Circuit diagram for power supply kit

[Dhanushka]

https://www.ebay.com/itm/0-30V-2mA-3A-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-Short-with-Protection/272492114559?hash=item3f71cbb27f:g:EXAAAOSwa~BYWQ85

Can any one give me the circuit diagram for this kit or any other one better than for this according to following specs?

0-30V variable output voltage with variable 0-3A current

Thanks

[lordvader88]

It's some type of buck/boost converter since the max Vcc is 24V but the outout goes to 30V .  I don't see any inductors tho, how is that powering 3A if there's no external inductors ?

[mariush]

Pictures in the link are clear enough to draw the schematic yourself.

[Dhanushka]

Dear lordvader88,

The peak value of 24 V is greater than 24 V. Therefore, it has high DC level of greater than 24 V after regulation. Also, it needs a at least 3A transformer for sufficient current of 3A. 

[MosherIV]

So you are saying that the kit needs a 24V 3A transformer?

Sounds like a linear type. With 24V input V, the psu will struggle to deliver  good clean  V above 22V under load. 24V transfers are called 24V for a reason - they are designed to deliver 24V under load.
Then the regulation of the psu will loose another 2V approximately.

Sounds like the suppliers either do not know what they are doing or they hope that buyers are not going to notice the poor high power performance or assume it is an assembly issue.

[JackJones]

http://www.paulvdiyblogs.net/2015/05/tuning-030v-dc-with-03a-psu-diy-kit.html

There's the schematic, along with some improvements made to it.

[xavier60]

It will output 30V or close with little loading.
As well as the 24VAC transformer, looks like a heat-sink and fan needs to be added.

[Zero999]

That kit contains some design flaws. At best it'll perform very poorly, at worse, it'll blow up. Here's a thread discussing it in detail.
https://www.eevblog.com/forum/beginners/0-30v-0-3a-psu-audiogurus-version/msg2232978/#msg2232978

[rstofer]

See what happens when it puts out 1V at 3A.  This is the mode where the pass transistor dissipates the most heat.

Real 30V 3A PSUs are really difficult to get right and $3 isn't likely to be enough.  Among other things, the AC transformer should have taps to reduce the rail voltage when the user selects a low output voltage.  You really want to minimize the voltage drop across the pass transistor.  There's a reason that bench supplies with a couple of 30V 3A outputs and a single 5V 3A output cost a lot of money.

[Kleinstein]

The kit is well known and not really capable of delivering 30 V / 3 A. It is more suitable for something like 16-18 V and 2 A, using a 18-20 V transformer. With the given parts a 24 V transformer is too high for the OPs.  Even with a 24 V transformer and luck with the OPs to survive too high a voltage the maximum voltage would hardly reach 30 V (no load) as the drop out is relatively high and the filter cap is more suitable for 1.5-2 A.

The kit also only consists of some part for the power supply: it still needs the case, transformer and heat sink / fan.  Though around for a long time already the board layout still seems to be poor old version, with lots of ripple in CC mode.

[lordvader88]

OP just use it for up to a few hundred mili-amps from a smaller transformer, and it would be fine for powering basic stuff on a breadboard.