Not Recommended for New Designs
B048x096y24A
9.0 SINE AMPLITUDE CONVERTER™ POINT OF LOAD CONVERSION
943 pH
IOIOUUTT
LOUT = 600 pH
ROUT
ROUT
LIN = 5.8 nH
7.8 mΩ
+
+
RCOUT
400 µΩ
R
RCIN
0.57 mΩ
COUT
R
0.5 Ω
1/5 • VIN
CIN
V•I
K
1/5 • IOUT
+
–
C
CININ
2 µF
COCUT
45 µF
+
–
OUT
VVOOUUTT
VIN
VIN
IQ
IQ
90 mA
–
–
Figure 13 — VI Chip® module AC model
The Sine Amplitude Converter (SAC™) uses a high frequency
resonant tank to move energy from input to output. (The
ROUT represents the impedance of the SAC, and is a function of
the RDSON of the input and output MOSFETs and the winding
resistance of the power transformer. IQ represents the
quiescent current of the SAC control, gate drive circuitry, and
core losses.
resonant tank is formed by Cr and leakage inductance Lr in the
power transformer windings as shown in the BCM module
Block Diagram. See Section 8). 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 use of DC voltage transformation provides additional
interesting attributes. Assuming that ROUT = 0 Ω and IQ = 0 A,
Eq. (3) now becomes Eq. (1) and is essentially load
independent, resistor R is now placed in series with VIN.
The B048x096y24A SAC can be simplified into the preceeding
model.
At no load:
R
R
SAC™
SAC
Vout
VOUT
+
–
K = 1/5
VIN
Vin
K = 1/32
•
VOUT = VIN
K
(1)
(2)
K represents the “turns ratio” of the SAC.
Rearranging Eq (1):
Figure 14 — K = 1/5 Sine Amplitude Converter™
VOUT
K =
with series input resistor
VIN
The relationship between VIN and VOUT becomes:
•
•
VOUT = (VIN – IIN R) K
(5)
In the presence of load, VOUT is represented by:
Substituting the simplified version of Eq. (4)
(IQ is assumed = 0 A) into Eq. (5) yields:
•
•
VOUT = VIN K – IOUT ROUT
(3)
(4)
and IOUT is represented by:
IIN – IQ
2
•
•
•
VOUT = VIN K – IOUT R K
(6)
IOUT
=
K
BCM® Bus Converter
Page 11 of 18
Rev 1.1
vicorpower.com
800 927.9474
08/2014
VICOR [ VICOR CORPORATION ]
