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 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.
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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.
386 Citations
31 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 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18)
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16. 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; 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.
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19. A lighting apparatus, comprising:
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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. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification