Methods, apparatuses, and systems for operating light emitting diodes at low temperature
US9924576B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 29, 2015 |
| Grant date | Mar 20, 2018 |
| Priority date | — |
| Expiry date | Oct 29, 2035 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B45/18
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Light-emitting diodes (LEDs) generate light more efficiently than high-intensity discharge lamps or high-intensity fluorescent lamps. Driving a series of LEDs with a constant-voltage primary supply and a low-voltage LED driver keeps efficiency high. Unfortunately, LED forward voltage varies as a function of temperature: at low temperature, the forward voltage rises. Placing the LEDs in series magnifies the forward voltage increases. This makes it difficult to drive a series of LEDs at low temperature with a constant-voltage supply because the forward voltage can exceed the power supply voltage. To account for this behavior, an exemplary LED lighting fixture includes a “bypass” circuit that, when engaged, effectively removes at least one LED from each series string of LEDs to bring the total forward voltage below the power supply voltage. The low-voltage driver circuit monitors temperature, and engages the “bypass” circuit when necessary to ensure that DC voltage is not exceeded.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.