Driver Circuit for Efficiently Driving a Large Number of LEDs
First Claim
1. A circuit for controlling a plurality of LEDs coupled in series, the circuit comprising:
- a switching converter operable as a current source to be coupled to the plurality of LEDs to provide a constant load current thereto, the switching converter including an inductor to be coupled in series with the plurality of LEDs such that when the LEDs are coupled the same load current flows through the inductor and the plurality of LEDs, wherein no substantial capacitance is coupled between the inductor and the plurality of LEDs; and
a plurality of floating driver circuits, each floating driver circuit to be coupled in parallel to a respective individual LED of the plurality of LEDs, each floating driver circuit configured to fully or partially take over the load current thereby bypassing the respective LED in accordance with a respective modulated input signal to control the intensity of light emitted by the respective LED.
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Accused Products
Abstract
A circuit can be used for controlling a plurality of LEDs coupled in series. A switching converter operates as a current source coupled to the plurality of LEDs to provide a constant load current thereto. The switching converter includes an inductor coupled in series with the plurality of LEDs such that the same load current flows through the inductor and the plurality of LEDs. No substantial capacitance is coupled between the inductor and the plurality of LEDs. A floating driver circuit is coupled in parallel with each individual LED of the plurality of LEDs. The floating driver circuit is configured to fully or partially take over the load current thereby bypassing the respective LED in accordance with a respective modulated input signal to control the intensity of the light emitted by the LED.
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Citations
23 Claims
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1. A circuit for controlling a plurality of LEDs coupled in series, the circuit comprising:
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a switching converter operable as a current source to be coupled to the plurality of LEDs to provide a constant load current thereto, the switching converter including an inductor to be coupled in series with the plurality of LEDs such that when the LEDs are coupled the same load current flows through the inductor and the plurality of LEDs, wherein no substantial capacitance is coupled between the inductor and the plurality of LEDs; and a plurality of floating driver circuits, each floating driver circuit to be coupled in parallel to a respective individual LED of the plurality of LEDs, each floating driver circuit configured to fully or partially take over the load current thereby bypassing the respective LED in accordance with a respective modulated input signal to control the intensity of light emitted by the respective LED. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A circuit for controlling a plurality of LEDs coupled in series, the circuit comprising:
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a current source to be coupled to the plurality of LEDs to provide a constant load current thereto; and a plurality of floating driver circuits, each floating driver circuit to be coupled in parallel to a respective individual LED of the plurality of LEDs, each floating driver circuit configured to fully or partially take over the load current thereby bypassing the respective LED in accordance with a respective modulated input signal to control the intensity of light emitted by the LED, wherein each floating driver circuit comprises; a bypass transistor having a load current path to be coupled in parallel to the corresponding LED; and an over voltage detection circuit to be coupled in parallel to the corresponding LED and configured to signal an over-voltage when a voltage across the load current path of the bypass transistor reaches a maximum voltage. - View Dependent Claims (15, 16, 17)
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18. A circuit for controlling a plurality of LEDs coupled in series, the circuit comprising:
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a current source to be coupled to the plurality of LEDs to provide a constant load current thereto; and a plurality of floating driver circuits, each floating driver circuit to be coupled in parallel to a respective individual LED of the plurality of LEDs, each floating driver circuit configured to fully or partially take over the load current thereby bypassing the respective LED in accordance with a respective modulated input signal to control the intensity of light emitted by the LED, wherein each floating driver circuit comprises; a bypass transistor having a load current path to be coupled in parallel to the corresponding LED; and a gate driver configured to drive the bypass transistor into an ON state and an OFF state in accordance with the modulated input signal; and a logic gate receiving the modulated input signal and an over-voltage signal indicative of whether a voltage across the load current path of the bypass transistor has at least once reached a maximum voltage or not, the logic gate configured to override the modulated input signal in case the over-voltage signal is active so as to permanently switch on the bypass transistor. - View Dependent Claims (19, 20)
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21. A circuit for controlling a plurality of LEDs coupled in series, the circuit comprising:
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a current source to be coupled to the plurality of LEDs to provide a constant load current thereto; and a plurality of floating driver circuits, each floating driver circuit to be coupled in parallel to a respective individual LED of the plurality of LEDs, each floating driver circuit configured to fully or partially take over the load current thereby bypassing the respective LED in accordance with a respective modulated input signal to control the intensity of light emitted by the respective LED, wherein each floating driver circuit comprises; a bypass transistor having a load current path being coupled in parallel to the corresponding LED; and a gate driver configured to drive the bypass transistor into an ON state and an OFF state in accordance with the modulated input signal, the gate driver being supplied by a supply line providing a constant current and is configured to sink this current, direct it through a gate-source capacitance of the bypass transistor to charge or discharge the gate, and to supply this current back to the supply line, such that no substantial bias current is injected into the load current path of the plurality of LEDs. - View Dependent Claims (22, 23)
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Specification