Power Conversion Device

Abstract

To reduce the number of insulation elements provided for a single conversion cell.SOLUTION: A power conversion device has an insulation type DC / DC converter, a plurality of conversion cells each having a pair of terminals connected to either an input side or an output side of the insulation type DC / DC converter and connected in series through the pair of terminals, and a plurality of insulation elements provided for the plurality of conversion cells respectively and transmitting a synchronization signal to the corresponding conversion cell among the plurality of conversion cells. Each of the plurality of conversion cells has a transformer, a first conversion circuit connected between the transformer and the pair of terminals, a control signal generation part generating a plurality of control signals synchronized with the synchronization signal, and a first drive circuit driving a plurality of switch elements included in the first conversion circuit according to the plurality of control signals.SELECTED DRAWING: Figure 16

Description

Technical Field

[0001] The present disclosure relates to a power conversion device.

Background Art

[0002] Conventionally, a multi-cell converter device including a plurality of conversion cells connected in series via a pair of input terminals, and a plurality of insulating components provided for each of the plurality of conversion cells and transmitting a plurality of control signals to a corresponding conversion cell among the plurality of conversion cells is known. Each of the plurality of conversion cells has a drive circuit that controls a DC / DC conversion unit based on a plurality of control signals received via one or more insulating components. By transmitting a control signal to a conversion cell via an insulating component, it is possible to transmit control signals that are electrically insulated from each other to each of the drive circuits operating at different reference potentials for each conversion cell (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When one insulating component transmits a plurality of control signals, one insulating element such as a digital isolator is assigned to the transmission of one control signal, so one insulating component includes a plurality of insulating elements. Therefore, in the conventional technology, as the number of control signals transmitted per conversion cell increases, the number of insulating elements provided per conversion cell also increases. Therefore, in a power conversion device in which a plurality of conversion cells are connected in series via a pair of terminals, the total number of insulating elements is at least (the number of series stages of conversion cells × the number of control signals transmitted per conversion cell), which becomes an enormous number. When the total number of insulating elements becomes enormous, for example, it is difficult to miniaturize and reduce costs.

[0005] The present disclosure provides a power conversion device that can reduce the number of insulating elements provided per conversion cell. [Means for solving the problem]

[0006] In one aspect of the present disclosure, an isolated DC / DC converter; and a plurality of conversion cells each having a pair of terminals connected to either the input side or the output side of the isolated DC / DC converter, the conversion cells being connected in series via the pair of terminals; a plurality of isolation elements provided for the plurality of conversion cells, each isolation element transmitting a synchronization signal to a corresponding one of the plurality of conversion cells; Each of the plurality of conversion cells comprises: Transformer and a first conversion circuit connected between the transformer and the pair of terminals; a control signal generating unit that generates a plurality of control signals synchronized with the synchronization signal; a first drive circuit that drives a plurality of switch elements included in the first conversion circuit in accordance with a plurality of the control signals. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, the number of insulating elements provided per conversion cell can be reduced. [Brief explanation of the drawings]

[0008]

Figure 1

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Figure 19

[0009] Hereinafter, multiple embodiments according to the present disclosure will be described with reference to the drawings. Note that "DC" and "AC" are abbreviations for "Direct Current" and "Alternative Current", respectively.

[0010] Fig. 1 is a diagram illustrating a configuration example of a power conversion device according to a first embodiment. Fig. 1 illustrates a configuration in which a power conversion device 1 includes three conversion cells 211, 212, and 213 connected in series on the DC output side, and one synchronization signal, multiple control signals, and a driving power supply are independently supplied to each of the conversion cells 211, 212, and 213. Note that Fig. 1 does not explicitly show a path for supplying the driving power, but a power supply voltage is supplied from a power supply unit (not shown) to components described below, such as drive circuits 204a and 204b, a control signal generating unit 208, and a carrier signal generating unit 207.

[0011] 1 is a multi-cell converter including a plurality of (three in this example) conversion cells 211, 212, and 213, and a control device 206 that controls the power conversion operations of the conversion cells 211, 212, and 213. Each of the conversion cells 211, 212, and 213 is a cell converter that boosts or lowers a DC voltage input from a common DC path and outputs a predetermined DC voltage. Each of the conversion cells 211, 212, and 213 has an isolated DC / DC converter 200 and a pair of terminals p and q.

[0012] 1, the pair of terminals p, q are output terminals connected to the output side of the isolated DC / DC converter 200. Of the pair of terminals p, q, the first terminal p is a terminal on the high potential side, and the second terminal q is a terminal on the low potential side.

[0013] The plurality of conversion cells 211, 212, 213 each have a pair of terminals p, q and are connected in series via the pair of terminals p, q. The plurality of conversion cells 211, 212, 213 are each such that their first terminal p is connected to the second terminal q of one conversion cell adjacent to itself, and their second terminal q is connected to the first terminal p of the other conversion cell adjacent to itself. Among the plurality of cell converters connected in series via the pair of terminals p, q, the first terminal p of the conversion cell (in this example, the conversion cell 211) located on the highest potential side is electrically connected to the high-potential side end of a load (not shown). On the other hand, among the plurality of cell converters connected in series via the pair of terminals p, q, the second terminal q of the conversion cell (in this example, the conversion cell 213) located on the lowest potential side is electrically connected to the low-potential side end of a load (not shown).

[0014] The isolated DC / DC converter 200 boosts or steps down the DC voltage input from a common DC path by the plurality of conversion cells 211, 212, 213 and outputs a predetermined DC voltage from the pair of terminals p, q. The isolated DC / DC converter 200 includes a transformer 202, a primary circuit 210a, and a secondary circuit 210b. The primary circuit 210a and the secondary circuit 210b are magnetically coupled by the transformer 202.

[0015] The transformer 202 has a primary coil and a secondary coil and is a transformer in which the primary coil and the secondary coil are magnetically coupled.

[0016] The primary circuit 210a has a capacitive element 203a, a primary full-bridge circuit 220a, and a drive circuit 204a. The primary circuit 210a may have a reactor 207a connected in series to the primary coil of the transformer 202.

[0017] The primary-side full-bridge circuit 220a includes a primary-side first half-bridge circuit in which a primary-side first upper arm 201a and a primary-side first lower arm 201b are connected in series, and a primary-side second half-bridge circuit in which a primary-side second upper arm 201c and a primary-side second lower arm 201d are connected in series. A primary-side coil of the transformer 202 (or a series circuit of the primary-side coil and the reactor 207a) is connected between an intermediate connection point between the primary-side first upper arm 201a and the primary-side first lower arm 201b and an intermediate connection point between the primary-side second upper arm 201c and the primary-side second lower arm 201d.

[0018] The secondary circuit 210b includes a capacitive element 203b, a secondary full-bridge circuit 220b, and a drive circuit 204a. The secondary circuit 210b may include a reactor 207b connected in series to the secondary coil of the transformer 202.

[0019] The secondary full-bridge circuit 220b includes a first secondary half-bridge circuit in which a first secondary upper arm 201e and a first secondary lower arm 201f are connected in series, and a second secondary half-bridge circuit in which a second secondary upper arm 201g and a second secondary lower arm 201h are connected in series. A secondary coil of the transformer 202 (or a series circuit of the secondary coil and the reactor 207b) is connected between an intermediate connection point between the first secondary upper arm 201e and the first secondary lower arm 201f and an intermediate connection point between the second secondary upper arm 201g and the second secondary lower arm 201h.

[0020] The secondary-side full-bridge circuit 220b is an example of a first conversion circuit connected between the secondary coil of the transformer 202 and a pair of terminals p and q. On the other hand, the primary-side full-bridge circuit 220a is an example of a second conversion circuit connected to the secondary-side full-bridge circuit 220b via the transformer 202, and is connected between the primary coil of the transformer 202 and a DC path common to the multiple conversion cells 211, 212, and 213.

[0021] A plurality of primary-side switch elements such as the primary-side first upper arm 201a, the primary-side first lower arm 201b, the primary-side second upper arm 201c, and the primary-side second lower arm 201d are driven by a primary-side drive circuit 204a. A plurality of secondary-side switch elements such as the secondary-side first upper arm 201e, the secondary-side first lower arm 201f, the secondary-side second upper arm 201g, and the secondary-side second lower arm 201h are driven by a secondary-side drive circuit 204b.

[0022] As specific examples of the primary-side switch element and the secondary-side switch element, semiconductor switching elements such as MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and IGBT (Insulated Gate Bipolar Transistor) can be mentioned. The drive circuits 204a and 204b are also referred to as GDUs (Gate Driver Unit).

[0023] The isolated DC / DC converter 200 is a power conversion circuit called a DAB (Dual Active Bridge) converter having a primary-side full-bridge circuit 220a provided on the primary side of the transformer 202 and a secondary-side full-bridge circuit 220b provided on the secondary side of the transformer 202. The DAB converter transmits power between the primary side and the secondary side when a voltage is applied to the leakage inductance of the transformer 202 or the external reactors 207a and 207b connected in series to the transformer 102. The transmitted power is controlled by the phase difference between the output voltage V1 output from two intermediate connection points of the primary-side inverter circuit (primary-side full-bridge circuit 220a) and the output voltage V2 output from two intermediate connection points of the secondary-side inverter circuit (secondary-side full-bridge circuit 220b). The power transmitted from the secondary side to the primary side is represented by the following simplified Equation 1.

[0024]

Equation

[0025] Since the circuit configuration of the DAB converter is a symmetric structure, the reference phase of the phase difference of the output voltage may be the secondary side of the high-voltage side or the primary side of the low-voltage side.

[0026] The secondary-side circuits 210b on the high-voltage side of the plurality of conversion cells 211, 212, and 213 each have a carrier signal generation unit 207, a control signal generation unit 208, and a drive circuit 204b. Further, the power conversion device 1 is provided for each of the plurality of conversion cells 211, 212, and 213, and includes a plurality of insulating elements 205 that transmit a synchronization signal to the corresponding conversion cell among the plurality of conversion cells 211, 212, and 213. Thereby, a synchronization signal that is electrically insulated from each other can be transmitted to each of the internal circuits (carrier signal generation unit 207, control signal generation unit 208, and drive circuit 204b) that operate at different reference potentials for each conversion cell.

[0027] A synchronization signal is a signal for controlling the phase difference between two or more periodically varying signals (voltages) to a constant value (which may be zero or a value other than zero). Synchronization means to correlate in time, and is not necessarily limited to controlling the phase difference between two or more periodically varying signals (voltages) to zero.

[0028] The control device 206 supplies, to each of the secondary side circuits 210b on the high voltage side of the plurality of conversion cells 211, 212, 213, a single synchronization signal for synchronizing the repetition start timing of the waveform of the output voltage V2, via the corresponding plurality of insulation elements 205. On the other hand, the control device 206 supplies, to each of the primary side circuits 210a on the low voltage side of the plurality of conversion cells 211, 212, 213, a plurality of control signals that define the repetition start timing of the waveform of the output voltage V1. As a result, when the duty ratios of the waveforms of the output voltages V1 and V2 are constant values such as 50%, the frequencies (periods) of the output voltages V1 and V2 and the repetition start timing of the waveforms of the output voltages V1 and V2 are determined for each of the conversion cells 211, 212, 213, so that the target output voltage can be generated.

[0029] The plurality of synchronization signals supplied to each of the secondary side circuits 210b on the high voltage side of the plurality of conversion cells 211, 212, 213 may have the same or different phases from each other.

[0030] The control device 206 has, for example, a memory and a processor (e.g., a CPU (Central Processing Unit)), and the functions of the control device 206 are realized by the operation of the processor according to a program stored in the memory. The control device 206 may be constituted by an FPGA (Field Programmable Gate Array).

[0031] Each insulation element 205 may be constituted by a single insulation element, or may be constituted by a plurality of insulation elements connected in series. Specific examples of the insulation element 205 include an insulation transformer, a pulse transformer, a digital isolator, an isolation amplifier, etc. The insulation element 205 may be an optical isolator such as a photocoupler.

[0032] The carrier signal generation unit 207 generates a carrier signal synchronized with the synchronization signal transmitted by the corresponding insulation element 205. The carrier signal is, for example, a sawtooth periodic signal having the same period as the synchronization signal and synchronized in phase.

[0033] The control signal generation unit 208 generates a plurality of control signals synchronized with the carrier signal from the carrier signal generated by the carrier signal generation unit 207. The plurality of control signals are, for example, rectangular wave signals whose phases are synchronized with the carrier signal. In this example, the control signal generation unit 208 generates four control signals for controlling the switching of each of the plurality of secondary side switch elements 201e, 201f, 201g, 201h.

[0034] The drive circuit 204b drives and switches the plurality of secondary side switch elements 201e, 201f, 201g, 201h according to the plurality of control signals generated by the control signal generation unit 208. On the other hand, the drive circuit 204a drives and switches the plurality of primary side switch elements 201a, 201b, 201c, 201d according to the plurality of control signals generated by the control device 206 that generates the synchronization signal. The control device 206 generates four control signals for controlling the switching of each of the plurality of primary side switch elements 201a, 201b, 201c, 201d.

[0035] FIG. 2 is a timing chart showing an example of the operation waveforms of the power conversion device in the first embodiment. The control device 206 outputs a synchronization signal to the carrier signal generation units 207 of the conversion cells 211, 212, 213 via the insulating elements 205 corresponding to the conversion cells 211, 212, 213, respectively. The control device 206 outputs the synchronization signal by pulse width modulation, which includes a first pulse having a pulse width equal to or greater than a predetermined first specified value at a constant period.

[0036] On the high-voltage side, the carrier signal generation unit 207 detects at least once a first pulse having a pulse width equal to or greater than a predetermined first specified value from the supplied synchronization signal, and generates a sawtooth carrier signal to be supplied to the control signal generation unit 208. As a countermeasure against misdetection of the first pulse, the carrier signal generation unit 207 may detect the synchronization signal a plurality of times at intervals shorter than the pulse width of the first specified value. Each time the carrier signal generation unit 207 detects the first pulse, it initializes the carrier signal, and then generates a sawtooth carrier signal by monotonically increasing or decreasing the carrier signal over time. FIG. 2 illustrates the case where the carrier signal is monotonically increased over time.

[0037] Note that, in order to determine that the pulse width is equal to or greater than the first specified value, the carrier signal generation unit 207 detects the start of the pulse of the synchronization signal (in FIG. 2, the rising edge of the pulse), and may confirm that there is a pulse of the synchronization signal (for example, maintaining a high level) up to the time corresponding to the first specified value using a counter or the like. Therefore, if it is confirmed that there is a pulse of the synchronization signal up to the time corresponding to the first specified value, the carrier signal generation unit 207 may initialize the carrier signal to zero at a time point before the falling edge of the pulse of the synchronization signal.

[0038] The control signal generation unit 208 generates a plurality of control signals for switching control of the plurality of secondary-side switch elements 201e, 201f, 201g, 201h by detecting an inversion of the magnitude relationship between the amplitude of the carrier signal and the median value of the amplitude of the carrier signal.

[0039] For example, the control signal generation unit 208 generates a pulse width modulation signal by comparing a carrier signal with a threshold value of 50% duty ratio (the median value of the amplitude of the carrier signal). When the amplitude of the carrier signal is lower than the threshold value of 50% duty ratio, the control signal generation unit 208 sets the level of the pulse width modulation signal to a high level, and when the amplitude of the carrier signal is higher than the threshold value of 50% duty ratio, the control signal generation unit 208 sets the level of the pulse width modulation signal to a low level. The control signal generation unit 208 generates a non-inverted signal of the pulse width modulation signal as a control signal for switching control of the switch element 201e and a control signal for switching control of the switch element 201h. On the other hand, the control signal generation unit 208 generates an inverted signal of the pulse width modulation signal as a control signal for switching control of the switch element 201f and a control signal for switching control of the switch element 201g.

[0040] The drive circuit 204b is an example of a first drive circuit that generates a plurality of gate signals for driving the switch elements 201e, 201f, 201g, and 201h included in the secondary full-bridge circuit 220b according to a plurality of control signals generated by the control signal generation unit 208. In this example, the plurality of gate signals have substantially the same phase as the corresponding control signals. The drive circuit 204b supplies the corresponding gate signals to the respective gates of the switch elements 201e, 201f, 201g, and 201h. As a result, a square-wave output voltage V2 with a duty ratio of 50% is applied to the secondary side of the transformer 202.

[0041] On the low-voltage side, the control device 206 determines the phase shift amount φ with respect to the above-mentioned synchronization signal supplied to the high-voltage side based on Equation 1, and outputs a plurality of control signals that are delayed or advanced by the time corresponding to the phase shift amount φ with respect to the synchronization signal. That is, the plurality of control signals output from the control device 206 to the low-voltage side are synchronized with the synchronization signal output to the high-voltage side. Also, the phase of each of the plurality of control signals supplied from the control device 206 to the low-voltage side is different from the phase of the corresponding control signal among the plurality of control signals generated by the control signal generation unit 208 on the high-voltage side. For example, the phase of the control signal (or gate signal) for the switch element 201a on the low-voltage side is different from the phase of the control signal (or gate signal) for the switch element 201e on the high-voltage side corresponding to the switch element 201a.

[0042] The control device 206 generates a plurality of control signals for switching control of each of the switch elements 201a, 201b, 201c, and 201d. The control device 206 generates a plurality of control signals to be supplied to each of the drive circuits 204a of the plurality of conversion cells 211, 212, and 213.

[0043] The drive circuit 204a is an example of a second drive circuit that generates a plurality of gate signals for driving the switch elements 201a, 201b, 201c, and 201d included in the primary full-bridge circuit 220a according to the plurality of control signals generated by the control device 206. In this example, the plurality of gate signals have substantially the same phase as the corresponding control signals. The drive circuit 204a supplies the corresponding gate signals to the gates of the switch elements 201a, 201b, 201c, and 201d respectively. Thereby, a square-wave output voltage V1 with a duty ratio of 50% is applied to the primary side of the transformer 202.

[0044] Therefore, since square-wave output voltages V1 and V2 with a phase difference are applied to the primary side and the secondary side of the transformer 202, a transformer current proportional to the integrated value of the difference between the output voltage V1 and the output voltage V2 flows, and power P in accordance with Equation 1 is transmitted between the primary side and the secondary side.

[0045] As described above, in the first embodiment, the phase of the output voltage V2 on the high-voltage side of the DAB converter is used as the reference for the phase difference of the DAB converters, and only the synchronization signal for synchronizing each DAB converter is transmitted to the high-voltage side of each DAB converter via the isolation element 205. Then, in the high-voltage secondary circuit 210b, multiple control signals for controlling the secondary-side full-bridge circuit 220b that generates the output voltage V2 are generated based on the synchronization signal received via the isolation element 205. Meanwhile, the low-voltage primary circuit 210a and the control device 206 share a common reference potential (ground). Therefore, even without the isolation element 205, multiple control signals for controlling the primary-side full-bridge circuit 220a that generates the output voltage V1 are generated based on the synchronization signal and the phase shift amount φ. In this way, the number of isolation elements 205 required per conversion cell can be reduced.

[0046] It should be noted that the generation of the control signal on the common potential side (in this example, the primary side) of the isolated DC / DC converter 200 in the first embodiment is not limited to the above method. It is sufficient that a phase difference can be correctly imparted to the output voltages on the primary and secondary sides. For example, the generation of the carrier signal and the control signal on the common potential side is not limited to being performed within the control device 206, but may be performed by a carrier signal generator and a control signal generator provided in the same way as on the high-voltage side. Furthermore, the carrier signal may be generated for each half-bridge circuit.

[0047] Although the reference phase for the phase difference of the output voltages is described as being on the secondary side, this is not limiting. As long as a phase difference can be accurately imparted between the primary and secondary output voltages, there is no operational problem even if the reference phase is on the primary side. Furthermore, the control signal generator 208 and the control device 206 may include a dead time generator that imparts dead times to multiple control signals to prevent short circuits between the upper and lower arms of the half-bridge circuit.

[0048] FIG. 3 is a timing chart showing an example of the operation waveform when the carrier signal generation unit 207 generates a triangular carrier signal. Regarding the same operations as those in the above-described operation example in this modification, the above description is incorporated by reference and thus omitted. Even when the carrier signal generation unit 207 generates a triangular carrier signal, as in FIG. 2, a plurality of control signals are generated by comparing with the median value of the carrier signal. Similar to FIG. 2, the two half-bridge circuits on the high voltage side output a square wave voltage.

[0049] For example, when the carrier signal generation unit 207 detects the first pulse, it generates a carrier signal that repeats monotonic increase and monotonic decrease over time. FIG. 3 illustrates a case where the carrier signal generation unit 207 switches the carrier signal from monotonic decrease to monotonic increase each time the first pulse is detected, and switches the carrier signal from monotonic increase to monotonic decrease before the elapse of a specified time from the detection of the first pulse until the next first pulse is detected.

[0050] FIG. 4 is a timing chart showing an example of the operation waveform when the peaks (e.g., maximum values) and valleys (e.g., minimum values) of the triangular carrier signal generated by the carrier signal generation unit are detected to generate a plurality of control signals. Regarding the same operations as those in the above-described operation example in this modification, the above description is incorporated by reference and thus omitted. In FIG. 4, the control signal generation unit 208 detects the peak (e.g., maximum value) or valley (e.g., minimum value) of the carrier signal, and switches the levels of the plurality of control signals from one level to the other level at the detection timing. Similar to FIG. 2, the two half-bridge circuits on the high voltage side output a square wave voltage.

[0051] FIG. 5 is a timing chart showing an example of an operation waveform when the carrier signal generation unit generates a sawtooth carrier signal faster than the period of the synchronization signal. In this modified example, the description of the same operations as those in the above-described operation example is omitted by referring to the above description. In FIG. 5, the control signal generation unit 208 detects the peak (e.g., maximum value) or trough (e.g., minimum value) of the carrier signal in the first cycle of the carrier signal, and switches the levels of the plurality of control signals from one level to the other level at the detection timing. Then, the control signal generation unit 208 detects the peak (e.g., maximum value) or trough (e.g., minimum value) of the carrier signal in the second cycle of the carrier signal, and switches the levels of the plurality of control signals from the other level to one level at the detection timing. Similar to FIG. 2, the two half-bridge circuits on the high voltage side output a square wave voltage.

[0052] FIG. 6 is a diagram showing a configuration example of the power conversion device according to the second embodiment. In the second embodiment, the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description of the same components and operations as those in the above-described embodiment is omitted by referring to the above description. In the power conversion device 2 shown in FIG. 6, the control device 206 distributes a common synchronization signal to the plurality of conversion cells 211, 212, 213 and supplies it to the plurality of insulating elements 205. Since the reference phase of the phase difference of the output voltage is on the secondary side, the synchronization signal may be a signal shared by the plurality of conversion cells 211, 212, 213. The plurality of conversion cells 211, 212, 213 are controlled independently of each other, and the phase shift amount φ is added to the common potential side. Therefore, on the high voltage side where the plurality of conversion cells 211, 212, 213 are connected in series, the synchronization signal can be shared.

[0053] FIG. 7 is a diagram showing a configuration example of a power conversion device according to the third embodiment. In the third embodiment, the same components as those in the above-described embodiments are denoted by the same reference numerals, and the description of the same components and operations as those in the above-described embodiments is omitted by referring to the above description. In the power conversion device 3 shown in FIG. 7, the control device 206 supplies a common synchronization signal to a plurality of series-connected insulating elements 205 in a plurality of conversion cells 211, 212, 213. Since the reference phase of the phase difference of the output voltage is the secondary side, the synchronization signal may be a signal shared by the plurality of conversion cells 211, 212, 213. The common synchronization signal among the plurality of conversion cells 211, 212, 213 is transmitted from the conversion cell 213 with a lower potential to the conversion cell 211 with a higher potential among the plurality of conversion cells 211, 212, 213.

[0054] FIG. 8 is a diagram showing a configuration example of a power conversion device according to the fourth embodiment. FIG. 9 is a timing chart showing a first operation example of the power conversion device according to the fourth embodiment. In the fourth embodiment, the same components as those in the above-described embodiments are denoted by the same reference numerals, and the description of the same components and operations as those in the above-described embodiments is omitted by referring to the above description. In the power conversion device 4 shown in FIG. 9, each of the plurality of conversion cells 211, 212, 213 has a signal cutoff determination unit 209 that determines the stop of the secondary full-bridge circuit 220b based on a synchronization signal. In this example, each signal cutoff determination unit 209 of the plurality of conversion cells 211, 212, 213 determines the stop and start of its own conversion cell according to the magnitude of the pulse width included in the synchronization signal.

[0055] In FIG. 9, assume that the synchronization signal includes a first pulse having a pulse width equal to or greater than a first specified value and a second pulse having a pulse width equal to or greater than a second specified value that is longer than the first specified value. For example, when the signal cutoff determination unit 209 detects the second pulse included in the synchronization signal supplied from the control device 206, the signal cutoff determination unit 209 sets the levels of the plurality of control signals output by the control signal generation unit 208 to an inactive level (low level in FIG. 9). The signal cutoff determination unit 209, for example, sets the output permission signal input to the control signal generation unit 208 to an inactive level (low level in FIG. 9) so that the plurality of control signals output by the control signal generation unit 208 become inactive levels. Thereby, the control device 206 can quickly stop the secondary full-bridge circuit 220b.

[0056] Note that the signal cutoff determination unit 209 may switch the output permission signal to an inactive level when the elapse of a time corresponding to the second specified value has been detected by a counter or the like after the generation of the pulse has been detected, and turn off all the gate signals.

[0057] In FIG. 9, assume that the synchronization signal includes a first pulse having a pulse width equal to or greater than a first specified value, a second pulse having a pulse width equal to or greater than a second specified value that is longer than the first specified value, and a third pulse having a pulse width equal to or greater than a third specified value that is longer than the first specified value and shorter than the second specified value. For example, when the signal cutoff determination unit 209 detects the third pulse included in the synchronization signal supplied from the control device 206, the signal cutoff determination unit 209 enables the generation of the plurality of control signals by the control signal generation unit 208. The signal cutoff determination unit 209, for example, sets the output permission signal input to the control signal generation unit 208 to an active level (high level in FIG. 9) so that the generation of the plurality of control signals by the control signal generation unit 208 becomes effective. Thereby, the signal cutoff determination unit 209 quickly permits the operation of the secondary full-bridge circuit 220b, and the control device 206 can quickly start the secondary full-bridge circuit 220b.

[0058] Note that, as a countermeasure against misdetection of the second pulse and the third pulse, the signal interruption determination unit 209 may detect the synchronization signal a plurality of times at intervals shorter than the pulse width of the first specified value. Further, the signal interruption determination unit 209 may detect a pulse having a pulse width equal to or greater than the first specified value a plurality of times, and based on the pulse widths of the pulses detected a plurality of times, determine startup and stop in the same manner as described above.

[0059] On the high voltage side, an overvoltage protection circuit for protecting the capacitor element 203b from overvoltage may be provided, or an overcurrent protection circuit for protecting the capacitor element 203b from overcurrent may be provided. When these protection circuits detect an overvoltage or overcurrent of the capacitor element 203b, for example, they individually stop a plurality of conversion cells.

[0060] Further, the signal interruption determination unit 209 may detect the pulse of the synchronization signal at least once, and when there is no pulse of the synchronization signal for a certain period of time, stop the secondary side full-bridge circuit 220b. For example, the control device 206 can stop all the conversion cells by stopping the supply of the synchronization signal.

[0061] In the embodiments of FIGS. 1, 6, and 7, due to generating the carrier signal from the pulse of the synchronization signal supplied from the control device 206, it may take time to determine the stop of the conversion cell due to the control device 206 stopping the supply of the synchronization signal. When changing the frequency of the carrier signal, the pulse interval of the synchronization signal will be changed, but it is difficult to determine whether it is a change in the carrier frequency or a stop of the conversion cell. On the other hand, in the embodiment of FIG. 8, by determining startup and stop based on the width of the pulse of the synchronization signal, startup and stop can be immediately executed. Also, as in FIGS. 6 and 7, if a plurality of conversion cells share the synchronization signal, the conversion cells sharing the synchronization signal can be immediately stopped.

[0062] FIG. 10 is a timing chart showing a second operation example of the power conversion device according to the fourth embodiment. The signal interruption determination unit 209 may determine whether to shut down or start up the converter cells based on the number of pulses of the synchronization signal during a predetermined period. For example, when the number of pulses included in the synchronization signal supplied from the control device 206 is equal to or greater than a fourth specified value, the signal interruption determination unit 209 sets the levels of the multiple control signals output by the control signal generation unit 208 to an inactive level (low level in FIG. 10). FIG. 10 illustrates an example in which the fourth specified value is "3." For example, the signal interruption determination unit 209 sets the output permission signal input to the control signal generation unit 208 to an inactive level (low level in FIG. 10) so that the multiple control signals output by the control signal generation unit 208 are at an inactive level. This allows the control device 206 to quickly shut down the secondary-side full-bridge circuit 220b.

[0063] For example, when the number of pulses included in the synchronization signal supplied from the control device 206 is equal to or greater than a fifth specified value that is greater than a fourth specified value, the signal interruption determination unit 209 enables the generation of multiple control signals by the control signal generation unit 208. FIG. 10 illustrates an example where the fifth specified value is "4." For example, the signal interruption determination unit 209 sets the output permission signal input to the control signal generation unit 208 to an active level (high level in FIG. 10) so that the generation of multiple control signals by the control signal generation unit 208 is enabled. This allows the signal interruption determination unit 209 to quickly enable the operation of the secondary-side full-bridge circuit 220b, and the control device 206 to quickly start up the secondary-side full-bridge circuit 220b.

[0064] The conditions for determining whether to start or stop based on the pulse width may be other than those described above.

[0065] FIG. 11 is a timing chart showing a third operation example of the power conversion device according to the fourth embodiment. FIG. 12 shows an example of a synchronization signal to which start / stop information of each conversion cell is added. As shown in FIGS. 11 and 12, it is assumed that the synchronization signal includes a pulse train each having a pulse width of a sixth specified value shorter than the first specified value after a predetermined time has elapsed since a first pulse having a pulse width equal to or greater than a predetermined first specified value is output. The signal cutoff determination unit 209 determines whether or not to permit the operation of the secondary full-bridge circuit 220b according to the arrangement pattern of the pulse train.

[0066] For example, the signal cutoff determination unit 209 latches at the timing of the separation signal of each of the plurality of conversion cells 211, 212, and 213 (when the separation signal is at a high level in FIG. 11). Thereby, the signal cutoff determination unit 209 extracts information on the stop and start of the corresponding conversion cell from the synchronization signal, and determines start and stop. The above separation signal becomes an active level (high level in FIG. 11) after a preset elapsed time for each conversion cell after detection of the first pulse having a pulse width equal to or greater than the first specified value of the synchronization signal. The separation signal corresponds in timing to the pulse train having start / stop information for each conversion cell included in the synchronization signal. Thereby, in the operation example of FIG. 11, even when only one conversion cell fails and it is desired to operate while reducing the number of conversion cells, the conversion cell can be immediately stopped individually.

[0067] FIG. 16 is a diagram showing a configuration example of the power conversion device according to the fifth embodiment. In the fifth embodiment, the same components as those in the above-described embodiments are denoted by the same reference numerals, and descriptions of the same configurations and operations as those in the above-described embodiments are omitted by referring to the above descriptions. In the power conversion device 5 shown in FIG. 16, the secondary circuits 210b on the high voltage side of the plurality of conversion cells 211, 212, and 213 each have a control signal generation unit 238 and a drive circuit 204b, but do not have a carrier signal generation unit 207. The power conversion device 5 generates a plurality of control signals for controlling a plurality of secondary side switch elements without generating a carrier signal. The absence of the carrier signal generation unit 207 enables miniaturization of the secondary circuit 210b, and thus enables miniaturization of the power conversion device 5.

[0068] Regarding the description of the control signal generation unit 238, the description of the same configuration and operation as the control signal generation unit 208 in the above-described embodiment is omitted by referring to the above description. The control signal generation unit 238 generates a plurality of control signals synchronized with the synchronization signal transmitted by the corresponding insulating element 205. The plurality of control signals are, for example, rectangular wave signals whose phases are synchronized with the synchronization signal. In this example, the control signal generation unit 238 generates four control signals for controlling the switching of each of the plurality of secondary side switch elements 201e, 201f, 201g, 201h.

[0069] FIG. 17 is a timing chart showing an example of the operation waveform of the power conversion device in the fifth embodiment. The control device 206 outputs a synchronization signal to the control signal generation units 238 of the conversion cells 211, 212, 213 via the insulating elements 205 corresponding to the conversion cells 211, 212, 213, respectively. The control device 206 outputs a synchronization signal including a first pulse having a pulse width equal to or greater than a predetermined first specified value at a constant period by pulse width modulation.

[0070] On the high voltage side, when the control signal generation unit 238 detects a first pulse having a pulse width equal to or greater than a predetermined first specified value from the supplied synchronization signal, it inverts the level of each of the plurality of control signals. For example, when the control signal generation unit 238 detects the first pulse, it switches the level of the control signal of a certain switch element from a first level (for example, high level) to a second level (for example, low level), and switches the level of the switch element facing that switch from the second level to the first level. Conversely, when the control signal generation unit 238 detects the first pulse, it switches the level of the control signal of a certain switch element from the second level to the first level, and switches the level of the switch element facing that switch from the first level to the second level. Thereby, each time the first pulse included in the synchronization signal is detected, a control signal that repeats the inversion of the logic level can be generated.

[0071] Note that, in order for the control signal generation unit 238 to determine that the pulse width is equal to or greater than the first specified value, it is only necessary to detect the start of the pulse of the synchronization signal (in FIG. 17, the rising edge of the pulse) and confirm that there is a pulse of the synchronization signal up to the time corresponding to the first specified value (for example, maintaining a high level) using a counter or the like. Therefore, if it is confirmed that there is a pulse of the synchronization signal up to the time corresponding to the first specified value, the control signal generation unit 238 may invert the level of the control signal at a time point before the falling edge of the pulse of the synchronization signal.

[0072] The drive circuit 204b is an example of a first drive circuit that generates a plurality of gate signals for driving the switch elements 201e, 201f, 201g, 201h included in the secondary full-bridge circuit 220b in accordance with the plurality of control signals generated by the control signal generation unit 238. In this example, the plurality of gate signals have substantially the same phase as the corresponding control signals. The drive circuit 204b supplies the corresponding gate signals to the respective gates of the switch elements 201e, 201f, 201g, 201h. As a result, an output voltage V2 in the form of a square wave with a duty ratio of 50% is applied to the secondary side of the transformer 202.

[0073] FIG. 18 is a diagram showing a configuration example of the power conversion device according to the sixth embodiment. FIG. 19 is a timing chart showing an operation example of the power conversion device according to the sixth embodiment. In the sixth embodiment, the same components as those in the above-described embodiments are denoted by the same reference numerals, and the description of the same components and operations as those in the above-described embodiments is omitted by referring to the above description. In the power conversion device 6 shown in FIG. 19, the plurality of conversion cells 211, 212, 213 each have a signal cutoff determination unit 239 that determines the stop of the secondary full-bridge circuit 220b based on the synchronization signal. In this example, each signal cutoff determination unit 239 of the plurality of conversion cells 211, 212, 213 determines the stop and startup of its own conversion cell according to the magnitude of the pulse width included in the synchronization signal.

[0074] The signal interruption determination unit 239 has the same configuration and operation as the signal interruption determination unit 209 in the above embodiment, and therefore the above description will be used to omit the description of the signal interruption determination unit 239. The signal interruption determination unit 239 may operate as in the operation examples shown in FIGS.

[0075] Next, a comparative example to be compared with the multiple embodiments of the present disclosure will be described. The description of the comparative example will be simplified by incorporating the above description.

[0076] Fig. 13 is a diagram showing a configuration example of an isolated DC / DC converter in a comparative embodiment. Fig. 14 is a timing chart showing an operation example of the isolated DC / DC converter in the comparative embodiment shown in Fig. 13. Fig. 15 is a diagram showing a configuration example of a power conversion device in a comparative embodiment in which the isolated DC / DC converters in the comparative embodiment shown in Fig. 13 are connected in series on the DC output side.

[0077] 15 illustrates a configuration in which, when a power conversion device includes three conversion cells 111, 112, and 113 connected in series on the DC output side, a plurality of control signals and driving power supplies are independently supplied to each of the conversion cells 111, 112, and 113. Note that, although Fig. 15 does not explicitly show a path for supplying driving power, a power supply voltage is supplied to the driving circuits 104a and 104b from a power supply unit (not shown).

[0078] 15 is a multi-cell converter including a plurality of (three in this example) converter cells 111, 112, and 113, and a control device 106 that controls the power conversion operations of the converter cells 111, 112, and 113. Each of the converter cells 111, 112, and 113 is a cell converter that boosts or drops a DC voltage input from a common DC path and outputs a predetermined DC voltage. Each of the converter cells 111, 112, and 113 has an isolated DC / DC converter 100 and a pair of terminals p and q.

[0079] The isolated DC / DC converter 100 includes a transformer 102, a primary circuit 110a, and a secondary circuit 110b. The primary circuit 110a has a capacitive element 103a, a primary full-bridge circuit 120a, and a drive circuit 104a. The primary circuit 110a may have a reactor 107a connected in series to the primary coil of the transformer 102. The primary full-bridge circuit 1 20a includes primary-side switch elements 101a, 101b, 101c, and 101d. The secondary circuit 110b has a capacitive element 103b, a secondary full-bridge circuit 120b, and a drive circuit 104b. The secondary circuit 110b may have a reactor 107b connected in series to the secondary coil of the transformer 102. The secondary full-bridge circuit 1 20b includes secondary-side switch elements 101e, 101f, 101g, and 101h.

[0080] The power conversion device shown in FIG. 15 is provided for each of a plurality of conversion cells 111, 112, 113, and includes a plurality of insulating components 105 that transmit a plurality of control signals to the corresponding conversion cell among the plurality of conversion cells 111, 112, 113. When one insulating component 105 transmits a plurality of control signals, one insulating element is assigned to the transmission of one control signal. Therefore, one insulating component 105 includes a plurality of insulating elements (in this example, insulating elements 105a, 105b, 105c, 105d).

[0081] The drive circuit 104b drives and switches the plurality of secondary-side switch elements 101e, 101f, 101g, 101h according to a plurality of control signals supplied from the control device 206 via the plurality of insulating elements 105a, 105b, 105c, 105d. On the other hand, the drive circuit 104a drives and switches the plurality of primary-side switch elements 101a, 101b, 101c, 101d according to a plurality of control signals supplied from the control device 206 without passing through the plurality of insulating elements.

[0082] In the isolated DC / DC converter in a comparative form shown in FIG. 13, since four control signals equal to the total number of switch elements on the high voltage side are used, at least four insulation elements corresponding to the number of control signals are provided. In a configuration where isolated DC / DC converters in a comparative form are connected in series like the multi-cell converter shown in FIG. 15, the total number of insulation elements is at least (the number of series stages of conversion cells × the number of insulation elements provided per conversion cell), which becomes an enormous number.

[0083] In contrast, in each embodiment according to the present disclosure, since the signal supplied per conversion cell for driving the switch element on the high voltage side is one synchronization signal, the number of insulation elements can be reduced. As a result, for example, miniaturization and cost reduction of the power conversion device become possible.

[0084] As described above, the power conversion device has been described by way of embodiments, but the present invention is not limited to the above embodiments. Various modifications and improvements such as combinations or substitutions with part or all of other embodiments are possible within the scope of the present invention.

[0085] For example, the present invention is not limited to a configuration in which a plurality of conversion cells are connected in series via a pair of output terminals p and q on the output side that output the output voltage of the isolated DC / DC converter as in the first embodiment of the present disclosure. For example, an inverter may be added between the output side of the isolated DC / DC converter and a pair of terminals on the output side of the conversion cell, and two intermediate connection points of the inverter may be connected to those pair of terminals on the output side, respectively. In this case, the first conversion circuit connected between the transformer and a pair of terminals on the output side of the conversion cell may be the added inverter.

[0086] The present invention may also be configured such that multiple conversion cells are connected in series via a pair of terminals connected to the input side of the isolated DC / DC converter. For example, an inverter may be added between the input side of the isolated DC / DC converter and a pair of input terminals of the conversion cell, and two intermediate connection points of the inverter may be connected to the pair of input terminals, respectively. In this case, the first conversion circuit connected between the transformer and the pair of input terminals of the conversion cell may be the added inverter.

[0087] For example, in the present invention, the isolated DC / DC converter is not limited to a configuration in which a full-bridge circuit is provided on each of the primary and secondary sides of the transformer, and the bridge circuit provided on at least one of the primary and secondary sides may be a half-bridge circuit.Furthermore, the isolated DC / DC converter is not limited to a DAB converter, and may be a converter of a type other than a DAB converter (for example, a flyback type, a feedforward type, etc.). [Explanation of symbols]

[0088] 1,2,3,4,5,6 Power conversion device 100 Isolated DC / DC Converter 101 Switch element 102 Trans 103a, 103b Capacitance elements 104a, 104b drive circuit 105 Insulating parts 106 Control device 107 Reactor 109a DC power supply 200 Isolated DC / DC Converter 201a, 201b, 201c, 201d Switch elements 201e, 201f, 201g, 201h Switch elements 202 Trans 203a, 203b Capacitance element 204a, 204b drive circuit 205 Isolation element 206 Control device 207 Carrier signal generation unit 208, 238 Control signal generation unit 209, 239 Signal cut-off determination unit 210b Primary-side circuit 210a Secondary-side circuit 211, 212, 213 Conversion cell 220a Primary-side conversion circuit 220b Secondary-side conversion circuit

Claims

1. An insulation type DC / DC converter, and a pair of terminals connected to either the input side or the output side of the insulation type DC / DC converter, and a plurality of conversion cells connected in series via the pair of terminals, A plurality of insulation elements provided for each of the plurality of conversion cells and transmitting a synchronization signal to the corresponding conversion cell among the plurality of conversion cells, A control device that supplies the synchronization signal to each of the plurality of conversion cells via the corresponding insulation element among the plurality of insulation elements, and is provided with: Each of the plurality of insulation type DC / DC converters, A transformer, A first conversion circuit connected between the transformer and the pair of terminals, a control signal generation unit that generates a plurality of control signals synchronized with the synchronization signal, and a first drive circuit that drives a plurality of switch elements included in the first conversion circuit according to the plurality of control signals, a first circuit on the pair of terminal sides of the transformer, A second conversion circuit connected to the first conversion circuit via the transformer, and a second drive circuit that drives at least one switch element included in the second conversion circuit according to at least one control signal supplied from the control device, a second circuit on the side opposite to the pair of terminals of the transformer, Having The synchronization signal is directly supplied from the control device to the first circuit via the corresponding insulation element, a power conversion device.

2. The control signal generation unit and the first drive circuit operate at different reference potentials for each conversion cell, the power conversion device according to claim 1.

3. At least one of the control signals supplied from the control device is synchronized with the synchronization signal, the power conversion device according to claim 1 or 2.

4. The plurality of switch elements driven by the first drive circuit are switch elements included in at least one half-bridge circuit of the first conversion circuit, The plurality of switch elements driven by the second drive circuit are switch elements included in at least one half-bridge circuit of the second conversion circuit, the power conversion device according to any one of claims 1 to 3.

5. The phases of the plurality of control signals supplied from the control device to the second circuit side are different from the phases of the plurality of control signals generated by the control signal generation unit on the first circuit side, the power conversion device according to any one of claims 1 to 4.

6. The synchronization signal includes a first pulse having a pulse width equal to or greater than a first specified value, When the control signal generation unit detects the first pulse, the control signal generation unit inverts the level of each of the plurality of control signals. The power conversion device according to any one of claims 1 to 5.

7. Each of the plurality of conversion cells includes a carrier signal generation unit that generates a carrier signal synchronized with the synchronization signal, The control signal generation unit generates the plurality of control signals synchronized with the carrier signal. The power conversion device according to any one of claims 1 to 5.

8. The synchronization signal includes a first pulse having a pulse width equal to or greater than a first specified value, When the carrier signal generation unit detects the first pulse at least once, the carrier signal generation unit generates the carrier signal having a sawtooth shape or a triangular wave shape. The power conversion device according to claim 7.

9. The synchronization signal includes a first pulse having a pulse width equal to or greater than a first specified value, When the carrier signal generation unit detects the first pulse, after initializing the carrier signal, the carrier signal generation unit monotonically increases or monotonically decreases the carrier signal over time. The power conversion device according to claim 7.

10. The synchronization signal includes a first pulse having a pulse width equal to or greater than a first specified value, When the carrier signal generation unit detects the first pulse, the carrier signal generation unit generates the carrier signal that repeats monotonic increase and monotonic decrease over time. The power conversion device according to claim 7.

11. The control signal generation unit generates the plurality of control signals by detecting an inversion of a magnitude relationship between an amplitude of the carrier signal and a median value of the amplitude of the carrier signal. The power conversion device according to any one of claims 7 to 10.

12. The control signal generation unit generates the plurality of control signals by detecting a peak or a valley of the carrier signal. The power conversion device according to any one of claims 7 to 10.

13. The plurality of switch elements driven by the first drive circuit are switch elements included in at least one half-bridge circuit included in the first conversion circuit, The control signal generation unit applies a dead time for preventing a short circuit of the half-bridge circuit to the plurality of control signals. The power conversion device according to any one of claims 1 to 12.

14. Each of the plurality of conversion cells, The power conversion device according to any one of claims 1 to 13, comprising a determination unit that determines the stop of the first conversion circuit based on the synchronization signal.

15. The power conversion device according to claim 14, wherein the determination unit detects the pulse of the synchronization signal at least once, and stops the first conversion circuit when there is no pulse of the synchronization signal for a certain period of time.

16. The synchronization signal includes a first pulse having a pulse width equal to or greater than a first specified value, and a second pulse having a pulse width equal to or greater than a second specified value that is longer than the first specified value. The power conversion device according to claim 14 or 15, wherein the determination unit stops the first conversion circuit when the second pulse is detected.

17. The synchronization signal includes a first pulse having a pulse width equal to or greater than a first specified value, a second pulse having a pulse width equal to or greater than a second specified value that is longer than the first specified value, and a third pulse having a pulse width equal to or greater than a third specified value that is longer than the first specified value and shorter than the second specified value. The power conversion device according to claim 14 or 15, wherein the determination unit stops the first conversion circuit when the second pulse is detected, and permits the operation of the first conversion circuit when the third pulse is detected.

18. The power conversion device according to claim 14 or 15, wherein the determination unit stops the first conversion circuit when the number of pulses of the synchronization signal is equal to or greater than a fourth specified value.

19. The power conversion device according to claim 18, wherein the determination unit permits the operation of the first conversion circuit when the number of pulses of the synchronization signal is equal to or greater than a fifth specified value that is greater than the fourth specified value.

20. The synchronization signal includes a first pulse having a pulse width equal to or greater than a first specified value, and a pulse train each having a pulse width shorter than the first specified value. The power conversion device according to claim 14 or 15, wherein the determination unit determines whether to permit the operation of the first conversion circuit according to the arrangement pattern of the pulse train.

21. The power conversion device according to any one of claims 1 to 20, wherein the synchronization signal is a common signal for the plurality of conversion cells.

22. The power conversion device according to claim 21, wherein the synchronization signal is transmitted from a conversion cell with a lower potential to a conversion cell with a higher potential among the plurality of conversion cells.

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