I would like to replace a center tapped transformer, which is directly connected to a full bridge rectifier, by two DC lab power supplies.

Does that make sense at all?

The power connector goes directly to the rectifier, and I do not think the rectified sinus shape is needed or useful.

Can I use the two power supplies to provide the DC power that is used behind the rectifiers originally?

(I want to temporarily power an stereo audio amplifier module (TDA8954). It does not need to be efficient, not even save.)

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    \$\begingroup\$ No, it doesn't make sense - draw a schematic. \$\endgroup\$ – Andy aka Aug 8 '19 at 7:50
  • \$\begingroup\$ @Andyaka The schematic would be like the one in the answer of Transistor, without the transformer and without earth. Could that make sense? \$\endgroup\$ – Volker Siegel Aug 8 '19 at 7:57
  • \$\begingroup\$ Without a schematic this isn't very clear. Perhaps you want to replace a symmetric power supply (consisting of a transformer with a center-tap at the output, bridge rectifier and filter caps.) with two lab supplies. You don't even need to draw the schematic as it is such a common circuit that you can find one using Google image search. If you lab supplies' outputs are floating (not grounded) then sure this is possible. Make sure you switch the supplies on/off simultaneously. \$\endgroup\$ – Bimpelrekkie Aug 8 '19 at 9:02
  • \$\begingroup\$ Ah, that makes sense and is consistent with Transistor's answer. Thank you! \$\endgroup\$ – Volker Siegel Aug 8 '19 at 9:05


simulate this circuit – Schematic created using CircuitLab

Figure 1. The DC supplies can be connected in as shown by V1 and V2.

You can leave everything else connected but disable the transformer AC supply so that nobody can reverse power V1 and V2 as they may not like it.

Note that V1 and V2 need to be isolated and can't, for example, have both their negatives connected to mains earth.

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  • \$\begingroup\$ There is no transformer connected, and no earth is no problem. \$\endgroup\$ – Volker Siegel Aug 8 '19 at 7:54
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    \$\begingroup\$ How will you make sure the voltages come up simultaneously? \$\endgroup\$ – analogsystemsrf Aug 8 '19 at 8:00
  • \$\begingroup\$ @analogsystemsrf chip seems to have power supply unbalance protection with 100 ms restart delay. Otherwise a mosfet based delay circuit would be required. \$\endgroup\$ – Indraneel Aug 8 '19 at 9:49

If your lab power supply offers the needed voltage range for each lane (positive and negative), this is easily possible.

Disconnect your former power supply (transformer + bridge rectifier).

Select +41V on both power supplies (nominal supply voltage for your TDA8954, might differ in your application) connect the outputs of your power supply in serial, tap the most positve output as +41V (power supply A (+) ), the most negative output as -41V (power supply B (-) ) and the connection between your power supply A (-) and power supply B (+) as ground reference.

This works, as lab power supplies are galvanically isolated.

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