基于Kinetis系列的FlexTimer和同步ADC用于场效应控制

　　It is a well-known fact that there would be no control without measurement. For a precise and fast control， it is necessary tohave the actual data before feedback system intervention. Particularly， a periodic signal must be measured at the right timeinstance， otherwise， an incorrect value may be obtained. Evidently， there is a requirement for quality sensing. The FTM andADC synchronization， together with quality ADCs and sensors， is an example of a system that provides the precise electricalquantity measurements.There are other benefits gained from this suggested solution：• The measurement is not influenced by disturbances and interferences from the switching of the power semiconductors.In other words， the synchronization helps to filter the measured currents， a process known as anti-aliasing.• Secondly， an average value can be obtained. If the measurement is made in the middle of the pulse length of a pulsewidth modulation （PWM）， an average value of the current is obtained without any additional calculation. See Figure 1.This principle works only on the condition that the motor electrical time constant must be many times higher than theswitching period. Therefore， the motor current waveform will be almost linear during the pulse of the PWM.• The final benefit is that all processing， until the ADC interrupt routine starts， can be done by hardware only， without

　　computing power.In specific cases， the FTM and ADC synchronization can be the only way to measure something. The discontinuous current，which forms only a part of the PWM period， can be taken as an exampl