Maker Pro
Maker Pro

TL 494 buck converter

Mawunze

Feb 20, 2017
6
Joined
Feb 20, 2017
Messages
6
Hie there I made a tl 494 circuit which I designed to oscilate at 40KHz with emitter follower outputs. the problem is a dc component appearing on the outputs superimposed on the square wave. The internal BJTs are Ok as I confirmed with a multimeter and if I apply a sufficient voltage on the deadtime control, the bjts are completely off showing that they are ok. my problem is this steady dc components on the outputs. How do I remove it.
 

duke37

Jan 9, 2011
5,364
Joined
Jan 9, 2011
Messages
5,364
Without seeing the schematic it is impossible to guess where the DC comes from.
 

Mawunze

Feb 20, 2017
6
Joined
Feb 20, 2017
Messages
6

I tied pin 8 and pin 11 to 17V positive supply so the dc is coming from pin 9 and pin 10 emitter outputs. The 40khz square wave can be detected but it is superimposed on a dc voltage. I will post a schematic
 

Mawunze

Feb 20, 2017
6
Joined
Feb 20, 2017
Messages
6
The circuit is supposed to output a 40khz square wave. I tied pin 8 and pin 11 of the tl 494 to 17V positive supply so the dc is coming from pin 9 and pin 10 emitter outputs. The 40khz square wave can be detected but it is superimposed on a dc voltage. I have connected 330 ohm resistors from the outputs to ground and the output is taken from the junction where the resistor and the output pin meet. A square wave can be detected at this point. It rises to about 17v peak value but falls to about 4.5V and rises to 17V again. How do i eliminate this 4.5v. I want the output to fall to zero so that when I connect a mosfet, it doesnt switch on continuously because of this 4.5v
 

Alec_t

Jul 7, 2015
3,587
Joined
Jul 7, 2015
Messages
3,587
What is pin 13 connected to? How are the error amplifiers configured? Are any pins floating?
 
Top