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] This invention is related to a method of detecting a fault at a high side in an electronic control unit and a control unit thereof.

Background of the invention

[0002] During PWM phases of Heating/Pump-Heat mode, it is expected that short circuit to battery at the high side error is reported when the high side sense current is less than the constant threshold current. But, when a higher duty cycle is requested, it was observed that high side sense current (sampled every 1ms) measures higher values of current even when short circuit to battery at the high side error created.

Brief description of the accompanying drawings
[0003] Figure 1 illustrates an electronic control unit for detecting a fault in a pulse width modulation (PWM) phase, in accordance with an embodiment of the invention; and
[0004] Figure 2 illustrates a flowchart of a method of detecting a fault in the electronic control unit during the PWM phase, in accordance with the present invention.

Detailed description of the embodiments
[0005] Figure 1 illustrates an electronic control unit for detecting a fault in a pulse width modulation (PWM) phase in accordance with one embodiment of the invention. The electronic control unit (ECU) 10 is connected to a battery 12 and the fault is identified/detected during a pulse width modulation (PWM) phase. The ECU 10 identifies an occurrence of fault at a high side 14 of the electronic control unit 10 and senses a variation in a high side 14 current and when the fault is occurred. The electronic control unit 10 considers a low side 16 current for a given point of time when the fault is occurred and calculates a threshold value from the considered low side 16 current and a calibration factor. The electronic control unit 10 detects the fault in the electronic control unit 10 upon comparing the high side 14 current to the threshold value.

[0006] Further the construction of the ECU 10 and the components connected to the ECU 10 is explained in detail. The ECU 10 comprises a high current side 14 and a lower current side 16. Each current sides (14 & 16) comprises a transistor /Switch connected to an analog to digital converter pin 20 in the ECU 10. A solenoid actuator 22 (an electromagnetic coil) is connected between the high current side 14 and the lower current side 16 of the ECU 10. As the coil /actuator 22 current is made to vary based on the PWM duty cycle, the disclosed method helps in identifying /detecting the occurrence of the fault in the ECU 10 based on a comparison between the high side 14 current and the low side 16 current. During the PWM phase of the heating/pump-heat mode, the occurrence of the fault will be higher when compared to the normal working conditions. During this scenario, the low side 16 current is maintained at a predefined level, but a variation in the high side 14 current is identified.

[0007] In normal working conditions of the ECU 10, the high side 14 current oscillates with the PWM frequency, i.e., higher the requested duty cycle, the high side 14 current oscillates at higher current range. Similarly, for lower duty cycles, the high side 14 current is lower. This is applicable during both the fault condition and the normal working conditions. At higher duty cycles, threshold current to detect fault which is (short circuit to battery fault at high side) is calibrated to low. However, during testing , it is observed that high side current is higher than threshold current. Due to this, the fault is not identified although fault is created at the high side terminal 14.

[0008] The control unit 10 is chosen from a group of control units like a microprocessor, a microcontroller, a digital circuit, an integrated chip and the like. occurrence of the fault at said high side 14 of the ECU 10 is identified when the ECU 10 is connected to the battery 12 . According to the one embodiment of the invention, the fault is a short circuit to battery occurred at the high side terminal 14.

[0009] Figure 2 illustrates a flowchart of a method of detecting a fault in the electronic control unit 10 during the PWM phase. In step S1, an occurrence of fault is identified at a high side of the electronic control unit (ECU) 10 . In step S2, a variation is sensed in a high side 14 current and when the fault is occurred. In step S3, a low side 16 current is considered for a given point of time when the fault is occurred. In step S4, a threshold value is calculated from the considered low side 16 current and a calibration factor. In step S5, the fault is detected in the electronic control unit 10 upon comparing the high side 14 current to the threshold value.

[0010] The method is explained in detail. During the normal working condition, the high side 14 current and the low side 16 current are maintained at a similar level. The occurrence of the fault is identified at the high side 14 of the electronic control unit 10 during the PWM phase. The variation in the high side 14 current is sensed, when the fault is occurred. But, during the PWM pulse phase, if the fault (short circuit to battery) is occurred, the high side 14 current starts varying from the normal level and will be in the reducing side when compared to the low side 16 current. Based on the duty cycle of the PWM signal, the high side 14 current varies. The larger the duty cycle, the reduction in the high side 14 current is less and the lesser the duty cycle, the reduction in the high side 14 current is more.

[0011] In order to detect or confirm the occurrence of the fault, the low side 16 current at a given point of time or at a particular instant is considered. The low side 16 current is used to calculate the threshold value. The threshold value comprises the values like a calibration factor and the low side current at a given point of time. The calibration factor is predefined during the calibration process. The Calibration factor is set within a predefined range, wherein the minimum value in the predefined rang is maintained above one, to detect the fault ( SCBHS ) at the earliest. For instance, an additional influencing factors like a tolerance of ADC current measurement across low side shunt resistance and a high side current measurement across signal period at different points and high side 14 current deviation are considered in defining the calibration factor range. According to one embodiment of the invention, the calibration factor is set between 1.8 – 2.2.

[0012] The low side 16 current and the calibration factor is considered in calculating the threshold value. The threshold value is calculated using the below formula :

The threshold value = (low current side value)/ (calibration factor).

[0013] The electronic control unit 10 confirms/detects the fault between the high side 14 and the battery 12, when the high side 14 current is less than or equal to the threshold value. With the above-disclosed method, latest sample of high side 14 current and latest period of the lower side 16 of threshold current is sufficient to detect the fault ( SCBHS ) even when the PWM phase is active. The dynamic lower side 16 threshold current strategy supports wide range of frequency, and the above method relies only on averaging of high side 14 current and supports a wide range of shorted wired resistance.

[0014] It should be understood that 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. An electronic control unit (ECU)(10) for detecting a fault during a pulse width modulation (PWM) phase , said ECU (10) adapted to :
- identify an occurrence of fault at a high side of said electronic control unit (10);
- sense a variation in a high side (14) current and when said fault is occurred;
- consider a low side (16) current for a given point of time when said fault is occurred ;
- calculate a threshold value from said considered low side (16) current and a calibration factor ;
- detect said fault in said electronic control unit (10) upon comparing said high side (14) current to said threshold value.

2. The ECU (10) as claimed in claim 1, wherein occurrence of said fault at said high side (14) of said ECU (10) is identified, when said ECU (10) is connected to a battery (12).

3. The ECU(10) as claimed in claim 1, wherein said fault is a short circuit to battery (12) fault at said high side of said ECU (10) .

4. A method of detecting a fault in an electronic control unit (10) during a pulse width modulation (PWM) phase, said method comprising :
- identifying an occurrence of fault at a high side (14) of said electronic control unit (10) (ECU);
- sensing a variation in a high side (14) current and when said fault is occurred;
- considering a low side (16) current for a given point of time when said fault is occurred ;
- calculating a threshold value from said considered low side (16) current and a calibration factor ;
- detecting said fault in said electronic control unit (10) upon comparing said high side (14) current to said threshold value.

5. The method as claimed in claim 4, wherein said calibration factor is set within a predefined range, a minimum value of said predefined range is set above one.

6. The method as claimed in claim 4, wherein said fault is detected when said high side (14) current is less than or equal to said threshold value.

7. The method as claimed in claim 4, wherein said variation in said high side (14) current is indirectly proportional to a duty cycle of said PWM signal.

8. The method as claimed in claim 7, wherein identifying a lower reduction in said high side (14) current for a larger value of said duty cycle of said PWM signal.