Littelfuse, Inc.

Brian D Crispim

Geoffrey Schwartz

Provided herein are improved apparatuses and methods for protecting polarity sensitive loads in DC power circuits that include a power source, a relay coupled to the power source, and a polarity sensitive load coupled to the relay. A diode can be coupled between the power source and the relay. When the power source provides a DC voltage of a desired polarity, the diode can block a current from flowing to a coil of the relay. Consequently, the relay can provide a current path to the polarity sensitive load. When the power source provides a DC voltage of an incorrect or reverse polarity, the diode can allow a current to flow to the coil of the relay. In turn, the coil of the relay can be energized, causing the relay to disrupt the current path provided to the load, thereby protecting the polarity sensitive load from the reverse polarity condition.

Method and apparatus for protecting a polarity sensitive load

Provided herein is a relay architecture for selecting between multiple power sources. In one approach, a first relay and first power source are electrically coupled to a first terminal. A second relay and second power source are electrically coupleable to a second terminal and to the first relay. A load is electrically coupled with at least one of the following in the case that a load voltage is below a predetermined threshold: the first terminal, the second terminal, and a third power source, wherein a power supply is provided to the load by the first power source in the case that the first power source is coupled to the first terminal. The power supply is provided to the load by the second power source when the second power source is coupled to the second terminal and the first power source is disconnected from the first terminal.

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Salem, NH, United States of America

Brian D Crispim