WO2016059354A1

WO2016059354A1 - Isolated dc/dc converter and method of voltage conversion

Info

Publication number: WO2016059354A1
Application number: PCT/FR2015/052782
Authority: WO
Inventors: Luis De Sousa
Original assignee: Valeo Systemes De Controle Moteur
Priority date: 2014-10-16
Filing date: 2015-10-16
Publication date: 2016-04-21
Also published as: FR3027470A1; FR3027470B1; CN107005174B; CN107005174A

Abstract

The invention relates to an isolated DC/DC converter (1) comprising: - a first branch (A) comprising series-connected switches (MA1, MA2); - a second branch comprising an inductance (L) having a first terminal connected to the midpoint of the branch (A) and a second terminal connected to the input of the isolated DC/DC converter (1); - a capacitor (C1) connected across the end terminals of the first branch (A); - a third branch (C) connected to the midpoint of the first branch (A) and comprising a magnetic component with a primary circuit and a secondary circuit separated by an electrical isolation barrier, said magnetic component being configured such that, when an input voltage (Ue) of the DC/DC converter (1) is converted into an output voltage (Uout), it acts as a transformer from the primary circuit to the secondary circuit and as an impedance storing power in the primary circuit.

Description

ISOLATED DC / DC CONVERTER AND METHOD OF CONVERTING

VOLTAGE

The present invention relates to an isolated DC / DC converter, as well as a voltage conversion method implemented with the converter according to the invention.

Isolated direct current / direct current (DC / DC) converters may have zero-voltage switching or ZVS (zero-voltage switching) or zero-current or ZCS switching (for zero current switching ") that reduce switching losses during voltage conversion. These converters are therefore particularly advantageous in an automotive application where the energy resource is limited. In a vehicle, a voltage converter can be used to adapt voltage levels between several electrical networks of the vehicle or to convert a voltage between a power source and an electrical consumer embedded in the vehicle.

There is known a DC / DC converter isolated from the patent US5754413, illustrated in Figure 1. The converter comprises two switches Ql, Q2 which are connected at their midpoint to a branch which comprises two transformers in series. The converter is arranged in a half-bridge. The switches control the transmission of energy through the transformers to convert the input voltage of the converter to an output voltage. Diodes connected to the secondary of the transformers make it possible to straighten the output signal. The output voltage is obtained by controlling the duty cycle of the switches. FIG. 2 shows a graph representing the gain G of the DC / DC converter isolated from the prior art, as a function of the duty cycle a of the isolated DC / DC converter. The gain G corresponds to the ratio between the output voltage of the DC / DC converter isolated on the input voltage of the isolated DC / DC converter. By changing the duty cycle to reach an output voltage target value, the gain of the converter is adjusted to reach the output voltage target value. In particular, when the input voltage of the isolated DC / DC converter varies, it is known to vary the duty cycle of the switches of the isolated DC / DC converter to regulate its output voltage, that is to say to maintain its output voltage to a desired value.

However, the voltage stress of the rectifying diodes is a function of the duty cycle of the converter switches. This stress can become important when the duty cycle becomes close to 0% or 100%. In order to limit the voltage stress of the rectifying diodes, the respective transformation ratios, which are different, are provided for the two transformers. But this complicates the design of the converter because the transformers can not be identical and the secondary current has discontinuities.

In addition, by working with a variable duty cycle, the output current ripples can vary greatly resulting in a variation of the efficiency of the converter. To maintain good performance, the report cyclical must be slightly variable. Now, the shape of the curve illustrated in FIG. 2 is parabolic, so that to obtain a variation of the gain, the duty cycle a of the isolated DC / DC converter must be strongly varied. On the other hand, in a vehicle, the voltage of a power source, such as a battery, can vary greatly depending on the available energy. Such a variation in input of the converter involves varying the gain, and therefore the duty cycle, correspondingly, which limits the use of the DC / DC converter isolated in a vehicle.

It is therefore sought a solution to improve the performance of an isolated DC / DC converter so as to allow its use in a motor vehicle.

In order to solve this problem, the invention relates to an isolated DC / DC converter comprising:

a first arm comprising switches in series;

a second arm comprising an inductor having a first terminal connected to the midpoint of the arm and a second terminal connected to the input of the isolated DC / DC converter;

a capacitor connected between the extremal terminals of the first arm;

a third arm connected to the mid-point of the first arm comprising a magnetic component comprising a primary circuit and a secondary circuit separated by an electrical insulation barrier, said magnetic component being configured for, during the conversion of an input voltage; From the isolated DC / DC converter to an output voltage, operate as a transformer from the primary circuit to the secondary circuit and as an impedance that stores energy at the primary circuit.

The first arm, as well as the capacitance, and the inductance of the second arm contribute to the control of the energy transfer through the magnetic component. Due to its configuration, the isolated DC / DC converter according to the invention has a gain that varies linearly with its duty cycle. Thus, in the isolated DC / DC converter according to the invention, the variation of the gain with respect to the duty cycle is higher than in a converter of the prior art. Unlike the prior art, it is not necessary to vary greatly the duty cycle to vary the gain of the DC / DC converter isolated according to the invention.

In particular, the inductance of the second arm is directly connected to the input of the isolated DC / DC converter. In particular, the output voltage of the isolated DC / DC converter is taken at the terminals of the secondary circuit of the magnetic component.

In particular, opening and closing successions of the switches of the first arm make it possible to convert an input voltage into an output voltage via the magnetic component.

In particular, the magnetic component functions as a transformer of the primary circuit to the secondary circuit and as an impedance which stores energy at the primary circuit on the same period of operation of the converter. In particular, the first arm is controlled by pulse width modulation ("pulses width modulation" in English) and, over the same period of time, modulation, the magnetic component functions as a transformer from the primary circuit to the secondary circuit and as an impedance that stores energy at the primary circuit.

According to one embodiment, the first arm is configured to control the output voltage of the isolated DC / DC converter by modifying the duty ratio of the first arm. Thus, a desired voltage value at the output of the isolated DC / DC converter is obtained by adjusting the duty ratio of the first arm to reach a gain value for delivering the desired output voltage value. For example, at each desired voltage value at the output of the isolated DC / DC converter corresponds a value of the duty cycle of the first arm.

In particular, the variations of the duty cycle of the first arm allow operation of the isolated DC / DC converter for any input voltage or within an operating range. For example, the difference between a minimum value and a maximum value of the input voltage of the isolated DC / DC converter is between 150 and 500V; for example, the minimum value of the input voltage is between 150 and 200 V; and the maximum value of the input voltage is between 400 and 500V, or even between 400 and 650V.

In particular, the variations of the duty ratio of the first arm allow operation of the isolated DC / DC converter for any output voltage or within an operating range. The operating range corresponds to an output voltage Uout between a minimum value Uoutmini and a maximum value Uout _max i. For example, the target voltage Uout at the output of the isolated DC / DC converter is between 12 and 16V. For example, the minimum value Uout _m i _n i of the output voltage is between 8 and 14V and the maximum value Uout _max i of the output voltage is between 15 and 16V.

According to one embodiment, the first arm is configured so that its duty cycle has a nominal value, in particular substantially equal to 50%. By nominal value is meant a preferred operating value, the duty cycle being liable to variations around this preferred value. In particular, the nominal value is a duty cycle value at which the losses of the converter are minimal or the efficiency of the converter is maximum. In particular, when the nominal value is equal to 50%, the output current of the isolated DC / DC converter, more particularly at the output of the secondary circuit of the magnetic component, has ripples which are weak because the currents in magnetising inductances of the isolated DC / DC converter, in particular those of the magnetic component, are compensated.

According to one embodiment, the converter comprises a circuit for implementing a loop so as to slave the duty cycle of the first arm to a difference between the value of the output voltage of the isolated DC / DC converter and an output voltage setpoint. isolated DC / DC converter.

According to one embodiment, the magnetic component is configured so that: - on a first part of an operating period of the converter, a first part of the primary circuit transfers energy to a first part of the secondary circuit and a second part of the primary circuit produces an inductance storing energy;

- On a second part of the operating period, a second part of the primary circuit transfers energy to a second part of the secondary circuit, and the first part of the primary circuit produces an inductance storing energy.

In particular, the first arm is controlled by pulse width modulation; the first part of the operating period corresponds to a first part of the modulation period; and the second part of the operating period corresponds to a second part of the modulation period. These first and second parts are in particular determined by the duty ratio of the first arm.

According to a variant, the primary circuit of the magnetic component comprises a primary winding and the secondary circuit of the magnetic component comprises at least a first secondary winding and at least a second secondary winding not magnetically coupled to each other, said first and second secondary windings being magnetically coupled. to the primary winding. It should be understood that the secondary circuit comprises at least one primary winding, at least a first primary winding and at least a second secondary winding. In particular, the primary circuit of the magnetic component comprises a single primary winding. In particular, the primary winding is connected to the midpoint of the first arm.

In particular, the output voltage of the isolated DC / DC converter is taken at the terminals of the first secondary windings and / or the secondary windings or second windings.

According to a particular variant, the magnetic component is configured to act on the one hand as a transformer from the primary winding to the secondary windings, in particular from a portion of the primary winding to the secondary windings; and on the other hand as an impedance which stores energy at the primary winding, in particular at another part of the primary winding.

In particular, the magnetic component is configured to act as a transformer from the primary winding, in particular from a part of the primary winding, either to the first secondary winding or to the second secondary winding or windings; while operating as an impedance that stores energy at the primary winding, especially at another part of the primary winding.

According to a particular variant, the secondary winding to which the magnetic component acts as a transformer depends on the voltage supplied at the primary winding. In other words, depending on the voltage supplied at the primary winding, the magnetic component operates as a transformer to either the first or the second secondary windings, or to the second or second secondary windings. According to one variant, the magnetic component comprises at least a first and a second transformer in series.

According to a particular variant:

the primary of the first transformer forms the first part of the primary circuit and the secondary of the first transformer forms the first part of the secondary circuit;

the primary of the second transformer forms the second part of the primary circuit and the secondary of the second transformer forms the second part of the secondary circuit.

In particular, the primary of the transformers are in series and connected to the midpoint of the first arm. In particular, the output voltage of the isolated DC / DC converter is taken across the secondary or secondary of the first transformer and / or the second transformer.

According to one embodiment, the first arm and the third arm comprising the magnetic component form a half-bridge structure. In particular, the third arm comprising the magnetic component is connected on the one hand to the midpoint of the second arm and on the other hand to a ground of the isolated DC / DC converter.

Alternatively, the first arm and the third arm comprising the magnetic component form a full bridge structure with other switches. In particular, the third arm comprising the magnetic component is connected firstly to the midpoint of the first arm and secondly to the midpoint of a fourth arm comprising switches in series.

According to one embodiment, at least one of the switches comprises a capacitor in parallel, in particular the switches of the first and / or fourth arm.

The invention also relates to a voltage conversion method comprising the steps of:

provide at least one isolated DC / DC converter according to the invention;

converting an input voltage of the isolated DC / DC converter into an output voltage.

In particular, the conversion of an input voltage into an output voltage comprises successions of opening and closing of the switches of the first arm which make it possible to convert an input voltage into an output voltage via the magnetic component.

According to one embodiment, the duty ratio of the first arm has a nominal value, in particular substantially equal to 50%.

The method according to the invention may comprise one of the characteristics described above in relation to the isolated DC / DC converter according to the invention.

The invention will be better understood with reference to the drawings, in which:

FIG. 1, already described, illustrates an example of an isolated DC / DC converter according to the prior art;

FIG. 2, already described, shows a graph representing the gain as a function of the duty cycle for the converter of FIG. 1; FIG. 3 illustrates an example of an isolated DC / DC converter according to the invention;

FIGS. 4 and 5 comprise equivalent diagrams of the converter of FIG. 3 on different parts of an operating period;

FIG. 6 includes timing diagrams illustrating an operation of the converter of FIG. 3;

FIG. 7 shows a graph representing the gain as a function of the duty cycle for the converter of FIG. 3;

FIG. 8 illustrates a variant of the converter of FIG. 3;

FIG. 9 illustrates a variant of the magnetic component of the converter of FIG. 3;

FIGS. 10a to 10e illustrate exemplary embodiments of the magnetic component illustrated in FIG. 9.

The converter according to the invention will be better understood with reference to FIG. 3 which presents an example of an isolated DC / DC converter according to the invention.

The isolated DC / DC converter 1 comprises a first arm A of switches in series. The arm A comprises MAI switches, MA2, a succession of openings and closures to control the output of the isolated DC / DC converter 1. The switch MA2, said switch low side, is connected to the lower terminal of the voltage source. This lower terminal corresponds in particular to a first mass GND1 of the isolated DC / DC converter 1. The other switch MAY, said switch side up, is connected to a terminal of a capacitor C1.

These switches may be transistors, such as MOSFET, IGBT or other transistors. A part, in particular the switches of the first arm A, or the whole of the isolated DC / DC converter 1 can be made from a semiconductor material such as silicon (Si), gallium nitride (GaN), carbide of silicon (SiC), or any other semiconductor material. Each switch MA1, MA2 may comprise a transistor in parallel with a freewheeling diode and / or a capacitance CA1, CA2. These CA1, CA2 capabilities are used to make a zero voltage switching or ZVS (for "Zero Voltage Switching" in English) when opening switches MAI, MA2. At the opening of a switch MAI, MA2 is used an inductance, including a leakage inductance of a magnetic component described by lasuite, to discharge and recharge the capacitance CA1, CA2 which is across the switch. Once the voltage is close to 0V, the switch is commanded, and thus a commutation under zero voltage is performed, which greatly reduces the switching losses. These capacitances CA1, CA2 may be intrinsically present in the semiconductor structure of the switches MA1, MA2, as parasitic elements. The parasitic capacitances of the switches MAI, MA2 may therefore be sufficient to perform the switching to zero voltage without adding additional capacity. The switches MAI, MA2 could dispense with these capabilities CA1, CA2.

A capacitor C1 is connected between the extremal terminals of the first arm A. In particular, the capacitor C1 is connected to the high side switch MAI of the first arm A and to the low side switch MA2 of the first arm A, to a respective terminal. who is different from the midpoint of the first arm A. The capacitance C1 makes it possible to create an internal DC bus to the isolated DC / DC converter 1.

The isolated DC / DC converter 1 comprises a second arm B which comprises an inductor L. The inductor L has a first terminal connected to the midpoint of the two switches MAI, MA2 of the first arm A, and a second terminal connected to the input isolated DC / DC converter 1.

The midpoint between the two switches MA1, MA2 of the first arm A is connected to a third arm C which comprises a magnetic component comprising two isolation transformers T1, T2 in series. Each transformer T1, T2 comprises a primary LU, L21 and a secondary L12, L22. The primary LU, L21 and secondary L12, L22 are respectively in series. Transformers T1, T2 have the same transformation ratio. However, transformers T1, T2 could have different transformation ratios. A capacitor C33 is in series with transformers T1, T2. However the isolated DC / DC converter 1 could do without this capacity C33. The capacitor C33 makes it possible to eliminate the DC component of the signal transmitted by the transformers T1, T2, in particular in the case of a half-bridge structure. The C33 capability can be removed in a full bridge structure. The secondary L12, L22 are in series, with their midpoint connected to the output Uout of the isolated DC / DC converter 1 and their other terminal connected to a second ground GND2 of the isolated DC / DC converter 1.

D31, D32 diodes are connected to the secondary L12, L22 to rectify the signal from the transformers T1, T2. For this purpose, each diode D31, D32 has its respective cathode connected to a secondary terminal L12, L22 different from the midpoint. The high output is taken at the middle point of the secondary L12, L22. The midpoint of the secondary L12, L22 is not connected to the second mass GND2.

A common terminal to the two diodes D31, D32 is connected to the second ground GND2.

In a variant, a diode D31 has its anode connected to a terminal of a secondary L12 and the other diode D32 has its anode connected to a terminal of the other secondary L22, these terminals being different from the midpoint of the two secondary L12s. ,

L22. The midpoint of the secondary L12, L22 is connected to the second mass GND2. The output of the isolated DC / DC converter 1 is taken between the diode terminal D31, D32 which is not connected to the secondary L12, L22 and which is common to the two diodes D31, D32 and the second ground GND2. The high output is therefore taken at the common terminal of the diodes D31, D32.

The diodes D31, D32 could advantageously be replaced by switches, in particular transistors, such as MOSFET, IGBT or other transistors, in order to obtain, for example, a synchronous rectification at the output of the transformers T1, T2. For high-current secondary applications, the use of transistors in place of the diodes makes it possible to improve the overall efficiency of the isolated DC / DC converter 1.

The isolated DC / DC converter 1 may include a capacitance (not shown) for filtering the output signal. The switches MA1, MA2 of the first arm A have a duty cycle which makes it possible to transfer energy through the transformers T1, T2. The operation of the isolated DC / DC converter 1 will be described with reference to FIGS. 4 to 6. The switches MA1, MA2 are controlled by a pulse width modulation with a modulation period T. The durations of first and second operating parts are defined by the duty cycle at switches MA1, MA2.

On a first operating part, that is to say on a first part of the modulation period T, illustrated in FIG. 4, the high side switch MAI is open and the bottom side switch MA2 is closed. The primary L21 of the second transformer T2 realizes an inductance storing energy, and the primary LU of the first transformer T1 transfers energy to the secondary L12 of the first transformer T1. The timing diagram illustrated in FIG. 6 represents the electrical signals of the converter on the first operating period of a duration T. The input current has an increasing speed which is determined by the inductance L of the second arm B. In the third C arm, the voltage across the capacitor C33 is equal to the voltage across the primary L1, L21 series. The voltage across the capacitor C33 being negative, the diode D31 connected to the secondary L12 of the first transformer T1 is conducting while the diode D32 connected to the secondary L22 of the second transformer T2 is blocked. Only the first transformer T1 can therefore transfer energy to the secondary circuit. The primary L21 of the second transformer T2 functions as an inductor thanks in particular to a magnetising inductance linked to the primary L21 of the second transformer T2, and controls the growth of the output current Iout.

On a second operating part, that is to say on a second part of the modulation period T, illustrated in FIG. 5, the high-side switch MAI is closed and the low-side switch MA2 is open. The primary LU of the first transformer Tl realizes an inductor storing energy and the primary L21 of the second transformer T2 transfers energy to the secondary L22 of the second transformer T2. The timing diagram illustrated in FIG. 6 represents the electrical signals of the converter on the second part of the modulation period of a duration (la) T. The input current has a decreasing rate which is determined by the inductance L of the second arm. The voltage across the inductance L is equal to the difference between the voltage across the capacitor C1 and the input voltage Ue. In the third arm C, the voltage across the capacitor C33 is equal to the voltage across the primary LU, L21 in series. The voltage across the capacitor C33 being positive, the diode D31 connected to the secondary L12 of the first transformer T1 is blocked while the diode D32 connected to the secondary L22 of the second transformer T2 is conducting. Only the second transformer T2 can therefore transfer energy to the secondary circuit. The primary LU of the first transformer T1 operates as an inductor thanks in particular to a magnetizing inductance linked to the primary LU of the first transformer T1, and controls the decrease of the output current Iout. Over a modulating period T, in average value, the voltage UC1 across the capacitors C1 is a function of the input voltage Ue of the isolated DC / DC converter 1 and the duty cycle a, and is given by the relation

Ue

Over a modulation period T, the sum of the voltages across the primary LU, L21 of the transformers T1, T2 is equal to zero. This implies the following relation:

N x Uout = (1 - a) a x UC1

Where N is the ratio between the transformation ratios of the transformers T1, T2 of the magnetic component. The relationship between the output voltage Uout and the input voltage Ue of the isolated DC / DC converter 1 is therefore given by the relation

Ue

Uout = a-

NOT

The isolated DC / DC converter 1 therefore has a gain G = Uout / Ue which varies linearly with its duty cycle a as illustrated in FIG. 7. Thus, in the isolated DC / DC converter according to the invention, the variation of the gain relative to the duty cycle is higher than in the converter of the prior art. Unlike the prior art, it is not necessary to vary the duty cycle to vary the gain of the isolated DC / DC converter 1.

In a variant, the switches MA1, MA2 of the first arm A operate with a duty cycle which has a nominal value. This duty cycle value is preferred during operation of the isolated DC / DC converter and corresponds to a given input voltage Ue and output Uout. However, the duty cycle remains variable to allow operation of the isolated DC / DC converter at different input and / or output voltage values.

In particular, when the input voltage Ue of the isolated DC / DC converter 1 varies, the first arm A ensures that the output voltage Uout retains a desired value. Thus, if the input voltage Ue of the isolated DC / DC converter 1 changes value, the duty cycle a is correspondingly modified to maintain the output voltage Uout at a desired value. This is particularly advantageous in an electric vehicle where the charge level of a battery can vary over time.

In particular, the nominal duty cycle value is substantially equal to 50%. The voltage stresses across the diodes D31, D32 are a function of the duty cycle a of the first arm A, and are given by the following expressions:

U (D31) = Uout / (l - a) and U (D32) = Uout / a

When the duty cycle a is substantially equal to 50%, the voltage stresses across two diodes D31, D32 are equal; the wear is the same between the diodes D31, D32. In addition, at a duty cycle of 50%, the current ripples due to the magnetising inductances of the transformers T1, T2 are compensated for each other. Thus, the secondary current L12, L22 is continuous. The isolated DC / DC converter 1 of FIG. 3 may comprise a control unit 5 of the first arm A, as illustrated for example in FIG. 8. The control unit 5 delivers a pulse width modulation signal S2 which controls the opening and closing of the switches MAI, MA2 of the first arm A to control the output voltage Uout of the isolated DC / DC converter 1. The switches MAI, MA2 of the first arm A are controlled in order to obtain a desired voltage value at the output of the isolated DC / DC converter 1.

More particularly, the control unit 5 carries out a first control loop of the duty cycle a of the first arm A at a difference between the value Uout mes of the output voltage of the isolated DC / DC converter 1 and a voltage

Uout desired at the output of the DC / DC isolated converter 1. For this purpose, the control unit 5 receives the voltage Uout mes measured at the output of the isolated DC / DC converter 1, possibly multiplied by a gain K1. The control unit 5 then compares a voltage setpoint U * with the voltage Uout mes measured. The voltage setpoint U * corresponds to the desired voltage Uout at the output of the converter

Isolated DC / DC 1. Depending on the result of the comparison, a controller 51 delivers to the first arm A a signal S2 determining the duty cycle a.

In the example illustrated in FIG. 3, the magnetic component of the isolated DC / DC converter 1 comprises a first T1 and a second T2 series transformers. The magnetic component may be replaced by a magnetic component illustrated in Figure 9. The magnetic component 31 comprises a primary circuit with a single primary winding 33 connected to the capacitor C33 and a secondary circuit with two secondary windings 35a and 35b. The two secondary windings 35a and 35b are magnetically coupled to the primary winding 33 but are not magnetically coupled to each other. Such a magnetic component 31 not only reduces the cost of the converter by reducing the number of components comprising ferrite, but also reduce the size of the converter to obtain a more compact converter.

The operation of the isolated DC / DC converter 1 remains the same. Magnetic component 31 operates in a manner similar to two perfect series transformers. On the first part of the modulation period, a first portion of the primary winding 33 transfers energy to the first secondary winding 35a and a second portion of the primary winding 33 provides an inductance. On the second part of the modulation period, the first part of the primary winding 33 produces an inductance and the second part of the primary winding 33 transfers the energy to the second secondary 35b.

Various configurations making it possible to obtain a magnetic component 31 enabling magnetic coupling between the primary winding 33 and the secondary windings 35a and 35b without there being any magnetic coupling between the secondary windings 35a and 35b are illustrated in FIGS. at 10c.

Figures 10d, 10e illustrate examples of magnetic component 31 which comprise at least two first secondary windings 35a in parallel and at least two second secondary windings 35b in parallel. These configurations are advantageous in applications where the current flowing in the isolated DC / DC converter 1 is high, for example greater than 100A, or even greater than 200A. The isolated DC / DC converter 1 then comprises a plurality of diodes D31, each connected to a respective first secondary winding 35a; and a plurality of diodes D32, each connected to a respective second secondary winding 35b. As in the example illustrated in FIG. 3, the diodes D31, D32 could be replaced by switches.

The components 31 illustrated in Figures 10a to 10e are described further in the French patent application 1458573 whose contents are incorporated in the present application.

The invention is not limited to the examples described. In particular, in the example illustrated in FIG. 3, the first arm A and the primary of the transformers T1, T2 form a half-bridge structure. However, the first arm A and the primary of the transformers T1, T2 could form a full bridge structure with a fourth switch arm in series. The switches of the fourth arm are preferably identical to those of the first arm A.

The isolated DC / DC converter can also be used in an AC-DC converter configured to convert an AC voltage into a DC voltage or vice versa, or into an AC-AC converter. Advantageously, the isolated DC / DC converter is then completed by an AC-DC converter upstream of the first arm and / or a DC-AC converter downstream of the isolated DC / DC converter.

Claims

An isolated DC / DC converter (1) comprising:

- a first arm (A) comprising switches (MAI, MA2) in series,; a second arm (B) comprising an inductor (L) having a first terminal connected to the midpoint of the arm (A) and a second terminal connected to the input of the isolated DC / DC converter (1);

a capacitance (C1) connected between the extremal terminals of the first arm (A);

a third arm (C) connected to the midpoint of the first arm (A) comprising a magnetic component comprising a primary circuit and a secondary circuit separated by an electrical insulation barrier, said magnetic component being configured for, during the conversion of an input voltage (Ue) of the isolated DC / DC converter (1) to an output voltage (Uout), operate as a transformer from the primary circuit to the secondary circuit and as an impedance which stores energy at the of the primary circuit.

2. Converter (1) according to claim 1, wherein the first arm (A) is configured to control the output voltage (Uout) of the isolated DC / DC converter (1) by changing the duty ratio of the first arm (A) .

3. Converter (1) according to claim 1 or 2, wherein the first arm (A) is configured so that its duty cycle (a) has a nominal value, in particular substantially equal to 50%.

4. Converter (1) according to one of the preceding claims, comprising a circuit (5) for implementing a loop so as to slave the duty cycle (a) of the first arm (A) to a difference between the value (Uout mes ) the output voltage of the isolated DC / DC converter (1) and an output voltage setpoint (U *) of the isolated DC / DC converter (1).

5. Converter (1) according to one of the preceding claims, wherein the magnetic component is configured so that:

during a first part of a period of operation of the converter, a first portion (LU) of the primary circuit transfers energy to a first portion (L12) of the secondary circuit and a second portion (L21) of the primary circuit produces a storage inductance; Energy ;

on a second part of the operating period, a second part (L21) of the primary circuit transfers energy to a second part (L12) of the secondary circuit, and the first part (LU) of the primary circuit produces an inductance which stores the 'energy.

Converter (1) according to one of the preceding claims, wherein the primary circuit of the magnetic component (31) comprises a primary winding (33) and the secondary circuit of the magnetic component (31) comprises at least a first secondary winding ( 35a) and at least one second secondary winding (35b) not magnetically coupled to each other, said first (35a) and second (35b) secondary windings being magnetically coupled to the primary winding (33).

7. Converter (1) according to the preceding claim, wherein the magnetic component (31) is configured to act as a transformer from the primary winding (33), either to the first or the first secondary windings (35a), or to the or the second secondary windings (35b) while operating as an impedance which stores energy at the primary winding (33).

8. Converter (1) according to one of claims 1 to 5, wherein the magnetic component comprises at least a first (T1) and a second (T2) transformers in series.

Converter (1) according to claim 5 and the preceding claim, wherein:

the primary (LU) of the first transformer (T1) forms the first part of the primary circuit and the secondary (L12) of the first transformer (T1) forms the first part of the secondary circuit;

- The primary (L21) of the second transformer (T2) forms the second part of the primary circuit and the secondary (L22) of the second transformer (T2) forms the second part of the secondary circuit.

A voltage conversion method comprising the steps of: - providing at least one isolated DC / DC converter (1) according to any one of claims 1 to 9;

converting an input voltage (Ue) of the isolated DC / DC converter (1) into an output voltage (Uout).

11. The method of claim 10, wherein the duty cycle (a) of the first arm (A) has a nominal value, in particular substantially equal to 50%.