Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.

Field of the invention:
[0001] The present invention relates to a diagnostic circuit for an electronic control unit (ecu) of a vehicle and method therefor.

Background of the invention:
[0002] Many Electronics Control Units (ECUs) are used to control the engine/ transmission / brake loads in the vehicle, in the form of Battery Control Units (BCU), Vehicle Control Unit (VCU), Anti-lock Braking System (ABS), Cluster Control Unit (CCU) in combustion based vehicles and electric vehicles. The ECU reads all the necessary operating data required for controlling and regulating the engine/ transmission / brake loads/ electric motor, etc., using sensors, switches as well as data from the bus systems.

[0003] During normal operation, the ECU is supplied from battery through main relay or directly from the battery. Each actuator/load is controlled by a high side switch or a low side switch or a high side and low side switch as known in the art. A controller in the ECU controls the actuator/load via low side/high side power stage based on the information processed. Due to the safety requirements, controller/power stage need to ensure proper connection between the power stage and the actuator and detecting and managing faults.

[0004] The faults have to be detected promptly by placing different circuits around the power stage. The primary faults which occur comprises an Open Load (OL) fault which corresponds to a broken wire or disconnected wire between actuator/load and the power stage. A Short to Battery (SCB) fault which corresponds to the wiring harness between the actuator/load and the power stage (ECU Pin) is directly connected to the battery of the vehicle. A Short Circuit to Ground (SCG) fault which corresponds to the wiring harness between the actuator and the power stage (ECU Pin) is directly connected to the vehicle ground.

[0005] The ECU controls the supply/power of the actuator/load using a low side/high side switch/power stage. In order to verify the proper connection between ECU and the actuator, certain diagnostic feature is necessary. Hence, the diagnosis of OL fault, SCG fault and SCB fault is provided by the low side/high side power stages. Usually, the time to diagnose and switch OFF the power stage is quite critical in automotive application. The conventional diagnostic method uses current source to identify the OL, SCG and SCB faults. The diagnostic time will be limited depending on the rating of the current source and the connected circuits. This limits the operational frequency of the loads/actuator connected to the low side/high side power stage. Since there is always an Electro-Static Discharge (ESD) capacitor (to protect the circuit from ESD pulses) placed at the power stage output, the current sources will charge the ESD capacitor at the first place. This causes an additional delay in detecting the faults. For this purpose, there is always a blanking time introduced to avoid any misdetections during the above case. This blanking time will limit the operational frequency of the load/actuator.

[0006] According to a prior art 353362 an automotive driver system with short circuit protection is disclosed. The prior art relates to a driver system with short circuit protection in automotive applications. The driver system makes use of off-the-shelf solid state switches such as power transistors or MOSFETs for driving high current automotive loads. The short circuit protection is provided by employing an opto-isolator based short circuit protection. The control unit triggers the solid state switch ON by means of an edge signal on an output pin. Thereafter, the out pin is re-configured as input for monitoring the short-circuit condition. The optocoupler isolator detects and protects the driver from the short circuit as well as notifying the input pin about the short circuit by means of voltage changes on the pin.

Brief description of the accompanying drawings:
[0007] An embodiment of the disclosure is described with reference to the following accompanying drawings,
[0008] Fig. 1 illustrates a block diagram of a diagnostic circuit for an Electronic Control Unit (ECU) of a vehicle, according to an embodiment of the present invention;
[0009] Fig. 2 illustrates waveforms indicating diagnosis of faults, according to an embodiment of the present invention, and
[0010] Fig. 3 illustrates a method for diagnosing connections of Electronic Control Unit (ECU) of a vehicle, according to the present invention.

Detailed description of the embodiments:
[0011] Fig. 1 illustrates a block diagram of a diagnostic circuit for an Electronic Control Unit (ECU) of a vehicle, according to an embodiment of the present invention. The diagnostic circuit 110 comprises a first isolator 104 connected in series and between a DC supply 102 and a current limiter 106. A first energy storing element 108 connected across the DC supply 102 and the current limiter 106. A second isolator 112 connects a junction of the current limiter 106 and the first energy storing element 108 to at least one output pin/port/contact 114 of the ECU 130. The second isolator 112 is connected to a second energy storing element 118 provided in the ECU 130. The second isolator 112 prevents a connection between a battery 124 and any one of the first energy storing element 108 and the DC supply 102. The output pin 114 of the ECU 130 is connected between a power stage 116 of the ECU 130 and a corresponding external load 122. The external load 122 is operated by the ECU 130 through the power stage 116. The power stage 116 is either a low side, high side or combination of low side and high side. Only the basic circuit elements are shown for simplicity in explanation and may require other electrical or electronic components or parts as known in the art. The same must not be understood in limiting manner.

[0012] According to an embodiment of the present invention, the first energy storing element 108 and the second energy storing element 118 are selected from capacitor or other similar components of predetermined capacitance as per circuit design requirements. In the present invention, the second energy storing element 118 is a capacitor used for Electro-Static Discharge (ESD) but not limited to the same. The first isolator 104 and the second isolator 112 are selected from a diode or similar components. The current limiter 106 is selected from a resistor or similar component. Further, the power stage 116 are semiconductor based switches such as MOSFETs or FETs or transistors, etc. The Low Side (LS) power stage 116, the High Side (HS) power stage 116 and the combination of LS and HS power stage 116 comprises the use of switches and similar components but not limited to the same. Further, one power stage 116 is provided for each output pin 114 of the ECUs 130. The terms used in the present invention are generalized in non-limiting manner.

[0013] According to the present invention, a controller 120 of the ECU 130 is configured to diagnose an Open Load (OL) fault, when voltage at the output pin 114 is less than a first threshold voltage. The controller 120 is configured to diagnose a Short Circuit to Ground (SCG) fault when voltage at the output pin 114 is near zero. The controller 120 is configured to diagnose a Short Circuit to Battery (SCB) fault when voltage at the output pin 114 is higher than a second threshold voltage. Further, the diagnosis of the OL fault and SCG fault is conducted during switched OFF state of the power stage 116. Similarly, the diagnosis of the SCB fault is conducted during switched ON state of the power stage 116.

[0014] According to an embodiment of the present invention, the controller 120 is configured to diagnose the OL fault, the SCG fault and the SCB fault based on the voltage of the second energy storing element 118 instead of the output pin 114.

[0015] According to the present invention, the controller 120 is equipped with necessary signal detection, acquisition, and processing circuits along with connection to other sensors (if required). The controller 120 is a control unit (computing device) 126 which comprises memory element (not shown) such as Random Access Memory (RAM) and/or Read Only Memory (ROM), Analog-to-Digital Converter (ADC) and a Digital-to-Analog Convertor (DAC), clocks, timers, counters and at least one micro-processor /micro-controller (capable of implementing machine learning) connected with each other and to other components through communication bus channels. The memory element is pre-stored with logics or instructions or programs or applications or modules/models and/or threshold values, which is/are accessed by the at least one processor as per the defined routines. The internal components of the controller 120 are not explained for being state of the art, and the same must not be understood in a limiting manner. The controller 120 may also comprise communication units to communicate with an external computing device such as the cloud, a remote server, etc., through wireless or wired means such as Global System for Mobile Communications (GSM), 3G, 4G, 5G, Wi-Fi, Bluetooth, Ethernet, serial networks, and the like.

[0016] According to an embodiment of the present invention, the controller 120 is implementable in the form of chips 128 or Integrated Circuits (ICs) such as but not limited to a System-in-Package (SiP) or a System-on-Chip (SOC), an Application-Specific Integrated Circuit (ASIC), an Application-Specific Standard Parts (ASSPs), a Field-Programmable Gate Arrays (FPGA) or any other known types. In this case where the controller 120 is provided as a chip 128, the chip 128 is integrated with the power stage 116 as a single unit to detect the fault directly. The detected result is then passed on to the control unit 126 for diagnosis and remedial action. For simplicity in understanding, in Fig. 1, the power stage 116 is to be considered including the chip 128. Hence, either the control unit 126 alone is provided or combination of control unit 126 and the chip 128 is provided.

[0017] According to an embodiment of the present invention, the Electronic Control Unit (ECU) 130 of the vehicle is provided. The ECU 130 comprises at least one output pin 114 internally connected with the power stage 116 and the controller 120, characterized in that, the controller 120 connected with the diagnostic circuit 110 at the output pin 114, and configured to diagnose an Open Load (OL) fault, when voltage at the output pin 114 is less than the first threshold voltage. The controller 120 configured to diagnose the Short Circuit to Ground (SCG) fault when voltage at the output pin 114 is near zero. The controller 120 is configured to diagnose the Short Circuit to Battery (SCB) fault when voltage at the output pin 114 is higher than the second threshold voltage. Further, diagnosis of the OL fault and the SCG fault is conducted during switched OFF state of the power stage 116, and diagnosis of the SCB fault is conducted during switched ON state of the power stage 116.

[0018] According to the present invention, the diagnostic circuit 110 connected to the ECU 130 comprises the first isolator 104 connected in series and between the DC supply 102 and the current limiter 106. The first energy storing element 108 connected across the DC supply 102 and the current limiter 106. The second isolator 112 connects the junction of the current limiter 106 and the first energy storing element 108 to at least one output pin 114 of the ECU 130.

[0019] According to another embodiment of the present invention, the Electronic Control Unit (ECU) 130 of the vehicle is provided. The ECU 130 comprises at least one output pin 114 internally connected with the power stage 116 and the controller 120, characterized in that, the controller 120 connected with the diagnostic circuit 110 at the output pin 114 to aid in the detection or diagnosis of the faults at the power stage 116 or the output pin 114 of the ECU 130. The diagnostic circuit 110 connected to the ECU 130 comprises the first isolator 104 connected in series and between the DC supply 102 and the current limiter 106. The first energy storing element 108 connected across the DC supply 102 and the current limiter 106. The second isolator 112 connects the junction of the current limiter 106 and the first energy storing element 108 to at least one output pin 114 of the ECU 130.

[0020] According to the present invention, a working of the diagnostic circuit 110 is envisaged with a Low Side (LS) power stage 116. Consider at least one load 122 is connected through wiring harness to the output interface of the ECU 130. In normal working conditions, the actuator/load 122 is controlled via Low Side (LS) power stage 116 operating at a particular Pulse Width Modulation (PWM) signal/ratio. The LS power stage 116 is shown connected to ground. A High Side (HS) stage or combination of LS and HS is also possible to be used. In the case of HS power stage 116, the ground is replaced by positive of the battery 124. When the LS power stage 116 is switched ON, the current flows through battery 124, the load 122 and the LS power stage 116 to the Ground (GND). The second isolator 112 isolates the diagnostic circuit 110 from the power stage 116. During this time, the first energy storing element 108 is charged by the DC supply 102 through the first isolator 104 and the current limiter 106. In addition, the first isolator 104 isolates the DC supply 102 from the first energy storing element 108 and the current limiter 106 limits the current. Further, the DC supply 102 is either independent source or dependent (derived) on the battery 124. During this case, the voltage at the output pin 114 is below the threshold level of diagnosis range. Hence, no bit is set which would be detected by the controller 120 indicating no fault.

[0021] Similarly, when the LS power stage 116 is switched OFF, there is no current flow through the LS power stage 116 and load 122 from the battery 124, but the second energy storing element 118 is charged. When the energy of second energy storing element 118 is less than the energy of first energy storing element 108, the current flows through the first energy storing element 108, the second isolator 112 to the second energy storing element 118. The current also flows from the battery 124, load 122 to the second energy storing element 118. However, when energy of second energy storing element 118 is more than the energy of first energy storing element 108, the current flows only from the battery 124, load 122 to the second energy storing element 118. During this case, the voltage at the output pin 114 is below the threshold level of diagnosis range. Hence, no bit is set which would be detectable by the controller 120 indicating no fault.

[0022] According to the present invention, an exemplary embodiment of the OL fault diagnosis is explained. The OL fault is diagnosed only when the power stage 116 is switched OFF. When the LS power stage 116 is switched OFF and the load 122 is not connected (or disconnected due to break), the second energy storing element 118 is charged when the energy of second energy storing element 118 is less than the energy of first energy storing element 108. The current flows only through first energy storing element 108, the second isolator 112 to the second energy storing element 118. During this case, the energy is transferred from first energy storing element 108 to the second energy storing element 118 based on the value of the first energy storing element 108 and the second energy storing element 118. Due to this, the voltage at the output pin 114 raises to a certain level. Hence, the OL fault is detected by the controller 120 and the corresponding bit is set. For example, the first energy storing element 108 is designed in such a way that the voltage at the output pin 114 is in the range of ~2.5V to ~5.5V to differentiate the failure conditions.

[0023] According to the present invention, an exemplary embodiment of the SCG fault diagnosis is explained. Similar to OL fault, the SCG fault is diagnosed only when the power stage 116 is switched OFF. When the LS power stage 116 is switched OFF and the output pin 114 is shorted to ground (GND), the second energy storing element 118 is discharged to the GND. During this case, the voltage at the output pin 114 is certain level less than 2.5V or near zero, the short to ground range. The values 2.5v and zero are given as examples. Hence, the controller 120 detects the SCG fault and corresponding bit is set.

[0024] According to the present invention, an exemplary embodiment of the SCB fault diagnosis is explained. The SCB fault is diagnosed only when the power stage 116 is switched ON. When the LS power stage 116 is switched ON and the output pin 114 is shorted to battery (Ubat) 124, the current flows from the battery 124 through the load 122 and the second energy storing element 118, as the second isolator 112 blocks the flow of current towards the diagnosing circuit 110. During this case, the voltage at the output pin 114 is equivalent to the product of the current flowing through the LS power stage 116 and the ON state resistance of the power stage 116, which is greater than ~5.5V, the SCB range. The value 5.5v is given as an example and may vary as per circuit design and requirement. Hence, the controller 120 detects SCB fault and sets corresponding bit.

[0025] Fig. 2 illustrates waveforms indicating diagnosis of faults, according to an embodiment of the present invention. A group of four waveforms 200 are shown with X-axis in time and Y-axis in voltage in suitable units with the help of diagnosing circuit. Specifically, the four waveforms are the result of the simulation shown here to ease the understanding of the invention. Since, the waveforms 200 are obtained by simulation, the same must not be understood in the limiting manner. An output of a detecting circuit connected to the output pin 114 is used. The detecting circuit is used either within the controller 120 or is in place of the controller 120. A first waveform 202 is the voltage at the output pin 114 or across the second energy storing element 118. A second waveform 204 is the output of a detecting circuit connected when SCG fault is detected. A third waveform 206 is the output of the detecting circuit when OL fault is detected. A fourth waveform 208 is the output of the detecting circuit when SCB is detected. An example comparison table is provided below which discloses the reaction time of the fault detection by the conventional method and the present invention for a specific second energy storing element 118 indicated by *.
Reaction time to detect the fault in the in conventional method Reaction time to detect the fault as per present invention
Open load 60-135uS ~28.5uS*
Short to Battery 60-135uS ~17.5uS*
Short to Ground 60-135uS ~17.5uS*

[0026] According to an embodiment of the present invention, a single diagnostic circuit 110 is used in common for multiple ECUs 130 in parallel which are connected with respective second isolator 112. Thus, reducing complexity and cost involved in multiple ECUs 130 system of the vehicle.

[0027] Fig. 3 illustrates a method for diagnosing connections of Electronic Control Unit (ECU) of a vehicle, according to the present invention. The method is characterized by the diagnostic circuit 110 connected to at least one output pin 114 of the ECU 130. The method comprises plurality of steps, of which a step 302 comprises diagnosing, by the controller 120 of the ECU 130, the Open Load (OL) fault, when voltage at the output pin 114 is less than the first threshold voltage. A step 304 comprises diagnosing, by the controller 120, the Short Circuit to Ground (SCG) fault when voltage at the output pin 114 is near zero. A step 306 comprises diagnosing, by the controller 120, the Short Circuit to Battery (SCB) fault when voltage at the output pin 114 is higher than the second threshold voltage.

[0028] The steps 302, 304 and 306 are independent of each other and are performed upon specific conditions. The method of diagnosing the OL fault and SCG fault is conducted during switched OFF state of the power stage 116, and diagnosing the SCB fault is conducted during switched ON state of the power stage 116.

[0029] According to an embodiment of the present invention, a power stage 116 diagnostic circuit 110, ECU 130, controller 120 and method is provided. The present invention enables a smaller number of components to be used, i.e., only first energy storing element 108, a first isolator 104 and the second isolator 112, and the current limiter 106. The filtering/reaction time to detect a fault is reduced thereby, the safety factor is improved. The frequency of operation can be extended (since the detection time is reduced) due to which current ripples are reduced thereby improving the EMC results. The diagnostic circuit 110 is used for diagnosis of OL, SCG and SCB faults instead of the conventional current sources. The time to detect the fault is highly minimized thereby maintaining the integrity of the vehicle system. Multiple power stages 116 can be cascaded to the same first energy storing element 108 with only addition of the isolator, i.e., only one diagnostic circuit 110 is used for different ECUs 130 of the vehicle. The detection circuits are minimized/eliminated by directly using the controllers 120 inside the ECU 130 which further decreases the time to detect these faults.

[0030] It should be understood that the embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.
, Claims:We claim:
1. A diagnostic circuit (110) for an Electronic Control Unit (ECU) (130) of a vehicle, characterized in that, said diagnostic circuit (110) comprises:
a first isolator (104) connected in series and between a DC supply (102) and a current limiter (106),
a first energy storing element (108) connected across said DC supply (102) and said current limiter (106), and
a second isolator (112) connects a junction of said current limiter (106) and said first energy storing element (108) to at least one output pin (114) of said ECU (130).

2. The diagnostic circuit (110) as claimed in claim 1, wherein said second isolator (112) is connected to a second energy storing element (118) provided in said ECU (130), said second isolator (112) prevents a connection between a battery (124) and any one of said first energy storing element (108) and said DC supply (102).

3. The diagnostic circuit (110) as claimed in claim 1, wherein said at least one output pin (114) of said ECU (130) is connected between a power stage (116) of said ECU (130) and at least one external load (122), said external load (122) is operated by said ECU (130) through said power stage (116).

4. The diagnostic circuit (110) as claimed in claim 1, wherein a controller (120) of said ECU (130) configured to,
diagnose an Open Load (OL) fault, when voltage at said output pin (114) is less than a first threshold voltage;
diagnose a Short Circuit to Ground (SCG) fault when voltage at said output pin (114) is near zero, and
diagnose a Short Circuit to Battery (SCB) fault when voltage at said output pin (114) is higher than a second threshold voltage.

5. The diagnostic circuit (110) as claimed in claim 4, wherein diagnosis of said OL fault and SCG fault is conducted during switched OFF state of said power stage (116), and diagnosis of said SCB fault is conducted during switched ON state of said power stage (116).

6. An Electronic Control Unit (ECU) (130) of a vehicle, said ECU (130) comprises at least one output pin (114) internally connected with a power stage (116) and a controller (120), characterized in that, said controller (120) connected with a diagnostic circuit (110) at said output pin (114), and configured to:
diagnose an Open Load (OL) fault, when voltage at said output pin (114) is less than a first threshold voltage;
diagnose a Short Circuit to Ground (SCG) fault when voltage at said output pin (114) is near zero, and
diagnose a Short Circuit to Battery (SCB) fault when voltage at said output pin (114) is higher than a second threshold voltage.

7. The ECU (130) as claimed in claim 6, wherein diagnosis of said OL fault and said SCG fault is conducted during switched OFF state of said power stage (116), and diagnosis of said SCB fault is conducted during switched ON state of said power stage (116).

8. The ECU (130) as claimed in claim 6, wherein said diagnostic circuit (110) comprises
a first isolator (104) connected in series and between a DC supply (102) and a current limiter (106),
a first energy storing element (108) connected across said DC supply (102) and said current limiter (106), and
a second isolator (112) connecting a junction of said current limiter (106) and said first energy storing element (108) to at least one output pin (114) of said ECU (130).

9. A method for diagnosing connections of Electronic Control Unit (ECU) (130) of a vehicle, characterized by, a diagnostic circuit (110) connected to at least one output pin (114) of said ECU (130), said method comprises the steps of
detecting, by a controller (120) of said ECU (130), an Open Load (OL) fault, when voltage at said output pin (114) is less than a first threshold voltage;
diagnosing, by said controller (120), a Short Circuit to Ground (SCG) fault when voltage at said output pin (114) is near zero, and
diagnosing, by said controller (120), a Short Circuit to Battery (SCB) fault when voltage at said output pin (114) is higher than a second threshold voltage.

10. The method as claimed in claim 9, wherein diagnosing said OL fault and SCG fault is conducted during switched OFF state of said power stage (116), and diagnosing said SCB fault is conducted during switched ON state of said power stage (116).