Resonant degaussing apparatus
US4737881A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 18, 1986 |
| Grant date | Apr 12, 1988 |
| Priority date | — |
| Expiry date | Apr 18, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N9/29
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A degaussing circuit for a cathode ray tube, of a video display apparatus includes a resonating capacitor that is charged prior to degaussing. A degaussing coil is disposed about the cathode ray tube. An SCR, responsive to an on/off control signal, is turned on by a control switch for coupling the resonating capacitor to the degaussing coil in order to generate an AC, degaussing current in the coil having an amplitude that diminishes to a low amplitude during a degaussing interval. Positive feedback is used for speeding up the turn-on time of the control switch. A series pass transistor switch couples a source of a supply voltage to a delay network. The series pass transistor switch is coupled in the current path of the current that is supplied by the power supply. An energizing voltage is developed at the output of the delay network. The magnitude of the energizing voltage exceeds a predetermined value after a predetermined delay time following the closing of the transistor switch, that is determined by the delay network. The delayed energizing voltage is coupled to a deflection circuit to initiate deflection circuit operation after conclusion of the degaussing.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.