Voltage regulation with two level switching - uses relay controlled by transistor circuit to couple transformer secondary coil to lamp over two pick up points

摘要

A voltage regulation system is used to control the secondary voltage of a transformer used to supply a consumer unit. The regulation is of a two level type with switch over being dependent upon the primary voltage. The system is particulary suited for application with projector lamp control. The secondary winding (2) has three tappings (3,4,5) that connects with a transistor circuit controlling a relay switching stage (7). The relay state determines whether the lamp (6) is coupled with either tapping (4,5). If the mains voltage rises above a set level, the transistor (15) is put into the conducting state and a second transistor (19) cuts off resulting in the relay dropping out. When the voltage falls the transistor states invert and the relay switches back.