Circuit and method for driving a light-emitting diode
First Claim
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1. A method for driving an LED from a secondary side of a transformer;
- the method comprising;
operating circuitry on a primary side of the transformer by;
continuously monitoring duty cycle of an input voltage to determine the power level intended to drive the LED by detecting a conduction angle of the input voltage;
decoding the conduction angle to generate a dimming profile representative of the intended brightness of the LED;
adjusting the current flow through the primary side of the transformer utilizing the dimming profile to make the power driving the LED equal to the power intended to drive the LED; and
continuously monitoring the input voltage to determine amplitude thereof; and
adjusting current through the primary side of the transformer utilizing feed forward control to control current through the LED, wherein power to drive the LED remains constant, and wherein all control of power to the LED is performed in the primary side circuitry.
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Abstract
Circuits and methods for driving an LED from a secondary side of a transformer are disclosed herein. An embodiment of the method includes monitoring an input voltage to determine the power level intended to drive the LED. The current flow through the primary side of the transformer is adjusted to make the power actually driving the LED equal to the power intended to drive the LED.
28 Citations
20 Claims
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1. A method for driving an LED from a secondary side of a transformer;
- the method comprising;
operating circuitry on a primary side of the transformer by; continuously monitoring duty cycle of an input voltage to determine the power level intended to drive the LED by detecting a conduction angle of the input voltage; decoding the conduction angle to generate a dimming profile representative of the intended brightness of the LED; adjusting the current flow through the primary side of the transformer utilizing the dimming profile to make the power driving the LED equal to the power intended to drive the LED; and continuously monitoring the input voltage to determine amplitude thereof; and
adjusting current through the primary side of the transformer utilizing feed forward control to control current through the LED, wherein power to drive the LED remains constant, and wherein all control of power to the LED is performed in the primary side circuitry.
- the method comprising;
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2. A method for driving an LED from a secondary side of a transformer;
- the method comprising;
monitoring an input voltage to determine the power level intended to drive the LED; and adjusting the current flow through the primary side of the transformer to make the power driving the LED equal to the power intended to drive the LED, wherein current flow through the primary side of the transformer is a pulse width modulated signal and wherein the adjusting comprises; multiplying the duty cycle of the pulse width modulated signal by the input voltage to yield a product; comparing the product to a reference voltage that is representative of the power level intended to be delivered to the LED to yield an error; and adjusting via a feed forward control the current flow through the primary side of the transformer based on the error, wherein power delivered to the LED remains constant. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- the method comprising;
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13. A circuit for driving an LED, the circuit comprising:
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a transformer having a primary side and a secondary side wherein the LED is connected to the secondary side; an input connected to the primary side of the transformer, wherein a voltage at the input is representative of the power to be delivered to the LED; a current regulator connected in series with the primary side of the transformer; a control circuit that controls the current regulator based on the voltage continuously monitored input voltage; an angle decode circuit for generating a dimming profile representative of intended brightness for the LED that matches characteristics of a dimmer; and a circuit for adjusting the current flow through the primary side of the transformer utilizing the dimming profile to make the power driving the LED equal to the power intended to drive the LED.
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14. A circuit for driving an LED, the circuit comprising:
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a transformer having a primary side and a secondary side wherein the LED is connected to the secondary side; an input connected to the primary side of the transformer, for continuously monitoring a voltage at the input that is representative of the power to be delivered to the LED; a current regulator connected in series with the primary side of the transformer; and a control circuit that controls the current regulator based on the voltage at the input, wherein the control circuit; drives the current regulator with a pulse width modulated signal; multiplies the duty cycle of the pulse width modulated signal with the voltage at the input yielding a product; compares the product to a reference voltage that is representative of the power intended to be delivered to the LED to yield an error; and controls the current regulator based on the error, wherein power delivered to the LED remains constant. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A circuit for driving an LED, the circuit comprising:
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a transformer having a primary side and a secondary side, the secondary side being connected to the LED, the primary side being driven by a signal having a conduction angle, wherein the conduction angle is proportional to dimming intended to applied to the LED; a current regulator connected in series with the primary side of the transformer; a control circuit that controls the current regulator based on the voltage continuously monitored input voltage; and an angle decode circuit for generating a dimming profile that matches characteristics of a dimmer; wherein the primary side of the transformer is driven based on current regulation when the dimming determined by the dimming profile is below a predetermined value; and wherein the primary side of the transformer is driven based on power regulation when the dimming determined by the dimming profile is greater than the predetermined value.
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Specification