Power converter, charger, and vehicle

Abstract

To provide a multi-phase power converter capable of realizing high-power output.SOLUTION: There are provided the N number of LLC circuits 10n. According to each of the LLC circuits 10n, a series resonant circuit comprising resonant inductors Lra, Lrb, primary windings Pa, Pb of a transformer T, and a resonance capacitor Cr is connected between an output point of a first switching leg and another output point of a second switching leg. There is provided a control part 20 that operates the N number of LLC circuits 10n with multi-phases of N phases comprising 360° / N phase-differences. The LLC circuits 10n each comprise an inter-phase connection resonance capacitor Crx connected to one end of the resonance capacitor Cr, and another inter-phase connection resonance capacitor Cry connected to the other end of the resonance capacitor Cr.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power converter that converts a DC voltage into a desired output voltage. [Background technology]

[0002] There is a demand for higher power output from charging devices that charge storage batteries mounted on electric vehicles, etc. A known power converter that achieves this is a multi-phase power converter that has multiple phases (number of operating phases) and drives each phase with a phase shift (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6696617 Summary of the Invention [Problem to be solved by the invention]

[0004] Increasing the number of phases is one way to achieve even higher power. However, the more phases there are, the more complementary switch drive signals (complementary gate drive signals) must be provided. Therefore, control becomes more complex as the number of phases increases, and the control-related circuits become larger in scale, making it difficult to expand power by increasing the number of phases.

[0005] One aspect of the present invention is to provide a multiphase power converter, a charging device, and a vehicle that can achieve high power without increasing the number of drive signals. [Means for solving the problem]

[0006] A power converter according to one aspect of the present invention includes N full-bridge LLC converters (N is a natural number equal to or greater than 2). Each full-bridge LLC converter has a first switching leg and a second switching leg, each including an upper switch element and a lower switch element connected in series. The first switching leg and the second switching leg are connected between a positive pole and a negative pole of a DC voltage. In the full-bridge LLC converter, a series resonant circuit including a resonant inductor, a primary winding of a transformer, and a first resonant capacitor is connected between an output point of the first switching leg and an output point of the second switching leg. The power converter includes a control unit that operates the N full-bridge LLC converters in N-phase multiphase operation with a phase difference of 360° / N. Each full-bridge LLC converter includes a second resonant capacitor for inter-phase connection connected to one end of the first resonant capacitor, and a third resonant capacitor for inter-phase connection connected to the other end of the first resonant capacitor. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to achieve higher power without increasing the drive signal. Compared to a half-bridge LLC converter, a full-bridge LLC converter can reduce the current flowing through the primary side of the transformer T by half for the same power, making it suitable for higher power and higher voltage input. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 10 is a diagram illustrating an example of use of a power converter as a charging device. [Figure 2] FIG. 1 is a diagram illustrating a configuration example of a power converter. [Figure 3] FIG. 4 is a diagram illustrating a drive signal output by a control unit. [Figure 4] FIG. 10 is a diagram illustrating another example of the configuration of the LLC circuit. [Figure 5] FIG. 1 is a diagram illustrating a configuration example of a full-bridge circuit compatible with HVDC input. [Figure 6] FIG. 10 is a diagram illustrating another example of the configuration of a power converter including a phase abnormality detection circuit. [Figure 7] FIG. 10 is a diagram illustrating another example of the configuration of a power converter in which the connection of the resonant capacitor is changed. [Figure 8] FIG. 10 is a diagram illustrating another example of the configuration of the phase abnormality detection circuit. [Figure 9] FIG. 10 is a diagram illustrating another example of the configuration of the secondary side circuit. [Figure 10] FIG. 10 is a diagram illustrating a switching operation of a secondary side circuit. [Figure 11] FIG. 10 is a diagram showing a drive signal when switching between three-phase and one-phase operation. [Figure 12] FIG. 10 is a diagram showing a change in resonant frequency due to switching between one-phase and three-phase operation. [Figure 13] FIG. 10 is a diagram showing a primary side resonant current of a third harmonic. [Figure 14] FIG. 1 is a diagram illustrating an example of the configuration of a power converter having an M-stage configuration. [Figure 15] FIG. 1 illustrates a power converter in always-on operation. [Figure 16] FIG. 10 is a diagram showing changes in impedance. [Figure 17] 5A and 5B are diagrams illustrating examples of output characteristics in each drive mode. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, components having similar functions will be given the same reference numerals and descriptions thereof will be omitted as appropriate.

[0010] Referring to FIG. 1, a power converter 1 according to this embodiment is used as a charging device for charging a storage battery 3 (battery) mounted on a vehicle 2 such as an electric car.

[0011] 1(a), when the power supplied to the vehicle 2 from outside the vehicle is an alternating current (AC) voltage such as a commercial power supply, the power converter 1 is mounted on the vehicle 2 together with a power factor correction (PFC) circuit 4. The PFC 4 converts the AC voltage supplied to the vehicle 2 into a direct current (DC) voltage, and the power converter 1 converts the DC voltage converted by the PFC 4 into a desired output voltage to charge the storage battery 3.

[0012] 1(b), when the power supplied from outside the vehicle to the vehicle 2 is a DC voltage, the power converter 1 is installed in a facility outside the vehicle 2, such as a charging station, together with a power factor correction (PFC) circuit 4. The PFC 4 converts the AC voltage supplied from a commercial power source or the like into a direct current (DC) voltage, and the power converter 1 converts the DC voltage converted by the PFC 4 into a desired DC voltage and supplies it to the vehicle 2 to charge the storage battery 3.

[0013] Referring to FIG. 2, the power converter 1 is an N-phase multiphase LLC converter. N is a natural number equal to or greater than 2, and FIG. 2 shows an example where N=3. The power converter 1 is made up of N full-bridge LLC resonant converters (hereinafter referred to as LLC circuits 10) whose input and output sides are connected in parallel and which operate in N-phase multiphase with a phase difference of 360° / N. n The subscript n indicates the number of phases (1 to N).

[0014] LLC circuit 10 n The LLC circuit 10 includes a full-bridge circuit 11. n In the figure, a first switching leg (upper switching element QH1 and lower switching element QL1) and a second switching leg (upper switching element QH2 and lower switching element QL2) are connected in parallel between the positive and negative poles of a DC voltage Vin. In the following description, when there is no distinction to be made based on the number of phases or switching legs, the subscripts will be omitted as appropriate.

[0015] The upper switch element QH and the lower switch element QL are configured, for example, by field-effect transistors (MOSFETs: metal-oxide-semiconductor field-effect transistors). The upper switch element QH and the lower switch element QL have a body diode between the source and drain. The upper switch element QH and the lower switch element QL may be switching elements such as IGBTs (insulated gate bipolar transistors), GaN (gallium nitride), and SiC (silicon carbide) devices.

[0016] The upper switch element QH connected to the positive terminal of the DC voltage Vin is the upper arm of the switching leg, and the lower switch element QL connected to the negative terminal of the DC voltage Vin is the lower arm of the switching leg.

[0017] LLC circuit 10 n The transformer T includes resonant inductors Lra and Lrb, a transformer T, and resonant capacitors Cr, Crx and Cry. The transformer T includes magnetically coupled primary windings Pa and Pb.

[0018] One end of the resonant inductor Lra is connected to the output point of the first switching leg (the connection point between the upper switch element QH1 and the lower switch element QL1), and the other end is connected to one end of the primary winding Pa. The resonant inductor Lrb has one end connected to the output point of the second switching leg (the connection point between the upper switch element QH2 and the lower switch element QL2), and the other end is connected to one end of the primary winding Pb. The other end of the primary winding Pa and the other end of the primary winding Pb are connected via the resonant capacitor Cr.

[0019] The connection point between the primary winding Pa and the resonant capacitor Cr is connected to a first neutral point X via a resonant capacitor Crx for inter-phase connection. The connection point between the primary winding Pb and the resonant capacitor Cr is connected to a second neutral point Y via a resonant capacitor Cry for inter-phase connection. LLC circuits 10 for each phase n via the first neutral point X and the second neutral point Y, the power converter 1 can balance the current between the phases.

[0020] The inductance of the resonant inductors Lra and Lrb is Lr, the capacitance of the resonant capacitor Cr is Cr0, and the capacitance of the resonant capacitors Crx and Cry is Cr a In these cases, the resonance frequency f can be calculated using the following equation (1).

[0021]

number

[0022] LLC circuit 10 n The inverter includes a rectifying and smoothing circuit 12 connected to the secondary winding of the transformer T. The rectifying and smoothing circuit 12 rectifies the AC current output from the secondary winding using an output capacitor to output an output voltage Vo. The rectifying and smoothing circuit 12 can employ a circuit method such as center tap rectification, bridge rectification, voltage doubler rectification, or Cock-Walton rectification. The rectifying and smoothing circuit 12 can also employ synchronous rectification using FETs instead of diodes.

[0023] The control unit 20 is a semiconductor device integrated on a substrate. As shown in FIG. 3, the control unit 20 generates a driving signal G having a phase difference of 120 degrees between the first, second, and third phases. n1 , G n2 Generates and outputs the drive signal G n1 is the upper switch element QH of the first switching leg. n1 and lower switch element QL n1 The drive signal G is a pulse signal (gate signal) with a duty of 50%. n2 is the upper switch element QH of the second switching leg. n2 and lower switch element QL n2 A drive signal G n1 The upper switch element QH of the first switching leg is a complementary pulse signal (gate signal) with a duty cycle of 50% and an inverted polarity. n1 and the lower switch element QL of the second switching leg n2 and the lower switching element QL of the first switching leg n1 and the upper switch element QH of the second switching leg n2 The two operate complementary with a duty of 50%.

[0024] The control unit 20 controls the frequency of the drive signal G n1 , G n2 By increasing the switching frequency, the output voltage Vo is decreased, and by decreasing the switching frequency, the output voltage Vo is increased.

[0025] LLC circuit 10 nAs shown in FIG. 4(a), the resonant inductors Lra and Lrb may be magnetically coupled, and the primary windings Pa and Pb may not be magnetically coupled. n The rectifying and smoothing circuits 12 may be connected in parallel after rectification as shown in Fig. 4(b). By connecting them in parallel after rectification, it is possible to prevent an ineffective circulating current between the secondary windings.

[0026] LLC circuit 10 n The full-bridge circuit 11 may be a full-bridge circuit 11a compatible with HVDC (High Voltage Direct Current) input, as shown in FIG. 5. The full-bridge circuit 11a includes a first switching leg (upper switching element QH 11 and lower switch element QL 11 ) and the second switching leg (upper switch element QH N2 and lower switch element QL N2 ) are connected in series. Capacitors Cin1 and Cin2 are connected in series between the positive and negative poles of a DC voltage Vin. The first switching leg is connected in parallel with capacitor Cin1, and the second switching leg is connected in parallel with capacitor Cin2.

[0027] The power converter 1a shown in FIG. 6 is configured to include a phase abnormality detection circuit 30 in addition to the power converter 1. The phase abnormality detection circuit 30 includes phase abnormality detection capacitors Csx and Csy and a phase abnormality detection resistor Rs. One end of the phase abnormality detection capacitor Csx is connected to the first neutral point X, and one end of the phase abnormality detection capacitor Csy is connected to the second neutral point Y. The other end of the phase abnormality detection capacitor Csx and the other end of the phase abnormality detection capacitor Csy are connected to each other and to a common potential via the phase abnormality detection resistor Rs. The phase abnormality detection capacitors Csx and Csy may have a capacitance that is sufficiently smaller than that of the resonance capacitors Crx and Cry, for example, approximately tens to one hundredth. The phase abnormality detection resistor Rs may have a capacitance of tens to hundreds of ohms.

[0028] Because the first and second switching legs of each phase operate with a 180° phase difference, the voltages at the first neutral point X and the second neutral point Y are symmetrical. When each phase is operating normally, the capacitor midpoint voltage Vc at the connection point between the phase abnormality detection capacitor Csx and the phase abnormality detection capacitor Csy is nearly zero V, and the voltage drop across the phase abnormality detection resistor Rs is also zero V. If a phase abnormality occurs in one or more phases during phase operation due to component damage or the like, the capacitor midpoint voltage Vc will have a large amplitude, causing a voltage drop across the phase abnormality detection resistor Rs. Therefore, the power converter 1a can detect a phase abnormality by monitoring the capacitor midpoint voltage Vc in the phase abnormality detection circuit 30.

[0029] The power converter 1b shown in FIG. n The resonance capacitors Crx and Cry are delta-connected. The connection point X between the n-phase primary winding Pa and the resonance capacitor Cr n In this case, a resonant capacitor Crx is connected between the connection point X1 and the connection point X2, between the connection point X2 and the connection point X3, and between the connection point X3 and the connection point X1. n In this case, the resonance capacitors Cry are connected between the connection points Y1 and Y2, between the connection points Y2 and Y3, and between the connection points Y3 and Y1. n , Y n Even if these are delta-connected with resonant capacitors Crx and Cry, the current between the phases can be balanced, just like the Y-connection of power converter 1 shown in Fig. 2. When using a delta connection, the capacitance of resonant capacitors Crx and Cry can be reduced to one-third of that when using a Y-connection.

[0030] The phase abnormality detection circuit 30a shown in FIG. 8(a) is a circuit for detecting a phase abnormality in the power converter 1b shown in FIG. 7. The phase abnormality detection circuit 30a includes phase abnormality detection capacitors Csx1 to Csx3, Csy1 to Csy3, and a phase abnormality detection resistor Rs. n One end of the n 2. Phase abnormality detection capacitor Csyn One end of the n The phase abnormality detection capacitor Csx is connected to n The other end of the phase abnormality detection capacitor Csy n The other ends of the phase abnormality detection capacitors Csx1 to Csx3 and Csy1 to Csy3 are connected to each other and to a common potential via a phase abnormality detection resistor Rs. The phase abnormality detection capacitors Csx1 to Csx3 and Csy1 to Csy3 may have a capacitance that is sufficiently small compared to the resonance capacitors Crx and Cry, for example, approximately several tens to one hundredth of that. The phase abnormality detection resistor Rs may have a resistance of several tens to several hundred ohms. When each phase is operating normally, the capacitor midpoint voltage Vc at the connection point between the phase abnormality detection capacitors Csx1 to Csx3 and the phase abnormality detection capacitors Csy1 to Csy3 does not fluctuate, but in the event of a phase abnormality, a voltage drop occurs across Rs due to voltage fluctuations. Therefore, the power converter 1b can detect a phase abnormality by monitoring the capacitor midpoint voltage Vc in the phase abnormality detection circuit 30a.

[0031] Either the phase abnormality detection capacitors Csx1 to Csx3 or the phase abnormality detection capacitors Csy1 to Csy3 may be omitted, as in the phase abnormality detection circuits 30b and 30c shown in Figures 8(b) and 8(c). For example, if the portion of the resonant capacitor Crx indicated by arrow A in Figure 8(b) is damaged, the phase abnormality can be detected by the phase abnormality detection capacitors Csy1 to Csy3 via the resonant capacitor Cr and resonant capacitor Cry indicated by arrow B.

[0032] FIG. 9 shows a rectifying / smoothing circuit 12a that can be switched between a Y-connection rectifying circuit and a voltage doubler rectifying circuit. The rectifying / smoothing circuit 12a includes a diode bridge circuit DB, an output capacitor Co, a voltage doubler capacitor Cd, a selector switch SW, and a surge diode Ds. The diode bridge circuit DB is a circuit in which six diodes Da to Df are bridge-connected. Three input terminals of the diode bridge circuit DB are connected to one end of each of the first to third phase secondary windings S1 to S3. The diode bridge circuit DB rectifies the AC induced in the first to third phase secondary windings S1 to S3 and outputs the rectified AC from the output terminal. The output capacitor Co is connected between the positive and negative output terminals of the diode bridge circuit DB.

[0033] The other ends of the mutually connected first to third phase secondary windings S1 to S3 are connected to the negative output terminal of the diode bridge circuit DB via a voltage doubler capacitor Cd and a selector switch SW. A surge diode Ds is connected between the connection point between the voltage doubler capacitor Cd and the selector switch SW and the positive output terminal of the diode bridge circuit DB, and flows a surge current to the output side when the selector switch SW is turned off.

[0034] The rectifying and smoothing circuit 12a functions as a Y-connection rectifying circuit by turning off the selector switch SW, and functions as a voltage doubler rectifying circuit by turning on the selector switch SW, which enables the power converter 1 to switch between one-phase and three-phase operation and suppress peak currents.

[0035] When operating at a switching frequency near the resonant frequency f, whether the rectifying smoothing circuit 12a is a Y-connection rectifier circuit or a voltage doubler rectifier circuit, the primary side resonant current has a waveform that is close to a sine wave, as shown in FIG. 10(a).

[0036] When the selector switch SW is turned on to make the rectifying and smoothing circuit 12a function as a voltage doubler rectifier circuit, the surge diode Ds is one, but the circuit functions as three voltage doubler rectifier circuits. Therefore, the power converter 1 can switch between one-phase and three-phase operation.

[0037] When the DC voltage Vin drops or the output voltage Vo increases, the switching frequency is controlled to decrease in order to maintain the output voltage Vo, and a boost period occurs during which the resonant capacitor Cr is charged, as shown in Figure 10(b). This boost period is an output disqualification period, as can be seen from the currents Da and Db flowing through the diodes Da and Db.

[0038] As the DC voltage Vin decreases and the output voltage Vo increases, the disqualification period increases, and the peak current increases during the output period in an attempt to obtain current. When the disqualification period increases and the peak current increases, a three-phase combined current flows through the voltage-doubler capacitor Cd, as shown in Figure 10(c). If the selector switch SW is turned off at this time, the combined current flowing through the voltage-doubler capacitor Cd has nowhere to go, and the three rectified currents (Da, Db, etc.) form waveforms with suppressed peaks, as shown in Figure 10(d). In accordance with the secondary currents (Da, Db, etc.), the primary current also takes on a waveform with suppressed peaks via the transformer. By turning off the selector switch SW and allowing the rectifier / smoothing circuit 12a to function as a Y-connection rectifier circuit, the peak current is suppressed, maintaining high efficiency even when the input is reduced or the output is increased.

[0039] As shown in FIG. 11, the power converter 1 generates a drive signal G 21 , G 22 , G 31 , G 32 1-phase / 3-phase operation can be switched by simply turning on / off the drive signal G n1 , G n2 may be turned on / off to switch between 1-phase and 3-phase operation.

[0040] The resonant frequency change Δf caused by switching between 1-phase and 3-phase operation is determined by the capacitance ratio α between resonant capacitor Cr and resonant capacitors Crx and Cry, as shown in Figure 12. If the capacitance of resonant capacitor Cr is αCr0, the capacitance of resonant capacitors Crx and Cry is (1-α)Cr0. Therefore, the frequency change caused by switching between 1-phase and 3-phase can be considered based on the capacitances of resonant capacitor Cr and resonant capacitors Crx and Cry.

[0041] For example, if α=0.5 and the capacitances of the resonant capacitors Cr, Crx, and Cry are all the same, the resonant frequency change Δf is about 15%. If a resonant frequency change Δf of about 15% is acceptable, taking into account component procurement, it is best to configure the resonant capacitors Cr, Crx, and Cry with the same components having the same capacitance.

[0042] For example, when α=1 / 9, a third-harmonic primary-side resonant current flows for a square-wave input voltage, as shown in Fig. 13. As a result, the third-harmonic current is added to the resonant current of resonant frequency fr flowing through resonant inductors Lra and Lrb, reducing the peak current and effective current, and reducing the conduction loss of switches, rectifiers, etc.

[0043] The power converter 1c shown in FIG. 14 is configured by changing the power converter 1 shown in FIG. 2 to an M-stage configuration. M is a natural number equal to or greater than 2. LLC circuits 10 of the same phase in each stage are n are the same drive signals G n1 , G n2 The secondary windings of the same phase are connected in series. n1 , G n2 High power can be easily achieved without increasing the

[0044] In the power converter 1c, the LLC circuit 10 in one or more stages n In normal switching operation, the LLC circuit 10 n Alternatively, each of the first and second switching legs may be driven in a normally-on operation. In the normally-on operation, as shown in Fig. 15(a), the upper switching element QH1 of the first switching leg and the upper switching element QH2 of the second switching leg are normally off, and the lower switching element QL1 of the first switching leg and the lower switching element QL2 of the second switching leg are normally on. Fig. 15 shows an example of a two-stage configuration with M=2.

[0045] The normally-on operation may be such that the upper switch element QH1 of the first switching leg and the upper switch element QH2 of the second switching leg are normally on, and the lower switch element QL1 of the first switching leg and the lower switch element QL2 of the second switching leg are normally off. In this case, however, it is necessary to prepare a separate voltage for keeping the upper switch element QH1 of the first switching leg and the upper switch element QH2 of the second switching leg normally on.

[0046] By constantly turning on the lower switch element QL1 of the first switching leg and the lower switch element QL2 of the second switching leg, the second-stage LLC circuit 10 n 15(b), a series resonant circuit of a resonant inductor Lr and a resonant capacitor Cr is formed. The impedance Z of the series resonant circuit of the resonant inductor Lr and the resonant capacitor Cr is given by the following equation (2). In equation (2), ω is the angular frequency, and is expressed as ω=2πf using the frequency f.

[0047]

number

[0048] When the angular frequency ω is ωr shown in the following equation (3), the impedance Z becomes zero as shown in the following equation (4).

[0049]

number

[0050]

number

[0051] The angular frequency ωr at which the impedance Z becomes zero is called the resonant angular frequency, and the resonant frequency fr is fr = ωr / 2π. As shown in Figure 16, the impedance Z becomes larger as the switching frequency moves away from the resonant frequency fr.

[0052] Since the impedance Z changes with frequency, the impedance also changes when viewed from the secondary side of the transformer T, and as shown in Figure 15(c), the second-stage transformer T can be represented as an equivalent circuit with variable impedance.

[0053] Particularly, at the resonance frequency fr where the impedance Z becomes zero, the second transformer T is short-circuited on the primary side. As shown in FIG. 15(d), the impedance on the secondary side also becomes zero. That is, the second transformer T is the same as if the secondary winding N2 is also short-circuited.

[0054] Therefore, the first-stage LLC circuit 10 n is operated in a switching manner near the resonance frequency fr where the efficiency is the highest, and the second-stage LLC circuit 10 n forms a series resonance circuit of the resonance inductor Lr and the resonance capacitor Cr. Then, as shown in FIG. 15(d), since the second stage can be regarded as being short-circuited, the power converter 1 can be regarded as only the first-stage LLC circuit 101. That is, the series connection operation of switching the first-stage LLC circuit 101 and the second-stage LLC circuit 102, and the single operation of switching only the first-stage LLC circuit 10 n can be switched without providing a switching switch on the secondary side.

[0055] FIG. 17 is an example of output characteristics of the switching frequency and the output voltage Vo in each drive mode (A mode to E mode). The first mode is an operation mode in which the first-stage and second-stage LLC circuits 10 n are operated normally. The second mode is an operation mode in which the first-stage LLC circuit 10 n is operated normally and the second-stage LLC circuit 10 n is constantly turned on. Referring to FIG. 17, the output voltage Vo at the same frequency is lower in the second mode than in the first mode. When X1 to X2 (X1 < X2) sandwiching the resonance frequency fr are set as the operating frequency range of the switching frequency, the A mode cannot output an output voltage Vo lower than the first threshold voltage Vth1. The power converter 1c can expand the output voltage Vo that can be output in the same operating frequency range to the lower voltage side than the first threshold voltage Vth1 by switching the drive mode.

[0056] (Summary) (1) The power converter 1 according to each embodiment of the present invention includes N (N is a natural number of 2 or more) full-bridge LLC converters (LLC circuits 10 n ). The full-bridge LLC converter has a first switching leg including an upper switching element QH1 and a lower switching element QL1 connected in series, and a second switching leg including an upper switching element QH2 and a lower switching element QL2 connected in series. The full-bridge LLC converter has the first switching leg and the second switching leg connected between the positive and negative poles of a DC voltage Vin. In the full-bridge LLC converter, a series resonant circuit including resonant inductors Lra and Lrb, primary windings Pa and Pb of a transformer T, and a first resonant capacitor (resonant capacitor Cr) is connected between the output point of the first switching leg (the connection point between the upper switching element QH1 and the lower switching element QL1) and the output point of the second switching leg (the connection point between the upper switching element QH2 and the lower switching element QL2). The power converter has a control unit 20 that operates the N full-bridge LLC converters in N-phase multiphase operation with a phase difference of 360° / N. The full-bridge LLC converter includes a second resonant capacitor (resonant capacitor Crx) for interphase connection connected to one end of the first resonant capacitor, and a third resonant capacitor (resonant capacitor Cry) for interphase connection connected to the other end of the first resonant capacitor.

[0057] The power converter 1 described in (1) above can achieve high power without increasing the number of drive signals. A full-bridge LLC converter can reduce the current flowing through the primary side of the transformer T by half compared to a half-bridge LLC converter for the same power, making it suitable for high power and high voltage input.

[0058] (2) In the power converter 1 described in (1) above, one end of the first resonant capacitor is connected to the first neutral point X via the second resonant capacitor, and the other end of the first resonant capacitor is connected to the second neutral point Y via the third resonant capacitor.

[0059] According to the power converter 1 described in (2) above, the second resonant capacitor and the third resonant capacitor are each connected in a Y-connection, thereby achieving current balance between the phases.

[0060] (3) In addition to the power converter 1 described in (2) above, the power converter 1a includes a phase abnormality detection circuit 30 including a first phase abnormality detection capacitor (phase abnormality detection capacitor Csx) having one end connected to the first neutral point X, a second phase abnormality detection capacitor (phase abnormality detection capacitor Csy) having one end connected to the second neutral point Y, and a phase abnormality detection resistor Rs connected between the other ends of the mutually connected first phase abnormality detection capacitor and second phase abnormality detection capacitor and a common potential.

[0061] According to the power converter 1a described in (3) above, by monitoring the capacitor midpoint voltage Vc in the phase abnormality detection circuit 30, a phase abnormality can be easily detected.

[0062] (4) In the power converter 1b, in the power converter 1 of (1) above, the second resonant capacitor is delta-connected with the second resonant capacitor of the other phase, and the third resonant capacitor is delta-connected with the third resonant capacitor of the other phase.

[0063] According to the power converter 1b described in (4) above, the second resonant capacitor and the third resonant capacitor are respectively connected in a delta configuration, thereby achieving current balance between the phases. The capacitance of the second resonant capacitor and the third resonant capacitor can be reduced to one-third of that of a Y-connection.

[0064] (5) In the power converter 1b described in (1) above, phase abnormality detection capacitors Csx and Csy are connected at one end to each side of at least one of the delta-connected second resonant capacitor and the delta-connected third resonant capacitor, respectively; The phase abnormality detection circuits 30a, 30b, and 30c include a phase abnormality detection resistor Rs connected between the other ends of the mutually connected phase abnormality detection capacitors Csx and Csy and a common potential.

[0065] According to the power converter 1b described in (5) above, a phase abnormality can be easily detected by monitoring the capacitor midpoint voltage Vc in the phase abnormality detection circuits 30a, 30b, and 30c.

[0066] (6) The power converters 1 and 1b described in (1) to (5) above are provided with a rectifying and smoothing circuit 12a that includes a diode bridge circuit DB connected to one end of the secondary windings S1, S2, and S3 of the transformer for each phase, rectifying the AC induced in the secondary windings S1, S2, and S3, and an output capacitor Co connected between the positive output terminal and the negative output terminal of the diode bridge circuit DB, and a voltage doubler capacitor Cd and a changeover switch SW connected in series between the other end of the secondary windings S1, S2, and S3 of each phase that are connected to each other and the negative output terminal of the diode bridge circuit DB.

[0067] According to the power converters 1 and 1b described in (6) above, the Y-connection rectifier circuit and the voltage doubler rectifier circuit can be switched by turning the changeover switch SW on and off, making it possible to switch between one-phase and three-phase operation and suppress peak currents.

[0068] (7) The power converter 1c is configured in the power converters 1 and 1b described in (1) to (6) above by configuring N full-bridge LLC converters (M is a natural number of 2 or more) in M ​​stages, each of which operates in N-phase multiphase with a phase difference of 360° / N, and the secondary windings of the transformers Tn1 to TnM of the same phase are connected in series.

[0069] According to the power converter 1c described above in (7), the multi-stage configuration allows the drive signal G n1 , G n2 High power can be easily achieved without increasing the

[0070] (8) In the power converter 1c described in (7) above, the control unit 20 drives one or more stages of the full-bridge LLC converter in a constantly-on operation in which one of the upper switching elements QH1, QH2 and the lower switching elements QL1, QL2 in the first switching leg and the second switching leg is always in an on state and the other is always in an off state.

[0071] According to the power converter 1c described in (8) above, the range of the output voltage Vo that can be output within the operating frequency range can be widened without providing a changeover switch on the output side, so that the operating frequency range can be set to a narrow range near the resonant frequency, thereby improving the conversion efficiency.

[0072] (9) A charging device for charging a storage battery 3, which charges the storage battery 3 with the output voltage Vo of the power converters 1, 1a, 1b, and 1c described above in (1) to (8).

[0073] According to the charging device described in (9) above, the storage battery 3 can be efficiently charged by increasing the power.

[0074] (10) A vehicle (2) equipped with a storage battery (3) includes the power converters (1, 1a, 1b, 1c) described above in (1) to (8) that convert externally supplied power into an output voltage Vo that charges the storage battery (3).

[0075] According to the vehicle 2 described in (10) above, the increased power makes it possible to efficiently charge the storage battery 3 mounted thereon.

[0076] Although the present invention has been described above with reference to specific embodiments, it goes without saying that the above embodiments are merely examples and can be modified and implemented without departing from the spirit of the present invention. [Explanation of symbols]

[0077] 1, 1a, 1b, 1c Power Converter 2 vehicles 3. Storage battery 10 LLC circuit (full-bridge LLC converter) 11, 11a full bridge circuit 12, 12a rectifier smoothing circuit 20 Control Unit 30, 30a, 30b, 30c Phase abnormality detection circuit Cd voltage doubler capacitor Csx, Csy phase abnormality detection capacitor Ds Surge Diode Cr, Crx, Cry resonant capacitors Lr Resonant inductor QH1, QH2 upper switch element QL1, QL2 lower switch element T transformer SW changeover switch

Claims

1. N (N is a natural number of 2 or more) full-bridge LLC converters each having a first switching leg and a second switching leg each including an upper switch element and a lower switch element connected in series, the first switching leg and the second switching leg being connected between a positive pole and a negative pole of a DC voltage, and a series resonant circuit including a resonant inductor, a primary winding of a transformer, and a first resonant capacitor being connected between an output point of the first switching leg and an output point of the second switching leg; a control unit that operates the N full-bridge LLC converters in a multi-phase operation of N phases having a phase difference of 360° / N, the full-bridge LLC converter includes a second resonant capacitor for inter-phase connection connected to one end of the first resonant capacitor; a third resonant capacitor for inter-phase connection connected to the other end of the first resonant capacitor.

2. one end of the first resonant capacitor is connected to a first neutral point via the second resonant capacitor; 2. The power converter according to claim 1, wherein the other end of the first resonant capacitor is connected to a second neutral point via the third resonant capacitor.

3. a first-phase abnormality detection capacitor having one end connected to the first neutral point; a second-phase abnormality detection capacitor having one end connected to the second neutral point; 3. The power converter according to claim 2, further comprising a phase abnormality detection circuit including a phase abnormality detection resistor connected between the other end of the first phase abnormality detection capacitor and the other end of the second phase abnormality detection capacitor, which are connected to each other, and a common potential.

4. the second resonant capacitor is delta-connected to the second resonant capacitor of another phase, The power converter according to claim 1 , wherein the third resonant capacitor is delta-connected with the third resonant capacitor of another phase.

5. a phase abnormality detection capacitor having one end connected to each side of at least one of the second resonant capacitor in a delta connection and the third resonant capacitor in a delta connection; 5. The power converter according to claim 4, further comprising a phase abnormality detection circuit including a phase abnormality detection resistor connected between the other end of the mutually connected phase abnormality detection capacitors and a common potential.

6. a diode bridge circuit connected to one end of the secondary winding of the transformer for each phase, and rectifying the AC induced in the secondary winding; an output capacitor connected between the positive output terminal and the negative output terminal of the diode bridge circuit; a voltage doubler capacitor and a selector switch connected in series between the other end of the secondary windings of each phase connected to each other and the negative output terminal of the diode bridge circuit. The power converter according to claim 1, further comprising a rectifying and smoothing circuit.

7. N full-bridge LLC converters are configured in M ​​stages (M is a natural number of 2 or more), each of which operates in N multiphase circuits having a phase difference of 360° / N; 2. The power converter according to claim 1, wherein the secondary windings of the transformers of the same phase are connected in series.

8. 8. The power converter according to claim 7, wherein the control unit drives one or more stages of the full-bridge LLC converter in a constantly-on operation in which one of the upper switch element and the lower switch element in the first switching leg and the second switching leg is always in an on state and the other is always in an off state.

9. A charging device for charging a storage battery, A charging device comprising the power converter according to claim 1 , wherein the DC voltage is converted into an output voltage for charging the storage battery.

10. A vehicle equipped with a storage battery, A vehicle comprising the power converter according to claim 1 , wherein the power converter converts power supplied from outside the vehicle into an output voltage for charging the storage battery.

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