Connecting several Voltage Regulators in parallel

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rich

Well-known member
Joined
Dec 10, 2004
Messages
84
To acheive greater current without damaging the regulators can you connect the outputs of 2 or more regulators in parallel, and or can you do it also in series to double the voltage etc.?
 
Ah... Voltage Regulators. You should perhaps edit the title, I was puzzled, since "VR" is the component abbreviation for 'Variable Resistor'.

Series Voltage Regulators -no, not how you describe it. There's only one input per regulator. They can be 'cascaded' to achieve higher vooltages (eg 48V from 24V revulators), but one will always be handling the current. The second will only be a reference for the second.

Parrallel: bad idea. They will probably start to pick a fight about who wants the higher voltage. It's like connecting the outputs of two audio amplifiers together. I highly suggest that you don't do it. You should use summind greistors, but then you lose some regulation, so...

The best idea is to use a higher-rating regulator, or feed a pass transistor, or do what manufacturers do, and build a discrete regulator.

Keith
 
Add a pass transistor, and fit both the transistor and the regulator on the same heatsink. That way the thermal shutdown will still work.

You can probably find a suitable schematic in a regulator data sheet.

Best regards,

Mikkel C. Simonsen
 
The thermal shutdown will almost work, but not if the transistor temperature rises to its destruction point (or safe operating area is exceeded, resulting in secondary breakdown), unless you add safe operating area protection. I've done this and it works but it is pretty easy to end up with a smoking pile of power supply... and load. Linear Tech and National have app notes on parallelling regulators. I worked on a pretty beefy one that had three Linear Tech TO-3 regulators in parallel. I don't remember the part number, though. There was circuitry in there to compensate for the voltage drops and balance things out, I think.
 

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