Load control device for controlling a driver for a lighting load
View Patent ↗If there is an interruption of power to an electrical load while the electrical load is operating at low end, the electrical load may not turn back on when power is restored. This undesired operation may be avoided by detecting the application of power to the electrical load, and automatically increasing the magnitude of a control signal being applied to the electrical load by a sufficient amount for a short period of time after power has been applied. This way, the electrical load may be turned back on to low end, instead of erroneously operating in an electronic off condition.
1. A load control device for controlling an amount of power delivered to a lighting load, the load control device comprising:
a communication circuit configured to generate a control signal for controlling the amount of power delivered to the lighting load, the control signal being capable of causing the lighting load to be turned on when a magnitude of the control signal rises above a threshold; and
a control circuit configured to control the communication circuit to adjust the magnitude of the control signal so as to adjust an intensity of the lighting load between a low-end intensity and a high-end intensity, the control signal having a magnitude less than the threshold when the intensity of the lighting load is being controlled to the low-end intensity;
wherein, when power has been applied to the lighting load, the control circuit is further configured to:
determine that a desired magnitude of the control signal is below the threshold; and
set the magnitude of the control signal to be equal to or greater than the threshold before decreasing the magnitude of the control signal to the desired magnitude.
2. The load control device of claim 1 , further comprising:
an intensity adjustment actuator;
wherein the control circuit comprises a potentiometer circuit responsive to the intensity adjustment actuator for determining the desired magnitude of the control signal.
3. The load control device of claim 2 , wherein the control circuit comprises a digital control circuit configured to control the communication circuit to set the magnitude of the control signal to be equal to or greater than the threshold when power has been applied to the lighting load, and decrease the magnitude of the control signal to the desired magnitude over a first period of time.
4. The load control device of claim 3 , wherein the control circuit is configured to maintain the magnitude of the control signal constant at a level equal to or greater than the threshold for a second period of time when power has been applied to the lighting load before decreasing the magnitude of the control signal to the desired magnitude over the first period of time.
5. The load control device of claim 3 , further comprising:
a sense circuit configured to provide an indication of when power has been applied to the lighting load.
6. The load control device of claim 2 , wherein the control circuit comprises an analog control circuit that includes a bump-up circuit coupled to a wiper of the potentiometer circuit for increasing the magnitude of the control signal.
7. The load control device of claim 1 , wherein the communication circuit comprises a current sink circuit.
8. A method implemented in a load control device for controlling a lighting load, the method comprising:
generating a control signal for controlling an amount of power delivered to the lighting load, the control signal being capable of causing the lighting load to be turned on when a magnitude of the control signal rises above a threshold;
adjusting, after the lighting load has been turned on, the magnitude of the control signal so as to control an intensity of the lighting load between a low-end intensity and a high-end intensity, the magnitude of the control signal being equal to or less than the threshold when the intensity of the lighting load is being controlled to the low-end intensity;
determining, when power has been applied to the lighting load, that a desired magnitude of the control signal is below the threshold; and
setting the magnitude of the control signal to be equal to or greater than the threshold before decreasing the magnitude of the control signal to the desired magnitude.
9. The method The method of claim 8 , further comprising:
sensing, via a sense circuit, that power has been applied to the lighting load.
10. The method of claim 8 , wherein the magnitude of the control signal is set to be equal to or greater than the threshold via a bump-up circuit coupled to a wiper of a potentiometer.
11. The method of claim 8 , wherein the magnitude of the control signal is set equal to or greater than the threshold via digital control circuit.
12. The method of claim 8 , wherein the magnitude of the control signal is decreased to the desired magnitude over a first period of time.
13. The method of claim 12 , wherein the magnitude of the control signal is maintained at a level equal to or greater than the threshold for a second period of time before being decreased to the desired magnitude over the first period of time.
14. A load control device for controlling an amount of power delivered to a lighting load, the load control device comprising:
a control circuit configured to adjust a magnitude of a control signal to control the amount of power delivered to the lighting load, the control signal being capable of causing the lighting load to be turned on when the magnitude of the control signal rises above a threshold, wherein the control circuit is further configured to:
when the lighting load is in an on state, adjust the magnitude of the control signal to control an intensity of the lighting load between a low-end intensity and a high-end intensity, the magnitude of the control signal being less than the threshold when the intensity of the lighting load is at the low-end intensity; and
when the lighting load is in an off state:
determine that power has been applied to the lighting load;
determine that a desired magnitude of the control signal is below the threshold; and
set the magnitude of the control signal to be greater than the threshold by an offset amount to turn on the lighting load.
15. The load control device of claim 14 , wherein the control circuit is further configured to decrease the magnitude of the control signal to the desired magnitude over a first period of time.
16. The load control device of claim 15 , wherein the control circuit is configured to maintain the magnitude of the control signal above the threshold for a second period of time before decreasing the magnitude of the control signal to the desired magnitude over the first period of time.
17. The load control device of claim 16 , wherein the control circuit is further configured to adjust the respective values of the offset amount, the first period of time, and the second period of time based on an external input.
18. The load control device of claim 14 , wherein the load control device is connected to a power source that powers the lighting load, the load control device further comprising:
a sense circuit configured to sense that power has been applied to the lighting load.
19. The load control device of claim 14 , further comprising:
a current sink circuit configured to generate the control signal by sinking current through a load regulation device that is controlling the lighting load.
20. The load control device of claim 19 , wherein the control circuit is further configured to determine that power has been applied to the lighting load based on a change in the magnitude of the control signal.
21. The load control device of claim 20 , wherein the change in the magnitude of the control signal includes an increase of the magnitude of the control signal from approximately zero volts to the desired magnitude.