Autonomous safety device and electrical system including the same

Abstract

Safety device, comprising: a. a main input terminal (A) intended to be connected to a first DC voltage source (BAT); b. a main output terminal (B) intended to be connected to a first electronic device (Ep1) and a second electronic device (Ep2); c. switching means (10, 100) comprising an input terminal (E), an output terminal (S) and a control terminal (G), the input terminal of the switching means (10, 100) being connected to the main input terminal (A), the output terminal of the switching means (10, 100) being connected to the main output terminal (B), said switching means (10, 100) comprising at least a first switch (Q1), the control terminal (G) of the switching means (10, 100) being connected to control means (30) so as to open or close said at least first switch (Q1); d. filtering means (20, 200) connected between the current input terminal (E) and the control terminal (G) of the switching means (10); e. characterized in that: when the switch control means (30) is ineffective and a discharge current flows through a parasitic inductance (L) between the first device (Ep1) and the second device (Ep2), said filtering means (20, 200) controls the switching means (10, 100) in its linear region.

Description

Technical Field

[0001] The present invention generally relates to a safety device for an electrical system in a motor vehicle. Background Art

[0002] More specifically, the present invention relates to an electrical system including a safety device, which is designed to control a switching device that allows dissipation of a discharge current generated by a parasitic inductance when disconnecting an electrical device from the electrical network of a motor vehicle. The safety device also makes it possible to filter electrical interference superimposed on the electrical network of the vehicle, thereby avoiding any untimely triggering of the switching device.

[0003] An electric vehicle or a hybrid vehicle is equipped with a power supply network for powering all electrical devices such as an alternator-starter or a DC voltage converter, and a switching device connected between a DC power supply and the electrical devices to disconnect them from the electrical network. In this type of electrical network, the connections between various electrical devices require cables of relatively long lengths, thus generating parasitic inductance and overvoltage.

[0004] A known problem is the dissipation of electrical energy contained in the parasitic inductance when disconnecting an electrical device from the electrical network of a motor vehicle.

[0005] This problem is particularly difficult to solve when disconnecting an electrical device supplied with at least 48V DC voltage from an electrical network including a switching device that is also sensitive to overvoltage caused by parasitic inductance and when it is necessary to dissipate a discharge current of approximately 500A or more.

[0006] Therefore, when disconnecting an electrical device from the electrical network of a motor vehicle, it is necessary to dissipate the discharge current so as not to damage the components of the electrical network.

[0007] To achieve this, in the prior art, an electrical system including a safety device as shown in, for example, Figure 1 is known. Such an electrical system SE1 includes a safety device 40, which includes:

[0008] a. A main input terminal A, which is designed to be connected to a first DC voltage source BAT

[0009] b. A main output terminal B, which is designed to be connected to a first electronic device Ep1 and a second electronic device Ep2,

[0010] c. A switching device 100, which includes an input terminal E, an output terminal S, and a control terminal G. The input terminal of the switching device 100 is connected to the main input terminal A, and the output terminal of the switching device 100 is connected to the main output terminal B. The switching device 100 includes at least a first switch Q1 and a second switch Q2, and the control terminal G of the switching device 100 is connected to a control device 30 to open or close the first switch Q1 or the second switch Q2.

[0011] d. A TVS filtering device, which is connected between the current output terminal S and the electrical ground;

[0012] Therefore, in the electrical system of the prior art, the safety device includes a transient voltage suppressor or a TVS component, such as a diode arranged to turn in the reverse mode (avalanche mode), which allows excessive current to be injected into the electrical ground to clamp the switching voltage. However, the TVS component has the problem of temperature drift, and its dynamic resistance is not clearly defined. In addition, when the voltage to be restricted is high, the selection of TVS is small, and the power induced in these TVSs is high. TVS components usually have a low impedance to limit overvoltage in the case of high discharge current, and these components also have a very high cost and a large volume. Summary of the Invention

[0013] The object of the present invention is to overcome the above problems at least partially.

[0014] To this end, according to a first aspect, what is proposed is an electrical system having a safety device, and the safety device includes:

[0015] a. A main input terminal, which is intended to be connected to a first DC voltage source;

[0016] b. A main output terminal, which is intended to be connected to a first electronic device and a second electronic device;

[0017] c. A switching device, which includes an input terminal, an output terminal, and a control terminal. The input terminal of the switching device is connected to the main input terminal, the output terminal of the switching device is connected to the main output terminal, the switching device includes at least a first switch, and the control terminal of the switching device is connected to a control device to open or close at least the first switch;

[0018] d. A filtering device, which is connected between the current input terminal and the control terminal of the switching device,

[0019] e. It is characterized in that: when the switch control device is invalid and the discharge current flows through the parasitic inductance between the first device and the second device, the filtering device controls the switching device in its linear region.

[0020] What is remarkable about this safety device is that the dissipation of the discharge current is achieved by the first switch and the second switch by using at least a part of the discharge current to control the first switch and the second switch in the linear region.

[0021] Therefore, the discharge current of the parasitic inductor is dissipated by the first switch and the second switch, and no transient overvoltage component is required anymore.

[0022] In a specific embodiment of the present invention, the switching device includes:

[0023] a. A first switch, including:

[0024] i. A current input terminal, which is connected to the input terminal of the switching device;

[0025] ii. A current output terminal, which is connected to the output terminal of the switching device;

[0026] iii. A control terminal, which is connected to the control terminal of the switching device.

[0027] In a specific embodiment of the present invention, the filtering device includes:

[0028] a. A first resistor, which is connected to the current input terminal on one side and connected to the control terminal of the switching device through a fourth diode on the other side;

[0029] b. A first capacitor, which is connected in parallel with the first resistor;

[0030] c. A fourth diode, whose positive electrode is connected to a resistor and whose negative electrode is connected to the control terminal of the switching device.

[0031] Optionally, the filtering device further includes a Zener diode, whose cathode is connected to the cathode of the fourth diode and whose anode is connected to the control terminal of the switching device.

[0032] Optionally, the switch is a MOSFET, or an IGBT, or a bipolar transistor.

[0033] In a specific embodiment of the present invention, the switching device includes a first switch and a second switch,

[0034] a. The first switch includes:

[0035] i. An input terminal, which is connected to the input terminal,

[0036] ii. An output terminal, which is connected to the output terminal of the second switch,

[0037] iii. A control terminal, which is connected to the control terminal of the switching device,

[0038] b. The second switch includes:

[0039] i. An input terminal, which is connected to the output terminal,

[0040] ii. An output terminal, which is connected to the current output terminal of the first switch,

[0041] iii. A control terminal, which is connected to the control terminal of the switching device.

[0042] In a specific embodiment of the present invention, the filtering device further comprises:

[0043] a. A diode bridge, which comprises:

[0044] i. A first branch, which is formed by a first diode in series with a second diode, the anode of the second diode is connected to the current output terminal of the second switch, the cathode of the first diode is connected to the cathode of the fourth diode, and the midpoint of the first diode and the second diode is connected to the output terminal of the switching device,

[0045] ii. A second branch, which is formed by a third diode and a fourth diode, the anode of the third diode is connected to the output terminal of the first switch, and the cathode of the third diode is connected to the anode of the fourth diode,

[0046] b. A second resistor, which is connected between the current output terminal of the second switch and the control terminal of the switching device.

[0047] Optionally, the filtering device further comprises a second capacitor, which is connected between the output terminal of the first switch and the control terminal of the switching device.

[0048] Optionally, a resistor is connected between the control terminal of the switching device and the control device to separate the control voltage of the switching device from the voltage of the control device (30).

[0049] According to a second aspect, another subject of the present invention is a voltage converter comprising a safety device according to the first aspect of the present invention.

[0050] Specifically, the voltage converter is a DC-DC voltage converter or an AC-DC voltage converter.

[0051] In other embodiments, it is also conceivable that the filtering device and the voltage converter according to the present invention have all or some of the above-mentioned feature combinations. Description of the Drawings

[0052] Figure 1 shows an electrical system including a safety device according to the prior art.

[0053] Figure 2 shows an electrical system including a safety device implementing the invention according to the first embodiment of the present invention.

[0054] ​​​Figure 3 shows an electrical system including a safety device implementing the invention according to the second embodiment of the present invention. Detailed Description

[0055] Reference Figure 2 , the electrical system SE2 implementing the present invention will now be described. The safety device 2 is integrated, for example, into the electrical network of a motor vehicle. In the example described, the switching device 10 includes a switch Q1, which is a MOSFET.

[0056] The electrical system SE2 includes:

[0057] a. A first electronic device Ep1 and a second electronic device Ep2, which are connected to the main output terminal B of the safety device 2.

[0058] b. A safety device 2, which includes:

[0059] i. A main input terminal A, which is connected to a first DC voltage source BAT, such as a battery supplying a voltage of 48V.

[0060] ii. A main output terminal B, which is connected to the first electronic device Ep1 and the second electronic device Ep2.

[0061] iii. A switching device 10, which includes:

[0062] 1. An input terminal E, connected to the main input terminal A,

[0063] 2. An output terminal S, connected to the main output terminal B,

[0064] 3. A control terminal G, connected to the control device 30 via a resistor R.

[0065] iV. A filtering device 20, which is connected between the current input terminal E and the control terminal G of the switching device 10;

[0066] v. A switch control device 30, which is connected to the control terminal G of the switching device 10 via a resistor R.

[0067] The first and second devices Ep1 and Ep2 are, for example, devices such as an alternator-starter, or a voltage converter such as an inverter. The first device Ep1 is connected to electrical ground and has a voltage Vep1 between its terminals, and the second device Ep2 is connected to electrical ground and has a voltage Vep2 between its terminals.

[0068] The electrical connection between the first electronic device Ep1 and the second electronic device Ep2 generates a wiring inductance or parasitic inductance L. Therefore, when the first electronic device Ep1 and the second electronic device Ep2 are supplied with electrical energy, a current I flows through this parasitic inductance.

[0069] The switching device 10 includes a first switch Q1. The drain current input terminal of the first switch Q1 is connected to the input terminal E, the current output terminal s1 of the first switch Q1 is connected to the output terminal S, and the control terminal g1 is connected to the control terminal G.

[0070] In this way, the control device 30 enables the opening or closing of the first switch Q1 to be controlled. When the control device 30 controls the first switch Q1 to be closed, the current I can flow in the direction from the input terminal E to the output terminal S, and when the control device 30 controls the first switch Q1 to be opened, no current flows from the input terminal E to the output terminal S.

[0071] The value of the resistor R connected between the control device 30 and the control terminal G is selected to protect the control device 30. The value of the resistor R is also selected to direct the currents If and Ip to the control terminal G. In other words, the value of the resistor R is non-zero and is selected to separate the voltage of the control device 30 from the control voltage of the switching device 10, and the resistance value R is selected to be preferably higher than 1 ohm, and even more preferably higher than 10 ohms.

[0072] In other words, when the first switch Q1 is controlled by the control device 30 to be closed, the first and second electronic devices Ep1 and Ep2 are supplied with electrical energy. When the first switch Q1 is controlled to be closed, the state of the first switch Q1 is in the saturation state, and when the switch Q1 is controlled to be opened, it is in the cut-off state.

[0073] In the example considered, the filtering device 20 includes:

[0074] a. A first resistor R1, which is connected to the current input terminal E on one side and is connected to the control terminal G of the switching device 10 via a fourth diode D4 and a zener diode DZ1.

[0075] b. A first capacitor C1, which is connected in parallel with the first resistor R1.

[0076] c. A fourth diode D4, which is connected in series with the first resistor R1, and the cathode is connected to the control terminal G via the zener diode DZ1. The anode is connected to the first resistor R1.

[0077] d. A zener diode DZ1, whose cathode is connected to the cathode of the diode D4, and whose anode is connected to the control terminal G.

[0078] Therefore, when the control device 30 controls the first switch Q1 to be closed, the current I flows through the parasitic inductor L. When the control device 30 controls the first switch Q1 to be opened, the parasitic inductor L generates a discharge current Id generated by the current I and a voltage across its terminals, which results in an overvoltage between the output terminal S and the input terminal E of the switching system 10.

[0079] Specifically, as defined in [Math.1], the voltage Va–Vb is directly applied to the switching voltage Vds of the first switch Q1.

[0080] [Math.1]

[0081] V ds = V A - V B

[0082] When the first switch Q1 is turned off, the filter circuit 20 makes it possible to avoid overvoltage and thus prevent the voltage between the output terminal S and the input terminal E from exceeding a predetermined threshold. In the example described, the voltage between the output terminal S and the input terminal E is the switching voltage Vds of the first switch Q1.

[0083] The relationship between the overvoltage or switching voltage Vds seen by the switch Q1 and the filter circuit 20 is defined as:

[0084] [Math.2]

[0085] V ds = V dz1 + V d4 + V gsth

[0086] As the first switch Q1 starts to turn off, the control voltage Vgs decreases, tending towards zero voltage, and thus the switching voltage Vds increases.

[0087] When the control voltage Vgs of the first switch Q1 decreases, the intrinsic resistance Rdson of the first switch Q1 increases.

[0088] Then the impedance of the filter circuit 20 is calculated such that when the impedance of the first switch Q1 increases, the current If derived from the discharge current Id can flow through the filter circuit 20. The current If is at least a part of the discharge current Id, which allows the first capacitor C1 to be charged. Correspondingly, the switching voltage Vds is applied to the first capacitor C1 to allow the first capacitor C1 to be charged.

[0089] The current flowing through the first capacitor C1 then supplies power to the control terminal G through the diode D4 and the Zener diode DZ1 to keep the first switch Q1 in the on state. The voltage across the terminals of the first capacitor C1 keeps the control voltage Vgs of the first transistor Q1 in its linear region, thus preventing the control voltage Vgs from being zero.

[0090] Advantageously, the first resistor R1 and the first capacitor C1 make it possible to filter low-frequency interference up to 1 kHz, preferably up to 10 kHz, to prevent interference from causing the switch Q1 to turn on again when the switch Q1 is controlled to be in the off state and when the electronic device Ep2 is inactive, and the voltage Vep2 is substantially zero.

[0091] Since the first switch Q1 is controlled in its linear region, its intrinsic resistance decreases and the switch voltage Vds also decreases.

[0092] In other words, the filtering device 20 enables the control voltage Vgs of the first switch Q1 to be feedback-controlled in its linear region to cancel out the discharge current transmitted by the parasitic inductor L.

[0093] When the first switch Q1 is controlled in its linear region, the time for canceling out the discharge current Id included in the parasitic inductor L is determined by [Math.3].

[0094] [Math.3]

[0095]

[0096] In other words, according to [Math.2] and [Math.3], the discharge current Id decreases at a slope determined by the sum of the Zener voltage Vdz1, the voltage across the terminals of the diode D4, and the control voltage Vgs, and thus the time (ΔT) for canceling out the discharge current Id directly depends on the sum of the voltages.

[0097] In another way of putting it, when the control device 30 is ineffective, the filtering device 20 enables the first switch Q1 to be controlled in its linear region so as to dissipate the discharge current Id via the first switch Q1. The dissipation of the discharge current occurs during the cancellation time defined by [Math.3]. When the first switch Q1 is controlled by the control device 30, the filtering device 20 is ineffective.

[0098] A second embodiment of the present invention will be described. Figure 3 shows this second embodiment. For simplicity, the same reference numerals are given to those elements that are common to the first embodiment and shown in Figure 2

[0099] In the example described, the electrical system SE3 includes:

[0100] a. A first electronic device Ep1 and a second electronic device Ep2.

[0101] b. The safety device 3 includes:

[0102] i. A main input terminal A.

[0103] ii. A main output terminal B.

[0104] iii. A switching device 100

[0105] iv. A filtering device 200

[0106] v. A switch control device 30

[0107] The switching device 100 includes a first switch Q1 and a second switch Q2 connected "back-to-back", in other words, the first switch Q1 and the second switch Q2 are connected in a "common source" configuration. In the example described herein, the first switch Q1 and the second switch Q2 are n-doped MOSFETs. The current input terminal d1 of the first switch Q1 is connected to the input terminal E, the current output terminal s1 of the first switch Q1 is connected to the current output terminal s2 of the second switch Q2, and the control terminal g1 is connected to the control terminal G. The current input terminal d2 of the second switch Q2 is connected to the output terminal S, and the control terminal g2 is connected to the control terminal G. Thus, when one of the first switch Q1 and the second switch Q2 is open, no current can flow between the input terminal E and the output terminal S. The control terminals of the first switch Q1 and the second switch Q2 are also connected to each other. Therefore, the control device 30 enables the opening of the first switch Q1 and the second switch Q2, and thus interrupts any current flow in both directions between the input terminal E and the output terminal S.

[0108] In the example considered, the filtering device (200) further comprises:

[0109] a. A diode bridge, which includes:

[0110] i. A first branch, which is formed by a first diode D1 in series with a second diode D2. The anode of the second diode D2 is connected to the current output terminal of the second switch Q2, the cathode of the first diode D1 is connected to the cathode of the fourth diode D4, and the midpoint of the first diode and the second diode is connected to the output terminal S of the switching device 10.

[0111] ii. A second branch, which is formed by a third diode D3 and a fourth diode D4. The anode of the third diode D3 is connected to the output terminal s1 of the first switch Q1, and the cathode of the third diode D3 is connected to the anode of the fourth diode D4.

[0112] b. A first resistor R1, which is connected on one side to the input terminal E and on the other side to the midpoint of the third diode D3 and the fourth diode D4.

[0113] c. A first capacitor C1, which is connected in parallel with the first resistor R1.

[0114] d. A second resistor R2, which is connected between the current output terminal s of the second switch Q2 and the control terminal G.

[0115] e. A second capacitor C2, which is connected between the current output terminal of the second switch Q2 and the control terminal G.

[0116] f. A Zener diode DZ1, whose cathode is connected to the cathodes of the diodes D1 and D4, and whose anode is connected to the control terminal G.

[0117] Therefore, the control device 30 can control the opening or closing of the first switch Q1 and the second switch Q2. When the DC voltage source BAT delivers a current I, the current I is considered positive, and the current I flows through the switching device 100 in the direction from the input terminal E to the output terminal S to supply power to the first electronic device Ep1 or the second electronic device Ep2. When the first electronic device Ep1 or the second electronic device Ep2 delivers a current I, the current I is considered negative, and the current I flows through the switching device 100 in the direction from the output terminal S to the input terminal E to supply power to the DC voltage source BAT. The resistor R is connected between the control terminal G of the switching device 100 and the control device 30 to separate the control voltage of the switching device 100 from the voltage of the control device 30.

[0118] When the first switch Q1 or the second switch Q2 is opened, the parasitic inductance L generates a discharge current Id and a voltage at its terminals, which results in an overvoltage between the output terminal S and the input terminal E of the switching system 100. Specifically, the voltage Va - Vb is directly applied to the voltage between the input terminal E and the output terminal S.

[0119] In other words, when the direction of the current I is positive, when the first transistor Q1 is opened, the overvoltage Va - Vb is directly applied to the switching voltage Vds1 of the first switch Q1, and the current I can flow through the intrinsic diode of the second switch Q2. When the current I is negative, when the second switch Q2 is opened, the overvoltage Va - Vb is directly applied to the switching voltage Vds2 of the second switch Q2.

[0120] Therefore, the filter circuit 200 makes it possible to limit the overvoltage when the first switch Q1 or the second switch Q2 is opened, and thus manage the overvoltage and ensure that the voltage between the output terminal S and the input terminal E does not exceed a predetermined threshold.

[0121] The overvoltages seen by the first switch Q1 or the second switch Q2 are defined respectively in [Math.4] and [Math.5] as:

[0122] [Math.4]

[0123] V ds1 = V dz1 + V d3 + V d4 + V gsth

[0124] [Math.5]

[0125] V ds2 = V dz1 + V d1 + V d2 + V gsth

[0126] As the first switch Q1 or the second switch Q2 starts to open, the control voltage Vgs decreases, tending towards zero voltage, and thus the voltage between the input terminal E and the output terminal S increases.

[0127] Then, the impedance of the filter circuit 200 is calculated such that when the impedance of the switching device 100 increases, the current If derived from the discharge current Id can flow through the filter device 200. The current If allows the capacitor C1 to be charged, and correspondingly, the voltage between the input terminal E and the output terminal S is applied to the capacitor C1 to allow the capacitor C1 to be charged.

[0128] The filter circuit 200 is also designed to conduct at least a part of the discharge current Id to the control terminal G of the switching device 100.

[0129] Specifically, when the discharge current Id is in the positive direction, the third and fourth diodes D3 and D4 allow the conduction of the current If which is part of the discharge current Id, so as to supply power to the control terminal G of the switching device 100 through the Zener diode DZ1. In addition, when the discharge current Id is in the negative direction, the first and second diodes D1 and D2 allow the conduction of the current Ip which is part of the discharge current Id, and thus allow power to be supplied to the control terminal G of the switching device 100 through the Zener diode DZ1.

[0130] In other words, when the discharge current Id is positive, the current If allows the control terminal G to be supplied with current, and the voltage across the terminals of the capacitor C1 allows the control voltage Vgs of the first switch Q1 to be maintained in its linear region. The discharge current Id thus flows through the first switch Q1 and then through the intrinsic diode of the second switch Q2. In addition, when the discharge current Id is negative, the current Ip allows the control terminal G to be supplied with current, and the voltage across the terminals of the capacitor C2 allows the control voltage Vgs of the second switch Q2 to be maintained in its linear region. The discharge current Id thus flows through the second switch Q2 and then through the intrinsic diode of the first switch Q1.

[0131] Therefore, the filter device 200 allows the control voltage Vgs applied to the first switch Q1 and the second switch Q2 to be maintained according to the direction of the positive or negative discharge current. In the case where the first switch Q1 or the second switch Q2 is controlled in the linear region, the voltage between the input terminal E and the output terminal S decreases, and thus overvoltage can be avoided when one of the switches Q1 or Q2 is opened.

[0132] More precisely, the filter device 200 allows the control voltage Vgs of the first and second switches Q1 and Q2 to be feedback-controlled in the linear region to cancel the discharge current generated by the parasitic inductance L, regardless of whether the discharge current is in the positive or negative direction.

[0133] When the first switch Q1 or the second switch Q2 is controlled in the linear region, the times for canceling the discharge current Id included in the parasitic inductance L are determined by [Math.6] and [Math.7], respectively:

[0134] [Math.6]

[0135]

[0136] [Math.7]

[0137]

[0138] According to [Math.6] and [Math.7], the discharge current Id decreases at a slope determined by the sum of the Zener voltage Vdz1, the diode voltages D3 and D4 (or diode voltages D1 and D2), and the control voltage Vgs, and thus the time for canceling the discharge current Id directly depends on the sum of the voltages.

[0139] The filtering device 200 further includes a second resistor R2, which allows the first and second switches Q1 and Q2 to remain open when the control device 30 is disconnected.

[0140] Advantageously, the first resistor R1 having the first capacitor C1 and the second resistor R2 having the second capacitor C2 form a band-pass filter as defined in [Math.8], defining the attenuation of interference as a function of frequency, and ensuring that the first and second switches Q1 and Q2 do not re-conduct within the frequency range defined by the selection of the components of the first and second resistors R1 and R2 and the first and second capacitors C1 and C2.

[0141] [Math.8]

[0142]

Claims

1. A safety device (2, 3), comprising: a. A main input terminal (A) intended to be connected to a first DC voltage source; b. A main output terminal (B) intended to be connected to a first electronic device (Ep1) and a second electronic device (Ep2); c. A switching device (10, 100) comprising an input terminal, an output terminal and a control terminal, the input terminal of the switching device (10, 100) being connected to the main input terminal (A), the output terminal of the switching device (10, 100) being connected to the main output terminal (B), the switching device (10, 100) comprising at least a first switch (Q1), the control terminal of the switching device (10, 100) being connected to a control device (30) so as to open or close the at least first switch (Q1); d. A filtering device (20, 200) connected between the current input terminal and the control terminal of the switching device (10), e. characterized in that: when the switch control device (30) is ineffective and a discharge current flows through a parasitic inductance (L) between the first device (Ep1) and the second device (Ep2), the filtering device (20, 200) controls the switching device (10, 100) in its linear region, the filtering device (20, 200) comprising: A first resistor (R1) connected on one side to the current input terminal and on the other side to the control terminal of the switching device (10, 100) through a fourth diode (D4); A first capacitor (C1) connected in parallel with the first resistor (R1); A fourth diode (D4) having its positive electrode connected to the first resistor (R1) and its negative electrode connected to the control terminal of the switching device (10, 100).

2. The safety device according to claim 1, wherein: a. The first switch (Q1) comprises: i. A current input terminal (d1) connected to the input terminal of the switching device (10, 100); ii. A current output terminal (s1) connected to the output terminal of the switching device (10, 100); iii. A control terminal (g1) connected to the control terminal of the switching device (10, 100).

3. The safety device according to claim 1, wherein, the filtering device (20, 200) further comprises a Zener diode (DZ1) having its cathode connected to the cathode of the fourth diode (D4) and its anode connected to the control terminal of the switching device (10, 100).

4. The safety device according to claim 1, wherein, the filtering device (20, 200) further comprises: a. A diode bridge, which comprises: i. A first branch formed by a first diode (D1) in series with a second diode (D2) wherein the anode of the second diode (D2) is connected to the current output terminal of a second switch (Q2), the cathode of the first diode (D1) is connected to the cathode of the fourth diode (D4), and the connection midpoint of the first diode and the second diode is connected to the output terminal of the switching device (10, 100), ii. The second branch, which is formed by a third diode (D3) and a fourth diode (D4), The anode of the third diode (D3) is connected to the output terminal (s2) of the first switch (Q1), The cathode of the third diode (D3) is connected to the anode of the fourth diode (D4), b. A second resistor (R2), which is connected between the current output terminal (s2) of the second switch (Q2) and the control terminal of the switching device (10, 100).

5. The safety device according to claim 4, wherein, The filtering device (20, 200) further includes a second capacitor (C2), which is connected between the output terminal (s1) of the first switch (Q1) and the control terminal of the switching device (10, 100).

6. The safety device according to claim 2, wherein, The switching device (10, 100) includes a second switch (Q2), b. The second switch (Q2) includes: i. An input terminal (d2), which is connected to the output terminal, ii. An output terminal (s2), which is connected to the current output terminal of the first switch (Q1), iii. A control terminal (g2), which is connected to the control terminal of the switching device (10, 100).

7. The safety device according to any one of the preceding claims, wherein, A resistor R is connected between the control terminal of the switching device (10, 100) and the control device (30) so as to separate the control voltage of the switching device (10, 100) from the voltage of the control device (30).

8. The safety device according to claim 1, wherein, One or more switches of the switching device (10, 100) are MOSFETs, or IGBTs, or bipolar transistors.

9. A voltage converter, comprising: a. The safety device according to any one of claims 1 to 8.

10. The voltage converter according to claim 9, wherein, The voltage converter is a direct current to direct current voltage converter or an alternating current to direct current voltage converter.

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