LED (light-emitting diode) string derived controller power supply
First Claim
1. A lighting circuit, comprising:
- a plurality of series-connected light-emitting diodes, wherein the series-connected light-emitting diodes are coupled between an input voltage source and an input voltage return associated with the input voltage source;
a switching power converter having a magnetic storage element and a switching element for controlling a current supplied through the plurality of series-connected light-emitting diodes;
a control circuit for controlling the switching element of the switching power converter, wherein a power supply input of the control circuit is provided by a power supply voltage generated from a terminal of the plurality of series-connected light-emitting diodes having a voltage substantially less than a voltage of the input voltage source;
a switching circuit coupled in series with the plurality of series-connected light-emitting diodes and the input voltage source, wherein the switching circuit alternatively couples the terminal of the plurality of series-connected light-emitting diodes to the input voltage return in a first switching state and to the power supply input of the control circuit in a second switching state; and
a second plurality of series-connected light-emitting diodes coupled between the switching circuit and the input voltage return, wherein the switching circuit alternatively supplies current to the second plurality of series-connected light-emitting diodes and to the power supply input.
4 Assignments
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Accused Products
Abstract
An LED lighting device includes an auxiliary power supply that supplies power to a control circuit of the LED lighting device that receives an input from a terminal of a light-emitting diode (LED) string of the lighting device that has a substantially lower voltage than the line voltage to which the lighting device is connected. The terminal may be within the LED string, or may be an end of the string. A linear regulator may be operated from the voltage drop across a number of the LEDs in the string so that the energy wasted by the auxiliary power supply is minimized. In other designs, the auxiliary power supply may be intermittently connected in series with the LED string only when needed. The intermittent connection can be used to forward bias a portion of the LED string when the voltage supplied to the LED string is low, increasing overall brightness.
72 Citations
8 Claims
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1. A lighting circuit, comprising:
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a plurality of series-connected light-emitting diodes, wherein the series-connected light-emitting diodes are coupled between an input voltage source and an input voltage return associated with the input voltage source; a switching power converter having a magnetic storage element and a switching element for controlling a current supplied through the plurality of series-connected light-emitting diodes; a control circuit for controlling the switching element of the switching power converter, wherein a power supply input of the control circuit is provided by a power supply voltage generated from a terminal of the plurality of series-connected light-emitting diodes having a voltage substantially less than a voltage of the input voltage source; a switching circuit coupled in series with the plurality of series-connected light-emitting diodes and the input voltage source, wherein the switching circuit alternatively couples the terminal of the plurality of series-connected light-emitting diodes to the input voltage return in a first switching state and to the power supply input of the control circuit in a second switching state; and a second plurality of series-connected light-emitting diodes coupled between the switching circuit and the input voltage return, wherein the switching circuit alternatively supplies current to the second plurality of series-connected light-emitting diodes and to the power supply input. - View Dependent Claims (2, 3)
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4. A method of generating an auxiliary power supply for a circuit controlling the transfer of power from an input voltage source to a lighting device comprising plurality of series-connected light-emitting diodes, the method comprising:
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controlling charging of a magnetic storage element from the input voltage source and discharging of the magnetic storage element to apply energy stored in the magnetic storage element to provide a voltage across the plurality of series-connected light-emitting diodes, wherein the controlling is performed by a control circuit that controls a switching circuit coupled to the magnetic storage element; and generating a power supply voltage supplied to a power supply input of the control circuit from a terminal of the plurality of series-connected light-emitting diodes having a voltage substantially less than a voltage supplied across the plurality of series-connected light-emitting diodes, wherein the generating comprises alternatively coupling the terminal of the plurality of series-connected light-emitting diodes to the input voltage return in a first switching state, to the power supply input of the control circuit in a second switching state and to a second plurality of series-connected light-emitting diodes in a third switching state. - View Dependent Claims (5)
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6. An integrated circuit for operating a lighting circuit comprising a plurality of series-connected light-emitting diodes coupled between an input voltage source and an input voltage return associated with the input voltage source by a switching power converter, the integrated circuit comprising:
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a control circuit for controlling a switching element of the switching power converter; and an auxiliary power supply input terminal for receiving a connection from another terminal of the plurality of series-connected light-emitting diodes having a voltage substantially less than a voltage of the input voltage source; an auxiliary power supply circuit for generating a voltage from the auxiliary power supply input terminal to provide a power supply voltage at a power supply input of the control circuit, wherein the auxiliary power supply circuit comprises a switching circuit coupled in series with the plurality of series-connected light-emitting diodes and the input voltage source, wherein the switching circuit alternatively couples the auxiliary power supply input terminal to the input voltage return in a first switching state and to the power supply input of the control circuit in a second switching state; and a lighting current output terminal for connection to a second plurality of series-connected light-emitting diodes, and wherein the switching circuit alternatively supplies current to the lighting current output terminal and to the power supply input. - View Dependent Claims (7, 8)
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Specification