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PDF NCP1215 Data sheet ( Hoja de datos )
| Número de pieza | NCP1215 | |
| Descripción | Low Cost Variable OFF Time Switched Mode Power Supply Controller | |
| Fabricantes | ON | |
| Logotipo |  |
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NCP1215
Product Preview
Low Cost Variable OFF Time
Switched Mode Power
Supply Controller
The NCP1215 is a controller for low power off−line flyback
Switchemode Power Supplies (SMPS) featuring low size, weight and
cost constraints together with a good low standby power performance.
The operating principle uses switching frequency reduction at light
load by increasing the OFF Time. Also, when OFF Time expands, the
peak current is gradually reduced down to approximately 1/4 of the
maximum peak current to prevent from exciting the transformer
mechanical resonances. The risk of acoustic noise is thus greatly
diminished while keeping good standby power performance.
A low power internal supply block also ensures very low current
consumption at startup without hampering the standby power
performance.
A special primary current sensing technique minimizes the impact
of SMPS switching on control IC operation. The choice of peak
voltage across the current sense resistor allows dissipation to be
further reduced. The negative current sensing technique offers
advantages over a traditional approach by avoiding the voltage drop
incurred by traditional MOSFET source sensing. Thus, the IC drive
capability is greatly improved.
Finally, the bulk input ripple ensures a natural frequency dithering
which smooths the EMI signature.
Features
• Pb−Free Package is Available
• Variable OFF Time Control Method
• Very Low Current Consumption at Startup
• Natural Frequency Dithering for Improved EMI Signature
• Current Mode Control Operation
• Peak Current Compression Reduces Transformer Noise
• Programmable Current Sense Resistor Peak Voltage
• Undervoltage Lockout
Typical Applications
• Auxiliary Power Supply
• Standby Power Supply
• AC−DC Adapter
• Off−line Battery Charger
This document contains information on a product under development. ON Semiconductor
reserves the right to change or discontinue this product without notice.
© Semiconductor Components Industries, LLC, 2004
October, 2004 − Rev. 2
1
http://onsemi.com
8
1
SOIC−8
D SUFFIX
CASE 751
MARKING
DIAGRAMS
8
P1215
ALYW
1
TSOP−6
6
6
(SOT23−6, SC59−6)
SN SUFFIX
FAAYW
1
CASE 318G
1
FAA = Specific Device Code
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
PIN CONNECTIONS
SOIC−8
FB 1
8 NC
CT 2
7 NC
CS 3
GND 4
6 VCC
5 Gate
(Top View)
TSOP−6
CS 1
6 Gate
GND 2
5 VCC
CT 3
4 FB
(Top View)
ORDERING INFORMATION
Device
Package
Shipping†
NCP1215DR2 SOIC−8 2500 Tape & Reel
NCP1215DR2G
NCP1215SNT1
SOIC−8
(Pb−Free)
TSOP−6
2500 Tape & Reel
3000 Tape & Reel
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
Publication Order Number:
NCP1215/D
1 page  
NCP1215
TYPICAL CHARACTERISTICS
11.6 8.8
11.5 8.7
11.4 8.6
11.3 8.5
11.2 8.4
11.1 8.3
11.0
−25
0 25 50 75 100
TJ, JUNCTION TEMPERATURE (°C)
125
Figure 3. Vstartup Threshold vs. Junction
Temperature
8.2
−25
0 25 50 75 100
TJ, JUNCTION TEMPERATURE (°C)
Figure 4. VUVLO Threshold vs. Junction
Temperature
125
0.990
0.985
0.980
0.975
0.970
0.965
0.960
−25
0 25 50 75 100
TJ, JUNCTION TEMPERATURE (°C)
125
Figure 5. Operating Current Consumption vs.
Junction Temperature
1.20
1.18
1.16
1.14
1.12
1.10
1.08
1.06
1.04
1.02
1.00
−25
0 25 50 75 100
TJ, JUNCTION TEMPERATURE (°C)
Figure 6. Offset Voltage vs. Junction
Temperature
125
49.0
48.5
48.0
47.5
47.0
46.5
46.0
45.5
−25
0 25 50 75 100
TJ, JUNCTION TEMPERATURE (°C)
125
Figure 7. Current Sense Source Current vs.
Junction Temperature
65
60
55
50
45
40
35
30
−25
0 25 50 75 100
TJ, JUNCTION TEMPERATURE (°C)
Figure 8. Current Sense Threshold vs.
Junction Temperature
125
http://onsemi.com
5
5 Page 
NCP1215
The EF16 core for transformer was selected. It has
cross−section area Ae = 20.1 mm2. The N67 magnetic
allows to use maximum operating flux density
Bmax = 0.28 Tesla.
The number of turns of the primary winding is:
np
+
Lp · Ippk
B max · Ae
+
4.14 ·
0.28
10−3 · 0.2047
· 20.1 · 10−6
+
150
turns
(eq. 20)
The AL factor of the transformer’s core can be calculated:
AL
+
Lp
(np)2
+
4.14 · 10−3
(150)2
·
+
184
nH
(eq. 21)
For an adapter output voltage of 6.5 V, the number of turns
of the secondary winding can be calculated accounting
Schottky diode for output rectifier as follows:
ns
+
(Vs
) Vfwd)(1 * d
d max · Vbulk−
max)np
min
(eq. 22)
+
(6.5
)
0.7)(1 * 0.5)150
0.5 · 127
+
8.5
+
9
turns
The number of turns for auxiliary winding can be
calculated similarly:
ns
+
(Vs
) Vfwd)(1 * d
d max · Vbulk−
max)np
min
(eq. 23)
+
(12
)
1)(1
0.5 ·
* 0.5)150
127
+
15.35
+
15
turns
The peak primary current is known from initial
calculations. The current sense method allows choosing the
voltage drop across the current sense resistor. Let’s use a
value of 0.5 V. The value of the current sense resistor can
then be evaluated as follows:
RCS
+
VCS
Ippk
+
0.5
0.2047
+
2.442
W
+
2.7
W
(eq. 24)
The voltage drop across the sense resistor needs to be
recalculated:
VCS + RCS · Ippk + 2.7 · 0.2047 + 0.553 V (eq. 25)
Using the above results the value of the shift resistor is:
Rshift
+
VCS
ICS
+
0.553
50 · 10−6
+
11.06
kW
+
11
kW
(eq.
26)
The value of timing capacitor for the off time control has
to be calculated for minimum bulk capacitor voltage since
at these conditions the converter should be able to deliver
specified maximum output power. The value of the timing
capacitor is then given by the following equation:
CT
+
1
fsw
*
1.2
Lp · Ippk
Vbulk− min
· 106
(eq. 27)
+
75
1
· 103
* 4.14 · 10*3 ·
127
0.12 · 106
0.2047
+
55.5
pF
+
56
pF
The value of the startup resistor for startup time of 200 ms
and Vcc capacitor of 200 nF is following:
Rstartup
+
CVcc
Vbulk− min
Vstartup
tstartup
)
ICC−start
MAX
+
200
·
10−9
127
12
0.2
)
10
·
10−6
+ 5.77 MW + 5.6 MW
(eq. 28)
The result of all the calculations is the application
schematic depicted in Figure 21.
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11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet NCP1215.PDF ] | |
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