Dear TI member,
Our Customer use the LM3409HV to design, and circuit as below,
And when Vin = 60V, The waveform looks good.
Ch.1 ILED
Ch.2 SW
Fig.1
But When we change Vin to 65V, The current ripple looks abnormal,
Finally, we add 2.2uF Cap at output, the current ripple just restore to fig.1.
Ch.1 ILED
Ch.2 SW
Fig.2
I have 3 question .
#1 Does Vin will affect to ILED ripple?
Because the Toff is fix, so IL peak-to-peak can't change, I think that if IL don't change, the current ripple don't change, too.
#2 Why do we change the VIN will lead to ILED current ripple abnormal?
#3 Why do we add output CAP can improve the abnormal ILED ripple?
