System and method for driving LED
First Claim
1. A system for providing power to one or more light emitting diodes, the system couplable to an energy source, the system comprising:
- a power converter comprising an inductor and a power switch, wherein the power converter is couplable to the one or more light emitting diodes, and wherein the power converter operable is configured to operate in a discontinuous current mode having a dual phase cycle comprising an on phase when the power switch is closed and an off phase when the power switch is open;
an output current sensor configured to sense an output current level;
a peak current sensor configured to sense a peak current level; and
a regulator coupled to the power converter, to the output current sensor, and to the peak current sensor, wherein the regulator is configured to;
determine an on phase time for the dual phase cycle having a substantially constant frequency;
determine an integrated output current level during the off phase;
compare the integrated output current level to a first reference current level; and
determine a next cycle on phase time by incrementing a current cycle on phase time by a determined or predetermined time amount, up to a maximum on phase time, when the integrated output current level is less than the first reference current level and by decrementing the current cycle on phase time by the determined or predetermined time amount when the integrated output current level is greater than the first reference current level.
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Accused Products
Abstract
A system drives one or a plurality of LEDs, regulating their brightness by controlling the LEDs'"'"' average current or voltage. The system includes a switching power converter and an integrated digital regulator with at least one of electrical, thermal, and optical feedbacks. The regulator is constructed as a hysteretic peak current mode controller for continuous mode of operation of the power converter. For a discontinuous mode of operation of the power converter, a pulse averaging sliding mode control is used. Average LED current is measured by integrating LED pulse current at off time and hysteretically adjusting on time of the power switch. An input battery is protected from discharging at abnormally low impedance of the output.
31 Citations
11 Claims
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1. A system for providing power to one or more light emitting diodes, the system couplable to an energy source, the system comprising:
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a power converter comprising an inductor and a power switch, wherein the power converter is couplable to the one or more light emitting diodes, and wherein the power converter operable is configured to operate in a discontinuous current mode having a dual phase cycle comprising an on phase when the power switch is closed and an off phase when the power switch is open; an output current sensor configured to sense an output current level; a peak current sensor configured to sense a peak current level; and a regulator coupled to the power converter, to the output current sensor, and to the peak current sensor, wherein the regulator is configured to; determine an on phase time for the dual phase cycle having a substantially constant frequency; determine an integrated output current level during the off phase; compare the integrated output current level to a first reference current level; and determine a next cycle on phase time by incrementing a current cycle on phase time by a determined or predetermined time amount, up to a maximum on phase time, when the integrated output current level is less than the first reference current level and by decrementing the current cycle on phase time by the determined or predetermined time amount when the integrated output current level is greater than the first reference current level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification