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UCC28810

UCC28811

Primary-Side Bias Regulator

The bias for the UCC28810 device is provided by a winding on the flyback inductor that is well coupled to the

output winding. When the LED string voltage varies due to dimming or different configurations of LED strings, a

primary-side bias regulator formed by D15, R18, and Q4 is needed to limit the range of voltage that is applied to

the UCC28810. If dimming is not used, and the LED string forward voltage is well known, then the bias regulator

can be removed and R14 can be populated to connect the winding voltage directly to the input supply of the

device.

Figure 20. Primary Side Bias Regulator

Copyright © 2008, Texas Instruments Incorporated

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Product Folder Link(s): UCC28810 UCC28811