自带12位DAC的单片机型号

stb***

sh*** 发表于 2024-10-6 17:09
现在需要驱动一个 比例伺服阀 输入要求  +-10V 1024分辨率

调这个比较麻烦，还费时，用DAC芯片吧

梁***

sh*** 发表于 2024-10-6 17:09
现在需要驱动一个 比例伺服阀 输入要求  +-10V 1024分辨率

比例伺服阀一般速度较慢，可以使用PWM经过RC滤波得到模拟电压，如果需要较大驱动电流，则使用一个运放缓冲（顺便做2阶低通滤波）可以输出10~20mA的电流，内阻小于0.1欧姆。

jm***

Shennong Ding published on 2024-9-13 09:23
Now PWM can be used to realize DAC, ADC detection feedback control accuracy

There are circuits around that attempt ripple cancellation to improve PWM ripple/response compromise, but the one in EDN comes out virtually identical to fewer parts used in a higher order filter
This from eevblog PWM ripple cancellation.asc


There is a modest improvement in PWM filtering you can get 'for free' (no added parts) and that is to change the second stage RC from a lazy equal-values ​​​​​​​​​choice to a lighter loading stage that has less effect on the roll-off
A second stage 4.5 x the resistance of the first, improves rise time ~ 20% better than the more complex ripple cancel, or 35~43% better rise time than the default equal-value RC (or you can choose less ripple)
If your design has a spare opamp, you can get the full improvement in roll-off.

梁***

jm*** 发表于 2024-10-21 04:50
There are circuits around that attempt ripple cancellation to improve PWM ripple/response compromis ...

两节无源RC滤波（2阶RC），则RC值最好是PWM周期的10倍以上。

两节RC滤波后输出模拟信号的截止频率  fo = 0.05955/RC = 0.06/RC。

实测          RC=1T  RC=2T  RC=4T  RC=8T    RC=16T   RC=5T   RC=10T  RC=20T
第一节mV  1100     560       280      140          70           224       112         56
第二节mV   140      40        10        2.5           0.6          6.4        1.6          0.4        = 160/N^2
纹波系数   2.8%     0.8%    0.2%    0.05%      0.012%    0.16%   0.04%     0.01%
截止频率   0.06f     0.03f    0.015f    0.0075f    0.00375f   0.012f   0.006f      0.003f    =0.06/RC = 0.06*f/N，f为PWM频率

jm***

梁*** 发表于 2024-10-21 14:11
两节无源RC滤波（2阶RC），则RC值最好是PWM周期的10倍以上。

两节RC滤波后输出模拟信号的截止频率  fo =  ...

That looks only at ripple, for a DAC spec, you should also look at Rise Time.
See the comparison here :