CN116260344B

CN116260344B - Multiphase resonant circuit and power supply device

Info

Publication number: CN116260344B
Application number: CN202310542703.6A
Authority: CN
Inventors: 石伟; 刘中伟; 肖正虎; 史耀华
Original assignee: Xi'an Topology Electric Power Technology Co ltd
Current assignee: Xi'an Topology Electric Power Technology Co ltd
Priority date: 2023-05-15
Filing date: 2023-05-15
Publication date: 2024-03-08
Anticipated expiration: 2043-05-15
Also published as: CN116260344A

Abstract

The embodiment of the disclosure relates to a multiphase resonant circuit and a power supply device. The multiphase resonant circuit comprises at least two transformers and half-bridge circuits corresponding to each transformer one by one; each half-bridge circuit comprises a resonant inductor, an excitation inductor, a resonant capacitor, a first switch element and a second switch element, wherein the resonant inductor, the excitation inductor and the resonant capacitor are sequentially connected in series, the resonant inductor is respectively connected with the first switch element and the second switch element, the first common end is used for being connected with the positive end of a direct current source, and the second common end is used for being connected with the negative end of the direct current source; the third common terminal is connected with the first common terminal or the second common terminal; the two ends of the exciting inductance of each half-bridge circuit are connected in parallel with the two ends of the primary winding of the corresponding transformer, and the second ends of the secondary windings of the transformers are connected with each other. The present disclosure solves the problem of resonant capacitor voltage unipolar and distortion by coupling a plurality of half-bridge circuits to corresponding transformers to form a multiphase resonant circuit.

Description

Multiphase resonant circuit and power supply device

Technical Field

The embodiment of the disclosure relates to the technical field of circuit devices for power supply or distribution, in particular to a multiphase resonant circuit and a power supply device.

Background

The resonant circuit is often referred to as an LLC circuit or LLC resonant circuit. LLC circuit: resonant converter circuits consisting of resonant inductance L, resonant capacitance C, and excitation inductance L are referred to in the industry as LLC circuits. The function is to convert the input DC voltage into high frequency AC voltage for use by the electronic device. The working process of the filter is that a high-frequency oscillation signal is generated through resonance between an inductor and a capacitor, and finally the cleanliness and the stability of an output signal are ensured through the filter and the regulator. The circuit has the characteristics of high efficiency, stability and self-regulation, so that the circuit is widely applied to the fields of communication, control, power and the like.

Typical LLC circuits are half-bridge LLC resonant circuits, full-bridge LLC resonant circuits, and three-phase LLC resonant circuits. The half-bridge LLC resonant circuit is widely applied to a low-power switching power supply because of simple circuit and few devices. The full-bridge LLC resonant circuit is usually used in occasions with slightly higher power, and because the LLC resonant circuit is sensitive to resonance parameters, the LLC resonant circuit is difficult to flow uniformly due to the fact that the LLC resonant circuit is connected in parallel, the full-bridge LLC resonant circuit is quite suitable, loss can be shared due to the fact that switching devices are added, and only one resonant cavity is arranged, and therefore the adoption of the full-bridge LLC resonant circuit can avoid the fact that two half-bridge LLC circuits are connected in parallel. The three-phase LLC resonant circuit is suitable for being applied to occasions with higher power, and has the outstanding characteristics of realizing the internal current sharing of the three-phase resonant tank and reducing current ripples of input and output sides. Depending on the application, a suitable LLC circuit is typically selected.

The half-bridge LLC circuit is formed by sequentially connecting a direct-current power supply, a group of bridge arm chopper switches on the primary side, a resonant tank circuit formed by connecting a resonant inductor and a resonant capacitor in series, and a transformer with an excitation inductor and a rectifying circuit in series. The half-bridge LLC is alternately conducted through a group of bridge arm chopper switches on the primary side, when the upper tube is turned on, the direct current power supply voltage Vs is applied to two ends of the resonant tank, the lower tube is turned on, 0V voltage is applied to two ends of the resonant tank, so that the voltage input into the resonant tank is Vs-0V-Vs-0V, the voltage actually entering the transformer is finally alternating current voltage due to the fact that the resonant capacitor has a blocking effect, the resonant capacitor bears 0.5 times of direct current bias voltage, and therefore the voltage waveform on the final resonant capacitor is 0.5 times of Vs direct current bias voltage superposition alternating current ripple voltage. The voltage across the resonant capacitor as a whole is a unipolar voltage, i.e. a dc voltage.

The full-bridge LLC resonant circuit is also called a two-phase full-bridge LLC resonant circuit, and is formed by sequentially connecting a direct-current power supply, two groups of bridge arm chopping switches on the primary side, a resonant tank circuit formed by connecting a resonant inductor and a resonant capacitor in series, and a transformer with an excitation inductor and a rectifying circuit in series. Wherein the midpoints of the first set of bridge arms and the second set of bridge arms are respectively connected to two input ends of the resonant tank circuit. The two groups of bridge arms are conducted in a complementary mode, the upper tube of the first group of bridge arms and the lower tube of the second group of bridge arms are conducted and turned off simultaneously, the upper tube of the first group of bridge arms and the upper tube of the second group of bridge arms are conducted simultaneously, the positive power voltage Vs is applied to the input end of the resonant tank circuit, the lower tube of the first group of bridge arms and the upper tube of the second group of bridge arms are conducted simultaneously, the reverse polarity of the power voltage Vs is applied to the input end of the resonant tank circuit, therefore, the voltage input into the resonant tank is (+ Vs) - (-Vs) - (+Vs) - (-Vs), the alternating voltage is an alternating voltage, only alternating current flows through the resonant capacitor, and the voltage at the two ends of the resonant capacitor is only the alternating voltage due to the fact that no direct current bias voltage exists.

The primary side of the three-phase LLC resonant circuit is provided with three groups of bridge arm chopping switches, each group of chopping bridge arm switches are staggered by 120 degrees in sequence, and the voltage input into the three-phase resonant tank is also alternating voltage with 120 degrees in phase difference. Because of three-phase symmetry, the analysis equivalent circuit has only two conditions, the first condition is that any two upper tubes of the three-phase bridge arm are conducted, the other lower tube is conducted, and according to the symmetry of the circuit, the midpoint voltage is Vs/3; the second condition is that any two phases of the three-phase bridge arm are conducted by the lower pipe, the other phase of the three-phase bridge arm is conducted by the upper pipe, the midpoint voltage is 2Vs/3 according to the symmetry of the circuit, therefore, the bias voltage of the midpoint is (+ Vs/3) - (+2 Vs/3) - (+Vs/3) - (+2 Vs/3), and the jump frequency of the bias voltage is 3 times of the working frequency. The resonant capacitor generates AC ripple voltage by flowing AC current, and then adds bias voltage of 3 times of working frequency. The voltage waveform across the resonant capacitor is more complex.

The resonant capacitor voltage of the half-bridge LLC circuit is unipolar voltage (direct current voltage), and the unipolar voltage can bring a plurality of benefits, for example, the voltage on the capacitor can be directly collected through the voltage dividing circuit to obtain the current of the resonant cavity, and the diodes can be connected in parallel at two ends of the capacitor to perform short-circuit protection and the like. The half-bridge LLC circuit is widely applied, and a circuit utilizing the unipolar voltage of the resonant capacitor is mature, but the full-bridge LLC resonant circuit and the three-phase LLC resonant circuit cannot simply use a plurality of method structures of the half-bridge LLC circuit because the voltage on the resonant capacitor is bipolar (alternating current voltage) or the waveform of the resonant capacitor voltage is complex.

Regarding the above technical solution, the inventors found that at least some of the following technical problems exist: for example, the resonant capacitors in the traditional full-bridge LLC circuit and the three-phase LLC circuit have no stable direct-current bias voltage, the resonant capacitor voltage of the full-bridge LLC circuit is completely alternating-current voltage, the voltage waveform of the resonant point capacitor in the three-phase LLC circuit is a square wave of alternating-current ripple superimposed with 6 times of frequency switching frequency, the waveform is complex, the voltage and current collection and short-circuit protection of the resonant capacitor cannot be simply utilized, and the resonant capacitor and the power ground are not grounded together.

Accordingly, there is a need to improve one or more problems in the related art as described above.

It should be noted that the information disclosed in the above background section is only for enhancing understanding of the background of the present disclosure and thus may include information that does not constitute prior art known to those of ordinary skill in the art.

Disclosure of Invention

An object of the embodiments of the present disclosure is to provide a multiphase resonant circuit and a power supply device, so as to at least solve the problems of single polarity and distortion of resonant capacitor voltage.

The invention adopts the following technical scheme:

in a first aspect, the present invention provides a multiphase resonant circuit comprising:

At least two transformers;

each half-bridge circuit comprises a resonant inductor, an excitation inductor, a resonant capacitor, a first switching element and a second switching element, wherein the second end of the resonant inductor is connected with the first end of the excitation inductor in series, the second end of the excitation inductor is connected with the first end of the resonant capacitor in series, the first end of the resonant inductor is respectively connected with the second end of the first switching element and the first end of the second switching element, the first end of the first switching element is connected with a first common end, the second end of the second switching element is connected with a second common end, and the second end of the resonant capacitor is connected with a third common end;

the first common end is used for being connected with the positive end of the direct current source, and the second common end is used for being connected with the negative end of the direct current source; the third common terminal is connected with the first common terminal or the second common terminal; the two ends of the excitation inductor of each half-bridge circuit are connected in parallel with the two ends of the primary winding of the corresponding transformer;

each secondary circuit comprises a third switching element and a fourth switching element, the first ends of secondary windings of the transformers are respectively connected with the second ends of the third switching elements and the first ends of the fourth switching elements, and the first ends of the third switching elements and the second ends of the fourth switching elements are respectively connected with two ends of the direct current elements; the second ends of the secondary windings of the transformer are connected to each other.

Optionally, the method comprises: a first transformer, a second transformer, a first half-bridge circuit corresponding to the first transformer, and a second half-bridge circuit corresponding to the second transformer;

the two ends of the excitation inductor of the first half-bridge circuit are connected in parallel with the two ends of the primary winding of the first transformer, the two ends of the excitation inductor of the second half-bridge circuit are connected in parallel with the two ends of the primary winding of the second transformer, the first end of the first switching element of the first half-bridge circuit and the first end of the first switching element of the second half-bridge circuit jointly form the first common end, the second end of the second switching element of the first half-bridge circuit and the second end of the second switching element of the second half-bridge circuit jointly form the second common end, and the second end of the resonant capacitor of the first half-bridge circuit and the second end of the resonant capacitor of the second half-bridge circuit jointly form the third common end; and the third common terminal is connected to the second common terminal.

The two ends of the excitation inductor of the first half-bridge circuit are connected in parallel with the two ends of the primary winding of the first transformer, the two ends of the excitation inductor of the second half-bridge circuit are connected in parallel with the two ends of the primary winding of the second transformer, the first end of the first switching element of the first half-bridge circuit and the first end of the first switching element of the second half-bridge circuit jointly form the first common end, the second end of the second switching element of the first half-bridge circuit and the second end of the second switching element of the second half-bridge circuit jointly form the second common end, and the second end of the resonant capacitor of the first half-bridge circuit and the second end of the resonant capacitor of the second half-bridge circuit jointly form the third common end; and the third common terminal is connected to the first common terminal.

Optionally, the method comprises: the transformer comprises a first transformer, a second transformer, a third transformer, a first half-bridge circuit corresponding to the first transformer, a second half-bridge circuit corresponding to the second transformer and a third half-bridge circuit corresponding to the third transformer;

the two ends of the excitation inductance of the first half-bridge circuit are connected in parallel with the two ends of the primary winding of the first transformer, the two ends of the excitation inductance of the second half-bridge circuit are connected in parallel with the two ends of the primary winding of the second transformer, the two ends of the excitation inductance of the third half-bridge circuit are connected in parallel with the two ends of the primary winding of the third transformer, the first end of the first switching element of the first half-bridge circuit, the first end of the first switching element of the second half-bridge circuit and the first end of the first switching element of the third half-bridge circuit form the first common end together, the second end of the second switching element of the first half-bridge circuit, the second end of the second switching element of the second half-bridge circuit and the second end of the second switching element of the third half-bridge circuit form the second common end together, and the second end of the resonance capacitor of the first half-bridge circuit and the third end of the resonance capacitor of the second half-bridge circuit form the common end together; and the third common terminal is connected to the second common terminal.

the two ends of the excitation inductance of the first half-bridge circuit are connected in parallel with the two ends of the primary winding of the first transformer, the two ends of the excitation inductance of the second half-bridge circuit are connected in parallel with the two ends of the primary winding of the second transformer, the two ends of the excitation inductance of the third half-bridge circuit are connected in parallel with the two ends of the primary winding of the third transformer, the first end of the first switching element of the first half-bridge circuit, the first end of the first switching element of the second half-bridge circuit and the first end of the first switching element of the third half-bridge circuit form the first common end together, the second end of the second switching element of the first half-bridge circuit, the second end of the second switching element of the second half-bridge circuit and the second end of the second switching element of the third half-bridge circuit form the second common end together, and the second end of the resonance capacitor of the first half-bridge circuit and the third end of the resonance capacitor of the second half-bridge circuit form the common end together; and the third common terminal is connected to the first common terminal.

Optionally, the first switching element and the second switching element each employ any one of the following: a diode, MOSFET or IGBT;

the third switching element and the fourth switching element each employ any one of: a diode, MOSFET or IGBT.

Optionally, the dc component employs a capacitor or a dc source.

Alternatively, all the first switching elements and all the second switching elements switch the switching states at the same frequency, and the switching states of the first switching elements and the second switching elements are always opposite.

Optionally, the number of the transformers is N, the working phases of the N half-bridge circuits are sequentially different by 360/N degrees, and N is an integer greater than or equal to 2.

In a second aspect, the present invention provides a power supply apparatus comprising: a multiphase resonant circuit as claimed in any one of the preceding claims.

The technical scheme provided by the embodiment of the disclosure can comprise the following beneficial effects:

in the embodiment of the disclosure, the primary winding of each transformer is connected with an equivalent half-bridge circuit, so that the multiphase resonant circuit maintains the circuit characteristic of half-bridge resonance, and the resonant capacitor has constant direct current bias and maintains unipolar voltage.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the disclosure and together with the description, serve to explain the principles of the disclosure. It will be apparent to those of ordinary skill in the art that the drawings in the following description are merely examples of the disclosure and that other drawings may be derived from them without undue effort.

FIG. 1 shows a schematic diagram of a multiphase resonant circuit in an exemplary embodiment of the present disclosure;

FIG. 2 shows a schematic diagram of a half-bridge LLC circuit in the related art;

FIG. 3 shows a schematic diagram of a half-bridge LLC circuit in the related art collecting resonant capacitor voltage and overload short-circuit protection;

FIG. 4 shows a schematic diagram of a full-bridge LLC circuit in the related art;

FIG. 5 shows a schematic diagram of a related art three-phase LLC circuit;

FIG. 6 shows a schematic diagram of a simulated waveform of a three-phase LLC circuit in the related art;

FIG. 7 shows a schematic diagram of a two-phase resonant circuit in an exemplary embodiment of the present disclosure;

FIG. 8 illustrates a schematic diagram of another two-phase resonant circuit in an exemplary embodiment of the present disclosure;

FIG. 9 shows a schematic diagram of a three-phase resonant circuit in an exemplary embodiment of the present disclosure;

FIG. 10 illustrates an operational waveform schematic of a three-phase resonant circuit in an exemplary embodiment of the present disclosure;

FIG. 11 illustrates a simulated waveform schematic of a three-phase resonant circuit in an exemplary embodiment of the present disclosure;

FIG. 12 illustrates a schematic diagram of another three-phase resonant circuit in an exemplary embodiment of the present disclosure;

fig. 13 shows a schematic diagram of another three-phase resonant circuit in an exemplary embodiment of the present disclosure.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments may be embodied in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

Furthermore, the drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus a repetitive description thereof will be omitted. Some of the block diagrams shown in the figures are functional entities and do not necessarily correspond to physically or logically separate entities. These functional entities may be implemented in software or in one or more hardware modules or integrated circuits or in different networks and/or processor devices and/or microcontroller devices.

In this example embodiment, there is first provided a multiphase resonant circuit. Referring to fig. 1, it includes: the transformer comprises at least two transformers, a half-bridge circuit corresponding to each transformer one by one and a secondary side circuit corresponding to each transformer one by one.

Each half-bridge circuit comprises a resonant inductor, an excitation inductor, a resonant capacitor, a first switching element and a second switching element, wherein the second end of the resonant inductor is connected with the first end of the excitation inductor in series, the second end of the excitation inductor is connected with the first end of the resonant capacitor in series, the first end of the resonant inductor is respectively connected with the second end of the first switching element and the first end of the second switching element, the first end of the first switching element is connected with a first common end, the second end of the second switching element is connected with a second common end, and the second end of the resonant capacitor is connected with a third common end.

The first common end is used for being connected with the positive end of the direct current source, and the second common end is used for being connected with the negative end of the direct current source; the third common terminal is connected with the first common terminal or the second common terminal; the two ends of the excitation inductance of each half-bridge circuit are connected in parallel with the two ends of the primary winding of the corresponding transformer.

Each secondary side circuit comprises a third switching element and a fourth switching element, a first end of a secondary side winding of the transformer is respectively connected with a second end of the third switching element and a first end of the fourth switching element, and the first end of the third switching element and the second end of the fourth switching element are respectively connected with two ends of a direct current element; the second ends of the secondary windings of the transformer are connected to each other.

It should be understood that, as shown in fig. 2, the half-bridge LLC circuit is formed by sequentially connecting in series a dc power supply, a set of bridge arm chopper switches, a resonant tank circuit formed by connecting a resonant inductor and a resonant capacitor in series, and a transformer having an excitation inductor and a rectifying circuit. The half-bridge LLC is alternately conducted through a group of bridge arm chopper switches, when an upper tube is turned on, a direct current power supply voltage Vs is added at two ends of a resonant tank, when a lower tube is turned on, 0V voltage is added at two ends of the resonant tank, so that the voltage input into the resonant tank is Vs-0V-Vs-0V, and because a resonant capacitor has a blocking effect, the voltage actually entering a transformer is finally alternating current voltage, the resonant capacitor bears 0.5 times of direct current power supply voltage Vs bias voltage, and the voltage waveform on the final resonant capacitor is 0.5 times of Vs DC bias voltage superposition alternating current ripple voltage. The voltage across the resonant capacitor as a whole is a unipolar voltage, i.e. a dc voltage.

As shown in fig. 3, taking the half-bridge LLC as an example, since the voltage on each resonant capacitor is unipolar and has a fixed dc bias, the voltage value of the lower capacitor can be detected by resistive-capacitive division, thereby indirectly obtaining the current of the resonant cavity. The diode can be connected in parallel at two ends of the resonant capacitor in an anti-parallel mode to realize LLC short-circuit protection, and the specific protection mode is that when the current of the resonant tank is too large, the voltage generated by the current flowing through the resonant capacitor exceeds 0V, the diode is conducted, so that the impedance of the resonant circuit is changed, at the moment, only the resonant inductor exists in the resonant circuit, and the resonant capacitor does not exist, so that the current of the resonant tank is further increased. The current of the resonant tank is limited by connecting diodes in parallel at two ends of the resonant capacitor, so that the short circuit and overload protection functions can be realized.

As shown in fig. 4, taking a full-bridge LLC circuit (also referred to as two phases) as an example, fig. 4 is a schematic diagram of a typical full-bridge LLC circuit. The full-bridge LLC circuit comprises a direct current source, two half-bridge arms, an LLC resonant circuit, a transformer and a full-bridge rectifying circuit. The working principle is that the first half-bridge upper pipe and the second half-bridge lower pipe are simultaneously turned on and off, the second half-bridge upper pipe and the first half-bridge lower pipe are simultaneously turned on and off, the first half-bridge upper pipe and the first half-bridge lower pipe are complementarily turned on and off, and the second half-bridge upper pipe and the second half-bridge lower pipe are complementarily turned on and off.

The voltage of the power supply DC is assumed to be Vs, when the first half-bridge upper pipe and the second half-bridge lower pipe are opened, the power supply voltage is connected to the input end of the resonant tank circuit in the forward direction, and the input end of the resonant tank is positive-polarity power supply voltage +Vs; when the second half-bridge upper tube and the first half-bridge lower tube are opened, the power supply voltage is reversely connected to the input end of the resonant tank circuit, and the input end of the resonant tank is negative power supply voltage-Vs; the voltage input to the resonant tank is an alternating rectangular square wave of (+vs) — (-Vs) — (+vs) — (-Vs) alternating, without a dc bias voltage. The resonant inductor has no impedance voltage drop effect on direct current voltage, the transformer has no impedance voltage drop effect on direct current voltage, and the resonant capacitor has impedance voltage drop effect on direct current voltage, but the resonant capacitor has no direct current bias voltage because no direct current bias voltage component exists in the voltage input into the resonant tank, so that the traditional full-bridge LLC circuit resonant capacitor has only alternating current voltage, no direct current bias voltage and bipolar voltage.

As shown in fig. 5, taking a three-phase LLC circuit as an example, fig. 5 is a schematic diagram of a typical three-phase LLC circuit. The three-phase LLC circuit comprises a direct current source, three half-bridge arms, three LLC resonant circuits, three transformers and a three-phase full-bridge rectifying circuit. The three half-bridge arms are mutually out of phase 120-degree same-frequency switch. The circuit is characterized in that the primary side of each transformer is connected with an LLC resonant circuit in series, the primary side is connected with three phases in star connection, the primary side is connected with the midpoints of three half-bridge arms respectively, the secondary side of the transformer is also connected with the star connection, and the secondary side is connected with a three-phase full-bridge rectifying circuit in three phases.

For ease of analysis, taking the example of a three-phase LLC circuit operating at the resonant frequency point, the resonant tank current is now very close to a sine wave current.

The voltage of the midpoint of the three-phase capacitor is firstly analyzed by taking the ground of the direct-current power supply as a voltage reference point.

The three-phase half-bridge arm uses 120 degree phase-shifting switch, and uses 60 degree as unit to divide a complete period into six phases, each phase switch action state uses 1 to represent on state, uses 0 to represent off state, and can list the following action time sequence list.

TABLE 1 action time sequence chart

As can be seen from table 1, stage 3 and stage 5 are where the two-phase upper pipes are on, the other phase lower pipe is off, the two-phase upper pipes in stage 2, stage 4 and stage 6 are off, and the other phase lower pipe is on. Since the three-phase circuit is symmetrical, there are two state equivalent circuits. The whole resonant tank is equivalent to an impedance model, when the two-phase upper pipe is opened and the one-phase lower pipe is closed, the midpoint voltage of the capacitor is equal to two thirds of the power supply voltage according to the impedance voltage division ratio, namely 2Vs/3; when the two-phase lower tube is switched on and the one-phase upper tube is switched off, the midpoint voltage of the capacitor is equal to one third of the power supply voltage according to the impedance voltage division ratio, namely Vs/3; because the three-phase circuit is symmetrical, the two equivalent circuits are mutually converted for 3 times in one period, so that the voltage change rule of the midpoint of the capacitor is 2 Vs/3-1 Vs/3-2 Vs/3-1 Vs/3 in one complete period; the frequency of the voltage change is 3 times the operating frequency.

The resonance capacitor itself flows through the alternating current resonance current, and alternating current ripple voltage is generated at two ends of the capacitor. And finally, taking the power ground as a reference point, wherein the voltage of the resonant capacitor is bias voltage superposition alternating current ripple voltage, the bias voltage is the voltage of the midpoint of the three-phase capacitor, and the voltage is a square wave with the working frequency of 3 times, the peak value is 2Vs/3, and the valley value is 1Vs/3. The actual voltage waveform of the superimposed resonant capacitor voltage is shown in fig. 6, and the waveform is very complex.

Fig. 6 is a waveform diagram of a conventional three-phase LLC actual simulation, in which the dc supply voltage is 300V, and the simulation result shows that the voltage of the midpoint voltage VC2 of the capacitor is a square wave, and the amplitude of the high level is 200V, and the amplitude of the low level is 100V. The voltage VC1 across the resonant capacitor is an ac voltage, and the voltage VC of the resonant capacitor reference power ground is a square wave bias voltage VC2 superimposed with the capacitor voltage VC1. From the simulation waveforms, it can be seen that the voltage waveform of the resonant capacitor is very complex. The voltage waveforms of the resonance capacitors of the other two phases are the same as Vc, and the phases are different by 120 degrees and 240 degrees in sequence.

VPt in the simulation waveform is the voltage waveform of the primary side of one-phase transformer, and it can be seen that the voltage waveform of the primary side of the transformer is a three-four level waveform, and the amplitudes are 200V, 100V, -100V and-200V respectively.

It should be further understood that in a specific practical application, the primary side of the multiphase resonant circuit of the present application is equivalent to a plurality of independent half-bridge LLC circuits, so that all protection circuits and methods applied to the half-bridge LLC circuits can be very conveniently transplanted to the multiphase resonant circuit. For example, the voltage of the resonant capacitor can be acquired through a resistor and capacitor voltage dividing circuit, and the current of the resonant tank can be indirectly acquired. Diodes can be reversely connected in parallel at two ends of each resonant capacitor to limit the maximum current of the resonant tank, thereby playing the roles of overload and short-circuit protection. These measures are not readily available on existing two-phase LLC, three-phase LLC, and other multiphase resonant circuits. Taking the example of collecting the voltage of the resonant capacitor, the resonant capacitor of the existing three-phase LLC circuit and the power supply reference ground do not share the reference ground potential, the 3-frequency multiplication high-frequency jump voltage exists, and the effective resonant current is difficult to identify by the sampling signal. Taking a protection circuit as an example, the resonant capacitor voltage of the existing three-phase LLC circuit is overlapped with 3 times of square waves, when the clamping of a diode is increased, the amplitude of the square waves is already 2Vs/3, then the alternating current ripple voltage generated by the resonant current is overlapped, the voltage exceeds the power supply voltage Vs easily, the anti-parallel diode is protected, and the actual effective load is very small, so that advanced protection can occur.

It should also be understood that the primary winding of the transformer of the present application is the primary of N half-bridge LLC circuits, and the secondary windings of the transformer are coupled together by a transformer star connection, also connected to the N secondary circuit outputs. First, the multiphase resonant circuit (multiphase LLC circuit) of the application maintains the circuit characteristics of the primary side half-bridge LLC of the transformer, and the resonant capacitor has constant direct current bias and maintains unipolar voltage. Secondly, the secondary windings of the transformer are coupled together through a star connection method, any one phase of current is inevitably connected with other phases of current in series to flow through the current, and the problem of unbalanced current of the resonant tank caused by inconsistent resonance parameters can be avoided by forced current sharing of the star connection method of the secondary windings.

It will also be appreciated that with the multi-phase resonant circuit (multi-phase LLC circuit) provided herein, a four-phase LLC circuit, a six-phase LLC circuit, can be readily constructed.

According to the multiphase resonant circuit, the primary winding of each transformer is connected with the equivalent half-bridge circuit, so that the multiphase resonant circuit maintains the circuit characteristic of half-bridge resonance, and the resonant capacitor has constant direct current bias and maintains unipolar voltage.

Next, each portion of the above-described multiphase resonance circuit in the present exemplary embodiment will be described in more detail with reference to fig. 1 to 13.

Alternatively, referring to fig. 7, the multiphase resonant circuit includes: the transformer comprises a first transformer, a second transformer, a first half-bridge circuit corresponding to the first transformer and a second half-bridge circuit corresponding to the second transformer.

The two ends of the excitation inductor of the first half-bridge circuit are connected in parallel with the two ends of the primary winding of the first transformer, the two ends of the excitation inductor of the second half-bridge circuit are connected in parallel with the two ends of the primary winding of the second transformer, the first end of the first switching element of the first half-bridge circuit and the first end of the first switching element of the second half-bridge circuit jointly form the first common end, the second end of the second switching element of the first half-bridge circuit and the second end of the second switching element of the second half-bridge circuit jointly form the second common end, and the second end of the resonance capacitor of the first half-bridge circuit and the second end of the resonance capacitor of the second half-bridge circuit jointly form the third common end; and the third common terminal is connected to the second common terminal.

It will be appreciated that the above circuit corresponds to a two-phase LLC circuit, i.e. the number of transformers is 2. Specifically, the two-phase LLC circuit comprises 2 half-bridge circuits, namely 2 resonant inductors, 2 resonant capacitors and 2 excitation inductors, wherein the input sides of the 2 half-bridge circuits are connected to a direct current source in parallel, the middle points of bridge arms of the half-bridge circuits are sequentially connected with the resonant inductors and the first end of a primary winding of a transformer, and after the second end of the primary winding of the transformer is connected with the resonant capacitors in series, the resonant capacitors are coupled to the direct current source. The first ends of the secondary windings of the 2 transformers are respectively connected with the middle points of bridge arms of the 2 circuits, and the second ends of the secondary windings of the 2 transformers are in short circuit connection to form a star connection method. The 2 half-bridge circuits operate at the same switching frequency, with phases differing in turn by 180 degrees.

The working principle is analyzed as follows:

in fig. 7, T1 is a first transformer, S1 is a first switching element corresponding to the first transformer T1, S2 is a second switching element corresponding to the first transformer T1, lr1 is a resonant inductance corresponding to the first transformer T1, lm1 is an excitation inductance corresponding to the first transformer T1, cr1 is a resonant capacitance corresponding to the first transformer T1, S5 is a third switching element corresponding to the first transformer T1, and S6 is a fourth switching element corresponding to the first transformer T1. T2 is a second transformer, S3 is a first switching element corresponding to the second transformer T2, S4 is a second switching element corresponding to the second transformer T2, lr2 is a resonant inductance corresponding to the second transformer T2, lm2 is an excitation inductance corresponding to the second transformer T2, cr2 is a resonant capacitance corresponding to the second transformer T2, S7 is a third switching element corresponding to the second transformer T2, and S8 is a fourth switching element corresponding to the second transformer T2.

With the transformer as a boundary, the circuits before the transformer are collectively called primary side circuits, and the circuits after the transformer are collectively called secondary side winding circuits. The primary side circuit of the transformer is equivalent to the primary side circuits of two half-bridge LLCs, and the two half-bridge LLCs are mutually staggered for 180 degrees. There are two operating states:

State 1: s1, S4 is opened, in the first path half-bridge LLC circuit, when the primary side works, the forward current path is: DC-S1-Lr 1-Lm 1 and T1 primary side-Cr 1-power ground (+); in the second half-bridge LLC circuit, when the primary side is in operation, the reverse current path is: power supply ground (-) -Cr 2-Lm 2 and T2 primary side-Lr 2-S4-power supply ground (+); the power ground (-) represents the current flowing from the power ground, and the power ground (+) represents the current flowing into the power ground.

State 2: s2, S3 is opened, in the first path half-bridge LLC circuit, when the primary side works, the reverse current path is: power supply ground-Cr 1-Lm 1 and T1 primary side-Lr 1-S2-power supply ground; in the second half-bridge LLC circuit, when the primary side is in operation, the current path in the forward direction is: DC-S3-Lr 2-Lm 2 and T2 primary side-Cr 2-power ground.

From the complete current loops of states 1 and 2 it can be seen that the two current loops actually overlap and cancel, the current of the first half-bridge LLC circuit flowing to the power ground when flowing to the power ground, the current of the second half-bridge LLC circuit always flowing in the opposite direction to that of the second half-bridge LLC circuit, and the current canceling at the location of the power ground. The equivalent current loop is:

State 1: s1 and S4 are opened, and the current paths are DC-S1-Lr 1-Lm 1, T1 primary side-Cr 1-Cr 2-Lm 2, T2 primary side-Lr 2-S4-power supply ground (+);

state 2: s2 and S3 are opened, and the current paths are DC-S3-Lr 2-Lm 2 and T2 primary sides-Cr 2-Cr 1-Lm 1 and T1 primary sides-Lr 1-S2-power supply ground (+).

From the operational equivalent of the circuit, the two-phase LLC circuit of the present application is virtually identical to the conventional full-bridge LLC circuit operational path. The difference is that under each working state, the current of the current application needs to flow through two resonant inductors, two resonant capacitors and two transformers simultaneously. In the current loop, two resonant inductors are connected in series, two resonant capacitors are connected in series, and the primary sides of the two transformers and the exciting inductor are connected in series. Because the inductance of the inductance series connection is doubled, the capacitance of the capacitance series connection is halved, and therefore, the natural resonant frequency of the current equivalent is the same as the natural resonant frequency of the traditional full-bridge LLC circuit adopting a single resonant inductance and a resonant capacitance. That is, the operating state of this circuit is completely equivalent to the operating state of a conventional full-bridge LLC circuit.

However, it can be seen that the primary side circuit of the two-phase LLC circuit of the present application is two separate half-bridge LLC circuits, having all the characteristics of a half-bridge circuit, in particular the voltage across the resonant capacitor is a unipolar voltage with a fixed bias voltage.

According to the equivalent current loop described above, the current is cancelled, in particular, completely cancelled or partially cancelled, at the power ground position, depending on whether the resonant circuit parameters are identical, when the resonant parameters of the two half-bridge LLC primary circuits are identical, the current is completely cancelled at the power ground position, but when the two resonant parameters are not identical, the current of the two half-bridge LLC primary circuits is not identical, at which point the current is not completely cancelled at the power ground position. In this case, the star connection of the secondary winding circuits of the transformers is used to ensure that the current on the load side is connected in series, so that the currents reflected to the primary windings of the two transformers are equal. The current offset of the power ground position is maintained to the maximum extent.

Alternatively, referring to fig. 8, the multiphase resonant circuit includes: the transformer comprises a first transformer, a second transformer, a first half-bridge circuit corresponding to the first transformer and a second half-bridge circuit corresponding to the second transformer.

It will be appreciated that, in the form of a half-bridge LLC circuit, it is contemplated that the half-bridge LLC primary circuit of the two-phase LLC circuit of the present application may also be a resonant capacitor as shown in fig. 7 with the point of the resonant capacitor being connected to the power supply positive, except that the bias voltage on the resonant capacitor is Vs/2. If the power supply is being used as a reference, the voltages of the two resonant capacitors are both unipolar voltages.

Alternatively, referring to fig. 9, the multiphase resonant circuit includes: the transformer comprises a first transformer, a second transformer, a third transformer, a first half-bridge circuit corresponding to the first transformer, a second half-bridge circuit corresponding to the second transformer and a third half-bridge circuit corresponding to the third transformer.

It will be appreciated that the difference compared to existing three-phase LLC circuits is the coupling of the midpoint of the resonant capacitance to the dc supply. Specifically, the multiphase resonant circuit of the application comprises a direct current source, 3 half-bridge circuits, 3 resonant inductors, 3 resonant capacitors, a 3-phase transformer and 3 secondary circuits. The input sides of the 3 half-bridge circuits are connected to a direct current source in parallel, the middle points of bridge arms of the half-bridge circuits are sequentially connected with a resonant inductor and the primary first end of the primary side of the transformer, and after the secondary ends of primary windings of the transformer are connected with a resonant capacitor in series, the resonant capacitor is coupled to the direct current source. The first ends of the secondary windings of the 3-phase transformer are respectively connected with the middle points of bridge arms of 3 secondary circuits (which can be half-bridge circuits), and the second ends of the secondary windings of the 3-phase transformer are short-circuited together to form a star connection method. The 3 half-bridge circuits operate at the same switching frequency, with 120 degrees out of phase in sequence.

From a circuit perspective, the midpoint of the three-phase resonant capacitor of the present application is connected to power ground as compared to an existing three-phase LLC circuit, but the state of the circuit of the present application is quite different from an existing three-phase LLC circuit. First, the primary side circuit of the transformer of the three-phase LLC circuit of the present application corresponds to three independent half-bridge LLC circuits, and secondary windings are coupled together through a star connection of the secondary windings of the transformer. Firstly, the middle point of the three-phase resonant capacitor is connected to the power ground, when the upper tube of the first phase half-bridge is turned on, the power voltage Vs is input into the resonant tank, and when the lower tube of the first phase half-bridge is turned on, the 0V voltage is input into the resonant tank, and as the analysis method of the half-bridge LLC circuit is completely the same, the two ends of the resonant capacitor can bear Vs/2 direct current bias voltage at first. Secondly, the resonant capacitor generates an alternating current ripple voltage after alternating current flows through the resonant capacitor, so that the power ground is used as a 0V potential reference point, and the voltage waveform of the resonant capacitor is Vs/2 direct current bias voltage superposition capacitor alternating current ripple voltage, and the voltage is generally a unipolar voltage. Thirdly, the waveform of the primary circuit input end of the first phase transformer is an alternating square wave, specifically, when the upper tube of the first phase half-bridge is turned on, the impedance of the resonant inductor and the resonant capacitor is very small in a resonant state, so that the voltage born by the transformer is the power supply voltage Vs minus the resonant capacitor bias voltage Vs/2, and the input positive voltage of the transformer is Vs/2; when the first phase half-bridge lower tube is opened, the voltage born by the transformer is the resonance capacitor bias voltage Vs/2, and the voltage polarity is opposite, so that the input negative voltage of the transformer is-Vs/2; it can be seen that the transformer primary equivalent input voltage is (+ Vs/2) - (-Vs/2) bipolar square wave voltage. It should be noted that the upper tube and the lower tube of one half bridge arm are complementarily opened, i.e. the upper tube is opened and the lower tube is closed; the upper tube is turned off and the lower tube is turned on.

Because the primary side circuit of the three-phase LLC circuit transformer is three independent half-bridge LLC primary side circuits, the analysis method of the other two phases is the same as the first phase analysis method, the results are consistent, and the difference is that all voltage phases are sequentially different by 120 degrees. Turning to a comparison between the three-phase LLC circuit of the present application and the existing three-phase LLC circuit, as shown in fig. 10, fig. 10 is a circuit operation waveform diagram of an embodiment of the three-phase LLC circuit of the present application, a dc power supply voltage of 300V, an upper waveform diagram is a first-phase resonant capacitor voltage waveform, and a lower waveform diagram is a voltage waveform diagram of a primary winding of a first-phase transformer. As can be seen from fig. 10, the dc bias voltage of the resonance capacitor is 150V, superimposed with the ac component; the voltage of the primary winding of the transformer is approximately square wave, and the amplitude is 150V and-150V respectively. The simulation waveform is consistent with the theoretical analysis result.

As shown in fig. 11, in order to compare the difference between the three-phase LLC circuit of the present application and the conventional three-phase LLC circuit, the supply voltage, the load condition, the resonance parameter, and the operating frequency are all kept identical, and the difference in the circuit operating waveforms is compared by means of simulation. For ease of lateral comparison, waveforms for devices of the same phase are placed on a curve. In fig. 11, the bold line waveform is a waveform curve of the three-phase LLC circuit of the present application, and the thin line is a waveform curve of the conventional three-phase LLC circuit. VX, VT2, I (L1) and VP1 in the curve are respectively resonant capacitor waveforms, voltage waveforms of primary windings of transformers, current waveforms of resonant inductors and output voltage waveforms in the three-phase LLC circuit; vc, VPt, I (L6) and VP6 in the curve are respectively a resonance capacitor waveform, a voltage waveform of a primary winding of a transformer, a current waveform of a resonance inductor and an output voltage waveform in the existing three-phase LLC circuit; it can be seen from the curve that the current waveform of the resonant inductor, namely the current waveform in the resonant tank, is the same, and the output voltage waveform is the same, but the voltage waveforms of the resonant capacitor and the primary winding of the transformer are completely different, that is, the three-phase LLC circuit can solve the problem of single-polarity voltage of the resonant capacitor, and can maintain the same effect as the existing three-phase LLC circuit.

Alternatively, referring to fig. 12, the multiphase resonant circuit includes: the transformer comprises a first transformer, a second transformer, a third transformer, a first half-bridge circuit corresponding to the first transformer, a second half-bridge circuit corresponding to the second transformer and a third half-bridge circuit corresponding to the third transformer.

It will be appreciated that, as such, in the form of a half-bridge LLC circuit, it is contemplated that the resonant capacitance in the half-bridge LLC primary circuit of the three-phase LLC circuit of the present application may be coupled to either power supply ground or power supply positive, or may be divided into equal halves and coupled to both power supply positive and power supply ground, respectively. From the circuit analysis point of view, in the small signal analysis model, the voltage source is usually equivalent to a short circuit, so that the resonant capacitor is coupled to the positive power supply or the resonant capacitor is coupled to the negative power supply, and for the small signal model, the direct current power supply is short-circuited, so that the final small signal equivalent model circuit is the same. The circuit in principle explains the different locations of capacitive coupling to the power supply, the final effect being the same.

Alternatively, referring to fig. 12, the first switching element and the second switching element each employ any one of the following: a diode, a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), or an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, IGBT); the third switching element and the fourth switching element each employ any one of: a diode, MOSFET or IGBT. It should be understood that for purposes of illustration in this application, the exemplary illustrations provided by the embodiments identify the rectifier switches with the symbols of diodes. It should be understood by an ordinary engineer that the upper and lower tubes in the half-bridge circuit of the present application refer to switches that can be turned on and off, and in particular diodes, MOSFETs or IGBTs in power electronics. And should not be construed simply as the diode rectifier circuit shown in the figures.

Alternatively, as shown with reference to fig. 13, the dc component employs a capacitor or dc source. It should be understood that when the dc component is a dc source, the dc source connected to the secondary winding of the transformer may be a dc source of a different parameter than the dc source connected to the primary winding of the transformer.

Alternatively, referring to fig. 8 to 10, all of the first switching element, the second switching element, the third switching element, and the fourth switching element switch the switching states at the same frequency, and the switching states of the first switching element and the second switching element are always opposite; the switching states of the third switching element and the fourth switching element are always opposite.

Alternatively, referring to fig. 8-10, the number of the transformers is N, and the working phases of the N half-bridge circuits are sequentially different by 360/N degrees, where N is an integer greater than or equal to 2. It is to be understood that the half-bridge circuit of the primary side circuit of the multiphase LLC circuit works at the same switching frequency, and the phases are sequentially different by 360/N degrees, so that the input and output current ripple problem is solved.

Further, in the present exemplary embodiment, a power supply apparatus is also provided. The power supply device includes: the multiphase resonant circuit of any of the embodiments above.

The specific manner in which the power supply device is described in detail in connection with the embodiments of the multiphase resonant circuit will not be described in detail here.

It should be noted that although in the above detailed description several modules or units of a device for action execution are mentioned, such a division is not mandatory. Indeed, the features and functionality of two or more modules or units described above may be embodied in one module or unit in accordance with embodiments of the present disclosure. Conversely, the features and functions of one module or unit described above may be further divided into a plurality of modules or units to be embodied. The components shown as modules or units may or may not be physical units, may be located in one place, or may be distributed across multiple network elements. Some or all of the modules may be selected according to actual needs to achieve the objectives of the disclosed solution. Those of ordinary skill in the art will understand and implement the present invention without undue burden.

Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any adaptations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims

1. A multiphase resonant circuit, comprising:

the transformer comprises a first transformer, a second transformer, a third transformer, a first half-bridge circuit corresponding to the first transformer, a second half-bridge circuit corresponding to the second transformer and a third half-bridge circuit corresponding to the third transformer;

each half-bridge circuit comprises a resonant inductor, an excitation inductor, a resonant capacitor, a first switching element and a second switching element, wherein the second end of the resonant inductor is connected with the first end of the excitation inductor in series, the second end of the excitation inductor is connected with the first end of the resonant capacitor in series, and the first end of the resonant inductor is respectively connected with the second end of the first switching element and the first end of the second switching element;

the first end of the first switching element of the first half-bridge circuit, the first end of the first switching element of the second half-bridge circuit and the first end of the first switching element of the third half-bridge circuit form a first common end together, the second end of the second switching element of the first half-bridge circuit, the second end of the second switching element of the second half-bridge circuit and the second end of the second switching element of the third half-bridge circuit form a second common end together, and the second end of the resonant capacitor of the first half-bridge circuit, the second end of the resonant capacitor of the second half-bridge circuit and the second end of the resonant capacitor of the third half-bridge circuit form a third common end together;

The first common end is used for being connected with the positive end of the direct current source, and the second common end is used for being connected with the negative end of the direct current source; the third common terminal is connected with the first common terminal or the second common terminal;

the two ends of the excitation inductor of the first half-bridge circuit are connected in parallel with the two ends of the primary winding of the first transformer, the two ends of the excitation inductor of the second half-bridge circuit are connected in parallel with the two ends of the primary winding of the second transformer, and the two ends of the excitation inductor of the third half-bridge circuit are connected in parallel with the two ends of the primary winding of the third transformer;

each secondary circuit comprises a third switching element and a fourth switching element, the first ends of secondary windings of the transformers are respectively connected with the second ends of the third switching elements and the first ends of the fourth switching elements, and the first ends of the third switching elements and the second ends of the fourth switching elements are respectively connected with two ends of the direct current elements; the second ends of the secondary windings of the transformer are connected with each other;

the resonance capacitor maintains a unipolar voltage; the working phases of the 3 half-bridge circuits are sequentially different by 120 degrees.

2. The multiphase resonant circuit of claim 1, wherein the first switching element and the second switching element each employ any one of the following: a diode, MOSFET or IGBT;

3. The multiphase resonant circuit of claim 1, wherein the dc component employs a capacitor or a dc source.

4. A multiphase resonant circuit according to any of claims 1-3, wherein all of the first switching element, the second switching element, the third switching element and the fourth switching element switch states at the same frequency, and wherein the switching states of the first switching element and the second switching element are always opposite; the switching states of the third switching element and the fourth switching element are always opposite.

5. A power supply device comprising a multiphase resonant circuit as claimed in any one of claims 1 to 4.