Controlling electronic switching units for supplying inductive power loads

Abstract

A method for controlling an electronic switch unit (1) for supplying electric power to an inductive power load, the method comprising the following steps: ‑ enabling an initial filter capacitor by connecting it between a power supply (3) of the electronic unit (1) and ground, and deactivating other capacitors of a filter capacitor bank (7); ‑ measuring a current flowing through the initial filter capacitor; ‑ if the current is above a predetermined rated current threshold, enabling an additional filter capacitor by connecting it between a power supply (3) of the electronic unit (1) and ground, in parallel with the initial filter capacitor.

Description

Technical Field

[0001] The present invention relates to the field of electronic switching circuits for supplying power from an electrical energy storage device to an inductive power load.

[0002] For example, in the automotive industry, inductive power loads (such as electric motors) are often used. These inductive power loads require a switching bridge (such as an inverter, an H-bridge, a DC-DC converter, etc.) to control them. In this type of architecture, an electrical energy storage device (such as a battery) thus supplies power to the inductive power load via a switching circuit including a switching bridge.

[0003] The inductive power load includes a coil that generates a high inrush current during a specific operating phase. For example, when an electric motor starts, or during a sharp acceleration, the electric motor will generate a current inrush, which may be very high. Background Art

[0004] Managing the large inrush current associated with an inductive power load requires adding filter capacitors, usually of the electrochemical type, between the power supply and the ground of the electronic switching circuit. These capacitors are used to stabilize the voltage bus of the battery whenever there is a large current inrush in the power function of the electronic switching circuit.

[0005] In this case, a large amount of electrical energy flows through the electrochemical capacitor, which is a sensitive component with specific specifications and a specific operating range. Non-compliance with the specifications and operating range can cause damage to these components. The damage of the electrochemical capacitor can lead to a short circuit between the battery and the ground, and cause damage to the electronic switching unit.

[0006] A common solution to avoid these serious consequences is to increase the equipment of the electrochemical filter capacitor. Therefore, the capacitor bank provided between the power supply and the ground consists of an excessive number of capacitors, and the capacitance of these capacitors is also excessive. The operating safety is obtained at the expense of the additional cost of manufacturing the electronic switching unit and the additional volume of the printed circuit of these units, which goes against the trend of reducing the manufacturing cost and the size of the computer, especially in the automotive industry.

[0007] Other solutions provide replacing the electrochemical capacitor with a capacitor of other technologies with less risk of failure. These capacitors are more expensive than the electrochemical capacitor, and these technologies are less suitable for the filtering function. Summary of the Invention

[0008] The object of the present invention is to improve the prior art electronic switching unit for supplying electric power to an inductive power load.

[0009] To this end, the present invention aims to provide a method for controlling an electronic switching unit for supplying electric power to an inductive power load, the electronic switching unit including:

[0010] - A power connector;

[0011] - A switching bridge adapted to be controlled according to a pulse width modulation signal having a rated operating frequency and a duty cycle;

[0012] - A power filter capacitor bank arranged between the ground and the power supply of the electronic switching unit.

[0013] The method comprises the following steps:

[0014] - Enabling the initial filter capacitor by connecting it between the power supply of the electronic unit and the ground, and disabling the other capacitors in the filter capacitor bank;

[0015] - Measuring the current flowing through the initial filter capacitor;

[0016] - If the current is higher than a predetermined rated current threshold, enabling an additional filter capacitor by connecting it between the power supply of the electronic unit and the ground, in parallel with the initial filter capacitor.

[0017] According to one embodiment, when all the capacitors in the filter capacitor bank are enabled, the method comprises the following steps:

[0018] - Measuring the current flowing through each of the filter capacitors;

[0019] - If the currents are higher than a predetermined rated current threshold, increasing the operating frequency of the pulse width modulation signal to a first predetermined protection frequency, which is greater than the rated operating frequency.

[0020] According to one embodiment, when the operating frequency is equal to a predetermined maximum protection frequency, the method comprises the following steps:

[0021] - Measuring the current flowing through each of the filter capacitors;

[0022] - If the currents are higher than a predetermined maximum current threshold corresponding to the predetermined maximum protection frequency, reducing the duty cycle of the pulse width modulation signal to a predetermined protection value.

[0023] The method according to the invention makes it possible to protect the electrochemical filter capacitors. For a specific electronic switching unit, this protection can be used to determine the size of the electrochemical capacitors as precisely as possible. Precisely determining the size of the electrochemical capacitors can reduce their cost. Furthermore, since the electrochemical capacitors are bulky components, reducing their number and their capacitance allows a considerable benefit to be obtained in terms of the volume of the printed circuit of the electronic unit and thus generally reduces the size of the electronic unit.

[0024] Furthermore, this protection enables the reliability of the electronic switching unit to be increased.

[0025] The method according to the invention may comprise the following additional features, alone or in combination:

[0026] - The method comprises the steps of: measuring the current flowing through each of the enabled filter capacitors; if these currents are higher than a predetermined rated current threshold, enabling an additional filter capacitor by connecting the additional filter capacitor between the power supply and ground of the electronic unit;

[0027] - Repeating the steps until all the capacitors in the filter capacitor bank are enabled;

[0028] - After the step of measuring the current flowing through each of the enabled filter capacitors, if the current flowing through each of the enabled capacitors is lower than a predetermined minimum threshold, disabling the last enabled capacitor;

[0029] - The predetermined minimum threshold is equal to half of the predetermined rated current threshold;

[0030] - When all the capacitors in the filter capacitor bank are enabled, the method comprises the steps of: measuring the current flowing through each of the filter capacitors; if these currents are higher than a predetermined rated current threshold, increasing the operating frequency of the pulse width modulation signal to a first predetermined protection frequency, the first predetermined protection frequency being greater than the rated operating frequency;

[0031] - The method comprises the steps of: measuring the current flowing through each of the filter capacitors; if these currents are higher than a first predetermined current threshold corresponding to the first predetermined protection frequency, increasing the operating frequency of the pulse width modulation signal to a second predetermined protection frequency;

[0032] - Repeating the following steps until the operating frequency reaches a predetermined maximum protection frequency: measuring the current flowing through each of the filter capacitors; if these currents are higher than an Nth predetermined current threshold corresponding to the Nth predetermined protection frequency, increasing the operating frequency of the pulse width modulation signal to the (N + 1)th predetermined protection frequency;

[0033] - When the operating frequency is equal to the (N + 1)th predetermined protection frequency, if the current flowing through each capacitor is lower than the Nth predetermined current threshold corresponding to the Nth predetermined protection frequency, reducing the operating frequency to the value of the Nth predetermined protection frequency;

[0034] - When the operating frequency is equal to a pre - determined maximum protection frequency, the method comprises the following steps: measuring the current in each of the filter capacitors; if these currents are higher than a pre - determined maximum current threshold corresponding to the pre - determined maximum protection frequency, reducing the duty cycle of the pulse - width modulation signal to a pre - determined protection value;

[0035] - Repeating the foregoing steps while gradually reducing the duty cycle until the current in each of the filter capacitors is lower than the pre - determined maximum current threshold corresponding to the pre - determined maximum protection frequency;

[0036] - Each time the method starts again, each capacitor of the filter capacitor bank is sequentially assigned the function of the initial filter capacitor. Description of the Drawings

[0037] With reference to the accompanying drawings, other features and advantages of the present invention will become apparent from the following non - restrictive description, in which:

[0038] - Figure 1 Figure 1 Schematically shows an electronic switch unit according to the present invention;

[0039] - Figure 2 Figure 2 Is a schematic diagram illustrating the method according to the present invention;

[0040] - Figure 3 Figure 3 Shows Figure 1 The operating curve of the filter capacitor of the electronic unit of Detailed Description of the Invention

[0041] Figure 1 Schematically shows an electronic switch unit 1 according to the present invention. In this illustrative example, the electronic unit 1 is an inverter designed to supply power to and control a three - phase electric motor 2 in a motor vehicle. The electronic unit 1 is powered by a battery of the motor vehicle, and a power supply line 3 of the battery at a potential of + 12 V is shown. The electronic unit 1 includes a power connector 4, which makes it possible to connect the electronic unit 1 to the power supply line 3, in particular.

[0042] The electronic unit 1 includes a switch bridge 5, which, in this example, is adapted to supply power to the three - phase motor 2. A microcontroller 6 forming part of the vehicle equipment transmits control set - points for controlling the motor 2 to the switch bridge 5. In this example, the switch bridge 5 is controlled by a pulse - width modulation (PWM) signal transmitted by the microcontroller 6. The pulse - width modulation signal has an operating frequency and a duty cycle.

[0043] ​​​The motor 2 is an inductive power load including a high-inductance coil, and the electronic unit 1 has an input filter capacitor bank 7. This capacitor bank 7 consists of a predetermined number of capacitors C 1 to C n which are electrochemical capacitors with a high capacitance (e.g., greater than 1 µF). These capacitors C 1 to C n protect the electronic unit 1 from large variations in electrical energy caused by high current surges occurring during certain operating phases of the motor 2 (such as start-up or acceleration).

[0044] The capacitors C 1 to C n are intended to be connected between the power supply line 3 (+12 V) and ground. The number of capacitors C 1 to C n is selected according to the power of the device. The electronic unit 1 further includes a device 8 for connecting the capacitors. For each of the capacitors C 1 to C n the device 8 includes a switch 9 such that the circuit between one electrode of the capacitor and ground can be opened or closed, and the other electrode of each capacitor is connected to the power supply line 3. Thus, all the capacitors C 1 to C n with their switches 9 closed are placed in parallel and connected between the power supply line 3 and ground (they are referred to as "enabled"), while the capacitors with their switches 9 open are outside the circuit and are referred to as "disabled".

[0045] The device 8 for connecting the capacitors is controlled by a control module 10 which is adapted to close and open the switches 9. The switches 9 are, for example, transistors, and the module 10 can be a module of the driver type.

[0046] Furthermore, the control module 10 receives a pulse-width modulation signal from the microcontroller 6. Thus, the module 10 has information related to the operating frequency and duty cycle which is given by the microcontroller 6 as a setpoint for controlling the motor 2. However, the control module 10 transmits this signal to the switch bridge 5 in order to effectively control the switch bridge 5 and thus control the motor 2, and is able to modify the signal.

[0047] The device 8 for connecting the capacitors further includes means for measuring the current flowing through each capacitor C 1 to C n which is schematically shown by the ammeter 11. In the Figure 1 schematic diagram only the ammeter 11 of the capacitor C 1 is shown, it being understood that for each capacitor C 1 to C nAll have such a measuring device. Therefore, the control module 10 has the current measurement values of each capacitor C 1 to C n .

[0048] The control method according to the invention enables the capacitor bank 7 to achieve its filtering function by protecting the electronic unit 1 from transient load surge currents that may be very high. The method also ensures the optimal operation and durability of the capacitors C 1 to C n , and thus improves the overall reliability of the electronic unit 1. The method is described with reference to Figure 2 the diagram of Figure 2 , which schematically shows the steps continuously implemented by the control module 10 for controlling the device 8 for connecting the capacitors.

[0049] The first step A1 involves the initial programming when the control module 10 starts running. During this step A1, the following data is stored in the control module 10:

[0050] - The number n of capacitors forming the capacitor bank 7;

[0051] - The rated operating frequency F T0 of the pulse-width modulation signal;

[0052] - The predetermined maximum protection frequency F TM of the pulse-width modulation signal;

[0053] - The predetermined intermediate protection frequencies F T1 , F T2 ,... between the rated frequency and the maximum protection frequency of the pulse-width modulation signal;

[0054] - The effective current thresholds I RMS_T0 , I RMS_T1 , I RMS_T2 ,..., I RMS_TM , which correspond to each operating frequency F T0 , F T1 , F T2 ,..., F TM .

[0055] The next step A2 involves initializing the selection of the initial filtering capacitor, which will be the only enabled capacitor when the method starts. During the first iteration of the method, the first capacitor C 1 is designated as the initial filtering capacitor.

[0056] During the next step A3, the initial capacitor (C 1 in the first iteration of the method) is enabled, and all other capacitors C 2to C n is deactivated. The capacitor is enabled or deactivated by switch 9 (see Figure 1 ). Thus, during this first iteration, step A3 includes closing switch 9 associated with the first capacitor C 1 , and opening all other switches 9 associated with the other capacitors C 2 to C n .

[0057] In the next step A4, the current flowing through the initial capacitor is measured using ammeter 11 (see Figure 1 ). If the measured current flowing through the initial capacitor is higher than the rated current threshold I RMS_T0 , then the method proceeds to the next step A5. Otherwise, the method loops back to step A4. The value of the rated current threshold I RMS_T0 is a predetermined value depending on the filtering capacitor used. This value corresponds to the maximum current that the capacitor (here capacitor C 1 as the initial filtering capacitor) is designed to safely withstand at the rated operating frequency F T0 . The rated operating frequency F T0 is the frequency of the pulse-width modulation signal sent by the microcontroller 6, and the control module 10 likewise transmits this signal to the switch bridge 5.

[0058] Thus, as long as the current flowing through the initial capacitor (which is capacitor C 1 in this first iteration and is the only active capacitor in the capacitor bank) remains below the rated current threshold I RMS_T0 , the method remains at step A4.

[0059] Advancing from step A4 to step A5 corresponds to the case where the current flowing through the initial capacitor C 1 is higher than the rated current threshold I RMS_T0 , and this current is considered too high for the initial capacitor C 1 . Step A5 includes enabling additional filtering capacitors in the capacitor bank 7. Here, the next capacitor C 2 will thus be enabled in step A5, that is, its switch 9 will be closed by the control module 10.

[0060] Starting from step A5, the capacitor bank 7 will thus consist of two capacitors C 1 and C 2 connected in parallel, and the current will thus be distributed across these two capacitors.

[0061] The method then proceeds to step A6, in which a new current measurement is performed. During this step A6, for each of these capacitors, the current flowing through the two enabled capacitors C 1 、C2 current. In this step A6, if the current flowing through the two capacitors C 1 and C 2 is lower than the rated current threshold I RMS_T0 , the situation is judged to be acceptable, and the capacitor bank 7 composed of the two capacitors C 1 and C 2 achieves its function without the risk of capacitor degradation. Then, the device proceeds to step A7, in which a new current-related check is performed.

[0062] During step A7, it is further evaluated for each capacitor C 1 and C 2 the measured current value (which is thus lower than the rated current threshold I RMS_T0 ) to determine whether these current measurement values are further lower than the minimum threshold. In this example, the minimum threshold is equal to half of the rated current threshold I RMS_T0 . If these two current measurement values are higher than the minimum threshold, the method loops back to step A6. Conversely, when the current flowing through the two capacitors C 1 and C 2 is lower than the minimum threshold (half of the rated current threshold I RMS_T0 ), the method then proceeds to step A8, where the second capacitor C 2 is deactivated. This situation corresponds to returning to a current that is judged to be low enough so that only a single capacitor in the filter capacitor bank 7 is needed.

[0063] The next step A9 consists of determining whether the power function is completed, that is, considering the operating phase of the motor 2, whether the filtering function achieved by the capacitor bank 7 is still needed. If this power function is not completed, the method returns to step A4. Conversely, if the power function is completed, the method proceeds to step A10, where a new initial capacitor will be designated for the next iteration of the method. In the first iteration of the method, the next capacitor C 2 is now designated as the initial capacitor. In the next iteration of step A3 and the subsequent steps, this capacitor C 2 will start by forming the filter capacitor bank 7 alone. After step A10, the method then loops back to step A3, during which this new initial capacitor C 2 will thus be enabled while all other capacitors will be deactivated, and the method then starts a new iteration of step A3 and the subsequent steps as described above.

[0064] Referring again to step A6 of the first iteration, different from above, if during this step, for each capacitor C 1 and C 2The measured current is higher than the rated current threshold I RMS_T0 , then the method does not continue with step A7, but instead proceeds to step B1 this time, where the next capacitor of the capacitor bank 7 is enabled. In this first iteration, the capacitors C 1 , C 2 , C 3 are thus enabled in step B1, while all other capacitors are disabled.

[0065] The method then proceeds to steps B2 and B3, which are similar to steps A6 and A7, but this time involve three capacitors C 1 , C 2 and C 3 .

[0066] In step B2, the current flowing through each of the capacitors C 1 to C 3 is measured and compared with the rated current threshold I RMS_T0 . If this current flowing through each capacitor is lower than the rated current threshold I RMS_T0 , then the method proceeds to step B3, where this current value is compared with the lowest current threshold (here also half of the rated threshold current I RMS_T0 ). If the current flowing through each capacitor is higher than the lowest current threshold, step B3 loops back to step B2. Conversely, if the current flowing through each capacitor is lower than the lowest current threshold, the method proceeds to step E14. In step E14, the capacitor that was just enabled (C 3 ) is then disabled.

[0067] The next step B5 consists of determining whether the power function is complete. If the power function is not complete, the method loops back to step A6. Conversely, if the power function is complete, the method proceeds to step B6, where a new initial capacitor will be designated for the next iteration of the method. In the first iteration of the method, the following capacitor C 2 is now designated as the initial capacitor. After step B6, the method then loops back to step A3, during which this new initial capacitor C 2 will thus be enabled, while all other capacitors will be disabled, and the method then initiates a new iteration of step A3 and the subsequent steps as described above.

[0068] If, in step B2, the measured current flowing through each of the capacitors C 1 , C 2 , C 3 is higher than the rated current threshold I RMS_T0 , then the method proceeds to step C1, in which additional capacitors are enabled. Subsequently, the following capacitors are enabled and added to the capacitor C1 , C 2 , C 3 , to form the filter capacitor bank 7. Thus, this method is repeated for each capacitor of the capacitor bank (which is schematically shown by the dashed line 13 in this Figure 2 ), so that as long as the current flowing through each capacitor is higher than the rated current threshold I RMS_T0 , a new capacitor is added to the capacitor bank 7 until the last capacitor C n .

[0069] Step C1 involves adding the capacitor C n , and thus includes enabling the last available capacitor C in the filter capacitor bank 7 n .

[0070] The steps from C1 to C6 are the same as the steps from B1 to B6. After step C1, step C2 thus involves comparing the current flowing through each capacitor (all capacitors C 1 to C n are enabled) with the rated current threshold I RMS_T0 . In step C2, the current flowing through each of the capacitors C 1 to C n is measured and compared with the rated current threshold IRMS T0. If this current flowing through each capacitor is lower than the rated current threshold I RMS_T0 , the method proceeds to step C3, where this current value is compared with the lowest current threshold (which is also half of the rated threshold current I RMS_T0 here). If the current flowing through each capacitor is higher than the lowest current threshold, step C3 loops back to step C2. On the contrary, if the current flowing through each capacitor is lower than the lowest current threshold, the method proceeds to step C4. In step C4, the capacitor that has just been enabled (C n ) is then disabled.

[0071] The next step C5 consists of determining whether the power function is completed. If this power function is not completed, the method returns to step B2 according to the dashed line 16 (if capacitor C n is the fourth and last capacitor of the filter capacitor bank) or for the capacitor before C n , it returns to the step equivalent to step B2. On the contrary, if the power function is completed, the method proceeds to step C6, where a new initial capacitor will be designated for the next iteration of the method.

[0072] Therefore, the method loops between steps A3 and C6, so that the number of capacitors used in the capacitor bank is always optimal.

[0073] Furthermore, the method always starts on a single capacitor, but due to steps A10, B6, and C6, this capacitor is rotated, that is to say, each capacitor C 1 to C n will thus successively play the role of the first enabled capacitor in the capacitor bank. This arrangement allows for regular wear of the capacitors by balancing the usage time of all capacitors, regardless of their position in the capacitor bank. The capacitors are enabled in a fixed, rotating order.

[0074] Furthermore, during step C2, if the measured value of the current flowing through each capacitor C 1 to C n is higher than the rated current threshold I RMS_T0 , then the method proceeds to step D1, in which the operating frequency of the pulse width modulation signal will be modified. This situation corresponds to detecting excessive use of the capacitors at the initially expected operating frequency F T0 . In other words, although all the capacitors in the capacitor bank have been enabled, it is determined that additional measures are necessary because, despite using the maximum capacitance of the capacitor bank, the current flowing through these capacitors is still higher than the rated current threshold I RMS_T0 .

[0075] During step D1, the operating frequency of the pulse width modulation signal is increased to a first protection frequency F T1 . The frequency of the pulse width modulation signal can be modified at the control module 10 or directly at the microcontroller 6. Since the first protection frequency F T1 is greater than the operating frequency F T0 , considering the specifications peculiar to electrochemical capacitors, the capacitors C 1 to C n of the capacitor bank thus receive a greater current (see Figure 3 ). By modifying the operating frequency to the value F T0 , a current higher than the rated current threshold I RMS_T0 no longer poses a risk to the filter capacitors. At this new frequency F T0 , the current threshold that poses a risk to the filter capacitor bank is now a first predetermined current threshold I RMS_T1 (and is thus higher than I RMS_T0 ), see Figure 3 .

[0076] In Figure 2 , step D2 consists of determining whether the current flowing through each capacitor C 1 to C n is higher than this first predetermined current threshold I RMS_T1 . If the current flowing through each capacitor C 1 to C nThe current is not higher than the first predetermined current threshold I RMS_T , then the method proceeds to step D3, where the current flowing through capacitor C 1 to C n in each of them is this time compared with the rated current threshold I RMS_T0 . If during step D3, the current is still higher than I RMS_T0 , then the method loops back to step D2. Conversely, if in step D3, the measured current flowing through the capacitor is now lower than I RMS_T0 , then the method proceeds to step D4, where the operating frequency returns to the initial operating frequency F T0 . This situation corresponds to the case where increasing the operating frequency is no longer judged to be useful, and then the method proceeds to step D5.

[0077] Similar to steps A9, B5, and C5, the next step D5 consists of determining whether the power function is completed. If the power function is not completed, then the method returns to step C2. Conversely, if the power function is completed, then the method proceeds to step D6, in which a new initial capacitor will be specified for the next iteration of the method (in this first iteration, C 2 is now specified as the initial capacitor).

[0078] Referring again to step D2, conversely, if the measured value of the current flowing through each capacitor C 1 to C n indicates that each of these currents is higher than the first predetermined current threshold I RMS_T1 , then the method proceeds to step E1, in which the operating frequency will this time be increased to the second protection frequency F T2 . In the same manner as steps D1 to D6, this part of the method starting from step E1 will increase the operating frequency to a new frequency F T2 , which is greater than F T1 , and thus enables further increasing the capacitance of the capacitor bank C 1 to C n , where all the capacitors are enabled. After step E1, the sequence is the same as for steps D1 to D6, and thus will not be described in detail here (this part of the method is schematically shown by the dashed line 17).

[0079] Repeat the same pattern for as many frequencies F T1 , F T2 etc. as were expected when initializing the method in step A1. Thus, in summary, when all the capacitors in the capacitor bank are enabled and the current flowing through the capacitors is still higher than the rated current threshold, the operating frequency is incrementally increased to F T1 , and then to F T2, and so on. Therefore, as long as the current flowing through the capacitor remains above a first predetermined current threshold I RMS_T1 , a second predetermined current threshold I RMS_T2 , etc., the operating frequency increases in steps. These thresholds respectively correspond to each predetermined frequency level F T1 , F T2 , etc.

[0080] This gradual increase in the operating frequency of the pulse width modulation signal ends at the maximum frequency F TM also defined during the initialization step A1. Thus, when the last frequency level has been reached and the current flowing through the capacitor is still higher than the predetermined current threshold corresponding to this last frequency level, the method proceeds to step F1. Then, the method proceeds to finally increase the operating frequency to the maximum frequency F TM (in step F1) in order to achieve the maximum capacity of the capacitor bank for this maximum protection frequency F TM .

[0081] Step F1 and the following steps unfold in the same way as step D1 and the following steps or step E1 and the following steps (not shown). Then, step F2 consists of determining whether the current flowing through each of the capacitors C 1 to C n is higher than the last current threshold I RMS_TM . If the current flowing through each of the capacitors C 1 to C n is not higher than the last current threshold I RMS_TM , the method proceeds to step F3, where the current flowing through each of the capacitors C 1 to C n is this time compared with the current threshold corresponding to the frequency applied just before the maximum frequency F TM (in this example, this is the frequency applied during step E1 and the subsequent steps). If during step F3, this current is still higher than the current threshold corresponding to the frequency applied just before the maximum frequency F TM , the method loops back to step F2. On the contrary, if in step F3, the measured current flowing through the capacitor is now lower than the above-mentioned current threshold corresponding to the frequency applied just before the maximum frequency F TM , the method proceeds to step F4, where the operating frequency returns to the frequency applied just before (in this example, during step E1 and the following steps). This situation corresponds to the case where increasing the operating frequency is no longer judged to be useful, and then the method proceeds to step F5.

[0082] Similar to steps A9, B5, C5, and D5, the next step F5 involves determining whether the power function is complete. If this power function is not complete, the method returns to the method part of step E1 and the next step (dashed line 18). Conversely, if the power function is complete, the method proceeds to step F6, in which a new initial capacitor will be specified for the next iteration of the method (as previously mentioned, in this first iteration, C 2 is specified as the initial capacitor).

[0083] Between step A3 and step F6, the filter capacitor bank is implemented while being protected from current peaks without disturbing the operation of the electronic switch unit.

[0084] Furthermore, in step F2, if the measured value of the current flowing through each capacitor indicates that this current is higher than the last predetermined current threshold I RMS_TM , this current threshold corresponding to the maximum allowable current at the maximum protection frequency F TM , the method proceeds to step G1, in which new measures will be implemented to protect the capacitor bank. This measure involves reducing the duty cycle of the pulse width modulation signal. Then, the method enters a degradation mode, in which the duty cycle is reduced and thus affects the operation of the controlled capacitive load, with the aim of protecting the filter capacitor bank.

[0085] In step G1, the duty cycle is thus reduced by a predetermined value, and in step G2, it is checked whether the measured value of the current flowing through each of the capacitors C 1 to C n has returned to be lower than the last predetermined current threshold I RMS_TM . If this is indeed the case, the method loops back to step F2, and if not, the method loops back to step G1 in order to reduce the duty cycle again.

[0086] Thus, in one or more iterations of step G1, the duty cycle of the pulse width modulation signal is reduced until the current flowing through the capacitor returns to be lower than the last predetermined current threshold I RMS_TM . During the repetition of steps G1 and G2, in order to protect the capacitors of the capacitor bank 7, an alarm flag can be enabled by the control module 10 to warn other devices of the vehicle or to warn the user that there are limitations in the control of the motor 2. However, except in abnormal situations, the duration of these phases of limiting the duty cycle is short and ultimately has little impact on the overall operation of the motor 2.

[0087] Figure 3 's curve shows the capacitance i of the capacitors of the filter capacitor bank capThe variation, i.e., the current that can be accepted by the capacitor as a function of its operating frequency f. This curve is valid for a given temperature (here 25 °C) and a defined voltage. The operating frequency is the frequency of the pulse-width modulation signal that controls the switching bridge 5. Figure 3 shows the various operating frequency variations of the pulse-width modulation signal and the associated current within the capacitors of the capacitor bank 7. Figure 3 is the characteristic curve of the electrochemical capacitor used in this embodiment.

[0088] Figure 3 is a characteristic of the electrochemical capacitor. FIG. 3 has a first straight-line portion with a positive gradient, which is associated with the stage in which the increase in the operating frequency applied to the capacitor is accompanied by an increase in its capacitance (i.e., an increase in the current it can withstand). The first straight-line portion of the straight line is limited by the maximum frequency F allowed by the capacitor. max Frequency F max is such a frequency that if exceeded, the capacitor may be damaged.

[0089] Figure 3 Also depicted are the frequencies F T0 , F T1 , F T2 … F TM , which are selected and initialized in the method just described. The frequency F TM is the maximum frequency that the capacitor will experience during this method. This frequency F TM is preferably less than F max to ensure the durability of the capacitor.

[0090] As described above, the method starts with a pulse-width modulation signal at an operating frequency F RMS_T0 corresponding to the maximum current threshold I of the capacitor. According to the described method, whenever the effective current flowing through the capacitor exceeds this value I T0 , a new capacitor within the capacitor bank 7 is enabled. When the last capacitor of the capacitor bank 7 has been enabled and the current is still greater than the value I RMS_T0 , the operating frequency is then modified and increased to the value F RMS_T0 corresponding to the new maximum current I flowing through the capacitor. RMS_T1 Each time the current flowing through the capacitor exceeds the corresponding current threshold I T1 , I RMS_T1 , I RMS_T2 , by continuously increasing the frequency to a predetermined frequency level F T1 , F T2 , until the maximum protection frequency F corresponding to the current threshold I RMS_TM TM ​, the operation of increasing the working frequency is repeated. Therefore, the current flowing through the capacitor bank 7 varies within the shaded range 14. Within this range, the capacitor bank is protected and the electronic switch unit 1 operates normally without affecting the operation of the motor 2.

[0091] According to steps G1 and G2 of the method, when the duty cycle is limited, the current of the capacitor varies within the second shaded range 15.

[0092] Without departing from the scope of the present invention, different embodiments can be implemented. Specifically, the pre-determined current thresholds I RMS_T0 , I RMS_T1 , I RMS_T2 … I RMS_TM and the corresponding working frequencies F T0 , F T1 , F T2 … F TM can be applied to specific applications and specific capacitors.

[0093] In addition, regarding steps G1 and G2, the duty cycle can be reduced continuously or in stages.

Claims

1. A method for controlling an electronic switch unit (1), the electronic switch unit (1) being used to provide electric power to an inductive power load, the electronic switch unit (1) comprising: - power connector (4); - a switching bridge (5) adapted to be controlled according to a pulse width modulated signal having a nominal operating frequency and a duty cycle; - a power supply filter capacitor bank (7) arranged between ground and the power supply (3) of the electronic switching unit (1); The method is characterized in that it comprises the following steps: - activating the initial filter capacitor by connecting it between the power supply (3) of the electronic switch unit (1) and ground, and deactivating the other capacitors of the power supply filter capacitor bank (7); - measuring the current flowing through the initial filter capacitor; - If the current is above a predetermined rated current threshold, an additional filter capacitor is activated by connecting it between the power supply (3) of the electronic switching unit (1) and ground, in parallel with the initial filter capacitor.

2. The method according to claim 1, characterized in that It includes the following steps: - measuring the current flowing through each of the enabled filter capacitors; If these currents are above a predetermined rated current threshold, an additional filter capacitor is enabled by connecting it between the power supply and ground of the electronic switching unit.

3. The method according to claim 2, characterized in that The steps are repeated until all capacitors in the power supply filter capacitor bank (7) are enabled.

4. The method according to claim 2 or 3, characterized in that: After the step of measuring the current flowing through each of the enabled filter capacitors, if the current flowing through each of the enabled capacitors is below a predetermined minimum threshold, then the last enabled capacitor is deactivated.

5. The method according to claim 4, characterized in that The predetermined minimum threshold value is equal to half of the predetermined rated current threshold value.

6. The method according to claim 3, characterized in that When all capacitors in the power supply filter capacitor bank (7) are enabled, the method comprises the following steps: - measuring the current flowing through each of the filter capacitors; - If these currents are above a predetermined rated current threshold, increasing the operating frequency of the pulse width modulated signal to a first predetermined protection frequency, said first predetermined protection frequency being greater than the rated operating frequency.

7. The method according to claim 6, characterized in that It includes the following steps: - measuring the current flowing through each of the filter capacitors; - if these currents are above a first predetermined current threshold corresponding to said first predetermined protection frequency, increasing the operating frequency of said pulse width modulated signal to a second predetermined protection frequency.

8. The method according to claim 7, characterized in that Repeat the following steps until the operating frequency reaches the predetermined maximum protection frequency: - measuring the current flowing through each of the filter capacitors; - If these currents are above the Nth predetermined current threshold corresponding to the Nth predetermined protection frequency, increasing the operating frequency of the pulse width modulated signal to the N+1th predetermined protection frequency.

9. The method according to claim 8, characterized in that When the operating frequency is equal to the N+1th predetermined protection frequency, if the current flowing through each capacitor is lower than the Nth predetermined current threshold corresponding to the Nth predetermined protection frequency, the operating frequency is reduced to the value of the Nth predetermined protection frequency.

10. The method according to claim 8, characterized in that When the operating frequency is equal to the predetermined maximum protection frequency, the method comprises the following steps: - measuring the current flowing through each of the filter capacitors; - if these currents are above a predetermined maximum current threshold corresponding to said predetermined maximum protection frequency, reducing the duty cycle of said pulse width modulation signal to a predetermined protection value.

11. The method according to claim 10, characterized in that Repeat the following steps of claim 10: - measuring the current flowing through each of the filter capacitors; - if these currents are above a predetermined maximum current threshold corresponding to said predetermined maximum protection frequency, reducing the duty cycle of said pulse width modulation signal to a predetermined protection value; At the same time, the duty cycle is gradually reduced until the current flowing through each of the filter capacitors is lower than the predetermined maximum current threshold corresponding to the predetermined maximum protection frequency.

12. The method according to any one of claims 1 to 3, characterized in that Each time the following steps of the method according to claim 1 are started again, each capacitor of the power supply filter capacitor bank (7) is successively assigned to the function of an initial filter capacitor: - enabling the initial filter capacitor by connecting it between the power supply (3) of the electronic switching unit (1) and ground, and deactivating the other capacitors of the power supply filter capacitor bank (7).

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