Abstract: A battery charger of the driven blocking oscillator type includes a three-winding transformer. The primary winding is connected in series with the collector-emitter path of a switching transistor. The secondary winding is connected in series with the collector-emitter path of a sense transistor which responds to the current flowing through the switching transistor. The tertiary winding is connected in series with the battery, series-connected batteries or series-connected battery packs sought to be recharged, via a diode, which may be connected in parallel with a capacitor. No smoothing capacitor is provided across the battery or batteries. The battery or batteries are charged by current pulses and discharge through the tertiary winding to repolarize the diode (and capacitor if present). The secondary winding is poled, with respect to the tertiary winding so that the blocking oscillator is driven by energy from the battery or batteries.

Abstract: A battery charger of the driven blocking oscillator type includes a three-winding transformer. The primary winding is connected in series with the collector-emitter path of a switching transistor. The secondary winding is connected in series with the collector-emitter path of a sense transistor which responds to the current flowing through the switching transistor. The tertiary winding is connected in series with the battery, series-connected batteries or series-connected battery packs sought to be recharged, via a diode, which may be connected in parallel with a capacitor. No smoothing capacitor is provided across the battery or batteries. The battery or batteries are charged by current pulses and discharge through the tertiary winding to repolarize the diode (and capacitor if present). The secondary winding is poled, with respect to the tertiary winding so that the blocking oscillator is driven by energy from the battery or batteries.