PRECHARGE DEVICE AND DC / DC VOLTAGE CONVERTER INCLUDING SUCH A PRECHARGE DEVICE

Abstract

The invention relates to a pre-charge device (3041, Shu, 110, 120, 130, 140, µC) for a load, for example a capacitor (Ca), from a DC voltage source (102) comprising a first safety transistor (3041) capable of connecting the load (Ca) to said DC voltage source (102), and a control circuit (Shu, 110, 120, 130, 140, µC) in linear mode of the first safety transistor (3041), characterized in that said control circuit (Shu, 110, 120, 130, 140, µC) regulates the product of the pre-charge current (Ipr) and the voltage difference between the voltage measured across said DC voltage source (102) and the voltage measured across said load (Ca) with respect to a power setpoint (CP). during the linear control of the first safety transistor (3041) during the pre-charging of said load (Ca) by said DC voltage source (102),said power setpoint (CP) increasing during a first time interval from a first predefined value, for example zero, to reach a constant or approximately constant value and remain there for a second time interval following the first time interval. Figure for the abbreviation: Fig. 4,

Description

Title of the invention: PRECHARGE DEVICE AND DC / DC VOLTAGE CONVERTER INCLUDING SUCH A PRECHARGE DEVICE

[0001] The present invention relates to a pre-charge device and a DC / DC voltage converter comprising such a pre-charge device.

[0002] Electric or hybrid vehicles are equipped with a dual-voltage electrical power supply network. In such a network, the two on-board networks have different nominal DC operating voltages, and a reversible DC-DC converter (better known to those skilled in the art as a DC-DC converter, DC being the initials for "Direct Current") arranged between the two networks is necessary to carry out the energy transfers from one to the other.

[0003] A known problem is that of the initial load of the on-board network having the highest nominal voltage by the other network up to the nominal voltage of the latter.

[0004] This technical problem is particularly difficult to solve when it comes to loading an onboard electrical system, the onboard system having a nominal voltage of at least 48V and including high-value capacitors, for example on the order of a few tens of mF, from a 12V system, for example, because a very large initial current inrush, on the order of 400 A or more, can occur. This technical problem also arises when the onboard electrical system has a voltage higher than 48V, for example greater than 100V, or even greater than or equal to 400V.

[0005] It is therefore appropriate, when loading the network with the highest nominal voltage, to limit this initial current in order not to degrade either the components of this network or the components of the voltage converter itself.

[0006] To this end, a pre-charge device for a capacitance Ch such as that shown in [Fig. 1] is known from the prior art. Such a pre-charge device comprises a transistor, here a MOSFET Mo, capable of connecting the charge Ch to an electrical energy storage unit, here a voltage source 102 such as a battery with a limiting effect on a pre-charge electrical current ICh that can flow between the electrical energy storage unit 102 and the capacitance Ch, and a linear control circuit 10 for the transistor Mo, this pre-charge device being characterized in that the control circuit 10 is equipped with a device for regulating the pre-charge current ICh to a fixed reference value Iref.

[0007] Thus, the control circuit 10 measures the pre-charge current, for example by means of a shunt resistor Sh, and compares it to a fixed reference value, then based on the comparison, the control device 10 controls the transistor Mo in linear mode so as to control the precharge current ICh to the desired reference value.

[0008] Fig. 2 shows the evolution of the pre-charge current ICh as well as the temperature TMo and the power received Pre by the transistor Mo during the pre-charge of a capacitance Ch of 60 mF for a reference value Iref=18A.

[0009] As can be seen in [Fig.2], at the beginning of the precharge, the transistor Mo suddenly receives a strong powerful Pre of the order of 350W which then decreases during the precharge.

[0010] To ensure the operation of the pre-charge device according to the prior art, the transistor Mo must be sized to withstand the high power received at the beginning of the pre-charge, whereas such sizing is greater than what is needed during the rest of the pre-charge, thus making the manufacture of the pre-charge device according to the prior art expensive.

[0011] In addition, the high power received at the beginning of the precharge causes a significant rise in temperature, here around 150°C, of ​​the first transistor Mo.

[0012] Such a solution is therefore costly and thermally unsatisfactory.

[0013] The invention aims to overcome, at least in part, the aforementioned problems.

[0014] To this end, according to a first aspect of the invention, a device for precharging a load, for example a capacitor, from a DC voltage source is proposed, comprising a first safety transistor capable of connecting the load to said DC voltage source and a linear control circuit for the first safety transistor, characterized in that said control circuit regulates the product of the precharging current and the voltage difference between the voltage measured across said DC voltage source and the voltage measured across said load with respect to a power setpoint during the linear control of the first safety transistor during the precharging of said load by said DC voltage source, said power setpoint increasing during a first time interval from a first predefined value, for example zero,to reach a constant or approximately constant value and maintain it for a second time interval following the first time interval.

[0015] Thus, thanks to the invention, the pre-charge current is regulated so that the power received by the first safety transistor increases in a controlled manner at the beginning of the pre-charge and then remains approximately constant for the remainder of the pre-charge. In this way, the first safety transistor does not receive excessive power at the beginning of the pre-charge, and its size can be reduced accordingly. Furthermore, regulating the power received by the first safety transistor throughout the pre-charge makes it possible to reduce its heating and thus improve the thermal performance of the precharge device.

[0016] A preload device according to the invention may further include one or more of the following optional features, taken individually or in any technically possible combination.

[0017] Optionally, the regulation of the received power around the power setpoint is carried out for a predetermined duration.

[0018] Optionally, the first safety transistor is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), for example in silicon (Si-MOSFET) or silicon carbide (SiC-MOSFET), or a FET (Field Effect Transistor), in gallium nitride or an IGBT (Insulated Gate Bipolar Transistor).

[0019] Optionally, the pre-charge electric current that can flow between the DC voltage source and the load is regulated by comparing the pre-charge electric current to the ratio of the power setpoint and the voltage difference between the voltage measured across the terminals of the DC voltage source and the voltage measured across the terminals of the load.

[0020] Optionally, the control circuit includes a voltage supply circuit for a control terminal of the first safety transistor, the supply circuit including an output terminal connected to the control terminal of the first safety transistor, a parallel arrangement of a capacitor and a first resistor, a first current source supplying current to the parallel arrangement only when the electrical pre-charge current is greater than the ratio, and a voltage follower circuit copying to the output terminal offset by a voltage offset the voltage present on the parallel arrangement.

[0021] Optionally, the voltage follower circuit includes a first pnp type bipolar transistor whose gate is connected directly or via a resistor to one of the terminals of the parallel assembly, whose collector is connected directly or via a resistor to the other terminal of the parallel assembly and whose emitter is connected directly or via a resistor to the output terminal and a second current source supplying current to the emitter of the first bipolar transistor.

[0022] Optionally, the parallel assembly is connected between an electrical ground and the gate of the first bipolar transistor.

[0023] Optionally, the second current source also supplies current to the output terminal connected to the control terminal of the first safety transistor.

[0024] Optionally, the second current source includes a terminal of a voltage reference intended to be connected to a reference voltage, a second pnp bipolar transistor, a third pnp bipolar transistor, a fourth npn bipolar transistor, a second and a fourth resistor, and wherein the gates of the second and third bipolar transistors are connected to each other and to the collector of the second bipolar transistor, the emitter of the third bipolar transistor is connected to the voltage reference terminal via a voltage source, the collector of the second bipolar transistor is connected to the voltage reference terminal via the second resistor, the collector of the fourth bipolar transistor is connected to the collector of the third bipolar transistor,The emitter of the fourth bipolar transistor is connected via the third resistor to an electrical ground, and the gate of the fourth bipolar transistor is intended to receive a control voltage when the pre-charge device charges the load.

[0025] Optionally, the first current source comprises the voltage reference terminal, the third bipolar transistor, the fourth bipolar transistor, the voltage source, the third resistor, a fifth pnp-type bipolar transistor, and a series combination of a switch and a fourth resistor, wherein the gate of the fifth bipolar transistor is connected to the gate of the second bipolar transistor, wherein the collector of the fifth bipolar transistor is connected to the parallel combination of the capacitor and the first resistor, as well as to the gate of the first bipolar transistor.in which the emitter of the fifth bipolar transistor is connected to the voltage reference terminal via the series association of the switch and the fourth resistor, and in which the switch is controlled to open when the pre-charge electrical current is greater than the ratio and to close otherwise.

[0026] Optionally, the control circuit includes a device for measuring the voltage across the capacitor.

[0027] Optionally, the control circuit includes a device for measuring the electrical precharge current.

[0028] Optionally, the control circuit includes a device for measuring the voltage across the terminals of the DC voltage source.

[0029] Optionally, the pre-charge electrical current measurement device further includes a shunt resistor.

[0030] Optionally, the shunt resistor is connected in series with the first safety transistor.

[0031] A voltage converter comprising a pre-charge device according to the first aspect of the invention is also proposed according to a second aspect of the invention.

[0032] Optionally, the voltage converter includes: - a device for pre-charging a load from a DC voltage source according to the first aspect of the invention; - a high-voltage terminal designed to present a high voltage relative to the electrical ground; - a ground terminal intended to be connected to the electrical ground; - a low-voltage terminal designed to present a low voltage relative to to the electrical ground; - at least one voltage conversion cell connected to the ground, high voltage and low voltage terminals to perform a conversion between high voltage and low voltage, said at least one voltage conversion cell being connected to the low voltage points via the first safety transistor of the pre-charge device, said high voltage terminal being electrically connected to said first safety transistor via said at least one voltage conversion cell when said load is connected between the high voltage terminal and the ground terminal and when the pre-charge device pre-charges said load.

[0033] A voltage converter according to the invention may further include one or more of the following optional features, taken individually or in any technically possible combination.

[0034] Optionally, the voltage converter further includes a safety device comprising said first safety transistor and a second safety transistor mounted in series between said at least one voltage conversion cell and said low voltage terminal.

[0035] Optionally, the second safety transistor is blocked when the pre-charge device pre-charges said load.

[0036] Optionally, the second transistor is in a blocked state when the pre-charge device pre-charges said load.

[0037] It is also proposed, according to a third aspect of the invention, a mobility device comprising a pre-charge device according to the first aspect of the invention or a voltage converter according to the second aspect of the invention.

[0038] A mobility device is, for example, a motorized land vehicle, an aircraft or a drone.

[0039] A motorized land vehicle is, for example, a motor vehicle, a motorcycle, a motorized bicycle, a motorized scooter or a motorized wheelchair.

[0040] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which:

[0041] Figure 1 is a diagram of a preload device according to the prior art,

[0042] Figure 2 presents, in the form of timing diagrams, the pre-charge current, the power received by the first safety transistor and the temperature of the first safety transistor when a precharge is carried out by the precharge device of [Fig.1],

[0043] Figure 3 is an electrical functional diagram of a DC / DC voltage converter in one embodiment of the invention.

[0044] Fig. 4 is an electrical circuit illustrating the pre-charge device of the DC / DC voltage converter of the [Fig.3],

[0045] The [Fig.5] is a schematic of a SW switch of the pre-charge device of the [Fig.4],

[0046] Figure 6 shows, in the form of timing diagrams, the pre-charge current, the power received by the first safety transistor, and the temperature of the first safety transistor when a pre-charge is performed by the pre-charge device of Figure 5, and

[0047] Figure 7 is an electrical functional diagram of a DC / DC voltage converter in another embodiment of the invention.

[0048] With reference to [Fig.3], a DC / DC voltage converter 106 intended to equip a mobility device, for example a motor vehicle, will now be described in an embodiment of the invention.

[0049] The DC / DC voltage converter 106 first includes a ground terminal BM connected to an electrical ground M, a high voltage terminal BHT intended to present a high voltage HT, for example of 48V, with respect to the electrical ground M, a low voltage terminal Bbt in order to present a low voltage BT with respect to the electrical ground M.

[0050] In the example described here, the low voltage terminal is connected to the + terminal of a DC voltage source 102, for example a battery, presenting a BT voltage between its terminals, for example 12V.

[0051] The DC / DC voltage converter further includes a capacitor Ci connected between the electrical ground M and the low-voltage terminal Bbt. The capacitor Ci is connected either directly or via the ground terminal BM to the electrical ground M.

[0052] The DC / DC voltage converter further includes a capacitor Ca connected between the electrical ground M and the high-voltage terminal BHT. The capacitor Ca is connected either directly or via the ground terminal BM to the electrical ground M.

[0053] The DC / DC voltage converter 106 further comprises at least one number N greater than or equal to 1 of voltage conversion modules connected in parallel between the high-voltage terminal BHt and the low-voltage terminal Bbt to achieve a conversion between high voltage (HV) and low voltage (LV).

[0054] In the example described, the number N is equal to two, i.e. the DC / DC voltage converter 106 comprises two voltage conversion modules connected in parallel.

[0055] Each of these two voltage conversion modules includes a voltage conversion cell 108i 2 electrically connected to the ground terminal BM, to the high voltage terminal BHT and to a midpoint PMi 2 and a safety device 126i 2 electrically connected to the midpoint PMi 2 and to the low voltage terminal Bbt.

[0056] In the example described, each cell 108i 2 is a switching cell.

[0057] We will now describe the switching cell 108b, the switching cell 1082 having the same structure as the switching cell 108b

[0058] This cell 1081 includes a switching arm having a high side switch 202i and a low side switch 204i connected to each other at a central point PCb. The switching arm is electrically connected between the high voltage terminal BHt and the ground terminal BM to receive the high voltage HT.

[0059] In the example described here, the switches 202b 204i are for example transistor switches such as silicon MOSFET (Si-MOSFET) or silicon carbide MOSFET (SiC-MOSFET).

[0060] In the example described here, the transistor 202i is of type N, its source is electrically connected to the center point PCi and its drain to the high-voltage terminal BHt-

[0061] In the example described here, the transistor 204i is of type N, its source is electrically connected to the ground terminal BM and its drain is electrically connected to the center point PCb

[0062] Each cell 108i further comprises an inductor 208i electrically connecting the center point PCi to the midpoint PMi and a capacitor 210i connecting the midpoint PMi to electrical ground M, for example directly or, as illustrated, by being connected to the ground terminal BM. Alternatively, cell 1081 does not comprise a capacitor 210i

[0063] The safety device 126i includes a first safety transistor 304b. In the example described here, the first safety transistor 304i is an N-type MOSFET transistor whose source is connected via a shunt resistor to the midpoint PMi and whose drain is connected to the low voltage terminal Bbt.

[0064] Optionally, the safety device 126i may also include a Zener diode Dz and a resistor Rgs connected between the gate and the source of the first safety transistor 304b. In this case, the anode of the Zener diode Dz is connected to the source of the first safety transistor 304b.

[0065] The safety device 1262 differs from the safety device 126i only in that it is connected directly to the midpoint PM2.

[0066] The DC / DC voltage converter finally includes a pre-charge device Dpr of the Ca capacity which will now be described with reference to [Fig.4].

[0067] The pre-charge device includes the shunt resistor Shu, the first safety transistor 304i and a linear control circuit CRlin of the first safety transistor 304b

[0068] The first safety transistor 304i is capable of connecting the load Ca to the DC voltage source 102 when the first safety transistor 304i is controlled in linear mode.

[0069] The linear control circuit CRlin of the first 304i safety transistor comprises: - a device for measuring the voltage across the terminals of the capacitor Ca, - a device for measuring the voltage across the terminals of the voltage source Continue 102, - a 140V power supply circuit for a control terminal of the first 304b safety transistor - a PC microcontroller, and - a device for measuring the electrical precharge current Ipr consisting here of the shunt resistor Shu, a device for measuring the voltage across the shunt resistor Shu and the microcontroller pC.

[0070] The microcontroller pC receives at its inputs the voltage measured across the capacitor Ca, the voltage measured across the voltage source 102, and the voltage measured across the shunt resistor Shu. From this last measured voltage, the microcontroller pC calculates the pre-charge current Ipr (by dividing the voltage measured across the shunt resistor Shu by the value of the shunt resistor Shu) and then compares this value to the ratio Ra of a power setpoint CP, calculated by the microcontroller pC, and the difference between the voltage measured across the voltage source 102 and the voltage measured across the capacitor Ca.

[0071] In the example described here, the microcontroller calculates the power setpoint CP as a function of time according to the equation [Math.l] below in which Pc is a constant power and r is a time constant.

[0072] [Math.l] CP = (W)P C .

[0073] In other words, the power setpoint CP is defined by a time-dependent function which is increasing from a first predefined value, here the zero value, and which also has a horizontal asymptote defined by the equation CP=Pc.

[0074] The choice of the time constant and the power setpoint CP is made according to the value of the capacitance Ca to be charged and the value of the DC voltage source 102 so that the pre-charge of the capacitance Ca takes place over a period predetermined. In other words, the previous choices are made so that the regulation of the power received by the first 304i safety transistor around the power setpoint takes place for a predetermined duration.

[0075] Thus, the power setpoint CP can be broken down into two time parts. The first time part prevents an excessively rapid increase in the power received by the first safety transistor at the beginning of pre-charge, and the second time part regulates this received power around the constant power PC.

[0076] Based on the comparison of the pre-charge current Ipr to the ratio Ra, the microcontroller pC controls the voltage supply circuit 140 which includes: - an output terminal Bs connected to the control terminal of the first safety transistor 304b - a capacity C, - a first current source SCI supplying current I5 to one terminal of the capacitor C only when the pre-charge electrical current Ipr is greater than the ratio Ra calculated by the microcontroller pC, and - a voltage follower circuit copying to the output terminal B s the voltage present on the terminal of the capacitor C supplied by the current I5 shifted by a voltage offset.

[0077] In the example described here, the voltage follower circuit includes a first pnp type bipolar transistor Qi and a second current source supplying current to the emitter of the first bipolar transistor Qb. The first bipolar transistor Qi has its gate connected directly to the terminal of the capacitor C supplied by the current I5, its collector connected directly to the other terminal of the capacitor C and its emitter connected directly to the output terminal Bs.

[0078] In addition, a first resistance Ri is connected between the gate of the first bipolar transistor Qi and ground M, i.e. across the terminals of the capacitor C.

[0079] The second current source comprises: - a reference voltage terminal Br connected to a reference voltage Vœ, for example 36V in the example described here, - a second bipolar transistor Q2 and a third bipolar transistor Q3 of the pnp type, the gates of the second bipolar transistor Q2 and the third bipolar transistor Q3 are connected to each other and to the collector of the third bipolar transistor Q3, the emitter of the third bipolar transistor Q3 is connected to the voltage reference terminal Br via a voltage source Sc, the emitter of the second bipolar transistor Q2 is connected to the reference terminal Br via a second resistor R2, the collector of the second bipolar transistor Q2 is connected to the output terminal B s, and - a fourth bipolar transistor Q4 of type npn whose collector is connected directly to the collector of the third bipolar transistor Q3, whose emitter is connected via a third resistor R3 to the electrical ground M and whose gate receives a control voltage SS supplied by the microcontroller pC.

[0080] In the example described here, the voltage source Sc is achieved by means of a voltage regulator, for example a TL431 whose cathode is connected to the reference terminal B s, whose anode is connected to the emitter of the third bipolar transistor Q3 and whose reference is connected to the cathode.

[0081] The first current source includes the voltage reference terminal Br, the third bipolar transistor Q3, the fourth bipolar transistor Q4, the voltage source Sc, the third resistor R3, as well as a fifth bipolar transistor Q5 of pnp type, a switch SW and a fourth resistor R4.

[0082] The gate of the fifth bipolar transistor Q5 is connected to the gate of the third bipolar transistor Q3, the collector of the fifth bipolar transistor Q5 is connected to the capacitor C as well as to the gate of the first bipolar transistor Qb. The emitter of the fifth bipolar transistor Q5 is connected to the voltage reference terminal Br via the series connection of the switch SW and the fourth resistor R4. In the example described, the switch SW is connected to the reference terminal Br and the fourth resistor is connected to the emitter of the fifth bipolar transistor Q5.

[0083] The SW switch is controlled to open or close upon receipt of an Off / On command issued by the microcontroller pC.

[0084] With reference to [Fig. 5], we will now describe a particular embodiment of the SW switch. In this particular embodiment, the SW switch comprises a sixth bipolar transistor Q6 of type npn, a seventh bipolar transistor Q7 of type pnp, a fifth resistor R5, and a sixth resistor R6. The emitter of the seventh bipolar transistor Q7 is connected to the reference terminal Br. The collector of the seventh bipolar transistor Q7 is connected to the fourth resistor R4. The gate of the seventh bipolar transistor Q7 is connected to the reference terminal Br via the sixth resistor R6. The collector of the sixth bipolar transistor Q6 is connected to the gate of the seventh bipolar transistor Q7. The emitter of the sixth bipolar transistor Q6 is connected to ground M via the fifth resistor R5.The gate of the sixth bipolar transistor Q6 is intended to receive the Off / On command in the form of a zero voltage and a positive voltage of a few volts respectively.

[0085] When a positive voltage (On control) is applied to the sixth grid With transistor Q6, this voltage is offset from the gate-emitter voltage of the bipolar transistor Q6 across resistor R5 and causes the current I6 to appear. This current I6 also causes a voltage across resistor R6 to appear, which has the effect of turning on transistor Q7 and thus closing switch SW.

[0086] Similarly, when a zero voltage (Off command) is applied to the gate of the sixth transistor Q6, transistor Q7 becomes blocked and switch SW is open.

[0087] With reference to [Fig.6], we will now describe the dynamic operation of the preload device.

[0088] Fig. 6 presents in the form of timing diagrams the pre-charge current Ipr, the power received by the first safety transistor 304i and the temperature of the first safety transistor 304i when the pre-charge of the capacitance Ca (identical in value to that of the capacitance Ch of Fig. 1) is carried out by the pre-charge device.

[0089] During the entire pre-charge, the switches of the switching arm are open and the high voltage terminal BHt is not connected to a high voltage source but only to the capacitor Ca.

[0090] Alternatively, the upper side switch 202i is closed and the lower side switch 204i is open.

[0091] At the beginning of the precharge, at time to, the capacitance Ca and the capacitance C are discharged, the first safety transistor 304i is in a blocked state and the precharge current Ipr is zero.

[0092] To start the precharge, the microcontroller pC sends a closing command On of the SW switch and a control voltage SS on the gate of the fourth bipolar transistor Q4.

[0093] The microcontroller pC then compares this zero pre-charge current Ipr to the ratio Ra of the power setpoint CP and the voltage measured across the terminals of the voltage source 102. Since the pre-charge current Ipr is less than this ratio, the microcontroller pC keeps the switch SW closed and the control voltage SS on the gate of the fourth bipolar transistor Q4.

[0094] The control voltage SS is referred, offset from the gate-emitter voltage of the bipolar transistor Q4, to the terminals of the third resistor R3, thus defining the value of the current flowing through the third resistor R3.

[0095] Due to the arrangement of bipolar transistors Q2 and Q3, the voltage across the voltage source Sc is also present across the second resistor R2, which defines the value of the current I2 flowing through this second resistor R2. This current I2 is also, up to the gate current of the first safety transistor 304b, the current flowing between the emitter and collector of the first bipolar transistor Qb. Thus, the first current source allows the biasing of the first bipolar transistor Qi and The gate power supply of the first 304b safety transistor

[0096] Due to the arrangement of bipolar transistors Q2 and Q5, and considering that switch SW is closed by the microcontroller pC, the voltage across the voltage source Sc is found across the fourth resistor R4, which defines the value of the current I5 flowing through this fourth resistor R4. This current flows through the collector of the fifth bipolar transistor Q5 and thus allows the charging of capacitor C to begin. As capacitor C charges, a voltage V1 appears across its terminals.

[0097] This voltage V1 is offset from the gate-emitter voltage of the first bipolar transistor Qise is found at the output terminal Bs, that is, between the emitter and the collector of the first bipolar transistor Q. Thus, a control voltage is applied between the gate (at potential VI) and the source (at zero potential) of the first safety transistor 304i, so that as it begins to conduct, the pre-charge current Ipr becomes non-zero.

[0098] This pre-charge current flows through the switching cell 1081 to the high voltage terminal BHt via the intrinsic diode of the high-side transistor 202i.

[0099] As long as the current Ipr remains below the ratio Ra, the voltage V1 on the gate of the first safety transistor 304i continues to increase and the power received by the first safety transistor 304i remains below the power setpoint CP.

[0100] When the current Ipr becomes greater than the ratio Ra, the power received by the first safety transistor 304i becomes greater than the power setpoint CP and the microcontroller pC issues an Off command to open the SW switch while maintaining the SS control voltage on the gate of the fourth bipolar transistor Q4.

[0101] Thus, the second current source remains active and the voltage VI remains present on the output terminal Bs, while the second current source becomes inactive, i.e. the current I5 is zero and the charging of the capacitance C is stopped.

[0102] Stopping the charging of capacitance C causes the voltage on the gate of transistor 304i to no longer increase, so that the current Ipr no longer increases either.

[0103] When the current Ipr becomes less than the ratio Ra, the power received by the first safety transistor 304i becomes less than the power setpoint CP and the microcontroller pC issues an On command to close the SW switch while maintaining the SS control voltage on the gate of the fourth bipolar transistor Q4.

[0104] Thus, the second current source becomes active again and a current I5 is again generated to charge the capacitor C, which causes an increase in the voltage at the gate of the first safety transistor 304p. This increase in the voltage at the gate of the first safety transistor 304i allows to increase the conduction of this first 304i safety transistor and the current Ipr starts to increase again.

[0105] Thus, thanks to the successive opening and closing of the SW switch, the power received by the first safety transistor 304i follows the evolution of the power setpoint CP.

[0106] During a first phase of the precharge (between times to and ti), the power received by the first safety transistor 304i gradually increases, then during a second phase of the precharge (between ti and t2), this received power oscillates around a power value close to the constant power Pc.

[0107] Thanks to this limitation of the power received by the first safety transistor 304i, the heating of this first transistor is limited. Thus, thanks to the invention, it is possible, compared to the prior art, to limit the size of the first safety transistor 304i and to improve the thermal efficiency of the precharge device.

[0108] When the microcontroller detects that the pre-charging of capacitor Ca is complete, i.e., by comparing the voltage across capacitor Ca to a threshold voltage value, the microcontroller pC issues an Off command to open switch SW and removes the control voltage SS from the gate of the fourth bipolar transistor Q4, so that the voltage supply circuit 140 no longer supplies voltage to the control terminal of the first safety transistor 304i, and so that capacitor C can discharge through the first resistor Rb.

[0109] With reference to [Fig.7], we will now describe a voltage converter 106' according to a second embodiment of the invention.

[0110] The voltage converter 106' differs from the voltage converter 106 in that it further comprises a second safety transistor 3042 mounted in series between the shunt resistor Shu and the first safety transistor 304b, the first safety resistor 304i and the second safety transistor 3042 being connected by their source.

[0111] During the pre-charging of capacitor Ca, this second safety transistor 3042 is switched on so that it behaves like an open switch. In other words, the pre-charging current passes through the intrinsic diode of the second safety transistor 3042 to power capacitor Ca.

[0112] Alternatively, when precharging the capacitance Ca, the second safety transistor 3042 is controlled to close so that it behaves like a closed switch.

[0113] It should also be noted that the invention is not limited to the embodiments described above. It will indeed be apparent to those skilled in the art that various modifications can be made to the embodiments described above, in light of of the teaching that has just been revealed to him.

[0114] For example, the invention can be implemented when the high voltage is greater than 48V, for example greater than 100V, or even greater than or equal to 400V.

[0115] In the detailed presentation of the invention given above, the terms used shall not be interpreted as limiting the invention to the embodiments set forth in this description, but shall be interpreted as including all equivalents which can be foreseen by a person skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

Claims

1. Precharging device (304b Shu, 110, 120, 130, 140, pC) for precharging a load, for example a capacitor (Ca), from a DC voltage source (102) comprising a first safety transistor (304i) capable of connecting the load (Ca) to said DC voltage source (102), and a control circuit (Shu, 110, 120, 130, 140, pC) in linear regime of the first safety transistor (304i), characterized in that said control circuit (Shu, 110, 120, 130, 140, pC) regulates the product of the precharging current (Ipr) and the voltage difference between the voltage measured at the terminals of said DC voltage source (102) and the voltage measured at the terminals of said load (Ca) with respect to a power setpoint (CP) during linear control of the first safety transistor (3040) during precharging of said load (Ca) by said direct voltage source (102),said power setpoint (CP) increasing during a first time interval from a first predefined value, for example zero, to reach a constant or approximately constant value and to remain there during a second time interval following the first time interval.,

2. Precharging device (304b Shu, 110, 120, 130, 140, pC) according to the preceding claim in which the precharging electric current (Ipr) which can flow between the direct voltage source (102) and the load (Ca) is regulated by comparing said precharging electric current (Ipr) to the ratio (Ra) of said power setpoint (CP) and the voltage difference between the voltage measured at the terminals of said direct voltage source (102) and the voltage measured at the terminals of said load (Ca).

3. Precharging device (304b Shu, 110, 120, 130, 140, pC) according to the preceding claim wherein the control circuit (Shu, 110, 120, 130, 140, pC) comprises a voltage supply circuit (140) for a control terminal of the first safety transistor (304i), said supply circuit (140) comprising: - an output terminal (Bs) connected to the control terminal of the first safety transistor (304i), - a parallel connection of a capacitor (C) and a first resistor (RJ, - a first current source supplying current (I5) to said parallel connection only when the precharge electric current (Ipr) is greater than said ratio (Ra), and - a voltage follower circuit copying onto said output terminal (Bs) offset by a voltage offset the voltage present on said parallel connection.

4. Precharging device (304b Shu, 110, 120, 130, 140, pC) according to the preceding claim wherein said voltage follower circuit comprises a first pnp type bipolar transistor (Qi) whose gate is connected directly or via a resistor to one of the terminals of said parallel circuit, whose collector is connected directly or via a resistor to the other of the terminals of said parallel circuit and whose emitter is connected directly or via a resistor to said output terminal (Bs) and a second current source supplying current to the emitter of the first bipolar transistor (Qi).

5. A precharging device (304b Shu, 110, 120, 130, 140, pC) according to the preceding claim wherein said second current source comprises a voltage reference terminal (Br) for connection to a reference voltage (VCc), a second pnp bipolar transistor (Q2), a third pnp bipolar transistor (Q3), a fourth npn bipolar transistor (Q4), a second (R2) and a fourth resistor (R4), and wherein the gates of the second (Q2) and third bipolar transistor (Q3) are connected to each other and to the collector of the second bipolar transistor (Q2), the emitter of the third bipolar transistor (Q3) is connected to said voltage reference terminal (Br) via a voltage source (Sc), the collector of the second bipolar transistor (Q2) is connected to said voltage reference terminal (Br) via through the second resistor (R2),the collector of the fourth bipolar transistor is connected to the collector of the third bipolar transistor (Q3), the emitter of the fourth bipolar transistor (Q4) is connected via the third resistor (R3) to an electrical ground (M) and the gate of the fourth bipolar transistor (Q4) is intended to receive a control voltage (SS) when said precharging device charges said load.,

6. Preloading device according to the preceding claim in which

7. said first current source comprises said voltage reference terminal (Br), said third bipolar transistor (Q3), said fourth bipolar transistor (Q4), said voltage source (Sc), said third resistor (R3) as well as a fifth pnp type bipolar transistor (Q5), and a series association of a switch (SW) and a fourth resistor (R4) and wherein the gate of the fifth bipolar transistor (Q5) is connected to the gate of the second bipolar transistor (Q2), wherein the collector of the fifth bipolar transistor (Q5) is connected to said parallel association of the capacitor (C) and said first resistor (RJ) as well as to the gate of the first bipolar transistor (Qi),in which the emitter of the fifth bipolar transistor (Q5) is connected to the voltage reference terminal (Br) via the series connection of the switch (SW) and the fourth resistor (R4) and in which the switch (SW) is controlled to open when the precharge electric current (Ipr) is greater than said ratio (Ra) and to close otherwise., Voltage converter (106) comprising: - a precharging device (304b Shu, 110, 120, 130, 140, pC) for a load (Ca) from a direct voltage source (102) according to one of the preceding claims - a high voltage terminal (BHt) intended to present a high voltage (HT) relative to the electrical ground (M); - a ground terminal (BM) intended to be connected to the electrical ground (M); - a low voltage terminal (Bbt) intended to present a low voltage (BT) with respect to the electrical ground (M), - at least one voltage conversion cell (1081, 1082) connected to the ground (BM), high voltage (BHT) and low voltage (Bbt) terminals to carry out a conversion between the high voltage (HT) and the low voltage (BT), said at least one voltage conversion cell (1081, 1082) being connected to the low voltage points via the first safety transistor (304i) of the precharging device (304i, Shu, 110, 120, 130, 140, pC), said high voltage terminal (BHt) being electrically connected to said first safety transistor (304i) via said at least one voltage conversion cell when said load is connected between the high voltage terminal and the ground terminal and when the precharging device precharges said load.

8. Voltage converter (106') according to the preceding claim further comprising a safety device comprising said first safety transistor (304i) and a second safety transistor (3042) connected in series between said at least one voltage conversion cell (1081, 1082) and said low voltage terminal (Bbt)-

9. Mobility device comprising a precharging device (304b Shu, 110, 120, 130, 140, pC) according to one of claims 1 to 6 or a voltage converter (106) according to one of claims 7 to 8.

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