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.
377 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