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Inverter kind of sort of works

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athandpr

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Hi Everyone, well I have gotten back into electronics as a hobby recently and I figure I would try my hand at an inverter. The problem that I am having is that the inverter is creating 120 VAC, but if I plug a lamp in, the lamp does not light and the voltage drops from 120 VAC to roughly 7 VAC!!! The attached image is the schematic that I pulled from the Internet.

I have seen other variations of this schematic thrown about the Internet. So someone must know what is wrong here. Also, I am using a 6-0-6 3Amp transformer and my power supply is a 6 VDC with 12 Amphours.

Also, I have tried all kinds of resistors. Everything from a 1/8 watt 2.2 Ohm all the way up to a 10 Watt 10 Ohm wire round resistor.

Thanks and I hope someone can help.
images(dot)elektroda(dot)net/64_1283451569(dot)gif

PS I live in the US, we don't use 240 VAC other than for washer, dryer, and oven.
 

It's a very basic inverter circuit, not applying for any efficiency.

Because the transformer is driven into partial saturation, the output frequency will be rather 40 than 60 Hz with a 6V transformer. Some load may have difficulties with it. The schematic says 220 ohm for the feedback resistors, so 2.2 or 10 is definitely too low.

What kind of lamp are you connecting to the circuit?
 

FvM said:
It's a very

What kind of lamp are you connecting to the circuit?
Click to expand...
I have tried a 15 W bulb, 25 Watt Bulb, and 100 Watt Bulb. I worked backwards with the previous bulbs. I even tried the LED lights as well . . .. no luck.

Are you saying that this circuit will not work, but instead is really to demonstrate an inverter circuit? If not, what should I do to make it practical? Thanks.
 

I don't say it doesn't work. But the performance is rather poor. The circuit looks like a reminiscence to early transistor electronics in my eyes. From older days, when integrated circuits haven't been yet invented and a DIY designer couldn't afford two additional transistors for a multivibrator to generate a fairly stable inverter frequency. Transistors have been really expensive at those days.

To effectively improve a self-oscillating inverter, you would need a small driver transformer, operated in saturation instead of the output transformer. It can achieve better efficiency than most BJT darlington circuits. Professional inverters from 50th and 60th have been designed this way. There are e.g. intelligent circuits utilizing current feedback. But it's no longer easy then.

There are lots of simple and fairly operational inverter circuits at edaboard and the whole internet.
 
Last edited:

FvM said:
I don't say it doesn't work. But the performance is rather poor. The circuit looks like a reminiscence to early transistor electronics in my eyes. From older days, when integrated circuits haven't been yet invented and a DIY designer couldn't afford two additional transistors for a multivibrator to generate a fairly stable inverter frequency. Transistors have been really expensive at those days.

To effectively improve a self-oscillating inverter, you would need a small driver transformer, operated in saturation instead of the output transformer. It can achieve better efficiency than most BJT darlington circuits. Professional inverters from 50th and 60th have been designed this way. There are e.g. intelligent circuits utilizing current feedback. But it's no longer easy then.

There are lots of simple and fairly operational inverter circuits at edaboard and the whole internet.
Click to expand...

Awesome. Right after I made my last reply I was wondering if using a toroidal transformer would work. I am using the E1 transformer. Also, I will search around for an inverter circuit. Are there any that you could recommend? Thanks.
 

Hi, I was tinkering with this circuit last night, I would like to add a passive low pass filter to it, but I am not sure where to even connect it into. Any thoughts would be appreciated.
 

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