Isolated DC-DC converter, electrical network comprising such a converter, and associated conversion method

Abstract

Isolated DC-DC electrical converter, electrical network comprising such an electrical converter and associated conversion method. The present invention relates to an isolated DC-DC electrical converter (2), configured to convert a first direct current under a first voltage received at input terminals (4) into a second direct current under a second voltage at output terminals (6), the electrical converter (2) comprising a first circuit (10) connected to the input terminals (4) and a second circuit (12) connected to the output terminals (6), the electrical converter (2) further comprising a magnetic coupler (14) coupling the first circuit (10) to the second circuit (12), the electrical converter (2) comprising a controller (8) configured to control controlled switches ( , , , , , , ) according to a control law defining at least a first duty cycle, defining a switching ratio of primary switches ( , , , ).according to a first function and / or according to a second function. Figure for the abbreviation: Figure 1,

Description

Title of the invention: Isolated DC-DC electrical converter, electrical network comprising such an electrical converter and associated conversion method

[0001] The present invention relates to an isolated DC-DC electrical converter. The invention further relates to an avionics electrical network intended to be on board an aircraft, and comprising such a DC-DC electrical converter.

[0002] The present invention further relates to a conversion method.

[0003] The invention relates to the field of isolated or continuous DC / DC converters- isolated DC. In particular, the invention relates to DC / DC converters compatible with constrained networks which are for example intended to be installed on board an aircraft, for example forming part of an avionics electrical network of the aircraft.

[0004] To convert electrical energy from a first DC voltage into a second DC voltage galvanically isolated from the first, it is known to use DC / DC converters. Depending on the intended application of the corresponding converter, these converters are subject to specific constraints. For example, in the aeronautical field, constraints concern operational safety, conversion efficiency requirements, and this in particular in the context of input and output voltages and / or electrical loads which are likely to have high dynamics. Added to this is the need for electromagnetic compatibility, which imposes a constant switching frequency of the DC / DC converters.

[0005] For example, converters having the dual active bridge topology are likely to be used in avionics applications. Solutions for controlling such converters according to given requirements are known per se. For example, soft switching makes it possible to increase the efficiency of this type of converter. On the other hand, the known solutions are often relatively complex.

[0006] For example, such solutions require complex control and / or calculation means, which is contrary to an objective of low-cost integration and small footprint. In particular, this complexity often requires the implementation of a digital controller, for example with one or more processor(s). This type of solution is particularly expensive to certify in the case of an avionics application.

[0007] An aim of the present invention is to at least reduce the aforementioned drawbacks.

[0008] In particular, an aim of the present invention is to obtain a converter DC-DC electrical, including an isolated DC-DC converter, configured to implement efficient electrical conversion, while being particularly simple to implement.

[0009] For this purpose, the invention relates to an isolated DC-DC electrical converter, configured to convert a first DC current under a first voltage Vj received at input terminals into a second DC current under a second voltage V2 at output terminals, the electrical converter comprising a first circuit connected to the input terminals and comprising controlled switches, called primary switches, and a second circuit connected to the output terminals and comprising controlled switches, called secondary switches, the first circuit and the second circuit each forming an inverter and / or a rectifier, the electrical converter further comprising a magnetic coupler coupling the first circuit to the second circuit, the magnetic coupler comprising primary terminals connecting the magnetic coupler to the first circuit and secondary terminals connecting the magnetic coupler to the second circuit,

[0010] the electrical converter comprising a controller configured to control the switches controlled according to a control law defining a frequency of fixed switching of the converter, so as to obtain electrical power average converted by the electrical converter less than or equal to a power predetermined constant, called limiting power, the average electrical power being the power transmitted on average by the electrical converter, for at least less than one switching period of said electrical converter, between the terminals input and output terminals, said control law defines at least a first duty cycle, defining a switching ratio of the primary switches, according to a first function defined as follows:

[0011] ^dvvî j , Q tminFP VlmmFP Dmax

[0012] and / or according to a second function defined as follows:

[0013] / iz 17 \ _ t VtminFP / / “> i or . ^11 V k” V2c ~~ “K VTÂ y^Dmax

[0014] l7ic is an adjusted value depending on the first voltage Vj;

[0015] V2c is an adjusted value depending on the second voltage V2;

[0016] ^dv is a constant value;

[0017] VimmFP is a predetermined minimum value of the first voltage Vj when the electrical converter converts maximum power;

[0018] ViminFP is a predetermined minimum value of the second voltage V2 when the electrical converter converts the maximum power;

[0019] D\max is a predetermined maximum value of the first duty cycle preferably D^ax < 1 / 2;

[0020] ^2max is a predetermined maximum value of a second duty cycle D2 defining a switching ratio between the secondary switches, preferably ^2max ^1 / 2,

[0021] CD„,„ is equal to 2D„„,„( + 2D^,,( lP^) - 1 / 2 .

[0022] According to other advantageous aspects of the invention, the converter comprises a or more of the following characteristics, taken individually or in all technically possible combinations: - The first duty cycle is controlled according to said first function if

[0023] ; V- . rp........— v IotA 2c / v ImmFP . Vv Y-Dmax

[0024] otherwise the first duty cycle D] being controlled according to said second function. - The said control law defines the second cyclic ratio D2 according to the following function:

[0025] p ( yy ) = « ™ d / v, Vn ï where: ^2\ v le* 2c / ^dVV^ A 2c /

[0026] « _ 2minJ~P . d V

[0027] - The electrical converter is defined by design parameters LDAB, n and LM, where:

[0028] Lm is the inductance measured across the terminals when the terminals are open circuit;

[0029] n is the ratio of the voltage measured at the terminals to the voltage measured at the terminals, when the current flowing in is zero;

[0030] ^dab is the inductance measured across the terminals when the terminals are short-circuited.

[0031] The design parameters ^dab, n and LM are defined to be equal to noph LDABopt and LMopJ respectively, where:

[0032] nopt— cv QAV-^A v„.w

[0033] j _ vUhmFP „ ; ^DABopt ''opt app ^Bmax ■ 1 .w 1 Um

[0034] , where:

[0035] F is a restricted domain of definition of the first and second voltage Vp V2 defined by: VlminFP ~ bninZVS - - ^îmaxZVS ^2minFP - ^2minZVS - ~ ^2maxZVS

[0036] Vxwcî with X being equal to 1 or 2, is a voltage Vy, X being equal to 1 or 2, of the couple (yy?j allowing to maximize the magnitude v2 on domain F; — a 4 / vM' iirn

[0037] FyHf.2 with X being equal to 1 or 2, is a voltage Vx, % being equal to 1 or 2 of the couple (y, y3 allowing to maximize the magnitude QÀ F) on the domain F; '' “ Fi

[0038] TZVs\ is a predetermined time period for charge transfer between the switches during a dead time to satisfy a zero voltage switching condition in the first circuit;

[0039] Tzv si is a predetermined time period for a charge transfer between the switches during a dead time to satisfy a zero voltage switching condition in the second circuit;

[0040] P nm is the limiting power;

[0041] is a maximum sum of charges stored in a parasitic capacitance drain-source dependent on the primary switches and the first voltage V], evaluated in F;

[0042] Q { ) is a maximum sum of charges stored in a parasitic capacitance drain-source depending on the secondary switches and the second voltage V2, evaluated at F2,vc2;

[0043] F,w is the switching frequency of the converter. - The controller is configured to control the controlled switches according to a control law defining a fixed switching frequency of the converter, so as to obtain an average electric current converted by the electric converter less than or equal to a predetermined constant current, called the limiting current. - The converter is a converter having the active dual bridge topology and / or the controller is an analog controller and / or includes non-programmable logic configured to control the switches.

[0044] The invention also relates to an avionics electrical network intended to be installed in an aircraft, comprising at least one load and an electrical converter according to any one of the preceding claims.

[0045] The invention further relates to a method of conversion by an electrical converter according to any one of the preceding claims, of the first direct current under the first voltage Vj received at the input terminals of the electrical converter into the second direct current under the second voltage V2 at the output terminals of the electrical converter, the conversion method comprising a step of conversion in which the switches are controlled according to the control law, the average electrical power converted by the electrical converter obtained being less than or equal to the limiting power.

[0046] These characteristics and advantages of the invention will appear on reading the description which follows, given solely by way of non-limiting example and made with reference to the appended drawings, in which: - [Fig.l] [Fig.l] is a schematic view of a direct-direct electrical converter according to the invention; - [Fig.2] [Fig.2] is a schematic graph of a development over time of a first alternating voltage from a transformer of the converter of [Fig.l]; - [Fig.3] [Fig.3] is a schematic graph of a development over time of a second alternating voltage of the transformer of the converter of [Fig.l]; - [Fig.4] [Fig.4] is a schematic graph of a voltage waveform of figures 2 and 3 when the voltages are out of phase with each other, as well as currents present in the converter, and - [Fig.5] [Fig.5] is a schematic view of a model of a magnetic coupler forming a coupler of the electrical converter of [Fig.l].

[0047] With reference to [Fig.l], a direct-direct electrical converter 2, or DC / DC converter, is schematically represented.

[0048] The converter 2 is for example configured to be on board an aircraft, not shown, but is not limited to this example. In particular, the converter 2 is configured to be integrated into an avionics electrical network which is on board the aircraft, such as a network of the 28 VDC type or of the rectified 115VAC type.

[0049] This avionics electrical network comprises for example at least one electrical load, not shown, as well as the converter 2 capable of supplying the or each electrical load.

[0050] The converter 2 comprises a pair of input terminals 4 and a pair of output terminals 6. According to one example, the terminals 4, 6 are capable of being connected to the avionics electrical network.

[0051] The converter 2 is configured to convert a first direct current under a first voltage V} received at the input terminals 4 into a second direct current under a second voltage V2 at the output terminals 6. The converter 2 is thus in particular configured to supply the second current under the second voltage V2 to the output terminals 6.

[0052] According to one example, the second current has a second voltage VL different from the first voltage Vb. According to another example, the second voltage VL is equal to the first voltage V(. In this case, the converter 2 makes it possible in particular to obtain galvanic isolation of the input terminals 4 from the output terminals 6.

[0053] According to one example, the converter 2 is an isolated converter. It therefore preferably has galvanic isolation between the input terminals 4 and the output terminals 6. The conversion is thus isolated or not, namely that the terminals 4 and 6 may or may not share a common potential.

[0054] The converter 2 is preferably a bidirectional converter. The converter is in particular capable of converting electrical power from the input terminals 4 to the output terminals 6 and vice versa.

[0055] The converter 2 is in particular dimensioned and then controlled to convert a direct current source under the first voltage at the input terminals 4 into a direct current source under the second voltage V2 at the output terminals 6.

[0056] According to one example, the converter 2 is configured to convert an electrical power in a range between 10 W and 10 kW.

[0057] The converter 2 comprises a plurality of controlled switches T2, T 7\ ^6, ^7, ^8- The switches T\ to are in particular bidirectional in current to closed state and unidirectional in current in the open state. Each switch Tf at T% is for example made up of, or similar in its operation to, a MOSFET type transistor (acronym for "metal-oxide-semiconductor field-effect transistor") or even an IGBT in parallel with a diode. Alternatively, the converter 2 includes more or fewer switches.

[0058] The converter 2 further comprises a controller 8 configured to control the switches T} to L8. For example, the controller 8 is connected to the switches T} to T8 by a connection 9 to control the switches T8. The connection 9 is illustrated in FIG. 1 only between the controller 8 and the switches Tb T5 and T7. Of course, the controller 8 is preferably connected by the connection 9 to each of the switches 7\ to Fs.

[0059] The converter 2 preferably has the dual active bridge topology or DAB topology (from the English “Dual Active Bridge”). According to other examples, the converter 2 has a topology comprising at least one half-bridge with one or more controlled switch arms. According to one example, each bridge of the converter is a half-bridge of controlled switches associated with a capacitive half-bridge.

[0060] The converter 2 comprises a first circuit 10, in particular in the form of a bridge, connected to the input terminals 4, a second circuit 12, in particular in the form of a bridge, connected to the output terminals 6, and a magnetic coupler 14 coupling the first circuit 10 to the second circuit 12. The magnetic coupler 14 comprises primary terminals 16 connecting the magnetic coupler 14 to the first circuit 10 and secondary terminals 18 connecting the magnetic coupler 14 to the second circuit 12.

[0061] The first circuit 10 comprises a portion of the plurality of switches T\ to T called primary switches T2, T4. The primary switches TY to / 4 are configured to generate a first alternating voltage Vaci at the primary terminals 16 of the magnetic coupler 14.

[0062] The second circuit 12 comprises the complementary part of this plurality of switches, called secondary switches T. The secondary switches T5 to are configured to generate a second alternating voltage Vaci, at the secondary terminals 18 of the magnetic coupler 14.

[0063] According to examples of operation of the converter 2, each circuit among the first circuit 10 and the second circuit 12 forms an inverter, generating in particular an alternating voltage and / or an alternating current, or forms a rectifier, generating in particular a direct voltage and / or a direct current. For example, when the converter 2 converts a power received at the input terminals 4 to the output terminals 6, the first circuit 10 forms an inverter and the second circuit 12 forms a rectifier. Conversely, when the converter 2 converts a power received at the output terminals 6 to the input terminals 4, the second circuit 12 forms an inverter and the first circuit 10 forms a rectifier.

[0064] Preferably, the controller 8 is configured to control the primary switches T T2, TT4 independently of a control of the secondary switches T6, T7, by the controller 8.

[0065] The controller 8 is preferably an analog controller. This is particularly advantageous for applications that are expensive to certify. According to one example, the controller 8 comprises non-programmable logic configured to control the switches T to Lg. By analog controller, for example, is meant a device for regulation and control by continuous value ranges (in particular in opposition to discrete values), preferably in real time and continuous, based on a continuous and real-time measurement of the controlled output, without time sampling or reading of information on a past measurement.For example, the analog controller is an operational amplifier assembly type circuit, open or closed loop, whose output voltage level is translated by a control circuit to generate, for example, a phase shift between primary and secondary bridges, a switching frequency, or the duty cycle of the bridges, over ranges of values ​​that are also continuous. This type of controller is thus particularly opposed to digital solutions based on a quantification of the measured and controlled values ​​on the one hand, sampled and stored on the other hand.

[0066] Referring for example to [Fig. 1], the magnetic coupler 14 forms a quadrupole having the primary terminals 16 and the secondary terminals 18. The magnetic coupler 14 comprises in particular a transformer 20 comprising a primary winding 22 and a secondary winding 24.

[0067] Preferably, with reference to Figure 5, the magnetic coupler 14 forms a model and can take different embodiments. In particular, the magnetic coupler 14 electrically corresponds to a perfect transformer of ratio fl, whose primary winding is parallel to a magnetizing inductance LM. A current passing through the magnetizing inductance LM is called According to the model of the magnetic coupler 14, the terminals of this winding electrically correspond to the primary terminals of the quadrupole. The other two terminals, called secondary terminals, are defined as those of the series connection of the secondary winding of the equivalent perfect transformer with an inductance of DAB LDAB. For example, the magnetic coupler 14 comprises a transformer with two coupled coils, connected in series or not with a dedicated inductive component.In particular, the ratio is a ratio of the voltage present between the secondary terminals 18 to the voltage present between the primary terminals 16, when a current, that is to say the current in the . branch of the magnetic coupler 14 comprising the inductance of DAB LDAB, is equal to 0. CONVERTER 2 PARAMETERS

[0068] The controller 8 is configured to control the switches according to a control law.

[0069] The following parameters are defined for the converter 2, and in particular for the controller 8 capable of controlling the switches according to the control law. The parameters include quantities and constants.

[0070] The quantities are in particular defined as follows.

[0071] Vj is the voltage at the input terminals 4, called the first voltage;

[0072] V2 is the voltage at the output terminals 6, called the second voltage;

[0073] Vk. is an adjusted value depending on the first voltage Vj;

[0074] V2c is an adjusted value depending on the second voltage V2;

[0075] VAC1 is a first alternating voltage at the primary terminals 16 of the magnetic coupler 14;

[0076] VAC2 is the second alternating voltage at the secondary terminals 18 of the magnetic coupler;

[0077] D] is a first duty cycle of the first circuit 10;

[0078] is a second duty cycle of the second circuit 12;

[0079] Vknï is the mode change voltage for Dv

[0080] 0 is a phase shift of Vaci with respect to VAci, in particular the phase shift between the fundamentals of the waveforms of VAC2 compared to VAC1. By "fundamentals of the waveforms" is meant the fundamental components resulting from the spectral decomposition over a theoretically infinite time of the respective waveforms of Vaci and in steady state.

[0081] is the maximum sum of a charge stored in a drain-source parasitic capacitance depending on the primary switches (T^ and the first voltage V].() is a function of V [.

[0082] Q2 is the maximum sum of a charge stored in a drain-source parasitic capacitance depending on the secondary switches (7 \ T7, T8) and the second voltage V2. ô2 is a function of V2.

[0083] Qï and ô2 are functions of Vj and V2 respectively, strictly increasing, and depend on the transistors chosen to form the switches T

[0084] The first duty cycle is in particular the duty cycle of the primary switches T2, TIn particular, by "first duty cycle D}" is meant the ratio between the duration, over a period of the first alternating voltage during which this voltage Vagi is positive, and the duration of this period.

[0085] The second duty cycle D2 is in particular the duty cycle of the secondary switches T5, T^, T^T^. In particular, by "second duty cycle D2" is meant the ratio between the duration, over a period of the second alternating voltage Vac2, during which this voltage Vac2 is positive, and the duration of this period.

[0086] Examples of the first and second duty cycle D2 are illustrated in [Fig.4],

[0087] The constants are in particular defined as follows.

[0088] Preferably, the constants are predetermined and / or fixed by an operator or a manufacturer of the converter 2.

[0089] Fw is the switching frequency of converter 2;

[0090] V imüiFP is a predetermined minimum value of the first voltage Vj when the converter 2 converts a maximum power, in particular a limiting power;

[0091] ViminFP is a predetermined minimum value of the second voltage V when the converter 2 converts the maximum power, in particular the limiting power;

[0092] V\jninzvs is a minimum value of the first voltage Vj, in particular a voltage minimum of the first voltage V1 beyond which the converter 2 implements a conversion according to the principle of zero voltage switching or ZVS (from the English “Zero Voltage Switching”), where preferably V imînzvs - ^immFP;

[0093] V2mmzvs is a minimum value of the second voltage V2, in particular a voltage minimum of the second voltage V2 beyond which the converter 2 implements a conversion according to the ZVS principle, where preferably V^nzvs - ^2minFP;

[0094] VimaxZVS is a maximum value of the first voltage Vb, in particular a maximum voltage of the first voltage below which the converter 2 implements a conversion according to the ZVS principle, where preferably IrnaxZVS “ IminZVS ,

[0095] V2tmxZvs is a maximum value of the second voltage V2, in particular a maximum voltage of the second voltage V2 below which the converter 2 implements a conversion according to the ZVS principle, where preferably V2,maxZVS ZminZVS,

[0096] F is a restricted domain of definition of the values ​​taken by and V2, defined by: i00971 f V, ™v <V < V, -7, / v / j ' ]jmnpp — f IminZVS — ~ r imaxZVS I y. . < y < y. [ ' 2mmFP ~ ' zminZVS ~ ' 2 ~ ' 2maxZVS

[0098] Pum is a limiting power of the electrical converter 2;

[0099] ViHYi and F2H,ci are the voltage values ​​of Vh respectively V2 allowing to maximize the magnitude v^p 4^ çy yy^y,) y2 on the domain F;

[0100] Fbw,2 and Vlwc2 are the voltage values ​​of F2 respectively allowing to maximize the magnitude Qd.F) on the domain F; ytvyjy

[0101] CDra„ = 20,,,,.,,(1-D|,„„) + 2D2lm(lD^) -1 / 2;

[0102] Tzvsl is a predetermined time period for charge transfer between the switches during a dead time to satisfy a zero voltage switching condition in the first circuit 10;

[0103] Tzvsi is a predetermined time period for charge transfer between the switches during a dead time to satisfy a zero voltage switching condition in the second circuit 12.

[0104] By "soft switching" is meant a switching by closing the switches ordered at a time when the voltage at the terminals of their respective channels is zero, or comparable to zero. For example, in the case of using MOSFET type transistors or equivalent, the voltage present at the drain-source terminals during so-called reverse conduction is considered to be zero.

[0105] Dunax is a predetermined maximum value of the first duty cycle, preferably 0 < Dlmax < 1 / 2, more preferably D}max being substantially equal to 1 / 2;

[0106] is a predetermined maximum value of the second duty cycle, preferably 0 < D2max 1 / 2, more preferably Dzmax being substantially equal to 1 / 2 ;

[0107] The predetermined minimum frequency is for example predetermined as a function of a filtering constraint of the first and / or second current received or supplied by the converter 2.

[0108] The minimum value of the first voltage V\minFP is preferably determined as a function of a system that may be connected to the input terminal 4, for example an electrical network, such as the avionics electrical network. The minimum value of the second voltage VzminFP is for example also determined as a function of a system that may be connected to the output terminal 6, for example the electrical network and / or an electrical load.

[0109] For example, the minimum value of the first and / or second voltage V bninFP, ^2mmFP is predetermined by a standard. For example, for an avionics network, the minimum values ​​of the first and second voltages are defined by corresponding standards. For example, the values ​​hninFP and VimmFP are equal to 28V.

[0110] Referring to Figure 2, an example of the first alternating voltage Vaci over time t is illustrated with an indication of the state of each primary switch T2, T3, r4 at each instant as controlled by the controller 8. The first alternating voltage VACi has three different values, namely Vaci ~ ^zi ; Vaci ~ 0 or ^Aci ~ ~ When the primary switches T{ and TA are closed, the first alternating voltage Vaci is equal to V}. When the primary switches T2 and TA or T ; and T3 are closed, the first alternating voltage Vaca is equal to 0. When the primary switches T2 and T 3 are closed, the first alternating voltage VAcf is equal to - In each of the above examples, the other two primary switches not mentioned are in the open state.

[0111] Referring to Figure 3, an example of the second alternating voltage Vaci over time t is illustrated, similarly to Figure 2. The second alternating voltage VAC2 has three different values, namely VAC2 = ^2; Vac2 — 0 or VAC2 ~ ~ ^2- When the secondary switches T5 and T8 are closed, the second alternating voltage Vac2 is equal to V2. When the secondary switches T6 and T% or T5 and Tj are closed, the second alternating voltage Vac2 is equal to 0. When the secondary switches T6 and T2 are closed, the second alternating voltage Vac2 is equal to - V2. In each of the above examples, the other two secondary switches not mentioned are in the open state.

[0112] The examples of figures 2 and 3 apply in particular to a magnetic coupler according to the preceding definition, comprising an equivalent perfect transformer of ratio n, such as illustrated in particular in figure 5, capable of generating a potential difference n VAC1 - VAC2 at the terminals of the inductance Ldab illustrated in [Fig.5].

[0113] With reference to Figure 4, the phase shift 0 between the alternating voltages Vac2 and VACi is illustrated, where the alternating voltages Vac2 illustrated in Figure 4 are those illustrated in the examples of Figures 2 and 3. The phase shift 0 corresponds in particular to the phase shift between fundamentals of the waveforms VAC2 and Vaci, expressed proportionally to the switching period.

[0114] With reference to Figure 4, when the controller 8 controls the switches according to the examples of Figures 2 and 3, the converter 2 has a current waveform i(LDAB) corresponding to a current flowing through the inductance Ldab and also has a current waveform i(LM) corresponding to a current flowing through the inductance LM. CONTROL LAW

[0115] The controller 8 is configured to control the switches T to T $ according to the control law defining a fixed switching frequency Fxw of the converter 2. The control law is such that an average electrical power converted by the converter 2 is less than or equal to a predetermined constant electrical power, called limiting power Pum in the present document. In particular, the controller 8 comprises an electronic circuit or electronic components specific to the control law.

[0116] The average electrical power is the power transmitted on average by the converter 2 during at least one switching period of the converter 2 between the input terminals 4 and the output terminals 6.

[0117] In particular, the average electrical power is the power which is transmitted on average during n periods, where n is an integer greater than or equal to 1.

[0118] For example, the average electrical power is the power that is transmitted by the converter on average during a single switching period. According to another example, the average electrical power is the power transmitted by the converter 2 during several switching periods.

[0119] According to one example, by “average electrical power” is meant the arithmetic mean of the power over one or more switching periods.

[0120] By “converter switching period” is meant in particular the duration, in the permanent state, between two successive closing times of a given switch of the converter 2.

[0121] Each switch at 7g has in particular either the open state or the closed state. The operation of the converter 2 is further defined by the switching frequency Fsw of the converter 2. The switching frequency Fw is the inverse of the switching period.

[0122] Preferably, the limiting power P um is adjusted by the controller 8.

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129]

[0130]

[0131]

[0132]

[0133]

[0134]

[0135]

[0136] The limiting power Pum depends, for example, on the operating requirements of the converter 2. For example, the limiting power Pum is set according to the nominal power of the loads and / or devices supplied by the converter 2 and / or according to a desired regulation dynamic, for example according to a requirement for rapid power-up of a device supplied by the converter 2. The control law defines the first duty cycle DY of converter 2 as a function of the adjusted values ​​V ]cj V2o according to a first function defined as follows: THE VhmnFP ri 1 V, V,, ''Dmax / y and / or according to a second function defined as follows: Ten / \ / Y_ 1 VlminFP l^imax V le V2c ~2 V.. ^Dimu In this case, the controller 8 is configured to control the primary switches T according to the first duty cycle D j defined by the control law. The adjusted value Vk depending on the first voltage Vj is in particular a voltage mathematically clipped by the controller 8. For example, the adjusted value Vle is equal to the maximum of the values ​​Vx and ViminFP - The adjusted value Vk is thus preferably equal to max(V1, VlminFP). The adjusted value V2c depending on the second voltage V2 is in particular a voltage clipped mathematically in an analogous manner. The adjusted value V2c is thus preferably equal to max(V2, V2mjnFP). According to one example, the control law is such that the first duty cycle is controlled according to said first function if < V] ( V2c ), where: \mnFP -- Otherwise, the first duty cycle is controlled according to the second function. According to one example, the control law further defines the second duty cycle D2 as being equal to a fixed value or as a function of the or each adjusted value VV2e. In this case, the controller 8 is configured to control the secondary switches T s to T$ according to the second duty cycle D2 defined by the control law according to the following formula: j _ ^2 2c _ is constant over the entire operating domain of the dV DtmaxV\mmFP converter 2.

[0137] According to examples, the phase shift 0 makes it possible to adjust the transmitted power. For example, the phase shift is a strictly increasing function of the converter power over the interval [0; *4].

[0138] The limiting power Pum is limited to a constant value, independent of the conditions on the first voltage Vj and the second voltage V2, and equal to:

[0139] p . _ ^2mmFP " pi rlim ~ ^FsuLdab hDmax

[0140] Furthermore, in the case where the second voltage V2 is constant, the second current is limited to a predetermined constant value, called the limiting current, equal to:

[0141] T = ±ImmFP n H™ ~ AF^Lp^Dmax

[0142] The converter 2, and in particular the magnetic coupler 14, is sized and configured to control the controlled switches according to the control law so as to obtain smooth switching operation of the controlled switches T \ over a predetermined operating range. In particular, the magnetic coupler 14 has a plurality of design parameters Ldab, n, and having values ​​determined according to formulas specific to the group of functions chosen from the control law.

[0143] A first design parameter Ldab is in particular the inductance of DAB of the magnetic coupler 14, obtained for example by impedance measurement on the coupler isolated at its secondary terminals 18, when its primary terminals 16 are short-circuited.

[0144] A second design parameter n is a ratio of V ac2 to VACi when a current in a branch of the magnetic coupler is equal to 0. The design parameter 11 corresponds in particular to the transformation ratio of the equivalent perfect transformer of the magnetic coupler 14. This ratio is for example measured from the ratio of the voltage of Vac2 to the voltage Kaci of the isolated magnetic coupler 14 when the current at the secondary terminals 18 is zero.

[0145] A third design parameter LM is in particular the magnetizing inductance Lm of the magnetic coupler 14. It is for example obtained by impedance measurement on the magnetic coupler 14 isolated at its primary terminals 16, when its secondary terminals 18 are in open circuit.

[0146] Preferably, each design parameter Ldab, n, and is determined so as to obtain zero voltage switching of the primary and / or secondary switches T j called the ZVS principle.

[0147] In particular, the design parameters LDAB and LM form design rules for obtaining, from the model forming the magnetic coupler 14, the converter 2.

[0148] In particular, there is a triplet \LDABopt, nop1, LM„p^ solution of the design parameters LDAb, n, and LM, making it possible to obtain optimal operation in terms efficient currents, while maintaining smooth switching within the converter.

[0149] opt ~ 1.

[0150] T __ ImâiFP 2nmFF ^DABopt — nopt 4 p[;m ^Dmax

[0151] _______________________________ Mopt v-,mü O.1V, ,1 , ,,!■«

[0152] ) s'Sn'9ue is evaluated in Viwci and g ( I^cz) s9ue ^2 is evaluated in V2wc2-

[0153] A conversion method implemented by the converter 2 is now described.

[0154] During the conversion process, the converter 2 converts the first direct current under the first voltage Vi received at the input terminals 4 into the second direct current at the output terminals 6 under the second voltage V2.

[0155] During a conversion step of the conversion method, the controller 8 controls the switches T1 to T2 according to the control law so as to obtain an average electrical power converted by the electrical converter 2 less than or equal to the limiting power Pnm. The control law is defined as described previously.

[0156] For example, the conversion method comprises several repetitions of the conversion step. Preferably, the controller 8 controls the switches T to Ts according to the control law so as to obtain the first and / or second alternating voltage VACi, ^4C2, with the first duty cycle and / or the second duty cycle D2 as defined by the control law.

[0157] It is understood that the converter 2 according to the invention, and in particular the control law, presents(s) a large number of advantages.

[0158] Indeed, the converter 2 makes it possible to implement an efficient electrical conversion, while being particularly simple to implement. The control law makes it possible to control the converter 2 in a simple and efficient manner, since it is sufficient to apply, for example, one of the examples of the control law to obtain the electrical conversion by the DC / DC converter. The control law makes it possible, for example, to use a controller 8 having a simple architecture, such as an analog controller and / or a controller having non-programmable logic. This is particularly advantageous in the aeronautical field, since certification of such a controller 8 is much less complex and / or expensive than a digital counterpart, for example. Alternatively, the controller 8 can be implemented by a microcontroller, an integrated circuit or an FPGA, from the English Field Pro- grammable Gate Array.

[0159] In particular, the elements constituting the converter 2 used are dimensioned, and said converter 2 is controlled in such a way that its active elements are switched to zero voltage on the one hand, and that the effective currents through its various active and passive elements are reduced. This operating mode, guaranteed over the entire operating range in output load values, input voltage, and output voltage, ensures a conversion with optimized efficiency on the one hand.

[0160] On the other hand, the switching frequency of the converter 2 is kept constant in order to guarantee electromagnetic compatibility of the converter 2, and to avoid more restrictive filtering steps than on existing converters.

[0161] Finally, the control law limits the maximum power and / or the maximum current to a constant value which are respectively the limiting power P um and the intensity which are independent of the input and output voltages.

[0162] Of course, other control laws can be envisaged, provided that the average electrical power converted by the electrical converter 2 is less than or equal to the limiting power Pnm and the switching frequency is kept constant.

Claims

1. Claims Isolated DC-DC electrical converter (2), configured to convert a first DC current under a first voltage received at input terminals (4) into a second DC current under a second voltage V2 at output terminals (6), the electrical converter (2) comprising a first circuit (10) connected to the input terminals (4) and comprising controlled switches, called primary switches (7'1, 74, ^3, ^4) and a second circuit (12) connected to the output terminals (6) and comprising controlled switches, called secondary switches (7'5, ^6, 7\ ^8), the first circuit (10) and the second circuit each forming an inverter and / or a rectifier, the electrical converter (2) further comprising a magnetic coupler (14) coupling the first circuit (10) to the second circuit (12),the magnetic coupler (14) comprising primary terminals (16) connecting the magnetic coupler (14) to the first circuit (10) and secondary terminals (18) connecting the magnetic coupler (14) to the second circuit (12), the electrical converter (2) comprising a controller (8) configured to control the controlled switches (Tb 74, ^3, 7^, 7^, ?4, T7, 7'g) according to a control law defining a fixed switching frequency of the converter, so as to obtain an average electrical power converted by the electrical converter (2) less than or equal to a predetermined constant power, called limiting power, the average electrical power being the power transmitted on average by the electrical converter, during at least one switching period of said electrical converter (2), between the input terminals (4) and the output terminals (6),said control law defines at least a first cyclic ratio 7?b defining a switching ratio of the primary switches (Tb according to a first function defined as follows:, and / or according to a second function defined as follows: DI T7 1 / ] i Irmn W 1 / ^ ■> WHERE 1 V le» V 2c “ ~ TJ ^Dmax \ / kl Imcix T Vlc is an adjusted value depending on the first voltage Vj; V2c is an adjusted value depending on the second voltage V2; Vdv is a constant value; V\minFP is a predetermined minimum value of the first voltage Vj when the electrical converter (2) converts a maximum power; ^2minFP is a predetermined minimum value of the second voltage V2 when the electrical converter (2) converts the maximum power; Dimax is a predetermined maximum value of the first duty cycle, preferably Dlmax < 1 / 2; is a predetermined maximum value of a second duty cycle / ¾ defining a switching ratio between the secondary switches (T^, preferably D2max 1 / 2, - 1 / 2.

2. Electrical converter (2) according to claim 1, wherein the first duty cycle is controlled according to said first function V (V 1 = V ___Ç—_X____ v lcrit V v 2c / v ïnünFP Id^ ---- otherwise the first duty cycle is controlled according to said second function.

3. Electrical converter (2) according to any one of the preceding claims, wherein said control law defines the second duty cycle D2 according to the following function: D2( Vv V*) = o / Vu, where: _ D?maxV 2minFP 1dV ~ D}maxV

4. An electrical converter (2) according to any preceding claim, wherein the electrical converter (2) is defined by design parameters LDAB, n and where: LM is the inductance measured across the terminals (16) when the terminals (18) are open circuited; n is the ratio of the voltage measured across the terminals (18) to the voltage measured across the terminals (16), when the current flowing in (18) is zero; Ldab is the inductance measured across the terminals (18) when the terminals (16) are short-circuited.

5. An electrical converter (2) according to claim 4, wherein the design parameters LDAB, n and LM are defined as being equal. respectively to nopt, LnABopt and Lwopt, where: VV _ P 2lninFP i 'DABopt ~ nopt 4 Fsw p / im ^Dmax , Or : ^Mopt - F is a restricted domain of definition of the first and second voltage Vf, V2 defined by: VïminFP < Vbm-nZVS < < VlmaxZVS ^2mlnFP - ^hninZVS - K, - V'lmaxZVS < FX(W?] with X being equal to 1 or 2, is a voltage Vx, X being equal to 1 or 2, of the couple (yy^ allowing to maximize the magnitude v^fp QS )V2 on the domain F; Vxwc2 with X being equal to 1 or 2, is a voltage VY, X being equal to 1 or 2 of the couple (yy?) allowing to maximize the magnitude on the domain F; DiCF^) v, TZy sf is a predetermined time period for a charge transfer between the switches (T T2, i F Tx 7\ during a dead time to satisfy a zero voltage switching condition in the first circuit (10); PZvs2 is a predetermined time period for a charge transfer between the switches (Tb T2,7\1\ TTx T^) during a dead time to satisfy a zero voltage switching condition in the second circuit (12); P nm is the limiting power; ô]( ^hrcî) is a maximum sum of charges stored in a drain-source parasitic capacitance depending on the primary switches (Tb F2, P3, P4) and the first voltage evaluated at V1H,d; Q^V 2wc2) is a maximum sum of charges stored in a

6. drain-source parasitic capacitance depending on the secondary switches (P5, P6, P7, Ps) and the second voltage V2, evaluated in V 2wc2; Fsw is the switching frequency of the converter (2). Electrical converter (2) according to any one of the claims previous, the controller (8) being configured to control the inter- controlled breakers (Tb T2, ^3, ^4, ^5, ^6, ^7, T8) according to a control law defining a fixed switching frequency of the converter, so as to obtain an average electric current converted by the electric converter (2) less than or equal to a predetermined constant current, called the limiting current.

7. Electrical converter (2) according to any one of the preceding claims, the converter (2) being a converter having the active double bridge topology and / or the controller (8) is an analog controller and / or comprises non-programmable logic configured to control the switches (7\, T2, T(> Tj, T8).

8. Avionics electrical network intended to be on board an aircraft, comprising at least one load and an electrical converter (2) according to any one of the preceding claims.

9. Method of conversion by an electrical converter (2) according to any one of the preceding claims, of the first direct current under the first voltage Vj received at the input terminals (4) of the electrical converter (2) into the second direct current under the second voltage V2 at the output terminals (6) of the electrical converter (2), the conversion method comprising a conversion step in which the switches (Tb) are controlled according to the control law, the average electrical power converted by the electrical converter (2) obtained being less than or equal to the limiting power.

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