AC driven solid state lighting apparatus with LED string including switched segments
First Claim
1. 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 that is proportional to a voltage of the rectified AC input signal to the plurality of light emitting diodes in response to the rectified AC input signal; and
a transistor configured to receive the control signal and to shunt current away from more than one of the plurality of light emitting devices in response to the control signal.
2 Assignments
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Accused Products
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.
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Citations
15 Claims
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1. A circuit for a light emitting apparatus including a plurality of light emitting devices coupled in a series, the diode selection circuit comprising:
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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 that is proportional to a voltage of the rectified AC input signal to the plurality of light emitting diodes in response to the rectified AC input signal; and a transistor configured to receive the control signal and to shunt current away from more than one of the plurality of light emitting devices in response to the control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A circuit for a light emitting apparatus including a plurality of light emitting devices coupled in a series, the diode selection circuit comprising:
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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, wherein the adjustable current sink is configured to be controlled in response to a pulse width modulation (PWM) signal.
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15. A circuit for a light emitting apparatus including a plurality of light emitting devices coupled in a series, the diode selection circuit comprising:
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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 that is proportional to a voltage level of the rectified AC input signal to the plurality of light emitting diodes in response 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 voltage controlled current source comprises a first PNP bipolar transistor, an emitter resistor coupled to an emitter of the first PNP bipolar transistor, a diode coupled to a base of the first transistor, a first resistor coupled to a first terminal of the diode and a second resistor coupled to a second terminal of the diode, and a terminal configured to receive the rectified AC input signal coupled to the emitter resistor and to the first resistor.
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Specification