MC33364 ON Semiconductor, MC33364 Datasheet - Page 10

• Manufacturer Part Number: MC33364
• Description: Critical Conduction GreenLine SMPS Controller
• Manufacturer: ON Semiconductor

maximum operating flux density of:
winding can be derived:
core with an A
of turns of the primary winding is:
(assuming a Schottky rectifier is used):
its number of turns is given by:
L p +
B max + 0.2 T
A c + 33.5 mm 2
B max +
n p +
n p +
A
n s +
naux +
L
The primary inductance value is given by:
The manufacturer recommends for that magnetic core a
The cross-sectional area A
The operating flux density is given by:
From this equation the number of turns of the primary
The A
From the manufacturer‘s catalogue recommendation the
The number of turns needed by the 6.0 V secondary is
The auxiliary winding to power the control IC is 16 V and
The approximate value of rectifier capacitance needed is:
+
B max A c
n 2 p
L p I
L p
max V
A
V s ) V
I
L p
L
ppk
L p I
L
(V aux ) V
N p A c
factor is determined by:
ppk
+
max V
1 2
ppk
L p B max A c
in(min)
L
f
L p I
fwd
min
+
+
of 100 nH is selected. The desired number
+
+
max(V
0.2 T 33.5 E- 6 m 2
(16 V ) 0.9 V)(1 * 0.5)139
in(min)
ppk
.00192 H ( 0.472 A )
1– max n p
6.0 V ) 0.3 V 1 * 0.5 139
fwd
( 0.00192 H )
+
( 100 nH )
( 0.472 A )( 70 kHz )
)(1 * max)n p
2
in(min)
2
[0.5(127 V)]
0.5 ( 127 V )
0.5 127 V
c
of the EF20 core is:
)
1 2
2
+ 139 turns
2
+ 105 nH
+ 1.92 mH
+ 19 turns
+ 7 turns
http://onsemi.com
MC33364
10
where the minimum ripple frequency is 2 times the 50 Hz
line frequency and t
haversine cycle, is assumed to be half the cycle period.
calculations for the value of the output filter capacitors will
be done at the lowest frequency, since the ripple voltage will
be greatest at this frequency. When selecting the output
capacitor select a capacitor with low ESR to minimize ripple
from the current ripple. The approximate equation for the
output capacitance value is given by:
one uses the peak current in the predesign consideration.
Since within the IC there is a limitation of the voltage for the
current sensing, which is set to 1.2 V, the design of the
current sense resistor is simply given by:
secondary, connected to the primary side via an optoisolator,
the MOC8102.
peak current flowing through the power switch during each
cycle. This pin will be connected to the feedback pin of the
MC33364, which will directly set the peak current.
the sense current through the voltage-sensing resistor
divider to be approximately 0.25 mA. One can immediately
calculate the value of the lower and upper resistor:
current through the optoisolator and the TL431 is set by the
minimum operating current requirements of the TL431.
This current is minimum 1.0 mA. Assign the maximum
current through the branch to be 5 mA. That makes the bias
resistor value equal to:
C1 +
C5 +
R7 +
R
R upper + R10 +
R
lower
bias
Because we have a variable frequency system, all the
Determining the value of the current sense resistor (R7),
The error amplifier function is provided by a TL431 on the
The voltage of the optoisolator collector node sets the
Starting on the secondary side of the power supply, assign
The value of the resistor that would provide the bias
t
V
(f
I
+ R
V cs
off
ppk
+ R11 +
min
ripple
(I
I out
in
S
+ 1.2 V
)(V
)
+
+
+
0.472 A
rip
6.0 V * [2.5V ) 1.4V]
V out * [V
(5 m sec)(0.118 A)
)
V
+
V out * V
off
ref
(70 kHz)(0.1 V)
, the discharge time of C1 during the
+ 2.54 W [ 2.2 W
I
(TL431)
5.0 mA
div
50 V
ref
I
2 A
div
ref
I
(TL431) ) V
LED
(TL431)
+ 2.5 V
+ 6.0 V * 2.5V
0.25 mA
+ 11.8 mF
+ 286 mF
0.25 mA
+ 420 W [ 430 W
LED
+ 10 k
]
+ 14 k