EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: TiTanerCZE on September 24, 2017, 05:22:48 pm
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Hi, I am trying to build simple two rail power supply, each channel max 15V 1A. I will use torid transformer with two ouputs, each with separed groud. I usually see similar circuit using 7815 for positive rail and 7915 for negative rail and transformer is with a center tap. Because each groud is seperd from the other i can use just 7815 and then connect them in series to get the "negative" rail?
Thanks.
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Yes, you can do that.
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It has always been the case that 78xx series regulators have been better behaved and more stable than 79xx, being less twitchy about decoupling. It's a sensible thing to do if you have two independent secondaries.
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OK ;) Thanks for reply.
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Looks good to me and it is the preferred way to do it if you have two floating secondaries. As Gyro says, the 78xx is better behaved than the 79xx although I doubt the difference matters.
Decoupling capacitors C7 and C14 are not required if the input capacitors are adjacent to the regulators. I would use small 10 to 100 microfarad aluminum electrolytics (or 1 to 10 microfarad solid tantalums) for C6 and C8 instead of small ceramic capacitors; high frequency decoupling needs to be located close to the load rather than the source and a low value low ESR ceramic or film capacitor is more likely to cause problems.