Method and apparatus for driving a pulse modulated output circuit
Light Emitting Diodes (LEDs) are increasingly used in illumination applications. To control multiple Light Emitting Diodes (LEDs), or any other controllable light source, this document introduces a single-wire multiple-LED power and control system. Specifically, individually controlled LED units are arranged in a series configuration that is driven by a control unit located at the head of the series. Each of the individually controlled LED units may comprise more than one LED that is also individually controllable. The head-end control unit provides both electrical power and control signals down a single wire to drive all of the LED units in the series in a manner that allows each LED unit to be controlled individually or in assigned groups.
1. An electronic circuit for driving a pulse modulated output circuit, said electronic circuit comprising:
a reduced flicker modulation system for generating a series of output pulses to said pulse modulated output circuit;
a turn-on delay value, said turn-on delay value corresponding to an amount of energy lost due to said output pulses generated by said reduced flicker modulation system being imperfect; and
an accumulator, said turn-on delay value added to said accumulator each time one of said series of output pulses is generated by said pulse modulation circuit;
wherein said reduced flicker modulation system adds a unit of on time for a later output pulse when said accumulator accumulates an amount of energy corresponding to said unit of on time.
2. The electronic circuit as set forth in claim 1 wherein said pulse modulated output circuit comprises a light emitting diode.
3. The electronic circuit as set forth in claim 2 wherein said series of output pulses comprises a series of output pulses of constant direct current.
4. The electronic circuit as set forth in claim 1 wherein said reduced flicker modulation system adds a unit of on time when said accumulator overflows.
5. The electronic circuit as set forth in claim 1 wherein said amount of energy lost due to said pulses generated by said reduced flicker modulation system being imperfect comprises an amount of energy lost due to a rise time minus an amount of energy gained by a fall time.
6. The electronic circuit as set forth in claim 1 wherein said reduced flicker modulation system creates a final output pattern by combining a set of bit position patterns.
7. The electronic circuit as set forth in claim 1 wherein said reduced flicker modulation system outputs pulses of variable widths in a single output period.
8. The electronic circuit as set forth in claim 1 wherein said series of output pulses generated by reduced flicker modulation system are scrambled.
9. A method for driving a pulse modulated output circuit, said method comprising the steps of:
generating a series of output pulses from a pulse modulation circuit to said pulse modulated output circuit, said series of output pulses substantially totaling a desired on time during a specified time period, each output pulse in said series of output pulses having a turn-on delay causing a small energy loss during each output pulse;
counting said output pulses output by said pulse modulation circuit; and
adding a unit of on time to a later output pulse from said pulse modulation circuit when a count of said output pulses accumulates an amount of lost energy due to said turn-on delays corresponds to said unit of on time.
10. The method for driving a pulse modulated output circuit as set forth in claim 9 wherein counting said output pulses output to said pulse modulated output circuit comprises adding a turn-on delay value to an accumulator.
11. The method for driving a pulse modulated output circuit as set forth in claim 10 wherein adding a unit of on time to a later output pulse occurs when said accumulator overflows.
12. The method for driving a pulse modulated output circuit as set forth in claim 9 wherein said pulse modulated output circuit comprises a light emitting diode (LED).
13. The method for driving a pulse modulated output circuit as set forth in claim 12 wherein said each of said output pulses comprise a constant current pulse.
14. The method for driving a pulse modulated output circuit as set forth in claim 9 wherein said small energy loss comprises an amount of energy lost due to a rise time minus an amount of energy gained by a fall time.
15. The method for driving a pulse modulated output circuit as set forth in claim 9 wherein said series of output pulses output during said specified time period comprise pulses of variable widths.
16. The method for driving a pulse modulated output circuit as set forth in claim 9 wherein said series of output pulses output during said specified time period are scrambled.
17. The method for driving a pulse modulated output circuit as set forth in claim 9 wherein said pulse modulation circuit comprises a reduced flicker modulation circuit that may output more than one output pulse per time period.