 DIY Simple Inverter design at home

You can easily make an inverter at home. To understand how to make an inverter easily, a simple step by step method is discussed in this post.

Earlier, our power (electrical) requirements were so less. But now, the scenario has changed a lot. From a simple induction to complex washing machines, from a Cell phone to our high end gadgets, every equipment related with our daily use requires power supply. It is the main reason for the recent increase in use of inverters at our home. There are different types of inverter available in market, but these circuits are complicated, high end and costly. So, let’s make our own inverter at home.

Circuit design

This circuit design does not have any functional limit and comes with an efficiency of more than 80%. And in addition, it is capable of compensating almost all of our power needs and that too at very most of your power requirement at a very reasonable cost.

CD4047 is a CMOS Low Power monostable/astable multivibrator mainly used for converting DC current signal to AC signal. It comes with a high voltage rating around 20-V. CD4047 is a 14 pin IC that operates on a logic techniques with an ability to allow negative or positive edge-triggered monostable multivibrator action layered with retriggering and external counting options. Accurate and complemented buffered output with low power consumption make this IC an ideal choice for Frequency Division and Time Delay applications.

Here is the link to the datasheet.

CD4047 is a low power inverter that comes with an ability to operate in both states: astable or monostable mode. In astable mode, it operates by charging a capacitor using a valuable resistor that is mainly used to adjust the output frequency near 50Hz. The output frequency is determined when a single capacitor is connected between PIN 2 and 3.

The IC will be operating is an Astable mode when we apply  HIGH on Pin 5 and LOW on Pin 4, generating the output toggling between HIGH and LOW.The oscillated output frequency on Pin 13 can be determined using the following formula

F = 1 / 4.4 x R*C

Similarly, the formula to find the time it takes to generate pulse will be given as:

t = 2.48 x R*C

Power output of Inverter

Now we have to decide what power output we want from the inverter. By increasing the number of mosfets in parallel we can increase the power output. The MOSFET that I have used is IRF3205. It can handle 50-60 amps of current. If you want a higher current then you have to connect more MOSFETS in parallel.

Lets see how we can design the same circuit for a 3000 watt inverter.
Since our output power is 3000 watt at 220V and input is 12V DC, we can calculate the current.
We know that, Current (I) = Power(P) / voltage(V)
So, Current = 3000 / 12 = 250 Amps

That means we need our MOSFETs to handle minimum 250 amps of current.
Now each IRF3205 can happily handle 50 amps current, hence we need 5 MOSFETs to be able to handle 250 amps current. Since we are using half bridge configuration so we need (3+3) 6 MOSFETs.

So the circuit diagram will look like this:

Transformer Selection

Finally after making the circuit the next device is obviously the transformer. We need a transformer which can handle 3000 watts of power.

One thing to note here is that you need a step up transformer and not the step down transformer. The windings are little different. Since this blog is not about transformer design so I am not going in details on this topic.