Vicor Micro Family of DC-DC Converter - Manual (Page 50)

Design Guide & Applications Manual
For Maxi, Mini, Micro Family DC-DC Converters and Configurable Power Supplies
Maxi, Mini, Micro Design Guide Rev 4.9 vicorpower.com
Page 49 of 88
Apps. Eng. 800 927.9474 800 735.6200
10. High Boost HAM
GATE IN (BAMD) Pin. The Gate In pin is an interface pin
to the Gate Out pin of a HAMD or BAMD depending on
configuration. The user should not make any other
connection to this pin.
GATE OUT Pin. The Gate Out pin is a synchronization pin
for HAMD/BAMD arrays; the user should not make any
other connection to this pin.
+OUT and -OUT Pin. Connect the +OUT of the HAM to
the +IN of the respective Vicor DC-DC converters with the
recommended fuse. Connect the -OUT of the HAM to the
-IN of the converters. In addition, an external hold-up
capacitor of 1,000 µF with a minimum voltage rating of
450 Vdc, is required (across the output of the HAM) for 16
ms ride through time at full power (500 µF for half power,
etc). This capacitor must be in close proximity to the HAM.
Do not exceed 3,000 µF of total output
capacitance. Lower values of capacitance may be used for
reduced hold up requirements, but not less than 500 µF.
Lower capacitance values may degrade power factor
specifications.
Auxiliary Supply (A/S) Pin. The HAM provides a low
voltage non isolated output Auxiliary Supply (A/S) that may
be used to power primary side control and monitoring
circuitry. This output is 19 – 23 Vdc, referenced to -OUT, at
3 mA max. Do not overload or short this output as the
HAM will fail. A typical use for A/S is to power an optical
coupler that isolates the Power OK signal (Figure 10-6).
Enable Output (E/O) Pin. The Enable Output (E/O) is used
to inhibit the DC-DC converters at start up until the hold
up capacitors are charged, at which time Enable is asserted
high (open state, Figure 10–8). If the AC line fails, E/O
goes low when the DC output of the HAM drops below
250 Vdc.
E/O must be connected to the Gate Input of all VI-26x and
VI-J6x drivers and/or the PC pin of the V375 DC-DC
converters (Figure 10-4); failure to do so may cause the
converters to toggle on and off. If an external load is
connected directly to the output of the HAM, do not apply
the load until the output hold up capacitor(s) are fully
charged.
In applications using VI-26x drivers and VI-26x boosters,
the E/O pin should be connected to the Gate In pin of the
driver module only, it is not necessary to connect this pin
to boosters as they are controlled by their respective driver.
The E/O pin ancillary circuitry illustrated in Figures 10–4
and 10–5 provides transient immunity. The illustrated
circuitry is the minimum required, see Figures 10–4 and
10–5.
Power OK (P/OK) Pin. Power OK is a monitor signal that
indicates the status of the AC mains and the DC output
voltage of the HAM. P/OK is asserted (active low) when
the output bus voltage is within normal operating range
(>270 Vdc) and 20 – 25 ms after DC-DC converters are
enabled by the E/O signal of the HAM. This provides suffi-
cient time for the converters to turn on and their output(s)
to stabilize prior to P/OK being asserted, (Figure 10–9).
For momentary interruptions of AC power, the HAM will
provide at least 16 ms of ride through or hold up time
(with 1,000 µF output capacitor). On loss of power or
brownout, (when the HAM output voltage drops below
270 Vdc) the P/OK signal will go to an open circuit state
(Figure 10–7), signaling an impending loss of input power
to the converter modules. P/OK will provide power fail
warning at least 1 ms prior to converter shut down.
When the HAM output voltage drops below 250 Vdc the
converters are disabled via Enable Output (E/O).
NOTE: Acoustic Noise. Audible noise may be emitted
from the module under no load, light load, or
dynamic loading conditions. This is considered
normal operation of the module.
SAFETY NOTES
Each HAM, HAMD or BAMD module must be
preceded by a safety agency recognized fast-blow
10A 3AG fuse.
The HAM is not isolated from the line – either input
or output; a line isolation transformer must be used
when making scope measurements. HAMs do not
provide input to output isolation. Differential probes
should be used when probing the input and output
simultaneously to avoid destructive ground loops.
PROTECTIVE FEATURES
Over Temperature Shut Down. The HAM is designed to
shut down when the temperature of the baseplate exceeds
90 °C. Do not operate the HAM above its maximum
operating temperature of 85°C.
Short Circuit Protection. The HAM contains output short
circuit protection. Operation of this function does not clear
the input fuse and the output will resume normal
operation after removal of the fault.
A short period of time may be required to allow for
cooling of an internal temperature sensor.
Output Over Voltage Protection. The HAM contains
output over voltage protection. In the event the output
voltage exceeds approximately 420 Vdc, the boost will
decrease to maintain 420 Vdc on the output. When the
peak of the AC line exceeds 420 V (approximately
293 Vac) the boost will have been reduced to zero and the
E/O line will be pulled low shutting down the
converters. Beyond this the protection circuit will be
enabled and the output voltage will decrease.