From selecting the type of power switch to PCB layout, many design decisions can affect the robustness of high-power inverter design. The following summarizes some key points in the design of high-power inverters:

The first step in designing a high-power inverter PCB system is to determine the type of power switch. Power switches have unique functions and requirements, such as voltage, temperature range, and operating frequency limitations, which will drive many design decisions for high-power inverters, including which type of gate driver to use. The four main power switches are:

Silicon MOSFET

Insulated Gate Bipolar Transistor (IGBT)

Silicon carbide (SiC)

Gallium Nitride (GaN)

Working voltage is another factor to consider in inverter PCB design. Designers must evaluate the maximum voltage that the system can withstand under normal conditions and ensure that the gate driver and power switch can meet these power requirements. For gate drivers, the rated operating voltage will exceed the maximum expected peak voltage. For power switches, the empirical rule is that the maximum expected peak voltage should be less than 80% of the rated voltage of the equipment series.

Gate drivers and power switches have critical protection requirements that must be addressed during inverter PCB design. For example, voltage issues can generate heat and efficiency losses. Overvoltage can cause damage to the power switch. Fortunately, these issues can be addressed through solutions such as desaturation detection, using Miller effect to prevent switch parasitic connections, and meticulous PCB layout techniques.

Another factor to consider in inverter PCB design is the dependency on the application program. For example, stable high-power applications such as stable operation of industrial motor inverters may not require much protection. On the contrary, dynamic applications such as electric vehicle traction inverters may require extensive system protection. PCB layout is also an important factor to consider in the inverter PCB design process, as it determines the performance, efficiency, and reliability of the power circuit. A carefully planned PCB layout can reduce parasitic inductance and capacitance, and improve reliability and efficiency.

The final consideration in inverter PCB design is how to supply power to the secondary side of the half bridge device. This task can be completed cautiously or comprehensively. Therefore, when designing high-power inverter PCBs, please find suitable power switch technology and gate drivers for your system application, consider key protection requirements, and choose gate drivers that can provide corresponding solutions.

Following the principle of "fixed before moving, large before small, and difficult before easy", priority is given to laying out important unit circuits and core components with fixed positions. For components that require positioning, such as tooling holes, connectors, etc., they are assigned an immovable attribute and their dimensions are labeled.

Temperature sensitive components should be kept away from heat generating components; Components with high heat generation should be placed at the air outlet or in a location conducive to convection. Components with high heat generation should be placed at the air outlet without blocking the air duct; The radiator should be placed in a location that is conducive to convection.

Decoupling components should be placed near the power input end. RF chips are very sensitive to power noise, so each chip uses some capacitors and shielding inductors to ensure that all power noise is filtered out. It is required that the filtering components be placed near the chip to ensure good filtering before power input, otherwise the noise will radiate to the entire PCB side.

Refer to the schematic diagram and layout the main components according to the important (critical) signal flow direction.

When laying out, try to meet the following requirements: the overall wiring should be as short as possible. The main signal line must be the shortest. The fewer through holes, the better. Thoroughly isolate high voltage and high current signals from low voltage and low current weak signals; During design, analog signals and digital signals need to be separated; Of course, high frequency and low frequency should also be separated; The spacing between high-frequency components should be sufficient.

The crystal oscillator should be placed closest to the chip, but not near the edge of the circuit board.

Inductors or magnetic beads cannot be placed side by side. If they are placed side by side, they will form hollow transformers and cause interference signals due to mutual induction. The distance between them should be at least greater than the height of one of the components or placed at a right angle to minimize mutual inductance.

Symmetric layout should be adopted as much as possible for voltage divider circuits, differential circuits, and circuit parts with the same structure; Put components with the same power supply together.

On the premise of meeting electrical performance, optimize the layout according to the principle of uniform distribution, balance the center of gravity, and try to be as beautiful and neat as possible.

The photovoltaic power generation system mainly includes inverters, controllers, photovoltaic cell arrays, energy storage devices, etc. Photovoltaic inverter, also known as photovoltaic inverter power supply, has a complex working principle. Its main function is to convert direct current energy (DC energy) into alternating current energy (AC energy) through semiconductor power switches, meeting the needs of AC loads, equipment power supply, and grid connected power generation. So PCB is the circuit board for photovoltaic inverters, as well as the circuit board for solar inverters.

According to the frequency of the AC power output by the inverter, the photovoltaic inverter PCB board can be divided into power frequency inverters (values 50-60Hz), medium frequency inverters (values 400HZ to XNUMX, XNUMXkHz), and high-frequency inverters (values XNUMX, XNUMXkHz to MHz).

According to the number of phases of the output AC power supply, photovoltaic inverter PCB boards can be classified into single-phase inverters, three-phase inverters, and multi-phase inverters by type; According to the direction of electrical energy, it can be divided into active inverters and passive inverters.

According to the main circuit structure, the PCB circuit of photovoltaic inverters can be divided into single ended inverters, half bridge inverters, full bridge inverters, and push-pull inverters.

According to the power level, photovoltaic inverter PCB circuits can be divided into low-power inverters (below 1kW), medium power inverters (1-10kW), and high-power inverters (above 10kW).

Photovoltaic inverters are mainly composed of semiconductor power devices, inverter drivers, control circuits, etc. Among them, high-power semiconductor switching devices include insulated gate transistors (IGBT), power field-effect transistors (VMOSFETT), turn off transistors (GTO), MOS control transistors (MCT), electrostatic induction transistors (EIT), electrostatic induction thyristors (SIT), intelligent power modules (IPM), etc.

In photovoltaic systems, the electrical energy of solar cells is stored and converted into 220V or 380V AC power by inverters. The output voltage fluctuates greatly, so the requirements for inverters are high. The steady-state output voltage change rate fluctuates around 5%, and when the load suddenly changes, the output voltage change rate should fluctuate around 10%.

In general, the waveform distortion rate should not exceed 5%. If the waveform distortion rate is too high, it will cause serious heating of the load components, which is not conducive to the service life of the equipment and devices, and even affect the use of the entire system.

The optimal frequency operating point of the motor is 50Hz. If the frequency is too high or too low, it can easily cause equipment heating, reduce the operating efficiency and service life of the system.

Ceramics are the best material for photovoltaic inverter PCBs, and they have many advantages.

Good insulation: Ceramic material PCB has good insulation and stability, with a breakdown voltage of up to 20kV/mm, and can instantly withstand sudden changes in high current and high voltage, ensuring the normal operation of devices and systems

High thermal expansion coefficient: The thermal expansion coefficient of ceramics and chips is close, and they will not produce excessive deformation when the temperature difference changes sharply, which may cause problems such as circuit desoldering and internal stress. It is a very suitable material for making photovoltaic inverter PCB boards.

Powerful temperature management capability: Ceramic material PCBs also have high thermal conductivity, good heat dissipation performance, and can work in harsh outdoor environments such as high and low temperatures, which can also improve the service life of photovoltaic systems.

China is a major exporter of photovoltaic products. Due to the increasing environmental protection requirements for photovoltaic products and the impact of product updates caused by overcapacity in our country's photovoltaic products, ceramic circuit boards made of inorganic materials, pollution-free, good heat dissipation, and high stability are used as important components of photovoltaic inverters and solar panels, also known as solar cell modules.

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