I am using the given schematic for voltage regulation using TL494. When feedback is not given, that is point A and B are not connected, then I am getting a pulse of 35% duty cycle of 0-12V. But when the feedback is given ( A and B gets connected), then in the output I am getting a 12V DC rather than a pulse even though the positive and negative terminal of error amplifiers have some difference of voltage and there's a sudden large amount of current flow at point C and D that is the primary side of the transformer. I am not unable to understand why the pulse is getting vanished with 12V dc and sudden large increase in current( i. e from 0.5 A to 1.6 A) in the primary side of the transformer circuit . Is there any blunder in the schematic.

 

Why are you using a TL494 to drive a flyback converter? There are hundreds of flyback ICs, some even have built-in power transistors.
All of them do a better job than a TL494.
https://www.onsemi.com/products/pow...products=fjI1MDI4NjN+dmFsdWV+MX5GTFlCQUNLfg==

 

Why are you using a TL494 to drive a flyback converter? There are hundreds of flyback ICs, some even have built-in power transistors.
All of them do a better job than a TL494.
https://www.onsemi.com/products/pow...products=fjI1MDI4NjN+dmFsdWV+MX5GTFlCQUNLfg==

Yes, TL494 is not suitable for this task.

 

Feedback should be applied to pin1, not pin 2.

 

Feedback should be applied to pin1, not pin 2.

That’s a surprise, as Pin 1 is the non-inverting input, and feedback generally goes to the inverting input, but not in this case.

 

Feedback should be applied to pin1, not pin 2.

why I couldn't use pin 2 for taking voltage feedback am unable to understand .

 

Why are you using a TL494 to drive a flyback converter? There are hundreds of flyback ICs, some even have built-in power transistors.
All of them do a better job than a TL494.
https://www.onsemi.com/products/pow...products=fjI1MDI4NjN+dmFsdWV+MX5GTFlCQUNLfg==

I have taken TL494 so that I will have an error amplifier and I can control the output voltage with the variation of duty cycle . I couldn't think of another alternative . please suggest me .

 

why I couldn't use pin 2 for taking voltage feedback am unable to understand .

From the TI datasheet :-

This shows feedback to pins 1 and 16 (the non-inverting inputs of the error amps. Pins 2 and 15 get a reference voltage. dreived from pin 14.

 

UC3842 is the ubiquitous choice!
What is the purpose of your power supply?
You have an isolating transformer, but the ground connections on the primary side and secondary side are connected together. Why have an isolating transformer?

 

UC3842 is the ubiquitous choice!
What is the purpose of your power supply?
You have an isolating transformer, but the ground connections on the primary side and secondary side are connected together. Why have an isolating transformer?

I

I am trying to design a power supply in which output voltage will be controlled by the increase and decrease of duty cycle of input PWM pulse. If m giving voltage feedback in pin 1 . Then initially no voltage will be there at pin 1 and so no PWM pulse can be generated and m not getting any output voltage. If I give any particular voltage to DTC pin that is pin 4 . Then duty cycle will be constant , it won't vary.

 

I am trying to design a power supply in which output voltage will be controlled by the increase and decrease of duty cycle of input PWM pulse. If m giving voltage feedback in pin 1 . Then initially no voltage will be there at pin 1 and so no PWM pulse can be generated and m not getting any output voltage. If I give any particular voltage to DTC pin that is pin 4 . Then duty cycle will be constant , it won't vary.

What is the purpose of your power supply?
You have an isolating transformer, but the ground connections on the primary side and secondary side are connected together. Why have an isolating transformer?