LED driver circuit and method
AssigneesSTMicroelectronics S.r.l., Lumileds Lighting U.S., LLC
InventorsDavid F. Swanson, James W. Stewart, Michael K. Lam, Marcello Criscione
Life of this patent
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Abstract
An LED driver circuit and method are disclosed where a plurality of arrays of light emitting diodes each have a transistor connected to each respective array of light emitting diodes. A PWM controller has an input for receiving a voltage reference and an output connected to selected transistors for driving the selected transistors and setting a PWM duty cycle for the selected arrays of light emitting diodes to determine the brightness of selected light emitting diodes. An oscillator is connected to the PWM controller for driving the PWM controller.
Claims37
An LED driver circuit comprising:
- a plurality of arrays formed from light emitting diodes;
- a transistor connected to each array of the plurality of arrays formed from light emitting diodes;
- a PWM controller having an input for receiving a voltage reference and an output connected to selected transistors and arrays of light emitting diodes for driving the selected transistors and setting a PWM duty cycle for the selected arrays of the light emitting diodes for determining brightness of the light emitting diodes;
- a feedback loop circuit connected to said light emitting diodes and having a switching controller operatively connected to a source of voltage and a reference voltage for sensing and regulating a load voltage;
- and
- an oscillator connected to the PWM controller and the switching controller for driving the PWM controller.
An LED driver circuit comprising:
- a plurality of arrays of light emitting diodes;
- a field effect transistor connected to each array of the plurality of arrays of light emitting diodes;
- a PWM controller having an input for receiving a voltage reference and an output connected to selected transistors and arrays of light emitting diodes for driving the selected transistors and setting a PWM duty cycle for the selected arrays of light emitting diodes for determining brightness of the light emitting diodes;
- a feedback loop circuit having a switching controller operatively connected to a source of voltage and reference voltage for sensing and regulating a load voltage;
- an oscillator connected to the PWM controller and the switching controller for driving the PWM controller;
- and
- a lamp outage detection circuit operatively connected to said PWM controller and said field effect transistors for synchronizing an “on” command with a measured current for detecting when a selected number of light emitting diodes are inoperative and compensating for any selected PWM duty cycle.
A method of driving an array of light emitting diodes comprising the steps of receiving a voltage reference within a PWM controller and outputting a signal for driving selected transistors connected to respective arrays of light emitting diodes and setting a PWM duty cycle for selected arrays of light emitting diodes to determine brightness of the light emitting diodes, and further comprising a step of receiving voltage signals within an input buffer circuit indicative of what combination of arrays of light emitting diodes should be lit.
A method of driving an array of light emitting diodes comprising the steps of receiving a voltage reference within a PWM controller and outputting a signal for driving selected transistors that are connected to respective arrays of light emitting diodes and setting a PWM duty cycle for selected arrays of light emitting diodes to determine brightness of the light emitting diodes, and sensing a regulating load voltage by a switching controller located within a feedback loop circuit of the selected arrays of light emitting diodes.
An LED driver circuit comprising:
- a plurality of arrays formed from light emitting diodes;
- a transistor connected to each array of the plurality of arrays formed from light emitting diodes;
- a controller having an input for receiving a voltage reference and an output connected to selected transistors and arrays of light emitting diodes for driving the selected transistors and setting a duty cycle for the selected arrays of light emitting diodes for determining brightness of the light emitting diodes;
- and
- a circuit connected to said light emitting diodes and to a source of voltage and a reference voltage for sensing and regulating a load voltage and providing a ramp down voltage to the selected arrays of light emitting diodes when a predetermined temperature is reached.
Dependencies are inferred from the claim text.