MPFC-115-270-QP Datasheet, PDF (8/16 Pages) SynQor Worldwide Headquarters – Internal inrush current limit

Application Section
Basic Operation & Features
The MPFCQor power factor correction module is an
essential building block of an overall high power AC-DC
power supply. As shown in Fig. A, a typical power supply
would be comprised of a SynQor MCOTS AC Line Filter,
a SynQor MPFCQor module, an energy storage hold-up
capacitor and one or more SynQor MCOTS DC-DC
converters, depending on how many output voltages are
required. Fuses are needed in various places to meet safety
requirements.
The primary purpose of the MPFCQor is to shape the input
current that is drawn from a single-phase sinusoidal AC source
into a nearly perfect sinusoidal waveform so that the AC-DC
power supply will present a very high power factor load (PF >
0.99) to this source. In doing this wave-shaping, the MPFCQor
ensures that the harmonic components of the AC current
waveform are below the levels called for in MIL-STD-1399. The
total harmonic distortion of the AC current waveform is less than
8%.
The MPFCQor accomplishes its wave-shaping task by first
rectifying the filtered AC source voltage, and then processing the
input power through a non-isolated, high-efficiency, high-
frequency “boost converter” that both gives the input AC current
its sinusoidal shape and provides a regulated DC voltage across
the hold-up capacitor.
The hold-up capacitor handles the cyclic imbalance between
the flow of energy drawn from the AC source and the flow of
energy delivered to the DC-DC converters. This energy
imbalance has a cyclic frequency twice that of the AC source
voltage (e.g. 120Hz for a 60Hz input). This relatively low
frequency makes the hold-up capacitor relatively large. Another
purpose of the hold-up capacitor is to be a source of energy so
that the DC-DC converters can continue to deliver load power
during a temporary brownout or dropout of the AC source. A
typical power supply will have sufficient hold-up capacitor to
give a “hold-up time” in the 20ms range, but longer times can be
achieved with yet more hold-up capacitance.
Besides shaping the AC current waveform, the MPFCQor
performs several other important functions. At start-up it controls
the level of inrush current drawn from the AC source to charge the
hold-up capacitor. It limits the DC current that can be drawn from
its output and it will shut-down if a short circuit appears across the
output. It will also shut-down if the AC input voltage is out of its
range (either too high or too low) for too long, or if the temperature
of the module is too high.
In addition, the MPFCQor has input and output control signals
that include PFC_ENABLE, and LOAD_ENABLE, (which doubles
as a POWER_OUT_GOOD signal). Both signals are described in
more detail below. There is also an auxiliary bias supply that can
MPFC-115-270-QP
Input:85-180Vrms
Output:270Vdc
Power:350W
be used to power a low power control circuit at the output of the
MPFCQor.
StartUp Sequence
When the AC source voltage is first applied, regardless of
whether the MPFCQor is enabled or disabled through its
PFC_ENABLE pin, the MPFCQor will pre-charge the
output hold-up capacitor with a current limited to
approximately 50mA. This pre-charging continues until
the output voltage is within approximately 10V of the peak
voltage of the AC source. If, at this time, the PFC_ENABLE
input is logically high, and the MPFCQor is therefore
disabled, the MPFCQor will remain in this pre-charged
state indefinitely.
NOTE: During both this pre-charging time and for
whatever time afterwards that the MPFCQor remains disabled
it is essential that all the load converters connected to the
output of the MPFCQor be disabled so that the total load
current seen by the MPFCQor is only a small fraction of the
50mA charging current. To help facilitate this requirement,
the MPFCQor’s LOAD_ENABLE output can be used to
disable the load converters.
When the PFC_ENABLE input pin is pulled low, and after
the pre-charging is completed if it is not already, the boost
converter within the MPFCQor will start operating and the
MPFCQor’s output voltage will be increased to its nominal
regulated value.
After this regulated voltage level is achieved, the MPFCQor
will provide a logical low signal on its LOAD_ENABLE output
pin. This signal should be used to enable the load converters so
that they can begin to draw power from the MPFCQor.
If the PFC_ENABLE input is de-asserted (pulled high or
allowed to float), the boost converter in the MPFCQor will shut
down and the LOAD_ENABLE output pin will return to a logic
high. This will then disable the load converters.
NOTE: The voltage across the hold-up capacitor will remain in
a charged state after the MPFCQor is disabled as long as the AC
source voltage is present.
Product # MPFC-115-270-QP
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Doc.# 005-0006727 Rev. B 03/31/2016
Page 8