Current offset circuits for phase-cut power control
First Claim
1. Apparatus for maintaining at least a holding current in a leading-edge phase-cut dimmer during a period of transient voltage variations, the apparatus connectable to the dimmer and connectable to a load connected to draw current from the dimmer, the apparatus comprising:
- an edge detector connected to receive a voltage from the dimmer and generate a leading-edge signal in response to a leading-edge of a phase-cut waveform; and
a current offset circuit connected to receive the leading-edge signal and draw a supplementary offset current in response to the leading-edge signal, wherein the supplementary offset current is sufficient to maintain at least a holding current in the dimmer during the period of transient voltage variations;
wherein the current offset circuit comprises a holding current circuit configured to draw a supplementary current at least as great as a difference between a holding current of the dimmer and a load current when the dimmer is in conduction and the load current is less than the holding current.
5 Assignments
0 Petitions
Accused Products
Abstract
Apparatus for maintaining at least a holding current in a leading-edge phase-cut dimmer during a period of transient voltage variations, the apparatus connectable to the dimmer and connectable to a load connected to draw current from the dimmer. The apparatus may comprise an edge detector connected to receive a voltage from the dimmer and generate a leading-edge signal in response to a leading-edge of a phase-cut waveform, and a current offset circuit connected to receive the leading-edge signal and draw a supplementary offset current in response to the leading-edge signal, wherein the supplementary offset current is sufficient to maintain at least a holding current in the dimmer during the period of transient voltage variations. The current offset circuit may comprise a holding current circuit which also draws supplementary current in response to an instantaneous value of load current.
50 Citations
20 Claims
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1. Apparatus for maintaining at least a holding current in a leading-edge phase-cut dimmer during a period of transient voltage variations, the apparatus connectable to the dimmer and connectable to a load connected to draw current from the dimmer, the apparatus comprising:
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an edge detector connected to receive a voltage from the dimmer and generate a leading-edge signal in response to a leading-edge of a phase-cut waveform; and a current offset circuit connected to receive the leading-edge signal and draw a supplementary offset current in response to the leading-edge signal, wherein the supplementary offset current is sufficient to maintain at least a holding current in the dimmer during the period of transient voltage variations; wherein the current offset circuit comprises a holding current circuit configured to draw a supplementary current at least as great as a difference between a holding current of the dimmer and a load current when the dimmer is in conduction and the load current is less than the holding current. - View Dependent Claims (2, 3, 4)
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5. Apparatus for maintaining at least a holding current in a leading-edge phase-cut dimmer during a period of transient voltage variations, the apparatus connectable to the dimmer and connectable to a load connected to draw current from the dimmer, the apparatus comprising:
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an edge detector connected to receive a voltage from the dimmer and generate a leading-edge signal in response to a leading-edge of a phase-cut waveform; and a current offset circuit connected to receive the leading-edge signal and draw a supplementary offset current in response to the leading-edge signal, wherein the supplementary offset current is sufficient to maintain at least a holding current in the dimmer during the period of transient voltage variations; wherein the edge detector comprises a capacitor and two resistors connected in series between a pair of voltage supply rails, and wherein the leading edge signal is generated at a node between the two resistors. - View Dependent Claims (6, 7, 8)
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9. Apparatus for maintaining at least a holding current in a leading-edge phase-cut dimmer during a period of transient voltage variations, the apparatus connectable to the dimmer and connectable to a load connected to draw current from the dimmer, the apparatus comprising:
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an edge detector connected to receive a voltage from the dimmer and generate a leading-edge signal in response to a leading-edge of a phase-cut waveform; and a current offset circuit connected to receive the leading-edge signal and draw a supplementary offset current in response to the leading-edge signal, wherein the supplementary offset current is sufficient to maintain at least a holding current in the dimmer during the period of transient voltage variations; wherein the edge detector comprises one or more resistors and one or more diodes connected in series between a pair of voltage supply rails, and the leading edge signal is generated at a node between the one or more resistors and the one or more diodes. - View Dependent Claims (10, 11, 12)
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13. A method for maintaining at least a holding current in a leading-edge phase-cut dimmer during a period of transient voltage variations, the method comprising:
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generating a leading-edge signal in response to a leading-edge of a phase cut waveform; and drawing a supplementary offset current from the dimmer through a current offset circuit in response to the leading-edge signal, wherein the supplementary offset current is sufficient to maintain at least a holding current in the dimmer during the period of transient voltage variations; wherein drawing the supplementary offset current comprises providing the leading edge signal to a holding current circuit, the holding current circuit configured to draw the supplemental offset current based on the leading edge signal, and configured to draw a supplementary current at least as great as a difference between a holding current of the dimmer and a load current when the dimmer is in conduction and the load current is less than the holding current. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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20. Apparatus for maintaining at least a holding current in a leading-edge phase-cut dimmer, the apparatus connectable to the dimmer and connectable to a load connected to draw current from the dimmer, the apparatus comprising:
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an edge detector connected to receive a voltage from the dimmer and generate a leading-edge signal in response to a leading-edge of a phase-cut waveform; and a holding current and offset circuit comprising a controlled current source connectable to draw current from the dimmer, a current monitor connected to receive at least a portion of the current drawn by the controlled current source and connectable to receive at least a portion of a load current drawn from the dimmer by the load, the current monitor operable to generate a current monitor signal indicative of a magnitude of the current in the current monitor, wherein the controlled current source is connected to receive the current monitor signal and is configured to draw a supplementary current at least as great as a difference between the holding current and the load current when the load current is less than the holding current, and wherein the holding current and offset circuit is connected to receive the leading-edge signal and draw a supplementary offset current in response to the leading-edge signal, wherein the supplementary offset current is sufficient to maintain at least a holding current in the dimmer during a period of transient voltage variations.
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Specification