DC-DC converter and associated control method

Description

[0001] The present invention relates to the field of direct voltage converters and in particular voltage converters used in motor vehicles.

[0002] Indeed, in motor vehicles, and in particular electric vehicles or hybrid vehicles, the vehicle generally includes a battery linked to the vehicle's drive which delivers a voltage greater than or equal to 60V, while many on-board devices operate with a power supply of between 12 and 14V, so it is necessary to use a voltage converter to be able to power the devices with the battery linked to the vehicle's drive.

[0003] In order to improve state-of-the-art voltage converters, one solution is to improve efficiency by reducing energy losses. A known solution from the state of the art is to apply zero voltage switching (ZVS) in order to reduce switching losses. Such a technique is for example applied to Full-Bridge type circuits. figure 1 represents an example of a direct voltage converter obtained from a Full-Bridge circuit. This converter 1 comprises a high-voltage circuit 3 comprising a bridge of two branches B1 and B2 each comprising two switches 5 in series, the ends of the branches B1 and B2 being connected to a high-voltage source 7. The midpoint of the branches is connected respectively to a first and a second end of the primary winding 9a of a transformer 9. The low-voltage circuit 11 of the converter 1 comprises a first 13 and a second 15 inductances connected on the one hand to the positive terminal of the low-voltage source 17 and on the other hand respectively to a first and a second end of the secondary winding 9b of the transformer 9.The low voltage circuit 11 also comprises a first and a second switch 5 connected on the one hand to ground and on the other hand respectively to the first and second ends of the secondary winding 9b of the transformer 9.

[0004] Furthermore, particularly in the context of motor vehicles, it is necessary to reduce the size and cost of various equipment and therefore of voltage converters. However, such an improvement is difficult with magnetic components because they generally require ferrite coils whose integration possibilities are limited.

[0005] Additionally, patent application US6069799A describes a transformer comprising a primary winding, a single secondary winding, and a drive winding. The drive winding is wound on the transformer and coupled between two synchronous rectifier switches.

[0006] Thus, the present invention aims not only to improve the efficiency of voltage converters of the state of the art but also to reduce the size and cost of the converters.

[0007] For this purpose the invention relates to a voltage converter as defined in claim 1. The invention is defined in the attached set of claims.

[0008] According to a further aspect of the present invention, the secondary winding to which the magnetic component acts as a transformer depends on the voltage supplied to the primary winding.

[0009] In other words, depending on the voltage supplied to the primary winding, the magnetic component operates as a transformer either to the first secondary winding(s) or to the second secondary winding(s).

[0010] According to another aspect of the present invention, the magnetic component comprises a generally non-closed figure-of-eight shaped magnetic circuit comprising a first loop with a first air gap, a second loop with a second air gap and a central portion common to the first and second loops, the primary winding being wound around the central portion, the first secondary winding being wound around the first loop, the second secondary winding being wound around the second loop.

[0011] According to a further aspect of the present invention, the magnetic component comprises a first and a second magnetic circuit distinct from the first, the primary winding being wound around both the first and second magnetic circuits, the first secondary winding being wound around the first magnetic circuit and the second secondary winding being wound around the second magnetic circuit.

[0012] In particular, each magnetic circuit is ring-shaped, for example circular or rectangular.

[0013] According to an additional aspect of the present invention, the first and second magnetic circuits respectively comprise an air gap.

[0014] According to one aspect of the present invention, the secondary circuit of the magnetic component comprises at least two first secondary windings in parallel and at least two second secondary windings in parallel.

[0015] According to a particular aspect, the magnetic circuit of the magnetic component further comprises: at least one first bar around which a first secondary winding is wound, said first bar comprising an air gap and being connected to the first loop so that the first secondary windings are parallel to each other; at least one second bar around which a second secondary winding is wound, said second bar comprising an air gap and being connected to the second loop so that the second secondary windings are parallel to each other.

[0016] In particular, the first bar(s) are symmetrical to the second bar(s) with respect to the central portion.

[0017] According to another particular aspect, the first magnetic circuit comprises at least two first bars around which a respective first secondary winding is wound, said first bars being connected so that the first secondary windings are parallel to each other; the second magnetic circuit comprises at least two second bars around which a respective second secondary winding is wound, said second bars being connected so that the second secondary windings are parallel to each other.

[0018] In particular, the first bars are symmetrical to the second bars with respect to the portion of the first and second magnetic circuits around which the primary winding is positioned. In particular, the first and second bars each comprise an air gap.

[0019] According to another aspect of the present invention, the high voltage circuit comprises an H-bridge comprising two branches connected in parallel and each comprising a high switching element and a low switching element connected in series, the ends of the branches being connected to the terminals of the high voltage source and the midpoints of the branches being connected respectively to a first and a second end of the primary winding.

[0020] According to a further aspect of the present invention, the high voltage circuit comprises a branch comprising a high switching element and a low switching element in series, the ends of the branch being connected respectively to a positive terminal and a negative terminal of the high voltage source, the midpoint of the branch being connected to a first end of the primary winding, the second end of the primary winding being connected to the negative terminal of the high voltage source via a capacitor.

[0021] According to an additional aspect of the present invention, the low voltage circuit comprises first and second switching elements connected respectively to the first and second secondary windings on the one hand and to ground on the other hand.

[0022] According to another aspect of the present invention, the low voltage circuit comprises a first and a second diodes connected respectively to the first and to the second secondary windings on the one hand and to ground on the other hand.

[0023] According to a further aspect of the present invention, the first and second secondary windings are connected to a positive terminal of the low voltage source, the negative terminal of the low voltage source being connected to ground.

[0024] According to an additional aspect of the present invention, the switching elements comprise transistors of the type included in the following list: MOSFET; IGBT; JFET; bipolar transistor.

[0025] According to another aspect of the present invention, the switching elements comprise a diode connected in anti-parallel to the transistor.

[0026] According to a further aspect of the present invention, the switching elements of the high voltage circuit comprise a capacitor connected in parallel with the transistor and the diode.

[0027] The present invention also relates to a method for controlling a voltage converter in which the switching elements of the high voltage circuit are controlled cyclically so that during a first part of the cycle, for the first branch, the high switching element connected to the positive terminal of the high voltage source is in the closed position and the low switching element connected to the negative terminal of the high voltage source is in the open position while for the second branch, the high switching element connected to the positive terminal of the high voltage source is in the open position and the low switching element connected to the negative terminal of the high voltage source is in the closed position and during a second part of the cycle, for the first branch,the upper switching element connected to the positive terminal of the high voltage source is in the open position and the lower switching element connected to the negative terminal of the high voltage source is in the closed position while for the second branch, the upper switching element connected to the positive terminal of the high voltage source is in the closed position and the lower switching element connected to the negative terminal of the high voltage source is in the open position.,

[0028] The present invention also relates to a method for controlling a voltage converter in which the switching elements of the high voltage circuit are controlled cyclically so that during a first part of the cycle, the high switching element connected to the positive terminal of the high voltage source is in the closed position and the low switching element connected to the negative terminal of the high voltage source is in the open position and during a second part of the cycle, the high switching element connected to the positive terminal of the high voltage source is in the open position and the low switching element connected to the negative terminal of the high voltage source is in the closed position.

[0029] According to a further aspect of the methods according to the invention, the switching elements of the low voltage circuit are synchronized with the switching elements of the high voltage circuit so that the switching element of the low voltage circuit connected to a secondary winding is closed when said secondary winding transfers energy to the low voltage source.

[0030] The method according to the invention may comprise any of the characteristics described previously in relation to the converter according to the invention and which are compatible therewith.

[0031] Other characteristics and advantages of the invention will appear in the description which will now be given, with reference to the appended drawings which represent, for informational but non-limiting purposes, possible embodiments.

[0032] On these drawings: there figure 1 represents an electrical diagram of a voltage converter according to an embodiment of the state of the art; the figure 2 represents a simplified diagram of a voltage converter according to the present invention; the figure 3 represents an electrical diagram of a voltage converter according to a first embodiment of the present invention; the figure 4 represents an electrical diagram of a voltage converter according to a second embodiment of the present invention; the figure 5 represents an equivalent electrical circuit of a voltage converter according to the present invention; the figure 6 represents an operation of the equivalent electrical circuit of the figure 5 during a first cycle; the figure 7 represents an operation of the equivalent electrical circuit of the figure 5 during a second cycle; the figure 8 represents an operation of the equivalent electrical circuit of the figure 5 during a transition phase between the first and second cycles; figures 9a, 9b, 9c , 9d et 9e represent diagrams of the different configurations of a magnetic component according to the present invention.

[0033] In these figures, like reference numbers designate like elements.

[0034] In the following description, we generally refer to: The term "non-magnetically coupled" to define a first and a second winding, means that a voltage variation at the first winding does not cause a voltage variation at the second winding and vice versa; The term "high voltage" to designate an electrical circuit, corresponds to a circuit in which the voltage can exceed 48 Volts, or even 60 Volts; The term "low voltage" to designate an electrical circuit, corresponds to a circuit in which the maximum voltage does not exceed 48 Volts, or even 60 Volts; The term "DC" corresponds to the acronym for "direct current" and means direct current; The term "IGBT" corresponds to the acronym for "Insulated Gate Bipolar Transistor" and designates an insulated gate bipolar transistor; The term "MOSFET" corresponds to the acronym for "Metal Oxide Semiconductor Field Effect Transistor" and designates a metal oxide semiconductor field effect transistor;The term "JFET" stands for "Junction Field Effect Transistor" and is a field effect transistor whose gate is in direct contact with the channel.

[0035] The idea of ​​the present invention is to group the magnetic components of a DC / DC voltage converter into a single magnetic component capable of performing the functions of energy transfer and storage.

[0036] There figure 2 represents a general diagram of a DC / DC voltage converter according to the present invention. The voltage converter 21 comprises a high voltage circuit 23 comprising a high voltage source 25, a low voltage circuit 27 comprising a low voltage source 29 and a magnetic component 31 connecting the high voltage circuit 23 and the low voltage circuit 27. The magnetic component 31 comprises a primary circuit with a primary winding 33 connected to the high voltage circuit 23 and a secondary circuit with two secondary windings 35a and 35b connected to the low voltage circuit 27. The two secondary windings 35a and 35b are magnetically coupled to the primary winding 33 but are not magnetically coupled to each other.

[0037] The different configurations of the high voltage circuit 23 and the low voltage circuit 27 allowing the operation of the voltage converter 1 will now be described in detail.

[0038] There figure 3 represents a first embodiment of the voltage converter 21 in which the high voltage circuit 23' comprises an H-bridge comprising a first and a second branch B1 and B2 mounted in parallel, the ends of the branches B1 and B2 being connected to the high voltage source 25. The first branch B1 comprises a high switching element denoted Q H1 connected to the positive terminal of the high voltage source 25 mounted in series with a low switching element denoted Q L1 connected to the negative terminal of the high voltage source 25. The midpoint of the first branch B1 located between the high switching elements Q H1 and low Q L1 is connected to a first end of the primary winding 33 of the magnetic component 31. The second branch B2 comprises a high switching element denoted Q H2 connected to the positive terminal of the high voltage source 25 mounted in series with a low switching element denoted Q L2 connected to the negative terminal of the high voltage source 25.The midpoint of the second branch B2 located between the high switching elements Q H2 and low switching elements Q L2 is connected to a second end of the primary winding 33 of the magnetic component 31. The negative terminal of the high voltage source 25 is connected to ground 34.

[0039] The low voltage circuit 27' comprises a first switching element Q 1 arranged between a first end of the first secondary winding 35a of the magnetic component 31 and the ground 34 and a second switching element Q 2 arranged between a first end of the second secondary winding 35b of the magnetic component 33 and the ground 34. The second ends of the first and second secondary windings 35a and 35b are connected to a positive terminal of the low voltage source 29. The negative terminal of the low voltage source 29 is connected to the ground 34.

[0040] The switching elements Q H1 , Q H2 , Q L1 , Q L2 , Q 1 and Q 2 comprise for example a transistor of the IGBT, MOSFET, JFET or bipolar type, a diode mounted in antiparallel to the transistor and a capacitor mounted in parallel with the transistor and the diode, however other types of transistor or controllable switch known to those skilled in the art can also be used within the scope of the present invention. Furthermore, it should be noted that these diodes and these capacitors can be added components or parasitic components intrinsic to the transistor.

[0041] There figure 4 represents a second embodiment of the voltage converter 21 in which the high voltage circuit 23" comprises a branch B comprising a high switching element QH connected to the positive terminal of the high voltage source 25 in series with a low switching element QL connected to the negative terminal of the high voltage source 25. The negative terminal of the high voltage source 25 is connected to ground 34. The midpoint of the branch B located between the high switching element QH and the low switching element QL is connected to a first end of the primary winding 33. The second end of the primary winding 33 is connected to ground via a capacitor 37.

[0042] The low voltage circuit 27" comprises a first diode D 1 arranged between a first end of the first secondary winding 35a of the magnetic component 31 and the ground 34 and a second diode D 2 arranged between a first end of the second secondary winding 35b of the magnetic component 33 and the ground 34. The second ends of the first and second secondary windings 35a and 35b are connected to a positive terminal of the low voltage source 29. The negative terminal of the low voltage source 29 is connected to the ground 34.

[0043] The first and second embodiments presented previously from the figures 3 And 4 can be combined so that the 23' high voltage circuit of the figure 3 can be combined with the 27" low voltage circuit of the figure 4 as well as the 23" high voltage circuit of the figure 4 can be combined with the 27' low voltage circuit of the figure 3 , the magnetic element 31 being the same for all embodiments.

[0044] The operation of the voltage converter 21, and in particular of the magnetic component 31, will now be described. The operation is the same regardless of the configuration of the high voltage 23 and low voltage 27 circuits. The magnetic component 31 operates in a manner similar to a double transformer in series shown in the figure 5 and modeled by a first perfect transformer 41 and a first magnetizing inductance L 1 connected to the terminals of the primary of the first perfect transformer 41; and a second perfect transformer 43 and a second magnetizing inductance L 2 connected to the terminals of the primary of the second perfect transformer 43. The modeling also includes a parasitic inductance noted LS also called leakage inductance. The configuration of the high voltage 23" and low voltage 27" circuits of the figure 5 corresponds to the configuration of the figure 4 described previously.

[0045] The operation of the voltage converter 21 will therefore be described using the equivalent diagram of the figure 5 . The operation comprises a first cycle for a duration αT where α is the duty cycle applied to the high switching element QH and T a reference period. In the first cycle, the voltage converter is in a first state represented on the figure 6 where the high switching element QH is conducting while the low switching element QL is open. On the figure 6 , the voltages and currents are represented by arrows. This state implies that the voltage Vi of the high voltage source 25 is applied between the midpoint of branch B and ground 34. The voltage across the capacitor 37 is noted Vc during this first cycle and is worth α*Vi on average. The voltage applied to the primaries of transformers 41 and 43, that is to say between points A and B is worth V AB =Vi-Vc. This voltage V AB is positive so that the voltage reflected at the secondary is also positive and blocks the first diode D1. The first transformer 41 therefore behaves like an open switch. The voltage across the low voltage source 29 is noted V 0 and the current flowing through it is noted i 0 .Thus, the current flowing at the secondary of the second transformer is equal to i 0 and the current flowing in the primary of the second transformer is equal to i 0 / N where N is the ratio between the number of turns of the primary and the secondary of the second transformer 43. This ratio N corresponds to the ratio between the number of turns of the primary winding 33 and the second secondary winding 35b. Since the diode D2 is conducting, the voltage across the secondary of the second transformer 43 is equal to V 0 . The voltage across the primary of the second transformer 43, denoted V TB, is therefore equal to N*V 0 .We therefore have on the one hand the voltage V AT at the terminals of the primary of the first transformer 41 which is worth V Ar =Vi-N*V 0 -α*Vi which allows energy storage at the level of the magnetizing inductance L 1 of the first perfect transformer 41 and on the other hand the voltage V TB at the terminals of the primary of the second transformer 43 which is worth V TB =N*V 0 which is transferred to the low voltage circuit via the second transformer.

[0046] In the case of an H-bridge assembly of the figure 3 , the first state, corresponding to the first cycle, corresponds to the closing of the high switching element Q H1 of the first branch B1 and the low switching element Q L2 of the second branch B2 and to the opening of the low level element Q L1 of the first branch B1 and the high switching element Q H2 of the second branch B2. At the low voltage circuit, the switching element Q1 is open while the switching element Q2 is closed during this first cycle in which the energy is transferred to the low voltage circuit via the second secondary winding 35b.

[0047] During a second cycle for a duration (1-α)T approximately, the converter is in a second state represented on the figure 7 where the high switching element QH is open while the low switching element QL is either conducting or closed. This state implies that the high voltage source 25 no longer supplies the primaries of the transformers 41 and 43. The voltage applied to the primaries of the transformers 41 and 43 is then negative. The voltage reflected at the secondary is also negative so that the first diode D1 is now conducting while the second diode D2 is blocking. The second transformer 43 then behaves like an open switch. The current flowing at the secondary of the first transformer 41 is I 0 ; the voltage across the secondary of the first transformer 41 is -V 0 ; and the voltage across the primary of the first transformer is therefore -N'*V0. This ratio N' corresponds to the ratio between the number of turns of the primary winding 33 and the first secondary winding 35a.In particular, this ratio N' is equal to the ratio N relative to the second secondary. We therefore have on the one hand the voltage V AT at the terminals of the primary of the first transformer 41 which is equal to V AT = -N*VO and which allows a transfer of energy to the low voltage circuit via the first transformer and on the other hand the voltage V TB at the terminals of the primary of the second transformer 43 which is equal to V TB =N*V 0 -Vc, and which is stored at the level of the magnetizing inductance L2.

[0048] In the case of an H-bridge assembly of the figure 3 , the second state, corresponding to the second cycle, corresponds to the opening of the high switching element Q H1 of the first branch B1 and the low switching element Q H2 of the second branch B2 and to the closing of the low level element Q L1 of the first branch and the high switching element Q H2 of the second branch B2. At the low voltage circuit, the switching element Q1 is closed while the switching element Q2 is open during this second cycle in which the energy is transferred to the low voltage circuit via the first secondary winding 35a.

[0049] Furthermore, in order to reduce switching losses, when switching from the configuration of the first state represented in figure 6 in the second state represented in figure 7 , that is, between the two cycles, the high and low switching elements (in the embodiment of the figure 3 , all the switching elements of the high voltage circuit 23') are opened simultaneously for a predetermined time so as to obtain a zero switching voltage. This transition state will be described from the figure 8 . Indeed, when the high switching element QH goes into the open position at the end of the first cycle, the current Ip in the loop of the high voltage circuit 23" is imposed by the first magnetizing inductance L1 and charges the capacitor CH of the high switching element QH and discharges the capacitor CL of the low switching element QL. Thus, the capacitors CH and CL make it possible to control the rise times of the voltage across the low switching element QL so that the current in the low switching element QL is canceled while the voltage across its terminals remains low so as to obtain zero voltage switching ("Zero Voltage Switching (ZVS)" in English).

[0050] When the two switching elements QH and QL of the high voltage circuit 23" are open, the voltage Vd between the midpoint and ground 34 decreases until it is equal to Vc. The voltage across the second ideal transformer 43 is imposed by the secondary, that is to say by the low voltage circuit 27" and is worth N*V 0 because the second diode D2 is conducting. The sum of the voltages across the first and second transformers must be zero (to obtain Vd=Vc), the voltage across the first transformer is therefore -N*V0. The first diode D1 can be conducting but at this stage diode D2 supplies all the current to the low voltage circuit and D1 none because the current sharing between the two diodes D1 and D2 has no reason to vary. On the other hand, the voltage Vd continues to decrease because the inductance L1 still imposes the charge of CH and the discharge of CL, the current then decreases rapidly.Indeed, the voltage across transformers 41 and 43 is always 0 Volts. The voltage across the parasitic inductance Ls denoted V LS will then take the value of the difference between Vd and Vc, so we have V LS = Vd-Vc. This negative voltage quickly lowers the current in the first transformer 41. However, since the magnetizing inductances L1 and L2 have values ​​that are a priori significantly higher than the leakage inductance Ls, the currents in the magnetizing inductances will vary only very little and the magnetizing currents of the inductances L1 and L2 are forced to flow towards the secondary windings. Once the capacitor CH is charged and the capacitor CL is discharged, the voltage across the bottom switching element QH is zero and the bottom switching element QL can be closed to start the second cycle.

[0051] Similarly, the transition from the second cycle to the first cycle requires a transition phase to achieve zero voltage switching.

[0052] The period T, the duty cycle α and the transition time between the first and second cycles described above are determined according to the characteristics of the different components of the voltage converter 21.

[0053] Thus, the use of a magnetic component 31 comprising a primary winding 33 and two secondary windings 35a and 35b magnetically coupled to the primary winding 33 but not magnetically coupled to each other makes it possible to obtain the same operation as two independent transformers connected in series. Such a magnetic component 31 therefore makes it possible both to store energy in the magnetizing inductance of the primary winding 33 while transferring energy to the secondary windings 35a and 35b, to the second secondary winding 35b during the first cycle and to the first secondary winding 35a during the second cycle.

[0054] The different configurations making it possible to obtain a magnetic component 31 allowing magnetic coupling between the primary winding 33 and the secondary windings 35a and 35b without there being magnetic coupling between the secondary windings 35a and 35b will now be described from the figures 9a à 9c .

[0055] According to a first embodiment shown in the figure 9a , the magnetic component 31 comprises a first M1 and a second M2 magnetic circuit distinct from the first M1, the primary winding 33 being wound around both the first M1 and the second M2 magnetic circuits, the first secondary winding 35a being wound around the first magnetic circuit M1 and the second secondary winding 35b being wound around the second magnetic circuit M2. Thus, the magnetic path connecting the first 35a and the second 35b secondary winding comprises a first air gap denoted Eab at the passage from the first M1 to the second M2 magnetic circuit then a second air gap denoted Eba for the passage from the second M2 to the first M1 magnetic circuit.

[0056] According to a second embodiment shown in the figure 9b , the magnetic component comprises a first M1' and a second M2' magnetic circuit distinct from the first M1', the first M1' and the second M2' magnetic circuits comprising an air gap denoted respectively E1' and E2'. The primary winding 33 being wound around both the first M1' and the second M2' magnetic circuits, the first secondary winding 35a being wound around the first magnetic circuit M1' and the second secondary winding 35b being wound around the second magnetic circuit M2'. Thus, the magnetic path connecting the first 35a and the second 35b secondary winding comprises a first air gap E2' at the second magnetic circuit M2', a second air gap at the passage from the second M2' to the first M1' magnetic circuit, a third air gap E1' at the first magnetic circuit M1' and a fourth air gap at the passage from the first M1' to the second M2'.

[0057] According to a third embodiment shown in the figure 9c ,the magnetic component 31 comprises a magnetic circuit in the general shape of a non-closed figure eight comprising a first loop with a first air gap denoted E1, a second loop with a second air gap denoted E2 and a central part common to the first and second loops, the primary winding 33 being wound around the central part, the first secondary winding 35a being wound around the first loop, the second secondary winding 35b being wound around the second loop. Thus, the magnetic path connecting the first S1 and the second S2 secondary winding comprises a first air gap E2 and a second air gap E1.

[0058] The magnetic circuits M1, M2 and M of the different embodiments are for example preferably made of ferrite but other materials such as iron-silicon, iron powder, Nickel-Iron, nanocrystalline or amorphous metals are possible and have for example a shape ranging from a right-angled shape (square, rectangle, etc.) to a circular shape via shapes with different angles or ovals. The number of turns of the primary winding 33 and the secondary windings 35a and 35b is chosen as a function of the voltages of the high-voltage source 25 and the low-voltage source 29.

[0059] According to a variant of the first, second and third embodiments illustrated in figures 9d et 9e , the secondary circuit of the magnetic component 31 comprises at least two first secondary windings 35a in parallel and at least two second secondary windings 35b in parallel.

[0060] In applications where the current flowing in the voltage converter 21 is high, for example greater than 100A, or even greater than 200A, it is preferable to use several first diodes D1, respectively several diodes D2, in parallel in the low voltage circuit 27" to distribute the current over several diodes and thus limit losses by Joule effect. However, it may happen that the current passes preferentially in one of the parallel diodes, due for example to variability in the specifications of the diodes. Generally, the voltage drop of the diode D1, D2 decreases with the temperature, which can lead to thermal runaway: the more the voltage drops, the more the current will be diverted to the diode with the lowest drop and therefore the more its temperature rises. Providing several secondary windings in parallel, each having its respective diode, makes it possible to avoid this problem.The currents flowing in the first secondary windings in parallel are less subject to variation from one winding to the next. The same is true for the second parallel secondary windings. Thus, the diodes undergo a substantially equal current and have uniform aging.

[0061] This variant has been described with diodes D1, D2 in the 27" low voltage circuit. However, diodes D1, D2 could be replaced by switches Q1, Q2, the converter according to this variant then having similar advantages to those described previously.

[0062] The example illustrated in figure 9d is similar to the magnetic component of the figure 9c , except that the magnetic circuit M further comprises a first bar 310 and a second bar 320 connected respectively to the first and second loops. The first and second bars 310, 320 respectively carry a first winding 35a and a second secondary winding 35b. Each bar 310, 320 comprises an air gap E1, E2.

[0063] The example illustrated in figure 9e is similar to the magnetic component of the figure 9a , except that the first M1 and second M2 magnetic circuits respectively comprise two first bars 310 and two second bars 320. The first and second bars 310, 320 respectively carry a first winding 35a and a second secondary winding 35b.

[0064] As in the example illustrated in figure 9b , the magnetic component of the figure 9dcould include a first air gap E2' at the level of the second magnetic circuit M2' and a third air gap E1' at the level of the first magnetic circuit M1'.

[0065] Thus, the use of a magnetic component 31 comprising a primary winding 33 and two secondary windings 35a and 35b in a DC / DC voltage converter 21 makes it possible to perform the functions of energy transfer between the primary and the secondary as well as energy storage, which makes it possible to replace a transformer and two inductors with a single component bringing together all the magnetic elements of the converter. Such a magnetic component 31 therefore makes it possible not only to reduce the cost of the converter by reducing the number of components and in particular the components comprising ferrite, but also to reduce the size of the converter by making it possible to obtain a more compact converter.These two advantages therefore meet the requirements of the automotive market and such a magnetic component can in particular be used in hybrid or electric vehicles comprising a high voltage source to power the motor and a low voltage source to power the on-board equipment.

Claims

1. DC voltage converter (21) comprising: - a magnetic component (31) allowing energy to be transferred between a primary circuit and a secondary circuit, - a high-voltage circuit (23, 23', 23") connecting a high-voltage source (25) to the primary circuit of the magnetic component (31), - a low-voltage circuit (27, 27', 27") connecting the secondary circuit of the magnetic component (31) to a low-voltage source (29), the primary circuit of the magnetic component (31) comprising a primary winding (33) and the secondary circuit of the magnetic component (31) comprising first (35a) and second (35b) secondary windings not magnetically coupled to each other, said first (35a) and second (35b) secondary windings being magnetically coupled to the primary winding (33), and characterized in that the magnetic component (31) is configured: - on the one hand, to transfer energy from the primary winding (33) only to the second secondary winding (35b) and not to the first secondary winding (35a) during a first cycle, and to transfer energy from the primary winding (33) only to the first secondary winding (35a) and not to the second secondary winding (35b) during a second cycle, wherein passage from the first cycle to the second cycle, or passage from the second cycle to the first cycle, requires a transition phase to obtain zero-voltage switching; and - on the other hand, to act as an impedance which stores energy at the primary winding (33), the primary winding (33) and the secondary windings (35a, 35b) of the magnetic component (31) being connected by at least one magnetic circuit (M, M1, M2, M1', M2') and wherein a magnetic path connecting the first and second secondary windings comprises at least two air gaps.

2. Voltage converter (21) according to Claim 1, wherein the secondary winding (35a, 35b) to which the magnetic component acts as a transformer depends on the voltage supplied at the primary winding (33).

3. Voltage converter (21) according to either of the preceding claims, wherein the magnetic component (31) comprises a magnetic circuit (M) having the general shape of an unclosed eight and comprising a first loop with a first air gap (E1), a second loop with a second air gap (E2) and a central portion common to the first and to the second loop, the primary winding (33) being wound around the central portion, the first secondary winding (35a) being wound around the first loop, the second secondary winding (35b) being wound around the second loop.

4. Voltage converter (21) according to any one of the preceding claims, wherein the magnetic component (31) comprises a first magnetic circuit (M1, M1') and a second magnetic circuit (M2, M2') distinct from the first, the primary winding (33) being wound around both the first (M1, M1') and second (M2, M2') magnetic circuits, the first secondary winding (35a) being wound around the first magnetic circuit (M1, M1') and the second secondary winding (35b) being wound around the second magnetic circuit (M2, M2').

5. Voltage converter (21) according to Claim 4, wherein the first (M1') and second (M2') magnetic circuits respectively comprise an air gap (E1', E2').

6. Voltage converter (21) according to one of the preceding claims, wherein the secondary circuit of the magnetic component (31) comprises at least two first secondary windings (35a) in parallel and at least two second secondary windings (35b) in parallel.

7. Voltage converter (21) according to Claims 3 and 6, wherein the magnetic circuit (M) of the magnetic component (31) further comprises: - at least one first bar (310) around which a first secondary winding (35a) is wound, said first bar (310) comprising an air gap (E1) and being connected to the first loop such that the first secondary windings (35a) are parallel to each other; - at least one second bar (320) around which a second secondary winding (35b) is wound, said second bar (320) comprising an air gap (E2) and being connected to the second loop such that the second secondary windings (35b) are parallel to each other.

8. Voltage converter (21) according to Claims 4 or 5, and Claim 7, wherein: - the first magnetic circuit (M1) comprises at least two first bars (310) around which a respective first secondary winding (35a) is wound, said first bars (310) being connected such that the first secondary windings (35a) are parallel to each other; - the second magnetic circuit (M2) comprises at least two second bars (320) around which a respective second secondary winding (35b) is wound, said second bars (320) being connected such that the second secondary windings (35b) are parallel to each other.

9. Voltage converter (21) according to one of the preceding claims, wherein the high-voltage circuit (23') comprises an H bridge comprising two branches (B1 and B2) connected in parallel and each comprising a high switching element (QH1, QH2) and a low switching element (QL1, QL2) connected in series, the ends of the branches (B1 and B2) being connected to the terminals of the high-voltage source (25) and the midpoints of the branches (B1 and B2) being connected to a first and a second end of the primary winding (33), respectively.

10. Voltage converter (21) according to one of Claims 1 to 8, wherein the high-voltage circuit (23") comprises a branch (B) comprising a high switching element (QH) and a low switching element (QL) in series, the ends of the branch (B) being connected to a positive and a negative terminal, respectively, of the high-voltage source (29), the midpoint of the branch (B) being connected to a first end of the primary winding (33), the second end of the primary winding (33) being connected to the negative terminal of the high-voltage source (25) via a capacitor (37).

11. Method of controlling a voltage converter (21) according to Claim 9, wherein the switching elements (QH, QL, QH1, QH2, QL1, QL2) of the high-voltage circuit (23') are driven cyclically such that, during a first cycle portion, for the first branch (B1), the high switching element (QH1) connected to the positive terminal of the high-voltage source (25) is in the closed position and the low switching element (QL1) connected to the negative terminal of the high-voltage source (25) is in the open position while for the second branch (B2), the high switching element (QH2) connected to the positive terminal of the high-voltage source (25) is in the open position and the low switching element (QL2) connected to the negative terminal of the high-voltage source (25) is in the closed position, and during a second cycle portion, for the first branch (B1), the high switching element (QH1) connected to the positive terminal of the high-voltage source (25) is in the open position and the low switching element (QL1) connected to the negative terminal of the high-voltage source (25) is in the closed position while for the second branch (B2), the high switching element (QH2) connected to the positive terminal of the high-voltage source (25) is in the closed position and the low switching element (QL2) connected to the negative terminal of the high-voltage source (25) is in the open position.

12. Method of controlling a voltage converter (21) according to Claim 10, wherein the switching elements (QH, QL) of the high-voltage circuit (23") are driven cyclically such that, during a first cycle portion, the high switching element (QH) connected to the positive terminal of the high-voltage source (25) is in the closed position and the low switching element (QL) connected to the negative terminal of the high-voltage source (25) is in the open position and, during a second cycle portion, the high switching element (QH) connected to the positive terminal of the high-voltage source (25) is in the open position and the low switching element (QL) connected to the negative terminal of the high-voltage source (25) is in the closed position.