Integrated device and method for driving lighting loads with a brightness compensation

1. A method for driving a lighting load, the method comprising:

reading a nominal duty-cycle from a first memory element, wherein the nominal duty-cycle corresponds to a nominal supply voltage;

detecting an actual supply voltage with an actual voltage acquisition element;

reading a load voltage drop from a second memory element;

calculating, with a processing unit, a voltage compensated duty-cycle according to equation:

DC

C

=

V

th

-

V

LED

V

B

-

V

LED

⁢

DC

n

wherein DCn is the nominal duty-cycle, VTH is the nominal supply voltage, VLED is the load voltage drop, and VB is the actual supply voltage; and

controlling switching of the lighting load with a pulse width modulation (PWM) according to the voltage compensated duty-cycle using a driver circuit.

2. The method of claim 1 , further comprising storing the voltage compensated duty-cycle and a load characteristic value indicative of the load voltage drop.

3. The method of claim 2 , wherein storing the voltage compensated duty-cycle and the load characteristic value comprises storing the voltage compensated duty-cycle in a first register, and storing the load characteristic value in a second register different from the first register, wherein the second memory element comprises the second register.

4. The method of claim 3 , wherein the first memory element comprises a third register, wherein the nominal duty-cycle is stored in the third register, and wherein the third register is different than the first and second registers.

5. The method of claim 4 , further comprising storing the nominal duty-cycle in the third register with 10 bit accuracy.

6. The method of claim 1 , further comprising storing an activation bit indicative of whether brightness of the lighting load is to be compensated for supply voltage.

7. The method of claim 1 , wherein detecting the actual supply voltage comprises determining an analog voltage value, the method further comprising converting the analog voltage value to a digital value.

8. The method of claim 1 , wherein the lighting load comprises a light emitting diode (LED).

9. The method of claim 8 , wherein the lighting load comprises a plurality of LEDs.

10. The method of claim 9 , further comprising driving each of the plurality of LEDs via respective load terminals.

11. The method of claim 1 , wherein the nominal supply voltage is substantially equal to 10 V.

12. The method of claim 1 , further comprising checking whether an activation bit indicative of whether brightness of the lighting load is to be compensated for supply voltage is set, wherein calculating the voltage compensated duty-cycle comprises calculating the voltage compensated duty-cycle when the activation bit is set.

13. The method of claim 12 , further comprising detecting the actual supply voltage by reading an output of an analog-to-digital converter (ADC).

14. The method of claim 1 , further comprising programming the nominal duty-cycle via serial peripheral interface (SPI) bus.

15. The method of claim 14 , further comprising controlling switching of the lighting load without using the SPI bus.

16. A method for driving a light emitting diode (LED), the method comprising:

reading a nominal duty-cycle from a first register, the nominal duty-cycle corresponding to a nominal supply voltage;

detecting an actual supply voltage by reading an output of an analog to digital converter;

reading a load voltage drop from a second register;

calculating a voltage compensated duty-cycle according to equation:

DC

C

=

V

th

-

V

LED

V

B

-

V

LED

⁢

DC

n

wherein DCn is the nominal duty-cycle, VTH is the nominal supply voltage, VLED is the load voltage drop, and VB is the actual supply voltage;

storing the voltage compensated duty-cycle in a third register; and

controlling switching of the LED with a pulse width modulation (PWM) according to the voltage compensated duty-cycle.

17. The method of claim 16 , further comprising checking whether an activation bit indicative of whether brightness of the LED is to be compensated for supply voltage is set, wherein calculating the voltage compensated duty-cycle comprises calculating the voltage compensated duty-cycle when the activation bit is set.

18. A method for driving a plurality of lighting loads, the method comprising:

reading a nominal duty-cycle from a first register, the nominal duty-cycle corresponding to a nominal supply voltage;

detecting an actual supply voltage by reading an output of an analog to digital converter;

for each respective lighting load of the plurality of lighting loads:

reading a load voltage drop of the respective lighting load,

calculating a voltage compensated duty-cycle of the respective lighting load according to equation:

DC

C

=

V

th

-

V

LED

V

B

-

V

LED

⁢

DC

n

wherein DCn is the nominal duty-cycle, VTH is the nominal supply voltage, VLED is the load voltage drop of the respective lighting load, and VB is the actual supply voltage; and

controlling switching of each respective lighting load of the plurality of lighting loads with a pulse width modulation (PWM) according to the voltage compensated duty-cycle of each respective lighting load.

19. The method of claim 18 , further comprising:

initializing a counter; and

increasing the counter by one after calculating the voltage compensated duty-cycle of the respective lighting load.

20. The method of claim 18 , further comprising checking whether a respective activation bit indicative of whether brightness of the respective lighting load is to be compensated for supply voltage is set, wherein calculating the voltage compensated duty-cycle of the respective lighting load comprises calculating the voltage compensated duty-cycle of the respective lighting load when the respective activation bit is set.