Thales NSS 100S-1 Component Maintenance Manual With Illustrated Parts List page 70

G. Operation of sub-unit Power supply PCB Z1 (see Figure 8)
(1) Functions
Using +28VFILT (+28VAVION mains filtered on the Z2 filter PCB), PCB Z1
is designed to supply:
- The voltage levels necessary for RPU operation:
- +15VUC, -15VUC, +15VHF -15VHF, +5VUC, -5VUC, +5VSPIL (+5 V backed up
by batteries), to guarantee that information remains stored during a
mains failure.
- The following service signals
. ITCOUPAL (power supply cut-off interrupt), MST (power on), SURPILE
(battery monitoring), STEMPE (temperature monitoring)
- An energy reserve in order to mask power transients on the +28VFILT.
(2) Protection and threshold circuit
This circuit protects the DC/DC converter, PS3 against polarity reversal
and feedback currents (in case the energy reserve is used).
This circuit uses a reference voltage = +17 V, used to make a "reserve
Command" signal,
- This circuit uses a reference voltage of +10 V, provided by PCB Z1 and
two threshold voltages:
- Energy command threshold = + 17 V, used to provide the "Reserve com-
mand" signal,
- Anti feedback blockage threshold = +20 V, used to command transistor
CMOS Q1; this transistor functions as an assisted diode; when the
+28VFILT is lower than + 20 V, transistor Q1 is blocked, which insu-
lates the RPU from the aircraft mains.
(3) DC/DC converter PS3
It is powered by the +28VFILT, filtered once again in the Z1 PCB by an
LC filter.
condary galvanic insulation) which generates voltages of +15V, -15V,
+5V, adjusted to +/- 5%, for an input voltage (+28VFILT) between +24 V
and + 30 V (steady state regime).
(4) Current limitation
This circuit detects the current discharged using a series resistor pla-
ced in the feedback signal 0VFILT.
Whenever the current is higher than 6 A, it generates the "I limit" si-
gnal which is applied to the amplitude limiter circuit.
commands transistor CMOS Q2 which functions as a variable resistor, the-
reby enabling a limitation of the current discharged.
COPYRIGHT SEXTANT Avionique 1995
c
The document reference is online, please check the correspondence between the online documentation and the printed version.
COMPONENT MAINTENANCE MANUAL
C17004
It comprises the PS3 circuit(converter with primary and se-
This circuit
34-57-96
Page 44
MAY 30/95