High frequency crm step-up pfc converter with self-adaptive optimization of thd

Abstract

The invention provides a high-frequency CRM Boost PFC converter for adaptively optimizing input current THD, which belongs to the field of AC-DC power conversion. It reduces the input current THD based on the variable conduction time control method: the digital look-up table method is used to generate the modulated wave signal, and the variable conduction time control is realized through the preset conduction time data table to solve the problem of poor control accuracy of the analog control method and digital real-time calculation The cost of the method is high; other circuits except the modulation wave signal generation circuit are realized by analog to overcome the limitation of the digital controller’s response speed to the MHz high-frequency signal and reduce the performance requirements of the digital controller; through the data sheet The limited data preset in the system can be converted, and the on-time control can be changed without output power detection to follow the input voltage and output power for adaptive adjustment, so as to adaptively optimize the input current THD and significantly reduce the system cost.

Description

technical field [0001] The invention relates to a high-frequency CRM Boost PFC converter capable of adaptively optimizing input current THD, which belongs to the technical scope of power conversion, and in particular relates to the technical fields of high-quality AC-DC power conversion and high-frequency power conversion. Background technique [0002] The wide application of power electronic devices in rectification occasions leads to a substantial increase in the harmonic content of the grid current and seriously endangers the normal and stable operation of the grid. The main hazards of harmonic current are as follows: a voltage drop occurs on the transmission line impedance, resulting in a non-sinusoidal grid voltage waveform; it is easy to interfere with the normal operation of adjacent electrical equipment, causing damage to electronic equipment, instruments and line protection devices, etc. Mismeasurement and malfunction; increase the additional loss and temperature ri...

AI Technical Summary

Problems solved by technology

[0008] 1. The additional conduction time only changes synchronously with the instantaneous value of the input voltage, and has no relationship with the output power, so it cannot achieve the optimal change of conduction time control, and it can improve the input current THD performance under different output powers The effects are very different and even cannot be taken into account;

[0009] 2. The acquisition of the additional on-time lacks accurate quantitative calculation, and can only achieve better input current THD performance under a certain input voltage and a certain output power within the working condition range of the converter. Therefore, the components of the control circuit The parameters need to be compromised after comparing and testing the input current THD performance under different working conditions (different input voltage and different output power) within the working condition range, which increases the design cycle and complexity;

[0010] 3. The actual required change of on-time is closely related to the switching frequency of the converter. The additional on-time that can be increased by existing commercial analog control chips is only suitable for a limited range of switching frequencies, most of which are between 30kHz and 200kHz. Meet the application needs of higher switching frequency

[0012] 1. The cost and power consumption of the digital controller will increase significantly;

[0013] 2. There is an upper limit in the calculation speed of the existing digital controller, so the calculation speed and control accuracy of the conduction time cannot be considered at the same time;

[0014] 3. Existing digital controllers have limited ability to detect high-frequency periodic signals

[0018] 2. The output current of the converter needs to be sampled to calculate the output power, which increases the system cost and implementation complexity

[0019] Therefore, the digital method based on the look-up table is difficult to meet the application requirements of high-frequency CRM Boost PFC converters in wide input voltage and wide load applications

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