chinese hyland 0-30v psu question

[ME]

I have 2x hyland 0-3a 0-30v psu kits , can i have two of these running from the same transformer and have the output from both boards in series to have 0-60v output?.

[madires]

Yes, if they are powered by different secondary windings. No, if they share the same secondary windings.

[Doctorandus_P]

The problem here is that this power supply has the current shunt in the GND wire. If you put two of these in parallel (from the same input power source) then this messes up the GND connection.

I really like these Hiland (with an "i") power supplies, even though they have their limitations and deficiencies (as does anything in life, but don't tell your girlfriend, she may get sulky or angy).

I like them because of their simplicity, low cost and easy availability. Because their cost is so low, they are also an excellent source to experiment with. One of the modifications you can make is to move the shunt resistor to the high side, and then use a differential amplifier (can be just a simple opamp with 4 selected (or trimmed) resistors.

Another simple modification is to add a charge pump if you want to use it from a DC (SMPS) power supply. Designing and building modifications like this are excellent ways to learn more about electronics. To really learn electronics, you have to build things. You can't learn it all from books and PC screens.

[lichurbagan]

Two supplies can provide a 0–60V series output. However, both outputs must remain electrically isolated. Check whether your Hyland boards provide that isolation. Also check if the transformer has suitable voltage ratings. The transformer must provide enough current for both. Do not connect outputs until isolation is confirmed. Connect the first supply's positive to the second negative. Use the remaining terminals as your output. Each supply should retain independent voltage adjustment. Avoid exceeding either board's current or voltage rating. For the front panel, For front-panel outputs, banana and tip connectors work well. They simplify connections between supplies and test equipment.

[BillyO]

I spend some time with one of these supplies.  It initially looked great but as I got further into the project warts started to show up.  If you build it as is, you will have trouble at the ends of the operational envelope.  As an example, if you try to draw 3A with the supply set to 0.25V, you will very quickly find that, as it stands (out of the box, so to speak), it will be eager to let the magic smoke out.  The suggested heat sink and the supplied pass transistor will NOT sustain the required 100W or so of dissipation.  There are other problems too, but you can get them solved.  Here's a list of things I found/did.

1) The supplied op-amps (TL081) are fakes (at least they were with mine) and even if they were genuine,  the absolute maximum voltage is only 36V, however, with a 24V transformer they will be subject to 40V under low loads.  To get passed this I went to a 20V transformer and dropped the expected output from 30V to 20V.

2) The negative supply Zener is 5.1V as supplied.  I dropped this to 3.9V to further reduce the stress on the op-amps.

3) I replaced the fake TLO81s with real 741s for the current error amp and the voltage reference and used a real TL081 for the voltage error amp.

4) I changed R12 to 27k to set the max output voltage to 20V.

5) Changed R18 to 80k to reduce the maximum current to 2.5A

6) Changed the negative supply resistor (R2) to a 1/2 watt.  The little 1/4 watt job will quickly burn itself up.

7) Massively increased the size of the heatsink and built a small temperature controlled fan for forced air cooling.

8 ) Added Coarse/Fine controls for both voltage and current

9) Added connectors for the fan, the pass transistor (which I mounted off board on the heatsink) and the current limit LED.

10) Increased the filter capacitor to 9,900uF (used 3 x 3,300uf Rubycons)

In the end I wound up with a highly stable and useable 0-20V, 0-2.5A power supply that will work reliably across it's entire operating envelope with essentially zero ripple and very decent response.  I use this supply almost daily.

I did 6 videos on the process if you are interested in seeing my failures, fixes and final "triumph".  https://www.youtube.com/playlist?list=PLAoY7fARPMX_rywPLGCvLJU9BJl97MIJg