Design Of A Programmable And Universal Load Module For Audio Amplifier Test System

Nowadays,people have a higher demand for the sound quality of car stereos,which makes it to have high quality surround sound,heavy bass sound and even have active noise control technology(ANC).Therefore,the on-board power amplifier,as the important part of car audio,has higher and higher performance requirements,and the number of output channels is also increasing.A new type of audio amplifier usually has 16 output channels.Testing not only requires pure resistive load,but sometimes also needs inductive impedance load in order to test its frequency response characteristics.However,the load module of the existing car amplifier testing system has low accuracy,weak expansibility and can not provide inductive impedance.In order to meet the test demand of new audio amplifier,a new test load module with high precision,strong expansibility and inductive impedance is urgently needed.In order to solve the problems of testing,by reserachiung the domestic and foreign audio power amplifier test system and test load,this paper puts forward the design of a new programmable load,with hardware and software system implementation,which combined with the current popular NI test platform,host computer uses LabVIEW as the control interface of the UI programming language,slave computer uses stmicroelectronics STM32F407 as main control chip,via a serial port communication between up and down system.The data transfer takes frame format with begin and end identification.Each load module can provide 8 channels,and the system can install 2 or 3 modules to increase the number of channels according to the requirements.The load impedance can be 1 ohm,2 ohm,4 ohm,8 ohm,etc.,and three additional inductive impedance can be added.Finally,the impedance accuracy of programmable load was improved to+/-0.1 ohms after the test of 4-line high-precision multimeter.Load module add 0? to 125? temperature test and 5%of the voltage fluctuation monitoring function;The number of channels can be expanded arbitrarily according to the requirements of the test system and verified on the new test system.The various functions and indicators meet the design requirements and can meet the test requirements of vehicle power amplifiers with different Numbers of channels on different platforms.This design has been appilied to the Auido test system of my company,and get the good profit and response.