Two bridge rectifiers on a centre tapped transformer?

Started by March 26, 2023
```I have a centre tapped transformer I wanted to get the most power out of.  Thinking a traditional full wave rectifier (just a diode on each side, calling the centre tap 0V at the output) is only running current through one half of the secondary at a time, which is inefficient (think of P=i^2R), I thought about putting a bridge rectifier on each half, then connecting the result in parallel.  I made the following diagram by adjusting someone else's, so it may look a bit odd.

https://i.imgur.com/d2TfZYO.jpg

I'm a bit confused here because you can trace the current flow and show the output has both 24V (if the current goes through the "wrong" bridge on the way back) and 12V at the same time, which isn't possible.  Can someone explain what would happen in this circuit?

Any way to make this work?  I want current flowing through both halves of the secondary all the time.  But I want half the full secondary's voltage.
```
```On Sunday, March 26, 2023 at 8:56:55&#8239;PM UTC-4, Commander Kinsey wrote:
> I have a centre tapped transformer I wanted to get the most power out of. Thinking a traditional full wave rectifier (just a diode on each side, calling the centre tap 0V at the output) is only running current through one half of the secondary at a time, which is inefficient (think of P=i^2R), I thought about putting a bridge rectifier on each half, then connecting the result in parallel. I made the following diagram by adjusting someone else's, so it may look a bit odd.
>
> https://i.imgur.com/d2TfZYO.jpg
>
> I'm a bit confused here because you can trace the current flow and show the output has both 24V (if the current goes through the "wrong" bridge on the way back) and 12V at the same time, which isn't possible. Can someone explain what would happen in this circuit?
>
> Any way to make this work? I want current flowing through both halves of the secondary all the time. But I want half the full secondary's voltage.

I don't expect you will see this post, because I think you have blocked google groups.  But this circuit will not work as you expect.  Rather than trace current, try figuring out the voltages.  That might be more clear.

You have two input terminals labeled "12", so it's hard to differentiate them verbally.  So I'm calling the top one 12up and the bottom one 12dn.  Actually, they don't need to be considered.  The contradiction in your circuit can be seen just by considering the 0 terminal.  When 12up is positive, the 0 terminal is connected to the lower end of the load through the upper bridge, with current flowing from the load to the 0 terminal.  At the same time, the 12dn terminal is negative wrt to the 0 terminal which is connected to the load upper terminal through the lower diode bridge.

What, what, what???  The same terminal is connected to both ends of the load at the same time???  How can that be?

To understand your circuit better, try connecting a load on the output of each bridge.  No common connections, other than the inputs.  Now consider the voltages on each load and the voltages between the two loads.

There are two problems with your idea.  One is that you can use two diode bridges in this way, you can't.  The other is the need.  Your two diode circuit with the center tap transformer shown, will give a 12V output.  You can use the full transformer with a SINGLE diode bridge and use the entire secondary winding at the same time... but you will get 24V output.  If you want 12V output with a bridge, you need a
```
```On Sunday, March 26, 2023 at 10:06:19&#8239;PM UTC-4, Ricky wrote:
> On Sunday, March 26, 2023 at 8:56:55&#8239;PM UTC-4, Commander Kinsey wrote:
> > I have a centre tapped transformer I wanted to get the most power out of. Thinking a traditional full wave rectifier (just a diode on each side, calling the centre tap 0V at the output) is only running current through one half of the secondary at a time, which is inefficient (think of P=i^2R), I thought about putting a bridge rectifier on each half, then connecting the result in parallel. I made the following diagram by adjusting someone else's, so it may look a bit odd.
> >
> > https://i.imgur.com/d2TfZYO.jpg
> >
> > I'm a bit confused here because you can trace the current flow and show the output has both 24V (if the current goes through the "wrong" bridge on the way back) and 12V at the same time, which isn't possible. Can someone explain what would happen in this circuit?
> >
> > Any way to make this work? I want current flowing through both halves of the secondary all the time. But I want half the full secondary's voltage.
> I don't expect you will see this post, because I think you have blocked google groups. But this circuit will not work as you expect. Rather than trace current, try figuring out the voltages. That might be more clear.
>
> You have two input terminals labeled "12", so it's hard to differentiate them verbally. So I'm calling the top one 12up and the bottom one 12dn. Actually, they don't need to be considered. The contradiction in your circuit can be seen just by considering the 0 terminal. When 12up is positive, the 0 terminal is connected to the lower end of the load through the upper bridge, with current flowing from the load to the 0 terminal. At the same time, the 12dn terminal is negative wrt to the 0 terminal which is connected to the load upper terminal through the lower diode bridge.
>
> What, what, what??? The same terminal is connected to both ends of the load at the same time??? How can that be?
>
> To understand your circuit better, try connecting a load on the output of each bridge. No common connections, other than the inputs. Now consider the voltages on each load and the voltages between the two loads.
>
> There are two problems with your idea. One is that you can use two diode bridges in this way, you can't. The other is the need. Your two diode circuit with the center tap transformer shown, will give a 12V output. You can use the full transformer with a SINGLE diode bridge and use the entire secondary winding at the same time... but you will get 24V output. If you want 12V output with a bridge, you need a

12V transformer.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209
```
```On 27/03/2023 01:56, Commander Kinsey wrote:
> I have a centre tapped transformer I wanted to get the most power out
> of.&nbsp; Thinking a traditional full wave rectifier (just a diode on each
> side, calling the centre tap 0V at the output) is only running current
> through one half of the secondary at a time, which is inefficient (think
> of P=i^2R), I thought about putting a bridge rectifier on each half,
> then connecting the result in parallel.&nbsp; I made the following diagram by
> adjusting someone else's, so it may look a bit odd.
>
> https://i.imgur.com/d2TfZYO.jpg
>
> I'm a bit confused here because you can trace the current flow and show
> the output has both 24V (if the current goes through the "wrong" bridge
> on the way back) and 12V at the same time, which isn't possible.&nbsp; Can
> someone explain what would happen in this circuit?
>
> Any way to make this work?&nbsp; I want current flowing through both halves
> of the secondary all the time.&nbsp; But I want half the full secondary's
> voltage.

No, you will get 24V rectification. Only the LHS 2 of the top 4 diodes
will be conducting, and the RHS 2 of the bottom 4 diodes. The rest will
be entirely superfluous.

You need to get into LT Spice. It's free. A man of your claimed IQ
should have no problem in confirming my presumption, or even proving me
wrong.

If you want 12V then use:

It doesn't make full use of the copper so you may have to down-rate the
transformer a little.

For different topologies:
https://circuitspedia.com/center-tapped-transformer-connection-diagram/
```
```On Mon, 27 Mar 2023 01:56:47 +0100, Birdbrain Macaw (aka "Commander Kinsey",
"James Wilkinson", "Steven Wanker","Bruce Farquar", "Fred Johnson, etc.),
the pathological resident idiot and attention whore of all the uk ngs,
blathered again:

<FLUSH the subnormal sociopathic trolling attention whore's latest

--
damduck-egg@yahoo.co.uk about Birdbrain Macaw's (now "Commander Kinsey" LOL)
trolling:
"He is a well known attention seeking troll and every reply you
make feeds him.
Starts many threads most of which die quick as on the UK groups anyone
with sense Kill filed him ages ago which is why he now cross posts to
the US groups for a new audience.
This thread was unusual in that it derived and continued without him
to a large extent and his silly questioning is an attempt to get
noticed again."
MID: <be195d5jh0hktj054mvfu7ef9ap854mjdb@4ax.com>

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"You're an annoying troll and I'm done with you and your
stupidity."

--
"Troll or idiot?...
You have been presented with a viewpoint with information, reasoning,
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ignore all going back to your idea which has no supporting information."
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--
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--
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--
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--
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MID: <0001HW.1EE2D20300E7BECC700004A512CF@news.eternal-september.org>

--
Sam Plusnet about Birdbrain  (now "Commander Kinsey" LOL):
"He's just desperate to be noticed.  Any attention will do, no matter how
negative it may be."
MID: <rOmdndd_O7u8iK7EnZ2dnUU78TGdnZ2d@brightview.co.uk>

--

--
Christie addressing endlessly driveling Birdbrain Macaw (now "Commander
Kinsey" LOL):
"What are you resurrecting that old post of mine for? It's from last
month some time. You're like a dog who's just dug up an old bone they
hid in the garden until they were ready to have another go at it."
MID: <59d8b0db.4113512@news.eternal-september.org>

--
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sponging failure who will always live alone and will die alone. You will not
be missed."
MID: <orree6\$on2\$1@dont-email.me>

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"You haven't bred?
Only useful thing you've done in your pathetic existence."
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--
clare@snyder.on.ca about Birdbrain (now "Commander Kinsey" LOL):
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mistake having him born alive -- A total waste of oxygen, food, space,
and bandwidth."
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--
Mr Pounder exposing sociopathic Birdbrain:
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running water with loads of stinking cats and a few parrots."
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--
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"He seems to have a reputation as someone of limited intelligence"

--
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```
```On Mon, 27 Mar 2023 03:38:29 +0100, Fredxx, the notorious, troll-feeding,
senile smartass, blathered again:

> No, you will get 24V rectification.

What he NEEDS is another prolonged stay in the loony bin, you troll-feeding
senile asshole!
```
```On 3/26/2023 10:38 PM, Fredxx wrote:
> On 27/03/2023 01:56, Commander Kinsey wrote:
>> I have a centre tapped transformer I wanted to get the most power out of.&nbsp; Thinking a traditional full wave rectifier (just a diode on each side, calling the centre tap 0V at the output) is only running current through one half of the secondary at a time, which is inefficient (think of P=i^2R), I thought about putting a bridge rectifier on each half, then connecting the result in parallel.&nbsp; I made the following diagram by adjusting someone else's, so it may look a bit odd.
>>
>> https://i.imgur.com/d2TfZYO.jpg
>>
>> I'm a bit confused here because you can trace the current flow and show the output has both 24V (if the current goes through the "wrong" bridge on the way back) and 12V at the same time, which isn't possible.&nbsp; Can someone explain what would happen in this circuit?
>>
>> Any way to make this work?&nbsp; I want current flowing through both halves of the secondary all the time.&nbsp; But I want half the full secondary's voltage.
>
> No, you will get 24V rectification. Only the LHS 2 of the top 4 diodes will be conducting, and the RHS 2 of the bottom 4 diodes. The rest will be entirely superfluous.
>
> You need to get into LT Spice. It's free. A man of your claimed IQ should have no problem in confirming my presumption, or even proving me wrong.
>
> If you want 12V then use:
>
>
> It doesn't make full use of the copper so you may have to down-rate the transformer a little.
>
> For different topologies:
>  &nbsp; https://circuitspedia.com/center-tapped-transformer-connection-diagram/

And whether filtered or unfiltered, the output is *unregulated*.

The output varies as a function of the load current.

Slapping a regulator on the output, makes an output suited
to driving a digital logic circuit. The regulator can be
an SMPS (efficient) or a linear regulator (inefficient).
Linear regulators are easier for hobbyists to assemble.

https://electrosome.com/variable-power-supply-lm317-voltage-regulator

And while just about every web page shows "1N4007" as The Diode, no,
there are other choices you can buy. The reason a lot of 1N4000 series
diodes get used, is because hobbyists can buy a bag with a considerable
number of them, for not a lot of money. But you can also get
wafer-style full wave bridge rectifiers, that will plug into your pegboard.
This handles a slight bit more current. The reason I picked this, is
I used something similar in my amp for the computer speakers.

https://www.nteinc.com/specs/53000to53099/pdf/nte53006_10.pdf

Paul
```
```Yes and the  switch mode type can cause a lot of interference if one is not
careful but they are efficient by comparison with  a series regulator. You
can even end up with  higher voltages than you started with. There was an
early example in a Sony Cassette deck I had. It ran on5  to 6 volts, but the
supply rails inside were 24 volts. A device marked Fuji did the work and
never broke a sweat.

Brian

--

--:
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"Paul" <nospam@needed.invalid> wrote in message
news:tvrjev\$34rsq\$1@dont-email.me...
> On 3/26/2023 10:38 PM, Fredxx wrote:
>> On 27/03/2023 01:56, Commander Kinsey wrote:
>>> I have a centre tapped transformer I wanted to get the most power out
>>> of. Thinking a traditional full wave rectifier (just a diode on each
>>> side, calling the centre tap 0V at the output) is only running current
>>> through one half of the secondary at a time, which is inefficient (think
>>> of P=i^2R), I thought about putting a bridge rectifier on each half,
>>> then connecting the result in parallel. I made the following diagram by
>>> adjusting someone else's, so it may look a bit odd.
>>>
>>> https://i.imgur.com/d2TfZYO.jpg
>>>
>>> I'm a bit confused here because you can trace the current flow and show
>>> the output has both 24V (if the current goes through the "wrong" bridge
>>> on the way back) and 12V at the same time, which isn't possible. Can
>>> someone explain what would happen in this circuit?
>>>
>>> Any way to make this work? I want current flowing through both halves of
>>> the secondary all the time. But I want half the full secondary's
>>> voltage.
>>
>> No, you will get 24V rectification. Only the LHS 2 of the top 4 diodes
>> will be conducting, and the RHS 2 of the bottom 4 diodes. The rest will
>> be entirely superfluous.
>>
>> You need to get into LT Spice. It's free. A man of your claimed IQ should
>> have no problem in confirming my presumption, or even proving me wrong.
>>
>> If you want 12V then use:
>>
>>
>> It doesn't make full use of the copper so you may have to down-rate the
>> transformer a little.
>>
>> For different topologies:
>>  https://circuitspedia.com/center-tapped-transformer-connection-diagram/
>
> And whether filtered or unfiltered, the output is *unregulated*.
>
> The output varies as a function of the load current.
>
> Slapping a regulator on the output, makes an output suited
> to driving a digital logic circuit. The regulator can be
> an SMPS (efficient) or a linear regulator (inefficient).
> Linear regulators are easier for hobbyists to assemble.
>
> https://electrosome.com/variable-power-supply-lm317-voltage-regulator
>
> And while just about every web page shows "1N4007" as The Diode, no,
> there are other choices you can buy. The reason a lot of 1N4000 series
> diodes get used, is because hobbyists can buy a bag with a considerable
> number of them, for not a lot of money. But you can also get
> wafer-style full wave bridge rectifiers, that will plug into your
> pegboard.
> This handles a slight bit more current. The reason I picked this, is
> I used something similar in my amp for the computer speakers.
>
> https://www.nteinc.com/specs/53000to53099/pdf/nte53006_10.pdf
>
>    Paul

```
```On Sunday, March 26, 2023 at 8:56:55&#8239;PM UTC-4, Commander Kinsey wrote:

>
> I'm a bit confused here because you can trace the current flow and show the output has both 24V (if the current goes through the "wrong" bridge on the way back) and 12V at the same time, which isn't possible. Can someone explain what would happen in this circuit?

Nothing interesting.

>
> Any way to make this work? I want current flowing through both halves of the secondary all the time. But I want half the full secondary's voltage.

Current flowing in both halves "at the same time" forces those halves to be in series. But you "want" half the full secondary voltage. You're not going to get it putting the half secondary's in series. You would need to split your load into two identical parts with a center tap.

```
```On 27/03/2023 09:17, Paul wrote:
> On 3/26/2023 10:38 PM, Fredxx wrote:
>> On 27/03/2023 01:56, Commander Kinsey wrote:
>>> I have a centre tapped transformer I wanted to get the most power out
>>> of.&nbsp; Thinking a traditional full wave rectifier (just a diode on each
>>> side, calling the centre tap 0V at the output) is only running
>>> current through one half of the secondary at a time, which is
>>> inefficient (think of P=i^2R), I thought about putting a bridge
>>> rectifier on each half, then connecting the result in parallel.&nbsp; I
>>> made the following diagram by adjusting someone else's, so it may
>>> look a bit odd.
>>>
>>> https://i.imgur.com/d2TfZYO.jpg
>>>
>>> I'm a bit confused here because you can trace the current flow and
>>> show the output has both 24V (if the current goes through the "wrong"
>>> bridge on the way back) and 12V at the same time, which isn't
>>> possible.&nbsp; Can someone explain what would happen in this circuit?
>>>
>>> Any way to make this work?&nbsp; I want current flowing through both
>>> halves of the secondary all the time.&nbsp; But I want half the full
>>> secondary's voltage.
>>
>> No, you will get 24V rectification. Only the LHS 2 of the top 4 diodes
>> will be conducting, and the RHS 2 of the bottom 4 diodes. The rest
>> will be entirely superfluous.
>>
>> You need to get into LT Spice. It's free. A man of your claimed IQ
>> should have no problem in confirming my presumption, or even proving
>> me wrong.
>>
>> If you want 12V then use:
>>
>>
>> It doesn't make full use of the copper so you may have to down-rate
>> the transformer a little.
>>
>> For different topologies:
>>
>> https://circuitspedia.com/center-tapped-transformer-connection-diagram/
>
> And whether filtered or unfiltered, the output is *unregulated*.
>
> The output varies as a function of the load current.
>
> Slapping a regulator on the output, makes an output suited
> to driving a digital logic circuit. The regulator can be
> an SMPS (efficient) or a linear regulator (inefficient).
> Linear regulators are easier for hobbyists to assemble.
>
> https://electrosome.com/variable-power-supply-lm317-voltage-regulator
>
> And while just about every web page shows "1N4007" as The Diode, no,
> there are other choices you can buy. The reason a lot of 1N4000 series
> diodes get used, is because hobbyists can buy a bag with a considerable
> number of them, for not a lot of money. But you can also get
> wafer-style full wave bridge rectifiers, that will plug into your pegboard.
> This handles a slight bit more current. The reason I picked this, is
> I used something similar in my amp for the computer speakers.
>
> https://www.nteinc.com/specs/53000to53099/pdf/nte53006_10.pdf

It would be most helpful to understand what Mr Hucker, AKA Kinsey, is
trying to do.

```