Dimming multiple lighting devices by alternating energy transfer from a magnetic storage element
First Claim
Patent Images
1. A circuit comprising:
- at least one output terminal for providing a first output current to a first string of light-emitting diodes and a second output current to a second string of light-emitting diodes; and
a power switching circuit having a magnetic storage element from which energy is alternatively supplied, from a single winding of the magnetic storage element, to the first string of light-emitting diodes during a first period and to the second string of light-emitting diodes during a second period not substantially overlapping the first period, whereby different current or voltages may be applied to the first output terminal and the second output terminal to control the relative intensity of light provided by the first string of light-emitting diodes and the second string of light-emitting diodes, wherein a first electrical path supplies current to the first string of light-emitting diodes, wherein all switching devices included in the first electrical path are passive switches provided by diodes, and wherein the power switching circuit includes an active switching element responsive to a control signal for controlling whether or not current is supplied to the second string of light-emitting diodes.
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Abstract
A single magnetic storage element is used to provide power to multiple lighting devices, which may be strings of light-emitting diodes (LEDs) of different color. A switching circuit controls alternating application of energy among the multiple lighting devices and another switching circuit may charge the primary winding to different energy levels to control the intensity of the multiple lighting devices. In particular, the multiple lighting devices may be controlled to provide a desired color profile while dimming the lighting devices, while requiring only a single magnetic storage element for supplying energy to the lighting devices.
63 Citations
29 Claims
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1. A circuit comprising:
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at least one output terminal for providing a first output current to a first string of light-emitting diodes and a second output current to a second string of light-emitting diodes; and a power switching circuit having a magnetic storage element from which energy is alternatively supplied, from a single winding of the magnetic storage element, to the first string of light-emitting diodes during a first period and to the second string of light-emitting diodes during a second period not substantially overlapping the first period, whereby different current or voltages may be applied to the first output terminal and the second output terminal to control the relative intensity of light provided by the first string of light-emitting diodes and the second string of light-emitting diodes, wherein a first electrical path supplies current to the first string of light-emitting diodes, wherein all switching devices included in the first electrical path are passive switches provided by diodes, and wherein the power switching circuit includes an active switching element responsive to a control signal for controlling whether or not current is supplied to the second string of light-emitting diodes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of supplying power to multiple lighting devices, comprising:
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first controlling charging of a magnetic storage element during charging intervals; second controlling discharging of the magnetic storage element to alternate application of energy stored in the magnetic storage element between the multiple lighting devices during alternating flyback intervals following the charging intervals, from a single winding of the magnetic storage element; first providing a first output current or voltage to a first one of the lighting devices during a first one of the flyback intervals through a first electrical path in which all switching devices are passive switches provided by; and second providing a second output current or voltage to a second one of the lighting devices during a second one of the flyback intervals through a second electrical path that includes an active switching element responsive to a control signal. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A circuit for powering two or more lighting devices, the circuit comprising:
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a first output terminal for providing a first output current or voltage to a first one of the lighting devices; a second output terminal for providing a second output current or voltage to a second one of the lighting devices; a first switching circuit coupled to an input power source; a transformer coupled to the first switching circuit and having a primary winding and a secondary winding, wherein the first switching circuit charges the transformer from the input power source during charging intervals; and a second switching circuit coupled to the transformer for providing the first output current or voltage to the first output terminal and the second output current or voltage to the second output terminal during alternating flyback intervals following the charging intervals, wherein the second switching circuit is controlled by information provided at the primary winding of the transformer and detected at the secondary winding of the transformer. - View Dependent Claims (27)
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28. A method of supplying power to multiple lighting devices, comprising:
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first controlling charging of a primary winding of a transformer during charging intervals; second controlling discharging of energy stored in the transformer through a secondary winding of the transformer to alternate application of energy stored in the transformer between the multiple lighting devices during alternating flyback intervals following the charging intervals, according to information provided at the primary winding of the transformer and detected at the secondary winding of the transformer; first providing a first output current or voltage to a first one of the lighting devices during a first one of the flyback intervals; and second providing a second output current or voltage to a second one of the lighting devices during a second one of the flyback intervals. - View Dependent Claims (29)
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Specification