A diagnosis method for the switching elements in a bidirectional DC-to-DC voltage converter comprising: charging a capacitor in the bidirectional DC-to-DC voltage converter to a predetermined first test voltage, then specifically actuating the switching elements in the bidirectional DC-to-DC voltage converter, and evaluating the voltage in the charged capacitor of the bidirectional DC-to-DC converter to identify a faulty switching element within the switching elements in the bidirectional DC-to-DC voltage converter.

The objective of the present invention is to provide a relay-welding detection device and method, the device and method capable of determining, whether a relay is welded, by using an analog-digital converter (ADC). Another relay-welding detection device according to the present invention comprises: a first ADC for measuring a voltage of a relay input terminal; a second ADC for measuring a voltage of a relay output terminal; and a CPU for comparing the voltage of the relay input terminal with the voltage of the relay output terminal and determining whether the relay is welded.

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.

According to one aspect, embodiments of the invention provide a UPS system comprising an input, an output, a neutral connection, an AVR transformer, relays configured to selectively couple a primary winding of the AVR transformer to the input and the output, a bypass relay configured to selectively couple the primary winding to the neutral connection, a DC/AC inverter, and a controller configured to operate the relays, the bypass relay, and the DC/AC inverter to provide output AC power derived from at least one of input AC power and backup DC power, wherein in a backup power mode, the controller is further configured to operate the DC/AC inverter to convert the backup DC power into AC power provided to a secondary winding of the AVR transformer, to monitor the AC output power, and to identify that the bypass relay has decoupled the primary winding from the neutral connection.

A relay device includes a controller, a capacitor included in a charger, and a discharge circuit that discharges electric charge charged to the capacitor. The discharge circuit includes a discharge resistance, a first relay switch connected to the discharge resistance and having a contact point that becomes a closed state by electric conduction to an exciting coil, and a second relay switch connected in parallel to the first relay switch and having a contact point that becomes an open state by electric conduction to an exciting coil. The controller, by mutually switching between a state in which the first relay switch is turned on and the second relay switch is turned off and a state in which the first relay switch is turned off and the second relay switch is turned on, determines abnormality of the first relay switch and the second relay switch.

A load control device (e.g., a switching device) for controlling power delivered from an AC power source to an electrical device (e.g., a lighting load) may be configured to detect that a relay is stuck closed and attempt to fix the relay. The relay of the load control device may be adapted to be coupled between the source and the electrical device to control the power delivered to the electrical device so as to generate a switched-hot voltage. The load control device may comprise a detect circuit configured to generate a detect signal indicating a magnitude of the switched-hot voltage, and a control circuit configured to monitor the detect signal. The control circuit may be configured to determine that the relay is stuck closed in response to the detect signal, and to control the relay in order to attempt to fix the relay by repeatedly closing and opening the relay.

In the present invention, the connection between an external power supply and a unit for detecting welding of a relay is disestablished at least when a short circuit is detected, thereby preventing the short circuit from being falsely detected in the event that the short circuit and the welding of the relay can both be detected. A device for detecting welding of a relay detects welding of a relay provided to a path via which a cell is charged by an external power supply. Welding of a power-supply-side relay or a ground-side relay is detected on the basis of a current flowing disproportionately more toward the external power supply than the power-supply-side relay or ground-side relay when a control unit has deactivated the power-supply-side relay or ground-side relay during an interrupting in charging. A disconnecting switch establishes or disestablishes the connection between the external power supply and a weld-detection switch.

A relay device includes a controller, a capacitor included in a charger, and a discharge circuit that discharges electric charge charged to the capacitor. The discharge circuit includes a discharge resistance, a first relay switch connected to the discharge resistance and having a contact point that becomes a closed state by electric conduction to an exciting coil, and a second relay switch connected in parallel to the first relay switch and having a contact point that becomes an open state by electric conduction to an exciting coil. The controller, by mutually switching between a state in which the first relay switch is turned on and the second relay switch is turned off and a state in which the first relay switch is turned off and the second relay switch is turned on, determines abnormality of the first relay switch and the second relay switch.

A power supply system includes a power source, a relay, a switch, and a controller. The relay is interposed between the power source and a load. The switch is configured to be coupled to the load in a state where the switch allows or disallows for power supply from the power source to the load when the relay is in a closed state. The controller is configured to control an operation of the switch. The controller is configured to execute forced driving control at a time of a closing operation of the relay. The forced driving control causes the switch to operate independently of a request for driving the load and thereby causes power to be supplied from the power source to the load.

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.