AC driven solid state lighting apparatus with LED string including switched segments
AssigneeCree, Inc.
InventorsAntony P. van de Ven, Terry Given
Life of this patent
Estimating the term…
Abstract
A diode selection circuit for a light emitting apparatus according to some embodiments includes a plurality of light emitting devices coupled in series. The diode selection circuit includes a comparator configured to receive a rectified AC input signal and a reference voltage and to generate a control signal in response to comparison of the rectified AC input signal with the reference voltage, a voltage controlled current source configured to supply a current to the plurality of light emitting diodes that is proportional to the rectified AC input signal, and a switch configured to receive the control signal and to shunt current away from at least one of the plurality of light emitting devices in response to the control signal.
Claims31
A circuit for a light emitting apparatus including a plurality of light emitting devices coupled in a series, the diode selection circuit comprising:
- a comparator configured to receive a rectified AC input signal and a reference voltage and to generate a control signal in response to comparison of the rectified AC input signal with the reference voltage;
- a voltage controlled current source configured to supply a current to the plurality of light emitting diodes that is proportional to the rectified AC input signal;
- a switch configured to receive the control signal and to shunt current away from at least one of the plurality of light emitting devices in response to the control signal;
- and
- an adjustable current sink coupled to the voltage controlled current source.
A circuit for a light emitting apparatus including a plurality of light emitting devices coupled in a series, the diode selection circuit comprising:
- a comparator configured to receive a rectified AC input signal and a reference voltage and to generate a control signal in response to comparison of the rectified AC input signal with the reference voltage;
- a voltage controlled current source configured to supply a current to the plurality of light emitting diodes that is proportional to the rectified AC input signal;
- and
- a switch configured to receive the control signal and to shunt current away from at least one of the plurality of light emitting devices in response to the control signal;
- wherein the switch comprises a field effect transistor including a gate terminal and source/drain terminals, wherein one of the source/drain terminals is coupled to an anode of the at least one light emitting device and another of the source/drain terminals is coupled to an cathode of the at least one light emitting device;
- the circuit further comprising a slew rate control capacitor coupled between the gate terminal of the field effect transistor and the anode of the at least one light emitting device.
A lighting apparatus, comprising:
- a terminal configured to receive an AC power signal;
- a full wave rectifier configured to generate a rectified AC input signal in response to the AC power signal;
- a reference voltage generator configured to generate a DC reference voltage in response to the rectified AC input signal;
- a plurality of light emitting devices coupled in series;
- a voltage controlled current source configured to supply a current to the plurality of light emitting diodes that is proportional to the rectified AC input signal;
- a diode selection circuit comprising a comparator configured to receive the rectified AC input signal and the reference voltage and to generate a control signal in response to comparison of the rectified AC input signal with the reference voltage, and a switch configured to receive the control signal and to shunt current away from at least one of the plurality of light emitting devices in response to the control signal;
- and
- an adjustable current sink coupled to the voltage controlled current source.
Dependencies are inferred from the claim text.