Switching device for driving a led array

• US 20050088209A1
• Filed: 02/06/2003
• Published: 04/28/2005
• Est. Priority Date: 02/14/2002
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Johannes Hendrik Wessels
• Inventors: Wessels, Johannes Hendrik
• Granted Patent: US 7,463,070 B2
• Time in Patent Office: Days
• US Class Current: 327/112
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/305 Frequency-control circuits
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/33 Pulse-amplitude modulation [PAM]
• CPC Class Codes: H05B 45/335 Pulse-frequency modulation [PFM]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

The invention relates to a circuit for driving a LED array, in particular a LED array for road marking. To control the brightness of the LED array, the current flowing through the array is regulated. According to the invention, the array is driven by a pulse-shaped current of which the mean value is regulated with at least one of the following types of modulation: frequency modulation, pulse-width modulation, and amplitude modulation. Preferably the mean current value is regulated by a combination of two types of modulation.

Claims

1. A switching device for driving a LED array, characterized in that the switching device comprises means for driving a LED array with a pulse-shaped current of mean strength and for regulating the mean strength of the current flowing through the LED array by means of at least one of the following types of modulation:

frequency modulation, pulse-width modulation, and amplitude modulation of the pulse-shaped current.

3. A switching device as claimed in claim 1, characterized in that the means regulate the mean strength of current flowing through the LED array by means of a combination of frequency modulation, pulse-width modulation, and amplitude modulation of the pulse-shaped current.

4. A switching device as claimed in claim 1, characterized in that the mean current has a nominal strength Inom and in that down to a strength of 0.05 Inom the mean strength is regulated by means of pulse-width modulation, and in that a strength of the mean current <

0.05 Inom is regulated by superimposing the pulse-width modulation, on the amplitude modulation.

5. A switching device as claimed in claim 4, characterized in that a mean current strength smaller than 0.05.10⁻

3 Inom is regulated by means of a further superimposition with the aid of frequency modulation.

2. A switching device as claimed in claim 2, characterized in that said means regulate the mean strength of current flowing through the LED array by a combination of two types of modulation of the pulse-shaped current.