BCM6123XD1E1368YZZ Datasheet, PDF (27/30 Pages) Vicor Corporation – Isolated Fixed-Ratio DC-DC Converter

Figure 23 shows a scenario where there is no bottom side cooling.
In this case, the heat flow path to the bottom is left open and the
equations now simplify to:
T_INT – PD₁ • Φ_INT-TOP = T_{CASE_TOP}
T_INT – PD₃ • Φ_INT-LEADS = T_LEADS
PD_TOTAL = PD₁+ PD₃
Power Dissipation (W)
Thermal Resistance Top
ΦINT-TOP
Thermal Resistance Bottom
ΦINT-BOTTOM
T_{CASE_BOTTOM}(°C)
MAX INTERNAL TEMP
Thermal Resistance Leads
ΦINT-LEADS
T_LEADS(°C)
T_{CASE_TOP}(°C)
+
–
V_PRI
+ _DC
BCM6123xD1E1368yzz
Z_{IN_EQ1}
Z_{IN_EQ2}
BCM^®1
R_{0_1}
Z_{OUT_EQ1}
V_SEC
BCM^®2
R_{0_2}
Z_{OUT_EQ2}
Load
Z_{IN_EQn}
BCM^®n
R_{0_n}
Z_{OUT_EQn}
Figure 24 — Top case thermal model
Figure 24 shows a scenario where there is no bottom side and
leads cooling. In this case, the heat flow paths to the bottom and
leads are left open and the equations now simplify to:
T_INT – PD₁ • Φ_INT-TOP = T_{CASE_TOP}
PD_TOTAL = PD₁
Please note that Vicor has a suite of online tools, including a
simulator and thermal estimator that greatly simplify the task of
determining whether or not a BCM thermal configuration is valid
for a given condition. These tools can be found at:
http://www.vicorpower.com/powerbench.
Current Sharing
The performance of the BCM topology is based on efficient
transfer of energy through a transformer without the need of
closed loop control. For this reason, the transfer characteristic
can be approximated by an ideal transformer with a positive
temperature coefficient series resistance.
This type of characteristic is close to the impedance characteristic
of a DC power distribution system both in dynamic (AC) behavior
and for steady state (DC) operation.
When multiple BCMs of a given part number are connected in an
array, they will inherently share the load current according to the
equivalent impedance divider that the system implements from the
power source to the point of load. Ensuring equal current sharing
among modules requires that BCM array impedances be matched.
Some general recommendations to achieve matched array
impedances include:
nnDedicate common copper planes within the PCB to deliver and
return the current to the modules.
nnProvide as symmetric a PCB layout as possible among modules
nnA dedicated input filter for each BCM in an array is required to
prevent circulating currents.
For further details see:
AN:016 Using BCM Bus Converters in High Power Arrays.
BCM^® Bus Converter
Page 27 of 30
Rev 1.1
04/2017
Figure 25 — BCM parallel array
Fuse Selection
In order to provide flexibility in configuring power systems, ChiP
modules are not internally fused. Input line fusing of ChiP products
is recommended at the system level to provide thermal protection
in case of catastrophic failure.
The fuse shall be selected by closely matching system requirements
with the following characteristics:
nnCurrent rating
(usually greater than maximum current of BCM)
nnMaximum voltage rating
(usually greater than the maximum possible input voltage)
nnAmbient temperature
nnNominal melting I²t
nnRecommend fuse: See safety agency approvals.
Reverse Operation
BCMs are capable of reverse power operation. Once the unit is
started, energy will be transferred from the secondary back to
the primary whenever the secondary voltage exceeds V_PRI • K.
The module will continue operation in this fashion for as long as
no faults occur.
Transient operation in reverse is expected in cases where there is
significant energy storage on the output and transient voltages
appear on the input.
The BCM6123xD1E1368y0R and BCM6123xD1E1368y0P are both
qualified for continuous operation in reverse power condition.
A primary voltage of V_{PRI_DC} > V_{PRI_UVLO+_R} must be applied first
to allow the primary reference controller and power train to
start. Continuous operation in reverse is then possible after a
successful startup.
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800 927.9474