FIELD OF THE INVENTION
The invention relates to a switch mode DC to DC converter. More particularly,
the invention relates to an Intelligent control power supply.
BACKGROUND OF THE INVENTION
In applications like traction and rechargeable, 110V battery supply is used as the
main source of control voltage, wherein the control electronics is designed with
+5V,+/-15V or in some cases with +/-24V. In some converter/inverter
application five types (+5V,+15V,-15V,+24V, and 24V) of regulated power
supply is also required. This power supply has a DC input and generates said five
different levels of output which are galvanocally isolated from the input. The
control electronics are generally designed with a common reference potential
which is referred as "OV". To eliminate possibility of common potential point
miss-match, all the out puts are designed with a common potential reference and
kept isolated from it's input source.
The output voltage ranges as described hereinabove, are very common in control
electronics application. Different levels of voltage can be achieved with a liner
regulator and switch mode power supply. A linear regulator provides the desired
output voltage by dissipating excess power in ohmic losses. A linear regulator
regulates either output voltage or current by dissipating the excess electric
power in the form of heat, and hence its maximum power efficiency is voltage-
out/voltage-in since the volt difference is wasted. In contrast, a switched-mode
power supply regulates either output voltage or current by switching ideal
storage element, like inductors and capacitors, into and out of different electrical
configurations. Ideal switching elements (e.g., transistors operator outside of
their active mode) have no resistance when "closed" and carry no current when
"open", and so the converters can theoretically operate with 100% efficiency
(i.e., all input power is delivered to the load, no power is wasted as dissipated
heat). Another advantage of Switch mode power supply is that isolated out puts
can be achieved by transformer isolation technique.
Dedicated switching devices to switch three high frequency transformers is
known in the art which in turn generate following 3 Levels of regulated DC
voltages:

+15 VOLT supply being generated from +24 V supply using another switch mode
buck regulator. And -15 V is being generated from -24 V supply with a liner
regulator. By these ways all the specified 5 Levels of Voltages are generated
which are galvanocally isolated from Input supply (110 V).
The prior art power supply in particular applicable to 3-phase electro-loco have
following major disadvantages:
Out of 5 outputs, 3 outputs are generated with switching mode concept.
Regulation is controlled with +5V and +24V supply only. +15V and -15V outputs
are dependent on loads of +5V. Therefore, without loading +5V, +/-15v output
supply can not be loaded instantaneously, if so, power supply trips and becomes
out of service. Cycle by cycle current is not sensed. So activation of short circuit
protection takes longer time causing overstressing of switching and other
semiconductors devices risking their life expectancy. The power supply can not
start with zero load. Automatic fault recovery mode does not exist.
However, it is evident that the periodical switching to obtain the regulated
outputs with variation of load and input supply requires a close loop control.
Accordingly, the present provides an active and passive snubber circuit and a
clamping circuit to eliminate the prior art problem of periodical switching.
Further, the noise immunity and generated electromagnetic noises according to
the inventive switching converter are kept within limit to satisfy international
standard IEC60571.
Automatic protection means are incorporated to operate with main control
electronics of the Inverter (where the power supply being used) to protect the
power supply itself and transmitting a signal to the control electronics for
isolation of the equipment from main power line of traction.
The inventive concept was to develop a reliable power supply to be compatable
with 3-phase Electro-loco in particular. The developed power supply has many
added features against a known general purpose DC DC power supply, for
example, protection logic, soft start up, ON-OFF-OUT OF SERVICE indication,
external Interfacing with control electronics for Inverter protection. Although
similar features are independently known in prior art, the invention however
improves each feature and provide a unique and innovative combination which
produces an improved result.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an Intelligent Control Power
Supply (ICPS) for control voltage supply of +5V,+/-15V and +/-24V in particular
to 3-phse electric-loco.
Another object of the invention is to propose an Intelligent Control Power Supply
(ICPS) in an Inverter being interfaced with main control electronics through a
digital logic.
A still another object of the invention is to propose an Intelligent Control Power
Supply (ICPS) which is enabled to receive pulses of 1.66Hz with duty cycle
<0.1% and shut down the power supply using the received pulses.
A further object of the invention is to propose an Intelligent Control Power
(ICPS) which automatically gets activated after thermal shutdown once the
temperature reduces to a preset hysteresys band.
A still further object of the invention is to propose an Intelligent Control Power
(ICPS) which is capable to provide independently regulated 5 levels of outputs.
SUMMARY OF THE INVENTION
According to the invention, there is provided Intelligent Control Power supply
device for 3-phase electro-locomotive including Inverter application.
The inventive power supply device is provided with a switch mode regulator, and
four outputs out of a total five outputs are generated under switching mode
mechanism. Each of the outputs is loaded independently and having individual
regulation control. According to the invention, output currents are sensed in
every cycle of switching, therefore protection against short-circuit is quite fast
which intern reduces flash-over during short-circuit. Further, the power supply is
shut down gradually without overstressing. The inventive power supply does not
require any initial loading, and is capable to regulate to zero load without any
dummy loading. In an event of thermal shutdown due to high temperature, the
power supply device gets automatically activated once the threshold temperature
is returned. This phenomenon allows elimination of frequent switching ON/OFF
of the device.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a Block diagram for +5V supply generation
Figure 2 - shows a Block diagram for +24V and +15V supply generation
Figure 3 - shows a Block diagram for +24V and -15V supply generation
Figure 4 - shows a Block diagram for protection and monitoring of the DC
-DC
Figure 5 - shows the component placement of the PCB of the switch mode
DC DC power supply including details of input and output
according to the invention
Figure 6 - shows a pictorial view of the switch mode DC DC power supply
according to the invention.
DETAIL DESCRIPTION OF THE INVENTION
In an Switch mode power supply, the output current flow depends on the input
power signal, the storage elements and circuit topologies used, and also on the
pattern used (e.g., pulse-width modulation with an adjustable duty cycle) to
drive the switching elements. Typically, the spectral density of these switching
waveforms has energy concentrated at relatively high frequencies. As such,
switching transients, like ripple, introduced onto the output waveforms can be
filtered with small LC filters.
SPECIFICATION:
A. Input : 110 V nominal
180 maximum
80 V minimum
B. Outputs:
i) Vol: 5 V, ± 1%, 4 Amp; Vripple = 50 mV.
ii) Vol2: +15 V, ± 2%, 1.2 Amp; Vripple = 150 mV.
iii) Vol3: -15 V, ± 2%, 1.2 Amp; Vripple = 150 mV.
iv) V04: + 24 V, ± 5%, 3.2 Amp; Vripple = 300 mV.
v) V05: -24 V, ± 5%, 3.2 Amp; Vripple = 300 mV.
Tolerances mentioned is '%' is the variation of outputs in the entire range of
Loading from 0 Amp to it's rated value as mentioned as Load current.
Vripple => Because, a switching mode power supply, there is essentially
switching of the inputs through magnetic circuit to convert it to a different level,
here it is reduced levels, as described in a buck converter. Because of the
switching associated duty cycle, there is certain period, when the input voltage is
made forcibly low (Ov) during turn on time (Ton) and during turn off time (Toff)
voltage is passed to output side. And therefore it generates a average value with
respected to time cycle. Voltage ripple is peak to peak voltage around the DC
value.
GENERATION OF DIFFERENT LEVEL OF SUPPLY
This is transformer isolated buck converters (step down) switched at primary
side of a transformer and secondary output of the transformer is related as
follows:
V in = (primary) X ns/np x Ton/T_= V_Sec.
Ns = transformer secondary Turn.
Np = transformer primary Turn.
Ton = O N time
T = cycle time 1/fs where fs = switching frequency.
The dedicated switching devices being used to switch three transformer primary
which intern generate following 3 Levels regulated DC voltages
1) 5 V
2) +24 V
3) -24 V
+15 VOLT supply being generated from +24 V supply with another switch mode
regulator. And -15 V is being generated from -24 V supply with a linear
regulator.
By the ways all the specified 5 Levels of Voltages are generated which are
galvanocally Primary supply (110 V).
INTERFACE LOGIC
The power supply is developed to suit with an exciting control electronics Rack.
The existing electronics Rack is used in 100KVa Aux. converter which controls a
semi controlled rectifier through firing angle of thyristor gate pulse and generate
3-phase pulses for GTO based inverter module. The inverter module gate driver

and rectifier gate is energized with +/-24V supply of the present art. It is
essential to turn off GTO's before shut down of the system otherwise GTO failure
is foreseen. In case of any fault in inverter, the GTO driver takes care about
protection of the GTO's but it is to be ensured that the +/-24 supply is present
during certain time. The thyristor pulses are directly being generated with the
same +/-24V. Therefore, in case of Thyristor and it's gate circuit problem the +/-
24V supply is directly affected and it's level can go down to zero. In a running
aux. converter, this situation can create severe damage in inverter modules. To
ensure safe turn off of GTO's before shutting down, the thryistor pulses are
monitored in control electronics to the Aux. converter. In case of any disturbance
in the thyristor firing and ifs gate circuit, same is detected and short digital
pusles (Wl) of 1.67Hz with duty cycle <1% are generated to send message to
locomotive central electronics about the occurrence of fault and to the power
supply to shut down the system. Thus the Aux. converter control electronics and
the locomotive centrals electronics gets the message of occurrence of the fault
and take necessary action for safety of the entire system, logs fault data before
the DC DC power supply gets shut down the system.
Therefore, it is the system safety requirement to interface correctly with the
CDPF signal of the Aux. converter electronics to the Switch mode DC DC
converter.
Another signals being generated in the power supply to illuminate two status
LED's.
1) GREEN LED: When glows, the power supply is ON and all the outputs are
available.
2) YELLOW LED: It's glows to indicate availability of input as well as the
power supply is out of service OR switch is off.
Truth table for indication and interface logic:
SW1 = Switch
Power on reset time = 300ms
HIGH VOLTAGE POWER ON RESET
Power on reset circuit is the temporary reset pulse for fixed duration at start up.
We are considering input voltage level as high voltage (77V to 180V) in
comparison to output voltage levels (+5V, +/-15V and +/-24V). Because of
multiple nos. of switching devices being used for multiple dc outputs and
presence of large nos of magnetic circuit and capacitors, it takes time to build up
all the outputs. The outputs build up time also depends on connected loads.
During the output build up times, since all the out puts are not reached to it's
specified limits, the inbuild output monitoring circuit may activate and detect the
output fault and which can not be possible to avoid. Therefore, the Power on
reset circuit for the specific delay of 300 ms is designed at input voltage levels to
immune to the fault detected at output voltage circuit monitoring during start up.
It is significant to mention here that the input circuit and output dc voltage
circuits are electrically isolated. Hence, the DC output fault signal is interfaced
with high voltage power on reset circuit through opto isolator and potential free
relay contact.
Simplified block diagram in Figure- 4 shows the protection, monitoring, power on
reset and interfacing of external fault signal form electronic rack of a
Inverter/Aux. converter. The indication signals for two LED's Yellow and Green
also shown in figure -4.
There are tow signals to drive two LED's to indicate the status of power supply:
3) Green LED: When glows, status the power supply is on and all the outputs
are available.
4) Yellow LED: It's glows to indicate availability of input as well as the power
supply is out of service or switch is at off state.
From the above, it is understood that function and logic behind the green LED is
simple that is only when all the outputs are available, then only this LED glows.
It is the status of healthiness of the power supply and in-service condition.
However, Yellow LED has wider and complex logics. It glows as below:
1) Input supply available but switch is not on.
2) Input supply available but switch is on and a fault occurred or failed to
build up the output before elapse of power on reset delay time.
3) Input supply available, switch is on and error generated is the electronic
rack due to a failure of pulse monitoring after power on reset time elapse.
Therefore, it is important to assign a definite power on reset time with linking
input supply availability and switching it on.
WE CLAIM
1. An Intelligent Control Power Supply (ICPS) device in 3-phase electro
locomotives for control voltage supply of +5V,+/-15V and +/-24V from
single DC input of range 77V to 200V, wherein all the outputs of +5V,
+15V, -15V, +24V, and -24Vare independent6ly regulated via a switch
mode regulator and loadable upto 4A, 1.4A,1.4A,3A and 3A respectively,
wherein the device is enabled to receive pulses of 1.66Hz with duty cycle
<0.1% including shut down the power supply with the receipted pulses,
and wherein the outputs of the device is automatically recoverable from
thermal shutdown once the temperature reduced to a preset hysteresys
band.
2. The device as claimed in claim 1, wherein the device is configured for
control voltage supply and reference generation in an inverter application
including interfacing with main control electronics through a digital logic.

The invention relates to an Intelligent Control Power Supply (ICPS) device in 3-
phase electro locomotives for control voltage supply of +5V,+/-15V and +/-24V
from single DC input of range 77V to 200V, wherein all the outputs of +5V,
+15V, -15V, +24V, and -24Vare independently regulated via a switch mode
regulator and loadable upto 4A, 1.4A,1.4A,3A and 3A respectively, wherein the
device is enabled to receive pulses of 1.66Hz with duty cycle <0.1% including
shut down the power supply with the receipted pulses, and wherein the outputs
of the device is automatically recoverable from thermal shutdown once the
temperature reduced to a preset hysteresys band.