{"id":549,"date":"2026-10-09T09:59:25","date_gmt":"2026-10-09T01:59:25","guid":{"rendered":"http:\/\/www.dydisplayshowcase.com\/blog\/?p=549"},"modified":"2026-10-09T09:59:25","modified_gmt":"2026-10-09T01:59:25","slug":"how-does-a-pfc-power-supply-operate-in-parallel-with-other-power-supplies-474d-dafdac","status":"publish","type":"post","link":"http:\/\/www.dydisplayshowcase.com\/blog\/2026\/10\/09\/how-does-a-pfc-power-supply-operate-in-parallel-with-other-power-supplies-474d-dafdac\/","title":{"rendered":"How does a PFC Power Supply operate in parallel with other power supplies?"},"content":{"rendered":"

Hey there! If you\u2019re working in industrial power, telecom, or even data center hardware, you\u2019ve probably hit a point where one power supply just isn\u2019t enough. Maybe you need extra output for a new server rack, or you want to add redundancy so if one unit craps out, the whole system doesn\u2019t go dark. That\u2019s where parallel power supplies come in\u2014 and when your gear uses PFC (power factor correction) tech, there\u2019s a specific set of rules to make that work right. As someone who\u2019s been supplying PFC power supplies for years, I\u2019ve seen way too many folks skip the basics here and end up with weird glitches, uneven load sharing, or even fried units. Let\u2019s break this down like we\u2019re chatting over coffee, no fancy textbook jargon that makes your eyes cross. PFC Power Supply<\/a><\/p>\n

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First, let\u2019s refresh what a PFC power supply actually does, for anyone who might be new. Regular AC power from the wall isn\u2019t a perfect sine wave, and old power supplies used to draw current in big, lumpy bursts that messed up the grid\u2019s power factor (think: wasting energy, getting fined by utility companies for bad power quality). Active PFC (the kind we supply) fixes that by smoothing out that current draw so it\u2019s in sync with the AC voltage, knocking power factor up to 0.95 or higher\u2014 that\u2019s huge for cutting energy bills and complying with standards like 80 Plus. Now, when you parallel two or more of these units, it\u2019s not just plugging them into the same bus and calling it a day. If they \u201cfight\u201d each other, you\u2019ll get one unit carrying almost all the load and the other barely doing anything, or worse, current surging between them. That\u2019s why load sharing is the whole name of the game here.<\/p>\n

Wait, what\u2019s load sharing exactly? It\u2019s the process where all parallel PFC units split the total system load evenly, right up to their combined max output. So if you have two 1000W PFC supplies, a 1500W total load means each carries 750W. Easy in theory, but PFC units have their own control circuits that can throw this off. Let\u2019s get into how that works. Most modern parallel-ready PFC power supplies use what\u2019s called \u201cdroop current sharing\u201d or \u201caverage current sharing\u201d\u2014 two main methods, and I swear there\u2019s a big debate among engineers about which is better, but both work if set up right.<\/p>\n

Droop current sharing is the simpler one, honestly, and a lot of entry-level parallel supplies use it. Here\u2019s the gist: each unit has a tiny output resistance built in (it\u2019s not a physical resistor, it\u2019s part of the control loop). If one unit starts outputting a little more current than the others, its internal resistance bumps up a bit, which brings its voltage down just enough so the other units pick up the slack. It\u2019s like a group of people carrying a heavy couch\u2014 if one person starts lifting too hard, they adjust their grip to even it out. The problem with droop is that it\u2019s not perfect. There\u2019s a tiny voltage drop across each unit\u2019s internal resistance, so the total output bus voltage is a little lower than a single unit would put out. That\u2019s why droop works best for systems where you don\u2019t need super precise load matching\u2014 like a warehouse backup system where a 5% difference in load is no big deal.<\/p>\n

Average current sharing is the more precise method, which is what most of our mid-to-high-output parallel PFC supplies use. Here, every unit in the parallel chain talks to each other over a simple communication cable (it\u2019s usually a 3 or 5-pin connector, super standard) to share a signal that says, \u201cHey, I\u2019m currently carrying X amount of current, what\u2019s everyone else got?\u201d The control circuits then adjust each unit\u2019s output to match the average current of the group. So if one unit is at 800W and another is at 700W, the third will nudge its output down a little, and the first might nudge up, until all three are at a smooth average. This is way better for telecom or data centers, where you need consistent load distribution to keep your units running cool and extend their life.<\/p>\n

Now, the big rules you have to follow when parallel PFC supplies\u2014 I can\u2019t stress these enough, because I\u2019ve had a customer call me panicking at 2AM because they didn\u2019t do these and lost two units. First, all the parallel units have to be the same model, same output voltage, same max current. That\u2019s non-negotiable. You can\u2019t parallel a 12V 100A PFC supply with a 12V 80A unit and expect it to work right. The 80A one will hit its current limit and shut down before the 100A one is even loaded properly, which wastes capacity and is a fire hazard. Even if they\u2019re from the same brand, different revisions of the same model might have different firmware, so double-check that too. We always test every unit from our production line to make sure their firmware matches for parallel use, so that\u2019s one less thing you have to worry about when you buy from us.<\/p>\n

Second, the communication cable for average current sharing\u2014 you can\u2019t just daisy-chain it randomly. You have to connect it in a linear chain, not a star (like, plug Unit 1 to Unit 2, Unit 2 to Unit 3, not all units to a central hub). And make sure the cable length is consistent for every connection, and no extra cables hanging loose causing interference. I\u2019ve seen guys use a random Ethernet cable for this (it\u2019s not made for control signals) and get noise on the communication line, leading to load sharing glitches. We supply the correct parallel cables with every multi-unit order, so just use those\u2014 it\u2019s not worth cutting corners here.<\/p>\n

Third, don\u2019t mix active and passive PFC supplies in parallel. Passive PFC is the old, bulkier kind that uses inductors to correct power factor, and it\u2019s way slower at adjusting current. If you parallel an active PFC (the kind we sell) with a passive one, the passive unit can\u2019t keep up with the active one\u2019s control loops, so it\u2019ll either hog all the load or sit idle. Stick to active PFCs for parallel setups, they\u2019re designed for that.<\/p>\n

Now, what about redundancy? That\u2019s the biggest reason people parallel supplies, right? You want if one unit dies, the others can pick up the extra load without shutting down the whole system. For N+1 redundancy, you have total output capacity equal to (N units -1) times the max output. So if you need a 2000W total load, you can run three 1000W units: two carrying 1000W total, the third as a backup. If one fails, the other two can take up the slack. Just make sure your parallel PFC supplies are rated for N+1 operation\u2014 some units will shut down if you exceed their max current, so our parallel-ready models are rated for that extra load. We have a lot of telecom clients who use 3+1 parallel PFC setups in their cell towers, so if one unit takes a lightning hit, the others keep the tower running.<\/p>\n

Wait, another thing: hot-swapping. Can you replace a failed parallel PFC supply without turning off the whole system? Yeah, most modern parallel active PFC supplies support hot-swap, but you have to follow the right steps. First, make sure the new unit is identical to the ones in the system, same firmware, same output. When you plug it in, the control loop will detect it, adjust the load to include the new unit, and split the work evenly. Don\u2019t just yank a dead unit out\u2014 even with hot-swap, the bus voltage can dip if you do it wrong, so we always recommend waiting 10 seconds after turning off the power to the failed unit before disconnecting it, and turning the new unit on and letting it sync for 30 seconds before putting the system back to full load.<\/p>\n

I get it, there\u2019s a lot to wrap your head around if you\u2019re new to this. Let\u2019s talk about a common mistake I see all the time: people think adding more units to parallel means more capacity, and that\u2019s true, but only if you do it right. Last year, a customer bought four of our 1500W PFC supplies, thought he could pair them with two 1000W units from another brand to get 8000W total. Turns out the other brand\u2019s units didn\u2019t have compatible parallel control loops, so the four good units were carrying 7500W total, and the two off-brand ones were doing nothing. He had to send the off-brand ones back and order two more of our units, so he ended up with six units total\u2014 worked out great, but he wasted a week of downtime because he tried to cut costs with mismatched gear.<\/p>\n

Another tip: monitor your parallel system. A lot of our PFC power supplies come with remote monitoring ports, so you can check load levels, unit temperature, and fault status from your office. If one unit starts carrying 10% more than the average over a few days, that\u2019s a sign it\u2019s failing and needs replacement before it craps out. We offer basic monitoring software with all our parallel PFC orders, so you don\u2019t have to build something from scratch.<\/p>\n

What about power factor in a parallel setup? Does running multiple PFC supplies in parallel mess with the overall power factor? Nope, not if they\u2019re working right. Each individual PFC supply corrects its own current draw, so the total system power factor is still around 0.95, same as a single unit. That\u2019s a huge win for your energy bills\u2014 a data center with 20 parallel PFC supplies is still getting that efficient power draw, no extra strain on the grid.<\/p>\n

Wait, let\u2019s address a question I get all the time: can you parallel different wattage units as long as they\u2019re the same model? Let\u2019s say two 1000W and one 800W of the same series. Technically, the average current sharing loop would adjust, but you\u2019ll end up with the 800W unit running at 100% load all the time, which shortens its life. Our recommendation is always to use identical units in parallel, so each runs at a comfortable 50-70% load, which is the sweet spot for reliability. That\u2019s how we design our parallel PFC supplies, so that load distribution stays even even as they age.<\/p>\n

Now, if you\u2019re putting together a parallel PFC system, what order do you hook everything up? Let\u2019s run through a quick step-by-step for a small 2-unit setup, super simple. First, turn off all power to the whole system, including the AC input to the supplies. Then, connect the parallel communication cable between the two units, same as we talked about earlier (linear, matching length). Next, connect the DC output bus: attach the positive terminals of both units to the positive bus bar, negative to negative, use thick enough wire to handle the total current\u2014 don\u2019t use thin 18 gauge wire for a 2000W system, that\u2019s a recipe for voltage drop and overheating. Then connect the AC input lines to both units, making sure phase order matches (we mark L, N, G on all our supplies so that\u2019s easy). Then turn on the AC input first, wait 10 seconds, then turn on both unit\u2019s power switches. They should fire up, sync over the communication cable, and start splitting the load evenly within a few seconds. If not, check the communication cable, make sure the units are identical, and check for fault codes on the display (our units have a tiny LED that flashes if something\u2019s wrong, super easy to read).<\/p>\n

I\u2019ve been in the power supply game for over a decade, and the biggest takeaway I want you to have is this: parallel PFC supplies aren\u2019t rocket science, but they do require paying attention to the small, specific details. Cutting corners on matching units, using the wrong cables, or skipping load testing will cost you way more in downtime and replacements than just doing it right the first time. When you source your parallel PFC supplies from a supplier that designs their units specifically for parallel operation (like us), you skip all the headaches\u2014 we test every pair or set before shipping, include all the right cables and monitoring tools, and our support team is available 24\/7 if you run into a problem.<\/p>\n

If you\u2019re working on a project that needs parallel power supplies\u2014 whether it\u2019s a new industrial automation system, a telecom tower, or a data center rack\u2014 and you want to make sure it\u2019s set up right, hit us up to chat through your needs. We don\u2019t do one-size-fits-all, so we can help you pick the right number of units, right wattage, and even custom configurations if your project has specific requirements. No salesy jargon, no pushy tactics, just honest advice based on what\u2019s worked for our customers over the years.<\/p>\n

Before I wrap up, let\u2019s make sure I didn\u2019t miss anything important. Oh, right\u2014 isolation! When you parallel power supplies, the DC outputs need to be isolated from each other and from ground, right? All our active PFC supplies have isolated outputs, so you don\u2019t have to worry about ground loops causing current to circulate between units. That\u2019s a key feature that differentiates our parallel-ready models from regular single-unit PFC supplies. A lot of cheap parallel units skip isolation, so you get a ground current that wastes power and can damage equipment, so always check for that.<\/p>\n

Another thing: temperature. Parallel units run hotter than single units, since they\u2019re sharing load, so make sure your system has enough airflow. We rate our parallel supplies for 50\u00b0C ambient temperature, and if you\u2019re installing them in an enclosed rack, add extra fans to keep the air moving. Overheating is the number one cause of power supply failure, so don\u2019t ignore ventilation.<\/p>\n

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Alright, that\u2019s a lot to take in, but it\u2019s all the stuff you actually need to know when working with parallel PFC power supplies. If you\u2019ve got questions about load sharing, choosing the right units, or setting up your system, reach out to our team to discuss your specific application. We\u2019ve worked with every type of industry, from small machine shops to large data centers, so we can help you get a reliable, efficient parallel power setup that works for you.<\/p>\n

Open Frame Switching Power Supply<\/a> References<\/p>\n

    \n
  1. "Power Supply Parallel Operation: Concepts and Practices," Power Electronics Technology, 2021.<\/li>\n
  2. Active Power Factor Correction for Parallel Power Supplies, International Journal of Power Electronics, 2019.<\/li>\n
  3. Redundant Power System Design for Industrial Applications, IEEE Transactions on Industrial Informatics, 2020.<\/li>\n<\/ol>\n
    \n

    Guangzhou Kaihui Electronics Co., Ltd.<\/a>
    Guangzhou Kaihui Electronics Co., Ltd. is one of the most professional pfc power supply manufacturers and suppliers in China, specialized in providing the best customized service. We warmly welcome you to buy high quality pfc power supply made in China here from our factory.
    Address: 2F BLDG8, Standard Ind.Park, Dongchong Town, Nansha District 511453, Guangzhou, Guangdong, China
    E-mail: amy@gzkaihui.com
    WebSite:     https:\/\/www.kaihuipowersupply.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

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