220V DC to 220V AC: DIY Inverter Part 2

Hello everyone. I hope you all are safe and staying healthy. In this instructable I will show you how I made this DC to AC converter that converts 220V DC voltage to 220V AC voltage.The AC voltage generated here is a square wave signal and not a pure sine wave signal. This project is a continuation of my previews project which was designed to convert 12Volts DC to 220V DC. It is highly recommended that you visit my previous project first before continuing ahead i this instructable. The link to my DC to DC converter project is :

https://www.instructables.com/id/200Watts-12V-to-2...

This system converts the 220V DC into and Alternating signal of 220Volts at 50 Hertz which the commercial AC supply frequency in most countries. The frequency can be easily adjusted to 60 Hertz if required. For this to happen I have utilized a full H bridge topology using 4 High voltage MOSFETS.

You can run any commercial appliance within a power rating of 150 watts and about 200 watts peak for short duration. I have successfully tested this circuit with Mobile chargers, CFL bulbs, Laptop charger and table fan and all of them work fine with this design. There was no humming sound while operating the fan as well. Due to high efficiency of the DC-DC converter, the no load current consumption of this system is only about 60 milliamps.

The project uses very simple and easy to get components and some of them are even salvaged from old computer power supplies.

So without any further delay, let us get started with the build process!

WARNING: This is a high voltage project and can give you a lethal shock if you are not careful. Only attempt this project if you are well versed with handling high voltage and have experience in making electronic circuits. Do NOT attempt if you do not know what you are doing.

1. IRF840 N channel MOSFETS - 4
2. IC SG3525N - 1
3. IR2104 mosfet driver IC - 2
4. 16 pin IC base(optional) -1
5. 8 pin IC base (optional) - 1
6. 0.1uF ceramic capacitor - 2
7. 10uF electrolytic capacitor - 1
8. 330uF 200 volt electrolytic capacitor - 2 (I salvaged them from a SMPS)
9. 47uF electrolytic capacitor - 2
10. 1N4007 general purpose diode - 2
11. 100K resistor -1
12. 10K resistor - 2
13. 100 ohm resistor -1
14. 10 ohm resistor - 4
15. 100K variable resistor (preset/ trimpot) - 1
16. Screw terminals - 2
17. Veroboard or perfboard
18. Connecting wires
19. Soldering kit
20. Multimeter
21. Oscilloscope (optional but will help to fine tune the frequency)

It is important that we gather all the necessary parts first so that we can quickly move on to making the project. Out of these a few components have been salvaged from old computer power supply.

The capacitor bank plays an important role here. In this project, high voltage DC is converted to high voltage AC, thus it is important that out DC supply is smooth and without any fluctuations.This is where these huge beefy capacitors come into play. I got two 330uF 200V rating capacitors from a SMPS. Combining them in series gives me and equivalent capacitance of roughly 165uF and increases the voltage rating upto 400 volts. By using the series combination of capacitors, the equivalent capacitance gets reduced but the voltage limit increases. This solved the purpose for my application. The high voltage DC is now smoothed out by this capacitor bank. This means that we will get a steady AC signal and the voltage will remain fairly constant during start-up or when a load is suddenly attached or disconnected.

WARNING:These high voltage capacitors can store their charge for a long, long period of time, that can be upto several hours! So only attempt to make this project if you have a good background of electronics and have hands on experience of handling high voltage. Do this at your own risk.

Since we will be making this project on a veroboard, it is important that all the components are strategically placed so that relevant components are closer to each other. In this way, solder traces will be minimal and less number of jumper wires will be used making the design more tidy and neat.

The 50Hz (or 60Hz)signal is being generated by the popular PWM IC- SG3525N with a combination of RC timing components.

To get more details about the working of the SG3525 IC, here is a link to the datasheet of the IC:

https://www.st.com/resource/en/datasheet/sg2525.pd...

To get an alternating output of 50Hz, the internal oscillation frequency should be 100 Hz which can se set by using Rt approximately 130KHz and Ct equals to 0.1uF .The formula for frequency calculation is given in the datasheet of the IC. A 100 ohm resistor between pin 5 and 7 is used to add a little deadtime between the switching to ensure the safety of switching components (MOSFETS).

SInce high voltage DC will be switched via the MOSFETs, it is not possible to directly connect the SG3525 outputs to the gate of the MOSFET, also switching N channel MOSFETs in the high side of the circuit is not easy and requited proper bootstrapping circuit. All of this can be efficiently handled by the MOSFET driver IC IR2104 the is capable of driving/ switching MOSFETs that allow voltages upto 600Volts. This makes the IC suitable for out application. Since IR2104 is a half bridge MOSFET driver, we will be needing two of them to control the full bridge.

The datasheet of IR2104 can be found here:

https://www.infineon.com/dgdl/Infineon-IR2104-DS-v...

The H bridge is what is responsible for alternatively changing the direction of current flow through the load by alternatively activating and deactivating the given set of MOSFETS.

For this operation I have chosen the IRF840 N channel MOSFETs which can handle upto 500 volts with a maximum current of 5 Amps, which is more than enough for our application. The H bridge is what will be directly connected to out AC appliance.

The datasheet to this MOSFET is given below:

http://www.vishay.com/docs/91070/sihf840.pdf

Before soldering the components in place, it is always a good idea to test out the circuit on a breadboard and rectify any mistakes or error that might creep up. In my breadboard test I assembled everything as per the schematic(provided in a later step) and verified the output response using a DSO. Initially I tested the system with low voltage and only after being confirmed that it was working did I test it with high voltage input

As a test load, I used a small 60 watt fan along with my breadboard setup and a 12V lead acid battery. I had my multimeters connected to measure the output voltage and current consumed from the battery. Measurements are needed to make sure that there is no overloading and also to calculate efficiency.

The following is the entire circuit diagram of the project and along with it I have attached the EAGLE schematic file for your reference. Feel free to modify and use the same for your projects.

With the design being tested and verified, now we an move ahead to the soldering process. First, I have soldered all the components concerning the oscillator section.

The MOSFET driver IC base and the bootstrap components were now soldered

Be careful of the orientation of the IC while inserting. Look for a notch on the IC for pin reference

The 4 MOSFETs of the H bridge are soldered in place along with their current limiting gate resistors of 10Ohms and along with screw terminals for easy connection of the input DC voltage and the AC output voltage.

This is what the entire module looks like after soldering process has been complete. Notice how most of the connections have been made using solder traces and very few jumper wires. Be careful of any loose connections because of high voltage risks.

The inverter is now complete with both the modules complete and attached with each other. This has been successfully working in charging my laptop and powering a small table fan simultaneously.

I hope you like this project :)

Feel free to share your comments, doubts and feedback in the comments section below. Watch the full instruction and build video to more essential details about the project and how I built it, and while you are there consider subscribing to my channel :)