TMS320F28335: generating ePWM using Action Qualifier Continuous Software Force Register (AQCSFRC)

Daniel Darvishrahimabadi

Hi ,

I have written a code for 28335 DSP . It is designed for a boost converter in which I want to generate PWM for my Mosfet manually using Action Qualifier register . below is my PWM configuration :

void InitEPwm3Example()
{
//PWM frequency 20 KHz
EPwm3Regs.TBPRD = 1875;
EPwm3Regs.TBPHS.half.TBPHS = 0x0000;
EPwm3Regs.TBCTR = 0x0000;

EPwm3Regs.TBCTL.bit.CTRMODE = 3; //TB_COUNT_UPDOWN;
EPwm3Regs.TBCTL.bit.PHSEN = TB_DISABLE;
EPwm3Regs.TBCTL.bit.HSPCLKDIV = 1;
EPwm3Regs.TBCTL.bit.CLKDIV = 0;

// Setup compare
EPwm3Regs.CMPA.half.CMPA = 0;
EPwm3Regs.CMPCTL.bit.SHDWAMODE = 0;
EPwm3Regs.CMPCTL.bit.LOADAMODE = 0;

// Set actions
EPwm3Regs.AQCTLA.bit.CAU = 1;
EPwm3Regs.AQCTLA.bit.CAD = 2;

// EPwm2Regs.AQCTLB.bit.CAU = AQ_CLEAR;
// EPwm2Regs.AQCTLB.bit.CAD = AQ_SET;

// Active high complementary PWMs - setup the deadband
EPwm3Regs.DBCTL.bit.OUT_MODE = 0x3; //Dead band is fully enabled
EPwm3Regs.DBCTL.bit.POLSEL = 0x2; // Active high complementary
EPwm3Regs.DBCTL.bit.IN_MODE = 0x0; //EPWMxA is the source for both Rising Edge delay and Falling Edge delayed signals
EPwm3Regs.DBRED = 75; //1us
EPwm3Regs.DBFED = 75;
// EPwm2_DB_Direction = DB_UP;

//Trip Zone Settings
EALLOW;
EPwm3Regs.TZCTL.all = 0xA; //Force Both epwmxA and ePWMxB to low state when in TZ.
EDIS;

// Interrupt where we will modify the deadband
// EPwm2Regs.ETSEL.bit.INTSEL = ET_CTR_ZERO; // Select INT on Zero event
// EPwm2Regs.ETSEL.bit.INTEN = 1; // Enable INT
// EPwm2Regs.ETPS.bit.INTPRD = 0x1; // Generate INT on 3rd event

}

I have initialized the PWM using this code :

EALLOW;
EPwm3Regs.TZFRC.bit.OST=0;
EPwm3Regs.TZCLR.bit.OST=1;
EDIS;

This one works and my switch turns on . but when I want to turn off the switch using this code : EPwm3Regs.AQCSFRC.all=1 to set the PWM low, this does not work and the Mosfet becomes short circuit . ( PWM always at high level ) .

What is the reason and could you please help me solve this problem?

(for some reason , I don't want to use TZ registers as my frequency is not constant )

over 6 years ago

0 Cody Watkins over 6 years ago

TI__Mastermind 42195 points

Daniel,

that looks like it should force PWMA low constantly and PWMB high constantly.

The PWM block act sequentially on the PWMx signals. You have forced PWMA low which then eventually goes into the DB where you tell it to ignore PWMB up to that point and create a complementary signal from PWMA. Since A is always low then B will always be high.

Is that what you are seeing? If so you can use the Trip Zone for force the PWM low because it takes effect after the Dead Band.

Regards,
Cody

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

Prodigy 40 points

Cody ,

In this code , I don't use PWMB , I only use PWMA but when I use Action Qualifier Continuous register to set the ePWM to zero , that never happens and PWMA is always high . I wonder maybe I wrote something wrong in my PWM configuration code . if I use TZ registers , Should I write EALLOW and EDIS too ?

Regards,

Daniel

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

TI__Mastermind 42195 points

Daniel,

if you are only using PWMA then I expect this to work. You may be having an EALLOW issue here, that is easy to check. Single step through your code and observe the register that you are modifying before and after you execute the line. If it changes, great you have not issues. If it stays the same, toggle the EALLOW bit and try running the code again.

Please note that all EALLOW protected registers are mentioned in the Datasheet. Look at the summary table that lists all of the registers in that module.

Regards,
Cody

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

Prodigy 40 points

Hello Cody ,

Thank you for your help . The problem was about something else that I found and solve it .

Thanks man

Daniel

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

TI__Mastermind 42195 points

Great to hear Daniel! What was the problem?

Thanks,
Cody

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

Prodigy 40 points

the problem was not related to ePWM . in fact the code is flawless . my sensors happened to malfunction .

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F28335: generating ePWM using Action Qualifier Continuous Software Force Register (AQCSFRC)