100 Watt Inverter 12V DC to 220V AC
The IC1 Cd4047 wired as an astable multivibrator produces two 180 degree out of phase 1/50 Hz pulse trains.These pulse trains are are preamplifes by the two TIP122 transistors. The out puts of the TIP 122 transistors are amplified by four 2N 3055 transistors (two transistors for each half cycle) to drive the inverter transformer. The 220V AC will be available at the secondary of the transformer. Nothing complex just the elementary inverter principle and the circuit works great for small loads like a few bulbs or fans. If you need just a low cost inverter in the region of 100 W, then this is the best.Notes:
* A 12 V car battery can be used as the 12V source.
* Use the POT R1 to set the output frequency to 50Hz.
* For the transformer get a 12-0-12 V, 10A step down transformer. But here the 12-0-12 V winding will be the primary and 220V winding will be the secondary.
* If you could not get a 10A rated transformer , don’t worry a 5A one will be just enough. But the allowed out put power will be reduced to 60W.
* Use a 10 A fuse in series with the battery as shown in circuit.
* Mount the IC on a IC holder.
* Remember, this circuit is nothing when compared to advanced PWM inverters.This is a low cost circuit meant for low scale applications.
Design Tips:
The maximum allowed output power of an inverter depends on two factors. The maximum current rating of the transformer primary and the current rating of the driving transistors.
For example ,to get a 100 Watt output using 12 V car battery the primary current will be ~8A ,(100/12) because P=VxI. So the primary of transformer must be rated above 8A.
Also here ,each final driver transistors must be rated above 4A. Here two will be conducting parallel in each half cycle, so I=8/2 = 4A .