LED matrix current control
View Patent ↗A system is employed to provide a substantially constant intensity light source via functional circuitry, the functional circuitry comprises a switching power supply. At least one signal is part of a matrix of LEDs connected in series and parallel and configured for redundancy. A monitoring circuit comprises a current sense circuit, wherein the current sense circuit includes an amplifier and at least one resistor in series with the amplifier. The current sense circuit includes a power converter circuit that senses a current of a flyback diode, recovers a dc component of a waveform via a low pass filter, and provides feedback control of the at least one signal.
1. A substantially constant intensity light source, comprising:
functional circuitry, said functional circuitry comprising a switching power supply;
at least one signal, said signal a matrix of LEDs connected in series and parallel and configured for redundancy; and
a monitoring circuit, said monitoring circuit comprises a current sense circuit;
wherein said current sense circuit includes an amplifier and at least one resistor in series with the amplifier and a power converter circuit, senses a current of a flyback diode, recovers a dc component of a waveform via a low pass filter, and provides feedback control of the at least one signal.
2. The light source of claim 1 , wherein the power converter circuit includes a current sense transformer.
3. The light source of claim 1 , wherein the current sense circuit further comprises a pole that is independent of pole C 7 /R load variations.
4. The light source of claim 3 , wherein voltage ripple across a first capacitor in the amplifier is independent of a second capacitor in the power converter circuit.
5. The light source of claim 4 , wherein the second capacitor is less than 500 μF.
6. The light source of claim 1 , wherein the LEDs are selected from a group consisting of red LEDs, green LEDs or yellow LEDs.
7. The light source of claim 1 , further comprising a first signal comprising a matrix of red LEDs connected in series and parallel and configured for redundancy, a second signal comprising a matrix of yellow LEDs connected in series and parallel and configured for redundancy, and a third signal comprising a matrix of green LEDs connected in series and parallel and configured for redundancy.
8. The light source of claim 1 , wherein the amplifier increases an output current to compensate for light reduction of LEDs at higher temperatures.
9. The light source of claim 1 , wherein the amplifier comprises a thermistor and at least one resistor having a resistivity that decreases above 25° C.
10. The light source of claim 1 , wherein an amplifier gain is reduced and a current across a resistor Rs is increased.
11. The light source of claim 6 , wherein the LEDs are yellow and the amplifier is connected in parallel with a first, a second, a third, a fourth, and a fifth resistor, and the first resistor is connected in parallel with the second, the third, the fourth and the fifth resistors, the second, the fourth and the fifth resistors are connected in series, the third resistor is connected in parallel with the second resistor and a capacitor and a resistor Rs are connected in series with the amplifier.
12. The light source of claim 6 , wherein the LEDs are red and the amplifier is connected in parallel with a first, a second and a third resistor and the first resistor is connected in parallel with the third resistor and in series with the second resistor and the second capacitor and a resistor Rs are connected in series with the amplifier.
13. The light source of claim 6 , wherein the LEDs are green and the amplifier is connected in parallel with a first, a second, a third, a fourth and a fifth resistor, the first resistor is connected in series with the second and the fourth resistor and in parallel with the third and the fifth resistor and the second capacitor and a resistor Rs are connected in series with the amplifier.