Light driver with adaptive TRIAC dimming

1 . A method of driving a light source by a light driver, the method comprising:

determining a dimming value based on an input from a phase-cut dimmer at the input of the light driver;

determining an offset for a dimmer transfer function of the light driver based on the dimming value and a minimum set point of the dimmer transfer function;

applying the offset to the dimmer transfer function of the light driver to generate an adjusted dimmer transfer function; and

determining a target light output of the light source based on the dimming value and the adjusted dimmer transfer function.

2 . The method of claim 1 , further comprising:

driving the light source to the target light output.

3 . The method of claim 1 , wherein the determining the dimming value comprises:

receiving a pulse-width modulation (PWM) signal having a duty cycle corresponding to a conduction angle of the phase-cut dimmer; and

generating the dimming value based on the duty cycle of the PWM signal.

4 . The method of claim 1 , wherein the dimmer transfer function maps dimming values to target light outputs.

5 . The method of claim 1 , wherein the minimum set point corresponds to a dimming level above which the light driver begins to increase light output from a lowest target output.

6 . The method of claim 5 , wherein the lowest target output is about 1% light output.

7 . The method of claim 1 , wherein the determining the offset of the dimmer transfer function comprises:

determining that the dimming value is less than a minimum threshold of the dimmer transfer function of the light driver; and

determining the offset as a maximum offset.

8 . The method of claim 1 , wherein the determining the offset of the dimmer transfer function comprises:

determining the dimming value is greater than or equal to a minimum threshold of the dimmer transfer function of the light driver; and

determining the offset based on the dimming value, the minimum set point, and a deadband value.

9 . The method of claim 8 , wherein the determining the offset comprises:

determining that the dimming value is greater than a difference between the minimum set point and the deadband value; and

setting the offset to zero.

10 . The method of claim 8 , wherein the determining the offset comprises:

determining that the dimming value is less than a difference between the minimum set point and the deadband value; and

calculating the offset by subtracting the dimming value from the difference between the minimum set point and the deadband value.

11 . The method of claim 1 , wherein the applying the offset to the dimmer transfer function of the light driver comprises:

subtracting the offset from the minimum set point of the dimmer transfer function to generate the adjusted dimmer transfer function.

12 . The method of claim 1 , wherein the applying the offset to the dimmer transfer function of the light driver comprises:

subtracting the offset from the minimum set point and a maximum set point of the dimmer transfer function to generate the adjusted dimmer transfer function.

13 . The method of claim 12 , wherein the maximum set point corresponds to a dimming level above which the light driver does not increase light output from a highest target output.

14 . The method of claim 13 , wherein the highest target output is about 100% light output.

15 . The method of claim 1 , wherein the determining the target light output of the light source comprises:

interpolating between data points of the adjusted dimmer transfer function to determine the target light output based on the dimming value.

16 . A light driver comprising:

a processor; and

a memory storing instructions that, when executed on the processor, cause the processor to perform:

determining a dimming value based on an input from a phase-cut dimmer at the input of the light driver;

determining an offset for a dimmer transfer function of the light driver based on the dimming value and a minimum set point of the dimmer transfer function;

applying the offset to the dimmer transfer function of the light driver to generate an adjusted dimmer transfer function; and

determining a target light output of a light source coupled to the light driver based on the dimming value and the adjusted dimmer transfer function.

17 . The light driver of claim 16 , further comprising:

a rectifier configured to receive a phase-cut input line voltage from the phase-cut dimmer at the input of the rectifier and configured to generate a rectified input line voltage; and

a pulse-width modulation (PWM) generator configured to generate a PWM signal based on the rectified input line voltage, the PWM signal having a duty cycle corresponding to a conduction angle of the phase-cut dimmer,

wherein the determining the dimming value is based on the PWM signal.

18 . The light driver of claim 17 , further comprising:

a converter configured to convert the rectified input line voltage into a drive signal for powering the light source coupled to the light driver,

wherein the drive signal is based on the target light output.

19 . The light driver of claim 17 , wherein the determining the offset of the dimmer transfer function comprises:

determining the dimming value is greater than or equal to a minimum threshold of the dimmer transfer function of the light driver; and

determining the offset based on the dimming value, the minimum set point, and a deadband value.

20 . The light driver of claim 17 , wherein the applying the offset to the dimmer transfer function of the light driver comprises:

adding the offset to the minimum set point of the dimmer transfer function to generate the adjusted dimmer transfer function.