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paulmil
New Member
Malaysia
2 Posts |
 Posted - May 30 2011 : 12:12:42 AM
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| High current power supply. In a lot of these circuits you often see 3 or 4 capacitors in the same place, such as C3, C4 and C5 in this circuit, between - and + output. They also appear on the input side as well. I don't understand why there are 3. Why not save money and just put 1 capacitor, of the same total size, as these 3? |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - May 30 2011 : 12:25:39 AM
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The main reason why they use multiple capacitors could be due to space constraints in the chassis or that buying a single capacitor would be not be as feasible as putting smaller capacitors in parallel. When I was designing a power supply I found this to be exactly why I chose to put a a lot of smaller capacitors in parallel as opposed to buying one big one. I think those could be the main reasons but there could be more that I'm forgetting.
For illustrative purposes:
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When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
Edited by - wasssup1990 on May 30 2011 01:13:52 AM |
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paulmil
New Member
Malaysia
2 Posts |
Posted - May 30 2011 : 01:58:43 AM
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| Makes sense if you know the size constraints. So you have no electrical reason to use 3 instead of 1 cap? I will make it 1 each side and see if anything bad happens. Maybe the designer is a capacitor salesman on the side and adds a few extra to increase his salary. Thanks for the reply. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - May 30 2011 : 02:39:57 AM
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I forgot to mention that when you parallel capacitors you will share the power dissipation between them over a larger area which decreases operating temperature in the vicinity of the capacitors. This power dissipation is produced by charge (or current) flowing through the series and parallel internal resistance in each capacitor. There is pretty much no electrical advantage you can achieve that I am aware of if you put capacitors in parallel, over just buying a big one. Often, you will find that getting a single capacitor is more expensive but the ESR will be lower than that of the ESR of a parallel capacitor solution.
EDIT:
One more thing! 
When I was searching for the right capacitors I found that the larger ones tended to be in lower stock quantities and the lead times were too long for me. The smaller capacitors tended to be ordered in larger quantities by the distributor. Also, when a large capacitor fails you might have trouble trying to get your hands on one which meets the exact specifications, not to mention the money you'll have to pay. The smaller capacitors are everywhere, cheaper and it is easy to find the right ones. |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
Edited by - wasssup1990 on May 30 2011 02:53:14 AM |
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3 caps in the same place
