Led driver and a method of driving leds
AssigneeNXP B.V.
InventorsArjan VAN DEN BERG, Jie CHEN
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Abstract
A method of driving current from an AC power supply through a series arrangement of a varying number of strings of LEDs is disclosed, the method comprising, adding LED strings to the series arrangement in a first order during an increasing voltage part of a cycle of the AC power supply cycle and subsequently removing LED strings from the series arrangement in a second order s during a decreasing voltage part of the cycle, wherein the second order is not the reverse of the first order. A driver for operating such a method is also disclosed, as is an IC embodying such a driver.
Claims11
A method of driving current from an AC power supply through a series arrangement of a varying number of strings of LEDs, the method comprising,
- adding LED strings to the series arrangement in a first order during an increasing voltage part of a cycle of the AC power supply cycle and subsequently
- removing LED strings from the series arrangement in a second order s during a decreasing voltage part of the cycle,
- wherein the second order is not the reverse of the first order,
The method of claim I wherein the second order is the same as the first order.
A driver for driving, current from an AC power supply through a series arrangement of a varying number of strings of LEDs by adding LED strings to the series arrangement during an increasing voltage pan of a cycle of an AC power supply cycle and subsequently removing LED strings from the series arrangement strings of LEDs during a decreasing voltage part of the cycle,
- the driver comprising
- at least:
- one short-circuit connection configured to be switchably connected across a one of the strings of LEDs, and
- at least:
- one current source configured to he connected to the series arrangement,
- and being configured to add the LED strings in a first order and remove LED strings in a second order which is not the reverse of the first order.
A driver for driving current from an AC power supply through a series arrangement of a varying number of strings of LEDs, the number of strings of LEDs being varied by adding LED strings to the series arrangement in a first order and subsequently removing LED strings from the series arrangement in a second order, the driver comprising
- a plurality of switches each configured to short-circuit at least one of the stings of LEDs.
Dependencies are inferred from the claim text.