Patent ID: 7288856

Claim:
A circuit for protecting a power switch in the event of a reverse battery connection, wherein the power switch comprises a MOSFET having a body diode and the MOSFET is connected in series with a load, the circuit comprising: terminals for being normally connected to respective positive and negative power potentials of the battery; and a switching circuit coupled to the terminals which turns on the power switch in the event that the terminals are connected with a reverse battery connection; wherein the switching circuit comprises: a first switch having a first main terminal coupled, when the battery is properly connected, to the negative battery connection and a second main terminal coupled to the gate of the power switch; the first switch having a control terminal coupled, when the battery is properly connected, to the negative battery connection, whereby said first switch is normally non-conductive in the event of a proper battery connection and conductive in the event of a reverse battery connection; a second switch having a control terminal coupled, when the battery is properly connected, to the positive battery connection and having a main terminal coupled to the first switch control terminal to maintain the first switch in an off state when the battery is properly connected; whereby in the event of a reverse battery connection, said first switch turns on thereby providing a positive battery potential to the gate of said power switch to turn the power switch on.