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Design Guide & Applications Manual

For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

VI-200 and VI-J00 Family Design Guide

Rev 3.4

vicorpower.com

Page 33 of 97

Apps. Eng. 800 927.9474

800 735.6200

OVERVIEW

In combination with VI-200 and VI-J00 Family of DC-DC
converter modules, the Alternating Input Module (AIM)
provides a high density, low profile, universal AC input
off-line switching power supply for systems requiring
up to 200 W of total output power. The AIM accepts
85 – 264 Vac, with a DC output voltage proportional to
the peak value of the AC line. The input voltage required
for the AIM to start operating is between 82 V and 90 Vrms
(non-distorted sinusoid).

The DC output of the AIM is the peak rectified line
(Vac RMS X 2 ), thus, 85 Vac corresponds to 120 Vdc
and 264 Vac corresponds to 373 Vdc. Since the DC
output range is wide, a “7” (100 – 375 V) designator for
input voltage in the part number of the DC-DC converter
is required. However, the “5” (100 – 200 V) designator
for the DC-DC converter part number is available for
domestic AC inputs only and the “6” (200 – 400 V)
designator for European AC inputs only, potentially
reducing the number of modules required in some
applications, based on output power capability.

SUMMARY OF COMPATIBLE DOWNSTREAM
DC-DC CONVERTERS

Use VI-x7x for inputs of 85–264 Vac; VI-x6x for inputs of
170–264 Vac; or VI-x5x for inputs of 85–135 Vac. EMC
filtering specifications of FCC Level A are met by adding
a 0.47 µF “X-type” capacitor to the input of the AIM
(Vicor Part #03047); “Y-type” bypass capacitors must also
be added from the +/– inputs of the DC-DC converters to
their respective baseplates, which are grounded (Vicor
Part #01000, 4,700 pF). To select the hold-up capacitor
appropriate for your application, (refer to Selecting
Capacitors for AIM Modules section that follows).

The output ripple of the AIM is a function of output load.
It is necessary to keep the ripple less than 20 V p-p to
ensure the under / overvoltage protection circuits will not
trigger. A fully loaded AIM (200 W of module output
power) requires a minimum of 680 µF of capacitance;
hold-up requirements can be met with this capacitor and
maximum total capacitance should not exceed 1,200 µF
(refer to Selecting Capacitors for AIM Modules section
that follows). The voltage rating of this capacitor will be
determined by the input operating voltage.

It is necessary to connect all “Driver” DC-DC converter
GATE IN pins to the GATE IN pin of the AIM . This GATE IN
to GATE IN connection is used to disable the converters at
turn-on to allow proper start-up of the AIM . The DC-DC
converters are then enabled through the GATE IN pin when
the output bus voltage is in the range of 113 – 123 Vdc.

Input overvoltage conditions cause the GATE IN pin of the
AIM to disable the converters when the output bus voltage
is in the range of 406 – 423 Vdc. Input undervoltage
conditions cause the GATE IN to disable the converters
when the output bus voltage drops within the range of
68 – 89 Vdc.

CAUTION: The AIM is not isolated. Do not place scope
probes on input and output of AIM simultaneously. Do
not connect the output of the AIM to earth ground.

The GATE OUT of the AIM must be connected to the
GATE OUT of only one DC-DC converter. This input signal
to the AIM controls a charge pump (D1, D2, C2) that
biases the gate of Q1, 10 V above its source, which turns
on Q1 to shunt out a PTC thermistor that limits inrush.
Multiple DC-DC converters operating from an AIM may
make it difficult to guarantee a 10% load on the DC-DC
converter that provides the GATE OUT signal to the AIM .
In this instance, other DC-DC converters can charge pump
the FET through the PARALLEL pin, with the addition of
two diodes and a capacitor to each Driver module.
(Figure 12– 4)

EMI
Filter

10 V

Vref
2

Vref 1

+OUT

–OUT

GATE IN

GATE OUT

PARALLEL

Level
Shift

L2/N

Figure 12–1