Patent ID: 7550944

Claim:
An interface circuit for charging a rechargeable battery from a power source, comprising: first and second input terminals adapted to be coupled to said power source; third and fourth output terminals adapted to be coupled to said rechargeable battery; a normally-closed relay having normally-closed switch contacts and a coil having a first end and a second end, wherein said normally-closed switch contacts and said coil are connected in series between said first and second input terminals; and an EMF conduction diode coupled between said fourth output terminal and a junction between said normally-closed switch contacts and said first end of said coil; wherein said second end of said coil is coupled to said third output terminal, wherein current supplied from said power source through said normally-closed switch contacts energizes said coil to generate an electromagnetic field that causes said normally-closed switch contacts to open and thus remove said supplied current from said coil so that said normally-closed switch contacts continue to oscillate between an open condition and a closed condition, and wherein energy transferred from said power source to said electromagnetic field of said coil when said normally-closed switch contacts are in said closed condition is transferred by discharging said electromagnetic field in response to current through said EMF conduction diode when said normally-closed switch contacts are in said open condition.