Low cost AC switch for electroluminescent lamps
US5347198A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 1, 1993 |
| Grant date | Sep 13, 1994 |
| Priority date | — |
| Expiry date | Jun 1, 2013 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02B20/30
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
DC bias does not accumulate on an EL lamp connected in series with a switch circuit including, in one embodiment, two, asymmetric, parallel current paths, one current path for each half cycle of the AC. The first current path includes a first diode for preventing DC bias on the lamp, the first diode is in series with a first transistor between a first terminal and a second terminal. The second current path includes a second diode in series with the base-collector junction of a second transistor between the first terminal and the second terminal. The base of the first transistor is connected to the emitter of the second transistor and to a control terminal. The first transistor and the second transistor are opposite conductivity types. The second current path takes advantage of the fact that the current through an electroluminescent lamp is small and uses the control terminal as a source of current for the lamp. In another embodiment, a large capacitor in series with the electroluminescent lamp prevents DC bias from accumulating on the EL lamp.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.