US 9,313,843 B2Granted

Systems and methods for driving light emitting diodes

AssigneeMarvell World Trade Ltd.

InventorsWei Lu, Stephen Leeboon Wong, William Mai, Tri Le

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Abstract

System and methods are provided for driving one or more light emitting diodes (LEDs) to reduce audible noise. An example system includes a switching component, a system controller, and a current generator. The switching component is configured to receive a dimming signal with a predetermined dimming frequency and configured to switch on or off the one or more LEDs in response to the dimming signal, the predetermined dimming frequency being outside a frequency band of the audible noise. The system controller is configured to receive a feedback signal related to a LED current that flows through the one or more LEDs and configured to generate a drive signal. Additionally, the current generator is configured to receive the drive signal, to generate a charging current to store energy during a charging period and to generate the LED current during a discharging period.

Claims20

Dependent claims

A system comprising:

a dimming controller configured to generate (i) a first dimming signal having a first dimming frequency, and (ii) a second dimming signal having a second dimming frequency;
a first LED switch configured to receive the first dimming signal, and to switch on or off a first LED string in response to the first dimming signal;
a second LED switch configured to receive the second dimming signal, and to switch on or off a second LED string in response to the second dimming signal, wherein the second LED string is coupled in parallel with the first LED string;
and
a detection circuit configured to generate a comparison signal indicating whether a first voltage drop of the first LED string is larger than a second voltage drop of the second LED string,
wherein the dimming controller is further configured control the first dimming signal and the second dimming signal to
(i) in response to the comparison signal indicating the first voltage drop is larger than the second voltage drop, keep the first LED string on when the second LED string is on, and
(ii) in response to the comparison signal indicating the first voltage drop is smaller than the second voltage drop in magnitude, keep the second LED string on when the first LED string is on.

5 more elements

A method comprising:

generating, by a dimming controller, (i) a first dimming signal having a first dimming frequency, and (ii) a second dimming signal having a second dimming frequency;
switching, by a first LED switch, on or off a first LED string in response to the first dimming signal;
switching, by a second LED switch, on or off a second LED string in response to the second dimming signal, wherein the second LED string is coupled in parallel with the first LED string;
generating, by a detection circuit, a comparison signal indicating whether a first voltage drop of the first LED string is larger than a second voltage drop of the second LED string,
controlling, by the dimming controller, the first dimming signal and the second dimming signal to
(i) in response to the comparison signal indicating the first voltage drop is larger than the second voltage drop, keep the first LED string on when the second LED string is on, and
(ii) in response to the comparison signal indicating the first voltage drop is smaller than the second voltage drop, keep the second LED string on when the first LED strong is on.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 14/815,212Filed 31 Jul 2015 · division
Priority: 31 Jan 2011
Published: US 2015/0341995 A126 Nov 2015
Granted: 12 Apr 2016
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

H05B 45/10
Circuit arrangements for operating light-emitting diodes [LED]: controlling the intensity of the light
H05B 45/325
Pulse-control circuits: pulse-width modulation [PWM]
H05B 45/46
With an active control inside an LED matrix: having LEDs disposed in parallel lines
H05B 45/48
With an active control inside an LED matrix: having LEDs organised in strings and incorporating parallel shunting devices

Family

Application61/437,978Us provisional application · filed 31 Jan 2011
Application13/356,796Parent of this division · filed 24 Jan 2012
US 2015/0341995 A1Pre-grant publication · published 26 Nov 2015
US 9,101,025 B2Parent of this division
US 2012/0194087 A1Published application
US 9,313,843 B2This patent

From the US filing history. Foreign family members aren’t listed.