FR3004602A1 - VOLTAGE CONVERTER AND VOLTAGE CONVERSION METHOD - Google Patents

Abstract

The voltage converter (100) includes: - an input terminal (128) for connection to an electrical source (130) for presenting an input voltage (Vin); an output terminal (136) intended to be connected to an output capacitor (132) for presenting an output voltage (Vout); a system (102) of coupled coils comprising: at least three coils (118n) each having two terminals and a magnetic coupling core (104) for the coils (118n); a switching system (138) for each coil (118n) for alternately causing energy to be stored in the coil (118n) by receiving from a terminal of the coil (118n) a current from the input terminal (128), and a reproduction at the output terminal (136) of stored energy. The magnetic core (104) comprises at least one closed magnetic flux-guiding loop, around which the coils (118n) are successively wound, the coils (118n) being such that the currents coming from the input terminal (128) ) travel the coils (118n) in rotational directions around the alternating closed loop from one coil (118n) to the next.

Description

The present invention relates to a voltage converter and a voltage conversion method. Yan Dong's "Investigation of Multiphase Coupled-Inductor Buck Converters in Point-of-Load Applications" thesis, dated July 24, 2009, and filed with the Faculty of the Virginia Polytechnic Institute and the State University. described in FIG. 1.26 (b): a system of coupled coils having at least three coils each having two terminals, and a magnetic coupling core of the coils, and a switching system intended, for each coil, to alternatively cause a storage of energy in the coil by the reception by a coil terminal of a current from the input terminal, and a reproduction, at the output terminal, of stored energy. More specifically, in this publication, the magnetic core comprises two parallel plates interconnected by transverse spacers around which the coils are wound. The coupled coil system described in the previous thesis has the disadvantage of requiring large plate thicknesses because the magnetic flux generated by the coils add up in these plates. Thus, a voltage converter using this system of coupled coils would have a large footprint. In order to at least partly solve this drawback, a voltage converter is proposed, comprising: an input terminal intended to be connected to an electrical source for presenting an input voltage, an output terminal intended to be connected to an output capacitor for presenting an output voltage, a system of coupled coils comprising: + at least three coils each having two terminals, + a magnetic coupling core of the coils, a switching system intended, for each coil, to alternately provoke energy storage in the coil by receiving a coil terminal of a current from the input terminal, and outputting stored energy to the output terminal, characterized in that the magnetic core comprises at least one closed magnetic flux-guiding loop, around which the coils are successively wound, the coils (118n) being such that the currents from the input terminal travel the coils in directions of rotation around the closed loop alternating from one coil to the next. Optionally, the winding directions alternate from one coil to the next. Also optionally, the winding directions are all the same. Also optionally, each closed loop comprises: a central bar around which the coils are wound; - a sidebar bypassing the coils; and end bars also bypassing the coils and respectively connecting the ends of the central bar to the ends of the side bar. Optionally also, the central bar is common to all closed loops.

Optionally also, the magnetic core further comprises, for each closed loop, transverse bars connecting the central bar to the side bar and separating the coils from each other. Also optionally, each closed loop has a reluctance at least ten times greater than the reluctance of the cross bars.

Optionally also, the central bar is provided with at least one gap. Optionally also, the crossbars have a smaller section than the section of the central bar. Optionally also, the voltage converter is intended to provide a higher output voltage than the input voltage.

Optionally also, the voltage converter comprises an even number of coils, and, the coils being arranged in their succession along each closed loop from a first coil to a last coil, the switching system is intended to make alternating a first phase in which the odd-rank coils store energy, while the even-rank coils provide energy, and a second phase in which the odd-rank coils provide energy, while even-rank coils store energy.

There is also provided a voltage conversion method, comprising: obtaining a voltage converter, comprising: + an input terminal intended to be connected to an electrical source for presenting an input voltage; + an output terminal intended to be connected to an output capacitor for presenting an output voltage; + a system of coupled coils comprising: at least three coils, and a magnetic coil coupling core, comprising at least one closed magnetic flux guide loop around which the coils are successively wound, the alternation, for each coil : + a storage of energy by the reception by a terminal of the coil of a current coming from the input terminal, and + a restitution, at the output terminal, of stored energy, the currents from the input terminal traversing the coils in directions of rotation around the closed loop alternating from one coil to the next. An exemplary embodiment of the invention will now be described with reference to the appended figures, in which: FIG. 1 is a simplified view from above of a voltage converter embodying the invention; FIG. 2 is a simplified view from above of a magnetic core of the voltage converter of FIG. 1; Figure 3 is a top view of an element for forming the magnetic core of Figure 2; and FIG. 4 is a block diagram illustrating the steps of a voltage conversion method implemented by the voltage converter of FIG. 1; FIG. 5 is a view similar to that of FIG. 2, illustrating magnetic fluxes in the magnetic core; and FIG. 6 is a set of two graphs illustrating the evolution of the current flowing through the coils of the voltage converter of FIG. 1.

With reference to FIG. 1, a voltage converter 100 embodying the invention will now be described. In the example described, the voltage converter 100 is a voltage booster (called "boost converter" or "step-up converter"), intended to receive a DC input voltage V, and to provide a DC output voltage Vc, greater than the DC input voltage V ,.

The voltage converter 100 first comprises a system 102 of coupled coils. The system 102 firstly comprises a magnetic core 104. In the example described, the magnetic core 104 is made of ferromagnetic material. The magnetic core 104 firstly comprises a central bar 108. In the context of the present invention, the term "bar" includes all the generally elongated elements, for example a rod or even a plate. In the example described, the central bar 108 is rectilinear and of rectangular section. The magnetic core 104 further comprises first and second lateral bars 110, 112, located on two sides of the central bar 108. In the example described, the first and second lateral bars 110, 112 are rectilinear and also of rectangular section, and extend parallel to the central bar 108. The magnetic core 104 further includes first and second end bars 114, 116. The first end bar 114 connects one end of the central bar 108 with the ends of the bars. 110, 112 side of the same side, while the second end bar 116 connects the other end of the central bar 108 with the other ends of the side bars 110, 112, located on the other side. In the example described, the first and second end bars 114, 116 rectilinear and also of rectangular section, and extend perpendicularly to the central bar 108.

The magnetic core 104 further comprises N-1 (N being greater than or equal to three, and preferably even - in the example described, N is equal to four) pairs of transverse bars 120, 122, (m varying from 1 at N-1). The transverse bars 120, 122, of each pair together connect the central bar 108 with respectively the first lateral bar 110 and the second lateral bar 112. In the example described, the transverse bars 120, n, 122 n, are rectilinear and of rectangular section, which extend perpendicularly to the central bar 108.

The system 102 further comprises N coils 118 '(N being greater than or equal to three, and n varying from 1 to N) successively wound around the central bar 108 and bypassed by the first and second end bars 114, 116 and the first and second lateral bars 110, 112. As known per se, each coil 118 'has two terminals defined by the winding direction of the coil: a winding start terminal and a winding end terminal. . In the example described, the winding directions of the coils 118 'alternate from one coil to the next in their succession. Thus, the central bar 108, the first and second end bars 114, 116 and the first and second lateral bars 110, 112 define two closed loops passing through all the coils 118 'and intended to guide magnetic flux. A closed loop is a path defined by the magnetic core 104 which returns to its starting point without passing twice in the same section of the magnetic core 104. In addition, the transverse bars 120, n, 122n, are interposed between the coils 118 ', so that each coil 118' is separated from the next along the central bar 108 by a pair of transverse bars 120, n, 122, n. Thus, the transverse bars 120, n, 122n, define magnetic flux leakage paths between the coils 118 '. The voltage converter 100 further comprises a ground terminal 124 connected to an electrical ground 126 and an input terminal 128 intended to have an input voltage V, with respect to the electrical ground 126.

The voltage converter 100 further comprises an electrical source 130 connected to the terminals 124, 128 for applying the input voltage V, to the input terminal 128 with respect to the ground terminal 124. In the example described, the electrical source 130 is a DC voltage source. The input terminal 128 is further connected to a first terminal of each coil 118 '. In the example described, the input terminal 128 is connected to the winding start terminals of the coils 118 '.

Thus, thanks to the alternate winding direction of the coils, the currents coming from the input terminal 128 traverse the coils 118 'in directions of rotation around the central bar 108 alternating from one coil to the next following their succession. . This alternation is represented in FIG. 1 by arrows in opposite directions on the coils 118 '. The voltage converter 100 further includes an output capacitor 132 having a first terminal 134 connected to the electrical ground 126 and a second terminal 136, called an output terminal, for presenting the output voltage V, ',' with respect to the first terminal 134.

The voltage converter 100 further comprises a switching system 138 for, for each coil 118 ', alternately causing, on the one hand, a storage of energy in the coil 118' by the reception by the terminal of the coil 118 connected to the input terminal 128 of a current from the input terminal 128, and, on the other hand, a supply of energy stored in the coil 118 'by supplying a current to the output terminal 136. In the example described, the switching system 138 comprises first, for each coil 118 ', a first controlled switch 140' connecting the terminal of the coil 118 'not connected to the input terminal 128, at the output terminal 136. The switching system 138 further comprises, for each coil 118 ', a second controlled switch 142' connecting the terminal of the coil 118 'not connected to the input terminal 128, to the electric mass 126. The switching system 138 further comprises a device f 144 for controlling the switches 140 ', 142'. The control device 144 is intended, for each coil 118 ', to alternately open the first controlled switch 140' and close the second 142 ', then open the second controlled switch 142' and close the first 140 '. In the first configuration, the coil 118 'supplies power to the output capacitor 132, and in the second configuration, the coil 118' stores energy from the voltage source 144. With reference to FIG. closed loops are represented by dotted lines and are respectively references 202 and 204. Furthermore, each transverse bar 120, n, 122n, has a reluctance value r between the central bar 108 and the first and second lateral bars 110, 112 respectively. Furthermore, in the example described, the two closed loops 202, 204 have the same value of reluctance R. Preferably, the reluctance value R is at least ten times higher than the reluctance value r. In the example described, this is first obtained by providing a section of the transverse bars 120, n, 122n, smaller than the section of the central bar 108, the end bars 114, 116 and the lateral bars 110, 112. In addition, the central bar 108 is provided with air gaps 206, that is to say cuts of material of a size preferably less than one centimeter. Since the transverse bars 120, n, 122n, have a smaller reluctance r than the other elements of the magnetic core 104, these transverse bars 120 '' 122m magnetically saturate for lower values of magnetic flux than the closed loops 202, 204. Referring to Figure 3, an element 300 of the magnetic core 104 will now be described. Of course, in other embodiments, other element shapes could be used.

The element 300 is E-shaped and has a base 302 and three parallel arms 304, 306, 308 extending from the base 302. The central arm 306 may be a little shorter than the other two surrounding it. Several elements such as the element 300 are stacked to form the magnetic core 104: the base 302 of each element forms either the end bar 116 or a section of the central bar 108 and a pair of transverse bars, the central arm 306 form a section of the central bar 108, and the other arms 304, 308 form sections of the side bars 110, 112. The arms 304, 308 are intended to come into contact with either the base 302 of the element 300 following the of the end bar 114. When the central arm 306 is shorter than the other two, an air gap is formed in the stack between the central arm 306 and either the base 302 of the next element or end bar 114. With reference to FIG. 4, a voltage conversion method 400 embodying the invention will now be described. During a step 402, the control device 144 controls the switches 140 ', 142' in the energy storage configuration (switches 140 'open, switches 142' closed).

During a step 404, all the coils 118 'therefore receive current from the electrical source 130 in an increasing manner, and a corresponding magnetic flux appears in the magnetic core 104. More precisely, each coil 118' creates, in each section magnetic core 104, a magnetic flux. Thus, in the example described, each section of the magnetic core 104 is traversed by four magnetic fluxes, one for each coil 118 '. However, thanks to the alternation, from one coil to the next, the directions of the currents flowing through the coils 118 '(which results from the winding directions of the coils 118', chosen judiciously as a function of the terminals of the coils 118 'connected to the input terminal 128), the magnetic fluxes are alternately in one direction of rotation and in the other. Thus, in the central bar 108, the lateral bars 110, 112 and the end bars 116, 114, the magnetic fluxes compensate at least in part (see for example the zone Z of the lateral bar 112 in FIG. 5). , so that the resulting field remains weak.

Thus, the system 102 has a low apparent inductance. As the resultant magnetic flux remains low, it is possible to use a weak section for the bars 108, 110, 112, 114, 116, which reduces the size of the system 102. On the other hand, the compensation phenomenon is less marked in the transverse bars 120, n, 122n, because in these places the magnetic fluxes generated by the two nearest coils 118 ', i.e. the two coils 118' surrounding each pair of bars transversal 120, n, 122n, are of the same direction and therefore add up. Thus, during a step 406, the transverse bars 120, n, 122n saturate magnetically so that their reluctance becomes very high. As these transverse bars are surrounded by the other parts of the magnetic core 104 which do not saturate, the radiation to the outside of the system 102, induced by these saturations, remain moderate. During a step 408, the control device 144 switches the switches 140 ', 142' from one configuration to another, so that each coil 118 'stores energy, then restores it. Preferably, as shown in FIG. 6, the tilts are opposite from one coil to the next (phase shift of 7C between each coil), so that when a coil is in a configuration, the next coil is in other configuration. Thus, the coils 118 'being arranged in their succession along each closed loop 202, 204 from a first coil 1184 to a last coil 1184, in a first phase, the odd-rank coils 1184, 1183 store the energy, while the even-rank coils 1182, 1184 supply energy, and in a second phase, the odd-rank coils 1184, 1183 provide energy, while the even-rank coils 1182, 1184 store energy. 'energy. Still with reference to FIG. 6, the current I (n) traveling through each coil 118 'thus has a continuous Im component (so-called "common mode" component), which is theoretically the same for all the coils, and an oscillating component i (n) varying around zero. It will be noted that FIG. 6 is not completely faithful to reality since each oscillating current i (n) should have several slopes, depending on the state of the other coils (in energy storage or in energy recovery ). At a given moment, the signs of the oscillating components i (n) are of alternating signs: one in two is positive (that is, the current I (n) is greater than its common mode component Im) and one in two is negative (i.e. the current I (n) is smaller than its common mode component Im). This alternation compensates, at least in part, the alternation of the rotational directions of the currents in the coils 118 ', so that the magnetic fluxes are no longer alternated as in step 402. Thus, the magnetic fluxes add up the along the closed loops 202, 204 of the magnetic core 104. The resulting magnetic flux is high, resulting in a high apparent inductance for the oscillating components i (n). Thus, despite the reduction in the size of the system 102 indicated above, the system 102 remains efficient. The invention is not limited to the embodiment described above, but defined by the following claims. For example, if the currents coming from the input terminal are received alternately, from one coil to the next, by the winding start terminal and the winding end terminal of the coils, the latter would then be wound in identical winding directions around the closed loop (s).

For example also, the ferromagnetic core could have only one sidebar, not two, and thus define a single closed loop. For example also, the cross bars could be omitted. In addition, the phase difference between successive coils could be of a value other than 7C. The phase shift may have a value adapted to the design of the converter to allow an apparent inductance, in particular not negligible, and / or to minimize the losses.

Claims (12)

REVENDICATIONS1. A voltage converter (100), comprising: an input terminal (128) for connection to an electrical source (130) for presenting an input voltage (V, '), an output terminal (136) for connected to an output capacitor (132) for presenting an output voltage (Vout), a system (102) of coupled coils comprising: + at least three coils (118 ') each having two terminals, + a magnetic core (104) ) for coupling the coils (118 '), a switching system (138) for alternately causing each coil (11' 8 ') to store energy in the coil (118') by receiving by a terminal of the coil (118 ') of a current from the input terminal (128), and a reproduction, at the output terminal (136), of stored energy, characterized in that the magnetic core (104) ) has at least one magnetic flux-guiding closed loop (202; 204) around which the coils (118 ') are successively the coils (118 ') being such that currents from the input terminal (128) travel through the coils (118') in rotational directions about the closed loop (202; 204) alternating from one coil (118 ') to the next. A voltage converter (100) according to claim 1, wherein the winding directions alternate from one coil (118 ') to the next. The voltage converter (100) of claim 1, wherein the winding directions (118 ') are all the same. A voltage converter (100) according to any one of claims 1 to 3, wherein each closed loop (202; 204) comprises: a central bar (108) around which the coils (118 ') are wound, a side bar (110; 112) bypassing the coils (118 '), end bars (114, 116) also bypassing the coils (118') and respectively connecting the ends of the central bar (108) to the ends of the bar lateral (110; 112). A voltage converter (100) according to claim 4, wherein the central bar (108) is common to all closed loops (202; 204). The voltage converter (100) according to claim 4 or 5, wherein the magnetic core (104) further comprises, for each closed loop (202; 204), transverse bars (120 ,,,; 122, n). connecting the central bar (108) to the side bar (110; 112) and separating the coils (118 ') from each other. The voltage converter (100) according to claim 4 or 5, wherein each closed loop (202; 204) has a reluctance (R) at least ten times greater than the reluctance (r) of the crossbars (120m, 122m). ). The voltage converter (100) according to claim 7, wherein the central bar (108) is provided with at least one air gap. A voltage converter (100) according to claim 7 or 8, wherein the transverse bars (120m, 122m) have a smaller section than the section of the central bar (108). A voltage converter (100) according to any one of claims 1 to 9, for providing an output voltage (V, ',') higher than the input voltage (V, '). A voltage converter (100) according to any one of claims 1 to 10, having an even number of coils (118 '), and wherein the coils (118') are arranged in their succession along each loop closed (202; 204) from a first coil (1184) to a last coil (1184), the switching system (138) is adapted to alternate a first phase in which the odd-order coils (1184, 1183) store energy, while the even-rank coils (1182, 1184) provide energy, and a second phase in which the odd-rank coils (1184, 1183) provide energy, while the coils of even rank (1182, 1184) store energy. A voltage conversion method (400), comprising: obtaining a voltage converter (100), comprising: + an input terminal (128) for connection to an electrical source (130) for presenting an input voltage (V, '); + an output terminal (136) for connection to an output capacitor (132) for presenting an output voltage (Vo't); + a coupled coil system (102) having: at least three coils (118 '), and a coil coupling magnetic core (104) having at least one closed loop (202; 204) for guiding the coils (118'). magnetic flux around which the coils (118 ') are successively wound, the alternation (408) for each coil (118'): + energy storage by the reception by a terminal of the coil (118 ') ) of a current from the input terminal (128), and + of a reproduction, at the output terminal (136), of stored energy, the currents coming from the input terminal (128) ) traveling through the coils (118 ') in rotational directions about the closed loop (202; 204) alternating from one coil (118') to the next.