Cheap inverter circuit for 12v to 220v led bulbs 36W

[RIKRIK]

OLD Design deleted, here is the new design.

find @ https://www.eevblog.com/forum/projects/it-was-meant-to-be-so-simple-(-square-wave-inverter-low-battery-indicator/

[Zero999]

The joys of simulators ay?

Of course the original poster probably meant 4.7µF.

I'd be more worried about the the voltage source supplying 188A!

I think there's some crossconduction going on, i.e. both MOSFETs turning on simultaneously.

This circuit will be fine, as long as the LED lamps don't have capacitive droppers, which won't like a squarewave. The frequency won't be important, since it will be converted to DC inside the lamp. The other potential issue is the peak output voltage will be 220V, rather than the 311V expected by the LED lamp.

[patrick1]

seriously dude, if you have an electronics store around,   you want too use a 555 timer going into a CD4017, which, for every 10 pulses of the 555, - gives you one per each of its 10 output pins.

meaning you can tie the output pins together in any way that suits, for eg 1,2,3 on 4,5 off, 6,7,8 on 9,10 off

then you can take 1,2,3   and 6,7,8  and use each set too drive a transistor for each side of your split primary.

bread and butter stuff. i still use it all the time for heaps of applications. very versitile

[Zero999]

Thanks for your reply's back . Don't worry i also bread boarded the circuit as I know tolerences in components can throw the numbers off,, il probably have to change the low battery indicator to include a trimpot, waiting on a 100k resistor to see if I can get away with out using one. 555 and CD is good, I'm guessing that's a modified sine wave inverter.

The frequency really isn't important for the majority of LED lamps, especially the higher power units, which will be perfectly happy with 300VDC.

My aim for the project was to make it as simple and cheap as possible , also repairable.

How about a blocking oscillator? It just needs one transistor.
https://en.wikipedia.org/wiki/Blocking_oscillator

[Audioguru again]

Dis you test the LED light bulbs to see if they produce any light from the much lower peak voltage of the inverter's squarewave instead of the much higher peak voltage of the mains sinewave?

[CJay]

A lot of LED bulbs will be happy with way less than 220V, indeed some of the ones I've played with lit dimly at 12VDC, so you might be able to relax your design requirements considerably.

[Zero999]

The 2N2222 is fine, but the whole circuit is more complex than necessary.

All that's needed is one transistor. The classic is the 2N3055, but there are better alternatives. Attached is the basic minimalist blocking oscillator design. It doesn't make the best use of the transformer, because it uses part of the primary as the feedback winding.


A better alternative is to add another winding for feedback, rather than a centre tap. The easiest way of doing this would be to use a toroidal transformer and add your own feedback winding.

An even better idea is to use the transformer as part of the astable multivibrator, but it requires a big inductor in series with the power supply to limit the current when both transistors turn on simultaneously. It can be a 100 or so turns wound over a large bolt.

[Zero999]

Have you done any real life tests yet or just simulation?

Try building the circuit I previously posted, with two transistors. You might be impressed with the performance, of such as simple circuit. There's also a variant of it which uses MOSFETs, but stick with BJTs for now.

[Yansi]

I think I have even seen an ooold inverter utilizing the CFPR (Current Fed Parallel Resonant) topology, with a couple of BJTs. (There might have even been a germanium transistors). Could produce I think something like up to 50W and had a quite nicer looking output waveform, than those multivibrator stuff above.

[Zero999]

I don't have any pictures but I've built the two circuits I posted previously and they both work quite well. The applications were different though. I used the blocking oscillator (the one with a single transistor) as a driver for an old TV flyback transformer for a high voltage experiment and the one with two transistor circuit as a fluorescent lamp driver. 

[RIKRIK]

OLD Design deleted, here is the new design.

find @ https://www.eevblog.com/forum/projects/it-was-meant-to-be-so-simple-(-square-wave-inverter-low-battery-indicator/

[CJay]

You seem to be wasting a lot of current in the battery indicator

[RIKRIK]

Thank-you for your comment, I'm going to use a switch to turn on the two circuits , so the battery monitor is only on when the lights are on . The battery will be continuously charged by a small panel and solar charge controller. But I will make up a few different circuits, and give them a test, it's a micro solar system, where the lights are ran off a small 12v and theres a two battery 24v system for tool charging,phone charging,radio, and other stuff. Obviously this solar set up for anyone living in a house looks bad, but if your in the middle of know where, then the idea doesn't seem that bad.

[Zero999]

The TL431 can be used to make a low battery voltage monitor.
https://www.edaboard.com/showthread.php?227827-shut-down-supply-voltage-comparator

There is no need for the inverter. Simply use 12V lamps in the first place. 12V MR16 LED lamps are widely available. It will be much cheaper and more efficient to use them instead, rather than 230V lamps and an inefficient inverter. If they need to be powered from the mains a cheap, efficient switched mode converter can be purchased.
https://www.google.com/search?client=firefox-b-d&q=MK16+LED
https://www.screwfix.com/c/electrical-lighting/light-bulbs/cat8350001?calclightbulbtechnology=led&lightbulbtype=mr16

I have a similar project in mind for lighting my shed, but will use efficient12V lamps, rather than an inverter and 230V lamps.

Oh and please refrain from deleting old designs, unless there's anything hugely dangerous or stupid. It's nice to see how a design progresses and comments made about the old design no longer make any sense, without it to refer to.

[dave_j_fan]

Try this grandma's recipe .

I have used it with 1000s of solar lanterns...

try adding 100K vr replacing leftmost 33k for ur needed voltages .
It works very well and  sharp turn on.

Add pc817 Opto to shutoff ur oscillator at low voltage( for small inverters )  .

[RIKRIK]

thankyou