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ON Semiconductor NCP1215 Manual

Low cost variable off time switched mode power supply controller
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NCP1215
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
© Semiconductor Components Industries, LLC, 2005
July, 2005 − Rev. 3
8
1
6
1
FAA
A
L
Y
W
GND
CS
GND
CT
ORDERING INFORMATION
Device
NCP1215DR2
NCP1215DR2G
NCP1215SNT1
†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.
1
http://onsemi.com
MARKING
DIAGRAMS
8
SOIC−8
P1215
D SUFFIX
ALYW
CASE 751
1
6
TSOP−6
(SOT23−6, SC59−6)
FAAYW
SN SUFFIX
CASE 318G
1
= Specific Device Code
= Assembly Location
= Wafer Lot
= Year
= Work Week
PIN CONNECTIONS
SOIC−8
FB
1
8
NC
CT
2
7
NC
CS
3
6
V
CC
4
5
Gate
(Top View)
TSOP−6
1
6
Gate
2
5
V
CC
3
4
FB
(Top View)
Package
Shipping
SOIC−8
2500 Tape & Reel
SOIC−8
2500 Tape & Reel
(Pb−Free)
TSOP−6
3000 Tape & Reel
Publication Order Number:
NCP1215/D
†

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Summary of Contents for ON Semiconductor NCP1215

  • Page 1 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 http://onsemi.com cost constraints together with a good low standby power performance.
  • Page 2 NCP1215 Line Line − Gate * If your application requires a gate−source resistor, please refer to design guidelines in this document. Figure 1. Typical Application Feedback Loop Control Reference − Regulator 12/8.5 V − Undervoltage Voffset Off−Time Lockout Comparator −...
  • Page 3 NCP1215 Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á Á...

  • Page 4: Electrical Characteristics

    NCP1215 ELECTRICAL CHARACTERISTICS = 12 V, for typical values T = 25°C, for min/max values T = 0°C to +105°C, unless otherwise noted.) Characteristic Symbol Unit VOLTAGE FEEDBACK Offset Voltage 1.05 1.19 1.34 offset Maximum CT Pin Voltage at FB Current = 25 mA (Including V offset CT−25mA...

  • Page 5: Typical Characteristics

    NCP1215 TYPICAL CHARACTERISTICS 11.6 11.5 11.4 11.3 11.2 11.1 11.0 −25 −25 , JUNCTION TEMPERATURE (°C) , JUNCTION TEMPERATURE (°C) Figure 3. V Threshold vs. Junction Figure 4. V Threshold vs. Junction startup UVLO Temperature Temperature 0.990 1.20 1.18 0.985 1.16...
  • Page 6 NCP1215 10.0 −25 −25 , JUNCTION TEMPERATURE (°C) , JUNCTION TEMPERATURE (°C) Figure 9. CT pin Source Current vs. Junction Figure 10. CT pin Threshold vs. Junction Temperature Temperature 60.0 = 25°C 50.0 source 40.0 30.0 sink 20.0 10.0 −25 , JUNCTION TEMPERATURE (°C)

  • Page 7: Application Information

    OFF−time dependant upon output power demand. the SMPS output voltage through the change of primary It can be seen from the typical application that NCP1215 is switch OFF time interval. It sets the peak voltage of the designed to operate with a minimum number of external timing capacitor, which varies upon the output power component.
  • Page 8 NCP1215 To Current Sense Comparator From Feedback Loop Block 17 k − Voffset Current 37.5 m 12.5 m Mirror to V offset − To Latch’s Set Input Figure 15. Feedback Loop − Current Sense Control 10 mA To Latch’s Output The resulting current sense regulation characteristic can be seen from Figure 16.
  • Page 9 NCP1215 Primary Current Sensing The primary current sensing method we described, brings The primary current sensing circuit is shown in Figure 19. the following benefits compared to the traditional approach: • Maximum peak voltage across the current sense resistor is determined and can be optimized by the value of the shift resistor.
  • Page 10 NCP1215 If the IC current consumption is assumed constant during Application Design Example An example of the typical wall adapter application is the startup phase, one can obtain resulting equation for described hereafter. startup resistor calculation: As a wall adapter it should be able to operate properly with...
  • Page 11 NCP1215 The EF16 core for transformer was selected. It has V CS R CS + + 2.442 W + 2.7 W (eq. 24) cross−section area A = 20.1 mm . The N67 magnetic I ppk 0.2047 allows maximum operating flux...
  • Page 12 NCP1215 Line 1 nF/Y − S250 D9 MBRS360T3 2.2 mH +6.5 V@ 800 mA C1 + 4.7 mH Neutral 2.2 mF/ 2.2 mF/ 470 mF/ 100 nF 400 V 400 V 16 V LL4448 10 mF/ 47 k 16 V +...
  • Page 13 However, dealing with an extremely low startup current implies a careful selection of the gate−source resistance. With the NCP1215, the gate−source resistor must be calculated to allow the growth of the V capacitor to 4.0 V in order to not interfere with the power−on sequence.
  • Page 14 0.25 (0.010) 5.80 6.20 0.228 0.244 SOLDERING FOOTPRINT* 1.52 0.060 0.275 0.155 1.270 0.024 0.050 SCALE 6:1 inches *For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. http://onsemi.com...

  • Page 15: Package Dimensions

    2.50 3.00 0.0985 0.1181 SOLDERING FOOTPRINT* 0.094 0.95 0.037 0.075 0.95 0.037 0.028 0.039 SCALE 10:1 inches *For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. http://onsemi.com...
  • Page 16 NCP1215 The product described herein (NCP1215), may be covered by the following U.S. patents: 6,385,060, 6,605,978. There may be other patents pending. ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein.