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.
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
simultaneously to the input and output as this will destroy the unit.
+In
N
ST
L
+V
BOK
EN
–V
Vicor
DC-DC
Converter
15Vdc
150kΩ
Micro-
controller
Gate In (PC)
Vico
DC-D
Conver
Gate Out (PR)
–In
To additional modules
Figure 9—Enable
(EN) function; See Fig.8 for details
+In
+5 Vdc
Vicor
DC-DC
Converter
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.
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.
The energy stored on a capacitor which has been charged to
voltage V is:
N
ST
L
15Vdc
27kΩ
Micro-
controller
+V
BOK
EN
–V
Secondary
referenced
Gate In (PC)
Gate Out (PR)
–In
To additional modules
D
Co
Figure 10—Bus
OK (B OK) isolated power status indicator
R1
Part
Description
1.0µF
4700pF
0.15µF
12A fuse
27µH
1.3mH
10Ω
150kΩ, 0.5W
2.2Ω
MOV
03040
00127-1503
Vicor
Part Number
02573
01000
03269
05147
14563
15016
L2/N
L1
Z1
L1
GND
R2
C1
L2
F1
R3
L3
C2
R4
ε
= 1/2(CV
2
)
Where:
(1)
N
ST
L
C1
C2, C3
C4
F1
ε
= stored energy
C = capacitance
V = voltage across the capacitor
C3
C4
L1, L2
L3
R1, R2
R3
Low power filter connections
R4
Z1
Energy is given up by the capacitors as they are discharged by
the converters. The energy expended (the power-time product)
is:
L2/N
Z1
390K
1/2W
10
1/2W
R2
C1
L3
4700pF
C3
4700pF
.22µF
(X2)
C4
N
C6
ε
= P∆t = C(V
12
–V
22
) / 2
Where:
(2)
R1
4700pF
C2
4700pF
C5
ST
L
L1
F1
L1
L2
L4
GND
Part
L1,L4
Description
1000µH 12A/6.5MΩ
22µH
.68µf (x type)
4700pf
.22µf (x type)
390k
1
/
2
W
10Ω
1
/
2
W
17A/250V
MOV
Vicor
Part Number
02134
11479
02573
03285
04068
P = operating power
∆t
= discharge interval
V
1
= capacitor voltage at the beginning of
∆t
V
2
= capacitor voltage at the end of
∆t
High power filter connections
L2, L3
C1
C2,C3,C4,C5
C6
R1
R2
F1
Z1
Rearranging equation 2 to solve for the required capacitance:
C = 2P∆t / (V
12
–V
22
)
(3)
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
Set your site on VICOR at www.vicorpower.com
VICOR [ VICOR CORPORATION ]
