This results in power losses, both at the output driver and at the relay contacts, which can be significantly reduced by the method according to the invention and by the circuit arrangement according to the invention.

[0005] Further advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically expedient manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, where further preferred embodiments of the invention are presented.

[0006] According to the invention, the switching contact is supplied with a switching current configured as a clocked square-wave signal. A predetermined maximum switching current is switched during the pulse phase and a predetermined minimum switching current is switched during the pause phase.

[0007] By using a preferred duty cycle of 1:1, both the power loss and the associated heat input within the switching device are significantly reduced. Heat input can be further reduced by further reducing the turn-on time. The minimum switching current is advantageously zero. This enables further variable options for reducing power loss.

[0008] The switching contact is supplied with a switching current configured as a clocked square wave with a variable pulse-pause ratio. This makes it possible to adapt the power loss reduction to the respective operating conditions.

[0009] Preferably, the pulse-pause ratio can be varied depending on at least one operating parameter, so that the reduction in power loss can be directly coupled with the power loss generated in the switching device during the switching state detection of the switching contacts.

[0010] According to another particularly preferred embodiment of the invention, the pulse-pause ratio can be preset such that different speeds for detecting the switching state of the switching contact can be specified. This allows for appropriate adaptation to the operating mode of the switching device and / or to the customer's requirements and / or the electromechanical switching contact used (e.g., relay), depending on the application of the switching device.

[0011] Furthermore, the invention can also be further developed in such a way that the period of the clocked current or voltage signal (test signal) is varied depending on at least one operating parameter.

[0012] In a likewise preferred embodiment of the invention, it can also be provided that, before the switching contact is subjected to a switching current embodied as a clocked current signal, the switching contact is subjected to a non-clocked switching current of a fixed magnitude for a predetermined burn-off time and only then transitions to a clocked mode. This can ensure improved contact cleanliness without generating unnecessary power loss.

[0013] Finally, the object underlying the invention is achieved by a circuit arrangement for detecting the switching state of a switching contact of an electromechanical switching device. The switching device according to the invention is particularly suitable for carrying out the method according to the invention and comprises an electromechanical switching device with at least one switching contact and an evaluation and control unit for controlling the electromechanical switching device and for evaluating a switching current flowing through the switching contact of the electromechanical switching device.According to the invention, the evaluation and control unit is designed such that, during an operating phase for detecting the switching state of the switching contact, the switching contact can be subjected to a switching current designed as a clocked current signal and the switching current can be analyzed to determine whether the switching contact is in a closed switching state or in an open switching state.

[0014] The evaluation and control unit advantageously comprises a clock signal generating device, a coupling unit, and an evaluation unit, wherein the switching contact of the electromechanical switching device is connected in series with the clock signal generating device and the coupling unit in a common path between a switching voltage potential and ground. The circuit arrangement is configured such that, in an operating cycle for detecting the switching state of the switching contact, the switching contact can be subjected to a switching current embodied as a clocked current signal, and the switching current flowing in the common path can be analyzed by the evaluation unit to determine whether the switching contact is in a closed switching state (on) or in an open switching state (off).

[0015] According to a further preferred embodiment of the subject matter of the invention, it can be provided that the clock signal generating device comprises a control unit and a semiconductor switch which can be controlled via the control unit and is connected in series in the current path of the switching contact.

[0016] Alternatively, the clock signal generating device can also be formed by a clocked current-resistant signal output of a computer or a microprocessor.

[0017] Finally, the invention can also be advantageously implemented in such a way that the coupling unit is configured to ensure a current limitation in the path of the switching contact and to detect the clocked switching current flowing through the switching contact or the voltage applied across the switching contact and to supply it to the evaluation unit, so that the state detection of the switching contact can be carried out depending on the detected switching current signal.

[0018] In summary, the relay contacts or the switching contacts of the electromechanical switching device are loaded with a clocked signal. The so-called high level of the signal corresponds to the switching voltage and current, while the so-called low level is the low-energy or zero-energy state. Depending on the set pulse-pause ratio, the power loss per period is significantly reduced compared to a continuous signal over the same period. The output driver is preferably controlled and clocked by a microcontroller.

[0019] The invention and the technical environment are explained in more detail below with reference to the figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and combine them with other components and findings from the present description and / or figures. In particular, it should be noted that the figures and in particular the proportional dimensions shown are only schematic. The same reference symbols denote the same objects, so that explanations from other figures can be used as a supplement if necessary.

[0020] They show: Figure 1 shows a circuit arrangement for detecting the switching state of a switching contact of an electromechanical switching device in a possible embodiment of the invention in a schematic representation, and Figure 2 shows a circuit arrangement for detecting the switching state of a switching contact of an electromechanical switching device in a possible embodiment of the invention in comparison to the embodiment according to Figure 1 modified design of a circuit arrangement for detecting the switching state of a switching contact of an electromechanical switching device in a schematic representation.

[0021] Figure 1shows a circuit arrangement 10 for detecting the switching state of a switching contact 1 of an electromechanical switching device 100 in a possible embodiment of the invention in a schematic representation. The circuit arrangement 10 shown comprises an electromechanical switching device 100 in the form of a relay or a contactor or the like with a coil S, which can be supplied with a voltage via two coil connections A1, A2, and a switching contact 1. In addition, the circuit arrangement 10 comprises an evaluation and control unit 200 connected in series with the switching contact 1 in the current path P1 for controlling the electromechanical switching device 100 and for evaluating a switching current I switching flowing through the switching contact 1 of the electromechanical switching device 100.The evaluation and control unit 200 is set up in such a way that, during an operating phase in order to detect the switching state of the switching contact 1, the switching contact 1 can be supplied with a switching current I Schalt in the form of a clocked current signal, and the switching current I Schalt can be analyzed to determine whether the switching contact 1 is in a closed switching state or whether the switching contact 1 is in an open switching state. The test signal S Test generated for this purpose by means of a clock signal generating device 201 is in the form of a square wave signal and, in the example shown, has a pulse-pause ratio of approximately 1:1. During the pulse phase, a predetermined maximum switching current I Schalt_on is switched as a so-called high signal H, and during the pause phase T off, a predetermined minimum switching current I Schalt_off , for example in the form of a zero signal (so-calledLow signal L), in particular, a minimum switching current I Switch_off of 0 mA is switched, so that the power loss during the operating phase of the state detection of the switching contact 1 is reduced accordingly.

[0022] For example, if the switching voltage and current for a 24V relay with gold contacts are 24V and 1mA, the required power – with a continuously applied (non-clocked) signal – is 24V * 1mA = 24mW. For a clocked test signal with a 1:1 pulse-to-pause ratio (50%), the power loss would be only 25V * 1mA * 0.5 = 12mW (50%). The pulse-to-pause ratio and the period duration are adjusted depending on the application and can assume different values ​​during operation depending on the situation. Example sequence according to Figure 2 : Microcontroller clock output (control unit 2011) activeMOSFET (semiconductor switch 2012) switches on 24 V. When switching contact 1 of the relay (electromechanical switching device 100) is closed, a current flows through the input module (coupling unit 202) and switching contact 1. The microcontroller input module senses whether a high signal (H) or a low signal (L) is present (H if contact is closed, L otherwise). Microcontroller clock output (control unit 2011) inactive . MOSFET (semiconductor switch 2012) blocks.

[0023] This is the essential process within a switching cycle.

[0024] Figure 2 shows a compared to the embodiment according to Figure 1 modified embodiment of a circuit arrangement 10 for detecting the switching state of a switching contact 1 of an electromechanical switching device 100 in a schematic representation. In contrast to the embodiment according to Figure 1a specific structure of a circuit arrangement 10 is shown, in which an evaluation and control unit 200 has a microcontroller which has the functionality of a control unit 2011 for generating a clocked control signal for controlling or switching a semiconductor switch 2012 designed as a MOSFET or the like. A coupling unit 202 is connected between the semiconductor switch 2012 and the switching contact 1, which coupling unit essentially combines the functionality of current limitation as well as the functionality of signal detection and forwarding. During an operating phase of the switching state detection of the switching contacts 1, a corresponding control signal is generated for the semiconductor switch 2012, so that a correspondingly clocked signal is generated via the semiconductor switch 2012 in the common current path with the switching contact 1 - orThe current path is closed and interrupted accordingly, corresponding to the control signal of the semiconductor switch 2012. If the switching contact 1 is closed accordingly, it is supplied with a correspondingly clocked switching current, and a switching current I switching with reduced power loss is detected by the coupling unit 202 and forwarded to the evaluation unit 203 in the microcontroller for appropriate analysis. If the switching contact 1 is opened accordingly and the common signal path P1 is thus interrupted, no switching current I switching is detected by the coupling unit 202, and this information is forwarded to the evaluation unit 203 within the microcontroller for appropriate analysis.

[0025] The invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood in such a way that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a priority. List of reference symbols

[0026] 1 Switching contact 10 Circuit arrangement 100 Electromechanical switching device 200 Evaluation and control unit 201 Clock signal generation device 2011 Control unit 2012 Semiconductor switch 202 Coupling unit 203 Evaluation unit U Switching voltage (via switching contact) I Switching current (through switching contact) T Period Period duration (control signal or switching signal)

Claims

1. A method for detecting the switching state of at least one contact pair of a switching contact (1) of an electromechanical switching device (100), wherein during an operational phase for detecting the switching state - the switching contact (1) is applied with a switching current (I_Schalt), and - the switching current (I_Schalt) is analyzed by means of an evaluation unit (2) as to whether the switching contact (1) is in a closed switching state or in an open switching state, that the switching contact (1) is applied with a switching current (I_Schalt) which is formed as a pulsed voltage or current signal, characterized in that the switching contact (1) is applied with a switching current (I_Schalt), which is formed as a pulsed square-wave signal with a variable pulse-pause ratio.

2. The method according to claim 1, characterized in that the switching contact (1) is applied with a switching current (I_Schalt), which is formed as a pulsed square-wave signal, wherein during the pulse phase (T_on) a predetermined maximum switching current (I_Schalt_on) is switched, and wherein during the pause phase (T_off) a predetermined minimum switching current (I_Schalt_off), in particular a minimum switching current (I_Schalt_off) of 0 mA, is switched.

3. The method according to claim 1, characterized in that the pulse-pause ratio is varied depending on at least one operating parameter.

4. The method according to any one of the preceding claims 1-3, characterized in that the pulse-pause ratio is preset such that different speeds for detecting the switching state of the switching contact (1) can be specified.

5. The method according to any one of the preceding claims, characterized in that the period duration (T_periode) is varied depending on at least one operating parameter.

6. The method according to any one of the preceding claims, characterized in that before the switching contact (1) is applied with a switching current (I_Schalt), which is formed as a pulsed current signal, the switching contact (1) is applied with a non-pulsed switching current (I_Schalt) of fixed magnitude for a predetermined burn-off time.

7. A circuit arrangement (10) for detecting the switching state of a switching contact (1) of an electromechanical switching device (100), comprising - an electromechanical switching device (100) with at least one switching contact (1), and - an evaluation and control unit (200) for driving the electromechanical switching device (100) and for analyzing a switching current (I_Schalt) flowing through the switching contact (1) of the electromechanical switching device (100), wherein the evaluation and control unit (200) is arranged such that, during an operational phase for detecting the switching state of the switching contact (1), the switching contact (1) can be applied with a switching current (I_Schalt) which is formed as a pulsed current signal, and the switching current (I_Schalt) can be analyzed to determine whether the switching contact (1) is in a closed switching state or in an open switching state, characterized in that the switching contact (1) is applied with a switching current (I_Schalt), which is formed as a pulsed square-wave signal with a variable pulse-pause ratio.

8. The circuit arrangement (10) according to claim 7, characterized in that - the evaluation and control unit (200) comprises: - a clock-signal generating device (201), - a coupling unit (202), and - an evaluation unit (203), wherein the switching contact (1) of the electromechanical switching device (100) is connected in series in a common path (P1) between a switching voltage potential (U) and ground (GND) with the clock-signal generating device (201) and the coupling unit (202), and wherein the circuit arrangement (10) is arranged such that, in an operational cycle for detecting the switching state of the switching contact (1), the switching contact (1) can be applied with a switching current (I_Schalt) which is designed as a pulsed current signal, and the switching current (I_Schalt) flowing in the common path (P1) can be analyzed by the evaluation unit (203) to determine whether the switching contact (1) is in a closed switching state or in an open switching state.

9. The circuit arrangement (10) according to claim 7 or 8, characterized in that the clock-signal generating device (201) comprises a control unit (2011) and a semiconductor switch (2012) that can be driven via the control unit (2011).

10. The circuit arrangement (10) according to any one of the preceding claims 7-9, characterized in that the coupling unit (202) is configured to ensure a current limitation in the path (P1) and to detect the pulsed switching current (I_Schalt) flowing through the switching contact (1) or the voltage (U_Schalt) present across the switching contact (1) and to supply it to the evaluation unit (203).