TMS320F28035: EPWM duty match while CBC occurs

Jack Tan80

Part Number: TMS320F28035

Hi C2000 expert,

I'm trying to use F28035 in HSFB topology with PCMC control algorithm.

Now I'd would like to know if this device support duty match or not?

For example, if epwm1A and epwm1b are connected to primary side mosfet, epwm2a, epwm2b are used to control sencondary side mosfet. If CBC occurs on EPWM1A, i would like EPWM1B have same duty cycle with EPWM1A, is it possible to relized?

Below is the waveform what I want, CBC occurs on EPWM1A, EPWM1B should keep the same pulswidth with EPWM1A, is it possible? Thanks...

over 6 years ago

0 Cody Watkins over 6 years ago

TI__Mastermind 41385 points

Jack,

I am looking into this. In your system, will the CBC trip always occur before ePWM1B is high? If so approximatly how long before?

Regards,
Cody

0 Jack Tan80 over 6 years ago in reply to Cody Watkins

Mastermind 7090 points

Code,

Regarding to HSFB topology, the pulse width of ePWM1A and ePWM1B are clamped within 50% duty, otherwise it will cause MOSFET damaged.

If there is no CBC while ePWM1A output 50% duty cycle, then ePWM1a just output 50% duty clcle, and epwm1B should have the same pulse width.

0 Jack Tan80 over 6 years ago in reply to Jack Tan80

Mastermind 7090 points

Sorry for the typo, you're cody.

Cody,

Regarding to HSFB topology, the pulse width of ePWM1A and ePWM1B are clamped within 50% duty, otherwise it will cause MOSFET damaged.

If there is no CBC while ePWM1A output 50% duty cycle, then ePWM1a just output 50% duty clcle, and epwm1B should have the same pulse width.

0 Jack Tan80 over 6 years ago in reply to Jack Tan80

Mastermind 7090 points

Cody/C2000 expert,

Can you please help update about this?

0 Cody Watkins over 6 years ago in reply to Jack Tan80

TI__Mastermind 41385 points

Edited 1/12/18/ 2:52 PM CST.

__________________________________________________________________

Jack,

due to the asynchronous nature of the CBC trip this would be difficult to predict within the PWM module. There are two ways around this.

Setup up the Digital Compare Counter Capture Register (DCCAP) to indicate the falling edge of ePWMA. That value can then be used to update the CMPx values for ePWMB.
Setup an eCAP module to measure the pulse width of ePWMA then use that measurement to set the CMPx values for ePWMB.

Note: When making symmetric waveforms it is often helpful for you to use up-down-count mode!

Regards,
Cody

0 Cody Watkins over 6 years ago in reply to Cody Watkins

TI__Mastermind 41385 points

Jack,
I am closing this thread due to inactivity feel free to reply here if the question is not answered.
Cody

0 Jack Tan80 over 6 years ago in reply to Cody Watkins

Mastermind 7090 points

Cody,

Sure, you can close this thread. We have added a external exponent to fixed this instead of inside the chip. Thanks anyway.

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TMS320F28035: EPWM duty match while CBC occurs