Variable transformer for use with electric toys and model railways - has output connected to bridge rectifier with Zener diode in one bridge arm to give half wave rectification at low voltages

摘要

The variable transformer for electric toys and model railways has its secondary winding (3) connected to a bridge rectifier circuit. The bridge circuit consists of four metal rectifiers (20) (21) (22) (23) and a Zener diode (24) in one of the arms of the bridge. Below a given voltage from the transformer (3) the rectifiers (20) to (23) allow only half waves from the a.c. supply to pass to provide a half wave d.c. supply at the terminals (6) (7). Above the given voltage the Zener diode (24) becomes conducting so that circuit becomes a full wave rectifier.