Battery charger providing charge state indication - emits intermittent sound signals with intervals between sounds decreasing on approach to full charge

摘要

This mains-driven battery-charger is for use with rechargeable batteries as used in electric shavers, dictating machines, etc. It emits sound signals of different types to indicate the state of charge. A half-wave rectifier and series resistance produce the d.c. charging current for the battery, while an inductive circuit across the battery produces a modulated frequency proportional to the battery voltage. If the voltage drops below a pre-set level, a buzzer emits a continuous noise when the device is plugged into the charger. As the battery charges the noise becomes intermittent and the pauses between 'bleeps' become longer. A load can be switched across the battery to check to see if the battery is fully charged.