Here I show how to make the Power stage of an homemade inverter. I'm using the following,
- Old UPS transformer
- 2x Alluminium Heatsink
- 2x N-MOSFET (IRF540N, P55NF06, B150NF55 etc)
- Screws, spade terminals, wires, etc
First we need to place the MOSFETs in the heatsinks in appropriate place so that the heat tab i.e, metal part of the MOSFET body is as close to the mid area of the heatsink. This way more heat will be dissipated by the heatsink.
Now we look at the transformer salvaged from a Microtek UPS. This has a lots of pins for different voltage outputs in one side and 3 input lines for 7.2V--0V--7.2V.
Now we attach the spade type connectors to the primary wires by using a pliers.
The pro of using spade type connector w.r.t using ring connectors is that we can easily mount/unmount them by loosening and tightening the screw, without completely unscrewing them.
We insert the terminals of both 7.2V lines to the heatsinks of the MOSFTEs in the same screws.
Now we connect the battery negative connector to both MOSFET's 3rd pin.
Now we take a 3pin connector and connect the middle pin with the negative line , and connect the rest two wires to the 1'st pins of the MOSFETs i.e, the GATE terminal.
Now this is ready to be connected to a battery and the connector can be connected to an inverter oscillator board like 74LS112 Inverter Oscillator.
oh great work Arup, that's a very good explanation for beginners, but you should also provide its power stage circuit diagram for good understanding,
Thanks ...
Good work; what is the VA rating of the UPS from which you salvaged the transformer?
It was salvaged from an years old 650VA Microtek UPS. Quite big transformer when I compare it to the INR 1200-1500 range's ordinary 600VA UPS's transformer.
You'r right Arup, Microtek is a standard brand and do follow some norms. Though I have not done any electrical tests, but still I doubt if those cheap local brands can even deliver 250 VA of power!
By the way, can you please publish a circuit for a small, mobile charger type SMPS power supply giving an output of about 12V-15V DC at around 100-200mA current. The specs are not very critical. Thanks a lot for all the good work. Keep it up.
I have just visited this website and I must say that these pages have many interesting projects and the information and pics are certainly very good for the DIY Electronic enthusiasts.
Thank you Mr. Arup and everyone.
hi arup your explanation was very good.arup, how many amount of load (in watt) in a ups transformer ??????reply me.thanks
It depends upon the transformer. Good ones like the above can handle 300-350Watts of load easily.
thanks for your responding .i ask more one question ,can you don't use the middle pin of the mosfet And can i use the 555 timer ic as like as a oscillator?please respond me quickly please.thanku
The middle pin and body(tab) both represents the collector. Since soldering the middle pin which is close to the emitter may cause accidental touch and fire, I use the body as collector.
With 555 IC, you get single output but driving two sets of MOSFETs we need dual output.
thanks,good night.
hi arup .can i use 555 ic and 4107 ic ?please reply me .
Yes, of course.
Hi,arup i have found a new type transformer in UMAX ups.in the transformer input has 2 wires and output has 4wires.the transformer has not center taped type.how to use the transformer in a inverter circuit?help me.
These are H-bridge inverters. These has a bit complex MOSFET driving circuitry but the only positive thing is that it requires less windings in transformers. This means less copper that's why cheap UPS makers go that way. IMO Push Pull is the simple and best.
please send me this type very simple inverter circuit .because a have a new transformer.2input 4output.
Here it is.
H bridge driver.
Hi arup , i have made a new inverter circuit using 1 mosfet and 555 ic the circuit is drive a 2input ups transformer,but the negative side of main battery wire hot slowly slowly.how can i give you my circuit diagram for the solution?
It's because of you need to take care of both phases of the input. With 555 and single driver MOSFET, you're controlling only single phase.
This approach is very bad and wastes much battery as well.
Hi arup today i experiment with 2mosfet and 4017ic with timer ic.i connect the to mosfetes gate terminal in 4017 ic leg no 2 and 7 .the 2 mosfets drain is connect in the 2 input transformer of ups.lastmosfet source in positive and 2nd mosfet i connect negative.the hol circuit work properly but only glow a neon light.when i give a load cfl the cfl just blink not to glow up.please help me.supply of volt 12 v 7amps.for ics regulated voltage using 7805.
You need 4 MOSFETs to drive a 2 input wire transformer. See the H-bridge circuit whose link I've given above.
arup please respond me i wait for your reply
Hi,what is the difference between single transister load and parellel transister load for inverter
In parallel transistors, you can give much more load onto it.
I tried to make this circuit as shown above, with different fets at different time but every time i test fets get big bang they bust, wht is wrong with me. am disappointed about this.
Check the datasheet for the particular FET. Probably you're connecting wrong pins.
Hi Arup,
Am getting amaized with your cct compared with what i made, was the battery shown on your connections above was it fully charged? How it happen am using the some ups battery 12v DC 7.2Ah when i connect the transformer and fets together without the driver cct the fets get burnt with burst. i did the some connections as you instructed above but i dont get the right result, please is there anything to do with fets before i solder them into a cct or wht to add to protect the fets. Please advice.
Just one thing to try at the position you are,
Connect 1Kilo-Ohm resistors from each MOSFET's GATE to NEGATIVE terminal. I mean the connector's left and right pin should connect 1K resistor to the middle pin.
can i use h bridge circuit to charge
In H-bridge configuration when you connect grid power to HV section of the transformer, battery is charged as the H-bridge works as a bridge rectifier.