NCP1280_05 Datasheet, PDF (1/18 Pages) ON Semiconductor – Active Clamp Voltage Mode PWM Controller for Off-Line Applications

NCP1280
Active Clamp Voltage Mode
PWM Controller for Off−Line
Applications
The NCP1280 provides a highly integrated solution for off−line
power supplies requiring high−efficiency and low parts count. This
voltage mode controller provides control outputs for driving a forward
converter primary MOSFET and an auxiliary MOSFET for active
clamp circuit. The second output with its programmable delay can also
be used for driving a synchronous rectifier on the secondary or for
asymmetric half bridge circuits. Incorporation of high voltage startup
circuitry (with 700 V capability) reduces parts count and system
power dissipation. Additional features such as line UV/OV protection,
soft−start, single resistor programmable (high) frequency oscillator,
line voltage feedforward, dual mode overcurrent protection and
maximum duty cycle control, allow converter optimization at minimal
cost. Compared to a traditional forward converter, an NCP1280 based
converter can offer significant efficiency improvements and system
cost savings.
Features
• Internal High Voltage Startup Regulator (25 V to 700 V)
• Dual Control Outputs with Adjustable Overlap Delay
• Programmable Maximum Duty Cycle Control
• Single Resistor Oscillator Frequency Setting
• Fast Line Feedforward
• Line Under/Overvoltage Lockout
• Dual Mode Overcurrent Protection
• Programmable Soft−Start
• Precision 5.0 V Reference
• Pb−Free Package is Available*
Typical Applications
• Off−Line Power Converters in 100−500 W Range
• Desktop Power Supplies (High−End)
• Industrial Power Supplies
• Plasma/LCD TV Front−End
http://onsemi.com
MARKING
DIAGRAM
16
16
1
SO−16
D SUFFIX
CASE 751B
NCP1280
AWLYWW
1
NCP1280 = Device Code
A
= Assembly Location
WL
= Wafer Lot
Y
= Year
WW = Work Week
PIN CONNECTIONS
1
V_in
NC
UV/OV
FF
CS
C_SKIP
R_T
DC_MAX
16
V_AUX
OUT1
GND
OUT2
t_D
V_REF
V_EA
SS
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 4 of this data sheet.
*For additional information on our Pb−Free strategy
and soldering details, please download the
ON Semiconductor Soldering and Mounting
Techniques Reference Manual, SOLDERRM/D.
TX1
L_out
+
V_{in −}
Startup
C_clamp
Feedforward
M_clamp
V_{in FF}
SR Drive
M3
C_out
+
V_out
−
NCP1280
UV/OV
OUT2
OUT1
Driver
M1
M2
Overlap ^tD
Delay
Opto
Error
Amplifier
Figure 1. Forward Converter for Off−line Applications Using PFC Inputs
© Semiconductor Components Industries, LLC, 2005
1
February, 2005 − Rev. 3
Publication Order Number
NCP1280/D