The performance of sine wave inverter power supply is related to the following factors:
Circuit topology structure
Push pull circuit: This type of circuit has a simple structure and uses relatively fewer power switching transistors. Its transformer core has a high utilization rate and can effectively convert DC to AC. For example, in some low-power inverter power supplies, push-pull circuits can provide relatively stable sine wave output. However, its disadvantage is that the power switch tube is subjected to high voltage stress, and in the case of high voltage input, the requirements for the switch tube are relatively high.
Full bridge circuit: The advantage of a full bridge circuit is that it has a high output power and is suitable for medium to high power inverter power supplies. It achieves inversion through the alternating conduction of four power switch tubes, which can better control the output waveform. Compared with push-pull circuits, each switch in a full bridge circuit bears relatively less voltage stress, but the circuit structure is relatively complex and the cost is also higher.
Half bridge circuit: Half bridge circuit is between push-pull and full bridge in terms of power capacity and switch voltage stress. Its circuit structure is relatively simple, and the requirements for power switch tubes are not as high as full bridge. It is commonly used in situations where power requirements are not particularly high but cost is sensitive.
control mode
Analog control method: Early inverter power supplies mostly used analog control method, which controlled the output waveform through analog circuit components (such as operational amplifiers, etc.). The advantage of this method is its fast response speed and the ability to adjust the output in real-time. However, analog circuits are easily affected by factors such as temperature and component aging, leading to a decrease in control accuracy, and the flexibility of the circuit is poor. Once the design is completed, it is difficult to modify the control parameters.
Digital control method: With the development of digital technology, digital control method has been widely used in sine wave inverter power supply. Complex control algorithms such as Space Vector Pulse Width Modulation (SVPWM) can be implemented through digital signal processors (DSPs) or microcontrollers (MCUs). The digital control method has the advantages of high control accuracy, good stability, and the ability to flexibly adjust control parameters. For example, in some situations where the quality of the output sine wave is extremely high, such as precision instrument power supply, the digital controlled inverter power supply can be optimized through algorithms to reduce the distortion of the output waveform to a very low level.
Characteristics of power devices
Switching speed: The switching speed of the power switch directly affects the operating frequency and conversion efficiency of the inverter power supply. Devices with fast switching speeds can enable the inverter power supply to operate at higher frequencies, which can reduce the volume of magnetic components such as transformers. For example, new wide bandgap semiconductor devices such as silicon carbide (SiC) and gallium nitride (GaN) have much faster switching speeds than traditional silicon-based power devices, which can effectively improve the power density of inverter power supplies.
On resistance: The on resistance of power devices can cause power loss. The smaller the on resistance, the less heat is generated in the on state, and the higher the efficiency of the inverter power supply. Reducing the on resistance of power devices is particularly important for high-power inverter power supplies, as it can reduce the burden on the heat dissipation system and improve the reliability of the entire system.
Voltage withstand level: The voltage withstand level determines the maximum voltage that power devices can withstand. When designing an inverter power supply, it is necessary to select power devices with appropriate withstand voltage levels based on the input voltage and circuit topology. If the withstand voltage level is insufficient, it may cause power devices to be broken down and damage the entire inverter power supply.
Filtering process
Filter types: Common filters include LC filters (composed of inductors and capacitors) and LCL filters (based on LC filters, an inductor is connected in series in the capacitor branch). LC filters have a simple structure and low cost, making them suitable for situations where the output waveform requirements are not particularly high. The LCL filter has better filtering effect on high-frequency harmonics and can obtain purer sine wave output, but its design and debugging are relatively complex because it has resonance problems and requires reasonable parameter design to avoid resonance.
Filter parameter design: The selection of inductance and capacitance parameters of the filter has a significant impact on the filtering effect. The values of inductance and capacitance need to be determined based on factors such as the output frequency, power, and requirements for harmonic suppression of the inverter power supply. If the filtering parameter design is not reasonable, it may not be able to effectively filter out harmonics, resulting in distortion of the output waveform and affecting the normal operation of the load.
Input power characteristics
Input voltage range: The input of a sine wave inverter power supply is usually a DC power supply, such as a battery. If the input voltage fluctuates greatly, it will affect the output performance of the inverter power supply. For example, when the input voltage is too low, it may not be possible to drive the power device normally, resulting in insufficient output power; When the input voltage is too high, it may also damage the power devices. Therefore, the inverter power supply needs to have a certain input voltage adaptation range and be able to maintain a relatively stable output at different input voltages.
Stability of input power supply: In addition to voltage range, stability of input power supply is also important. If there are significant voltage ripples or sudden changes in current in the input power supply itself, it will cause interference to the control loop of the inverter power supply, affecting the quality and stability of the output waveform. For example, in some inverter systems that use solar panels as input power, the output of the solar panels may fluctuate due to factors such as light intensity and temperature. Therefore, it is necessary to add a voltage regulator circuit or energy storage device at the front end of the inverter power supply to ensure the relative stability of the input power supply.