Solid state switch for railway equipment

Abstract

A solid state switch for railroad equipment having an isolation boundary galvanically isolating a first zone from a second zone, a switch for switching a current in the first zone between a switch input terminal and a switch output terminal, a relay to receive an operating signal indicating whether to switch the switch and at least two channels. Each channel has a switch module in the first zone that includes a switch module input terminal, a switch module output terminal and a semiconductor switch. Each channel has a programmable device in the second zone with an input terminal, a switch driving terminal for driving the switch module, a monitoring terminal for monitoring the switch module, a control connection with a photovoltaic isolator for bridging the isolation boundary, and a monitoring circuit connecting the monitoring terminal to the switch module input terminal and output terminal.

Description

TITLE SOLID STATE SWITCH FOR RAILWAY EQUIPMENT BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION

[0001] The present disclosure relates to a solid-state switch and, in particular, a solidstate switch for railway equipment. 2. DESCRIPTION OF THE RELATED ART

[0002] An electromechanical relay is an electrically operated switch that is often usedfor railway equipment. An electro-mechanical relay requires regular testing and maintenance of its moving parts to confirm functionality as these parts experience wear over time and can thus fail to operate properly. Mechanical relays can be expensive due in part to a time- consuming assembly process. Mechanical relays are also subject to failure if the contacts arc when opening or closing due to release of stored energy in inductive loads such as a railroad switch machine motor. While there are solid state relays, these devices have not been typically used for the vital functions associated with railway equipment because of failure modes in their design that prevent them from being able to meet safety requirements. Accordingly, there is a need in the art for a solid state switch that can be used with railway equipment. BRIEF SUMMARY OF THE INVENTION

[0003] The present invention is a solid state switch for railway equipment and amethod for operating a solid state switch. According to one aspect, a solid state switch is provided, in particular for railroad equipment, comprising: an isolation boundary, the isolation boundary galvanically isolating a first zone from a second zone; at least one switch, each switch being adapted to switch a current in the first zone between a switch input terminal and a switch output terminal; at least one relay operating signal input terminal adapted to receive an operating signal, the operating signal indicating whether to switch the at least one switch; at least two channels, each channel comprising: for each switch a switch module in the first zone, each switch module comprising a switch module input terminal, a switch module output terminal and a semiconductor switch adapted to switch the current between the switch module input terminal and the switch module output terminal; at least one programmable device in the second zone, the at least one programmable device comprising an input terminal for receiving the operating signal, at least one switch driving terminal for driving the switch module of the respective channel and at least one monitoring terminal for each switch module for monitoring the respective switch module; a control connection 1 21883881.v2-7 / 14 / 25connecting the switch driving terminal of the at last one programmable device and a control terminal of the semiconductor switch, wherein the control connection comprises at least one first photovoltaic isolator for bridging the isolation boundary; at least one monitoring circuit for each switch module connecting the respective monitoring terminal of the at least one programmable device, wherein the monitoring circuit comprises at least one galvanic isolator for bridging the isolation boundary, wherein the monitoring circuit connects to at least one of the switch module input terminal and the switch module output terminal.

[0004] Further embodiments may relate to one or more of the following features,which may be combined in any technical feasible combination: for each channel, the at least one programmable device is adapted to inject a test signal on one side of a switch module of a switch and to measure a voltage on the other side of the same switch module in order to determine whether the semiconductor switch is in an open or closed state; the programmable devices of each channel is an FPGA; for each switch, the switch modules of the respective channels are connected in series, such that the semiconductor switches of the respective switch modules of each switch are connected in series; the semiconductor switch is a field effect transistor, in particular a metal oxide semiconductor field effect transistor, wherein the control terminal is a gate of the field effect transistor; the monitoring circuit of a respective channel connects the programmable device, in particular the monitoring terminal of the programmable device, to both, the switch module input terminal and the switch module output terminal of the same channel; the semiconductor switch of the switch module of the first channel and the semiconductor switch of the switch module of the second channel are arranged in opposite directions, wherein, in particular the drains of both semiconductor switches or the sources of both semiconductor switches are coupled; the at least one galvanic isolator of the monitoring circuit of each channel comprises respectively a photovoltaic isolator, a secondary side of the galvanic isolator of the monitoring circuit of the first channel is electrically connected between the first input of an isolation amplifier and the switch module input terminal of the switch module of the first channel, the switch module input terminal having the same electrical potential as the switch input terminal, and a secondary side of the galvanic isolator of the monitoring circuit of the second channel is electrically connected between the first input of the isolation amplifier and the switch module output terminal of the switch module of the second channel, the switch module output terminal having the same electrical potential as the switch output terminal, the second input of the isolation amplifier being coupled to the switch module output terminal of the switch module of the first channel; the at least one galvanic isolator of the monitoring circuit is selected from 2 21883881.v2-7 / 14 / 25the group consisting of a capacitor, a second photovoltaic isolator, and an isolation amplifier; the programmable device is adapted to apply a test signal to the monitoring circuit; and / or the test signal is a rectangular signal.

[0005] According to another aspect, a railroad equipment is provided comprising asolid state switch, the solid state switch comprising: an isolation boundary, the isolation boundary galvanically isolating a first zone from a second zone; at least one switch, each switch being adapted to switch a current in the first zone between a switch input terminal and a switch output terminal; at least one relay operating signal input terminal adapted to receive an operating signal, the operating signal indicating whether to switch the at least one switch;at least two channels, each channel comprising: for each switch a switch module in the first zone, each switch module comprising a switch module input terminal, a switch module output terminal and a semiconductor switch adapted to switch the current between the switch module input terminal and the switch module output terminal; at least one programmable device in the second zone, the at least one programmable device comprising an input terminal for receiving the operating signal, at least one switch driving terminal for driving the switch module of the respective channel and at least one monitoring terminal for each switch module for monitoring the respective switch module; a control connection connecting the switch driving terminal of the at last one programmable device and a control terminal of the semiconductor switch, wherein the control connection comprises at least one first photovoltaic isolator for bridging the isolation boundary; at least one monitoring circuit for each switch module connecting the respective monitoring terminal of the at least one programmable device, wherein the monitoring circuit comprises at least one galvanic isolator for bridging the isolation boundary, wherein the monitoring circuit connects to at least one of the switch module input terminal and the switch module output terminal.

[0006] According to another aspect, a method for operating a solid state switch isprovided , the solid state switch comprising: an isolation boundary, the isolation boundary galvanically isolating a first zone from a second zone; at least one switch, each switch being adapted to switch a current in the first zone between a switch input terminal and a switch output terminal; at least one relay operating signal input terminal adapted to receive an operating signal, the operating signal indicating whether to switch the at least one switch; at least two channels, each channel comprising: for each switch a switch module in the first zone, each switch module comprising a switch module input terminal, a switch module output terminal and a semiconductor switch adapted to switch the current between the switch module input terminal and the switch module output terminal; at least one programmable 3 21883881.v2-7 / 14 / 25device in the second zone, the at least one programmable device comprising an input terminal for receiving the operating signal, at least one switch driving terminal for driving the switch module of the respective channel and at least one monitoring terminal for each switch module for monitoring the respective switch module; a control connection connecting the switch driving terminal of the at last one programmable device and a control terminal of the semiconductor switch, wherein the control connection comprises at least one first photovoltaic isolator for bridging the isolation boundary; at least one monitoring circuit for each switch module connecting the respective monitoring terminal of the at least one programmable device, wherein the monitoring circuit comprises at least one galvanic isolator for bridging the isolation boundary, wherein the monitoring circuit connects to at least one of the switch module input terminal and the switch module output terminal, the method comprising: upon receiving by each programmable device of an operating signal, providing by each programmable device a switch drive signal to the switch modules; for each channel, the respective programmable device determining for at least one switch module of the channel whether the semiconductor switch is in an open or closed state by injecting a test signal into the monitoring circuits and reading the monitoring circuits; in response of detection of a failure of a switch module of a switch by one of the programmable devices informing the programmable device of the other channels about this failure; and in response to receiving an information about a failure of a first switch module of a switch by a programmable device of another channel, deactivating, by the programmable device, a second switch module of the switch.

[0007] According to an embodiment, the method further comprising determining forat least one switch module of the channel whether the semiconductor switch is in an open or closed state includes injecting the test signal on one side of the respective switch module and measuring on the other side of the switch module. Further advantages, features, aspects and details are evident from the dependent claims, the description and the drawings. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0008] The present invention will be more fully understood and appreciated byreading the following Detailed Description in conjunction with the accompanying drawings, in which:

[0009] FIG. 1 is a schematic of the overall architecture of a solid state switchaccording to an embodiment of the present invention;

[0010] FIG. 2 is a schematic of an electrical circuit of the solid state switch of FIG. 1;

[0011] FIG. 3 is a schematic of the solid state switch of FIGS. 1 and 2;4 21883881.v2-7 / 14 / 25

[0012] FIG. 4 is a schematic of the electric circuit for a switch module;

[0013] FIG. 5 is a schematic of the electric circuit for a switch; and

[0014] FIG. 6 is a schematic of a solid state switch according to another embodimentbeing a variant of FIG.1. DETAILED DESCRIPTION OF THE INVENTION

[0015] Referring to the figures, wherein like numerals refer to like parts throughout,there is seen in FIG.1 a solid state switch. A solid state relay (SSR) or a solid state switch is an electronic switching device that switches on or off an electrical connection between at least one pair of contacts when an external voltage is applied across its control terminals. The connection between a pair of contacts can be a normally open (NO) or a normally closed (NC) switch. The switch may be a normally open contact (NO) when current flow is inhibited between the pair of contacts when the electromechanical relay is in its non-actuated state, or may be a normally closed (NC) switch when a current flow is enabled between the pair of contacts when the relay is in its non-actuated state. A solid state switch requires less maintenance or testing and has lower assembly costs. Further, there are no moving parts subject to vibration. Further, substantially no minimum contact current is required and no arcing is possible.

[0016] With respect to safety functions, vital relays must comply with safetystandards, in particular have a particular safety integrity level (SIL). The InternationalElectrotechnical Commission′s (IEC) standard IEC 61508 defines SIL using requirementsgrouped into two categories: systematic safety integrity and hardware safety integrity. A device or system must meet the requirements for both categories to achieve a specific SIL. In order to achieve a given SIL, the device must meet targets for the maximum probability of dangerous failure and a minimum safe failure fraction. According to an embodiment, the solid state switch of the present invention achieves the SIL4 level. According to another embodiment, the solid-state switch is a fail-safe solid state switch. The solid state switch may be adapted to switch voltages between 0V and 230V, and switch currents between 0 A and 60 A.

[0017] FIG. 1 shows the overall architecture of a solid state switch 1 according to anembodiment. The dashed line 3 indicates an isolation boundary. The isolation boundary isolates galvanically a first zone 3a from a second zone 3b. In other words, no direct current flow is permitted between the first zone 3a and the second zone 3b. A voltage source 5 powers the solid state switch 1. The voltage source 5 provides also the operating signal whether to switch the pair of contacts of the solid state switch 1. The voltage source can 5 21883881.v2-7 / 14 / 25provide AC or DC power. In other embodiments, it can be also be AC or DC return / ground.The voltage source 5 provides a ′high′ or ′low′ signal for switching the pair of contacts ofsolid state switch 1. The voltage source 5 is connected to a relay operating signal input terminal 6.

[0018] Further, FIG. 1 shows a DC / DC converter 7 adapted to power the internalcircuitry of solid state switch 1. The input of the DC / DC converter 7 is connected to the voltage source 5. The output of the DC / DC converter 7 powers different devices of solid state switch 1. In an embodiment, the DC / DC converter 7 is continuously powered by a separate conductor 10. The conductor is connected to a separate power source (not shown). The conductor 10 is optional. The failure rate is further reduced, when using the conductor 10 connected to a separate, additional power source. For example, a plurality of solid state switches 1 can be powered via a conductor 10 using the same power source. In an embodiment, the solid-state relays can be daisy chained.

[0019] Further, there is provided a threshold device 12. The threshold device 12 isadapted to forward the operating signal only if the operating signal received from the voltagesource 5 exceeds a predetermined threshold. According to an embodiment, the threshold isset in firmware or software. In other embodiments, the threshold is set with an analog circuit. In an example, the threshold is independently monitored by two full independent and isolated channels and cross-checked between channels to confirm the threshold has been met.

[0020] Solid state switch 1 comprises at least two programmable devices 14′, 14″.The programmable devices are powered from the DC / DC converter 7. According toembodiments, the programmable devices 14′, 14″ are respectively a FPGA (Fieldprogrammable gate array). An FPGA is an integrated circuit that can be programmed or reprogrammed after manufacturing. It consists of an array of programmable logic blocks and interconnects that can be configures, in particular, to perform various functions. Also other types of programmable devices can be used, for example processors, ASICS, CPLD, EEPROMs etc.

[0021] The programmable devices 14′, 14″ are adapted to communicate with eachother via a signal connection 16. The at least two programmable devices are adapted to cross- check each other, for example via the signal connection 16.

[0022] Further, the programmable devices 14′, 14″ are respectively adapted to receivethe operating signal from the voltage source 5, in particular via the threshold device 12. Forexample, the programmable devices 14′, 14″ are respectively adapted to receive the operatingsignal at an input terminal 14a′, 14a″. In an embodiment, the programmable devices 14′, 14″6 21883881.v2-7 / 14 / 25are adapted to cross check, in particular via the signal connection 16, whether they have received the same signal from the voltage device 5 and / or the threshold device 12.

[0023] The programmable devices 14′, 14″ further comprise at least one switchdriving terminal 14b′, 14b″ for driving a switch module of a switch and at least onemonitoring terminal 14c′, 14c″ for each switch module for monitoring the respective switchmodule. Thus, each programmable device 14′, 14″ comprises, for each switch, a respectiveswitch driving terminal. In other words, in FIG. 1, each programmable device 14′, 14″comprises three switch driving terminals 14b′, 14b″.

[0024] The programmable devices 14′, 14″ are adapted to independently read thevoltage input, in particular of an operating signal, that dictates whether or not the contacts ofthe relay should change states. Further, the programmable devices 14′, 14″ are adapted todrive the switch driving terminal 14b′, 14b″, in particular based or depending on the readvoltage input, and to drive the monitoring circuits or the at least one monitoring terminal14c′, 14c″, as it will be explained further below. In other words, the programmable devices14′, 14″ are adapted to generate a switch drive signal based on the read or received operatingsignal. In an embodiment, they only drive the switch driving terminals 14b′, 14b″ in case theprogrammable devices 14′, 14″ have cross-checked that they have received the same signalfrom the voltage device 5 and / or the threshold device 12, for example the same ′high′ signal.

[0025] Solid state switch 1 comprises at least two channels A, B. For example, thefirst channel A comprises first programmable device 14′ and the second channel comprisesthe second programmable device 14″. In other words, each programmable device 14′, 14″defines a control channel for controlling and operating a switch in parallel. In other words,each programmable device 14′, 14″ controls and operates each switch, in particularindependently.

[0026] In the example shown in FIG. 1, solid state switch 1 is provided with acommon contact 18, a normally open (NO) output contact 20, and a normally closed (NC) output contact 22.

[0027] In case when there is a signal provided by the voltage source 5, which is inparticular above the threshold provided by the threshold device 12, then a current flow is enabled between the common contact 18 and the NO output contact 20, and a current flow is inhibited between the common contact 18 and the NC output contact 22. In case when there is no signal provided by the voltage source 5 or when it is below the threshold provided by the threshold device 12, then a current flow is enabled between the common contact 18 and 7 21883881.v2-7 / 14 / 25the NC output contact 22, and a current flow is inhibited between the common contact 18 and the N0 output contact 20.

[0028] It should be noted that it is not necessary to have both a NO output contact anda NC output contact. The solid-state relay may have an arbitrary number of NO output contacts and an arbitrary number of NC output contacts. For example, the solid-state relay may have only one NC output contact or only one NO output contact.

[0029] FIG. 1 further discloses, as an example, a power switch 24, which iselectrically connected at its input terminal 24a with the common contact 18. The power switch 24 has further an output terminal 24b. The power switch is provided to activate or deactivate the function of the solid state switch 1. According to embodiments, the power switch 24 provides an independent and secondary shutdown mechanism if an electronic failure is detected on the normally open circuitry.

[0030] Further, solid state switch 1 comprises a normally open switch 26. The NOswitch 26 comprises a NO switch input terminal 26a and a NO switch output terminal 26b. The NO switch input terminal 26a is electrically connected between the output terminal 24b of the power switch 24. The NO switch output terminal 26b is electrically connected with the NO output contact 20.

[0031] Solid state switch 1 further comprises a normally closed switch 28. The NCswitch 28 comprises a NC switch input terminal 28a and a NC switch output terminal 28b. The NC switch input terminal 28a is electrically connected between the output terminal 24b of the power switch 24. The NC switch output terminal 28b is electrically connected with the NC output contact 22.

[0032] In some embodiments, which may be combined with other embodimentsdisclosed herein the power switch 24 is omitted. In other words, the common contact 18 is directly connected to the switch input terminals 26a, 28a of the NO switch 26 and / or the NC switch 28.

[0033] Another embodiment is shown in FIG. 6, which is a variant of FIG. 1. In thiscase, the NC switch input terminal 28a is electrically connected between the common contact18. Thus, even in case of failure of one or both programmable devices 14′, 14″, which resultsin an open power switch 24, there would be still an electrical connection between the common contact 18 and the NC output contact 22.

[0034] Referring back to FIG. 1, each of the programmable devices 14′, 14″ controlsthe power switch 24 and the respective switches 26, 28, in particular via control connections30′, 30″. The programmable devices 14′, 14″ is adapted to control the switches 24, 26, 288 21883881.v2-7 / 14 / 25simultaneously, for example by the same current, or independently. As, according to embodiments, the switches 24, 26, 28 are controlled independently, each switch 24, 26, 28 isconnected with an individual control connection 30′, 30″ to each of the programmabledevices 14′, 14″. For example, during operation of the solid state switch, as long as theprogrammable devices 14′, 14″ are powered, the control the power switch 24 to be closed.The switches 24, 26 are then controlled in response to the received operating signal at therespective input terminals 14a′, 14a″.

[0035] Further, in an embodiment, each set of contacts 18, 20, 22 or switches 24, 26,28 could be independent. Since each set of contacts or switch 24, 26, 28 can be in an embodiment fully isolated and independent, each set of contacts or switch 24, 26, 28 can switch a different source or the same source to provide current sharing between channels.

[0036] The control connections 30′ are assigned to the first channel A and the controlconnections 30″ are assigned to the second channel B.

[0037] Further, each of the programmable devices 14′, 14″ monitors the switches 24,26, 28 via respective a monitoring circuits 24c, 24c′, 24c″, 26c, 26c′, 26c″, 28c, 28c′, 28c″.

[0038] FIG. 2 shows schematically as an electrical circuit of the solid state switch 1including the switches 24, 26, 28. Each of the switches 24, 26, 28 comprises respective monitoring circuits 24c, 26c and 28c. The monitoring circuits provide information about the state of the respective switches 24, 26, 28 as it will be later explained.

[0039] FIG. 3 shows a more detailed view of solid state switch 1 of FIG. 1 and 2. Thesame reference signs relate to the same features as in FIG.1 and 2.

[0040] The isolation boundary 3 on both sides relates to the same isolation boundary3. However, in order to simplify the drawings the output connections of the respective switches have been drawn towards the right and the left side.

[0041] Each switch 24, 26, 28 comprises respectively at least two switch modules24d′, 24d″, 26d′, 26d″, 28d′, 28d″ which comprise respectively at least one transistor oranother type of solid state switch. for switching the current between the respective switch input terminal 24a, 26a, 28a and the respective output terminal 24b, 26b, 28b. The number ofswitch modules 24d′, 24d″, 26d′, 26d″, 28d′, 28d″ corresponds to the number ofprogrammable devices 14′, 14″. Each switch modules 24d′, 24d″, 26d′, 26d″, 28d′, 28d″ of aswitch 24, 26, 28 is assigned to a different channel. For example the switch modules 24d′,26d′, 28d′ are assigned to the first channel A controlled by the first programmable device 14′and the switch modules 24d″, 26d″, 28d″ are assigned to the second channel B controlled bythe second programmable device 14″.9 21883881.v2-7 / 14 / 25

[0042] Within each switch 24, 26, 28, the respective switch modules 24d′, 24d″, 26d′,26d″, 28d′, 28d″, in particular the transistor of the respective switch modules 24d′, 24d″, 26d′,26d″, 28d′, 28d″, are connected in series between the respective switch input terminal 24a,26a, 28a and the respective switch output terminal 24b, 26b, 28b. In other words, the switch module of a first channel A is connected in series with the switch module of a second channel B.

[0043] According to an embodiment, the switch modules 24d′, 24d″ for the powerswitch 24 are of the same type, the switch modules 26d′, 26d″ of the NO switch are of thesame type, and the switch modules 28d′, 28d″ of the NC switch are of the same type. Thesame type means that for each switch 24, 26, 28, the respective semiconductor switch of theswitch modules 24d′, 24d″, 26d′, 26d″, 28d′, 28d″ for switching the current between theirrespective input terminal 24f′, 24f″, 26f′, 26f″, 26f′, 26f″ and the respective output terminal24g′, 24g″, 26g′, 26g″, 28g′, 28g″ is of the same type in order to provide the same functionupon activation.

[0044] The control connections 30′, 30″ between the programmable devices 14′, 14″and the respective switch modules 24d′, 24d″, 26d′, 26d″, 28d′, 28d″ include respectively agalvanic isolator in a galvanic isolator group 24e, 26e, 28e, for example in form of photovoltaic isolators. Alternatively, opto-isolators may be used in each galvanic isolatorgroup. It should be noted that the control connections 30′, 30″ between each programmabledevices 14′, 14″ and each of the switches 24, 26, 28 are independent, even if they have thesame control connection 30′ or 30″ respectively. In other words, each galvanic isolator group24e, 26e, 28e provides for each control connection 30′, 30″ a separate galvanic isolator inform of a photovoltaic isolator. For example, in case of two channels A, B, each galvanic isolator group 24e, 26e, 28e includes two photovoltaic isolators, one for each channel A, B. The galvanic isolator, in particular the photovoltaic isolator bridges the isolation boundary.

[0045] A photovoltaic isolator (PVI) and the opto-isolator are electronic componentsthat transfer electrical signals between two isolated circuits by using light. The PVI and the opto-isolator comprise respectively a pair of a light emitting diode (LED) and a light detector. The photovoltaic isolator includes as a light detector a photovoltaic diode. The photovoltaic isolator has the advantage that the output behaves like a power source.

[0046] The opto-isolator comprises as a light detector a phototransistor.

[0047] The PVI or the opto-isolator is provided in a light-tight housing. The lightemitted by the LED is adapted to be captured by the light detector of the respective pair. 10 21883881.v2-7 / 14 / 25

[0048] According to embodiments, each switch module 24d′, 24d″, 26d′, 26d″, 28d′,28d″ is controlled by a respective monitoring connections 24c, 26c, 28c. Each monitoringconnection 24c, 26c, 28c comprises for each channel A, B a monitoring circuit 24c′, 24c″,26c′, 26c″, 28c′, 28c″. The monitoring circuits 24c′, 26c′, 28c′ of the first channel A areadapted to monitor the respective switch module 24d′, 26d′, 28d′ of the first channel A. Themonitoring circuits 24c″, 26c″, 28c″ of the second channel B are adapted to monitor therespective switch module 24d″, 26d″, 28d″ of the second channel B. The monitoring circuitsof the first channel A are connected to the first programmable device 14′ and the monitoringcircuits of the second channel B are connected to the second programmable device 14″.

[0049] In the embodiment of FIG. 3, for that purpose each monitoring circuit 24c′,24c″, 26c′, 26c″, 28c′, 28c″ is electrically connected to the input terminals 24f′, 24f″, 26f′,26f″, 28f′, 28f″ and output terminals 24g′, 24g″, 26g′, 26g″, 28g′, 28g″ of the respectiveswitch modules via respective galvanic isolators 24h′, 24i′, 24h″, 24i″, 26h′, 26i′, 26h″, 26i″,28h′, 28i′, 28h″, 28i″. In some embodiments, in case the same electrical potential is used acommon connection to an input / output terminal may be used. For example the outputterminal 24g′ has the same electrical potential as the input terminal 24f″, so that only a singlegalvanic isolator may be used, combining the galvanic isolators 24i′ and 24h″. The multipleswitches 24, 26, 28 provide DC and AC blocking when the connections are not intended to be made and test signals being injected via the monitoring circuits across each switch module24d′, 24d″, 26d′, 26d″, 28d′, 28d″ are used for detecting a failure of a switch module as it willbe explained below.

[0050] The programmable devices 14′, 14″ are adapted to emit via the monitoringcircuit a predefined test signal to the input terminals 24f′, 24f″, 26f′, 26f″, 28f′, 28f″ of theswitch modules 24d′, 24d″, 26d′, 26d″, 28d′, 28d″, for example a square signal, a sinus waveor a pulse signal with one or more pulses. , and to measure a signal at the output terminals24g′, 24g″, 26g′, 26g″, 28g′, 28g″ of the respective switch modules. The test signal used totest the state of the switch modules 24d′, 24d″, 26d′, 26d″, 28d′, 28d″ via a galvanic isolator24h′, 24i′, 24h″, 24i″, 26h′, 26i′, 26h″, 26i″, 28h′, 28i′, 28h″, 28i″, for example a PVI or acapacitor, to generate a differential voltage across the respective switch module to detect if its open or closed. Because the energy passing through the contacts 18, 20, 22 is single ended, the differential voltage used across the switch module does not impact the energy passing through the set of contacts 18, 20, 22. 11 21883881.v2-7 / 14 / 25

[0051] Thus, according to embodiments the switches 24, 26, 28 could be blocking forthe currents passing through the set of contacts, but the test signals may still be used to determine whether the switches are correctly operating.

[0052] For example, for the first channel A, the first programmable devices 14′ isadapted to emit via the sub-monitoring circuits 24c′, 26c′, 28c′ the predefined test signal tothe input terminals 24f′, 26f′, 28f′ and to measure the signals at the respective outputterminals 24g′, 26g′, 28g′ of the switch modules. The same applies for the second channel B.The form and / or voltage of the test signal may have no relation to the current / voltage passingthrough the contacts 18, 20, 22 or the input terminals 24f′, 24f″, 26f′, 26f″, 28f′, 28f″ andoutput terminals 24g′, 24g″, 26g′, 26g″, 28g′, 28g″ of the respective switch modules.

[0053] FIG. 4 shows a more detailed view of a switch module 32 and its connectionsof a single channel. Such a switch module may be used as switch module 24d′, 24d″, 26d′,26d″, 28d′, 28d″ in one of the channels. The same letters after the number indicate the samefunctions as in FIG.3. The principal difference between the power switch 24 or NO / NC switches 26, 28 is the type of semiconductor switch used in the switch modules in order to provide a NO or NC switch. For example, the input terminal 32f is connected, in an embodiment to a common contact or pole or to an output of another switch module as shown in FIG.3. The output terminal 32g is connected, for example, to another switch module as shown in FIG.3 or to a NO or NC output contact.

[0054] The photovoltaic isolator (PVI) 32e has a primary side 32k, which isconnected via a control connection 30 to a switch driving terminal of a programmable device,for example the switch driving terminal 14b′, 14b″ of one of the programmable devices 14′,14″. Thus, the PVI 32e bridges the isolation boundary, in particular by maintaining thegalvanic isolation. The primary side 32k comprises a light source in form of a LED (light emitting diode). Further, the PVI 32e has a secondary side 32m, which is provided on the other side of the isolation boundary 3. The secondary side 32m includes a light detector, for example a photovoltaic diode. The PVI is provided in a light-tight housing. The light emitted by the LED is adapted to be captured by the light detector. Then a corresponding current is generated on the secondary side 32m of the control connection 30, which is connected to the switch module 32d. In other words, the control connection 30 is used to control the switch module 32d and to switch between the open and closed state, which includes the PVI 32e.

[0055] The PVI 32e provides an isolated voltage source to the switch module 32d, inparticular the semiconductor switch 32n of the switch module, but is unable to source any significant current that under failure mode could be supplied to the load going through the 12 21883881.v2-7 / 14 / 25relay pole, for example via the input terminal 32f or output terminal 32g. In embodiments, the PVI is only capable to source microamperes of current, which is sufficient to energize a MOSFET (metal oxide semiconductor field effect semiconductor) but not railroad equipment.In other words, the programmable device 14′, 14″ enables / disables the PVI, which opens orcloses the switch module including a semiconductor switch.

[0056] The switch module 32d includes a semiconductor switch 32n, for example afield effect semiconductor (FET), in particular a MOSFET. The semiconductor switch comprises a control terminal, in particular a gate, for controlling the operation of the semiconductor switch.

[0057] The MOSFET may be a PFET, NFET, or JFET for the switch modules of thepower switch 24, a PFET, NFET, or JFET for the switch modules of the NO switches 26, anda PFET, NFET, or JFET for the switch modules of the NC switches 28.

[0058] The switch module 32d further includes, optionally, a surge protection 32o.The surge protection 32o is connected between the source and the drain of the semiconductor switch 32n and / or connected between the input terminal 32f and the output terminal 32g of the switch module 32d. The surge protection 32o provide protection against lightning / transients.

[0059] The galvanic isolators 32h, 32i shown in FIG. 4 are capacitors, for example Ycapacitors. In other embodiments, also PVI may be used. Y capacitors are for example defined in the norm IEC / EN 60384-14. The galvanic isolators 32h, 32i provide an electrical isolation between the digital circuitry and the isolated signal that is passing through the relay pole. In other words, the monitoring circuit 32c comprises the galvanic isolators 32h, 32i.

[0060] As already stated above, the monitoring circuit 32c is adapted to be providedwith an isolated test signal, for example generated by the programmable devices 14′, 14″. Thetest signal, for example a square signal, is injected through the galvanic isolator 32h to the input terminal 32f of the switch module 32d. The test signal is then routed through the semiconductor switch 32n, for example a MOSFET, and then read via the output terminal 32g, a second galvanic isolator 32i as a feedback signal. The galvanic isolators 32h, 32i are bridging the isolation boundary 3. This allows a closed loop testing of the respective semiconductor switch 32n to determine if the switch is open or closed and to detect a failure. The signal path is critical in that it is single ended, meaning the ground reference does not go to the isolated relay pole net (e.g. the common contact 18, NO output contact 20 and the NC output contact 22). The test signal injected to test the switches is independent from the current / voltage passing through the set of contacts 18, 20, 22. This avoids being able to 13 21883881.v2-7 / 14 / 25falsely energize whatever load is connected to the relay pole. There is no shared ground reference between the isolated poles (e.g. the common contact 18, NO output contact 20 andthe NC output contact 22) and the (test) signals of the programmable devices 14′, 14″. Thisallows monitoring of the FET or MOSFET position without impacting the isolated pole and load.

[0061] As described above, the solid state switch includes several channels A, B.According to embodiments, in case the programmable device 14′ of a first channel A detectsa failure of a switch module 24d′, 26d′, 28d′ of the first channel A in a switch 24, 26, 28, itcan inform the programmable device 14″ of the second channel B, in particular via the signalconnection 16 shown in FIG. 1, and the second programmable device 14″ can react on thisinformation, and for example actuate the respective switch 24d″, 26d″, 28d″ of the secondchannel A in the same switch 24, 26, 28, which is in particular connected in series with the failed switch. In other words, the duplication and reaction on faults enable a fast reaction. According to embodiments, when a switch is tested to be in the wrong state theprogrammable devices 14′, 14″ will react by opening all of the other switches. This avoidsfalsely allowing energy to pass from common contact 18 to the NO contacts 20 or NC contacts 22 in the event of an electronic component failure.

[0062] According to the disclosure, the status of the solid state switch can be remotelymonitored but does not require the use of optical fibers. Further, power can be also daisy- chained from one device to another and therefore reduce the number of power wires or cables necessary to power the devices. Further, it can replace an inductive relay coil with analog design that guarantees it will not energize without sufficient energy applied, even under failure modes.

[0063] FIG. 5 shows another embodiment of a schematic electric circuit for a switch.The general structure of the switch may be a power switch, a NC switch or a NO switch. The only difference between these switches is the type of semiconductor switch used. The same letters after the number indicate the same functions as in FIGS.3 and 4. The switchcomprises two switch modules 34d′, 34d″ connected in series. The switch may be connectedvia the input terminal 34f′ of the first switch module 34d′ to a common contact or to anotherswitch. The output terminal 34g″ of the second switch module 34d″ is connected to anotherswitch or a NO or NC contact. As for the previous switches the programmable devices 14′,14″ provide a command for actuating the switch via the control connections 30′, 30″respectively. The galvanic isolators 34e′, 34e″ are of the same type as in FIG. 4, namely theyare photovoltaic isolators. 14 21883881.v2-7 / 14 / 25

[0064] The monitoring connections 34c comprises a first galvanic isolator 34h′, inparticular in form of a photovoltaic isolator, a second galvanic isolator 34h″, in particular inform of a photovoltaic isolator, and an isolation amplifier 34p. Optionally the monitoring connections 34c includes a second amplifier 34q. An isolation amplifier is a differential amplifier that allow measurement of small signals by providing electrical isolation and anelectrical safety barrier. The isolation amplifier 34p bridges the isolation boundary 3.′

[0065] The first galvanic isolator 34h′ is assigned to the first monitoring circuit 34c′of the first channel A. In other words, the monitoring circuit 34c′ of the first channelcomprises the first galvanic isolator 34h′. The second galvanic isolator 34h″ is assigned to thesecond monitoring circuit 34c′ of the second channel B. In other words the monitoring circuit34c″ of the second channel comprises the second galvanic isolator 34h″. Each galvanicisolator 34h′, 34h″ of the monitoring circuit has a primary side 34r′, 34r″ secondary side 34s′,34s″. The primary side 34r′, 34r″ is electrically connected to the respective programmabledevice 14′, 14″ of the same channel A, B. The respective programmable device 14′, 14″ isadapted to apply a test signal, for example a square signal, to the primary sides 34r′, 34r″ ofthe respective galvanic isolators 34h′, 34h″.

[0066] The secondary side 34s′ of the first galvanic isolator 34h′ is electricallyconnected between the negative input of the isolation amplifier 34p and the input terminal34f′ of the switch module 34d′ of the first channel A. The input terminal 34f′ of the switchmodule 34d′ of the first channel A has the same electrical potential as the input terminal ofthe switch. The secondary side 34s″ of the second galvanic isolator 34h″ is electricallyconnected between the negative input of the isolation amplifier 34p and the output terminal34g″ of the switch module 34d″ of the second channel B. The output terminal 34g″ of theswitch module 34d″ of the second channel B has the same electrical potential as the outputterminal of the switch. It should be noted that respectively the cathode of the light detector ofthe galvanic isolators 34h′, 34h″, in particular the photovoltaic diode, are connected to thenegative input of the isolation amplifier 34p. The positive input of the isolation amplifier 34pis connected to the output terminal 34g′ of the switch module 34d′ of the first channel Aand / or the input terminal 34f″ of the switch module 34d″ of the second channel B.

[0067] In other embodiments, the design could be also inverted, which means that thesecondary side 34s′ of the first galvanic isolator 34h′ is electrically connected between thepositive input of the isolation amplifier 34p and the input terminal 34f′ of the switch module34d′ of the first channel A and the positive input of the isolation amplifier 34p is connected to15 21883881.v2-7 / 14 / 25the output terminal 34g′ of the switch module 34d′ of the first channel A and / or the inputterminal 34f″ of the switch module 34d″ of the second channel B.

[0068] The semiconductor switch 34n′ of the switch module 34d′ of the first channelA and the semiconductor switch 34n″ of the switch module 34d″ of the second channel B arearranged in opposite directions, wherein, in particular the drains of both semiconductorswitches 34n′, 34n″ or the sources of both semiconductor switches 34n′, 34n″ are coupled.

[0069] The output of the isolation amplifier 34p is provided, in particular via anoptional second amplifier 34q, to the programmable devices 14′, 14″ of each of the channelsA, B.

[0070] Generally, a voltage is generated on one side of each switch module and thevoltage is measured on the other side of the switch. If there is a voltage, then the switch is closed. If there is no voltage, then the switch is open. With the circuit of FIG.5 it is possible to inject a voltage at two different locations to independently test each of the switches by measuring the voltage at the midpoint between the switches through an isolated interface.

[0071] According to embodiments, which may be combined with any embodimentdisclosed herein, for each switch 24, 26, 28, the semiconductor switch of the switch module24d′, 26d′, 28d′, 34d′ of the first channel A and the semiconductor switch of the switchmodule 24d′, 26d′, 28d′, 34d′ of the second channel B are arranged such that they areconnected in series with the drain and source inverted between them. In other words, thedrain of the semiconductor switch of the switch module 24d′, 26d′, 28d′, 34d′ of the firstchannel A is connected to the drain of the semiconductor switch of the switch module 24d′,26d′, 28d′, 34d′ of the second channel B. Alternatively, the source of the semiconductorswitch of the switch module 24d′, 26d′, 28d′, 34d′ of the first channel A is connected to thesource of the semiconductor switch of the switch module 24d′, 26d′, 28d′, 34d′ of the secondchannel B. According to embodiments, in case the use of a FET, for example a MOSFET,due to their internal body diode internal they inherently block current from passing in one direction when in the off state (i.e. when it should not conduct current between the source and the drain). In other words, often semiconductor switches, for example MOSFETs, are unidirectional switches. In order to block AC currents between the contacts 18, 20, 22, in anembodiment the semiconductor switch of the switch module 24d′, 26d′, 28d′, 34d′ of the firstchannel A and the semiconductor switch of the switch module 24d′, 26d′, 28d′, 34d′ of thesecond channel B are arranged such that they are connected in series with the drain and source inverted between them. 16 21883881.v2-7 / 14 / 25

[0072] According to embodiments, one of the programmable devices 14′, 14″ of oneof the channels emit the test signal to one of the switch modules to generate a voltage acrossone of the semiconductor switches 34n′, 34n″ of the same channel and then the feedback stateis read from an isolated feedback signal that is fed to the programmable devices 14′, 14″ ofeach channel A, B, in particular via the isolation amplifier 34p. This enables to detect failuresof one of the semiconductor switches 34n′, 34n″ of a first channel and in particular to react, incase of a detected failure, by opening the other semiconductor switches of the second channel to ensure safe operation. Then, the other processer of the other channel may emit a test signal to the switch module one of the switch modules to generate a voltage across one of thesemiconductor switches 34n′, 34n″ of the same channel and then the feedback state is readfrom an isolated feedback signal that is fed to the programmable devices 14′, 14″ of eachchannel A, B. This enables to detect failures of one of the semiconductor switches 34n′, 34n″of a second channel and in particular to react.

[0073] According to embodiments disclosed herein, it is possible to inject a voltageon a relay contact or electronic circuit without sending the energy to the load that the switch is controlling.

[0074] According to embodiments, a method for operating a solid state switchasdescribed herein may include the followings steps: upon receiving by each programmabledevice 14′, 14″ of an operating signal, providing by each programmable device 14′, 14″ aswitch drive signal to the switch modules 24d′, 24d″, 26d′, 26d″, 28d′, 28d″, 32d, 34d′, 34d″.For example the control connections 30, 30′, 30″ are used for that purpose. The signal isprovided via the PVI 32e, 34e′, 34e″.

[0075] For each channel A, B, the respective programmable device 14′, 14″determines for the switch modules 24d′, 24d″, 26d′, 26d″, 28d′, 28d″, 32d, 34d′, 34d″ of thechannel whether the semiconductor switch 32n, 34n′, 34n″ is in an open or closed state byinjecting a test signal into the monitoring circuits and reading the monitoring circuits. For example, a test signal is a rectangular signal. The test signal is injected by one of the conductors of the monitoring circuit and read by another conductor of the monitoring circuit.

[0076] In the embodiment according to FIG. 4, the test signal is injected via thegalvanic isolator 32h, traverses the semiconductor switch 32n or the switch module and is read or measured via the galvanic isolator 32i. In other words, the test signal traverses the semiconductor switch via the same input and output terminals 32f, 32g as the current to be switched in the first zone 3a. This is provided in the same manner for each channel A, B. This means that the test signal is injected on one side of a switch module of a switch and a voltage 17 21883881.v2-7 / 14 / 25is measured by the at least one programmable device on the other side of the same switch module in order to determine whether the semiconductor switch is in an open or closed state.

[0077] In the embodiment according to FIG. 5, the test signal is injected via thegalvanic isolator 34h′, 34h″, for example by one programmable devices 14′, 14″. The testsignal traverses the respective semiconductor switch 34n′, 34n″ and is read via an output of acommon isolation amplifier 34′ for each of the test circuits of the different channels A, B.This enables to detect failures of one the semiconductor switches 34n′, 34n″ and react, in caseof a detected failure, by opening the other semiconductor switches to ensure safe operation.

[0078] According to embodiments, determining for at least one switch module of thechannel whether the semiconductor switch is in an open or closed state includes injecting thetest signal on one side of the respective switch module 24d′, 24d″, 26d′, 26d″, 28d′, 28d″,32d, 34d′, 34d″ and measuring on the other side of the switch module 24d′, 24d″, 26d′, 26d″,28d′, 28d″, 32d, 34d′, 34d″.

[0079] In response of detection of a failure of a switch module 24d′, 24d″, 26d′, 26d″,28d′, 28d″, 32d, 34d′, 34d″ of a switch 24, 26, 28 by one of the programmable devices 14′,14″ informing the other programmable devices 14′, 14″ of the other channels about thisfailure. For example, if the programmable device 14′ of the first channel A detects a failure ofthe switch module 24d′, the programmable device 14′ informs the programmable device 14″of the second channel B.

[0080] In response to receiving information about a failure of a first switch module24d′, 24d″, 26d′, 26d″, 28d′, 28d″, 32d, 34d′, 34d″ of a switch 24, 26, 28 by a programmabledevice 14′, 14″ of another channel, deactivating, by the programmable device 14′, 14″, asecond switch module of the switch. For example, if the programmable device 14″ of thesecond channel B receives the information that the switch module 24d′ of switch 24 hasfailure, the programmable device 14″ of the second channel B deactivates the second switchmodule 24d″ of the switch 24.

[0081] In an embodiment, where one of the programmable devices detects that aswitch module of a normally open switch fails, for example switch module 26d′ of normallyopen switch 26, in addition to deactivate the second switch module, for example switchmodule 26d″, of the same switch, one at least one of the programmable devices 14′, 14″commands to open also another normally open switch like the power switch 24. This provides an enhanced security.

[0082] The written description uses examples to disclose the invention, including thebest mode, and also to enable any person skilled in the art to make and use the invention. 18 21883881.v2-7 / 14 / 25While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the claims. Especially, mutually non-exclusive features of the embodiments described above may be combined with each other. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.

[0083] List of reference signs:A first channel B second channel 1 solid state switch 3 isolation boundary 5 voltage source 6 relay operating signal input terminal 7 DC / DC converter 10 conductor 12 threshold device14′, 14″ programmable device14a′, 14a″ input terminal14b′, 14b″ switch driving terminal14c′, 14c″ monitoring terminal16 Signal connection 18 common contact 20 NO output contact 22 NC output contact 24 power switch 24a power switch input terminal 24b power switch output terminal 24c monitoring connections24c′, 24c″ monitoring circuit24d′, 24d″ switch module24e galvanic isolator group24f′, 24f″ input terminal24g′, 24g″ output terminal24h′, 24i′ galvanic isolator19 21883881.v2-7 / 14 / 2524h″, 24i″ galvanic isolator26 NO switch 26a NO switch input terminal 26b NO switch output terminal 26c monitoring connections26c′, 26c″ monitoring circuit26d′, 26d″ switch module26e galvanic isolator group26f′, 26f″ input terminal26g′, 26g″ output terminal26h′, 26i′ galvanic isolator26h″, 26i″ galvanic isolator28 NC switch 28a NC switch input terminal 28b NC switch output terminal 28c monitoring connections26c′, 26c″ monitoring circuit28d′, 28d″ switch module28e galvanic isolator group28f′, 28f″ input terminal28g′, 28g″ output terminal28h′, 28i′ galvanic isolator28h″, 28i″ galvanic isolator30, 30′, 30″ control connections32c monitoring circuit 32d switch module 32e galvanic isolator 32f input terminal 32g output terminal 32h galvanic isolator 32i galvanic isolator 32k primary side 32m secondary side 32n semiconductor switch 20 21883881.v2-7 / 14 / 2532o surge protection 34c monitoring connection34c′, 34c″ monitoring circuit34d′, 34d″ switch module34e′, 34e″ galvanic isolator34f′, 34f″ input terminal34g′,34g″ output terminal34h′, 34h″ galvanic isolator34k′, 34k″ primary side34m′, 34m″ secondary side34n′, 34n″ semiconductor switch34p isolation amplifier 34q amplifier34r′, 34r″ primary side34s′, 34s″ secondary side.21 21883881.v2-7 / 14 / 25

Claims

CLAIMS What is claimed is:

1. A solid state switch for railroad equipment, comprising: an isolation boundary galvanically isolating a first zone from a second zone; at least one switch adapted to switch a current in the first zone between a switch input terminal and a switch output terminal; at least one relay operating signal input terminal adapted to receive an operating signal indicating whether to switch the at least one switch; and at least two channels, wherein each channel comprises a switch module in the first zone for each at least one switch, wherein each switch module comprises a switch module input terminal, a switch module output terminal and a semiconductor switch adapted to switch the current between the switch module input terminal and the switch module output terminal; at least one programmable device in the second zone, the at least one programmable device comprising an input terminal for receiving the operating signal, at least one switch driving terminal for driving the switch module of the respective channel and at least one monitoring terminal for each switch module for monitoring the respective switch module; a control connection connecting the switch driving terminal of the at least one programmable device and a control terminal of the semiconductor switch, wherein the control connection comprises at least one first photovoltaic isolator for bridging the isolation boundary; and at least one monitoring circuit for each switch module connecting the respective monitoring terminal of the at least one programmable device, wherein the monitoring circuit comprises at least one galvanic isolator for bridging the isolation boundary, wherein the monitoring circuit connects to at least one of the switch module input terminal and the switch module output terminal.

2. The solid state switch according to claim 1, wherein for each channel the at least one programmable device is adapted to inject a test signal on one side of a switch module of a switch and to measure a voltage on the other side of the switch module in order to determine whether the semiconductor switch is in an open or closed state.

3. The solid state switch according to claim 1, wherein the at least one programmable device of each channel is an FPGA. 22 21883881.v2-7 / 14 / 254. The solid state switch according to claim 1, wherein for each switch, the switch module of the respective channels are connected in series, such that the semiconductor switch of the respective switch module of each switch are connected in series.

5. The solid state switch according to claim 1, wherein the semiconductor switch is a metal oxide semiconductor field effect transistor and control terminal is a gate of the metal oxide semiconductor field effect transistor.

6. The solid state switch according to claim 1, wherein the monitoring circuit of each of the at least two channels connects the monitoring terminal of the programmable device to both the switch module input terminal and the switch module output terminal of the same channel.

7. The solid state switch according to claim 1, wherein the semiconductor switch of the switch module of a first of the at least two channels and the semiconductor switch of the switch module of a second of the at least two channels are arranged in opposite directions and one of either a drain or a source of both the semiconductor switch of the switch module of the first channel and the semiconductor switch of the switch module of the second channel are coupled.

8. The solid state switch according to claim 7, wherein the at least one galvanic isolator of the monitoring circuit of each channel comprises, respectively, a photovoltaic isolator, a secondary side of the galvanic isolator of the monitoring circuit of the first channel is electrically connected between a first input of an isolation amplifier and the switch module input terminal of the switch module of the first channel, the switch module input terminal having the same electrical potential as the switch input terminal, and a secondary side of the galvanic isolator of the monitoring circuit of the second channel is electrically connected between the first input of the isolation amplifier and the switch module output terminal of the switch module of the second channel, the switch module output terminal having the same electrical potential as the switch output terminal, a second input of the isolation amplifier being coupled to the switch module output terminal of the switch module of the first channel.

9. The solid state switch according to claim 1, wherein the at least one galvanic isolator of the monitoring circuit is selected from the group consisting of a capacitor, a second photovoltaic isolator, and an isolation amplifier.

10. The solid state switch according to claim 1, wherein the programmable device is adapted to apply a test signal to the monitoring circuit.

11. The solid state switch according to claim 10, wherein the test signal is a rectangular signal. 23 21883881.v2-7 / 14 / 2512. An item of railroad equipment having a solid state switch, the solid state switch comprising: an isolation boundary galvanically isolating a first zone from a second zone; at least one switch adapted to switch a current in the first zone between a switch input terminal and a switch output terminal; at least one relay operating signal input terminal adapted to receive an operating signal indicating whether to switch the at least one switch; and at least two channels, each channel comprising: a switch module in the first zone for each at least one switch, wherein each switch module comprises a switch module input terminal, a switch module output terminal and a semiconductor switch adapted to switch the current between the switch module input terminal and the switch module output terminal; at least one programmable device in the second zone, the at least one programmable device comprising an input terminal for receiving the operating signal, at least one switch driving terminal for driving the switch module of the respective channel and at least one monitoring terminal for each switch module for monitoring the respective switch module; a control connection connecting the switch driving terminal of the at least one programmable device and a control terminal of the semiconductor switch, wherein the control connection comprises at least one first photovoltaic isolator for bridging the isolation boundary; and at least one monitoring circuit for each switch module connecting the respective monitoring terminal of the at least one programmable device, wherein the monitoring circuit comprises at least one galvanic isolator for bridging the isolation boundary, wherein the monitoring circuit connects to at least one of the switch module input terminal and the switch module output terminal.

13. A method for operating a solid state switch, comprising the steps of: providing a solid state switch having an isolation boundary galvanically isolating a first zone from a second zone, at least one switch being adapted to switch a current in the first zone between a switch input terminal and a switch output terminal, at least one relay operating signal input terminal adapted to receive an operating signal, the operating signal indicating whether to switch the at least one switch, and at least two channels, each channel comprising: 24 21883881.v2-7 / 14 / 25a switch module in the first zone for each at least one switch, wherein each switch module comprises a switch module input terminal, a switch module output terminal and a semiconductor switch adapted to switch the current between the switch module input terminal and the switch module output terminal; at least one programmable device in the second zone, the at least one programmable device comprising an input terminal for receiving the operating signal, at least one switch driving terminal for driving the switch module of the respective channel and at least one monitoring terminal for each switch module for monitoring the respective switch module; a control connection connecting the switch driving terminal of the at least one programmable device and a control terminal of the semiconductor switch, wherein the control connection comprises at least one first photovoltaic isolator for bridging the isolation boundary; at least one monitoring circuit for each switch module connecting the respective monitoring terminal of the at least one programmable device, wherein the monitoring circuit comprises at least one galvanic isolator for bridging the isolation boundary, wherein the monitoring circuit connects to at least one of the switch module input terminal and the switch module output terminal: upon receiving an operating signal by each at least one programmable device, providing a switch drive signal from each at least one programmable device to the switch modules; determining for each channel whether the semiconductor switch is in an open or closed state with the at least one programmable device by injecting a test signal into the monitoring circuit and reading the monitoring circuit; informing the programmable device of the other channel of any detection of a failure of the switch module of the switch by the at least one programmable device; and deactivating, by the programmable device, the switch module of the switch of the other channel in response to being informed about a failure.

14. The method of claim 13, wherein the step of determining for each channel whether the semiconductor switch is in an open or closed state includes injecting the test signal on one side of the switch module and measuring on the other side of the switch module. 25 21883881.v2-7 / 14 / 25

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