Power conversion device and method for controlling the same
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- MIRAXIA EDGE TECH CO LTD
- Filing Date
- 2023-07-31
- Publication Date
- 2026-06-23
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical field]
[0001] The present disclosure relates to a power conversion device and a control method thereof, and in particular to a resonant DC / DC converter. [Background technology]
[0002] Conventionally, various circuits have been proposed as resonant DC / DC converters (i.e., power conversion devices) that have the characteristics of high efficiency and low noise (see, for example, Patent Document 1). According to the technology of Patent Document 1, a power conversion device includes a DC / DC converter and a control circuit. The DC / DC converter has a pair of first terminals, a first winding, one or more first switching elements, one or more first diodes, a pair of second terminals, a second winding, one or more second switching elements, and one or more second diodes. In synchronous rectification, the control circuit switches the second switching element from off to on at a second timing that is delayed by a delay time from a first timing at which the first switching element is switched from on to off.
[0003] Synchronous rectification is a control for reducing loss in a diode by turning on a switching element connected in parallel to the diode during a rectification period by the diode. [Prior art documents] [Patent documents]
[0004] [Patent Document 1] JP 2022-153069 A Summary of the Invention [Problem to be solved by the invention]
[0005] However, in the technology of Patent Document 1, the synchronous rectification period is determined based on a predetermined operating state of the power conversion device (parameters such as the voltage, power, or operating frequency to be handled). Therefore, when a transient event occurs in which the voltage or power changes suddenly due to a load fluctuation or the like, the power conversion device cannot follow the transient event because proper synchronous rectification is not performed. Another problem is that the power conversion device cannot operate in a wide voltage adjustment range (i.e., wide range).
[0006] Therefore, an object of the present disclosure is to provide a power conversion device that operates over a wide range and can operate appropriately even if a transient event occurs by following the transient event, and a control method thereof. [Means for solving the problem]
[0007] In order to achieve the above object, a power conversion device according to one embodiment of the present disclosure is a power conversion device that converts power supplied from a DC power source and outputs the power from a pair of output terminals, and includes a first bridge circuit connected between terminals of the DC power source, a second bridge circuit connected between the pair of output terminals, a resonant circuit including an isolation transformer having a first winding connected to the first bridge circuit and a second winding connected to the second bridge circuit, and a control circuit that controls the first bridge circuit and the second bridge circuit, wherein the first bridge circuit includes a plurality of first switch elements connected between terminals of the DC power source, and the second bridge circuit has a plurality of second switch elements connected between the pair of output terminals and a plurality of second diode elements connected in parallel with each of the plurality of second switch elements, and the control circuit has a detection circuit that detects a voltage across each of the plurality of second diode elements or a current flowing through the second winding and specifies a synchronous rectification period, which is a rectification period by the second bridge circuit, in accordance with the detected voltage across each of the plurality of second diode elements or the detected current, and a drive circuit that performs switching control on the plurality of second switch elements in accordance with the specified synchronous rectification period.
[0008] In order to achieve the above object, a control method for a power conversion device according to one embodiment of the present disclosure is a control method for a power conversion device that converts power supplied from a DC power supply and outputs the power from a pair of output terminals, the power conversion device including a first bridge circuit connected between terminals of the DC power supply, a second bridge circuit connected between the pair of output terminals, and a resonant circuit including an isolation transformer having a first winding connected to the first bridge circuit and a second winding connected to the second bridge circuit, the first bridge circuit including a plurality of first switch elements connected between terminals of the DC power supply, and a second winding connected in parallel with each of the plurality of first switch elements. the second bridge circuit has a plurality of second switch elements connected between the pair of output terminals and a plurality of second diode elements connected in parallel with each of the plurality of second switch elements, and the control method includes a detection step of detecting a voltage across each of the plurality of second diode elements or a current flowing through the second winding, and specifying a synchronous rectification period, which is a rectification period by the second bridge circuit, in accordance with the detected voltage across each of the plurality of second diode elements or the detected current, and a drive step of performing switching control on the plurality of second switch elements in accordance with the specified synchronous rectification period. Effect of the Invention
[0009] The present disclosure provides a power conversion device and a control method thereof that operates over a wide range and can operate appropriately even if a transient event occurs by following the transient event. [Brief description of the drawings]
[0010] [Figure 1] FIG. 1 is a circuit block diagram showing a configuration of a power conversion device according to an embodiment. [Diagram 2] FIG. 2 is a circuit diagram showing details of the detection circuit in FIG. [Diagram 3] FIG. 3 is a timing chart showing the operation of the detection circuit shown in FIG. [Figure 4A]FIG. 4A is a flowchart showing the operation of the power conversion device according to the embodiment. [Figure 4B] FIG. 4B is a diagram showing switching control modes of the power conversion device according to the embodiment. [Diagram 5] FIG. 5 is a diagram illustrating the operating frequency of the power conversion device according to the embodiment. [Figure 6A] FIG. 6A is a timing chart when the power conversion device according to the embodiment operates in a full-bridge control mode (low-frequency type operating frequency). [Figure 6B] FIG. 6B is a timing chart when the power conversion device according to the embodiment operates in the full-bridge control mode (high-frequency I-type operating frequency). [Figure 6C] FIG. 6C is a timing chart when the power conversion device according to the embodiment operates in the full-bridge control mode (high-frequency type II operating frequency). [Figure 7] FIG. 7 is a timing chart when the power conversion device according to the embodiment operates in the primary side phase shift control mode. [Figure 8A] FIG. 8A is a timing chart when the power conversion device according to the embodiment operates in a full-bridge control mode with primary side phase shift control (phase shift 0 type). [Figure 8B] FIG. 8B is a timing chart when the power conversion device according to the embodiment operates in a full-bridge control mode with primary-side phase shift control (phase shift type I). [Figure 8C] FIG. 8C is a timing chart when the power conversion device according to the embodiment operates in a full-bridge control mode with primary-side phase shift control (phase shift type II). [Figure 9A] FIG. 9A is a timing chart when the power conversion device according to the embodiment operates in a secondary side phase shift control (zero phase shift) mode. [Figure 9B]FIG. 9B is a timing chart when the power conversion device according to the embodiment operates in the secondary side phase shift control (type I phase shift) mode. [Figure 9C] FIG. 9C is a timing chart when the power conversion device according to the embodiment operates in the secondary side phase shift control (phase shift type II) mode. [Figure 10] FIG. 10 is a circuit block diagram showing a configuration of a power conversion device according to a modified example of the embodiment. [Figure 11] FIG. 11 is a diagram showing a switching control mode during power conversion from the second bridge circuit to the first bridge circuit by the power conversion device according to the modified example of the embodiment. [Figure 12] FIG. 12 is a diagram illustrating an example of application of a power conversion device according to a modification of the embodiment and a conventional power conversion device to a V2H system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present disclosure. The values of voltage, current, power, etc., circuit components, connection positions and connection forms of circuit components, operation timing, processing steps, order of processing steps, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. In addition, each figure is not necessarily illustrated precisely. In each figure, the same reference numerals are used for substantially the same configuration, and duplicated explanations are omitted or simplified. In addition, "A and B are connected" means that A and B are electrically connected, and includes not only the case where A and B are directly connected, but also the case where A and B are indirectly connected with another circuit element interposed between A and B.
[0012] Fig. 1 is a circuit block diagram showing a configuration of a power conversion device 5 according to an embodiment. The power conversion device 5 is an LLC resonant DC / DC converter that converts power supplied from a DC power source and outputs the converted power from a pair of output terminals 8a and 8b, and includes a first bridge circuit 10 connected between terminals 6a and 6b of the DC power source, a second bridge circuit 20 connected between the pair of output terminals 8a and 8b, a resonant circuit 30 including an insulating transformer 31 having a first winding 31a connected to the first bridge circuit 10 and a second winding 31b connected to the second bridge circuit 20, and a control circuit 40 that controls the first bridge circuit 10 and the second bridge circuit 20. In this figure, a smoothing capacitor 7 connected between the terminals 6a and 6b of the DC power source and a smoothing capacitor 9 connected between the pair of output terminals 8a and 8b are also shown.
[0013] In the present embodiment, the first bridge circuit 10 serves as a primary circuit, the second bridge circuit 20 serves as a secondary circuit, and the power conversion device operates as a unidirectional power conversion device that converts a DC voltage input to the primary circuit into a desired DC voltage and outputs it from the secondary circuit. However, as described later, the power conversion device according to the present disclosure can also operate as a bidirectional power conversion device.
[0014] In this embodiment, the first bridge circuit 10 constitutes a primary side circuit, and has a plurality of first switch elements connected between terminals 6a and 6b of a DC power supply, and a plurality of first diode elements connected in parallel with each of the plurality of first switch elements. Hereinafter, in this embodiment, the first bridge circuit 10 is also referred to as the "primary side circuit."
[0015] More specifically, the first switch elements include a first switch element 11a and a second switch element 12a connected in series between the terminals 6a and 6b of the DC power supply, and a third switch element 13a and a fourth switch element 14a connected in series between the terminals 6a and 6b of the DC power supply, and the first diode elements include a first diode 11b, a second diode 12b, a third diode 13b, and a fourth diode 14b connected in parallel with the first switch element 11a, the second switch element 12a, the third switch element 13a, and the fourth switch element 14a, respectively. In this embodiment, all of the first switch elements are NMOS transistors, and all of the first diode elements are parasitic diodes (i.e., body diodes) of the corresponding NMOS transistors.
[0016] In this embodiment, the second bridge circuit 20 constitutes a secondary circuit and has a plurality of second switch elements connected between a pair of output terminals 8a and 8b, and a plurality of second diode elements connected in parallel with each of the plurality of second switch elements. Hereinafter, in this embodiment, the second bridge circuit 20 is also referred to as the "secondary circuit."
[0017] More specifically, the second switch elements include a fifth switch element 21a and a sixth switch element 22a connected in series between a pair of output terminals 8a and 8b, and a seventh switch element 23a and an eighth switch element 24a connected in series between the pair of output terminals 8a and 8b, and the second diode elements include a fifth diode 21b, a sixth diode 22b, a seventh diode 23b, and an eighth diode 24b connected in parallel with the fifth switch element 21a, the sixth switch element 22a, the seventh switch element 23a, and the eighth switch element 24a, respectively. In this embodiment, all of the second switch elements are NMOS transistors, and all of the second diode elements are parasitic diodes (i.e., body diodes) of the corresponding NMOS transistors.
[0018] The resonant circuit 30 is an LLC resonant circuit that is composed of an isolation transformer 31 and capacitors 32 and 33 and resonates at a predetermined resonant frequency. The isolation transformer 31 has a first winding 31a connected between the connection point between the first switch element 11a and the second switch element 12a in the first bridge circuit 10 and the connection point between the third switch element 13a and the fourth switch element 14a, and a second winding 31b connected between the connection point between the fifth switch element 21a and the sixth switch element 22a in the second bridge circuit 20 and the connection point between the seventh switch element 23a and the eighth switch element 24a. The capacitor 32 is connected in series with the first winding 31a, and the capacitor 32 is connected in series with the second winding 31b.
[0019] In addition, "XH", "XL", "YH", and "YL" in the first bridge circuit 10 are drive signals that perform switching control on the first switch element 11a, the second switch element 12a, the third switch element 13a, and the fourth switch element 14a, respectively. Furthermore, "AH", "AL", "BH", and "BL" in the secondary side circuit are drive signals that perform switching control on the fifth switch element 21a, the sixth switch element 22a, the seventh switch element 23a, and the eighth switch element 24a, respectively. The drive signals XH, XL, YH, YL, AH, AL, BH, and BL are output from the drive circuit 42 of the control circuit 40.
[0020] Moreover, in the second bridge circuit 20, "VAH" is the voltage across the fifth diode 21b (strictly speaking, the potential of the cathode with respect to the anode of the fifth diode 21b), "VAL" is the voltage across the sixth diode 22b (strictly speaking, the potential of the cathode with respect to the anode of the sixth diode 22b), "VBH" is the voltage across the seventh diode 23b (strictly speaking, the potential of the cathode with respect to the anode of the seventh diode 23b), "VBL" is the voltage across the eighth diode 24b (strictly speaking, the potential of the cathode with respect to the anode of the eighth diode 24b), and "It2" is the current flowing through the second winding 31b of the insulating transformer 31. These voltages VAH, VAL, VBH, VBL, and the current It2 are detected (i.e., monitored) by the detection circuit 41 of the control circuit 40 and are used to specify the synchronous rectification period.
[0021] The control circuit 40 controls the switching timing of the first bridge circuit 10 and the second bridge circuit 20 by combining full-bridge control, voltage doubling control, and secondary-side phase shift control, which are synchronous rectification for the secondary side circuit, with primary-side phase shift control for the primary side circuit, according to the input DC voltage and output power as a switching control mode (hereinafter also simply referred to as "mode"). For this purpose, the control circuit 40 has a detection circuit 41 and a drive circuit 42. The control circuit 40 not only performs synchronous rectification, but also performs control without synchronous rectification according to the input DC voltage and output power.
[0022] For synchronous rectification, the detection circuit 41 detects the voltages across each of the multiple second diode elements (voltages VAH, VAL, VBH, and VBL) or the current (current It2) flowing through the second winding 31b, and determines the synchronous rectification period during which synchronous rectification is performed on the second bridge circuit 20 according to the detected voltages across each of the multiple second diode elements or current.
[0023] The drive circuit 42 generates and outputs drive signals XH, XL, YH, YL, AH, AL, BH, and BL for each switch element constituting the first bridge circuit 10 and the second bridge circuit 20. The waveforms of the drive signals XH, XL, YH, and YL are determined when it is determined in which mode they are to be operated (based on external information). Therefore, when synchronous rectification is performed, the drive circuit 42 calculates the synchronous rectification period detected by the detection circuit 41 and the drive signals XH, XL, YH, YL, etc., for the drive signals AH, AL, BH, and BL, and outputs optimal AH, AL, BH, and BL.
[0024] Fig. 2 is a circuit diagram showing the details of the detection circuit 41 in Fig. 1. The circuits shown in Fig. 2(a) and (b) are logic circuits that specify the synchronous rectification period using voltages VAH, VAL, VBH, and VBL, and Fig. 2(c) is a logic circuit that specifies the synchronous rectification period using a voltage VIt corresponding to a current It2. The detection circuit 41 operates in either one of two ways based on a preset setting: specifying the synchronous rectification period using the two logic circuits shown in Fig. 2(a) and (b), or specifying the synchronous rectification period using the logic circuit shown in Fig. 2(c).
[0025] The logic circuit shown in (a) of FIG. 2 includes a comparator 51 that compares a voltage VAH with a reference voltage Voffset corresponding to a first threshold, a comparator 52 that compares a voltage VBL with the reference voltage Voffset, and a logical OR gate 56 that outputs the logical OR of the outputs from the two comparators 51 and 52.
[0026] The logic circuit shown in FIG. 2(b) includes a comparator 53 that compares the voltage VAL with a reference voltage Voffset, a comparator 54 that compares the voltage VBH with the reference voltage Voffset, and a logical OR gate 57 that outputs the logical OR of the outputs from the two comparators 53 and 54.
[0027] 2(c) includes a comparator 55a that compares a voltage VIt corresponding to the current It2 with a reference voltage "-Ioffset" when a voltage corresponding to the second threshold is Ioffset, a comparator 55b that compares the voltage VIt with a reference voltage "+Ioffset", and an OR gate 58 that outputs the logical OR of the outputs from the two comparators 55a and 55b. The voltage VIt is a voltage that corresponds to the current It2 detected by a current sensor such as a shunt resistor (not shown).
[0028] The reference voltages Voffset and Ioffset are the smallest significant voltages greater than zero, and are values that can be considered as the smallest voltages that exceed the characteristic variations of the components, and are, for example, 0.01 to 0.1 V. The reference voltages Voffset and Ioffset are not limited to fixed values, and may be variable values that can be changed by adjustment. The comparators 51 to 54, 55a, and 55b shown in FIG. 2 may be comparators with hysteresis characteristics.
[0029] Fig. 3 is a timing chart showing the operation of the detection circuit 41 shown in Fig. 2. Shown here are the synchronous rectification period specified by the detection circuit 41, the timing of a signal specifying the synchronous rectification period using each voltage of the secondary side circuit (the operation of the logic circuit shown in Fig. 2(a) and (b)), and the timing of a signal specifying the synchronous rectification period using the current of the secondary side circuit (the operation of the logic circuit shown in Fig. 2(c)).
[0030] As shown in "When using each voltage of the secondary circuit" in Fig. 3, when the synchronous rectification period is determined using each voltage of the secondary circuit, the detection circuit 41 (specifically, the logic circuit shown in Fig. 2(b)) determines a period in which the voltage VAL or the voltage VBH is larger (lower in terms of potential) than the reference voltage Voffset as one of the synchronous rectification periods. Similarly, the detection circuit 41 (specifically, the logic circuit shown in Fig. 2(a)) determines a period in which the voltage VAH or the voltage VBL is larger (lower in terms of potential) than the reference voltage Voffset as another of the synchronous rectification periods.
[0031] In addition, since the voltages VAH, VAL, VBH, and VBL are voltages seen in the forward direction of the fifth diode 21b, etc., they swing between zero potential and a potential that is lower than zero potential by the forward voltage VF of the fifth diode 21b, etc.
[0032] Furthermore, as shown in “When the current of the secondary circuit is used” in FIG. 3, when the synchronous rectification period is identified using the current of the secondary circuit, the detection circuit 41 (specifically, the logic circuit shown in FIG. 2(c)) identifies the period during which the absolute value of the current It2 exceeds the reference voltage Ioffset as the synchronous rectification period.
[0033] Next, the operation of the power conversion device 5 according to the present embodiment configured as above will be described.
[0034] 4A is a flowchart showing the operation of the power conversion device 5 according to the embodiment, which shows a procedure for generating drive signals for each switch element of the secondary side circuit when the power conversion device 5 performs synchronous rectification (i.e., a method for controlling the power conversion device 5).
[0035] First, the detection circuit 41 of the control circuit 40 detects the voltages (voltages VAH, VAL, VBH, and VBL) across each of the second diode elements in the secondary circuit, or the current (current It2) flowing through the second winding 31b (S10), and specifies the synchronous rectification period according to the detected voltages or currents by the logic circuit shown in Fig. 2 (S11). Note that steps S10 and S11 are collectively referred to as a detection step.
[0036] Then, the drive circuit 42 of the control circuit 40 generates and outputs drive signals AH, AL, BH, and BL for each switch element of the secondary side circuit so as to turn them on during a period obtained by performing an operation such as a logical product (AND) between the synchronous rectification period identified by the detection circuit 41 and the on-timing of the corresponding switch element of the primary side circuit (drive step S12).
[0037] In this way, the power conversion device 5 according to the embodiment specifies the synchronous rectification period in a wide range by using the actual voltage or actual current in the secondary circuit, and determines the on-timing of the secondary circuit according to the specified synchronous rectification period. This realizes the power conversion device 5 that performs appropriate synchronous rectification in a wide range and can operate appropriately by following a transient event even if the transient event occurs.
[0038] 4B is a diagram showing switching control modes of power conversion device 5 according to the embodiment, in which the horizontal axis represents input voltage (V) and the vertical axis represents output power (W).
[0039] When the input voltage input to the primary circuit is high, the control circuit 40 performs full-bridge control ("full-bridge control" (solid line frame) in FIG. 4B) which is synchronous rectification that generates a DC voltage that is one time the input voltage for the secondary circuit, and when the input voltage is low, the control circuit 40 performs voltage-doubler control ("voltage-doubler control" (dashed line frame) in FIG. 4B) which is synchronous rectification that generates a DC voltage that is twice the input voltage for the secondary circuit. In addition, since the generated DC voltage is determined according to the turns ratio of the insulating transformer 31, a DC voltage that is n times the input voltage may be generated with a turns ratio of 1:n.
[0040] In addition, in the full-bridge control and voltage doubler control, when the gain is reduced, the control circuit 40 increases the switching frequency of the primary side circuit and the secondary side circuit, and when low power is output, it performs primary side phase shift control ("+phase shift" (dotted area) in FIG. 4B) to shift the phase with respect to the primary side circuit.
[0041] Furthermore, when the boost gain is insufficient, the control circuit 40 performs secondary side phase shift control ("secondary side phase shift" (dotted frame) in FIG. 4B) which is synchronous rectification that shifts the phase with respect to the secondary side circuit.
[0042] 4B is a region of possible combinations of input voltage and output power. In addition, the control circuit 40 not only performs synchronous rectification as described above, but also operates without performing synchronous rectification when the output power is low.
[0043] 5 is a diagram for explaining the operating frequency of the power conversion device 5 according to the embodiment. In this figure, the current "It (primary)" flowing through the primary circuit, the current "It (secondary)" flowing through the secondary circuit, the drive signals XH and YL ("XH / YL") supplied to the primary circuit, and the drive signals XL and YH ("XL / YH") supplied to the primary circuit are shown at each of four operating frequencies in the full-bridge control or voltage doubler control mode. The operating frequency means the switching frequency of the primary circuit and the secondary circuit by the control circuit 40.
[0044] FIG. 5 shows, from lowest operating frequency, a low-frequency type (when the operating frequency is lower than the resonant frequency; FIG. 5(a)), a low-frequency type with an operating frequency higher than that of FIG. 5(a) (when the operating frequency is lower than the resonant frequency; FIG. 5(b)), a high-frequency type I (when the operating frequency is higher than the resonant frequency; FIG. 5(c)), and a high-frequency type II (when the operating frequency is higher than the resonant frequency and the positive / negative reversal point of the current occurs earlier than the half cycle of the switching waveform; FIG. 5(d)).
[0045] Here, as shown in (a) to (c) of Figure 5, in the two low-frequency types mentioned above (hereinafter, the two low-frequency types mentioned above will also be simply referred to as "low-frequency types") and the high-frequency I type, the secondary side circuit basically needs to be operated in synchronization with the primary side circuit.
[0046] In the conventional power conversion device, the on-timing of the secondary circuit is determined by adding a fixed delay time Tx to the on-timing of the primary circuit based on the operating frequency and the input / output voltage and power. The delay time Tx is determined by evaluation or the like so that it exceeds the timing at which the positive and negative of the current flowing through the primary circuit is inverted from the falling edge of the drive signal of the primary circuit, and the delay time Tx is determined by prior evaluation or the like. Therefore, when a transient event occurs in which the voltage or power changes suddenly due to a load fluctuation or the like, there is a problem that the power conversion device cannot follow the event because appropriate synchronous rectification is not performed.
[0047] In addition, in the high frequency type II, the positive / negative inversion point of the current is earlier than the half cycle of the switching waveform, so it is impossible to infer the on-timing of the secondary circuit from the on-timing of the primary circuit. For this reason, conventional power conversion devices cannot operate in the high frequency type II. Furthermore, the frequency at which the high frequency type I and the high frequency type II are switched is a value determined depending on the characteristics and implementation form of various circuit elements, and cannot be known in advance.
[0048] Therefore, in the power conversion device 5 according to the present embodiment, the synchronous rectification period is specified using the actual voltages in the secondary circuit (i.e., the voltages VAH, VAL, VBH, and VBL) or the actual current It2, and the on-timing of the secondary circuit is determined from the specified synchronous rectification period. This realizes the power conversion device 5 that, unlike conventional power conversion devices, operates even when a transient event occurs, and can operate not only in the two low frequency types and high frequency type I, but also in the extremely high frequency type II, and can operate in a wide range.
[0049] 6A to 6C are timing charts when the power conversion device 5 according to the embodiment operates in full-bridge control modes (operating frequencies of low frequency type, high frequency type I, and high frequency type II, respectively). That is, the timing charts are shown when the power conversion device 5 according to the embodiment performs full-bridge control on the secondary side circuit.
[0050] These figures show the current "It (primary)" flowing through the primary circuit, the current "It (secondary)" flowing through the secondary circuit, drive signals XH and YL ("XH / YL") supplied to the primary circuit, drive signals XL and YH ("XL / YH") supplied to the primary circuit, drive signals in the case of "no synchronous rectification" ("AH", "AL", "BH", "BL"), the "synchronous rectification period" in the case of "synchronous rectification", and drive signals in the case of "synchronous rectification" ("NAH", "NAL", "NBH", "NBL") at each operating frequency of the low frequency type (Figure 6A), high frequency type I (Figure 6B), and high frequency type II (Figure 6C).
[0051] Note that "in the case of synchronous rectification" refers to the case where the secondary circuit is synchronously rectified by full-bridge control. Also, the drive signals "NAH", "NAL", "NBH", and "NBL" in "in the case of synchronous rectification" respectively mean the drive signals AH, AL, BH, and BL in the case of synchronous rectification, and are represented by symbols to distinguish them from the drive signals AH, AL, BH, and BL in the case of no synchronous rectification.
[0052] 6A to 6C, the "synchronous rectification period" in the case of synchronous rectification is the synchronous rectification period shown in FIG. 3, and is the period detected by the detection circuit 41 shown in FIG.
[0053] In Figures 6A to 6C, as shown at the right end of the timing chart for "synchronous rectification," the drive signal NAH in the case of synchronous rectification is generated by the drive circuit 42 calculating a logical product (AND) of the synchronous rectification period and the drive signal XH, the drive signal NAL in the case of synchronous rectification is generated by the drive circuit 42 calculating a logical product (AND) of the synchronous rectification period and the drive signal XL, the drive signal NBH in the case of synchronous rectification is generated by the drive circuit 42 calculating a logical product (AND) of the synchronous rectification period and the drive signal YH, and the drive signal NBL in the case of synchronous rectification is generated by the drive circuit 42 calculating a logical product (AND) of the synchronous rectification period and the drive signal YL.
[0054] In other words, the on-timing for each switch element of these secondary circuits is expressed as a logical product (AND) of the synchronous rectification period and the on-timing (drive signal is High) of the corresponding switch element of the primary circuit. This is the same for the low-frequency type (FIG. 6A), high-frequency type I (FIG. 6B), and high-frequency type II (FIG. 6C).
[0055] Thus, according to the power conversion device 5 of this embodiment, in the full-bridge control mode, the synchronous rectification period is identified using the actual voltage in the secondary circuit (i.e., voltages VAH, VAL, VBH, and VBL) or the actual current It2, and the on-timing of the secondary circuit is determined from the identified synchronous rectification period and the on-timing of the primary circuit, so that appropriate synchronous rectification is performed in any of the low frequency type, high frequency type I, and high frequency type II.
[0056] Incidentally, even when the power conversion device 5 according to the present embodiment operates in the voltage doubler control mode, it basically operates in the same manner as the timing charts shown in Figs. 6A to 6C. However, in the voltage doubler control, the drive circuit 42 always outputs the drive signal BH fixed to Low, and outputs the drive signal BL fixed to High, regardless of whether or not synchronous rectification is performed. As a result, in the voltage doubler control mode, appropriate synchronous rectification is performed in any of the low frequency type, high frequency type I, and high frequency type II.
[0057] 7 is a timing chart when the power conversion device 5 according to the embodiment operates in a mode of primary side phase shift control. In each of three types of phase shift control (phase shift 0 type (FIG. 7(a)), phase shift I type (FIG. 7(b)), and phase shift II type (FIG. 7(c))) in order from the largest phase shift amount, the current "It (primary)" flowing through the primary side circuit, the current "It (secondary)" flowing through the secondary side circuit, the drive signal XH ("XH"), the drive signal XL ("XL"), the drive signal YH ("YH"), and the drive signal YL ("YL") supplied to the primary side circuit are shown.
[0058] In the timing chart of this figure, a period indicated by "diagonal" means a period during which two switch elements arranged in a diagonal (i.e., cross) position in the first bridge circuit 10 shown in FIG. 1 are simultaneously turned on, and a period indicated by "horizontal" means a period during which two switch elements arranged in a horizontal (i.e., left and right in the figure) position in the first bridge circuit 10 shown in FIG. 1 are simultaneously turned on.
[0059] When the power conversion device 5 according to this embodiment is to reduce the gain, it increases the switching frequency of the primary side circuit and the secondary side circuit. Furthermore, when outputting a lower power, it selects and operates in phase shift type II, phase shift type I, or phase shift type 0, whichever reduces the gain the least, as shown in the figure.
[0060] 8A to 8C are timing charts when the power conversion device 5 according to the embodiment operates in a full-bridge control mode with primary-side phase shift control (phase shift 0 type, phase shift I type, and phase shift II type, respectively). That is, the timing charts are shown when the power conversion device 5 according to the embodiment performs primary-side phase shift control on the primary-side circuit and performs control according to the primary-side circuit.
[0061] 8A to 8C, the primary side phase shift control is divided into three types shown in FIG. 7 (phase shift type 0 (FIG. 8A), phase shift type I (FIG. 8B), and phase shift type II (FIG. 8C)), and in each mode, the current "It (primary)" flowing through the primary side circuit, the current "It (secondary)" flowing through the secondary side circuit, the drive signals XH and YL ("XH / YL") supplied to the primary side circuit, the drive signals XL and YH ("XL / YH") supplied to the primary side circuit, the drive signals ("AH", "AL", "BH", "BL") when "synchronous rectification is not performed), the "synchronous rectification period", and the drive signals ("NAH", "NAL", "NBH", "NBL") when "synchronous rectification is performed" are shown. Note that "when synchronous rectification is performed" means a case where the secondary side circuit is synchronously rectified by control according to the primary side circuit.
[0062] 8A to 8C, the "synchronous rectification period" in the case of synchronous rectification is the synchronous rectification period shown in FIG. 3, and is the period detected by the detection circuit 41 shown in FIG.
[0063] As shown at the right end of the timing chart for "synchronous rectification" in Figs. 8A to 8C, the drive signals NAH, NAL, NBH, and NBL in the case of synchronous rectification are generated by the drive circuit 42 calculating the logical product (AND) of the synchronous rectification period and the drive signals XH, XL, YH, and YL, respectively. This is the same as the case of full-bridge control without primary-side phase shift control shown in Figs. 6A to 6C. That is, the on-timing for each switch element of these secondary-side circuits is expressed by the logical product (AND) of the synchronous rectification period and the on-timing (drive signal is High) of the switch element of the corresponding primary-side circuit. This is the same for any of the phase shift 0 type (Fig. 8A), phase shift I type (Fig. 8B), and phase shift II type (Fig. 8C).
[0064] Thus, according to the power conversion device 5 of this embodiment, even in a full-bridge control mode with primary-side phase shift control, similar to the case of full-bridge control without primary-side phase shift control shown in Figures 6A to 6C, the synchronous rectification period is identified using the actual voltage in the secondary circuit (i.e., voltages VAH, VAL, VBH, and VBL) or the actual current It2, and the on-timing of the secondary circuit is determined from the identified synchronous rectification period and the on-timing of the primary circuit, so that appropriate synchronous rectification is performed in any of phase shift 0 type, phase shift I type, and phase shift II type.
[0065] In addition, even when the power conversion device 5 according to the present embodiment operates in a mode of voltage doubler control accompanied by primary side phase shift control, it basically operates in the same manner as the timing charts shown in Figs. 8A to 8C. However, in voltage doubler control, the drive circuit 42 always outputs the drive signal BH fixed to Low, and outputs the drive signal BL fixed to High, regardless of whether synchronous rectification is performed or not. As a result, in the mode of voltage doubler control accompanied by primary side phase shift control, appropriate synchronous rectification is performed in any of phase shift 0 type, phase shift I type, and phase shift II type.
[0066] 9A to 9C are timing charts when the power conversion device 5 according to the embodiment operates in a mode of secondary-side phase shift control (phase shift type 0, phase shift type I, and phase shift type II, respectively). That is, the timing charts are shown when the power conversion device 5 according to the embodiment performs secondary-side phase shift control on the secondary-side circuit.
[0067] Here, the secondary side phase shift control is divided into three types corresponding to FIG. 7 (phase shift type 0 (FIG. 9A), phase shift type I (FIG. 9B), and phase shift type II (FIG. 9C)), and in each mode, the current "It (primary)" flowing through the primary side circuit, the current "It (secondary)" flowing through the secondary side circuit, the drive signals XH and YL ("XH / YL") supplied to the primary side circuit, the drive signals XL and YH ("XL / YH") supplied to the primary side circuit, the drive signals in the "case of no synchronous rectification" ("AH", "AL", "BH", "BL"), the "synchronous rectification period", and the drive signals in the "case of synchronous rectification" ("NAH", "NAL", "NBH", "NBL"). Note that "case of synchronous rectification" refers to the case where the secondary side circuit is synchronously rectified by the secondary side phase shift control.
[0068] In this figure, the "synchronous rectification period" in the case of synchronous rectification is the synchronous rectification period shown in FIG. 3, and is the period detected by the detection circuit 41 shown in FIG.
[0069] In this figure, as shown at the right end of the timing chart for "synchronous rectification," the drive signal NAH in the case of synchronous rectification is generated by the drive circuit 42 calculating a logical product (AND) of the synchronous rectification period, the drive signal XH, and the drive signal BL, the drive signal NAL in the case of synchronous rectification is generated by the drive circuit 42 calculating a logical product (AND) of the synchronous rectification period, the drive signal XL, and the drive signal BL, and the drive signal AL in the case of no synchronous rectification, the drive signal NBH in the case of synchronous rectification is generated by the drive circuit 42 calculating a logical product (AND) of the synchronous rectification period, the drive signal YH, and the drive signal AL, and the drive signal NBL in the case of synchronous rectification is generated by the drive circuit 42 calculating a logical product (AND) of the synchronous rectification period, the drive signal YL, and the drive signal AL, and the drive signal BL in the case of no synchronous rectification.
[0070] That is, the on-timing for each switch element of these secondary circuits is expressed by a logical product (AND) of the synchronous rectification period and the on-timing (drive signal is High) of the corresponding switch element of the primary circuit. This is the same for phase shift 0 type (FIG. 9A), phase shift I type (FIG. 9B), and phase shift II type (FIG. 9C).
[0071] As described above, according to the power conversion device 5 of this embodiment, even in the secondary side phase shift control mode, as in the case of the full bridge control shown in Figures 6A to 6C, the synchronous rectification period is specified using the actual voltage in the secondary side circuit (i.e., voltages VAH, VAL, VBH, and VBL) or the actual current It2, and the on-timing of the secondary side circuit is determined from the specified synchronous rectification period and the on-timing of the primary side circuit, etc., and appropriate synchronous rectification is performed in any of phase shift 0 type, phase shift I type, and phase shift II type.
[0072] As the power conversion device 5 according to the present embodiment, an example has been described in which the device operates as a unidirectional power conversion device with the first bridge circuit 10 as a primary side circuit and the second bridge circuit 20 as a secondary side circuit, but the present invention is not limited to this and can also operate as a bidirectional power conversion device. Hereinafter, a power conversion device that performs power conversion in both directions will be referred to as a power conversion device according to a modified example of the embodiment.
[0073] 10 is a circuit block diagram showing a configuration of a power conversion device 5a according to a modified example of the embodiment. The power conversion device 5a is a bidirectional LLC resonant DC / DC converter including a first bridge circuit 10, a second bridge circuit 20, a resonant circuit 30a, and a control circuit 40a, and in addition to converting DC power input to the first bridge circuit 10 and outputting it from the second bridge circuit 20 as in the embodiment, the power conversion device 5a also has a function of converting DC power input to the second bridge circuit 20 and outputting it from the first bridge circuit 10, with the second bridge circuit 20 as a primary side circuit and the first bridge circuit 10 as a secondary side circuit.
[0074] For this reason, in addition to the configuration of the resonant circuit 30 in the embodiment, the resonant circuit 30a has a current sensor such as a shunt resistor inserted in the first winding 31a for detecting the current It1 flowing through the first winding 31a.
[0075] The detection circuit 41a of the control circuit 40a performs an operation for power conversion in the opposite direction to that of the embodiment in addition to the operation in the embodiment. That is, instead of the voltages VAH, VAL, VBH, VBL, and current It2 in the embodiment, the detection circuit 41a detects the voltage VXH (strictly speaking, the cathode potential with respect to the anode of the first diode 11b) across the first bridge circuit 10, the voltage VXL (strictly speaking, the cathode potential with respect to the anode of the second diode 12b) across the second diode 12b, the voltage VYH (strictly speaking, the cathode potential with respect to the anode of the third diode 13b) across the third diode 13b, the voltage VYL (strictly speaking, the cathode potential with respect to the anode of the fourth diode 14b) across the fourth diode 14b, and the current It1 flowing through the first winding 31a of the isolation transformer 31, respectively, and specifies the synchronous rectification period according to the logic circuit shown in FIG. 2.
[0076] The drive circuit 42 of the control circuit 40a performs an operation for power conversion in the opposite direction to that of the embodiment in addition to the operation in the embodiment. That is, the drive circuit 42 performs switching control on the first bridge circuit 10 and the second bridge circuit 20 by replacing the drive signals XH, XL, YH, and YL in the embodiment with the drive signals AH, AL, BH, and BL in accordance with the synchronous rectification period identified by the detection circuit 41a.
[0077] Such a power conversion device 5a according to the modified example of the embodiment performs bidirectional power conversion in various switching control modes similar to those of the embodiment.
[0078] 11 is a diagram showing a switching control mode during power conversion from the second bridge circuit 20 to the first bridge circuit 10 by the power conversion device 5a according to the modified embodiment. That is, this diagram shows a switching control mode when the power conversion device 5a uses the second bridge circuit 20 as a primary side circuit and the first bridge circuit 10 as a secondary side circuit, converts DC power input to the second bridge circuit 20, and outputs it from the first bridge circuit 10. The horizontal axis indicates input voltage (V) and the vertical axis indicates output power (W).
[0079] When the input voltage input to the primary circuit is high, the control circuit 40a performs full-bridge control ("full-bridge control" (solid line frame) in FIG. 11), which is synchronous rectification that generates a DC voltage that is one time the input voltage for the secondary circuit, and when the input voltage is low, the control circuit 40a performs voltage-doubler control ("voltage-doubler control" (dashed line frame) in FIG. 11), which is synchronous rectification that generates a DC voltage that is twice the input voltage for the secondary circuit. In addition, since the generated DC voltage is determined according to the turns ratio of the isolation transformer 31, a DC voltage that is n times the input voltage may be generated with a turns ratio of 1:n.
[0080] In addition, in the full-bridge control and voltage doubler control, when the gain is reduced, the control circuit 40a increases the switching frequency of the primary side circuit and the secondary side circuit, and when low power is output, it performs primary side phase shift control ("+phase shift" (dotted area) in Figure 11) to shift the phase with respect to the primary side circuit.
[0081] 11 indicates a region of possible combinations of input voltage and output power. In addition, the control circuit 40a not only performs synchronous rectification as described above, but also operates without performing synchronous rectification when the switching frequency is low.
[0082] Furthermore, when performing power conversion from the first bridge circuit 10 to the second bridge circuit 20, the power conversion device 5a according to the modification of the embodiment operates in the switching control mode shown in FIG. 4B, similarly to the embodiment.
[0083] Fig. 12 is a diagram showing an example of application of a power conversion device 5a according to a modified example of the embodiment and a conventional power conversion device 62 to a Vehicle to Home (V2H) system. More specifically, (a) of Fig. 12 shows an example of application of a power conversion device 5a according to a modified example of the embodiment to a V2H system, and (b) of Fig. 12 shows an example of application of a conventional power conversion device 62 to a V2H system.
[0084] As shown in (a) of FIG. 12, a V2H system using a power conversion device 5a according to a modified example of the embodiment is connected between a vehicle 60 which is a DC power source and a grid 64 which is an AC power source, and is composed of the power conversion device 5a and a bidirectional inverter 63, and performs power conversion in both directions, that is, discharging from the vehicle 60 to the grid 64 and charging from the grid 64 to the vehicle 60.
[0085] On the other hand, as shown in FIG. 12(b), a V2H system using a conventional power conversion device 62 is connected between a vehicle 60, which is a DC power source, and a grid 64, which is an AC power source, and is composed of a bidirectional chopper converter 61, a power conversion device 62, and a bidirectional inverter 63, and performs power conversion in both directions, that is, discharging from the vehicle 60 to the grid 64 and charging from the grid 64 to the vehicle 60.
[0086] The vehicle 60 is a battery of an electric vehicle. The bidirectional chopper converter 61 is a DC / DC converter that boosts the voltage when discharging from the vehicle 60 and drops the voltage when charging the vehicle 60. The power conversion device 62 is a conventional LLC resonant type DC / DC converter. The bidirectional inverter 63 converts DC power from the power conversion device 5a or 62 into AC power and outputs it to the grid 64, and converts AC power from the grid 64 into DC power and outputs it to the power conversion device 5a or 62. The grid 64 is AC commercial power. The control device 65 is a Micro Controller Unit that controls each component that constitutes the V2H system.
[0087] 12(a) and (b), the power conversion device 5a according to the modified embodiment performs proper synchronous rectification even at a high-frequency type II operating frequency, unlike the conventional power conversion device 62, as described in the above embodiment, and therefore can perform discharging and charging over a wide range with the bus voltage on the second bridge circuit 20 side kept constant even if the DC voltage on the first bridge circuit 10 side fluctuates. Therefore, unlike the V2H system using the conventional power conversion device 62, the bidirectional chopper converter 61 is not required.
[0088] As described above, the power conversion device 5 and the like according to the present embodiment and the modified example are DC / DC converters that convert power supplied from a DC power supply and output the converted power from a pair of output terminals 8a and 8b, and include a first bridge circuit 10 connected between the terminals 6a and 6b of the DC power supply, a second bridge circuit 20 connected between the pair of output terminals 8a and 8b, a resonant circuit 30 including an isolation transformer 31 having a first winding 31a connected to the first bridge circuit 10 and a second winding 31b connected to the second bridge circuit 20, and a control circuit 40 that controls the first bridge circuit 10 and the second bridge circuit 20. The first bridge circuit 10 includes a plurality of first switch elements (a first switch element 11a, a second switch element 12a, a third switch element 13a, a fourth switch element 14a) connected between the terminals 6a and 6b of the DC power supply, and a plurality of first diode elements (a third switch element 15a, a fourth switch element 16a, a fourth switch element 17a, a fourth switch element 18a, a fifth switch element 19a, a sixth switch element 20a, a sixth switch element 21a, a seventh switch element 22a, a seventh switch element 23a, a seventh switch element 24a, a seventh switch element 25a, a seventh switch element 26a, a seventh switch element 27a, a seventh switch element 28a, a seventh switch element 29a, a seventh switch element 30a, a seventh switch element 31b, a seventh switch element 32a, a seventh switch element 33a, a seventh switch element 34a, a seventh switch element 35a, a seventh switch element 36a, a seventh switch element 37a, a seventh switch element 38a, a seventh switch element 39a, a seventh switch element The second bridge circuit 20 has a plurality of second switch elements (a fifth switch element 21a, a sixth switch element 22a, a seventh switch element 23a, and an eighth switch element 24a) connected between a pair of output terminals 8a and 8b, and a plurality of second diode elements (the fifth diode 21b, the sixth diode 22b, the seventh diode 23b, and the eighth diode 24b) connected in parallel with each of the plurality of second switch elements. The control circuit 40 and the like have a detection circuit 41 and the like that detects a voltage across each of the plurality of second diode elements or a current flowing through the second winding 31b and specifies a synchronous rectification period, which is a rectification period by the second bridge circuit 20, in accordance with the detected voltage across each of the plurality of second diode elements or the detected current, and a drive circuit 42 that performs switching control on the plurality of second switch elements in accordance with the specified synchronous rectification period.
[0089] As a result, the synchronous rectification period is specified using the actual voltage or actual current in the secondary circuit, and the on-timing of the secondary circuit is determined according to the specified synchronous rectification period, so that proper synchronous rectification is performed. Thus, a power conversion device that operates in a wide range and can operate properly by following a transient event even if the transient event occurs is realized.
[0090] Furthermore, the detection circuit 41 etc. detect whether or not the voltage across each of the second diode elements is greater than a first threshold value, and the drive circuit 42 specifies, for each of the second diode elements, a period during which the detection circuit 41 etc. detects that the voltage across each of the second diode elements is greater than the first threshold value, as a synchronous rectification period. This allows proper synchronous rectification to be performed using the actual voltage in the secondary side circuit.
[0091] Here, the first threshold value may be a variable value, which allows the synchronous rectification period determined by the voltage in the secondary circuit to be properly tuned.
[0092] Furthermore, the detection circuit 41 etc. detect whether the absolute value of the current flowing through the second winding 31b is greater than a second threshold value, and the drive circuit 42 specifies the period during which the detection circuit 41 etc. detects that the absolute value of the current flowing through the second winding 31b is greater than the second threshold value as the synchronous rectification period. This allows proper synchronous rectification to be performed using the actual current in the secondary side circuit.
[0093] Here, the second threshold value may be a variable value, which allows the synchronous rectification period determined by the current in the secondary circuit to be properly tuned.
[0094] Furthermore, the detection circuit 41 etc. may include a comparator with a hysteresis characteristic, which suppresses chattering and enables stable synchronous rectification even if the voltage or current in the secondary circuit used to specify the synchronous rectification period contains noise.
[0095] Furthermore, the drive circuit 42 turns on each of the second switch elements during a period obtained by a logical operation between the period during which the corresponding first switch element is turned on and the synchronous rectification period, thereby enabling synchronous rectification during the synchronous rectification period determined by the actual voltage or current in the secondary side circuit.
[0096] The first switch elements include a first switch element 11a and a second switch element 12a connected in series between the terminals 6a and 6b of the DC power supply, and a third switch element 13a and a fourth switch element 14a connected in series between the terminals 6a and 6b of the DC power supply. The first diode elements include a first diode 11b, a second diode 12b, a third diode 13b, and a fourth diode 14b connected in parallel with the first switch element 11a, the second switch element 12a, the third switch element 13a, and the fourth switch element 14a, respectively. The second switch elements include a fifth switch element 21a and a sixth switch element 22a connected in series between a pair of output terminals 8a and 8b, and a seventh switch element 23a and an eighth switch element 24a connected in series between a pair of output terminals 8a and 8b, and the second diode elements include a fifth diode 21b, a sixth diode 22b, a seventh diode 23b, and an eighth diode 24b connected in parallel with the fifth switch element 21a, the sixth switch element 22a, the seventh switch element 23a, and the eighth switch element 24a, respectively. This makes the primary side circuit and the secondary side circuit have a full-bridge configuration, enabling synchronous control such as full-bridge control and voltage doubler control.
[0097] Further, the control method of the power conversion device 5 and the like according to the present embodiment and the modified example is a control method of the power conversion device 5 and the like that converts power supplied from a DC power supply and outputs the power from a pair of output terminals 8a and 8b, and the power conversion device 5 and the like includes a first bridge circuit 10 connected between terminals 6a and 6b of the DC power supply, a second bridge circuit 20 connected between the pair of output terminals 8a and 8b, a resonant circuit 30 including an isolation transformer 31 having a first winding 31a connected to the first bridge circuit 10 and a second winding 31b connected to the second bridge circuit 20, and the like. The first bridge circuit 10 includes a plurality of first switch elements connected between the terminals 6a and 6b of the DC power supply, and a plurality of second switch elements connected between the terminals 6a and 6b of the DC power supply. the second bridge circuit 20 has a plurality of second switch elements connected between a pair of output terminals 8 a and 8 b, and a plurality of second diode elements connected in parallel to each of the plurality of second switch elements, and the control method includes a detection step of detecting a voltage across each of the plurality of second diode elements or a current flowing through the second winding 31 b, and specifying a synchronous rectification period, which is a rectification period by the second bridge circuit 20, in accordance with the detected voltage across each of the plurality of second diode elements or the detected current, and a drive step of performing switching control on the plurality of second switch elements in accordance with the specified synchronous rectification period.
[0098] As a result, the synchronous rectification period is specified using the actual voltage or actual current in the secondary circuit, and the on-timing of the secondary circuit is determined according to the specified synchronous rectification period, so that proper synchronous rectification is performed. Thus, a control method for a power conversion device that operates in a wide range and can operate properly by following a transient event even if the transient event occurs is realized.
[0099] Although the power conversion device and the control method thereof according to the present disclosure have been described above based on the embodiment and the modified examples, the present disclosure is not limited to these embodiment and modified examples. As long as it does not deviate from the gist of the present disclosure, various modifications conceived by a person skilled in the art to the present embodiment and modified examples, and other forms constructed by combining some of the components in the embodiment and modified examples are also included within the scope of the present disclosure.
[0100] For example, in the embodiments and the like, the first bridge circuit 10 and the second bridge circuit 20 are of a full bridge type, but are not limited to this and may be of a half bridge type.
[0101] In the embodiment and the like, the capacitors 32 and 33 constituting the resonant circuit 30 are inserted at one end of the first winding 31a and the second winding 31b, respectively, but they may be inserted at the opposite positions, that is, at the other ends of the first winding 31a and the second winding 31b. Furthermore, an inductor connected in series to the first winding 31a and an inductor connected in series to the second winding 31b may be inserted.
[0102] Furthermore, in the modification of the embodiment, the power conversion device 5a discharges and charges the vehicle 60, but the power conversion device 5a may have a configuration in which it only discharges or only charges the vehicle 60.
[0103] In addition, in the embodiments, the logic circuit shown in FIG. 2(a) and the logic circuit shown in FIG. 2(b) are shown as detection circuit 41, but the detection circuit 41 may be configured to output the logical sum of the output of the logic circuit shown in FIG. 2(a) and the output of the logic circuit shown in FIG. 2(b). [Industrial Applicability]
[0104] INDUSTRIAL APPLICABILITY The power conversion device according to the present disclosure can be used as a resonant DC / DC converter, in particular as a power conversion device that operates over a wide range and can operate appropriately in response to a transient event even if the transient event occurs, for example, as an LLC resonant DC / DC converter applied to a V2H system. [Explanation of symbols]
[0105] 5, 5a Power conversion device 6a, 6b DC power supply terminals 7, 9, 32, 33 Capacitors 8a, 8b output terminals 10 First bridge circuit 11a First switch element 11b First Diode 12a Second switch element 12b Second Diode 13a Third switch element 13b Third Diode 14a Fourth switch element 14b 4th diode 20 Second bridge circuit 21a Fifth switch element 21b 5th diode 22a Sixth switch element 22b 6th diode 23a Seventh switch element 23b 7th diode 24a 8th switch element 24b 8th Diode 30, 30a resonant circuit 31 Isolation transformer 31a Winding No. 1 31b Second winding 40, 40a Control circuit 41, 41a Detection circuit 42 Drive circuit 51, 52, 53, 54, 55a, 55b Comparators 56, 57, 58 Logical OR gate 60 vehicles 61 Bidirectional Chopper Converter 63 Bidirectional inverter 64 lines 65 Control device
Claims
1. A power conversion device that converts power supplied from a DC power source and outputs the converted power from a pair of output terminals, a first bridge circuit connected between terminals of the DC power supply; a second bridge circuit connected between the pair of output terminals; a resonant circuit including an isolation transformer having a first winding connected to the first bridge circuit and a second winding connected to the second bridge circuit; a control circuit for controlling the first bridge circuit and the second bridge circuit, The first bridge circuit includes: a plurality of first switch elements connected between terminals of the DC power source; a plurality of first diode elements connected in parallel with each of the plurality of first switch elements; The second bridge circuit includes: a plurality of second switch elements connected between the pair of output terminals; a plurality of second diode elements connected in parallel with each of the plurality of second switch elements; The control circuit includes: a detection circuit that detects a voltage across each of the second diode elements or a current flowing through the second winding, and identifies a synchronous rectification period, which is a rectification period by the second bridge circuit, according to the detected voltage across each of the second diode elements or the detected current; and a drive circuit that performs switching control on the second switch elements in accordance with the specified synchronous rectification period. Power conversion equipment.
2. the detection circuit detects, for each of the second diode elements, whether or not a voltage across the second diode element is greater than a first threshold; the drive circuit specifies, as the synchronous rectification period, a period during which the detection circuit detects that the voltage across each of the second diode elements is greater than the first threshold value for each of the second diode elements; The power converter according to claim 1 .
3. The first threshold is a variable value. The power converter according to claim 2.
4. The detection circuit detects whether an absolute value of a current flowing through the second winding is greater than a second threshold value, the drive circuit specifies, as the synchronous rectification period, a period during which the detection circuit detects that the absolute value of the current flowing through the second winding is greater than the second threshold value. The power converter according to claim 1 .
5. The second threshold is a variable value. The power converter according to claim 4.
6. the detection circuit includes a comparator having a hysteresis characteristic; The power conversion device according to any one of claims 1 to 5.
7. the drive circuit turns on each of the second switch elements during a period obtained by a logical operation between a period during which the corresponding first switch element is turned on and the synchronous rectification period; The power conversion device according to any one of claims 1 to 6.
8. the plurality of first switch elements include a first switch element and a second switch element connected in series between terminals of the DC power supply, and a third switch element and a fourth switch element connected in series between terminals of the DC power supply, the plurality of first diode elements include a first diode, a second diode, a third diode, and a fourth diode connected in parallel with the first switch element, the second switch element, the third switch element, and the fourth switch element, respectively; the plurality of second switch elements include a fifth switch element and a sixth switch element connected in series between the pair of output terminals, and a seventh switch element and an eighth switch element connected in series between the pair of output terminals, the plurality of second diode elements include a fifth diode, a sixth diode, a seventh diode, and an eighth diode connected in parallel with the fifth switch element, the sixth switch element, the seventh switch element, and the eighth switch element, respectively; The power conversion device according to any one of claims 1 to 7.
9. A control method for a power conversion device that converts power supplied from a DC power source and outputs the converted power from a pair of output terminals, comprising the steps of: The power conversion device is a first bridge circuit connected between terminals of the DC power supply, a second bridge circuit connected between the pair of output terminals, and a resonant circuit including an isolation transformer having a first winding connected to the first bridge circuit and a second winding connected to the second bridge circuit, the first bridge circuit includes a plurality of first switch elements connected between terminals of the DC power supply, and a plurality of first diode elements connected in parallel with each of the plurality of first switch elements, the second bridge circuit includes a plurality of second switch elements connected between the pair of output terminals, and a plurality of second diode elements connected in parallel with each of the plurality of second switch elements, The control method includes: a detection step of detecting a voltage across each of the second diode elements or a current flowing through the second winding, and specifying a synchronous rectification period, which is a rectification period by the second bridge circuit, according to the detected voltage across each of the second diode elements or the detected current; and a driving step of performing switching control for the plurality of second switch elements according to the specified synchronous rectification period. Control methods.