Cirrus Logic AN361 - Manual (Page 4)

AN361
4 AN361REV2
Step 3) Voltage Separation Between V
line
and V
link
The peak value of the line voltage is . Use Equation 4 to calculate the voltage separation.
The value t=0.0053 is the time it takes the unit to reach the minimum difference between V
line
and V
link.
Step 4) Overvoltage Protection of V
link
Verify that the overvoltage protection criterion is satisfied by calculating V
ovp
using Equation 5.
Use Equation 6 to validate that the peak output voltage is less than V
ovp
.
Step 5) Hold-up Time
There is no hold-up time requirement in this design. Four 3.3
F film capacitors from EPCOS are used. The manu-
facturer part number of these capacitors is B32674D4335K. In mass production, the capacitor tolerance should also
be taken into account. When using a film capacitor with 5% tolerance, as in this design example, the cap value needs
to be 13.2
F/0.95 = 13.9F. When an electrolytic capacitor with 10% tolerance is used in this design, the cap value
needs to be 13.2 F/0.9 = 14.7F.
2 265  375 V =
v
link
v
line
–  
t
m  in V
link
0.5 V
link rip  
4 f
line
t   sin     – V
line peak  
2 f
line
t   sin  –  
t
[Eq. 12]
5 400 0.5 27 180 t   sin     – 375 90 t   sin  –   
t 0.0053 =
5 24V  16V 
V
ovp
1.05 V
link
1.05 400 420 V =  =  = [Eq. 13]
V
link
0.5 V
link rip  
   + 400 = 0.5  27  413.5 V =  + 420 V 
[Eq. 14]