IC 555 Inverter Circuit

The demand for portable power solutions is ever growing especially in scenarios where access to mains outlets is limited such as in cars, trailers or cottages.

Constructing your own DC/AC power inverter provides a versatile solution to power various household appliances like radios, DVD players, electric shavers and more.

What is a IC 555 Inverter Circuit:

An IC 555 inverter circuit is a circuit that uses the popular IC 555 circuit to generate an oscillating waveform, which is then used to drive a power inverter.

A power inverter is a device that converts direct current DC power into alternating current AC power.

The IC 555 is commonly used in electronic circuits due to its versatility and ease of use.

This article will guide you through the construction of a power inverter, incorporating key components such as the 555 IC, MOSFETs, transformers and heatsinks.

Circuit Working:

Parts List:

Frequency Generation with 555 IC

To generate a stable 50Hz frequency a well known 555 IC is employed.

The frequency is determined by the values of resistance Rx and capacitor Cx.

The formula for frequency (f) is given by:

f = 1 / 0.693 × ( Rx + 2 × R1 ) × Cx

where,

• f: is a oscillation frequency (f) in an inverter circuit based on an IC 555 .
• Rx: This resistor controls the timing capacitors Cx rate of charging and discharging in conjunction with R1, The oscillations timing interval is set by it.
• R1: By affecting the capacitors rate of charging and discharging, R1 influences the oscillation frequency in conjunction with Rx.
• Cx: This capacitor creates the timing network that regulates oscillation frequency along with Rx and R1.
• The square wave output is produced by the capacitor charging and discharging through Rx and R1.

MOSFETs and Logic Inverter

Two N type MOSFETs act as switches in the inverter.

One is directly driven by the 555 IC, while the other is controlled through a logic inverter using a BC547 transistor.

The use of MOSFETs ensures efficient power switching.

The overall circuit design must account for proper isolation and grounding.

Transformer Selection

Select a mains transformer with two secondary windings of 12V each.

The transformer should be designed to handle the maximum load requirements.

The formula for power P is given by:

P = V × I

where:

• P is power
• V is voltage and
• I is current.

Heatsink Considerations

Ensure the heatsink for the power transistors is appropriately sized based on the anticipated load.

The heatsinks should be mounted on isolation pads to prevent unwanted grounding.

Alternatively, separate heatsinks for each transistor can be used provided they do not touch each other or ground.

Power Supply and Frequency Adjustment

Maintain a sufficiently hard 12V supply with a voltage range of about 11 to14V.

Integrate a proper fuse in series with the power input for safety.

For applications not reliant on a 50Hz frequency, a higher frequency 100 to 300Hz can be utilized to reduce standby power.

Adjust the frequency by modifying the values of Rx and Cx.

MOSFET Selection

Select the appropriate MOSFET based on the load requirements:

IRFZ44 for loads up to 200W

IRFZ48 for loads up to 350W

IRF3205 for loads up to 600W Combine multiple IRF3205 transistors in parallel for outputs exceeding 600 watts.

The IRF1405 is also recommended for its excellent parameters.

Frequency Generation

Connect the 555 IC to the breadboard.

Connect Rx and capacitor Cx to the 555 IC as per the selected values for frequency.

Use the formula mentioned earlier to determine the resistor and capacitor values for the desired frequency.

MOSFETs and Logic Inverter

Connect two N type MOSFETs to the breadboard.

Connect one MOSFET directly to the 555 IC and the other through a BC547 transistor acting as a logic inverter.

Ensure proper grounding and isolation to prevent unwanted interference.

Transformer Connection

Connect the mains transformer to the circuit, ensuring both 12V secondary windings are utilized.

Size the transformer according to the anticipated maximum load.

Heatsink Integration

Mount the power transistors on the heatsink.

Use isolation pads to prevent grounding.

Alternatively, use separate heatsinks for each transistor ensuring they do not touch each other or ground.

Power Supply and Fuse

Integrate a 12V power supply with a voltage range of 11 to 14V.

Include a proper fuse in series with the power input to enhance safety.

Frequency Adjustment and MOSFET Selection

Adjust the frequency by modifying the values of Rx and Cx as needed.

Choose the appropriate MOSFET based on the anticipated load, referring to the provided guidelines.

Warning:

Exercise extreme caution while working with the power inverter, as the output voltage can be lethal.

Although the input is safe touching both output terminals can pose a serious danger.

The output voltage is isolated from the ground, but users must be vigilant.

The construction and operation of the inverter are undertaken at the users own risk, and the author bears no responsibility for any harm incurred.

Always prioritize safety precautions and adhere to proper guidelines when working with electrical components.

Conclusion:

By following these process and adhering to safety norms, you can successfully construct a DC/AC power inverter for portable power applications.

Always double check your connections, ensure proper insulation, and prioritize safety throughout the construction process.