Can I hook two RD6006's in serial at 120VDC? Other noob power supply questions. - Page 1
Forum section: electronics / beginners

author: SuperNerd
author_rank: Newbie
timestamp: July 25, 2020, 12:30:11 pm
content: I know you can hook battery's up to double the voltage. I can do the same with a load. For example I have 4 2.7v LED's running in serial off of a 13V cell. But I do not think this works if the load is uneven.Instead of needing to make a hefty 1:2 turn transformer, I am hopping I can wire two RD6006 power supply's in serial. So I have a bag full of 10amp rectifier diodes. I am hopping I can just use eight of them to make a 20amp bridge rectifier. (Or would that be 40AMP because each side of the bridge has 20amps?) Put the pack of electrolytic caps across the DC ripple output to smooth it a bit, hook the positive side of the capacitor to the first RD6006, hook the negative side of the first RD6006 to the positive side of the 2nd RD6006, and the negative side of the 2nd RD6006 to the negative side of the capacitor/bridge node.What would happen, would they both fry? Would they work so long as the current and voltage are both set the same on each?I assume that as soon as I put an uneven load on them one would be taking up a larger share of the 120v. It would be a voltage divider that changes with load, this is my assumption. But it is switching, I have no idea how it would behave. I am all for experimental learning, but I do not want to buy a 2nd, hook it up and end up frying $130 worth of bench supply's. If the current and voltage are set the same on both, would they both be using 60V? Would the voltage going to each change if I need different voltage, or current limit from each? If both are variables effecting the input voltage divider, I assume it would be a linear graph. So the input voltage with both could be 60v if one is set to 6v 6amp with a large load, and the other being set to 12v 3amp. Or maybe only current effects the difference on the input? Maybe just the output voltage? Maybe neither. If neither effects the voltage diver on the input, other people would already be doing this. So I assume there will be downsides.How about on the outputs. I know that with a computer power supply you can disconnect the ground from both AC cords and you can have a 24v supply by connecting the outputs in series. Can you do the same with the RD6006 if they are both connected in parallel to a 60VDC supply? If that works, will they still work if connected in series to a 120VDC supply? For example, lets say I want 100VDC at 5amp. I would set the both the RD6006's, to 50V 5amp, hook RD1+ to my load, hook RD1- to RD2+ hook RD2- to the other side of my load and have the load running at 100V 500W. Is this correct?If I can not hook them up like this, plan B is to custom wind a microwave transformer secondary. I need/want several power supply's, I do not think they need to be linear. Would I be wise to get two more RD supply's and cut a front plate with three rectangular holes. Then run them off the same input circuit? Maybe independently fuse them. Thank you for your help in advance. -Just a eager yet crazy EET student.

author: tunk
author_rank: Super Contributor
timestamp: July 25, 2020, 12:41:11 pm
content: Remember that when you rectify and smooth 120VAC you will get around 170VDC.

author: SuperNerd
author_rank: Newbie
timestamp: July 25, 2020, 01:09:43 pm
content: Because it is not RMS I am guessing. I need to read up more about AC. So my revised question would be. If I have THREE RD6006 in serial.(In place of all my references to two.)

author: David Hess
author_rank: Super Contributor
timestamp: July 27, 2020, 01:01:24 am
content: Yes, you can do that with power supplies and loads with some caveats. For instance the series connection of two floating power supplies with one side grounded will raise the common mode voltage of the other power supply and there are limits to how high it can go. The same applies to two transformer secondaries, but only 60 volts DC should be fine.

author: SuperNerd
author_rank: Newbie
timestamp: July 30, 2020, 06:29:52 pm
content: Thank you David. The thought crossed my mind that I can test things out with a sub 60v supply without risking burning any of the supply's out. I will likely be ordering more of them. My testing will start out by splitting the 42v supply I have now, between two of them.