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.
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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