Solid state switch, in particular for railway equipment

A railroad equipment comprising a solid 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;
• and
• 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 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.

A method for operating a solid 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;
• and
• 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 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,
• wherein the method comprises:
• 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 said 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.