BCM400P500T1K8A30 Datasheet, PDF (19/25 Pages) Vicor Corporation – Fixed Ratio DC-DC Converter

Sine Amplitude Converter™ Point of Load Conversion
L_{PRI_IN_LEADS} ^{= 6.7 nH}
+
V_VPRINI
C_{PRI_INT_ESR}
21.5 mΩ
C_{PRI_INT}
0.37 µF
C_IN
RC_IN
I ^IPRI__QQ
25 mA
L_{PRI_INT} = 0.56 µH
–
1/8 • I_SEC
I_O^IS_UEC_T
1.76 nH
V•I
++
138 mΩ
1/8 • V_PRI
––
K
BCM400x500y1K8A3z
RSEC
2_R2_O.6_UTmΩ
C_OUT
L_{SEC_OUT_LEADS} ^{= 1.3 nH}
RC5_C1SE_0OC__UµIN_TΩT_ESR
C_{SEC_INT}
25.6 µF
+
V^V_O^SE_U^C_T
–
Figure 16 — 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 tank is formed by Cr and leakage inductance Lr in the power
transformer windings as shown in the BCM module Block Diagram).
The resonant LC tank, operated at high frequency, is amplitude
modulated as a function of input voltage and output 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 BCM400x500y1K8A3z SAC can be simplified into the preceeding
model.
At no load:
The use of DC voltage transformation provides additional interesting
attributes. Assuming that R_SEC = 0 Ω and I_{PRI_Q} = 0 A, Eq. (3) now
becomes Eq. (1) and is essentially load independent, resistor R is now
placed in series with V_IN.
R_RIN
VV_Pi_Rn_I
+
–
S^SA^AC^C™
K^K=⁼1¹/3^/82
V^VSoEuC t
V_SEC = V_PRI • K
K represents the “turns ratio” of the SAC.
Rearranging Eq (1):
K = ^VSEC
V_PRI
In the presence of load, V_OUT is represented by:
(1)
Figure 17 — K = 1/8 Sine Amplitude Converter
with series input resistor
The relationship between V_PRI and V_SEC becomes:
(2)
V_SEC = (V_PRI – I_PRI ^• R_IN) ^• K
(5)
Substituting the simplified version of Eq. (4)
(I_{PRI_Q} is assumed = 0 A) into Eq. (5) yields:
V_SEC = V_PRI • K – I_SEC • R_SEC
(3)
V_SEC = V_PRI ^• K – I_SEC ^• R_IN ^• K²
(6)
and I_OUT is represented by:
I_SEC =
I_PRI – I_{PRI_Q}
K
(4)
R_OUT represents the impedance of the SAC, and is a function of the
R_DSON of the input and output MOSFETs and the winding resistance of
the power transformer. I_Q represents the quiescent current of the SAC
control, gate drive circuitry, and core losses.
BCM^® Bus Converter
Page 19 of 25
Rev 1.4
07/2015
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