Patent ID: 6169587
Filing Date: 2001-01-02
Classification: H04N

Abstract:
A raster vertical scan size adjustment circuit of a video display apparatus, said video display apparatus including a flyback transformer (FBT) which includes a primary winding and a secondary winding, the secondary winding having a terminal generating a high voltage to an anode of a cathode ray tube (CRT) of the video display apparatus via an external loading, the secondary winding having a voltage reference terminal, the raster vertical scan size adjustment circuit comprising: means for providing a compensated signal responsive to variation of the external loading, wherein the means comprises a compensation circuit having an input terminal adapted to connect said voltage reference terminal of the secondary winding for detecting voltage change at said voltage refernce terminal responsive to variation of the external loading, the compensation circuit having an output terminal generating the compensated signal, wherein said compensation circuit comprises: a filter used to remove spike due to horizontal deflection operation of said video display apparatus sensed at the voltage reference terminal of the secondary winding of the FBT, said filter having an output terminal: a compensation network having an output terminal generating the compensated signal based on voltage variation at the output terminal of said filter; a raster vertical scan size control circuit, responsive to the compensated signal, for adjusting the raster vertical scan size of the video displayed on the CRT such that the raster vertical scan size is substantially unchanged.