Light source comprising a LED strip
A LED light source comprising a LED strip supplied by a switch mode power supply is disclosed. The LED light source has a low power dissipation and is to a large extent independent of the magnitude of the DC voltage supplying the switch mode power supply. The LED light source allows arbitrary positioning of a light or a presence detector.
1. An LED light source comprising a first LED strip including
input terminals for connection to a DC-supply source,
a load comprising a plurality of parallel series arrangements, each series arrangement comprising an LED string and a resistor in series and having a common terminal between the LED string and the resistor,
a plurality of conductive paths connecting the series arrangements between the input terminals; and
a sensing conductive path connecting the common terminals of each of the series arrangements of the plurality of series arrangements.
2. The LED light source as claimed in claim 1 , further comprising a switch mode power supply for generating a current out of a DC supply voltage, said switch mode power supply comprising
output terminals coupled to the input terminals of the first LED strip,
input terminals coupled to the DC supply voltage
a circuit provided between the input terminals and the output terminals, including a switch and an inductive element in series arrangement, and an unidirectional element restricting the current flow between the output terminals to one direction only, and
a control circuit equipped with an output terminal coupled to the switch for controlling the conductive state of the switch and with an input terminal coupled by the sensing conductive path to the common terminals of the resistors and the LED strings for sensing the current in each of the LED strings.
3. The LED light source as claimed in claim 2 , wherein the switch mode power supply is a down converter.
4. The LED light source as claimed in claim 1 , wherein the first LED strip comprises a series arrangement of a sensor and a resistor coupled in parallel with all the series arrangements of a resistor and a LED string comprised in the load and wherein a common terminal of the sensor and the resistor is connected to all the common terminals of the resistors and the LED strings comprised in the load.
5. The LED light source as claimed in claim 4 , wherein the sensor is a presence sensor.
6. The LED light source as claimed in claim 4 , wherein the sensor is a light sensor.
7. The LED light source as claimed in claim 2 , wherein the LED light source comprises a second LED strip including
input terminals connected to the input terminals of the first LED strip,
a further load comprising a plurality of parallel series arrangements connected between the input terminals, wherein each series arrangement comprises a LED string and a resistor in series and the common terminals of the resistors and the LED strings are all connected to each other and to the input terminal of the control circuit.
8. The LED light source according to claim 1 , wherein the resistor of at least one of said series arrangements is a controllable resistor, connected to at least one associated lamp control device to control the resistance of said resistor.
9. The light source according to claim 8 , wherein the resistor of each series arrangement is controllable and is connected to said at least one lamp control device.
10. The LED light source according to claim 9 , wherein the LED light source is a track light source comprising an electrical supply track.
11. The LED light source according to claim 10 , wherein the series arrangement of LED string and resistor is comprised in a lighting device, said lighting device being removable connectable with said electrical supply track.