Realization of Circuit Diagram of Sinusoidal Wave Output Inverter Power Supply Controlled by Single Chip Microcomputer

Single chip microcomputer STM32L151CCU6

Probe domestic double-head probe 038-BB-5.7L The shape of the two ends of the needle is outside the pointed needle

1206RGB (single)

MOS power IC full range

Overview:
Introduction Low-voltage small-power inverter power supplies have been widely used in industrial and civil applications. In particular, the development and utilization of new energy sources, such as the widespread use of solar cells, requires an inverter system to convert the DC voltage output from the solar cell into 220V, 50Hz AC voltage for ease of use. This paper presents a design of a sine wave output inverter power supply controlled by a single-chip microcomputer. It uses 12V DC power supply as input and outputs 220V, 50Hz, 0~150W sine wave AC power to meet the power supply requirements of most conventional small appliances. . The power supply adopts push-pull boost and full-bridge inverter two-stage conversion, and the front and rear stages are completely isolated. In the control circuit, the pre-stage push-pull boost circuit is controlled by SG3525 chip, and the sampling transformer winding voltage is used for closed-loop feedback. The inverter part adopts single-chip digital SPWM control mode, sampling DC bus voltage for voltage feedforward control, and sampling current for feedback. Control; in protection, it has multiple protection function circuits such as input overvoltage, undervoltage protection, output overload, short circuit protection, overheat protection, etc., which enhances the reliability and safety of the power supply.
The power supply can output 220V±10V sine wave AC voltage within the range of input voltage from 10.5V to 15V, frequency 50Hz±O.5Hz, DC component

l The main circuit of the main circuit inverter power supply adopts push-pull boost and full-bridge inverter two-stage conversion, as shown in Figure 1.



One end of the input voltage is connected to the middle tap of the primary side of the transformer, and the other end is connected to the midpoint of the switch tubes S1 and S2. Control S1 and S2 turn on in turn, form a high-frequency AC voltage on the primary side of the transformer, and obtain about 370 V DC voltage on capacitor C1 through transformer boosting, rectification and filtering. The inverter bridge composed of S3 to S6 adopts sinusoidal pulse width modulation, and the inverter output voltage is filtered by the inductor L and the capacitor C2, and finally a 220 V, 50 Hz sine wave alternating current is obtained on the load. The use of high-frequency transformers to achieve isolation between the front and rear stages is beneficial to improve the safety of the system.
Input voltage 10.5 ~ 15 V, input maximum current 15 A, consider double the margin, push-pull circuit switch tube S1 and S2 withstand voltage not less than 30 V, forward current is not less than 30 A, select IRFZ48N.
The design of the step-up high-frequency transformer should be such that when the input voltage is lowest, the secondary voltage is not less than the minimum voltage required by the inverter part after rectification is 350 V. When the input voltage is the highest, the secondary voltage cannot be too high to avoid damage. Device. At the same time, the voltage drop and heat generation on the winding must also be considered. The EE type ferrite core is selected, and the primary and secondary windings are 7 匝: 300 匝.
The output secondary rectifier bridge of the transformer consists of four HER307. The filter capacitor uses 68μF and 450V electrolytic capacitors.
According to the output power requirement, the effective value of the output current is 0 6 to 0.77 A. Considering a certain voltage and current margin, the S3 to S6 in the inverter bridge selects the IRF840. The inverter part adopts unipolar SPWM control mode, and the switching frequency fs=16 kHz.
If the time constant of the filter is 16 times of the switching period, that is, the resonance frequency is 1 kHz, the filter inductor LC is 2.5×10-3, and L=5 mH and C=4.7μF can be selected. The filter inductor L is a ring-shaped iron powder core with an inner diameter of 20 mm and an outer diameter of 40 mm. The winding is made of 2 strands of enameled wire with a diameter of 0.4 mm and the number of turns is 180 匝.

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