| The subject of this article is taken from a company’s air defense alarm device with an output power of 1k W.After testing,the company’s products have too many harmonic components during use,and the temperature of the device is too high during operation.The research in this article is mainly to solve The above problem.The technical theoretical research takes the 1k W air defense alarm as the background,introduces the components and working principle of the alarm device in detail,and designs and implements an air defense alarm with an output power of 1k W that is different from the traditional alarm principle.Traditional alarm devices require a modulation circuit to compare the audio frequency with the triangle wave to generate PWM to drive the next-stage class D power amplifier circuit.After observation,the PWM error output by the traditional modulation method is too large,which eventually causes too many harmonics to be output,which affects the quality of the audio.And content,although the audio quality and content may not be very important compared to alarm devices,the methods proposed in the paper to improve the output audio quality are also used in stage audio,village radio and other devices.The function of the modulator part in this article will be realized by STM32.Insert the SD card storing audio into the STM32 single-chip microcomputer.The single-chip microcomputer decodes the audio in the SD card and outputs PWM through a series of algorithms to drive the next level circuit.The internal clock of the single-chip microcomputer Therefore,the accuracy of the output PWM can be guaranteed.In the power tube selection of the power amplifier circuit,SiC MOSFET is used to replace Si MOSFET,because SiC material MOSFET has higher switching speed and can reduce the distortion of the system.The circuit uses a full-bridge drive circuit to drive the power tube,which can guarantee D Similar to the sensitivity of the power amplifier circuit,a reasonable LC filter circuit is designed as a low-pass filter to restore the audio waveform,and the device as a whole achieves the purpose of power amplification.This article has completed the program design,MATLAB/Simulink modeling and overall circuit simulation,schematic design and PCB production,etc.The specific research content is as follows:(1)Modulator design: Select the STM32 single-chip microcomputer,determine the main body of the modulator part,use the Keil software programming tool to reflect the required algorithm in the single-chip microcomputer program,and finally configure the STM32 single-chip microcomputer to send out accurate PWM.(2)SiC MOSFET modeling: In order to reduce the generation of harmonics,Si MOSFETs will be replaced by higher switching frequency SiC MOSFETs,and the loss during the operation of class D power amplifier circuits can also be reduced.The modeling of SiC MOSFETs is done in MATLAB software Simulink tool to complete the design,and compare the designed model with the characteristic curve given by the manufacturer to confirm whether the design model is reasonable.(3)Simulink simulation system circuit: Design a power amplifier circuit with SiC material MOSFET as the switch tube,and finally confirm whether the circuit design can meet the design requirements of this article by comparing the original waveform with the output waveform.(4)Physical production and testing: Use Altium designer software to design the schematic diagram of the hardware circuit,generate a PCB in it,and power on to complete the final test after the soldering is completed. |
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