LED driving device with variable light intensity
First Claim
1. A device for driving a light-emitting-diode element, with variable light intensity and having a turning-on threshold voltage, the device comprising:
- a supply stage having an output to be connected to said light-emitting-diode element, said supply stage being configured so as to have a first operating mode and a second operating mode, wherein, in said first operating mode, said supply stage generates a controlled supply current and, in said second operating mode, said supply stage generates a controlled supply voltage no greater than said turning-on threshold voltage;
a current sensor, connectable to said output for generating, in use, a current-feedback signal correlated to the current flowing in said light-emitting-diode element and sent to said supply stage in said first operating mode, an intensity-control stage generating a mode-control signal sent to said supply stage and controlling sequential switching between said first and second operating modes of said supply stage according to a desired light intensity.
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Accused Products
Abstract
In a device for driving LEDs with variable light intensity, a supply stage has a first operating mode, in which a controlled supply current is generated, and a second operating mode, in which a controlled supply voltage is generated. A LED is connected to the supply stage, receives the controlled supply current or voltage, and has a turning-on threshold voltage higher than the controlled supply voltage. A current sensor generates a current-feedback signal that is correlated to the current flowing in the LED and is supplied to the supply stage in the first operating mode. An intensity-control stage generates a mode-control signal that is sent to the supply stage and controls sequential switching between the first and the second operating modes of the supply stage.
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Citations
31 Claims
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1. A device for driving a light-emitting-diode element, with variable light intensity and having a turning-on threshold voltage, the device comprising:
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a supply stage having an output to be connected to said light-emitting-diode element, said supply stage being configured so as to have a first operating mode and a second operating mode, wherein, in said first operating mode, said supply stage generates a controlled supply current and, in said second operating mode, said supply stage generates a controlled supply voltage no greater than said turning-on threshold voltage;
a current sensor, connectable to said output for generating, in use, a current-feedback signal correlated to the current flowing in said light-emitting-diode element and sent to said supply stage in said first operating mode, an intensity-control stage generating a mode-control signal sent to said supply stage and controlling sequential switching between said first and second operating modes of said supply stage according to a desired light intensity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 29, 30, 31)
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13. A method for driving a light-emitting-diode element with variable light intensity, comprising the steps of:
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supplying said light-emitting-diode element with a controlled supply current in a first operating mode, supplying said light-emitting-diode element with a controlled supply voltage in a second operating mode, said controlled supply voltage being no greater than a turning-on threshold voltage of said light-emitting-diode element; and
controlling alternately a sequential switching between said first and second operating modes. - View Dependent Claims (14, 15, 16)
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17. A circuit for driving a light-emitting-diode component, the light-emitting-diode component having a turn-on threshold voltage and the circuit comprising:
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a supply stage circuit having an output adapted to be coupled the light-emitting-diode component and operable in a current control mode and a voltage control mode responsive to a mode control signal, the supply stage circuit operable in the current control mode responsive to the mode control signal being active to supply a current to the light emitting-diode component, with the current having a value that is a function of current feedback signal, and the supply stage circuit operable in the voltage control mode responsive to the mode control signal being inactive to apply a voltage to the light emitting-diode component, the voltage having a value that is no greater than the turn-on threshold voltage;
a current sensor coupled to the supply stage circuit and adapted to be coupled to the light emitting-diode component, the current sensor operable to generate the current feedback signal having a value that is a function of the current flowing through the light-emitting-diode component in the current-control mode of operation; and
an intensity control circuit coupled to the supply stage circuit and adapted to receive an intensity signal, the intensity control circuit operable to develop the mode control signal responsive to the intensity signal and the intensity-control circuit alternately activating and deactivating the mode control signal as a function of the intensity signal to control an intensity of light generated by the light-emitting-diode component. - View Dependent Claims (18, 19, 20)
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21. An electronic system, comprising:
an electronic subsystem including, a light-emitting-diode component having a turn-on threshold voltage;
a driver circuit coupled to the light-emitting-diode component, the driver circuit including, a supply stage circuit having an output adapted to be coupled the light-emitting-diode component and operable in a current control mode and a voltage control mode responsive to a mode control signal, the supply stage circuit operable in the current control mode responsive to the mode control signal being active to supply a current to the light emitting-diode component, with the current having a value that is a function of current feedback signal, and the supply stage circuit operable in the voltage control mode responsive to the mode control signal being inactive to apply a voltage to the light emitting-diode component, the voltage having value that is no greater than the turn-on threshold voltage;
a current sensor coupled to the supply stage circuit and adapted to be coupled to the light emitting-diode component, the current sensor operable to generate the current feedback signal having a value that is a function of the current flowing through the light-emitting-diode component in the current-control mode of operation; and
an intensity control circuit coupled to the supply stage circuit and adapted to receive an intensity signal, the intensity control circuit operable to the develop the mode control signal responsive to the intensity signal and the intensity-control circuit alternately activating and deactivating the mode control signal as a function of the intensity signal to control an intensity of light generated by the light-emitting-diode component. - View Dependent Claims (22, 23, 24)
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25. A method of controlling an intensity of light generated by a light-emitting-diode component, the method comprising:
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supplying a current to the light-emitting-diode component, a magnitude of the current corresponding to a desired color light to be generated by the light-emitting-diode component;
sensing current through the light-emitting-diode component;
adjusting the current through the light-emitting-diode component responsive to the sensed current to achieve the desired color of light;
coupling a resistive network in parallel across the light-emitting-diode component to limit the voltage across the light-emitting-diode component to a voltage that is no greater than a turn-on threshold voltage of the light-emitting-diode component; and
sequentially switching between supplying the current to the light-emitting-diode component and coupling the resistive network to the component to control the intensity of the light generated by the light-emitting-diode component. - View Dependent Claims (26, 27, 28)
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Specification