# Three phase 230V input to single phase 5V/5W power supply [closed]

How can I design a 5V/5W DC power supply derived from 3 phase 230V AC input supply? My application need to work, even if, only one phase is available.

• what peak current, power factor and ESR is the load? 100W at 5% duty cycle?? One does not need 3 phases to supply measly 5W or is it because any 1 phase is unreliable? – Tony Stewart Sunnyskyguy EE75 May 16 '17 at 12:48
• Is this not a duplicate of electronics.stackexchange.com/questions/229010/…? – longneck May 16 '17 at 16:30
• @longneck That question doesn't need an isolated power supply. Normally you would want that. The answer to that question shows a non-isolated version, which I don't think apply here. – pipe May 16 '17 at 18:11
• When you say "230V three phase" do you mean the phase to neutral voltage is 230V or the phase to phase voltage is 230V? – Peter Green May 16 '17 at 18:31
• Yes, I mean 3 phase 4 wire configuration. Where phase to neutral voltage is 230. – Sreenath P V May 17 '17 at 4:19

SMPS operated by AC normally first do rectification of the input voltage, i.e. they work also with DC or pulsating supply voltage.

So you can simply connect all three phases by diodes and use that as input to such a SMPS.

simulate this circuit – Schematic created using CircuitLab

But make sure you use such a SMPS. It will definitely NOT work with a simple 50/60Hz transformer supply.

• Except the DC peak voltage will be 565V. – Jeroen3 May 16 '17 at 12:55
• @Jeroen3: you will get the same peak voltage as if you rectify only one 230V phase, i.e. 325V. Just the ripple will be less (better). – Curd May 16 '17 at 12:59
• you edited it right after my comment. You meant a three-phase half-wave rectifier. – Jeroen3 May 16 '17 at 12:59
• Yes, that's what I meant. I just added the schematic to make it clear. – Curd May 16 '17 at 13:01
• Or use a three-phase full-wave rectifier for even less ripple :) industrial-electronics.com/image/three-phase-bridge_7-6.jpg ... errr, looks like @Andyaka already has that in his answer! – Doktor J May 16 '17 at 20:28

My application need to work, even if, only one phase is available

Use a 3 phase rectifier like this: -

You'll still need a smoothing capacitor because if one wire is lost, the ripple voltage will worsen. Of course there will be a significantly higher peak voltage using this method.

If you have 3 phase and neutral wires, single half wave rectifiers will suffice for a 5 watt converter: -

And, providing you have a good neutral wire, you can "lose" two phase wires and it should still operate. This produces the same peak DC voltage as a conventional single phase SMPS. However, if you "lose" the neutral wire then this will stop working.

You should use a three phase rectifier with capacitors rated for approximately 500V.

The circuit being something like:

OR

STMicroelectronics Provides a three phase SMPS AN2264

I think, I can use 3 Hi-link modules ( http://www.hlktech.net/product_detail.php?ProId=60 ), to derive 5W un uninterruptible supply.

simulate this circuit – Schematic created using CircuitLab

The problem here is, I need to use 3 Hi-link modules( Cost is around \$9 ) and it require more footprint.

• Please don't post new questions as answeres. An ideal solution for you would be @Andyaka six pulse rectifier followed by an SMPS capable of 600 Vdc input. I know ST has an eval kit for one such device for power meetering. If you are afraid to loose one phase or neutral, you can "sacrifice" 12 diodes (they're cheap) and build three full wave rectifiers. You still need a 600 V capable SMPS after it, but you can loose any and possibly multiple inputs and still keep on running. – winny May 17 '17 at 5:31