Electronic – On a 3-terminal bench power supply (+, -, GND), are there positive and negative drivers behind each of the terminals

power supplyvoltagevoltage-regulator

In a 3-terminal power supply like this, are there individual regulators behind the positive and negative terminals? For example a LM317 on the positive and a LM337 on the negative?

If not, what kind of circuitry drives a floating output like this, in general?

Side question, probably related: If you can connect either terminal to ground, why doesn't the connected terminal dump current into ground?

I want to build or buy a bench power supply, and I'm having trouble understanding how one control set can drive positive or negative voltage.

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Best Answer

This type of power supply only has one regulator placing a settable voltage between the + and - (red and black) terminals.

The green terminal ties into the safety GND of the power cord and hopefully to the earth grounded network in your building.

In operation of the power supply you have the choice of a fully isolated output or you can tie one or the other of the + or - terminals to the green terminal if you want to have the supply output referenced to the safety ground.