Please explain this INVERTER circuit

Question

http://www.elecfree.com/electronic/wp-content/uploads/2008/06/circuit-inverter-100w-12v-to-220v-by-transistor.jpg

hi i am a freshman n i ve made a 60watts inverter for my Electronics project. i only ve some concepts abt the diodes n bjts thats all cause im a beginner, i ve my viva tomorrow so can anyone tell me the basics of this ckt in easy language n tht wht is the particular component for what is it doing n all. they wont be going into the deep but i need to ve some rudimentary knowledge atleast. thnks

Answer 1

The left pair of transistors are a standard astable multivibrator oscillator circuit, the diodes are not used at lower voltages, but at over 6 volts, the switching spikes could cause reverse breakdown of the base-emitter junction, as this normally has a breakdown voltage of around 7 volts.

The middle pair appear to be a clocked bistable, halving the frequency and ensuring equal duty cycle to avoid DC bias in the transformer.

The final 4 transistors are the power driver stage, in a configuration that is close to darlington pairs. The diodes are to protect the transitors against negative going spikes.

The normal diode configuration when driving an inductive load, such as a relay coil, motor etc., where the diode would be arranged to dump positive back emf into the positive supply rail, is not possible, as the autotransformer action in the transformer primary will cause the opposite end to go to 24V when the other end is driven to 0V.

The circuit generates a low quality squarewave output, that may not be suitable for all devices.

Answer 2

Please learn how to spell. I count about 30 spelling and grammar mistakes!

You will get more and better answers. Plus, i do believe you will do better in college if you can spell.

I can't explain the entire circuit in this space, but you seem to have a free running multivibrator on the left, probably generating the 120 Hz frequency. The next stage is some sort of AC coupled latch, probably a divide by 2 to get 60 Hz.

Then there is a driver and output stages to gain the power needed, driving a transformer push-pull with a +/- 12 volt square wave. This is shifted in the transformer to a 120 volt (I assume) square wave output at 60 hz.

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