Pseudo planning.. am I in left field? Is it dumb to use a case switch in a while loop?

//Rookie Code may cause the infinite loop, decrements not set, still planning
I am planning my code for the Roman Numeral Converter at FreeCodeCamp… I watched the highest ranked tutorials last year, what I don’t remember directly or find in the hints… I’m trying to improvise in my own style (which obviously is a work in progress) I guess my main question is if I’m off base to be trying to use a case switch inside of a while loop? Is this a logical course to pursue? Or is there some obvious rookie mistake like the infinite loop I’m about to embark upon the wrong tree?
also, I’ve only seen case switches used with variables, not really conditions… should I be wrapping them in parenthesises?

//Rookie Code may cause an infinite loop, decrements not set, still planning
function convertToRoman(num) {

while (num > 1){

switch (num) {
  case num > 1000:
    console.log('M');
    break;
  case num > 500:
    console.log('D');
    break;    
  case num > 100:
    console.log('C');
    break;
  case num > 50:
    console.log('L');
    break;    
  case num > 10:
    console.log('X');
    break;
  case num > 5:
    console.log('V');
    break;    
  case num > 1:
    console.log('I');
    break;
  default:
    console.log(num);
}//end of switch
//decrement num!!
}//end of while..


return num;
}

convertToRoman(36);

//  1       I  
//  5       V  
//  10      X  
//  50      L  
//  100     C  
//  500     D  
//  1000    M