Lamp current control using profile synthesizer
First Claim
1. A controller for a current-mode inverter comprising:
- a clock generator configured to output a periodic timing waveform;
a current profile generator configured to produce a profile signal in a programmable waveform shape defined by at least a capacitor and two input control signals, wherein the profile signal is provided to a current regulator to generate a regulated current with the programmed waveform shape; and
a register state machine configured to control the operations of the current profile generator with reference to the periodic timing waveform.
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Abstract
An efficient and flexible current-mode driver delivers power to one or more light sources in a backlight system. In one application, the current-mode driver is configured as an inverter with an input current regulator, a non-resonant polarity-switching network, and a closely-coupled output transformer. The input current regulator can output a regulated current source in a variety of programmable wave shapes. The current-mode driver may further include a rectifier circuit and a second polarity-switching network between the closely-coupled output transformer and a lamp load. In another application, the current-mode driver delivers power to a plurality of light sources in substantially one polarity by providing a regulated current to a network of time-sharing semiconductor switches coupled in series with different light sources coupled across each semiconductor switch.
219 Citations
20 Claims
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1. A controller for a current-mode inverter comprising:
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a clock generator configured to output a periodic timing waveform; a current profile generator configured to produce a profile signal in a programmable waveform shape defined by at least a capacitor and two input control signals, wherein the profile signal is provided to a current regulator to generate a regulated current with the programmed waveform shape; and a register state machine configured to control the operations of the current profile generator with reference to the periodic timing waveform. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method to generate a current profile for a current regulator in a current-mode inverter, the method comprising the acts of:
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periodically setting the current profile to a reference level, wherein the period is determined by a periodic triangular waveform; comparing a first control input signal to the periodic triangular waveform to determine an active duration of the current profile in each period, wherein the current profile increases at a programmable rising rate and a capacitor starts charging at about the beginning of the active duration; holding the current profile at a substantially constant level when the voltage across the capacitor is about equal to or above a predefined holding threshold, wherein the voltage of the periodic triangular waveform is noted at about the time the voltage across the capacitor crosses the predefined holding threshold and the capacitor stops charging; reducing the level of the current profile at a programmable falling rate and discharging the capacitor when the voltage of the periodic triangular waveform is approximately less than the noted voltage, wherein the current profile returns to the reference level by the end of the active duration. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A controller for a current-mode inverter comprising:
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means for generating a periodic timing signal; means for defining a rising slope, a plateau, and a falling slope of a current profile signal with a capacitor and two input control signals, wherein the current profile signal determines the wave shape of a regulated current source; and means for generating a pair of substantially identical wave shapes for every two cycles of the periodic timing signal. - View Dependent Claims (18, 19, 20)
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Specification