Shunt device in lighting control system without neutral wire

Abstract

A device ( 340, 440, 540 ) is connected to an output terminal of a controller( 330 ), having a single input terminal connected to a first power terminal of an external power source ( 305 ) which outputs an AC voltage between the first power terminal and a second power terminal. The device includes a bleeding circuit( 342, 442, 542 ), and a switching arrangement ( 344/346, 444/446, 544/546 ) to detect whether the controller powers a load ( 320 or disables the load. When the controller is in an OFF state, the switching arrangement connects the bleeding circuit between the output terminal of the controller and the second power terminal to provide a current path between the output terminal of the controller and the second power terminal. When the controller is in an ON state, the switching arrangement disconnects the bleeding circuit between the output terminal of the controller and the second power terminal.

The invention claimed is: 
     
       1. A system, comprising:
 an electronic controller, having: 
 a single input terminal connected to a first power terminal of an external power source which is external to the electronic controller and which outputs an AC voltage between the first power terminal and a second power terminal thereof, and 
 a single output terminal connected to a first load terminal of a load which includes at least one light source and which has the first load terminal and a second load terminal, wherein the second load terminal is connected to the second power terminal of the external power source, and wherein the load is configured to receive a load voltage between the first and second load terminals and is further configured to allow a load current to flow between the first and second load terminals, 
 wherein the electronic controller is configured to control at least one of the load voltage and the load current so as to selectively power the load when electronic controller is in an ON state, and to disable the load when electronic controller is in an OFF state; and 
 a shunt device, comprising: 
 a series combination of a bleeding circuit in series with a switch, the series combination having a first terminal directly connected to an output terminal of the electronic controller and having a second terminal directly connected to the second power terminal of the external power source, and a switch control device that is configured to: 
 control the switch to connect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the electronic controller is in an OFF state and the load is powered OFF to provide a current path for leakage current between the output terminal of the electronic controller and the second power terminal of the external power source, 
 control the switch to disconnect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the electronic controller is in an ON state and the load is powered ON, and 
 before disconnecting the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source, cause a delay of at least 100 msec after transition of the electronic controller from the OFF state to the ON state to enable the electronic controller to remain operable during an initial ON state, wherein the leakage current continues to have a current path between the output terminal of the electronic controller and the second power terminal of the external power source for the duration of the delay. 
 
     
     
       2. The system of  claim 1 , wherein the switch control device includes a voltage measurement device connected between the first and second load terminals and configured to measure the load voltage, and to close the switch to connect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source to provide the current path between the output terminal of the electronic controller and the second power terminal of the external power source when the measured load voltage is less than a first threshold voltage while the electronic controller is in the OFF state, and to control the switch to open the switch to disconnect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the measured load voltage exceeds the threshold voltage while the electronic controller is in the ON state. 
     
     
       3. The system of  claim 1 , wherein the switch control device includes a current measurement device configured to measure the load current and to close the switch to connect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source to provide the current path between the output terminal of the electronic controller and the second power terminal of the external power source when the measured load current is less than a threshold current, and to control the switch to open the switch to disconnect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the measured load current exceeds the threshold current. 
     
     
       4. The system of  claim 3 , wherein the current measurement device is connected between the output terminal of the electronic controller and the first load terminal. 
     
     
       5. The system of  claim 3 , wherein the current measurement device is connected between the second load terminal and the second power terminal of the external power source. 
     
     
       6. The system of  claim 1 , wherein the electronic controller includes a dimming circuit for adjusting an amount of power supplied to the load. 
     
     
       7. The system of  claim 1 , wherein the electronic controller includes a wireless receiver configured to receive a wireless signal and in response thereto to control an amount of power supplied to the load. 
     
     
       8. The system of  claim 1 , wherein the electronic controller is installed in a building at a location where a connection to the second power terminal is not provided, and wherein the shunt device is separated and spaced apart from the electronic controller by a distance of at least one foot. 
     
     
       9. The system of  claim 8 , wherein the first terminal of the load is directly connected to the output terminal of the electronic controller. 
     
     
       10. The system of  claim 1 , wherein the second terminal of the load is directly connected to the second power terminal of the external power source. 
     
     
       11. A method of supplying power to a load having first and second load terminals, via an electronic controller connected to an external power source which is external to the electronic controller and which external power source outputs an AC voltage between a first power terminal thereof and a second power terminal thereof, wherein the load is configured to receive a load voltage between the first and second load terminals and is further configured to allow a load current to flow between the first and second load terminals, and wherein the electronic controller is configured to control at least one of the load voltage and the load current so as to selectively power the load and disable the load, the method comprising:
 providing a series combination of a bleeding circuit in series with a switch, the series combination having a first terminal directly connected to an output terminal of the electronic controller and having a second terminal directly connected to the second power terminal of the external power source, 
 operating the switch to connect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the electronic controller is in an OFF state and the load is powered OFF, the bleeding circuit providing a current path for leakage current between the output terminal of the electronic controller and the second power terminal of the external power source, 
 operating the switch to disconnect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the electronic controller is in an ON state and the load is powered ON, and 
 before disconnecting the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source, delaying the disconnection of least 100 msec after transition of the electronic controller from the OFF state to the ON state to enable the electronic controller to remain operable during an initial ON state, wherein the leakage current continues to have a current path between the output terminal of the electronic controller and the second power terminal of the external power source for the duration of the delay. 
 
     
     
       12. The method of  claim 11 , further comprising:
 measuring the load current; 
 comparing the measured load current to a threshold current; 
 connecting the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the measured current is less than the threshold current; and 
 disconnecting the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the measured current exceeds the threshold current. 
 
     
     
       13. The method of  claim 11 , further comprising:
 measuring the load voltage; 
 comparing the measured load voltage to a threshold voltage; 
 connecting the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the measured load voltage is less than the threshold voltage; and 
 disconnecting the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the measured load voltage exceeds the threshold voltage. 
 
     
     
       14. A device configured to be connected to an output terminal of an electronic controller, which in turn has a single input terminal connected to a first power terminal of an external power source which is external to the electronic controller and which external power source outputs an AC voltage between the first power terminal and a second power terminal thereof, the device comprising:
 a series combination of a bleeding circuit in series with a switch, the series combination having a first terminal configured to be directly connected to an output terminal of the electronic controller and having a second terminal configured to be directly connected to the second power terminal of the external power source; and 
 a switch control device configured to detect whether the electronic controller powers a load or disables the load, the switch control device further configured to: 
 connect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the electronic controller is in an OFF and the load is powered OFF state such that the bleeding circuit provides a current path for leakage current between the output terminal of the electronic controller and the second power terminal of the external power source, 
 disconnect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the electronic controller is in an ON state and the load is powered ON, and 
 before disconnecting the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source, delay the disconnection by least 100 msec after transition of the electronic controller from the OFF state to the ON state to enable the electronic controller to remain operable during an initial ON state, wherein the leakage current continues to have a current path between the output terminal of the electronic controller and the second power terminal of the external power source for the duration of the delay. 
 
     
     
       15. The device of  claim 14 , wherein the switch control device includes a voltage measurement device connected between first and second load terminals of load and configured to measure the load voltage, and to close the switch to connect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source to provide a current path between the output terminal of the electronic controller and the second power terminal of the external power source when the measured load voltage is less than a threshold voltage, and to control the switch to open the switch to disconnect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the measured load voltage exceeds the threshold voltage. 
     
     
       16. The device of  claim 14 , wherein the switch control device includes a current measurement device configured to measure the load current and to close the switch to connect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source to provide a current path between the output terminal of the electronic controller and the second power terminal of the external power source when the measured load current is less than a threshold current, and to control the switch to open the switch to disconnect the bleeding circuit between the output terminal of the electronic controller and the second power terminal of the external power source when the measured load current exceeds the threshold current. 
     
     
       17. The device of  claim 14 , wherein the electronic controller is installed in a building at a location where a connection to the second power terminal is not provided, and wherein the device is separated and spaced apart from the electronic controller by a distance of at least one foot.