V048X320Y009A Datasheet, PDF (11/18 Pages) Vicor Corporation – High Efficiency, Sine Amplitude Converter

Not Recommended for New Designs
V048x320y009A
11.0 SINE AMPLITUDE CONVERTER^TM POINT OF LOAD CONVERSION
The Sine Amplitude Converter (SAC) uses a high frequency
resonant tank to move energy from input to output. (The
resonant tank is formed by Cr and leakage inductance Lr in the
power transformer windings as shown in the VTM module
Block Diagram. See Section 10). 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 V048x320y009A SAC can be simplified into the following
model:
L_IN = 5.8 nH
+
V^VIN_IN
C^C_ININ
R0_{RC.C5IN7IN mΩ}
2 µF
I^I_Q^Q
73 mA
–
2/3 • I_OUT
I_O^IO_UU_TT
8800 pH
V•I
++
0.5 Ω
2/3 • V_IN
––
K
R^R_OOU_UT_T
97.4 mΩ
C_O^C_UO_TUT
L_OUT = 600 pH
+
R^R8C_5CO_0OU_µT_UΩT
4.2 µF
V^VO_OU_UT_T
–
Figure 14 — VI Chip^® module AC model
At no load:
V_OUT = V_IN ^• K
K represents the “turns ratio” of the SAC.
Rearranging Eq (1):
The use of DC voltage transformation provides additional
interesting attributes. Assuming that R_OUT = 0 Ω and I_Q = 0 A,
(1)
Eq. (3) now becomes Eq. (1) and is essentially load
independent, resistor R is now placed in series with V_IN as
shown in Figure 15.
K = ^VOUT
V_IN
(2)
RR
VV_INin
+
–
S_SA_AC_C™
K^K =⁼ 1¹/^/3³2²
VV_Oo_Uu_Tt
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:
(3)
Figure 15 — K = 1/32 Sine Amplitude Converter™
with series input resistor
I_OUT
=
I_IN
–
K
I_Q
(4)
The relationship between V_IN and V_OUT becomes:
R_OUT represents the impedance of the SAC, and is a function of ^{VOUT = (VIN – IIN • R) • K}
(5)
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 and gate drive circuitry.
Substituting the simplified version of Eq. (4)
(I_Q is assumed = 0 A) into Eq. (5) yields:
V_OUT = V_IN • K – I_OUT • R • K²
(6)
VTM^® Current Multiplier
Page 11 of 18
Rev 1.0
01/2014
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