LED DRIVER WITH PRECHARGE AND TRACK/HOLD
First Claim
1. A method comprising:
- controlling, at a light emitting diode (LED) driver, an output voltage provided to a head end of each of a plurality of LED strings based on relationship between at least one tail voltage of the plurality of LED strings and a reference voltage;
receiving, at the LED driver, a pulse width modulation (PWM) data to control activation of a plurality of LED strings; and
adjusting the reference voltage based on the PWM data.
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Accused Products
Abstract
A power source provides an output voltage to drive a plurality of light emitting diode (LED) strings. A feedback controller monitors the tail voltages of the LED strings to identify the minimum tail voltage and adjusts the output voltage based on a relationship between the minimum tail voltage and a reference voltage. The feedback controller implements precharging of the output voltage, including one or both of short-term precharging or long-term precharging. Further, the feedback controller incorporates a track/hold circuit that tracks the minimum tail voltage while the LED strings are active and holds the minimum tail voltage at the last tracked minimum tail voltage while the LED strings are inactive and uses the held minimum tail voltage for controlling the output voltage while the LED strings are inactive so as to permit the power source to supply an appropriate output voltage when the LED strings are subsequently activated again.
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Citations
20 Claims
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1. A method comprising:
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controlling, at a light emitting diode (LED) driver, an output voltage provided to a head end of each of a plurality of LED strings based on relationship between at least one tail voltage of the plurality of LED strings and a reference voltage; receiving, at the LED driver, a pulse width modulation (PWM) data to control activation of a plurality of LED strings; and adjusting the reference voltage based on the PWM data. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method comprising:
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providing an output voltage to a head end of each of a plurality of light-emitting diode (LED) strings, the output voltage based on a relationship between a first reference voltage and a second reference voltage; receiving, at a light emitting diode (LED) driver, a pulse width modulation (PWM) data to control activation of a plurality of LED strings, the PWM data comprising a first state to activate at least one LED string of the plurality of LED strings and a second state to deactivate the plurality of LED strings; while the PWM data is in the first state, tracking the first reference voltage to a minimum tail voltage of tail voltages of the plurality of LED strings to determine a tracked minimum tail voltage and providing the tracked minimum tail voltage as the first reference voltage; and while the PWM data is in the second state, holding the first reference voltage to a minimum tail voltage of tail voltages of the plurality of LED strings occurring at a transition of the PWM data from the first state to the second state. - View Dependent Claims (8, 9, 10)
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11. A system comprising:
a light emitting diode (LED) driver comprising; a voltage controller configured to control adjustment of an output voltage provided to a head end of each of a plurality of LED strings based on a relationship between at least one tail voltage of the plurality of LED strings and a first reference voltage; an input to receive a pulse width modulation (PWM) data to control activation of the plurality of LED strings; and a first precharge circuit configured to adjust the first reference voltage responsive to a state of the PWM data. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A system comprising:
a light emitting diode (LED) driver comprising; a voltage controller configured to control adjustment of an output voltage provided to a head end of each of a plurality of LED strings based on a relationship between at least one tail voltage of the plurality of LED strings and a first reference voltage; an input to receive a pulse width modulation (PWM) data to control activation of the plurality of LED strings, the PWM data comprising a first state to activate at least one LED string of the plurality of LED strings and a second state to deactivate the plurality of LED strings; and a track/hold circuit configured to; while the PWM data is in the first state, track the first reference voltage to a minimum tail voltage of tail voltages of the plurality of LED strings; and while the PWM data is in a second state, hold the first reference voltage to a minimum tail voltage of tail voltages of the plurality of LED strings occurring at a transition of the PWM data from the first state to the second state. - View Dependent Claims (18, 19, 20)
Specification