Television apparatus having kinescope spot burn protection circuit with extended grid cut-off time constant
US5130615A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 1, 1991 |
| Grant date | Jul 14, 1992 |
| Priority date | — |
| Expiry date | Jul 1, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N3/20
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A source of switched supply voltage is applied to a potential divider and coupled to an output terminal via a capacitor. An output tap of the potential divider is coupled to the output terminal via the conduction path of a grounded base transistor. In operation the transistor (1) operates in an inverted mode for initially charging the capacitor, (2) operates in either a normal or an inverted mode for regulating a grid bias voltage at said output terminal for grid current flow of either direction relative to the output terminal and (3) operates in an isolation mode upon removal of the switched supply voltage whereby the capacitor applies a negative grid cut-off bias to the output terminal, said transistor in said isolation mode preventing discharge of the capacitor thereby providing a grid cut-off bias at said output terminal having an extended cut-off time constant due to the lack of any discharge path for the capacitor other than leakage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.