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MPC5643L_PWMsignal change during one period

Question asked by na yan on Oct 25, 2016

I want to use MPC5643L to control a FB(full bridge) DC/DC converter ,which relies on EDMA,ADC.

Fllowing is circuit diagram and the PWM signal I want to get .




The principle of the program is following(fig3), code is in attachment.


Q1: I set shift_AD =200, shift_BC =400. During 10us, at first interrupt(T1CR),let shift=shift_BC; at second irst interrupt(T3CR),let shift=shift_AD;so we can get  the waveform should be ,and correspoding isr code is in attachment.



But the actual waveform looks like following(the PWM signal is changing during one period 5us):


It’s unbeliveable. Becase no matter which case,the inner register (val register) should be constant during one period(5us),then ,how a constant val register produce a varing PWMA and PWMB driver signal during one period?

Does anyone has a clue?


Thanks very much!




Q2:during closeloop debuggingI power the MPC5643L only without input voltage,it means vc(control signal) should be very large,because there  no output voltage. So we can know that shift should be max value.

But the actual waveform is following.


In fact,the figure cannot descript the actual phenomenon,I saved a video(about actual PWM signal),but cant be put I put it in this website,you can see it in this URL (PWM drive signal—在线播放—优酷网,视频高清在线观看  ) the first channel (yellow) is A.  the second channel is D .


Did anyone have the same experience, or have the idea which may cause this phenomenon?



Thanks very much!


Original Attachment has been moved to: community_2016_10_25.rar