BCM48BX120Y120B00 Datasheet, PDF (14/20 Pages) Vicor Corporation – Isolated Fixed Ratio DC-DC Converter

Sine Amplitude Converter™ Point of Load Conversion
BCM48Bx120y120B00
I_IN
+
V_IN
I_Q
–
I_OUT
R_OUT
K • I_OUT
V•I
+
+
K • V_IN
–
–
K
+
V_OUT
–
Figure 18 — VI Chip^® module DC model
The Sine Amplitude Converter (SAC™) uses a high frequency
resonant tank to move energy from input to output. 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 input and output stages of the
module is sufficient for full functionality and is key to achieving
power density.
The BCM48Bx120y120B00 SAC can be simplified into the
preceeding model.
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.
The use of DC voltage transformation provides additional
interesting attributes. Assuming that R_OUT = 0Ω and I_Q = 0A, Eq. (3)
now becomes Eq. (1) and is essentially load independent, resistor R
is now placed in series with V_IN.
At no load:
V_OUT = V_IN • K
K represents the “turns ratio” of the SAC.
Rearranging Eq (1):
K = ^VOUT
V_IN
In the presence of load, V_OUT is represented by:
V_OUT = V_IN • K – I_OUT • R_OUT
and I_OUT is represented by:
I ^{OU T = IIN}
–
K
I_Q
R
(1)
V_Vinin
+
–
S_SA_AC_C™
K^K=⁼1¹/3^/42
VV_oo_uu_tt
Figure 19 — K = 1/4 Sine Amplitude Converter
(2)
with series input resistor
The relationship between V_IN and V_OUT becomes:
V_OUT = (V_IN – I_IN • R) • K
(5)
(3)
Substituting the simplified version of Eq. (4)
(I_Q is assumed = 0A) into Eq. (5) yields:
(4)
V_OUT = V_IN • K – I_OUT • R • K²
(6)
BCM^® Bus Converter
Page 14 of 20
Rev 1.3
08/2016
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