FIELD OF THE INVENTION:
The present invention relates to power electronic control as the supply power block/voltage
conditioning unit to ensure transmission of regulated power in correct format so that the
margin of safety to an existing system and its operation is significantly more reliable, within
its designed tolerance for operating parameters. More specifically, the present invention
pertains to a voltage conditioner and regulator for the input power to any application and its
utility, in particular, for applications having wide range of variations in input voltage on the
higher side. The system of the present invention has within its specification, a specified
tolerance limit for input voltage on which the system performance and reliability depends.
The present invention is an interface device to be used to regulate/cushion harsh voltage
upsurge in supply power to a wide range of domestic and industrial appliances, including
application in Cold Rolling Steel Mills.
BACKGROUND ART:
It is well known in the art of controlling/regulating power supply to different industrial
applications/equipments, that the variation in input power supply, particularly in the devices
using power electronics is a common occurrence. However, if the variation in input supply is
higher than that recommended for safe limit for a specific application, it is necessary to
regulate the incoming voltage from safety point of view. This aspect of power input
regulation is also relevant and important for the electronic device to perform satisfactorily
and reliably within its designed range of specified tolerance for input supply conditions.
A conventional linear regulated power supply block, normally used for such control of input
power characteristics, is functionally divided into the following three stages:
Stage 1: In this stage, the incoming high alternating voltage is stepped down to a low level
and rectified with a bridge rectifier in full wave configuration. The ripple carrying DC is next
smoothened using capacitor filter and thus an unregulated DC output is obtained from the
stage 1.
Stage 2: This stage incorporates a control scheme to convert the unregulated DC into
regulated Dc with minimum ripple content. A sample of the output voltage is fed back for
control. Protection features like voltage limiting and current limiting are part of the scheme.
2

The control circuit is based on operational amplifiers and voltage references. The output of
this segment is a regulated voltage having a minimum current sourcing capability in the
range of milliamps.
Stage 3: The voltage output from the stage 2 has a very limited current sourcing capability.
What is expected is a regulated output capable of sourcing tens of amperes of output
current while maintaining a fixed output voltage.
The existing problem in such a linear regulated power supply block relates to a key
component of the function of stage 3 i.e. a power transistor operating in emitter follower
configuration. This configuration is characterized by unity voltage gain and a high current
gain. The transistor mounted on appropriate heat sink has its collector connected to the
unregulated dc voltage out of the stage 1.The transistor accepts regulated output from the
control section at its input base and delivers a current enhanced output at its emitter. The
transistor operates in the active region generating much heat. The power dissipated is given
by the following equation:
P = Vce x Ic, where Vce is the voltage drop between collector and emitter and Ic is the
collector current.
The power dissipated is proportional to the voltage. Since the output is fixed, any increase
in the unregulated voltage ,caused by increase in input voltage to the device ,increases the
voltage drop between the collector and the emitter. This in turn increases the heat
generation by the transistor by multiple degrees. If the heatsink does not support the extra
heat,the transistor fails squelching the system regulation. This condition is catastrophic for
systems where even a slight change of voltage regulation is not desirable. The impact of
extra voltage can be pronounced at even a very low ampere drawal. This undesirable
characteristic shook the very existence of a linear regulated power supply for cases with
high input voltage. The extra voltage also has a deleterious effect on the life of filter
capacitors warranting periodic replacement and causing irritation to the service personnel.
In typical application areas, the input voltage varies from 220vAC to as high as 290vAC.A
way out of this situation is achieved by adopting use of SMPS(Switched Mode Power
Supply).But the major impediments are the cost and time factors since the inventory may
be quite huge. Another probable solution to the situation was tried by using Constant
3

Voltage Transformer(CVT) at the input to the power supply ,but this time the CVT had to
bear the brunt of the extra impact due to the overvoltage. Such a constrained scenario
compelled us to find a suitable solution to the ongoing problem within the existing
framework and with the help of commonly available resources.
OBJECTS OF THE INVENTION:
The basic object of the present invention is directed to achieving enhanced reliability of
regulated input power supply block/module, by eliminating the limitations of the
conventional linear regulated power block.
A further object of the present invention is to provide means for reducing heat generation in
the transistor in the power regulator block due to power dissipation owing to proportionate
voltage drop between the collector and the emitter by providing resistance of appropriate
rating connected in series with the unregulated DC before being fed to the power amplifier
circuit, and hence providing some extra cushion of protection to the transistor.
A still further object of the present invention is aimed at minimizing the frequent failure and
replacement of components such as the transistors, filter capacitors and the like, due to
power dissipation/heat generation as observed in the conventional power regulator block.
Another object of the present invention is directed to minimize the frequent failure and
replacement of components such as the transistors, filter capacitors and the like, due to
power dissipation/ heat generation as observed in the conventional power regulator block.
Another object of the present invention is to obtain said voltage correction circuit of the
regulated power supply module, simple and maintenance free, using less costly and
commonly available components, yet providing high reliability in performance of the
module/system as a whole.
A further object of the present invention is to maintain the difference between the collector
and the emitter voltage at a minimum, in order to reduce the amount of heat generated by
a power transistor operating in the active region for longer operational life, implemented by
adopting voltage limiting resistance in the circuit. This is successfully achieved in circuits
using pass transistors.
4

SUMMARY OF THE INVENTION:
Thus according to the basic aspect of the present invention there is provided a voltage-
conditioning unit for use as a protective interface between incoming power supply and an
application device comprising:
-a resistance of appropriate rating in tandem with the maximum current drawal operatively
connected in series with said unregulated dc output before being fed to a power amplifier
comprising a control circuit including operational amplifiers and voltage references to output
regulated voltage;
-incoming voltage sensing circuitry where a circuit compares a sample of the incoming
voltage with a reference voltage, such that when the incoming voltage goes below a certain
level, the operative connection of the unregulated dc output voltage is bypassed and the
said unregulated dc output voltage is directly fed to the power amplifier for further
processing. The connection is provided when the input voltage level is above a particular
value.
A further aspect of the present invention is a voltage conditioning unit wherein the said
resistance of appropriate rating is so selected that the effect of extra increase in input
voltage is nullified by voltage drop across the resistance element causing the resistance to
get heated thereby reducing the voltage input to the power amplifier and also reduce the
heat generated by the power amplifier.
A still further aspect of the present invention is directed to a voltage conditioning unit
wherein said comparator means is adapted such that on comparing the incoming voltage
with a reference voltage the same actuates a relay, the N/O contact of which is connected
across the resistance element such that when the incoming voltage is below a certain level,
the said contact shorts and bypasses the resistance element such that when the incoming
voltage is below a certain level, the said contact shorts and bypasses the resistance
normalizing the circuit back to its usual path without said operative connection in series of
said resistance with said unregulated dc output before being fed to the power amplifier.
Yet another aspect of the present invention is directed to a voltage conditioning unit
wherein said voltage limiting resistance of appropriate rating in tandem with the maximum
5

current drawal operatively connected in series with said unregulated dc output before being
fed to a power amplifier is adapted for reducing the amount of heat generated by a
transistor operating in the active region for longer operational life.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES:
Figure 1 is the illustration of the block diagram of the conventional linear regulated power
supply block;
Figure 2 is the illustration of the modified circuit of the regulated power supply module
providing means for eliminating heat generation due to power dissipation.
Figure 3 is the illustration of the modified circuit of the regulated power supply module
according to the present invention providing enhanced reliability.
Figure 4 is the illustration of circuit diagram with further modification incorporating input AC
under voltage sensing circuit, for enhanced reliability of the module /system according to
the present invention.
DETAILED DESCRIPTION WITH REFERENCE TO THE ACCOMPANYING FIGURES:
The present invention relates to power electronic control on the supply power block to
ensure transmission of regulated power in correct format so that the margin of safety to an
existing electronic/drive system and its operation is significantly more reliable, within its
designated tolerance for operating parameters. More specifically, the present invention is
directed to a voltage conditioner and regulator for the input power to any application.
Reference is first invited to the accompanying figure 1, wherein a conventional linear
regulated power supply block, normally used for such control of input power characteristics,
has been illustrated with a diagram to elaborate its functioning divided into the following
three stages, as already described, comprising:
Stage 1 : : In this stage, the incoming high alternating voltage is stepped down to a low
level and rectified with a bridge rectifier in full wave configuration. The ripple carrying DC is
6

next smoothened using capacitor filter and thus an unregulated DC output is obtained from
the stage 1.
Stage 2: This stage incorporates a control scheme to convert the unregulated DC into
regulated DC with minimum ripple content. A sample of the output voltage is fed back for
control. Protection features like voltage limiting and current limiting are part of the scheme.
The control circuit is based on operational amplifiers and voltage references. The output of
this segment is a regulated voltage having a minimum current sourcing capability in the
range of milliamps.
Stage 3: The voltage output from the stage 2 has a very limited current sourcing capability.
What is expected is a regulated output capable of sourcing tens of amperes of output
current while maintaining a fixed output voltage. Stage 3, also known as the power
amplifier section accomplishes this task of a current enhanced voltage output.
Such a linear regulated power supply block suffers from a limitation in the failure of Stage 3
which consists of a series pass transistor operating in emitter follower configuration. This
configuration is characterized by unity voltage gain and a high current gain. The transistor
mounted on heatsink has its collector connected to the unregulated DC voltage out of stage
l.The transistor accepts regulated output from the control section at its input base and
delivers a current enhanced output at its emitter. The transistor operates in the active
region generating much heat.The power dissipated is given by the equation:
P = Vce x Ic, where Vce is the voltage drop between collector and the emitter and Ic is the
collector current.
The power dissipated is proportional to the voltage. Since the output is fixed, any increase
in the unregulated voltage, caused by increase in input voltage to the device, increases the
voltage drop between the collector and the emitter. This in turn increases the heat
generation by the transistor by multiple degrees. If the heat sink does not support the extra
heat, the transistor fails squelching the system regulation. This condition is particularly
disadvantageous for systems where even a slight change in voltage regulation leads to
chaos. The situation is prevalent even at a very low ampere drawn and is a highly
undesirable characteristic, which shook the very existence of the functioning of the series
pass transistor in the linear model. Increase in input voltage also has a deleterious effect on
7

the life of the filter capacitors warranting periodic replacement and causing irritation to the
service personnel.
The present invention is thus directed to eliminating the limitations of the existing linear
regulated power supply block to enhance reliability of performance of the module,
incorporating required modifications in the circuit design and can be considered as a voltage
conditioning unit to act as an interface between the input power supply and an existing
electronic device needing regulated supply for safe operation. Reference is now invited to
accompanying figure 2, wherein the aspect of controlling power dissipation and heat
generation by the transistor corresponding to a proportionate voltage drop between
collector and emitter caused due to unregulated input voltage to the device specifically on
higher range than normal, has been illustrated. The regulated power supply block of the
present invention provides means for controlling overheating of the transistor in said
block/module, mounted on a heatsink. This is achieved by partially diverting the heat
component from the transistor to some other element capable to withstand/absorb the odd
effect of overheating and hence providing some extra cushion of protection to the transistor.
For this purpose, a resistance of appropriate rating in tandem with the maximum current
drawal is connected in series with the unregulated DC supply before being fed to the power
amplifier circuit. The resistance has been so selected that the effect of the extra increase in
input voltage is nullified by the voltage drop across the resistance element causing the
resistance to get heated and thereby reducing the voltage input to the power amplifier and
also reducing the heat generated by the power amplifier. Resultantly, with lesser amount of
heat generation, the power element is less prone to failure enhancing reliability of the
module/system.
With the aforesaid modification in the circuit over the conventional regulated power supply
system, recurrent failure of the power electronic components were avoided; but some other
problems were still impeding reliable performance of the module, that needed further
modification or improvisation of the invented system. The circuit so modified started
malfunctioning when the incoming AC voltage became lower than a particular level, which is
quite a regular phenomena in industries. Thus to arrest this problem, a second stage of
modification in the invented design of the circuit was incorporated by introduction of an
incoming voltage sensing circuit that is functional by comparing a sample of the unregulated
DC with a reference voltage. This aspect is illustrated in figure 3.
8

The comparator output on comparing the incoming voltage with a reference voltage
actuates a relay, the IM/O contact of which is connected across the resistance element so
that when the incoming voltage goes below a certain level, the contact shorts and bypasses
the resistance normalizing the circuit back to the original condition. This second stage
modification to the power control circuit of the module/system of the present invention
incorporating the comparator and relay means comprised in the undervoltage sensing circuit
has been illustrated in the accompanying figure 4.
9

WE CLAIM:
1. A voltage conditioning unit for use as a protective interface between incoming power
supply and an application device comprising:
(a) A resistance of appropriate rating in tandem with the maximum current drawal,
operatively connected in series with said unregulated dc output before being fed to a
power amplifier.
(b) Incoming voltage sensing circuitry with comparator means adapted such that
when the comparator output on comparing the incoming voltage with a reference
voltage goes below a certain level the operative connection of the unregulated dc
output before being fed to the power amplifier is bypassed and the said unregulated
dc output is directly fed to said power amplifier.

2. A voltage conditioning unit as claimed in 1 wherein the said resistance of appropriate
rating is selected such that the effect of the extra increase in input voltage is nullified
by voltage drop across the resistance element causing the resistance to get heated
to thereby reduce the voltage input to the power amplifier and also reduce the heat
generated by the power amplifier.
3. A voltage conditioning unit as claimed in anyone of claims 1 or 2 wherein said
comparator means is adapted such that on comparing the incoming voltage with a
reference voltage the same actuates a relay , the N/O contact of which is connected
across the resistance element such that when the incoming voltage is below a certain
level, the said contact shorts and bypasses the resistance normalizing the circuit
back to its usual path without said operative connection in series with said
unregulated dc output before being fed to the power amplifier.
4. A voltage conditioning unit as claimed in anyone of claims 1 to 3 wherein said
voltage limiting resistance of appropriate rating in tandem with the maximum current
drawal operatively connected in series with said unregulated dc output before being
fed to a power amplifier is adapted for reducing the amount of heat generated by a
transistor operating in active region for longer operational life.
10

5. A voltage conditioning unit for use as protective interface between incoming power
supply and an application device and a circuitry comprising series pass transistors
including a voltage limiting resistance substantially as hereindescribed and illustrated
with reference to the accompanying figures.

Dated this 26th day of July, 2007

Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

11

ABSTRACT
A VOLTAGE CONDITIONING UNIT FOR USE AS PROTECTIVE INTERFACE BETWEEN
INCOMING POWER SUPPLY AND AN APPLICATION DEVICE.
A voltage conditioning unit for use as protective interface between incoming power supply
and an application device to ensure transmission of regulated power in correct format so
that the margin of safety to an existing system/device and its operation is significantly more
reliable, within its designed tolerance for operating parameters. More specifically, the
present invention is directed to a voltage conditioner and regulator for the input power to
any application and its utility, in particular, for applications having wide range of variations
in input voltage on the higher or lower side. The system of the present invention has within
its specification, a specified tolerance limit for input voltage based on which the system
performance and reliability depends. The present invention is an interface device to be used
to regulate/cushion harsh voltage upsurge in supply power to a wide range of domestic and
industrial appliances, including application in cold rolling steel mills.
Figure 4.
12

A voltage conditioning unit for use as protective interface between incoming power supply
and an application device to ensure transmission of regulated power in correct format so
that the margin of safety to an existing system/device and its operation is significantly more
reliable, within its designed tolerance for operating parameters. More specifically, the
present invention is directed to a voltage conditioner and regulator for the input power to
any application and its utility, in particular, for applications having wide range of variations
in input voltage on the higher or lower side. The system of the present invention has within
its specification, a specified tolerance limit for input voltage based on which the system
performance and reliability depends. The present invention is an interface device to be used
to regulate/cushion harsh voltage upsurge in supply power to a wide range of domestic and
industrial appliances, including application in cold rolling steel mills.