BCM4414xD1E13A2yzz
HV VIA Isolation Drawing
EMI
- LO
- LO
Receiver
+HI
-HI
+LO
+LO
ChiP
Input
Output
LISN
LISN
+HI
+LO
Single
DC
Power
Supply
Screen
Room /
Filters
SELV
VIA Input Board
VIA Output Board
VIA BCM
(DUT)
Load
–HI
–LO
RI
- LO
- LO
FI
BI
PE
Figure 27 — Typical test setup block diagram for
Conducted Emissions
Hot-Swap
Many applications use a power architecture based on a 380VDC
distribution bus. This supply level is emerging as a new standard
for efficient distribution of power through board, rack and chassis
mounted Telecom and Datacom systems. The interconnection
between the different modules is accomplished with a backplane
and motherboard. Power is commonly provided to the various
module slots via a 380VDC distribution bus.
Figure 26 — BCM in a VIA package after final assembly
Filtering
The BCM in a VIA package has built-in single stage EMI filtering
with Hot-Swap circuitry located on the high voltage side. The
integrated EMI filtering consists of a common mode choke,
differential mode capacitors, and Y2 common mode capacitors. A
typical test set-up block diagram for conducted emissions is shown
in Figure 27.
In the event of a fault, removal of the faulty module from the rack
is relatively easy, provided that the remaining power modules can
support the step increase in load. Plugging in the replacement
module has more potential for problems, as it presents an
uncharged capacitor load and will draw a large inrush current. This
could cause a momentary, but unacceptable interruption or sag
in the backplane power bus if not limited. Additional problems
may arise if ordinary power module connectors are used, since
the connector pins will engage and disengage in a random and
unpredictable sequence during insertion and removal.
The built-in EMI filtering reduces the HI side voltage ripple. External
LO side filtering can be added as needed, with ceramic capacitance
used as a LO side bypass for this purpose. The filtering, along
with Hot-Swap circuitry, protects the BCM in a VIA package from
overvoltage transients imposed by a system that would exceed
maximum ratings. VIA HI side and LO side voltage ranges shall not
be exceeded. An internal overvoltage function prevents operation
outside of the normal operating HI side range. However, the VIA
is exposed to the applied voltage even when disabled and must
withstand it.
Hot-Swap or hot-plug is a highly desirable feature in many
applications, but also results in several issues that must be
addressed in the system design. A number of related phenomena
occur with a live insertion and removal event, including contact
bouncing, arcing between HI side connector pins, and large voltage
and current transients. Hot-Swap circuitry in the converter modules
protects the module itself and the rest of the system from the
problems associated with live insertion.
The source response is generally the limiting factor in the
overall system response, given the wide bandwidth of the BCM.
Anomalies in the response of the source will appear at the LO side
of the module multiplied by its K factor.
Total load capacitance at the LO side of the BCM shall not exceed
the specified maximum to ensure correct operation in startup.
Due to the wide bandwidth and small LO side impedance of the
BCM, low frequency bypass capacitance and significant energy
storage may be more densely and efficiently provided by adding
capacitance at the HI side of the BCM.
This module provides a high level of integration for DC-DC
converters in 380VDC distribution systems, saving design time
and board space. To allow for the maintenance, reconfiguration,
redundancy and system upgrades, the BCM in a VIA package is
designed to address the function of Hot-Swapping at the 380VDC
distribution bus. Hot-Swap circuitry, as shown in Figure 28, uses
an active MOSFET switching device in series with the HI side line.
During module insertion, the MOSFET is driven into a resistive state
to limit the inrush current as the input capacitance of the inserted
unit is charged. The MOSFET is fully enhanced once the module’s
HI side capacitor has sufficiently charged to minimize losses
during normal operation. Verification of the Hot-Swap circuitry
performance is illustrated through plots of the module’s response
to a live insertion event in Figures 30 and 31.
At frequencies less than 500kHz, the BCM appears as an
impedance of RLO between the source and load. Within this
frequency range, capacitance connected at the HI side appears as
an effective scaled capacitance on the LO side per the relationship
defined in equation (15).
This enables a reduction in the size and number of capacitors used
CHI
CLO
=
(15)
2
K
in a typical system.
BCM® in a VIA Package
Page 23 of 42
Rev 1.5
10/2016
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