It still stinks. Siglent claim you can parallel these power supply outputs - but is that true given any one PSU switched off is going to try load down the others for maximum smoke?
Siglent needs to explicity state whether their power supply can charge batteries. This is very important.

Something not mentioned is quite a few bench power supplies will get damaged charging batteries.
I saw one that the front panel melted and burned up, because overnight AC power cut out and then backfeed damaged the control board. There is no fuse involved and the battery had enough energy to nearly cause a fire.
I'll say it again - all can look OK charging a battery but switching a PSU off or a mains failure can cause an unexpected happening for engineers.

I like my old bench linear power supplies - they don't mind a car battery, well except in reverse lol.

 

I would CERTAINLY define such a function as a "DESIGN FLAW", with no apology! While a theoretically perfect regulated power supply represents "A Zero Impedance Power Source", short circuiting the output terminals intentionally does not seem to have a rational explanation, although it does have an IRRATIONAL explanation.

 

I did exactly the same thing except I fried the channel.

Another victim of this unexpected 'feature' here, just fried a channel by having a battery connected for charging before hitting the on switch.

I wonder if our failure modes are the same: I now have 1 dead channel (A), 2 healthy channels (B and fixed outputs). The 'dead' channel A turns on but is permanently stuck in constant current, presumably due to a component in the output stage having failed short. I'm hoping it's a simple single component replacement. I have a fear they might classify this as 'misuse' under warranty... Anyone had a look inside? There' doesn't seem to be much useful info in the service manual

 

Another victim of this unexpected 'feature' here, just fried a channel by having a battery connected for charging before hitting the on switch.

I wonder if our failure modes are the same: I now have 1 dead channel (A), 2 healthy channels (B and fixed outputs). The 'dead' channel A turns on but is permanently stuck in constant current, presumably due to a component in the output stage having failed short. I'm hoping it's a simple single component replacement. I have a fear they might classify this as 'misuse' under warranty... Anyone had a look inside? There' doesn't seem to be much useful info in the service manual

I didn‘t open it because it was still working.

 

Several years ago a boss used a Sorenson brand power supply for a battery charger. It did smoke a bit when he connected it befoe switching it on, but it did work. And it continued to be useful for several years. So I am not sure just what smoked. So it is possible to design one that does not short circuit the output in the "off" condition.

 

Please clarify for me. If the outputs are a "dead short", then how can anything attached to those terminals be affected?

 

Please clarify for me. If the outputs are a "dead short", then how can anything attached to those terminals be affected?

Because batteries really don't like to be connected to a dead short. It tends to cause a large amount of current to flow.

 

Because batteries really don't like to be connected to a dead short. It tends to cause a large amount of current to flow.

Ahhh, I see it now. The power was external supply, terminals closed that loop. I wonder what internal damage gets done?
Thanks for the clarify.

 

Ahhh, I see it now. The power was external supply, terminals closed that loop. I wonder what internal damage gets done?
Thanks for the clarify.

Probably rather a lot, because one normally assumes that an internal fuse in the power supply will prevent any damage, so doesn't add an external fuse.

 

The only possible application of an output short would be if a string of power supplies were operated in series, and switched on and off to control the voltage. I have not seen that done, except by one fool.

 

That power supply (as do many others) has an overvoltage protection circuit that triggers on overvoltage and shorts the outputs to prevent damage to external circuits. Sounds like when supply shuts off, your battery is backfeeding the crowbar circuit and causing it to trigger and since battery won't give, you burn up something in the PS. Really should be using a diode to prevent back-feeding the power supply.

 

Just reread the original post and you definitely triggered the overvoltage protection circuit. The OVP would be monitoring the output terminals and comparing to an internal reference voltage. When you powered the supply back on, the internal reference was probably ramping up and when compared against the battery voltage present the OVP was triggered, hence the short. Not sure where any power supply manufacturer recommends connecting a PS directly to a battery.

 

Just reread the original post and you definitely triggered the overvoltage protection circuit. The OVP would be monitoring the output terminals and comparing to an internal reference voltage. When you powered the supply back on, the internal reference was probably ramping up and when compared against the battery voltage present the OVP was triggered, hence the short. Not sure where any power supply manufacturer recommends connecting a PS directly to a battery.

You misread. What happens is, no matter what is connected to the terminals, during power up the terminals are connected together with a very low resistance for a brief period. This is the case with no load, a load, or a source.

 

That condition still comes across as a poor design.
Is there any chance that we can actually see the circuit?? That can possibly show us if it is intentional or an accidental condition.
Or has seeing the actual circuit already been requested and denied??

 

That condition still comes across as a poor design.
Is there any chance that we can actually see the circuit?? That can possibly show us if it is intentional or an accidental condition.
Or has seeing the actual circuit already been requested and denied??

Schematics are not shared outside the factory.
I've had a few of these apart to repair various faults which are invariably in the Digital (front panel) PCB.

Earlier units with the now older V1 HW used a small circular 2A bridge for the digital supply and in later early production these rectifier bridges ran hot and could drop one of their diodes resulting in excessive ripple and continuous resets and the like.
Earliest production units never gave any problems other than from operator error but something changed and these bridges occasionally popped. I'm guessing the bridge manufacturer production went too close to a 2A max spec so some failed, sometimes in very new units.
Fairly simple to uprate the bridge to a higher current version although difficult to fit in the same footprint, but simple enough to mount it remotely via 4 flying leads.

Latest V2 production went to a 6 or 8A SIL bridge with a PCB redesign and the above problems vanished.

Each output has a reverse biased IN5000 something diode across the terminals and if these short it would explain these PSU's instantly going into CC mode.
I've seen fused high current traces on these too which can only indicate a whoops moment by its operator.

Any PSU used as a charger should really be used with a series diode ...... IMO.

 

It would seem that there should be a warning on the front panel against using the supply for battery charging or connecting it to any voltage source.

 

Has anyone reached out to Siglent? there opinion about this would be relevant. If a fault is suspected, report it and let them respond.