Fixed frequency, variable duty cycle, square wave dimmer for high intensity gaseous discharge lamp
US4170747A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 22, 1978 |
| Grant date | Oct 9, 1979 |
| Priority date | — |
| Expiry date | Sep 22, 1998 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S315/07
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A dimmer circuit for an HID lamp is provided for supplying a square wave current therethrough at a constant frequency, but whose duty cycle is variable dependent on a sensed current level. The circuit employs a first pair of transistor switches for reversing polarity through the lamp at a low frequency rate. Associated with each of those transistors is a circuit having a transistor switch connected to a drive circuit employing a timer network. The timer network produces an output that is a square wave, the leading edge of which occurs at regular intervals at a high frequency rate. The trailing edge occurs dependent on a dim/bright voltage setting and upon the amount of current through a sensing resistor in series with the lamp.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.