This is the 3rd part of my note on building a diy 12V to 220V AC Inverter using TL494 PWM controller IC. In the previous notes How to Design 12V DC to 220V AC Inverter Circuit and DIY 12V DC to 220V AC Inverter using TL494 PWM, I showed how to build the circuit. I explained the components and their roles in the inverter circuit. Here I will be showing how the inverter circuit actually works through simulation.
The circuit diagram of the inverter is shown below.
Then when the circuit simulation starts, you will see the wires will turn red and green. The red line indicates high voltage connection - 12V or voltage above ground. And the greenish color shows the ground or near ground. If you look at the AC voltmeter reading, the output voltage is not as expected, and the circuit is not oscillating.
To make the circuit oscillate, we need to adjust the frequency adjustment control potentiometer RV1. The RV1 potentiometer and C1 capacitor function together as the RC timing network that sets the inverter's operating frequency. Connected to the TL494’s RT (pin 6) and CT (pin 5) terminals, they determine the speed of the internal oscillator; adjusting RV1 varies the resistance to fine-tune the output to a stable frequency. This calibration is essential to compensate for component tolerances, ensuring the transformer and connected AC loads operate at their designed frequency for maximum efficiency and safety.
To show how the circuit works, we need to connect a 12V lead acid battery like car battery to the input, J1 connector header, connect 220V bulb and connect AC voltmeter at the output, J2 header, to see the voltage at the load, that is the bulb.
Then when the circuit simulation starts, you will see the wires will turn red and green. The red line indicates high voltage connection - 12V or voltage above ground. And the greenish color shows the ground or near ground. If you look at the AC voltmeter reading, the output voltage is not as expected, and the circuit is not oscillating.
To make the circuit oscillate, we need to adjust the frequency adjustment control potentiometer RV1. The RV1 potentiometer and C1 capacitor function together as the RC timing network that sets the inverter's operating frequency. Connected to the TL494’s RT (pin 6) and CT (pin 5) terminals, they determine the speed of the internal oscillator; adjusting RV1 varies the resistance to fine-tune the output to a stable frequency. This calibration is essential to compensate for component tolerances, ensuring the transformer and connected AC loads operate at their designed frequency for maximum efficiency and safety.
Watch the TL494 output pins 9 and 10 while adjusting frequency adjustment potentiometer RV1. The output from these pins will turn on and off alternatively as the signals are generated. Then you will see at certain RV1 value, the circuit starts oscillating and the bulb turns on.
As you can see the high side and low side turn on and off alternatively. The AC voltmeter shows 220V which illustrates that this circuit works.
To confirm the output, we then analyze the output signal waveform and the frequency spectrum of the signal. To do this we will use the oscilloscope and fourier spectrum graph.
The oscilloscope shows output signal is a nice and clean square wave.
To see the output signal spectrum, a voltage probe is added at the output. The Fourier Graph is used to view the output signal in frequency domain.
The output signal frequency spectrum is shown below.
The peak is around 17.8KHz. So, the output signal is a 17.8KHz square wave.
That's it. The simulation is complete. The simulation showed that this inverter design with TL494 is working. The simulation showed how to connect input and analyze the output signal, voltage, signal waveform and frequency analysis.
The video below shows the complete simulation analysis of the TL494 based Inverter design.
Don't forget to see the first and second part of the tutorial.
