Control apparatus and method for use with digitally controlled light sources

• US 20070153026A1
• Filed: 10/12/2005
• Published: 07/05/2007
• Est. Priority Date: 10/12/2004
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Ashdown, Ian
• Granted Patent: US 7,738,002 B2
• Time in Patent Office: Days
• US Class Current: 345/691
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: H03K 7/08 Duration or width modulation ; Duty cycle modulation
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: H04W 64/006 with additional information processing, e.g. for direction or speed determination
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

The present invention provides an extension to a standard N-bit digital pulse width control method which can discriminate 2^N discrete pulse widths per pulse cycle. The present invention provides a method and apparatus that can modulate the pulse widths over a period of 2^M pulse cycles in which each pulse cycle can have its own pulse width or respective duty cycle. The resulting time averaged or effective pulse width therefore can be controlled with a resolution of 2^N+M states rather than a resolution of 2^N states as is common with standard methods.

Claims

1. An apparatus for control of a luminaire including one or more light-emitting elements in one or more colours, each of the one or more light-emitting elements supplied with electrical current to produce light, said apparatus comprising

a) means to adjust the electrical current to the one or more light-emitting elements using pulse width modulation or pulse code modulation, each of said pulse width modulation and pulse code modulation having a pulse cycle;

and

b) means to modulate a pulse width for each pulse cycle, thereby increasing control resolution of the one or more light-emitting elements.

2. The apparatus according to claim 1, wherein said means to modulate the pulse width comprises a N-bit adder operatively coupled to a controller, said N-bit adder providing the controller with control signals for controlling the electrical current to the one or more light-emitting elements, the means to modulate further comprising a M-bit programmable counter coupled to the N-bit adder, said means to modulate the pulse width thereby providing a control resolution of 2^N+M states.

3. The apparatus according to claim 1, wherein said means to modulate the pulse width comprises an incrementer operatively coupled to a controller, said incrementer providing the controller with control signals for controlling the electrical current to the one or more light-emitting elements, the means to modulate the pulse width further comprising a M-bit programmable counter coupled to the N-bit adder.

4. The apparatus according to claim 2, wherein said means to modulate the pulse width further comprises an exception handling circuit operatively connected to the M-bit programmable counter and the N-bit adder.

5. The apparatus according to claim 4, wherein said means to modulate the pulse width further comprises a divide by N counter operatively connected to the M-bit programmable counter, said divide by N counter for resetting the M-bit programmable counter.

6. The apparatus according to claim 1, wherein said apparatus operates at a cycle frequency greater than or equal to about 20 kHz.

7. The apparatus according to claim 6, wherein said apparatus operates at a cycle frequency of about 30 kHz.

8. An extended pulse width modulation method for transforming a (N+M)-bit signal into a stream of 2^M words of N-bit width for a total of 2^M pulse cycles, the method comprising the steps of:

a) receiving the (N+M)-bit signal;

b) splitting the (N+M)-bit signal into an N-bit portion and an M-bit portion;

c) interpreting the N-bit portion as a binary coded number n;

d) interpreting the M-bit portion as a binary coded number m;

e) encoding (n+1) in a form of a binary N-bit word and feeding the word for m pulse cycles into the stream; and

f) encoding n in a form of a binary N-bit word for (2^M−

m) pulse cycles and feed the word into the stream;

thereby forming the stream of 2^M words of N-bit width for a total of 2^M pulse cycles.

9. An extended pulse width modulation apparatus for transforming a (N+M)-bit signal into a stream of 2^M words of N-bit width for a total of 2^M pulse cycles, the apparatus comprising:

a) means for receiving the (N+M)-bit signal;

b) means for splitting the (N+M)-bit signal into an N-bit portion and an M-bit portion;

c) means for interpreting the N-bit portion as a binary coded number n;

d) means for interpreting the M-bit portion as a binary coded number m;

e) means for encoding (n+1) in a form of a binary N-bit word and feeding the word for m pulse cycles into the stream; and

f) means for encoding n in a form of a binary N-bit word for (2^M−

m) pulse cycles and feed the word into the stream;

thereby forming the stream of 2^M words of N-bit width for a total of 2^M pulse cycles.