Cirrus Logic AN361 - Manual (Page 2)

AN361
2 AN361REV2
2.3 Voltage Separation Between V
line
and V
link
To ensure proper operation as a boost converter, a minimum voltage separation of 16V between the input AC
voltage (V
line
) and V
link
is required. The ripple on V
link
should also be taken into account. The voltage separation
requirement is defined by the following equation:
Where:
v
link
= the instantaneous value with respect to time of link voltage
v
line
= the instantaneous value with respect to time of line voltage
Expanding on Equation 3:
The left side of Equation 4 reaches the minimum value when:
2.4 Overvoltage Protection of V
link
Overvoltage protection in the CS1601 is triggered when V
link
exceeds 105% of its nominal value.
While in the overvoltage protection state, the gate drive output is disabled. The gate driver is reactivated when
V
link
falls below its nominal value. To prevent triggering the overvoltage protection event during normal opera-
tion, the link voltage, V
link
, plus the link ripple voltage, V
link(rip)
, should be less than V
ovp
.
2.5 Hold-up Time
In some applications, the output capacitor may be required for hold-up time. The equation below is used to cal-
culate the capacitance to meet the hold-up time requirement:
V
link
V
line
– 16V 
[Eq. 3]
min V
link
0.5 V
link rip  
4 f
line
t   sin     – V
line peak  
2 f
line
t   sin  –  
t
16V 
[Eq. 4]
2 f
line
t
V
line peak  
2
8 V
link rip  
 
2
 + V
line peak  
–
4 V
link rip  

----------------------------------------------------------------------------------------------------------------------------
 
 
 
 
acos = [Eq. 5]
V
ovp
1.05 V
link
 = [Eq. 6]
V
link
0.5 V
link rip  
   + 1.05 V
link
 
[Eq. 7]
C
out hold  
2 P
o
t
hold
 
V
link
V
link rip  
2
----------------------------- –
 
 
2
V
link min  
2
–
------------------------------------------------------------------------------------------- = [Eq. 8]