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Will this buckboost LED driver be stable?

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T

treez

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Hello,
I have designed a buckboost LED driver and have only so far simulated it. (in LTspice)
The schematic is attached.
Also attached is a LTspice waveform from the simulation. It shows the COMP pin and LED current at startup.
(COMP pin is output of error amplifier)
When I calculated the feedback loop with a certain method, it gave a crossover frequency of >100KHz and no phase margin, and yet the simulation runs as smooth as can be.

spec of buckboost led driver is:-
Constant off time,
fsw = 119KHz at 10vin
vOUT = ~35v (9 series LEDs)
ILEDS= 500mA
CCM

LTspice simulation also attached
 

Attachments

  • bukboost UC3843.txt
    10 KB · Views: 43
  • bukboost UC3843.pdf
    33.5 KB · Views: 83
  • comp pin and led currnt.jpg
    comp pin and led currnt.jpg
    52.9 KB · Views: 152

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