# Current sharing parallel power supplies

Recently, I purchased two 48v 25A power supplies. I want to put them both in parallel. In reality, each PSU consists of 2 smaller individual units(see picture), so 4 units in total. Pin 8 of that ribbon wire connector is the pins you need to connect in order for the two smaller PSUs to output 48v at 25A.

So I know that linking both pin 8’s of the connectors in one power supply will make the 2 smaller units work together.

My question is, could I simply daisy chain the current share pins of all 4 sub-power supplies(what is done in picture) to make them all work together to output 48v at 50A? Reason asked is because these were very expensive and don’t want to cook anything.

Original: https://prnt.sc/q5aqyu

• it probably need some othjer connection too Commented Dec 3, 2019 at 0:35
• what are your voltage error and ripple specs? What is your expected current signature? worst case range? Commented Dec 3, 2019 at 1:19
• Artesyn has a live chat available for questions like this. Have you tried it? They'll probably have more reliable information than anyone here. Commented Dec 3, 2019 at 5:23

No you cannot blindly connect all 4 supplies ganged together and expect rated performance with any load.

Current sharing can be active or passive. They support the 2 module active current share using the signal on pin 8 to be compared with internal current sense so that parallel current share is kept within 2% of total rated current. This is not possible with 4 modules.

Passive current sharing is when you have no active feedback for sharing current and rely only on the matching of voltage divided by wire resistance from source to dynamic load to determine the current share.

The challenge is to define load regulation error and current share imbalance which are tradeoffs.

The following shows an imbalance in average output impedance and voltage mismatching on current sharing errors.

0.4% or 20 mV max @ 25 A , 48V means ESR = 20mV/25A = 0.8 mΩ

However if the voltage error was nulled then drifted to 5mV or 0.1% with no load the parallel supplies now share an ESR`= 1.6 mΩ (=2x 0.8 mΩ)

Thus a hypothetically mismatched circulation current occurs at 1mV/1.6mΩ = 0.625A per mV of error.

e.g. a 0.4% voltage error or 20mV difference results in a 28% current sharing imbalance and a system failure.

Obviously System Specs need to be defined and then stability assumptions not mentioned to verified at worst case loads. Current sharing causes disturbances in each others active voltage regulation and current sharing, both which can cause instability or actually unstable oscillation and system fault.

• Thanks so much! Answers everything. However, is there a way to parallel them so that they share the current equally? This power supply setup I am trying to make is for a ZVS induction heater btw Commented Dec 3, 2019 at 1:44
• I am not that good with electronics. I understand what active and passive current sharing is, just don’t know how to parallel them without blowing stuff up. Commented Dec 3, 2019 at 1:56
• Then you need to consult with someone who can understand this Commented Dec 3, 2019 at 1:59