CATHODE RAY TUBE FILAMENT VOLTAGE CONTROL WITH A MULTIFREQUENCY DEFLECTION SCANNER

摘要

A power supply for a video display tube (10) includes a deflection transformer (22) with a primary winding (22P) powered with a scan voltage which has a first value when displaying signal according to a first video standard and a second voltage when displaying video according to a second standard. A secondary winding (22HV) of the transformer produces filament voltage for the display tube. A variable coupler couples the filament voltage to the filament of the picture tube in an amount established by a control signal. A memory (60) produces a first control signal in response to the first scan voltage and a second control signal in response to the second scan voltage. The first and second control signals are selected so that the voltage coupled from the transformer to the filament is the same at both scan voltages.