Claims:1. A system for isolated conversion of voltage to logical level, the system comprising:
an input voltage;
a surge protection circuit;
a rectifier;
a threshold setting component;
a voltage conditioning circuit;
a capacitive filter;
an isolation circuit;
a comparator;
a control section;
wherein the surge protection unit operatively connected to the input voltage;
the surge protection circuit operatively connected to the threshold setting component, wherein the threshold setting component is adapted for setting predetermined input threshold;
the surge protection circuit operatively connected to the rectifier such that an output of the surge protection circuit is feeding to the rectifier through the threshold setting component;
the rectifier operatively connected to the threshold setting component, wherein the rectifier is adapted for detecting the input voltage threshold set by the threshold setting component;
the rectifier operatively connected to the voltage conditioning circuit such that the rectifier is adapted for feeding the input voltage to the voltage conditioning circuit;
wherein the voltage condition circuit is adapted for providing attenuation and/or regulation of voltage;
the voltage condition circuit operatively connected to the capacitive filter such that an output of the voltage condition circuit is feeding to the capacitive filter, wherein the capacitive filter is adapted for suppressing low frequency components;
the capacitive filter operatively connected to the isolation circuit such that an output of the capacitive filter is feeding to the isolation circuit;
the isolation circuit operatively connected to the comparator such that an output of the isolation circuit is feeding to the comparator, the comparator being adapted for generating a logic high or logic low signal; and
the comparator operatively connected to the control section such that the comparator is adapted for providing the generated logic high or logic low signal to the control section.

2. The system as claimed in claim 1, wherein the input voltage is AC and/or DC.

3. The system as claimed in claim 1, wherein the threshold setting component is a bidirectional TVS diode.

4. The system as claimed in claim 3, wherein the bidirectional TVS diode is adapted for detecting both cycles of the input voltage.

5. The system as claimed in claim 1, wherein the system comprises a resistive network, which is adapted for reducing the voltage level.

6. The system as claimed in claim 5, wherein the resistive network is R2 and R3, wherein R2 is connected serially to R3.

7. The system as claimed in claim 1, wherein the isolation circuit comprises an optocoupler, which is adapted for providing isolation between analog and digital ground level.

8. The system as claimed in claim 1 or 7, wherein the optocoupler is adapted for changing its output when the input voltage crosses the predetermined input threshold.

9. The system as claimed in claim 1, wherein the system comprises a Zener, which is adapted for protecting the optocoupler from high voltage.

10. The system as claimed in claim 1, wherein the control section comprises at least one processor.
, Description:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to converting the AC/DC voltage signal to an isolated logical input level, and more particularly protection relay system to read the analog input voltage digitally.

BACKGROUND

[002] In electrical systems, the inputs given are generally analog in nature but for making them compatible with processing device there is a need to design a logic level sensing interface between them. The input voltage level has to be converted and sensed in the form of logic high or logic low level. Once the logic input is determined they can be given to the control circuitry of any electrical device, for example a protection relay, for carrying various processing tasks. In general, it is required isolation between analog input and control circuitry to maintain ground isolation.

[003] CN 201320375702 entitled “logic input interface “discloses an interface comprises an AC voltage input end, a voltage reduction circuit, a voltage stabilizing circuit, an optical coupler and a logic level output end. The voltage reduction circuit comprises a voltage dividing resistor and a first capacitor that are in series connection. The voltage stabilizing circuit is in series connection with the optical coupler. The voltage stabilizing circuit and optical coupler are in parallel connection with the voltage dividing resistor. The logic input interface is characterized by further comprising a first voltage dividing element. The first voltage dividing element and the voltage reduction circuit are in series connection and then connected between the first end and the second end of the AC voltage input end.

[004] US 9541604 B2 entitled “Loop powered isolated contact input circuit and method for operating the same” discloses a voltage is sensed at a switching device and the voltage is associated with a status of a switching device. The sensed voltage is converted to a useable voltage regardless of the value and type of the sensed voltage. At a single self-contained integrated circuit that is powered by the sensed voltage, the usable voltage is converted into a digital representation. The digital representation is configured to be usable by a processing device to determine the value of the voltage at the switching device.

[005] EP0107797 A1 entitled “An input circuit for converting an a.c. input voltage to a logic level voltage” discloses the input circuit (10) includes a rectifier (12) for converting a sensed a.c. voltage which is supplied through coupling impedance (20) to the light emitter (28) of an optical isolator (30). While the a.c. voltage is below a first predetermined voltage, a switchable low impedance circuit path (46, 48) in parallel with the light emitter is rendered conductive to maintain a low voltage across the light emitter to prevent it from becoming conductive until the sensed a.c. voltage reaches the predetermined voltage. A switchable high impedance circuit path (52, 54) in parallel with the low impedance circuit path (46,48) becomes conductive once the a.c. voltage reaches the first predetermined voltage to place a high voltage across the light emitter (28) to exhibit a sharp "turn-on". The high impedance circuit path (52, 54) remains conductive to keep the light emitter (28) energized until the a.c. voltage drops to a second predetermined voltage so that the light emitter exhibits a sharp "turn-off".

[006] In the existing technology, the system is complicated, not flexible, not possible to modify easily over time to account for changes in the threshold level, not possible to provide low cost threshold level setting solution to the user, and provides pulsating output through the optocoupler, which may not work for a few applications.

[007] Thus, there is a need to develop a system for isolated conversion of voltage to logical level to overcome the problems in the existing technology. To meet this requirement, an additional isolation and comparator section is needed to the interface. Also the present invention provides analog voltage surge protection at the input.

SUMMARY
[008] This summary is provided to introduce concepts related to, a system for isolated conversion of voltage to logical level, and the same are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.
[009] According to one aspect of the invention, there is provided a system for isolated conversion of voltage to logical level, the system comprising: an input voltage; a surge protection circuit; a rectifier; a threshold setting component; a voltage conditioning circuit; a capacitive filter; an isolation circuit; a comparator; a control section; wherein the surge protection unit operatively connected to the input voltage; the surge protection circuit operatively connected to the threshold setting component, wherein the threshold setting component is adapted for setting predetermined input threshold; the surge protection circuit operatively connected to the rectifier such that an output of the surge protection circuit is feeding to the rectifier; the rectifier operatively connected to the threshold setting component, wherein the rectifier is adapted for detecting the input voltage; the rectifier operatively connected to the voltage conditioning circuit such that the rectifier is adapted for feeding the input voltage to the voltage conditioning circuit; wherein the voltage condition circuit is adapted for providing attenuation and/or regulation of voltage; the voltage condition circuit operatively connected to the capacitive filter such that an output of the voltage condition circuit is feeding to the capacitive filter, wherein the capacitive filter is adapted for suppressing low frequency components; the capacitive filter operatively connected to the isolation circuit such that an output of the capacitive filter is feeding to the isolation circuit; the isolation circuit operatively connected to the comparator such that an output of the isolation circuit is feeding to the comparator; and the comparator operatively connected to the control section such that the comparator is adapted for providing a generated logic high or logic low signal to the control section.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0010] The detailed description is described with reference to the accompanying figures. In the figures, the digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.

[0011] Figure 1 illustrates a system level diagram of present invention used for logic input detection.

[0012] Figure 2 illustrates a schematic diagram of the present invention.

[0013] Figure 3 illustrates a schematic diagram of signal conditioning circuitry of the present invention.

[0014] It is to be understood that the attached drawings are for purposes of illustrating the concepts of the invention and may not be to scale.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0015] The following clearly describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are merely a part rather than all of the embodiments of the present invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0016] A detailed description of one or more embodiments of the invention is provided below along with accompanying figures that illustrate the principles of the invention. The invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. These details are provided for the purpose of example and the invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured.

[0017] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components, modules, units and/or circuits have not been described in detail so as not to obscure the invention.

[0018] Although embodiments of the invention are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more”. The terms “plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently.

[0019] Referring to figure 1, the system comprises a surge protection, a full wave rectifier, a voltage conditioning circuit, capacitive filter, an isolation circuit using optocoupler and a comparator which provides a logical input to the control circuit. The present invention works for sensing universal signal (AC/DC) over a wide range and converting them into a logical level usable for the control section of any device that mainly consists of the processors and controllers. High voltage surge protection is provided which restricts the entry of any high voltage spikes in the circuit. Input to output isolation is provided for preventing disturbance at the input from reflecting to the output side. The signal conditioning circuits helps to attain a perfect logic high and logic low level with high accuracy.

[0020] Referring to figures 2&3, as per requirement a desired analog input threshold can be set using threshold setting component which is bidirectional TVS diode (TVS1). Using bi direction TVS diode one can detect both the cycles of the AC signal which provides a faster response. As per the need, different values of TVS diode can be used in the present invention to set Analog Ac threshold for generating the logical high and low levels. The input signal threshold is flexible, which can be easily set as per design requirement by varying the rating of the bi directional TVS.

[0021] The surge protection component (RV1) prevents the high voltage spikes from damaging the low voltage circuitry. The full wave rectifier (D1) detects both half cycles of the AC input voltage and feeds it to voltage attenuation and regulation block. So that faster sensing is possible within a half cycle irrespective of negative or positive peak of AC signal. In particular, the input to output response is very fast, less than half a cycle:
At 110 Vrms : The turn on time is 3ms
At 230 Vrms : The turn on time is 4ms

[0022] The voltage conditioning circuit consists of two major sections attenuation and regulation. Attenuation through resistive network (R2, R3) is done to reduce the voltage level such it can be fed to optocoupler (U1). After stepping down the voltage it is regulated by a Zener (D3) to protect optocoupler from high voltage damage. To suppress low frequency components, the signal is passed through a capacitive filter (C1) and then given to the isolation block.

[0023] The optocoupler provides isolation between the analog and digital ground level. The output of optocoupler changes as and when the input voltage crosses the threshold.

[0024] Since the ripples at the optocoupler are not completely suppressed, a signal conditioning circuitry with consists majorly of a comparator (U3A) is added. This is again a unique feature because of which a perfect logic high or logic low signal can be generated and given to the control section (processors). The Vref, which is a fixed comparator reference voltage, can be generated by number of ways for example using resistive divider circuit across operational amplifier supply.

[0025] The present system can sense and convert AC/DC signal over a wide range of input voltages with high accuracy and faster response time of less than half cycle of the input signal. Also the analog and digital signals are isolated here so that any disturbance at input side will not affect at control circuitry.

[0026] The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. a system for isolated conversion of voltage to logical level as described above does not limit the scope of the present invention. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.

[0027] Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.

[0028] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.