GENERAL INFORMATION:
The “AA” 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
that provide high reliability and low cost.
DESIGN METHODOLOGY:
The “AA” 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 “AA” 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 “AA” 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 “AA” Series features a voltage
monitor on pin 9 referenced to Signal Ground
pin 5. The scale factor is 100:1 on models
from 1kV to 6kV, and 10:1 on models below
1kV. The monitor output impedance is calibrated
for use with a 10- Megohm input impedance
meter. Overall accuracy is ±2.0% with
a temperature coefficient of ±100
ppm per °C.
For
applications requiring a different scale
factor, such as an ADC-compatible design,
an external resistor may be added in parallel
with the output.
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OUTPUT CURRENT MONITOR:
The “AA” 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, compensable,
linear-offset voltage. See Application
Note 13.
REMOTE CONTROL:
The “AA” Series is remotely programmed
with 0 to +5 VDC to produce an output voltage.
Input may be from a control voltage, DAC,
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 464 ohm output impedance. See Figure’s
E & F or Application
Note 1 for more
information.
STANDBY MODE:
The “AA” 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/disable mode, 1 mA will have
to be sunk for proper shutdown.
MECHANICAL:
“AA” Series converters are in PCB-mountable plastic cases requiring
a footprint of 4.46 In² and only 3.35 In³ of volume. Mounting plates and brackets
are available for chassis mounting. 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 “AA” 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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