PWM (Pulse Width Modulation) method and device

The invention discloses a PWM method and device. The method comprises the following steps: generating a first PWM signal based on a sinusoidal signal when the pulse width of a current acting level is greater than a preset pulse width, and controlling a multi-level power topology circuit based on the first PWM signal; and when the pulse width of the current acting level is not greater than the preset pulse width, generating a second PWM signal through a positive level and a negative level or through the positive level, a zero level and the negative level so as to control the multi-level power topology circuit. Due to the fact that the two PWM signals meet the volt-second principle, when the three-level power topology circuit is controlled, the functions and effects of the two PWM signals are the same; and the pulse width of a current acting level in the second PWM signal is larger than the pulse width of the current acting level in the first PWM signal, so when the multi-level power topology circuit is control