Method and IC driver for series connected R, G, B LEDs

1. An adaptive boost converter adapted for supplying electrical current to a number of series connected RGB LEDs for energizing the operation thereof, the series connected RGB LEDs being connectible in series with a current generator, the adaptive boost converter comprising:

a. a power input terminal for receiving electrical power from an energy source;

b. a plurality of LED switches equal in number to the number of series connected RGB LEDs, each LED switch:

i. being connectible across one of the RGB LEDs; and

ii. operating responsive to a binary digital switching signal so that the LED switch:

1) when open permits electrical current to flow through the RGB LED across which the LED switch is connectible; and

2) when closed shorts across and thereby shunts current around the RGB LED across which the LED switch is connectible;

c. a comparator connectible to the current generator for sensing voltage across the current generator; and

d. a voltage boosting circuit for increasing voltage of electrical power received from the energy source to a higher voltage to be applied across series connectible RGB LEDs and series connectible current generator, the voltage applied across series connected RGB LEDs and series connectible current generator varying responsive to an output signal produced by the comparator;

whereby the voltage appliable across series connectible RGB LEDs and series connectible current generator is only that required by those series connectible RGB LEDs whose operation is then being energized by the adaptive boost converter plus a bias voltage required to ensure proper operation of the current generator.

2. The adaptive boost converter of claim 1 wherein the plurality of LED switches and the comparator are included in an IC.

3. The adaptive boost converter of claim 2 wherein the IC further comprises a current generator that is adapted for being connected in series with series connected RGB LEDs.

4. The adaptive boost converter of claim 1 wherein the voltage boosting circuit is a DC to DC boost converter.

5. The adaptive boost converter of claim 1 wherein the voltage boosting circuit is a charge pump.

6. A LED driver IC adapted for:

a. supplying electrical current to a number of series connected RGB LEDs for energizing operation thereof; and

b. controlling operation of those series connected RGB LEDs;

the LED driver IC comprising:

a. a power input terminal for receiving electrical power from an energy source;

b. a plurality of LED switches equal in number to the number of series connected RGB LEDs, each LED switch:

i. being connectible across one of the RGB LEDs; and

ii. operating responsive to a binary digital switching signal:

1) so that the LED switch:

a) when open permits electrical current to flow through the RGB LED across which the LED switch is connectible; and

b) when closed shorts across and thereby shunts current around the RGB LED across which the LED switch is connectible; and

2) having a repetition rate which fast enough to avoid ocularly perceptible flicker in light producible by series connected RGB LEDs that are connectible to the LED driver IC;

c. a current generator that is connectible in series with series connected RGB LEDs;

d. a comparator connected to the current generator for:

i. sensing voltage across the current generator; and

ii. producing a comparator output signal which responds to the voltage across the current generator;

e. a boost control circuit that:

i. receives the comparator output signal from the comparator; and

ii. responsive to the comparator output signal generates a digital boost control signal which has a frequency significantly higher than the repetition rate of the binary digital switching signals for operating the LED switches; and

f. a voltage-boost switch that:

i. receives the boost control signal from the boost control circuit;

ii. responsive to the boost control signal repetitively turns on and off at the frequency of the boost control signal; and

iii. has a switch output terminal which is connectible to one terminal of an inductor, the inductor being connectible between:

1) series connected RGB LEDs; and

2) the power input terminal of the LED driver IC;

whereby the LED driver IC is adapted for supplying electrical power to series connected RGB LEDs and the current generator at a voltage which is:

a. greater than a voltage at which the LED driver IC receives electrical power from the energy source; and

b. only that required for operating those series connectible RGB LEDs which are not being shorted across by a LED switch plus a bias voltage required to ensure proper operation of the current generator.

7. The LED driver IC of claim 6 wherein the boost control signal generated by the boost control circuit is pulse width modulated (“PWM”).

8. The LED driver IC of claim 6 further comprising a digital interface which stores digital data that specifies:

a. relative proportions of light producible respectively by series connected RGB LEDs as are connectible to the LED driver IC; and

b. overall brightness of light producible by such series connected RGB LEDs as are connectible to the LED driver IC.

9. The LED driver IC of claim 8 wherein the digital interface receives via a serial digital data bus the digital data specifying:

a. relative proportions of light producible respectively by series connected RGB LEDs as are connectible to the LED driver IC; and

b. overall brightness of light producible by such series connected RGB LEDs as are connectible to the LED driver IC.

10. The LED driver IC of claim 8 further comprising:

g. a brightness digital-to-analog converter (“DAC”) which:

i. receives from the digital interface digital data specifying overall brightness of light produced by such series connected RGB LEDs as are connectible to the LED driver IC; and

ii. produces responsive to the received digital data a brightness analog signal which is coupled to the current generator for controlling how much electrical current flows through series connected RGB LEDs as are connectible to the LED driver IC when all of the LED switches are open;

whereby the LED driver IC is adapted for controlling overall brightness of light producible by series connected RGB LEDs as are connectible across the LED switches of the LED driver IC.

11. The LED driver IC of claim 8 further comprising:

g. a plurality of switch-controlling DACs which equal in number the number of LED switches included in the LED driver IC, each of the switch-controlling DACs respectively:

i. receiving from the digital interface digital data specifying a relative proportion of light to be produced by one of the series connected RGB LEDs as are connectible across the LED switches of the LED driver IC; and

ii. producing responsive to the received digital data an analog LED-control output-signal;

h. a plurality of switch control comparators which equal in number the number of LED switches included in the LED driver IC, each switch control comparator respectively:

i. receiving:

1) at an inverting input of the switch control comparator a LED-control output-signal produced by one of the switch-controlling DACs; and

2) at a non-inverting input of the switch control comparator a triangular-waveform signal that is generated within the LED driver IC; and

ii. producing responsive both to the LED-control output-signal and to the triangular-waveform signal the binary digital switching signal:

1) which is coupled to one of the LED switches included in the LED driver IC; and

2) to which the LED switch responds by opening and closing the LED switch;

whereby the LED driver IC is adapted for controlling relative proportions of light producible by series connected RGB LEDs as are connectible across the LED switches of the LED driver IC.