High-efficiency lighting devices having dimmer and/or load condition measurement

1. A lighting circuit for powering one or more lighting devices from an output of a thyristor-switched dimmer circuit, comprising:

input terminals for coupling the lighting circuit to the output of the thyristor-switched dimmer circuit, wherein the thyristor-switched dimmer circuit supplies an input voltage and an input current to the lighting circuit at the input terminals;

a power converter having an input coupled to the input terminals and at least one output for supplying energy to the one or more lighting devices, wherein the power converter transfers energy from the input terminals to the at least one output during an active time period;

an input current control circuit for controlling the input current at least during the active time period;

a sensing circuit for sensing the input voltage and determining a first attach current characteristic for positive half cycles of an AC line voltage supplied to the input of the thyristor-switched dimmer circuit and a second attach current characteristic for negative half cycles of the AC line voltage indicative of a load at the input terminals including external loads coupled to the output of the thyristor-switched dimmer circuit; and

a storage circuit for storing information indicative of the first and second attach current characteristics, and wherein the input current control circuit alternatively selects between the first and second attach current characteristics at the alternating half cycles of the AC line voltage and controls the input current in conformity with the selected attach current characteristic.

2. The lighting circuit of claim 1 , wherein the first and second attach current characteristics comprise one or more of a starting value of the input current, a peak value of the input current, a steady-state hold value of the input current or at least one timing value indicating a time at which the input current was equal to a predetermined value.

3. The lighting circuit of claim 2 , wherein the first and second attach current characteristics comprise the at least one timing value, and wherein the at least one timing value is relative to a time of a leading edge of the input voltage.

4. The lighting circuit of claim 3 , wherein the at least one timing value includes a value at which the input current is equal to the starting value of the input current, the peak value of the input current or the steady-state hold value of the input current.

5. The lighting circuit of claim 1 , wherein the sensing circuit iteratively adjusts the first and second attach current characteristics in conformity with subsequent measurements of the input voltage.

6. The lighting circuit of claim 1 , wherein the sensing circuit determines, from the input voltage, whether or not other lighting devices are connected to the output of the thyristor-switched dimmer circuit, and wherein the sensing circuit further selects from among differing attach current characteristics for each of the first and second attached current characteristics in conformity with whether or not other lighting devices are connected to the output of the thyristor-switched dimmer circuit.

7. The lighting circuit of claim 1 , wherein the one or more lighting devices are light-emitting diode (LED) devices.

8. A method of powering one or more lighting devices from an output of a thyristor-switched dimmer circuit, comprising:

receiving the output of the thyristor-switched dimmer circuit at input terminals;

supplying energy to the one or more lighting devices by converting energy drawn from the input terminals during an active time period;

controlling an input current drawn by the receiving from the input terminals at least during the active time period;

sensing an input voltage across the input terminals and determining a first attach current characteristic for positive half cycles of an AC line voltage supplied to the input of the thyristor-switched dimmer circuit and a second attach current characteristic for negative half cycles of the AC line voltage indicative of a load across the input terminals including external loads coupled to the output of the thyristor-switched dimmer circuit; and

storing information indicative of the first and second attach current characteristics, and wherein the controlling alternatively selects between the first and second attach current characteristics at the alternating half cycles of the AC line voltage and controls the input current in conformity with the selected attach current characteristic.

9. The method of claim 8 , wherein the first and second attach current characteristics comprise one or more of a starting value of the input current, a peak value of the input current, a steady-state hold value of the input current or at least one timing value indicating a time at which the input current was equal to a predetermined value.

10. The method of claim 9 , wherein the first and second attach current characteristics comprise the at least one timing value, and wherein the at least one timing value is relative to a time of a leading edge of the input voltage.

11. The method of claim 10 , wherein the at least one timing value includes a value at which the input current is equal to the starting value of the input current, the peak value of the input current or the steady-state hold value of the input current.

12. The method of claim 8 , wherein the sensing comprises iteratively adjusting the first and second current characteristics in conformity with subsequent measurements of the input voltage.

13. The method of claim 8 , wherein the sensing determines, from the input voltage, whether or not other lighting devices are connected to the output of the thyristor-switched dimmer circuit, and wherein the sensing further selects from among differing attach current characteristics for each of the first and second attached current characteristics in conformity with whether or not other lighting devices are connected to the output of the thyristor-switched dimmer circuit.

14. The method of claim 8 , wherein the one or more lighting devices are light-emitting diode (LED) devices.

15. An integrated circuit for operating a circuit that powers one or more lighting devices from an output of a thyristor-switched dimmer circuit, comprising:

a power converter control circuit having an output for controlling a power converter for supplying current to the one or more lighting devices from the output of the thyristor-switched dimmer circuit, wherein the power converter transfers energy during an active time period;

an input current control circuit for controlling the input current at least during the active time period;

a sensing circuit for sensing the input voltage and determining a first attach current characteristic for positive half cycles of an AC line voltage supplied to the input of the thyristor-switched dimmer circuit and a second attach current characteristic for negative half cycles of the AC line voltage indicative of a load at the input terminals including external loads coupled to the output of the thyristor-switched dimmer circuit; and

a storage circuit for storing information indicative of the first and second attach current characteristics, and wherein the input current control circuit alternatively selects between the first and second attach current characteristics at the alternating half cycles of the AC line voltage and controls the input current in conformity with the selected attach current characteristic.

16. The integrated circuit of claim 15 , wherein the first and second attach current characteristics comprise one or more of a starting value of the input current, a peak value of the input current, a steady-state hold value of the input current or at least one timing value indicating a time at which the input current was equal to a predetermined value.