Energy saving lighting systems and units providing coordinated operation of holding current units

1. A lighting system comprising:

a dimmer that requires at least a holding current to be drawn for proper operation;

a plurality of solid state light sources connected in parallel to an output of the dimmer, each of the solid state light sources comprising:

a light emitter;

a holding current circuit operable to draw a current from the dimmer; and

a control circuit connected to selectively control the current drawn by the holding current circuit; and

a control system configured to automatically reduce an excess of the sum of the currents drawn by the holding current circuits over the holding current

wherein the control system comprises a path by way of which the control circuits of the solid state light sources are configured to exchange information and the control circuits are configured to disable the corresponding holding current circuits or reduce the current drawn by the corresponding holding current circuit in response to information received from other ones of the control circuits.

2. The lighting system according to claim 1 wherein the control system comprises a separate controller in data communication with the solid state light sources and the separate controller is configured to command one or more of the solid state light sources to disable its holding current circuit or to reduce the current drawn by its holding current circuit.

3. The lighting system according to claim 1 wherein the solid state light source control circuits are configured to disable the corresponding holding current circuits upon receipt of a signal indicating that a holding current circuit of another solid state light source is drawing a holding current.

4. The lighting system according to claim 3 wherein the path comprises a power line connected to supply power from the dimmer to the solid state light sources and the solid state light sources comprise circuits for transmitting and receiving ACTIVE signals comprising signals higher in frequency than a powerline frequency.

5. The lighting system according to claim 3 wherein the control circuit in each of the solid state light sources is configured to control a signal transmitter to periodically transmit ACTIVE signals receivable by other solid state light sources when the holding current circuit is enabled and wherein the control circuit in each of the solid state light sources is configured to monitor for ACTIVE signals transmitted by other solid state light sources for a period of time and to maintain the holding current circuit enabled if no ACTIVE signals are detected in the period of time.

6. The lighting system according to claim 5 wherein the periods of time for different ones of the solid state light sources commence at different times.

7. The lighting system according to claim 5 wherein the control circuit in each of the solid state light sources is configured to monitor for ACTIVE signals transmitted by other solid state light sources for a first period of time and for a second period of time commencing after the end of the first period of time, to disable the corresponding holding current circuit if an ACTIVE signal is detected in the first or second period of time, and to maintain the holding current circuit enabled if no ACTIVE signals are detected in the first or second periods of time.

8. The lighting system according to claim 1 wherein the control circuit is configured and connected to selectively control a maximum current drawn by the holding current circuit.

9. The lighting system according to claim 1 wherein each of the solid state light sources comprises a monitoring circuit connected to detect a characteristic of electrical power from the dimmer that can change in response to a total current being drawn from the dimmer falling below the holding current and the monitoring circuit is connected to enable and disable the corresponding holding current circuit and comprises a comparison circuit configured to compare the characteristic as measured with the holding current circuit enabled to the characteristic as measured with the holding current circuit disabled.

10. The lighting system according to claim 9 wherein the comparison circuit comprises first and second sample and hold circuits and control logic that in a first stage disables the holding current and operates the first sample and hold circuit to obtain a first measure of the characteristic with the holding current circuit disabled and in a second stage before or after the first stage enables the holding current and operates the second sample and hold circuit to obtain a second measure of the characteristic with the holding current circuit enabled.

11. The lighting system according to claim 9 wherein the control circuit is configured to reduce the current drawn by the holding current circuit in response to an output of the monitoring circuit indicating a total current being drawn from the dimmer is not falling below the holding current and wherein the control circuit is configured to increase the current drawn by the holding current circuit in response to an output of the monitoring circuit indicating a total current being drawn from the dimmer is falling below the holding current.

12. The lighting system according to claim 1 wherein one or more of the solid state light sources comprises:

a power input connectable to receive electrical power from the dimmer;

a power output connectable to supply power to one or more additional solid state light sources;

an electrical conductor connected between the power input and the power output; and a current monitor connected to monitor an electrical current in the conductor;

wherein the control circuit of the one or more of the solid state light sources is configured to control the current drawn by the holding current circuit at least in part in response to a signal from the current monitor.

13. A solid state light source comprising:

a light emitter,

a holding current circuit operable to draw a holding current, and

a control circuit connected to selectively enable or disable the holding current circuit or to selectively control a value for the upper limiting current that the holding current circuit is configured to draw

wherein the solid state light source comprises a signal input for receiving signals and the control circuit is configured to disable the holding current circuit upon receipt of a signal indicating that another solid state light source is drawing a holding current.

14. The solid state light source according to claim 13 comprising a signal transmitter operable to periodically transmit ACTIVE signals receivable by other solid state light sources when the holding current circuit is enabled wherein the control circuit is configured to monitor for ACTIVE signals transmitted by other solid state light sources for a period of time and to maintain the holding current circuit enabled if no ACTIVE signals are detected in the period of time.

15. A solid state light source comprising:

a light emitter,

a holding current circuit operable to draw a holding current, and

a control circuit connected to selectively enable or disable the holding current circuit or to selectively control a value for the upper limiting current that the holding current circuit is configured to draw

wherein the holding current circuit comprises a variable attenuator connected in series in a holding current path and the control circuit is configured to set an impedance of the variable attenuator.

16. The solid state light source according to claim 15 wherein the holding current circuit is configured to provide a holding current having a magnitude up to a maximum holding current and the maximum holding current is selectively variable.