Hello All

I have designed the circuit for limiting the current at 100mA, by following the below video's.

I just checked that does the circuit will work when decrease the load resistor to that can draw 1A current. In this case, the NPN transistor that is connected to the power supply is switched ON after few seconds, but it shouldn't be switch ON as per the designed and explained in the below video's.

I was measured the Base, Collector, and Emitter voltages, and the base voltage is lower than the emitter voltage. The measured values are Vb=40V, Vc=48V, Ve=41V. Since the NPN transistor is in the cut-off region as per characteristics and measured values, then, how the transistor is Switched ON. I'm saying it is switched on because I measured emitter current that it is 0.9A almost.

Could you explain why and how the transistor is switched ON, and why current limit circuit is not working?.

Thank you.

 

Could you explain why and how the transistor is switched ON, and why current limit circuit is not working?.

Post a schematic of the circuit in question so we don't have to watch the videos.

 

First: What portion of the circuit are you actually utilizing??? The current limiter for the circuit displayed functions by shunting the base drive current from the output of the error amplifier so that the series pass transistor drive is reduced.
By not showing us the actual circuit that you are using, you are asking us to do mind reading at a distance. THAT is an ability that I TOTALLY LACK.
If you are using the whole circuit as shown in the second yoo toob display, that is the one my reference relates to. If you are only using that tiny segment with R1 and Q2, it will not work without the whole circuit present.

 

When designing a Power-Supply, You should follow a step-by-step procedure.
Start by calculating the following ............

What is the required Minimum-Output-Voltage during less than 100mA operation?

What is the Minimum available Input-Voltage with a ~200mA-Load, or under any other normal condition ?

What is the exact purpose of limiting the Current to 100mA ?,
( including ALL of your reasons for wanting Current-Limiting in the first place ).
.
.
.

 

For an NPN transistor, the collector should be positive of the emitter. From the voltages you post the collector is negative of the emitter.
Something is wrong here.

 

I explained how the current limiter function works back in post #3. What did the TS actually design???