Thermal management methods, related thermal management strategies, and control units specifically designed for motor vehicles.

Abstract

This invention relates to a thermal management method for an electric heating device, the electric heating device including at least one resistive element subassembly configured to be powered and a support for circuitry for powering the resistive element, wherein the power supply to the resistive element is controlled according to a power setpoint (P_(sub)system_target_0), temperature (T_(sub)system_target_0), current amplitude (i_(sub)system_target_0), resistance (R_(sub)system_target_0), or even the duty cycle of a control signal (PWM_(sub)system_target_0). According to the invention, the method includes the steps of: recording the temperature (T_PCB) of the support for the circuitry supplying the resistive element; comparing the recorded temperature (T_PCB) with at least one predetermined temperature threshold (T1); and if the recorded temperature (T_PCB) is greater than or equal to at least one predetermined temperature threshold (T1), generating a command to decrease the setpoint by a predetermined step. The invention also relates to a corresponding thermal management strategy and control unit.

Description

Technical Field

[0001] This invention relates to a thermal management method for an electric heating device used for heating fluids. In particular, it addresses the problem of electric heating devices intended for use in motor vehicles. Non-limitingly, the electric heating device can be configured to heat, for example, an airflow intended to pass through the heating device. The invention is equally applicable to high-voltage and low-voltage electric heating devices. The invention also relates to thermal management strategies applied during the operation of the electric heating device. Furthermore, the invention relates to a control unit for implementing at least a portion of the thermal management method and / or thermal management strategy.

[0002] This invention is particularly applicable to motor vehicle heating and / or ventilation and / or air conditioning equipment that includes such a heating device. Background Technology

[0003] Motor vehicles are typically equipped with heating and / or ventilation and / or air conditioning systems that regulate the aerodynamic thermal parameters of the airflow delivered to the passenger compartment, particularly the temperature of the airflow. For this purpose, the system typically includes one or more heat treatment devices, especially electric heating devices (also known as electric heaters) for heating fluids such as airflow.

[0004] The electric heating device includes an electric heating module. For example, the electric heating module may be arranged to be directly exposed to the airflow passing through the electric heating device.

[0005] According to one known solution, the heating module includes resistive elements, such as PTC resistive elements (PTC is an abbreviation for positive temperature coefficient), such as PTC ceramic, also known as PTC ceramic resistors.

[0006] This is a problem where the resistance of the component changes significantly with temperature. More precisely, the ohmic value of the PTC resistor increases very rapidly, exceeding the predetermined temperature threshold.

[0007] The resistive element can be powered by an onboard voltage source, i.e., a battery. An electrical connector can be connected to a voltage source located on the vehicle, allowing the required power to be supplied to the electric heating device, particularly the resistive element. Furthermore, the resistive element is controlled by an electronic control unit, which typically includes power supply circuitry. This power supply circuitry is, for example, mounted on a printed circuit board.

[0008] Especially in the case of high-voltage electric heating devices, this could be a problem with the vehicle's main heating system, which could therefore be very powerful.

[0009] In case of overheating, the device may reach the temperature limit for proper system operation at at least one point. PTC resistors are used to prevent overheating, which could cause a fire, thus ensuring passenger safety.

[0010] However, certain components near electric heating devices, such as plastic parts of heating and / or ventilation and / or air conditioning equipment, may be more sensitive, especially under certain conditions, such as high temperatures when the louvers of the heating and / or ventilation and / or air conditioning equipment are intentionally or due to undetected mechanical failure.

[0011] Therefore, it is advantageous to control the temperature of the electric heating device to avoid damaging surrounding components. Summary of the Invention

[0012] The purpose of this invention is to provide a thermal management solution that allows at least some of the disadvantages of the prior art to be avoided.

[0013] Therefore, one subject of the present invention is a thermal management method for an electric heating device, the device comprising a carrier of at least one subset of resistive elements configured to be powered and a power supply circuit for the resistive elements, wherein the power supply to the resistive elements is controlled according to a power setpoint or a temperature setpoint or a current setpoint or a resistance setpoint or even according to a duty cycle setpoint of a control signal.

[0014] According to the present invention, the method includes the following steps: recording the temperature of the carrier of the power supply circuit of the resistive element, comparing the recorded temperature with at least one predetermined temperature threshold, and generating a command to reduce the setpoint by a predetermined increment if the recorded temperature is higher than or equal to the at least one predetermined temperature threshold.

[0015] The method may also include one or more of the following features, implemented individually or in combination:

[0016] According to one embodiment, a predetermined number of temperature thresholds are defined, the rank of which is n, and varies from 1 to a predetermined maximum number m.

[0017] The method may include the following steps: comparing the recording temperature of the carrier with a temperature threshold of rank n, and if the recording temperature is higher than or equal to a given temperature threshold of rank n and lower than a temperature threshold of a higher rank n+1, for n varying from 1 to m-1, the higher the rank n of the temperature threshold, the more significant the reduction of the set point.

[0018] According to one aspect of the invention, after a temperature threshold of rank n has been exceeded and after a related reduction command, the method includes the following steps: recording and again comparing the temperature of the carrier with the temperature threshold of rank n and a higher rank n+1 temperature threshold; maintaining the reduced setpoint set by the previous reduction command if and only as long as the recorded temperature is higher than or equal to the temperature threshold of rank n and lower than the higher rank n+1 temperature threshold; returning to the previous command to reduce the setpoint if the recorded temperature is lower than the temperature threshold of rank n; and generating a command to further reduce the setpoint if the recorded temperature is higher than or equal to the higher rank n+1 temperature threshold, thereby strengthening the reduction.

[0019] According to one aspect, the setpoint decreases in a constant, predetermined increment. The increment can be between 5% and 30% of the setpoint or the maximum permissible setpoint value, for example, 20%.

[0020] Alternatively, the setpoint may be reduced in predetermined increments, which may vary depending on the temperature threshold.

[0021] A maximum temperature threshold higher than the at least one temperature threshold can be defined. The method includes the step of comparing a recorded temperature with the maximum temperature threshold, and if the maximum temperature threshold has been reached, the method includes the step of generating a command to stop power supply to the at least one subset of resistive elements.

[0022] After the power supply to the at least one subset of resistive elements has been stopped, the method may include at least one step of verifying conditions that allow the power supply to be restored.

[0023] The first verification step may include the following sub-steps: after power is cut off, record the temperature of the carrier using a maximum temperature threshold, and verify whether the recorded temperature of the carrier is lower than the maximum temperature threshold.

[0024] The method may include an additional verification step, which includes the following sub-steps: recording the temperature of the carrier of the power supply circuit of the resistive element and comparing it with a predetermined recovery temperature threshold, and if the recorded temperature is lower than the predetermined recovery temperature threshold, generating a command to restore the power supply to the at least one subset of resistive elements.

[0025] The predetermined recovery threshold is, for example, lower than or equal to the at least one threshold and / or lower than the maximum threshold. The recovery threshold is, for example, equal to the at least one threshold, or alternatively equal to the at least one threshold minus a certain temperature (e.g., 10°C), or alternatively equal to the maximum threshold minus a certain temperature (e.g., 10°C).

[0026] Power supply may restart at a limited setpoint or the maximum permissible setpoint value.

[0027] The present invention also relates to a thermal management strategy for an electric heating device, the device comprising a carrier of at least one subset of resistive elements configured to be powered and a power supply circuit for the resistive elements, wherein the power supply of the resistive elements is controlled using a pulse width modulation control signal based on a power setpoint or a temperature setpoint or a current setpoint or a resistance setpoint or even a duty cycle setpoint of a control signal.

[0028] Thermal management strategies include one or more of the following control phases.

[0029] The first stage is to verify whether at least one operating parameter of the electric heating device satisfies the condition of limiting the user-requested setpoint of the device to the maximum permissible setpoint determined according to the at least one operating parameter.

[0030] The second stage is to monitor the temperature of the carrier of the power supply circuit of the resistive element, and adjust the requested setpoint or maximum permissible setpoint according to the temperature of the carrier, as described above.

[0031] When the setpoint is an electric power setpoint, a temperature setpoint, a current setpoint, or a resistance setpoint, the third stage may be: if and only if the duty cycle of the control signal exceeds the corresponding detection threshold, or at least one parameter used to monitor overheating has reached the corresponding detection threshold, then the setpoint is gradually limited in a predetermined increment; otherwise, the setpoint is increased.

[0032] When the setpoint is the setpoint of the duty cycle of the control signal, the third stage can be: if and only if at least one parameter used to monitor overheating exceeds the corresponding detection threshold, then gradually limit it in a predetermined increment; otherwise, increase the setpoint.

[0033] The fourth stage is: monitoring the resistance of the at least one subset of resistive elements, and if the resistance has reached or exceeded a predetermined threshold, generating a command to stop the power supply to the resistive elements within a predetermined time.

[0034] The fifth stage is: monitoring the temperature of the carrier of the power supply circuit of the resistive element and generating a command to stop the power supply to the resistive element within a predetermined time if the temperature of the carrier reaches the maximum temperature threshold.

[0035] The predetermined stop time in the fourth or fifth stage is, for example, about 130 seconds.

[0036] Regarding the fifth stage, the maximum temperature threshold is higher than that of the second stage.

[0037] Advantageously, the application conditions of the control phase were verified sequentially from the first phase to the fifth phase.

[0038] After a 130-second pause, the setpoint can be set to 100%, or alternatively, it can be limited to, for example, 55%.

[0039] The present invention also relates to a control unit for an electric heating device, the device comprising a carrier of at least one subset of resistive elements configured to be powered and a power supply circuit for the resistive elements, the control unit being configured to generate a control signal based on a setpoint of power setpoint, temperature setpoint, current setpoint, resistance setpoint, or even a duty cycle of a control signal.

[0040] The control unit includes at least one processing means for: recording the temperature of the carrier of the power supply circuit of the resistive element, comparing the recorded temperature with at least one predetermined temperature threshold, and generating a command to lower the setpoint by a predetermined increment if the recorded temperature is higher than or equal to the at least one predetermined temperature threshold.

[0041] The control unit may include at least one temperature sensor, such as a negative temperature coefficient (NTC) probe, for recording the temperature of the carrier of the power supply circuit for the resistive element. The temperature sensor may be mounted on the carrier.

[0042] Alternatively, the temperature sensor can be mounted "near" the carrier, for example at a distance of 5 mm to 50 mm.

[0043] The control unit may include a comparator for comparing the recorded temperature with a predetermined first temperature threshold.

[0044] The control unit may include a computer or microprocessor configured to adjust the setpoint and / or generate commands to stop power supply to the resistive element and / or generate commands to restore power supply after a stop.

[0045] The control unit generates pulse width modulation control signals to control the power supply to the resistive elements.

[0046] Resistive elements can have a positive temperature coefficient.

[0047] According to a variant embodiment, the resistive element has a negative temperature coefficient.

[0048] The control unit may include one or more processing devices for at least partially implementing at least one control phase of the thermal management strategy as defined above. Attached Figure Description

[0049] Other features and advantages of the invention will become more apparent from the following description and accompanying drawings, which are given by way of illustrative and non-limiting example, wherein:

[0050] Figure 1 A flowchart of the various steps of the thermal management method according to the present invention is shown.

[0051] Figure 2aIt is a graph showing the change in the electrical power setpoint as a function of the temperature threshold reached by the power supply circuit carrier in the first example.

[0052] Figure 2b It is a graph showing the change in the electrical power setpoint as a function of the temperature threshold reached by the power supply circuit carrier in the second example.

[0053] Figure 2c It is a graph showing the change in the electrical power setpoint as a function of the temperature threshold reached by the power supply circuit carrier in the third example.

[0054] Figure 3 A flowchart illustrating the various control stages according to a thermal management strategy is shown.

[0055] Figure 4a It shows that according to Figure 3 The flowchart shows the steps of a thermal management method, which is the first example of a thermal management strategy in the control phase.

[0056] Figure 4b It shows that according to Figure 3 The flowchart shows the steps of the control phase of the thermal management strategy, as shown in the second example.

[0057] Figure 4c It shows that according to Figure 3 The flowchart of each step of the thermal management method in the third example of the control phase of the thermal management strategy.

[0058] In these figures, the same elements are represented by the same reference numerals. Detailed Implementation

[0059] The following embodiments are examples. Although the description relates to one or more embodiments, this does not necessarily mean that every reference relates to the same embodiment, or that a feature applies only to a single embodiment. Various features of the various embodiments may also be combined or interchanged to create other embodiments.

[0060] This invention relates to the field of heating and / or ventilation and / or air conditioning equipment (not shown) that employs airflow, which is intended to be equipped in motor vehicles to regulate the aerodynamic thermal parameters of the airflow delivered to one or more areas of the vehicle's passenger compartment.

[0061] More specifically, this invention relates to an electric heating device (also called an electric heater) for motor vehicles, particularly equipped with such a device. This concerns electrical devices for heating fluids. In a non-limiting sense, this could also be a problem with devices for heating airflow. The following description refers to airflow, but the invention can be applied to other fluids.

[0062] Specifically, this could be a problem with a high-voltage radiator or an electric heating device. The terms "high voltage" and "high-voltage" define voltages such as 90V or 120V. As a variant, this could also be a problem with a low-voltage radiator.

[0063] The electric heating device is configured to convert electrical energy, for example, drawn from a vehicle, into heat energy, which is then transferred to the airflow passing through heating and / or ventilation and / or air conditioning equipment.

[0064] The electric heating device may include a predetermined number of heating modules. These heating modules may be arranged to be directly exposed to the airflow passing through the electric heating device.

[0065] More precisely, each heating module may include a resistive element. Therefore, the electric heating device includes multiple resistive elements configured to be powered by a voltage source.

[0066] Resistive elements can be positive temperature coefficient (PTC) resistive elements. For example, resistive elements may be in the form of PTC ceramic, such as PTC ceramic resistors. As a variation, this can be problematic with negative temperature coefficient (NTC) resistive elements.

[0067] Electric heating devices typically also include an electronic control unit for controlling the heating module. This control unit comprises one or more electronic and / or electrical components. In particular, the control unit includes a power supply circuit (not shown) for supplying power to the resistive elements. The power supply circuit is mounted, for example, on a circuit carrier, such as a printed circuit board (or PCB, as commonly known).

[0068] For example, the power supply circuit includes transistors (not shown), each of which allows or disallows current from passing through a predetermined number of heating modules.

[0069] The resistive element is intended to be powered by, for example, a vehicle's power source (not shown), such as a battery. The power supply to the resistive element is controlled by pulse width modulation (or, as commonly known, PWM).

[0070] The control unit is configured to generate pulse-width modulation (PWM) control signals for controlling the power supply to resistive elements, particularly at least one subset of resistive elements. Different subsets of resistive elements can be independently controlled by the PWM. The resistive elements, particularly at least one subset forming a subsystem, can be powered according to a setpoint.

[0071] According to a preferred embodiment, the setpoint is the electrical power setpoint P_(sub)system_target_0( Figure 1The heating device is controlled in a closed-loop mode. As a variation, the resistive element can be powered according to the temperature setpoint T_(sub)system_target_0. Alternatives with a constant voltage and current setpoint i_(sub)system_target_0 or an optional resistance setpoint R_(sub)system_target_0 are conceivable.

[0072] Alternatively, this method can be used for open-loop control. Resistive elements, particularly at least one subset of resistive elements forming a subsystem, can be powered according to a pulse width modulation setpoint, which is specified below as the PWM setpoint. The prefix "sub" in parentheses indicates that the setpoint relates to either a subset or all of the resistive elements.

[0073] The prefix "sub" in parentheses indicates that the setting is related to a subset or all of the resistor elements.

[0074] Thermal management methods

[0075] Figure 1 The steps of a thermal management method for detecting overheating of an electric heating device and preventing the electric heating device from reaching a critical temperature are illustrated schematically.

[0076] At the start of this method, the control resistor element is configured with an initial setpoint, which corresponds to the minimum value between the setpoint received from the control unit of the control resistor element and the maximum permissible setpoint. For example, for the power setpoint, the initial power setpoint P_(sub)system_target_0 or the maximum permissible power setpoint is, for example, equal to 80% of the maximum power.

[0077] Typically, thermal management requires monitoring the temperature of the power supply circuitry carrier, T_PCB.

[0078] The thermal management method includes a preliminary step E1 of recording the temperature T_PCB of the carrier of the power supply circuit for the resistive element. The temperature T_PCB of the carrier is recorded, for example, by a temperature sensor, such as a negative temperature coefficient thermal probe.

[0079] In step E2, the recording temperature T_PCB of the carrier can be compared with at least one predetermined temperature threshold Tn, such as at least one first threshold T1.

[0080] In particular, also refer to Figures 2a to 2c A predetermined number of temperature thresholds Tn are defined. The rank n of the temperature thresholds Tn varies from 1 to a predetermined maximum number m. As a non-limiting example, four or five temperature thresholds can be defined. The maximum threshold Tm can be between 115°C and 130°C, for example, approximately 120°C.

[0081] If the recording temperature T_PCB of the carrier is below the first threshold T1, the method can be repeated, and in particular, the measurement and comparison steps E1 to E2 can be repeated.

[0082] If the recording temperature T_PCB of the carrier reaches or exceeds the temperature threshold T1 by comparison, the method may include step E3: verifying whether the recording temperature T_PCB of the carrier has reached the maximum temperature threshold Tm that will not be exceeded.

[0083] If the maximum temperature threshold Tm is not reached, a command to lower the setpoint is generated (step E4).

[0084] Then, the method can be repeated by recording the carrier temperature T_PCB again in subsequent iterations and comparing this temperature T_PCB with a first temperature threshold T1, and in particular with various temperature thresholds Tn. If the recorded temperature T_PCB is lower than the first temperature threshold T1, the method returns to the previous setpoint command.

[0085] If and only if the recording temperature T_PCB of the carrier is at or above the rank n temperature threshold Tn, that is, if and only if the recording temperature T_PCB is higher than or equal to the rank n temperature threshold Tn, such as T1 or T2, and is lower than the higher rank n+1 temperature threshold Tn+1, such as T2 or T3, for n varying from 1 to m-1, the higher the rank n of the temperature threshold Tn, the more the set point is reduced.

[0086] Until the maximum temperature threshold Tm is reached, the setpoint is reduced by a larger amount each time the recording temperature T_PCB of the carrier reaches or even exceeds a higher temperature threshold Tn+1.

[0087] Until the maximum temperature threshold Tm is reached, the setpoint can be decreased by a predetermined increment for each temperature threshold Tn reached. Therefore, the setpoint decreases gradually. The increment can be constant between different temperature thresholds. Alternatively, the increment of the setpoint decrease can vary between different temperature thresholds Tn.

[0088] For safety reasons, if the recording temperature T_PCB of the carrier reaches or even exceeds the maximum temperature threshold Tm, a command to stop the power supply to the resistive element can be generated (step E5).

[0089] To illustrate an example of implementing this method, in Figure 2a The figure schematically illustrates the variation of the carrier temperature T_PCB with a setpoint and different temperature thresholds T1 to T5. The figure is plotted as a percentage of the maximum permissible power setpoint P_(sub)system_target_0; however, this example can be applied to other setpoints.

[0090] Therefore, referring to Figure 1 and 2a , in step E1, the temperature T_PCB of the carrier is recorded, and subsequently in step E2 it is compared with temperature thresholds T1 to T5. The first temperature threshold T1 is, for example, approximately 95 °C. This first temperature threshold T1 is lower than the maximum temperature threshold Tm, which corresponds to Figure 2a T5 in the example of

[0091] and is approximately 120 °C, for example. The first temperature threshold T1 is placed far enough from the maximum temperature threshold Tm to allow the system to anticipate overheating and apply cooling before reaching the maximum temperature threshold Tm.

[0092] If the recorded temperature T_PCB of the carrier is lower than the first temperature threshold T1, the setpoint is not reduced and the temperature T_PCB of the carrier remains monitored (steps E1 - E2).

[0093] Once the recorded temperature T_PCB of the carrier reaches or exceeds one of the temperature thresholds T1 to T4, i.e., it becomes higher than or equal to that temperature threshold T1, T2, T3, T4, a command to reduce the setpoint may be generated in step E4.

[0094] If the first temperature threshold T1 has been reached, then in step E4, the setpoint (in this example the power setpoint) changes from P0 to P1 (P1 < P0), i.e., changes by a predetermined increment. This increment can be, for example, a percentage of the setpoint or the value of the maximum allowable setpoint P_(sub)system_target_0, for example between 5% and 30%, especially 20%.

[0095] After step E4 where the command to reduce the setpoint is issued, the change in the temperature T_PCB of the carrier is kept monitored and the method is repeated.

[0096] In the second iteration, the temperature T_PCB of the carrier is recorded again in step E1 and compared in step E2 with the first temperature threshold T1 and the other temperature thresholds T2 to T5.

[0097] If the recorded temperature T_PCB of the carrier is lower than the predetermined first temperature threshold T1, the method returns to the previous setpoint command.

[0098] If the second predetermined temperature threshold T2 is reached, where the second threshold T2 is higher than the first temperature threshold T1 and lower than the maximum threshold Tm, i.e., if the recording temperature T_PCB of the carrier is higher than or equal to the second temperature threshold T2, then in step E4, a command to further reduce the setpoint can be generated, i.e., more than in the case where only the first threshold T1 is exceeded, in order to reinforce the reduction of the setpoint, which in this example is the power setpoint, and is transmitted to P2 (P2 < P1).

[0099] After step E4 where the setpoint is commanded to be reduced, the change in the temperature T_PCB of the carrier is continuously monitored, and the method is repeated as described above. The temperature T_PCB of the carrier is recorded again in step E1 and compared with the temperature threshold Tn.

[0100] If the temperature T_PCB of the carrier reaches the third temperature threshold T3, then in step E4, a command to further reduce the setpoint is generated, i.e., more than in the case where the previous thresholds T1 and T2 are exceeded, in order to further reinforce the reduction of the setpoint, which in this example is the power setpoint, and is transmitted to P3 (P3 < P2). And so on: If in step E2, the temperature T_PCB of the carrier reaches a predetermined fourth temperature threshold T4, which is higher than the third temperature threshold T3 and lower than the maximum temperature threshold T5 in this example, then the reduction of the setpoint is further reinforced, and the setpoint (which is the power setpoint in this example) is transmitted to P4 (P4 < P3).

[0101] If the temperature T_PCB of the carrier reaches or even exceeds the maximum threshold (corresponding to Figure 2a T5 in the example), then in step E5, the setpoint is not re-restricted, but a command to stop supplying power to the resistive element is generated.

[0102] In Figure 2a the example, upon receiving the relevant command to reduce, the setpoint is reduced in constant predetermined increments between P0, P1, P2, P3, P4.

[0103] Alternatively, as Figure 2b schematically shown, the setpoint (which is the power setpoint in this example) can be reduced in different predetermined increments between P0, P1, P2, P3, P4. The increments between the different thresholds Tn (which are the thresholds T1 to T5 in this example) can thus vary. The variable increments can be calculated, for example, by an algorithm stored in the command of the electric heating device. For example, based on test results, a large increment can be selected at the beginning (e.g., between P0 and P1), and then the subsequent increments become smaller and smaller. The increment between P4 and P3 is less than the increment between P3 and P2, which itself is less than the increment between P2 and P1, which in turn is less than the increment between P1 and P0. The reverse is also conceivable, where the increment becomes larger as the temperature threshold reached or exceeded increases.

[0104] Figure 2b Another example of a variable increment is shown, where the increment is large at the beginning and then becomes smaller. Different temperature thresholds can be used; for example, a maximum temperature threshold Tm can be set as a fourth temperature threshold T4.

[0105] Refer again Figure 1 After the power supply to the resistive element has been stopped in step E5, the method may include at least one step (step E6): verifying the conditions that allow the power supply to be restored.

[0106] The first verification step may include the following sub-steps: after power is cut off, record the temperature T_PCB of the carrier using the maximum temperature threshold Tm, and verify whether the recorded temperature T_PCB of the carrier is lower than the maximum temperature threshold Tm.

[0107] For example, additional verification may include the following sub-steps: recording the temperature T_PCB of the carrier after stopping and comparing it with a predetermined recovery temperature threshold T0. When the recorded temperature T_PCB of the carrier is lower than the predetermined recovery temperature threshold T0, power supply to the resistive element is allowed to be restored, and a command to restore power supply to the resistive element is generated in step E7.

[0108] The predetermined recovery threshold T0 can take any value between, for example, a value lower than or equal to a first threshold T1 and a maximum temperature threshold Tm. For instance, the recovery threshold T0 might be set to the first temperature threshold T1 (T0 = T1). Alternatively, the recovery threshold T0 could correspond to the first threshold minus a certain temperature, such as 10°C: T0 = T1 – 10, or alternatively, to the maximum temperature threshold Tm minus a certain temperature, such as 10°C: T0 = Tm – 10.

[0109] After disconnection, the power supply to the resistive element may restart at the limited setpoint or the maximum permissible setpoint.

[0110] The above reference Figures 1 to 2c The described thermal management method provides a margin between a first temperature threshold T1 and a maximum temperature threshold Tm, operating within this margin and allowing the heating device to cool down before reaching a critical temperature. This makes it easy to detect any overheating and protect the heating device by protecting the carrier of the power supply circuit.

[0111] Heat management strategy

[0112] refer to Figure 3 The operation of an electric heating device according to a thermal management strategy, which includes one or more control stages as described below, will now be described. The control stages are advantageously implemented in a specified order.

[0113] In operation, particularly in motor vehicles, a user can use controls to activate an electric heating device, as described above, which includes one or more subsets of resistive elements, for example, to heat at least one area of ​​the passenger compartment of the motor vehicle. This activation results in a request for a setpoint, such as a power setpoint P_(sub)system_target_0, being generated in the control unit.

[0114] Phase 1

[0115] In the first stage, the setpoint requested by the user of the heating device through its heating control (e.g., power setpoint P_(sub)system_target_0) may or may not be limited by applying the first filter F1. The first filter F1 determines the maximum allowable setpoint P_max_allowed based on at least one operating parameter of the electric heating device. If the requested setpoint P_(sub)system_target_0 is higher than the maximum allowable setpoint P_max_allowed, the setpoint is limited to the latter.

[0116] Operating parameters can be selected from the inlet temperature of the airflow (e.g., temperature data transmitted by a measuring sensor), airflow rate, fan or blower speed, information about the position of at least one baffle in the airflow duct, whether the heating device is upstream or downstream in the airflow direction, or even whether a mode of heating the airflow by means of an element upstream of at least one subset of elements in the airflow direction is activated.

[0117] Such limitations are known to those skilled in the art of electric heating devices for motor vehicle heating and / or ventilation and / or air conditioning equipment that utilize airflow, and will not be elaborated upon further below.

[0118] If the setpoint (e.g., the power setpoint) is limited by the first filter F1, then at the end of the first phase, the setpoint P_(sub)system_target_1 is equal to the determined maximum allowed setpoint P_max_allowed (arrow Y).

[0119] In the opposite case (arrow N), at the end of the first stage, the setpoint P_(sub)system_target_1 remains the requested initial setpoint, such as the requested initial power setpoint P_(sub)system_target_0.

[0120] Phase Two

[0121] After determining whether to apply the first filter F1 to initially limit the setpoint, the second control phase is implemented. In this second phase, the setpoint P_(sub)system_target_1 at the end of the first phase can be adjusted based on the temperature of the carrier of the power supply circuit of the resistive element and any temperature threshold reached or exceeded, as referenced above. Figures 1 to 2c The described thermal management methods are consistent.

[0122] If filter 1 is not applied to the requested initial setpoint P_(sub)system_target_0 at the end of the first control phase, then filter 2 may be applied thereto, or alternatively, filter 2 may be applied to the maximum allowed setpoint P_max_allowed determined in the first phase.

[0123] If the setpoint (e.g., the power setpoint) is limited by the second filter F2 (arrow Y), then the setpoint P_(sub)system_target_2 at the end of the second stage is equal to the setpoint P_(sub)system_target_1 at the end of the first stage as described above, reduced by a predetermined factor or increment, depending on the temperature threshold reached or exceeded by the carrier of the power supply circuit.

[0124] In the opposite case (arrow N), at the end of the second stage, the setpoint (e.g., power setpoint P_(sub)system_target_2) remains at the setpoint (e.g., power setpoint P_(sub)system_target_1) at the end of the first stage.

[0125] Phase Three

[0126] After determining whether to apply the second filter F2 to limit the setpoint, the third control phase is implemented. In this third phase, at the end of the second phase, the setpoint P_(sub)system_target_2 can be gradually limited in predetermined increments.

[0127] The third filter F3 can be applied to the initial setpoint P_(sub)system_target_2 at the end of the second phase. If no filter is applied, this may be due to a problem with the requested initial setpoint P_(sub)system_target_0; if the first filter F1 is applied, this may be due to a problem with the maximum allowed setpoint P_max_allowed; or if the second filter F2 is applied, this may be due to a problem with the setpoint P_(sub)system_target_1 at the end of the first phase being reduced by a predetermined factor or increment based on the temperature of the power supply circuitry's carrier.

[0128] In this third stage, typically, the setpoint can be gradually adjusted in one direction, for example, by being restricted or reduced, and then increased in another direction, based on the change of a given parameter relative to a customized variable threshold adjusted for each setpoint.

[0129] According to one option, the setpoint is preferably the electrical power setpoint P_(sub)system_target_2, and the heating device is controlled in closed-loop mode. As a variation, the resistive element can be powered according to the temperature setpoint. Alternatives with constant voltage / current setpoints or potential resistance setpoints are conceivable.

[0130] refer to Figure 4a Overheating of the heating device can be detected by recording the duty cycle PWM_(sub)system of the control signal forming at least one subset of resistive elements in the subsystem in step E30 and by monitoring its changes, so as to detect when the duty cycle PWM_(sub)system of the control signal exceeds the corresponding detection threshold PWM_(sub)system_lim_i representing overheating (step E31).

[0131] Overheating is detected if and only if the duty cycle of the control signal PWM_(sub)system exceeds the detection threshold PWM_(sub)system_lim_i. For example, for a resistive element with a positive temperature coefficient, overheating is detected when the duty cycle of the control signal PWM_(sub)system is higher than, more precisely, strictly higher than, the detection threshold PWM_(sub)system_lim_i.

[0132] In the first adjustment phase A, the setpoint is gradually adjusted in one direction, for example, by decreasing it. This restriction is repeated until the duty cycle of the control signal no longer represents overheating. In this case, the setpoint can be adjusted in the second adjustment phase B in the opposite direction of change to that of the first phase A, for example, by increasing it this time. Advantageously, this adjustment is also gradual until the initial setpoint is reached. One or both of adjustment phases A and B are advantageously iterated or repeated at a predetermined period, which can be less than 10 seconds, for example, about 4 seconds. This allows the heating device time to react without being too slow. Alternatively, the period can be variable. The period can depend, for example, on the degree of overheating.

[0133] The detection threshold is effective for the subsystem or the entire system. During each setpoint adjustment, whether limiting or increasing, a new threshold is determined based on the new setpoint value. Specifically, the detection threshold PWM_(sub)system_lim_i can be defined based on a pair consisting of the supply voltage and the setpoint, thus obtaining a matrix of possible detection thresholds. In each iteration i, the detection threshold PWM_(sub)system_lim_i for the duty cycle of the control signal is redefined based on the new setpoint value.

[0134] If the limit value of the setpoint reaches the predetermined limit setpoint value, the first stage A is not repeated, and a command to stop the power supply to the resistive element is generated in step E32.

[0135] Reference Figure 4b Alternatively, at least one parameter i_(sub)system_max, R_(sub)system, P_(sub)system, and T_(sub)system is recorded for monitoring overheating. If this parameter reaches or exceeds the corresponding detection threshold i_(sub)system_max_lim_i, R_(sub)system_lim_i, P_(sub)system_lim_i, and T_(sub)system_lim_i, overheating is detected, taking into account the power supply setpoint.

[0136] As mentioned earlier, the setpoint is preferably the electrical power setpoint P_(sub)system_target_2, and the heating device is controlled in a closed-loop mode. As a variation, the resistive element can be powered according to the temperature setpoint. Alternatives with constant voltage / current setpoints or potential resistance setpoints are conceivable.

[0137] To monitor overheating of the electric heating device, this parameter advantageously depends on the current amplitude. This could be a matter of the resistance R_(sub)system of a predetermined number of resistive elements, the electrical power P_(sub)system of a predetermined number of resistive elements, or the current i_(sub)system_max flowing through a predetermined number of resistive elements. This parameter can also be a multiple or power of the current flowing through the predetermined number of resistive elements. Non-exhaustive references can be made to the square or cube of the current, twice the current, or even the ratio of the current to the duty cycle of the pulse width modulation control signal.

[0138] Alternatively, this parameter may be independent of the current amplitude. For example, the temperature T_(sub)system of a predetermined number of resistive elements can be mentioned.

[0139] The “sub” prefix, written between parentheses, indicates that the parameter involves a subset or all of the resistive elements.

[0140] Overheating of the heating device can be detected by recording the selected parameters in step E33 and by monitoring their changes in order to detect when it reaches or exceeds the corresponding detection thresholds i_(sub)system_max_lim_i,R_(sub)system_lim_i,P_(sub)system_lim_i,T_(sub)system_lim_i representing overheating (step E34).

[0141] Depending on the nature of the parameter and the nature of the resistive element, the recorded parameter value may exceed the detection threshold, for example, becoming higher or lower than the detection threshold. For example, in the case of a PTC resistive element, if the recorded value of the current i_(sub)system_max flowing through the resistive element is lower than, more precisely, strictly lower than the detection threshold i_(sub)system_max_lim_i, overheating is detected.

[0142] According to another example, in the case of a PTC resistive element, overheating is detected if the calculated value of the resistance R_(sub)system of the resistive element is higher than, more precisely, strictly higher than the detection threshold R_(sub)system_lim_i.

[0143] Overheating is detected if and only if the selected parameters i_(sub)system_max, R_(sub)system, P_(sub)system, T_(sub)system are at or above the detection thresholds i_(sub)system_max_lim_i, R_(sub)system_lim_i, P_(sub)system_lim_i, T_(sub)system_lim_i. (Arrow Y)

[0144] In the first adjustment phase A, the setpoint is gradually adjusted in one direction, for example, by decreasing it. This constraint is repeated until the selected parameters i_(sub)system_max, R_(sub)system, P_(sub)system, T_(sub)system no longer represent overheating. In this case, the setpoint can be adjusted in the second adjustment phase B in the opposite direction of the change in the first phase A. This adjustment is advantageously also gradual until the initial setpoint is reached. One or both of the adjustment phases A and B are advantageously iterated or repeated at a predetermined period, which can be less than 10 seconds, for example, about 4 seconds, and can be constant or variable.

[0145] During each setpoint adjustment, whether limiting or increasing, a new threshold is determined based on the new setpoint value. Specifically, the detection thresholds i_(sub)system_max_lim_i, R_(sub)system_lim_i, P_(sub)system_lim_i, T_(sub)system_lim_i can be defined based on pairs consisting of the supply voltage and the setpoint, thus obtaining a matrix of possible detection thresholds. In each iteration i, the detection thresholds of parameters i_(sub)system_max_lim_i, R_(sub)system_lim_i, P_(sub)system_lim_i, T_(sub)system_lim_i are redefined based on the new setpoint value.

[0146] If the limit value of the setpoint reaches the predetermined limit setpoint value, the first stage A is not repeated, and a command to stop the power supply to the resistive element is generated in step E35.

[0147] According to another option, the power supply setpoint is the setpoint for the duty cycle of the control signal, which is hereinafter referred to as the PWM setpoint. If and only if at least one parameter P_(sub)system; R_(sub)system; i_(sub)system_max (which depends on the current) used for monitoring overheating exceeds the corresponding detection threshold P_(sub)system_lim_i; i_(sub)system_max_lim_i; R_(sub)system_lim_i, then in each iteration i, the PWM setpoint PWM_(sub)system_target_i is gradually adjusted in a predetermined increment.

[0148] Overheating of the heating device can be detected by recording the selected parameters in step E36 and by monitoring their changes in order to detect when it exceeds the corresponding detection thresholds i_(sub)system_max_lim_i,R_(sub)system_lim_i,P_(sub)system_lim_i representing overheating (step E37).

[0149] Depending on the nature of the parameter and the nature of the resistive element, the recorded parameter value may exceed the detection threshold, for example, becoming higher or lower than the detection threshold.

[0150] In the first adjustment phase A, the PWM setpoint is gradually adjusted in one direction, for example, by decreasing it. This constraint is repeated until the selected parameters i_(sub)system_max, R_(sub)system, P_(sub)system no longer represent overheating. In this case, the PWM setpoint can be adjusted in the second adjustment phase B in the opposite direction to that of the first phase A. This adjustment is advantageously also gradual until the initial setpoint is reached. One or both of the adjustment phases A and B are advantageously iterated or repeated at a predetermined period, which can be less than 10 seconds, for example, about 4 seconds, and can be constant or variable.

[0151] Each time the PWM setpoint is adjusted, whether limiting or increasing, a new threshold is determined based on the new value of the setpoint PWM_(sub)system_target_i. Specifically, the detection thresholds i_(sub)system_max_lim_i, R_(sub)system_lim_i, and P_(sub)system_lim_i can be defined based on pairs consisting of the supply voltage and the PWM setpoint, thus obtaining a matrix of possible detection thresholds. In each iteration i, the detection thresholds i_(sub)system_max_lim_i, R_(sub)system_lim_i, and P_(sub)system_lim_i are re-determined based on the new value of the PWM setpoint PWM_(sub)system_target_i.

[0152] If the limit value of the setpoint PWM_(sub)system_target_i reaches the predetermined limit setpoint value, the first stage A is not repeated, and a command to stop the power supply of the resistive element is generated in step E38.

[0153] It is possible to apply the third control stage together to all resistive elements, or independently to each subset of resistive elements, each subset using one or more transistors for control. The strategy also varies depending on the nature of the resistive elements, such as whether they are positive temperature coefficient (PTC) or negative temperature coefficient (NTC) resistive elements.

[0154] Refer again Figure 3 If the setpoint (e.g., the power setpoint) is limited by the third filter F3 (arrow Y), then the setpoint P_(sub)system_target_3 at the end of the third stage is equal to the setpoint P_(sub)system_target_2 at the end of the second stage, but is adjusted according to one of the options for the third stage mentioned above.

[0155] In the opposite case (arrow N), at the end of the third stage, the setpoint, for example, the power setpoint P_(sub)system_target_3, remains at the setpoint at the end of the second stage, for example, the power setpoint P_(sub)system_target_2.

[0156] Phase 4

[0157] If the setpoint adjustment value does not reach the limit setpoint value when applying the third filter F3, the fourth control stage can be implemented.

[0158] In this fourth stage, the resistance of at least one subset of resistive elements can be determined and compared with a predetermined threshold. The resistance is calculated based on preliminary measurements of the supply voltage and current.

[0159] If the resistance reaches the threshold (arrow Y), the fourth filter F4 is applied, thereby generating a command to stop supplying power to the resistive element within a predetermined time. After applying the fourth filter F4 (arrow Y), the setpoint, such as the power setpoint, is reduced to 0%.

[0160] In the opposite case (arrow N), the setpoint at the end of the fourth stage, for example, the power setpoint P_(sub)system_target_3, remains the same as the setpoint at the end of the third stage, for example, the power setpoint P_(sub)system_target_3.

[0161] Phase 5

[0162] If the fourth filter F4, used to cut off power supply, is not applied, the fifth control phase can be implemented.

[0163] Refer again Figures 1 to 2c In this fifth stage, the temperature T_PCB of the power supply circuit carrier of the resistive element is recorded and monitored. The maximum temperature threshold T_max is higher than the temperature threshold Tn of the second stage, where n varies from 1 to m-1 (see...). Figures 1 to 2c ).

[0164] If the recorded carrier temperature T_PCB reaches the maximum temperature threshold Tm, the fifth filter F5 can be applied. The fifth filter F5 includes generating a command to stop the power supply to the resistive elements within a predetermined time. After applying the fifth filter F5 (arrow Y), the setpoint, such as the power setpoint, is reduced to 0%.

[0165] In the opposite case (arrow N), the setpoint at the end of the fifth stage, for example, the power setpoint P_(sub)system_target_5, remains the same as the setpoint at the end of the third stage, for example, the power setpoint P_(sub)system_target_3.

[0166] From the first stage to the fifth stage, the application conditions of the control stage are verified sequentially.

[0167] If the setpoint adjustment value has reached the limit setpoint value when the third filter F3 is applied, or if the power supply to the resistor element has been cut off when the fourth filter F4 or the fifth filter F5 is applied, the predetermined stop time is, for example, about 130 seconds.

[0168] After disconnecting the power supply to the resistive element, the method may include the step of generating a command to restore the power supply to the resistive element.

[0169] A command to restore power can be generated at the end of the predetermined stop time. This strategy can then restart from scratch, monitoring the temperature of the power supply circuitry again. After this stop, the setpoint can be set to 100%, or alternatively, it can be limited to, for example, 55% of the maximum permissible setpoint.

[0170] By adjusting the setpoint according to the thermal strategy, that is, by sequentially applying one or more filters F1-F5 from the first to the fifth, the system can act on each increment and detect conditions that may not have been detected in the previous stage, thereby ensuring effective temperature control.

[0171] Control components

[0172] For example, refer to the above. Figures 1 to 2c The described thermal management method can be implemented through a control unit (not shown in the figure). This is a matter for the electronic control unit. In particular, the thermal management method can be implemented by a control unit that is already used to control the heating module of the electric heating device and / or detect overheating.

[0173] The control unit includes at least one processing device for implementing the steps of the thermal management method.

[0174] The control unit may include at least one processing device for recording the temperature T_PCB of the carrier of the power supply circuit of the resistive element. For example, this could be a problem with the temperature sensor, such as a thermal probe with a negative temperature coefficient.

[0175] The control unit may include a comparator for comparing the recorded carrier temperature T_PCB with a predetermined temperature threshold Tn or with a recovery threshold T0 after the power supply to the resistive element has stopped.

[0176] The control unit includes one or more processing devices for recording power setpoints, temperature setpoints, current setpoints, or even resistance setpoints.

[0177] The control unit may include a computing device or a microprocessor for determining whether the setpoint must be adjusted based on the results of a comparison and for adjusting the setpoint based on the temperature threshold reached.

[0178] The control unit may include another or the same computing device or microprocessor for generating a command to stop the power supply to the resistive element within a predetermined stop time when the adjusted setpoint value reaches the limit setpoint value defined for the first adjustment phase A.

[0179] Finally, the control unit may typically include one or more processing devices, such as measuring or computing devices or microprocessors, for monitoring changes in one or more parameters in order to verify whether the application conditions of one or more filters F1 to F5 have been met in the order of the control phases, and to apply one or more filters F1 to F5 to adjust the setpoint as described above.

Claims

1. A thermal management method for an electric heating device, the electric heating device comprising a carrier of at least one subset of resistive elements configured to be powered and a power supply circuit for the resistive elements, wherein the power supply to the resistive elements is controlled according to a power setpoint (P_(sub)system_target_0) or a temperature setpoint (T_(sub)system_target_0) or a current setpoint (i_(sub)system_target_0) or a resistance setpoint (R_(sub)system_target_0) or even according to a setpoint of the duty cycle of a control signal (PWM_(sub)system_target_0), characterized in that, The method includes the following steps: a. The temperature (T_PCB) of the carrier's power supply circuit for the resistive element is recorded by a temperature sensor mounted on or near the carrier. b. Compare the recorded temperature (T_PCB) with at least one predetermined temperature threshold (T1), and c. If the recorded temperature (T_PCB) is higher than or equal to the at least one predetermined temperature threshold (T1), a command is generated to lower the setpoint by a predetermined increment, and The method defines a predetermined number of temperature thresholds (Tn), the rank of which is n and varies from 1 to a predetermined maximum number m. The method includes the following steps: The recording temperature (T_PCB) of the carrier is compared with the rank n temperature threshold (Tn), and If the recorded temperature (T_PCB) is higher than or equal to a given rank n temperature threshold (Tn) and lower than a higher rank n+1 temperature threshold (Tn+1), then for n varying from 1 to m-1, the higher the rank n of the temperature threshold, the more significant the reduction of the setpoint.

2. The method as described in the preceding claim, wherein, After the temperature threshold (Tn) of rank n has been exceeded, and after the relevant reduction command, the method includes the following steps: a. Record and compare the temperature of the carrier (T_PCB) again with the rank n temperature threshold (Tn) and the higher rank n+1 temperature threshold (Tn+1). b. If and only if the recorded temperature (T_PCB) is higher than or equal to the rank n temperature threshold (Tn) and lower than the higher rank n+1 temperature threshold (Tn+1), then maintain the reduced setpoint set by the previous reduction command. c. If the recorded temperature (T_PCB) is lower than the rank n temperature threshold (Tn), then return to the previous command to lower the setpoint. d. If the recorded temperature is higher than or equal to the temperature threshold (Tn+1) of the higher rank n+1, a command is generated to further reduce the setpoint, thereby strengthening the reduction.

3. The method as described in any of the preceding claims, wherein, The method defines a maximum temperature threshold (Tm) that is higher than the at least one predetermined temperature threshold (T1), and includes the step (E3) of comparing the recorded temperature (T_PCB) with the maximum temperature threshold (Tm), and if the maximum temperature threshold (Tm) has been reached, the method includes the step (E5) of generating a command to stop the power supply to the at least one subset of resistive elements.

4. The method as described in the preceding claim, wherein, After the power supply to the at least one subset of resistive elements has been stopped, the method may include at least one step of verifying conditions that allow the power supply to be restored.

5. The method as described in the preceding claim, wherein, The first verification step includes the following sub-steps: a. After power is cut off, record the temperature of the carrier (T_PCB) using the maximum temperature threshold (Tm), and b. Verify that the recording temperature (T_PCB) of the carrier is below the maximum temperature threshold (Tm).

6. The method as described in the preceding claim, wherein, The additional verification steps include the following sub-steps: a. Record the temperature of the carrier of the power supply circuit of the resistive element (T_PCB) and compare it with a predetermined recovery temperature threshold (T0), and b. If the recorded temperature is below a predetermined recovery temperature threshold (T0), a command is generated to restore power supply to the at least one subset of resistive elements.

7. The method as claimed in the preceding claim, wherein, The predetermined recovery temperature threshold (T0) is lower than or equal to the at least one predetermined temperature threshold (T1) and / or lower than the maximum temperature threshold (Tm).

8. A thermal management strategy for an electric heating device, the electric heating device comprising a carrier of at least one subset of resistive elements configured to be powered and a power supply circuit for the resistive elements, wherein the power supply to the resistive elements is controlled using a pulse width modulation control signal based on a power setpoint (P_(sub)system_target), a temperature setpoint (T_(sub)system_target), a current setpoint (i_(sub)system_target), a resistance setpoint (R_(sub)system_target), or even a duty cycle setpoint (PWM_(sub)system_target) of a control signal. Its features are, The thermal management strategy includes the following control phases: a. A first stage of verifying whether at least one operating parameter of the electric heating device satisfies the condition of limiting the user-requested power setpoint (P_(sub)system_target_0) of the device to the maximum allowable setpoint (P_max_allowed) determined according to the at least one operating parameter. b. The method according to any one of claims 1 to 7, comprising a second stage of monitoring the temperature (T_PCB) of the carrier of the power supply circuit of the resistive element and adjusting the requested power setpoint (P_(sub)system_target_0) or the maximum allowable setpoint (P_max_allowed) based on the temperature (T_PCB) of the carrier. c. The third stage, in which... i. If and only as long as the duty cycle of the control signal (PWM_(sub)system) exceeds the corresponding detection threshold (PWM_(sub)system_lim_i), or at least one parameter used for monitoring overheating (R_(sub)system; i_(sub)system_max; P_(sub)system; T_(sub)system) has reached the corresponding detection threshold (i_(sub)system_max_lim_i; R_(sub)system_lim_i; P_(sub)system_lim_i; T_(sub)system_lim_i), then the power setpoint, temperature setpoint, current setpoint, or resistance setpoint is gradually restricted in a predetermined increment; otherwise, the setpoint increases, or ii. If and only if at least one parameter (P_(sub)system; R_(sub)system; i_(sub)system_max) used for monitoring overheating exceeds the corresponding detection threshold (P_(sub)system_lim_i; i_(sub)system_max_lim_i; R_(sub)system_lim_i), then the setpoint (PWM_(sub)system_target) of the duty cycle of the control signal is gradually restricted in a predetermined increment; otherwise, the setpoint is increased. d. A fourth stage involves monitoring the resistance of at least one subset of resistive elements and generating a command to stop power supply to the resistive elements within a predetermined time if the resistance has reached or exceeded a predetermined threshold. e. The fifth stage involves monitoring the temperature (T_PCB) of the carrier of the power supply circuit for the resistive element and generating a command to stop the power supply to the resistive element within a predetermined time if the temperature (T_PCB) of the carrier reaches the maximum temperature threshold (T_max).

9. The strategy as described in the preceding claim, wherein, The application conditions for the control phase were verified sequentially from the first phase to the fifth phase.

10. A control unit for an electric heating device, the electric heating device comprising a carrier of at least one subset of resistive elements configured to be powered and a power supply circuit for the resistive elements, the control unit being configured to generate a control signal based on a power setpoint (P_(sub)system_target_0) or a temperature setpoint (T_(sub)system_target_0) or a current setpoint (i_(sub)system_target_0) or a resistance setpoint (R_(sub)system_target_0) or even a setpoint of the duty cycle of a control signal (PWM_(sub)system_target_0), characterized in that, The control unit includes at least one processing device for: a. The temperature (T_PCB) of the carrier supplying the resistive element is recorded by a temperature sensor installed on or near the carrier. b. Compare the recorded temperature (T_PCB) with at least one predetermined temperature threshold (T1), and c. If the recorded temperature (T_PCB) is higher than or equal to the at least one predetermined temperature threshold (T1), a command is generated to lower the setpoint by a predetermined increment, and The device defines a predetermined number of temperature thresholds (Tn), the rank of which is n and varies from 1 to a predetermined maximum number m. The processing apparatus is also used for the following: The recording temperature (T_PCB) of the carrier is compared with the rank n temperature threshold (Tn), and If the recorded temperature (T_PCB) is higher than or equal to a given rank n temperature threshold (Tn) and lower than a higher rank n+1 temperature threshold (Tn+1), then for n varying from 1 to m-1, the higher the rank n of the temperature threshold, the more significant the reduction of the setpoint.

11. The control unit as claimed in the preceding claim, wherein, The resistive element has a positive temperature coefficient.

12. The control unit of any one of claims 10 and 11, comprising one or more processing means for at least partially implementing at least one control phase of the thermal management strategy of claim 8 or 9.

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