Vicor Westcor PFC Mini Power Factor Corrected AC-DC Switcher - Manual (Page 4)

UG:115 vicorpower.com Applications Engineering: 800 927.9474 Page 4
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 outputs.
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 adjustment range for output; low EMI/RFI
emission and high efficiencies.
At initial power-up, the PFC Mini outputs are disabled to limit the inrush current and
to allow the DC bus potential 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 V
CC
comes up within two seconds after the application of
input power. Once the high voltage bus is within operating limits, the AC Power OK
signal asserts to a TTL "1," indicating the input power is OK, and enables the power
outputs. An auxiliary V
CC
output of 5 Vdc sourcing up to 0.3 A is provided for
peripheral use.
An output Enable/Disable function is provided by using an optocoupler to control
Vicor’s DC-DC converters. If the Enable/Disable control pin is pulled low, the
optocoupler turns on and disables the output. The nominal delay associated for an
output to come up when measured from release of the Enable/Disable pin is 5-10 ms.
The General Shutdown function controls all outputs simultaneously and works in a
similar manner.
Line Filter Rectifier
Soft Start
Circuit
Boost Converter
PFC Control
E/D Control
Output Card #1
Output Card #2
Output Card #3
Fan
Isolated
Housekeeping
Power
Customer
Interface
Power
Output
Power
Output
Power
Output
Input
High Voltage
Bus
Enable/Disable Control
Current
Sample
Waveform
Sample
Figure 1.