A safety circuit for fail-safe shutdown of a dangerous technical system with a plurality of disconnectable system component groups comprises a plurality of safety switching devices electrically connected to one another in series to form a closed-loop monitoring circuit in which electric monitoring current flows through the safety switching devices. Each of the safety switching devices includes: a fail-safe control unit that detects and evaluates information about a current operating state of any system component group assigned to it; and a current flow adjuster that changes the current flow within the monitoring circuit to interrupt the monitoring circuit in response to detection of a safety command by the safety switching device. The fail-safe control units generate a shutdown signal in response to an interruption of the current flow within the monitoring circuit, which causes the fail-safe shutdown of any of the system component group not already shut down.

A controller 10 performs a first welding check and a second welding check in any order, and then performs a third welding check before a fourth welding check and also performs a fifth welding check before a sixth welding check. The first welding check is performed by turning on a first relay 18. The second welding check is performed by turning on a second relay 19. The third welding check is performed by turning on an in-phase relay, a third relay 20, and a fourth relay 21. The fourth welding check is performed by turning on an out-of-phase relay, the third relay 20, and the fourth relay 21. The fifth welding check is performed by turning on the in-phase relay, a fifth relay 22, and a sixth relay 23. The sixth welding check is performed by turning on the out-of-phase relay, the fifth relay 22, and the sixth relay 23.

A switch control circuit and a switch control system includes a plurality of parallel-connected signal processing units. A first voltage signal and second voltage signal control turning-on and turning-off of the first controllable switch, and converting the first voltage signal into a third voltage signal; and the third voltage signal being connected with the first port of the controller; and the controller, configured to send a switch control instruction to a to-be-controlled terminal based on the third voltage signal. This circuit converts a electrical signal of a high voltage in strong electricity into a stable electrical signal of a low voltage in weak electricity, implements multiplex switch control in conjunction with the controller, and only processes voltage signals in the whole circuit, thereby avoiding processing signals of a plurality of types, and guaranteeing the reliability of the multiplex switch control.

A battery pack including first and second battery contactors respectively having first ends electrically connected to positive and negative electrode terminals of a battery; first and second charging contactors respectively having first ends electrically connected to second ends of the first and second battery contactors; a second power connector of a charger having first and second output terminals respectively electrically connected to the first and second input terminals being connected to the first power connector; and a control unit configured to, when a second power connector of a charger is electrically connected to the first power connector, receive a charging end request signal from the charger, control changes of the first and second charging contactors between turn-on and turn-off states, and diagnose a fault of each of the first and second charging contactors based on first, second or third measured voltages across the first, second or third resistors, respectively.

The present invention realizes a relay device that can prevent malfunction due to occurrence of reverse flow of current in any of paths. A control unit that is provided in a relay device functions as a switching control unit, keeps an ON state of a first relay unit and a second relay unit if both of currents flowing through a first conduction path and a second conduction path flow in a normal direction (direction toward a load, and if the current flows in the reverse direction in one of the paths, switches one relay unit that is provided in a reverse flow path in which the current flows in a reverse direction to an OFF state.

A safety circuit coupled between a first direct current (DC) circuit and a second DC circuit, wherein the first DC circuit supplies power to the second DC circuit. The safety circuit comprises a first series connection between positive poles of the first and second DC circuits (the first series connection comprising a first diode, a second diode and a first controllable switch), a second series connection between negative poles of the first and second DC circuits (the second series connection comprising a third diode, a fourth diode and a second controllable switch), a first energy storage device (coupled between the positive pole of the second DC circuit and the first terminal of the second controllable switch), and a second energy storage device (coupled between the negative pole of the second DC circuit and the first terminal of the first controllable switch). The safety circuit further comprises a first feedback circuit for indicating an active state of the first controllable switch and a second feedback circuit for indicating an active state of the second controllable switch.

A relay apparatus comprises input ports, output ports, and first and second relays. The first relay comprises: a first contact group comprising n?2 first contacts arranged in parallel and moveable between open and closed positions by a first common armature; and a second contact group comprising n second contacts arranged in parallel and movable between open and closed positions by a second common armature, wherein the first and second contacts are arranged in series in pairs. The second relay includes m<n contacts arranged in parallel and moveable between open and closed positions by a third common armature. The first and second relays are arranged in series between the input and output ports such that the relay apparatus has plural parallel switching paths. A contact of the second relay is arranged in series with a first contact of the first contact group in m switching paths.

In order to specify a method, which is improved in comparison to the prior art, for monitoring an electrical switching arrangement having at least two channels, which each electrically conductively connect an electrical source supplying the respective channel, forming an electrical supply quantity, to an output of the respective channel, the switching arrangement is fed not only an external safety signal, from which an internal safety signal is respectively generated for the at least two channels in order to therewith control a voltage interrupter connected in series in the respective channel, but also a pulsed diagnostic signal, which is superimposed on the internal safety signals in order to alternately open and close again the voltage interrupters connected in the respective channels and to thus respectively alternately interrupt the supply quantities appearing in the respective channels.

A safety switching device for fail-safely disconnecting an electrical load has an input part for receiving a safety-relevant input signal, a logic part for processing the at least one safety-relevant input signal, and an output part. The output part has a relay coil and four relay contacts. The first and second relay contacts are arranged electrically in series with one another. The third and fourth relay contacts are also arranged electrically in series with one another. The first and the third relay contacts are mechanically coupled to each other and form a first group of positively driven relay contacts. The second and the fourth relay contacts are mechanically coupled to each other and form a second group of positively driven relay contacts. The logic part redundantly controls the first and the second groups of positively driven relay contacts to selectively allow, or to interrupt in a fail-safe manner, a current flow to the electrical load, depending on the safety-relevant input signal. The relay coil is electromagnetically coupled to the first and second groups of positively driven relay contacts so that the logic part can control the relay contacts together via a single relay coil.

A relay circuit and a method for performing a self-test. The relay circuit has four relays, each relay having a first forcibly guided contact and a second forcibly guided contact. The four relays are arranged in a first and a second pair of two in series connected first forcibly guided contacts. The first and second relay pair are arranged in parallel between a power supply connection and a load connection for switching a power supply to a load through the first forcibly guided contacts. Such a relay circuit enables supplying power via one of the relay pairs, while cutting power via the other relay pair, which facilitates testing of the relay pair which has cut power without interrupting the process supervised by the Safety Instrumented System which the relay circuit forms part of.