Need to build a simple mains power supply for linear amplifier (28V 30A)
 

The important is to limit the output voltage to 28V and have maximum
output voltage when input drop under ripple
One solution I can figure out is
http://www.noding.com/la8ak/12345/images/28vReg-4.gif

another more commonly found solution is
http://www.noding.com/la8ak/12345/images/28vReg-3.gif

the advantage of the first over the second is that the it needs single
supply voltage and the power fet can be mounted directly in chassis

73
Jan-Martin, LA8AK
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/91n.htm

I may be missing something, but neither one of the schematics shown in
your link will work as you want.

For example, in link 2, you cannot get 70V out from a 24V AC source
without some sort of voltage trippling or use of reactive components.
Neither of these is present.

In link 1, you show a 24V regulater incorrectly wired and employed
above its ratings.

Did you leave something out perhaps, like your input and output leads?
Your post leaves me a little confused, but for me that's nothing new.
:-)


Harry C.

On 20 Mar 2005 11:25:38 -0800, wrote:

I may be missing something, but neither one of the schematics shown in
your link will work as you want.

For example, in link 2, you cannot get 70V out from a 24V AC source
without some sort of voltage trippling or use of reactive components.
Neither of these is present.
Sorry, you are right, I wasn't really awake

In link 1, you show a 24V regulater incorrectly wired and employed
above its ratings.
It is really tested 30 years ago, and the construction is shown on
http://home.online.no/~la8ak/g1.htm , but it used 2N3055, not power
fet, it should be the same - in principle

Did you leave something out perhaps, like your input and output leads?
Your post leaves me a little confused, but for me that's nothing new.
:-)

-JM
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/91n.htm

You will also have to get power transformer to drop
your mains and that will add to the cost.

You can try to locate surplus power supplies,
linear type by Lambda, lambda/coutant, Nemic Lambda,
also switching supplies very inexpensive used surplus.
Telco power supplies also would be attractive.

ps_dude

On Sun, 20 Mar 2005 22:06:51 GMT, ps_dude wrote:

You will also have to get power transformer to drop
your mains and that will add to the cost.

You can try to locate surplus power supplies,
linear type by Lambda, lambda/coutant, Nemic Lambda,
also switching supplies very inexpensive used surplus.
Telco power supplies also would be attractive.

ps_dude

only the freight is very expensive

---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/91n.htm

On Sun, 20 Mar 2005 22:06:51 GMT, ps_dude wrote:

You will also have to get power transformer to drop
your mains and that will add to the cost.

You can try to locate surplus power supplies,
linear type by Lambda, lambda/coutant, Nemic Lambda,
also switching supplies very inexpensive used surplus.
Telco power supplies also would be attractive.

ps_dude

only the freight is very expensive
had some requests from Australia for some TWT amplifiers, but when we
checked the price for postage you could just forget it very soon

---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/91n.htm

Hi,

I am not talking Linear but Switching power supplies.
(class B fcc type very low ripple and work very well)

Lambda has several lines of switching supplies, under 3 kilo !

http://www.lambdapower.com/products/...-dc-series.htm

Lambda ultraflex, alpha or vega show up surplus
many times a week on auction ebay and trader lists.

These are expensive new but go for a lot less used or old stock,
newer models displaced this series.

I have a few I got for under $ 20 usd that were new in box.

pd_dude





J M Noeding wrote:

On Sun, 20 Mar 2005 22:06:51 GMT, ps_dude wrote:

You will also have to get power transformer to drop
your mains and that will add to the cost.

You can try to locate surplus power supplies,
linear type by Lambda, lambda/coutant, Nemic Lambda,
also switching supplies very inexpensive used surplus.
Telco power supplies also would be attractive.

ps_dude

only the freight is very expensive
had some requests from Australia for some TWT amplifiers, but when we
checked the price for postage you could just forget it very soon

---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/91n.htm

On Tue, 22 Mar 2005 15:01:25 GMT, "ps)dude"
wrote:

Hi,

I am not talking Linear but Switching power supplies.
(class B fcc type very low ripple and work very well)

Lambda has several lines of switching supplies, under 3 kilo !

http://www.lambdapower.com/products/...-dc-series.htm

Lambda ultraflex, alpha or vega show up surplus
many times a week on auction ebay and trader lists.

These are expensive new but go for a lot less used or old stock,
newer models displaced this series.

I have a few I got for under $ 20 usd that were new in box.

pd_dude

OK,

I am promissed 3 new Eltek power supplies, variable between 0-60V,
30A, but still I want to experiment and improve the old power supplies
for definite purpose, no problem when one has all the components

-JM
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/91n.htm

Neither schematic shows the most expensive components: the transformer
and filter caps.

If you have a 24VAC transformer and a full-wave rectifier you have
something like 31 or 32VDC under full load. That's not a lot of
headroom if you have brownouts etc to worry about.

It also seems that neither has any overcurrent/crowbar protection. If
your pass transistor fails shorted and everything still works and
nothing blows up... maybe you didn't need a regulator in the first
place :-).

Tim.

On 22 Mar 2005 11:02:07 -0800, "Tim Shoppa"
wrote:

Neither schematic shows the most expensive components: the transformer
and filter caps.

If you have a 24VAC transformer and a full-wave rectifier you have
something like 31 or 32VDC under full load. That's not a lot of
headroom if you have brownouts etc to worry about.

It also seems that neither has any overcurrent/crowbar protection. If
your pass transistor fails shorted and everything still works and
nothing blows up... maybe you didn't need a regulator in the first
place :-).

Tim.

In nearly 40 years years I have dealt with semiconductors I have never
experienced that crowbar has been a need for the power supplies used
on this side, but what I can say about many constructions seen, I
would use them without crowbar because they are sensible to RF, and
often not well designed in other ways
I usually have current protection, but for simplicity it isn't shown
here, I also considered to use a simple thing as an old fuse since
shortcircuiting the output hasn't really occured more than a few times
here.

I intend to use toroid transformer, and believe the output voltage
varies somewhat more than for a standard E-core transformer

73
jan-martin, LA8AK
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/91n.htm