Method for monitoring operation of on-board electrical system

Abstract

The invention relates to a method for monitoring the operation of an on-board electrical system (50), in which a component temperature (62) of a component (56) in an on-board electrical system circuit (52, 54) of the on-board electrical system (50), an ambient temperature (66) of the component (56) and a current (70) flowing through the component (56) are ascertained in the on-board electrical system circuit (52, 54), and if an overload of the component (56) is detected, the component temperature (62) of the component (56), the ambient temperature (66) of the component (56) and the current (70) flowing through the component (56) are detected. If the component (56) is overloaded, a time period (72) is calculated until the component (56) is overloaded, the heat input (Pein) into the component (56) and the heat loss (Pus) of the component (56) being used to ascertain the time period (72) until the component (56) is overloaded.

Description

[0001] The invention relates to a method for monitoring the operation of an onboard electrical system and to a component for carrying out the method. Background Art

[0002] In automotive applications, the onboard electrical system (also called power supply network) is understood to be the totality of all electrical components in a motor vehicle. It therefore includes both electrical consumers and energy sources or power supply sources, such as batteries. In motor vehicles, it is important to ensure that electrical energy is available in such a way that the motor vehicle can be started at any time and that sufficient current is available during operation. However, when stationary, electrical consumers should still be able to operate for a suitable period of time without affecting the subsequent start.

[0003] The task of the onboard power supply is therefore to supply energy to the electrical consumers. It should be noted that the increasing electrification of the assembly and the introduction of new vehicle functions place higher demands on the safety and reliability of the electrical energy supply in the motor vehicle. This is especially true for safety-critical or safety-relevant consumers.

[0004] In a vehicle electrical system, situations may arise at safety-critical consumers in which the electrical system circuit, for example the output circuit of an electrical power distributor or ePDU or the output circuit of an electrical system monitoring device or power supply protection device (PNG), must operate the consumer under overload in an emergency situation. It is useful to supply the required current for as long as possible but to disconnect it in good time before an overload in the form of a thermal accident occurs in the electrical system circuit.

[0005] In this context, the onboard electrical system circuit supplies power to safety-relevant consumers, such as electric brakes or steering systems. This usually involves switches, such as MOSFETs, which can disconnect the consumers from the onboard electrical system in safety situations.

[0006] So what we strive for is to be able to predict how long a circuit can operate in an overload before a critical condition occurs and the circuit may no longer be usable.

[0007] A system for monitoring semiconductor components of a vehicle is known from DE 102019104246 A1. The system comprises at least one semiconductor component and at least one sensor unit, which is arranged on or integrated in the at least one semiconductor component, wherein the at least one sensor unit is arranged to detect at least one operating parameter of the semiconductor component. A monitoring module is arranged to determine a deviation between the detected operating parameter and a reference value.

[0008] An abnormality diagnosis device and an abnormality diagnosis method are known from DE 112018008225 T5. They are designed to identify the remaining time until a motor and a load cause a fault or a defect. Summary of the invention

[0009] Against this background, a method having the features of claim 1 and an arrangement according to claim 13 are proposed.

[0010] Embodiments emerge from the dependent claims and the description.

[0011] The proposed method is used to monitor the operation of an onboard power system. In the method, the temperature of a component in the onboard power system circuit, the ambient temperature of the component, and the current flowing through the component are measured in the onboard power system circuit of the onboard power system. If a component overload is detected, the time or time period until the component is overloaded is calculated. Overload means that the component is operated in an operating state that does not conform to its rated operation, so that a component temperature rise occurs that is not within the rated range. Overload means that the overload causes the operation of the component to be affected, and in extreme cases, causes the component to be destroyed.

[0012] In one specific embodiment, the temperature dependency of the electrical behavior of the component is taken into account. For example, the temperature dependency of the electrical resistance of the component may be included in this.

[0013] Furthermore, the method can be carried out for an output circuit of an electrical power distributor or an output circuit of an onboard power supply monitoring device.

[0014] The proposed method can therefore be used to predict how long the onboard power supply circuit can be operated in an overload state before an overload occurs, ie a critical state occurs, and the onboard power supply circuit must be shut down.

[0015] The method is based on the predictive prediction of the time or time period during which a certain current can be applied to the output circuit before thermal damage to the switch components can occur. The prediction or prediction of the remaining time opens up further possibilities: if the current supply to a safety-critical consumer is overloaded, optimized emergency measures can be implemented after the remaining time has expired.

[0016] Based on the calculated time period, optimized, ie, situation-adapted emergency measures can be activated or taken. After the time period has expired, the onboard power supply circuit can be disconnected.

[0017] The proposed component is used to carry out the method and is implemented, for example, in hardware and / or software. The component can be integrated into a controller in the vehicle electrical system or be designed as a controller.

[0018] Furthermore, an onboard electrical system is proposed which has the components described here and is provided for carrying out the proposed method.

[0019] Further advantages and embodiments of the invention are apparent from the description and the drawings.

[0020] It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively stated combination but also in other combinations or alone, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A possible sequence of the proposed method is shown in the flow chart.

[0022] Figure 2 The schematic illustration shows an onboard electrical system having components for carrying out the method.

[0023] Embodiments of the invention

[0024] The invention is illustrated schematically in the drawing using embodiments and is described in more detail below with reference to the drawing.

[0025] exist Figure 1 In the flowchart, a possible process of the method described here is shown. The variables used are partly in Figure 2 Shown in.

[0026] In a first step 10, the variables current 70 or i, component temperature 62 and ambient temperature 66 or T are calculated. umg Take measurements.

[0027] In the subsequent step 12, it is checked whether there is overload operation. In this embodiment, the heat input P is checked here. ein Is the specific heat loss P aus Here the heat input P can be calculated ein and / or heat loss P aus , and / or evaluate other overload conditions derived therefrom. Equations 1-3 explained later can be used here.

[0028] For example, we can target time point t start The starting temperature T of the component 56 is used in Equations 1 and 3. start . Then, for example, the following overload conditions can be evaluated:

[0029]

[0030] Where, R: resistance of component 56,

[0031] Rt: thermal resistance of component 56, in units such as K / W

[0032] Or, if we consider the temperature dependence of the resistance R:

[0033]

[0034] If this is not the case (not overload operation), a jump is made (arrow 14) to step 10. If this is the case (arrow 16), a time t until overload is reached is checked in step 18. überlast Calculation of . In this case, an overload state or an impending overload is detected. Subsequently, an overload operation is performed in step 20. The variable t is transmitted or reported. überlast , so that the optimized emergency measures can be selected. Then jump to step 10 (arrow 22).

[0035] exist Figure 2 In the diagram, an onboard power supply is shown in a schematic, highly simplified representation, which is generally designated by reference numeral 50. This onboard power supply 50 comprises a first onboard power supply circuit 52 and a second onboard power supply circuit 54. A component 56 is shown in the second onboard power supply circuit 54, the operation of which is monitored. For this purpose, a component 58 is provided, which is equipped with a first unit 60, for example a first temperature sensor 60, for detecting a component temperature 62, a second unit 64, for example a second temperature sensor, for detecting an ambient temperature 66, and a current measuring device 68 for measuring a current 70 flowing through the component 56. For example, an electric switch (for example a MOSFET) is used as the component 56, which is, for example, a safety-related consumer (for example an electric brake or a steering system) or a safety-related onboard power supply branch fuse. In the event of an impending fault, for example an overload, an overvoltage, etc., the safety-related consumer can be disconnected by the component 56. Component 56 can also be used, in the event of a fault in a non-safety-relevant onboard power supply branch, to separate a safety-relevant onboard power supply branch from the faulty onboard power supply branch, in which, for example, safety-relevant loads are supplied with power.

[0036] Unit 60 can be implemented with a temperature sensor or, for example, also using a thermal model of component 56. Component temperature 62 can be inferred from the determined operating variables of component 56. It is therefore irrelevant whether component temperature 62 is measured directly or determined in another way.

[0037] It is also possible to detect only the starting temperature T of the component temperature 62. start .

[0038] Based on the detected variables, namely the component temperature 62, the ambient temperature 66 and the current 70, the component 58 calculates the time or time period 72 until the component 56 is overloaded, as described in detail below. Based on this, an overload operation of at least the second onboard power supply circuit 54 or the entire onboard power supply 50 is initiated by selecting an emergency measure and then also initiating it. This may lead to the disconnection of the second onboard power supply circuit 54 or even the disconnection of the entire onboard power supply 50. Switches such as MOSFETs are typically used for this purpose.

[0039] The method is based on the fact that the current flowing through the electrical component generates heat. This heat in turn generates heat in the element or in the component 56 according to its heat capacity or heat capacity Ct. At the same time, when the ambient temperature 66 or T umg When the temperature of the component 56 is lower than the component temperature 62 or T itself, the heat loss P caused by the component 56 aus If the thermal capacity Ct of component 56 and the maximum permissible temperature before the component is thermally damaged are known, it is possible to calculate the time (or time period 72 until component 56 is overloaded) during which current 70 or i can still flow in order to perform safety actions in an emergency.

[0040] However, this prediction is only valid if current 70 or i remains constant. If a higher-level control unit takes over emergency measures, for example in the case of an overload of an ABS circuit (ABS: Antilock Braking System) and emergency braking measures, for calculating the remaining time (or the time period 72 until component 56 is overloaded), not only the measured current 70 or i is used, but also the measured current 70 or i plus the expected current increase due to the emergency measure, for example the measured current plus the rated current, or two separate calculations are performed for an optimistic and a pessimistic time prediction.

[0041] For example, the current 70 or i, the component temperature 62 and the ambient temperature 66 or T are required. umg as input variables.

[0042] The following variables contribute to determining the time period 72 until the component 56 is overloaded:

[0043] First, based on the ambient temperature 66 (e.g., in degrees Celsius) or T umg , use the following equation to describe or, if necessary, calculate the heat loss P of component 56 aus (For example, the unit is W):

[0044] Equation 1:

[0045] Where, T(t): the change in component temperature 62 over time (e.g., in degrees Celsius) and

[0046] Rt: thermal resistance of component 56, for example, the unit is K / W=C / W.

[0047] Instead calculate P at the beginning of an overload period or potential overload period aus , the determined starting temperature T of the component 62 may be enabled start .

[0048] The heat input P caused by the current 70 or i (for example in A) to the component 62 via its resistance R (for example in Ohm) ein (For example, the unit is W) can be described or calculated as follows:

[0049] Equation 2: P ein =i 2 *R.

[0050] If the electrical resistance or ohmic resistance R of the component 62 is temperature-dependent, this may also be taken into account:

[0051] Equation 3: P ein =i 2 *R 20 (1+(T(t)-20)*α).

[0052] Among them, R 20 : Resistance R of component 56 at 20°C,

[0053] α: Temperature coefficient, unit is Ohm / K.

[0054] The thermal differential equation for component 56 is also known:

[0055] Equation 4:

[0056] Wherein, Ct is the heat capacity of the component 56, for example, the unit is J / K.

[0057] This results, using equations 1 and 3:

[0058] Equation 5:

[0059] And finally, thus by solving the differential equation and solving according to time and considering the condition T(t überlast )=T(end) to obtain:

[0060] Equation 6:

[0061] P ein : Heat input

[0062] P aus : Heat loss

[0063] T umg : Ambient temperature 66

[0064] R 20 : Resistance at 20℃

[0065] R inv : The reciprocal of thermal resistance, Rt inv =1 / Rt

[0066] Ct inv : The reciprocal of heat capacity, Ct inv =1 / Ct

[0067] α: Temperature correction coefficient of resistance per degree Celsius

[0068] t überlast : Time period 72 until component 56 is overloaded

[0069] T start : Starting temperature of component 56.

[0070] If the temperature dependence of the component 56 is not taken into account, the formula is simplified to:

[0071] Equation 7:

[0072] The proposed method is particularly suitable for use in conjunction with a power supply protection device in order to increase the availability of the onboard power supply circuit in this way.

Claims

1. A method for monitoring the operation of an onboard power supply (50), in which method a component temperature (62) of a component (56) in the onboard power supply circuit (52, 54), an ambient temperature (66) of the component (56) and a current (70) flowing through the component (56) are ascertained in an onboard power supply circuit (52, 54) of the onboard power supply circuit (52, 54), and, if an overload of the component (56) is detected, calculating a time period (72) until said component (56) is overloaded, in, The heat input (P) into the component (56) is used ein ) and the heat loss (P aus ) for determining a time period (72) until the component (56) is overloaded.

2. The method according to claim 1, characterized in that The heat loss (P(t)) is calculated based on the component temperature (62; T(t)) and / or the ambient temperature (66) and / or the thermal resistance (Rt) of the component (56). aus ), in particular by the following formula:

3. The method according to any one of the preceding claims, characterized in that According to the current (70; i) and / or the resistance (R) of the component (56) and / or the initial temperature (T start ) to obtain the heat input (P ein ), in particular by the following formula: P ein =i 2 *R。 4. The method according to any one of the preceding claims, characterized in that The resistance (R) of the component (56) is temperature dependent.

5. The method according to any one of the preceding claims, characterized in that Using a thermal differential equation, a time period (72) until the component (56) is overloaded is determined, in particular Where T(t) is the change of the component temperature (62) with time, P ein is the heat input, P aus is the heat loss, and Ct is the heat capacity of the component (56).

6. The method according to any one of the preceding claims, characterized in that When the heat input (P ein ) exceeds the heat loss (P aus ), overload operation is detected.

7. A method according to one of the preceding claims, which is used for an output circuit of an electric power distributor and / or an onboard power supply monitoring device, and / or uses an electric switching device as the component (56), in particular for controlling safety-related consumers.

8. The method according to claim 1, wherein, as a function of the calculated time period (72) until overload, suitable emergency measures are initiated for the onboard power supply circuit (52, 54) during overload operation.

9. The method as claimed in claim 1, in which, when calculating the time period (72) until the overload, the current increase caused by the emergency measures is additionally taken into account.

10. The method as claimed in claim 1, in which the onboard power supply circuit (52, 54) is disconnected as a function of a calculated time period (72) until an overload occurs.

11. The method according to claim 1, wherein the time period until overload (72) is calculated using the following equation:

12. A component for monitoring the operation of an onboard electrical system (50), the component being configured to carry out a method according to one of claims 1 to 10.

13. The component according to claim 13, comprising: a first unit (60), in particular a temperature sensor (60), for detecting a component temperature (62) of a component (56) of the onboard power supply system (50); a second unit (64), in particular a temperature sensor (64), for detecting an ambient temperature (66) of the component (56); and a current measuring device (68) for measuring a current (70) flowing through the component (56).

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