Isolated dc-to-dc electrical converter, electrical network comprising such an electrical converter and associated conversion method

Abstract

The present invention relates to an isolated DC-to-DC electrical converter (2) configured to convert a first direct current at a first voltage V 1 received at input terminals (4) into a second direct current at a second voltage V 2 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 (T 1, T 2 , T 3 , T 4 , T 5 , T 6 , T 7 , T 8 ) according to a control law defining at least a first duty cycle D 1 that defines a switching ratio of primary switches (T 1, T 2 , T 3 , T 4 ) according to a first function and / or according to a second function.

Description

[0001]TITLE: 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. The invention further relates to an avionics electrical network intended to be mounted in an aircraft, and comprising such a DC-DC electrical converter. The present invention further relates to a conversion method. The invention relates to the field of isolated DC / DC or isolated DC-DC converters. In particular, the invention relates to DC / DC converters compatible with constrained networks which are for example intended to be mounted in an aircraft, for example forming part of an avionics electrical network of the aircraft. 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. For example, converters with 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, known solutions are often relatively complex. 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. An aim of the present invention is to at least reduce the aforementioned drawbacks. In particular, an aim 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. To this end,the subject of the invention is an isolated DC-DC electrical converter, configured to convert a first DC current under a first voltage ^^1 received at input terminals into a second DC current under a second voltage ^^2 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,the electrical converter comprising a controller 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 electrical power converted by the electrical converter 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, between the input terminals and the 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:, and / or according to a second function defined as follows: ^^1 ^^ is an adjusted value depending on the first voltage ^^1;^^2 ^^ is an adjusted value depending on the second voltage ^^2;^^ ^^ ^^ is a constant value;^^1 ^^ ^^ ^^ ^^ ^^ is a predetermined minimum value of the first voltage ^^1 when the electrical converter converts a maximum power;^^2 ^^ ^^ ^^ ^^ ^^ is a predetermined minimum value of the second voltage ^^2 when the electrical converter converts the maximum power; 3^^1 ^^ ^^ ^^ is a predetermined maximum value of the first duty cycle ^^1, preferably ^^1 ^^ ^^ ^^ ≤ 1 / 2;^^2 ^^ ^^ ^^ is a predetermined maximum value of a second duty cycle ^^2 defining a switching ratio between the secondary switches, preferably ^^2 ^^ ^^ ^^ ≤ 1 / 2,^^ ^^ ^^ ^^ ^^ is equal to 2 ^^1 ^^ ^^ ^^(1 − ^^1 ^^ ^^ ^^) + 2 ^^2 ^^ ^^ ^^(1 − ^^2 ^^ ^^ ^^) − 1 / 2.According to other advantageous aspects of the invention, the converter comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations: -The first duty cycle ^^1 is controlled according to said first function if otherwise the first duty cycle ^^1 being controlled according to said second function. - Said control law defines the second duty cycle ^^2 according to the function s uivante : -The electrical converter is defined by design parameters ^^ ^^ ^^ ^^, ^^ and ^^ ^^, where:^^ ^^ is the inductance measured at the terminals when the terminals are in open circuit;^^ is the ratio of the voltage measured at the terminals to the voltage measured at the terminals, when the current flowing in is zero;^^ ^^ ^^ ^^ is the inductance measured at the terminals when the terminals are short-circuited.The design parameters ^^ ^^ ^^ ^^ , ^^ and ^^ ^^ are defined as being equal to ^^ ^^ ^^ ^^ , ^^ ^^ ^^ ^^ ^^ ^^ and ^^ ^^ ^^ ^^ ^^, respectively, where: 4 ℱis a restricted domain of definition of the first and second voltage ^^2defined by ^^ ^^ ^^ ^^1 ac ^ nt al to or 2, e a tension ^^ ^^, ^^ being equal to 1 or 2, of the couple allowing to maximize the ^^1( ^^1, ^^2) ^^1on the domain ℱ ;^^ ^^ ^^ ^^2 with ^^ being equal to 1 or 2, is a tension ^^ ^^, ^^ being equal to 1 or 2 of the couple ( ^^ , ^^2) allowing to maximize the magnitude ^^1( ^^1, ^^2) ^^1 on the domain ℱ^^ ^^ ^^ ^^1 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 first circuit;^^ ^^ ^^ ^^2 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;^^ ^^ ^^ ^^ is the limiting power;^^1( ^^1 ^^ ^^1) is a maximum sum of charges stored in a drain-source parasitic capacitance depending on the primary switches and the first voltage^^1, evaluated at ^^1 ^^ ^^1;^^2( ^^2 ^^ ^^2) is a maximum sum of charges stored in a drain-source parasitic capacitance depending on the secondary switches and the second voltage^^2,evaluated in ^^2 ^^ ^^2 ;^^ ^^ ^^ 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 electrical current converted by the electrical converter less than or equal to a predetermined constant current, called the limiting current. - The converter is a converter having the active double bridge topology and / or the controller is an analog controller and / or comprises non-programmable logic configured to control the switches. The invention also relates to an avionics electrical network intended to be on board an aircraft,comprising at least one load and an electrical converter according to any one of the preceding claims. 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 ^^1 received at the input terminals of the electrical converter into the second direct current under the second voltage ^^2 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. 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 1] Figure 1 is a schematic view of a DC-DC electrical converter according to the invention; - [Fig 2] Figure 2 is a schematic graph of a development over time of a first alternating voltage of a transformer of the converter of Figure 1; - [Fig 3] Figure 3 is a schematic graph of a development over time of a second alternating voltage of the transformer of the converter of Figure 1; - [Fig 4] Figure 4 is a schematic graph of a waveform of the voltages of Figures 2 and 3 when the voltages have a phase shift relative to each other, as well as currents present in the converter, and - [Fig 5] Figure 5 is a schematic view of a model of a magnetic coupler forming a coupler of the electrical converter of Figure 1. With reference to Figure 1, a DC-DC electrical converter 2, or DC / DC converter,is schematically represented. 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. 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. 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. The converter 2 is configured to convert a first direct current under a first voltage ^^1 received at the input terminals 4 into a second direct current under a second voltage ^^2 at the output terminals 6. The converter 2 is thus in particular configured to supply the second current under the second voltage ^^2 at the output terminals 6. According to one example, the second current has a second voltage ^^2 different from the first voltage, According to another example, the second voltage ^^2 is equal to the first voltage ^^1. 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. 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. 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. The converter 2 is in particular sized and then controlled to convert a direct current source under the first voltage ^^1 at the input terminals 4 into a direct current source under the second voltage ^^2 at the output terminals 6.According to one example, the converter 2 is configured to convert electrical power in a range between 10 W and 10 kW. The converter 2 comprises a plurality of controlled switches ^^1, ^^2, ^^3, ^^4, ^^5, ^^6, ^^7, ^^8. The switches ^^1 to ^^8 are in particular bidirectional in current in the closed state and unidirectional in current in the open state. Each switch ^^1 to ^^8 is for example made up of, or comparable in its operation to, a MOSFET type transistor (acronym for "metal-oxide-semiconductor field-effect transistor") or even to an IGBT in parallel with a diode. Alternatively, the converter 2 comprises more or fewer switches. The converter 2 further comprises a controller 8 configured to control the switches ^^1 to ^^8.For example, controller 8 is connected to switches ^^1 to ^^8 by a connection 9 to control switches ^^1 to ^^8. Connection 9 is shown in Figure 1 only between controller 8 and switches ^^1, ^^3, ^^5 and ^^7. Of course, controller 8 is preferably connected by connection 9 to each of switches ^^1. à ^^8.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. 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.The first circuit 10 comprises a portion of the plurality of switches ^^1 to ^^8, called primary switches ^^1, ^^2, ^^3, ^^4. The primary switches ^^1 to ^^4 are configured to generate a first alternating voltage ^^. ^^ ^^1 to the primary terminals 16 of the magnetic coupler 14. The second circuit 12 comprises the complementary part of this plurality of switches, called secondary switches ^^5, ^^6, ^^7, ^^8. The secondary switches ^^5 to ^^8 are configured to generate a second alternating voltage ^^ ^^ ^^2, to the secondary terminals 18 of the magnetic coupler 14. 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. Preferably, the controller 8 is configured to control the primary switches ^^1, ^^2, ^^3, ^^4 independently of a control of the secondary switches ^^5, ^^6, ^^7, ^^8 by the controller 8.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 ^^1 to ^^8. 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, in open or closed loop, for example the output voltage level of which 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 ranges of values ​​that are also continuous. This type of controller is thus in particular 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. With reference 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.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 ^^, the primary winding of which is parallel to a magnetizing inductance ^^. ^^ . A current flowing through the magnetizing inductance ^^ ^^ is called ^^( ^^ ^^ ). According to the model of the magnetic coupler 14, the terminals of this winding correspond electrically 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 ^^ ^^ ^^ ^^. For example, the magnetic coupler 14 comprises a transformer with two coupled coils, placed 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 ^^ ^^ ^^ ^^ , is equal to 0. PARAMETERS OF CONVERTER 2 The controller 8 is configured to control the switches ^^1 to ^^8 according to a control law. The following parameters are defined for the converter 2, and in particular for the controller 8 capable of controlling the switches ^^1 to ^^8 according to the control law. The parameters include quantities and constants. The quantities are in particular defined as follows. ^^1 is the voltage at the input terminals 4, called the first voltage;^^2 is the voltage at the output terminals 6, called the second voltage;^^1 ^^ is an adjusted value depending on the first voltage ^^1; ^^ 2 ^^ is an adjusted value depending on the second voltage ^^2 ; ^^ ^^ ^^1 is a first alternating voltage at the primary terminals 16 of the magnetic coupler 14;^^ ^^ ^^2 is the second alternating voltage at the secondary terminals 18 of the magnetic coupler;^^1 is a first duty cycle of the first circuit 10;^^2 is a second duty cycle of the second circuit 12;^^1 ^^ ^^ ^^ ^^ is the mode change voltage for ^^1.^^ is a phase shift of ^^ ^^ ^^2 with respect to ^^ ^^ ^^1, in particular the phase shift between the fundamentals of the waveforms of ^^ ^^ ^^2 compared to ^^ ^^ ^^1. By "waveform fundamentals" is meant the fundamental components resulting from the spectral decomposition over a theoretically infinite time of the respective waveforms of ^^ ^^ ^^2 and ^^ ^^ ^^1 in steady state.^^1 is the maximum sum of a charge stored in a drain-source parasitic capacitance depending on the primary switches ( ^^1, ^^2, ^^3, ^^4) and the first voltage ^^1. ^^1 is a function of ^^1.^^2 is the maximum sum of a charge stored in a drain-source parasitic capacitance depending on the secondary switches ( ^^5, ^^6, ^^7, ^^8) and the second voltage^^2. ^^2 is a function of ^^2. ^^1 and ^^2 are functions of ^^1 and ^^2 respectively, strictly increasing, and depend on the transistors chosen to form the switches ^^1 to ^^8. The first duty cycle ^^1 is in particular the duty cycle of the primary switches ^^1, ^^2, ^^3, ^^4. In particular, by "first duty cycle ", it is understood the ratio between the duration, over a period of the first alternating voltage ^^ ^^ ^^1 , during which this tension ^^ ^^ ^^1 is positive, and the duration of this period. The second duty cycle ^^2 is in particular the duty cycle of the secondary switches ^^5, ^^6, ^^7, ^^8. In particular, by "second duty cycle ^^2" is meant the ratio between the duration, over a period of the second alternating voltage ^^ ^^ ^^2 , during which this tension ^^ ^^ ^^2is positive, and the duration of this period. Examples of the first and second duty cycle ^^1, ^^2 are illustrated in Figure 4. The constants are in particular defined as follows. Preferably, the constants are predetermined and / or set by an operator or manufacturer of the converter 2.^^ ^^ ^^ is the switching frequency of the converter 2;^^1 ^^ ^^ ^^ ^^ ^^ is a predetermined minimum value of the first voltage ^^1 when the converter 2 converts a maximum power, in particular a limiting power;^^2 ^^ ^^ ^^ ^^ ^^ is a predetermined minimum value of the second voltage ^^2, when the converter 2 converts the maximum power, in particular the limiting power;^^1 ^^ ^^ ^^ ^^ ^^ ^^ is a minimum value of the first voltage ^^1, in particular a minimum voltage of the first voltage ^^1 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 ^^1 ^^ ^^ ^^ ^^ ^^ ^^ ≥ ^^1 ^^ ^^ ^^ ^^ ^^ ;^^2 ^^ ^^ ^^ ^^ ^^ ^^ is a minimum value of the second voltage ^^2, in particular a minimum voltage of the second voltage ^^2 beyond which the converter 2 implements a conversion according to the principle of ZVS, where preferably ^^2 ^^ ^^ ^^ ^^ ^^ ^^ ≥ ^^2 ^^ ^^ ^^ ^^ ^^ ;^^1 ^^ ^^ ^^ ^^ ^^ ^^ is a maximum value of the first voltage ^^1, in particular a maximum voltage of the first voltage ^^1 below which the converter 2 implements a conversion according to the ZVS principle, where preferably ^^1 ^^ ^^ ^^ ^^ ^^ ^^ ≥ ^^1 ^^ ^^ ^^ ^^ ^^ ^^ ;^^2 ^^ ^^ ^^ ^^ ^^ ^^ is a maximum value of the second voltage ^^2, in particular a maximum voltage of the second voltage ^^2 below which the converter 2 implements a conversion according to the ZVS principle, where preferably ^^2 ^^ ^^ ^^ ^^ ^^ ^^ ≥ ^^2 ^^ ^^ ^^ ^^ ^^ ^^ ;ℱ is a restricted domain of definition of the values ​​taken by ^^1 and ^^2, defined by:{; ^^ ^ ^ 1 ^^ ^^ ^^ ^^ ^^ ≤ ^^ ≤ ^^ ≤ ^^≤ ^^ 1 ^^ ^^ ^^ ^^ ^^ ^^≤ ^^ 1 1 ^^ ^^ ^^ ^^ ^^ ^^2^^ ^^ ^^ ^^ ^^ 2 ^^ ^^ ^^ ^^ ^^ ^^ 2 ≤ ^^2 ^^ ^^ ^^ ^^ ^^ ^^^ ^^ ^^ is a limiting power of the electrical converter 2;^^1 ^^ ^^1 and ^^2 ^^ ^^1 are the voltage values ​​of ^^1, respectively ^^2 allowing to maximize the magnitude on the domain ℱ ;^^1 ^^ ^^2 and ^^1 ^^ ^^2 are the voltage values ​​of ^^1, respectively ^^2 allowing to maximize the magnitude on the domain ℱ ;^^ ^^ ^^ ^^ ^^ = 2 ^^1 ^^ ^^ ^^(1 − ^^1 ^^ ^^ ^^) + 2 ^^2 ^^ ^^ ^^(1 − ^^2 ^^ ^^ ^^) − 1 / 2 ;^^ ^^ ^^ ^^1 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 first circuit 10 ;^^ ^^ ^^ ^^2 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 12. By "soft switching" is meant an orderly closing switching of the switches at an instant when the voltage across 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.^^1 ^^ ^^ ^^ is a predetermined maximum value of the first duty cycle, preferably 0 ≤ ^^1 ^^ ^^ ^^ ≤ 1 / 2, more preferably ^^1 ^^ ^^ ^^ being substantially equal to 1 / 2;^^2 ^^ ^^ ^^ is a predetermined maximum value of the second duty cycle, preferably 0 ≤ ^^2 ^^ ^^ ^^≤ 1 / 2, more preferably ^^2 ^^ ^^ ^^being substantially equal to 1 / 2; 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. The minimum value of the first voltage ^^1 ^^ ^^ ^^ ^^ ^^ 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 ^^2 ^^ ^^ ^^ ^^ ^^ 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. For example, the minimum value of the first and / or second voltage ^^1 ^^ ^^ ^^ ^^ ^^,^^2 ^^ ^^ ^^ ^^ ^^ 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 ​​^^1 ^^ ^^ ^^ ^^ ^^ and ^^2 ^^ ^^ ^^ ^^ are equal to 28V.Referring to Figure 2, an example of the first alternating voltage ^^. ^^ ^^1 over time t is illustrated with an indication of the state of each primary switch ^^1, ^^2, ^^3,^^4 at each instant as controlled by controller 8. The first alternating voltage ^^ ^^ ^^1 has three different values, namely ^^ ^^ ^^1 = ^^1; ^^ ^^ ^^1 = 0 or ^^ ^^ ^^1 = − ^^1. When the primary switches ^^1 and ^^4 are closed, the first alternating voltage ^^ ^^ ^^1 is equal to ^^1. When the primary switches ^^2 and ^^4 or ^^1 and ^^3 are closed, the first alternating voltage ^^ ^^ ^^1 is equal to 0. When the primary switches ^^2 and ^^3 are closed, the first alternating voltage ^^ ^^ ^^1 is equal to − ^^1. In each of the above examples, the other two primary switches not mentioned are in the open state. Referring to Figure 3, an example of the second AC voltage ^^ ^^ ^^2over time t is illustrated, analogously to Figure 2. The second alternating voltage ^^ ^^ ^^2 has three different values, namely ^^ ^^ ^^2 = ^^2; ^^ ^^ ^^2 = 0 or ^^ ^^ ^^2 = − ^^2. When the secondary switches ^^5 and ^^8 are closed, the second alternating voltage ^^ ^^ ^^2 is equal to ^^2. When the secondary switches ^^6 and ^^8 or ^^5 and ^^7 are closed, the second alternating voltage ^^ ^^ ^^2 is equal to 0. When the secondary switches ^^6 and ^^7 are closed, the second alternating voltage ^^ ^^ ^^2 is equal to − ^^2. In each of the above examples, the two other secondary switches not mentioned are in the open state. The examples in Figures 2 and 3 apply in particular to a magnetic coupler according to the previous definition, comprising an equivalent perfect transformer of ratio ^^, as illustrated in particular in Figure 5, capable of generating a potential difference n V AC1− V AC2 across the inductance L DAB illustrated in Figure 5. With reference to Figure 4, the phase shift ^^ between the alternating voltages ^^ ^^ ^^2 and ^^ ^^ ^^1 is illustrated, where the alternating voltages ^^ ^^ ^^1, ^^ ^^ ^^2 illustrated in Figure 4 are those illustrated in the examples of Figures 2 and 3. The phase shift ^^ corresponds in particular to the phase shift between fundamentals of the waveforms ^^ ^^ ^^2 and ^^ ^^ ^^1 , expressed proportionally to the switching period. With reference to Figure 4, when the controller 8 controls the switches ^^1 to ^^8 according to the examples of Figures 2 and 3, the converter 2 has a current waveform i(L DAB ) corresponding to a current flowing through the inductance L DAB and further presents a current waveform i(L M ) corresponding to a current flowing through the inductance LM.CONTROL LAW The controller 8 is configured to control the switches ^^1 to ^^8 according to the control law defining a switching frequency ^^ ^^ ^^ fixed of converter 2. The control law is such that an average electrical power converted by converter 2 is less than or equal to a predetermined constant electrical power, called limiting power ^^ ^^ ^^ ^^in this document. In particular, the controller 8 comprises an electronic circuit or electronic components specific to the control law. 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. 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. For example, the average electrical power is the power which 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. According to one example, by "average electrical power", is meant the arithmetic mean of the power over one or more switching periods.By "switching period of the converter" is meant in particular the duration, in the permanent state, between two successive closing times of a given switch of the converter 2. Each switch ^^1 to ^^8 in particular has either the open state or the closed state. The operation of the converter 2 is further defined by the switching frequency^^ ^^ ^^ of the converter 2. The switching frequency ^^ ^^ ^^ is the inverse of the switching period. Preferably, the limiting power ^^. ^^ ^^ ^^ is set by controller 8. The limiting power ^^ ^^ ^^ ^^ depends for example on the operating requirements of the converter 2. For example, the limiting power ^^ ^^ ^^ ^^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 limiting power ^^ ^^ ^^ ^^is the maximum power achievable by the converter 2, and is in particular reached in the event of a fault at the output terminals 6, for example in the event of failure of the loads supplied by the converter 2. In the converters known from the state of the art, in the event of a fault at the output terminals, the value of the limiting power depends on the first voltage and the second voltage of the converter. The value of the limiting power is consequently uncontrolled and unbounded and can prove destructive for the converter, or the electrical network of which it is part. In the converter 2 described here, the controller 8 is configured to control the switches ^^1 to ^^8, such that, including in the event of a fault at the output terminals 6, the electrical power supplied by the electrical converter remains less than or equal to the limiting power ^^ ^^ ^^ ^^, which is constant, which therefore does not depend on the first voltage ^^1. In particular, the limiting power ^^ ^^ ^^ ^^ is chosen such that it cannot cause the destruction of the converter 2 or the network of which it is part. Thus, in the event of a failure at the output terminals 6, the electrical power supplied by the electrical converter is equal to the limiting power ^^ ^^ ^^ ^^ , constant, and safe for converter 2. The control law defines the first duty cycle ^^1 of converter 2 based on the adjusted values ​​^^ 1 ^^ , ^^ 2 ^^ , according to a first function defined as follows: and / or according to a second function defined as follows: In this case, the controller 8 is configured to control the primary switches ^^1 to ^^4 according to the first duty cycle ^^1 defined by the control law. The adjusted value ^^ 1 ^^depending on the first voltage ^^1 is in particular a voltage mathematically clipped by the controller 8. For example, the adjusted value ^^ 1 ^^ is equal to the maximum of the values ​​^^1 and ^^1 ^^ ^^ ^^ ^^ ^^. The adjusted value ^^ 1 ^^ is thus preferably equal to max ( ^^1, ^^1 ^^ ^^ ^^ ^^ ^^). The adjusted value ^^ 2 ^^ dependent on the second voltage ^^2 is in particular a mathematically clipped voltage in an analogous manner. The adjusted value ^^ 2 ^^ is thus preferably equal to max ( ^^2, ^^2 ^^ ^^ ^^ ^^ ^^). According to an example, the control law is such that the first duty cycle is controlled according to said first function if ^^ 1 ^^ ≤ ^^1 ^^ ^^ ^^ ^^( ^^ 2 ^^ ), Or : Otherwise, the first cyclic ratio is controlled according to the second According to an example, the control law further defines the second duty cycle^^2 as being equal to a fixed value or as a function of the or each adjusted value ^^ 1 ^^ , ^^ 2 ^^ . In this case, controller 8 is configured to control the secondary switches ^^5 à ^^ 8according to the second duty cycle ^^2defined by the control law according to the following formula:^^2( ^^1 ^^, ^^2 ^^) = ^^ ^^1 ^^ ^^ ^^ ^^ 2 ^^^^1( ^^1 ^^, ^^2 ^^) ;^^ ^^2 ^^ ^^ ^^ 2 ^^ ^^ ^ ^^ ^^ = ^^1 ^^1 ^^ = ^ ^^ ^^^^1 ^^ ^^ ^^ ^^1 ^^ ^^ ^^ ^^ ^^ is constant over the entire operating range of converter 2. According to examples, the phase shift ^^ allows the transmitted power to be adjusted. For example, the phase shift ^^ is a strictly increasing function of the converter power over the interval [0 ; ¼]. The limiting power ^^ ^^ ^^ ^^is limited to a constant value, independent of the conditions on the first voltage ^^1 and the second voltage ^^2, and equal to: Furthermore, in the case where the second voltage ^^2 is constant, the second current is limited to a predetermined constant value, called the limiting current, equal to: The converter 2, and in particular the magnetic coupler 14, is sized and configured to control the controlled switches ^^1 to ^^8 according to the control law so as to obtain smooth switching operation of the controlled switches ^^1 to ^^8, over a predetermined operating range. In particular, the magnetic coupler 14 has a plurality of design parameters ^^ ^^ ^^ ^^ , ^^, and ^^ ^^ having values ​​determined according to formulas specific to the group of functions chosen from the control law. A first design parameter ^^ ^^ ^^ ^^is in particular the DAB 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. A second design parameter ^^ is a ratio of ^^ ^^ ^^2 on ^^ ^^ ^^1 when a current ^^( ^^ ^^ ^^ ^^ ) in a branch of the magnetic coupler is equal to 0. The design parameter ^^ 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 ^^ ^^ ^^2 on the tension ^^ ^^ ^^1 of the isolated magnetic coupler 14 when the current at the secondary terminals 18 is zero. A third design parameter ^^ ^^ is in particular the magnetizing inductance ^^ ^^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. Preferably, each design parameter ^^ ^^ ^^ ^^ , ^^, and ^^ ^^ is determined in such a way as to obtain zero voltage switching of the primary and / or secondary switches ^^1 to ^^8, called the ZVS principle. In particular, the design parameters ^^ ^^ ^^ ^^ , ^^, and ^^ ^^ form design rules to obtain, from the model forming the magnetic coupler 14, the converter 2. In particular, there is a triplet { ^^^^ ^^ ^^ ^^ ^^ ^^, ^^ ^^ ^^ ^^ , ^^^^ ^^ ^^ ^^} design parameter solution ^^ ^^ ^^ ^^ , ^^, and ^^ ^^ , allowing optimal operation in terms of effective currents to be obtained, while maintaining smooth switching within the converter. ^ ^ (^^1 ^^ ^^1 ) means that is evaluated at ^^1 ^^ ^^1 and ^^2 ( ^^2 ^^ ^^2 ) means that ^^2 evaluated at ^^ 2 ^^ ^^2 . A conversion method implemented by the converter 2 is now described. During the conversion method, the converter 2 converts the first direct current under the first voltage ^^1 received at the input terminals 4 into the second direct current at the output terminals 6 under the second voltage ^^2. During a conversion step of the conversion method, the controller 8 controls the switches ^^1 to ^^8 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 ^^ ^^ ^^ ^^. The control law is defined as described above. For example, the conversion method comprises several repetitions of the conversion step. Preferably, the controller 8 controls the switches ^^1 to ^^8 according to the control law so as to obtain the first and / or second alternating voltage ^^ ^^ ^^1,^^ ^^ ^^2, with the first duty cycle and / or the second duty cycle ^^2 as defined by the control law. It is understood that the converter 2 according to the invention, and in particular the control law, has a large number of advantages. 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 Programmable Gate Array. In particular, the elements constituting the converter 2 used are dimensioned, and said converter 2 is controlled so that its active elements are switched at 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. 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.Finally, the control law limits the maximum power and / or the maximum current to a constant value which are respectively the limiting power ^^ ^^ ^^ ^^ and the intensity^^ ^^ ^^ ^^ which are independent of the input and output voltages. 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 ^^. ^^ ^^ ^^ and the switching frequency ^^ ^^ ^^ be kept constant.

Claims

CLAIMS 1. Isolated DC-DC electrical converter (2), configured to convert a first DC current under a first voltage ^^1 received at input terminals (4) into a second DC current under a second voltage ^^2 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 ( ^^1, ^^2, ^^3, ^^4) and a second circuit (12) connected to the output terminals (6) and comprising controlled switches, called secondary switches ( ^^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 ( ^^1, ^^2, ^^3, ^^4, ^^5, ^^6, ^^7, ^^8) 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 duty cycle ^^1,defining a switching ratio of the primary switches (^^1, ^^2, ^^3, ^^4), according to a first function defined as follows:, and / or according to a second function defined as follows: ^^ ^^ is an adjusted value depending on the first voltage and is equal to max ( ^^1, ^^1 ^^ ^^ ^^ ^^ ^^) ;^^2 ^^ is an adjusted value depending on the second voltage ^^2 and is equal to max ( ^^2, ^^2 ^^ ^^ ^^ ^^ ^^) ;^^ e ^^2 ^^ ^^ ^^ ^^2 ^^ ^^ ^^ ^^ ^^^^ ^^ is a constant value such that ^^ ^^ ^^ = ^^1 ^^ ^^ ^^ ^^1 ^^ ^^ ^^ ^^ ^^; 19^^1 ^^ ^^ ^^ ^^ ^^ is a predetermined minimum value of the first voltage ^^1 when the electrical converter (2) converts a maximum power;^^2 ^^ ^^ ^^ ^^ ^^ is a predetermined minimum value of the second voltage ^^2 when the electrical converter (2) converts the maximum power;^^1 ^^ ^^ ^^ is a predetermined maximum value of the first duty cycle ^^1, preferably ^^1 ^^ ^^ ^^ ≤ 1 / 2;^^2 ^^ ^^ ^^ is a predetermined maximum value of a second duty cycle ^^2 defining a switching ratio between the secondary switches ( ^^5, ^^6, ^^7, ^^8), preferably ^^2 ^^ ^^ ^^ ≤ 1 / 2, in which the first duty cycle ^^1 is controlled according to said first functioni ^^1 ^^ ≤ ^^1 ^^ ^^ ^^ ^^( ^^2 ^^), where: otherwise the first cyclic ratio being controlled according to said second 2. Electrical converter (2) according to claim 1, in which said control law defines the second duty cycle ^^2 according to the following function:

3. Electrical converter (2) according to any one of the preceding claims, wherein the electrical converter (2) is defined by design parameters ^^ ^^ ^^ ^^, ^^ and ^^ ^^, where: ^^ ^^ is the inductance measured at the terminals (16) when the terminals (18) are in circuit ouvert ;^^ is the ratio of the voltage measured at terminals (18) to the voltage measured at terminals (16), when the current flowing in (18) is zero;^^ ^^ ^^ ^^ is the inductance measured at terminals (18) when terminals (16) are short-circuited.

4. Electrical converter (2) according to claim 3, wherein the design parameters ^^ ^^ ^^ ^^, ^^ and ^^ ^^ are defined as being equal to ^^ ^^ ^^ ^^ , ^^ ^^ ^^ ^^ ^^ ^^ ^^ and ^^ ^^ ^^ ^^ ^^, respectively, where:ℱ is a restricted domain of definition of the first and second voltages ^^1, ^^2 defined by: { ^^1 ^^ ^^ ^^ ^^ ^^ ≤ ^^1 ^^ ^^ ^^ ^^ ^^ ^^ ≤ ^^1 ≤ ^^1 ^^ ^^ ^^ ^^ ^^ ^^^^2 ^^ ^^ ^^ ^^ ^^ ^^ ≤ ^^2 ≤ ^^2 ^^ ^^ ^^ ^^ ^^ ^^^ ^^ ^^ ^^1 with ^^ being equal to 1 or 2, is a voltage ^^ ^^, ^^ being equal to 1 or 2, of the couple ( ^^ 1, ^^2) allowing to maximize the magnitude^^1( ^^1, ^^2) ^^1 on the domain ℱ ;^^ ^^ ^^ ^^2 with ^^ being equal to 1 or 2, is a voltage ^^ ^^, ^^ being equal to 1 or 2 of the torque ( ^^ ^^2( ^^2)1, ^^2) allowing to maximize the magnitude ^^1( ^^1, ^^2) ^^1 on the domain ℱ ;^^ ^^ ^^ ^^1 is a predetermined time period for a charge transfer between the switches ( ^^1, ^^2, ^^3, ^^4, ^^5, ^^6, ^^7, ^^8) during a dead time to satisfy a zero voltage switching condition in the first circuit (10);^^ ^^ ^^ ^^2 is a predetermined time period for a charge transfer between the switches ( ^^1, ^^2, ^^3, ^^4, ^^5, ^^6, ^^7, ^^8) during a dead time to satisfy a zero voltage switching condition in the second circuit (12); ^^ ^^ ^^ ^^is the limiting power;^^1( ^^1 ^^ ^^1) is a maximum sum of charges stored in a drain-source parasitic capacitance depending on the primary switches ( ^^1, ^^2, ^^3, ^^4) and the first voltage ^^1, evaluated at ^^1 ^^ ^^1;^^2( ^^2 ^^ ^^2) is a maximum sum of charges stored in a drain-source parasitic capacitance depending on the secondary switches ( ^^5, ^^6, ^^7, ^^8) and the second voltage ^^2, evaluated at ^^2 ^^ ^^2;^^ ^^ ^^ is the switching frequency of the converter (2).

5. Electrical converter (2) according to any one of the preceding claims, the controller (8) being configured to control the controlled switches (^^1, ^^2, ^^3, ^^4, ^^5, ^^6, ^^7, ^^8) according to a control law defining a fixed switching frequency of the converter, so as to obtain an electric current average converted by the electrical converter (2) less than or equal to a predetermined constant current, called the limiting current.

6. 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 ( ^^1 , ^^ 2 , ^^ 3 , ^^ 4 , ^^ 5 , ^^ 6 , ^^ 7 , ^^8).

7. 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.

8. 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 ^^1 received at the input terminals (4) of the electrical converter (2) into the second direct current under the second voltage ^^2 at the output terminals (6) of the electrical converter (2), the conversion method comprising a conversion step in which the switches ( ^^1, ^^2, ^^3, ^^4, ^^5, ^^6, ^^7, ^^8) 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.

Images