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

Abstract

Isolated DC-DC electrical converter, electrical network comprising such a converter and associated conversion method. 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 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 at least one control law, the control law defining a variation of a switching frequency of the electrical converter (2) as a function of at least one voltage value.said adjusted value, depending at least on the first voltage and / or the second voltage. Figure for the abbreviation: Figure 1,

Description

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

[0001] The present invention relates to an isolated DC-DC electrical converter.

[0002] The invention further relates to an avionics electrical network intended to be carried in an aircraft, and comprising such a DC-DC electrical converter.

[0003] The present invention further relates to a conversion method.

[0004] The invention relates to the field of isolated or direct-DC converters isolated continuous. In particular, the invention relates to DC / DC converters compatible with constrained networks which are for example intended to be carried on board an aircraft, for example forming part of an aircraft avionics electrical network.

[0005] To convert electrical energy from a first DC voltage into a second DC voltage galvanically isolated from the first, DC / DC converters are known to be used. Depending on the intended application of the corresponding converter, these converters are subject to specific constraints. For example, in the aeronautical field, constraints relate to operational safety and conversion efficiency requirements, particularly in the context of input and output voltages and / or electrical loads that are likely to exhibit high dynamic ranges.

[0006] For example, converters with a 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, smooth switching can increase the efficiency of this type of converter. However, the known solutions are often relatively complex.

[0007] For example, such solutions require complex control and / or computing means, which is contrary to the objective of low-cost and small-size integration. In particular, this complexity often necessitates the implementation of a digital controller, for example, with one or more processors. This type of solution is particularly expensive to certify in the case of an avionics application.

[0008] One object of the present invention is to at least reduce the aforementioned disadvantages.

[0009] In particular, an object of the present invention is to obtain a DC-DC electrical converter, in particular an isolated DC-DC converter, configured to implement efficient electrical conversion, while being particularly simple to implement.

[0010] To this end, the invention relates to an isolated DC-DC electrical converter, configured to convert a first DC current under a first voltage received at input terminals into a second DC current under a second voltage at output terminals, the electrical converter comprising a first circuit connected to the input terminals and having controlled switches, called primary switches, and a second circuit connected to the output terminals and having 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,

[0011] the electrical converter comprising a controller configured to control the controlled switches according to at least one control law so as to obtain an average electrical power converted by the electrical converter less than or equal to a predetermined constant power, called the 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, between the input terminals and the output terminals,

[0012] the control law defining a variation of a switching frequency of the electrical converter as a function of at least one voltage value, called the adjusted value, depending at least on the first voltage and / or the second voltage.

[0013] According to other advantageous aspects of the invention, the converter comprises one or more of the following features, taken individually or in all technically possible combinations:

[0014] - the control law defines at least one duty cycle of the switches primary, said first duty cycle, as a function of the first voltage and / or the second voltage, the controller being configured to control the primary switches according to said first duty cycle;

[0015] - the control law defines at least one duty cycle of the switches secondary, said second duty cycle, as a function of the first voltage and / or the second voltage, or as being equal to a fixed value, the controller being configured to control the secondary switches according to said second duty cycle;

[0016] - the magnetic coupler is sized and configured to control the switches controlled switches according to the control law, so as to obtain a function soft switching operation of switches controlled over a predetermined operating range;

[0017] - the control law defines the switching frequency of the converter, the first duty cycle of the primary switches and / or the second duty cycle of the secondary switches according to at least one group from the following groups of functions:

[0018] - according to a first group of functions, the control law defining: [00191 Vic) = 1 [ 1 -^-^(^-(1-2¾^)2] ] ;

[0020] D, = 4- « t°021l ^.(^.)=¾^.

[0022] where:

[0023] F,sw is the switching frequency of the converter;

[0024] F min is a predetermined minimum switching frequency of the converter;

[0025] VvmnFP is a predetermined minimum value of the first voltage when the electrical converter converts a maximum power;

[0026] VimtnFP is a predetermined minimum value of the second voltage when the electrical converter converts the maximum power;

[0027] is the first cyclic ratio;

[0028] D2 is the second cyclic ratio;

[0029] Vu- is the adjusted value depending on the first voltage;

[0030] is the adjusted value depending on the second voltage;

[0031] Q is equal to g^ / riimX *iimJ

[0032] $}i is a predetermined limit value of a phase shift of Vac2 with respect to Vaci, preferably < 1 / 4 and $ < ;

[0033] Vaci is a first alternating voltage corresponding to a voltage across the terminals primary components of the magnetic coupler;

[0034] Vac2 is a second alternating voltage corresponding to a voltage at the secondary terminals of the magnetic coupler;

[0035] Dbnax is a predetermined maximum value of the first duty cycle, preferably 1 / 2;

[0036] D^max is a predetermined maximum value of the second duty cycle, preferably D-^ - 1 / 2;

[0037] - according to a second group of functions, the control law defining:

[0038]

[0039] Z92 = ^;et

[0040] FdVl(. V2d=Fnün-r^^- V 16 mlnVVmnFP V2mmFP

[0041] - according to a third group of functions, the control law defining: ["M2);

[0043] D2 = |;et 100441 F iv V i- F ' ■wl ^k-' r minV-, , a 1-D, \ dC / 2min / FAL Imt

[0045] preferably, according to the third group of functions, ~ 1 / 4;

[0046] - according to a fourth group of functions, the control law defining:

[0047] :

[0048]

[0049] then, if > JL, the control law according to the fourth group of functions de-2 — 4 ending, moreover:

[0050] . M k, 2J - minvlimitFPV2mblFf.

[0051] otherwise, if < 1, the control law according to the fourth group of functions defining:

[0052] p / 1 / t / \ _ p __________8DhmaD2rnas:__________ • v k.” v 2e ' ~ r min 4 / ) On W fl

[0053] - the magnetic coupler of the electrical converter has a plurality of pa design parameters having values ​​determined according to formulas specific to the chosen group of functions of the control law from among the first, second, third and fourth group of functions;

[0054] - the magnetic coupler forms a four-terminal network having the primary terminals and the secondary terminals, and includes a transformer having a primary winding and a secondary winding; the primary winding being connected to the terminals in parallel with an inductive component, or not, and the secondary winding being connected to the terminals, via or not a second inductive component in series with said winding;

[0055] - the isolated magnetic coupler includes the design parameters n, LDAB and LM such as:

[0056] LM is the inductance measured across the terminals when the terminals are in an open circuit;

[0057] n is the ratio of the voltage measured across the terminals to the voltage measured across the terminals (16), when the current flowing through is zero;

[0058] Ldab is the inductance measured across the terminals when the terminals are short-circuited,

[0059] in which the design parameters LDAB, n and LM are defined as being equal respectively to Ldabopi, n<>pt and LMopt, where , when the control law is defined by the first group of functions:

[0060] „ _ ________ 1 _________________________ PF / V r > t 1 ri V + M 1^1 S l ¥ ÎNW.Z1 SL ' jjltj j-, il!n,

[0061] j _ vimmFp v2,!li!lFP_____________________________________i__, and ^DABont RFP,., v F / vr t1 v ' CZ[ iffC'-2D^rl M

[0062] Ldab^ [ [Q(w D^)2] ' ^Mopt ^DABopt r i--------r-----------------------------------------,-] v

[0063]

[0064] when the control law is defined by the second group of functions: y „ < V*'4 P- 1 7 P-vr ' - uni

[0065] T _ ^hninFP V2minFP_________________1_________________, and DABiVl P !im F ni» SV^5 (, P^ Ci P**

[0066] J _ ______________ 1 ______________________________ • Mopt / 1 W ^zv^àr. i r- 1 » j Lr,.K,„ ( V, V1 ° V, r„V, n'>pl 1 1 1 my, r„ V, „ PZVSl \ 1 iw.ZVS ¥ Iw.fP àwnPP °P' / * J / .ucfF ■Im'iB-P

[0067]

[0068] when the control law is defined by the third group of functions: _ V2mmZVS__1______________, Dimca ^ itrmiFP |+( ]_p * l"»** ) Ci™ JXS Uzvgl

[0069] T __ ImifiFF ^'ZHilnZVS and ^DABopt- 4F P , 1+'A"*™* vlmM JP^

[0070] t _ ____________________________!) f- , \mi„FP____________________________ ; and ^Mopt — ) D a._ 2^ ( V^vs^ ,w)+2 Fmm ™ - 17^1

[0071]

[0072] when the control law is defined by the fourth group of functions: _ ' TK [4

[0073] J _ VlminFP______________________4 Puna2 PlmaA _______________________ DABopt 8 p [ I z[ p H pv i-»» >■ jt ,.| p । p \ T 1

[0074] then if ry vi,ninr-p, p.>1 / 9, then : ^ImaxV, 7,-v C'imaxV-, wc — 1 / hj? <iYZV<8 2tnaxZ\ 5 / D, V T __ _______________________________________________________\<mHFP_____________________________________________________ j \ v v 4dz«4:^iia,, '■'• n V n I' U-9 F V ‘ c.M' V.I irMxV ^kZ-,; I - Lvxm\ ~nax yimmTP n«l> < uimax tawFP^-f mw VIKm- V^rp i'zml

[0075] otherwise n vinunFP , < 1 / 9 then : \inaxV, 7VV ' ^'imaxy^ z,„ — / ' k / iaxZy.S * ZjnavZy S 1

[0076] r> vj ________________________________________________________________ !______________________________________________________________• ^Mopt ~ D^x , (rvnv 1 ^r>mn । lowt â** ZminFP' "''pi: ^hruix}nimFP]

[0077]

[0078] PH,tt is the limiting power; Xminzvs, % being equal to 1 or 2, is a minimum value of the voltage Vx, X being . equal to 1 or 2, in particular a minimum voltage of the voltage Vy beyond which the converter 2 implements a conversion according to a zero voltage switching principle, also called ZVS, where preferably Vxminzvs - VXminFP;

[0079] VXmaxzvs% being equal to 1 or 2, is a maximum value of the voltage Vx, X being equal to 1 or 2, in particular a maximum voltage of the voltage Vx below which the converter implements a conversion according to the ZVS principle, where preferably VXmaxZvs v Xminzvs;

[0080] Izvsi is a minimum value of a current at the primary terminals of the magnetic coupler at the time of switching of the primary switches defining that this switching is a soft switching;

[0081] ^zvsi is a minimum current value in the LDAB inductance, or at the secondary terminals of the magnetic coupler at the time of switching of the secondary switches defining that this switching is a soft switching;

[0082] Pzvsmin is a predetermined value of electrical power converted by the converter beyond which the converter implements a conversion according to the ZVS principle;

[0083] - the controller is configured to determine the change in the communication frequency mutation independent of the electrical power of the converter;

[0084] - the controller is an analog controller and / or the controller includes logic non-programmable configured to control switches;

[0085] - the control law further defines at least the variation of the communication frequency mutation of the converter as a function at least of the first voltage and / or the second voltage, so as to obtain the first and / or the second current less than or equal to a predetermined constant maximum current.

[0086] The invention also relates to an avionics electrical network intended to be carried on board an aircraft, comprising at least one load and one electrical converter.

[0087] The invention further relates to a method of conversion by an electrical converter, of the first direct current under the first voltage received at the input terminals of the electrical converter into the second direct current under the second voltage at the output terminals of the electrical converter, the conversion method comprising a conversion step 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.

[0088] These features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and with reference to the accompanying drawings, in which:

[0089] - [Fig. 1] [Fig. 1] is a schematic view of a DC electrical converter- continuous according to the invention;

[0090] - [Fig.2] [Fig.2] is a schematic graph of a time development of a first alternating voltage of a transformer of the converter of the [Fig.l];

[0091] - [Fig.3] [Fig.3] is a schematic graph of a time development of a second alternating voltage of the transformer of the converter of the [Fig.l];

[0092] - [Fig.4] [Fig.4] is a schematic graph of a voltage waveform of the Figures 2 and 3 show that the voltages exhibit a phase shift relative to each other, as well as the currents present in the converter, and

[0093] - [Fig. 5] [Fig. 5] is a schematic view of a model of a magnetic coupler forming a coupler of the electrical converter of the [Fig.l].

[0094] With reference to [Fig.1], a DC-DC electrical converter 2, or DC / DC converter, is schematically represented.

[0095] Converter 2 is, for example, configured to be installed in an aircraft, not shown, but is not limited to this example. In particular, converter 2 is configured to be integrated into an avionics electrical network installed in the aircraft, such as a 28 VDC or 115 VAC rectified network.

[0096] This avionics electrical network includes, for example, at least one electrical load, not shown, as well as the converter 2 capable of supplying the electrical load or each electrical load.

[0097] The converter 2 includes a pair of input terminals 4 and a pair of output terminals 6. According to one example, terminals 4, 6 are suitable for connection to the avionics electrical network.

[0098] The converter 2 is configured to convert a first direct current under a first voltage Vj 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 at the output terminals 6.

[0099] In one example, the second current has a second voltage L2 different from the first voltage Vj. In another example, the second voltage V2 is equal to the first voltage. In this case, the converter 2 notably provides galvanic isolation of the input terminals 4 from the output terminals 6.

[0100] According to one example, 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.

[0101] The converter 2 is preferably a bidirectional converter. The converter is in particular suitable for converting electrical power from the input terminals 4 to the output terminals 6 and vice versa.

[0102] The converter 2 is in particular sized and then controlled to convert a DC current source under the first voltage Vj at input terminals 4 into a DC current source under the second voltage V2 at output terminals 6.

[0103] According to one example, converter 2 is configured to convert electrical power in the range of 10 W to 10 kW.

[0104] Converter 2 comprises a plurality of controlled switches Tb, T2, T5, Tj, T^. The switches at T^ are, in particular, bidirectional in current in the closed state and unidirectional in current in the open state. Each switch at T^ is, for example, made up of, or can be considered equivalent in its operation to, a MOSFET (metal-oxide-semiconductor field-effect transistor) or an IGBT in parallel with a diode. Alternatively, converter 2 comprises more or fewer switches.

[0105] The converter 2 further includes a controller 8 configured to control switches T1 to T8. For example, the controller 8 is connected to switches T1 to T8 via a connection 9 to control switches T1 to T8. Connection 9 is shown in Figure 1 only between the controller 8 and switches T1 and T8. Of course, the controller 8 is preferably connected via connection 9 to each of the switches T1 to T8.

[0106] Converter 2 preferably has a dual active bridge topology or DAB topology (from the English "Dual Active Bridge"). In other examples, converter 2 has a topology comprising at least one half-bridge with one or more arms of controlled switches. In one example, each bridge of the converter is a half-bridge of controlled switches associated with a capacitive half-bridge.

[0107] 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.

[0108] The first circuit 10 comprises a portion of the plurality of switches called primary switches T2, T4. The primary switches T1 are configured to generate a first alternating voltage at the primary terminals 16 of the magnetic coupler 14.

[0109] The second circuit 12 includes the complementary part of this plurality of switches, called secondary switches T. The secondary switches T are configured to generate a second alternating voltage Vac2, at the secondary terminals 18 of the magnetic coupler 14.

[0110] According to examples of converter 2 operation, each circuit between 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 converter 2 converts 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 converter 2 converts 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.

[0111] Preferably, the controller 8 is configured to control the primary switches T T2, T Tin independently of a control of the secondary switches TT Tj, T8 by the controller 8.

[0112] 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 includes non-programmable logic configured to control the switches T. By analog controller, it is understood, for example, to be a regulation and control device by continuous value ranges (in particular as opposed 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 information on a past measurement.For example, an analog controller is an operational amplifier circuit, either open-loop 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 cycles of the bridges, over continuous value ranges. This type of controller thus contrasts with digital solutions based on the quantization of measured and controlled values ​​on the one hand, and sampled and stored values ​​on the other.

[0113] With reference for example to [Fig. 1], the magnetic coupler 14 forms a four-terminal network having primary terminals 16 and secondary terminals 18. The magnetic coupler 14 includes in particular a transformer 20 comprising a primary winding 22 and a secondary winding 24.

[0114] Preferably, with reference to Figure 5, the magnetic coupler 14 forms a model and can take different embodiments. In particular, the magnetic coupler 14 corresponds electrically to a perfect transformer with a ratio n, whose primary winding is parallel to a magnetizing inductor LM. A current flowing through the magnetizing inductor LM is called... According to the model of the magnetic coupler 14, the terminals of this winding correspond electrically to the primary terminals of the four-terminal network. The two other terminals, called secondary terminals, are defined as those of the series connection of the secondary winding of the equivalent ideal transformer with a DAB inductor 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 n is a ratio of the voltage present between the secondary terminals 18 to the voltage present between the primary terminals 16, when a current i(LDAB), that is, the current in the branch of the magnetic coupler 14 containing the DAB inductor LDAB, is equal to 0. CONVERTER SETTINGS 2

[0115] The controller 8 is configured to control the switches 7 to T8 according to at least one control law.

[0116] The following parameters are defined for the converter 2, and in particular for the controller 8 capable of controlling the switches Tj to 7 8 according to the control law. The parameters include quantities and constants.

[0117] The quantities are in particular defined as follows.

[0118] Fsw is the switching frequency of converter 2;

[0119] V, is the voltage across input terminals 4, called the first voltage;

[0120] V2 is the voltage across output terminals 6, called the second voltage;

[0121] Vlc is an adjusted value dependent on the first voltage Vj;

[0122] V2c is an adjusted value dependent on the second voltage V2;

[0123] Vaci is a first alternating voltage at the primary terminals 16 of the magnetic coupler 14;

[0124] Vac2 is the second alternating voltage at the secondary terminals 18 of the ma coupler genetics;

[0125] is a first duty cycle of the first circuit 10;

[0126] D2 is a second duty cycle of the second circuit 12;

[0127] 0 is a phase shift of VAC2 with respect to Vaci, in particular the phase shift between the fundamentals of the waveforms of Vac2 with respect to VAci. By "fundamentals of the waveforms", it is understood that the fundamental components resulting from the spectral decomposition over a theoretically infinite time of the respective waveforms of Vaci and Vac i in steady state.

[0128] The first duty cycle D1 is in particular the duty cycle of the primary switches T2, T4. In particular, by "first duty cycle", it is understood the relationship between the duration, over a period of the first alternating voltage Vaci, during which this voltage VAcl is positive, and the duration of this period.

[0129] The second duty cycle D2 is in particular the duty cycle of the secondary switches T5, T7, T$. In particular, by "second duty cycle D2", it is understood the relationship between the duration, over a period of the second alternating voltage Vac2, during which this voltage Vacz is positive, and the duration of this period.

[0130] Examples of the first and second duty cycle D2 are illustrated in [Fig.4],

[0131] The constants are in particular defined as follows.

[0132] Preferably, the constants are predetermined and / or fixed by an operator or manufacturer of converter 2.

[0133] F min is a minimum frequency of the switching frequency Fsw of the converter 2, called predetermined minimum switching frequency;

[0134] V iminFP is a predetermined minimum value of the first voltage Vj when the converter 2 converts a maximum power, in particular a limiting power;

[0135] V2minFP is a predetermined minimum value of the second voltage V2, when converter 2 converts the maximum power, including the limiting power;

[0136] Viminzvs is a minimum value of the first voltage Fi, in particular a minimum voltage 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 Vimînzvs - ^bntnFP;

[0137] V2minzvs is a minimum value of the second voltage V2, in particular a minimum voltage of the second voltage V2 beyond which the converter 2 implements a conversion according to the principle of the ZVS, where preferably V2minzvs - ^2™^;

[0138] V}maxZvs is a maximum value of the first voltage Vb, in particular a maximum voltage of the first voltage Vj below which the converter 2 implements a conversion according to the ZVS principle, where preferably V, V, 7„€ •

[0139] V2maxzvs 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 2maxZVS “ 2minZVS ,

[0140] P Un, is a limiting power of the electrical converter 2;

[0141] Pzvsmin is a predetermined value of electrical power converted by the converter 2 beyond which converter 2 implements a conversion according to the ZVS principle;

[0142] I\Um is a predetermined value of a current, called the limiting current, across the terminals input 4 of converter 2;

[0143] I2lim is a predetermined value of a current, called limiting current, at the output terminals 6 of the converter 2;

[0144] Izvs 1 is a minimum value of a current at the primary terminals 16 of the magnetic coupler 14 at the time of switching of the primary switches defining that this switching is a soft switching;

[0145] !z\ s 2 is a minimum current value in the inductor or across the terminals secondary 18 of the magnetic coupler 14 at the time of switching of the secondary switches defining that this switching is a soft switching;

[0146] By "soft switching" is meant a switching action in which the switches close ordered at an instant when the voltage across their respective channels is zero, or approximated to zero. For example, in the case of using MOSFETs or equivalent transistors, the voltage present across the drain-source terminals during reverse conduction is approximated to zero.

[0147] Dlmax is a predetermined maximum value of the first duty cycle, preferably 0 < Dbnax < 1 / 2, preferably Dlmax being substantially equal to 1 / 2;

[0148] Dimax is a predetermined maximum value of the second duty cycle, preferably 0 < Dlmax 1 / 2, preferably D2max being substantially equal to 1 / 2;

[0149] is a predetermined limit value of the phase shift ¢ between V aci and Vaci, called the limiting phase shift, in particular between fundamental waveforms Vac~2 and Kici' where preferably < 1 / 4 and < d^+d, , preferably even $ljm "lim — 2 being approximately equal to 1 / 4;

[0150] Qestégalà80 / V

[0151] In particular, the predetermined minimum frequency Fmin is the minimum switching frequency of converter 2. The predetermined minimum frequency Fmin is, for example, predetermined based on a filtering constraint for the first and / or second current received or supplied by converter 2. In particular, a lower frequency implies a larger filter size. Thus, for example, the minimum frequency is predetermined based on a given filter size.

[0152] The minimum value of the first voltage VminFP is preferably determined based on a system that can be connected to the input terminal 4, for example, an electrical network, such as an avionics power supply. The minimum value of the second voltage VminFP is also determined, for example, based on a system that can be connected to the output terminal 6, for example, the electrical network and / or an electrical load.

[0153] For example, the minimum value of the first and / or second voltage ViminFP is predetermined by a standard. For example, for an avionics network, the minimum values ​​of the first and second voltages are defined by standards. corresponding. For example, the values ​​V\minFP and 2minFP are equal to 28V.

[0154] With reference to Figure 2, an example of the first alternating voltage Vacï over time t is shown with an indication of the state of each primary switch Tb T2, T2, T4 at each instant as controlled by the controller 8. The first alternating voltage has three different values, namely; Vaci = 0 or V aci = When the primary switches 7 ] cl T4 are closed, the first The alternating voltage Kaci is equal to Vj. When the primary switches 74 cl T4 or T] and T3 are closed, the first alternating voltage VAC1 is equal to 0. When the primary switches T2 and T3 are closed, the first alternating voltage VAC1 is equal to - In each of the above examples, the two other primary switches not mentioned are in the open state.

[0155] With reference to Figure 3, an example of the second alternating voltage Vac2 over time t is illustrated, analogously to Figure 2. The second alternating voltage Vac2 has three different values, namely Vac2 = 2; Vac2 = 0; or Vac2 = -2. When secondary switches T5 and T6 are closed, the second alternating voltage Vac2 is equal to V2. When secondary switches T5 and T6, or T5 and T2, are closed, the second alternating voltage Vac2 is equal to 0. When secondary switches T7 and T7 are closed, the second alternating voltage Vac2 is equal to -V2. In each of the above examples, the two other secondary switches not mentioned are in the open state.

[0156] The examples in Figures 2 and 3 apply in particular to a magnetic coupler according to the preceding definition, comprising an equivalent perfect transformer of ratio n, as illustrated in particular in Figure 5, capable of generating a potential difference n VAC1 - VAC2 across the terminals of the inductance LDAB illustrated in [Fig.5].

[0157] With reference to Figure 4, the phase shift ¢ between the alternating voltages Vacz and Vaci is illustrated, where the alternating voltages VACi, Vac2 illustrated in Figure 4 are those illustrated in the examples in Figures 2 and 3. The phase shift ÿ corresponds in particular to the phase shift between fundamentals of the waveforms Vac2 and EACb expressed proportionally to the switching period.

[0158] With reference to Figure 4, when the controller 8 controls the switches T} to T8 according to the examples in Figures 2 and 3, the converter 2 presents a current waveform i(LDAB) corresponding to a current through the inductance LDAB and also presents a current waveform i(LM) corresponding to a current through the inductance LM. EXAMPLES OF THE LAW OF COMMAND

[0159] The controller 8 is configured to control the switches T1 to Ts according to the law control is implemented to obtain an average electrical power converted by converter 2 that is less than or equal to a predetermined constant electrical power, referred to as the limiting power Pnm in this document. In particular, the controller 8 includes an electronic circuit or electronic components specific to the control law.

[0160] 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.

[0161] In particular, the average electrical power is the power that is transmitted on average over n periods, where n is an integer greater than or equal to 1.

[0162] 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 converter 2 over several switching periods.

[0163] According to one example, "average electrical power" means the arithmetic mean of the power over one or more switching periods.

[0164] By "converter switching period", it is understood in particular as the duration, in the steady state, between two instants of successive closures of a given switch of converter 2.

[0165] Each switch TY has, in particular, either the open state or the closed state. The operation of converter 2 is further defined by the switching frequency Fsw of converter 2. The switching frequency Fsw is the inverse of the switching period.

[0166] Preferably, the limiting power P nm is set by the controller 8.

[0167] The limiting power Pam depends, for example, on the requirements of the function operation of converter 2. For example, the limiting power Pum is set according to the nominal power of the loads and / or devices supplied by converter 2 and / or according to a desired regulation dynamic, for example according to a requirement for rapid energization of a device supplied by converter 2.

[0168] According to an example, the limiting power Pnm is determined as follows:

[0169] p, _ V\minFP ^InunFP n.

[0170] According to one example, the controller 8 is further configured to control the switches 7'i to Ts according to the control law so as to obtain the limiting current 7, I■vim- For example the limiting current is j_ and the 1 Uim ~y, . Y InunFP current limitation is / _ pi«« . 1 2lim y, . „„ v ItmnFP

[0171] The control law defines a variation of the switching frequency Fsw of the converter 2 as a function of at least one voltage value, called the adjusted value V\c, V2c, depending at least on the first voltage V j and / or the second voltage V2.

[0172] The adjusted value V dependent 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 VhmnFP- The adjusted value Vjc is thus preferably equal to max(V1, Vlm,nFP).

[0173] The adjusted value L2< depending on the second voltage V2 is in particular a mathematically clipped voltage in a similar manner. The adjusted value V2c. is thus preferably equal to max(V2, V2minFP).

[0174] According to one example, the controller 8 is configured to determine the change in switching frequency independently of the average electrical power of a previous switching period of the converter 2.

[0175] For example, the control law defines the first duty cycle as a function of the or each fitted value Vk > V2c. In this case, the controller 8 is configured to control the primary switches 11 to / 4 according to the first duty cycle Dv defined by the control law.

[0176] For 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$ according to the second duty cycle D2 defined by the law of order.

[0177] According to one example, the fixed value is equal to 0.5.

[0178] Preferably, the control law defines the switching frequency F,w of converter 2, the first duty cycle D} of the primary switches at Tet / or the second duty cycle D2 of the secondary switches T5 at T&.

[0179] According to examples, the phase shift 7 allows the transmitted power to be adjusted. For example, the phase shift $ is imposed by closed-loop regulation.

[0180] In what follows, four examples of control laws are described. The control laws are notably independent of each other.

[0181] According to a first example, the control law defines the switching frequency F^ as being proportional to the adjusted value V2c depending on the second voltage, and further defines the second duty cycle D2 at a fixed value.

[0182] According to one implementation mode of the first example, the control law defines the control of switches 7, at 7S by the controller 8 according to a first group of functions, namely: 101831;

[0184]

[0185]

[0186]

[0187]

[0188]

[0189]

[0190]

[0191]

[0192]

[0193]

[0194]

[0195]

[0196]

[0197]

[0198]

[0199]

[0200]

[0201] :cl According to a second example, the control law defines the switching frequency Fsw as being proportional to the fitted value Vy depending on the first voltage and proportional to the fitted value V2c depending on the second voltage, and further defines the first and second duty cycle D], D2 to a fixed value. According to one implementation mode of the second example, the control law defines the control of the switches T to Ts by the controller 8 according to a second group of functions, namely: D<=1; ; And ^2 2 / \ V, V. F i VV i — F ic__• I ' le, r ~ 1 mmv rt, V-, T,, \ AC / ymm-F 2mm r P According to a third example, the control law defines the product of the first duty cycle and the adjusted value Vic depending on the first voltage as constant, and further defines the second duty cycle D2 at a fixed value. According to one implementation mode of the third example, the control law defines the control of switches T to Fs by controller 8 according to a third group of functions, namely: D2=i , s iz 1-0 F IV V}—F ..... ............-77..¾.... 1 wy k-, v 2I —1 min y, . „„ {- / y x AC f 2mmt P 1 Preferably, according to the third group of functions, the control law further defines: <Æ. «1 / 4. r hm According to a fourth example, the control law defines the product of the first duty cycle and the adjusted value Vk, depending on the first voltage, as constant, and further defines the product of the second duty cycle D2 and the adjusted value V2c, depending on the second voltage, as constant. According to one implementation mode of the fourth example, the control law defines the control of switches F to F by the controller 8 according to a fourth group of functions, namely: D (V i — F) tmmFP ■ }c)~ Ubnax Vk 1 / D2(V2c)=D2,m,x-^ ; If £7¾ > 2, the fourth group of functions further defines:

[0202] Vlc v2c 4 p Jy () 44 (1-d^^)+Q-2 SM on 2c.}minFP ^ïmütFP 4

[0203] Otherwise, if ££ / £ 1, the fourth group of functions further defines:

[0204] p / yy} — F ________^'waPïmax________ . the 2nd day, minute 4

[0205] According to one example, the control law further defines at least the variation of the switching frequency Fsw of the converter 2 at least as a function of the adjusted value Vic, V2c so as to obtain the first and / or second current less than or equal to a predetermined maximum current, in particular in addition to the determined maximum converted power.

[0206] The converter 2, and in particular the magnetic coupler 14, is dimensioned and configured to control the controlled switches T at T% according to the control law so as to obtain smooth switching operation of the controlled switches over a predetermined operating range. In particular, the magnetic coupler 14 has a plurality of design parameters LDAB and LM having values ​​determined according to formulas specific to the selected function group of the control law from among the first, second, third, and fourth function groups.

[0207] A first LDAB design parameter is in particular the LDAB inductance 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.

[0208] A second design parameter n is a ratio of Vac2 to Vaci when a current i(LDA^) in a branch of the magnetic coupler is equal to 0. The design parameter n corresponds in particular to the turns ratio of the equivalent ideal transformer of the magnetic coupler 14. This ratio is for example measured from the ratio of the voltage of Vac2 to the voltage Vaci of the isolated magnetic coupler 14 when the current at the secondary terminals 18 is zero.

[0209] A third design parameter LM is in particular the magnetizing inductance Lm of the magnetic coupler 14. It is obtained for example by impedance measurement on the magnetic coupler 14 isolated at its primary terminals 16, when its secondary terminals 18 are in open circuit.

[0210] Preferably, each design parameter LDAB, n and LM is determined so as to obtain zero voltage switching of the primary and / or secondary switches called the ZVS principle.

[0211] In particular, the design parameters LDAB, and LM form design rules to obtain, from the model forming the magnetic coupler 14, the converter 2.

[0212] For each of the control laws, there exists in particular a triplet {LDAB()pl, nopt, LMop} that is a solution of the design parameters LDAB, l, and LM, allowing optimal operation in terms of RMS currents, while maintaining smooth switching within the converter.

[0213] The design rules are preferably as follows, according to the first example of the control law.

[0214] llmt = ............................................................1............................... '-2 UzvkI

[0215] _ \mmFP V2m„rp 1 ^DABopt SP P , rr |

[0216] Ldaboix [ 1-2] ^Mopl LDABopt y2 rjr . ^ ] , nopt y, v, ■ ,..v [ ^imarl ] ^UAliopty y . 'ZVSl

[0217] The design rules are preferably the following according to the second example of the control law.

[0218] ' Il / ' PzVStw i 1 / \f 4 La, p 1 p

[0219] J _ \minFP ^2minFP 1 ^DABopt pHm Fmm

[0220] j _ ______________ 1______________________________ Mopt / y;w„zv,,. 1 LpARl^t Pzvsw, . \ . 4 T? if ! ^DAL^p; y V y / ZVlVII

[0221] The design rules are preferably the following according to the third example of the control law.

[0222] _ VlminZVS__1______________ a D^max V ^„„,17 / 1 i+| |_p UzvsîI

[0223] t _ ^2minFP ^IminZVS ^DABopt- p , 1+1 1 |

[0224] D, VT _ ________________________________________________________________________________________________________________________________________________ K i+min i

[0223] t _ ^2minFP ^IminZVS ^DABopt- p , 1+1

[0225] The design rules are preferably the following according to the fourth example of the order law. b / ifnFI' i J r\ ^hui-A'P jJ Ti 2mbu"P / i \ , x'' -7 1 2w-r.ZVS ! A / VV immFP ' 4 [ 1 1 1 ^IMA V^s ] '1 1 lJl,naX V^, ) 1 C ÿ

[0227] l _ Dlmrn V2mWP_____________________________________________ DABopt 8 Fj ^ Pj^ pi [4 nfipv ^p., \ 4 pj ^ pj^ pi [4 nfipv ^p., \ 4 p ^ p28 / p2 r> vF„inFP .> > vi,ni»FP « / 9 then : ^Amaxy z,„ ^'2.maxW 7V„ — 1 / * ImaxjFVS * 2}mixZv>> /

[0229] D- V r _ __________________________________________________________ !,Cat ^linFP__________________________________________________________ ^Mopt ! VV --|ID J---Il ''''F 1 T) TZ Vl v5 F~5 ,W“A * w.-xs \ ....... '-41... / ( . \ ' / V ImuFF n«!« Ulwm. v XmnFFy^im V^p IIP ll l'ZVSll .

[0230] Otherwise, according to the fourth example, it is defined +D2ma^^- < 1 / 2' in which case: imax v lmfaZVS v2TMxZVS /

[0231] f =______________________________________________________ ^Mopt . ________8 D'jw________ |< j , n:V (n V „ D vi ^rmin ' ZVS" L,MB^ ' ImmFF noi* ImmFP]

[0232] A conversion process implemented by converter 2 is now described.

[0233] During the conversion process, the converter 2 converts the first direct current under the first voltage V] received at the input terminals 4 into the second direct current at the output terminals 6 under the second voltage V2.

[0234] During a conversion step of the conversion process, the controller 8 controls the switches T to L8 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 Pum. The control law is preferably defined according to one of the aforementioned examples.

[0235] For example, the conversion process includes several repetitions of the conversion step. Preferably, the controller 8 controls the switches T} according to the control law so as to obtain the first and / or second alternating voltage VACb AC2, with the switching frequency F the first duty cycle and / or the second duty cycle D2 as defined by the control law.

[0236] It is understood that the converter 2 according to the invention, and in particular the control law, presents a large number of advantages.

[0237] Indeed, converter 2 enables efficient electrical conversion while being particularly simple to implement. The control law allows converter 2 to be controlled very simply and efficiently, as it is sufficient to apply, for example, one of the examples in the control law to obtain the electrical conversion by the DC / DC converter. The control law allows, for example, the use of a controller 8 with a very simple architecture, such as an analog controller and / or a controller with 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 that of a digital counterpart, for example.

[0238] In particular, the components of the converter 2 used are dimensioned, and said converter 2 is controlled so that its active components are switched at zero voltage on the one hand, and that the effective currents through its various active and passive components are reduced. This operating mode, guaranteed over the entire operating range in terms of output load values, input voltage, and output voltage, ensures conversion with optimized efficiency on the one hand.

[0239] On the other hand, the converter's switching frequency is imposed according to input and output voltage values ​​to ensure constant power and / or current limiting over the entire operating range.

[0240] Finally, the control parameters of converter 2 are preferably defined by functions, namely the control law, dependent on the values ​​of the first and / or the second voltage, ensuring simplicity of implementation.

[0241] Of course, other control laws combining in particular the aforementioned examples of the control law can be envisaged, provided that the average electrical power converted by the electrical converter 2 is less than or equal to the limiting power Pum.

Claims

Claims

1. 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 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 (^2, ^3, ^4), and a second circuit (12) connected to the output terminals (6) and comprising controlled switches, called secondary switches (^5, ^6, ^7, ^s), 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 P2, 7 g) according to at least one control law 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), the control law defining a variation of a switching frequency of the electrical converter (2) as a function of at least one voltage value, called adjusted value,depending at least on the first voltage and / or the second voltage.,

2. Electrical converter (2) according to claim 1, in which the control law defines at least one duty cycle of the primary switches (Tb T2, called first duty cycle, as a function of the first voltage and / or the second voltage, the controller (8) being configured to control the primary switches (T T2, T4) according to said first duty cycle.

3. Electrical converter (2) according to claim 2, in which the control law defines at least one duty cycle of the se- secondary (T^ T7, rg), called second duty cycle, as a function of the first voltage and / or the second voltage, or as being equal to a fixed value, the controller (8) being configured to control the secondary switches (F^ Tj, T^) according to said second duty cycle.

4. Electrical converter (2) according to claim 3, in which the magnetic coupler (14) is sized and configured to control the controlled switches (rb T2, T7, Ts) according to the control law, so as to obtain smooth switching operation of the controlled switches (T T3j TT\ T Ty, over a predetermined operating range.

5. Electrical converter (2) according to claim 3, in which the control law defines the switching frequency of the converter (2), the first duty cycle of the primary switches (Th T2, F, and / or the second duty cycle of the secondary switches (T^ T^Tj, T8) according to at least one group among the following groups of functions: - according to a first group of functions, the control law defining: ^1(^1..)=5(1-^-^1^-(1-20^,,)2] ]; ^2=4 'and FsW(V2c)^Fmi 2crp ' where: Fsw is the switching frequency of the converter (2); Fmin is a predetermined minimum switching frequency of the converter (2); VMnFP is a predetermined minimum value of the first voltage when the electrical converter (2) converts maximum power; ViminFP is a predetermined minimum value of the second voltage when the electrical converter (2) converts maximum power; is the first duty cycle; D2 is the second duty cycle; Vic is the adjusted value dependent on the first voltage; V2c is the adjusted value dependent on the second voltage; Q is equal to ); lim \ hm / is a predetermined limit value of a phase shift of Vaci by. relative to VAC1, preferably < 1 / 4 and < D]+d2; ^lim— 2 VACl is a first alternating voltage corresponding to a voltage at the primary terminals (16) of the magnetic coupler (14); VAC2 is a second alternating voltage corresponding to a voltage at the secondary terminals (18) of the magnetic coupler (14); ^imax is a predetermined maximum value of the first duty cycle, preferably Dhnax < 1 / 2; D^max is a predetermined maximum value of the second duty cycle, preferably D2tnax 1 / 2; - according to a second group of functions, the control law defining: D — - ; TF-- ; and ^2 2 ^2c) “ min ■ FP V, • FP ' - according to a third group of functions, the control law defining: D2=± j rj InmJ'P F (v V \ -F —--- sw\ 2 J min^ ^Dll)KK preferably, according to the third group of functions, $}i ~ 1 / 4 ; - according to a fourth group of functions, the control law defining: d{v J ; = d2„u,F^ ; then, if > 1, the control law according to the fourth group of 2 4 functions further defining: otherwise, if dj+d2 < 1 the control law according to the fourth group of ■ — ~ _i or functions defining: mln 4 D^. ((FD^Ï

6. An electrical converter (2) according to claim 4, wherein the magnetic coupler (14) of the electrical converter (2) has a plurality of design parameters having values ​​determined according to formulas specific to the group of functions chosen from the control law among the first, second, third and fourth group of functions.

7. Electrical converter (2) according to any one of the preceding claims, in which the magnetic coupler (14) forms a quadrupole having the primary terminals (16) and the secondary terminals (18), and comprises a transformer (20) comprising a primary winding (22) and a secondary winding (24); the primary winding (22) being connected to the terminals (16) in parallel with an inductive component, or not, and the secondary winding (24) being connected to the terminals (18), via or not a second inductive component in series with said winding.

8. Electrical converter (2) according to claim 6 taken in combination with claim 5, wherein the isolated magnetic coupler (14) comprises the design parameters n, LDAB and LM such that: LM is the inductance measured at the terminals (16) when the terminals (18) are in open circuit; n is the ratio of the voltage measured at the terminals (18) to the voltage measured at the terminals (16), when the current flowing in (18) is zero;LDAB is the inductance measured across terminals (18) when terminals (16) are short-circuited, in which the design parameters LDAB, n and LM are defined as being equal to LDABop^ n„pt and LMop^ respectively where , when the control law is defined by the first group of functions: 1 / r J 17 , OT r 1 -t VVVJ — ___________________________l___________________________ DABopt AF i Plm । r M ? n pi | , and ^DABopt ^Mopt ^DABopt r | v . ,, | F *W[ t 4* [C* ] ] 1 KzVSll when the control law is defined by the second group of functions:; when the control law is defined by the third group of functions: _ V2nmZVS ! , 2 IminFP _ VminFP ^IminZVS ^^lintvr , et 'DABopt ap . p„ < v, ,v \ r, ,,.vx-! 4 i »«„ * »» 1+( w _ _________________________DlmmVltninFP________________________ 'Mopt ~ :........ 2 Lî}^.;t ( IiimsZVS^ XmmFP llnpi )+-4,. P min V^irw l^ZVS'i and Therefore the command list is defined by the fourth group of functions: ImjnFP~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ OPt ” H ^'>F' 8 p^, [4 D^-^; ( )+4 )+Q2 then yes r> v iminFP , ,) v2mmFP i / 9 alors : ^IwoxV, / v< rL'2maxV, ~ 1 ! itwtxZVS 2rnnxZ\ SJ synonym / ) VmmFP , T) V2mmFP ^VnaxV, ïmiuZvS 2m«xZvS < 1 / 2' alors : ^Mopt ~ Dt V ______________________________________ IminFP___________________________________ 2 F mi » 4¾^ I {pzmm 2mmFP~ n»pl ^bgmPP, Ppm is the limiting power; VXminzvs, being equal to 1 or 2, is a minimum value of the voltage Vx, X being equal to 1 or 2, in particular a minimum voltage of the voltage Vx beyond which the converter 2 implements a conversion according to a zero voltage switching principle, also called ZVS, where preferably Vxminzvs vXminFP; VXmaxZV$X being equal to 1 or 2, is a maximum value of the voltage Vx, X being equal to 1 or 2, in particular a maximum voltage of the voltage Vx below which the converter (2) implements a conversion according to the ZVS principle, where preferably ^XmaxZVS ~ ^XminZVS ; Izvsi is a minimum value of a current at the primary terminals (16) of the magnetic coupler (14) at the time of switching of the primary switches defining that this switching is a soft switching; Izvsi is a minimum value of current in the inductance LDAB, or at the secondary terminals (18) of the magnetic coupler (14) at the time of switching of the secondary switches defining that this switching is a soft switching; Pzvsmn is a predetermined value of an electrical power converted by the converter (2) beyond which the converter (2) implements a conversion according to the ZVS principle.

9. An electrical converter (2) according to any preceding claim, wherein the controller (8) is configured to determine the change in the switching frequency independently of the electrical power of the converter (2).

10. An electrical converter (2) according to any preceding claim, wherein the controller (8) is an analog controller and / or the controller (8) comprises non-programmable logic configured to control the switches (TT2, TT TT

11. Electrical converter (2) according to any one of the preceding claims, in which the control law further defines at least the variation of the switching frequency of the converter (2) as a function at least of the first voltage and / or the second voltage, so as to obtain the first and / or the second current less than or equal to a predetermined constant maximum current.

12. 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.

13. A method of converting by an electrical converter (2) according to any one of the preceding claims, the first direct current under the first voltage received at the input terminals (4) of the electrical converter (2) into the second direct current under the second voltage at the output terminals (6) of the electrical converter (2), the conversion method comprising a conversion step in which the switches (TT2, T3, T4, 76, 74. T8) 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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