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D36V28F12 stability problems

Purchased a D36V28F12 for a quick test and it seemed fine.
Have now purchased 10 for a project and find that it does not work well.

Here is the key data:
OUT 12V at no load
Our 11,6V at load
Load 1,66A
Temperature of component 70°C
Shuts down after 20-30 seconds
With air cooling via fan 40°C and shutdown a little later
Power supply for VIN Meanwell IRM-90-48
Fan 0.09 amps
LED strip 0.97 amps
Relay 0.64 amps with blocking diode
Relay 0.54 amps with blocking diode
Ambient temperature 21 °C

The maximum continuous load is therefore 2.24 amps.
The 0.54 amp relay is only switched on for 50 seconds every 60 minutes to replenish the water.

The ambient temperature can rise to 35°C, depending on where the end customer uses the product.

The real continuous load 24/7 is 1.7 amps.
The leads are all soldered.

The module switches off after approx. 30 seconds.

The module did not tolerate 4 resets / restarts and is now defective.
I have also tried the D36V50F12 variant with basically the same result. The only difference is that the shutdown happens much later.

According to the description, the controller should be safe because it has overcurrent protection and short-circuit protection, a thermal shutdown function and a soft-start function that limits the inrush current and increases the output voltage at start-up and gradually raises it.

Do you have any help/explanation on this?


I’m sorry to hear your are having issues with your regulators. Since the voltage is dropping and the regulator is going into thermal shutdown, it sounds like your load is just too much for the regulator. If you try just powering one part of your load, do the regulators work normally? If so, you could add the other loads one at a time to see how much they can handle. How did you determine how much current is drawn by each of your loads?

You mentioned that one of your regulators became damaged. Is it just one? Could you post more about what was happening when the damage occurred?

I expect the D36V28F12 regulator to handle ~1.7A continuously and ~3A for a few seconds with 48V in and 22°C ambient temperatures in free air. Likewise, I expect the D36V50F12 to handle ~2.2A continuously and 5.5A for a few seconds.

By the way, 48V is really close to those regulators’ maximum input voltages; if you have not already, I recommend implementing some transient suppression to ensure that voltage spikes do not exceed the maximum.


Hi Claire,

we took our orientation from the key features and read there a working range of 2A - 3.3A.
If we lower the load to 1.6A, the test worked for 5 hours without any problems.
The destroyed controller simply stopped operating at approx. 2.2A.
The measurements were made with professional measuring devices from Fluke and Tektronix.
Since we need about 2.5A continuously, we will have to look for another solution.
Too bad, because your controllers are very small and fit into our micro environment.

Regards Mike

Hi, Mike.

Is it possible for you to split up your load and power the two parts of it with two separate regulators?

The D36V28F12 can handle 3.3A at lower input voltages so the features section is referencing that. As you mentioned, these regulators have over-current, short-circuit, and over-temperature protection, so it seems most likely to me that the broken unit was damaged by an input voltage spike. A spike like that could be caused by the load changing suddenly, or the output off the regulator cutting in and out while overheating.


A split is possible and we had already considered it.
But it is too expensive in terms of costs.
Another small transformer is half as expensive as two D36Vxxx, even though it takes up more space that we actually need.
We have intercepted voltage peaks with diodes because we are switching two relays.
But something will have happened and since we are moving in the limits it is always a ride on the blade.
Since we are building a commercial product for the professional sector, we can never be sure that everything is running in the optimal range.
That’s why we always have to measure the critical parameters with 80-100% overhead.
But you will know that.
A controller with VIN 48V on 12V/ 2.5A continuous load would be optimal.
A continuous load of 4A would be perfect and would still have some room for small expansions.