The main circuit of several kinds of inverter of photovoltaic junction box all need to have control circuit to realize, generally have square wave and positive and weak wave two kinds of control way, square wave output inverter power circuit is simple, low cost, but low efficiency, large harmonic component.Sine wave output is the development trend of inverter. With the development of microelectronics technology, the microprocessor with PWM function has come out. Therefore, sine wave output inverter technology has been mature.

1, square wave output inverter is currently used pulse width modulation integrated circuit, such as SG3525, TL494 and so on.Practice has proved that using SG3525 integrated circuit and power field effect tube as switching power component can realize inverter with higher performance and price. Because SG3525 has the ability to directly drive power field effect tube and has internal reference source, operational amplifier and under-voltage protection function, its peripheral circuit is very simple.

2, sine wave output of the inverter control integrated circuit, the output sine wave inverter, the control circuit can be controlled by microprocessor, the microcontroller is of multiplex PWM generator, and can be set up, on the bridge arm between the dead zone time, sine wave output circuit is realized by using 80 c196n, 80 c196n complete sine wave signal, and detection of ac output voltage, voltage regulator.

Selection of power components for the main circuit of photovoltaic junction box inverter:

Inverter is important, however, the choice of the main power of the components currently used more power components with darlington power transistor, the power field effect tube, insulated gate transistors and can turn off thyristor, etc., in a small capacity more for MOSFET device is used in low voltage system, because of MOSFET has lower pressure drop and high switch frequency, in the high voltage large capacity system generally adopts IGBT module, this is because the MOSFET with the increase of voltage its on state resistance also increase, and the advantage of IGBT in the capacity of the system in a large, and in big volume in the system,GTO is generally used as the power element.