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零件编号 NCP1340
描述 Controller Featuring Valley Lock-Out Switching
制造商 ON Semiconductor
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NCP1340 数据手册, 描述, 功能
NCP1340
Product Preview
High-Voltage,
Quasi-Resonant, Controller
Featuring Valley Lock-Out
Switching
The NCP1340 is a highly integrated quasi−resonant flyback
controller suitable for designing high−performance off−line power
converters. With an integrated active X2 capacitor discharge feature,
the NCP1340 can enable no−load power consumption below 30 mW.
The quasi−resonant current−mode flyback stage features a
proprietary valley−lockout circuitry, ensuring stable valley switching.
This system works down to the 6th valley and transitions to a
frequency foldback mode to reduce switching losses. As the load
decreases further, the NCP1340 enters quiet−skip mode to manage the
power delivery.
To help ensure converter ruggedness, the NCP1340 implements
several key protective features such as internal brownout detection, a
non−dissipative Over Power Protection (OPP) for constant maximum
output power regardless of input voltage, a latched over voltage and
NTC−ready overtemperature protection through a dedicated pin, and
line removal detection to safely discharge the X2 capacitors when the
line is removed.
If transient load capability is desired, the NCP1341 offers the same
performance and features with the addition of power excursion mode
(PEM).
Features
Integrated High−Voltage Startup Circuit with Brownout Detection
Integrated X2 Capacitor Discharge Capability
Wide VCC Range from 9 V to 28 V
28 V VCC Overvoltage Protection
Abnormal Overcurrent Fault Protection for Winding Short Circuit or
Saturation Detection
Internal Temperature Shutdown
Valley Switching Operation with Valley−Lockout for Noise−Free
Operation
Frequency Foldback with 25 kHz Minimum Frequency Clamp for
Increased Efficiency at Light Loads
Skip Mode with Quiet−Skip Technology for Highest Performance
During Light Loads
Minimized Current Consumption for No Load Power Below 30 mW
Frequency Jittering for Reduced EMI Signature
Latching or Auto−Recovery Timer−Based Overload Protection
Adjustable Overpower Protection
Fixed or Adjustable Maximum Frequency Clamp
Fault Pin for Severe Fault Conditions, NTC Compatible for OTP
4−ms Soft−Start Timer
This document contains information on a product under development. ON Semiconductor
reserves the right to change or discontinue this product without notice.
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1
SOIC−9 NB
D SUFFIX
CASE 751BP
8
1
SOIC−8 NB
D SUFFIX
CASE 751
MARKING DIAGRAM
9
1340xz
ALYW
G
1
1340xz = Specific Device Code
x = A or B
z = 1, 2 or 3
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G = Pb−Free Package
PIN CONNECTIONS
1
Fault
HV
FMAX
FB
VCC
ZCD/OPP
DRV
CS GND
1
Fault
FB
ZCD/OPP
CS
(Top Views)
HV
VCC
DRV
GND
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 2 of this data sheet.
© Semiconductor Components Industries, LLC, 2016
April, 2016 − Rev. P1
1
Publication Order Number:
NCP1340/D







NCP1340 pdf, 数据表
NCP1340
INTRODUCTION
The NCP1340 implements a quasi−resonant flyback
converter utilizing current−mode architecture where the
switch−off event is dictated by the peak current. This IC is
an ideal candidate where low parts count and cost
effectiveness are the key parameters, particularly in ac−dc
adapters, open−frame power supplies, etc. The NCP1340
incorporates all the necessary components normally needed
in modern power supply designs, bringing several
enhancements such as non−dissipative overpower
protection (OPP), brownout protection, and frequency
reduction management for optimized efficiency over the
entire power range. Accounting for the needs of extremely
low standby power requirements, the controller features
minimized current consumption and includes an automatic
X2 capacitor discharge circuit that eliminates the need to
install power−consuming resistors across the X2 input
capacitors.
High−Voltage Start−Up Circuit: Low standby power
consumption cannot be obtained with the classic
resistive start−up circuit. The NCP1340 incorporates a
high−voltage current source to provide the necessary
current during start−up and then turns off during normal
operation.
Internal Brownout Protection: The ac input voltage is
sensed via the high−voltage pin. When this voltage is
too low, the NCP1340 stops switching. No restart
attempt is made until the ac input voltage is back within
its normal range.
X2−Capacitor Discharge Circuitry: Per the
IEC60950 standard, the time constant of the X2 input
capacitors and their associated discharge resistors must
be less than 1 s in order to avoid electrical shock when
the user unplugs the power supply and inadvertently
touches the ac input cord terminals. By providing an
automatic means to discharge the X2 capacitors, the
NCP1340 eliminates the need to install X2 discharge
resistors, thus reducing power consumption.
Quasi−Resonant, Current−Mode Operation:
Quasi−Resonant (QR) mode is a highly efficient mode
of operation where the MOSFET turn−on is
synchronized with the point where its drain−source
voltage is at the minimum (valley). A drawback of this
mode of operation is that the operating frequency is
inversely proportional to the system load. The
NCP1340 incorporates a valley lockout (VLO) and
frequency foldback technique to eliminate this
drawback, thus maximizing the efficiency over the
entire power range.
Valley Lockout: In order to limit the maximum
frequency while remaining in QR mode, one would
traditionally use a frequency clamp. Unfortunately, this
can cause the controller to jump back and forth between
two different valleys, which is often undesirable. The
NCP1340 patented VLO circuitry solves this issue by
determining the operating valley based on the system
load, and locking out other valleys unless a significant
change in load occurs.
Frequency Foldback: As the load continues to
decrease, it becomes beneficial to reduce the switching
frequency. When the load is light enough, the NCP1340
enters frequency foldback mode. During this mode, the
peak current is frozen and dead−time is added to the
switching cycle, thus reducing the frequency and
switching operation to discontinuous conduction mode
(DCM). Dead−time continues to be added until skip
mode is reached, or the switching frequency reaches its
minimum level of 25 kHz.
Skip Mode: To further improve light or no−load power
consumption while avoiding audible noise, the
NCP1340 enters skip mode when the operating
frequency reaches its minimum value. foldback isavoid
acoustic noise, the circuit prevents the switching
frequency from decaying below 25 kHz. This allows
regulation via burst of pulses at 25 kHz or greater
instead of operating in the audible range.
Quiet−Skip: To further reduce acoustic noise, the
NCP1340 incorporates a novel circuit to prevent the
skip mode burst period from entering the audible range
as well.
Internal OPP: In order to limit power delivery at high
line, a scaled version of the negative voltage present on
the auxiliary winding during the on−time is routed to
the ZCD/OPP pin. This provides the designer with a
simple and non−dissipative means to reduce the
maximum power capability as the bulk voltage
increases.
Frequency Jittering: In order to reduce the EMI
signature, a low frequency triangular voltage waveform
is added to the iniput of the PWM comparator. This
helps by spreading out the energy peaks during noise
analysis.
Internal Soft−Start: The NCP1340 includes a 4 ms
soft−start to prevent the main power switch from being
overly stressed during start−up. Soft−start is activated
each time a new startup sequence occurs or during
auto−recovery mode.
Dedicated Fault Input: The NCP1340 includes a
dedicated fault input. It can be used to sense an
overvoltage condition and latch off the controller by
pulling the pin above the overvoltage protection (OVP)
threshold. The controller is also disabled if the Fault pin
is pulled below the overtemperature protection (OTP)
threshold. The OTP threshold is configured for use with
a NTC thermistor.
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NCP1340 equivalent, schematic
NCP1340
Figure 12. Valley Timeout Circuitry
Frequency Foldback
As the output load decreases (FB voltage decreases), the
valleys are incremented from 1 to 6. When the sixth valley
is reached, if the FB voltage further decreases to 0.8 V, the
peak current setpoint becomes internally frozen to Vfreeze
(0.2 V typically), and the controller enters frequency
foldback mode (FF). During this mode, the controller
regulates the power delivery by modulating the switching
frequency.
In frequency foldback mode, the controller reduces the
switching frequency by adding dead−time after the 6th
valley is detected. This dead−time increases as the FB
voltage decreases. There is no discontinuity when the
system transitions from VLO to FF and the frequency
smoothly reduces as FB decreases.
The dead−time circuit is designed to add 0 ms dead−time
when VFB = 0.8 V and linearly increases the total dead−time
to tDT(3) (32 ms minimum) as VFB falls down to 0.4 V. The
minimum frequency clamp prevents the switching
frequency from dropping below 25 kHz to eliminate the risk
of audible noise.
Figure 13 summarizes the VLO to FF operation with
respect to the FB voltage.
Operating Mode
FF
Valley 6
Valley 5
Valley 4
Valley 3
Valley 2
Valley 1
0.8 0.9 1.0 1.1 1.2 1.4 1.5 1.6 1.7 1.8 2.0
Figure 13. Valley Lockout Thresholds
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