BCM6123XD1E5126YZZ Datasheet, PDF (24/30 Pages) Vicor Corporation – Isolated Fixed-Ratio DC-DC Converter

BCM6123xD1E5126yzz
Sine Amplitude Converter™ Point of Load Conversion
L_{PRI_IN_LEADS} ^{= 6.7nH}
+
VV_PRINI
C_{PRI_INT_ESR}
21.5mΩ
C_{PRI_INT}
0.37µF
C_IN
RC_IN
I ^IPRI__QQ
25.8mA
L_{PRI_INT} = 1.20µH
–
1/8 • I_SEC
I_O^IS_UEC_T
1.77nH
V•I
++
139mΩ
1/8 • V_PRI
––
K
R_SEC
2_R4_O.2_Um_T Ω
C_OUT
L_{SEC_OUT_LEADS} ^{= 1.3nH}
RCC_{SEOC_UINTT_ESR}
510µΩ
C_{SEC_INT}
25.6µF
+
V^V_O^SE_U^C_T
–
Figure 19 — BCM module AC model
The Sine Amplitude Converter (SAC™) uses a high frequency
resonant tank to move energy from Primary to secondary and
vice versa. The resonant LC tank, operated at high frequency,
is amplitude modulated as a function of primary voltage and
secondary current. A small amount of capacitance embedded in
the primary and secondary stages of the module is sufficient for full
functionality and is key to achieving high power density.
The BCM6123xD1E5126yzz SAC can be simplified into the
preceeding model.
At no load:
V_SEC = V_PRI • K
(1)
K represents the “turns ratio” of the SAC.
Rearranging Eq (1):
K=
V_SEC
V_PRI
(2)
In the presence of load, V_SEC is represented by:
V_SEC = V_PRI • K – I_SEC • R_SEC
(3)
and I_SEC is represented by:
I_SEC
=
I_PRI – I_{PRI_Q}
K
(4)
R_SEC represents the impedance of the SAC, and is a function of
the R_DSON of the primary and secondary MOSFETs and the winding
resistance of the power transformer. I_{PRI_Q} represents the quiescent
current of the SAC control, gate drive circuitry, and core losses.
The use of DC voltage transformation provides additional
interesting attributes. Assuming that R_SEC = 0Ω and I_{PRI_Q} = 0A,
Eq. (3) now becomes Eq. (1) and is essentially load independent,
resistor R is now placed in series with V_PRI.
R
+
V^V_Pⁱ_Rⁿ_{I –}
S^SA^AC^C™
K^K=⁼1¹/3^/82
V_So_Eu_C t
Figure 20 — K = 1/8 Sine Amplitude Converter
with series primary resistor
The relationship between V_PRI and V_SEC becomes:
( ) ^V_SEC ^{= V}_PRI ^{– I}_PRI ^{• R • K}
(5)
Substituting the simplified version of Eq. (4)
(I_{PRI_Q} is assumed = 0A) into Eq. (5) yields:
V_SEC = V_PRI • K – I_SEC • R • K²
(6)
This is similar in form to Eq. (3), where R_SEC is used to represent the
characteristic impedance of the SAC™. However, in this case a real
R on the primary side of the SAC is effectively scaled by K² with
respect to the secondary.
Assuming that R = 1Ω, the effective R as seen from the secondary
side is 16mΩ, with K = 1/8.
BCM^® Bus Converter
Page 24 of 30
Rev 1.1
01/2017
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