Forced, resonant degaussing system and method
AssigneeHughes Aircraft Company
InventorRobert M. Bentley
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Abstract
A degaussing system for color monitors is disclosed. During a degaussing cycle, the system successively reverses the coupling in a bridge circuit between a degaussing coil and a storage capacitor so as to generate oppositely directed degaussing currents through the coil. To insure that the residual magnetism after degaussing is substantially zero, feedback signals are developed in a feedback circuit and applied through a control circuit to the bridge circuit to successively decrease the coil's current magnitudes until they reach a predetermined threshold. Simultaneously, the feedback signals are adjusted to cause the time-integrated current in one direction of the coil to substantially equal the time-integrated current in the other coil direction.
Claims20
A degaussing system for degaussing a color cathode-ray tube, comprising:
- an energy source having an outlet port;
- a coil having first and second ends and arranged to have a magnetic field coupling with said cathode-ray tube;
- a control circuit configured to successively generate first and second coupling commands;
- and
- a switching network arranged to couple said coil and said energy source in series with said first end adjacent said outlet port in response to said first coupling command and to couple said coil and said energy source in series with said second end adjacent said outlet port in response to said second coupling command;
- the coupling between said energy source and said coil thereby producing successive, oppositely directed currents through said coil and successive, differently oriented magnetic fields.
A display monitor system, comprising:
- a color cathode-ray tube;
- an energy source having an outlet port;
- a coil having first and second ends and arranged to have a magnetic field coupling with said cathode-ray tube;
- a control circuit configured to successively generate first and second coupling commands;
- and
- a switching network arranged to couple said coil and said energy source in series with said first end adjacent said outlet port in response to said first coupling command and to couple said coil and said energy source in series with said second end adjacent said outlet port in response to said second coupling command;
- the coupling between said energy source and said coil thereby producing successive, oppositely directed currents through said coil and successive, differently oriented magnetic fields.
A method of degaussing a cathode-ray tube, comprising the steps of:
- arranging a coil to couple its magnetic field with said cathode-ray tube;
- successively reversing the coupling direction of said coil with an energy source to generate successive currents through said coil in successively different directions;
- and
- resonantly receiving, with said energy source after each successive reversal, at least a portion of the current generated in said coil in the preceding coupling.
Dependencies are inferred from the claim text.