Simple IC 555 Inverter Circuit: 5 Designs Explored

The IC 555 is a popular timer IC which we can use for making different types of inverter circuits. With a few extra components we can make the IC 555 generate switching pulses, and then we can use these pulses for converting battery DC into AC power.

In this article we will look at 5 different inverter designs using the IC 555. These include simple square wave inverters, full bridge inverters, SPWM sine wave inverters and one design with automatic battery protection.

Each design works in a different way and has its own good points and limitations. So you can select the design according to your requirement and then visit the respective detailed article to understand the complete circuit diagram, component values and working principle.

Important: These circuits can generate dangerous high voltage AC. Some designs also use high voltage DC internally. So let us be careful and never touch the circuit while it is powered. We must also check the circuit properly before building it, since not every circuit has been practically tested.

1. Basic IC 555 Inverter Circuit

This is one of the simplest types of inverter circuits using an IC 555 timer. Here we configure the IC as an astable oscillator so that it can generate low frequency switching pulses.

We can use these pulses to operate a power transistor or MOSFET stage connected to a suitable transformer. The transformer then converts the battery voltage into a higher AC voltage.

This type of transistor inverter can be quite simple to build, so you can use it for understanding the basic working principle of an inverter.

The output is generally a square wave, but it is not the same as the pure sine wave that we get from a normal household AC supply.

We must select the oscillator frequency, transistor ratings, transformer rating and battery capacity correctly, so that the circuit can work properly.

Read the complete circuit here: [BASIC IC 555 INVERTER ARTICLE URL]

2. IC 555 Full Bridge Inverter Circuit

A full bridge inverter uses four switching devices arranged in an H-bridge configuration. Here the switching devices work in pairs so that they can reverse the polarity applied to the load or transformer.

We can use the IC 555 as an oscillator for generating the required low frequency switching signal. But we also need additional circuitry to produce the correct switching sequence and prevent the two devices in the same bridge leg from conducting at the same time.

A full bridge arrangement can make better use of a suitable DC supply and transformer, but the actual performance depends on the circuit design and the switching devices we use.

The original circuit shown in this design uses an unusual supply arrangement, so we must check it carefully before construction. We should not assume that it is a tested 200 watt inverter.

Read the complete circuit here: [IC 555 FULL BRIDGE INVERTER ARTICLE URL]

3. IC 555 Modified Square Wave Inverter Circuit

A basic IC 555 inverter produces square wave AC. But if we want to get a waveform closer to a sine wave, then we can use a pulse width modulation technique.

In this design an operational amplifier circuit generates the reference waveforms required for producing SPWM pulses. The IC 555 is then used to generate pulses whose widths change according to the modulation signal.

These pulses control the power switching stage and transformer. With a properly designed output stage and suitable filtering, we can get an AC waveform that is closer to a sine wave.

The quality of the output depends on the PWM generation method, switching stage, transformer, output filter and load.

This circuit is more complicated than the basic square wave inverter, so we must check the oscillator frequency and switching arrangement carefully before building it.

Read the complete circuit here: [IC 555 Modified Squarewave INVERTER ARTICLE URL]

4. IC 555 Sine Wave Inverter Using SPWM

This is an easy way of making an SPWM inverter using the IC 555 together with an operational amplifier such as the IC 741.

In this design a high frequency triangular waveform is compared with a lower frequency reference waveform to produce pulses with changing widths. These SPWM pulses are then used to control the inverter power stage.

The IC 555 oscillator provides the timing signal, while the additional circuit generates the modulation required for shaping the output waveform.

The good thing about this method is that we can build the timing and modulation sections using commonly available components.

But we must make sure that the switching frequency, output frequency and gate or base drive signals remain properly synchronized. A suitable output filter may also be required, depending on the design.

Read the complete circuit here: [IC 555 SPWM INVERTER ARTICLE URL]

5. IC 555 Transformerless Inverter Circuit

This design uses an IC 555 oscillator to control a full bridge made from four N-channel MOSFETs.

Unlike a normal low voltage transformer inverter, this arrangement uses a DC-to-DC converter module to get a high voltage DC supply. The MOSFET bridge then switches this DC supply to produce an AC output.

So in this design the high voltage conversion takes place electronically instead of using a conventional low frequency transformer.

This arrangement can reduce the size of the magnetic components, but it also needs some extra care during design. The DC-to-DC converter, MOSFET bridge, gate drivers and protection circuits must all be suitable for the operating voltage and load.

Safety warning: The high voltage DC bus can be lethal even when the input comes from a low voltage battery. So we should not treat this as a beginner circuit.

Read the complete circuit here: [TRANSFORMERLESS IC 555 INVERTER ARTICLE URL]

Which IC 555 Inverter Circuit Should You Choose?

The best design depends on what you want to build.

A basic square wave inverter is the simplest starting point, so you can use it to understand how an inverter works. A full bridge design may be suitable when its switching and driver stages are designed properly. An SPWM inverter needs some extra circuitry, but it can produce a waveform closer to a sine wave.

A transformerless inverter is more complicated since it uses a high voltage DC bus. A design with Arduino battery monitoring adds control and protection functions, but it also needs suitable programming and testing.

Before selecting a circuit, let us check the required output voltage, output frequency, continuous power rating, battery voltage, transformer rating and expected load.

We should not select an inverter only by looking at the power rating mentioned in the circuit description. The actual output power depends on the complete design and the ratings of the components we use.

Final Words

The IC 555 is a useful timer IC which we can use for making many types of inverter circuits. By changing the oscillator, modulation circuit and power stage, we can build different inverter designs for different purposes.

The 5 designs explained above gives us a starting point for understanding these possibilities. You can visit the individual circuit articles to see the detailed schematics and explanations before selecting a design for construction.