Designing a Modified Sine Wave Inverter Circuit is made easier by this article.
Two tiny electrical chips called the IC 4017 and IC 555 are used to produce a smoother version of a square wave converter.
The circuit helps in closely examining each component and showing the circuits connections.
Understanding Modified Sine Wave Inverter:
Battery power can be converted into household power using several kinds of inverter designs.
A modified sine wave inverter is superior to a basic version that produces a blocky wave!
For certain appliances it produces a smoother wave.
The key difference is that unlike a switch which goes up and down straight but in a modified sine wave inverter simply maintains the voltage at zero before changing directions.
Comparing Square Wave and Modified Sine Wave Inverters:
A light switch that can turn ON and OFF really fast.
That is kind of how a square wave inverter works the electricity turns ON and OFF suddenly
This can be rough on some appliances.
A modified sine wave inverter is smoother like a dimmer switch.
Instead of going straight ON and OFF it holds the electricity at zero for a tiny bit before switching directions.
This makes the electricity cleaner and less likely to cause problems with its devices.
While it is not perfect but it cannot be as smooth as a true sine wave but it is a big improvement over the square wave.
Understanding the Modified Inverter Circuit:
Parts List:
| Component | Quantity |
|---|---|
| Resistors (all 1/4 watt) | |
| 36k | 2 |
| Capacitors | |
| PPC 0.1µF | 2 |
| Electrolytic 1000µF 25V | 1 |
| Semiconductors | |
| Diode 1N4007 | 1 |
| IC 4017 | 1 |
| IC 555 | 1 |
| MOSFET IRF540 | 2 |
| Transformer 6-0-6V / 25A / 220V | 1 |
| Battery 12V 25Ah | 1 |
The modified inverter circuit produces a modified sine wave at its output which will be divided into the following stages:
Oscillator Stage IC 555:
The oscillator circuit plays a crucial role in generating the required clock signal for the inverter making it the heart of the entire circuit.
To achieve this we require the versatile IC 555 as the oscillator.
Our objective is to produce a 200Hz square wave with a 50% duty cycle which will be further divided by four using IC 4017 to obtain a 50Hz AC modified sine wave output.
The frequency of the IC 555 oscillator is calculated using the following formula:
Formulas and Calculations:
Below are the formulas with calculations for Designing a Modified Sine Wave Inverter Circuit:
Frequency = 1.44 / (R1 + R2) * C
Duty Cycle = R1 / (R1 + R2)
We can calculate by putting the component values from the circuit diagram into these formulas:
Frequency = 1.44 / (36000 + 36000) * 0.1 x 10-6 = 200 Hz
Duty Cycle = 36000 / (36000 + 36000) = 0.5
Duty Cycle = 0.5 x 100% = 50%
Let us analyze this on the scope:
As far as component limitations are involved the scope measurements show that the circuit somehow falls inside these estimated values.
Important Note:
The 0.1uF capacitor at pin 5 of the IC 555 is essential because it offers stability against outside noise.
The frequency and duty cycle will change from the calculated values if this capacitor is left out.
Wave Shaping Stage IC 4017:
In the wave shaping stage we feed the 50Hz, 50% duty cycle signal to the IC 4017 a decade counter that produces the modified sine wave.
The IC 4017 boasts 10 output pins and one input pin 14
When a clock signal is applied to the input pin each of the 10 output pins becomes active sequentially.
For instance applying 5 clock pulses activates the 5th output while the rest of the pins remain inactive.
Pin 15 can be used to reset the count back to zero if all 10 outputs are not required.
In our case we use only 4 output pins: pin 3, 2, 4 and 7 (outputs Q0, Q1, Q2, Q3).
Pin 15 is connected to output pin Q4 or pin 10 causing the output pins 3, 2, 4 and 7 to remain active while the other 6 output pins stay inactive.
With the 200Hz signal fed into the clock pin of IC 4017 we only connect two alternate outputs: Q0/pin 3 and Q2/pin 4.
The remaining pins are left unconnected.
The modified sine wave which will be further amplified by MOSFETs in the final stages of the circuit construction will be acquired by using an oscilloscope to observe the waveform on pins 3 and 4.
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