NCP1651DR2G ON Semiconductor, NCP1651DR2G Datasheet - Page 13

• Manufacturer Part Number: NCP1651DR2G
• Description: IC PFC CONTROLLER CCM/DCM 16SOIC
• Manufacturer: ON Semiconductor

Specifications of NCP1651DR2G

• Mode: Continuous Conduction (CCM), Discontinuous Conduction (DCM)
• Frequency - Switching: 250kHz
• Current - Startup: 8.5mA
• Voltage - Supply: 10 V ~ 18 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Switching Frequency: 25 KHz to 250 KHz
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: NCP1651DR2GOS; NCP1651DR2GOS; NCP1651DR2GOSTR

Introduction
lines is becoming more and more important. There are a
number of reasons for this.
requiring Power Factor Correction PFC. Many of these are
originating in Europe. Regulations such as IEC1000- -3- -2
are forcing equipment to utilize input stages with topologies
other than a simple off- -line front end which contains a
bridge rectifier and capacitor.
PFC. In order to obtain the maximum power from an
existing circuit in a building, the power factor is very critical.
The real power available from such a circuit is:
0.5 to 0.6, which means that for a given circuit breaker rating
only 50% to 60% of the maximum power is available. If the
power factor is increased to unity, the maximum available
power can be obtained.
limited supply of power is available from the on- -board
generators. Increasing the power factor will increase the
load on the aircraft without the need for a larger generator.
being in phase with the voltage, and undistorted. Therefore,
Optimizing the power factor of units operating off of AC
There are a growing number of government regulations
There are also system requirements that dictate the use of
A typical off- -line converter will have a power factor of
There is a similar situation in aircraft systems, where a
Unity power factor is defined as the current waveform
v, i
v, i
Figure 25. Voltage and Current Waveforms
OFF--LINE CONVERTER
P real = V rms × I rms × PF
PFC CONVERTER
V
V
t
t
I
I
THEORY OF OPERATION
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13
there are two causes of power factor degradation – phase
shift and distortion. Phase shift is normally caused by
reactive loads such as motors which are inductive, or
electroluminescent lighting which is highly capacitive. In
such a case the power factor is relatively simple to analyze,
and is determined by the phase shift.
current.
complicated to analyze and is normally measured with AC
analyzers, although most circuit simulation programs can
also calculate power factor. One of the major causes of
distortion is rectification of the line into a capacitive filter.
This causes current spikes that do not follow the input
voltage waveform. An example of this type of waveform is
shown in the upper diagram in Figure 25.
the input waveform. This reduces the peak current, the rms
current and eliminates any phase shift.
harmonics, and improve the input power factor, designers
have historically used a boost topology. The boost topology
can operate in the Continuous (CCM), Discontinuous
(DCM), or Critical Conduction Mode.
designed to use the universal input ac power 85- -265 Vac, 50
or 60 Hz, and provide a regulated DC bus (typically
400 Vdc). In most applications, the load can not operate off
the high voltage DC bus, so a DC- -DC converter is used to
provide isolation between the AC source and load, and
provide a low voltage output. The advantages to this system
configuration are, low THD, a power factor close to unity,
excellent voltage regulation, and transient response on the
isolated DC output. The major disadvantage of the boost
topology is that two power stages are required which lowers
the systems efficiency, increases components count, cost,
and increases the size of the power supply.
alternative for Power Factor Correction designs, where the
NCP1651 has been designed to control a PFC circuit
operating in a flyback topology. There are several major
advantages to using the flyback topology. First, the user can
create a low voltage isolated secondary output, with a single
power stage, and still achieve a low input current distortion,
and a power factor close to unity. A second advantage,
compared to the boost topology with a DC- -DC converter, is
a lower component count which reduces the size and the cost
of the power supply.
Discontinuous Mode of operation, the following analysis
will help to highlight the advantages of Continuous versus
Discontinuous Mode of operation.
Where θ is the phase angle between the voltage and the
Reduced power factor due to distortion is more
A power converter with PFC forces the current to follow
In most modern PFC circuits, to lower the input current
Most PFC applications using the boost topology are
ON Semiconductor’s NCP1651 offers a unique
The NCP1651 can operate in either the Continuous or
PF = cos θ