Strange LED flicker when powered via buck converter
There is a high frequency common mode ground noise causing spurious conduction.

Using a pullup resistor of 10k to 100k from Collector to V+ should be enough to disable this effect by shunting the voltage across the LEDstrip when off.

The base current needs to be at least 5% of LEDstrip current when ON.

You can also apply low ESR caps to the 3.3V ESP load to reduce ripple and use twisted pairs to reduce EMI.







simulate this circuit &ndash; Schematic created using CircuitLab