28069 Digital compare module and deadband

Mohammad Ebrahimi1

Hello All,

I'm trying to use the output of the analog comparators in a 28069 DSP to generate PWM signals to implement a peak current mode controller. As I'm driving a full bridge, I need output signals to be complementary with deadbands. I'm using the output of the digital compare block for triggering the trip zone block, however this scheme does not allow me to put the desired deadband between the PWM signals.

Any suggestions for implementing this scheme?

Thank you all for considering this question

Cheers,

Mohammad

over 10 years ago

0 Subrahmanya over 10 years ago

TI__Mastermind 24095 points

Hi Mohammad,

Your understanding is correct. Deadband delays will not be inserted if you are using the trip zone event triggers on 28069.
There some app notes you can refer and see if these help in implementing peak current mode control.

http://www.ti.com/lit/an/sprabr1/sprabr1.pdf
http://www.ti.com/lit/wp/spry205/spry205.pdf

-Bharathi.

0 Mohammad Ebrahimi1 over 10 years ago in reply to Subrahmanya

Prodigy 170 points

Hello Bharathi,

Thanks a lot for your response.
Both of the documents you referred to, are implementing a peak current controller. PWM modules are configured to respond to the analog comparator output using Trip Zone, however no dead band is set for them in the c code (From control suite). So I think they cannot be used for my case.

Regards,
Mohammad

0 Subrahmanya over 10 years ago in reply to Mohammad Ebrahimi1

TI__Mastermind 24095 points

Hi MOhammad,

Can you refer to the implementation of HV Phase Shifted Full Bridge Developer's Kit

http://www.ti.com/tool/tmdshvpsfbkit

0 Mohammad Ebrahimi1 over 10 years ago in reply to Subrahmanya

Prodigy 170 points

Thank for your comment Bharathi.

This is exactly the project that I considered after your first comment. As I said before, according to this projects' C code from Control Suit, the EPWM1 is configured as a constant frequency PWM with 50% duty cycle and has a dead band. However, the EPWM2 that is configured to respond to the peak current comparator output (which is exactly what I need), does not have any deadband. Therefore I think this project doesn't match what I'm looking for.
So any help would be still much appreciated!

Regards,
Mohammad

0 Subrahmanya over 10 years ago in reply to Mohammad Ebrahimi1

TI__Mastermind 24095 points

Hi Mohammad,

In HV Phase Shifted Full Bridge Developer's Kit, you would note that the deadband for EPWM2 is also realized via. s/w configuration.
The standard HW deadband configuration will not work in this case (PCMC) because the active PWM edges are controlled by trip events.
Hence, the deadband is achieved in software reconfiguration inside the ISR to control the corresponding edges.
Please go through the software and ISR reconfiguration for achieving the deadband.
Do you have the kit with you already?

-Bharathi.

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28069 Digital compare module and deadband