Southern Avionics Company SD100 Manual Do Utilizador
SD SERIES TRANSMITTER
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Southern Avionics Company
2.2.2 RF PA Power Supply PCB
SLP10003 RF PA Power Supply
The PA Power Supply (PAPS)
The PA Power Supply consists of three sub-sections, namely, the Inrush Current section , the DC Controller,
and the DC-DC Converter. Included with these are associated signal sense and fault circuitry. Taking them one at a
time in the general structure of their usage follows.
time in the general structure of their usage follows.
1.) The Inrush Current Section:
After receiving the HV-ON signal from the Controller / Monitor, this section switches on HV-DC
and controls the charge rate of the HV DC supply capacitors to avoid damagingly high inrush currents. It
does this by limiting the charge current and monitoring the voltage build-up on the large capacitor bank
until it reaches an acceptable charge level, after which unlimited current is applied. The Raw HV is sampled
and fed back to the Controller / Monitor.
does this by limiting the charge current and monitoring the voltage build-up on the large capacitor bank
until it reaches an acceptable charge level, after which unlimited current is applied. The Raw HV is sampled
and fed back to the Controller / Monitor.
2.) The DC Controller
This section is a buck regulator with feedback control to reduce the Raw HV DC down to level
usable by the RF Power Amplifier section. Under Controller / Monitor control, the output of this section can
be varied, which in turn will vary the power output of the RF Power Amplifier. The feedback allows the DC
Controller to respond to the peak power demands of the PA greatly reducing or eliminating carrier droop.
This section Also isolates the PA from input power fluctuations and or “brown-outs”, and maintains a steady
power output over widely varying conditions. Since the DC Controller controls the RF power output and the
PA sections modulator can run a constant carrier level duty cycle, power can be changed with out resetting
the modulation percentage. The DC Controllers Voltage and Current output is sampled and fed back to the
Controller / Monitor for monitoring. Fault conditions for current and voltage will automatically shut down
the section and report to the Controller / Monitor which can attempt to bring the unit back on line if the
problem was transitory or perhaps switch transmitters if the system is a dual configuration.
be varied, which in turn will vary the power output of the RF Power Amplifier. The feedback allows the DC
Controller to respond to the peak power demands of the PA greatly reducing or eliminating carrier droop.
This section Also isolates the PA from input power fluctuations and or “brown-outs”, and maintains a steady
power output over widely varying conditions. Since the DC Controller controls the RF power output and the
PA sections modulator can run a constant carrier level duty cycle, power can be changed with out resetting
the modulation percentage. The DC Controllers Voltage and Current output is sampled and fed back to the
Controller / Monitor for monitoring. Fault conditions for current and voltage will automatically shut down
the section and report to the Controller / Monitor which can attempt to bring the unit back on line if the
problem was transitory or perhaps switch transmitters if the system is a dual configuration.
3.) The DC-DC Converter
The converter will take an optional 48VDC battery back-up source and produce HV which is
combined with the normal AC HVDC to provide a seamless transition from AC to DC operation in the event
of a Brownout or AC power failure. It is purposely set lower than the nominal AC HVDC to allow for
simple diode combining and to preserve battery life while outputting a legal signal. It is NOT regulated but
rather will slowly output less HV as the batteries drain. If regulated it would draw more and more current as
the batteries became weaker. Since the system is computer controlled decisions can be made to stay on the
air at reduced power levels in emergency situations allowing battery conservation . The Converter is a basic
Chopped DC-DC converter with over-current sensing and local fault shutdown latches. The fault condition
is also reported to the Controller / Monitor. A Reset of all latched fault logic states can be is performed by
the Controller / Monitor as necessary. A dual low voltage +12VDC supply 12VA and 12VB is fed by
+50VDC derived from the AC line or 48VDC supplied by the battery backup ensuring continuous operation
of the low level stages after the initial power on. The separated 12V feeds ensures minimal cross-talk
between the DC-DC Controller and the DC Controller. As an aside the 50VDC supply (located elsewhere
of a Brownout or AC power failure. It is purposely set lower than the nominal AC HVDC to allow for
simple diode combining and to preserve battery life while outputting a legal signal. It is NOT regulated but
rather will slowly output less HV as the batteries drain. If regulated it would draw more and more current as
the batteries became weaker. Since the system is computer controlled decisions can be made to stay on the
air at reduced power levels in emergency situations allowing battery conservation . The Converter is a basic
Chopped DC-DC converter with over-current sensing and local fault shutdown latches. The fault condition
is also reported to the Controller / Monitor. A Reset of all latched fault logic states can be is performed by
the Controller / Monitor as necessary. A dual low voltage +12VDC supply 12VA and 12VB is fed by
+50VDC derived from the AC line or 48VDC supplied by the battery backup ensuring continuous operation
of the low level stages after the initial power on. The separated 12V feeds ensures minimal cross-talk
between the DC-DC Controller and the DC Controller. As an aside the 50VDC supply (located elsewhere