12v to 220v MOSFET based Inverter Circuit

Inverters are widely used devices in electronics and electrical circuits. An inverter converts corresponding DC voltage into AC. We are very familiar with linear dc power supplies, which is used to convert 220v Ac into low voltage high ampere DC. In the same way, A high ampere battery or supply is required to step up voltage to required value. Transformers are very helpful in all of these cases. Induced EMF is based on number of turns and wire gauge.

Note** High voltage/ Square wave on high AC/ Circuit can handle 100w maximum with this driver stage. Overheating may occur if there is any further push in power limits.

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Type of Transformer required:

Step-down transformer is used to convert high voltage AC into DC. AC is supplied to the primary winding has a greater number of turns as compared to secondary and thus induced emf generate voltage in secondary winding. In the same way if we reverse the procedure, it can generate high voltage. For small loads (less than 100W) these transformers are great but we need more powerful and dedicated center tapped transformer. Which will cost more and need heavy driver circuitry with separate microcontroller unit. To get more grip on the topic of transformer follow this article here.

In this project, we are using Centre tapped Step down 12-0-12volt Iron core transformer as voltage booster.

IC CD4047:

CD4047 is a 14-pin IC, It is a low-power CMOS logic-based multivibrator circuit IC. It can operate in the monostable mode or astable mode. This IC is easy to use for both modes and requires fewer external components to operate. It has a voltage range of 3V-15V and works best at 5V DC supply.

The answer is that We have to drive the gates of MOSFET. So this task is done by CD4047 by generating square wave or PWM. Most of the power inverter uses this technique to drive the MOSFETs or transistors.

Components required:

1) CD4047 IC

2) IRF Z44N MOSFET with heatsink

3) 1nF capacitor

4) 100K-1M potentiometer

5) 330ohms resistor

6) 1N4007 Diode

7) 12v battery

8) Custom PCB JLCPCB

9) Centre Tapped Transformer(12-0-12)

10) Wires and soldering tools.

Circuit Diagram:

The circuit is simple, IC CD4047 drives the two MOSFETs which are in push-pull configuration. As, the usual transformer cannot work on DC, so we have to make voltage and current changing circuit w.r.t time. So, the flux will induce in the core which will induce a voltage on the secondary winding. You can adjust the potentiometer to get the desired frequency. Usually, the frequency is 50 or 60 Hz.The rating of the transformer should be enough to bear the output power.

Battery should be greater than 10Ah so that battery voltage should not drop, and it should work for a long time. The LED here indicates that the power inverter is ON. So, whenever it is ON, don’t touch the inverter otherwise you will get harmed.

PCB designs:

Download Gerber files and Circuit schematics from here.

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Working:

CD4047 works in the astable mode it continuously changes output at pin no 10 and 11 and thus giving a square wave output they are opposite to each other.

These two output pins are connected to the gate of the two MOSFETs which are arranged in push-pull configuration. So at a time, only one transistor is on. These transistors can handle a very high current through them.

The source of both the MOSFETs is connected to the ground and the drain is connected to the two ends of the secondary winding of the transformer. The centre taped wire is connected to +12VCC.

when the first MOSFET Q1 is on the current path is { +ve terminal => transformer => transistor Q1 => -ve terminal of battery}, and when MOSFET Q2 is on the current path is { +ve terminal => transformer => transistor Q2 => -ve terminal of battery}.

By this method, an alternating current(AC) is produced in the secondary winding (having a smaller number of turns) of the transformer. This alternating current induces a High Voltage AC in the primary(having more number of turns) winding of the transformer. This induced current is not sinusoidal, it is an alternating square wave. this current can easily run 100W bulb a small table fan and some other non-sensitive electronic devices.