Tl494 half bridge smps

[aksnis]

Hello everyone,
I was studying a tl494 based half bridge smps
I came across the current sense section opamp pin 15 & pin16
Now pin16 is connected directly to the ground
But there is some arrangment made to pin 15

I have drawn a part of it
Please can anyone help me what is a purpose of “103 trimpot” and why does the transistor “ 2n2222a” is also used which Is connected to microcontroller pic18f452

 

[ronsimpson]

The TL494 has two "error amplifiers" pins 1,2 and 15,16 with the output on pin 3. The two amplifiers are the same and can do any job. Usually one is usd to watch the output voltage and the other is used for over current limit.

The two resistors (0.1) are current sense. It is over current limit. The computer pulls up on pin 15 to change the point where the TL494 goes into current limit.

 

[aksnis]

So why is the trimpot used then???
And i am sorry sir i did not understand your last statement
“The computer pulls up on pin 15 to change the point............................”

 

[ronsimpson]

So why is the trimpot used then???

here is a link. look at the last posts.