Patent ID: 6339412
Filing Date: 2002-01-15
Classification: G09G

Abstract:
A video display device, comprising:a monitor including a deflection coil; a controller coupled to receive vertical and horizontal synchronous signals from a video card installed in a computer system, for discriminating an operation mode of said video card in response to frequencies of the vertical and horizontal synchronous signals and controlling operation of said video display device in a discriminated operation mode; a vertical drive circuit including a first phase locked loop circuit for performing a phase locked operation in response to the vertical synchronous signal to produce a vertical drive signal; a vertical output circuit for generating a vertical deflection signal in response to the vertical drive signal from said first phase locked loop circuit and applying the vertical deflection signal to said deflection coil to deflect electron beams generated by said monitor in a vertical direction; a horizontal drive circuit including a second phase locked loop circuit for performing a phase locked operation in response to the horizontal synchronous signal to produce a horizontal drive signal; a horizontal output circuit for generating a horizontal deflection signal in response to the horizontal drive signal from said second phase locked loop circuit and applying the horizontal deflection signal to said deflection coil to deflect electron beams generated by said monitor in a horizontal direction; a transient state detector for detecting a transient state of said second phase locked loop circuit in response to a change in the operation mode of said video card; and said controller generating the vertical and horizontal synchronous signals with frequencies corresponding to an operation mode of said video display device before the change in the operation mode of said video card, when said transient state detector detects the transient state of said second phase locked loop circuit.