Multiphase LLC resonant converter circuit

Abstract

A multiphase LLC resonant converter circuit (10) is provided with first to third LLC resonant converters. The first to third LLC resonant converters are provided with: series circuits (S1-S3) connected in parallel to a DC power supply (30), in which a first switch and a second switch are connected in series; a high-frequency transformer (T1-T3) provided with a primary winding and a secondary winding; a resonance circuit (41-43) provided with a resonance reactor (Lr1-Lr3) connected between a connection point between the first switch and the second switch and one end of the primary-side winding, and a resonance capacitor (Cr1-Cr3) having one end connected to the other end of the primary-side winding; and rectification circuits (51-53) for rectifying the output of the secondary side winding. The multiphase LLC resonant converter circuit (10) is further provided with: a neutral line (N1) that connects the other ends of the resonant capacitors of the first to third LLC resonant converters to each other; and a neutral line reactor (Ln) connected between the neutral line and a power supply line of the DC power supply.

Description

Technical Field

[0001] The present invention relates to a multi-phase LLC resonant converter (CONVERTER) circuit for converting a first DC voltage of a DC power supply into a second DC voltage and outputting the second DC voltage. Background Art

[0002] Conventionally, as a converter circuit for converting a first DC voltage of a DC power supply into a second DC voltage and outputting the converted voltage, a multi-phase (N-phase) LLC resonant converter circuit is known (see Patent Documents 1-4). This circuit connects a plurality (N) of LLC resonant converters in parallel to a DC power supply, and turns on and off the switches of each LLC resonant converter so that the resonant current of the resonant circuit connected to the primary side winding of the high-frequency transformer of each LLC resonant converter has a phase difference of 360° / N.

[0003] Preferably, the LLC resonant converter is designed so that when the voltage value of the DC power supply is rated (for example, 380V), the switching frequency of turning on and off the switch becomes close to the resonant frequency of the resonant circuit. On the other hand, when the voltage value of the DC input voltage is reduced (for example, reduced to 300V), if the boost operation is performed by reducing the switching frequency of the switch, the circuit loss increases and the efficiency decreases. Considering that under the same output power, if the voltage value of the DC input voltage is reduced, the value of the DC input current increases in inverse proportion to it, so the efficiency naturally decreases to a certain extent. However, in reality, the increase in the peak value of the resonant current flowing through the resonant circuit exceeds the increase in the value of the DC input current. Most of the unnecessary current that increases the resonant current is the third (higher) harmonic current with a frequency three times the switching frequency.

[0004] Figure 7 A multi-phase (three-phase) LLC resonant converter circuit 11 of a first prior art is shown. In this circuit, a third harmonic current component passes through a neutral line N1 connected to one end of a resonant circuit 41, 42, 43 connected to primary windings Lp1, Lp2, Lp3 of high-frequency transformers T1, T2, T3 of each LLC resonant converter, and flows out of the resonant circuit (see Patent Document 1). When the DC input voltage Vin of the DC power supply 30 is rated (for example, 380 V), as shown in FIG. Figure 8 As shown in (a), the resonant current ir (ir1, ir2, ir3) of each phase flowing through the resonant circuits 41, 42, 43 is approximately sinusoidal. Figure 8 As shown in (b), the value of the neutral line current in flowing through the neutral line N1 is substantially zero. On the other hand, when the DC input voltage Vin of the DC power supply 30 is reduced (for example, reduced to 300V), if the voltage is stepped up by reducing the switching frequency of the switch, Fig. 9As shown in (a), since the third harmonic component is generated in the resonant current ir, the effective value of the resonant current ir increases. Fig. 9 As shown in (b), in the neutral line N1, a third harmonic current is generated as a neutral line current in. In addition, in the multi-phase LLC resonant converter circuit 11 of the first conventional example, one end of the resonant circuits 41, 42, and 43 is connected to the power line of the DC power supply Vin through the neutral line N1. Therefore, when the load is reduced, it is possible to switch from the multi-phase operation mode in which multiple LLC resonant converters are operated to the single-phase operation mode in which only one LLC resonant converter is operated.

[0005] Fig.10 A second conventional example of a multi-phase (three-phase) LLC resonant converter circuit 12 is shown in FIG. In this circuit, the neutral line N1 connected to one end of the resonant circuits 41, 42, and 43 connected to the primary side of the high-frequency transformers T1, T2, and T3 of each LLC resonant converter is floating, and there is no path for the third harmonic current (see Patent Document 2). In the second conventional example of the multi-phase LLC resonant converter circuit 12, the increase in resonant current during the boost operation when the DC input voltage Vin decreases can be suppressed. However, since it is impossible to switch from the multi-phase operation mode to the single-phase operation mode, the efficiency is low when the load is reduced.

[0006] Fig.11 A third prior art example of a multi-phase LLC resonant converter circuit 13 is shown. The circuit has both a first neutral line N1 connected to the power line of the DC power supply Vin as in the first prior art example and a second floating neutral line N2 as in the second prior art example (refer to patent documents 3 and 4). The third prior art example of a multi-phase LLC resonant converter circuit 13 can naturally balance the AC resonant currents ir1, ir2, ir3 flowing through the resonant circuits 41, 42, 43 in the multi-phase operation mode, and can switch from the multi-phase operation mode to the single-phase operation mode. However, when the DC input voltage Vin of the DC power supply 30 is reduced from the rated value (for example, 380 V) (for example, to 300 V), if a boost operation is performed by reducing the switching frequency of the switch, then, as in the first prior art example, Fig. 9 As shown in (a), since the third harmonic component is generated in the resonant current ir (ir1, ir2, ir3), the effective value of the resonant current ir increases. Fig. 9 As shown in (b), a third harmonic current flows through the first neutral line N1 as a neutral line current in.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: U.S. Patent Publication No. 2008-0298093

[0010] Patent Document 2: U.S. Patent No. 9780678

[0011] Patent Document 3: Japanese Patent No. 6696617

[0012] Patent Document 4: Japanese Patent Application Publication No. 2021-153382 Summary of the invention

[0013] Problems to be solved by the invention

[0014] One aspect of the present invention is to provide a multi-phase LLC resonant converter circuit, which, in a multi-phase operation mode, can suppress the increase in resonant current during a boost operation when a DC input voltage drops below a rated value and the generation of a third harmonic current flowing through a neutral line, while being able to switch from a multi-phase operation mode to a single-phase operation mode.

[0015] Means for solving problems

[0016] A multi-phase LLC resonant converter circuit according to one embodiment of the present invention is used to convert a first DC voltage of a DC power supply into a second DC voltage for output. The multi-phase LLC resonant converter circuit comprises first to Nth (N is an integer greater than 2) LLC resonant converters, and the first to Nth NLLC resonant converters respectively comprise: a series circuit connected in parallel to the DC power supply, in which a first switch and a second switch are connected in series; a high-frequency transformer comprising a primary winding and a secondary winding; a resonant circuit comprising a resonant inductor connected between a connection point between the first switch and the second switch and one end of the primary winding, and a resonant capacitor having one end connected to the other end of the primary winding; and a rectifier circuit for rectifying the output of the secondary winding. The multi-phase LLC resonant converter circuit also includes: a neutral line connecting the other ends of the resonant capacitors of the first to Nth NLLC resonant converters to each other; a neutral line inductor connected between the neutral line and a power line of either the positive or negative pole of the DC power supply; and an output capacitor connected in parallel to the output side of the rectifier circuit of the first to Nth LLC resonant converters and used to output the second DC voltage at both ends. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : is a circuit diagram showing the configuration of a multi-phase LLC resonant converter circuit according to the first embodiment.

[0018] Figure 2 (a) is a timing chart showing a waveform of a resonant current when a voltage (300 V) of a DC power supply is boosted in the multi-phase LLC resonant converter circuit according to the first embodiment. Figure 2 (b) is a timing chart showing the waveform of the neutral line current when the voltage (300 V) of the DC power supply is stepped up.

[0019] Figure 3 The diagram is a graph showing effective values ​​of the resonant current plotted against a DC input voltage (rated: 380 V) when a DC input voltage boost operation is performed in the multi-phase LLC resonant converter circuit of the first embodiment (solid line) and the first conventional example (dashed line).

[0020] Figure 4 : is a circuit diagram showing the configuration of a multi-phase LLC resonant converter circuit according to the second embodiment.

[0021] Figure 5 This is a diagram showing a structure in which a resonant reactor and a neutral line reactor used in a multi-phase LLC resonant converter circuit according to a second embodiment are magnetically coupled via separate magnetic cores.

[0022] Figure 6 This is a diagram showing a structure in which a resonant reactor and a neutral line reactor used in a multi-phase LLC resonant converter circuit according to a modification of the second embodiment are magnetically coupled via a five-legged magnetic core.

[0023] Figure 7 1 is a circuit diagram showing a configuration of a multi-phase LLC resonant converter circuit according to a first conventional example.

[0024] Figure 8 (a) is a timing chart showing the waveform of the resonant current when the voltage of the DC power supply is the rated voltage (380 V) in the multi-phase LLC resonant converter circuit of the first conventional example, Figure 8 (b) is a timing chart showing the waveform of the neutral line current when the voltage of the DC power supply is the rated voltage (380 V).

[0025] Fig. 9 (a) is a timing chart showing the waveform of the resonant current when the voltage (300 V) of the DC power supply is boosted in the multi-phase LLC resonant converter circuit of the first conventional example. Fig. 9 (b) is a timing chart showing the waveform of the neutral line current when the voltage (300 V) of the DC power supply is stepped up.

[0026] Fig.10 : is a circuit diagram showing the structure of a multi-phase LLC resonant converter circuit according to a second conventional example.

[0027] Fig.11 : is a circuit diagram showing the structure of a multi-phase LLC resonant converter circuit according to a third conventional example. DETAILED DESCRIPTION

[0028] A multi-phase LLC resonant converter circuit according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The present invention is not limited to the embodiment described below.

[0029] (First Embodiment)

[0030] Figure 1 : is a circuit diagram showing the configuration of a multi-phase LLC resonant converter circuit 10 according to the first embodiment. Here, the configuration of the multi-phase LLC resonant converter circuit 10 in which the number of phases N=3 (three-phase LLC resonant converter circuit) will be described.

[0031] The multi-phase LLC resonant converter circuit 10 includes: a first series circuit S1 in which a first switch Q11 and a second switch Q12 are connected in series, and the first series circuit S1 is connected in parallel to a DC power supply 30 having a DC voltage value Vin; a second series circuit S2 in which a first switch Q21 and a second switch Q22 are connected in series; and a third series circuit S3 in which a first switch Q31 and a second switch Q32 are connected in series.

[0032] In the first embodiment, N-channel MOSFETs are used for the switches Q11 , Q12 , Q21 , Q22 , Q31 , and Q32 , but other switching elements may be used.

[0033] One end of the first resonant reactor (Reactor) Lr1 is connected to the connection point of the first switch Q11 and the second switch Q12 of the first series circuit S1. One end of the second resonant reactor Lr2 is connected to the connection point of the first switch Q21 and the second switch Q22 of the second series circuit S2. One end of the third resonant reactor Lr3 is connected to the connection point of the first switch Q31 and the second switch Q32 of the third series circuit S3.

[0034] One end of the primary winding Lp1 of the first high-frequency transformer T1 is connected to the other end of the first resonant reactor Lr1, and one end of the first resonant capacitor Cr1 is connected to the other end of the primary winding Lp1 of the first high-frequency transformer T1, thereby forming a first resonant circuit 41. The first high-frequency transformer T1 includes a core, a primary winding Lp1, and a secondary winding Ls1. The primary winding Lp1 and the secondary winding Ls1 are insulated from each other.

[0035] One end of the primary winding Lp2 of the second high-frequency transformer T2 is connected to the other end of the second resonant inductor Lr2, and one end of the second resonant capacitor Cr2 is connected to the other end of the primary winding Lp2 of the second high-frequency transformer T2, thereby forming a second resonant circuit 42. The second high-frequency transformer T2 includes a magnetic core, a primary winding Lp2, and a secondary winding Ls2. The primary winding Lp2 and the secondary winding Ls2 are insulated from each other.

[0036] One end of the primary winding Lp3 of the third high-frequency transformer T3 is connected to the other end of the third resonant inductor Lr3, and one end of the third resonant capacitor Cr3 is connected to the other end of the primary winding Lp3 of the third high-frequency transformer T3, thereby forming a third resonant circuit 43. The third high-frequency transformer T3 includes a magnetic core, a primary winding Lp3, and a secondary winding Ls3. The primary winding Lp3 and the secondary winding Ls3 are insulated from each other.

[0037] The other end of the first resonant capacitor Cr1 , the other end of the second resonant capacitor Cr2 , and the other end of the third resonant capacitor Cr3 are connected to each other through a neutral line N1 .

[0038] Neutral line N1 is connected to a power line on the negative electrode side of DC power supply 30 via neutral line inductor Ln. Alternatively, neutral line N1 may be connected to a power line on the positive electrode side of DC power supply 30 via neutral line inductor Ln.

[0039] The resonant reactors Lr1, Lr2, and Lr3 are set to have the same inductance value L r When magnetic coupling is not used as in the second embodiment described later, the resonant reactors Lr1, Lr2, and Lr3 can use the leakage inductance of the high-frequency transformers T1, T2, and T3. The resonant capacitors Cr1, Cr2, and Cr3 are set to have equal electrostatic capacitance C r The inductance value L of the resonant reactors Lr1, Lr2, and Lr3 is r and the electrostatic capacitance C of the resonant capacitors Cr1, Cr2, and Cr3 r The inductance value L of the neutral line reactor Ln is determined by the expected resonant frequency. n is set to the same inductance value L as the resonant reactors Lr1, Lr2, and Lr3. r The same size is sufficient.

[0040] The high-frequency transformers T1, T2, and T3 can use high-frequency transformers of the same specifications. The primary windings Lp1, Lp2, and Lp3 have the same number of turns Np and are set to the same inductance value L. p The secondary windings Ls1, Ls2, and Ls3 are set to have equal turns Ns and equal inductance L. sThe ratio of the number of turns Np of the primary winding Lp to the number of turns Ns of the secondary winding Ls may be determined according to the ratio of the DC input voltage Vin to the DC output voltage Vo.

[0041] The negative electrode (cathode) of the first rectifier diode D1a is connected to the negative electrode side of the secondary winding Ls1 of the first high-frequency transformer T1, and the negative electrode of the second rectifier diode D1b is connected to the positive electrode side of the secondary winding Ls1 of the first high-frequency transformer T1. The first rectifier circuit 51 is composed of the first rectifier diode D1a and the second rectifier diode D1b. The neutral point of the secondary winding Ls1 of the first high-frequency transformer T1 is connected to one end of the output capacitor Co, and the positive electrodes (anodes) of the first rectifier diode D1a and the second rectifier diode D1b are connected to the other end of the output capacitor Co, so that the AC voltage output to both ends of the secondary winding Ls1 is full-wave rectified and smoothed.

[0042] The cathode of the third rectifier diode D2a is connected to the cathode side of the secondary winding Ls2 of the second high-frequency transformer T2, and the cathode of the fourth rectifier diode D2b is connected to the anode side of the secondary winding Ls2 of the second high-frequency transformer T2. The second rectifier circuit 52 is composed of the third rectifier diode D2a and the fourth rectifier diode D2b. The neutral point of the secondary winding Ls2 of the second high-frequency transformer T2 is connected to one end of the output capacitor Co, and the anodes of the third rectifier diode D2a and the fourth rectifier diode D2b are connected to the other end of the output capacitor Co, so that the AC voltage output to both ends of the secondary winding Ls2 is smoothed while being full-wave rectified.

[0043] The cathode of the fifth rectifier diode D3a is connected to the cathode side of the secondary winding Ls3 of the third high-frequency transformer T3, and the cathode of the sixth rectifier diode D3b is connected to the anode side of the secondary winding Ls3 of the third high-frequency transformer T3. The third rectifier circuit 53 is composed of the fifth rectifier diode D3a and the sixth rectifier diode D3b. The neutral point of the secondary winding Ls3 of the third high-frequency transformer T3 is connected to one end of the output capacitor Co, and the anodes of the fifth rectifier diode D3a and the sixth rectifier diode D3b are connected to the other end of the output capacitor Co, so that the AC voltage output to both ends of the secondary winding Ls3 is smoothed while being full-wave rectified.

[0044] In addition, although the rectifying circuits 51 , 52 , and 53 use rectifying diodes as an example, any configuration is possible as long as the output voltages of the secondary-side windings Ls1 , Ls2 , and Ls3 can be rectified.

[0045] The first LLC resonant converter is composed of a first series circuit S1, a first resonant circuit 41, a first high-frequency transformer T1, and a first rectifier circuit 51. Similarly, the second LLC resonant converter is composed of a second series circuit S2, a second resonant circuit 42, a second high-frequency transformer T2, and a second rectifier circuit 52, and the third LLC resonant converter is composed of a third series circuit S3, a third resonant circuit 43, a third high-frequency transformer T3, and a third rectifier circuit 53.

[0046] The outputs of the first to third LLC resonant converters are connected in parallel to both ends of the output capacitor Co, and output a DC output voltage Vo.

[0047] The multi-phase LLC resonant converter circuit 10 includes a control circuit 60 connected to gates of the switches Q11, Q12, Q21, Q22, Q31, and Q32 to control on and off of the switches Q11, Q12, Q21, Q22, Q31, and Q32.

[0048] The control circuit 60 generates a first resonant current ir1 flowing through the first resonant circuit 41 by alternately turning on and off the first switch Q11 and the second switch Q12 of the first series circuit S1. The control circuit 60 generates a second resonant current ir2 flowing through the second resonant circuit 42 by alternately turning on and off the first switch Q21 and the second switch Q22 of the second series circuit S2. The control circuit 60 generates a third resonant current ir3 flowing through the third resonant circuit 43 by alternately turning on and off the first switch Q31 and the second switch Q32 of the third series circuit S3.

[0049] The control circuit 60 controls the gate signals for turning on and off the switches Q11 , Q12 , Q21 , Q22 , Q31 , and Q32 at a predetermined frequency f, thereby generating resonant currents ir1 , ir2 , and ir3 having the predetermined frequency f.

[0050] The control circuit 60 has a multi-phase operation mode and a single-phase operation mode. The multi-phase operation mode operates all of the first, second, and third LLC resonant converters of the multi-phase LLC resonant converter circuit 10. The single-phase operation mode operates any one of the first, second, and third LLC resonant converters of the multi-phase LLC resonant converter circuit 10 and stops the operations of the other LLC resonant converters.

[0051] In the multi-phase operation mode, the control circuit 60 controls the opening and closing of all switches Q11, Q12, Q21, Q22, Q31, and Q32 of the series circuits S1, S2, and S3 so that the resonant currents ir1, ir2, and ir3 flowing through the resonant circuits 41, 42, and 43 have a phase difference of 360° / 3=120° with each other.

[0052] Resonant frequency f in multi-phase operation mode r1 The resonant frequency of the resonant circuits 41 , 42 , and 43 is expressed as in Formula 1.

[0053] [Number 1]

[0054]

[0055] In the multi-phase operation mode, the predetermined frequency f, which is the switching frequency for turning on and off the switch, is determined based on the resonant frequency f of the resonant circuits 41, 42, and 43. r1 Just use formula 1 to set it.

[0056] As a result, resonant currents iri1 , ir2 , and ir3 are generated which flow through the resonant circuits 41 , 42 , and 43 .

[0057] When the DC input voltage Vin of the DC power supply 30 is at a rated value (e.g., 380 V) in the multi-phase operation mode, the components of the resonant currents ir1, ir2, and ir3 having a phase difference of 120° are eliminated, so the current ir1+ir2+ir3 flowing through the neutral line N1 is generally substantially zero. Figure 8 (a) Similarly, the neutral line current in flowing through the neutral line N1 is the same as that shown in the first conventional example. Figure 8 (b) Likewise.

[0058] When the DC input voltage Vin of the DC power source 30 is lower than the rated value (for example, 300 V) in the multi-phase operation mode, if the switching frequency f is lower than f r1 If the voltage is increased, for example, in the case of the first conventional example, the neutral line N1 will have a voltage as follows: Fig. 9 (b) shows a third harmonic component of the neutral line current in. In this regard, as in the first embodiment, by connecting a neutral line reactor Ln between the neutral line N1 and the power line on the negative side (or positive side) of the DC power supply 50, the generation of the third harmonic component of the neutral line current in can be suppressed. Figure 2 Showing this situation, Figure 2 (a) is the resonant current ir flowing through a resonant circuit during the boost operation. Figure 2 (b) is the neutral line current in flowing through the neutral line N1 during the step-up operation.

[0059] In this way, Figure 2 The neutral line current in flowing through the neutral line N1 during the voltage step-up operation in the first embodiment shown in (b) is Fig. 9 Compared with the neutral line current in flowing through the neutral line N1 during the boost operation in the first conventional example shown in (b), the magnitude of the neutral line current in can be suppressed. Figure 2 In the first embodiment shown in (a), the resonant current ir flowing through one resonant circuit during the step-up operation is Fig. 9 Compared with the resonant current ir flowing through one resonant circuit during the step-up operation in the first conventional example shown in (a), the magnitude of the harmonic component can be suppressed.

[0060] Figure 3 When the DC input voltage Vin is below the rated value (380V), Figure 8 The structure of the first conventional example shown (dashed line) and Figure 1 The diagram is a comparison of the effective values ​​of the resonant current ir (ir1, ir2, ir3) flowing through any of the resonant circuits 41, 42, 43 in the configuration of the first embodiment (solid line) shown in FIG. 1 (the inductance value is set to L n =L r ).according to Figure 3 It can be seen that in the first embodiment, the increase in the effective value of the resonant current can be suppressed compared to the first conventional example.

[0061] In the single-phase operation mode, the control circuit 60 controls the opening and closing of the first switch and the second switch of any one of the series circuits of the first, second, and third LLC resonant converters, and controls the first switches and the second switches of the other two LLC resonant converters in a manner that they are closed. Here, in the single-phase operation mode, the following case is considered, in which the control circuit 60 controls the opening and closing of the first switch Q11 and the second switch Q12 of the series circuit S1 of the first LLC resonant converter, and controls the first switches Q21, Q31 and the second switches Q22, Q32 of the series circuits S2 and S3 of the second and third LLC resonant converters in a manner that they are closed.

[0062] Resonant frequency f in single-phase operation mode r2 Considering the resonant circuit 41 and the neutral line reactor Ln, it is as shown in Equation 2.

[0063] [Number 2]

[0064]

[0065] In the single-phase operation mode, the switching frequency f of the switches Q11 and Q12 of the first series circuit S1 is turned on and off according to the resonant frequency f of formula 2. r2 Just set it.

[0066] Here, consider the case where the resonant inductors Lr1, Lr2, Lr3 and the neutral line inductor Ln are wound on the same specification magnetic core. If the number of turns of the resonant inductors Lr1, Lr2, Lr3 is set to Nr, the number of turns of the neutral line inductor Ln is set to Nn, and the turns ratio is set to Nn / Nr=n, then Equation 2 can be rewritten as Equation 3.

[0067] [Number 3]

[0068]

[0069] In addition, as the magnetic core, for example, a three-legged magnetic core can be used, and each of the reactors Lr1, Lr2, Lr3, and Ln can be wound around the middle leg of the three-legged magnetic core, but other methods can also be used.

[0070] In the polyphase LLC resonant converter circuit 10 according to the first embodiment, the neutral line N1 is connected to the power line on the negative side (or positive side) of the DC power supply 30 via the neutral line reactor Ln, so that it can operate by switching between the polyphase operation mode and the single-phase operation mode. In addition, the neutral line reactor Ln exhibits a high impedance value with respect to the AC current of high-frequency components. Therefore, during the boost operation in the polyphase operation mode, harmonic components such as third harmonics included in the resonant currents ir1, ir2, and ir3 flowing through the resonant circuits 41, 42, and 43 are suppressed, and the increase in the effective value is suppressed. At the same time, harmonic components such as third harmonics included in the neutral line current in flowing from the neutral line N1 to the negative (or positive) pole of the DC power supply 30 via the neutral line reactor Ln can be suppressed.

[0071] In the first embodiment, a three-phase LLC resonant converter circuit with a phase number N = 3 has been described, but it can also have a structure such as a polyphase LLC resonant converter circuit including N LLC resonant converters with N = 2 or N > 3. In this case, during the polyphase operation mode, it operates through the control circuit 60 so that the phase difference of the resonant current ir of each LLC resonant converter is 360° / N. The control circuit 60 can be used to operate N1 (N1 < N) of the N LLC resonant converters and stop the operation of the remaining (N - N1) LLC resonant converters. The so-called "controlling the opening and closing of the first switch and the second switch of the first LLC resonant converter at the second frequency corresponding to the second resonant frequency of the resonant circuit and the neutral line reactor, and closing the first switch and the second switch of the second to the Nth LLC resonant converters" in this specification can also mean that the "first LLC resonant converter" is a plurality of LLC resonant converters. For example, it is also possible to control 2 switches out of 4 LLC resonant converters at the second frequency and close the remaining 2 switches. Alternatively, it is also possible to control 2 or 3 switches out of 6 LLC resonant converters at the second frequency and close the remaining 4 or 3 switches.

[0072] In addition, during the single-phase operation mode, only any one of the N LLC resonant converters with N = 2 or N > 3 needs to operate. In this case, it can also operate in the same manner as the single-phase operation mode of the polyphase LLC resonant converter circuit 10 according to the first embodiment.

[0073] (Second Embodiment)

[0074] Figure 4 : is a circuit diagram showing the configuration of a multi-phase LLC resonant converter circuit 10A according to the second embodiment.

[0075] Relative to Figure 1 The multiphase LLC resonant converter circuit 10A of the first embodiment shown is different in that it includes three neutral line reactors connected in series, namely, a first neutral line reactor Ln1, a second neutral line reactor Ln2, and a third neutral line reactor Ln3. Only the differences will be described here, and the description of the common points will be omitted.

[0076] like Figure 4 , 5 As shown, the first neutral line inductor Ln1 is magnetically coupled to the first resonant inductor Lr1 through the first magnetic core Tn1, the second neutral line inductor Ln2 is magnetically coupled to the second resonant inductor Lr2 through the second magnetic core Tn2, and the third neutral line inductor Ln3 is magnetically coupled to the third resonant inductor Lr3 through the third magnetic core Tn3.

[0077] exist Figure 5 In the embodiment, a tripod core is used as a magnetic core, and each reactor is wound around a leg in the middle of the tripod cores Tn1, Tn2, and Tn3. An air gap is provided near the center of the leg in the middle of the tripod cores Tn1, Tn2, and Tn3.

[0078] As Figure 5 A variation of Figure 6 In FIG. 1 , a five-legged core Tn is used as a core, and each reactor is wound around three legs on the center side. The three legs on the center side of the five-legged core Tn have air gaps near the center of each leg. When the number of phases N is other than 3, a core with (N+2) legs can be used, and a similar structure can be set. In addition, the core can be used according to the intended use state. Figure 5 , 6 Any core other than the cores shown in FIG.

[0079] exist Figure 5 , 6In the figure, for convenience, the first neutral line reactor Ln1 and the first resonant reactor Lr1, the second neutral line reactor Ln2 and the second resonant reactor Lr2, and the third neutral line reactor Ln3 and the third resonant reactor Lr3 are separately represented. In fact, in order to improve the mutual coupling, the first neutral line reactor Ln1 and the first resonant reactor Lr1, the second neutral line reactor Ln2 and the second resonant reactor Lr2, and the third neutral line reactor Ln3 and the third resonant reactor Lr3 are set to be tightly coupled by stacking or bifilar winding, respectively.

[0080] By setting Figure 5 , 6 The structure can reduce the number of magnetic cores compared to the case where individual magnetic cores are used for each of the resonant inductors Lr1, Lr2, Lr3 and the neutral line inductor Ln as in the first embodiment.

[0081] In the second embodiment, the resonance frequency f of the three-phase operation mode is r3 In terms of the fundamental waves of the resonant currents ir1, ir2, and ir3, the phase difference is 120°, and the fundamental wave component of the current in flowing through the neutral line N1 is zero. Since the self-inductance of the neutral line reactors Ln1, Ln2, and Ln3 and the mutual inductance between the resonant reactors Lr1, Lr2, and Lr3 and the neutral line reactors Ln1, Ln2, and Ln3 can be ignored, it is expressed as in Formula 4 in the same manner as in the first embodiment.

[0082] [Number 4]

[0083]

[0084] On the other hand, the third harmonic current superimposed on the resonant current ir1, ir2, ir3 becomes the same phase in each phase, and the current superimposed on the third harmonic current of each phase flows through the neutral line N1 and the neutral line reactors Ln1, Ln2, Ln3. Therefore, the third harmonic current generates components of the self-inductance of the neutral line reactors Ln1, Ln2, Ln3 and the mutual inductance of the resonant reactors Lr1, Lr2, Lr3 and the neutral line reactors Ln1, Ln2, Ln3.

[0085] Here, the number of turns of the resonant reactors Lr1, Lr2, and Lr3 is assumed to be Nr. In addition, in order to compare with the first embodiment, the total number of turns of the neutral line reactors Ln1, Ln2, and Ln3 is assumed to be Nn, that is, the number of turns of each neutral line reactor Ln1, Ln2, and Ln3 is assumed to be Nn / 3. The turn ratio of each resonant reactor Lr1, Lr2, and Lr3 to the neutral line reactor Ln1, Ln2, and Ln3 is assumed to be (Nn / 3) / Nr=n / 3. If the self-inductance value of each neutral line reactor Ln1, Ln2, and Ln3 is assumed to be ln , then considering the self-inductance and mutual inductance, the resonant inductance value L of each resonant reactor for the third harmonic current rt As shown in formula 5.

[0086] [Number 5]

[0087]

[0088] Here, k is the coupling coefficient between the resonant reactor winding and the neutral line reactor winding. In this way, the inductance value of the resonant reactor Lr can be increased relative to the third harmonic.

[0089] The total neutral line inductance L of three series-connected neutral line reactors for the third harmonic current in three-phase operation mode nt As shown in Formula 6.

[0090] [Number 6]

[0091]

[0092] Note that the resonant reactor is considered to be connected in parallel, and the total inductance value L for the third harmonic current is t As shown in Formula 7.

[0093] [Number 7]

[0094]

[0095] On the other hand, the total inductance value L for the third harmonic current in the first embodiment is t As shown in formula 8.

[0096] [Number 8]

[0097]

[0098] The total inductance value L of the second embodiment for the third harmonic current t The condition that becomes greater than that of the first embodiment is obtained as in Formula 9 by comparing Formula 7 and Formula 8.

[0099] [Number 9]

[0100] n<k

[0101] ...(Formula 9)

[0102] That is, in the case where the coupling coefficient is k to 1 and the turns ratio n<1 (n / 3<1 / 3=0.333) in the strong coupling, the total inductance value of the second embodiment becomes larger than the total inductance value of the first embodiment compared to the third harmonic current. In other words, in the case where the turns ratio n<1 (n / 3<0.333), even if the total number of turns of the neutral line reactors Ln1, Ln2, and Ln3 of the second embodiment is set smaller than the number of turns Nn of the neutral line reactor Ln of the first embodiment, the total inductance value of the second embodiment can be made substantially equal to the total inductance value of the first embodiment.

[0103] Next, consider the total resonant inductance value L in single-phase operation mode. rt1 Considering the self-inductance and mutual inductance of Lr1, the total resonant inductance value L in single-phase operation is rt1 As shown in formula 10.

[0104] [Number 10]

[0105]

[0106] Similarly, consider the total neutral line inductance L in single-phase operation mode. nt1 The total neutral line inductance value L during single-phase operation nt1 As shown in Formula 11, for Ln1, self-inductance and mutual inductance are considered, and for Ln2 and Ln3, only self-inductance is considered.

[0107] [Number 11]

[0108]

[0109] Therefore, the resonant frequency f in single-phase operation mode is r4 For the resonant reactor Lr, the total inductance value L including the mutual inductance is also used. rt1 , thus as shown in Equation 12.

[0110] [Number 12]

[0111]

[0112] In the single-phase operation mode, the switching frequency f of the switches Q11 and Q12 of the first series circuit S1 is turned on and off according to the resonant frequency f of formula 11. r4 Just set it.

[0113] In the multi-phase LLC resonant converter circuit 10A according to the second embodiment, as in the first embodiment, the neutral line N1 is connected to the power line on the negative side (or positive side) of the DC power supply 30 via the neutral line reactors Ln1, Ln2, and Ln3, so that the operation of switching between the multi-phase operation mode and the single-phase operation mode can be performed. The neutral line reactors Ln1, Ln2, and Ln3 show a high impedance value for the AC current of the high frequency component, so that during the step-up operation in the multi-phase operation mode, the harmonic components such as the third harmonic contained in the resonant current ir1, ir2, and ir3 flowing through the resonant circuits 41, 42, and 43 are suppressed to suppress the increase in the effective value. Furthermore, the harmonic components such as the third harmonic contained in the neutral line current in flowing from the neutral line N1 through the neutral line reactors Ln1, Ln2, and Ln3 through the power line on the negative side (or positive side) of the DC power supply 30 can be suppressed.

[0114] Description of Reference Numerals

[0115] 10. 10A Multi-Phase LLC Resonant Converter Circuit

[0116] 30 DC power supply

[0117] 41, 42, 43 Resonance circuit

[0118] 51, 52, 53 rectifier circuit

[0119] Co output capacitor

[0120] Cr1, Cr2, Cr3 resonant capacitors

[0121] fSwitching frequency

[0122] f r1 、f r2 、f r3 、f r4 Resonant frequency

[0123] inNeutral current

[0124] ir, ir1, ir2, ir3 resonant current

[0125] Ln neutral line reactor

[0126] Lr1, Lr2, Lr3 resonant reactor

[0127] N1 neutral line

[0128] Q11, Q21, Q31 first switch

[0129] Q21, Q22, Q32 second switch

[0130] S1, S2, S3 series circuit

[0131] T1, T2, T3 high frequency transformer

[0132] Vin DC input voltage

[0133] Vo DC output voltage

Claims

1. A multi-phase LLC resonant converter circuit, which is used to convert a first DC voltage of a DC power supply into a second DC voltage for output, The multi-phase LLC resonant converter circuit includes first to N-th LLC resonant converters, where N is an integer greater than 2. The first to Nth LLC resonant converters respectively have: a series circuit connected in parallel to the DC power supply, in which a first switch and a second switch are connected in series; A high frequency transformer having a primary winding and a secondary winding; a resonant circuit including a resonant inductor connected between a connection point between the first switch and the second switch and one end of the primary-side winding, and a resonant capacitor having one end connected to the other end of the primary-side winding; as well as a rectifier circuit, used for rectifying the output of the secondary winding, The multi-phase LLC resonant converter circuit further comprises: a neutral line connecting the other ends of the resonant capacitors of the first to Nth LLC resonant converters to each other; A neutral line reactor connected between the neutral line and a power line of either the positive electrode or the negative electrode of the DC power source; as well as An output capacitor is connected in parallel to the output side of the rectifier circuit of the first to Nth LLC resonant converters and is used to output the second DC voltage at both ends.

2. The multi-phase LLC resonant converter circuit according to claim 1, further comprising: a control circuit, configured to control the on and off of the first switch and the second switch of the first to Nth LLC resonant converters, The control circuit comprises: a multi-phase operation mode, controlling the opening and closing of each of the first switch and the second switch of the first to N-th LLC resonant converters by a first frequency corresponding to a first resonant frequency of the resonant circuit and in such a manner that the resonant current of the first frequency flowing through the resonant circuit of the first to N-th LLC resonant converters becomes a phase difference of 360° / N; and In the single-phase operation mode, the first switch and the second switch of the first LLC resonant converter are turned on and off by controlling the second frequency corresponding to the second resonant frequency of the resonant circuit and the neutral line inductor, and the first switch and the second switch of the second to N-th LLC resonant converters are turned off.

3. The multi-phase LLC resonant converter circuit according to claim 1 or 2, wherein: The resonant inductor is the leakage inductance of the high-frequency transformer.

4. The multi-phase LLC resonant converter circuit according to claim 1 or 2, wherein: The neutral line reactor comprises N reactors having equal inductance values ​​connected in series, namely, first to Nth neutral line reactors. The resonant reactors of the first to Nth LLC resonant converters and the first to Nth neutral line reactors are magnetically coupled through first to Nth magnetic cores, respectively.

5. The multi-phase LLC resonant converter circuit according to claim 1 or 2, wherein: The neutral line reactor comprises N reactors having equal inductance values ​​connected in series, namely, first to Nth neutral line reactors. The resonant inductors of the first to Nth LLC resonant converters are magnetically coupled with the first to Nth neutral line inductors through the second to (N+1)th middle legs of the (N+2)th leg magnetic core, respectively.

6. The multi-phase LLC resonant converter circuit as claimed in claim 4, wherein: The resonant reactors of the first to Nth LLC resonant converters and the first to Nth neutral line reactors are stacked.

7. The multi-phase LLC resonant converter circuit as claimed in claim 4, wherein: The resonant reactors of the first to Nth LLC resonant converters and the first to Nth neutral line reactors are bifilar-wound.

8. The multi-phase LLC resonant converter circuit of claim 5, wherein: The resonant reactors of the first to Nth LLC resonant converters and the first to Nth neutral line reactors are stacked.

9. The multi-phase LLC resonant converter circuit of claim 5, wherein: The resonant reactors of the first to Nth LLC resonant converters and the first to Nth neutral line reactors are bifilar-wound.

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