// *****************************************************************
//
//  PWMswCM.va - current mode PWM switch CCM-DCM auto-togggling // // 
***************************************
//  Owner	: Nicolas Cyr
//  E-mail	: nicolas.cyr@onsemi.com
// ***************************************
//
// Using Christophe Basso's model from his book "Switch-Mode Power // 
Supplies" (McGraw-Hill, 2008); based on Dr. Vatché Vorpérian // 
initial concept developped in 1986 at Virginia Polytech Institute // 
(in "Simplified Analysis of PWM Converters Using the Model of the // 
PWM Switch", Transactions on Aerospace and Electronics Systems, // 
vol. 26, no. 3, May 1990).
//
// ***************************************
//  Revision history
//
//	2008 Jan 23 - Nico Cyr - creation
//  2009 August 25th - correction on the CS line reported by James 
Kohout // // 
*****************************************************************
// Modifications by RK, Feb 2012
//  - added dependency on simulation type for Cs calculation via 
initial_step //  - Ri to internal Rii to limit>0 for div operations // 
*****************************************************************

`include "constants.vams"
`include "disciplines.vams"



module PWMswCM(a, c, p, Verr, DC, Mode);

inout a;	electrical a;			// "active" terminal
inout c;	electrical c;			// "common" terminal
inout p;	electrical p;			// "passive" terminal

input Verr;	electrical Verr;		// "error voltage" input

output DC;	electrical DC;			// "duty cycle" input
output Mode;	electrical Mode;		// "mode of operation" output
						// (1 for DCM, 0 for CCM)

parameter real L=75u from (0:inf);		// inductance value
parameter real Fsw=100k from (0:inf);		// switching frequency
parameter real Ri=1 from (-inf:inf);		// sense resistor
parameter real Sa=0 from [0:inf);		// slope of compensation ramp
parameter real DCmax=0.99 from (0:1);		// duty cycle max clamp
parameter real DCmin=0.016 from (0:DCmax);	// duty cycle min clamp


real d_1, d1cl, d1clh, d_2, d2cl, d2clh, Cs, mode, Iverr, Imju, Ics, 
Rii; integer simtype;

analog begin
	
              @(initial_step("ac","stb")) begin
	  simtype = 0;
	end
	
	@(initial_step("tran","dc")) begin
	 simtype = 1;
	end
	
	@(initial_step) begin
                 Rii = Ri;	
	 if( Ri<= 0.0) begin
	 Rii = 1.0e-6;
	 $strobe("\nRi NULL AND THEREFORE BOUNDED TO 1uOhm !!!");
	 end
	end

	// calculate and clamp duty cycle d2
	// (which corresponds to OFF time in CCM, and to demagnetization time 
in DCM)

	d_2 = (2*L*Fsw*I(p,c) / ((V(DC)*V(a,c))+1u)) - V(DC);				
	d2clh = (d_2>= (1-V(DC))) ? (1-V(DC)) : d_2;
	d2cl = (d2clh<= DCmin) ? DCmin : d2clh;
		
	// calculate and clamp ON-time duty cycle d1

	d_1 = d2cl*V(c,p) / (V(a,p)-V(c,p)+1u);						
	d1clh = (d_1>= DCmax) ? DCmax : d_1;
	d1cl = (d1clh<= DCmin) ? DCmin : d1clh;
		
	// evaluate mode of operation (1=DCM, 0=CCM)

	mode = (d2cl<(1-d1cl)) ? 1 : 0;							

	// calculate capacitor for subharmonic oscilllations in AC simulation 
(0 if DCM or Tran)

	Cs = (mode==1 || simtype==1) ? 0 : 4 / (L*4*pow(`M_PI,2)*pow(Fsw,2));		

	// calculate contributors to Ic current

	Iverr = V(Verr) / Rii;
	Imju  = Sa*d1cl/(Rii*Fsw) + V(c,p)*d2cl*( 1-((d1cl+d2cl)/2))/(L*Fsw);		
	Ics   = Cs*ddt(V(c,p));
	
	
	// assign values to currents and voltages
	
	I(a,p)<+ I(p,c)*d1cl / (d1cl+d2cl+1u);						
	I(p,c)<+ Iverr - Imju - Ics;							
	
	// Assign values to outputs

	V(DC)<+ d1cl;
	V(Mode)<+ mode;
	
end

endmodule