[tekno]

Hey all. Im looking for a good regulator circuit. I have a 52 V and want to drop it to 40 Vdc. Of course it will need to handle 20 amps.

[Al_The_Man]

Do you need the 52 as well?
If not check the viability of taking turns off, much more efficient.
Al.

[jwstolk]

is the 52 V DC or AC ?

[bkukowski]

Tekno-did you just post this question on kleinbauer's forum?

I had suggested taking windings off the secondary in the thread on kleinbauer's forum...but I think we later found out it was a switching power supply. DC

[jwstolk]

if it's a switching power supply, can't you adjust it to 40V output ?

[rgammage]

Hello

Switch mode power supplies CAN be adjusted, but is not straight forward ... do you have the circuit? Post regulation is also a possibility but it would also be better as a switcher.

[pminmo]

Do you need regulation or just a circuit that drops 12V at 0 to 20A?

[stevenmotor]

Dear All,
I suggest to ask Pminmo.He have more experince in circuit production and designing.I always found high performance circuit form him.

Steven
[email protected]

[tekno]

Do you need regulation or just a circuit that drops 12V at 0 to 20A?

I have a transformer thats 35V ac. with the bridge and caps it ends up being about 52V DC. My motors will fry the picstep boards with there feedback. I was hoping to drop the dc down to 40V DC.

this is the only forum I posted on and the transformer.
its link link here

[Al_The_Man]

Why not use one side of the secondary, it should be simple to reduce the last winding by removing turns as required, it is probabally wound at around 1.5~2turns/volt.
This way you would only use the one reduced side and employ a bridge rectifier instead of the full wave centre tap design. Go to the Plitron site if you want a diagram of the different configurations.
With fullwave centre tap, only one side is conducting at any given time anyway.
You would need to reduce to approx. 28~30 AC to obtain 40vdc.
Al.

[pminmo]

If you can rewind the transformer that would be the best approach. The below circuit I believe will work, but it's gonna cook, 200+watts, big heat sink, fan....

I wonder if you could reduce the ac input with an out of phase 6.3V transformer............

Actuall 35VAC and a full wave bridge loaded will probably be more like 48V. The bridge will drop it 1.4V minimum and probably closer to 2V. The lmd is rated 55V at 3A with an additional 5V max margin 60V.

[Al_The_Man]

If you can rewind the transformer that would be the best approach.

A rewind should not be necessary, with a Toroid it is usually simple to remove turns as required. The secondary is usually always on the outside.
Al.

[tekno]

I wonder if you could reduce the ac input with an out of phase 6.3V transformer............

what do you mean? did you look @ the transformer do you think I can dewine it?

[tekno]

A rewind should not be necessary, with a Toroid it is usually simple to remove turns as required. The secondary is usually always on the outside.
Al.

I got 2 so I'll try it out on one of them.. this also means that I wiull lose some amprage right?

[Al_The_Man]

The VA will remain the same, if you reduce the secondary voltage the available current will be higher, but may be limited by wire diameter.
The Txfr is fairly small, physically so you would have to monitor it for overheating.
Al.

[pminmo]

I didn't realize it was a torridal xformer, sorry. How much current are you thinking it's going to be able to supply?

[chrbau]

Why not use the voltage drop of a bunch of diods? Simple is often good

[tekno]

right now I think its 650 VA so @ 35 V (its rating) that would be 18 amps.

in the link I show the data but Im not 100% on the VA rating its just whats printed on it


I have looked eveywhere trying to find out more about this transformer

[Al_The_Man]

This is off the spec sheet,

"Overload Test:

With the primary connected for 120 V AC operation, and with 120 V AC applied, and with the secondary loaded so that the primary input current is 0.75 A, transformer temperature will not exceed 155 C."

Al.

[tekno]

This is off the spec sheet,

"Overload Test:

With the primary connected for 120 V AC operation, and with 120 V AC applied, and with the secondary loaded so that the primary input current is 0.75 A, transformer temperature will not exceed 155 C."

Al.

I have no idea what that means :cheers: