kilowattski
Okay, I reviewed page 2 of the second link once again and I understand how the center tap works to bring a positive and negative supply with an accompanying ground but my proposed layout is not represented. What I hoped to see was a single winding with multiple parallel connections all paired to a common ground which was not center tapped. You may say, this will not produce a negative supply but to me, it appears that it can if we reverse the orientation of the first and third diodes so that the primary wave splits positive and negative and then pairs with a common ground. This should work with half the diodes. The only difference is that now the supplies are 90° out of phase.
Okay, I reviewed page 2 of the second link once again and I understand how the center tap works to bring a positive and negative supply with an accompanying ground but my proposed layout is not represented. What I hoped to see was a single winding with multiple parallel connections all paired to a common ground which was not center tapped. You may say, this will not produce a negative supply but to me, it appears that it can if we reverse the orientation of the first and third diodes so that the primary wave splits positive and negative and then pairs with a common ground. This should work with half the diodes. The only difference is that now the supplies are 90° out of phase.
If I understand what you are saying, it will not work because there will be no return path for the current to flow through without a center tap. If you still think your circuit will work, try it, but make sure you have a fire extinguisher close at hand. I assume you are asking about this because you already have a transformer with no center tap. If this is not the case simply get one with a center tap or dual secondaries. For an Aleph X 100 watt the transformer would be only about $100.
William and kilowattski
After I spent nearly two hours trying to draw what I had in mind, I realized that without a center tap, the capacitors would have to provide the ground reference so it appears that page 2 of that link is absolutely correct "you must have a center tap in order to create a positive and negative power supply". Oh well, maybe I can strip that big toroid and rewire it.
After I spent nearly two hours trying to draw what I had in mind, I realized that without a center tap, the capacitors would have to provide the ground reference so it appears that page 2 of that link is absolutely correct "you must have a center tap in order to create a positive and negative power supply". Oh well, maybe I can strip that big toroid and rewire it.
STPS80H100TV
Nice work William!
It seems we've got the same type of diodes!!
I couldn't find any "ready made" data fitting in the PSUD data format, so I tried to set up the data for the STPS80H100TV device in PSUD myself, but I'm not sure if I got it right.
Do you have the correct values for this device for PSUD or do you know how to do this from the data available in the datasheet?
Are you using snubbers for the rectifiers?
Also I would like to know the brand/type/supplier of those nice looking transformers you are using!
Nice work William!
It seems we've got the same type of diodes!!
I couldn't find any "ready made" data fitting in the PSUD data format, so I tried to set up the data for the STPS80H100TV device in PSUD myself, but I'm not sure if I got it right.
Do you have the correct values for this device for PSUD or do you know how to do this from the data available in the datasheet?
Are you using snubbers for the rectifiers?
Also I would like to know the brand/type/supplier of those nice looking transformers you are using!
Hi Byteboy,
I don´t have any aditional information on the diodes but I think Schottkys don´t need snubbers (that´s why I didn´t use them).
The transformers are from Tauscher in Germany, 600VA 147x90mm but I would wait until my amps are working to see how they "humm".
These are the first big transformers I am using from them so I have no experience whatsoever.
William
I don´t have any aditional information on the diodes but I think Schottkys don´t need snubbers (that´s why I didn´t use them).
The transformers are from Tauscher in Germany, 600VA 147x90mm but I would wait until my amps are working to see how they "humm".
These are the first big transformers I am using from them so I have no experience whatsoever.
William
wuffwaff
Okay, I am following your earlier suggestion and posting a schematic. I am planning on rewinding my 8KVA wopper with dual secondaries and only one center tap return. I am assuming that both secondaries can use a common return. Is there anyone who can suggest why this isn't better than two separate return windings? Oh, and while I'm at it, what is the expected loss from a typical soft recovery type diode. Will they dissipate as much power on the return as on the ground section?
Okay, I am following your earlier suggestion and posting a schematic. I am planning on rewinding my 8KVA wopper with dual secondaries and only one center tap return. I am assuming that both secondaries can use a common return. Is there anyone who can suggest why this isn't better than two separate return windings? Oh, and while I'm at it, what is the expected loss from a typical soft recovery type diode. Will they dissipate as much power on the return as on the ground section?
Attachments
The reason why transformers come with two separate identical windings is that if a user wants more current he can simply parallel the secondaries or more voltage by putting them in series. For example if your transformer comes with two 20 volt secondaries rated at 20 amps each they can be used separately as two 20 volt secondaries at 20 amps, a single 40 volt secondary at 20 amps by putting the secondaries in series or a single 20 volt secondary at 40 amps by paralleling the secondaries.
A word of caution on your transformer. You have what is called an autotransformer. The evidence of this is the common ground between the primary and secondary. The problem with autotransformers is that they provide no isolation and could prove an electrocution hazard in some cases. If you rewind your transformer, be sure you break any contact between the primary and secondary. If you do this you will be all set.
As a rule of thumb there is usually a 0.7 volt drop across a silicon diode junction. With a bridge rectifier you will have to account for two junctions or 1.4 volts.
I don't understand your return vs ground question. If you clarify it a bit I will be happy to answer your question.
A word of caution on your transformer. You have what is called an autotransformer. The evidence of this is the common ground between the primary and secondary. The problem with autotransformers is that they provide no isolation and could prove an electrocution hazard in some cases. If you rewind your transformer, be sure you break any contact between the primary and secondary. If you do this you will be all set.
As a rule of thumb there is usually a 0.7 volt drop across a silicon diode junction. With a bridge rectifier you will have to account for two junctions or 1.4 volts.
I don't understand your return vs ground question. If you clarify it a bit I will be happy to answer your question.
kilowattski
Thanks for your attention. What I meant was that there are two sides to the diode bridge; the side that makes the voltage rail (pole side) and the side that makes the ground (return side). Will the diodes on either side dissipate the same amount of power? I thought there might be a pole side bias which could be exploited in the layout to effect a kind of 'heat averaging'.
Thanks for your attention. What I meant was that there are two sides to the diode bridge; the side that makes the voltage rail (pole side) and the side that makes the ground (return side). Will the diodes on either side dissipate the same amount of power? I thought there might be a pole side bias which could be exploited in the layout to effect a kind of 'heat averaging'.
If you are rewinding it is much better to do a bifilar-type or in your 8kw case quadrifilar, unless you have 8 gauge magnet wire laying around. That way you get two perfectly identical voltages out of the trafo. Keeping two secondaries separated by two fullwave bridges is much better than having a single CT/two rectifiers combination.
It is an undisputed electronics fact. There was a very good expl. on the forum by Fred, but that's ancient diyaudio.com hystory. See if you can find it with a search.
It is an undisputed electronics fact. There was a very good expl. on the forum by Fred, but that's ancient diyaudio.com hystory. See if you can find it with a search.
hi,
After your comment about X cancellation I am not sure anymore of what we are talking about because that would have no bearing in this PS discussion.
But it is better, much, if the transformer and the amp gnd are never connected directly and better yet if the two secondaries are never connected directly. In a sense gnd is not "really" gnd between the trafo and the diodes where all kinds of transient phenomena go on when diodes start/stop conducting. By using two secondaries/two bridges the transformer secondaries are never in direct contact with the gnd of the amp and with each other because there are diodes in between (preferably soft recovery).
This is in essence the very qualitative story. there is so much knowledge printed on this forum too bad it is so scattered and out of reach.
After your comment about X cancellation I am not sure anymore of what we are talking about because that would have no bearing in this PS discussion.
But it is better, much, if the transformer and the amp gnd are never connected directly and better yet if the two secondaries are never connected directly. In a sense gnd is not "really" gnd between the trafo and the diodes where all kinds of transient phenomena go on when diodes start/stop conducting. By using two secondaries/two bridges the transformer secondaries are never in direct contact with the gnd of the amp and with each other because there are diodes in between (preferably soft recovery).
This is in essence the very qualitative story. there is so much knowledge printed on this forum too bad it is so scattered and out of reach.
grataku
My point is your point so I think you understood me but perhaps I didn't understand you. Why wouldn't noise on the power supply have a bearing on the downstream circuit? The artifacts of diodes on a common return will result in equal measure on the common ground used for the positive and negative supply. I had suggested that this would be more effectively dealt with than two noise sources from two different sets of grounds. Even if the noise on the single ground is louder, it is one common noise.
My point is your point so I think you understood me but perhaps I didn't understand you. Why wouldn't noise on the power supply have a bearing on the downstream circuit? The artifacts of diodes on a common return will result in equal measure on the common ground used for the positive and negative supply. I had suggested that this would be more effectively dealt with than two noise sources from two different sets of grounds. Even if the noise on the single ground is louder, it is one common noise.
Transformer screens
Sorry Wuffwaff, for taking this thread off-topic.
The (real-) reason I was re-reading this thread was that I was curious about the transformer type of Tauscher you use.
I had a look at their website and read there that they have a number of screening types availlable.
Do you have any screens in your transformer and if so what type?
Sorry Wuffwaff, for taking this thread off-topic.
The (real-) reason I was re-reading this thread was that I was curious about the transformer type of Tauscher you use.
I had a look at their website and read there that they have a number of screening types availlable.
Do you have any screens in your transformer and if so what type?
The off topic discussion can be found here:
http://www.diyaudio.com/forums/showthread.php?postid=547795#post547795
/Hugo
http://www.diyaudio.com/forums/showthread.php?postid=547795#post547795
/Hugo
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.