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Balancing dual secondary rails


Guest Enforcer83

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Guest Enforcer83

Hey everyone,

I have an Auxillary transformer that I am using to generate a +5V@1A, +12V1@1A, +12V2@1A, and -5V@500mA.  This transformer has a dual secondary from which the negative rail is generated.

So my question is this, using linear regulators only, is there a way to balance the load on the two secondaries?

Currently I am using LM1085 for my positive voltage regulators and an LM2990 for my negative regulator.

Enforcer

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Guest Enforcer83

The reason is I want to be able to utilize the full capabilities (current) of both secondaries.  If I had to increase current draw on one of the positive voltage rails at some point, or add a voltage rail, I would like to be able to use the side that currently has a negative regulator connected to it so I don't overload one side (which won't be anytime soon but it is something to consider.)  Attached is the my configuration.

post-0-14279144252897_thumb.jpg

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There's no way to do it without using switching regulators.

The circuit you've posted has several issues:

The filter capacitors are undersized by at lease two orders of a magnitude.

No fuses are required on the output because the voltage regulator ICs will limit the current.

Only one bridge rectifier is required, not two.

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