SMPS (Switch Mode Power Supply) is used to provide -48V DC power for equipment that requires DC voltage, as UPS only provides AC voltage. SMPS converts the AC supply to DC through rectification and switching technology. It has advantages like high efficiency over 94%, modularity, and easy maintenance. Key components of SMPS include lightening protection, switch mode rectifiers to convert AC to DC, a control unit to monitor parameters, and an interface to connect to external signals and batteries. SMPS is used redundantly in pairs to power critical telecom equipment in DMRC requiring -48V DC supply through distribution boxes.

1. SWITCH MODE POWER
SUPPLY (SMPS):

2. SWITCH MODE POWER SUPPLY (SMPS):
 Although we have UPS but still we require SMPS
because of the reason that UPS provides ac voltage and
there are certain equipments used in DMRC, which
operates on dc voltage. So SMPS fulfills the requirement
and provides –48Vdc supply so that the equipments can
be operated properly.
SMPS Technology:
 High frequency switching
 MOSFET / IGBT as power elements
 High efficiency
ISO 9001:2008

3. SMPS Advantages:
 Modularity and redundancy
 High efficiency, better than 94%
 Easy maintenance and servicing
SMPS consists of following sections:
 Lightening and Surge Protection (LPDS)
 Switch Mode Rectifiers (SMR)
 CSU (Display Unit)
 MUIB and MMIB
 LVDS (Low Voltage disconnection switch)
ISO 9001:2008

4.  Lightening Protection Devices: These devices are
provided in the system for protection of the circuits. AC
supply first passes through LPD and then to system
 AC input OV/UV protection: Protection against over
and under voltage is provided through input contactor
that will isolate the Rectifiers in case the input falls below
or above pre-defined limits. This contactor will
automatically reconnect the Rectifiers with the mains AC
as soon as it’s normal restoration
 LVDS: Low Voltage Disconnect Switch
ISO 9001:2008

5. AC SUPPLY MINI CSU ALARMS
ISO 9001:2008
AC DISTRIBUTION
SMR
RACK
DC DISTRIBUTION
MUIB
Tambient
LVDS
1 or 2 Batteries
T batteries

6. Switch Mode Rectifiers (SMR): SMR is full wave rectifier with
load capacity of 25A. Details of each individual rectifier modules in a
rack can be checked in CSU.
Control and Supervisory Unit (CSU): CSU is a micro
controller based menu driven control unit with LCD display, whose
operation is manually interfaced through number of push buttons. It
can monitor all parameters and communicates with all rectifiers and
external world.
Mains User Interface Board (MUIB): MUIB is the nterface
between CSU and external signals like battery current, LVDS,
temperature, alarms, etc.
Main Monitoring Interface Board (MMIB): It senses mains
input voltage, current & frequency and send these signals to CSU via
MUIB
Low Voltage Disconnect Switch (LVDS): LVDS protects
battery from deep discharge by disconnecting battery from Load, while
discharging.
ISO 9001:2008

7. SMPS connections at DMRC:
SMPS-1 SMPS-2
48V DC 48V DC
ISO 9001:2008
AC
SUPPLY
LPD
LOAD
(From battery bank 2)
(From battery bank 1) (From battery bank 2)
LPD- Light Protecting Device

8. ISO 9001:2008
SMPS Panel:
1
LED LED LED
CSU
(Control and Supervisory Unit)
SMR
1
SMR
2
SMR
3
1 2 3
4 5 6
Functions of button 1-6:
1-SMR 2-Battery 3-CSU
4-Increase 5-Decrease 6-Enter
Number of SMR
depends on the
DC voltage
requirement.
For example, there
are 13 SMRs at
Rajendera Place
station and 6
SMRs at Ramesh
Nagar station due
to EBTS rack.

9. OPERATION:
 Two incomer supplies, one main and other emergency,
goes to input isolator which is a transformer. Input
cubicle supplies input to UPS-1, UPS-2, SMPS, SCVS,
Cell Charger and Spare.
 Input to UPS-1 and -2 gives 3-phase AC stabilized
output, which is passed to ACDB (AC Distribution Box).
From ACDB it is supplied to Telecom equipments and
signaling equipments. Telecom equipments, which use
AC supply, are PIDS/PAS, Clocks, CCTV and NP-SCADA.
All systems except PIDS/PAS use 1-phase
ISO 9001:2008
supply.
 Cell charger is used to charge cell, but can’t charge cell
below 1.75V


10.  SCVS (Servo Controlled Voltage Stabilizer) also
stabilizes the input 3-phase supply, in case main supply
is missing output from SCVS is used for bypass static
and maintenance supply. SCVS consists of Zener Diode
and control protection Circuits.
 Battery current sharing cubicle works as battery
isolator in case of battery maintenance or batteries
discharged below 346V.
 SMPS takes AC supply converts it to DC. It is used by
Telecom equipments requiring DC voltage like SDH,
EBTS and EPABX through DCDB (DC Distribution Box).
In DMRC, two SMPS are used for redundancy. Two
battery banks for each SMPS are provided for supporting
function in absence of main supply.


ISO 9001:2008

11. Any Questions?
ISO 9001:2008

12. THANK YOU
ISO 9001:2008