Abstract

A constant voltage inductive power coupling for magnetically transferring electrical power from a power source through an air gap to a load comprising a first electromagnetic inductor connected to a power source to generate a shaped alternating magnetic field, a said inductor with a saturable core separated by an air gap from the first inductor and magnetically coupled thereto to receive the shaped magnetic field, the core being responsive to the field to enter a state of magnetic saturation. A coil is electromagnetically coupled to the saturable core and has output leads connected to the load. A capacitor is in electrical communication with the coil to form a tuned circuit that is below resonance at the coupling operating frequency. The magnetic field induced by the first inductor to the second inductor causes voltage in the coil, whose magnitude is determined by the amount of magnetic flux in the core. The saturable core is responsive to any change in input voltage to magnetically counteract such change so as to maintain the core in its state of saturation thereby tending to keep the output voltage constant. Also any increase in load current is associated with a closer approach of the tuned circuit to a resonant condition tending to maintain the output voltage at a constant level. The invention is particularly useful in battery charging circuits or for other applications where the voltage required must be kept at a constant level.