User's Manual

Model 1150A DVOR
Rev. - November, 2008
This document contains proprietary information and such information may not be disclosed
to others for any purposes without written permission from SELEX Sistemi Integrati Inc.
2-63
2.3.2.20
Battery Charger Detailed Circuit Theory
Refer to Figure 11-20. The Fanless BCPS CCA provides over 700 watts of DC power which may include up to 250
watts of battery charging power. The Fanless BCPS CCA connects to the Carrier Backplane CCA through 47-pin
right angle cPCI connector P1.
AC input power (line, neutral, and earth) enters through the cPCI connector P1 and fuse F3 to terminal block TB1.
Terminal block TB1 wires through RFI filter FL2 to terminal block TB2 and then to converter brick PS3. Converter
brick PS3 uses capacitors C57, C58, C61, C64, and C65 to create an internal +385Vdc which is stepped-down to
approximately +51Vdc on the output of converter brick PS3 (48VPS1). Resistor RT1 provides a slow start-up of
48VPS1 upon power-up to prevent nuisance openings of fuse F3.
Capacitors C8, C54, C55, C59, and C56 filter the 48VPS1 output of converter brick PS3 before routing to bridge
diodes CR1 and CR45. If another BCPS is present and wired appropriately on the Carrier Backplane, its output
(48VPS2) enters via cPCI connector P1-1 to bridge diodes CR1 and CR47.
The OR’d output of bridge diode CR1 is measured by op-amp U1 across current-sense resistor R2. The output of op-
amp U1-5 is filtered by resistor R4 and capacitor C49 before routing to multiplexer U11-24. The OR’d output after
current-sense resistor R2 is called +48BUSS and routes to several places.
+48BUSS is fused by F1 before powering DC-DC converter U15-1. Capacitors C27 and C28 provide bulk filtering
while zener diodes CR37 and CR39, resistors R47 and R68, capacitor C26, and SCR Q6 provide over-voltage
protection. Inductor L1 and diode CR36 provide feedback to U15-4 to create the +5Vdc (VCC) output which powers
the input of DC-DC converter PS2-3 (as well as many other on-board integrated circuits).
DC-DC converter PS2 creates both +15Vdc and -15Vdc. Resistors R69, R77, R78, and R79 establish a constant load
to keep the outputs of PS3 within regulation. The -15Vdc output of PS2-1 is filtered by capacitors C34 and C36 and
inductor L2 before linear regulator U16 steps it down to -12Vdc (-12ANA). The +15Vdc output of PS2-8 is filtered
by capacitors C35 and C37 and inductor L3 before linear regulator U17 steps it down to +12Vdc (+12ANA). The -
12ANA and +12ANA outputs power many other on-board integrated circuits with the +12ANA also powering the
reference U18-2. The reference U18-6 output (+5VREF) sets the range of the microcontroller U8-6 internal A-D
converter as well as the battery switch voltage level on resistor network RN2-16 and comparator U19-3.
+48BUSS is also fused by F2 before powering DC-DC converter PS1 (if transistor Q11 is on). Microcontroller U8-
33 turns on transistor Q11 by turning on transistor Q12. Microcontroller U8 can verify the input power status of DC-
DC converter PS1 by reading PS1-4 (DC-DC_VIN) after it’s scaled by resistors R101 and R104 on multiplexer
U11-4 as DC-DC_SCALED.
The output of DC-DC converter PS1-9 may be turned on by microcontroller U8-26 through transistor Q5; which
connects to DC-DC converter PS1-5 (~CHG_ENABLE). When ~CHG_ENABLE is low the output of DC-DC
converter PS1-9 is enabled. Resistors R82 and R97 trim the output of DC-DC converter PS1-9 to approximately
+54.2Vdc; the desired battery charge level.
Battery charging is stopped for short times periodically to test whether batteries are connected or have become too
weakened. Microcontroller U8 takes ~CHG_ENABLE high to shut off the output of DC-DC converter PS1-9 then
turns on transistor Q4 (~BATT_DISCHARGE) which places resistors R6, R7, R9, and R10 as a load on the battery.
If the battery is not healthy, this load will lower the scaled battery voltage of resistor network RN3 and
microcontroller U8 will read it at multiplexer U11-25 (BATT_VOLT). Microcontroller U8-32 will then light the
BATT_FAULT LED CR51 through buffer U7.
Battery charging and discharging current is measured by op-amps U4 and U5 across current-sense resistor R14. Op-
amp U4-5 reports charging current after filtering by resistor R85 and capacitor C51 as BATT_CURR_CHG at
multiplexer U11-26. Op-amp U5-5 reports discharging current after filtering by resistor R86 and capacitor C50 as
BATT_CURR_DISCHARGE at multiplexer U11-11.