DESC:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to communication of data signal, and more particularly to transmitting and receiving data signal between master and slave units.

BACKGROUND

[002] Microprocessor/ microcontroller based protection relay is well known in the art. The microprocessor converts the monitored current which is an analog signal, periodically sampled into a series of digital signals. This derived digital value may be processed over time to determine a processed value which is a function of both the monitored current and time. The circuit breaker or a switching device is tripped when a processed value is not within preset limits. Such microprocessor/ microcontroller based current protection relay provide end-users with the capability to remotely monitor a variety of equipment via automatic monitoring devices. This allows more precise data and decreases human resource requirements, industrial automation, monitoring etc.

[003] Microprocessor or microcontroller-based protection relay communicate with other computer, via various communications protocols such as the Ethernet for a local area network or the MODBUS® (hereafter “Modbus”) communication protocol. While RS-232 is the most commonly used serial-data standard for PC and telecommunication applications, RS-485 and RS-422 are among the successful standards for industrial applications. Among the features provided by this communication protocol is a means for the user to access data from either an RS-232 or RS-485 serial connection from the slave device to the master controller.

[004] Currently, the protection relays are provided with the modbus communication feature using modbus-RTU protocol. In current design, two wires RS485 serial link is used as a serial interface between a CPU board to a display board and Ethernet board for communication data. To use RS485 serial communication, the transreceiver ICs are employed that generates a differential transmitting and receiving signal at both end of CPU and display board. Also, at display board, there is individual power supply unit to generate voltage and drive display module. To drive the display module +5VDC is required. However, such power supply modules create noises due to pulse transformer and MOSFET switching operation in transmission of data.

[005] The use of Transreceiver ICs such as SN65HVD12 and power supply module in the existing current protection relays increases the overall cost of protection devices. In Electronics, Electrical and Power Electronics industries, product cost and feature is an important factor for consideration. Also, Transreceiver ICs may also require small outline integrated circuit (SOIC) in the proposed topology.

[006] Thus, in view the industrial requirement for an electrical power system, there is need to reduce the cost of protection devices by providing the same features and thus making the product more robust and economically significant.

SUMMARY OF THE INVENTION

[007] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[008] An object of the present invention is to reduce the cost of a device by replacing a power supply module and a transreceiver ICs with less expensive component for serial communication between a master unit and a slave unit.

[009] Another object of the present invention is to provide a Transistor-Transistor Logic (TTL) logic circuit in place of Transreceiver ICs to generate transmitting (Tx) and receiving (Rx) signal for data communication between master unit and slave unit.

[0010] Accordingly, the present invention provides a mechanism for communication of data signals between a master controller and a slave device comprising means for replacing transreceiver ICs for generating transmitting (Tx) and receiving (Rx) signals; and means for serial communication using a communication link.

[0011] In one implementation, a RS485 serial data communication interface is used for signal reception and/or send between a master unit and a slave unit using Modbus-RTU protocol.

[0012] In one implementation, the power supply module from the display board is removed, and the control power supply from the CPU side is provided along with the RS485 serial communication link of shielded cable. This enables to reduce the power supply design cost as well reduces the effort to pass the EMI EMC test.

[0013] In one implementation, the transreceiver ICs with Transistor- transistor logic circuit from both end CPU are replaced and a display board with use for two wires RS485 serial communication over modbus-RTU protocol is introduced. This enables to reduces the cost of Transreceiver ICs and work same as before.

[0014] In one implementation, Transistor-Transistor logic (TTL) circuits comprising transistors and resistors means is used for generating differential transmitting (Tx) and receiving (Rx) signals that is communicated between a master unit and a slave unit. In one exemplary embodiment, the TTL circuit is positioned at both sides of a master unit and a slave unit.

[0015] Accordingly, in one implementation, a protection relay device comprising a display module and a central processing unit (CPU) is disclosed. The protection relay device is technically advanced as compared to the conventional devices such that a control power supply from the CPU is coupled to the display module to generate voltage and drive a display, and the display module communicably coupled with the central processing unit (CPU) using transistor- transistor logic (TTL) circuit using a serial communication over Modbus-RTU protocol.

[0016] In one implementation, a protection relay device comprising a display module and a central processing unit (CPU), wherein a control power supply from the CPU is coupled to the display module to generate voltage and drive a display is disclosed.

[0017] In one implementation, a protection relay device comprising a display module and a central processing unit (CPU) wherein the display module communicably coupled with the central processing unit (CPU) using a Modbus communication implementing a Modbus- remote terminal unit (RTU) protocol is disclosed.

[0018] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0019] Figure 1 illustrates TTL logic circuit positioned at central processing unit (CPU), in accordance with an embodiment of the present subject matter.

[0020] Figure 2 illustrates TTL logic circuit positioned at the display unit, in accordance with an embodiment of the present subject matter.

[0021] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0022] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0023] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0024] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0025] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0026] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0027] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0028] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0029] Currently, a display unit is provided with power supply to drive the display module. To drive the display module it require the +5VDC. In the present invention, the VDC voltage along with two wire RS485 serial line from CPU board is provided to drive the display module. Further, in the present invention, four control wires with shielded cable named RX, TX, +24VDC and GND are provided to the display module. A +24VDC is converted into +5VDC with adjustable converter IC and then used for driving the display module. Also the present invention is tested with 5mtr,10mtr and 20mtr length of shielded cable and it is not pick upping the noise in transmission of data and voltage also not go down below the +23.5VDC at end of the display module.

[0030] The control power supply +24VDC is provided from CPU board side and transmitted along with RX and TX serial line to display module it reduces the power supply module cost. Power supply module create the noises due to pulse transformer and MOSFET switching operation, It effect in EMI EMC testing and sometimes it’s not allowed to pass EMI – EMC test.

[0031] In one implementation, the Transreceiver ICs likes SN65HVD12, that are used in the convention devices, are replaced with a TTL Logic circuit for RS485 Modbus – RTU protocol communication. In this topology, the present invention enables to provide the TTL logic circuit using the Transistors and resisters both side of CPU and display module for RS485 communication. The Modbus communication enables to provide half duplex communication between the CPU and display module. RX and TX signal is provided from processor to TTL logic circuit and then transmitted along with control power supply to the display module. At display side also the TTL logic circuit is provided. It will receive the data information from processor queried by display master module and give to the display module’s controller RX and TX pin. From the both side CPU board and display board Transreceiver ICs are replaced with TTL Logic circuit and work same like Transreceiver. It reduces the cost of Transreceiver ICs and also reduces the cost of product. In one example, transreceiver ICs are standard chip to generate the transmitting and receiving differential signal. While in TTL logic we can generate signal with settable gain for transmit and receiving signal.

[0032] Figure 1 illustrates the TTL logic circuit positioned at the CPU unit. A person skilled in the art will appreciate that for understanding purpose the present invention is explained with the help of electronic protection relay however the disclosed method shall not be considered as the limiting factor for the scope of present invention.

[0033] Figure 2 illustrates the TTL logic circuit positioned at the display unit. A person skilled in the art will appreciate that for understanding purpose the present invention is explained with the help of electronic protection relay however the disclosed method shall not be considered as the limiting factor for the scope of present invention.

[0034] Referring now to figure 1, in one exemplary embodiment, the master unit in the present invention is a CPU unit that comprises a TTL logic circuit. The TTL logic circuit further comprises resistors (R1, R2, R3, R4 and R5) and transistors (Q1 and Q2) for generating differential transmitting (Tx) and receiving (Rx) signal in addition to control power supply (+24VDC). Four control wires with shielded cable named RX, TX, +24VDC and GND are given to the slave unit.

[0035] Referring now to figure 2, in one exemplary embodiment, the slave unit in the present invention is a display module that comprises a TTL logic circuit which further comprises resistors (R1, R2, R3, R4 and R5) and transistors (Q1 and Q2) for receiving Tx, Rx, +24VDC and ground (GND) signals from the CPU unit and subsequently generating Rx and Tx signals for reception and/or transmission to the CPU unit. The Rx terminal at the display unit is Tx terminal at the CPU unit and Rx terminal at the CPU unit is a Tx terminal at the display unit.

[0036] In one implementation a Control power supply, +24VDC is made to transmit from the master unit along with Rx and Tx signal to the slave unit for eliminating the requirement of a power supply module for driving a slave unit.

[0037] In one implementation, 5mtr, 10mtr and 20mtr length of shielded cable is used as four control wires for effective transmission of data and voltage at the display unit do not go below the +23.5VDC and also not pick up the noise.

[0038] In one implementation the +24VDC voltage from the CPU unit is converted to +5VDC using an adjustable converter IC and that is used for driving the operations of a display unit. An Adjustable ICs are placed in peripheral modules like display, expansion DIO etc., to convert the required voltage to drive the Peripheral Module.

[0039] In one implementation, the TTL Logic circuit for the display module comprises at least two Q1 and Q2 transistors and resistors for receiving and transmitting a communication signal. It may be one type of digital circuit made from a BJT transistors and resistors for gating and amplification of the signals. Also on receiving +24V DC to the display, it will be converted to +5V DC through adjustable IC to supply the LCD and Controller of the display module. It may be understood by the person skilled in the art that, some small changes may be done in existing circuit while implementation of conventional TTL circuit for protection and reducing the noise to communication signals.

[0040] In one implementation, the TTL Logic circuit for the CPU comprises same number of component as in display module above. For protection purposes, diodes and capacitors is added. It may works same like display module but it communicates vice-versa. The CPU along with power supply module send the +24V DC to display module. It reduces the cost total product and also helpful to pass the EMI EMC test etc. It may be understood by the person skilled in the art that, some small changes may be done in existing circuit while implementation of conventional TTL circuit for protection and reducing the noise to communication signals.

[0041] Some of the important features of the present invention, considered to be noteworthy are mentioned below:
1. The present invention provides a mechanism for low cost and reliable data communication between a master unit and slave unit devices.
2. The present invention provides a mechanism for generating control power supply that eliminates noise in transmission of data.
,CLAIMS:1. A protection relay device comprising a display module and a central processing unit (CPU), wherein
a control power supply from the CPU is coupled to the display module to generate voltage and drive a display; and
the display module communicably coupled with the central processing unit (CPU) using transistor- transistor logic (TTL) circuit using a serial communication over Modbus-RTU protocol.

2. A protection relay device comprising a display module and a central processing unit (CPU), wherein
a control power supply from the CPU is coupled to the display module to generate voltage and drive a display.

3. A protection relay device having a display module and a central processing unit (CPU), the protection relay device comprising:
the display module communicably coupled with the central processing unit (CPU) using a Modbus communication implementing a Modbus- remote terminal unit (RTU) protocol.

4. The protection relay device as claimed in any of the preceding claims, wherein the display module and the CPU are communicable coupled by a serial communication using the transistors transistor logic.

5. The protection relay device as claimed in any of the preceding claims, wherein the Modbus communication provides a half-duplex communication between the CPU and the display module.

6. The protection relay device as claimed in claim 5, wherein a RX signal and a TX signal from a processor of the CPU are provided to the TTL circuit of the CPU and thereby the RX signal and the TX signal are transmitted with the control power supply of the CPU to the display module.

7. The protection relay device as claimed in claim 6, wherein the TX signal from the CPU is received by RX of the display module and the RX signal from the CPU is received by TX of the display module.