End-of-life protection circuit and method for high intensity discharge lamp ballast
US8212496B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 23, 2009 |
| Grant date | Jul 3, 2012 |
| Priority date | — |
| Expiry date | Oct 14, 2030 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02B20/00
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An apparatus and method for detecting an end of life (EOL) condition of a lamp that exhibits a re-ignition behavior. A voltage is applied to the lamp to cause the lamp to start emitting light, and a lamp re-ignition voltage to normal lamp voltage difference after a mask-off period expires is monitored. The lamp is determined to have reached the EOL condition when a predetermined percentage of high difference half cycles occur during a set number of lamp voltage half cycles that are measured during a measurement window. The method continuously monitors the lamp re-ignition voltage to normal lamp voltage difference and records whenever the lamp re-ignition voltage to normal lamp voltage difference is higher than the re-ignition difference threshold level at any lamp voltage half cycle. An EOL lamp is detected when a predetermined number of high difference half cycles occurs in a set total number of lamp voltage half cycles measured in a rolling measurement window.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.