FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules  2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION

“Protection circuit for Electronic Control Unit (ECU)”

APPLICANTS:

Name : Mahindra & Mahindra Ltd.

Nationality : Indian

Address : Mahindra Research Valley  Mahindra
World City  Plot No. 41/1  Anjur P.O
Chengalpattu – 603204  Kancheepuram
Dist  Tamilnadu.

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

FIELD OF INVENTION
[001] This invention relates to automotive electronics and more particularly to protection of Electronic control unit (ECU) from supply voltage fluctuations and excessive negative voltage levels.

BACKGROUND OF INVENTION
[002] An Electronic Control Unit (ECU) in an automobile may be considered as an embedded system that controls one or more electrical systems and sub systems in a vehicle. The ECU may act as an easy access point for controlling and coordinating working of all the embedded modules present in the vehicle. The ECU may receive manual inputs from the user and sensor inputs that are measured automatically required for operation of specific embedded systems present in the vehicle.
[003] A few examples of embedded systems that are normally used in the vehicles are air bag  body control modules  door control units  engine control units  speed control unit break control unit and so on. The ECU may provide interfaces for the users to control and/or monitor functionalities of various embedded systems present in the vehicle.
[004] The ECU is an Integrated Circuit (IC) comprises minute electronics components such as capacitors  resistors  chips  diodes and so on that constitute the whole circuitry. Each of the components may be having own specification rating i.e. voltage and current ratings to operate. Fluctuations in the input voltage may lead to damage of the components and in turn damage of the whole ECU. Electrical Over Stress (EOS) is a major factor that leads to damage of ECU  especially in off road driving conditions.
[005] EOS is a lower voltage (<100V) and large peak current (>10A) event that occurs over longer time frame (generally >1ms). Electrical Over-Stress (EOS) causes thermal damage i.e. as a result of excessive heat produced when an electronic device/component is subjected to a current or voltage that is beyond the specification limits of the device/component. The excessive temperature affects and damages the circuit components.
[006] If the ECU module gets damaged  various functionalities of the vehicle may get affected. Further  the ECU can not be repaired once damaged and is to be replaced  which adds to cost of the system.

OBJECT OF INVENTION
[007] The principal object of this invention is to protect an Electronic Control Unit (ECU) circuit from excessive negative pulses and fluctuations in the input voltage.
[008] Another object of the invention is to identify negative pulses in the input voltage above a set level and to block the excess negative pulses from reaching the ECU  thereby protecting the ECU from thermal damage due to excessive voltage.

STATEMENT OF INVENTION
[009] Accordingly the invention provides a method of protecting electronic control circuit (ECU)  said method comprises checking if negative pulses in input voltage to said ECU is more than a set level and removing negative voltage pulses above the set level on negative pulses in said input voltage being more than the set level.
[0010] There is also provided an system comprising of an electronic control unit  a protection circuit and a main relay circuit  wherein the system is configured for protecting the ECU from over voltage by checking if negative pulses in input voltage to said ECU is more than a set level using a protection circuit and removing negative voltage pulses above the set level on negative pulses in the input voltage being more than the set level using the protection circuit.
[0011] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood  however  that the following descriptions  while indicating preferred embodiments and numerous specific details thereof  are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof  and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF FIGURES
[0012] This invention is illustrated in the accompanying drawings  through out which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings  in which:
[0013] FIG. 1 illustrates a block diagram that shows protection circuit implemented between Electronic control unit (ECU) and main rely circuit  according to embodiments as disclosed herein;
[0014] FIG. 2 is a flow diagram showing various steps involved in the process of the protection circuit preventing excessive voltage flow to the ECU  as disclosed in the embodiments herein; and
[0015] FIGS. 3A and 3B illustrate example simulation diagrams showing voltage regulation to the ECU by the protection circuit at -28V and -33V respectively  as disclosed in the embodiments herein.

DETAILED DESCRIPTION OF INVENTION
[0016] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly  the examples should not be construed as limiting the scope of the embodiments herein.
[0017] The embodiments herein achieve an over voltage protection for Electronic Control Unit (ECU) by using a protection circuit. Referring now to the drawings  and more particularly to FIGS. 1 through 3  where similar reference characters denote corresponding features consistently throughout the figures  there are shown preferred embodiments.
[0018] FIG. 1 illustrates a block diagram that shows protection circuit implemented between Electronic control unit (ECU) and main rely circuit  according to embodiments as disclosed herein. Supply from the Main rely circuit 103 to the ECU 101 is through the protection circuit 102. The ECU further comprises an input module 101.a  a processor module 101.b  a controller module 101.c and an interface module 101.d.
[0019] The ECU 101 is an embedded module that acts as a one touch point to control and coordinate functionalities of various embedded systems present in the vehicle  the ECU is present. The input module 101.a receives inputs from the input channels for further processing. The inputs may be from sensors associated with other embedded systems or may be manual user inputs. The received inputs are then transferred to the processor module 101.b. The processing module 101.b processes the received inputs and decides actions based on the processed contents. For example  the received input may be from an air bag sensor and may be indicating excessive pressure detection caused due to an accident. The processor module 101.b decides an action according to the detected pressure value. For example  the action may be opening the airbags to rescue passenger in the vehicle.
[0020] Further  the processor module 101.b instructs the controller module 101.c to perform the action being decided based on the received input. The controller module 101.c in turn instructs the embedded systems from which the input is received  to perform specific action. The embedded systems may be connected to the ECU 101 through the interface module 101.d.
[0021] The protection circuit 102 resides between the ECU 101 and the main rely circuit 103 and checks if level of negative pulses in the input supply to the ECU 101 is more than a set limit. If the level of negative pulses in the input voltage is more than the set limit  the protection circuit 102 blocks the excessive negative pulses from the input supply and allows other voltage components to pass through and reach the ECU 101. In a preferred embodiment  the protection circuit 102 clips the excessive negative voltage pulses using a diode based circuit  thus protecting the ECU 101 from damages that may be caused due to excessive negative voltage and heat.
[0022] FIG. 2 is a flow diagram showing various steps involved in the process of the protection circuit preventing excessive voltage flow to the ECU  as disclosed in the embodiments herein. The protection circuit 102 is connected between the ECU 101 and the main rely circuit 103. The rely circuit 103 may be set to deliver low power signals to the ECU 101. Any component of an electrical/electronics system has a particular specification limit  voltage/current above which may damage the components.
[0023] Some times due to issues like Electrical Over Stress (EOS)  level of negative pulses in the input voltage increases  which in turn is harmful to the components and the ECU circuit as a whole. EOS is a lower voltage (<100V) and a large peak current (>10A) event that occurs for generally a time frame greater than 1ms. For example  when a vehicle is being used in off road conditions  EOS may occur resulting in increase of negative pulses in the supply voltage. This further damages the ECU  affecting functionality of the associated embedded systems. When the ECU stops working  major functions of the vehicle gets affected and the vehicle itself may stop functioning.
[0024] A protection circuit is employed to monitor the input power supply for excessive negative voltage components and to block the negative voltage components above a set limit. Input supply voltage from a source such as a battery is passed through the main rely 103. The main rely 103 acts as a switch  regulating amount of supply voltage to the system. The protection circuit 102 measures (201) input voltage and checks (202) if negative pulses/negative component of voltage is more than a set limit. In a preferred embodiment  the protection circuit 102 may compare the input voltage value with a set reference voltage value to identify whether the negative pulse level in the input voltage is more than the set value. The reference voltage value may be stored in a database associated with the system.
[0025] If value of the negative pulses in the input voltage is identified to be within the set limit  it is fed (204) to the ECU 101. If the value of the negative pulses in the input voltage is identified to be more than the set limit then the protection circuit 102 removes (205) the excess negative pulses in the input voltage. In a preferred embodiment  the protection circuit may clip the excess negative voltage pulses using a diode based circuitry. After removing/clipping the excess voltage pulses  the input supply voltage is fed (206) to the ECU 101.
[0026] The various actions in method 300 may be performed in the order presented  in a different order or simultaneously. Further  in some embodiments  some actions listed in FIG. 3 may be omitted.
[0027] FIGS. 3A and 3B illustrate example simulation diagrams showing voltage regulation to the ECU by the protection circuit at -28V and -33V respectively  as disclosed in the embodiments herein. Allowed voltage for an ECU is normally up to -15 V. But damages to the ECU are observed at -22V. The protection circuit 102 connected between the ECU 101 and the main rely circuit 103 detects and removes/clips the excess negative voltage pulses and feeds voltage pulses in the set limit to the ECU 101. The graph as in Fig. 3A depicts working of the protection circuit 102 for an input voltage of -28V and Fig. 3B depicts working of the protection circuit 102 for an input voltage of -33V. In both cases  the protection circuit 102 limits the negative pulses to set limit i.e. 15V and pass them on to the ECU 101.
[0028] The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the network elements. The network elements shown in Fig. 1 include blocks which can be at least one of a hardware device  or a combination of hardware device and software module.
[0029] The embodiment disclosed herein describes a system and method for protecting Electronic control unit (ECU) from voltage fluctuations and excessive negative voltages. Therefore  it is understood that the scope of the protection is extended to such a program and in addition to a computer readable means having a message therein  such computer readable storage means contain program code means for implementation of one or more steps of the method  when the program runs on a server or mobile device or any suitable programmable device. The method is implemented in a preferred embodiment through or together with a software program written in e.g. Very high speed integrated circuit Hardware Description Language (VHDL) another programming language  or implemented by one or more VHDL or several software modules being executed on at least one hardware device. The hardware device can be any kind of portable device that can be programmed. The device may also include means which could be e.g. hardware means like e.g. an ASIC  or a combination of hardware and software means  e.g. an ASIC and an FPGA  or at least one microprocessor and at least one memory with software modules located therein. The method embodiments described herein could be implemented partly in hardware and partly in software. Alternatively  the invention may be implemented on different hardware devices  e.g. using a plurality of CPUs.
[0030] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can  by applying current knowledge  readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept  and  therefore  such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore  while the embodiments herein have been described in terms of preferred embodiments  those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

CLAIMS
We claim 
1. A method of protecting electronic control circuit (ECU)  said method comprises:
checking if negative pulses in input voltage to said ECU is more than a set level; and
removing negative voltage pulses above said set level on negative pulses in said input voltage being more than said set level.

2. The method as in claim 1  wherein said checking whether the negative pulses in the input voltage is more than said set level further comprises comparing negative pulse level in said input voltage with a reference voltage value.

3. The method as in claim 2  wherein said reference voltage value is manually configured.

4. The method as in claim 1  wherein said removing of negative pulses more than the set level from said input voltage further comprises clipping of said negative pulses from said input voltage.

5. The method as in claim 1  wherein input voltage after removing negative pulses above said set level is fed to said ECU.

6. The method as in claim 1  wherein said set level of negative pulse for input voltage is -22V.

7. A system for protecting electronic circuit unit (ECU) from over voltage  wherein said system configured with at least one means configured for:
checking if negative pulses in input voltage to said ECU is more than a set level using a protection circuit; and
removing negative voltage pulses above said set level on negative pulses in said input voltage being more than said set level using said protection circuit.

8. The system as in claim 7 is further configured for checking whether the negative pulses in the input voltage is more than said set level by comparing negative pulse level in said input voltage with a reference voltage value.

9. The system as in claim 7 is further configured for removing negative pulses more than said set limit from the input voltage by clipping said negative pulse from said input voltage.

10. The system as in claim 7 is further configured for feeding input voltage after removing negative pulses above said set level to the ECU.

Date: 21st September 2012 Signature

Dr. Kalyan Chakravarthy
Patent Agent

ABSTRACT

This invention relates to automotive electronics and more particularly to protection of Electronic control unit (ECU) from supply voltage fluctuations and excessive negative voltage levels. A protection circuit is connected between the Electronic Control Unit (ECU) and a main relay circuit. Input supply voltage from the relay circuit is checked by the protection circuit for excessive negative voltage pulses by comparing with a set limit. Further  the protection circuit removes excessive voltage pulses present in the input voltage if any using a diode based clipping circuit. Further  the input voltage in the set limit is passed to the ECU.
FIG. 1