In the process of rectification and inversion, the upper and lower bridges of the same phase cannot be turned on at the same time, otherwise the power supply will be short-circuited. Theoretically, the PWM generated by the DSP will not be turned on at the same time, but the PWM of the device cannot be an instantaneous level jump. It always descends in a trapezoidal shape, which may make the upper and lower bridges pass through. Therefore, set a very short time to close the upper and lower bridges, and then selectively open them to avoid the direct connection of the upper and lower bridges. In actual control, the dead zone will lead to control performance. Difference.
The triodes of the upper and lower bridge arms of the PWM cannot be turned on at the same time. If it is turned on at the same time, it will be a short circuit at both ends of the power supply. Therefore, the two trigger signals should disconnect the triode within a period of time. This area is called the "dead zone".
The duty cycle of the PWM determines the average voltage output to the DC motor, and the PWM does not regulate the current. PWM means pulse width regulation, which is to adjust the time ratio of square wave high level and low level. A 20% duty cycle waveform will have 20% high level time and 80% low level time, and a A waveform with a 60% duty cycle has 60% high level time and 40% low level time. The larger the duty cycle and the longer the high level time, the higher the output pulse amplitude, that is, the higher the voltage . If the duty cycle is 0%, then the high level time is 0, then there is no voltage output. If the duty cycle is 100%, then the full voltage is output.
Therefore, by adjusting the duty cycle, the purpose of adjusting the output voltage can be achieved, and the output voltage can be continuously adjusted steplessly...
