# How to achieve maximum power output from a center tapped transformer.

Discussion in 'Power Electronics' started by Farukh Khan, Jun 11, 2021 at 3:40 AM.

1. ### Farukh Khan

158
2
Jun 12, 2015
Hello,

I have two center tapped transformers with the following specifications on the secondary side >
*12V x 2 or 24V from the full secondary coil. And, 12V on each side of the center tap.
* 3000mA rating.

I am trying to create a simple bridge rectifier solution to output all the power the transformer has to offer, most efficiently possible. Now, for the center tap, I am confused how do I use this transformer to output the maximum DC overall voltage and amps it can deliver. While searching online I came across this schematic and am not really sure how this schematic is working. Is this a good solution to implement for getting the maximum available power from a center tapped transformer?

Please need some suggestions regarding this. And also, in the future I am willing to use these two transformer's DC output either in parallel or series configuration to increase the overall output power whenever necessary and whichever configuration necessary. Thank you.

2. ### Bluejets

4,748
999
Oct 5, 2014
power out is equal to power in less any losses no matter how you connect it using all outputs.
Also note transformers output ac not dc.

3. ### crutschow

43
15
May 7, 2021
Using the bridge with a center tap gives you a plus and minus output voltage.
Using the voltage from each side of the bridge output, and not using the center-tap, will give you a single output at twice the voltage.
Either way will give the maximum DC power you can get from the transformer without adding a filter inductor.

Note that, due to the high peak current from the filtered, rectified output, which gives high RMS losses in the transformer winding resistance, the maximum DC output current will be about 60% of the transformer rated RMS output, or about 1.8Adc from your 3A rated transformer.
But since the DC output voltage is near 1.4 times the RMS transformer AC voltage, the maximum DC power output will be about 1.4 * 60% = 84% of the transformer power rating.

If you use Schottky rectifiers for the bridge you should get about 2% or so more output power.

4. ### Bluejets

4,748
999
Oct 5, 2014
No, one may be able to get a higher voltage due to less losses by using a schottky, but the available power output of the transformer remains the same.

5. ### crutschow

43
15
May 7, 2021
I obviously meant DC output power, not transformer power.

6. ### Bluejets

4,748
999
Oct 5, 2014
Transformer power out is power in less any losses, cannot increase it .

7. ### crutschow

43
15
May 7, 2021
That is quite obvious. I never said otherwise.
I didn't mentioned transformer power, I'm taking about the DC power output.
A standard diode bridge has slightly more power loss than a Schottky bridge so it will output slightly less power.

8. ### Bluejets

4,748
999
Oct 5, 2014
dc power output is limited by the power into and out of the transformer. you cannot get more out than goes in less losses no matter what you do on the dc side.
where you are getting confused is voltage losses, not power.

9. ### crutschow

43
15
May 7, 2021
No confusion on my part, but apparently yours.
Where did I suggest you get more power out then you put in, which is obviously impossible.
The power and current from the transformer are the same, but a lower voltage at a given current will have less power.
The output power will thus be slightly different between the two types of bridges.
Why is that hard to understand?

10. ### Harald KappModeratorModerator

11,415
2,619
Nov 17, 2011
@Bluejets , @crutschow : The two of you seem to be talking at cross purposes meaning the same and then again quite not.
The original question was:
So the op wants to maximize power on the DC output side.

While Bluejets is correct in stating power out = power in - losses, crutschow is also correct in stating that the use of Schottky dides minimizes losses in the rectifier. The two of you meet when combining both statements: power out = power in - (minimized losses through Schottky diodes).
Of course the transformers max. power output remains unchanged.
Of course by using Schottky diodes the power available at the DC output is increased.

I hope that settles the discussion.

11. ### crutschow

43
15
May 7, 2021
Does for me.
Thanks.

Harald Kapp likes this.