What is a sine wave inverter

A sine wave inverter is a type of inverter, which is a power electronic device that converts DC electrical energy (power cells, batteries) into AC power (usually 220V, 50Hz sine wave). An inverter is the opposite process to an ACDC converter. As the ACDC converter or power adapter will be 220V AC rectified into DC to use, and the role of the inverter is the opposite, so the name!

The sine wave inverter is a power conversion device that converts DC power into AC power, and it accomplishes the inversion task through the conduction and shutdown of power semiconductor devices according to a specific law. Modern inverter technology is a science that studies the theory and application of inverter circuits and design methods, which is established on the basis of industrial electronics, semiconductor device technology, modern control technology, modern power electronics, pulse width modulation technology, semiconductor converter technology and magnetic materials and other sciences, a practical technology, so the application of sinusoidal wave inverters throughout the society and life in many fields.

Basic Structure of Sine Wave Inverter

Sine wave inverter is a conversion device that converts DC power into AC power. It converts DC power into AC power by controlling the conduction and shutdown of semiconductor power switching devices (such as SCRs, GTOs, GTRs, IGBTs, and power MOSFETs, etc.). Control power switching tube conduction and shutdown circuit is the inverter control circuit, the control circuit outputs a certain voltage pulse, so that the power conversion circuit in the power switching tube in accordance with a certain law of conduction and shutdown, then the output of the main power circuit for a specific harmonic combination, and finally through the filter circuit to get the required voltage waveform. The basic structure of the sinusoidal inverter system is shown in Fig. 1.

Input circuit

The input to the inverter is usually DC (or DC obtained from the utility power after rectification and filtering), which includes DC grid, storage battery, photovoltaic battery and DC obtained by other means. Usually, these power can not be directly used as the input voltage of the inverter, but through certain filtering circuit and EMC circuit before being used as the input of the inverter.

Inverter main circuit

The main circuit of the inverter is a power conversion circuit composed of power switching devices. There are many different types of main circuit structure, and under different input and output conditions, the main circuit form is not the same, each type of power conversion circuit has its advantages and disadvantages, and the most suitable circuit topology should be considered as the main circuit structure in the actual design.

Control circuit

The control circuit generates one or more sets of pulse voltages according to the output requirements of the inverter through certain control techniques, and acts on the power switching tubes through the driving circuit, so that the power switching tubes are turned on or off according to the specified order, and the required voltage waveforms are finally obtained at the output of the main circuit. The role of the control circuit is crucial to the inverter system, and the performance of the control circuit directly determines the quality of the inverter output voltage waveform.

Output Circuit

The output circuit generally includes output filter circuit and EMC circuit, and if the output is DC, a rectifier circuit should be added at the back. For the isolated output inverter, the output circuit should also have an isolation transformer at the front stage. According to whether the output needs a voltage regulator circuit, the output circuit can be divided into open-loop and closed-loop control. The output of the open-loop system is only determined by the control circuit, while the output in the closed-loop system is also affected by the feedback loop to make the output more stable.

Auxiliary power supply

Control circuits and input/output circuits have specific input voltage requirements for certain parts or chips, and the auxiliary power supply can meet the specific voltage requirements in the circuit. Usually the auxiliary power supply consists of one or several DC-DC converters. For AC input, the auxiliary power supply consists of the rectified voltage combined with the DC-DC converter.

Protection circuits

Protection circuits usually include input overvoltage and undervoltage protection, output overvoltage and undervoltage protection, overload protection, overcurrent and short circuit protection. There are other protections for inverters working in specific applications, such as temperature protection for very low or high temperatures, air pressure protection for certain air pressure changes, and humidity protection for humid environments.