Power converter, charging device, and vehicle

Abstract

In an LLC circuit (10n), a series resonant circuit including resonant inductors (Lra, Lrb), primary windings (Pa, Pb) of a transformer (T), and a resonant capacitor (Cr) is connected between an output point of a first switching leg and an output point of a second switching leg. This power converter is provided with a control unit (20) that causes the N LLC circuits (10n) to operate in a multi-phase of N phases having a phase difference of 360° / N. The LLC circuit (10n) comprises: an inter-phase connection resonant capacitor (Crx) connected to one end of the resonant capacitor (Cr); and an inter-phase connection resonant capacitor (Cry) connected to the other end of the resonant capacitor (Cr).

Description

Power converter, charging device and vehicle

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

[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 demand 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).

[0003] Patent No. 6696617

[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) are required. Therefore, control becomes more complex as the number of phases increases, and the control circuits become larger in scale, making it difficult to expand power through multi-phase operation.

[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.

[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 an 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.

[0007] According to one aspect of the present invention, higher power can be achieved 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.

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

[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 mounted on a vehicle 2 such as an electric vehicle.

[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, a power converter 1 is mounted on the vehicle 2 together with a power factor correction circuit (PFC) 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 PFC (power factor correction circuit) 4. The PFC 4 converts 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 The first switching leg (upper switch element QH １ and the lower switch element QL １ ) and the second switching leg (upper switch element QH ２ and the lower switch element QL ２ ) are connected in parallel. 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), or SiC (silicon carbide) devices.

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

[0017] LLC circuit 10 ｎ The inverter 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] The resonant inductor Lra has one end connected to the output point of the first switching leg (upper switch element QH １ and the lower switch element QL １ The resonant inductor Lrb has one end connected to the output point of the second switching leg (the connection point of the upper switch element QH ２ and the lower switch element QL ２ The other end of the primary winding Pa is connected to one end of the primary winding Pb via a 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 phase-to-phase resonant capacitor Crx. The connection point between the primary winding Pb and the resonant capacitor Cr is connected to a second neutral point Y via a phase-to-phase resonant capacitor Cry. 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 resonance inductors Lra and Lrb is Lr, and the capacitance of the resonance capacitor Cr is Cr ０ , the capacitance of the resonance capacitors Crx and Cry is Cr ａ In these cases, the resonant frequency f can be calculated using the following equation (1).

[0021]

[0022] LLC circuit 10 ｎThe inverter includes a rectifying and smoothing circuit 12 connected to a secondary winding of a 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 drive signal G having a phase difference of 120 degrees between the first, second, and third phases. ｎ１ , G ｎ２ The driving signal G ｎ１ is the upper switch element QH of the first switching leg ｎ１ and the lower switch element QL ｎ１ The driving 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 the lower switch element QL ｎ２ A driving 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 switch 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 ｎ As shown in FIG. 4A, the resonant inductors Lra and Lrb may be magnetically coupled, and the primary windings Pa and Pb may not be magnetically coupled. ｎThe rectifying and smoothing circuit 12 may be connected in parallel after rectification, as shown in Fig. 4(b). By connecting the secondary windings in parallel after rectification, it is possible to prevent unnecessary circulating currents 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 switch element QH １１ and the lower switch element QL １１ ) and the second switching leg (upper switch element QH Ｎ２ and the 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 several tens to one hundredth. The phase abnormality detection resistor Rs may have a capacitance of several tens to several hundred ohms.

[0028] Because the first and second switching legs of each phase operate with a 180° phase difference, the voltage at the first neutral point X and the voltage at 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 approximately 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, the connection point X １ and connection point X ２ Between and, connection point X ２ and connection point X ３ Between and, connection point X ３ and connection point X １ A resonance capacitor Crx is connected between the n-phase primary winding Pb and the resonance capacitor Cr. ｎ In this case, the connection point Y １ and connection point Y ２ Between and connection point Y ２ and connection point Y ３ Between and connection point Y ３ and connection point Y １ A resonance capacitor Cry is connected between each of the connection points X of each phase. ｎ , Y ｎ Even if these are delta-connected with resonant capacitors Crx and Cry, current balance between the phases can be achieved, similar to the Y-connection of the power converter 1 shown in Fig. 2. When using a delta connection, the capacitance of the 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 detects a phase abnormality in the power converter 1b shown in Fig. 7. １ ~Csx ３ , Csy １ ~Csy ３ and a phase abnormality detection resistor Rs. ｎ One end of the ｎ 2, a phase abnormality detection capacitor Csy ｎ 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 Csx and Csx are connected to each other and are connected to a common potential via a phase abnormality detection resistor Rs. １ ~Csx ３ , Csy １ ~Csy ３ The capacitance of the phase abnormality detection resistor Rs may be several tens to several hundreds of ohms. When each phase is operating normally, the phase abnormality detection capacitor Csx １ ~Csx ３ and phase abnormality detection capacitor Csy １ ~Csy ３ The capacitor midpoint voltage Vc at the connection point between Rs and Rs does not fluctuate, but when a phase abnormality occurs, 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] Phase abnormality detection capacitor Csx １ ~Csx ３ and a phase abnormality detection capacitor Csy １ ~Csy ３ For example, if the resonance capacitor Crx shown by the arrow A in FIG. 8B is damaged, the resonance capacitor Crx is damaged, and the resonance capacitor Cry is damaged. １ ~Csy ３Phase anomalies can be detected.

[0032] 9 shows a rectifying and smoothing circuit 12a that can be switched between a Y-connection rectifying circuit and a voltage doubler rectifying circuit. The rectifying and smoothing circuit 12a includes a diode bridge circuit DB, an output capacitor Co, a voltage doubler capacitor Cd, a changeover 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 the first to third phase secondary windings S １ ~S ３ The diode bridge circuit DB is connected to one end of the first to third phase secondary windings S １ ~S ３ The output capacitor Co is connected between the positive and negative output terminals of the diode bridge circuit DB.

[0033] The first to third phase secondary windings S are connected to each other. １ ~S ３ The other end of the diode bridge circuit DB is connected to the negative output terminal of the diode bridge circuit DB via a voltage doubler capacitor Cd and a selector switch SW. The 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 allows a surge current to flow 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, thereby enabling 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 Figure 10(a).

[0036] When the selector switch SW is turned on to cause the rectifying and smoothing circuit 12a to 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 voltage boost period occurs during which the resonant capacitor Cr is charged, as shown in Fig. 10(b). This voltage 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 is large, a three-phase combined current flows through the voltage-doubler capacitor Cd, as shown in FIG. 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 currents, etc.) form waveforms with suppressed peaks, as shown in FIG. 10(d). In accordance with the secondary currents (Da, Db currents, etc.), the primary current also takes on a waveform with suppressed peaks via the transformer. By turning off the selector switch SW and causing the rectifying and smoothing circuit 12a to function as a Y-connected rectifier circuit, the peak current is suppressed, and high efficiency can be maintained even when the input is reduced or the output is increased.

[0039] As shown in FIG. 11, the power converter 1 is configured to generate a drive signal G ２１ , G ２２ , G ３１ , G ３２ The single-phase / three-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 one-phase and three-phase operation.

[0040] The change in resonant frequency Δf due to switching between one-phase and three-phase operation is determined by the capacitance ratio α between the resonant capacitor Cr and the resonant capacitors Crx and Cry, as shown in FIG. ０ Then, the capacitance of the resonant capacitors Crx and Cry is (1-α)Cr ０ Therefore, the change in frequency during one-phase / three-phase switching can be considered based on the capacitances of the resonance capacitors Cr and 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 parts procurement, it is advisable to configure the resonant capacitors Cr, Crx, and Cry using the same parts with 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 the resonant frequency fr flowing through the resonant inductors Lra and Lrb, making it possible to reduce the peak current and effective current, and also to reduce the conduction loss of the switches, rectifiers, etc.

[0043] The power converter 1c shown in FIG. 14 is an M-stage configuration of the power converter 1 shown in FIG. 2. M is a natural number of 2 or more. Each stage has an LLC circuit 10 of the same phase. 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 of one or more other stages ｎ The always-on operation may be achieved by driving the upper switch element QH of the first switching leg in a normally-on mode, as shown in FIG. １and the upper switch element QH of the second switching leg ２ and the lower switch element QL of the first switching leg are always in the OFF state. １ and the lower switch element QL of the second switching leg ２ 15 shows an example of a two-stage configuration where M=2.

[0045] The normally-on operation is performed by the upper switch element QH of the first switching leg. １ and the upper switch element QH of the second switching leg ２ and the lower switch element QL of the first switching leg are always in the ON state. １ and the lower switch element QL of the second switching leg ２ However, in this case, the upper switch element QH of the first switching leg may be always in the OFF state. １ and the upper switch element QH of the second switching leg ２ A separate voltage must be provided to keep the transistors in a constantly on state.

[0046] Lower switch element QL of the first switching leg １ and the lower switch element QL of the second switching leg ２ By keeping the second stage LLC circuit 10 in a constantly on state, 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 expressed by the following equation (2). In equation (2), ω is an angular frequency, and is expressed as ω=2πf using frequency f.

[0047]

[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]

[0050]

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

[0053] In particular, at the resonant frequency fr where the impedance Z is zero, the second-stage transformer T is short-circuited on the primary side, and the impedance on the secondary side also becomes zero, as shown in Fig. 15(d). In other words, the second-stage transformer T is equivalent to the secondary winding N2 being short-circuited.

[0054] Therefore, the first stage LLC circuit 10 ｎ The second stage LLC circuit 10 is switched at the most efficient resonant frequency fr. ｎ 15(d), the second stage can be considered to be short-circuited, and the power converter 1 can be considered to be short-circuited, so that the first stage LLC circuit 10 １ That is, the first stage LLC circuit 10 １ and the second stage LLC circuit 10 ２ and a series connection operation for switching the first stage LLC circuit 10 ｎ This allows switching between a single operation in which only the first and second inverters are switched on and off without providing a changeover switch on the secondary side.

[0055] 17 shows an example of output characteristics of the switching frequency and the output voltage Vo in each drive mode (mode A to mode E). In the first mode, the first and second stage LLC circuits 10 ｎ In the second mode, the first stage LLC circuit 10 is operated normally. ｎ is operated normally, and the second stage LLC circuit 10 ｎ17, the output voltage Vo at the same frequency is lower in the second mode than in the first mode. When the operating frequency range of the switching frequency is set to X1 to X2 (X1<X2) sandwiching the resonant frequency fr, the output voltage Vo cannot be lower than the first threshold voltage Vth1 in the A mode. By switching the drive mode, the output voltage Vo that can be output in the same operating frequency range is expanded to lower voltages than the first threshold voltage Vth1.

[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 comprises an upper switch element QH connected in series. １ and the lower switch element QL １ a first switching leg including an upper switch element QH connected in series with the first switching leg; ２ and the lower switch element QL ２ and a second switching leg including a first switching leg and a second switching leg including a first switching leg and a second switching leg including a second switching leg and a second switching leg including a first ... １ and the lower switch element QL １ ) and the output point of the second switching leg (upper switch element QH ２ and the lower switch element QL ２ The power converter includes a control unit 20 that operates the N full-bridge LLC converters in multiphase operation with N phases having a phase difference of 360° / N. The full-bridge LLC converters include a second resonant capacitor (resonant capacitor Crx) for inter-phase connection that is connected to one end of the first resonant capacitor, and a third resonant capacitor (resonant capacitor Cry) for inter-phase connection that is 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. 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 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 end 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 1 a 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 another phase, and the third resonant capacitor is delta-connected with the third resonant capacitor of another 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 circuits 30a, 30b, and 30c are provided, each including phase abnormality detection capacitors Csx and Csy, one end of which is connected to each side of at least one of the delta-connected second resonant capacitor and the delta-connected third resonant capacitor, and a phase abnormality detection resistor Rs, which is connected between the other end of the interconnected 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) In the power converters 1 and 1b described in (1) to (5) above, the secondary winding S of the transformer of each phase １ , S ２ , S ３ and the secondary winding S １ , S ２ , S ３ The diode bridge circuit DB is connected to a positive output terminal and a negative output terminal of the diode bridge circuit DB, and the secondary windings S of each phase are connected to each other. １ , S ２ , S ３ and a rectifying and smoothing circuit 12a including a voltage doubler capacitor Cd and a changeover switch SW connected in series between the other end of the first input terminal 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 selector switch SW on and off, making it possible to switch between one-phase and three-phase operation and suppress peak currents.

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

[0069] According to the power converter 1c described above in (7), 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 controls the upper switching elements QH １ , Q.H. ２ and the lower switch element QL １ , Q.L. ２ A full-bridge LLC converter having one or more stages is driven in a constantly-on operation in which one of the two 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 the 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) and including 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 allows the on-board storage battery 3 to be efficiently charged.

[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.

[0077] 1, 1a, 1b, 1c Power converter 2 Vehicle 3 Storage battery 10 LLC circuit (full-bridge LLC converter) 11, 11a Full-bridge circuit 12, 12a Rectification 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 Resonance capacitor Lr Resonance inductor QH １ , Q.H. ２ Upper switch element QL １ , Q.L. ２ Lower switch element T Transformer SW Changeover switch

Claims

1. A power converter comprising: 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 the positive and negative poles of a DC voltage, and a series resonant circuit, each 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; and a control unit that operates the N full-bridge LLC converters in N-phase multiphase operation with a phase difference of 360° / N, wherein the full-bridge LLC converters each include: 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.

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

3. A power converter according to claim 2, further comprising a phase abnormality detection circuit including: 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; and a phase abnormality detection resistor connected between the other ends of the first phase abnormality detection capacitor and the second phase abnormality detection capacitor, which are connected to each other, and a common potential.

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

5. A power converter according to claim 4, comprising a phase abnormality detection circuit including: phase abnormality detection capacitors, one end of which is 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; and a phase abnormality detection resistor, connected between the other end of the mutually connected phase abnormality detection capacitors and a common potential.

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

7. The power converter according to claim 1, wherein N full-bridge LLC converters operating in multiphase, N-phase arrangements with a phase difference of 360° / N are configured in M ​​stages (M is a natural number of 2 or greater), and secondary windings of the transformers of the same phase are connected in series.

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 on and the other is always off.

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

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

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