Help me design a 1/2 kW SMPS 2-50V 0-10A

[naseerak]

Re: 1/2 kW SMPS 2-50V 0-10A

Hi Also check this. **broken link removed**

 

[DeepOne]

Re: 1/2 kW SMPS 2-50V 0-10A

It can accept 110V input, but with half output voltage only.

In PC PSU this restriction usually avoid with voltage doubler.

Or, certainly, possible change parameters of the transformer.

Close to subject "1/2 kW SMPS 2-50V 0-10A" - i think it is possible do a simple and reliable device, considering output power and big range of voltage change, on the base of ir2153 on high side and step up\dn converter on the lower side. Or even simply with tap from secondary windings of the transformer.

 

[naseerak]

Re: 1/2 kW SMPS 2-50V 0-10A

Hi
what changes to transformer?. In our country the Grid voltage varies from 80v to 270v during the summers as we have some poor transmission systems so changing the input tape is not the best of option rather this supply should do it in a linear way by adjusting the pwm like we have in offline supplies in the form of laptop and mobile phone chargers etc.

 

[FvM]

Re: 1/2 kW SMPS 2-50V 0-10A

what changes to transformer?. In our country the Grid voltage varies from 80v to 270v during the summers as we have some poor transmission systems so changing the input tape is not the best of option rather this supply should do it in a linear way by adjusting the pwm like we have in offline supplies in the form of laptop and mobile phone chargers etc.

In other words, you wan't to use a different converter topology, e.g. a flyback converter as used in most small and medium power wide range input SMPS.

 

[naseerak]

Re: 1/2 kW SMPS 2-50V 0-10A

But what about single or tw0 transistor forward converter in such a wide range PS

 

[DeepOne]

Re: 1/2 kW SMPS 2-50V 0-10A

Hi Also check this. **broken link removed**

and this, too
**broken link removed**

 

[karthick1987]

Re: 1/2 kW SMPS 2-50V 0-10A

Hey DeepOne,

are they just snubbers you are using at the input of your Push pull stage? If so Why?

https://obrazki.elektroda.pl/56_1344448819.gif ?

Cheers
K

 

[DeepOne]

Re: 1/2 kW SMPS 2-50V 0-10A

There no snubbers in circuit since all beautifully work without them. However in this scheme it is necessary to understand with feedback on voltage, because in such type possible do not work.
Also, it is necessary to note that TL494 is outdated chip and used mainly by the reason of its small price.

 

[karthick1987]

Re: 1/2 kW SMPS 2-50V 0-10A

There no snubbers in circuit since all beautifully work without them. However in this scheme it is necessary to understand with feedback on voltage, because in such type possible do not work.
Also, it is necessary to note that TL494 is outdated chip and used mainly by the reason of its small price.

I was trying to understand why you need the 4700nF(or is it uF?)? it would be good if you can explain that to me

 

[DeepOne]

Re: 1/2 kW SMPS 2-50V 0-10A

the 4700nF(or is it uF?)

Is the speech about this?

 

[AMSA84]

Re: 1/2 kW SMPS 2-50V 0-10A

Yes DeepOne. I have that doubt too.

I don't understand why that is done what for what purpose that is done. Could you explain me why that is done what is the purpose of that?

 

[FvM]

Re: 1/2 kW SMPS 2-50V 0-10A

I rather guess this capacitors

I think the circuit operation won't change substantially when omitting the RC combination.

 

[AMSA84]

Re: 1/2 kW SMPS 2-50V 0-10A

And what about those 2 capacitors that DeepOne has posted? A rally still don't understand. Sorry for inconvenience.

 

[FvM]

Re: 1/2 kW SMPS 2-50V 0-10A

They are half bridge capacitors, as DeepOne already mentioned. There are different ways to connect the passive side of the output transformer in a half bridge. E.g. a dual input voltage as in post #22 or a single capacitor to ground. By using two capacitors you get a direct return path for switching frequent currents through the high side switch.

 

[goldsmith]

Re: 1/2 kW SMPS 2-50V 0-10A

Hi AMSA84
In addition to the FvM's post i think this picture can show you how those capacitors will play the role . see below , please :

Best Wishes
Goldsmith

- - - Updated - - -

I rather guess this capacitors



I think the circuit operation won't change substantially when omitting the RC combination.

Hi Dear FvM
I think that capacitor will increase the speed of driver at transient time . because that capacitor will be short circuit at transient time and thus the rise time and won't be high . but most of the times i prefer to use a reversed bias diode , thus it's reversed bias capacitor will be short circuit at transient time and when signal is zero it will help to discharge the input capacitor as fast as possible .
But i agree if we don't put these things the circuit still will work fine .
Best Regards
Goldsmith

 

[FvM]

Re: 1/2 kW SMPS 2-50V 0-10A

My analysis of the driver RC circuit is as such:
There's no DC current flowing through the resistors.

Without parallel capacitors, they would limit the dynamic current and reduce the edge speed.

With parallel capacitors, they are effectively useless and can be replaced by a short.

 

[karthick1987]

Re: 1/2 kW SMPS 2-50V 0-10A

My analysis of the driver RC circuit is as such:
There's no DC current flowing through the resistors.

I think you meant no DC current through capacitor.

Goldsmith,

I thought about that same reasoning but 4700nF seemed like a high valve for that purpose. I would have gone with 4.7nF. To sharpen a transient we would want to have the capacitance as low as possible so that we have a more ideal "short". Dont you think?

 

[FvM]

Re: 1/2 kW SMPS 2-50V 0-10A

I think you meant no DC current through capacitor.

No, I mean't effectively no DC current through the resistor. The capacitor will no charge up to a noticable voltage, the voltage drop across the RC combination is constantly zero.

 

[AMSA84]

Re: 1/2 kW SMPS 2-50V 0-10A

Hello there guys, again.

Taking the advantage of this post, I'd like to ask you guys something 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.

 

[naseerak]

Re: 1/2 kW SMPS 2-50V 0-10A

I will suggest to follow threads on **broken link removed**