Energy recovery circuit for electrotherapy device

Abstract

An energy recovery system for an electrotherapy device, particularly for bone healing, which permits the device to be small, light and portable, and to have extended battery life. Included are a drive voltage source and a ground reference potential. Driving transistors are between an inductive load and, relatively, the voltage source and ground potential, with a storage capacitor connected between the latter two. The voltage source is commonly a battery, preferably a zinc-air battery. Induction load power is applied when both transistors turn on simultaneously. For energy recovery, diodes are connected between the first terminal of the inductive load and the ground potential and between the second terminal of the inductive load and the high voltage source, such that they are reversed biased when the drive transistors are conducting. When drive power is removed from the inductive load by switching off the drive transistors, a reverse EMF is established in the inductive load. As the inductive load magnetic field collapses, a reverse voltage is developed across the inductor higher than the applied voltage by an amount sufficient to forward bias the diodes. Thus, current flows from the inductive load through the diodes to the storage capacitor. Recovery of the energy stored in the inductor continues until the energy remaining is insufficient to maintain current flow to the storage capacitor.