12-Vdc-battery-operated-120-vac-power-source

Description: A simple 120 V to 24 V center-tapped control transformer, along with four additional components, can accomplish the task. This circuit produces a clean 200 V peak-to-peak square wave at 60 Hz and is capable of supplying up to 20 W. The circuit operates in a self-starting and free-running mode. If transistor Q1 has a faster response time and higher gain than transistor Q2, it will turn on first when input power is applied, keeping Q2 off. The load current and transformer magnetizing current then flow through the upper half of the primary winding, and the auto transformer action provides the necessary base drive until the transformer reaches saturation. Once saturation occurs, Q1 loses its base drive.

As Q1 turns off, the transformer voltages reverse, activating Q2 and repeating the cycle. The output frequency is influenced by the transformer core material and the input voltage, remaining largely unaffected by the load. Typically, the frequency will range from 50 to 60 Hz when utilizing a 60 Hz transformer in conjunction with a car battery or equivalent power source. The output voltage is determined by the turns ratio and the difference between the input voltage and the saturation voltage of the transistors. For applications requiring higher power, larger transformers and transistors should be utilized. This type of inverter is commonly employed in radios, phonographs, hand tools, shavers, and small fluorescent lamps. However, it is not suitable for reactive loads (such as motors) or loads with high inrush currents, including coffee pots, frying pans, and heaters.

The circuit design employs a center-tapped transformer which plays a crucial role in generating the required square wave output. The transformer is configured to step down the input voltage from 120 V to 24 V, allowing for efficient operation within the specified power range. The inclusion of transistors Q1 and Q2 in a push-pull configuration enables the inverter to alternate the conduction between the two devices, effectively creating the square wave output.

The self-starting feature of the inverter is essential for reliable operation, ensuring that the circuit can initiate without external triggering mechanisms. The feedback loop created by the transformer’s auto transformer action is vital, as it provides base drive to Q1 until saturation is reached. This saturation condition is a critical point in the operation, as it facilitates the transition to Q2, allowing for continuous oscillation and stable output.

The output waveform is characterized by its peak-to-peak voltage, which is a function of the transformer turns ratio and the applied input voltage. The design must consider the saturation characteristics of the transistors to ensure that the output remains within operational limits. Additionally, the inverter's inability to handle reactive loads must be taken into account during application, as this could lead to circuit failure or inefficiency.

In practical applications, the choice of components, particularly the transformer and transistors, should align with the desired output specifications. Larger transformers and transistors can enhance performance and reliability for higher power applications. The circuit's simplicity makes it an attractive solution for low-power devices, while its limitations should guide the selection of appropriate use cases.A simple 120 V: 24 V, center-tapped control transformer and four additional components can do the job. This circuit outputs a clean 200 V pk-pk square wave at 60 Hz and can supply up to 20 W. The circuit is self-starting and free-running. If Q1 is faster and has a higher gain than Q2, it will tum on first when you apply the input power and will hold Q2 off.

Load current and transformer magnetizing current then flows in the upper half of the primary winding, and auto transformer action supplies the base drive until the transformer saturates. When that action occurs, Q1 loses its base drive. As it turns off, the transformer voltages reverse, turning Q2 on and repeating the cycle. The output frequency depends on the transformer iron and input voltage, but not on the load. The frequency will generally range between 50 to 60 Hz with a 60-Hz transformer and car battery or equivalent source. The output voltage depends on turns ratio and the difference between input voltage and transistor saturation voltage.

For higher power, use larger transformers and transistors. This type of inverter normally is used in radios, phonographs, hand tools, shavers, and small fluorescent lamps. It will not work with reactive loads (motors) or loads with high inrush currents, such as coffee pots, frying pans, and heaters.