Testing SMPS IC output signal using a LED

Thread Starter

Willen

Joined Nov 13, 2015
327
A SMPS has just a power N-MOSFET which is driver of the main ferrite transformer. The switching IC gives the gate signal as this: IC>Series Resistor>Zener to Gnd>Gate of the N-Fet.

To know the signal exist or not (IC damaged or not) I added a LED (with limiter resistor): Gate to +lead of the LED and Source to -lead of the LED. Does this arrangement turns ON the LED if the IC generating signal correctly?

In fact, the LED acting as it's connected to a damp oscillator. I mean when I press Power ON button then LED blinks few times and becomes dim and dim and dim and goes off.
 
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