NCP1351 ON Semiconductor, NCP1351 Datasheet - Page 21

• Manufacturer Part Number: NCP1351
• Description: Variable Off Time Controller Featuring Short-circuit Protection
• Manufacturer: ON Semiconductor

low value capacitor (4.7 mF) and a bigger one (100 mF). The
4.7 mF capacitor ensures a low startup time, whereas the
second capacitor keeps the V
(where the switching frequency can be low). Due to D
does not hamper startup time.
Application Results
what is described on Figure 27. Here are the obtained
results:
P
P
even at low output levels. It clearly shows the benefit of the
variable frequency implemented in the NCP1351.
in
in
On this circuit, the V
We assembled a board with component values close to
The efficiency stays flat to above 80%, and keeps good
@ no-load = 152 mW, V
@ no-load = 164 mW, V
HV-Bulk
+
C12
100mF
400V
100n
0.4
R6
C4
R15
3.7k
2.5k
R5
270pF
U1B
C8
C15
22p
CC
Figure 27. The 19 V Adapter Featuring the Elements Calculated Above
capacitor is split in two parts, a
1
2
3
4
in
in
U2
= 230 Vac
= 100 Vac
CC
NCP1351B
100n
alive in standby mode
C9
2.2k
R1
8
7
6
5
C10
0.1m
Option
4.7m
25V
OVP
C3
1M
1M
R7
R2
+
http://onsemi.com
100nF
C1
MUR
6
160
47k
D2
R3
, it
NCP1351
1N4148
R16
D6
10
R18
47k
1N4937
R13
47k
21
25V
D3
R4
22
Figure 28. Efficiency Measured at Various Operating
C2
10n
400V
88
86
84
82
80
78
76
74
72
+
C17
100m
0
L
N
N
Type = Y1
T1
MBR20200
6A/600V
M1
P
P
P
:N
:N
= 500mH
2.2nF
D5
S
aux
1.2mF
0.5
C13
= 1:0.25
C5a
25V
= 0.18
+
U1A
1
1.2mF
C5b
25V
V
+
in
Points
= 230 Vac
1.5
I
out
R8
1k
IC2
TL431
(A)
2.2m
220mF
L2
R14
2.2k
25V
2
C7
V
GND
in
100n
C6
= 100 Vac
+
2.5
GND
R12
4k
R10
62k
R9
10k
V
OUT
3
19V/3A
3.5