Claims:1. An apparatus to limit transient peak of a original signal in circuit breaker of a signal conditioning circuit (SCC), comprising:
at least one air core sensor optimally connected to a filter stage that includes a passive filter configured to output a reduced gain as the original signal, wherein an amplification stage is configured to compensate for the loss in the original signal amplitude caused by the passive filter; and
at least one buffer between the filter stage and the amplification stage, wherein the at least one buffer isolates the filter and amplification stage while not altering the gain of the SCC, and modifies the original signal in an inverting terminal of the amplification stage so as to limit the transient peak.
2. The apparatus as claimed in claim 1, wherein the SCC is configured in accordance with AC gain when every DC source is reduced to zero with the relation:

where, Rint is the resistance of the filter stage; Xcint is equivalent impedance of filter capacitor Cint, given by
Xcint = 1/2pfCint
where, f is operating frequency, Rf is gain setting feedback resistor, Rf is gain setting feedback resistor, and Ri is gain setting input resistor to inverting terminal of the amplification stage.
3. The apparatus as claimed in claim 1, wherein the SCC is configured in accordance with DC offset when every AC source is open circuited with the relation:

where, R1 and R2 are voltage divider resistors required to set DC offset value; Rp is parallel input resistance to the SCC; Rf is gain setting feedback resistor, Rint is the resistance of the filter stage, and Ri is gain setting input resistor to inverting terminal of the amplification stage; and R0 is internal impedance of the at least one air core sensor that is a rogowski coil.
4. The apparatus as claimed in claim 3, wherein a compensatory change is made in any of the voltage divider resistors, R1 or R2, to balance the DC offset value.
5. The apparatus as claimed in claim 1, wherein output of the filter stage is coupled with the amplification stage and fed as input to an ADC of microcontroller, and the at least one air core sensor is a rogowski coil and the at least one buffer is a unity gain buffer.
6.The apparatus as claimed in claim 1, wherein the apparatus further comprises microcontroller configured to actuate a trip mechanism, wherein the microcontroller detects output of the amplification stage in comparison to a threshold value.
7. A method to trip a circuit breaker using an electronic trip unit, the method comprising the steps of:
providing, at least one air core sensor corresponding to at least one phase of the circuit breaker; and
integrating, the at least one air core sensor with an passive integrator corresponding thereto, wherein an amplification circuit corresponds to each of the passive integrator, so as to detect, at a microcontroller, output of the amplification circuit in comparison to a threshold value, and ultimately trip, by a trip mechanism, the circuit breaker based on the detection of the microcontroller.
8. The method of claim 7, wherein the at least one air core sensor is rogowski coil.
9. The method of claim 7, wherein the method further comprises configuring a DC offset in order to accommodate entire signal in a format that is readable by ADC of the microcontroller.
10. The method of claim 7, wherein the at least one phase is any or a combination of R, Y, B, and N.
, Description:
TECHNICAL FIELD
The present disclosure generally relates to the field of circuit breakers. In particular, it pertains to a method and apparatus to limit the transient peak of passive filters while obviating use, and thereby limitations, of conventional core balance current transformer.

BACKGROUND
Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Circuit breakers have been widely employed due to high degrees of reliability, and thereby, safety provided by their tripping action under abnormal working conditions (unusually high current scenarios). So, faultless operation during their application has attracted most attention from development point of view, among other technical considerations. Opposed to a fuse, which can be employed merely for a single application of damage protection, a circuit breaker can be readily employed repeatedly by reconfiguring, either manually or automatically, to its original configuration.
From operational point of view, a circuit breaker is a manually or automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. One variant of Circuit breakers are microprocessor based circuit breakers. These Circuit Breakers make use of an Electronic Trip unit as the nucleus of sensing the fault condition. An electronic trip unit is an intelligent device that is used in conjunction with an electro-mechanical circuit breaker to measure system parameters such as voltage, current, power etc and protect the system against faults such as overload, short circuit, earth fault, etc and control the electro mechanical device in cases of occurrences of such faults.
Most Circuit Breakers use the conventional core balance current transformer as the sensor to detect the current flowing through the system. However, due to drawbacks like saturation of the core and extended losses of the conventional core balance current transformer, the use of Air Core sensors, preferably Rogowski coil (or simply rogowski) has progressed over the years.
Technically, while the output of the Core balance current transformer is proportional to the input current, the output of the rogowski is proportional to the first time derivative of primary current (di/dt).
E=L di/dt
where ,
E is the output voltage of the rogowski coil measured in volts.
L is the mutual inductance of the rogowski coil measured in Henry.
i is the primary current measured in Amperes.
Hence, the output of the rogowski is fed to an integrator circuit. The integrator is used because the measured voltage is proportional to the first time derivative of the primary current. In order to obtain the equivalent value of current that is proportional to the primary current, the rogowski output voltage is integrated.
Now, Integrator Circuits can be broadly divided into two categories, Passive integrator and Active Integrator. From implementation perspectives, First order Passive Integrator circuits use simple passive components like resistors and capacitors to integrate the input signal. Due to their simple construction, Passive integrators are preferred for most applications. However, there are certain inherent problems that are faced when the output of passive integrators is fed to consecutive circuitry.
Like the differentiated voltage output of the rogowski, when fed to the passive integrator, gives an output with a reduced gain as the original signal. Hence, to make the signal equivalent to the original signal, the output of the Passive integrator is transmitted through an operational Amplifier circuit (op amp circuit) that compensates for the loss in the signal amplitude caused by the passive integrator. It is observed that an inherent problem, among possible other shortcomings, of the passive integrator is an initial transient peak, caused by the charging of the capacitor within the R-C network of the passive integrator. This transient peak tends to get amplified when passed through the Operational Amplifier Circuit, becoming instrumental in conveying incorrect signals to the microcontroller circuitry that follows the Operational Amplifier Circuit.
There is therefore need in the art to provide a method and apparatus to reduce the inherent peak of the Passive filter, while ensuring that the original signal properties are not altered.
All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

OBJECTS OF THE INVENTION
A general object of the present disclosure is to provide a method and apparatus to limit the transient peak of passive filters while dealing with the drawbacks of the integrator circuit.
An object of the present disclosure is to obviate application of conventional core balance current transformer for desired waveform of signal conditioning circuits.
Another object of the present disclosure is to address amplitude error introduced in the transient response of passive integrator.
Another object of the present disclosure is to provide a means to isolate the integrator stage from amplification stage to compensate for transient peak of passive filters.
Yet another object of the present disclosure is to provide implementation of unity gain buffer circuitry for smoothing the waveform at output of signal conditioning circuit.
Still another object of the present disclosure is to provide a two stage system consisting of a low pass passive filter, in combination with operational amplifier gain stage.

SUMMARY
Aspects of the present disclosure generally relates to the field of circuit breakers. In particular, it pertains to a method of limiting the transient peak of passive filters using air core sensor, preferably rogowski rather than conventional core balance current transformer, achieved through analog circuitry. More specifically it discloses application of a unity gain buffer to isolate the integrator stage from the amplification stage to compensate for the transient peak.
In an aspect, the present disclosure provides an apparatus to limit transient peak of a original signal in circuit breaker of a signal conditioning circuit (SCC) that includes (i) at least one air core sensor optimally connected to a filter stage that includes a passive filter configured to output a reduced gain as the original signal, wherein an amplification stage can be configured to compensate for the loss in the original signal amplitude caused by the passive filter; and (ii) at least one buffer between the filter stage and the amplification stage, wherein the at least one buffer can isolate the filter and amplification stage while not altering the gain of the SCC, and can modify the original signal in an inverting terminal of the amplification stage so as to limit the transient peak.
In an aspect, output of the filter stage can be coupled with amplification stage and fed as input to an ADC of microcontroller, and at least one air core sensor can be a rogowski coil and at least one buffer can be a unity gain buffer
In an aspect, apparatus of the present disclosure can further comprise a microcontroller configured to actuate a trip mechanism, wherein the microcontroller can detect output of amplification stage in comparison to a threshold value.
In an aspect, SCC of the present disclosure can be configured in accordance with AC gain when every DC source of the SCC is reduced to zero, with the relation:

where, Rint is the resistance of the filter stage; Xcint is equivalent impedance of filter capacitor Cint, given by
Xcint = 1/2pfCint
where, f is operating frequency, Rf is gain setting feedback resistor, Rf is gain setting feedback resistor, and Ri is gain setting input resistor to inverting terminal of the amplification stage.
In an aspect, SCC of the present disclosure can be configured in accordance with DC offset when every AC source is open circuited, with the relation:

where, R1 and R2 are voltage divider resistors required to set DC offset value; Rp is parallel input resistance to the SCC; Rf is gain setting feedback resistor, Rint is the resistance of the filter stage, and Ri is gain setting input resistor to inverting terminal of the amplification stage; and R0 is internal impedance of the at least one air core sensor that is a rogowski coil. Furthermore, a compensatory change can be made in any of the voltage divider resistors, R1 or R2, to balance the DC offset value.
In an aspect, the present disclosure provides a method to trip a circuit breaker using an electronic trip unit, the method including the steps of (i) providing, at least one air core sensor corresponding to at least one phase of the circuit breaker; and (ii) integrating, the at least one air core sensor with an passive integrator corresponding thereto, wherein an amplification circuit corresponds to each of the passive integrator, so as to detect, at a microcontroller, output of the amplification circuit in comparison to a threshold value, and ultimately trip, by a trip mechanism, the circuit breaker based on the detection of the microcontroller.
In an aspect, at least one air core sensor can be a rogowski coil, and at least one phase can be any or a combination of R, Y, B, and N.
In an aspect, method of the present disclosure can further comprise configuring a DC offset in order to accommodate entire signal in a format that is readable by ADC of the microcontroller
Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components

BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
FIG.1 illustrates an exemplary block diagram of electronic trip unit in accordance with an embodiment of the present disclosure.
FIG. 2 illustrates an exemplary electrical circuit diagram for two stage system including a low pass passive filter and an operational amplifier gain stage, in accordance with an embodiment of the present disclosure.
FIG. 3 illustrates exemplary graphical representation of transient peak observed at the output of Signal Conditioning Circuit (SCC) in accordance with an embodiment of the present disclosure.
FIG.4 illustrates an exemplary electrical circuit diagram for two stage system including a low pass passive filter and an operational amplifier gain stage, along with a unity gain buffer circuitry in accordance with an embodiment of the present disclosure.
FIG. 5 illustrates an exemplary graphical representation of waveforms observed at the output of SCC, with the implementation of a unity gain buffer circuitry in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS
The following is a detailed description of embodiments of the disclosure illustrated in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
Embodiments of the present disclosure generally relates to the field of circuit breakers. In particular, it pertains to a method of limiting the transient peak of passive filters using air core sensor, preferably rogowski rather than conventional core balance current transformer, achieved through analog circuitry. More specifically it discloses application of a unity gain buffer to isolate integrator stage from amplification stage to compensate for the transient peak.
In an aspect, the present disclosure provides an apparatus to limit transient peak of a original signal in circuit breaker of a signal conditioning circuit (SCC) that includes (i) at least one air core sensor optimally connected to a filter stage that includes a passive filter configured to output a reduced gain as the original signal, wherein an amplification stage can be configured to compensate for the loss in the original signal amplitude caused by the passive filter; and (ii) at least one buffer between the filter stage and the amplification stage, wherein the at least one buffer can isolate the filter and amplification stage while not altering the gain of the SCC, and can modify the original signal in an inverting terminal of the amplification stage so as to limit the transient peak.
In an aspect, output of the filter stage can be coupled with amplification stage and fed as input to an ADC of microcontroller, and at least one air core sensor can be a rogowski coil and at least one buffer can be a unity gain buffer
In an aspect, apparatus of the present disclosure can further comprise a microcontroller configured to actuate a trip mechanism, wherein the microcontroller can detect output of amplification stage in comparison to a threshold value.
In an aspect, SCC of the present disclosure can be configured in accordance with AC gain when every DC source of the SCC is reduced to zero, with the relation:

where, Rint is the resistance of the filter stage; Xcint is equivalent impedance of filter capacitor Cint, given by
Xcint = 1/2pfCint
where, f is operating frequency, Rf is gain setting feedback resistor, Rf is gain setting feedback resistor, and Ri is gain setting input resistor to inverting terminal of the amplification stage.
In an aspect, SCC of the present disclosure can be configured in accordance with DC offset when every AC source is open circuited, with the relation:

where, R1 and R2 are voltage divider resistors required to set DC offset value; Rp is parallel input resistance to the SCC; Rf is gain setting feedback resistor, Rint is the resistance of the filter stage, and Ri is gain setting input resistor to inverting terminal of the amplification stage; and R0 is internal impedance of the at least one air core sensor that is a rogowski coil. Furthermore, a compensatory change can be made in any of the voltage divider resistors, R1 or R2, to balance the DC offset value.
In an aspect, the present disclosure provides a method to trip a circuit breaker using an electronic trip unit, the method including the steps of (i) providing, at least one air core sensor corresponding to at least one phase of the circuit breaker; and (ii) integrating, the at least one air core sensor with an passive integrator corresponding thereto, wherein an amplification circuit corresponds to each of the passive integrator, so as to detect, at a microcontroller, output of the amplification circuit in comparison to a threshold value, and ultimately trip, by a trip mechanism, the circuit breaker based on the detection of the microcontroller.
In an aspect, at least one air core sensor can be a rogowski coil, and at least one phase can be any or a combination of R, Y, B, and N.
In an aspect, method of the present disclosure can further comprise configuring a DC offset in order to accommodate entire signal in a format that is readable by ADC of the microcontroller
FIG.1 illustrates an exemplary block diagram of electronic trip unit 100 in accordance with an embodiment of the present disclosure, wherein the unit consists of an air core sensor (rogowski in a preferred embodiment) which is a device that is used for measuring alternate current or high speed current pulses. The output of the rogowski is proportional to the first time derivative of primary current (di/dt).
E=L di/dt
where,
E is the output voltage of the rogowski coils measured in volts.
L is the mutual inductance of the rogowski coil measured in Henry.
i is the primary current measured in Amperes.
As illustrated, the output of air core sensor (shown as 102, 108, 114, and 120 for individual phases namely R, Y, B, and N) can be fed to Passive Low Pass Filter Circuit (also referred to as filter circuit or filter stage or passive integrator and all these terms used interchangeably hereinafter) shown as 104, 110, 116, and 122 respectively (as per phase), which can have its functionality similar to that of an integrator.
Further, output of the Passive Low Pass Filter Circuit (104, 110, 116, and 122) is fed to the Operational Amplifier Circuit (also referred to as op amp circuit or amplification stage and all these terms used interchangeably hereinafter) shown as 106, 112, 118, and 124 for R, Y, B, and N phases, respectively. The operational amplifier acts as an amplifier with the help of gain setting resistors. Notably, a DC offset can be provided in order to accommodate the entire signal within Vcc and GND, a format that is readable by the ADC of a controller (microcontroller) 126. Now, in case of a fault condition, the Controller 126 can give an output signal to trip mechanism 128, which can comprise of an electromechanical device that in turn can propagate, say the mechanical section of, the Circuit Breaker to open (or trip) the Electrical Circuit.
In implementation of the present disclosure, integrator is used because its measured voltage is proportional to the first time derivative of the primary current. In order to obtain the equivalent value of current that is proportional to the primary current, the rogowski output voltage is integrated. The cut off frequency of the Passive Low Pass Filter Circuit is kept as low as possible. The integrator offers large impedance to high frequency signal and hence filters out the external noises that are high frequency in nature.
FIG. 2 illustrates an exemplary electrical circuit diagram 200 for two stage system that includes a low pass passive filter 202, in combination with an operational amplifier gain stage 204, in accordance with an embodiment of the present disclosure. As illustrated in the given schematic of FIG. 2, the overall gain of the signal conditioning circuit can be split into two sections: Low Pass filter stage 202 (alternatively, filter stage) and amplification stage 204. In an embodiment, the Passive Low Pass Filter Circuit 202 can have a -3db point at 15Hz with a -20db/decade roll-off. The Passive Low Pass Filter Circuit 202 can provide a steep slope, hence faster response to the input signal, with a cut-off frequency of 15Hz.
The output of the Passive Low Pass Filter Circuit 202 is coupled with the operational amplifier circuit 204 and fed as input to ADC of the micro controller 126. The micro controller 126 can read this input and check whether the value exceeds a predefined fault pick-up value (say a threshold value) and persist more than set duration. In such cases, the microcontroller 126 can issue trip command to the trip mechanism 128.
In an aspect, output of Air Core Sensor (as illustrated in Fig. 2) is the input to signal conditioning circuit (SCC), whose output is supplied to microcontroller 126 Circuit, preceded by trip mechanism 128. From technical point of view, the following can be stated:
Vout = G * Vin
where, Vout = Output of the SCC
Vin = Output of the Rogowski coil and input to the signal Conditioning circuit
G = Gain of the signal conditioning Circuit
Hence, G = Vout/Vin
In order to understand the signal conditioning circuit in totality, AC and DC analysis need to be performed on the circuit.

AC ANALYSIS OF THE SIGNAL CONDITIONING CIRCUIT
In an implementation, in accordance with an aspect of the present disclosure, in order to perform AC analysis of Signal Conditioning Circuit (SCC) illustrated in Fig. 2, all the DC sources are reduced to zero. Hence Vdc = 0. This leaves us with an equation for AC gain illustrated by

Where,
Rint is the resistance of the Integrator Circuit
Xcint is the Equivalent Impedance of Integrator Capacitor Cint,
given by
Xcint = 1/2pfCint
Where, Cint is the capacitance in farad
f is the operating frequency in Hertz
Rf is the gain setting Feedback resistor
Ri is the gain setting input resistor to the inverting terminal of the operational amplifier.

DC OFFSET ANALYSIS OF THE SIGNAL CONDITIONING CIRCUIT
In an implementation, in accordance with an aspect of the present disclosure, in order to perform DC analysis of the Signal Conditioning Circuit illustrated in Fig. 2, all the AC sources are open circuited. This leaves us with an equation for DC offset illustrated by

where,
R1 and R2 are the Voltage divider resistors, required to set the DC offset value
Rp is the parallel input resistance to the signal conditioning circuit
R0 is the internal impedance of the rogowski coil.
Instant figure illustrates a schematic illustration of an embodiment of a Passive Low Pass Filter Circuit 202, Operational Amplifier Circuit 204, as illustrated in FIG. 1. However, as would be apparent to a person having ordinary knowledge in the relevant art, the schematic representation of FIG. 2 (or any other figure of the present disclosure) shall be referenced for illustration purposes only, as embodiments of the proposed invention may be readily implemented using any alternative arrangements/combinations/types of electronic components as would be known in the relevant art.
While FIG.2 illustrates the signal path in only one phase of the circuit breaker, it will be appreciated and understood by one skilled in the art that similar schematics may be used for the other phases, and coupled appropriately at the output side.
FIG. 3 illustrates exemplary graphical representation 300 of transient peak observed at the output of SCC in accordance with an embodiment of the present disclosure. The signal, as illustrated, shows waveform of the output of the SCC of FIG. 2. Once the SSC is powered ON, it takes 4ms for the Output to rise to its peak value of 1.74V and then it begins to drop, taking 20ms to settle to the 80% percent value of 1.65V. Hence the overall settling time calculated for the signal to reach 80% of the actual value results to 24ms. The ideal signal expected at the output of the SCC of FIG.2. would be a steep rise with 0 ms rise time, becoming constant at the actual value of 1.65V, but due to the charging time of the capacitor, an initial rise time followed by settling time is seen.
In an aspect, while considering only Passive Low pass Filter circuit 202, to analyze the cause of the initial peak, the output of the passive low pass filter can be computed as:
Vout = [Xcint/(Rc+Xcint)]* Vin
where, Rc is the Integrator Resistor R8
Xcint is the Equivalent Impedance of Capacitor C4 given by
Xcint = 1/2pfCint
where, Cint is the capacitance in farad
f is the operating frequency in Hertz.
Now, at time t=0+, the voltage across Capacitor C is 0, hence the initial gain (Vout/Vin) of the passive low pass filter is 0. Since the DC analysis of the SCC is carried out keeping two aspects in mind, the Passive Low pass filter 202 as well as the operational amplifier circuit 204, the DC offset of both the circuits plays a key role in deciding the output signal. Now, since at t=0+, the passive low pass filter gain is 0, the operational amplifier circuit 204 tries to compensate for the loss faced in the integrator section, in turn corresponding to the initial peak. The rogowski signal rides on this DC signal obtained. When the rogowski signal rides on the peak, the controller senses the peak signal as a fault signal and issues a trip command to trip mechanism 128, which in turn trips the circuit breaker. Therefore, a problematic situation of nuisance trip on Power On arises for certain protection settings, which is highly undesirable.
FIG.4 illustrates an exemplary electrical circuit diagram 400 for two stage system that includes a low pass passive filter 202 and an operational amplifier gain stage 204, along with a unity gain buffer 402 circuitry in accordance with an embodiment of the present disclosure. To cater to the foretold problematic situation (of nuisance trip), the peak observed during the transient phase of the power ON cycle needs to be clipped.
In an aspect, the transient voltage peak observed is an outcome of the inherent nature of the R- C filter. Thus, isolating the filter section 202 (alternatively, filter stage) from the amplification section 204 (alternatively, amplification stage) would not amplify the inherent transient peak. If the two sections namely the filter section 202 and the amplification section 204 are treated separately, the AC and DC analysis would be altered as illustrated in Table herein below.
Table: Comparison of the AC and DC analysis in a combined and separated form
Analysis Mode Filter and amplification stage combined Filter and amplification stages separated
Filter stage Amplification stage
AC Analysis

DC analysis Does not play a role in DC analysis

Now, the DC analysis displays the DC transient peak, which is thus removed by treating both the filter 202 and amplification 204 stages as independent stages. Theoretically the two stages can be analyzed separately but the present disclosure teaches an implementation for the same.
Now, in an aspect, to practically implement the separation in accordance with the present disclosure, a circuit is required between the two stages, that would offer a very high input impedance to the preceding stage (to avoid loading effect) while not altering the gain of SCC.
In a preferred aspect, a unity gain buffer 402 can be implemented between the filter 202 and amplification 204 stages, wherein the buffer 402 can isolate the two circuits and the unity gain would not alter the gain of SCC.
By isolating the two circuits, it is observed that the AC gain is not altered while the DC offset peak is clipped off. However, the DC offset now remains constant at a much higher voltage than the required voltage. So, a compensatory change is needed to be made in one of the voltage divider resistors R1 or R2, to balance the DC offset value as per the requirement. By modifying the value of R2, the required compensation can be achieved. Thus in order to clip the DC transient voltage caused by the filter stage 202 of the signal conditioning circuit, a unity gain buffer 402 is preferably required. The implementation of the buffer in turn increases the level of voltage of DC offset and thus the voltage divider resistor is needed to be modified in value to realize the value of DC offset as per the designed application.
FIG. 5 illustrates an exemplary graphical representation 500 of waveforms observed at the output of Signal Conditioning Circuit, with the implementation of an unity gain buffer 402 circuitry in accordance with an embodiment of the present disclosure.
While the embodiments illustrated while making reference to different drawings and tables described hereinbefore are presently preferred, it should be understood that these embodiments are offered by way of example only. In line with similar reasons, while the method of designing de-rating concept chosen here is by altering the gain setting resistors as well as the voltage divider resistors, other methods of de-rating namely by modifying the software downloaded in the microcontroller of the ETU have also been contemplated upon, and therefore well within the scope of the present disclosure.
Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION
The present disclosure provides a method and apparatus to limit the transient peak of passive filters while dealing with the drawbacks of the integrator circuit.
The present disclosure obviates application of conventional core balance current transformer for desired waveform of signal conditioning circuits.
The present disclosure addresses amplitude error introduced in the transient response of passive integrator.
The present disclosure provides a means to isolate the integrator stage from amplification stage to compensate for transient peak of passive filters.
The present disclosure provides implementation of unity gain buffer circuitry for smoothing the waveform at output of signal conditioning circuit.
The present disclosure provides a two stage system consisting of a low pass passive filter, in combination with operational amplifier gain stage.