Stacked LED Controllers
First Claim
1. A light emitting diode (LED) driver comprising:
- a first controller comprising;
a first voltage input terminal;
a first output terminal;
a first current source coupled to the first voltage input terminal, the first current source having at least one terminal for connection to a first LED to drive the first LED;
a first detector coupled to the first voltage input terminal for detecting whether a voltage across the first voltage input terminal and the first output terminal is above a first threshold, the first threshold being a voltage greater than that needed to turn on the first LED;
a normally-on first bypass switch having a first current handling terminal coupled to the first voltage input terminal, the first bypass switch having a second current handling terminal, the first detector being coupled to a control terminal of the first bypass switch to turn the first bypass switch off when the voltage across the first voltage input terminal and first output terminal is above the first threshold;
a second controller comprising;
a second voltage input terminal coupled to the second current handling terminal of the first bypass switch;
a second output terminal coupled to the first voltage input terminal of the first controller;
a second current source coupled to the second voltage input terminal, the second current source having at least one terminal for connection to a second LED to drive the second LED;
a second detector coupled to the second voltage input terminal for detecting whether a voltage across the second voltage input terminal and the second output terminal is above a second threshold, the second threshold being a voltage greater than that needed to turn on the second LED;
a normally-on second bypass switch having a first current handling terminal coupled to the second voltage input terminal, the second bypass switch having a second current handling terminal, the second detector being coupled to a control terminal of the second bypass switch to turn the second bypass switch off when the voltage across the second voltage input terminal and the second output terminal is above the second threshold;
whereby the first detector does not turn off the first bypass switch when the voltage detected by the first detector is below the first threshold, so that the first bypass switch substantially connects the second voltage input terminal to the first voltage input terminal to bypass the second controller, andwhereby the first detector turns off the first bypass switch when the voltage detected by the first detector is above the first threshold, allowing the second controller to receive a current through its second voltage input terminal.
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Accused Products
Abstract
A driver for driving a plurality of light emitting diodes (LEDs) is formed of a plurality of LED controllers connected in series between a power supply and a reference voltage. Each controller drives one or more LEDs directly connected to it. Each controller has a voltage input terminal coupled to an output terminal of an adjacent upstream controller, and an output terminal coupled to the voltage input terminal of an adjacent downstream controller. Each controller has a normally-on bypass switch coupled between its voltage input terminal and the voltage input terminal of the adjacent upstream controller. The bypass switch completely bypasses the adjacent upstream controller when the adjacent downstream controller detects that its input voltage is below a threshold insufficient to drive the LED in the adjacent upstream controller. The bypass switch is turned off if the voltage is above the threshold.
97 Citations
22 Claims
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1. A light emitting diode (LED) driver comprising:
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a first controller comprising; a first voltage input terminal; a first output terminal; a first current source coupled to the first voltage input terminal, the first current source having at least one terminal for connection to a first LED to drive the first LED; a first detector coupled to the first voltage input terminal for detecting whether a voltage across the first voltage input terminal and the first output terminal is above a first threshold, the first threshold being a voltage greater than that needed to turn on the first LED; a normally-on first bypass switch having a first current handling terminal coupled to the first voltage input terminal, the first bypass switch having a second current handling terminal, the first detector being coupled to a control terminal of the first bypass switch to turn the first bypass switch off when the voltage across the first voltage input terminal and first output terminal is above the first threshold; a second controller comprising; a second voltage input terminal coupled to the second current handling terminal of the first bypass switch; a second output terminal coupled to the first voltage input terminal of the first controller; a second current source coupled to the second voltage input terminal, the second current source having at least one terminal for connection to a second LED to drive the second LED; a second detector coupled to the second voltage input terminal for detecting whether a voltage across the second voltage input terminal and the second output terminal is above a second threshold, the second threshold being a voltage greater than that needed to turn on the second LED; a normally-on second bypass switch having a first current handling terminal coupled to the second voltage input terminal, the second bypass switch having a second current handling terminal, the second detector being coupled to a control terminal of the second bypass switch to turn the second bypass switch off when the voltage across the second voltage input terminal and the second output terminal is above the second threshold; whereby the first detector does not turn off the first bypass switch when the voltage detected by the first detector is below the first threshold, so that the first bypass switch substantially connects the second voltage input terminal to the first voltage input terminal to bypass the second controller, and whereby the first detector turns off the first bypass switch when the voltage detected by the first detector is above the first threshold, allowing the second controller to receive a current through its second voltage input terminal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A driver for a plurality of light emitting diodes (LEDs) comprising:
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a plurality of LED controllers connected in series between a power supply and a reference voltage, controllers in a direction of the power supply being upstream controllers, controllers in a direction of the reference voltage being downstream controllers, the controllers comprising; a first controller connected to receive an input voltage from upstream controllers and having an output connected to the reference voltage, a second controller connected to receive an input voltage from the power supply, and one or more intermediate controllers connected between the first controller and the second controller, each intermediate controller comprising; a first voltage input terminal; a first output terminal coupled to a second voltage input terminal of an adjacent downstream controller; a first current source coupled to the first voltage input terminal, the first current source having at least one terminal for connection to a first LED to drive the first LED; a first detector coupled to the first voltage input terminal for detecting whether a voltage across the first voltage input terminal and the first output terminal is above a first threshold, the first threshold being a voltage greater than that needed to turn on the first LED; a normally-on first bypass switch having a first current handling terminal coupled to the first voltage input terminal, the first bypass switch having a second current handling terminal coupled to a third voltage input terminal of an adjacent upstream controller, the first detector being coupled to a control terminal of the first bypass switch to turn the first bypass switch off when the voltage between the first voltage input terminal and the first output terminal is above the first threshold; whereby the first detector does not turn off the first bypass switch when the voltage detected by the first detector is below the first threshold, so that the first bypass switch substantially connects the first voltage input terminal to the third voltage input terminal of the adjacent upstream controller to bypass the adjacent upstream controller, and whereby the first detector turns off the first bypass switch when the voltage detected by the first detector is above the first threshold, allowing the adjacent upstream controller to receive a current through its third voltage input terminal. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A method performed by a driver to drive a plurality of light emitting diodes (LEDs), the driver comprising a plurality of LED controllers connected in series between a power supply and a reference voltage, controllers in a direction of the power supply being upstream controllers, controllers in a direction of the reference voltage being downstream controllers, the controllers comprising a first controller connected to receive an input voltage from upstream controllers and having an output connected to a reference voltage, a second controller connected to receive an input voltage from the power supply, and one or more intermediate controllers connected between the first controller and the second controller, each intermediate controller performing the method comprising:
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receiving a voltage at a first voltage input terminal coupled to an output of an adjacent upstream controller; outputting a voltage at a first output terminal coupled to a second voltage input terminal of an adjacent downstream controller; sourcing a current to an LED when sufficient voltage is applied across the first voltage input terminal and the first output terminal; detecting, by a detector, whether a voltage across the first voltage input terminal and the first output terminal is above a threshold, the threshold being a voltage greater than that needed to turn on the LED; controlling a normally-on bypass switch to turn the bypass switch off when the voltage between the first voltage input terminal and the first output terminal is above the threshold, the normally-on bypass switch having a first current handling terminal coupled to the first voltage input terminal, the bypass switch having a second current handling terminal coupled to a third voltage input terminal of an adjacent upstream controller, whereby the detector does not turn off the bypass switch when the voltage detected by the detector is below the threshold, so that that the bypass switch substantially connects the first voltage input terminal to the third voltage input terminal of the adjacent upstream controller to bypass the adjacent upstream controller, and whereby the detector turns off the bypass switch when the voltage detected by the detector is above the threshold, allowing the adjacent upstream controller to receive a current through its third voltage input terminal. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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Specification