TL494, NCV494
V
ref
6
5
R
T
C
T
R
T
Master
C
T
R
S
V
in
> 40V
1N975A
V
Z
= 39V
V
ref
270
V
CC
12
5.0V
Ref
Gnd
7
6
R
T
5
C
T
Slave
(Additional
Circuits)
Figure 18. Slaving Two or More Control Circuits
Figure 19. Operation with V
in
> 40 V Using
External Zener
+V
in
= 8.0V to 20V
12
1
2
1M
33k
0.01 0.01
3
15
16
+
−
Comp
−
+
OC V
REF
DT
13
4.7k
4.7k
14
+
10
10k
15k
0.001
4
5
C
T
6
R
T
Gnd
7
9
E
1
10
E
2
TL494
C
2
11
Tip
32
47
V
CC
C
1
8
47
Tip
32
+
50
25V
1N4934
240
T
1
1N4934
22
k
+
50
35V
4.7k
1.0
+V
O
= 28 V
I
O
= 0.2 A
L
1
+
50
35V
All capacitors in
mF
Figure 20. Pulse Width Modulated Push−Pull Converter
Test
Line Regulation
Load Regulation
Output Ripple
Short Circuit Current
Efficiency
Conditions
V
in
= 10 V to 40 V
V
in
= 28 V, I
O
= 1.0 mA to 1.0 A
V
in
= 28 V, I
O
= 1.0 A
V
in
= 28 V, R
L
= 0.1
W
V
in
= 28 V, I
O
= 1.0 A
Results
14 mV 0.28%
3.0 mV 0.06%
65 mV pp P.A.R.D.
1.6 A
71%
L1 − 3.5 mH @ 0.3 A
T1 − Primary: 20T C.T. #28 AWG
T1 −
Secondary: 12OT C.T. #36 AWG
T1 −
Core: Ferroxcube 1408P−L00−3CB
http://onsemi.com
9
ONSEMI [ ON SEMICONDUCTOR ]
