Power conversion circuit and power conversion control method

Abstract

A power conversion circuit (10) comprises: an input terminal (PI1) to which a first voltage of three-phase AC power is input; an input terminal (PI2) to which a second voltage of the three-phase AC power is input; an input terminal (PI3) to which a third voltage of the three-phase AC power is input; a switch circuit (40) which is connected to the input terminal (PI1), the input terminal (PI2), and the input terminal (PI3), includes a plurality of switch elements (Q11-Q16, Q21-Q26), and generates a primary-side voltage; an isolation transformer (70) which converts the primary-side voltage into a secondary-side voltage; a rectifier circuit (81) which is connected to the isolation transformer (70); and a control unit (101) which controls the on / off of the plurality of switch elements (Q11-Q16, Q21-Q26). The control unit (101) controls the on / off of the switch elements on the basis of sections in which a plurality of control states for setting the on / off of the switch elements are arranged in time series. The control unit (101) performs skip control to skip the on / off control of the switch elements in control states in which the durations of the plurality of control states are less than a skip threshold value (Th).

Description

Power conversion circuit and power conversion control method

[0001] The present invention relates to a power conversion circuit that converts three-phase AC power into DC power and outputs the DC power.

[0002] Patent Document 1 describes a power conversion circuit that receives three-phase AC power and outputs DC power.

[0003] The power conversion circuit of Patent Document 1 sets sectors at 60-degree intervals for a three-phase input voltage having a phase difference of 120°. The power conversion circuit of Patent Document 1 converts the voltage into a predetermined power by controlling the on / off switching of switch elements of a matrix rectifier in accordance with the vector sequence of each sector.

[0004] The vector sequence is set on the assumption that the switching elements are ideal, that is, that the switching elements are switched on and off in substantially 0 seconds.

[0005] US Patent Application Publication No. 2018 / 0262103

[0006] However, in actual switch elements, for example, it takes a certain time for the switch element to turn on after an on control signal is input. Therefore, when an actual switch element is used, it is not possible to perform on / off switching (switching without a time lag) like an ideal switch element. This means that there is a possibility that undesired switching may actually occur, resulting in a switching loss.

[0007] Therefore, the present invention provides a power conversion circuit capable of suppressing switching loss.

[0008] A power conversion circuit according to one embodiment of the present invention includes: a first input terminal to which a first voltage of three-phase AC power is input; a second input terminal to which a second voltage of three-phase AC power is input; a third input terminal to which a third voltage of three-phase AC power is input; a switch circuit connected to the first input terminal, the second input terminal, and the third input terminal, including a plurality of switch elements, and generating a primary voltage; an isolation transformer that converts the primary voltage into a secondary voltage; a rectifier circuit connected to the isolation transformer; and a control unit that controls the on / off of the plurality of switch elements.

[0009] In this configuration, unnecessary switching is suppressed.

[0010] According to the present invention, it is possible to configure a power conversion circuit in which switching loss is suppressed.

[0011] FIG. 1 is a circuit diagram of a power conversion circuit according to an embodiment of the present invention. FIG. 2 is a circuit diagram of a portion of the power conversion circuit according to an embodiment of the present invention, including a switch circuit. FIG. 3 is a diagram illustrating a concept of setting sections in a power conversion control method according to an embodiment of the present invention. FIG. 4 is a table illustrating an example of a control state in the power conversion control method according to an embodiment of the present invention. FIG. 5 is a flowchart illustrating an example of a power conversion control method according to an embodiment of the present invention. FIG. 6 is a state diagram of multiple switching elements illustrating an example of a normal sequence. FIG. 7 is a diagram illustrating the on / off states of multiple switching elements set in the normal sequence. FIG. 8 is a state diagram of multiple switching elements illustrating an example of a skip sequence. FIG. 9 is a state diagram of multiple switching elements illustrating an example of a skip sequence. FIG. 10 is a diagram illustrating the on / off states of multiple switching elements set in the skip sequence. FIG. 11 is a table illustrating an example of switch elements that are subjected to skip control for each section. FIG. 12 is a state diagram of multiple switching elements illustrating another example of a skip sequence.

[0012] A power conversion circuit according to an embodiment of the present invention will be described with reference to the drawings.

[0013] (Circuit Configuration 1 of Power Conversion Circuit) Fig. 1 is a circuit diagram of a power conversion circuit according to an embodiment of the present invention. Fig. 2 is a circuit diagram of a part including a switch circuit of the power conversion circuit according to an embodiment of the present invention.

[0014] 1 and 2, the power conversion circuit 10 includes a plurality of input terminals PI1, PI2, and PI3, a high-side DC output terminal POH, and a low-side DC output terminal POL. The input terminal PI1 corresponds to the "first input terminal" of the present invention, the input terminal PI2 corresponds to the "second input terminal" of the present invention, and the input terminal PI3 corresponds to the "third input terminal" of the present invention.

[0015] A three-phase AC power supply 80 is connected to multiple input terminals PI1, PI2, and PI3. The frequency of the input power (input voltage, input current) is, for example, 60 Hz. The voltage and current of each phase input to the input terminals PI1, PI2, and PI3 have a phase difference of 120°. The input voltage to the input terminals PI1, PI2, and PI3 is, for example, approximately 200 V to 500 V, and the input current is approximately 30 A. In other words, power on the order of kW is input to the power conversion circuit 10. The power conversion circuit 10 converts this three-phase AC power into DC power (DC output voltage, DC output current) and outputs it to a load LD connected to the high-side DC output terminal POH and the low-side DC output terminal POL.

[0016] The power conversion circuit 10 includes a plurality of filter inductors 21-23 (filter inductor 21, filter inductor 22, filter inductor 23), a plurality of filter capacitors 31-33 (filter capacitor 31, filter capacitor 32, filter capacitor 33), a switch circuit 40, a resonant inductor 60, an isolation transformer 70, a rectifier circuit 81, an output smoothing inductor 82, an output smoothing capacitor 83, a control unit 101, and an output voltage detection circuit 102.

[0017] The filter inductors 21, 22, and 23 have the same configuration. The filter capacitors 31, 32, and 33 have the same configuration.

[0018] The switch circuit 40 includes switch circuit input terminals Pi41, Pi42, and Pi43, and switch circuit output terminals Po1 and Po2.

[0019] The switch circuit 40 includes a plurality of high-side bidirectional switch elements 41, 43, 45 (high-side bidirectional switch element 41, high-side bidirectional switch element 43, high-side bidirectional switch element 45) and a plurality of low-side bidirectional switch elements 42, 44, 46 (low-side bidirectional switch element 42, low-side bidirectional switch element 44, low-side bidirectional switch element 46).

[0020] The high-side bidirectional switch element 41 includes a switch element Q11 and a switch element Q21. The high-side bidirectional switch element 43 includes a switch element Q13 and a switch element Q23. The high-side bidirectional switch element 45 includes a switch element Q15 and a switch element Q25.

[0021] The low-side bidirectional switch element 42 includes a switch element Q12 and a switch element Q22. The low-side bidirectional switch element 44 includes a switch element Q14 and a switch element Q24. The low-side bidirectional switch element 46 includes a switch element Q16 and a switch element Q26.

[0022] The multiple switch elements Q11-Q16 (Q11, Q12, Q13, Q14, Q15, Q16) and Q21-Q26 (Q21, Q22, Q23, Q24, Q25, Q26) are power semiconductor elements and include body diodes.

[0023] The switch element Q11 corresponds to the "first switch element" of the present invention, and the switch element Q21 corresponds to the "second switch element" of the present invention. The switch element Q14 corresponds to the "third switch element" of the present invention, and the switch element Q24 corresponds to the "fourth switch element" of the present invention. The switch element Q13 corresponds to the "fifth switch element" of the present invention, and the switch element Q23 corresponds to the "sixth switch element" of the present invention. The switch element Q16 corresponds to the "seventh switch element" of the present invention, and the switch element Q26 corresponds to the "eighth switch element" of the present invention. The switch element Q15 corresponds to the "ninth switch element" of the present invention, and the switch element Q25 corresponds to the "tenth switch element" of the present invention. The switch element Q12 corresponds to the "eleventh switch element" of the present invention, and the switch element Q22 corresponds to the "twelfth switch element" of the present invention.

[0024] The source terminal of the switch element Q11 and the source terminal of the switch element Q21 that constitute the high-side bidirectional switch element 41 are connected together. The body diodes of the switch elements Q11 and Q21 are connected in the reverse direction.

[0025] The source terminal of the switch element Q14 and the source terminal of the switch element Q24 that constitute the low-side bidirectional switch element 44 are connected together. The body diodes of the switch elements Q14 and Q24 are connected in the reverse direction.

[0026] The high-side bidirectional switch element 41 and the low-side bidirectional switch element 44 are connected in series to form a first series circuit. More specifically, the drain terminal of the switch element Q11 of the high-side bidirectional switch element 41 and the drain terminal of the switch element Q24 of the low-side bidirectional switch element 44 are connected to form a first series circuit by the high-side bidirectional switch element 41 and the low-side bidirectional switch element 44.

[0027] A connection node ND1 between the high-side bidirectional switch element 41 and the low-side bidirectional switch element 44 in the first series circuit is connected to a switch circuit input terminal Pi41.

[0028] The source terminal of the switch element Q13 and the source terminal of the switch element Q23 that constitute the high-side bidirectional switch element 43 are connected together. The body diodes of the switch elements Q13 and Q23 are connected in the reverse direction.

[0029] The source terminal of the switch element Q16 and the source terminal of the switch element Q26 that constitute the low-side bidirectional switch element 46 are connected together. The body diodes of the switch elements Q16 and Q26 are connected in the reverse direction.

[0030] The high-side bidirectional switch element 43 and the low-side bidirectional switch element 46 are connected in series to form a second series circuit. More specifically, the drain terminal of the switch element Q13 of the high-side bidirectional switch element 43 and the drain terminal of the switch element Q26 of the low-side bidirectional switch element 46 are connected to form a second series circuit by the high-side bidirectional switch element 43 and the low-side bidirectional switch element 46.

[0031] A connection node ND2 between the high-side bidirectional switch element 43 and the low-side bidirectional switch element 46 in the second series circuit is connected to the switch circuit input terminal Pi42.

[0032] The source terminal of the switch element Q15 and the source terminal of the switch element Q25 that constitute the high-side bidirectional switch element 45 are connected together. The body diodes of the switch elements Q15 and Q25 are connected in the reverse direction.

[0033] The source terminal of the switch element Q12 and the source terminal of the switch element Q22 that constitute the low-side bidirectional switch element 42 are connected together. The body diodes of the switch elements Q12 and Q22 are connected in the reverse direction.

[0034] The high-side bidirectional switch element 45 and the low-side bidirectional switch element 42 are connected in series to form a third series circuit. More specifically, the drain terminal of the switch element Q15 of the high-side bidirectional switch element 45 and the drain terminal of the switch element Q22 of the low-side bidirectional switch element 42 are connected to form a third series circuit by the high-side bidirectional switch element 45 and the low-side bidirectional switch element 42.

[0035] A connection node ND3 between the high-side bidirectional switch element 45 and the low-side bidirectional switch element 42 in the third series circuit is connected to a switch circuit input terminal Pi41.

[0036] The first series circuit formed by the high-side bidirectional switch element 41 and the low-side bidirectional switch element 44, the second series circuit formed by the high-side bidirectional switch element 43 and the low-side bidirectional switch element 46, and the third series circuit formed by the high-side bidirectional switch element 45 and the low-side bidirectional switch element 42 are connected in parallel.

[0037] More specifically, the drain terminal of the switch element Q21 of the high-side bidirectional switch element 41, the drain terminal of the switch element Q23 of the high-side bidirectional switch element 43, and the drain terminal of the switch element Q25 of the high-side bidirectional switch element 45 are connected to one another and are connected to the switch circuit output terminal Po1.

[0038] The drain terminal of the switch element Q14 of the low-side bidirectional switch element 44, the drain terminal of the switch element Q16 of the low-side bidirectional switch element 46, and the drain terminal of the switch element Q12 of the low-side bidirectional switch element 42 are connected to one another. These drain terminals are connected to the switch circuit output terminal Po2.

[0039] The input terminal PI1 is connected to one terminal of a filter inductor 21. The other terminal of the filter inductor 21 is connected to a connection node ND1 of the first series circuit of the switch circuit 40 via a switch circuit input terminal Pi41 of the switch circuit 40.

[0040] The input terminal PI2 is connected to one terminal of the filter inductor 22. The other terminal of the filter inductor 22 is connected to a connection node ND2 of the second series circuit of the switch circuit 40 via a switch circuit input terminal Pi42 of the switch circuit 40.

[0041] The input terminal PI3 is connected to one terminal of the filter inductor 23. The other terminal of the filter inductor 23 is connected to a connection node ND3 of the third series circuit of the switch circuit 40 via a switch circuit input terminal Pi43 of the switch circuit 40.

[0042] One terminal of the filter capacitor 31 is connected to the connection node ND1, one terminal of the filter capacitor 32 is connected to the connection node ND2, and one terminal of the filter capacitor 33 is connected to the connection node ND3.

[0043] The other terminal of filter capacitor 31, the other terminal of filter capacitor 32, and the other terminal of filter capacitor 33 are connected to each other.

[0044] In this embodiment, the filter capacitors 31, 32, and 33 are star-connected, but they may also be delta-connected.

[0045] One terminal of a resonant inductor 60 is connected to a switch circuit output terminal Po1 of the switch circuit 40. The other terminal of the resonant inductor 60 is connected to one terminal of a primary coil 71 of an isolation transformer 70. The other terminal of the primary coil 71 of the isolation transformer 70 is connected to a switch circuit output terminal Po2 of the switch circuit 40. Note that the resonant inductor 60 may use the leakage inductance of the primary coil 71 of the isolation transformer 70.

[0046] A rectifier circuit 81 is connected to the secondary coil 72 of the isolation transformer 70. The rectifier circuit 81 is configured by a bridge circuit of a plurality of switch elements Q81, Q82, Q83, and Q84.

[0047] The high-side output terminal of the rectifier circuit 81 is connected to the high-side DC output terminal POH through an output smoothing inductor 82. The low-side output terminal of the rectifier circuit 81 is connected to the low-side DC output terminal POL.

[0048] The output smoothing capacitor 83 is connected between the high-side DC output terminal POH and the low-side DC output terminal POL.

[0049] The control unit 101 is configured by, for example, an IC having an arithmetic processing function such as an MCU. The control unit 101 is connected to a plurality of switch elements Q11-Q16, Q21-Q26. The control unit 101 generates control signals that control the on / off of the plurality of switch elements Q11-Q16, Q21-Q26. At this time, the control unit 101 performs power conversion control based on the output voltage detected by the output voltage detection circuit 102. The control unit 101 synchronizes the control signals for the plurality of switch elements Q11-Q16, Q21-Q26 and outputs them to the plurality of switch elements Q11-Q16, Q21-Q26.

[0050] The output voltage detection circuit 102 is configured using, for example, a photodiode and a photocoupler. However, the output voltage detection circuit 102 is not limited to this configuration, and may have any configuration that can detect the output voltage of the power conversion circuit 10 or the output voltage of the rectifier circuit 81 corresponding to the output voltage.

[0051] The output voltage detection circuit 102 is connected to, for example, the output terminal of the rectifier circuit 81. The output voltage detection circuit 102 detects the output voltage at a predetermined sampling period and outputs the detected output voltage to the control unit 101.

[0052] In this configuration, the power conversion circuit 10 converts the input three-phase AC power into DC power of a predetermined voltage and a predetermined current, and outputs it to the load ZD.

[0053] More specifically, the control unit 101 performs on / off control (switching control) of the multiple switch elements Q11-Q16 and Q21-Q26 of the switch circuit 40 based on a power conversion control method described later.

[0054] The multiple switch elements Q11-Q16, Q21-Q26 of the switch circuit 40 sequentially transition between on and off operating states based on control signals from the control unit 101. As a result, the switch circuit 40 generates high-frequency (on the order of several tens to several hundreds of kHz, for example, 80 kHz) AC power for conversion (primary-side AC power (primary-side AC voltage, primary-side AC current)) from AC power of the commercial frequency (60 Hz), and outputs it to a primary coil 71 of the isolation transformer 70 via the resonant inductor 60.

[0055] A secondary output current corresponding to the coupling coefficient between the primary coil 71 and the secondary coil 72 is excited in the secondary coil 72 of the isolation transformer 70. As a result, a secondary AC voltage is generated across the secondary coil 72. The rectifier circuit 81 rectifies the secondary output current of the isolation transformer 70. The output smoothing inductor 82 and the output smoothing capacitor 83 smooth the rectified current. As a result, the power conversion circuit 10 outputs a desired DC voltage and DC current to the load ZD from the high-side DC output terminal POH and the low-side DC output terminal POL.

[0056] (Specific Example of Power Conversion Control Method) Fig. 3 is a diagram showing a concept of setting sections in a power conversion control method according to an embodiment of the present invention. Fig. 4 is a table showing an example of control states in a power conversion control method according to an embodiment of the present invention.

[0057] When performing switching control, the control unit 101 of the power conversion circuit 10 sets multiple sections SC1-SC6 for the input voltage. The multiple sections SC1-SC6 are set by dividing one wavelength of the input voltage into six equal parts. For example, in the case of FIG. 3 , the timing of the maximum amplitude is set to a phase of 0° for the input voltage vA input to the switch circuit input terminal Pi41. Section SC1 is set for a phase range of ±30° centered on phase 0°. Section SC2 follows section SC1 in time series and is set for a phase range of ±30° centered on phase +60°. Section SC3 follows section SC2 in time series and is set for a phase range of ±30° centered on phase +120°.

[0058] Section SC4 follows section SC3 in time series and is set for a phase range of ±30° centered on a phase of +180°. Note that in FIG. 3, since the phase is centered on 0°, the latter half of section SC4 is set for a phase range of −180° to −150°.

[0059] Section SC5 follows section SC4 in time series and is set for a phase range of ±30° centered on a phase of +240°. Note that in FIG. 3, since the phase is centered on 0°, section SC5 is set for a phase range of −150° to −90°.

[0060] Section SC6 follows section SC5 in time series and is set for a phase range of ±30° centered on a phase of +300°. Note that in FIG. 3, since the phase is centered on 0°, section SC6 is set for a phase range of −90° to −30°.

[0061] The multiple sections SC1-SC6 are further divided into 30° phase ranges. In the following, a phase range of −180° to +180° is set with a phase of 0° as the center.

[0062] Section SC1 is set to have a section SC1a with a phase range of -30° to 0° and a section SC1b with a phase range of 0° to +30°. Section SC2 is set to have a section SC2a with a phase range of +30° to +60° and a section SC2b with a phase range of +60° to +90°. Section SC3 is set to have a section SC3a with a phase range of +90° to +120° and a section SC3b with a phase range of +120° to +150°.

[0063] Section SC4 is set to have a section SC4a with a phase range of +150° to +180° and a section SC4b with a phase range of -180° to -150°. Section SC5 is set to have a section SC5a with a phase range of -150° to -120° and a section SC5b with a phase range of -120° to -90°. Section SC6 is set to have a section SC6a with a phase range of -90° to -60° and a section SC6b with a phase range of -60° to -30°.

[0064] The control unit 101 performs control in the order of section SC1, section SC2, section SC3, section SC4, section SC5, and section SC6, and then repeats control while maintaining this order. More specifically, the control unit 101 performs control in the order of section SC1a, section SC1b, section SC2a, section SC2b, section SC3a, section SC3b, section SC4a, section SC4b, section SC5a, section SC5b, section SC6a, and section SC6b, and then repeats control while maintaining this order.

[0065] The control unit 101 sets 14 types of control states for each of the sections SC1a, SC1b, SC2a, SC2b, SC3a, SC3b, SC4a, SC4b, SC5a, SC5b, SC6a, and SC6b, as shown in Fig. 4. The control states are settings of the on / off states of multiple switch elements Q11-Q16 and Q21-Q26. The time lengths of the control states are not necessarily constant and are set by a power conversion control method, the details of which will be described later.

[0066] Specifically, the control unit 101 sets a plurality of control states ST1-ST14 for the section SC1a. The control unit 101 performs control during the section SC1a in ascending order of control state numbers, and then repeats the control while maintaining this order. More specifically, the control is performed in the order of control state ST1, control state ST2, control state ST3, control state ST4, control state ST5, control state ST6, control state ST7, control state ST8, control state ST9, control state ST10, control state ST11, control state ST12, control state ST13, and control state ST14, and then repeats the control while maintaining this order.

[0067] The control unit 101 performs similar control on sections SC1b, SC2a, SC2b, SC3a, SC3b, SC4a, SC4b, SC5a, SC5b, SC6a, and SC6b.

[0068] That is, the control unit 101 sets a plurality of control states ST15-ST28 for section SC1b, performs control during section SC1b in ascending order of control state numbers, and then repeats control while maintaining this order.

[0069] The control unit 101 sets a plurality of control states ST29-ST42 for section SC2a, performs control during section SC2a in ascending order of control state numbers, and then repeats control while maintaining this order. The control unit 101 sets a plurality of control states ST43-ST56 for section SC2b, performs control during section SC2b in ascending order of control state numbers, and then repeats control while maintaining this order.

[0070] The control unit 101 sets a plurality of control states ST57-ST70 for section SC3a, performs control in ascending order of control state numbers during section SC3a, and then repeats control while maintaining this order. The control unit 101 sets a plurality of control states ST71-ST84 for section SC3b, performs control in ascending order of control state numbers during section SC3b, and then repeats control while maintaining this order.

[0071] The control unit 101 sets a plurality of control states ST71-ST84 for section SC4a, performs control during section SC4a in ascending order of control state numbers, and then repeats control while maintaining this order. The control unit 101 sets a plurality of control states ST85-ST98 for section SC4b, performs control during section SC4b in ascending order of control state numbers, and then repeats control while maintaining this order.

[0072] The control unit 101 sets a plurality of control states ST99-ST112 for section SC5a, performs control during section SC5a in ascending order of control state numbers, and then repeats control while maintaining this order. The control unit 101 sets a plurality of control states ST113-ST126 for section SC5b, performs control during section SC5b in ascending order of control state numbers, and then repeats control while maintaining this order.

[0073] The control unit 101 sets a plurality of control states ST127-ST140 for section SC6a, performs control during section SC6a in ascending order of control state numbers, and then repeats control while maintaining this order. The control unit 101 sets a plurality of control states ST141-ST154 for section SC6b, performs control during section SC6b in ascending order of control state numbers, and then repeats control while maintaining this order.

[0074] The control unit 101 sets a plurality of sections and control states in this way and performs switching control as shown in Fig. 5. Fig. 5 is a flowchart showing an example of a power conversion control method according to an embodiment of the present invention.

[0075] The control unit 101 sets a normal sequence for the section next to the section for which switching control is being performed (S11). The normal sequence is a sequence in which the on / off control of the multiple control states constituting the section and the time length T of the multiple control states are set when the multiple control states are switched by ideal switch elements.

[0076] More specifically, the control unit 101 sets the modulation factor based on the input voltage and the output voltage detected by the output voltage detection circuit 102. The control unit 101 sets the on or off state of the multiple switching elements in the multiple control states and the time lengths T of the multiple control states based on the modulation factor.

[0077] The control unit 101 stores a skip threshold value Th. The skip threshold value Th is set, for example, based on the activation time of the multiple switch elements Q11-Q16 and Q21-Q26. The activation time is the time it takes for a switching element in an OFF state (open state) to change to an ON state (conducting state) after an ON control signal is input to the switching element. The skip threshold value Th is set, for example, to be approximately the same as the activation time, or to be approximately 1.5 or 2.0 times the activation time.

[0078] The setting of this skip threshold Th is just one example, and is set to a threshold such that in a control state where switching control (on control) from an off state to an on state is set, the on time is hardly secured, or even if the on time is secured, it is so short that it does not function effectively as a function of the switch circuit 40.

[0079] The control unit 101 compares the time lengths T of the plurality of control states with the skip threshold Th. If there are no control states with a time length less than the skip threshold Th (S12: NO), the control unit 101 performs switching control according to the normal sequence that has already been set (S13).

[0080] If there is a control state whose time length is less than the skip threshold Th (S12: YES), the control unit 101 detects whether there is a switch element that performs ON control in this control state. If there is a switch element that performs ON control (S14: YES), the control unit 101 performs switching control using a skip sequence that skips this control state (S15). Here, skipping a control state means that in the sequence of multiple states that are executed in the above-mentioned chronological order, the control state to be skipped is not executed, and the control state next to the skipped control state is executed.

[0081] More specifically, skipping a control state (skip control) is control that does not input an ON control signal to a switch element that is not intentionally transitioned to the ON state. Alternatively, skip control may be control that supplies an ON control signal to a switch element that is not intentionally transitioned to the ON state for a time period that prevents the switch element from turning ON. Furthermore, skip control may be control that supplies an ON control signal to a switch element that is not intentionally transitioned to the ON state at a voltage value that prevents the switch element from turning ON.

[0082] Such skip control can be detected by measuring the voltages supplied from the control unit 101 to the gate terminals of the plurality of switch elements Q11-Q16 and Q21-Q26.

[0083] Furthermore, even if there is a control state with a time length less than the skip threshold Th (S12: YES), if there is no switch element to perform on control (S14: NO), the control unit 101 performs switching control using the normal sequence that has already been set (S13).

[0084] By performing such power conversion control, the power conversion circuit 10 can eliminate on-control of switch elements that is not practically effective, thereby enabling the power conversion circuit 10 to suppress unnecessary switching loss.

[0085] (Example of Specific Power Conversion Control) Fig. 6 is a state diagram of a plurality of switching elements showing an example of a normal sequence, Fig. 6 shows an example of section 2a.

[0086] As shown in FIG. 6, section 2a is made up of a plurality of control states ST29-ST42, which are arranged in chronological order.

[0087] The control unit 101 sets the on / off states of the multiple switch elements Q11-Q16, Q21-Q26 in the multiple control states ST29-ST42 and the time lengths T29-T42 of the multiple control states ST29-ST42 based on the modulation rate so that the desired output voltage is obtained from the input voltage.

[0088] In the case of Fig. 6, in control states ST30-ST34, the on / off states of multiple switch elements Q11-Q16 and Q21-Q26 should be set as shown in Fig. 7. Fig. 7 is a diagram showing the on / off states of multiple switch elements set in the normal sequence.

[0089] For example, as shown in FIG. 7, in the control state ST30, in the first series circuit, the switch elements Q11, Q21, and Q14 are set to the ON state, and the switch element Q24 is set to the OFF state.

[0090] In the control state ST30, in the second series circuit, the switch elements Q13 and Q23 are set to the OFF state, the switch element Q16 is set to the ON state, and the switch element Q26 is set to the OFF state.

[0091] In the control state ST30, in the third series circuit, the switch element Q15 is set to the ON state, the switch element Q25 is set to the OFF state, and the switch elements Q12 and Q22 are set to the ON state.

[0092] Although detailed description is omitted, as shown in FIG. 7, in the control states ST31 to ST34, the on / off states of the multiple switch elements Q11 to Q16 and Q21 to Q26 are set based on the normal sequence shown in FIG.

[0093] The control unit 101 compares the durations T29-T42 of the plurality of control states ST29-ST42 in the normal sequence with the skip threshold Th. In the case of Fig. 6, the control unit 101 detects that the duration T31 of the control state ST31, the duration T32 of the control state ST32, the duration T38 of the control state ST38, and the duration T39 of the control state ST39 are all less than the skip threshold Th.

[0094] In the control state ST31, the control unit 101 selects a switch that is a starting point at which a change in the current path through the switch circuit 40 occurs. The switch that is the starting point at which the current path changes is the switch element Q13 that is scheduled to transition from an OFF state to an ON state during the time length T31 ​​of the control state ST31.

[0095] Similarly, in control state ST38, the control unit 101 selects a switch that will be the starting point at which the current path through the switch circuit 40 changes. The switch that will be the starting point at which the current path changes is switch element Q26 that is scheduled to transition from the OFF state to the ON state during time length T38 of control state ST38. Note that the switch that will be the starting point at which the current path changes is determined for each section, and therefore may be set in advance in the memory of the control unit, etc.

[0096] Furthermore, because the switch element Q13, which is scheduled to transition to the ON state in control state ST31 in the normal sequence, maintains the ON state until control state ST33, the control unit 101 sets a skip for not only control states ST31 and ST32 but also the subsequent control state ST33. The reason for skipping control state ST33, which has a time length T33 greater than the skip threshold Th, is as follows. The control states ST31, ST32, and ST33 are switched as a set, allowing the expected current to flow through the switch circuit 40. However, if the switch control is performed without any one of the control states ST31, ST32, and ST33, an unexpected current may flow through the switch circuit 40, resulting in reduced efficiency. Furthermore, control state ST34 is a control state in which the switch element Q13 is in the OFF state. Therefore, the switch element Q13 does not become the starting point for a change in the current path, and therefore is not skipped.

[0097] Similarly, in the normal sequence, the switch element Q26 that is scheduled to transition to the ON state in control state ST38 maintains the ON state until control state ST40. The control unit 101 sets not only control states ST38 and ST39 but also the subsequent control state ST40 to be skipped.

[0098] In this way, the control unit 101 sets the skip sequence so as to skip the control states ST31, ST32, ST38, and ST39.

[0099] There are several ways to set the skip sequence.

[0100] Fig. 8 is a state diagram of a plurality of switching elements showing an example of a skip sequence. Fig. 8 shows an example of section 2a, similar to Fig. 6. As shown in Fig. 8, the control unit 101 skips only the on control of the switch element Q13 for the control states ST31, ST32, and ST33 that should be skipped.

[0101] Furthermore, the control unit 101 skips only the on control of the switch element Q26 for the control states ST38, ST39, and ST40 that should be skipped. By using such a power conversion control method, the power conversion circuit 10 can suppress unnecessary switching loss and suppress the generation of noise caused by changes in the frequency of the voltage output from the switch circuit 40.

[0102] As another example, Fig. 9 is a state diagram of a plurality of switching elements showing an example of a skip sequence. Fig. 9 shows an example of section 2a, similar to Fig. 6. Fig. 10 is a diagram showing the on / off states of a plurality of switch elements set in a skip sequence.

[0103] The control unit 101 corrects the section 2a so that control states ST31, ST32, and ST33 are skipped, and control states ST38, ST39, and ST36 are skipped.

[0104] In the skip sequence, the control unit 101 sets the control states ST29, ST30, ST34, ST35, ST36, ST37, ST41, and ST42 for section 2a so that they are arranged in chronological order. In other words, in the skip sequence, the control unit 101 does not set control states ST31, ST32, or ST33 after control state ST30, but sets control state ST34 after control state ST30. Furthermore, the control unit 101 does not set control states ST38, ST39, or ST40 after control state ST37, but sets control state ST41 after control state ST37.

[0105] Furthermore, the control unit 101 controls the switching of the switch element Q11, which transitions from the on state to the off state during the control states ST31, ST32, and ST33 in the normal sequence, to the off state in the control state ST34.

[0106] That is, as shown in FIG. 10, the control state changes from a control state ST30 in which the switch elements Q11, Q21, Q14, Q16, Q15, Q12, and Q22 are in the ON state and the switch elements Q24, Q13, Q23, Q26, and Q25 are in the OFF state to a control state ST34 in which only the switch element Q23 has transitioned to the ON state.

[0107] This allows the power conversion circuit 10 to eliminate the need to turn on the switch element Q13, which is likely to be ineffective, and therefore the power conversion circuit 10 can suppress unnecessary switching loss.

[0108] Furthermore, the control unit 101 controls the switching of the switch element Q23, which transitions from the OFF state to the ON state during the control states ST38, ST39, and ST40 in the normal sequence, to the ON state in the control state ST34.

[0109] This allows the power conversion circuit 10 to eliminate the need to turn on the switch element Q26, which is likely to be ineffective, and thus reduces unnecessary switching loss.

[0110] Furthermore, the control unit 101 sets the time length T30A of the control state ST30 before the skipped control states ST31, ST32, and ST33. More specifically, the control unit 101 sets the time length T30A of the control state ST30 to the sum of the time lengths T30, T31, T32, and T33 of the control states ST30, ST31, ST32, and ST33 in the normal sequence.

[0111] Similarly, the control unit 101 sets the time length T37A of the control state ST37 before the skipped control states ST38, ST39, and ST40. More specifically, the control unit 101 sets the time length T37A of the control state ST37 to the sum of the time lengths T37, T38, T39, and T40 of the control states ST37, ST38, ST39, and ST40 in the normal sequence.

[0112] As a result, the time length of section 2a when the skip sequence is used is the same as that of the normal sequence, and therefore the power conversion circuit 10 can suppress undesired changes in the frequency of the AC power supplied from the switch circuit 40 to the isolation transformer 70. As a result, the power conversion circuit 10 can suppress, for example, the generation of noise caused by changes in frequency.

[0113] In the above example, the control unit 101 adjusts the time length of the control state before the skipped control state. However, the control unit 101 may adjust the time length of the control state after the skipped control state. For example, when skipping the above-described control states ST31, ST32, and ST33, the control unit 101 may adjust the time length T34 of the control state ST34.

[0114] Although the above description is directed to section 2a, such skip control is set for each section. Fig. 10 is a table showing an example of a switch element that controls skip for each section.

[0115] 11, the control unit 101 uses the above-described power conversion control method to set the switching elements to be skipped for each section. For example, in section 1a, switching elements Q12 and Q25 are skip-controlled, and in section 1b, switching elements Q16 and Q23 are skip-controlled. In section 2a, switching elements Q13 and Q26 are skip-controlled, and in section 2b, switching elements Q11 and Q24 are skip-controlled.

[0116] In section 3a, switching elements Q14 and Q21 are skip-controlled, and in section 3b, switching elements Q12 and Q25 are skip-controlled. In section 4a, switching elements Q15 and Q22 are skip-controlled, and in section 4b, switching elements Q13 and Q26 are skip-controlled.

[0117] In section 5a, switching elements Q16 and Q23 are skip-controlled, and in section 5b, switching elements Q14 and Q21 are skip-controlled. In section 6a, switching elements Q11 and Q24 are skip-controlled, and in section 6b, switching elements Q15 and Q22 are skip-controlled.

[0118] In this way, the control unit 101 performs skip control on a pair of high-side switch elements and low-side switch elements connected to any of the connection nodes ND1, ND2, and ND3 in one section. Furthermore, the control unit 101 performs skip control on switch elements through which a current flows corresponding to a combination of input voltages vA, vB, and vC with a small potential difference in each combination in one section.

[0119] By performing such skip control, the power conversion circuit 10 can suppress disturbances in the output voltage and output current (primary side AC power (primary side AC voltage, primary side AC current)) of the switch circuit 40 caused by the skip control.

[0120] 12 is a state diagram of a plurality of switching elements showing another example of a skip sequence. In the power conversion control method shown in FIG. 12, the control unit 101 adjusts the time lengths of the control states before and after the control state to be skipped.

[0121] Specifically, when skipping control states ST31, ST32, and ST33, the control unit 101 sets the time length T30B of the preceding control state ST30 and the time length T34B of the following control state ST34. The control unit 101 sets the time length T30B and the time length T34B to be the same. More specifically, the control unit 101 sets the time length T30B of the control state ST30 and the time length T34B of the control state ST34 to a value obtained by multiplying the sum of the time lengths T30, T31, T32, T33, and T34 of the control states ST30, ST31, ST32, ST33, and ST34 in the normal sequence by 1 / 2.

[0122] Furthermore, when skipping control states ST38, ST39, and ST40, the control unit 101 sets the time length T37B of the preceding control state ST37 and the time length T41B of the following control state ST41 using a concept similar to the concept for setting the time length T30B of control state ST30 and the time length T34B of control state ST34. Note that the correction of time length by skip control is not limited to this, and it is sufficient that the time length of the section in the skip sequence is the same as the time length of the section in the normal sequence.

[0123] At this time, if there is a switch element in which an on / off state transition occurs during the period in the skipped control state, the control unit 101 performs on / off switching control during the skipped control state. For example, when skipping control states ST31, ST32, and ST33, the control unit 101 performs on / off switching control when switching from control state ST30 to control state ST34.

[0124] By using such a power conversion control method, the power conversion circuit 10 can suppress unnecessary switching loss and can suppress the generation of noise caused by changes in the frequency of the voltage output from the switch circuit 40.

[0125] <1> A power conversion circuit comprising: a first input terminal to which a first voltage of three-phase AC power is input; a second input terminal to which a second voltage of the three-phase AC power is input; a third input terminal to which a third voltage of the three-phase AC power is input; a switch circuit connected to the first input terminal, the second input terminal, and the third input terminal, the switch circuit including a plurality of switch elements and generating a primary-side AC voltage; an isolation transformer converting the primary-side voltage to a secondary-side voltage; a rectifier circuit connected to the isolation transformer; and a control unit controlling on / off of the plurality of switch elements, wherein the control unit controls on / off of the switch elements based on a section in which a plurality of control states that set on / off of the switch elements are arranged in chronological order, and performs skip control to skip on / off control of the switch elements for a control state of the plurality of control states whose time length is less than a skip threshold.

[0126] <2> The power conversion circuit according to <1>, wherein the skip control includes control performed on a specific switch that transitions from an off state to an on state during a specific control state whose time length is less than the skip threshold.

[0127] <3> The power conversion circuit according to <2>, wherein the control unit performs the skip control on the specific switch in a control state that is consecutive to the specific control state and in which the specific switch is in an on state, even if the time length is equal to or greater than the skip threshold.

[0128] <4> The power conversion circuit according to any one of <1> to <3>, wherein the skip control is performed on all switches.

[0129] <5> The power conversion circuit according to any one of <1> to <4>, wherein the control unit performs the skip control on the switch elements corresponding to a combination of the first voltage, the second voltage, and the third voltage in the control state, where the potential difference is small.

[0130] <6> The plurality of switch elements of the switch circuit include: a first switch element and a second switch element connected in series to the high side of the first input terminal, having body diodes in opposite directions to each other, and connected in sequence from the first input terminal side; a third switch element and a fourth switch element connected to the low side of the first input terminal, having body diodes in opposite directions to each other, and connected in sequence from the opposite side to the first input terminal side; a fifth switch element and a sixth switch element connected in series to the high side of the second input terminal, having body diodes in opposite directions to each other, and connected in sequence from the second input terminal side; a seventh switch element and an eighth switch element connected to the low side of the second input terminal, having body diodes in opposite directions to each other, and connected in sequence from the opposite side to the second input terminal side; and a ninth switch element and a tenth switch element connected in series to the high side of the third input terminal, having body diodes in opposite directions to each other, and connected in sequence from the third input terminal side. the control unit performs the skip control on, in one section, a pair of a high-side switch element and a low-side switch element for a first connection node connected to the first input terminal, a pair of a high-side switch element and a low-side switch element for a second connection node connected to the second input terminal, or a pair of a high-side switch element and a low-side switch element for a third connection node connected to the third input terminal.

[0131] <7> The power conversion circuit according to any one of <1> to <6>, further comprising an output voltage detection circuit that detects the output voltage of the rectifier circuit and outputs the detected output voltage to the control unit, wherein the control unit sets a modulation factor based on an input voltage and the output voltage, and sets a time of the control state based on the modulation factor.

[0132] <8> The power conversion circuit according to any one of <1> to <7>, wherein the control unit adjusts the time length of a control state set before or after the control state that performs the skip control based on the time length of the control state that performs the skip control so that the time length of the section does not change.

[0133] <9> The power conversion circuit according to any one of <1> to <8>, wherein the control unit adjusts the time lengths of the control states set before and after the control state that performs the skip control based on the time length of the control state that performs the skip control so that the time length of the section does not change.

[0134] <10> A power conversion circuit comprising: a first input terminal to which a first voltage of three-phase AC power is input; a second input terminal to which a second voltage of the three-phase AC power is input; and a third input terminal to which a third voltage of the three-phase AC power is input; a switch circuit connected to the first input terminal, the second input terminal, and the third input terminal and including a plurality of switch elements to generate a primary-side AC voltage; an isolation transformer that converts the primary-side voltage generated by the switch circuit into a secondary-side voltage; a rectifier circuit connected to the isolation transformer; and a control unit that controls on / off of the plurality of switch elements, wherein the control unit controls on / off of the switch elements based on a section in which a plurality of control states that set on / off of the switch elements are arranged in chronological order, and performs skip control to skip a control state of the plurality of control states whose time length is less than a skip threshold.

[0135] <11> A power control method for a power conversion circuit including: a switch circuit including a plurality of switch elements and generating a primary-side AC voltage from three-phase AC power; an isolation transformer converting the primary-side voltage to a secondary-side voltage; a rectifier circuit connected to the isolation transformer; and a control unit controlling on / off of the plurality of switch elements, wherein the control unit controls on / off of the switch elements based on a section in which a plurality of control states that set on / off of the switch elements are arranged in chronological order, and performs skip control that skips on / off control of the switch elements for a control state of the plurality of control states whose time length is less than a skip threshold.

[0136] 10: Power conversion circuit 21, 22, 23: Filter inductor 31, 32, 33: Filter capacitor 40: Switch circuit 41, 43, 45: High-side bidirectional switch element 42, 44, 46: Low-side bidirectional switch element 60: Resonant inductor 70: Isolation transformer 71: Primary coil 72: Secondary coil 80: Three-phase AC power supply 81: Rectifier circuit 82: Output smoothing inductor 83: Output smoothing capacitor 101: Control unit 102: Output voltage detection circuit LD: Load ND1, ND2, ND3: Connection node PI1, PI2, PI3: Input terminals Pi41, Pi42, Pi43: Switch circuit input terminals Po1, Po2: Switch circuit output terminals POH: High-side DC output terminal POL: Low-side DC output terminal Q11-Q16, Q21-Q26: Switch elements Q81-Q84: Switch elements SC1, SC1a, SC1b, SC2, SC2a, SC2b, SC3, SC3a, SC3b, SC4, SC4a, SC4b, SC5, SC5a, SC5b, SC6, SC6a, SC6b: Sections ST1-ST154: Control states T, T29-T42, T30A, T30B, ​​T34B, T37A, T37B, T41B: Time length Th: Skip threshold vA, vB, vC: Input voltage ZD: Load

Claims

1. A first input terminal to which a first voltage of three-phase AC power is input, a second input terminal to which a second voltage of the three-phase AC power is input, a third input terminal to which a third voltage of the three-phase AC power is input, a switch circuit connected to the first input terminal, the second input terminal, and the third input terminal, including a plurality of switch elements, and generating a primary-side voltage, an isolation transformer for converting the primary-side voltage into a secondary-side voltage, a rectifier circuit connected to the isolation transformer, and a control unit for controlling on / off of the plurality of switch elements. The control unit controls on / off of the switch elements based on a section in which a plurality of control states for setting on / off of the switch elements are arranged in time series, and performs skip control for skipping on / off control of the switch elements in a control state whose time length is less than a skip threshold value. A power conversion circuit.

2. The skip control includes control performed on a specific switch that transitions from an off state to an on state during a specific control state whose time length is less than the skip threshold value. The power conversion circuit according to claim 1.

3. The control unit performs the skip control on the specific switch even when the time length is equal to or greater than the skip threshold value in a control state that is continuous with the specific control state and in which the specific switch is in an on state. The power conversion circuit according to claim 2.

4. The skip control is control performed on all switches. The power conversion circuit according to any one of claims 1 to 3.

5. The control unit performs the skip control on the switch elements corresponding to a combination in which the potential difference in each combination of the first voltage, the second voltage, and the third voltage in the control state is small. The power conversion circuit according to any one of claims 1 to 4.

6. The plurality of switch elements of the switch circuit include: - A first switch element and a second switch element that are serially connected to the high side of the first input terminal and have body diodes in opposite directions to each other, and are connected in order from the first input terminal side; - A third switch element and a fourth switch element that are connected to the low side of the first input terminal and have body diodes in opposite directions to each other, and are connected in order from the side opposite to the first input terminal side; - A fifth switch element and a sixth switch element that are serially connected to the high side of the second input terminal and have body diodes in opposite directions to each other, and are connected in order from the second input terminal side; - A seventh switch element and an eighth switch element that are connected to the low side of the second input terminal and have body diodes in opposite directions to each other, and are connected in order from the side opposite to the second input terminal side; - A ninth switch element and a tenth switch element that are serially connected to the high side of the third input terminal and have body diodes in opposite directions to each other, and are connected in order from the third input terminal side; - An eleventh switch element and a twelfth switch element that are connected to the low side of the third input terminal and have body diodes in opposite directions to each other, and are connected in order from the side opposite to the third input terminal side. The control unit performs the skip control on a pair of a high-side switch element and a low-side switch element for a first connection node connected to the first input terminal, a pair of a high-side switch element and a low-side switch element for a second connection node connected to the second input terminal, or a pair of a high-side switch element and a low-side switch element for a third connection node connected to the third input terminal in one section. The power conversion circuit according to any one of claims 1 to 5.

7. An output voltage detection circuit that detects the output voltage of the rectifier circuit and outputs it to the control unit is provided. The control unit sets a modulation rate based on the input voltage and the output voltage, and sets the time of the control state based on the modulation rate. The power conversion circuit according to any one of claims 1 to 6.

8. The control unit adjusts, based on the time length of a control state that performs the skip control, the time lengths of control states set before or after the control state that performs the skip control so that the time length of the section does not change. The power conversion circuit according to any one of claims 1 to 7.

9. The control unit adjusts, based on the time length of a control state that performs the skip control, the time lengths of control states set before and after the control state that performs the skip control so that the time length of the section does not change. The power conversion circuit according to any one of claims 1 to 8.

10. A first input terminal to which a first voltage of three-phase AC power is input, a second input terminal to which a second voltage of the three-phase AC power is input, a third input terminal to which a third voltage of the three-phase AC power is input, a switch circuit connected to the first input terminal, the second input terminal, and the third input terminal, including a plurality of switch elements, and generating a primary-side voltage, an isolation transformer that converts the primary-side voltage generated by the switch circuit into a secondary-side voltage, a rectifier circuit connected to the isolation transformer, and a control unit that controls on / off of the plurality of switch elements. The control unit controls on / off of the switch elements based on a section in which a plurality of control states for setting on / off of the switch elements are arranged in time series, and performs skip control for skipping a control state having a time length less than a skip threshold value among the plurality of control states. A power conversion circuit.

11. In a power control method in a power conversion circuit including a switch circuit including a plurality of switch elements and generating a primary-side voltage from three-phase AC power, an isolation transformer that converts the primary-side voltage into a secondary-side voltage, a rectifier circuit connected to the isolation transformer, and a control unit that controls on / off of the plurality of switch elements, the control unit controls on / off of the switch elements based on a section in which a plurality of control states for setting on / off of the switch elements are arranged in time series, and performs skip control for skipping on / off control of a switch element in a control state having a time length less than a skip threshold value among the plurality of control states. A power conversion control method.

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