LED system with two wire control circuit
An LED module can be powered by two conductors and the LED module includes a constant current driver. The constant current driver is configured to provide a predetermined current so long as the input voltage provided on the two conductors exceeds a predetermined level. The constant current driver powers an LED string supported by the LED module and can adjust the current to the LED string based on an input signal. A conversion circuit converts the input voltage to an input signal and provides that input signal to the constant current driver so that dimming can be provided while only using two conductors to provide power.
1. An LED module, comprising:
a housing;
an LED string supported by the housing;
a first terminal and a second terminal supported by the housing;
a constant current driver coupled to the first and second terminal, the constant current driver configured to provide a constant output current to power the LED string for a range of voltages above a minimum voltage V F , the constant current driver further configured to vary the output current based on an input signal; and
a conversion circuit positioned in the housing and configured to receive a voltage from the first and second terminals and to convert the voltage to a signal level that ranges between a first level and a level that is less than the first level, the conversion circuit configured to provide the signal level as the input signal.
2. The LED module of claim 1 , wherein the conversion circuit includes a resistive voltage divider.
3. The LED module of claim 2 , wherein the conversion circuit includes a voltage subtraction circuit.
4. The LED module of claim 1 , wherein the LED string comprises at least one LED.
5. An LED system, comprising:
a fixture including a first contact and a second contact, the first and second contacts electrically separated from the fixture and each other;
a voltage module supported by the fixture, the voltage module configured to provide a first voltage to the first and second contacts; and
an LED module removably mounted to the fixture, the module including a constant current driver and an LED string and a conversion circuit configured to convert the first voltage to a signal voltage that is less than the first voltage, wherein the constant current driver is configured to adjust a current output in response to the signal voltage.
6. The LED system of claim 5 , wherein the voltage module is configured to provide a variable first voltage.
7. The LED system of claim 5 , wherein the conversion circuit is configured to provide a signal voltage that is between 0 volts and 1.5 volts.
8. The LED system of claim 5 , wherein the conversion circuit is configured to provide a signal voltage that is at least 10 times less than the first voltage.
9. The LED system of claim 5 , wherein the fixture and the first and second contacts are elongated so as to provide a track-like shape.
10. The LED system of claim 5 , wherein the LED string comprises at least one LED.
11. The LED system of claim 6 , wherein the voltage module is configured to receive a control input wirelessly and to vary the first voltage in response to the control input.