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LTpowerCAD LTC3895 problem



		

			

									
					    KAYDIN556
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Mar 25, 2022 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi AD,
    

    I'm tring to simulate LTC3895 buck controller. 
    

    My specs: 80V input
    

    Fsw: 150kHz,
    

    Vout=41.68V
    

    Iout=15A
    

    Ta=25C
    

    Control Mosfet : BSC093N15S5 ( x4)
    

    Sync Mosfet : BSC093N15S5 ( x2)
    

    Output Cap :1mF-150mR Cap ( x4)
    

    

    My question is when I put the 4.4uH inductor, It shows the Ploss for control mosfet is 0.529Watt but When I put the 4.5uH inductor, It shows the Ploss for control mosfet 1.221Watt.  Note that; I just changed the inductor value. 
    

    Why is it happening ? are there any logical explanation ?
    

    By the way, I know the ripple current for inductor is too much. I just want to ask the problem. 
    

    for 4.4uH results;
    

    

     
    

    

    for 4.5uH results;
    

    

     
    

    

    Thanks 
    

    Best Regards,
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	















    
	
    
	
    
					



			








	
	
	
	



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													+1
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
			                            
                        
                on Mar 25, 2022 4:07 PM
            
            
					
      
	
      

		
		
      
					
      With 4.4uH, there is likely over 200% inductor ripple meaning the inductor current is negative when the control MOSFET turns on. LTpowerCAD assumes zero voltage switching (switch node driven high by the negative inductor current) and the zero turn-on losses (2.793W control fet turn on losses below pie chart) disappear. Good luck with your design.
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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													+1
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
			                            
                        
                on Mar 25, 2022 4:07 PM
            
            
					
      
	
      

		
		
      
					
      With 4.4uH, there is likely over 200% inductor ripple meaning the inductor current is negative when the control MOSFET turns on. LTpowerCAD assumes zero voltage switching (switch node driven high by the negative inductor current) and the zero turn-on losses (2.793W control fet turn on losses below pie chart) disappear. Good luck with your design.
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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