Transformer Converter with Resonant Switch

Abstract

Embodiments of the present disclosure relate to a transformer converter of a resonant switch. The electronic converter includes a first electronic switch and a second electronic switch connected between a positive input terminal and an output terminal, wherein an intermediate node between the first electronic switch and the second electronic switch represents a first switching node. A third electronic switch and a fourth electronic switch are connected between a positive output terminal and a negative input terminal, wherein an intermediate node between the third electronic switch and the fourth electronic switch represents a second switching node. A first terminal of a primary winding of the transformer is connected to the second switching node, and a capacitor and an inductor are connected in series between a second terminal of the primary winding and the first switching node. A fifth electronic switch and a sixth electronic switch are connected between the positive output terminal and the negative output terminal, wherein a first terminal of the secondary winding is connected to an intermediate node between the fifth electronic switch and the sixth electronic switch.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of Italian Application No. IT102019000006719, filed on May 10, 2019, which is incorporated herein by reference. Technical Field

[0003] Embodiments of the present disclosure relate to electronic converters. Background Art

[0004] Power circuits (e.g., AC / DC or DC / DC switched-mode power supplies) are well known in the art. There are many types of electronic converters, which are mainly divided into isolated converters and non-isolated converters. For example, non-isolated electronic converters are "buck", "boost", "buck-boost", "SEPIC" and "ZETA" type converters. Conversely, isolated converters are, for example, "flyback", "forward", "half-bridge" and "full-bridge" type converters. Such types of converters are well known to those skilled in the art.

[0005] Figure 1 is a schematic diagram of a DC / DC electronic converter 20. Specifically, a general electronic converter 20 includes two input terminals 200a and 200b for receiving a DC voltage V in and two output terminals 12a and 12b for providing a DC voltage V OUT For example, the input voltage V in can be supplied by a DC current generator 10 such as a battery, or can be obtained from an AC voltage by means of a rectifier circuit such as a diode bridge and a possible filter circuit. Conversely, the output voltage V out can be used to supply a load 30.

[0006] Generally, as is well known, an electronic switching converter 20 includes one or more reactive elements (e.g., capacitors and / or inductors) and one or more electronic switches, and one or more electronic switches manage the energy transfer from the input 200a / 200b to one or more reactive elements and / or from one or more reactive elements to the output 202a / 202b.

[0007] Power distribution is evolving from various perspectives such as power density, efficiency, and solution cost.

[0008] For example, it is desirable to find such a converter solution that scales the required input voltage V in by a factor N CONV i.e., V OUT = Vin / N CONV ) The application is more efficient, while being compact and easy to use. For example, such a step-down voltage converter is widely used in the field of power management (e.g., in the context of a computer such as a server).

[0009] For example, in order to meet the increasingly stringent requirements for power density, it is necessary to reduce the size of magnetic components (inductors, such as inductors or transformers), and for this purpose, it is necessary to increase the operating frequency of the system. However, as is well known, as the operating frequency increases, the switching losses also increase linearly. Therefore, as the switching frequency of the system increases, it is necessary to minimize the switching losses by, for example, increasing the speed of switches such as FETs (field effect transistors) (e.g., MOSFETs (metal oxide semiconductor field effect transistors)). In order to meet these increasingly stringent requirements for high efficiency, switching elements have been developed that have improved performance, for example, in terms of switching speed and quality factor (the resistance Rdson of the MOSFET in the closed state multiplied by the charge Qg required until the MOSFET closes).

[0010] Therefore, the demand for switches / MOSFETs with higher switching speeds makes it possible to increase the switching frequency in order to reduce the magnetic components (inductors), and thereby increase the power density of the conversion system. However, using faster transistors requires the development of more costly technologies, which has a significant impact on the cost of the final solution of the converter.

[0011] Another way to minimize the switching losses is to operate the switch / MOSFET under ZVS (zero voltage switching) or ZCS (zero current switching) conditions, or to operate the switch with a lower voltage (e.g., to operate the MOSFET with a lower drain-source voltage V DS to operate). For example, solutions have been developed for operating the FET with a fraction of the input voltage V in . In this context, the document US 9,916,517 can be cited, for example. Summary of the Invention

[0012] In view of the foregoing, an object of various embodiments of the present specification is to provide a more efficient electronic converter.

[0013] According to one or more embodiments, the above object is achieved by an electronic converter having distinguishing elements specifically set forth in the appended claims.

[0014] The claims form part of the technical teachings provided in the description herein.

[0015] As previously mentioned, various embodiments relate to an electronic converter. In various embodiments, the electronic converter includes a positive input terminal and a negative input terminal for receiving an input voltage, and a positive output terminal and a negative output terminal for supplying an output voltage, wherein the negative output terminal is connected to the negative input terminal.

[0016] In various embodiments, a first electronic switch and a second electronic switch are connected between the positive input terminal and the positive output terminal, wherein an intermediate node between the first electronic switch and the second electronic switch represents a first switching node.

[0017] In various embodiments, a third electronic switch and a fourth electronic switch are connected between the positive output terminal and the negative input terminal, wherein an intermediate node between the third electronic switch and the fourth electronic switch represents a second switching node.

[0018] In various embodiments, the electronic converter includes a transformer, which includes a primary winding and a secondary winding. A first terminal of the primary winding is connected to the second switching node, and a capacitor and an inductor (which is implemented using the distributed inductance of an inductor and / or a transformer) are connected in series between a second terminal of the primary winding and the first switching node.

[0019] In various embodiments, a fifth electronic switch and a sixth electronic switch are connected between the positive output terminal and the negative output terminal, wherein a first terminal of the secondary winding is connected to an intermediate node between the fifth electronic switch and the sixth electronic switch.

[0020] In various embodiments, a second terminal of the secondary winding is connected to the first terminal of the primary winding.

[0021] Alternatively, the electronic converter may include a seventh electronic switch and an eighth electronic switch, which are connected between the positive output terminal and the negative output terminal, wherein a second terminal of the secondary winding is connected to an intermediate node between the seventh electronic switch and the eighth electronic switch.

[0022] In various embodiments, the electronic converter includes a control circuit configured to generate corresponding drive signals for the first electronic switch, the second electronic switch, the third electronic switch, and the fourth electronic switch in such a way that the following switching steps are repeated during a switching cycle:

[0023] - During a first switching step, closing the first electronic switch and the third electronic switch and opening the second electronic switch and the fourth electronic switch; and

[0024] - During a second switching step, opening the first electronic switch and the third electronic switch and closing the second electronic switch and the fourth electronic switch.

[0025] For example, the first electronic switch, the second electronic switch, the third electronic switch, and the fourth electronic switch can be implemented using FETs (e.g., MOSFETs).

[0026] The fifth electronic switch and the sixth electronic switch, and possibly the seventh electronic switch and the eighth electronic switch, can be implemented using an electronic switch having a control terminal such as an FET (e.g., MOSFET), or can include a diode or be obtained using a diode.

[0027] In particular, using an electronic switch having a control terminal, the control circuit can also generate corresponding drive signals for the fifth electronic switch and the sixth electronic switch in the following manner:

[0028] - During the first switching step, the fifth electronic switch is turned off and the sixth electronic switch is turned on; and

[0029] - During the second switching step, the fifth electronic switch is turned on and the sixth electronic switch is turned off.

[0030] Conversely, when the fifth electronic switch and the sixth electronic switch include corresponding diodes, these diodes can be configured in the following manner:

[0031] - During the first switching step, the diode of the fifth electronic switch is turned off and the diode of the sixth electronic switch is turned on; and

[0032] - During the second switching step, the diode of the fifth electronic switch is turned on and the diode of the sixth electronic switch is turned off.

[0033] Similarly, when the electronic converter includes a seventh electronic switch and an eighth electronic switch in the form of an electronic switch having a control terminal, the control circuit can also generate corresponding drive signals for the seventh electronic switch and the eighth electronic switch in the following manner:

[0034] - During the first switching step, the seventh electronic switch is turned on and the eighth electronic switch is turned off; and

[0035] - During the second switching step, the seventh electronic switch is turned off and the eighth electronic switch is turned on.

[0036] Conversely, when the seventh electronic switch and the eighth electronic switch include corresponding diodes, these diodes can be configured in the following manner:

[0037] - During the first switching step, the diode of the seventh electronic switch is turned on and the diode of the eighth electronic switch is turned off; and

[0038] - During the second switching step, the diode of the seventh electronic switch is turned off and the diode of the eighth electronic switch is turned on.

[0039] In various embodiments, the first switching step and the second switching step have the same duration.

[0040] In various embodiments, the capacitor and the inductor define a resonant circuit having a resonant period. In such a case, the duration of the first switching step can be between 0.7 and 1.3 times the resonant half-period, preferably between 0.9 and 1.1 times the resonant half-period, and preferably is one resonant half-period.

[0041] In various embodiments, the electronic converter includes an additional positive output terminal for supplying an additional output voltage. In such a case, the transformer can have a center-tapped secondary winding that includes a first secondary winding and a second secondary winding, where an intermediate node between the first secondary winding and the second secondary winding is connected to the additional positive output terminal.

[0042] In various embodiments, the electronic converter further includes a first switch connected between the second electronic switch and the positive output terminal, where the first switch is configured to connect the second electronic switch to:

[0043] - the positive output terminal; or

[0044] - the negative input terminal; or

[0045] - optionally, the additional positive output terminal.

[0046] In various embodiments, the electronic converter includes a second switch connected between the first terminal of the primary winding and the second switching node, where the second switch is configured to connect the first terminal of the primary winding to:

[0047] - the second switching node; or

[0048] - a reference voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Embodiments of the present disclosure will now be described with reference to the accompanying drawings, which are provided purely by way of non-limiting example, and in which:

[0050] Figure 1 an electronic converter is shown;

[0051] Figure 2 a first embodiment of an electronic converter according to the present specification is shown;

[0052] Figure 3A and Figure 3B two switching states of the Figure 2 electronic converter are shown;

[0053] Figure 4Shows Figure 2 various waveforms of the electronic converter;

[0054] Figure 5 Shows Figure 2 an example of an embodiment of the electronic converter;

[0055] Figure 6 Shows a second embodiment of the electronic converter according to the present specification;

[0056] Figure 7 Shows Figure 6 an example of an embodiment of the electronic converter; and

[0057] Figure 8 Shows a third embodiment of the electronic converter according to the present specification. Detailed Description of the Invention

[0058] In the following description, various specific details are described in order to provide a deep understanding of the embodiments. Embodiments may be obtained without one or more specific details, or by using other methods, components, materials, etc. In other cases, well-known structures, materials, or operations are not shown or described in detail so that various aspects of the embodiments are not obscured.

[0059] References to "an embodiment" or "one embodiment" in the context of this specification are intended to indicate that a particular configuration, structure, or characteristic described in relation to that embodiment is included in at least one embodiment. Thus, phrases such as "in an embodiment" or "in one embodiment" that may appear throughout this specification do not necessarily refer to the same embodiment. In addition, the particular configurations, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0060] The reference numerals used herein are provided for convenience only and thus do not limit the scope of protection or the scope of the embodiments.

[0061] In the following Figures 2 - 8 has been referred to Figure 1 the components, elements, or assemblies described are denoted by the same reference numerals as previously used in that figure; in order not to burden this detailed description, the descriptions of these elements presented previously will not be repeated.

[0062] Figure 2 Shows a first embodiment of an electronic converter 20a according to the present disclosure. Also in this case, the electronic converter 20a includes:

[0063] - two input terminals 200a and 200b configured to receive a DC input voltage V in ; and

[0064] - configured to supply a DC output voltage V out to two output terminals 202a and 202b.

[0065] In the considered embodiment, the negative output terminal 202b is connected (e.g., directly connected) to the negative input terminal 200b, and the negative input terminal 200b represents a reference voltage (e.g., ground GND).

[0066] In the considered embodiment, four electronic switches Q1, Q2, Q3, and Q4 are connected in series (e.g., directly in series) between the input terminals 200a and 200b. For example, in various embodiments, the switches Q1, Q2, Q3, and Q4 are FETs, preferably n-channel FETs, such as MOSFETs. Thus, in the considered embodiment, the first terminal of switch Q1 is connected (e.g., directly connected) to terminal 200a, and the second terminal of switch Q1 is connected (e.g., directly connected) to the first terminal of switch Q2, and the first terminal of switch Q2 thus represents the first switching node PH1. The second terminal of switch Q2 is connected (e.g., directly connected) to the first terminal of switch Q3, and the first terminal of switch Q3 thus represents the second switching node SN. The second terminal of switch Q3 is connected (e.g., directly connected) to the first terminal of switch Q4, and the first terminal of switch Q4 thus represents the third switching node PH2. Finally, the second terminal of switch Q4 is connected (e.g., directly connected) to terminal 200b.

[0067] In the considered embodiment, the node SN is connected (e.g., directly connected) to the output terminal 202a.

[0068] In the considered embodiment, the electronic converter 20a further includes:

[0069] - a capacitor C RES ;

[0070] - an inductor L RES ; and

[0071] - a transformer T, which includes a primary winding T1 and a secondary winding T2 having a given turns ratio N:1.

[0072] In particular, in the considered embodiment, the capacitor C RES , the inductor L RES and the primary winding T1 of the transformer T are connected in series (e.g., directly connected) between the node PH1 (the intermediate node between switches Q1 and Q2) and PH2 (the intermediate node between switches Q3 and Q4). For example, in the considered embodiment, the first terminal of the capacitor C RES is connected (e.g., directly connected) to the node PH1, and the capacitor C RESThe second terminal of () is connected (e.g., directly connected) to the inductor L RES to the first terminal of, and the inductor L RES The second terminal of is connected (e.g., directly connected) to the node PH2 through the primary winding T1. Generally, in the considered embodiment, the capacitor C RES and the inductor L RES The positions of can also be reversed.

[0073] For example, the capacitance of the capacitor C RES can be between 1 μF and 300 μF, and / or the inductance of the inductor L RES can be between 10 nH and 1 μH.

[0074] In the considered embodiment, the secondary winding T2 is connected to the output terminals 202a and 200b through the rectifier circuit R.

[0075] In particular, in the considered embodiment, the rectifier circuit includes four electronic switches Q5, Q6, Q7, and Q8, where:

[0076] - The switches Q5 and Q6 are connected (e.g., directly connected) between the terminals 202a and 202b, where the first terminal of the secondary winding T2 of the transformer T is connected to the midpoint between the switches Q5 and Q6; and

[0077] - The switches Q7 and Q8 are connected (e.g., directly connected) between the terminals 202a and 202b, where the second terminal of the secondary winding T2 of the transformer T is connected to the midpoint between the switches Q7 and Q8.

[0078] Therefore, the electronic switches Q5, Q6, Q7, and Q8 are configured to reverse the connection of the secondary winding T2 to the output terminals 202a and 202b.

[0079] For example, in various embodiments, the switches Q1, Q2, Q3, and Q4 are FETs, preferably n-channel FETs, such as MOSFETs. In various embodiments, the electronic switches Q5, Q6, Q7, and Q8 can also include diodes or be composed of diodes in a manner to implement a diode bridge rectifier R.

[0080] In various embodiments, an additional capacitor can also be connected between the terminals 202a and 202b to filter the output voltage V out .

[0081] In the embodiment considered, the electronic converter 20a further comprises a control circuit 210 such as an analog and / or digital circuit (e.g., a microprocessor programmed via software code), the control circuit 210 being configured to generate corresponding drive signals DRV1, …, DRV4 for switches Q1, …, Q4, and possibly corresponding drive signals DRV5, …, DRV8 for switches Q5, …, Q8.

[0082] For example, as will be described in more detail hereinafter, the control circuit 210 is configured to generate the corresponding drive signals DRV1, …, DRV4 for switches Q1, …, Q4, and possibly the corresponding drive signals DRV5, …, DRV8 for switches Q5, …, Q8, in such a way that the following two operating intervals are repeated periodically:

[0083] - During a first interval A, switches Q1, Q3, Q6 and Q7 are closed and switches Q2, Q4, Q5 and Q8 are open (see Figure 3A ); and

[0084] - During a second interval B, switches Q2, Q4, Q5 and Q8 are closed and switches Q1, Q3, Q6 and Q7 are open (see Figure 3B ).

[0085] Thus, as Figure 4 illustrated, during the first interval A having a duration T A , node PH1 is connected to terminal 200a / voltage V in , and during the second interval B having a duration T B , node PH1 is connected to terminal 202a / voltage V out . Conversely, during the first interval A having a duration T A , node PH2 is connected to terminal 202a / voltage V out , and during the second interval B having a duration T B , node PH2 is connected to terminal 202b / reference voltage (ground).

[0086] In particular, as Figure 3A illustrated, and also considering the fact that the output voltage V out is lower than the input voltage V in (V out < V in ), during step A, the current I PRI through the primary winding T1 flows from terminal 200a (voltage V in ) through switch Q1, network L RES / C RES, the primary winding T1 of the transformer T, the switch Q3, and finally go to the output terminal 202a. Conversely, the current I passing through the secondary winding T2 of the transformer T SEC (by definition, which is equal to the current of the primary winding divided by N) flows from the terminal 202b (grounded) through the switch Q6, the secondary winding T2, the switch Q7, and goes to the terminal 202a.

[0087] In particular, by appropriately sizing the components, the (positive) current I PRI will include oscillations having a resonance period T RES :

[0088]

[0089] In various embodiments, the duration T A is selected such that it substantially corresponds to the half period of the aforementioned oscillation. For example, 0.7(T RES / 2) < T A < 1.3(T RES / 2), preferably 0.9(T RES / 2) < T A < 1.1(T RES / 2).

[0090] During this step A, the capacitor C RES is thus on average charged to the voltage V CRES，A :

[0091] V CRES，A = V in -(N + 1)·V out (2)

[0092] Conversely, as Figure 3B illustrated, during step B, the current I passing through the primary winding T1 PRI flows from the terminal 200b (reference voltage, such as ground) through the switch Q4, the primary winding T1 of the transformer T, the network L RES / C RES , the switch Q2, and finally goes to the output terminal 202a. Conversely, the current I passing through the secondary winding T2 of the transformer T SEC (by definition, which is equal to the current of the primary winding divided by N) flows from the terminal 202b (grounded) through the switch Q8, the secondary winding T2, the switch Q5, and goes to the terminal 202a.

[0093] During this step B, the capacitor C RES is thus on average charged to the voltage V CRES，B :

[0094] V CRES，B = (N + 1)·V out(3)

[0095] Thus, also in this case, the (negative) current I PRI will include oscillations having a resonance period T RES . In various embodiments, the duration T B is selected such that it substantially corresponds to the half period of the aforementioned oscillations, e.g., 0.7(T RES / 2) < T B < 1.3(T RES / 2), preferably 0.9(T RES / 2) < T B < 1.1(T RES / 2).

[0096] In various embodiments, the duration T A corresponds to the duration T B , i.e., T A = T B . Thus, in various embodiments, the control circuit 210 can generate two drive signals:

[0097] - A first drive signal for driving switches Q1, Q3 (and possibly Q6 and Q7), wherein the signal has a constant frequency f, and the constant frequency f is determined according to the period TRES and a 50% duty cycle; and

[0098] - A second drive signal for driving switches Q2, Q4 (and possibly Q5 and Q8), and the second drive signal corresponds to the inverted first drive signal.

[0099] Thus, in the simplest case, the first drive signal can correspond to a clock signal supplied by an oscillator (e.g., a voltage controlled oscillator (VCO)), and the second drive signal can be obtained by supplying the first drive signal to an analog inverter.

[0100] In various embodiments, the electronic converter is thus non - adjustable and operates with a constant switching period T SW = T A + T B .

[0101] In particular, when the durations T A and T B correspond to T RES / 2, the switches Q1,..., Q4 are switched using zero - current switching (ZCS).

[0102] Generally, the switching period T SW can also include a first (short) interval T A between the intervals T B ​D1 , and an interval T B and T A a second (short) interval T between them D2 ; that is, T SW = T A + T B + T D1 + T D2 . These intervals (which are similar to interval T A and T B can be constant) can be useful for achieving the ZVS switching conditions of switches Q1,..., Q4. In particular, in this case, the duration T A should be selected in such a way that the current I PRI is positive at the end of interval A; the duration T B should be selected in such a way that the current I PRI is negative at the end of interval B. For example, in various embodiments, the durations T A and T B are slightly shorter than the resonant half-period; for example, T A (and similarly, T B ) can be between 0.7 and 0.99 times of T RES / 2.

[0103] Generally, the transformer T can be modeled as an ideal transformer, a dispersion inductance (which is usually connected in series with the primary winding T1), and a magnetization inductance (usually connected in parallel with the primary winding T1). Thus, in various embodiments, the inductor L RES can also be implemented using the dispersion inductance of the transformer T, or the inductance L RES can correspond to the sum of the inductance of an inductor (connected in series with the primary winding T1) and the dispersion inductance of the transformer T.

[0104] By the charge balance law of the capacitor C RES in steps A and B, the conversion ratio N CONV of the electronic converter can thus be written as follows:

[0105] N CONV = V in / V out = 2 N + 2 (4)

[0106] That is, the conversion ratio N CONV is mainly determined by the turns ratio N:1 of the transformer T. Specifically, as can be noted from equation (4), the conversion ratio N CONV exhibits an additional factor equal to 2; this means that the transformer T can be sized using a turns ratio reduced by 1.

[0107] For example, for an LLC electronic converter, the conversion ratio N CONV corresponds to 2N. Thus, assuming that the number of turns on the secondary is equal to 4, such an LLC converter would require 8 turns on the primary to achieve a conversion ratio N of 4:1 CONV . In contrast, with the proposed solution, the same conversion ratio N CONV can be obtained with a reduced number of turns on the primary to 4.

[0108] As previously mentioned, one or more of the switches Q1, ..., Q8 can be FETs (e.g., MOSFETs).

[0109] For example, Figure 5 shows an embodiment in which the switches Q1, ..., Q4 are n-channel FETs (e.g., MOSFETs). In this case, the drain terminal of transistor Q1 is connected to terminal 200a, the source terminal of transistor Q1 is connected to the drain terminal of transistor Q2, the source terminal of transistor Q2 is connected to the drain terminal of transistor Q3, the source terminal of transistor Q3 is connected to the drain terminal of transistor Q4, and the source terminal of transistor Q4 is connected to terminal 200b.

[0110] In the embodiment under consideration, the rectifier circuit R is also implemented using four n-channel FETs. In this case, the drain terminal of transistor Q7 is connected to terminal 202a, the source terminal of transistor Q7 is connected to the drain terminal of transistor Q8, and the source terminal of transistor Q8 is connected to terminal 202b. Similarly, the drain terminal of transistor Q5 is connected to terminal 202a, the source terminal of transistor Q5 is connected to the drain terminal of transistor Q6, and the source terminal of transistor Q6 is connected to terminal 202b.

[0111] Figure 5 It is also shown that the switches Q5, ..., Q7 can include or consist of diodes. For example, Figure 5 the body diodes of transistors Q1, ..., Q8 are also shown, and these body diodes of transistors Q5, ..., Q8 (where the cathodes of these body diodes are connected to the drain terminals and the anodes of these body diodes are connected to the source terminals) implement a diode bridge rectifier. In any case, by using transistors for these switches, the electrical losses caused by these switches can be reduced.

[0112] Figure 6 Shows a second embodiment of the electronic converter 20a. In particular, as previously described, the switches Q3 / Q4 and the switches Q7 / Q8 are both connected between terminals 202a and 202b and are driven in a synchronous manner. Thus, the switch nodes of these two half-bridges can be combined and only one half-bridge is used.

[0113] Thus, in the embodiment considered, the switches Q7 / Q8 have been removed as compared to Figure 2 that shown. Thus, the terminals of the secondary winding T2 remain connected to the midpoint between switches Q5 and Q6. Conversely, now, the second terminal of the secondary winding T2 is no longer connected to the switches Q7 / Q8, but to the midpoint between switches Q3 (which is now denoted by the reference numeral Q3_Q7) and Q4 (which is now denoted by the reference numeral Q4_Q8), i.e., node PH2.

[0114] The advantage of this structure is that the construction of the transformer T can benefit from the simplification. In fact, only three terminals are required, and in practice, the resulting structure of the transformer T is that of an auto-transformer. However, the current circulating in the switch pairs Q3_Q7 and Q4_Q8 is now equal to I PRI +I SEC , i.e., (N + 1)·I PRI , which should be taken into account during the sizing of the switches.

[0115] Figure 7 An equivalent embodiment is shown in which the switches Q1, Q2, Q3_Q7, and Q4_Q8 and possibly the switches Q5 and Q6 are n-channel FETs (e.g., MOSFETs).

[0116] The inventors have noted that the proposed structure can also be generalized to obtain different gains using the same single transformer T. In fact, this makes it possible to avoid the sizing and customization of the transformer T for each type of converter. For different conversion ratios N CONV using the same transformer T, different conversion ratios can be obtained by modifying only some of the connections of the presented topology.

[0117] In particular, as compared to Figure 6 the following modifications have been made, which can also be used individually:

[0118] - The transformer T is a center-tapped transformer, which thus includes a first secondary winding T2a and a second secondary winding T2b connected in series;

[0119] - A first switch S1 has been added, which makes it possible to set the voltage at node SN to a first reference voltage and thus to the voltage applied to node PH1 (based on the switching of switches Q1 and Q2, V in or the voltage at node SN); and

[0120] - A second switch S2 is added, which enables the node PH2 to be connected to the midpoint between switches Q3 / Q3_Q7 and Q4 / Q4_Q8, or to the second reference voltage CM.

[0121] Typically, switches S1 and / or S2 can be implemented using:

[0122] - One or more electronic switches, and / or

[0123] - A mechanical connection, for example, by providing metal slots on a printed circuit and fixing (e.g., welding) a jumper such as a 0Ω resistor between two metal slots.

[0124] Basically, a center-tapped transformer enables an output voltage V to be obtained at the midpoint of the secondary winding T2 (between windings T2a and T2b). out2 The output voltage V out2 corresponds to half of the output voltage V out , that is, V out2 = V out / 2.

[0125] In particular, again, switches Q5 and Q6 are connected between terminals 202a and 202b, where terminal 202b is connected to terminal 200b representing the reference voltage (e.g., ground GND). Also, again, switches Q3_Q7 and Q4_Q8 are connected between terminals 202a and 202b. Additionally, the secondary winding T2 (which includes windings T2a and T2b) is connected between the midpoint between switches QS / Q6 and the midpoint between switches Q3_Q7 / Q4_Q8.

[0126] In the considered embodiment, the electronic converter includes an additional output terminal 202c, and the additional output terminal 202c is connected (e.g., directly connected) to the midpoint between windings T2a and T2b. Thus, the voltage V out2 between terminals 202c and 202b corresponds to half of the voltage V out between terminals 202a and 202b.

[0127] In the considered embodiment, again, switches Q1 and Q2 are connected in series between terminal 200a and node SN. Additionally, capacitor C RES and inductor L RES are connected in series to the primary winding T1, and the primary winding T1 is between node PH1 (the midpoint between switches Q1 and Q2) and node PH2.

[0128] As previously explained, switch S1 enables the voltage at node SN to be set to the reference voltage. For example, in the considered embodiment, switch S1 is configured to connect node SN to:

[0129] - Terminal 202a (which corresponds to Figure 6 the illustrated embodiment); or

[0130] - Terminal 200b (ground); or

[0131] - Optionally, terminal 202c.

[0132] Conversely, switch S2 is configured to connect the terminal of the primary winding T1 / node PH2 to:

[0133] - The midpoint between switches Q3_Q7 and Q4_Q8 (which corresponds to Figure 6 the embodiment shown in

[0134] ), now designated by the reference numeral SEC, or

[0135] - The second reference voltage CM. out or V out2 ). Thus, in the various embodiments considered, switch S1 is configured to enable the connection of node PH2 to node 200a, 200b or 200c.

[0136] Thus, when node SN (e.g., via switch S1) is connected to terminal 202a, and node PH2 (e.g., via switch S2) is connected to the midpoint SEC between switches Q3_Q7 and Q4_Q8, converter 20a presents Figure 6 the illustrated configuration. Conversely, when node SN (e.g., via switch S1) is connected to terminal 200b, and node PH2 (e.g., via switch S2) is connected to voltage CM (e.g., connected to terminal 200b), converter 20a presents the configuration of a conventional LLC converter, where the secondary winding T2 can even be isolated from the primary winding T1.

[0137] However, other configurations with different conversion ratios N CONV can also be implemented. In particular, two conversion ratio tables V in / V out and V in / V out2 can be defined according to the connections of switches S1 and S2:

[0138]

[0139] Therefore, Figure 8The converter can use different transformation ratios (N) of the transformer to obtain the same conversion ratio. The optimal transformation ratio can be obtained based on the conversion characteristics. For example, it may be useful to minimize the total number of windings in order to reduce the resistance of the windings themselves. Other factors can be considered, such as the maximum value of the drain-source voltage V DS present on the MOSFET. In this case, the transformation ratio can be sized to have a maximum value V DS within certain preset limits.

[0140] For example, if the goal is to obtain a conversion ratio equal to 5 for the voltage V out , then if the configuration S1 = V out and S2 = SEC are adopted, the minimum transformation ratio N will be 1.5. Considering that the minimum number of turns on the secondary of the center-tapped transformer T is equal to 1 + 1, the primary winding T1 should have 3 turns. If, instead, the output V OUT2 is used to have a conversion ratio equal to 5, and again considering that the number of turns on the secondary is equal to 1 + 1, then in the case of using the configuration S1 = V out2 and S2 = CM, the minimum transformation ratio N is 1. From the perspective of the number of turns of the transformer, the second option is more interesting, but it requires the transistors Q3_Q7, Q4_Q8, Q5, and Q6 to have a BV DSS (drain-source breakdown voltage) that is twice that of the first solution.

[0141] Of course, without prejudice to the principles of the present invention, the details of the construction and embodiments can vary widely relative to what has been described and illustrated herein by way of example only, without thereby departing from the scope of the present invention as defined in the appended claims.

Claims

1. An electronic converter, comprising: A first node that is switchably coupled to a positive input terminal in a first switching state or to a first positive output terminal in a second switching state; A negative input terminal that is connected to a negative output terminal; A resonant circuit that is serially connected between the first node and a first terminal of a primary winding of a transformer; A second node that is connected to a second terminal of the primary winding and that is switchably coupled to the first positive output terminal in the first switching state or to the negative input terminal in the second switching state; A first terminal of a secondary winding of the transformer that is switchably coupled to the first positive output terminal in the first switching state or to the negative input terminal in the second switching state; And A second terminal of the secondary winding that is switchably coupled to the negative input terminal in the first switching state or to the first positive output terminal in the second switching state.

2. The electronic converter according to claim 1, wherein the resonant circuit comprises a capacitor and an inductor connected in series.

3. The electronic converter according to claim 1, further comprising a control circuit configured to switch the electronic converter between the first switching state and the second switching state.

4. The electronic converter according to claim 3, wherein the control circuit is connected to corresponding electronic switches to perform the switching.

5. The electronic converter according to claim 4, wherein the control circuit is configured to generate corresponding drive signals to control the corresponding electronic switches.

6. The electronic converter according to claim 5, wherein each of the corresponding electronic switches comprises a diode.

7. The electronic converter according to claim 3, wherein the control circuit is further configured to repeat the switching between the first switching state and the second switching state during a switching cycle.

8. The electronic converter according to claim 7, wherein the first switching state and the second switching state have the same duration during the switching cycle.

9. The electronic converter according to claim 8, wherein the resonant circuit has a resonant period, and wherein the duration is between 0.7 times and 1.3 times a half period of the resonant period.

10. The electronic converter according to claim 8, wherein the resonant circuit has a resonant period, and wherein the duration is between 0.9 times and 1.1 times a half period of the resonant period.

11. The electronic converter according to claim 8, wherein the resonant circuit has a resonant period, and wherein the duration is equal to a half period of the resonant period.

12. The electronic converter according to claim 1, further comprising: A first electronic switch disposed between the first node and the positive input terminal; A second electronic switch disposed between the first node and the first positive output terminal; A third electronic switch disposed between the second node and the positive input terminal; and A fourth electronic switch is disposed between the second node and the negative input terminal.

13. The electronic converter according to claim 12, further comprising: A fifth electronic switch disposed between the second terminal of the secondary winding and the first positive output terminal; A sixth electronic switch disposed between the second terminal of the secondary winding and the negative input terminal; A seventh electronic switch disposed between the first terminal of the secondary winding and the first positive output terminal; and An eighth electronic switch disposed between the first terminal of the secondary winding and the negative input terminal.

14. The electronic converter according to claim 13, wherein each of the corresponding electronic switches includes a diode.

15. The electronic converter according to claim 13, further comprising a control circuit connected to the electronic switches and configured to switch the electronic converter between the first switching state and the second switching state.

16. The electronic converter according to claim 15, wherein the first electronic switch, the third electronic switch, the sixth electronic switch, and the seventh electronic switch are closed in the first switching state, and the second electronic switch, the fourth electronic switch, the fifth electronic switch, and the eighth electronic switch are open in the first switching state.

17. The electronic converter according to claim 15, wherein the first electronic switch, the third electronic switch, the sixth electronic switch, and the seventh electronic switch are open in the second switching state, and the second electronic switch, the fourth electronic switch, the fifth electronic switch, and the eighth electronic switch are closed in the second switching state.

18. The electronic converter according to claim 13, wherein the secondary winding is a center-tapped secondary winding, the center-tapped secondary winding includes a first secondary winding and a second secondary winding, and wherein the electronic converter includes: A second positive output terminal; and A middle node between the first secondary winding and the second secondary winding, connected to the second positive output terminal.

19. The electronic converter according to claim 18, wherein the second electronic switch is switchably coupled to the first positive output terminal or the second positive output terminal in the first switching state.

20. The electronic converter according to claim 19, further comprising: A ninth electronic switch coupled to the second electronic switch and configured to switch between the first positive output terminal and the second positive output terminal in the first switching state.

21. The electronic converter according to claim 19, wherein the second terminal of the primary winding is switchably coupled to the second node or a reference voltage in the first switching state.

22. The electronic converter according to claim 21, further comprising: The tenth electronic switch is coupled to the second terminal of the primary winding, and the tenth electronic switch is configured to switch between the second node and the reference voltage in the first switching state.

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