VLMF Compensating Coil
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
Very Low-Frequency Magnetic Field (VLMF) emissions from the scan circuits of cathode ray tube (CRT) display monitors must be restricted in order to satisfy national safety standards of several countries. The majority of emissions that originate from the scan coils on the CRT neck can be effectively suppressed by cancellation coils also fitted on the CRT yoke. Additional emissions from other components being driven at line scan rate must also be suppressed, but using scan cancellation coils for this purpose can mean interference with convergence of the CRT beam asymmetrically across the screen. This disclosure describes a method of cancelling out the majority of emissions from driver circuitry concentrated in one location, such as an analog driver card, without interfering with the convergence of the CRT beam.