Cuk converter ripple current

[Arouse1973]

The voltages seem a bit high for 5 and 12 Volt. Your circuit by the way is for a positive and negative PSU? I would be looking for a dual secondary transformer with two bridge rectifiers attached one for each output with separate smoothing capacitors.

I would use high current Schottky barrier rectifiers for the high current 5 volt and standard rectifiers for the 12 Volts.

I would start by working out the ratio of the lowest mains input with respect to the different outputs. You know 180 Volts is your low input and so when the input goes to 240 your stuck with what's on the secondary otherwise it won't work at 180 Volts.

So for the 5 Volt say you needed 6.5 volts peak on the input to the diodes because of the diode drop and regulator drop at max current, remember diodes and regulators drop larger voltages as the current increases. This would be 6.5 / 1.414 =4.59 Vrms 180/4.59 = 39.21:1

So when the voltage on the input is 240, this is then 6.12 Vrms which is 8.65 V peak. Remember this is at max load, the secondary voltage will be even higher maybe 20%, you would need to mention this and consult the transformer datasheet for the regulation information.

Adam

 

[Baxter Burgundy]

So more like this power supply?

 

[Baxter Burgundy]

Ok Adam, one more bit of help if you don't mind. As with before the notes for the question I am attempting are far from clear so I don't know even where to begin in solving this one. So any pointers to get me started would be great.

Derive an expression the shows that the gain of the illustrated sallen key filter is as follows:-

 

[Arouse1973]

What course are you doing, is this a free course you can send me a link to? I can't believe they expect you to work this out without any course notes or an example, this is advanced stuff.
Adam

 

[Baxter Burgundy]

It's a paid electronics course. I do have notes but in my opinion they do not explain it very well, or not in a way I can get my head around. If you give me your email I'll send you the notes so you can see what I mean.

 

[Arouse1973]

[email protected]

 

[Arouse1973]

Ok Adam, one more bit of help if you don't mind. As with before the notes for the question I am attempting are far from clear so I don't know even where to begin in solving this one. So any pointers to get me started would be great.

Derive an expression the shows that the gain of the illustrated sallen key filter is as follows:-

So you know this is the transfer function for that particular opamp configuration. This is the gain Vout/Vin. What I think they want is for you to put all the Cs and Rs into the equation to get the gain. but you will also need to know the frequency. Doesn't look like it's in there does it? It is but it's hidden in the (s) which is sigma. Sigma is J*Omega which is J*2*pi*f. So all you need to so is add the Cs and Rs split up sigma into J*2*pi*f remove J and you should be able to punch in some numbers. Oh k is DC gain which is the same for the gain of a non inverting opamp.
Adam

 

[Baxter Burgundy]

Thanks Adam. I'll have a look over this over the next couple of days and see if I can get my head around it.

 

[Arouse1973]

Thanks Adam. I'll have a look over this over the next couple of days and see if I can get my head around it.

Ok

 

[Baxter Burgundy]

Can you suggest any internet articles or texts on the subject for further study. As it is I can't get my head around it, and I think the best thing to do is start again, but try to learn the subject from a decent source.

 

[Arouse1973]

What dont you understand David
Adam

 

[Baxter Burgundy]

Ok, I'm struggling to understand how the maths all fits together. So because of that I don't really get where to start with transposing the equations to get to where I need to. It's frustrating because I'm quite good at maths normally.

 

[Arouse1973]

I struggle with maths myself. We were never told what any of it was used for so I didnt understand what use it had. l'll see if I cant put something together for you, but might be a few days as I have to do a bit of shopping.
Adam

 

[Baxter Burgundy]

Thanks very much Adam.