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 CURRENT 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.
|
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.
|
