TPS61196: the Dimming Question in TPS61196

Hi

May I know which one is the "dimming FET" on your schematic?

BR

Patrick

Hi,

as following figure.

Hi,

This is because, when dimming FET off, the LED current will drop to 0 gradually, therefore, the voltage drop on LED string will also decrease gradually.

However, the output capacitor will prevent the output voltage dropping quickly. So the "extra" voltage is added on the dimming FET until the LED string is totally off.

BR

Patrick

Hi,

thank you very much!

so, may I can to understanding the behavior as your mention as following figure? thanks!

Hi,

I mean because LED string needs time to turn off, its voltage decreases gradually, so the extra voltage is added on dimming FET. This is related to your red line.

For your blue line, when the LED string is finally turn off, the dimming FET is disconnected with Vout.

So the dimming FET Vds will increase first and then quickly decrease.

May I know if this voltage spike caused any issue in your end equipment?

BR

Patrick