Convergence correction apparatus

摘要

A convergence correction apparatus comprising a core for producing a bias magnetic field. The core has first, second, third and fourth coils provided thereon. The first and second coils are wound to produce a magnetic field in a direction opposite to the direction of the bias magnetic field. The third and fourth coils are wound to produce a magnetic field in the same direction as the direction of the bias magnetic field. The first and fourth coils are connected to form a first series circuit connected in parallel with a second series circuit of the third and second coils. A first terminal is connected to a junction between the first and third coils. A second terminal is connected to a junction between the second and fourth coils. A convergence correction coil is connected at one end thereof to a junction between the first and fourth coils and at the other end thereof to a junction between the second and third coils. A horizontal deflection current is applied between the first and second terminals. The bias magnetic field is produced by a bias coil provided on the core and supplied with a vertical synchronization current having a parabolic waveform. Alternatively, the basic magnetic field is produced by a combination of at least one permanent magnet provided on the core and a bias coil provided on the core and supplied with a vertical synchronization current having a parabolic waveform.