# How to increase low voltages modified AC Sine wave up to 220 VAC with 0.25 Watt?

#### Abdul Basit_1537853368

Joined Sep 25, 2018
1
I am working on Inverter and successfully achieved modified sine wave with 7 level, that is much better according to my requirement. But the problem is output AC voltages is too low which is 10-12 VAC. Every thing works fine. Output frequency is 50Hz and required modified sine wave are achieved. But how can I increase this low AC voltages to 180-220 VAC with 0.25 watt? In Input side I connect 3 individual batteries with 12 Volt DC 1 Amp. Here is the circuit Diagram of my 7-level H-bridge inverter.

The output modified Sine wave of my result is here.

Is it possible that I use 1:22 step up transformer to increase the voltages from 10 VAC to 220 VAC ?
because some people suggest me that idea but i am not sure about that.

#### DickCappels

Joined Aug 21, 2008
9,614
From my experience with analog sine waves is that the first issue with stepping up the voltage using a transformer is the magnetizing current.

This was an early experiment in which a 5V, 50 Hz filament transformer was driven with an autio amplifier IC. Current is 1.4 A P-P when the unloaded secondary is 219 VAC. Primary is driven by a 6.43 volt RMS 48.8 Hz sine wave coupled through a large capacitor. The IR drop because of the magetizing current through the low voltage winding reduces the output voltage considerably.

You might find the right transformer, but it will probably be custom.

If power is a critical factor, it might be better to step up the voltage to 630 VDC or higher with a resonant converter or quasi-resonant converter to and then make your step-wise approximation using MOSFETs and AC couple the output with a capacitor. Just a thought.