Switching systems and methods with dead time, and corresponding computer programs.

Abstract

The invention relates to a switching system comprising: - a switching arm (110) comprising two switches, a high-side switch (Q6) and a low-side switch (Q2); - a control system (114) designed to switch the switching arm (110) alternately between a first configuration in which the high-side switch (Q6) is open and the low-side switch (Q2) is closed, and a second configuration in which the high-side switch (Q6) is closed and the low-side switch (Q2) is open, the control system (114) being designed to, for each switching operation command, open the switch that was initially closed, then command the closing of the switch that was initially open at the end of a dead time; and - a measuring device (116) for measuring a switching voltage (LVCE) present between the terminals (LC, LE) of one of the switches (Q2). The control system (114) is also designed to, for each of at least one switching operation: - monitor the measured switching voltage (LVCE) after the command to open the switch that was initially closed; and - determine the dead time of the switching operation under consideration on the basis of the monitored switching voltage (LVCE).

Description

TECHNICAL FIELD

[0001] The present invention relates to a switching system with dead time, a switching method with dead time and a corresponding computer program. BACKGROUND

[0002] The prior art discloses a type of switching system comprising:

[0003] - a switching arm comprising two switches, a high-side switch and a low-side switch, each switch having a current input terminal and a current output terminal, the current output terminal of the high-side switch and the current input terminal of the low-side switch being connected to each other;

[0004] - a control system for controlling the switching arm, designed to alternate switching the switching arm between a first configuration in which the high-side switch is open and the low-side switch is closed, and a second configuration in which the high-side switch is closed and the low-side switch is open, the control system being designed to, for each switching operation:

[0005] • command the switch that was initially closed to open, then,

[0006] • at the end of a dead time, command the switch that was initially open to close; and

[0007] - a measuring device for measuring the switching voltage present between the terminals of one of the switches.

[0008] Such a switching system is used, for example, in a DC / DC converter, or in an integrated charger (on-board charger or OBC), or even in an inverter / rectifier connected to an electric machine capable of operating selectively in motor mode and in generator mode.

[0009] There is generally a measuring device in order to implement various functions, in particular detecting the desaturation state of the switch on which the measuring device is provided.

[0010] The dead time is used first of all to ensure that the switch that was commanded to open is actually properly open before commanding the other switch to close, to ensure that the two switches are not simultaneously in the on state (cross-conduction).

[0011] In addition, it is known to place in parallel with each switch a capacitor that allows soft switching, that is to say switching with virtually no losses, also denoted by the acronym ZVS (for Zero Voltage Switching). The complete charging or discharging of these capacitors is necessary to allow the switch to close with a voltage of zero or almost zero at its terminals. The dead time thus makes it possible to ensure the complete charging or discharging of the capacitors.

[0012] It is first known to set the dead-time to a fixed value, which for example corresponds to a value that always satisfies the soft-switching condition, regardless of the inverter / rectifier / DC-DC or motor value, and regardless of the switching frequency. Thus, in many cases, the dead-time determined in this way is too long.

[0013] It is also known to vary the duration of the dead-time based on a value of the dead-time that is predetermined in the laboratory. The control system can then use a predefined table, for example a table stored in a flash memory, giving the duration of the dead-time as a function of the state of charge of the battery and / or of the operating point of the motor and / or of the switching frequency. This table generally contains data for only a few particularly important operating points. The drawback of this solution is the need for sensors, means for determining the operating point based on measurements from the sensors, a memory containing the predefined table and means for accessing the memory. All these elements take up space and have a non-negligible cost.

[0014] It can therefore be desirable to provide a switching system that is able to overcome at least some of the above-mentioned problems and constraints. SUMMARY

[0015] It is thus proposed a switching system of the above-mentioned type, characterized in that the control system is further designed to, for each of the at least one switching operation:

[0016] - monitor the measured switching voltage after the command to open the initially closed switch; and

[0017] - determine the dead-time of the considered switching operation based on the monitored switching voltage.

[0018] According to the invention, the determination of the dead-time requires few additional elements. More specifically, only the operation of the control system needs to be adjusted. Now, the control system is generally implemented by a microcontroller executing a computer program, and already receives the switching voltage measurements in order to implement other functions, such as the detection of the desaturation state. Thus, in the simplest case, the adjustment of the control system can be reduced to simply updating its computer program.

[0019] Optionally, to determine the dead-time of the considered switching operation based on the monitored switching voltage, the control system is designed to:

[0020] - detect when the switching voltage crosses a predetermined threshold; and

[0021] - determine the dead-time of the considered switching operation based on the detection of the crossing.

[0022] Also optionally, the determined dead-time extends from the command to open the initially closed switch until the crossing is detected.

[0023] Also optionally, the control system is designed to determine, based on a time interval between the command to open the initially closed switch and the detection of the crossing, a dead time of the switching operation under consideration, so that the end of this dead time is later than the detection of the crossing.

[0024] Also optionally, the switch voltage is a voltage present between the terminals of the low-side switch.

[0025] Also optionally, the at least one switching operation comprises a switching operation from the first configuration to the second configuration.

[0026] Also optionally, the control system is further designed to, for each of the at least one switching operation:

[0027] - command the initially closed switch to open;

[0028] - determine, based on the dead time of the preceding switching operation, a dead time of the switching operation under consideration;

[0029] - at the end of the determined dead time, command the initially open switch to close.

[0030] Also optionally, the determined dead time is equal to the dead time of the preceding switching operation.

[0031] Also optionally, the determined dead time is greater than the dead time of the preceding switching operation, for example equal to the dead time of the preceding switching operation plus a predefined duration.

[0032] Also optionally, the at least one switching operation comprises at least two successive switching operations.

[0033] Also optionally, the switch system further comprises a capacitor between the terminals of the high-side switch and a capacitor between the terminals of the low-side switch.

[0034] A method for switching a switch arm comprising a high-side switch having a current input terminal and a current output terminal and a low-side switch having a current input terminal and a current output terminal, the current output terminal of the high-side switch and the current input terminal of the low-side switch being connected to each other, the method comprising:

[0035] - alternatingly switching the switch arm between a first configuration in which the high-side switch is closed and the low-side switch is open and a second configuration in which the high-side switch is open and the low-side switch is closed, each configuration switching operation comprising a command to open the initially closed switch and then a command to close the initially open switch at the end of a dead time;

[0036] characterized in that it further comprises:

[0037] - monitoring, after the command to open the closed switch, a switch voltage present between the terminals of one of the switches; and

[0038] - The dead time of the current switching operation is determined based on the monitored switching voltage.

[0039] The present invention also relates to a switching system, comprising:

[0040] - A switch arm for connection to a voltage source designed to provide DC voltage and comprising two switches, a high-side switch and a low-side switch, each switch having a current input terminal and a current output terminal, the current output terminal of the high-side switch and the current input terminal of the low-side switch being connected to each other at a center tap;

[0041] - A control system for controlling the switching arm is designed to alternately switch the switching arm in two directions between a first configuration and a second configuration. In the first configuration, the high-side switch is open and the low-side switch is closed, resulting in zero voltage at the center tap. In the second configuration, the high-side switch is closed and the low-side switch is open, resulting in DC voltage at the center tap. The control system is designed to provide the following for each switching operation:

[0042] • The switch that was initially closed was opened, and then,

[0043] • At the end of the dead time, the switch that was initially disconnected is closed; and

[0044] - Measuring device for measuring the switching voltage present between the terminals of one of the switches;

[0045] The control system is also designed to perform a first switching operation for switching the switch arm in the first direction of the two directions:

[0046] - After the command to disconnect the initially closed switch, monitor and measure the switch voltage; and

[0047] - Based on the monitored switching voltage, the dead time for this first switching operation is determined as follows:

[0048] • Detect when the switching voltage crosses a predefined threshold between zero voltage and DC voltage, and

[0049] • The dead time for the first handover operation is determined based on the detection of the crossover.

[0050] Furthermore, the control system is also designed to handle a second switching operation following the first switching operation, wherein the switch arm switches in the other of the two directions:

[0051] - The command initially closed the switch to open;

[0052] - Determine the dead time for the second handover operation based on the dead time of the previous first handover operation; and

[0053] - At the end of the dead time determined for this second switching operation, the switch that was initially disconnected by the command is closed.

[0054] Optionally, the determined dead time extends from the command to disconnect the initially closed switch until a crossover is detected.

[0055] Alternatively, the control system is designed to determine the dead time of the first switching operation based on the time interval between the command to disconnect the initially closed switch and the detection of the crossover, such that the dead time ends later than the detection of the crossover.

[0056] Alternatively, the switching voltage is the voltage between the terminals of the low-side switch.

[0057] Alternatively, the first switching operation can be a switching operation from the first configuration to the second configuration.

[0058] Alternatively, the dead time of the second switching operation can be equal to the dead time of the first switching operation.

[0059] Alternatively, the dead time of the second handover operation may be greater than the dead time of the first handover operation, for example, equal to the dead time of the first handover operation plus a predefined duration.

[0060] Alternatively, the switching system may also include capacitors between the terminals of the high-side switch and capacitors between the terminals of the low-side switch.

[0061] A method for switching an arm designed to connect to a voltage source designed to provide DC voltage is also proposed, comprising a high-side switch having current input and current output terminals and a low-side switch having current input and current output terminals, wherein the current output terminal of the high-side switch and the current input terminal of the low-side switch are connected to each other at a center tap, the method comprising:

[0062] - Alternately switch the switch arm in two directions between a first configuration and a second configuration. In the first configuration, the high-side switch is open and the low-side switch is closed, so that the center tap has zero voltage. In the second configuration, the high-side switch is closed and the low-side switch is open, so that the center tap has DC voltage. Each configuration switching operation includes a command to open the initially closed switch and then a command to close the initially open switch at the end of the dead time.

[0063] The first switching operation, in which the switch arm switches in the first direction of the two directions, further includes:

[0064] - After a command to disconnect a closed switch, monitor the switching voltage present between the terminals of one of the switches; and

[0065] - Based on the monitored switching voltage, the dead time for this current first switching operation is determined as follows:

[0066] • Detect when the switching voltage crosses a predefined threshold between zero voltage and DC voltage, and

[0067] • The dead time for the first handover operation is determined based on the detection of the crossover.

[0068] It also includes a second switching operation following the first switching operation, wherein the switch arm switches in the other of the two directions:

[0069] - The command initially closed the switch to open;

[0070] - Determine the dead time for the second handover operation based on the dead time of the first handover operation; and

[0071] - At the end of the dead time determined for this second switching operation, the switch that was initially disconnected by the command is closed.

[0072] A computer program capable of being downloaded from a communication network and / or stored on a computer-readable medium is also proposed, characterized in that, when executed on a computer, the computer program includes instructions for performing steps of the switching method according to the invention. Attached Figure Description

[0073] The invention will be better understood with the aid of the following description, which is given by way of example only and with reference to the accompanying drawings, wherein:

[0074] Figure 1 This is a circuit diagram illustrating a switching system according to an embodiment of the present invention.

[0075] Figure 2 This is a block diagram illustrating the steps of a switching method according to an embodiment of the present invention.

[0076] Figure 3 This is a sequence diagram showing when implementation... Figure 2 When using the method, Figure 1 The evolution of electrical quantity in the switching system over time

[0077] Figure 4 This is a block diagram illustrating the steps of a switching method according to another embodiment of the present invention, and

[0078] Figure 5 This is a sequence diagram showing when implementation... Figure 4 When using the method, Figure 1 The evolution of electrical charge in the switching system over time. Detailed Implementation

[0079] refer to Figure 1 An example of an electrical device 100 that implements the present invention will now be described.

[0080] Electrical equipment 100, for example, forms part of a motor vehicle, such as a vehicle with electric or thermoelectric hybrid propulsion.

[0081] Electrical equipment 100 primarily includes a motor having three phases U, V, W, for example, stator phases. The motor is designed, for example, to selectively operate in motor mode and generator mode.

[0082] The electrical device 100 also includes a DC voltage source 102 designed to provide a DC voltage VHT relative to the electrical ground 104 of the electrical device 100. The voltage source 102 includes, for example, a battery. The voltage VHT is typically high, for example, greater than 100V.

[0083] The electrical equipment 100 also includes a voltage converter 106, which is designed to perform the conversion between the DC voltage VHT and the AC phase voltage that appear on phases U, V, and W, respectively.

[0084] To this end, voltage converter 106 includes three switching arms 108, 110, and 112, dedicated to the motor's phases U, V, and W respectively, and designed to alternately connect the relevant phases U, V, and W to voltage source 102 (i.e., DC voltage VHT) and electrical ground 104 (i.e., zero voltage). When the motor operates in motor mode, voltage converter 106 is designed to operate in inverter mode to convert DC voltage VHT into phase voltages. When the motor operates in generator mode, voltage converter 106 is designed to operate in rectifier mode to convert phase voltages into DC voltage VHT, for example, to recharge DC voltage source 102.

[0085] Switch arms 108, 110, and 112 are identical, so only switch arm 110 will be described in detail.

[0086] The switching arm 110 includes a high-side switch Q6 with a current input terminal HC and a current output terminal HE, and a low-side switch Q2 with a current input terminal LC and a current output terminal LE. The current output terminal HE of the high-side switch 104 and the current input terminal LC of the low-side switch 106 are connected to each other at a center tap M, which itself is connected to one of the corresponding phases of the motor, i.e., phase V for the switching arm 110. Furthermore, the current input terminal HC of the high-side switch Q6 is connected to a DC voltage source 102, and the current output terminal LE of the low-side switch Q2 is connected to electrical ground 104.

[0087] Each switch Q6, Q2 also has control terminals, labeled HG and LG, respectively. Each control terminal HG, LG is designed to receive commands to selectively open and close the corresponding switch Q6, Q2. When open and closed, respectively, switches Q6, Q2 are designed to prevent and allow current to flow from their current input terminals HC, LC through them to their current output terminals HE, LE, respectively. This command is typically in the form of a voltage between the control terminals and the current output terminals, denoted as HVGE for the high-side switch Q6 and LVGE for the low-side switch Q2.

[0088] The switch arm 110 also includes capacitor C2 between terminals HC and HE of the high-side switch Q6 and capacitor C4 between terminals LC and LE of the low-side switch Q2. Capacitors C2 and C4 are soft-switching capacitors, abbreviated as ZVS (representing zero-voltage switching).

[0089] Switches Q6 and Q2 are, for example, semiconductor transistors, such as MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or IGBT (Insulated Gate Bipolar Transistor).

[0090] The voltage converter 106 also includes a control system 114 for controlling the switching arms 108, 110, and 112, which is designed to alternately switch each switching arm 108, 110, and 112 between a first configuration and a second configuration, in which the high-side switch is open and the low-side switch is closed, and in the second configuration, the high-side switch is closed and the low-side switch is open. Therefore, in the first configuration, the phases U, V, and W associated with the switching arms 108, 110, and 112 are connected to electrical ground 104 to apply zero voltage thereto, while in the second configuration, the phases U, V, and W associated with the switching arms 108, 110, and 112 are connected to a DC voltage source 102 to apply a DC voltage VHT thereto. For this purpose, the control system 114 is designed to command the initially closed switch to open for each configuration switching operation, and then command the initially open switch to close at the end of the dead time. The initially closed or open switch is understood to be the switch that was in a closed or open state, respectively, at the start of the current switching operation.

[0091] The operation of control system 114 will be referred to below. Figures 2 to 5 To provide a more detailed description.

[0092] The voltage converter 106 also includes a measuring device 116 for measuring the switching voltage between the current input and output terminals of one of the switches Q6 and Q2.

[0093] In the described example, the measured switching voltage is the voltage LVCE between the current input and output terminals LC and LE of the low-side switch Q2.

[0094] In the described example, the measuring device 116 is designed to provide the control system 114 with a measured voltage VM representing the voltage LVCE. More specifically, in the described example, the measured voltage VM is the waveform of the voltage LVCE. For this purpose, the measuring device 116 includes, for example, a high-frequency filtering element designed to filter the high frequencies of the voltage LVCE so as to retain only the low frequencies that form the waveform of the voltage LVCE.

[0095] In the described example, the measuring device 116 first includes an output point PS intended to have a measuring voltage VM.

[0096] The measuring device 116 also includes an input diode D2 connected between the center tap M and the output point PS, allowing conduction in the direction of the center tap M.

[0097] The measuring device 116 also includes, for example, a first DC voltage source V4 of 12V.

[0098] The measuring device 116 also includes a high-frequency filtering circuit, which includes a capacitor C1 and a resistor R6 connected in parallel between the DC voltage source V4 and the output point PS.

[0099] The measuring device 116 also includes, for example, a second DC voltage source V3 of 12V and a voltage divider circuit, which includes resistors R2 and R5 connected to each other at the center tap.

[0100] The measuring device 116 also includes a diode D1 connected between the center tap of resistors R2 and R5 and the output terminal S.

[0101] refer to Figure 2 and 3 An example of a switching method 200 according to a first embodiment of the present invention will now be described.

[0102] At the start of method 200, in step 202, switch arm 110 is in a first configuration: high-side switch Q6 is open, while low-side switch Q2 is closed.

[0103] In step 204, the control system 114 initiates the switching operation from the first configuration to the second configuration at time t1 by commanding to open the initially closed switch (that is, the low-side switch Q2 in this case).

[0104] In step 206, after the command to disconnect the low-side switch Q2 is given, the control system 114 monitors the switching voltage LVCE of the low-side switch Q2 by monitoring the measured voltage VM.

[0105] In step 208, the control system 114 determines the dead time TM of the current switching operation based on the monitored switching voltage LVCE.

[0106] Therefore, in step 210, the control system 114 detects at time t2 that the switching voltage LVCE crosses a predefined threshold S. Using a waveform advantageously allows for the limitation of rapid oscillations near the threshold, and thus limits unwanted detection.

[0107] Next, in step 212, the control system 114 determines the dead time TM based on the detection of the crossover. In the described example, the dead time TM extends from the disconnect command (time t1) to the detection of the crossover (time t2).

[0108] Therefore, the dead time TM is determined by the following formula:

[0109]

Mathematical Formula 1

[0110] TM = t2 – t1

[0111] Alternatively, the dead time TM can be determined based on the time interval t2–t1 between the command to disconnect the low-side switch Q2 (time t1) and the detection of the crossover (time t2), such that the dead time TM ends later than the detection of the crossover t2, so that it can be used for the current switching operation.

[0112] For example, the dead time TM can be extended from the disconnect command (time t1) to the detection of a crossover (time t2) plus a predefined duration P1. Therefore, the dead time TM will be determined using the following equation:

[0113]

Mathematical Formula 2

[0114] TM = t2 – t1 + P1

[0115] In step 216, the control system 114 records the dead time TM.

[0116] In step 218, the control system 114 commands the initially open switch to be closed at the end of the dead time TM, that is, in this case, the high-side switch Q6.

[0117] Therefore, when the dead time TM extends from the disconnect command (time t1) to the detection of the crossover (time t2), the control system 114 commands the initially disconnected switch to close when the crossover is detected, that is, in this case, the high-side switch Q6.

[0118] Step 218 can be performed before or during step 216.

[0119] The switching operation from the first configuration to the second configuration is thus completed, and in step 220, the switch arm 110 is correctly in its second configuration: the high-side switch Q6 is closed and the low-side switch Q2 is open.

[0120] In step 222, the control system 114 initiates a new switching operation at time t3 by commanding the initially closed switch (that is, the high-side switch Q6 in this case) to open.

[0121] In step 224, the control system 114 determines the dead time of the current switching operation based on the dead time TM of the previous switching operation.

[0122] In the example described, the dead time of the current switching operation is equal to the dead time TM of the previous switching operation.

[0123] Therefore, at the end of the dead time TM, in step 226, the control system 114 commands the initially open switch to be closed, that is, in this case, the low-side switch Q2.

[0124] Alternatively, the determined dead time can be greater than the dead time TM of the previous handover operation, for example, equal to the dead time of the previous handover operation plus a predefined duration P2. In this case, the following equation can be used:

[0125]

Mathematical Expression 3

[0126] TM(after) = TM(before) + P2

[0127] The switching operation from the second configuration to the first configuration is thus completed, and at the end of step 230, the switch arm 110 is correctly in its first configuration: the high-side switch Q6 is closed and the low-side switch Q2 is open.

[0128] Method 200 can then be repeated by returning to step 202.

[0129] refer to Figure 4 and 5 An example of a switching method 400 according to a second embodiment of the present invention will now be described.

[0130] In this second embodiment of the invention, the dead time of each successive switching operation is determined based on the monitored switching voltage, whereas in the first embodiment of the invention, the dead time of each switching operation from the second configuration to the first configuration is determined based on the dead time of the previous switching operation (the switching operation from the first configuration to the second configuration).

[0131] When threshold crossing is used to determine dead time, different thresholds are preferably used for handover operations from the first configuration to the second configuration and from the second configuration to the first configuration. These thresholds are denoted as S1 and S2, respectively, and threshold S1 is greater than threshold S2.

[0132] More specifically, method 400 includes steps 202 to 220, which are already described in relation to the switching operation from the first configuration to the second configuration.

[0133] For a reverse switching operation (from the second configuration to the first configuration), method 400 includes steps 204', 206', 208' and 218' which are the same as steps 204, 206, 208 and 218 respectively, except that the roles of the switches are reversed and threshold S2 is used instead of threshold S1, thereby potentially giving a dead time TM2 for the current switching operation that is different from the dead time TM1 of the previous switching operation.

[0134] As described above, in the first configuration of switch arms 108, 110, 112, the center tap M is connected to electrical ground 104 to apply zero voltage to it, thus having the zero voltage, while in the second configuration, the center tap M is connected to DC voltage source 102 to apply DC voltage VHT to it, thus having the DC voltage VHT.

[0135] Furthermore, advantageously and as shown in the figure, each predetermined threshold S, S1, S2 is between zero voltage and DC voltage VHT. In the described example, since DC voltage VHT is positive, these thresholds are positive. Additionally, for example, thresholds S and S1 are between 85% and 95% of DC voltage VHT, respectively, while threshold S2 is, for example, between 5% and 15% of DC voltage VHT.

[0136] Clearly, the switching system described above allows the dead time to be determined solely based on the switching voltage and predefined data (P1, P2 in this example), independent of the operating state of the voltage converter and / or the motor. Furthermore, since the dead time is determined by measuring the switching voltage, it exhibits fundamentally similar reliability regardless of the motor's operating point and requires very simple hardware: adaptability to both the control system and the measuring device, which can be quite simple, for example… Figure 1 The measuring device shown.

[0137] It will also be noted that the present invention is not limited to the embodiments described above. In fact, it will be apparent to those skilled in the art, based on the teachings just disclosed to them, that various modifications can be made to the embodiments described above.

[0138] Specifically, the dead time of the current switching operation can be determined based on the monitored switching voltage in a manner different from the detection threshold crossing. For example, the dead time of the current switching operation can be determined based on the slope of the monitored switching voltage.

[0139] In addition, the measured switching voltage can be the voltage of the high-side switch, for example, between the center tap M and the DC voltage source 102.

[0140] Furthermore, the present invention can be adapted to any electrical device that uses a switching arm, such as a DC / DC voltage converter or an on-board charger, especially when soft switching is desired.

[0141] Furthermore, the described steps can be performed in any other technically feasible order.

[0142] In the detailed disclosure of the invention given above, the terminology used should not be construed as limiting the invention to the embodiments disclosed herein, but should be interpreted to include all equivalents thereof, provided within the capacity of those skilled in the art to implement the teachings just disclosed to them by applying their general knowledge.

Claims

1. A switching system comprising: - a switching arm (110) for connection to a voltage source (102) designed to provide a DC voltage (VHT) and comprising two switches, a high-side switch (Q6) and a low-side switch (Q2), each switch having a current input terminal (HC, LC) and a current output terminal (HE, LE), the current output terminal (HC) of the high-side switch (Q6) and the current input terminal (LC) of the low-side switch (Q2) being connected to each other at a center tap (M); - a control system (114) for controlling the switching arm (110) designed to switch the switching arm (110) in two directions alternately between a first configuration in which the high-side switch (Q6) is open and the low-side switch (Q2) is closed so that the center tap (M) has a zero voltage and a second configuration in which the high-side switch (Q6) is closed and the low-side switch (Q2) is open so that the center tap (M) has the DC voltage (VHT), the control system (114) being designed to, for each switching operation: • command the switch that was initially closed to open, then, • at the end of a dead time (TM; TM1, TM2), command the switch that was initially open to close; and - a measuring device (116) for measuring a switching voltage (LVCE) present between the terminals (LC, LE) of one of the switches (Q2); wherein the control system (114) is further designed to, for a first switching operation in which the switching arm is switched in a first one of said two directions: - monitor the measured switching voltage (LVCE) after the command to open the switch that was initially closed; and - determine the dead time (TM; TM1; TM2) for this first switching operation based on the monitored switching voltage (LVCE) by: • detecting when the switching voltage (LVCE) crosses a predefined threshold (S; S1, S2) between the zero voltage and the DC voltage (VHT), and • determining the dead time (TM; TM1, TM2) for this first switching operation based on the detection of said crossing; wherein the control system (114) is further designed to, for a second switching operation after the first switching operation and in which the switching arm is switched in the other one of said two directions: - command the switch that was initially closed to open; - determine the dead time (TM) for this second switching operation based on the dead time (TM) of the previous first switching operation; and - at the end of the dead time (TM) determined for this second switching operation, command the switch that was initially open to close, and wherein the control system (114) is designed to determine the dead time of said first switching operation based on the time interval between the command to open the switch that was initially closed and the detection of said crossing, so that the end of this dead time is later than the detection of said crossing.

2. The switching system of claim 1 wherein, The switching voltage (LVCE) is the voltage between the terminals (LC, LE) of said low-side switch (Q2).

3. The switch system of any of claims 1-2, wherein, The first switching operation is a switching operation from said first configuration to said second configuration.

4. The switch system of any one of claims 1 to 2, wherein, The dead time of the second switching operation is equal to the dead time of the first switching operation.

5. The switch system of any of claims 1 to 2, wherein, The dead time of the second switching operation is greater than the dead time of the first switching operation, for example equal to the dead time of the first switching operation plus a predefined duration.

6. The switching system of any one of claims 1 to 2, further comprising a capacitor (C2) between the terminals (HC, HE) of the high-side switch (Q6) and a capacitor (C4) between the terminals (LC, LE) of the low-side switch (Q2).

7. A method (200; 400) for switching a switch arm (110) intended to be connected to a voltage source (102) designed to provide a DC voltage (VHT) and comprising a high-side switch (Q6) having a current input terminal (HC) and a current output terminal (CE) and a low-side switch (Q2) having a current input terminal (LC) and a current output terminal (LE), the current output terminal (LE) of the high-side switch (Q6) and the current input terminal (LC) of the low-side switch (Q2) being connected to each other at a center tap (M), the method (200; 400) comprises: - alternating switching of the switching arm (110) between a first configuration in which the high-side switch is open and the low-side switch is closed so that the center tap (M) has a zero voltage, and a second configuration in which the high-side switch is closed and the low-side switch is open so that the center tap (M) has a DC voltage (VHT), in both directions, each configuration switching operation comprising a command to open the initially closed switch, and then a command to close the initially open switch at the end of a dead time; for a first switching operation in which the switching arm is switched in a first one of said two directions, further comprising: - monitoring (206) a switching voltage (LVCE) present between the terminals (LC, LE) of one of the switches (Q2) after the command to open (204) the closed switch (Q2); and - determining (208) a dead time for this first switching operation based on the monitored switching voltage (LVCE) by: • detecting when the switching voltage (LVCE) crosses a predefined threshold (S; S1, S2) between the zero voltage and the DC voltage (VHT), and • determining a dead time (TM; TM1, TM2) for this first switching operation based on the detection of said crossing; characterized in that it further comprises for a second switching operation following the first switching operation and in which the switching arm is switched in the other one of said two directions: - commanding the initially closed switch to open; - determining a dead time (TM) for this second switching operation based on the dead time (TM) of the preceding first switching operation; and - commanding the initially open switch to close at the end of the dead time (TM) determined for this second switching operation, and in which the control system (114) is designed to determine the dead time of said first switching operation based on the time interval between the command to open the initially closed switch and the detection of said crossing, so that the end of this dead time is later than the detection of said crossing.

8. A computer program product downloadable from a communication network and / or stored on a computer readable medium, characterized in that, The computer program when executed on a computer comprises instructions for performing the steps of the switching method as claimed in claim 7. The computer program when executed on a computer comprises instructions for performing the steps of the switching method as claimed in claim 7.

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