wiring 2 24v-12v dc converters to make 48v-12v

[Rafabaca]

just a quick question, could you wire 2 24v-12v dc to dc converters in series to a 48v power supply. in theory it should work, but it just seems too silly to.

instead of buying a 48v-12v dc converter i was flirting with the idea of using cheap 24v-12v converters to use with a 200w amp stereo system i was thinking of putting on my bike.

i was looking at this one in particular
http://www.virtualvillage.com/24v-to-12v-dc-dc-car-power-supply-converter-30a-007808-040.html

 

[texaspyro]

There are an awful lot of things that can go wrong...

 

[Jeremy Harris]

The chances are that, unless they both draw exactly the same current, they won't end up with 24V at each input. Say one of the two converters momentarily draws twice the current of the other. The result would be that it would be running on an input voltage of 16V whilst the less heavily loaded converter would have an input voltage of 32V, which may be enough to damage it.

I think it's very unlikely that two converters would load share evenly, so there's a strong risk that the input voltages will end up being quite different. In theory they should even up, if their outputs are paralleled, but my gut feeling is that this may not happen in practice.

I managed to find some cheap 48V to 12V converters for my motorcyle (with an actual input operating range of 36 to 72V) on ebay that werem't too expensive. I've just had another quick look and found this one: http://cgi.ebay.com/Artesyn-DC-DC-Converter-Module-BXB75-48V-12V-6A-OUT-/310270339655?pt=LH_DefaultDomain_0&hash=item483d8daa47 with a 6A output, but there are probably more around.

Jeremy

 

[Rafabaca]

ya, thats right.in my mind i was thinking in absolute values, but the real world doesn't work that way. i considered it after wiring speakers together and getting the right impedance, thought it would be great if all electronics worked that way.

thanks agian jeremy

 

[Rafabaca]

ya, thats right.in my mind i was thinking in absolute values, but the real world doesn't work that way. i considered it after wiring speakers together and getting the right impedance, thought it would be great if all electronics worked that way.

thanks agian jeremy

 

[jag]

just a quick question, could you wire 2 24v-12v dc to dc converters in series to a 48v power supply. in theory it should work, but it just seems too silly to.

As others have commented, it can go wrong.

However it might work. It depends on how the internal control circuit in the converters behaves. Two things that may help: Two capacitors across the primaries to filter PWM effects. Two series resistors on the secondary side, before paralleling.

I run two BLDC fan controllers in series. Works well, as the fans are very nice loads. Similarly the resistors will tend to damp the system.

Another safer option: Buy 2-3 trimmable 48V to 5V converters and series the output.. Just typing 48V 5V in ebay search brings up page fulls of inexpensive options. Either trim two up to 6V each, or trim 3 down somewhat.