EN1C11_15 Datasheet, PDF (8/13 Pages) Vicor Corporation – Component Power Front-end System for EN Compliance

APPLICATION NOTE (CONT.)
Off-Line Power Supply Configuration
The ENMod system maintains the DC output bus voltage
between 250 and 370 Vdc over the entire input voltage range,
which is compatible with all Vicor 300 V input converters.
Autoranging automatically switches to the proper bridge or
doubler mode at startup depending on the input voltage,
eliminating the possibility of damage due to improper line
connection. The ENMod system is rated at 575 W output
power. These modules can serve as the AC front-end for any
number and combination of compatible converters as long as
the maximum power rating is not exceeded.
FARM3 Module Pin Descriptions
(see Figures 1a, 18a and 18b)
Strap (ST) Pin. In addition to input and output power pin
connections, it is necessary to connect the Strap pin to the
center junction of the series hold-up capacitors (C1, C2) for
proper (autoranging) operation. Varistors V1 and V2 provide
capacitor protection. The bleeder resistors (R1, R2) discharge
the hold-up capacitors when power is switched off. Capacitors
C7 and C8 are recommended if the hold-up capacitors are
located more than 3 inches (75mm) from the output pins.
Enable (EN) Pin. The Enable pin must be connected to the PC
or Gate-In pin of all converter modules to disable the converters
during power-up. Otherwise, the converters would attempt to
start while the hold-up capacitors are being charged through the
current limiting thermistor, preventing the bus voltage from
reaching the thermistor bypass threshold, thus disabling the
power supply. The Enable output (the drain of an N channel
MOSFET) is internally pulled up to 15 V through a 150 kΩ
resistor. (see Figure 11)
A signal diode should be placed close to and in series with the
PC or (Gate-In) pin of each converter to eliminate the
possibility of control interference between converters. The
Enable pin switches to the high state (15 V) with respect to the
SR pin to turn on the converters after the power-up inrush is
over. The Enable function also provides input overvoltage
protection for the converters by turning off the converters if
the DC bus voltage exceeds 400 Vdc. The thermistor bypass
switch opens if this condition occurs, placing the thermistor in
series with the input voltage, reducing the bus voltage to a
safe level while limiting input current in case the varistors
conduct. The thermistor bypass switch also opens if a fault or
overload reduces the bus voltage to less than 180 Vdc.
(see Figure 9)
CAUTION: There is no input to output isolation in the ENMods,
hence the –Out of the ENMods and thus the –In of the downstream
DC-DC converter(s) are at a high potential. If it is necessary to
provide an external enable / disable function by controlling the
DC-DC converter’s PC pin (referenced to the –In) of the converter
an opto-isolator or isolated relay should be employed.
EN1xxx
Bus-OK (BOK) Pin. (see Figure 12) The Bus-OK pin is
intended to provide early-warning power fail information and
is also referenced to the SR pin.
CAUTION: There is no input to output isolation in the ENMods. 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.
L, N Pins. Line and neutral input.
+, – Pins. Positive and negative outputs.
SR Pin. Signal return for BOK and EN outputs.
MiniHAM Module Pin
(see Figures 1a, 18a, and 18b)
Filter (see Figure 1b)
The input EMI filter consists of differential and common
mode chokes,Y– rated capacitors (line-ground) and X– rated
capacitors (line-line). This filter configuration provides
sufficient common mode and differential mode insertion loss
in the frequency range between 100 kHz and 30 MHz to
comply with the Level B conducted emissions limit, as
illustrated in Figures 8a thru 8c.
ENMODS™
Page 8 of 13
Rev 3.1
06/2015
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