DC to DC battery charger

Claim 1

A DC to DC battery charger for a vehicle comprising: adapter plug means for making electrical connections to a first battery through a cigarette lighter socket in said vehicle; means for making electrical connections to a second battery to be charged; a DC to AC converter and an AC to DC rectifier for elevating the voltage from said first battery to a voltage above that of said second battery; integrated circuit means for generating a pulse width modulated current as a function of the charged condition of said second battery; transistor switch means supplied with said pulse width modulated current for developing a charging voltage; a choke coil and a capacitor serially connected to said transistor switch means; and a diode connected across said choke coil and said capacitor whereby said capacitor is charged during pulses of current from said transistor switch means through said choke coil, said choke coil reversing polarity at the termination of said pulses of current and continuing to charge said battery through said diode, said DC rectified voltage being controlled by said integrated circuit means for regulating current through said choke coil.