Hello there guys. I'm new here and I hope that you can help me out here with some doubts that I have related to the feedback.
If we look to this circuit:
We can see that the voltage feedback control (to the IC that controls the PSU) is taken from an auxiliary winding on the primary. And as we can see too, the current is taken from the 0,27Ohm resistor, that is connected in series wih the MOSFET.
In this case:
We see that the voltage feedback control is taken directly from the output (red). On the other hand, the current is sensed through the current transformer
To finish, in this circuit:
We can see respectively the voltage and current feedback.
My questions are:
In the first circuit, why the voltage is taken from the auxiliary winding and not through an optocoupler, like in third circuit? What are the main differences between doing in one way and in another? How accurate is taking the voltage from the secondary winding when compared with the optocoupler, that takes directly from the output, in contrary to what is done with the auxiliary winding? The variation on voltage is sensed in the same way?
On the other hand, if we look to the 2nd circuit, we see that the voltage feedback is taken directly from the output. As I can see, the control circuit is in the primary (taking into account that the TR1 is the main transfomer, HF transformer), and doing in that way there is no galvanic isolation, I mean, aren't the ground being mixed? The ground of the secondary is connected to the ground of the MOSFET, that is at the primary, right?
About the current feedback, in the first circuit, we can see that it is taken from a series resistor, in contrary, in the 2nd circuit is taken by a current transformer. Why? What are the differences between one method and another?
To finish, why the current feedback is taken from the primary and not in the secondary, like the voltage (not counting with the situation of the auxiliary winding).
Sorry for the long post and the questions, that might be a little noob, but I'm new on this.
Regards to all and thanks in advance.
PS.: Those pics were taken from dany's website.
If we look to this circuit:
We can see that the voltage feedback control (to the IC that controls the PSU) is taken from an auxiliary winding on the primary. And as we can see too, the current is taken from the 0,27Ohm resistor, that is connected in series wih the MOSFET.
In this case:
We see that the voltage feedback control is taken directly from the output (red). On the other hand, the current is sensed through the current transformer
To finish, in this circuit:
We can see respectively the voltage and current feedback.
My questions are:
In the first circuit, why the voltage is taken from the auxiliary winding and not through an optocoupler, like in third circuit? What are the main differences between doing in one way and in another? How accurate is taking the voltage from the secondary winding when compared with the optocoupler, that takes directly from the output, in contrary to what is done with the auxiliary winding? The variation on voltage is sensed in the same way?
On the other hand, if we look to the 2nd circuit, we see that the voltage feedback is taken directly from the output. As I can see, the control circuit is in the primary (taking into account that the TR1 is the main transfomer, HF transformer), and doing in that way there is no galvanic isolation, I mean, aren't the ground being mixed? The ground of the secondary is connected to the ground of the MOSFET, that is at the primary, right?
About the current feedback, in the first circuit, we can see that it is taken from a series resistor, in contrary, in the 2nd circuit is taken by a current transformer. Why? What are the differences between one method and another?
To finish, why the current feedback is taken from the primary and not in the secondary, like the voltage (not counting with the situation of the auxiliary winding).
Sorry for the long post and the questions, that might be a little noob, but I'm new on this.
Regards to all and thanks in advance.
PS.: Those pics were taken from dany's website.
