Application Note, continued
Bus-OK (B OK) Pin. (See Fig. 10). The Bus-OK pin is
intended to provide early-warning power fail information
and is also referenced to the negative output pin.
Vicor
DC-DC
Converter
+In
Gate In (PC)
Caution: There is no input to output isolation in the ARM.
It is necessary to monitor Bus-OK via an optoisolator if it is to
be used on the secondary (output) side of the converters. A line
isolation transformer should be used when performing scope
measurements. Scope probes should never be applied
+V
15Vdc
N
Vico
DC-D
Conver
BOK
EN
150kΩ
Micro-
controller
ST
L
Gate Out (PR)
–In
–V
simultaneously to the input and output as this will destroy the unit.
To additional modules
Filter. Two input filter recommendations are shown for low
power VI-ARM-1 and high power VI-ARM-2 (See Fig. 11).
Both filter configurations provide sufficient common mode and
differential mode insertion loss in the frequency range between
100kHz and 30MHz to comply with the Level B conducted
emissions limit.
Figure 9—Enable (EN) function; See Fig.8 for details
Vicor
DC-DC
+In
Converter
Hold-up Capacitors. Hold-up capacitor values should be
determined according to output bus voltage ripple, power fail
hold-up time, and ride-through time. (See Fig. 12). Many
applications require the power supply to maintain output
regulation during a momentary power failure of specified
duration, i.e., the converters must hold-up or ride-through such
an event while maintaining undisturbed output voltage
regulation. Similarly, many of these same systems require
notification of an impending power failure in order to allow time
to perform an orderly shutdown.
+5 Vdc
Gate In (PC)
+V
15Vdc
N
D
Secondary
referenced
BOK
EN
27kΩ
Micro-
controller
ST
L
Co
Gate Out (PR)
–In
–V
To additional modules
Figure 10—Bus OK (B OK) isolated power status indicator
The energy stored on a capacitor which has been charged to
voltage V is:
R1
ε = 1/2(CV2)
(1)
Vicor
Part Number
Part
C1
Description
1.0µF
L3
C2
C3
02573
N
L2/N
C2, C3
C4
4700pF
0.15µF
12A fuse
27µH
01000
L1
L2
R4
R3
Z1
C1
ST
L
03269
Where: ε = stored energy
F1
05147
L1
L1, L2
L3
14563
F1
C = capacitance
C4
1.3mH
15016
GND
R1, R2
R3
10Ω
V = voltage across the capacitor
R2
150kΩ, 0.5W
2.2Ω
00127-1503
03040
R4
Low power filter connections
Z1
MOV
Energy is given up by the capacitors as they are discharged by
the converters. The energy expended (the power-time product)
is:
R2
2
2
10
1/2W
ε = P∆t = C(V1 –V2 ) / 2
(2)
L2/N
N
C4
C3
4700pF
4700pF
L3
C1
C6
.22µF
(X2)
390K
1/2W
R1
Z1
ST
L
C5
C2
Where: P = operating power
4700pF
4700pF
L1
∆t = discharge interval
L4
L1
F1
L2
V1 = capacitor voltage at the beginning of ∆t
Vicor
Part Number
GND
V2 = capacitor voltage at the end of ∆t
Part
L1,L4
L2, L3
C1
Description
1000µH 12A/6.5MΩ
22µH
02134
11479
02573
03285
04068
High power filter connections
.68µf (x type)
Rearranging equation 2 to solve for the required capacitance:
C2,C3,C4,C5 4700pf
C6
R1
R2
F1
Z1
.22µf (x type)
390k 1 2 W
10Ω 1 2 W
/
2
2
/
C = 2P∆t / (V1 –V2 )
(3)
17A/250V
MOV
03040
Figure 11—Filter connections
Vicor Corp. Tel: 800-735-6200, 978-470-2900 Fax: 978-475-6715
ARM, Autoranging Rectifier Module
Rev. 2.4
Page 7 of 12
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