Multiphase LLC resonant converter circuit

Abstract

To provide a multi-phase LLC resonant converter circuit capable of suppressing an increase in a resonance current at a step-up operation of an input voltage and switching a multi-phase operation and a single-phase operation.SOLUTION: A multi-phase LLC resonant converter circuit 10 comprises: first to third LLC resonant converters each of which includes series circuits S1-S3 to which a first switch and a second switch connected in parallel to a DC power supply 30 are connected in series, high-frequency transformers T1-T3 including a primary-side winding and a secondary-side winding, resonant circuits 41-43 including resonant reactors Lr1-Lr3 connected between a connection point between the first switch and the second switch and one end of the primary-side winding and resonant capacitors Cr1-Cr3 in which one end is connected to the other end of the primary-side winding, and rectification circuits 51-53 rectifying an output from the secondary-side winding; a neutral line N1 connecting 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 line of the DC power supply.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multiphase LLC resonant converter circuit for converting a first DC voltage of a DC power supply into a second DC voltage and outputting it. [Background technology]

[0002] Conventionally, a multiphase (N-phase) LLC resonant converter circuit is known as a converter circuit for converting a first DC voltage of a DC power supply into a second DC voltage for output (see Patent Documents 1-4). In this circuit, multiple (N) LLC resonant converters are connected in parallel to a DC power supply, and the switches of each LLC resonant converter are turned on and off so that the resonant current of the resonant circuit connected to the primary winding of the high-frequency transformer of each LLC resonant converter has a phase difference of 360° / N.

[0003] When an LLC resonant converter is powered by a DC power supply at its rated voltage (e.g., 380V), it is best to design the switching frequency of the switch to be near the resonant frequency of the resonant circuit. On the other hand, when the DC input voltage drops (e.g., to 300V), boosting the voltage by lowering the switching frequency increases circuit losses and reduces efficiency. When considering the same output power, it is natural that efficiency decreases to some extent because the DC input current increases inversely proportionally to the decrease in DC input voltage. However, in reality, the peak value of the resonant current flowing through the resonant circuit increases more than the increase in the DC input current. The majority of the unwanted current increasing the resonant current is a third-harmonic current with a frequency three times that of the switching frequency.

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

[0005] Figure 10 shows a second conventional example of a multiphase (three-phase) LLC resonant converter circuit 12. In this circuit, the neutral wire N1 to which 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 connected is floating, and there is no path for the third harmonic current (see Patent Document 2). In the second conventional example of a multiphase LLC resonant converter circuit 12, the increase in resonant current during boost operation when the DC input voltage Vin decreases can be suppressed. However, since it is not possible to switch from multiphase operation mode to single-phase operation mode, the efficiency is low when the load is reduced.

[0006] Figure 11 shows a third conventional example of a multiphase LLC resonant converter circuit 13. This circuit has both a first neutral wire N1 connected to the power supply line of the DC power supply Vin, as in the first conventional example, and a floating second neutral wire N2, as in the second conventional example (see Patent Documents 3 and 4). In the multiphase operation mode, the third conventional example of the multiphase LLC resonant converter circuit 13 can naturally balance the AC resonant currents ir1, ir2, and ir3 flowing through the resonant circuits 41, 42, and 43, and can also switch from the multiphase operation mode to the single-phase operation mode. However, when the DC input voltage Vin of the DC power supply 30 drops from its rated value (e.g., 380V) to (e.g., 300V), if the switching frequency of the switch is lowered to perform a boost operation, the effective value of the resonant current ir increases due to the generation of a third harmonic component in the resonant current ir(ir1, ir2, ir3), as shown in Figure 9(a), similar to the first conventional example. Furthermore, as shown in Figure 9(b), a third harmonic current flows through the first neutral wire N1 as the neutral wire current in. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Patent Publication No. 2008-0298093 [Patent Document 2] U.S. Publication No. 9780678 [Patent Document 3] Patent No. 6696617 [Patent Document 4] Japanese Patent Publication No. 2021-153382 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] One aspect of the present invention provides a multiphase LLC resonant converter circuit that, in multiphase operation mode, can suppress the increase in resonant current and the generation of third-harmonic current flowing through the neutral wire during boost operation when the DC input voltage falls below the rated voltage, and that can switch from multiphase operation mode to single-phase operation mode. [Means for Solving the Problem]

[0009] A multiphase LLC resonant converter circuit according to one aspect of the present invention is a multiphase LLC resonant converter circuit for converting a first DC voltage from a DC power supply into a second DC voltage and outputting the same, the multiphase LLC resonant converter circuit comprising: first to N-th LLC resonant converters (N is an integer of 2 or more), each of the first to N-th LLC resonant converters comprising: 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 including a primary winding and a secondary winding; a resonant circuit including a resonant reactor connected between a connection point of 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 an output of the secondary winding; a neutral wire connecting the other ends of the resonant capacitors of the first to N-th LLC resonant converters to each other; a neutral reactor connected between the neutral wire and either a positive power supply line or a negative power supply line of the DC power supply; and an output capacitor connected in parallel to an output side of the rectifier circuits of the first to N-th LLC resonant converters for outputting the second DC voltage across both ends thereof. [Effect of the Invention]

[0010] According to the above aspect, in a multiphase operation mode, it is possible to provide a multiphase LLC resonant converter circuit that can suppress an increase in resonant current and generation of third harmonic current flowing through the neutral wire during a step-up operation when a DC input voltage drops below a rating, and is capable of being switched from the multiphase operation mode to a single-phase operation mode. [Brief Description of the Drawings]

[0011] [Figure 1] FIG. 1 is a circuit diagram showing a configuration of the multiphase LLC resonant converter circuit according to a first embodiment. [Figure 2]Fig. 2(a) is a time chart showing the waveform of a resonant current when a voltage (300V) of a DC power supply is subjected to a step-up operation in the multi-phase LLC resonant converter circuit according to the first embodiment, and Fig. 2(b) is a time chart showing the waveform of a neutral line current when a voltage (300V) of the DC power supply is subjected to the step-up operation. [Figure 3] Fig. 3 is a diagram plotting the effective value of a resonant current with respect to the value of a DC input voltage (rated: 380V) when a step-up operation of the DC input voltage is performed in the multi-phase LLC resonant converter circuits of the first embodiment (solid line) and the first conventional example (dashed line). [Figure 4] Fig. 4 is a circuit diagram showing the configuration of a multi-phase LLC resonant converter circuit according to a second embodiment. [Figure 5] Fig. 5 is a diagram showing a configuration in which a resonant reactor and a neutral line reactor used in the multi-phase LLC resonant converter circuit according to the second embodiment are magnetically coupled by separate cores. [Figure 6] Fig. 6 is a diagram showing a configuration 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 by a five-legged core. [Figure 7] Fig. 7 is a circuit diagram showing the configuration of a multi-phase LLC resonant converter circuit of a first conventional example. [Figure 8] Fig. 8(a) is a time chart showing the waveform of a resonant current when the voltage of a DC power supply is at a rated value (380V) in the multi-phase LLC resonant converter circuit of the first conventional example, and Fig. 8(b) is a time chart showing the waveform of a neutral line current when the voltage of the DC power supply is at the rated value (380V). [Figure 9] Fig. 9(a) is a time chart showing the waveform of a resonant current when a voltage (300V) of a DC power supply is subjected to a step-up operation in the multi-phase LLC resonant converter circuit of the first conventional example, and Fig. 9(b) is a time chart showing the waveform of a neutral line current when a voltage (300V) of the DC power supply is subjected to the step-up operation. [Figure 10] Fig. 10 is a circuit diagram showing the configuration of a multi-phase LLC resonant converter circuit of a second conventional example. [Figure 11]Figure 11 is a circuit diagram showing the configuration of a third conventional example of a multiphase LLC resonant converter circuit. [Modes for carrying out the invention]

[0012] The multiphase LLC resonant converter circuit according to an embodiment of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiments described below.

[0013] (First Embodiment) Figure 1 is a circuit diagram showing the configuration of the multiphase LLC resonant converter circuit 10 according to the first embodiment. Here, we will describe the configuration of the multiphase LLC resonant converter circuit 10 when the number of phases N=3 (three-phase LLC resonant converter circuit).

[0014] The multiphase 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, 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, all connected in parallel to a DC power supply 30 having a DC voltage value Vin.

[0015] In the first embodiment, N-channel MOSFETs are used for each switch Q11, Q12, Q21, Q22, Q31, and Q32, but other switching elements may be used.

[0016] One end of the first resonant reactor Lr1 is connected to the connection point between 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 between 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 between the first switch Q31 and the second switch Q32 of the third series circuit S3.

[0017] 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 the first resonant circuit 41. The first high-frequency transformer T1 comprises 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.

[0018] One end of the primary winding Lp2 of the second high-frequency transformer T2 is connected to the other end of the second resonant reactor 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 comprises a core, a primary winding Lp2, and a secondary winding Ls2. The primary winding Lp2 and the secondary winding Ls2 are insulated from each other.

[0019] One end of the primary winding Lp3 of the third high-frequency transformer T3 is connected to the other end of the third resonant reactor 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 comprises a core, a primary winding Lp3, and a secondary winding Ls3. The primary winding Lp3 and the secondary winding Ls3 are insulated from each other.

[0020] 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 by a neutral wire N1.

[0021] The neutral wire N1 is connected to the negative power line of the DC power supply 30 via the neutral wire reactor Ln. Alternatively, the neutral wire N1 may be connected to the positive power line of the DC power supply 30 via the neutral wire reactor Ln.

[0022] Each of the resonant reactors Lr1, Lr2, and Lr3 has an equal inductance value L rIt is set to the following. When magnetic coupling is not used as in the second embodiment described later, the leakage inductance of the high-frequency transformers T1, T2, T3 can also be used for each of the resonant reactors Lr1, Lr2, Lr3. Each of the resonant capacitors Cr1, Cr2, Cr3 has an equal capacitance C r The inductance values ​​L of the resonant reactors Lr1, Lr2, and Lr3 are set to L. r and the capacitance C of the resonant capacitors Cr1, Cr2, and Cr3 r This is determined by the desired resonant frequency value. The inductance value L of the neutral wire reactor Ln. n This is the inductance value L of the resonant reactors Lr1, Lr2, and Lr3. r You should set it to roughly the same size.

[0023] High-frequency transformers T1, T2, and T3 can be of the same specifications, and the primary windings Lp1, Lp2, and Lp3 each have the same number of turns Np and the same inductance value L. p The settings are configured such that the secondary windings Ls1, Ls2, and Ls3 each have the same number of turns Ns and the same inductance value L s It is set to this. The ratio of the number of turns Np of the primary winding Lp to the number of turns Ns of the secondary winding Ls should be determined according to the ratio of the DC input voltage Vin to the DC output voltage Vo.

[0024] The cathode of the first rectifier diode D1a is connected to the negative terminal side of the secondary winding Ls1 of the first high-frequency transformer T1, and the cathode of the second rectifier diode D1b is connected to the positive terminal side of the secondary winding Ls1 of the first high-frequency transformer T1. The first rectifier circuit 51 is formed by 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 anodes of the first rectifier diode D1a and the second rectifier diode D1b are connected to the other end of the output capacitor Co, thereby full-wave rectifying and smoothing the AC voltage output across the secondary winding Ls1.

[0025] The cathode of the third rectifier diode D2a is connected to the negative terminal 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 positive terminal side of the secondary winding Ls2 of the second high-frequency transformer T2. The third rectifier diode D2a and the fourth rectifier diode D2b constitute the second rectifier circuit 52. 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, thereby full-wave rectifying and smoothing the AC voltage output across the secondary winding Ls2.

[0026] The cathode of the fifth rectifier diode D3a is connected to the negative terminal 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 positive terminal side of the secondary winding Ls3 of the third high-frequency transformer T3. The fifth rectifier diode D3a and the sixth rectifier diode D3b constitute the third rectifier circuit 53. 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, thereby full-wave rectifying and smoothing the AC voltage output across the secondary winding Ls3.

[0027] Although the rectifier circuits 51, 52, and 53 are shown as examples using rectifier diodes, any configuration is acceptable as long as it can rectify the output voltages of the secondary windings Ls1, Ls2, and Ls3.

[0028] A first LLC resonant converter is formed by a first series circuit S1, a first resonant circuit 41, a first high-frequency transformer T1, and a first rectifier circuit 51. Similarly, a second LLC resonant converter is formed by a second series circuit S2, a second resonant circuit 42, a second high-frequency transformer T2, and a second rectifier circuit 52, and a third LLC resonant converter is formed by a third series circuit S3, a third resonant circuit 43, a third high-frequency transformer T3, and a third rectifier circuit 53.

[0029] The outputs of the first to third LLC resonant converters are connected in parallel across the output capacitor Co, and a DC output voltage Vo is output.

[0030] The multiphase LLC resonant converter circuit 10 is connected to the gates of switches Q11, Q12, Q21, Q22, Q31, and Q32 and includes a control circuit 60 for controlling the on / off state of switches Q11, Q12, Q21, Q22, Q31, and Q32.

[0031] The control circuit 60 generates a first resonant current ir1 flowing through the first resonant circuit 41 by alternately switching 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 switching 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 switching on and off the first switch Q31 and the second switch Q32 of the third series circuit S3.

[0032] The control circuit 60 generates resonant currents ir1, ir2, and ir3 having a predetermined frequency f by controlling the gate signals that turn switches Q11, Q12, Q21, Q22, Q31, and Q32 on and off at a predetermined frequency f.

[0033] The control circuit 60 has a multiphase operation mode in which all of the first, second, and third LLC resonant converters of the multiphase LLC resonant converter circuit 10 are operated, and a single-phase operation mode in which any one of the first, second, and third LLC resonant converters of the multiphase LLC resonant converter circuit 10 is operated and the operation of the other LLC resonant converters is stopped.

[0034] When operating in multiphase mode, the control circuit 60 controls the on / off state of all switches Q11, Q12, Q21, Q22, Q31, Q32 in series circuits S1, S2, S3 so that the resonant currents ir1, ir2, ir3 flowing through the resonant circuits 41, 42, 43 have a phase difference of 360° / 3 = 120° from each other.

[0035] In the multiphase operation mode, the resonance frequency f r1 is expressed as shown in Equation 1 as the resonance frequency provided by resonance circuits 41, 42 and 43.

Math.

[0036] In the multiphase operation mode, the predetermined frequency f, which serves as the switching frequency for turning on and off the switches, may be set in accordance with the resonance frequency f of the resonance circuits 41, 42 and 43 r1 which is given by Equation 1.

[0037] Accordingly, resonance currents iri1, ir2 and ir3 flowing through the resonance circuits 41, 42 and 43 are generated.

[0038] In the multiphase operation mode, when the DC input voltage Vin of the DC power supply 30 is at a rated value (e.g., 380 V), the resonance currents ir1, ir2 and ir3 having a phase difference of 120° from each other cancel out their components, so the current ir1+ir2+ir3 flowing through the neutral line N1 is normally substantially zero. At this time, the resonance current ir flowing through one resonance circuit is the same as that shown in FIG. 8(a) described in the first conventional example, and the neutral line current in flowing through the neutral line N1 is the same as that shown in FIG. 8(b) described in the first conventional example.

[0039] In the multiphase operation mode, when the DC input voltage Vin of the DC power supply 30 is less than the rated value (e.g., 300 V), the switching frequency f is set to f r1If the voltage is reduced to a smaller value to perform the boost operation, for example, in the first conventional example, a neutral wire current in with a third harmonic component, as shown in Figure 9(b), is generated in the neutral wire N1. In contrast, as in the first embodiment, by connecting a neutral wire reactor Ln between the neutral wire N1 and the power line on the negative (or positive) side of the DC power supply 50, the generation of a neutral wire current in with a third harmonic component can be suppressed. This is shown in Figure 2, where Figure 2(a) is the resonant current ir flowing through one resonant circuit during the boost operation, and Figure 2(b) is the neutral wire current in flowing through the neutral wire N1 during the boost operation.

[0040] Thus, the neutral wire current in flowing through the neutral wire N1 during the boost operation in the first embodiment shown in Figure 2(b) can be made to have a smaller magnitude compared to the neutral wire current in flowing through the neutral wire N1 during the boost operation in the first conventional example shown in Figure 9(b). Furthermore, the resonant current ir flowing through one resonant circuit during the boost operation in the first embodiment shown in Figure 2(a) can be made to have a smaller magnitude compared to the resonant current ir flowing through one resonant circuit during the boost operation in the first conventional example shown in Figure 9(a), which can have a smaller magnitude compared to the resonant current ir flowing through one resonant circuit during the boost operation in the first conventional example.

[0041] Figure 3 compares the effective values ​​of the resonant currents ir(ir1,ir2,ir3) flowing through any of the resonant circuits 41, 42, and 43 in the configuration of the first conventional example shown in Figure 8 (dashed line) and the configuration of the first embodiment shown in Figure 1 (solid line) when the DC input voltage Vin is less than or equal to the rated value (380V) (inductance value is L n =L r (Set to [value]). From Figure 3, it can be seen that in the first embodiment, the increase in the effective value of the resonant current is suppressed compared to the first conventional example.

[0042] When in single-phase operation mode, the control circuit 60 controls the on / off state of the first and second switches of one of the series circuits of the first, second, and third LLC resonant converters, while controlling the first and second switches of the other two LLC resonant converters to be turned off. Here, we consider the case where, when in single-phase operation mode, the control circuit 60 controls the on / off state of the first switch Q11 and second switch Q12 of the series circuit S1 of the first LLC resonant converter, while controlling 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 to be turned off.

[0043] Resonant frequency f in single-phase operation mode r2 This can be expressed as shown in Equation 2 by considering the resonant circuit 41 and the neutral wire reactor Ln.

number

[0044] In single-phase operation mode, the switching frequency f for turning switches Q11 and Q12 of the first series circuit S1 on and off is the resonant frequency f in Equation 2. r2 You can set it according to your needs.

[0045] Now, let's consider the case where the resonant reactors Lr1, Lr2, and Lr3 and the neutral reactor Ln are wound on a core of the same specifications. If we let Nr be the number of turns of the resonant reactors Lr1, Lr2, and Lr3, Nn be the number of turns of the neutral reactor Ln, and the turns ratio be Nn / Nr=n, then Equation 2 can be rewritten as Equation 3.

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[0046] For the core, for example, a tripod core can be used, and the respective reactors Lr1, Lr2, Lr3, and Ln can be wrapped around the middle leg of the tripod core, but other configurations may also be used.

[0047] In the multiphase LLC resonant converter circuit 10 according to the first embodiment, since the neutral line N1 is connected to the power supply line on the negative electrode side (or positive electrode side) of the DC power supply 30 via the neutral line reactor Ln, operation can be performed by switching between the multiphase operation mode and the single-phase operation mode. In addition, the neutral line reactor Ln exhibits a high impedance value for alternating current of high frequency components. Therefore, during a step-up operation in the multiphase operation mode, harmonic components such as third harmonics contained in the resonant currents ir1, ir2, and ir3 flowing through the resonant circuits 41, 42, and 43 are suppressed to inhibit an increase in the effective value, and harmonic components such as third harmonics contained in the neutral line current in flowing from the neutral line N1 to the negative electrode (or positive electrode) of the DC power supply 30 via the neutral line reactor Ln can be suppressed.

[0048] In the first embodiment, a three-phase LLC resonant converter circuit with the number of phases N=3 has been described, but a configuration like a multiphase LLC resonant converter circuit including N LLC resonant converters with N=2 or N>3 may also be adopted. In this case, in the multiphase operation mode, the control circuit 60 may operate the LLC resonant converters such that the phase difference of the resonant current ir of each LLC resonant converter becomes 360° / N. It is also possible to cause the control circuit 60 to operate N1 (N1<N) of the N LLC resonant converters and stop the operation of (N-N1) LLC resonant converters. As used herein, "controlling the on / off of the first switch and the second switch of the first LLC resonant converter at a second frequency corresponding to the second resonant frequency formed by the resonant circuit and the neutral line reactor, and turning off the first switches and the second switches of the second to N-th LLC resonant converters" allows the "first LLC resonant converter" to be a plurality of LLC resonant converters. For example, two switches among four LLC resonant converters may be controlled at the second frequency, and the remaining two switches may be turned off. Alternatively, two or three switches among six LLC resonant converters may be controlled at the second frequency, and the remaining four or three switches may be turned off.

[0049] Furthermore, in single-phase operation mode, only one of the N LLC resonant converters (N=2 or N>3) needs to be operated. Even in this case, it can operate in the same way as the single-phase operation mode of the multiphase LLC resonant converter circuit 10 according to the first embodiment.

[0050] (Second Embodiment) Figure 4 is a circuit diagram showing the configuration of the multiphase LLC resonant converter circuit 10A according to the second embodiment.

[0051] The multiphase LLC resonant converter circuit 10A differs from the first embodiment shown in Figure 1 in that it includes three neutral wire reactors connected in series: a first neutral wire reactor Ln1, a second neutral wire reactor Ln2, and a third neutral wire reactor Ln3. Here, only the differences will be explained, and the similarities will not be described.

[0052] As shown in Figures 4 and 5, the first neutral reactor Ln1 is magnetically coupled to the first resonant reactor Lr1 and the first core Tn1, the second neutral reactor Ln2 is magnetically coupled to the second resonant reactor Lr2 and the second core Tn2, and the third neutral reactor Ln3 is magnetically coupled to the third resonant reactor Lr3 and the third core Tn3.

[0053] In Figure 5, a tripod core is used as the core, and each reactor is wrapped around the middle leg of the tripod core Tn1, Tn2, and Tn3. An air gap is provided near the center of the middle leg of the tripod core Tn1, Tn2, and Tn3.

[0054] As a modification of Figure 5, Figure 6 shows a configuration in which a five-legged core Tn is used as the core, with each reactor wound around the three central legs. An air gap is provided near the center of each of the three central legs of the five-legged core Tn. Even when the number of phases N is not 3, a similar configuration can be achieved by using a (N+2)-legged core. Furthermore, depending on the intended use, any core other than those shown in Figures 5 and 6 can be used.

[0055] In Figures 5 and 6, for convenience, the first neutral reactor Ln1 and the first resonant reactor Lr1, the second neutral reactor Ln2 and the second resonant reactor Lr2, and the third neutral reactor Ln3 and the third resonant reactor Lr3 are shown separately. In reality, to increase the degree of coupling between them, the first neutral reactor Ln1 and the first resonant reactor Lr1, the second neutral reactor Ln2 and the second resonant reactor Lr2, and the third neutral reactor Ln3 and the third resonant reactor Lr3 are each tightly coupled using staggered winding or bifilar winding.

[0056] By using the configuration shown in Figures 5 and 6, the number of cores can be reduced compared to the case where a separate core is used for each resonant reactor Lr1, Lr2, Lr3 and the neutral reactor Ln, as in the first embodiment.

[0057] In the second embodiment, the resonant frequency f of the three-phase operating mode r3 The fundamental waves of the resonant currents ir1, ir2, and ir3 have a phase difference of 120°, and the fundamental wave component in the current in flowing through the neutral wire N1 is zero. The self-inductance of the neutral wire reactors Ln1, Ln2, and Ln3, and the mutual inductance between the resonant reactors Lr1, Lr2, and Lr3 and the neutral wire reactors Ln1, Ln2, and Ln3 can be ignored, and are expressed as shown in Equation 4, similar to the first embodiment.

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[0058] In contrast, the third harmonic currents superimposed on the resonant currents ir1, ir2, and ir3 have the same phase in each phase, and the neutral wire N1 and the neutral wire reactors Ln1, Ln2, and Ln3 are superimposed with the third harmonic currents of each phase. As a result, the third harmonic currents generate components of self-inductance in the neutral wire reactors Ln1, Ln2, and Ln3, and mutual inductance between the resonant reactors Lr1, Lr2, and Lr3 and the neutral wire reactors Ln1, Ln2, and Ln3.

[0059] Here, let Nr be the number of turns of the resonant reactors Lr1, Lr2, and Lr3, and for comparison with the first embodiment, let Nn be the total number of turns of the neutral reactors Ln1, Ln2, and Ln3, that is, let Nn / 3 be the number of turns of each neutral reactor Ln1, Ln2, and Ln3. The turns ratio of each resonant reactor Lr1, Lr2, and Lr3 to the neutral reactors Ln1, Ln2, and Ln3 is (Nn / 3) / Nr = n / 3. Let l be the self-inductance value of each neutral reactor Ln1, Ln2, and Ln3. n Therefore, the resonant inductance value L of each resonant reactor with respect to the third harmonic current is... rt This can be expressed as shown in Equation 5 by considering the self-inductance and mutual inductance.

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[0060] The total neutral wire inductance L of three series-connected neutral wire reactors for the third harmonic current in three-phase operation mode. nt This can be expressed as shown in Equation 6.

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[0061] Total inductance value L for third harmonic current t Note that the resonant reactors are considered to be connected in parallel, and this can be expressed as shown in Equation 7.

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[0062] On the other hand, the total inductance value L for the third harmonic current in the first embodiment t This can be expressed as shown in Equation 8.

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[0063] Total inductance value L in the second embodiment for third harmonic current t The condition for which is greater than in the first embodiment can be obtained by comparing Equation 7 and Equation 8, as shown in Equation 9.

number

[0064] In other words, in the case of tight coupling with a coupling coefficient of k~1 and a turns ratio n<1 (n / 3<1 / 3=0.333), the total inductance value of the second embodiment is greater than the total inductance value of the first embodiment for third harmonic currents. To put it another way, for the case of a turns ratio n<1 (n / 3<0.333), the total inductance value of the second embodiment can be made approximately equal to the total inductance value of the first embodiment even if the total number of turns of the neutral reactor Ln1, Ln2, Ln3 in the second embodiment is smaller than the number of turns Nn of the neutral reactor Ln in the first embodiment for third harmonic currents.

[0065] Next, the total resonant inductance value L in single-phase operation mode. rt1 Let's consider the total resonant inductance value L during single-phase operation. rt1 This can be expressed as shown in Equation 10 by considering the self-inductance and mutual inductance of Lr1.

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[0066] Similarly, the total neutral wire inductance value L in single-phase operation mode nt1 Let's consider the total neutral wire inductance value L during single-phase operation. nt1 For Ln1, we need to consider both the self-inductance and mutual inductance, and for Ln2 and Ln3, we only need to consider the self-inductance, so it can be expressed as shown in Equation 11.

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[0067] Therefore, the resonant frequency f in single-phase operation mode r4 For the resonant reactor Lr, the total inductance value L, including mutual inductance, is also considered. rt1 By using this, it can be expressed as shown in Equation 12.

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[0068] In single-phase operation mode, the switching frequency f for turning switches Q11 and Q12 of the first series circuit S1 on and off is the resonant frequency f in Equation 11. r4 You can set it according to your needs.

[0069] In the multiphase LLC resonant converter circuit 10A according to the second embodiment, similar to the first embodiment, the neutral wire N1 is connected to the negative (or positive) power line of the DC power supply 30 via the neutral wire reactors Ln1, Ln2, Ln3, so it is possible to switch between multiphase operation mode and single-phase operation mode. Since the neutral wire reactors Ln1, Ln2, Ln3 exhibit high impedance values ​​for AC currents with high frequency components, during boost operation in multiphase operation mode, harmonic components such as the third harmonic contained in the resonant currents ir1, ir2, ir3 flowing through the resonant circuits 41, 42, 43 are suppressed, thereby suppressing the increase in the effective value. Furthermore, harmonic components such as the third harmonic contained in the neutral wire current in flowing from the neutral wire N1 to the negative (or positive) power line of the DC power supply 30 via the neutral wire reactors Ln1, Ln2, Ln3 can be suppressed. [Explanation of Symbols]

[0070] 10,10A Multiphase LLC Resonant Converter Circuit 30 DC power supply 41,42,43 Resonant circuit 51,52,53 Rectifier circuit Co output capacitor Cr1, Cr2, Cr3 Resonant Capacitors f switching frequency f r1 ,f r2 ,f r3 ,f r4 resonant frequency in neutral wire current ir,ir1,ir2,ir3 Resonant current Ln Neutral Reactor Lr1,Lr2,Lr3 Resonant reactor N1 neutral wire Q11, Q21, Q31 First Switch Q21, Q22, Q32 Second Switch S1,S2,S3 series circuit T1, T2, T3 High-Frequency Transformers Vin DC input voltage Vo DC output voltage

Claims

1. A multiphase LLC resonant converter circuit for converting a first DC voltage of a DC power supply to a second DC voltage and outputting it, A series circuit in which a first switch and a second switch are connected in series is connected in parallel to the DC power supply, A high-frequency transformer having a primary winding and a secondary winding, A resonant circuit comprising a resonant reactor connected between the connection point of the first switch and the second switch and one end of the primary winding, and a resonant capacitor with one end connected to the other end of the primary winding, A rectifier circuit for rectifying the output of the secondary winding, A first to Nth (where N is an integer greater than or equal to 2) LLC resonant converter, each equipped with the following: The neutral wires connecting the other ends of the resonant capacitors of the first to the nth LLC resonant converters, A neutral wire reactor connected between the neutral wire and either the positive or negative power line of the DC power supply, An output capacitor for outputting the second DC voltage is connected in parallel to the output side of the rectifier circuit of the first to the nth LLC resonant converter, A control circuit for controlling the on / off state of the first switch and the second switch of the first to the nth LLC resonant converters, Equipped with, The aforementioned control circuit is A multiphase operating mode is provided in which the on / off states of the first and second switches of the first to the nth LLC resonant converters are controlled at a first frequency corresponding to the first resonant frequency of the resonant circuit, and the resonant current of the first frequency flowing through the resonant circuit of the first to the nth LLC resonant converters has a phase difference of 360° / N. The on / off state of the first LLC resonant converter is controlled at a second frequency corresponding to the second resonant frequency of the resonant circuit and the neutral wire reactor, and the first switch and second switch of the second to the Nth LLC resonant converter are turned off in a single-phase operation mode. Equipped with, Multiphase LLC resonant converter circuit.

2. The resonant reactor is the leakage inductance of the high-frequency transformer. The multiphase LLC resonant converter circuit according to claim 1.

3. A multiphase LLC resonant converter circuit for converting a first DC voltage of a DC power supply to a second DC voltage and outputting it, A series circuit in which a first switch and a second switch are connected in series is connected in parallel to the DC power supply, A high-frequency transformer having a primary winding and a secondary winding, A resonant circuit comprising a resonant reactor connected between the connection point of the first switch and the second switch and one end of the primary winding, and a resonant capacitor with one end connected to the other end of the primary winding, A rectifier circuit for rectifying the output of the secondary winding, A first to Nth (where N is an integer greater than or equal to 2) LLC resonant converter, each equipped with the following: The neutral wires connecting the other ends of the resonant capacitors of the first to the nth LLC resonant converters, A neutral wire reactor connected between the neutral wire and either the positive or negative power line of the DC power supply, An output capacitor for outputting the second DC voltage is connected in parallel to the output side of the rectifier circuit of the first to the nth LLC resonant converter, Equipped with, The neutral wire reactor comprises a first to nth neutral wire reactor, which is a series connection of N reactors having equal inductance values. The resonant reactors and neutral wire reactors of the first to nth LLC resonant converters are magnetically coupled by the first to nth cores, respectively. Multiphase LLC resonant converter circuit.

4. A multiphase LLC resonant converter circuit for converting a first DC voltage of a DC power supply to a second DC voltage and outputting it, A series circuit in which a first switch and a second switch are connected in series is connected in parallel to the DC power supply, A high-frequency transformer having a primary winding and a secondary winding, A resonant circuit comprising a resonant reactor connected between the connection point of the first switch and the second switch and one end of the primary winding, and a resonant capacitor with one end connected to the other end of the primary winding, A rectifier circuit for rectifying the output of the secondary winding, A first to Nth (where N is an integer greater than or equal to 2) LLC resonant converter, each equipped with the following: The neutral wires connecting the other ends of the resonant capacitors of the first to the nth LLC resonant converters, A neutral wire reactor connected between the neutral wire and either the positive or negative power line of the DC power supply, An output capacitor for outputting the second DC voltage is connected in parallel to the output side of the rectifier circuit of the first to the nth LLC resonant converter, Equipped with, The neutral wire reactor comprises a first to nth neutral wire reactor, which is a series connection of N reactors having equal inductance values. The resonant reactors and neutral wire reactors of the first to nth LLC resonant converters are magnetically coupled by the second to (N+1) middle legs of the (N+2) leg core, respectively. Multiphase LLC resonant converter circuit.

5. The resonant reactor and the neutral wire reactor of the first to nth LLC resonant converters are wound in a superimposed manner. The multiphase LLC resonant converter circuit according to claim 3 or 4.

6. The resonant reactor and the neutral wire reactor of the first to nth LLC resonant converters are bifilar wound. The multiphase LLC resonant converter circuit according to claim 3 or 4.

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