CCS/UCD3138: Problems about DPWM period and duty cycle swtiching actions

user5800841

Part Number: UCD3138
Other Parts Discussed in Thread: PMP21529

Tool/software: Code Composer Studio

Hi,

In one UCD3138 BUCK-BOOST application,I have problems in the dynamic actions of DPWM period and dutycycle swtiching.
Current swtiching procedure is as follows:
1.shut down PWM output
2.set LoopMuxRegs.PWMGLBPER
3.set LoopMuxRegs.FLTERKCOMPA.bit.KCOMP0
4.set other trigger points of period
5.set FlLTER output threshold
6.stop loop intergration(if need)
7.set output duty
8.delay 15 us
9.turn on PWM out

Because of the interruption of PWM,output voltage will be influenced during the switching procedure.
In STEP 8,if the delay time is shorted a little,it will lead to wrong output.So what delay time is suitable,and,what is the actual action procedure in the DPWM ? If there is any dependable opperation steps to make sure that the output is fast and correct?

over 6 years ago

0 Amiel Hussain over 6 years ago

TI__Expert 4070 points

Hello,

An engineer is looking into this and will respond.

0 Bosheng Sun over 6 years ago in reply to Amiel Hussain

TI__Expert 7260 points

what is your topology? what is the purpose to do this procedure?

0 user5800841 over 6 years ago in reply to Bosheng Sun

Prodigy 100 points

Topology:Bulk-Boost Bidirection Power Supply

To test the switching procedure of DPWM period and duty cycle, my way is to shut down the DPWMs, update configurations,delay,and turn on them.However,if the delay time isn't big enough, it will lead to the error output,as is shown in the picture,and I am not sure what big value should I give to the delay time.

What I want to know is that the working procedure inter the DPWM, time that configurations cost and how low delay time I can give to the switching procedure.

0 Bosheng Sun over 6 years ago in reply to user5800841

TI__Expert 7260 points

I have done the similar work in one of my design PMP21529, I also found it takes about 15us for a success transition. The device needs time to stop existing configuration and reconfigure, there is no way to make it faster. You may need to add more output cap to help the voltage diviation.

0 Sean Xu over 6 years ago in reply to Bosheng Sun

TI__Genius 14580 points

The question is closed. If you have more question, please open one thread.

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CCS/UCD3138: Problems about DPWM period and duty cycle swtiching actions