Apparatus and method to provide a hybrid linear/switching current source, such as for high-efficiency, wide dimming range light emitting diode (LED) backlighting
US7535183B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Apr 27, 2007 |
| Grant date | May 19, 2009 |
| Priority date | — |
| Expiry date | Nov 12, 2027 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02B20/30
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A hybrid power supply provides powers to a load, such as a light emitting diode (LED) backlight display, using pulse wave modulation (PWM) enable signal to control activation of a linear power supply and a switching power supply. During an initial part of an active portion of a duty cycle of the PWM enable signal, the linear power supply is activated to supply the load with constant current. During the remainder of the active portion of the duty cycle of the PWM enable signal, the linear power supply is deactivated and the switching power supply is activated to provide current to the load. A bias current and voltage may be provided to the LED during an inactive portion of the duty cycle of the PWM enable signal. The hybrid power supply combines the high efficiency of the switching power supply with smooth dimming control at low luminance of the linear power supply.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.