Vicor Javelin III - Manual (Page 5)

Javelin III Power Supply Operator’s Manual
Rev. 05/11/2012 Mission Power Solutions (760) 631-6846 [email protected] Pg. 5
Technical Description
The Javelin III consists of an off-line single phase or three phase power-factor-corrected front end (or optional
DC), with EMI filter, cooling fans, customer interface, associated housekeeping circuits, and a selection of Vi-
cor’s DC-DC converters. Three power supply units are placed in parallel to provide the final output current
capability.
Input AC mains (or DC) voltage is applied to a 2-, 3-, or 4-pin power terminal strip (see Table 1, Pg. 2). The
input current is passed through three individual EMI filters designed to meet conducted noise limit “A” specifi-
cation of FCC Part 15 and EN55022 level “B.”
At start-up, inrush current is limited in each power supply unit by a PTC thermistor. The PTC is shunted out
shortly after initial power-up by a DC bus voltage sense circuit driving a thyristor. After rectification, the input
voltage is applied to a boost converter that keeps the AC input current sinusoidal and synchronized with the
input AC voltage (in compliance with EN61000-3-2). The boost converter delivers a regulated input to the
hold-up capacitors and a high voltage backplane. The backplane supplies power to the DC-DC converters that
provide the desired low voltage, regulated output.
Voltage conversion is achieved by Vicor’s family of Zero-Current-Switching (ZCS) DC-DC converters. These
are forward converters in which the main switching element switches at zero current. This patented topology
has a number of unique attributes: low switching losses, high frequency operation (resulting in reduced size for
magnetics and capacitors), excellent line and load regulation, wide output adjustment range, low EMI/RFI
emission, and high efficiency.
At initial power-up, the Javelin III output is disabled to limit the inrush current and to allow the DC bus poten-
tial to settle out to the correct operating level. A low-power flyback converter operating with PWM current-
mode control converts the high voltage DC bus into regulated low voltage to power the internal housekeeping
circuits and DC cooling fans.
The internal housekeeping Vcc comes up within 1 second after the application of input power. Once the high
voltage bus is within operating limits, the AC Power OK signal changes its output to a TTL “1,” which indi-
cates the input power is OK and allows the power output to come up 15-30 ms later. An auxiliary Vcc output
of 5VDC, capable of sourcing up to 300mA, is provided for peripheral use.
An output Inhibit/Enable function is provided by using an optocoupler to control Vicor’s DC-DC converters. If
the Inhibit control pin is pulled low and the Enable pin is high or open, the optocoupler will turn on and disable
the output. The delay for an output to come up when measured from release of the Enable pin is 5-10 ms. See
Table 2 (Pg. 3) for a logic table.
To utilize trim capabilities, consult Mission Power Solutions’ Engineering Department.