Broadcom Corporation

Tivadar Szabo

Sridhar Kotikalapoodi

Farzan Roohparvar

Manisha Pandya

James Zeng

Manisha P Pandyn

An LED driver circuit is disclosed that can drive a plurality of LED strings that are arranged in parallel, each LED string having a plurality of component LEDs that are series-connected. The LED strings can be the same type of LEDs in each string, or have different types of LEDs from one string to another. The LED driver includes a voltage control loop that dynamically regulates the output voltage across the parallel arrangement of LED strings. The output voltage is dynamically adjusted to accommodate the LED string with the largest operational voltage drop. This enables LED displays to constructed using different types of LEDs strings, but still supply the LED strings in a power efficient manner. Further, each LED string also includes its own individual current regulation loop so that the current, and therefore brightness, of each LED string can be individually adjusted.

Single inductor serial-parallel LED driver

Traditionally, system loads are placed in parallel with the battery. This simple topology wastes the available power if the USB power and/or wall adapter is present. Recent topologies have made some improvements by powering the load by the maximum available voltage. Thus, if a USB power source or wall adapter is present, the load is powered by them rather than the battery, thus improving the system efficiency. However, since the USB power and wall adapter power are current limited, if the load requires higher current than the current limited USB or adapter, then the entire system is powered at voltage of the battery. The present invention further improves the system efficiency by distinguishing the load and powering the constant power loads by the maximum voltage and placing the constant current loads in parallel with the battery.

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Santa Clara, CA, United States of America

Tivadar Szabo