GENERAL INFORMATION:
The “A” Series of high-voltage,
regulated DC-DC converters addresses the needs
of the miniature-PCB-mount-regulated- high-voltage-power-supply
user. Designed and built utilizing state-of-the-art
power conversion topology, these units feature
surface mount technology and encapsulation
techniques providing high reliability and low
cost.
DESIGN METHODOLOGY:
The “A” converters
utilize
a dual-ended
forward
converter
topology
with a
nominal
switch
frequency
of <100kHz.
A precision
reference
is provided
so the
remote
control
can program
the power
supply
for a specific
voltage.
Once input
voltage
stabilizes,
under-voltage
lockout
is released.
As soon
as enable
is raised
above a
TTL 1,
the converter
begins
to switch.
The soft-start
circuit
brings
the converter
to full
power over
a 1mS period,
reducing
surges
on the
source
supply.
A constant-frequency
PWM regulation
system
controls
the MOSFET
push-pull
power stage,
which drives
the high
voltage
transformer.
The power
stage is
protected
from output
current
overloads
or short
circuits
via a secondary
current
limit circuit.
High voltage
is developed
by a multistage
multiplier
while feedback
voltage
is developed
and sent
to the
CTRL circuit
to maintain
regulation.
Internal
filters
are provided
to reduce
input current
ripple
and output
voltage
ripple.
WIDE INPUT RANGE:
The “A” Series
is
designed
for
full
power
operation
at
up
to
90%
efficiency.
A
wide
input
range
of
+11
to
+16VDC
or
+23
to
+30VDC
will
maintain
full
power
output
without
derating.
The
derated
input
range
is
+9
to
+32VDC.
See
Application
Note
16 for
protection
information.
WIDE OUTPUT RANGE:
The “A” Series
is
a
non-isolated,
unipolar
converter.
Positive
or
negative
output
must
be
specified.
Output
voltage
is
adjustable
from
0
to
62,
125,
250,
500,
1kV,
2kV,
4kV,
or
6kV.
As
the
output
voltage
is
reduced
towards
0,
the
maximum
current
capability
remains
unchanged.
OUTPUT VOLTAGE MONITOR:
The “A” Series features an output
current monitor. Current from the high-voltage
multiplier can be monitored by reading the
voltage appearing between Output Monitor
pin 3 and Signal Ground Return pin 5. Internal
voltage dividers create a small linear offset
voltage. See Application
Note 13.
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REMOTE CONTROL:
The “A” Series is remotely programmed with 0 to +5 VDC to produce
an output voltage. Input may be from a control voltage, a DAC, or from a variable
or fixed resistor. On a negative output converter the programming logic of
the remote adjust would be inverted, i.e.: +5 to 0VDC. Connections are on the
converter for the internal reference, analog remote adjust and the signal ground.
The reference is +5.0VDC, temperature compensated with a 464Ω output impedance.
See Figure E & F or Application Note 1 for more information.
STANDBY MODE:
The “A” converters also have
an enable function. When the enable is TTL
0 (<+0.7V Isink=1mA) the converter is
in a standby mode and input current is reduced
to <30 mA. All functions other than the
internal reference are shut down. If the
enable pin is left unconnected, TTL 1, or
at greater voltages up to +32VDC the converter
operates normally. The open circuit output
voltage from the Enable pin is <+5VDC.
In the inhibit mode, 1 mA will have to be
sunk for proper shutdown.
MECHANICAL:
“A” Series converters are in PCB mountable plastic cases requiring
a footprint of 5.5 in² and only 4.3 in³ of volume. Mounting plates and brackets
are available for chassis mounting. This Series is also available in an RF-tight
metal PCB/chassis mount package. See Application Note 6 for thermal considerations
and mounting configurations. All models are available with optional, six-sided,
wrap-around Mu-Metal Shielding.
ENVIRONMENTAL:
The “A” Series provides full
power operation at case temperatures from
-40 to +65°C. All units receive a 24-hour
burn-in prior to final testing. Extended
temperature range is available along with
other enhanced capabilities. Please contact
the factory.
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