Simple Inverter Circuit using Two 2N3055 Transistors

In this post we will discuss how to build a very simple cross coupled inverter circuit using just a couple of 2N3055 transistors.

This simple inverter is capable of generating 220V 100 W which can be used to power small home appliances using a 12V battery.

How the Circuit Works:

Parts List:

Below mentioned are the process of circuit working:

The inverter operates as a saturable core oscillator.

It uses a filament transformer and two general purpose germanium power transistors.

Cross coupled connections in the manner of a multivibrator generate the necessary feedback for oscillation.

The inverter is designed to be powered from an automobile battery.

The filament transformer plays a crucial role in the circuit.

The transformer helps step up or step down the voltage to the required level for the inverter operation.

The germanium power transistors act as switches in the circuit.

During oscillation these transistors switch on and off alternatively generating an AC output.

At full load the efficiency of the inverter is approximately 75%.

The output voltage is around 220V.

A mild pi section filter is employed to despike the output waveform.

This filter causes a trapezoid wave rather than the usual square wave to be available at the output.

The filtered waveform is more suitable for powering radios, recorders and other electronic equipment.

The efficiency, frequency, output voltage and starting ability are interdependent.

Experimentation with biasing resistances especially R1 may be necessary to optimize performance.

Balancing the biasing networks for the two transistors is crucial to avoid waveform asymmetry and malfunctions.

After assembling the circuit power it on and test its performance.

Use a multimeter to measure the output voltage and ensure it meets the design specifications.

Fine tune the circuit parameters if necessary to achieve the desired performance.

Remember, for an actual implementation you would need a detailed circuit diagram with component values and connections.

This description provides a conceptual overview of how the inverter works allowing you to better understand its operation during the construction process.

Formulas:

The cross coupled transistor based inverter functions primarily as a flip flop or bistable multivibrator circuit and does not require capacitors, instead it uses resistors exclusively for timing.

In these kinds of circuits, resistor timing along with transistor characteristics rather than capacitive charging and discharging determines the frequency.

In this instance, the time constants established by the resistors and the intrinsic characteristics of the transistors (such as switching speed and propagation delays) are often used to compute the frequency at which the flip flop circuit oscillates.

An approximation of the frequency formula for this type of circuit is:

f = 1 / 2 * R * C_eff​

where,

• f: is the oscillation frequency in hertz Hz
• R: represents the timing resistors resistance in ohms Ω (simplistically assuming equal resistors)
• C_eff : denotes the effective capacitance because of to the transistors junction capacitances and parasitic capacitances.
• In real terms, C_eff stands for the effective capacitance that modifies the circuit timing.
• It comprises any parasitic capacitances in the circuit as well as the transistor junction capacitances.

The particular transistors utilized and the circuit design might affect C_effs precise value.

It is crucial to remember that, in contrast to conventional oscillator circuits using capacitors the properties of the transistor and the cross coupled arrangement also have a role in determining the frequency in a resistor based flip flop circuit.

Consequently, in real world applications, accurate frequency computation frequently necessitates simulation or empirical measurement.

How to Build:

Building a Simple 50 Hz Inverter circuit:

• Collect all the necessary components listed above.
• Ensure that you have the correct values for resistors, capacitors, and inductors as specified in the design.
• Study the circuit diagram provided, paying attention to the connections, transistor placement, and the overall configuration.
• Understand the purpose of each component in the circuit.
• Place the components on the breadboard or solder them onto the PCB according to the circuit diagram.
• Be meticulous in your connections, ensuring that there are no short circuits or loose connections.
• Connect the inverter to the automobile battery.
• Ensure the polarity is correct and that the battery has sufficient charge.
• Experiment with the biasing resistances particularly R1 to optimize the performance of the inverter.
• It may be necessary to balance the biasing networks for both transistors to avoid waveform asymmetry and other issues.
• Power on the inverter and test its performance.
• Use a multimeter to measure the output voltage ensuring it is approximately 220V.
• Verify that the inverter can handle the intended load without overheating or malfunctioning.
• If needed, fine tune the circuit parameters to achieve the desired efficiency frequency and starting ability.
• This may involve further adjustments to biasing resistances or other components.

Caution:

• Be cautious while working with electronic components and power supplies.
• Follow safety guidelines and take necessary precautions to avoid electrical hazards.
• By following these steps and carefully implementing the circuit design, you can build a functional 50 Hz inverter capable of powering various electronic devices.
• Lets describe the working principle of the simple 50Hz inverter based on the information given.
• You can use this description to create or find a detailed circuit diagram for implementation.

Conclusion:

By following this construction details provided in this post, enthusiasts and professionals alike can create a functional and efficient 50Hz simple cross coupled inverter circuit using just two 2N3055 transistors.

Leveraging proven designs and learning from the empirical design debugging conducted by manufacturers will undoubtedly lead to successful outcomes in building and optimizing such circuits.

References

Cross- Coupled Inverter Circuit

Data sheet 2N3055