使用PWM实现DAC

1 Introduction Many embedded microcontroller applications require generation of analog signals. Sometimes an integrated or stand-alone digital-to-analog converter(DAC) is used for this purpose.

However, PWM signals can often be used for generating the required analog signals. PWM signals can be used to create both dc and ac analog signals. The report below discusses using a PWM timer as a DAC and shows an example of simultaneously creating a sinusoid,a ramp, and a dc level and adding the dc level and sine wave to produce an offset ac signal. This report uses the PWM timer Timer_B. Timer_A could also be used in a similar manner.

2 Theory of Operation A PWM signal is a digital signal with fixed frequency but varying duty cycle. An example of a PWM signal is shown in Figure 1. If the duty cycle of the PWM signal is varied with time, and the PWM signal is filtered, the output of the filter will be an analog signal.