TMS320F28335: ePWM Duty Cycle Adjustment with Voltage Control trough ADC pins

Part Number: TMS320F28335
Other Parts Discussed in Thread: SYSCONFIG

Hello all.

I would like to ask a question about my related work.

I am trying to build an SMPS circuit and instead of using an IC for generating a PWM and controlling the output voltage, I am using TMS320F28335 because I want to develop my embedded and software skills. My goal is to rectify the grid voltage as an input voltage and transform it with a Flyback transformer (KA5038) and having an output voltage of 14.7V and 2.7A of current.

According to my calculations, I need to have a PWM signal with around %23 duty cycle and I generated the code successfully from the examples of the TI.

Right now I want to control my output voltage with digital control. I bought a Voltage Sensor (MAX471) to sense the output voltage and from my understanding, I am going to put the output of the sensor (3.3V) to one of the ADC pins. 

But I am stuck with the software part of the work. I would like to change the duty cycle ratio according to the output voltage and this time I couldn't find any specific examples to play on from the Resource Explorer. 

I look forward to your suggestions and help.

Best of regards. ( I also added the code which is written in the Example_2833x_ePWMDeadBand )

#include "DSP2833x_Device.h"

// external function prototypes
extern void InitSysCtrl(void);
extern void InitPieCtrl(void);
extern void InitPieVectTable(void);
extern void InitCpuTimers(void);
extern void ConfigCpuTimer(struct CPUTIMER_VARS *, float, float);
Uint16 PWM_Duty;



// Prototype statements for functions found within this file.
void Gpio_select(void);
void Setup_ePWM1A(void);
interrupt void cpu_timer0_isr(void);

//###########################################################################
//                        main code
//###########################################################################
void main(void)
{
    int counter=0;    // binary counter for digital output

    InitSysCtrl();    // Basic Core Init from DSP2833x_SysCtrl.c

    EALLOW;
       SysCtrlRegs.WDCR= 0x00AF;    // Re-enable the watchdog
       EDIS;            // 0x00AF  to NOT disable the Watchdog, Prescaler = 64

    DINT;                // Disable all interrupts

    Gpio_select();        // GPIO9, GPIO11, GPIO34 and GPIO49 as output
                        // to 4 LEDs at Peripheral Explorer)

    Setup_ePWM1A();        // init of ePWM1A

    InitPieCtrl();        // basic setup of PIE table; from DSP2833x_PieCtrl.c

    InitPieVectTable();    // default ISR's in PIE

    EALLOW;
    PieVectTable.TINT0 = &cpu_timer0_isr;
    EDIS;

    InitCpuTimers();    // basic setup CPU Timer0, 1 and 2

    ConfigCpuTimer(&CpuTimer0,150,100000);

    PieCtrlRegs.PIEIER1.bit.INTx7 = 1;

    IER |=1;

    EINT;
    ERTM;

    CpuTimer0Regs.TCR.bit.TSS = 0;    // start timer0

  // LED BLINK
    while(1)
    {
              while(CpuTimer0.InterruptCount == 0);
            CpuTimer0.InterruptCount = 0;

            EALLOW;
            SysCtrlRegs.WDKEY = 0x55;    // service WD #1
            EDIS;

              counter++;
            if(counter&1) GpioDataRegs.GPASET.bit.GPIO9 = 1;
                else GpioDataRegs.GPACLEAR.bit.GPIO9 = 1;
            if(counter&2) GpioDataRegs.GPASET.bit.GPIO11 = 1;
                else GpioDataRegs.GPACLEAR.bit.GPIO11 = 1;
            if(counter&4) GpioDataRegs.GPBSET.bit.GPIO34 = 1;
                else GpioDataRegs.GPBCLEAR.bit.GPIO34 = 1;
            if(counter&8) GpioDataRegs.GPBSET.bit.GPIO49 = 1;
                else GpioDataRegs.GPBCLEAR.bit.GPIO49 = 1;

    }
}

void Gpio_select(void)
{
    EALLOW;
    GpioCtrlRegs.GPAMUX1.all = 0;        // GPIO15 ... GPIO0 = General Puropse I/O
    GpioCtrlRegs.GPAMUX1.bit.GPIO0 = 1;    // ePWM1A active

    GpioCtrlRegs.GPAMUX2.all = 0;        // GPIO31 ... GPIO16 = General Purpose I/O
    GpioCtrlRegs.GPBMUX1.all = 0;        // GPIO47 ... GPIO32 = General Purpose I/O
    GpioCtrlRegs.GPBMUX2.all = 0;        // GPIO63 ... GPIO48 = General Purpose I/O
    GpioCtrlRegs.GPCMUX1.all = 0;        // GPIO79 ... GPIO64 = General Purpose I/O
    GpioCtrlRegs.GPCMUX2.all = 0;        // GPIO87 ... GPIO80 = General Purpose I/O

    GpioCtrlRegs.GPADIR.all = 0;
    GpioCtrlRegs.GPADIR.bit.GPIO9 = 1;    // peripheral explorer: LED LD1 at GPIO9
    GpioCtrlRegs.GPADIR.bit.GPIO11 = 1;    // peripheral explorer: LED LD2 at GPIO11


    GpioCtrlRegs.GPBDIR.all = 0;        // GPIO63-32 as inputs
    GpioCtrlRegs.GPBDIR.bit.GPIO34 = 1;    // peripheral explorer: LED LD3 at GPIO34
    GpioCtrlRegs.GPBDIR.bit.GPIO49 = 1; // peripheral explorer: LED LD4 at GPIO49
    GpioCtrlRegs.GPCDIR.all = 0;        // GPIO87-64 as inputs
    EDIS;
}

// PWM SETUP
void Setup_ePWM1A(void)
{
    EPwm1Regs.TBCTL.bit.CLKDIV =  0;    // CLKDIV = 1
    EPwm1Regs.TBCTL.bit.HSPCLKDIV = 1;    // HSPCLKDIV = 2
    EPwm1Regs.TBCTL.bit.CTRMODE = 2;    // up - down mode
    EPwm1Regs.AQCTLA.all = 0x0006;        // ZRO = set, PRD = clear

    EPwm1Regs.TBPRD = 576;            // 65KHz - PWM signal
    EPwm1Regs.CMPA.half.CMPA = (Uint16)((0.23 * EPwm1Regs.TBPRD) * 2 );    // Set compare A value, duty cycle

    EPwm1Regs.AQCTLA.bit.CAU = 1; //count up active
    EPwm1Regs.AQCTLA.bit.CAD = 1; //count down active
    EPwm1Regs.CMPCTL.all = 0x0002;
    EPwm1Regs.TBCTL.bit.SWFSYNC = 1;
}

interrupt void cpu_timer0_isr(void)
{
    CpuTimer0.InterruptCount++;
    EALLOW;
    SysCtrlRegs.WDKEY = 0xAA;    // service WD #2
    EDIS;
    PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;
}
//===========================================================================
// End of SourceCode.
//===========================================================================