TMS320F28335: Operating two converters using one controller(28335) for battery charger

Shubham Dhiman

Prodigy 50 points

Part Number: TMS320F28335

Dear Sir,

I am trying to control two converters using a single DSP.

Converter 1: Three-phase active front end converter(fsw=10kHz) ----sampling frequency= 10kHz(100us)

Converter 2: DC-DC phase shift full bridge converter ( fsw= 50kHz)---- sampling frequnecy= 50 kHz(20 us)

I have implemented ADC in a dual sequence mode where:

SEQ1= Converter 1, SEQ2= Converter 2

When SEQ1 ISR is called:( 100us sampling)

the ADC value of Conv1 is read from the result register only.

When SEQ2 ISR is called:(20us sampling)

1. the ADC value of Conv2 is read from the Result register

2. control loop calculation for Conv1

3. control loop calculation for Conv2

In my opinion, this approach will work fine if SEQ2 ISR operates under less than 20us. On the other hand, writing code for control loop calculation for such time constraint is a challenge in itself.

I am interested to know if there is a better way to approach this problem.

Please let me know if you need any more information.

over 4 years ago

0 Chen Jiang ti over 4 years ago

TI__Genius 16085 points

Hi Shubham,

Do you need both control loops to be ran under 50kHz?

Regards,

Chen

0 Shubham Dhiman over 4 years ago

Prodigy 50 points

Not compulsory. Both converters operate independently. (Typical two-stage charger where O/P of AC-DC converter is given to the I/P of DC/DC converter)

The control loop for conv1 can be in SEQ1 ISR and the control loop for conv2 can be in SEQ2 ISR.

The problem is when both ISRs occur at the same time. In this case, SEQ1 gets higher priority and after that SEQ2 ISR is executed. So, this means SEQ1 ISR computation time +SEQ2 ISR computation time should be less than 20uS( next ISR event).

0 Chen Jiang ti over 4 years ago in reply to Shubham Dhiman

TI__Genius 16085 points

Hi Shubham,

Sorry, I missed your reply. That makes sense for me. I don't know if there is better ways other than reduce the ISR control freq. Or you may consider optimize your control code or using device with CLA

Regards,

Chen

0 Shubham Dhiman over 4 years ago in reply to Chen Jiang ti

Prodigy 50 points

Thanks for your response. I have optimized the code using IQMATH (earlier it was a floating point) and the ISR time is significantly reduced to 10us (approx.) which is well within limits.

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TMS320F28335: Operating two converters using one controller(28335) for battery charger