TMS320F28027: Not able to Create Dead Band on Trip Zone Event

TI-CSC

Genius 16385 points

Part Number: TMS320F28027
Other Parts Discussed in Thread: C2000WARE, CONTROLSUITE

Hello E2E Experts,

Good day.

I am using 28027 for Synchronous buck operation PCMC.

PWM 1A is used for high side switch and PWM 1B is used for low side switch.

I am able to control the peak current however, at trip event I am not able to insert dead band when PWM 1A goes low and PWM 1B goes high. This creates shot through instance.

PWM configuration is as follows. Comments may not match since experiential. However PCMC is working.

EPwm1Regs.TBCTL.bit.PRDLD = TB_IMMEDIATE; // set Immediate load

EPwm1Regs.TBPRD = period;

EPwm1Regs.CMPA.half.CMPA = 290; // Fix duty at 50%

EPwm1Regs.CMPB = 290;

EPwm1Regs.TBPHS.half.TBPHS = 0;

EPwm1Regs.TBCTR = 0;

EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP;

EPwm1Regs.TBCTL.bit.PHSEN = TB_DISABLE;

EPwm1Regs.TBCTL.bit.SYNCOSEL = TB_CTR_ZERO; //used to sync EPWM(n+1) "down-stream"

EPwm1Regs.TBCTL.bit.HSPCLKDIV = TB_DIV1;

EPwm1Regs.TBCTL.bit.CLKDIV = TB_DIV1;

EPwm1Regs.AQCTLA.bit.ZRO = AQ_SET;

EPwm1Regs.AQCTLA.bit.CAU = AQ_CLEAR;

EPwm1Regs.AQCTLB.bit.ZRO = AQ_SET;

EPwm1Regs.AQCTLB.bit.CBU = AQ_CLEAR;

EPwm1Regs.DBCTL.bit.IN_MODE = 0;

EPwm1Regs.DBCTL.bit.POLSEL = DB_ACTV_HIC; // Active Hi Complimentary

EPwm1Regs.DBCTL.bit.OUT_MODE = 2;

EPwm1Regs.DBRED = 20; // dummy value for now

EPwm1Regs.DBFED = 20; // dummy value for now

// Interrupt where we will change the Deadband

EPwm1Regs.ETSEL.bit.INTSEL = ET_CTR_ZERO; // Select INT on Zero event

EPwm1Regs.ETSEL.bit.INTEN = 1; // Enable INT

EPwm1Regs.ETPS.bit.INTPRD = ET_3RD; // Generate INT on 3rd event

//Comparator configuration

SysCtrlRegs.PCLKCR3.bit.COMP1ENCLK = 1;

//Enable Comparator & DAC

Comp1Regs.COMPCTL.bit.COMPDACEN = 1; // Enable DAC / Power up Comparator 1 locally

//-----------DAC configuration------------ //

Comp1Regs.DACCTL.bit.FREE_SOFT = 2; // Free run

Comp1Regs.DACCTL.bit.RAMPSOURCE = 0; // PWMSYNC1

Comp1Regs.DACCTL.bit.DACSOURCE = 1; // 0- DAC, 1 - Ramp

//-----------Comp configuration------------ //

Comp1Regs.COMPCTL.bit.SYNCSEL = 0; // Asynchronous output for comparator

Comp1Regs.COMPCTL.bit.QUALSEL = 2; // Qualification period for synchronized output of the comparator

Comp1Regs.COMPCTL.bit.COMPSOURCE = 0; // Connect the inverting input to the internal DAC

Comp1Regs.COMPCTL.bit.CMPINV = 0; // 0- direct, 1- Invert Comparator output is passed directly

EPwm1Regs.HRPCTL.bit.PWMSYNCSEL = 1; // Ramp sync source :PWMSYNC3 at TBCTR = 0

EPwm2Regs.HRPCTL.bit.PWMSYNCSEL = 1; // Ramp sync source :PWMSYNC3 at TBCTR = 0

EPwm3Regs.HRPCTL.bit.PWMSYNCSEL = 1; // Ramp sync source :PWMSYNC3 at TBCTR = 0

EPwm4Regs.HRPCTL.bit.PWMSYNCSEL = 1; // Ramp sync source :PWMSYNC3 at TBCTR = 0

//-----------Digital Compare Configuration-------//

EPwm1Regs.DCTRIPSEL.bit.DCAHCOMPSEL = 8; // COMP1 Output as input

EPwm1Regs.DCACTL.bit.EVT2SRCSEL = 0; // DCAEVT2 is Source signal select

EPwm1Regs.DCACTL.bit.EVT2FRCSYNCSEL = 1; // ASync signal

//-----------PWM TRIPZONE Configuration-------//

EPwm1Regs.TZSEL.bit.DCAEVT2 = 1; // CBC source to ePWM

EPwm1Regs.TZDCSEL.bit.DCAEVT2 = TZ_DCAH_HI; //4

EPwm1Regs.TZCTL.bit.TZA = TZ_FORCE_LO;

EPwm1Regs.TZCTL.bit.TZB = TZ_FORCE_HI;

Thank you in advance for your suggestions.

Regards,

CSC

over 3 years ago

0 Pranali Gaydhane over 3 years ago

TI__Prodigy 470 points

Hi,

The expert is out of the office because of Holiday. Please expect a reply by Tuesday.

Thanks.

0 TI-CSC over 3 years ago in reply to Pranali Gaydhane

TI__Genius 16385 points

Hello Pranali,

Thank you. Below is additional information:

How to insert Deadband in PWM 1a & 1b trip event transition using the digital compare module?

Regards,

CSC

0 Ryan Ma over 3 years ago in reply to TI-CSC

TI__Mastermind 27736 points

Hi TI-CSC,

Currently with ePWM for this device, there is not a configurable option to insert deadband in PWM after trip event transition. Upon a fault condition from the trip zone submodule, outputs will be forced to either of the 4 states immediately. (High, low, high-impedance, and no action taken)

However there is a work around which is talked about in this thread here. This is using the event filter feature.

Best,

Ryan Ma

0 TI-CSC over 3 years ago in reply to Ryan Ma

TI__Genius 16385 points

Hello Ryan,

Good day.

Valley switching feature is not available in the 2802x series.

Also, there is one reference design developed by TI HVPSFB_V1.1 which uses this dead band on trip events.

However, I am not able to logically how it is implemented.

Can you please explain only the Comparator and synchronous rectifier PWM linking with deadband in that reference design?

Regards,

CSC

0 Ryan Ma over 3 years ago in reply to TI-CSC

TI__Mastermind 27736 points

Hi TI-CSC,

I am going to talk to another expert on this and will get back to you latest by end of day tomorrow.

Best,

Ryan Ma

0 Shamim Choudhury over 3 years ago in reply to Ryan Ma

TI__Genius 12225 points

Please use our newer MCUs F28004x, F28002x series to implement peak current mode control where you can insert dead-band easily on trip zone events.

We also have a reference designs TIDM-2000 to illustrate this. For this please download C2000Ware to review this TIDM-2000

0 TI-CSC over 3 years ago in reply to Shamim Choudhury

TI__Genius 16385 points

Hello Shamim,

Good day.

My design is already in the testing phase. It was done on the reference of the HVPS FB by Hrushikesh Nene.

I need to work out the solution for the same, which I believe is available in the implementation of HVPSFB.

Regards,

CSC

0 Shamim Choudhury over 3 years ago in reply to TI-CSC

TI__Genius 12225 points

Hrishi no longer works at TI. There is no one to support this old code in ControlSuite. You have to see how this dead-band insertion is implemented there and then follow the same.

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TMS320F28027: Not able to Create Dead Band on Trip Zone Event