Switching device for supplying current from a battery of a vehicle, fed by a dynamo, to a refrigerator to be carried along.

摘要

Switching device for supplying current from a battery of a vehicle, an automobile for instance, to a refrigerator to be carried along, by a caravan coupled to an automobile for instance. The switching device comprises an input to be coupled to the battery, an output to be coupled to the refrigerator, and a relay having a normally open contact which couples the input and the output of the switching device. The switching device further comprises a drive device, coupled to the input of the switching device, for driving the relay. The drive device is provided with a control device for driving the delay during successive cycles. Each cycle consists of a measuring time interval, during which the control device does not drive the relay. The measuring time interval is followed by an operating time interval, during which the control device drives the relay. The drive device is further provided with a voltage comparing device having an input, which is coupled to the input of the switching device for receiving a test voltage, and an output for delivering a control signal, when the test voltage is higher than a threshold voltage related to the nominal voltage of the battery. In a measuring time interval the control device turns the relay on relatively shortly after having received the control signal, as a result of which an operating time interval begins and the relay is driven for a relatively long time, after which the relay releases when the test voltage is lower than the threshold voltage, as a result of which a measuring time interval begins. In an embodiment the drive device is further provided with an auxiliary voltage comparing device. The auxiliary voltage comparing device has an input, which is coupled to the input of the switching device for receiving the test voltage, and an output for delivering an auxiliary control signal, when the test voltage is lower than an auxiliary threshold voltage which is lower than the threshold voltage and which is higher than a voltage related to the maximum release voltage of the relay. The auxiliary control signal causes the control device to break off a running cycle prematurely by de-energizing the relay, as a result of which a measuring time interval begins. Other embodiments concern associated methods.