This invention relates to power supply module for data acquisition systems for
use with flight data recorders and, more particularly, to flight data acquisition units for
10 receiving flight data signals in a variety of signal forms.
BACKGROUND OF THE INVENTION
Flight data recorders are monitoring and recording instruments, carried aboard
15 an aircraft, which systematically monitor and store the instantaneous values of various
aircraft parameters. Early recorders were analog electromechanical devices which
periodically marked, in analog form, the value of a given airplane parameter on a
moving wire or other permanent storage medium. The time of occurrence of the
parameter was also suitably scribed into the medium opposite the mark for the sensed
20 parameter. Subsequently, digital flight data recorders have been developed which
operate by converting each analog aircraft parameter into a corresponding digital signal,
and storing the digital signals on a permanent storage medium such as magnetic tape.
The development of solid state memory devices, such as electrically erasable
25 read-only memory, has led to the design of all solid state flight data recorders. The solid
state flight data recorders commonly employ a data acquisition system (DAS) which
receives and processes the various aircraft input signals to be monitored and stored
under the control of a central processing unit (CPU). The analog signals are converted
to digital signals by the DAS and, under CPU control, are passed over a data bus to the
30 solid state memory devices. Programming within the CPU controls the processing of
input airplane signals to corresponding digital signals through the DAS and the
subsequent transference of these digital signals to controlled locations in the solid state
memory.
All dc supply voltages required by FDAU of FDR are generated from 28V dc
35 Aircraft battery. 28V dc is passed via EMI Filter to DC-DC converter, which delivers
following isolated outputs for both FDAU with approximate current ratings are given
below:
FDAU Power Supply
40 • +5 V @ 1.2A
• +15 V @ 0.4A & -15V @ 0.34A
• +5 V (excitation) @ 1.2A
Annexure‐II
Power supply requirement complies with MIL-STD704E including emergency
condition (16V to 31.5V). The SSFDR power consumption is not more than 40Watts.
5
SUMMARY OF PRESENT INVENTION
The power supply module is a sub-assembly of Solid State Flight Data Recorder.
Its function is to convert an aircraft 28V DC supply into five outputs, which are
10 independently short circuit protected and jointly isolated from input. The nominal values
of the five outputs are +5V(1.2A), +15V(0.4A), -15V(0.34A), +3.3V(0.5A) and +5V
excitation (1.2A).
The power supply card contains the following:
15 • Filter Module
• Spike suppressors & capacitor filtering circuit
• +5V & ± 15V DC to DC Converter module
• +3.3V DC to DC Converter module for Flash Memory
• +5V excitation circuit
20
This module accepts the 28V DC aircraft supply and feed to input over voltage
protection circuit, which is protected against over voltage. After over voltage protection,
capacitor & diode are used for reducing at the noise of input supply & prevent the
spikes. Then input signal is fed to filter module. This filter module is specially designed
25 to reduce the input line reflected current. The module is used for protection against
spikes up to ± 600V (50ohm) source impedance. After filtering, the signals are feed to
triple output DC-DC converter (5V,± 15V), single output (+3.3V) DC-DC converter &
single output (+5V excitation) DC-DC converter.
30 BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the present invention will become more apparent
and descriptive in the description when considered together with figures/flow charts
presented:
35
Figure 1: is a Block Diagram of Power Supply Module (PSM)
40
Annexure‐II
DETAILED DESCRIPTION
Figure: 2 is a block diagram illustrating the principal components of a Power
Supply Module (PSM) 5 ) of flight data acquisition unit. A flight data recorder is carried
aboard an aircraft and systematically monitors and stores information related to aircraft
parametric data. Such recorded data may be analyzed at a subsequent time to yield
information related to the source of an aircraft mishap, or simply to provide a diagnostic
and information tool as to the aircraft's performance.
10
The power supply module is a sub-assembly of FDAU. Its function is to convert
an aircraft 28V DC supply into four outputs, which are independently short circuit
protected and jointly isolated from input. The nominal values of the four outputs are +5V
(1.2A), +15V (0.4A), -15V (0.34A), and +5V excitation (1.2A).
15
This module accepts the 28V DC aircraft supply and feed to input over voltage
protection circuit, which is protected against over voltage. After over voltage protection,
capacitor & diode are used for reducing at the noise of input supply & prevent the
spikes. Then input signal is fed to EMI filter module which is specifically designed to
20 reduce the reflected input ripple current of DC/DC converters. After filtering, the signals
are feed to triple output DC-DC converter (5V,± 15V), & single output (+5V excitation)
DC-DC converter.
DC-DC Converter generated outputs are passed through capacitor filter to
25 reduce the noise at the output. DC-DC converter +15V is also passed through +5V IC
regulator circuit to set +5V excitation voltage.
FILTER MODULE (EMI Filter Module):
30 The EMI filter module is specifically designed to reduce the input line reflected
ripple current using inter point’s high frequency DC-DC converter. They are intended for
use in +28VDC to +40VDC application, which must meet MIL – STD-461C CE03 level
of conducted emission.
35 The module is used for protection against spikes of up to ± 600V (50Ω source
impedance) for up to 10 μsec. The 28V will pass on but not be damaged by transients of
± 100V (0.5Ω source for 100msec). The capacitors & diode are used for reducing the
noise of the input supply & prevent the spikes.
40 DC TO DC CONVERTER - (+5V, +15V & -15V Output):
The MTR series of high frequency DC-DC converter offers up to 30 watts of
output power from triple output (+5V, +15V & -15V) configuration. They operate over the
full military temperature range with up to 84% efficiency. Thick film hybrid technique
45 provides military aerospace reliability levels and optimum miniaturization.
Annexure‐II
DC TO DC CONVERTER (5V Output):
This DC/DC converter produces +5V excitation & delivers 1.5W of output power.
5 This converter incorporates a continuous fly back topology with a constant switching
frequency of approximately 370 kHz. Current mode pulse width modulation (PWM)
provides output voltage regulation. Output error voltage is magnetically fed back to the
input side of the PWM to regulate output voltage. This converter includes a soft-start
function to prevent large current draw & minimize overshoot. The converter also
10 provides short circuit protection by restricting the current

WE CLIAMS:-
Accordingly, the description of the present invention is to be considered as illustrative only and is for the purpose of teaching those skilled in the art of the best mode of carrying out the invention. The details may be varied substantially without departing from the spirit of the invention, and exclusive use of all modifications which are within the scope of the appended claims is reserved. The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Function of PSM of FDAU is to convert an aircraft 28V DC supply into four outputs, which are independently short circuit protected and jointly isolated from input. The nominal values of the four outputs are +5V (1.2A), +15V (0.4A), -15V (0.34A), and +5V excitation (1.2A).

2. A PSM as claimed in any of the preceding claims wherein this accepts the 28V DC aircraft supply and feed to input over voltage protection circuit, which is protected against over voltage.

3. A PSM as claimed in any of the preceding claims wherein after over voltage protection, capacitor & diode are used for reducing at the noise of input supply & prevent the spikes.

4. A PSM as claimed in claim 3 wherein input signal is fed to EMI filter module which is specifically designed to reduce the reflected input ripple current of DC/DC converters.

5. A PSM as claimed in claim4 wherein after filtering, the signals are feed to triple output DC-DC converter (5V, 15V), & single output (+5V excitation) DC-DC converter.

6. A PSM as claimed in claim 5 wherein a DC-DC Converter generated outputs are passed through capacitor filter to reduce the noise at the output. DC-DC converter +15V is also passed through +5V IC regulator circuit to set +5V excitation voltage.

7. A PSM as claimed in any of the preceding claims wherein line and load regulation of supply module is less than 80 mV.

8. A PSM as claimed in any of the preceding claims wherein input voltage variation is 16-32V.

9. A PSM as claimed in any of the preceding claims wherein this module complied as per MIL-STD-704E

10. A PSM as claimed in any of the preceding claims wherein module ripple & noise is 50 mV p-p, typical (Max. 1%) ,TagSPECI:As per Annexure-II