Resonant DC-DC voltage converter

Abstract

The subject matter of the invention is a three-phase resonant DC-DC voltage converter, notably for an electric or hybrid vehicle, said converter including a plurality of resonant circuits. First inductive elements of the resonant circuits are coupled together and primary windings of the transformers of each resonant circuit are coupled together.

Claims

1. A resonant DC-DC voltage converter, notably for an electric or hybrid vehicle, said converter including a plurality of resonant circuits, each resonant circuit including: a first inductive element, a resonance capacitor connected to said first inductive element, a transformer including at least one primary winding and at least one secondary winding, said first inductive element, the resonance capacitor and the primary winding of the transformer being comprised in a branch of the resonant circuit, designated “resonance branch”, converter in which the first inductive elements of the resonant circuits are coupled together, and the primary windings of the transformers of the resonant circuits are coupled together, wherein the primary windings of the resonance branches of the converter are all connected to a first neutral point, the first neutral point being connected to a ground of the DC-DC converter via at least one of the resonance branches including at least one impedance configured to store energy and to enable zero voltage switching of the switches of the resonant DC-DC converter.

2. The converter according to claim 1, in which the transformer of each resonant circuit includes a second inductive element in order to form a resonant circuit of LLC type.

3. The converter according to claim 1, in which the secondary windings are coupled together.

4. The converter according to claim 1, in which branches, each including one of said secondary windings of the transformers, are all connected to a second neutral point.

5. The converter according to claim 4, in which the second neutral point is connected to a ground of the DC-DC converter via a branch including at least one impedance configured to store energy and to enable zero voltage switching of the switches of the resonant DC-DC converter.

6. The converter according to claim 5, in which said impedance includes an inductance in series with a capacitor.

7. The converter according to claim 1, in which the first neutral point is configured so as to have a floating electric potential.

8. The converter according to claim 1, in which, at least one first resonant circuit of the converter includes a half-bridge input structure including an upper switch and a lower switch wherein both the upper switch and the lower switch are connected to a mid-point node, said mid-point node being connected to the resonance branch of said first resonant circuit.

9. The converter according to claim 7, in which each resonant circuit includes a half-bridge input structure including an upper switch and a lower switch connected at the level of a mid-point node, said mid-point node being connected to the respective resonance branch of said resonant circuit.

10. The converter according to claim 7, including n resonant circuits, n being a natural integer greater than or equal to two, and in which a number p, p being a non-zero natural integer strictly less than n, of said resonant circuits includes a half-bridge input structure including an upper switch and a lower switch connected at the level of a mid-point, said mid-point being connected to the respective resonance branch, said converter being configured such that in one operating mode, said switches of the p resonant circuits periodically switch in such a way as to transmit energy through the resonant circuits, and the resonance branches of the n-p other resonant circuits being either in open circuit or connected to a ground of the resonant DC-DC converter, for the duration of this operating mode.

11. The converter according to claim 10 including a control unit, said control unit being configured to control the switches of the n-p resonant circuits in order to place them either in open circuit for the duration of said operating mode or in connection with the earth of the resonant DC-DC converter for the duration of said operating mode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood on reading the description that follows, given only as an example, and by referring to the appended drawings given as non-limiting examples, in which identical references are given to similar objects and in which:

(2) FIG. 1 represents an example of electrical circuit including three interleaved resonant DC-DC converters of the prior art,

(3) FIG. 2 represents a first embodiment of a converter according to the invention,

(4) FIG. 3 represents a second embodiment of a converter according to the invention,

(5) FIG. 4 represents a third embodiment of a converter according to the invention,

(6) FIG. 5 represents a fourth embodiment of a converter according to the invention,

(7) FIG. 6 represents a fifth embodiment of a converter according to the invention.

(8) It should be noted that the figures explain the invention in a detailed manner for implementing the invention, said figures obviously being able to serve to better define the invention if needs be.

DETAILED DESCRIPTION

(9) In the description that will be made hereafter, the invention will be described in its application to an electric or hybrid automobile vehicle without this limiting the scope of the present invention.

(10) For example, such a vehicle may notably include an electrical machine, an inverter, a set of converters, a high voltage power supply battery, an on board high voltage electrical network, a low voltage power supply battery, an on board low voltage electrical network and a plurality of auxiliary items of electrical equipment.

(11) The set of converters according to the invention is described hereafter in its implementation for an electrical charger, notably on board a vehicle, without however this limiting the scope of the present invention. It will thus be noted that the set of converters could be a DC-DC converter on board the vehicle.

(12) The on board low voltage electrical network connects the low voltage power supply battery and the plurality of auxiliary items of electrical equipment in order that the low voltage power supply battery supplies said auxiliary items of electrical equipment, such as on board computers, window winding motors, a multimedia system, etc. The low voltage power supply battery typically delivers for example a voltage of the order of 12 V, 24 V or 48 V. The recharging of the low voltage battery is carried out from the high voltage battery via a direct current into direct current voltage converter, commonly called DC-DC converter.

(13) The on board high voltage electrical network connects the high voltage power supply battery and the inverter in order that the high voltage power supply battery ensures a function of supplying the electrical machine with energy via the inverter. The high voltage power supply battery typically delivers a voltage comprised between 100 V and 900 V, preferably between 100 V and 500 V. The recharging of the high voltage power supply battery with electrical energy is carried out by connecting it, via the DC high voltage electrical network of the vehicle, to an external electrical network, for example the domestic AC electrical network.

(14) The electrical machine is a rotating electrical machine, preferably configured to drive the wheels of the vehicle from the energy supplied by the high voltage power supply battery. More specifically, the electrical machine is an alternating current electrical machine supplied by a polyphase current source. For example, the electrical machine may be an alternating current motor. In the preferred example described hereafter, the electrical machine is supplied by a three-phase current source without this limiting the scope of the present invention.

(15) In this example, the control of the electrical machine is achieved by means of the inverter. Said inverter makes it possible to convert the direct current supplied by the high voltage power supply battery into three alternating control currents, for example sinusoidal. In other words, the function of the inverter is to transform the direct current delivered by the high voltage power supply battery into three phase currents making it possible to control the electrical machine. Conversely, in another operating mode, the electrical machine can also supply three alternating currents to the inverter in order that said inverter transforms them into a direct current making it possible to charge the high voltage power supply battery.

(16) In FIGS. 2 to 6 are represented five embodiments of the electrical converter according to the invention. The converter 10-1, 10-2, 10-3, 10-4, 10-5 optionally includes a control unit UC.

(17) In these examples, the converter 10-1, 10-2, 10-3, 10-4, 10-5 is a resonant converter configured to convert a direct current voltage into a direct current voltage and includes three resonant circuits. However, it could include a different number of resonant circuits.

(18) Notably, each resonant circuit comprises a transformer, including at least one primary winding P1, P2, P3 and at least one secondary winding S1, S2, S3. Each resonant circuit further includes a resonance capacitor CR1, CR2, CR3 and a first inductive element L1, L2, L3. The primary winding P1, P2, P3, the resonance capacitor CR1, CR2, CR3 and the first inductive element L1, L2, L3 are for example comprised in a branch of the resonant circuit, and are notably in series. For example, the first inductive element L1, L2, L3 may be connected to a terminal of the resonance capacitor CR1, CR2, CR3, the other terminal of the resonance capacitor CR1, CR2, CR3 being connected to a terminal of the primary winding P1, P2, P3 of the transformer, optionally via a resistor (not represented).

(19) The first inductive elements L1, L2, L3, are preferably induction coils. The first inductive elements L1, L2, L3 of the three resonant circuits are coupled together (TX1 coupling in FIGS. 2 to 6). Similarly, the primary windings P1, P2, P3 of the three transformers of the resonant circuits are coupled together (TX2 coupling in FIGS. 2 to 6). A galvanic insulation is formed between the primary windings P1, P2, P3 and the secondary windings S1, S2, S3 of the transformers of the three resonant circuits. A first earth M1 constitutes a reference potential of the primary side converter 10-2, 10-3, 10-4, 10-5, and a second earth M2 constitutes a reference potential of the secondary side converter 10-2, 10-3, 10-4, 10-5.

(20) Each resonant circuit includes a half-bridge output structure including an upper transistor Q7, Q9, Q11 and a lower transistor Q8, Q10, Q12, for example of MOS type, connected at the level of a mid-point connected to the secondary winding S1, S2, S3 of the transformer of said resonant circuit.

(21) In an advantageous manner, a second inductive element (not represented) may be added in parallel with the secondary winding S1, S2, S3 of the transformer of said resonant circuit or in parallel with the primary winding P1, P2, P3 of the transformer of said resonant circuit. This second inductive element is preferably an induction coil. This second inductive element makes it possible to form, with the first inductive element L1, L2, L3 and the resonance capacitor CR1, CR2, CR3, a resonant circuit of LLC type. It will be noted that, in an alternative manner, the second inductive element may be the secondary winding S1, S2, S3 of the transformer of the resonant circuit when said secondary winding S1, S2, S3 has a magnetising inductance, or the primary winding P1, P2, P3 of the transformer of the resonant circuit when said primary winding P1, P2, P3 has a magnetising inductance. Such a magnetising inductance may be formed by an air gap in the core of the transformer.

(22) In the examples illustrated in FIGS. 2 to 6, the resonant circuits are such that the resonance branches that include the primary winding P1, P2, P3 are connected to a first so-called “neutral” point PN1 and the branches that include the secondary windings S1, S2, S3 are connected to a second so-called “neutral” point PN2. The first neutral point PN1 and the second neutral point PN2 contribute to the balancing of the currents circulating in the resonant circuits.

(23) In the example illustrated in FIG. 2, the neutral points PN1 and PN2 have a floating electric potential, which makes it possible to limit the number of components of the resonant DC-DC converter. In the examples illustrated in FIGS. 3 to 6, the first neutral point PN1 and/or the second neutral point PN2 are not floating.

(24) In an alternative, the first neutral point PN1 is connected to the first earth M1 of the DC-DC converter via a first so-called “resonance” branch B.sub.R1 including at least one impedance configured to store energy and to enable zero voltage switching of the switches of the resonant DC-DC converter. The first branch B.sub.R1 connected to the first neutral point PN1 makes it possible to operate the converter 10-2, 10-3, 10-4, 10-5 in ZVS whatever the operating point of the converter 10-2, 10-3, 10-4, 10-5, when the resonant DC-DC converter transfers energy from the primary to the secondary.

(25) In an alternative, the second neutral point PN2 is connected to the second earth M2 of the DC-DC converter via a second so-called “resonance” branch B.sub.R2 including at least one impedance configured to store energy and to enable zero voltage switching of the switches of the resonant DC-DC converter. The second branch B.sub.R2 connected to the second neutral point PN2 makes it possible to operate the converter 10-2, 10-3, 10-4, 10-5 in ZVS whatever the operating point of the converter 10-2, 10-3, 10-4, 10-5, when the resonant DC-DC converter transfers energy from the secondary to the primary.

(26) In the examples illustrated in FIGS. 3 to 6, the first neutral point PN1 is connected to the first earth M1 via an inductance LB1 and a capacitor CB1 and the second neutral point PN2 is connected to the second earth M2 also via an inductance LB2 and a capacitor CB2.

(27) In a first embodiment, illustrated in FIG. 2, and a second embodiment, illustrated in FIG. 3, each resonant circuit includes a half-bridge input structure of transistors including an upper transistor Q1, Q3, Q5 and a lower transistor Q2, Q4, Q6, for example of MOS type, connected at the level of a mid-point, said mid-point being connected to the resonance branch of said resonant circuit, in particular at a point different from the first neutral point PN1. This configuration enables the circuits to operate with three input currents, notably on three different phases. Such a configuration makes it possible to operate the converter on the six arms of the three half-bridges of the input structures of the three resonant circuits, in a three-phase manner, in order notably to reduce at one and the same time the RMS current, the size, the weight and the costs of the electromagnetic compatibility filters. In particular, the transistors Q1-Q6 periodically switch in such a way as to transmit energy through the resonant DC-DC converter 10-2.

(28) In a third embodiment illustrated in FIG. 4, only the first resonant circuit (the resonant circuit placed at the top in the figures) comprises a half-bridge input structure of transistors Q1, Q2, the mid-point of said input structure being connected to the resonance branch. The second resonant circuit (resonant circuit placed in the middle in the figures) and the third resonant circuit (resonant circuit placed at the bottom in the figures) are without half-bridge input structure of transistors, their resonance branches both being connected to the first earth M1. Such a configuration makes it possible to operate the converter 10-3 on two arms of switches in a single phase manner (voltage divider bridge). In particular, only the transistors Q1, Q2 of the first resonant circuit periodically switch in such a way as to transmit energy through the resonant DC-DC converter 10-3.

(29) In a fourth embodiment illustrated in FIG. 5, the first resonant circuit and the second resonant circuit each comprise a half-bridge input structure of transistors Q1/Q2 and Q3/Q4. The mid-point of the input structure of the first resonant circuit is connected to the resonance branch of the first resonant circuit. The mid-point of the input structure of the second resonant circuit is connected to the resonance branch of the second resonant circuit. The resonance branch of the third resonant circuit is connected to the first earth M1. Such a configuration makes it possible to operate the converter 10-3 on four arms of switches, in a two phase manner. In particular, only the transistors Q1, Q2, Q3, Q4 of the first and the second resonant circuits periodically switch in such a way as to transmit energy through the resonant DC-DC converter 10-4.

(30) In the fifth embodiment illustrated in FIG. 6, the first resonant circuit and the third resonant circuit each comprise a half-bridge input structure of transistors Q1/Q2 and Q5/Q6. The mid-point of the input structure of the first resonant circuit is connected to the resonance branch of the first resonant circuit. The mid-point of the input structure of the third resonant circuit is connected to the resonance branch of the third resonant circuit. In the second resonant circuit, the resonance branch is in open circuit. One end VP2 of the resonance branch thereby constitutes a floating potential point. Such a configuration makes it possible to operate the converter on four arms of switches, in a two-phase manner. In particular, only the transistors Q1, Q2, Q5, Q6 of the first and the third resonant circuits switch periodically in such a way as to transmit energy through the resonant DC-DC converter 10-5.

(31) The first to fifth embodiments are each advantageous over an operating range of the resonant DC-DC converter.

(32) In an alternative, the converter illustrated in FIG. 3 includes a control unit UC which is configured to control the branching of the first inductive elements L1, L2, L3 of the resonant circuits according to different configurations here corresponding to the different embodiments described in FIGS. 4 to 6 in order to switch between different operating modes. In other words, the control unit UC makes it possible to obtain the configurations illustrated in FIGS. 4 to 6 from the circuit illustrated in FIG. 3. For example, the circuit illustrated in FIG. 4 may be obtained from that illustrated in FIG. 3, by maintaining closed the lower switches Q4, Q6 of the second and third resonant circuits and by maintaining open the upper switches Q3, Q5 of the second and third resonant circuits. The switches Q1, Q2 of the first resonant circuit periodically switch in such a way as to transmit energy through the resonant DC-DC converter. Thus, a wider operating range is obtained compared to an operation in which all the half-bridge input structures of transistors periodically switch to transfer energy through the resonant DC-DC voltage converter. It is moreover possible to implement degraded modes. The converter illustrated in FIG. 2 may include a similar control unit UC making it possible to obtain the input structure configurations of FIGS. 4 to 6.

(33) In the examples illustrated in FIGS. 3 to 6, the switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8, Q9, Q10, Q11, Q12 are connected respectively in parallel with a capacitor C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12 in order to ensure ZVS operation.