Method and device for detecting PWM wave

1. A method for detecting a Pulse-Width Modulation (PWM) wave, comprising:

starting a first counting when the PWM wave is detected;

interrupting the first counting when the first counting reaches a predetermined value;

determining whether an electric level of the PWM wave is a high electric level or a low electric level when the first counting is interrupted;

clearing a value of the first counting, starting a second counting, and interrupting the second counting when the second counting reaches the predetermined value;

determining whether the electric level of the PWM wave is a high electric level or a low electric level when the second counting is interrupted;

repeating, for a period of the PWM wave:

clearing a value of a previous counting, starting a next counting, and interrupting the next counting when the next counting reaches the predetermined value;

determining whether the electric level of the PWM wave is a high electric level or a low electric level when the next counting is interrupted; and

calculating a duty ratio of the PWM wave based on the number of high electric level and the number of low electric level determined within one period of the PWM wave.

2. The method of claim 1 , further comprising:

determining whether the duty ratio of the PWM wave satisfies a set of predetermined requirements; and

adjusting the PWM wave if the duty ratio of the PWM wave does not satisfy the set of predetermined requirements.

3. The method of claim 1 , wherein the duty ratio M of the PWM wave is calculated using a formula M=P h /(P h +P l ), where P h is the number of high electric level determined within one period of the PWM wave, and P l is the number of low electric level determined within one period of the PWM wave.

4. A device for detecting a PWM wave, comprising:

a PWM wave generating module, configured to generate the PWM wave;

a detecting module coupled to the PWM wave generating module, configured to receive the PWM wave and determine an electric level of the PWM wave;

a timer coupled to the detecting module, configured to start a counting when the detecting module receives the PWM wave, and to interrupt the counting when the counting reaches a predetermined value, the detecting module determining whether the electric level of the PWM wave is a high electric level or a low electric level when the counting is interrupted; and

a calculating module coupled to the detecting module, configured to calculate a duty ratio of the PWM wave based on a number of high electric level and a number of low electric level of the PWM wave determined within one period of the PWM wave.

5. The device of claim 4 , further comprising: a determining module coupled to the calculating module and configured to determine whether the duty ratio of the PWM wave satisfies a set of predetermined requirements, and to adjust the PWM wave if the duty ratio of the PWM wave does not satisfy the set of predetermined requirements.

6. The device of claim 4 , wherein the calculating module is configured to calculate the duty ratio of the PWM wave using a formula M=P h /(P h +P l ), where P h is a number of high electric level determined within one period of the PWM wave, and P l is a number of low electric level determined within one period of the PWM wave.

7. The device of claim 4 , wherein the PWM wave generating module, the detecting module, the timer, and the calculating module are integrated into a Micro-Controller Unit (MCU).

8. The device of claim 7 , wherein an interval time between consecutive interruptions of the timer is determined based on a bus time of the MCU and a frequency division value of the timer.