基于PWM的高精度数模转换方法
首发时间:2018-10-08
摘要:本文首次提出了基于脉宽调制(PWM)方式模拟产生脉冲密度调制(PDM)信号,实现高精度数模转换(D/A)的方法。利用单片机直接存储器访问(DMA)的高速特性,在一个给定的时间内,使PWM的占空比按预定的规则变化,而不是恒定不变,使"0"和"1"的分布在给定时间内均匀分布,通过占空比不同的PWM信号的排列组合,产生高低电平均匀分布的PDM信号。将产生的PDM信号通过低通滤波器滤除高频信号,就可以得到比较稳定的模拟信号。实验结果表明,在PWM频率为288 kHz、单片机主频为50Mhz时,相比于传统的PWM,本方法分辨率从7.4位提升至12.6位,非差分线性度最大值从2 LSB降低至0.4 LSB。
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High-precision digital-to-analog conversion method based on PWM
Abstract:In this paper, for the first time, we propose a novel method for achieving D/A conversion with high precision, in which the pulse-density modulation (PDM) signal is generated by the simulation of pulse-width modulation (PWM). In this technique,based on the high-speed of direct memory access (DMA) on singlechip microcomputer(MCU), the duty cycle of PWM signal is changed by predetermined rules to achieve a uniform distribution of \'0\' and \'1\' within a given time.Then the PWM signals with different duty cycle are arranged and combined, so that the PDM signal with uniform distribution of high and low levels is generated. The PDM signal is then sent to a low pass filter to filter the high-frequency signal and the stable analog signal is generated. The experimental results show that when the PWM frequency is 288kHz and the main frequency of the MCU is 50MHz, the resolution of this method is improved from 7.43 bits to 12.6 bits and the maximum non-difference linearity is reduced from 2 LSB to 0.4 LSB compared with the traditional PWM method.
Keywords: PWM PDM DMA D/A conversion
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