TRANSFORMER-ISOLATED LED LIGHTING CIRCUIT WITH SECONDARY-SIDE DIMMING CONTROL
First Claim
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1. An integrated circuit for supplying current to one or more light-emitting diodes (LEDs), comprising:
- an input circuit for coupling to a secondary winding of an external transformer that isolates the integrated circuit and the LEDs from a primary-side circuit that provides pulses through the transformer for supplying energy to the LEDs;
a decoder coupled to the input circuit for decoding a dimming value encoded in a voltage waveform provided across the secondary winding; and
a power converter control circuit for controlling a current supplied to the LEDs in conformity with the dimming value.
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Abstract
A transformer isolated LED lighting circuit supplies current from a secondary-side storage capacitor to one or more LED strings in conformity with one or more dimming values. The dimming values are communicated through the transformer by patterns or codes provided in pulses of a power converter circuit that charges the storage capacitor from the primary side of the transformer, or alternatively by a special modulated signal provided in addition to the switching pulses.
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Citations
31 Claims
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1. An integrated circuit for supplying current to one or more light-emitting diodes (LEDs), comprising:
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an input circuit for coupling to a secondary winding of an external transformer that isolates the integrated circuit and the LEDs from a primary-side circuit that provides pulses through the transformer for supplying energy to the LEDs; a decoder coupled to the input circuit for decoding a dimming value encoded in a voltage waveform provided across the secondary winding; and a power converter control circuit for controlling a current supplied to the LEDs in conformity with the dimming value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An integrated circuit for supplying current to one or more light-emitting diodes (LEDs), comprising:
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an input circuit for coupling to a source of AC line voltage having a characteristic waveform that differs from sinusoidal by action of a thyristor-based dimmer circuit; a dimming detector for determining a dimming value from the characteristic waveform of the AC line voltage; a power converter control circuit for controlling a switch coupled to a primary winding of an external transformer that supplies energy to the one or more LEDs via pulses of a primary-side power converter waveform, wherein the one or more LEDs are coupled to a secondary winding of the external transformer and are isolated from the integrated circuit; and an encoding circuit that encodes the dimming value at the primary winding of the external transformer. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A lighting device having one or more light-emitting diodes (LEDs), comprising:
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a dimming detector for generating a dimming value from a shape of a waveform of an input source of AC line voltage; a first power converter for supplying pulses to the primary winding of a transformer and further information indicative of the dimming value forming a primary-side power converter waveform; a rectifier circuit for generating a DC voltage from a voltage across an isolated secondary winding of the transformer, wherein the rectifier circuit comprises a capacitor for storing energy transferred through the transformer by the pulses; a detector for detecting the further information indicative of the dimming value from a voltage waveform across the secondary winding of the transformer and determining a detected dimming value; and a second power converter having an input coupled to the capacitor for supplying energy to the one or more light-emitting diodes from the capacitor, wherein at least one current supplied to the one or more light-emitting diodes is controlled in conformity with the detected dimming value. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. A method of supplying energy to one or more light-emitting diodes (LEDs), the method comprising:
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generating a dimming value from a shape of a waveform of an input source of AC line voltage; supplying pulses to the primary winding of a transformer and further information indicative of the dimming value forming a primary-side power converter waveform; generating a DC voltage from a voltage across a secondary winding of the transformer, and storing energy in a capacitor by charging the capacitor from the DC voltage; detecting the further information indicative of the dimming value and determining a detected dimming value from a voltage waveform across the secondary winding of the transformer; and supplying energy to the one or more light-emitting diodes from the capacitor, wherein at least one current supplied to the one or more light-emitting diodes is controlled in conformity with the detected dimming value. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31)
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Specification