NCP1653A データシートの表示（PDF） - ON Semiconductor
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NCP1653A Datasheet PDF : 19 Pages
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NCP1653, NCP1653A
FUNCTIONAL DESCRIPTION
Introduction
The NCP1653 is a Power Factor Correction (PFC) boost
controller designed to operate in fixed−frequency
Continuous Conduction Mode (CCM). It can operate in
either peak current−mode or average current−mode.
Fixed−frequency operation eases the compliance with
EMI standards and the limitation of the possible radiated
noise that may pollute surrounding systems. The CCM
operation reduces the application di/dt and the resulting
interference. The NCP1653 is designed in a compact 8−pin
package which offers the minimum number of external
components. It simplifies the design and reduces the cost.
The output stage of the NCP1653 incorporates ±1.5 A
current capability for direct driving of the MOSFET in
high−power applications.
The NCP1653 is implemented in constant output voltage
or follower boost modes. The follower boost mode permits
one to significantly reduce the size of the PFC circuit
inductor and power MOSFET. With this technique, the
output voltage is not set at a constant level but depends on
the RMS input voltage or load demand. It allows lower
output voltage and hence the inductor and power MOSFET
size or cost are reduced.
Hence, NCP1653 is an ideal candidate in high−power
applications where cost−effectiveness, reliability and high
power factor are the key parameters. The NCP1653
incorporates all the necessary features to build a compact
and rugged PFC stage.
The NCP1653 provides the following protection features:
1. Overvoltage Protection (OVP) is activated and
the Drive Output (Pin 7) goes low when the
output voltage exceeds 107% of the nominal
regulation level which is a user−defined value.
The circuit automatically resumes operation when
the output voltage becomes lower than the 107%.
2. Undervoltage Protection (UVP) is activated and
the device is shut down when the output voltage
goes below 8% of the nominal regulation level.
The circuit automatically starts operation when
the output voltage goes above 12% of the
nominal regulation level. This feature also
provides output open−loop protection, and an
external shutdown feature.
3. Overpower Limitation (OPL) is activated and the
Drive Output (Pin 7) duty ratio is reduced by
pulling down an internal signal when a computed
input power exceeds a permissible level. OPL is
automatically deactivated when this computed input
power becomes lower than the permissible level.
4. Overcurrent Protection (OCP) is activated and
the Drive Output (Pin 7) goes low when the
inductor current exceeds a user−defined value.
The operation resumes when the inductor current
becomes lower than this value.
5. Thermal Shutdown (TSD) is activated and the
Drive Output (Pin 7) is disabled when the
junction temperature exceeds 150_C. The
operation resumes when the junction temperature
falls down by typical 30_C.
CCM PFC Boost
A CCM PFC boost converter is shown in Figure 25. The
input voltage is a rectified 50 or 60 Hz sinusoidal signal.
The MOSFET is switching at a high frequency (typically
102 kHz in the NCP1653) so that the inductor current IL
basically consists of high and low−frequency components.
Filter capacitor Cfilter is an essential and very small value
capacitor in order to eliminate the high−frequency
component of the inductor current IL. This filter capacitor
cannot be too bulky because it can pollute the power factor
by distorting the rectified sinusoidal input voltage.
Iin
IL
L
Vin
Vout
Cfilter
Cbulk
Figure 25. CCM PFC Boost Converter
PFC Methodology
The NCP1653 uses a proprietary PFC methodology
particularly designed for CCM operation. The PFC
methodology is described in this section.
IL
Iin
t1
t2
time
T
Figure 26. Inductor Current in CCM
As shown in Figure 26, the inductor current IL in a
switching period T includes a charging phase for duration
t1 and a discharging phase for duration t2. The voltage
conversion ratio is obtained in (eq.1).
Vout
Vin
+
t1
)
t2
t2
+
T
T
*
t1
Vin
+
T
*
T
t1
Vout
(eq.1)
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