Owner's manual

AN368
54 AN368REV2
e. Determine the Flyback Nominal Timing T1 and T2
Calculate Mode 1 duty ratio D
MODE1
, and Mode 2 duty ratio D
MODE2
, using Equations 11 and 12, respectively:
Calculate period TT
CH1
using Equation 13:
Calculate switching frequency F
sw2
using Equation 14:
Calculate period TT
CH2
using Equation 15:
Calculate total switching periods for channel 1, TT
CH1
, and channel 2, TT
CH2
, using Equations 16 and 17,
respectively:
Calculate total period TT using Equation 18:
Calculate switching frequency F
sw
using Equation 19:
D
MODE1
NV
MODE1

V
BST
NV
MODE1
+
----------------------------------------------------------
5.57 20.95V
200V 5.57 20.95V+
------------------------------------------------------------------
0.37== =
[Eq. 90]
D
MODE2
NV
MODE2

V
BST
NV
MODE2
+
----------------------------------------------------------
5.57 10.4V
200V 5.57 10.4V+
--------------------------------------------------------------
0.225== =
[Eq. 91]
T1
CH1
T2
CH1
+
1
F
sw1
-----------
1
70kHz
------------------
14.29s== =
[Eq. 92]
F
sw2
F
sw1
V
BST
NV
MODE1
+
V
BST
NV
MODE2
+
----------------------------------------------------------
I
MODE1
V
MODE2

I
MODE2
V
MODE1

------------------------------------------=
[Eq. 93]
70kHz=
200V 5.57 20.95V+
200V 5.57 10.4V+
------------------------------------------------------------------
213mA 10.4V
275mA 20.95V
-------------------------------------------
53.3kHz=
T1
CH2
T2
CH2
+
1
F
sw2
-----------
1
53.3kHz
----------------------
18.76s===
[Eq. 94]
TT
CH1
T1
CH1
T2
CH1
T3
CH1
++=
[Eq. 95]
15.29= s
14.29= s1s+
TT
CH2
T1
CH2
T2
CH2
T3
CH2
++=
[Eq. 96]
19.76= s
18.76= s1s+
TT TT
CH1
TT
CH2
+ 15.29s 19.76s+ 35.05s== =
[Eq. 97]
F
sw
1
TT
-------
1
35.05s
----------------------
28.53kHz== =
[Eq. 98]