CONTROLLED VOLTAGE SOURCE FOR LED DRIVERS

• US 20100019693A1
• Filed: 12/03/2007
• Published: 01/28/2010
• Est. Priority Date: 12/06/2006
• Status: Active Grant

• Current Assignee: SK Hynix Inc.
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Mobers, Antonius M. G., Hoogzaad, Gian
• Granted Patent: US 8,319,449 B2
• Time in Patent Office: Days
• US Class Current: 315/294
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

The present invention relates to an electronic device for driving a light emitting semiconductor device, which includes controlling means (CNTL) being adapted for controlling a switch mode power supply for supplying the light emitting semiconductor device in response to a sensing value received by the controlling means which is indicative of a voltage across a current source for determining a current through the light emitting semiconductor device, wherein the switch-mode power supply is controlled such that the voltage across the current source is minimum.

Claims

1. An electronic device for driving a light emitting semiconductor device, the electronic device comprising:

a controller being adapted for controlling a switch mode power supply (SMPS) for supplying the light emitting semiconductor device in response to a sensing value (VS) received by the controller which is indicative of a voltage across a current source for determining a current through the light emitting semiconductor device, wherein the switch-mode power supply (SMPS) is controlled such that the voltage across the current source is minimum.

2. The electronic device according to claim 1, comprising further the current source, wherein the current source is a switched current source or a linear current source.

3. The electronic device according to claim 1, wherein the controller provides signals to switch the current through the light emitting semiconductor device on and off, in particular by a pulse width modulated signal (PWMr).

4. The electronic device according to claim 1, wherein the controller is further adapted to control timing of a sampling for sampling the sensing value, which is indicative of the voltage across the current source, such that sampling occurs when the current through the current source is turned on.

5. The electronic device according to claim 1, wherein the light emitting semiconductor device is a light emitting diode, the electronic device comprising further the switch-mode power supply (SMPS), wherein the switch-mode power supply and the controller are adapted to control the output voltage of the switch-mode supply with a control resolution of substantially less than the variation of a forward voltage of the light emitting diode to be driven.

6. The electronic device according to claim 1, wherein the light emitting semiconductor device is a light emitting diode, the electronic device being further adapted to provide pulse width modulating signals for the light emitting diode for dimming the light emitting diode.

7. The electronic device according to claim 6, wherein the light emitting diodes are arranged in at least one string.

8. The electronic device according to claim 7, wherein the string of light emitting diodes are dimmed with pulse width modulated signal (PWM1).

9. The electronic device according to claim 7, comprising further a plurality of current sources and a minimum selector (MINSEL), wherein the string of light emitting diodes is coupled to the plurality of current sources and the minimum selector (MINSEL) is adapted to select the minimum voltage across the plurality of current sources, wherein the selected minimum voltage is used as a reference for controlling the switch-mode power supply.

10. The electronic device according to claim 1, wherein the controller is electrically decoupled from the light emitting semiconductor devices, in particular by an inductive power converter or by an opto-coupler.

11. The electronic device according to claim 1, further comprising an input pin to receive the sensing value (Vs).