CCS/TMS320F28027: questions about TMS320F28027: Piccolo HVPSFB(PCMC)

I'm looking into the above question. I will give an update by tommorow US CST time.

Best,
Matthew

Hi user5277039,

1. All those parameters are already based on Z domain.
for example: Kdc(z - fz1)(z - fz2)/((z - fp1)(z - f p2)).

2. The +side is the current feedback value which comes from the GPIO used as a Comparater/ADC. You can refer to the Analog Subsystem Block Diagram in the TRM of the device to find it out. It is purely based on Analog connection. There is no code settings needed.

3. I am not sure about this, maybe because once there is no output of EPWM1A/B, the freewheeling current will decrease until zero though EPWM2B or EPWM2A. I will get back to you on this.

4.You might be right since it is an old comment. I will get back to you on this as well.

Regards,
Chen

1.Then  ,Kdc(z - fz1)(z - fz2)/((z - fp1)(z - f p2))=Kdc(z^2-(fz1+fz2)z+fz1*fz2)/(z^2 - (fp1+fp2)z+fp1*fp2)

=Kdc(1-(fz1+fz2)z^(-1)+fz1*fz2*z^(-2))/(1 - (fp1+fp2)z^(-1)+fp1*fp2*z^(-2)).

It compare with (b0+b1*z^(-1)+b2*z^(-2))/(1+a1*z^(-1)+a2*z^(-2)),

b0=Kdc

b1=-Kdc(fz1+fz2)

b2=Kdc*fz1*fz2

a1=-(fp1+fp2)

a2=fpa*fp2

But,in excel calculation ,

Values is diferrence.

Hi user5277039,

I think I didn't explain it correctly last time. Yes, it is changed from s domain to Z domain. Please take a look at two thread below.
e2e.ti.com/.../428178
e2e.ti.com/.../53646

Regards,
Chen

I checked these threads.
But in the thread,
the meaning of the following expression is not told

 fs=100000; //100Khz
 fz1=2000;
 fz2=(fs/3.14);
 fp2=(fs/3.14);
 fp1=0;
 Kdc=6000;
 pi=3.14;wz1 = 2*pi*fz1;
 wz2 = 2*pi*fz2;
 wp1 = 0; //Integrator pole at f=0
 wp2 = 2*pi*fp2;
 

 wr = sqrt(wz1*wz2);
 Q = wz1*wz2/((wz1+wz2)*wr);
 
 c2 = Kdc/(wr*wr);
 c1 = Kdc/(Q*wr);
 c0 = Kdc;
 
 d2 = 1/wp2;
 d1 = 1;
 d0 = 0;
 
 den =  4*d2*fs*fs + 2*d1*fs + d0;
 
 B0_I = (4*c2*fs*fs + 2*c1*fs + c0)/den;
 B1_I = (-8*c2*fs*fs           + 2*c0)/den;
 B2_I = (4*c2*fs*fs - 2*c1*fs + c0)/den;
 
 A1_I = ((-8*d2*fs*fs           + 2*d0)/den)*-1.0;
 A2_I = ((4*d2*fs*fs - 2*d1*fs + d0)/den)*-1.0;

I'd like to know the derivation process above expressions.

And ,
Accoding to the 「DiscretePIDcontroller.pdf」 in the thread,
The derivative term uses s = (z-1)/Tz.
The integral term uses s=(2*(z-1))/(T*(z+1)).

Then
About K(s - fz1)(s - fz2)/(s - fp1)(s - fp2),
which s is s = (z-1)/Tz or  s=(2*(z-1))/(T*(z+1))?