JP2022032919A - Power conversion device - Google Patents

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

The present disclosure relates to a power converter.

Conventionally, a plurality of conversion cells connected in series via a pair of input terminals and a plurality of control signals are provided for each of the plurality of conversion cells, and a plurality of control signals are transmitted to the corresponding conversion cells among the plurality of conversion cells. A multi-cell converter device including a plurality of insulating components to be transmitted is known. Each of the plurality of conversion cells has a drive circuit that controls a DC / DC converter based on a plurality of control signals received via one or a plurality of insulating components. By transmitting the control signal to the conversion cell via the insulating component, the control signal electrically isolated 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). ).

Japanese Unexamined Patent Publication No. 2018-6436

When one insulating component transmits a plurality of control signals, one insulating component such as a digital isolator is assigned to the transmission of one control signal. Therefore, one insulating component includes a plurality of insulating elements. ing. Therefore, in the conventional technique, as the number of control signals transmitted per conversion cell increases, the number of insulating elements provided for each 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 is a huge number. When the total number of insulating elements becomes enormous, it is difficult to reduce the size and cost, for example.

The present disclosure provides a power conversion device capable of reducing the number of insulating elements provided for each conversion cell.

In one aspect of the disclosure,
It has 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 is connected in series via the pair of terminals. With multiple conversion cells
A plurality of insulating elements provided for each of the plurality of conversion cells and transmitting a synchronization signal to the corresponding conversion cells among the plurality of conversion cells are provided.
The plurality of conversion cells are each
With 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,
A power conversion device including a first drive circuit for driving a plurality of switch elements included in the first conversion circuit according to the plurality of control signals is provided.

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

It is a figure which shows the structural example of the power conversion apparatus in 1st Embodiment. It is a timing chart which shows an example of the operation waveform of the power conversion apparatus in 1st Embodiment. It is a timing chart which shows an example of the operation waveform when a carrier signal generation part generates a triangular wave shape carrier signal. It is a timing chart which shows an example of the operation waveform in the case of generating a plurality of control signals by detecting the peak (for example, the maximum value) and the valley (for example, the minimum value) of a triangular wave-shaped carrier signal. It is a timing chart which shows an example of the operation waveform in the case of generating a serrated carrier signal faster than the period of a synchronization signal. It is a figure which shows the structural example of the power conversion apparatus in 2nd Embodiment. It is a figure which shows the structural example of the power conversion apparatus in 3rd Embodiment. It is a figure which shows the structural example of the power conversion apparatus in 4th Embodiment. It is a timing chart which shows the 1st operation example of the power conversion apparatus in 4th Embodiment. It is a timing chart which shows the 2nd operation example of the power conversion apparatus in 4th Embodiment. It is a timing chart which shows the 3rd operation example of the power conversion apparatus in 4th Embodiment. It is a figure which shows an example of the synchronization signal to which the start / stop information is attached. It is a figure which shows the structural example of the isolated type DC / DC converter in one comparative form. It is a timing chart which shows the operation example of the isolated type DC / DC converter in one comparative form. It is a figure which shows the structural example of the power conversion apparatus in one comparative form. It is a figure which shows the structural example of the power conversion apparatus in 5th Embodiment. It is a timing chart which shows an example of the operation waveform of the power conversion apparatus in 5th Embodiment. It is a figure which shows the structural example of the power conversion apparatus in 6th Embodiment. It is a timing chart which shows the operation example of the power conversion apparatus in 6th Embodiment.

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.

FIG. 1 is a diagram showing a configuration example of a power conversion device according to the first embodiment. FIG. 1 shows a synchronization signal and one synchronization signal for each conversion cell 211,212,213 when the power conversion device 1 includes three conversion cells 211,212,213 connected in series on the DC output side. An example is a configuration in which a plurality of control signals and a power source for driving are independently supplied. Although the path for supplying the drive power is not specified in FIG. 1, it is not shown in the later configurations of the drive circuits 204a and 204b, the control signal generation unit 208, the carrier signal generation unit 207, and the like. The power supply voltage is supplied from the power supply unit of.

The power conversion device 1 shown in FIG. 1 includes a plurality of (three in this example) conversion cells 211,212,213 and a control device 206 for controlling the power conversion operation of each of the conversion cells 211,212,213. It is a multi-cell converter equipped with. The plurality of conversion cells 211, 212, and 213 are cell converters that increase or decrease the DC voltage input from a common DC path and output a predetermined DC voltage, respectively. Each of the plurality of conversion cells 211, 212, and 213 has an isolated DC / DC converter 200 and a pair of terminals p and q.

In the example shown in FIG. 1, the pair of terminals p and q are output terminals connected to the output side of the isolated DC / DC converter 200. Of the pair of terminals p and q, the first terminal p is the terminal on the high potential side, and the second terminal q is the terminal on the low potential side.

The plurality of conversion cells 211, 212, and 213 have a pair of terminals p and q, respectively, and are connected in series via the pair of terminals p and q. Each of the plurality of conversion cells 211, 212, and 213 is connected to the second terminal q of one conversion cell in which its first terminal p is adjacent to itself, and its second terminal q is adjacent to itself in the other. It is connected to the first terminal p of the conversion cell. Of a plurality of cell converters connected in series via a pair of terminals p and q, the first terminal p of the conversion cell (conversion cell 211 in this example) located on the highest potential side is not shown. It is electrically connected to the high potential side end of the load. On the other hand, among a plurality of cell converters connected in series via a pair of terminals p and q, the second terminal q of the conversion cell on the lowest potential side (conversion cell 213 in this example) is not shown. It is electrically connected to the low potential end of the load.

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

The transformer 202 is a transformer having a primary side coil and a secondary side coil, and the primary side coil and the secondary side coil are magnetically coupled to each other.

The primary side circuit 210a includes a capacitive element 203a, a primary side full bridge circuit 220a, and a drive circuit 204a. The primary circuit 210a may have a reactor 207a connected in series with the primary coil of the transformer 202.

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 upper arm. It has a primary side second half bridge circuit in which the 201c and the primary side second lower arm 201d are connected in series. The primary side coil (or series circuit of the primary side coil and the reactor 207a) of the transformer 202 is an intermediate connection point between the primary side first upper arm 201a and the primary side first lower arm 201b and the primary side. It is connected between the intermediate connection point between the second upper arm 201c and the primary side second lower arm 201d.

The secondary side circuit 210b includes a capacitive element 203b, a secondary side full bridge circuit 220b, and a drive circuit 204a. The secondary circuit 210b may have a reactor 207b connected in series with the secondary coil of the transformer 202.

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

The secondary side full bridge circuit 220b is an example of a first conversion circuit connected between the secondary side coil of the transformer 202 and the 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 the primary side coil of the transformer 202 and a plurality of conversion cells 211, It is connected to a common DC path at 212 and 213.

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 on the primary side. It is driven by the 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 on the secondary side. It is driven by the drive circuit 204b.

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 Units).

The isolated DC / DC converter 200 has a DAB (Dual) 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. Active Bridge) A power conversion circuit called a converter. 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 with the transformer 102. The transmitted power is the output voltage V1 output from the two intermediate connection points of the inverter circuit on the _primary side (full bridge circuit 220a on the primary side) and the inverter circuit on the secondary side (full bridge circuit on the secondary side). It is controlled by the phase difference with the output voltage V2 output from the _two intermediate connection points of 220b). The transmission power from the secondary side to the primary side is expressed by the following simplified equation 1.

Ｐは伝送電力、Ｖ_１は１次側出力電圧の振幅、Ｖ_２は２次側出力電圧の振幅、Ｌは漏れインダクタンスあるいは外付けリアクトルのインダクタンス、φはＶ_１とＶ_２との位相差、πは円周率、ω（＝２πｆ）は各スイッチ素子のスイッチングの角周波数を表す。ｆは、各スイッチ素子のスイッチング周波数を表す。なお、上記の式１は、各スイッチ素子のスイッチングのデューティ比が５０％のとき（Ｖ_１，Ｖ_２がデューティ比５０％の方形波（略方形波を含む）のとき）の式である。

P is the transmission power, V ₁ is the amplitude of the primary output voltage, V ₂ is the amplitude of the secondary output voltage, L is the leakage inductance or the inductance of the external reactor, φ is the phase difference between V ₁ and V ₂ . π represents the circumferential ratio, and ω (= 2πf) represents the angular frequency of switching of each switch element. f represents the switching frequency of each switch element. The above equation 1 is an equation when the switching duty ratio of each switch element is 50% (when V ₁ and V ₂ are square waves having a duty ratio of 50% (including substantially square waves)).

Since the circuit configuration of the DAB converter has a symmetrical structure, the reference phase of the phase difference of the output voltage may be the secondary side on the high voltage side or the primary side on the low voltage side.

The secondary circuit 210b on the high voltage side of the plurality of conversion cells 211, 212, 213 has a carrier signal generation unit 207, a control signal generation unit 208, and a drive circuit 204b, respectively. Further, the power conversion device 1 is provided for each of the plurality of conversion cells 211,212, 213, and a plurality of insulating elements for transmitting a synchronization signal to the corresponding conversion cells among the plurality of conversion cells 211,212, 213. It is equipped with 205. As a result, synchronization signals that are electrically isolated 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.

The synchronization signal is a signal for controlling the phase difference of two or more periodically fluctuating signals (voltages) to a constant value (either zero or a non-zero value). Synchronization refers to linking in time, and is not limited to controlling the phase difference of two or more periodically fluctuating signals (voltages) to zero.

The control device 206 sends 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, and 213. It is supplied via a plurality of corresponding insulating elements 205. On the other hand, the control device 206 supplies a plurality of control signals defining 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. .. As a result, when the duty ratio of the waveforms of the _output voltages V1 and V2 is _a constant value such as 50%, _each conversion cell _211,212,213 has the frequency (period) of the output voltages V1 and V2 and the period. Since the repetition start timing of the waveforms of the _output voltages _V1 and V2 is determined, the output voltage can be generated as intended.

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

The control device 206 has, for example, a memory and a processor (for example, a CPU (Central Processing Unit)), and the function of the control device 206 is realized by operating the processor by a program stored in the memory. The control device 206 may be configured by an FPGA (Field Programmable Gate Array).

Each insulating element 205 may be composed of one insulating element or may be composed of a plurality of vertically connected insulating elements. Specific examples of the insulating element 205 include an isolation transformer, a pulse transformer, a digital isolator, an isolation amplifier, and the like. The insulating element 205 may be an optical isolator such as a photocoupler.

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 serrated periodic signal having the same period in which the phase is synchronized with the synchronous signal.

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 wavy signals whose phase is 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, and 201h.

The drive circuit 204b drives and switches a plurality of secondary 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 the plurality of primary 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, and 201d.

FIG. 2 is a timing chart showing an example of the operation waveform of the power conversion device according to the first embodiment. The control device 206 outputs a synchronization signal to each carrier signal generation unit 207 of the conversion cells 211, 212, 213 via the insulating element 205 corresponding to each of the conversion cells 211, 212, 213. The control device 206 outputs a synchronization signal including a first pulse having a pulse width equal to or larger than a predetermined first predetermined value at a fixed cycle by pulse width modulation.

On the high voltage side, the carrier signal generation unit 207 detects a first pulse having a pulse width equal to or larger than a predetermined first specified value at least once from the supplied synchronization signal, and causes the control signal generation unit 208 to detect the first pulse. Generates a serrated carrier signal to supply. As a countermeasure against erroneous detection 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. The carrier signal generation unit 207 initializes the carrier signal each time the first pulse is detected, and then monotonically increases or decreases the carrier signal with the passage of time to generate a serrated carrier signal. FIG. 2 illustrates a case where the carrier signal is monotonically increased with the passage of time.

In order to determine that the pulse width is equal to or larger than the first specified value, the carrier signal generation unit 207 detects the start of the pulse of the synchronization signal (the rising edge of the pulse in FIG. 2), and uses a counter or the like to detect the first specified value. It suffices to confirm that there is a pulse of the synchronization signal until the time corresponding to (for example, maintaining a high level). Therefore, if it is confirmed that the carrier signal generation unit 207 has a pulse of the synchronization signal until the time corresponding to the first specified value, the carrier signal generation unit 207 sets the carrier signal to zero at a time before the fall point of the pulse of the synchronization signal. It may be initialized.

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

For example, the control signal generation unit 208 generates a pulse width modulated signal by comparing the carrier signal with the threshold value of the duty value of 50% (median 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 the amplitude of the carrier signal is higher than the threshold value of the duty value of 50%. In this case, the level of the pulse width modulated signal is set to low level. The control signal generation unit 208 generates a non-inverting 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.

The drive circuit 204b generates a plurality of gate signals for driving the switch elements 201e, 201f, 201g, 201h included in the secondary side full bridge circuit 220b according to the plurality of control signals generated by the control signal generation unit 208. 1 This is an example of a drive circuit. 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, the output voltage V2 of the square wave having a duty ratio of 50% is applied to the _secondary side of the transformer 202.

On the low voltage side, on the other hand, 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 the time of the phase shift amount φ with respect to the synchronization signal. Outputs multiple control signals that are delayed or advanced. 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. Further, 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. ..

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 the respective drive circuits 204a of the plurality of conversion cells 211, 212, 213.

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

Therefore, since the output voltages V ₁ and V ₂ of the square wave having a phase difference are applied to the primary side and the secondary side of the transformer 202, the integrated value of the difference between the output voltage V ₁ and the output voltage V ₂ is used. A proportional transformer current flows, and the power P according to Equation 1 is transmitted between the primary side and the secondary side.

As described above, in the first embodiment, the phase of the output voltage V ₂ 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 synchronizing with each of the DAB converters is each DAB. It is transmitted to the high voltage side of the 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 side full bridge circuit 220b that generates the output voltage V2 are based on the synchronization signal received via the insulating element 205. Generated. On the other hand, the reference potential (ground) of the primary side circuit 210a on the low voltage side and the control device 206 is common. Therefore, even without the insulating element 205, a plurality of 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 insulating elements 205 provided for each conversion cell can be reduced.

The generation of the control signal on the common potential side (primary side in this example) of the isolated DC / DC converter 200 in the first embodiment is not limited to the above method. It is sufficient that the phase difference is correctly given to the output voltages on the primary side and the secondary side. For example, the processing of carrier signal generation and control signal generation on the common potential side is not limited to the case where it is performed in the control device 206, and the carrier signal generation unit and the control signal generation are provided in the same manner as on the high voltage side. It may be done in the department. Further, the carrier signal may be generated for each half-bridge circuit.

Further, the reference phase of the phase difference of the output voltage has been described as the secondary side, but the present invention is not limited to this. Since it is sufficient that the phase difference is correctly given to the output voltages on the primary side and the secondary side, there is no operational problem even if the reference phase is set to the primary side. Further, the control signal generation unit 208 and the control device 206 may have a dead time generation unit that assigns 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.

FIG. 3 is a timing chart showing an example of an operation waveform when the carrier signal generation unit 207 generates a triangular wave-shaped carrier signal. In this modification, the description of the same operation as the above-mentioned operation example will be omitted by referring to the above-mentioned explanation. Even when the carrier signal generation unit 207 generates a triangular wave-shaped carrier signal, a plurality of control signals are generated as compared with the median value of the carrier signal, as in FIG. Similar to FIG. 2, the two half-bridge circuits on the high voltage side output a square wave voltage.

For example, when the carrier signal generation unit 207 detects the first pulse, it generates a carrier signal that repeats monotonically increasing and monotonically decreasing with the passage of time. FIG. 2 shows that each time the carrier signal generation unit 207 detects the first pulse, the carrier signal is switched from monotonically decreasing to monotonically increasing, and a specified time has elapsed from the detection of the first pulse and before the next first pulse is detected. , The case where the carrier signal is switched from monotonous increase to monotonous decrease is illustrated.

FIG. 4 is an example of an operation waveform when a plurality of control signals are generated by detecting peaks (for example, maximum value) and valleys (for example, minimum value) of a triangular wave-shaped carrier signal generated by a carrier signal generation unit. It is a timing chart showing. In this modification, the description of the same operation as the above-mentioned operation example will be omitted by referring to the above-mentioned explanation. In FIG. 4, the control signal generation unit 208 detects a peak (for example, maximum value) or valley (for example, minimum value) of a carrier signal, and at the detection timing, the level of a plurality of control signals is changed from one level to the other. Switch to level. Similar to FIG. 2, the two half-bridge circuits on the high voltage side output a square wave voltage.

FIG. 5 is a timing chart showing an example of an operation waveform when the carrier signal generation unit generates a serrated carrier signal faster than the period of the synchronization signal. In this modification, the description of the same operation as the above-mentioned operation example will be omitted by referring to the above-mentioned explanation. In FIG. 5, the control signal generation unit 208 detects the peak (for example, maximum value) or valley (for example, minimum value) of the carrier signal in the first cycle of the carrier signal, and the levels of the plurality of control signals at the detection timing. From one level to the other. Then, the control signal generation unit 208 detects a peak (for example, maximum value) or valley (for example, minimum value) of the carrier signal in the second cycle of the carrier signal, and sets the levels of the plurality of control signals to the other at the detection timing. Switch from one level to one level. Similar to FIG. 2, the two half-bridge circuits on the high voltage side output a square wave voltage.

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 configurations as those of the above-described embodiment are designated by the same reference numerals, and the description of the same configurations and operations as those of the above-described embodiments will be omitted by referring to the above-mentioned explanations. 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 the common synchronization signal to the plurality of insulating elements 205. Since the reference phase of the phase difference of the output voltage is set to the secondary side, the synchronization signal may be a signal shared by a plurality of conversion cells 211, 212, 213. Since 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, the plurality of conversion cells 211,212,213 are connected in series on the high voltage side. , Sync signal can be shared.

FIG. 7 is a diagram showing a configuration example of the power conversion device according to the third embodiment. In the third embodiment, the same configurations as those of the above-described embodiment are designated by the same reference numerals, and the description of the same configurations and operations as those of the above-described embodiments will be omitted by referring to the above-mentioned explanations. In the power conversion device 3 shown in FIG. 7, the control device 206 supplies a synchronization signal common to the plurality of conversion cells 211, 212, 213 to the plurality of insulating elements 205 connected in cascade. Since the reference phase of the phase difference of the output voltage is set to the secondary side, the synchronization signal may be a signal shared by a plurality of conversion cells 211, 212, 213. The synchronization signal common to the plurality of conversion cells 211,212,213 is transmitted from the conversion cell 213 having a low potential among the plurality of conversion cells 211,212,213 to the conversion cell 211 having a high potential.

FIG. 8 is a diagram showing a configuration example of the 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 configurations as those of the above-described embodiment are designated by the same reference numerals, and the description of the same configurations and operations as those of the above-described embodiments will be omitted by referring to the above-mentioned explanations. In the power conversion device 4 shown in FIG. 9, each of the plurality of conversion cells 211, 212, and 213 has a signal cutoff determination unit 209 for determining the stoppage of the secondary side full bridge circuit 220b based on the synchronization signal. In this example, the signal cutoff determination unit 209 of each of the plurality of conversion cells 211, 212, and 213 determines the stop and start of its own conversion cell according to the magnitude of the pulse width included in the synchronization signal.

In FIG. 9, it is assumed that the synchronization signal includes a first pulse having a pulse width equal to or more than the first specified value and a second pulse having a pulse width longer than the first specified value and having a pulse width equal to or more than the second 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 level of the plurality of control signals output by the control signal generation unit 208 to an inactive level (FIG. 9). Then set to low level). For example, the signal cutoff determination unit 209 sets the output permission signal input to the control signal generation unit 208 to an inactive level so that a plurality of control signals output by the control signal generation unit 208 become inactive levels (FIG. 9). Then set to low level). As a result, the control device 206 can quickly stop the secondary side full bridge circuit 220b.

The signal cutoff determination unit 209 switches the output permission signal to the inactive level when the passage of time corresponding to the second specified value is detected by the counter or the like after the pulse generation is detected, and all the signals are cut off. The gate signal may be turned off.

In FIG. 9, the synchronization signal has a first pulse having a pulse width equal to or more than the first specified value, a second pulse having a pulse width longer than the first specified value and having a pulse width equal to or more than the second specified value, and the first specified value. Also includes a third pulse having a pulse width equal to or greater than the third specified value, which is longer 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 208 enables the control signal generation unit 208 to generate a plurality of control signals. For example, the signal cutoff determination unit 209 sets an output permission signal to be input to the control signal generation unit 208 at 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 becomes effective. To. As a result, the signal cutoff determination unit 209 promptly permits the operation of the secondary side full bridge circuit 220b, and the control device 206 can promptly start the secondary side full bridge circuit 220b.

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 as a countermeasure against erroneous detection of the second pulse and the third pulse. Further, the signal cutoff determination unit 209 detects a pulse having a pulse width equal to or larger than the first specified value a plurality of times, and determines start and stop in the same manner as described above based on the pulse width of the pulse detected a plurality of times. You may.

On the high voltage side, an overvoltage protection circuit that protects the capacitive element 203b from overvoltage may be provided, or an overcurrent protection circuit that protects 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.

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

In the embodiments of FIGS. 1, 6 and 7, the conversion cell is stopped by the control device 206 stopping the supply of the synchronization signal because the carrier signal is generated from the pulse of the synchronization signal supplied from the control device 206. It may take some time to determine. When changing the frequency of the carrier signal, the pulse interval of the synchronization signal is changed, but it is difficult to judge whether the carrier frequency is changed or the conversion cell is stopped. On the other hand, in the embodiment of FIG. 8, the start and stop can be executed immediately by determining the start and stop based on the width of the pulse width of the synchronization signal. Further, as shown in FIGS. 6 and 7, if the synchronization signal is shared by a plurality of conversion cells, the conversion cell sharing the synchronization signal can be stopped immediately.

FIG. 10 is a timing chart showing a second operation example of the power conversion device according to the fourth embodiment. The signal cutoff determination unit 209 may determine the stop and start of the conversion cell based on the number of pulses of the synchronization signal during a predetermined fixed period. For example, the signal cutoff determination unit 209 inactivates the levels of a plurality of control signals output by the control signal generation unit 208 when the number of pulses included in the synchronization signal supplied from the control device 206 is equal to or greater than the fourth specified value. Set to level (low level in FIG. 10). FIG. 10 illustrates the case where the fourth specified value is “3”. For example, the signal cutoff determination unit 209 sets the output permission signal input to the control signal generation unit 208 to an inactive level so that a plurality of control signals output by the control signal generation unit 208 become inactive levels (FIG. 10). Then set to low level). As a result, the control device 206 can quickly stop the secondary side full bridge circuit 220b.

For example, when the number of pulses included in the synchronization signal supplied from the control device 206 is the fifth specified value or more, which is larger than the fourth specified value, the signal cutoff determination unit 209 may use the control signal generation unit 208 for a plurality of control signals. Enable generation. FIG. 10 illustrates the case where the fifth specified value is “4”. For example, the signal cutoff determination unit 209 sets an output permission signal to be input to the control signal generation unit 208 at 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 becomes effective. To. As a result, the signal cutoff determination unit 209 promptly permits the operation of the secondary side full bridge circuit 220b, and the control device 206 can promptly start the secondary side full bridge circuit 220b.

The conditions for determining start or stop based on the pulse width may be other than the above.

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, the synchronization signal is shorter than the first specified value after a certain predetermined time has elapsed from the output of the first pulse having a pulse width equal to or larger than the predetermined first specified value. 6 It is assumed that a pulse train having a specified pulse width is included. The signal cutoff determination unit 209 determines whether or not the operation of the secondary side full bridge circuit 220b is permitted or rejected according to the enumeration pattern of the pulse train.

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

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 configurations as those of the above-described embodiment are designated by the same reference numerals, and the description of the same configurations and operations as those of the above-described embodiments will be omitted by referring to the above-mentioned explanations. In the power conversion device 5 shown in FIG. 16, the secondary circuit 210b on the high voltage side of the plurality of conversion cells 211, 212, 213 has a control signal generation unit 238 and a drive circuit 204b, respectively, but a carrier signal generation unit. Does not have 207. The power conversion device 5 does not generate a carrier signal, but generates a plurality of control signals for controlling a plurality of secondary switch elements. Since the carrier signal generation unit 207 is not provided, the secondary circuit 210b can be miniaturized, and the power conversion device 5 can be miniaturized.

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 of the above-described embodiment will be 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 wavy signals whose phases are synchronized with the synchronization signal. In this example, the control signal generation unit 238 generates four control signals that control the switching of each of the plurality of secondary side switch elements 201e, 201f, 201g, and 201h.

FIG. 17 is a timing chart showing an example of the operation waveform of the power conversion device according to the fifth embodiment. The control device 206 outputs a synchronization signal to each control signal generation unit 238 of the conversion cells 211,212, 213 via the insulating element 205 corresponding to each of the conversion cells 211,212 and 213. The control device 206 outputs a synchronization signal including a first pulse having a pulse width equal to or larger than a predetermined first predetermined value at a fixed cycle by pulse width modulation.

On the high voltage side, when the control signal generation unit 238 detects a first pulse having a pulse width equal to or larger than a predetermined first specified value from the supplied synchronization signal, the control signal generation unit 238 inverts the level of each of the plurality of control signals. Let me. 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 the first level (for example, high level) to the second level (for example, low level). The level of the switch element facing the switch is switched from the second level to the first level. On the contrary, when the control signal generation unit 238 detects the first pulse, the level of the control signal of a certain switch element is switched from the second level to the first level, and the level of the switch element facing the switch is set to the first level. Switch from the level of to the second level. As a result, it is possible to generate a control signal that repeats inversion of the logic level each time the first pulse included in the synchronization signal is detected.

In order to determine that the pulse width is equal to or larger than the first specified value, the control signal generation unit 238 detects the start of the pulse of the synchronization signal (the rising edge of the pulse in FIG. 17) and uses a counter or the like to detect the first specified value. It suffices to confirm that there is a pulse of the synchronization signal until the time corresponding to (for example, maintaining a high level). Therefore, if it is confirmed that there is a pulse of the synchronization signal until the time corresponding to the first specified value, the control signal generation unit 238 sets the level of the control signal at a time before the fall point of the pulse of the synchronization signal. It may be inverted.

The drive circuit 204b generates a plurality of gate signals for driving the switch elements 201e, 201f, 201g, 201h included in the secondary side full bridge circuit 220b according to the plurality of control signals generated by the control signal generation unit 238. 1 This is an example of a drive circuit. 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, the output voltage V2 of the square wave having a duty ratio of 50% is applied to the _secondary side of the transformer 202.

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 configurations as those of the above-described embodiment are designated by the same reference numerals, and the description of the same configurations and operations as those of the above-described embodiments will be omitted by referring to the above-mentioned explanations. 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 stoppage of the secondary side full bridge circuit 220b based on the synchronization signal. In this example, the signal cutoff determination unit 239 of each of the plurality of conversion cells 211, 212, and 213 determines whether to stop and start the conversion cell itself according to the magnitude of the pulse width included in the synchronization signal.

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 will be 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.

Next, one comparative embodiment compared to the plurality of embodiments according to the present disclosure will be described. The explanation of the comparative form will be simplified by referring to the above explanation.

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

FIG. 15 shows a case where the power conversion device includes three conversion cells 111, 112, 113 connected in series on the DC output side, and a plurality of control signals and drives for each conversion cell 111, 112, 113. An example is a configuration in which the power supply for the power supply is independently supplied. Although the path for supplying the power for driving is not specified in FIG. 15, the power supply voltage is supplied to the drive circuits 104a and 104b from the power supply unit (not shown).

The power conversion device shown in FIG. 15 includes a plurality of (three in this example) conversion cells 111, 112, 113, and a control device 106 that controls the power conversion operation of each of the conversion cells 111, 112, 113. It is a multi-cell converter. Each of the plurality of conversion cells 111, 112, and 113 is a cell converter that boosts or lowers the DC voltage input from a common DC path and outputs a predetermined DC voltage. Each of the plurality of conversion cells 111, 112, and 113 has an isolated DC / DC converter 100 and a pair of terminals p and q.

The isolated DC / DC converter 100 includes a transformer 102, a primary circuit 110a, and a secondary circuit 110b. The primary side circuit 110a includes a capacitive element 103a, a primary side full bridge circuit 120a, and a drive circuit 104a. The primary circuit 110a may have a reactor 107a connected in series with the primary coil of the transformer 102. The primary side full bridge circuit 220a includes primary side switch elements 101a, 101b, 101c, 101d. The secondary side circuit 110b includes a capacitive element 103b, a secondary side full bridge circuit 120b, and a drive circuit 104b. The secondary circuit 110b may have a reactor 107b connected in series with the secondary coil of the transformer 102. The secondary side full bridge circuit 220b includes secondary side switch elements 101e, 101f, 101g, 101h.

The power conversion device shown in FIG. 15 is provided for each of the plurality of conversion cells 111, 112, 113, and a plurality of control signals are transmitted to the corresponding conversion cells among the plurality of conversion cells 111, 112, 113. The insulating component 105 of the above is provided. 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 has a plurality of insulating elements (in this example, a plurality of insulating elements). Insulating elements 105a, 105b, 105c, 105d) are included.

The drive circuit 104b drives a plurality of secondary 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. Switch. On the other hand, the drive circuit 104a drives and switches the plurality of primary switch elements 101a, 101b, 101c, 101d according to the plurality of control signals supplied from the control device 206 without the intervention of the plurality of insulating elements.

In the isolated DC / DC converter in one comparative mode 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 insulating elements are provided according to the number of control signals. Be done. In a configuration in which isolated DC / DC converters are connected in series as in the multi-cell converter shown in FIG. 15, the total number of insulating elements is at least (the number of series stages of conversion cells × per conversion cell). The number of insulating elements to be provided), which is a huge number.

On the other hand, 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 insulating elements can be reduced. .. As a result, for example, the power conversion device can be miniaturized and the cost can be reduced.

Although the power conversion device has been described above according to the embodiment, the present invention is not limited to the above embodiment. Various modifications and improvements, such as combinations and substitutions with some or all of the other embodiments, are possible within the scope of the present invention.

For example, in the first embodiment of the present invention, a plurality of conversion cells are connected in series via a pair of output-side terminals p and q that output the output voltage of an isolated DC / DC converter. It is not limited to the configuration. For example, an inverter is added between the pair of terminals on the output side of the isolated DC / DC converter and the output side of the conversion cell, and the two intermediate connection points of the inverter are connected to each of the pair of terminals on the output side. The configuration may be the same. 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.

Further, the present invention may have a configuration in which a plurality of conversion cells are connected in series via a pair of terminals connected to the input side of the isolated DC / DC converter. For example, add an inverter between the input side of an isolated DC / DC converter and the pair of terminals on the input side of the conversion cell, and connect the two intermediate connection points of the inverter to those pair of terminals on the input side, respectively. The configuration may be the same. 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.

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

1, 2, 3, 4, 5, 6 Power converter 100 Insulated DC / DC converter 101 Switch element 102 Transformer 103a, 103b Capacitive element 104a, 104b Drive circuit 105 Insulated component 106 Control device 107 Reactor 109a DC power supply 200 Insulated type DC / DC converter 201a, 201b, 201c, 201d Switch element 201e, 201f, 201g, 201h Switch element 202 Transformer 203a, 203b Capacitive element 204a, 204b Drive circuit 205 Insulation element 206 Control device 207 Carrier signal generator 208, 238 Control signal Generation unit 209,239 Signal cutoff 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 (22)

It has 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 is connected in series via the pair of terminals. With multiple conversion cells
A plurality of insulating elements provided for each of the plurality of conversion cells and transmitting a synchronization signal to the corresponding conversion cells among the plurality of conversion cells are provided.
The plurality of conversion cells are each
With 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,
A power conversion device comprising a first drive circuit for driving a plurality of switch elements included in the first conversion circuit according to the plurality of control signals. A control device for supplying the synchronization signal to the plurality of isolated circuits is provided.
The plurality of conversion cells are each
A second conversion circuit connected to the first conversion circuit via the transformer, and a second conversion circuit.
The power conversion device according to claim 1, further comprising a second drive circuit for driving at least one switch element included in the second conversion circuit according to at least one control signal supplied from the control device. The power conversion device according to claim 2, wherein at least one control signal supplied from the control device synchronizes with the synchronization signal. 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 power conversion device according to claim 2 or 3, wherein the plurality of switch elements driven by the second drive circuit are switch elements included in at least one half bridge circuit included in the second conversion circuit. The power conversion device according to claim 4, wherein the phase of the plurality of control signals supplied from the control device is different from the phase of the plurality of control signals generated by the control signal generation unit. The synchronization signal includes a first pulse having a pulse width equal to or larger than the first specified value.
The power conversion device according to any one of claims 1 to 5, wherein the control signal generation unit inverts the level of each of the plurality of control signals when the first pulse is detected. Each of the plurality of conversion cells has a carrier signal generation unit that generates a carrier signal synchronized with the synchronization signal.
The power conversion device according to any one of claims 1 to 5, wherein the control signal generation unit generates a plurality of the control signals synchronized with the carrier signal. The synchronization signal includes a first pulse having a pulse width equal to or larger than the first specified value.
The power conversion device according to claim 7, wherein the carrier signal generation unit detects the first pulse at least once and generates the carrier signal having a sawtooth shape or a triangular wave shape. The synchronization signal includes a first pulse having a pulse width equal to or larger than the first specified value.
The power conversion device according to claim 7, wherein the carrier signal generation unit monotonically increases or decreases the carrier signal with the passage of time after initializing the carrier signal when the first pulse is detected. The synchronization signal includes a first pulse having a pulse width equal to or larger than the first specified value.
The power conversion device according to claim 7, wherein the carrier signal generation unit generates the carrier signal that repeats monotonically increasing and monotonically decreasing with the passage of time when the first pulse is detected. One of claims 7 to 10, wherein the control signal generation unit generates a plurality of the control signals by detecting an inversion of the magnitude relationship between the amplitude of the carrier signal and the median of the amplitude of the carrier signal. The power conversion device according to paragraph 1. The power conversion device according to any one of claims 7 to 10, wherein the control signal generation unit generates a plurality of the control signals by detecting peaks or valleys of the carrier signal. 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 power conversion device according to any one of claims 1 to 12, wherein the control signal generation unit assigns a dead time for preventing a short circuit of the half bridge circuit to the plurality of control signals. The plurality of conversion cells are each
The power conversion device according to any one of claims 1 to 13, further comprising a determination unit for determining the stop of the first conversion circuit based on the synchronization signal. 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 in a certain time period. The synchronization signal includes a first pulse having a pulse width equal to or larger than the first specified value, and a second pulse having a pulse width longer than the first specified value and having a pulse width equal to or larger 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. The synchronization signal includes a first pulse having a pulse width equal to or more than the first specified value, a second pulse having a pulse width longer than the first specified value and having a pulse width equal to or more than the second specified value, and a second pulse having a pulse width larger than the first specified value. Includes a third pulse that is longer and has a pulse width greater than or equal to the third specified value, which is shorter than the second specified value.
The power according to claim 14 or 15, wherein when the determination unit detects the second pulse, the first conversion circuit is stopped, and when the third pulse is detected, the operation of the first conversion circuit is permitted. Converter. 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 the fourth specified value or more. 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 greater than or equal to the fifth predetermined value larger than the fourth specified value. The synchronization signal includes a first pulse having a pulse width equal to or larger than the first specified value, and a pulse train 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 or not the operation of the first conversion circuit is permitted according to the sequence pattern of the pulse train. The power conversion device according to any one of claims 1 to 20, wherein the synchronization signal is a signal common to the plurality of conversion cells. The power conversion device according to claim 21, wherein the synchronization signal is transmitted from a conversion cell having a low potential to a conversion cell having a high potential among the plurality of conversion cells.

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