Controlling current through serial LEDs using a low voltage transistor when using a high voltage driver
US7880404B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jan 25, 2008 |
| Grant date | Feb 1, 2011 |
| Priority date | — |
| Expiry date | Aug 20, 2029 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02B20/30
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Various circuits are described herein where a series transistor used to control current through a string of LEDs, driven by a high voltage, is not subjected to the high voltage when the transistor is turned off pursuant to a PWM signal. To avoid the transistor experiencing the high voltage, the HV regulator is disabled shortly before the transistor is turned off and is enabled shortly after the transistor has turned back on. Control circuits for controlling the regulator and transistor include delay circuits and/or voltage sensing circuits to ensure that the transistor is always on prior to the voltage regulator being enabled pursuant to the incoming PWM signal, and the voltage regulator is always disabled when the first transistor is off pursuant to the incoming PWM signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.