Lighting device with dimming reference control method to stabilize low output current

1. A lighting device comprising:

a power stage comprising one or more switching elements and configured to generate an output current to a lighting mode based on a regulated switching operation; and

control circuitry configured to generate control signals for regulating the switching operation of the power stage based at least in part on a feedback signal regarding the output current and a reference signal,

wherein the control circuitry is further configured

to define each of an upper boundary and a lower boundary as offset values with respect to a measured average control value, the offset values respectively extending linearly from a minimum control value to a maximum control value,

wherein each of the upper boundary and the lower boundary are defined corresponding to a difference between a current control value and the maximum control value, and linearly and progressively approach the control value as the control value increases, and

the control circuitry is further configured to enable adjustments to the reference signal only when changes to the control value exceed the upper boundary or the lower boundary.

2. The lighting device of claim 1 , further comprising a filtering circuit comprising a resistor and a capacitor coupled in series to filter high frequency noise in the reference signal.

3. The lighting device of claim 1 , wherein the control circuitry comprises

a microcontroller configured to receive a dimming control input signal as the control value and to programmatically generate the reference signal based on a stored dimming curve and further based on the upper and lower boundaries, and

a comparator configured to receive the feedback signal and the reference signal and to generate the control signals to a gate driving circuit.

4. The lighting device of claim 3 , further comprising an analog dimming interface circuit coupled to receive a dimming input voltage from an external device, and to generate the dimming control input signal to the microcontroller based thereon.

5. A method of controlling a power stage of a lighting device to stabilize operation at low output current, the method comprising:

sensing an output current from the lighting device as a feedback signal;

defining an upper boundary and a lower boundary for a control band as offset values with respect to an average sensed input control value, respectively extending linearly from a minimum control value to a maximum control value and corresponding to a difference between the actual sensed input control value and the maximum control value, wherein the upper and lower boundaries linearly and progressively approach the average sensed control value as the average sensed control value increases;

generating a reference signal corresponding to the average sensed input control value, wherein adjustments to the reference signal are enabled only when an actual sensed input control value extends beyond the control band; and

generating control signals for driving one or more switching elements in the power stage, based at least in part on the feedback signal and the generated reference signal.

6. The method of claim 5 , wherein the average sensed control value comprises a measured average of a dimming control input signal.

7. A lighting device comprising:

a power stage comprising one or more switching elements and configured to generate an output current to a lighting mode based on a regulated switching operation;

control circuitry configured to generate control signals for regulating the switching operation of the power stage based at least in part on a feedback signal regarding the output current and a reference signal,

wherein the control circuitry is further configured to define an upper boundary and a lower boundary as offset values with respect to a measured average control value, respectively extending non-linearly from a minimum control value to a maximum control value,

wherein each of the upper boundary and the lower boundary are defined corresponding to a difference between a current control value and the maximum control value, and progressively approach the control value as the control value increases, and

wherein the control circuitry is further configured to enable adjustments to the reference signal only when changes to the control value exceed the upper boundary or the lower boundary.

8. The lighting device of claim 7 , further comprising a filtering circuit comprising a resistor and a capacitor coupled in series to filter high frequency noise in the reference signal.

9. The lighting device of claim 7 , wherein the control circuitry comprises

a microcontroller configured to receive a dimming control input signal as the control value and to programmatically generate the reference signal based on a stored dimming curve and further based on the upper and lower boundaries, and

a comparator configured to receive the feedback signal and the reference signal and to generate the control signals to a gate driving circuit.

10. The lighting device of claim 9 , further comprising an analog dimming interface circuit coupled to receive a dimming input voltage from an external device, and to generate the dimming control input signal to the microcontroller based thereon.

11. A lighting device comprising:

a power stage comprising one or more switching elements and configured to generate an output current to a lighting mode based on a regulated switching operation;

a controller configured to

receive a dimming control input signal and determine a control value as a measured average thereof,

programmatically generate a reference signal based on a stored dimming curve and further based on upper and lower boundaries defined with respect to the control value, and to enable adjustments to the reference signal only when changes to the control value exceed the upper boundary or the lower boundary; and

a comparator configured to generate control signals to a gate driving circuit for regulating the switching operation of the power stage, the control signals based at least in part on a feedback signal regarding the output current and further based at least in part on the reference signal.

12. The lighting device of claim 11 , further comprising an analog dimming interface circuit coupled to receive a dimming input voltage from an external device, and to generate the dimming control input signal to the controller based thereon.

13. The lighting device of claim 11 , further comprising a filtering circuit comprising a resistor and a capacitor coupled in series to filter high frequency noise in the reference signal.

14. A method of controlling a power stage of a lighting device to stabilize operation at low output current, the method comprising:

sensing an output current from the lighting device as a feedback signal;

defining an upper boundary and a lower boundary for a control band about an average sensed input control value, wherein each of the upper boundary and the lower boundary are defined as offset values with respect to the average sensed control value, respectively extending non-linearly from a minimum control value to a maximum control value;

generating a reference signal corresponding to the average sensed input control value, wherein adjustments to the reference signal are enabled only when an actual sensed input control value extends beyond the control band; and

generating control signals for driving one or more switching elements in the power stage, based at least in part on the feedback signal and the generated reference signal.

15. The method of claim 14 , wherein each of the upper boundary and the lower boundary are defined corresponding to a difference between an average sensed control value and the maximum control value, further inversely proportional to the average sensed control value.

16. The method of claim 15 , wherein the upper and lower boundaries progressively approach the average sensed control value as the average sensed control value increases.

17. The method of claim 14 , wherein the average sensed control value comprises a measured average of a dimming control input signal.