Power conversion device

Abstract

To reduce the number of insulation elements provided for each conversion cell.SOLUTION: An electric power conversion system comprises: an insulation-type DC / DC converter; a plurality of conversion cells having a pair of terminals connected to either of an input-side or an output-side of the insulation-type DC / DC converter respectively, the plurality of conversion cells serially connected to each other through the pair of terminals; and a plurality of insulation elements, provided in the plurality of conversion cells respectively, and transmitting synchronization signals to the corresponding conversion cells of the plurality of conversion cells. Each of the plurality of conversion cells has: a transformer; a first conversion circuit connected to a space among the transformer and the pair of terminals; a determining part that determines motion patterns of the first conversion circuit on the basis of the synchronization signals; a control signal generating part that generates a plurality of control signals corresponding to the motion patterns determined by the determining part; and a first driving circuit that drives a plurality of switch elements included in the first conversion circuit, in accordance with the plurality of control signals.SELECTED DRAWING: Figure 20

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, a control signal that is electrically insulated from each other can be transmitted 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), resulting in 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 capable of reducing the number of insulating elements provided for each conversion cell.

Means for Solving the Problems

[0006] In one aspect of the present disclosure, an isolated DC / DC converter, and a pair of terminals connected to either the input side or the output side of the isolated DC / DC converter, and a plurality of conversion cells connected in series via the pair of terminals, a plurality of insulating 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, each of the plurality of conversion cells includes a transformer, a first conversion circuit connected between the transformer and the pair of terminals, a determination unit that determines an operation pattern of the first conversion circuit based on the synchronization signal, a control signal generation unit that generates a plurality of control signals corresponding to the operation pattern determined by the determination unit, a first drive circuit that drives a plurality of switch elements included in the first conversion circuit according to the plurality of control signals, the synchronization signal includes a pulse having a pulse width corresponding to a switching pattern of the plurality of switch elements included in the first conversion circuit, the determination unit determines the operation pattern of the first conversion circuit based on a difference in the pulse width of the pulse, and a power conversion device is provided.

Advantages of the Invention

[0007] According to one aspect of the present disclosure, the number of insulating elements provided for each conversion cell can be reduced.

Brief Description of the Drawings

[0008]

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Embodiments for Carrying Out the Invention

[0009] Hereinafter, a plurality of 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 showing a configuration example of the power conversion device in the first embodiment. FIG. 1 illustrates a configuration in which the power conversion device 1 includes three conversion cells 211, 212, and 213 connected in series on the DC output side, and supplies one synchronization signal, a plurality of control signals, and a driving power source to each of the conversion cells 211, 212, and 213 independently. Although not shown in FIG. 1, a power supply voltage is supplied from a power supply unit (not shown) to components such as the drive circuits 204a and 204b, the control signal generation unit 208, and the carrier signal generation unit 207 in the configuration described later.

[0011] The power conversion device 1 shown in FIG. 1 is a multi-cell converter including a plurality (in this example, three) of conversion cells 211, 212, 213 and a control device 206 that controls the power conversion operations of the conversion cells 211, 212, 213. The plurality of conversion cells 211, 212, 213 are each cell converters that boost or step down a DC voltage input from a common DC path and output a predetermined DC voltage. The plurality of conversion cells 211, 212, 213 each have an isolated DC / DC converter 200 and a pair of terminals p, q.

[0012] In the example shown in FIG. 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 the high-potential side terminal, and the second terminal q is the low-potential side terminal.

[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. For each of the plurality of conversion cells 211, 212, 213, its first terminal p is connected to the second terminal q of one conversion cell adjacent to itself, and its second terminal q is connected to the first terminal p of the other conversion cell adjacent to itself. Of the plurality of cell converters connected in series via the pair of terminals p, q, the first terminal p of the conversion cell located on the highest potential side (in this example, the conversion cell 211) is electrically connected to the high-potential side end of a load (not shown). On the other hand, of the plurality of cell converters connected in series via the pair of terminals p, q, the second terminal q of the conversion cell located on the lowest potential side (in this example, the conversion cell 213) 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 the 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 side circuit 210a, and a secondary side circuit 210b. The primary side circuit 210a and the secondary side 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 includes a capacitive element 203a, a primary full-bridge circuit 220a, and a drive circuit 204a. The primary circuit 210a may include a reactor 207a connected in series to the primary coil of the transformer 202.

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

[0020] The secondary 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 full-bridge circuit 220a is an example of a second conversion circuit connected to the secondary full-bridge circuit 220b via the transformer 202, and is connected between the primary coil of the transformer 202 and a common DC path with a plurality of 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 the 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 the secondary-side drive circuit 204b.

[0022] Specific examples of the primary-side switch element and the secondary-side switch element include semiconductor switching elements such as MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and IGBT (Insulated Gate Bipolar Transistor). 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 full-bridge circuit 220a provided on the primary side of a transformer 202 and a secondary 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 by applying a voltage 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 full-bridge circuit 220a) and the output voltage V2 output from two intermediate connection points of the secondary-side inverter circuit (secondary full-bridge circuit 220b). The power transmitted from the secondary side to the primary side is represented by the following simplified Equation 1.

[0024] [Number] P is the transmitted power, V1 is the amplitude of the primary-side output voltage, V2 is the amplitude of the secondary-side output voltage, L is the leakage inductance or the inductance of the external reactor, φ is the phase difference between V1 and V2, π is the ratio of the circumference of a circle to its diameter, and ω (= 2πf) represents the angular frequency of the switching of each switching element. f represents the switching frequency of each switching element. Note that the above Equation 1 is the equation when the duty ratio of the switching of each switching element is 50% (when V1 and V2 are square waves (including quasi-square waves) with a duty ratio of 50%).

[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, 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, 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, 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 non-zero value). Synchronization means making them related 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 one synchronization signal for synchronizing the repetition start timing of the waveform of the output voltage V2 to each of the secondary-side circuits 210b on the high-voltage side of the plurality of conversion cells 211, 212, 213 via the corresponding plurality of insulating elements 205. On the other hand, the control device 206 supplies a plurality of control signals that define the repetition start timing of the waveform of the output voltage V1 to each of the primary-side circuits 210a on the low-voltage side of the plurality of conversion cells 211, 212, 213. Thereby, when the duty ratios of the waveforms of the output voltages V1 and V2 of each of the conversion cells 211, 212, 213 are a constant value 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, 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 insulating element 205 may be constituted by a single insulating element or may be constituted by a plurality of insulating elements connected in series. Specific examples of the insulating element 205 include an insulating transformer, a pulse transformer, a digital isolator, an isolation amplifier, etc. The insulating 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 insulating element 205. The carrier signal is, for example, a sawtooth periodic signal having the same period with a phase synchronized with the synchronization signal.

[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 having a phase 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 a plurality of secondary-side switch elements 201e, 201f, 201g, 201h according to a plurality of control signals generated by the control signal generation unit 208. On the other hand, the drive circuit 204a drives and switches a plurality of primary-side switch elements 201a, 201b, 201c, 201d according to a plurality of control signals generated by the control device 206 that generates a 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 insulation 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.

[0036] On the high voltage side, the carrier signal generation unit 207 detects at least one first pulse having a pulse width equal to or greater than a predetermined first specified value from the supplied synchronization signal and supplies it to the control signal generation unit 208 to generate a sawtooth carrier signal. 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 for the carrier signal generation unit 207 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. 2, 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 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 the carrier signal with a threshold value of a duty value of 50% (the median value of the amplitude of the carrier signal). When the amplitude of the carrier signal is lower than the threshold value of the duty value of 50%, 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 the duty value of 50%, 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 in accordance with 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. Thereby, an output voltage V2 of a square wave with a duty ratio of 50% is applied to the secondary side of the transformer 202.

[0041] On the other hand, on the low voltage side, the control device 206 determines the phase shift amount φ with respect to the above-described synchronization signal supplied to the high voltage side based on Equation 1, and outputs a plurality of control signals 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 the switch elements 201a, 201b, 201c, and 201d. The control device 206 generates a plurality of control signals to be supplied to the respective 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 a 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 respective gates of the switch elements 201a, 201b, 201c, and 201d. As a result, 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 according to 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 a reference for the phase difference of the DAB converter, and only the synchronization signal for synchronization in each DAB converter is transmitted to the high-voltage side of each DAB converter via the insulating element 205. Then, in the secondary-side circuit 210b on the high-voltage side, a plurality of control signals for controlling the secondary full-bridge circuit 220b that generates the output voltage V2 are generated based on the synchronization signal received via the insulating element 205. On the other hand, the reference potentials (grounds) of the primary-side circuit 210a and the control device 206 on the low-voltage side are common. Therefore, even without the insulating element 205, a plurality of control signals for controlling the primary 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 insulating elements 205 provided for each conversion cell can be reduced.

[0046] Note 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 only necessary to correctly introduce a phase difference between the output voltages on the primary side and the secondary side. For example, the processes of generating the carrier signal and the control signal on the common potential side are not limited to being performed within the control device 206, and may be performed by a carrier signal generation unit and a control signal generation unit provided in the same way as on the high voltage side. Further, the carrier signal may be generated for each half-bridge circuit.

[0047] Also, although the reference phase of the phase difference of the output voltage is described as the secondary side, it is not limited to this. Since it is only necessary to correctly introduce a phase difference between the output voltages on the primary side and the secondary side, there is no operational problem even if the reference phase is the primary side. Further, the control signal generation unit 208 and the control device 206 may include a dead time generation unit that applies a dead time for preventing a short circuit between the upper and lower arms of the half-bridge circuit to a plurality of control signals.

[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. The description of the same operation as in the above operation example in this modification is omitted by referring to the above description. Even when the carrier signal generation unit 207 generates a triangular carrier signal, a plurality of control signals are generated by comparing with the median value of the carrier signal, similar to FIG. 2. 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 repeatedly increases monotonically and decreases monotonically over time. FIG. 3 illustrates a case where the carrier signal generation unit 207 switches the carrier signal from monotonically decreasing to monotonically increasing each time it detects the first pulse, and switches the carrier signal from monotonically increasing to monotonically decreasing 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 an operation waveform when the carrier signal generation unit detects the peaks (e.g., maximum values) and valleys (e.g., minimum values) of the triangular carrier signal it generates and generates a plurality of control signals. In this modification example, the description of the same operations as those in the above operation example is omitted by referring to the above description. 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 modification example, the description of the same operations as those in the above 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 valley (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 valley (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 the 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 in 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 among the plurality of conversion cells 211, 212, 213 and supplies it to the plurality of insulation 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 among 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 the power conversion device in the third embodiment. In the third 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 3 shown in FIG. 7, the control device 206 supplies a common synchronization signal among the plurality of conversion cells 211, 212, 213 to the plurality of insulation elements 205 connected in cascade. 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 among 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 the lowest potential to the conversion cell 211 with the highest 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, the plurality of conversion cells 211, 212, 213 each have 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 startup 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 from 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 from 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 is detected by a counter or the like after the generation of the pulse, 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, it enables the generation of a plurality of control signals by the control signal generation unit 208. The signal cutoff determination unit 209 sets, for example, 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 a plurality of control signals by the control signal generation unit 208 is enabled. Thereby, the signal cutoff determination unit 209 promptly permits the operation of the secondary full-bridge circuit 220b, and the control device 206 can promptly 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 cutoff 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 cutoff 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 make a determination of start and stop in the same manner as above based on the pulse widths of the pulses detected a plurality of times.

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

[0060] Further, the signal cutoff determination unit 209 may detect the pulse of the synchronization signal at least once, and stop the secondary full-bridge circuit 220b when there is no pulse of the synchronization signal for a certain period of time. 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, since the carrier signal is generated from the pulses 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 stop of the supply of the synchronization signal from the control device 206. When changing the frequency of the carrier signal, the pulse interval of the synchronization signal is changed, but it is difficult to determine whether the carrier frequency is changed or the conversion cell is stopped. On the other hand, in the embodiment of FIG. 8, by determining startup and stop based on the width of the pulses of the synchronization signal, startup and stop can be executed immediately. 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 in the fourth embodiment. The signal cutoff determination unit 209 may determine the stop and startup of the conversion cell based on the number of pulses of the synchronization signal during a predetermined fixed 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 cutoff determination unit 209 sets the levels of a plurality of control signals output by the control signal generation unit 208 to inactive levels (low levels in FIG. 10). FIG. 10 illustrates the case where the fourth specified value is "3". 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. 10) so that a 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 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 the fourth specified value, the signal interruption determination unit 209 enables the generation of a plurality of control signals by the control signal generation unit 208. FIG. 10 illustrates the case where the fifth specified value is "4". The signal interruption determination unit 209 sets, for example, 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 a plurality of control signals by the control signal generation unit 208 is enabled. Thereby, the signal interruption determination unit 209 promptly permits the operation of the secondary full-bridge circuit 220b, and the control device 206 can promptly start up the secondary full-bridge circuit 220b.

[0064] Note that the conditions for determining startup or stop based on the pulse width may be other than the above.

[0065] FIG. 11 is a timing chart showing a third operation example of the power conversion device in the fourth embodiment. FIG. 12 shows an example of a synchronization signal to which the startup / 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 lapse of a certain predetermined time from the output of the first pulse having a pulse width equal to or greater than a predetermined first specified value. The signal interruption determination unit 209 determines whether 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 interruption determination unit 209 latches at the timing of the separation signal of each of the plurality of conversion cells 211, 212, 213 (in FIG. 11, when the separation signal is at a high level). Thereby, the signal interruption 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 a first pulse having a pulse width equal to or greater than a first specified value of the synchronization signal. The separation signal corresponds in timing to a 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 individual conversion cells can be immediately stopped.

[0067] FIG. 16 is a diagram showing a configuration example of a 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 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 5 shown in FIG. 16, the secondary side circuits 210b on the high voltage side of the plurality of conversion cells 211, 212, 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 side 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 those of the control signal generation unit 208 in the above-described embodiments 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 waveforms of the power conversion device according to the fifth embodiment. The control device 206 outputs a synchronization signal to the control signal generation units 238 of the conversion cells 211, 212, and 213 via the insulation elements 205 corresponding to the respective conversion cells 211, 212, and 213. The control device 206 outputs, by pulse width modulation, 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.

[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 (e.g., high level) to a second level (e.g., 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 may 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 (e.g., 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, and 201h included in the secondary full-bridge circuit 220b according to a 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, and 201h. As a result, an output voltage V2 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 a 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 embodiment are denoted by the same reference numerals, and the description of the same configuration and operation as those in the above-described embodiment is omitted by referring to the above description. In the power conversion device 6 shown in FIG. 19, each of the plurality of conversion cells 211, 212, and 213 has a signal cutoff determination unit 239 that determines the stop of the secondary full-bridge circuit 220b based on a synchronization signal. In this example, each signal cutoff determination unit 239 of the plurality of conversion cells 211, 212, and 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] Note that since the signal cutoff determination unit 239 has the same configuration and operation as the signal cutoff determination unit 209 of the above-described embodiment, the description of the signal cutoff determination unit 239 is omitted by referring to the above description. The signal cutoff determination unit 239 may operate as in the operation examples shown in FIGS. 10, 11, and 12.

[0075] FIG. 20 is a diagram showing a configuration example of a power conversion device according to the seventh embodiment. In the seventh embodiment, the description of the same configuration and operation as in the above-described embodiments is omitted by referring to the above description. The power conversion device 7 shown in FIG. 20 uses a low-breakdown-voltage semiconductor switch by configuring an isolated DC / DC converter 300 as a three-level power converter, and an efficiency improvement effect can be obtained by reducing the breakdown voltage of the semiconductor switch. On the other hand, as the number of semiconductor switches increases, the switching pattern becomes complicated. By transmitting information for generating a complicated switching pattern of the three-level power converter using only one synchronization signal, reduction in the number of isolation elements provided in the conversion cell is realized.

[0076] The isolated DC / DC converter 300 boosts or buck-boosts a DC voltage input from a common DC path by a plurality of conversion cells 311, 312, 313, and outputs a predetermined DC voltage from a pair of terminals p and q. The isolated DC / DC converter 300 includes a transformer 302, a primary-side circuit 310a, and a secondary-side circuit 310b. The primary-side circuit 310a and the secondary-side circuit 310b are magnetically coupled by the transformer 302.

[0077] The primary-side circuit 310a has a first capacitive element 303a, a second capacitive element 303b, a primary-side diode clamp full-bridge circuit 320a, and a drive circuit 304a. The primary-side circuit 310a may have a reactor 307a connected in series to the primary-side coil of the transformer 302.

[0078] The primary-side diode clamp type full-bridge circuit 320a is configured as a three-level power converter using a plurality of semiconductor switches and a plurality of diodes. Two capacitor elements 303a and 303b are connected in series between the DC terminals of the primary-side diode clamp type full-bridge circuit 320a, and the midpoint therebetween is also referred to as the DC neutral point. The primary-side diode clamp type full-bridge circuit 320a has diodes 314a and 314c with anodes connected to the DC neutral point, and diodes 314b and 314d with cathodes connected to the DC neutral point. The cathode of diode 314a is connected between the primary-side first arm 301a and the primary-side second arm 301b. The anode of diode 314b is connected between the primary-side third arm 301c and the primary-side fourth arm 301d. The cathode of diode 314c is connected between the primary-side fifth arm 301e and the primary-side sixth arm 301f. The anode of diode 314d is connected between the primary-side seventh arm 301g and the primary-side eighth arm 301h.

[0079] The secondary-side circuit 310b has a first capacitor element 303c, a second capacitor element 303d, a secondary-side diode clamp type full-bridge circuit 320b, and a drive circuit 304b. The secondary-side circuit 310b may have a reactor 307b connected in series to the secondary-side coil of the transformer 302.

[0080] The secondary-side diode-clamped full-bridge circuit 320b is configured as a three-level power converter using a plurality of semiconductor switches and a plurality of diodes. Two capacitor elements 303c and 303d are connected in series between the DC terminals of the secondary-side diode-clamped full-bridge circuit 320b, and the midpoint therebetween is also referred to as the DC neutral point. The secondary-side diode-clamped full-bridge circuit 320b has diodes 314e and 314g whose anodes are connected to the DC neutral point, and diodes 314f and 314h whose cathodes are connected to the DC neutral point. The cathode of diode 314e is connected between the secondary-side first arm 301i and the secondary-side second arm 301j. The anode of diode 314f is connected between the secondary-side third arm 301k and the secondary-side fourth arm 301l. The cathode of diode 314g is connected between the secondary-side fifth arm 301m and the secondary-side sixth arm 301n. The anode of diode 314h is connected between the secondary-side seventh arm 301o and the secondary-side eighth arm 301p.

[0081] In the above, as the primary-side full-bridge circuit 320a and the secondary-side full-bridge circuit 320b, an example of a diode-clamped power converter is shown, but the configuration of the full-bridge circuit is not limited to the diode-clamped type, and for example, a T-type, a flying capacitor type, etc. may also be used.

[0082] Here, as an example, an example of a three-level power converter is shown, but the number of levels is not limited to three, and a power converter with two or more levels may also be used.

[0083] The primary first arm 301a, the primary second arm 301b, the primary third arm 301c, the primary fourth arm 301d, the primary fifth arm 301e, the primary sixth arm 301f, the primary seventh arm 301g, and the primary eighth arm 301h are driven by the primary drive circuit 304a. The secondary first arm 301i, the secondary second arm 301j, the secondary third arm 301k, the secondary fourth arm 301l, the secondary fifth arm 301m, the secondary sixth arm 301n, the secondary seventh arm 301o, and the secondary eighth arm 301p are driven by the secondary drive circuit 304b.

[0084] The isolated DC / DC converter 300 is a DAB converter having a primary-side diode-clamped full-bridge circuit 320a provided on the primary side of the transformer 302 and a secondary-side diode-clamped full-bridge circuit 320b provided on the secondary side of the transformer 302. Similar to the isolated DC / DC converter 200, the transmitted power is controlled by the phase difference between the output voltage V1 output from two intermediate connection points of the primary-side diode-clamped full-bridge circuit 320a and the output voltage V2 output from two intermediate connection points of the secondary-side diode-clamped full-bridge circuit 320b.

[0085] The secondary-side circuits 310b on the high-voltage side of the plurality of conversion cells 311, 312, 313 each have an output mode determination unit 340, a control signal generation unit 341, and a drive circuit 304b. Further, the power conversion device 7 includes a plurality of insulation elements 305 provided for each of the plurality of conversion cells 311, 312, 313 and transmitting a synchronization signal to the corresponding conversion cell among the plurality of conversion cells 311, 312, 313. Thereby, a synchronization signal that is electrically insulated from each other can be transmitted to each of the internal circuits (output mode determination unit 340, control signal generation unit 341, and drive circuit 304b) that operate at different reference potentials for each conversion cell.

[0086] The control device 306 supplies a common synchronization signal to a plurality of series-connected insulating elements 305 in a plurality of conversion cells 311, 312, 313. 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 311, 312, 313. The common synchronization signal in the plurality of conversion cells 311, 312, 313 is transmitted from the conversion cell 313 with a lower potential to the conversion cell 311 with a higher potential among the plurality of conversion cells 311, 312, 313.

[0087] The synchronization signal generated by the control device 306 is a signal for determining the output mode of the control signal in the output mode determination unit 340, and is a signal having two values of high level and low level. The control device 306 can change the pulse width of one level of the synchronization signal (in this example, the period of the high level) at an arbitrary width and at an arbitrary timing.

[0088] The drive circuit 304b drives and switches a plurality of secondary-side switch elements 301i, 301j, 301k, 301l, 301m, 301n, 301o, 301p according to a plurality of control signals generated by the control signal generation unit 341 based on the determination result in the output mode determination unit 340. On the other hand, the drive circuit 304a drives and switches a plurality of primary-side switch elements 301a, 301b, 301c, 301d, 301e, 301f, 301g, 301h according to a plurality of control signals generated by the control device 306. The control device 306 generates eight control signals for controlling the switching of each of the plurality of primary-side switch elements 301a, 301b, 301c, 301d, 301e, 301f, 301g, 301h.

[0089] FIG. 21 is a timing chart showing an example of the operation waveforms of the power conversion device according to the seventh embodiment. The control device 306 generates a synchronization signal including pulses having pulse widths corresponding to the switching patterns of the plurality of secondary-side switch elements 301i, 301j, 301k, 301l, 301m, 301n, 301o, 301p. The output mode determination unit 340 determines the operation pattern of the secondary-side diode clamp full-bridge circuit 320b based on the difference in the pulse widths of the pulses included in the synchronization signal generated by the control device 306.

[0090] FIG. 22 is a timing chart showing an example of the generation process of the high-voltage side control signal of the power conversion device according to the seventh embodiment. On the high-voltage side, the output mode determination unit 340 detects the start of a pulse (the rising edge of the pulse in FIG. 22) from the supplied synchronization signal and counts up to the end of the pulse (the falling edge of the pulse in FIG. 22) using a counter or the like. The output mode determination unit 340 determines the output mode of the corresponding control signal by comparing the detected count value with a predetermined reference value. This determined output mode is updated as the output mode determination result after a predetermined fixed time (referred to as the "pulse width determination time") has elapsed since the rising edge or falling edge of the pulse of the synchronization signal was detected. The control signal generation unit 341 generates (updates) a predetermined control signal according to the output mode determination result updated by the output mode determination unit 340. Thereby, it is possible to transmit information for generating the control signals of the eight secondary-side switch elements 301i, 301j, 301k, 301l, 301m, 301n, 301o, 301p using only one synchronization signal generated by the control device 306.

[0091] Figure 23 shows an example of the output mode of the high-voltage side control signal. The output mode determination unit 340 determines the output mode of the control signal according to the counter determination condition based on the counter value of the detected pulse width. The control signal generation unit 341 generates a plurality of control signals corresponding to each output mode so that the secondary side switch elements 301i, 301j, 301k, 301l, 301m, 301n, 301o, 301p are in the switching pattern illustrated in Figure 23. In the example shown in Figure 23, the 10th specified value is the largest, the 1st specified value is the smallest, and the specified values decrease as the number of the specified values becomes smaller. "H" represents that the level of the corresponding gate signal is high level, and "L" represents that the level of the corresponding gate signal is low level. When the detected pulse width is within the specified range (in this example, within the range from the 2nd specified value to the 10th specified value), the control signal generation unit 341 updates a plurality of control signals so that the plurality of switch elements are in the switching pattern corresponding to the detected pulse width. On the other hand, when the detected pulse width is outside the specified range (in this example, smaller (shorter) than the 2nd specified value), the control signal generation unit 341 updates a plurality of control signals so that the plurality of switch elements are in the all-off switching pattern corresponding to the detected pulse width.

[0092] When the counter value of the detected pulse width is larger than a predetermined 1st specified value and equal to or less than a predetermined 2nd specified value, the output mode determination unit 340 determines that the output mode is the signal cut-off mode M2. The control signal generation unit 341 turns off all control signals so that they are in the switching pattern corresponding to the signal cut-off mode M2.

[0093] When the counter value of the detected pulse width is equal to or less than a predetermined 1st specified value, the output mode determination unit 340 determines that the output mode is the previous value holding mode M1. The control signal generation unit 341 holds the previous value of the control signal so that the current control signal has the same pattern as the previous control signal.

[0094] Next, a comparative form compared with a plurality of embodiments according to the present disclosure will be described. The description of the comparative form will be simplified by referring to the above description.

[0095] FIG. 13 is a diagram showing a configuration example of an isolated DC / DC converter in a comparative form. FIG. 14 is a timing chart showing an operation example of the isolated DC / DC converter in the comparative form shown in FIG. 13. FIG. 15 is a diagram showing a configuration example of a power conversion device in a comparative form in which the isolated DC / DC converters shown in FIG. 13 are connected in series on the DC output side.

[0096] FIG. 15 illustrates a configuration in which, when the 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 a driving power source are independently supplied to each of the conversion cells 111, 112, and 113. Although FIG. 15 does not explicitly show the path for supplying the driving power source, a power supply voltage is supplied to the drive circuits 104a and 104b from a power supply unit (not shown).

[0097] The power conversion device shown in FIG. 15 is a multi-cell converter including a plurality (three in this example) of conversion cells 111, 112, and 113 and a control device 106 that controls the power conversion operations of the conversion cells 111, 112, and 113, respectively. The plurality of conversion cells 111, 112, and 113 are cell converters that boost or step down a DC voltage input from a common DC path and output a predetermined DC voltage, respectively. The plurality of conversion cells 111, 112, and 113 each have an isolated DC / DC converter 100 and a pair of terminals p and q.

[0098] 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 120a includes primary side switch elements 101a, 101b, 101c, 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 120b includes secondary side switch elements 101e, 101f, 101g, 101h.

[0099] The power conversion device shown in FIG. 15 includes a plurality of insulation components 105 provided for each of the plurality of conversion cells 111, 112, 113, and transmits a plurality of control signals to the corresponding conversion cell among the plurality of conversion cells 111, 112, 113. When one insulation component 105 transmits a plurality of control signals, one insulation element is assigned to the transmission of one control signal, so one insulation component 105 includes a plurality of insulation elements (in this example, insulation elements 105a, 105b, 105c, 105d).

[0100] The drive circuit 104b drives and switches the plurality of secondary side switch elements 101e, 101f, 101g, 101h according to the plurality of control signals supplied from the control device 206 via the plurality of insulation 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 the plurality of control signals supplied from the control device 206 without passing through the plurality of insulation elements.

[0101] In an 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 isolation 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 a multi-cell converter shown in FIG. 15, the total number of isolation elements becomes at least (the number of series stages of conversion cells × the number of isolation elements provided per conversion cell), which is an enormous number.

[0102] 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 isolation elements can be reduced. As a result, for example, miniaturization and cost reduction of the power conversion device become possible.

[0103] As described above, the power conversion device has been described with reference to the embodiments, but the present invention is not limited to the above embodiments. Various modifications and improvements such as combinations or substitutions with some or all of other embodiments are possible within the scope of the present invention.

[0104] 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 the pair of terminals on the output side of the conversion cell may be the added inverter.

[0105] Further, in the present invention, a plurality of conversion cells may be 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 terminals on the input side of the conversion cell, and two intermediate connection points of the inverter may be respectively connected to those pair of terminals on the input side. In this case, the first conversion circuit connected between the transformer and the pair of terminals on the input side of the conversion cell may be the added inverter.

[0106] 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 side and the secondary side of the transformer, and the bridge circuit provided on at least one of the primary side and the secondary side may be a half-bridge circuit. Further, the isolated DC / DC converter is not limited to a DAB converter, and may be a converter of a form other than the DAB converter (for example, flyback type, forward type, etc.).

Explanation of Reference Numerals

[0107] 1, 2, 3, 4, 5, 6, 7 Power conversion device 100 Isolated DC / DC converter 101 Switch element 102 Transformer 103a, 103b Capacitance element 104a, 104b Drive circuit 105 Insulating component 106 Control device 107 Reactor 109a DC power supply 200 Isolated DC / DC converter 201a, 201b, 201c, 201d Switch element 201e, 201f, 201g, 201h Switch element 202 Transformer 203a, 203b Capacitance element 204a, 204b Drive circuit 205 Insulating 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 300 Isolated DC / DC converter 301a, 301b, 301c, 301d Primary side switch element 301e, 301f, 301g, 301h Primary side switch element 301i, 301j, 301k, 301l Secondary side switch element 301m, 301n, 301o, 301p Secondary side switch element 302 Transformer 303a, 303b, 303c, 303d Capacitor element 305 Insulating element 306 Control device 310a Primary side circuit 310b Secondary side circuit 311, 312, 313 Conversion cell 314a, 314b, 314c, 314d Diode 314e, 314f, 314g, 314h Diode 320a Primary side diode clamp type full bridge circuit 320b Secondary side diode clamp type full bridge circuit 340 Output mode determination unit 341 Control signal generation unit

Claims

1. An insulated DC / DC converter and a pair of terminals connected to either the input side or the output side of the insulated DC / DC converter, and a plurality of conversion cells connected in series via the pair of terminals, a plurality of insulating 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, each of the plurality of conversion cells includes a transformer, a first conversion circuit connected between the transformer and the pair of terminals, a determination unit that determines an operation pattern of the first conversion circuit based on the synchronization signal, a control signal generation unit that generates a plurality of control signals corresponding to the operation pattern determined by the determination unit, a first drive circuit that drives a plurality of switch elements included in the first conversion circuit according to the plurality of control signals, the synchronization signal includes a pulse having a pulse width corresponding to a switching pattern of a plurality of the switch elements included in the first conversion circuit, the determination unit determines an operation pattern of the first conversion circuit based on a difference in pulse width of the pulse, a power conversion device.

2. The control signal generation unit updates the plurality of control signals according to a determination result of the operation pattern by the determination unit after a certain time from detecting a rising edge or a falling edge of a pulse of the synchronization signal. The power conversion device according to claim 1.

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