BCM6123X60E10A5YZZ Datasheet, PDF (26/29 Pages) Vicor Corporation – 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 (°C)
LEADS
T_{CASE_TOP}(°C)
+
–
V_PRI
+ _DC
BCM6123x60E10A5yzz
Z_{PRI_EQ1}
Z_{PRI_EQ2}
BCM^®1
R_{0_1}
Z_{SEC_EQ1}
V_SEC
BCM^®2
R_{0_2}
Z_{SEC_EQ2}
Load
Z_{PRI_EQn}
BCM^®n
R_{0_n}
Z_{SEC_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 which 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 SAC™ 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 BCM modules 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.
Some general recommendations to achieve matched array
impedances include:
n Dedicate common copper planes within the PCB
to deliver and return the current to the modules.
n Provide as symmetric a PCB layout as possible among modules
n An input filter is required for an array of BCMs in order to
prevent circulating currents.
For further details see AN:016 Using BCM Bus Converters
in High Power Arrays.
Figure 25 — BCM module array
Fuse Selection
In order to provide flexibility in configuring power systems
VI Chip^® modules are not internally fused. Input line fusing
of VI Chip products is recommended at 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:
n Current rating
(usually greater than maximum current of BCM module)
n Maximum voltage rating
(usually greater than the maximum possible input voltage)
n Ambient temperature
n Nominal melting I²t
n Recommend fuse: ≤ 40A Littelfuse 456 Series (primary side)
Reverse Operation
BCM modules are capable of reverse power operation. Once the
unit is started, energy will be transferred from 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 secondary and transient voltages
appear on the primary.
BCM^® Bus Converter
Page 26 of 29
Rev 1.2
07/2016
vicorpower.com
800 927.9474