Power conversion device

Abstract

The present invention provides a power conversion device that reduces the number of insulating elements provided for each conversion unit. The power conversion device includes: a plurality of conversion units, each having an insulating DC / DC converter and a pair of terminals connected to either the input or output side of the insulating DC / DC converter, wherein the plurality of conversion units are connected in series via the pair of terminals; and a plurality of insulating elements provided relative to each of the plurality of conversion units for transmitting synchronization signals to corresponding ones of the plurality of conversion units. The plurality of conversion units each include: a transformer; a first conversion circuit connected between the transformer and the pair of terminals; a control signal generating unit for generating a plurality of control signals synchronized with the synchronization signal; and a first drive circuit for driving a plurality of switching elements included in the first conversion circuit based on the control signals.

Description

Technical Field

[0001] The present invention relates to a power conversion device. Background Art

[0002] Conventionally, a multi-unit converter device is known, comprising: a plurality of conversion units connected in series via a pair of input terminals; and a plurality of insulating components, disposed relative to each of the plurality of conversion units, for transmitting a plurality of control signals to a corresponding one of the plurality of conversion units. Each of the plurality of conversion units includes a drive circuit that controls a DC / DC converter based on the plurality of control signals received via one or more insulating components. By transmitting the control signals to the conversion units via the insulating components, the control signals can be transmitted to the respective drive circuits, each operating at a different reference potential for each conversion unit, which is electrically isolated from each other (see, for example, Patent Document 1).

[0003] <Prior Art Literature>

[0004] <Patent Document>

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-64436 Summary of the Invention

[0006] <Problems to be Solved by the Invention>

[0007] When transmitting multiple control signals through a single insulating component, a single insulating element, such as a digital isolator, is allocated to each control signal, resulting in multiple insulating elements within the same insulating component. Therefore, in conventional technology, as the number of control signals transmitted by each conversion unit increases, the number of insulating elements required for each conversion unit also increases. Consequently, in a power conversion device with multiple conversion units connected in series via a pair of terminals, the total number of insulating elements is at least (the number of series-connected conversion units x the number of control signals transmitted by each conversion unit), a significant number. This large number of insulating elements makes it difficult to achieve miniaturization or reduce costs.

[0008] The present invention provides a power conversion device capable of reducing the number of insulating elements provided relative to each conversion unit.

[0009] <Methods used to solve the problem>

[0010] In one embodiment of the present invention, there is provided a power conversion device comprising:

[0011] a plurality of conversion units, each having an insulating DC / DC converter and a pair of terminals connected to either an input side or an output side of the insulating DC / DC converter, wherein the plurality of conversion units are connected in series via the pair of terminals; and

[0012] a plurality of insulating elements, which are arranged relative to each of the plurality of conversion units and are used to transmit synchronization signals to corresponding conversion units in the plurality of conversion units;

[0013] The above-mentioned multiple conversion units respectively have:

[0014] transformer;

[0015] a first conversion circuit connected between the transformer and the pair of terminals;

[0016] a control signal generating unit configured to generate a plurality of control signals synchronized with the synchronization signal; and

[0017] The first driving circuit drives the plurality of switching elements included in the first conversion circuit based on the plurality of control signals.

[0018] <Effects of the Invention>

[0019] According to one embodiment of the present invention, the number of insulating elements provided for each conversion unit can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a diagram showing a configuration example of the power conversion device in the first embodiment.

[0021] Figure 2 This is a timing chart showing an example of an operation waveform of the power conversion device in the first embodiment.

[0022] Figure 3 This is a timing chart showing an example of an operation waveform when the carrier signal generating unit generates a triangular wave carrier signal.

[0023] Figure 4 This is a timing chart showing an example of an operation waveform when a peak (eg, maximum value) and a trough (eg, minimum value) of a triangular wave carrier signal are detected and a plurality of control signals are generated.

[0024] Figure 5 This is a timing chart showing an example of an operation waveform when a sawtooth-shaped carrier signal having a cycle shorter than that of a synchronization signal is generated.

[0025] Figure 6 It is a diagram showing a configuration example of a power conversion device in the second embodiment.

[0026] Figure 7 It is a diagram showing a configuration example of a power conversion device in a third embodiment.

[0027] Figure 8 It is a diagram showing a configuration example of a power conversion device in a fourth embodiment.

[0028] Figure 9 It is a timing chart showing a first operation example of the power conversion device in the fourth embodiment.

[0029] Figure 10 It is a timing chart showing a second operation example of the power conversion device in the fourth embodiment.

[0030] Figure 11 It is a timing chart showing a third operation example of the power conversion device in the fourth embodiment.

[0031] Figure 12 This is a diagram showing an example of a synchronization signal to which start / stop information is added.

[0032] Figure 13 This is a diagram showing a configuration example of an isolated DC / DC converter in a comparative embodiment.

[0033] Figure 14 This is a timing chart showing an operation example of an isolated DC / DC converter in a comparative embodiment.

[0034] Figure 15 This is a diagram showing a configuration example of a power conversion device in a comparative embodiment.

[0035] Figure 16 It is a diagram showing a configuration example of a power conversion device in the fifth embodiment.

[0036] Figure 17 This is a timing chart showing an example of an operation waveform of the power conversion device in the fifth embodiment.

[0037] Figure 18 It is a diagram showing a configuration example of a power conversion device in the sixth embodiment.

[0038] Figure 19 It is a timing chart showing an operation example of the power conversion device in the sixth embodiment. DETAILED DESCRIPTION

[0039] Hereinafter, various embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that "DC" and "AC" are abbreviations for "Direct Current" and "Alternative Current," respectively.

[0040] Figure 1 It is a diagram showing a configuration example of the power conversion device in the first embodiment. Figure 1The example shows that the power conversion device 1 includes three conversion units 211, 212, and 213 connected in series on the DC output side, and a synchronization signal and multiple control signals and a driving power supply are independently supplied to each conversion unit 211, 212, and 213. Figure 1 Although the path for supplying driving power is not clearly shown, the power voltage is supplied from the power supply unit (not shown) to the later-described components such as the driving circuits 204a and 204b, the control signal generating unit 208, and the carrier signal generating unit 207.

[0041] Figure 1 The illustrated power conversion device 1 is a multi-cell converter that includes a plurality (three in this example) of conversion cells 211, 212, and 213, and a control device 206 for controlling the power conversion operations of each of these conversion cells 211, 212, and 213. Each of these conversion cells 211, 212, and 213 is a unit converter that steps up or steps down a DC voltage input from a shared DC path to output a predetermined DC voltage. Each of these conversion cells 211, 212, and 213 includes an isolated DC / DC converter 200 and a pair of terminals p and q.

[0042] exist Figure 1 In the example shown, a 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 a high-potential terminal, and the second terminal q is a low-potential terminal.

[0043] Multiple conversion cells 211, 212, and 213 each have a pair of terminals p and q and are connected in series via the terminals p and q. Each of the multiple conversion cells 211, 212, and 213 has its first terminal p connected to the second terminal q of an adjacent conversion cell, and its second terminal q connected to the first terminal p of another adjacent conversion cell. Among the multiple unit converters connected in series via the pair of terminals p and q, the first terminal p of the conversion cell at the highest potential (in this example, conversion cell 211) is electrically connected to the high-potential end of a load (not shown). Meanwhile, the second terminal q of the conversion cell at the lowest potential (in this example, conversion cell 213) among the multiple unit converters connected in series via the pair of terminals p and q is electrically connected to the low-potential end of a load (not shown).

[0044] Insulated DC / DC converter 200 boosts or steps down the DC voltage input from a shared DC path in multiple conversion units 211, 212, and 213, outputting a predetermined DC voltage from a pair of terminals p and q. Insulated DC / DC converter 200 includes a transformer 202, a primary-side circuit 210a, and a secondary-side circuit 210b. Primary-side circuit 210a and secondary-side circuit 210b are magnetically coupled via transformer 202.

[0045] 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.

[0046] The primary-side circuit 210a includes a capacitor 203a, a primary-side full-bridge circuit 220a, and a drive circuit 204a. The primary-side circuit 210a may further include a reactor 207a connected in series with the primary-side coil of the transformer 202.

[0047] Primary-side full-bridge circuit 220a includes a primary-side first half-bridge circuit, in which a primary-side first upper arm 201a and a primary-side first lower arm 201b are connected in series, and a primary-side second half-bridge circuit, in which a primary-side second upper arm 201c and a primary-side second lower arm 201d are connected in series. The primary-side coil of transformer 202 (or a series circuit of a primary-side coil and reactor 207a) is connected between the midpoint between primary-side first upper arm 201a and primary-side first lower arm 201b, and the midpoint between primary-side second upper arm 201c and primary-side second lower arm 201d.

[0048] The secondary circuit 210b includes a capacitor 203b, a secondary full-bridge circuit 220b, and a drive circuit 204a. The secondary circuit 210b may further include a reactor 207b connected in series with the secondary coil of the transformer 202.

[0049] Secondary-side full-bridge circuit 220b includes a secondary-side first half-bridge circuit in which a secondary-side first upper arm 201e and a secondary-side first lower arm 201f are connected in series, and a secondary-side second half-bridge circuit in which a secondary-side second upper arm 201g and a secondary-side second lower arm 201h are connected in series. The secondary-side coil of transformer 202 (or a series circuit of a secondary-side coil and reactor 207b) is connected between the midpoint between the secondary-side first upper arm 201e and the secondary-side first lower arm 201f, and the midpoint between the secondary-side second upper arm 201g and the secondary-side second lower arm 201h.

[0050] Secondary-side full-bridge circuit 220b is an example of a first conversion circuit connected between the secondary-side winding of transformer 202 and a pair of terminals p and q. Meanwhile, primary-side full-bridge circuit 220a is an example of a second conversion circuit connected to secondary-side full-bridge circuit 220b via transformer 202. It is connected between the primary-side winding of transformer 202 and a DC path shared by multiple conversion units 211, 212, and 213.

[0051] The primary-side switching elements, including 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. The secondary-side switching elements, including 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.

[0052] Specific examples of the primary-side switching element and the secondary-side switching 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).

[0053] The isolated DC / DC converter 200 is a power conversion circuit known as a DAB (Dual Active Bridge) converter, comprising a primary-side full-bridge circuit 220a provided on the primary side of transformer 202 and a secondary-side full-bridge circuit 220b provided on the secondary side of transformer 202. The DAB converter transfers power between the primary and secondary sides by applying voltage to external reactors 207a and 207b connected in series with the leakage inductance of transformer 202 or transformer 102. The transferred power is controlled by the phase difference between the output voltage V1 output from the two intermediate connection points of the primary-side inverter circuit (primary-side full-bridge circuit 220a) and the output voltage V2 output from the two intermediate connection points of the secondary-side inverter circuit (secondary-side full-bridge circuit 220b). The power transferred from the secondary side to the primary side is expressed by the simplified equation 1 below.

[0054] (Mathematical formula 1)

[0055]

[0056] P represents the transmitted power, V1 represents the amplitude of the primary-side output voltage, V2 represents the amplitude of the secondary-side output voltage, L represents the leakage inductance or the inductance of the external reactor, φ represents the phase difference between V1 and V2, π represents the circumference of the circle, and ω (= 2πf) represents the angular frequency of each switching element. f represents the switching frequency of each switching element. It should be noted that Equation 1 above assumes a 50% switching duty cycle for each switching element (when V1 and V2 are square waves (including substantially square waves) with a 50% duty cycle).

[0057] It should be noted that since the DAB converter circuit structure is symmetrical, the reference phase for the output voltage phase difference can be the secondary side (high voltage side) or the primary side (low voltage side).

[0058] The secondary-side circuit 210b on the high-voltage side of each of the multiple conversion units 211, 212, and 213 includes a carrier signal generator 207, a control signal generator 208, and a drive circuit 204b. Furthermore, the power conversion device 1 includes multiple insulating elements 205, each provided for each of the multiple conversion units 211, 212, and 213, for transmitting synchronization signals to the corresponding conversion units 211, 212, and 213. This allows for the transmission of electrically isolated synchronization signals to the internal circuits (carrier signal generator 207, control signal generator 208, and drive circuit 204b) that operate at different reference potentials for each conversion unit.

[0059] A synchronization signal is a signal used to control the phase difference between two or more periodically fluctuating signals (voltages) to a constant value (which can be zero or a value other than zero). Synchronization refers to temporal correlation and is not limited to controlling the phase difference between two or more periodically fluctuating signals (voltages) to zero.

[0060] The control device 206 supplies a synchronization signal for synchronizing the repetition start time of the output voltage V2 waveform to each of the multiple conversion units 211, 212, and 213 in the secondary-side circuit 210b on the high-voltage side, via the corresponding multiple insulating elements 205. Meanwhile, the control device 206 supplies multiple control signals that specify the repetition start time of the output voltage V1 waveform to each of the primary-side circuits 210a on the low-voltage side of the multiple conversion units 211, 212, and 213. This allows each of the conversion units 211, 212, and 213 to generate a desired output voltage, since the frequency (period) and repetition start time of the output voltages V1 and V2 waveforms are determined when the duty cycle of the output voltages V1 and V2 waveforms is a constant value, such as 50%.

[0061] The phases of the multiple synchronization signals supplied to the respective secondary-side circuits 210b on the high-voltage side of the multiple conversion units 211, 212, and 213 may be the same as or different from each other.

[0062] The control device 206 includes, for example, a memory and a processor (eg, a CPU (Central Processing Unit)). The functions of the control device 206 are realized by the processor operating according to a program stored in the memory. The control device 206 may be formed of an FPGA (Field Programmable Gate Array).

[0063] Each insulating element 205 may be composed of a single insulating element or a plurality of insulating elements connected in cascade. Specific examples of insulating elements 205 include insulating transformers, pulse transformers, digital isolators, and isolation amplifiers. Insulating elements 205 may also be optical isolators such as optocouplers.

[0064] The carrier signal generating unit 207 generates a carrier signal synchronized with the synchronization signal transmitted through the corresponding insulating element 205. The carrier signal is, for example, a sawtooth-shaped periodic signal having the same period as the synchronization signal and having a phase synchronized with the synchronization signal.

[0065] Based on the carrier signal generated by carrier signal generator 207, control signal generator 208 generates multiple control signals synchronized with the carrier signal. These multiple control signals are, for example, rectangular wave signals whose phases are synchronized with the carrier signal. In this example, control signal generator 208 generates four control signals for controlling the switching of each of secondary-side switching elements 201e, 201f, 201g, and 201h.

[0066] Drive circuit 204b drives multiple secondary-side switching elements 201e, 201f, 201g, and 201h for switching based on multiple control signals generated by control signal generator 208. Meanwhile, drive circuit 204a drives multiple primary-side switching elements 201a, 201b, 201c, and 201d for switching based on multiple control signals generated by control device 206, which generates synchronization signals. Control device 206 generates four control signals for controlling each of primary-side switching elements 201a, 201b, 201c, and 201d.

[0067] Figure 2This is a timing chart showing an example of an operating waveform of the power conversion device in the first embodiment. Control device 206 outputs a synchronization signal to carrier signal generator 207 of each conversion unit 211, 212, and 213 via insulation element 205 corresponding to each conversion unit 211, 212, and 213. Control device 206 uses pulse width modulation to output a synchronization signal that includes first pulses having a predetermined pulse width greater than a first predetermined value at a predetermined period.

[0068] On the high-voltage side, the carrier signal generator 207 detects a first pulse with a predetermined pulse width greater than or equal to a first predetermined value at least once based on the supplied synchronization signal, and generates a sawtooth-shaped carrier signal to be supplied to the control signal generator 208. As a countermeasure to false detection of the first pulse, the carrier signal generator 207 may detect the synchronization signal multiple times at intervals shorter than the first predetermined pulse width. The carrier signal generator 207 initializes the carrier signal each time it detects the first pulse, and then monotonically increases or decreases the carrier signal over time, thereby generating a sawtooth-shaped carrier signal. Figure 2 An example is shown in which the carrier signal is monotonically increased over time.

[0069] It should be noted that, in order to determine whether the pulse width is greater than the first predetermined value, the carrier signal generating unit 207 starts the pulse of the synchronization signal (at Figure 2 The carrier signal generator 207 can detect the rising edge of the synchronization signal pulse and confirm, using a counter or the like, that the synchronization signal pulse exists (for example, is maintained at a high level) for a time period corresponding to the first predetermined value. Therefore, if the synchronization signal pulse exists for a time period corresponding to the first predetermined value, the carrier signal generator 207 can initialize the carrier signal to zero at a time prior to the falling edge of the synchronization signal pulse.

[0070] The control signal generating unit 208 generates a plurality of control signals for switching control of the plurality of secondary-side switching elements 201e, 201f, 201g, and 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.

[0071] For example, the control signal generator 208 generates a pulse-width modulated signal by comparing the carrier signal with a 50% duty cycle threshold (the median value of the carrier signal's amplitude). If the carrier signal's amplitude is lower than the 50% duty cycle threshold, the control signal generator 208 sets the pulse-width modulated signal's level to high. If the carrier signal's amplitude is higher than the 50% duty cycle threshold, the control signal generator 208 sets the pulse-width modulated signal's level to low. The control signal generator 208 generates the non-inverted pulse-width modulated signal as the control signal for switching element 201e and the control signal for switching element 201h. Conversely, the control signal generator 208 generates the inverted pulse-width modulated signal as the control signal for switching element 201f and the control signal for switching element 201g.

[0072] Drive circuit 204b is an example of a first drive circuit that generates multiple gate signals for driving switching elements 201e, 201f, 201g, and 201h included in secondary-side full-bridge circuit 220b in accordance with multiple control signals generated by control signal generator 208. In this example, the multiple gate signals have approximately the same phase as their corresponding control signals. Drive circuit 204b supplies the corresponding gate signals to the gates of each switching element 201e, 201f, 201g, and 201h. This results in a 50% duty cycle square wave output voltage V2 being applied to the secondary side of transformer 202.

[0073] On the low-voltage side, the control device 206 determines, based on Equation 1, the phase offset φ of the synchronization signal supplied to the high-voltage side, and outputs multiple control signals that are delayed or advanced by the phase offset φ relative to the synchronization signal. In other words, the multiple 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. Furthermore, the phase of each of the multiple control signals supplied from the control device 206 to the low-voltage side differs from the phase of the corresponding control signal among the multiple control signals generated by the control signal generator 208 on the high-voltage side. For example, the phase of the control signal (or gate signal) for the low-voltage switching element 201a differs from the phase of the control signal (or gate signal) for the high-voltage switching element 201e corresponding to the switching element 201a.

[0074] The control device 206 generates a plurality of control signals for controlling the switching of the switching elements 201 a , 201 b , 201 c , and 201 d . The control device 206 generates a plurality of control signals to be supplied to the drive circuits 204 a of the respective conversion units 211 , 212 , and 213 .

[0075] Drive circuit 204a is an example of a second drive circuit that generates multiple gate signals for driving switching elements 201a, 201b, 201c, and 201d included in primary-side full-bridge circuit 220a based on multiple control signals generated by control device 206. In this example, the multiple gate signals have approximately the same phase as their corresponding control signals. Drive circuit 204a supplies the corresponding gate signals to the gates of switching elements 201a, 201b, 201c, and 201d. This generates a square wave output voltage V1 with a 50% duty cycle applied to the primary side of transformer 202.

[0076] Therefore, since square wave output voltages V1 and V2 with a phase difference are applied to the primary and secondary sides of transformer 202, a transformer current proportional to the integrated value of the difference between output voltages V1 and V2 flows, thereby transmitting power P according to equation 1 between the primary and secondary sides.

[0077] In this way, in the first embodiment, the phase of the high-voltage-side output voltage V2 of the DAB converter is set as the reference for the phase difference between the DAB converters. Only the synchronization signal used to synchronize the DAB converters is transmitted to the high-voltage side of each DAB converter via the isolation element 205. Furthermore, in the high-voltage-side secondary circuit 210b, the multiple control signals used to control the secondary-side full-bridge circuit 220b that generates the output voltage V2 are generated based on the synchronization signal received via the isolation element 205. Meanwhile, the low-voltage-side primary circuit 210a and the control device 206 share a common reference potential (ground). Therefore, even without the isolation element 205, the multiple control signals used to control the primary-side full-bridge circuit 220a that generates the output voltage V1 are generated based on the synchronization signal and the phase offset φ. This reduces the number of isolation elements 205 required per conversion unit.

[0078] It should be noted that the generation of control signals 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 method described above. Any method is sufficient as long as the phase difference between the primary and secondary output voltages can be accurately applied. For example, the generation of the carrier signal and the control signal on the common potential side are not limited to being performed within the control device 206; they can also be performed in the same carrier signal generation unit and control signal generation unit as those on the high voltage side. Furthermore, the carrier signal can be generated for each half-bridge circuit.

[0079] Furthermore, while the reference phase for the output voltage phase difference is set to the secondary side in this description, this is not limiting. As long as the phase difference between the primary and secondary output voltages can be accurately assigned, there are no operational issues even if the reference phase is set to the primary side. Furthermore, the control signal generator 208 and the control device 206 may include a dead time generator for assigning a dead time (dead time) to the multiple control signals to prevent short circuits between the upper and lower arms of the half-bridge circuit.

[0080] Figure 3 This is a timing chart showing an example of an operation waveform when the carrier signal generating unit 207 generates a triangular wave carrier signal. In this modification, the description of the same operation as the above operation example is omitted by citing the above description. When the carrier signal generating unit 207 generates a triangular wave carrier signal, the same operation waveform is also used. Figure 2 Similarly, multiple control signals are generated by comparing with the center value of the carrier signal. Figure 2 Similarly, the two half-bridge circuits on the high-voltage side output square-wave voltage.

[0081] For example, when the carrier signal generating unit 207 detects the first pulse, it generates a carrier signal that repeats monotonically increasing and monotonically decreasing with the passage of time. Figure 2 An example is given in which the carrier signal generating unit 207 switches the carrier signal from monotonically decreasing to monotonically increasing each time the first pulse is detected, and switches the carrier signal from monotonically increasing to monotonically decreasing before the next first pulse is detected after a specified time has passed since the detection of the first pulse.

[0082] Figure 4 This is a time chart showing an example of an operation waveform in which a plurality of control signals are generated by detecting the peaks (e.g., maximum values) and troughs (e.g., minimum values) of a triangular wave carrier signal generated by a carrier signal generating unit. In this modification, the description of the same operations as those in the above operation example is omitted by citing the above description. Figure 4 In the embodiment, the control signal generating unit 208 detects the peak (eg, maximum value) or trough (eg, minimum value) of the carrier signal and switches the levels of the plurality of control signals from one level to another at the detection moment. Figure 2 Similarly, the two half-bridge circuits on the high-voltage side output square-wave voltage.

[0083] Figure 5 This is a timing chart showing an example of an operation waveform in which the carrier signal generating unit generates a sawtooth carrier signal having a shorter period than the synchronization signal. In this modification, the description of the same operation as the above operation example is omitted by citing the above description. Figure 5In the embodiment, the control signal generating unit 208 detects a peak (e.g., maximum value) or a trough (e.g., minimum value) of the carrier signal in the first cycle, and switches the levels of the plurality of control signals from one level to another at the detection time. Furthermore, the control signal generating unit 208 detects a peak (e.g., maximum value) or a trough (e.g., minimum value) of the carrier signal in the second cycle, and switches the levels of the plurality of control signals from another level to one level at the detection time. Figure 2 Similarly, the two half-bridge circuits on the high-voltage side output square-wave voltage.

[0084] Figure 6 This is a diagram showing an example of the configuration of a power conversion device in the second embodiment. In the second embodiment, the same reference numerals are given to the same configurations as those in the above embodiment, and the description of the same configurations and operations as those in the above embodiment is omitted by citing the above description. Figure 6 In the illustrated power conversion device 2, the control device 206 distributes a common synchronization signal among the multiple conversion units 211, 212, and 213 and supplies it to the multiple insulating elements 205. Since the reference phase for the output voltage phase difference is set on the secondary side, the synchronization signal can be a common signal among the multiple conversion units 211, 212, and 213. Since the multiple conversion units 211, 212, and 213 are independently controlled and the phase offset φ is added to the common potential side, the synchronization signal can be shared on the high-voltage side of the multiple conversion units 211, 212, and 213 connected in series.

[0085] Figure 7 This is a diagram showing an example of the configuration of a power conversion device in a third embodiment. In the third embodiment, the same reference numerals are given to the same configurations as those in the above embodiment, and the description of the same configurations and operations as those in the above embodiment is omitted by citing the above description. Figure 7 In the illustrated power conversion device 3, the control device 206 supplies a synchronization signal common to multiple conversion units 211, 212, and 213 to multiple cascade-connected insulation elements 205. Since the reference phase for the output voltage phase difference is set on the secondary side, the synchronization signal only needs to be a signal common to the multiple conversion units 211, 212, and 213. The synchronization signal common to the multiple conversion units 211, 212, and 213 is transmitted from the conversion unit 213, which has a lower potential, to the conversion unit 211, which has a higher potential.

[0086] Figure 8 It is a diagram showing a configuration example of a power conversion device in a fourth embodiment. Figure 9This is a timing chart showing a first example of operation of the power conversion device in the fourth embodiment. In the fourth embodiment, the same reference numerals are given to the same configurations as those in the above embodiment, and the description of the same configurations and operations as those in the above embodiment is omitted by citing the above description. Figure 9 In the illustrated power conversion device 4, each of the multiple conversion units 211, 212, and 213 includes a signal blocking determination unit 209 that determines whether to stop the secondary-side full-bridge circuit 220b based on the synchronization signal. In this example, the signal blocking determination unit 209 of each of the multiple conversion units 211, 212, and 213 determines whether to stop or start the corresponding conversion unit based on the pulse width included in the synchronization signal.

[0087] exist Figure 9 In the embodiment, the synchronization signal is set to include a first pulse having a pulse width greater than a first predetermined value and a second pulse having a pulse width greater than a second predetermined value longer than the first predetermined value. For example, when the signal blocking determination unit 209 detects the second pulse included in the synchronization signal supplied from the control device 206, it sets the levels of the plurality of control signals output by the control signal generation unit 208 to an inactive level (in the case of a 100% lag). Figure 9 The signal blocking determination unit 209 sets the output permission signal input to the control signal generating unit 208 to a non-active level (in the case of a low level) so that the plurality of control signals outputted from the control signal generating unit 208 become non-active levels. Figure 9 Thus, the control device 206 can quickly stop the secondary-side full-bridge circuit 220b.

[0088] It should be noted that the signal blocking determination unit 209 may detect the time when a time corresponding to the second predetermined value has passed after detecting the generation of the pulse by a counter or the like, switch the output permission signal to an inactive level, and set all gate signals to off.

[0089] exist Figure 9 In the embodiment, the synchronization signal is set to include a first pulse having a pulse width greater than a first prescribed value, a second pulse having a pulse width greater than a second prescribed value longer than the first prescribed value, and a third pulse having a pulse width greater than a third prescribed value longer than the first prescribed value and shorter than the second prescribed value. For example, if the signal blocking determination unit 209 detects the third pulse included in the synchronization signal supplied from the control device 206, the generation of multiple control signals based on the control signal generation unit 208 is set to be valid. For example, the signal blocking determination unit 209 sets the output permission signal input to the control signal generation unit 208 to a valid level (at a level greater than 0.05) in such a manner that the generation of multiple control signals based on the control signal generation unit 208 becomes valid. Figure 9Thus, the signal blocking determination unit 209 quickly permits the operation of the secondary-side full-bridge circuit 220b, and the control device 206 can quickly start the secondary-side full-bridge circuit 220b.

[0090] It should be noted that, as a countermeasure against erroneous detection of the second and third pulses, the signal blocking determination unit 209 may detect the synchronization signal multiple times within intervals shorter than the pulse width of the first predetermined value. Furthermore, the signal blocking determination unit 209 may detect pulses having a pulse width greater than the first predetermined value multiple times and make start and stop determinations based on the pulse widths of the multiple detected pulses in the same manner as described above.

[0091] On the high voltage side, an overvoltage protection circuit can be provided to protect the capacitor element 203b from overvoltage, and an overcurrent protection circuit can be provided to protect the capacitor element 203b from overcurrent. For example, if these protection circuits detect overvoltage or overcurrent in the capacitor element 203b, they can individually stop the multiple conversion units.

[0092] Furthermore, the signal blocking determination unit 209 can detect at least one synchronization signal pulse and, if there is no synchronization signal pulse within a certain period of time, stop the secondary-side full-bridge circuit 220b. For example, the control device 206 can stop all conversion units by stopping the supply of the synchronization signal.

[0093] exist Figure 1 、 6 In the embodiment of 7, in order to facilitate the generation of the carrier signal based on the pulse of the synchronization signal supplied from the self-control device 206, it sometimes takes time to determine whether the conversion unit stops when the control device 206 stops supplying the synchronization signal. When the frequency of the carrier signal is changed, although the pulse interval of the synchronization signal is changed, it is difficult to determine whether the carrier frequency is changed or the conversion unit is stopped. On the other hand, in Figure 8 In the embodiment, the start and stop are determined based on the width of the pulse width of the synchronization signal, so that the start and stop can be performed immediately. Figure 6 、 7 As shown, as long as the synchronization signal is shared by multiple conversion units, the conversion units that share the synchronization signal can be stopped immediately.

[0094] Figure 10This is a timing chart showing a second example of operation of the power conversion device in the fourth embodiment. The signal blocking determination unit 209 can determine whether to stop or start the conversion unit based on the number of pulses of the synchronization signal in a predetermined period. For example, when the number of pulses included in the synchronization signal supplied from the control device 206 is greater than the fourth predetermined value, the signal blocking determination unit 209 sets the levels of the multiple control signals output by the control signal generation unit 208 to an inactive level (in the case of Figure 10 (low level in the middle). Figure 10 The example shows a case where the fourth predetermined value is "3". The signal blocking determination unit 209 sets the output permission signal input to the control signal generation unit 208 to a non-valid level (in the case of a plurality of control signals output by the control signal generation unit 208) so that the plurality of control signals output by the control signal generation unit 208 become non-valid levels. Figure 10 Thus, the control device 206 can quickly stop the secondary-side full-bridge circuit 220b.

[0095] 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 predetermined value that is greater than a fourth predetermined value, the signal blocking determination unit 209 sets the generation of the plurality of control signals by the control signal generation unit 208 to be valid. Figure 10 The example shows a case where the fifth predetermined value is "4". The signal blocking determination unit 209 sets the output permission signal input to the control signal generation unit 208 to a valid level (at the time of the 5th predetermined value "4") so that the generation of multiple control signals based on the control signal generation unit 208 becomes valid. Figure 10 Thus, the signal blocking determination unit 209 quickly permits the operation of the secondary-side full-bridge circuit 220b, and the control device 206 can quickly start the secondary-side full-bridge circuit 220b.

[0096] It should be noted that the conditions for determining whether to start or stop based on the pulse width may be other than the above conditions.

[0097] Figure 11 It is a timing chart showing a third operation example of the power conversion device in the fourth embodiment. Figure 12 FIG. 1 shows an example of a synchronization signal to which start / stop information of each conversion unit is assigned. Figure 11 、 12 As shown, the synchronization signal is configured to include a pulse train having a pulse width shorter than a predetermined first value after a predetermined time has elapsed since a first pulse having a pulse width greater than or equal to a predetermined first value is output. The signal blocking determination unit 209 determines whether the secondary-side full-bridge circuit 220b is permitted to operate based on the pulse train pattern.

[0098] For example, the signal blocking determination unit 209 determines the timing of the separation signals of the plurality of conversion units 211, 212, and 213 (at the time of the separation signal). Figure 11 The separation signal is latched when it is at a high level. Thus, the signal blocking determination unit 209 extracts information on the stop and start of the corresponding conversion unit from the synchronization signal and determines whether to start or stop. After the detection of the first pulse having a pulse width greater than the first predetermined value of the synchronization signal, the separation signal becomes an effective level (at a predetermined time) after a time period previously set for each conversion unit has elapsed. Figure 11 The timing of the separation signal corresponds to the timing of the pulse train with start and stop information for each conversion unit included in the synchronization signal. Figure 11 In the operation example, even if only one conversion unit fails and the number of conversion units is reduced for operation, the conversion units can be individually stopped immediately.

[0099] Figure 16 This is a diagram showing an example of the configuration of a power conversion device in the fifth embodiment. In the fifth embodiment, the same reference numerals are given to the same configurations as those in the above embodiment, and the description of the same configurations and operations as those in the above embodiment is omitted by quoting the above description. Figure 16 In the illustrated power converter 5, the secondary-side circuit 210b on the high-voltage side of each of the multiple conversion units 211, 212, and 213 includes a control signal generator 238 and a drive circuit 204b, but does not include a carrier signal generator 207. Instead of generating a carrier signal, the power converter 5 generates multiple control signals for controlling the multiple secondary-side switching elements. The absence of the carrier signal generator 207 allows for a smaller secondary-side circuit 210b, further miniaturizing the power converter 5.

[0100] Regarding the description of the control signal generator 238, the description of the configuration and operation identical to those of the control signal generator 208 in the above embodiment will be omitted by reference to the above description. The control signal generator 238 generates multiple control signals synchronized with the synchronization signal transmitted through the corresponding insulating element 205. These multiple control signals are, for example, rectangular wave signals whose phases are synchronized with the synchronization signal. In this example, the control signal generator 238 generates four control signals for controlling the switching of the multiple secondary-side switching elements 201e, 201f, 201g, and 201h.

[0101] Figure 17This is a timing chart showing an example of an operating waveform of the power conversion device in the fifth embodiment. The control device 206 outputs a synchronization signal to the control signal generation unit 238 of each conversion unit 211, 212, and 213 via the insulation element 205 corresponding to each conversion unit 211, 212, and 213. The control device 206 outputs a synchronization signal using pulse width modulation that includes first pulses having a predetermined pulse width greater than a first predetermined value at a predetermined period.

[0102] On the high-voltage side, when the control signal generator 238 detects a first pulse with a pulse width greater than a predetermined first value from the supplied synchronization signal, it inverts the levels of each of the multiple control signals. For example, when the control signal generator 238 detects the first pulse, it switches the level of the control signal for a certain switching element from a first level (e.g., high) to a second level (e.g., low), and also switches the level of the switching element opposite that switch from the second level to the first level. Conversely, when the control signal generator 238 detects the first pulse, it switches the level of the control signal for a certain switching element from the second level to the first level, and also switches the level of the switching element opposite that switch from the first level to the second level. This allows the generation of control signals whose logic levels repeatedly invert each time a first pulse included in the synchronization signal is detected.

[0103] It should be noted that the control signal generating unit 238 detects the start of the pulse of the synchronization signal (at the beginning of the pulse of the synchronization signal) in order to determine whether the pulse width is greater than the first predetermined value. Figure 17 The control signal generator 238 can invert the level of the control signal at a time prior to the falling edge of the synchronization signal pulse if the synchronization signal pulse is confirmed to be present for a time corresponding to the first predetermined value (e.g., the rising edge of the pulse in the synchronization signal).

[0104] Drive circuit 204b is an example of a first drive circuit that generates multiple gate signals for driving switching elements 201e, 201f, 201g, and 201h included in secondary-side full-bridge circuit 220b based on multiple control signals generated by control signal generator 238. In this example, the multiple gate signals have approximately the same phase as their corresponding control signals. Drive circuit 204b supplies the corresponding gate signals to the gates of switching elements 201e, 201f, 201g, and 201h. This results in a square wave output voltage V2 with a 50% duty cycle being applied to the secondary side of transformer 202.

[0105] Figure 18 It is a diagram showing a configuration example of a power conversion device in the sixth embodiment. Figure 19This is a timing chart showing an example of the operation of the power conversion device in the sixth embodiment. In the sixth embodiment, the same reference numerals are given to the same configurations as those in the above embodiment, and the description of the same configurations and operations as those in the above embodiment is omitted by quoting the above description. Figure 19 In the illustrated power conversion device 6, each of the multiple conversion units 211, 212, and 213 includes a signal blocking determination unit 239 that determines whether to stop the secondary-side full-bridge circuit 220b based on the synchronization signal. In this example, the signal blocking determination unit 239 of each of the multiple conversion units 211, 212, and 213 determines whether to stop or start the corresponding conversion unit based on the pulse width included in the synchronization signal.

[0106] It should be noted that the signal blocking determination unit 239 has the same structure and operation as the signal blocking determination unit 209 of the above embodiment, so the description of the signal blocking determination unit 239 is omitted by citing the above description. Figure 10 、 11 , perform the action as shown in the action example 12.

[0107] Next, a comparative method for comparing with multiple embodiments of the present invention will be described. The description of the comparative method will be simplified by citing the above description.

[0108] Figure 13 This is a diagram showing a configuration example of an isolated DC / DC converter in a comparative embodiment. Figure 14 It shows Figure 13 A timing chart showing an operation example of an isolated DC / DC converter in a comparative embodiment is shown. Figure 15 It shows that Figure 13 A diagram showing a configuration example of a power conversion device in a comparative embodiment in which isolated DC / DC converters in a comparative embodiment are connected in series on the DC output side.

[0109] Figure 15 The example shows that when the power conversion device includes three conversion units 111, 112, and 113 connected in series on the DC output side, a plurality of control signals and driving power supplies are independently supplied to each conversion unit 111, 112, and 113. Figure 15 Although the path for supplying driving power is not clearly shown, the power voltage is supplied to the driving circuits 104a and 104b from a power supply unit (not shown).

[0110] Figure 15The illustrated power conversion device is a multi-cell converter that includes multiple (three in this example) conversion units 111, 112, and 113, and a control device 106 for controlling the power conversion operations of each of these conversion units 111, 112, and 113. Each of these conversion units 111, 112, and 113 is a unit converter that steps up or steps down the DC voltage input from a shared DC path to output a predetermined DC voltage. Each of these conversion units 111, 112, and 113 includes an isolated DC / DC converter 100 and a pair of terminals p and q.

[0111] The isolated DC / DC converter 100 includes a transformer 102, a primary-side circuit 110a, and a secondary-side circuit 110b. The primary-side circuit 110a includes a capacitor 103a, a primary-side full-bridge circuit 120a, and a drive circuit 104a. The primary-side circuit 110a may further include a reactor 107a connected in series with the primary-side winding of the transformer 102. The primary-side full-bridge circuit 220a includes primary-side switching elements 101a, 101b, 101c, and 101d. The secondary-side circuit 110b includes a capacitor 103b, a secondary-side full-bridge circuit 120b, and a drive circuit 104b. The secondary-side circuit 110b may further include a reactor 107b connected in series with the secondary-side winding of the transformer 102. The secondary-side full-bridge circuit 220b includes secondary-side switching elements 101e, 101f, 101g, and 101h.

[0112] Figure 15 The illustrated power conversion device includes multiple insulating components 105, which are disposed relative to each of the multiple conversion units 111, 112, and 113 and are configured to transmit multiple control signals to the corresponding conversion units 111, 112, and 113. When one insulating component 105 transmits multiple control signals, one insulating component is allocated for each control signal, thus including multiple insulating components (in this example, insulating components 105a, 105b, 105c, and 105d).

[0113] Drive circuit 104b drives secondary-side switching elements 101e, 101f, 101g, and 101h for switching based on control signals supplied from control device 206 via insulating elements 105a, 105b, 105c, and 105d. Drive circuit 104a drives primary-side switching elements 101a, 101b, 101c, and 101d for switching based on control signals supplied from control device 206 without passing through insulating elements.

[0114] exist Figure 13In the insulating DC / DC converter of the comparative embodiment shown in FIG. 1 , since four control signals are used, which are equal to the total number of switching elements on the high voltage side, at least four insulating elements corresponding to the number of control signals are provided. Figure 15 In a configuration where one comparative insulating DC / DC converter is connected in series, as in the multi-cell converter shown, the total number of insulating elements is at least (the number of series-connected converter units × the number of insulating elements provided per converter unit), which is a very large number.

[0115] In contrast, in each embodiment of the present invention, the signal supplied to each conversion unit to drive the high-voltage switching element is a single synchronous signal, reducing the number of insulating elements. This results in, for example, miniaturization and cost reduction of the power conversion device.

[0116] While the power conversion device has been described above using the embodiments, the present invention is not limited to the above embodiments. Various modifications and improvements, such as combination with or replacement of part or all of another embodiment, are possible within the scope of the present invention.

[0117] For example, the present invention is not limited to the configuration in which multiple conversion units are connected in series via a pair of output terminals p and q for outputting the output voltage of the isolated DC / DC converter, as in the first embodiment of the present invention. For example, an inverter may be added between the output side of the isolated DC / DC converter and the pair of output terminals of the conversion units, with the two intermediate connection points of the inverter connected to the pair of output terminals. In this case, the first conversion circuit connected between the transformer and the pair of output terminals of the conversion units may be the additional inverter.

[0118] Furthermore, the present invention may include a configuration in which multiple conversion units are connected in series via a pair of terminals connected to the input side of an isolated DC / DC converter. For example, an inverter may be added between the input side of the isolated DC / DC converter and the pair of terminals on the input side of the conversion unit, with the two intermediate connection points of the inverter connected to the 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 unit may be the additional inverter.

[0119] 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 both the primary and secondary sides of the transformer. The bridge circuit provided on at least one of the primary and secondary sides may also be a half-bridge circuit. Furthermore, the isolated DC / DC converter is not limited to a DAB converter and may also be a converter of a type other than a DAB converter (e.g., a flyback type, a feedforward type, etc.).

[0120] Description of Reference Numerals

[0121] 1, 2, 3, 4, 5, 6 Power conversion devices

[0122] 100 Insulated DC / DC Converter

[0123] 101 Switching Elements

[0124] 102 Transformer

[0125] 103a, 103b capacitor elements

[0126] 104a, 104b driving circuit

[0127] 105 Insulation parts

[0128] 106 Control Device

[0129] 107 Reactor

[0130] 109a DC power supply

[0131] 200 Insulated DC / DC Converter

[0132] 201a, 201b, 201c, 201d switching elements

[0133] 201e, 201f, 201g, 201h switch elements

[0134] 202 Transformer

[0135] 203a, 203b capacitor elements

[0136] 204a, 204b driving circuit

[0137] 205 Insulation Components

[0138] 206 Control Device

[0139] 207 Carrier signal generation unit

[0140] 208, 238 Control signal generation unit

[0141] 209, 239 Signal blocking determination unit

[0142] 210b Primary side circuit

[0143] 210a Secondary side circuit

[0144] 211, 212, 213 conversion units

[0145] 220a Primary-side conversion circuit

[0146] 220b secondary side conversion circuit

Claims

1. A power conversion device comprising: a plurality of conversion units, each having an insulating DC / DC converter and a pair of terminals connected to either an input side or an output side of the insulating DC / DC converter, wherein the plurality of conversion units are connected in series via the pair of terminals; a plurality of insulating elements, which are arranged relative to each of the plurality of conversion units and are used to transmit a synchronization signal to a corresponding conversion unit among the plurality of conversion units; and a control device for supplying the synchronization signal to the plurality of conversion units respectively through corresponding insulation elements in the plurality of insulation elements; Each of the plurality of isolated DC / DC converters includes a transformer, a first circuit on the pair of terminals of the transformer, and a second circuit on the side of the transformer opposite to the pair of terminals. The first circuit has: a first conversion circuit connected between the transformer and the pair of terminals; a control signal generating unit configured to generate a plurality of control signals synchronized with the synchronization signal; and a first driving circuit, which drives a plurality of switching elements included in the first conversion circuit based on the plurality of control signals; The second circuit has: A second conversion circuit connected to the first conversion circuit via the transformer; and a second drive circuit that drives at least one switching element included in the second conversion circuit based on at least one control signal supplied from the control device; The synchronization signal is directly supplied from the control device to the first circuit through the corresponding insulation element.

2. The power conversion device according to claim 1, wherein: The control signal generating unit and the first driving circuit operate at a different reference potential for each conversion unit.

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

4. The power conversion device according to claim 1, wherein: The plurality of switching elements driven by the first driving circuit are switching elements included in at least one half-bridge circuit of the first conversion circuit. The plurality of switching elements driven by the second drive circuit are switching elements included in at least one half-bridge circuit included in the second conversion circuit.

5. The power conversion device according to claim 4, wherein: The phases of the plurality of control signals supplied from the control device to the second circuit side are different from the phases of the plurality of control signals generated by the control signal generating unit on the first circuit side.

6. The power conversion device according to any one of claims 1 to 5, wherein: The synchronization signal includes a first pulse having a pulse width greater than a first predetermined value, When the control signal generating unit detects the first pulse, the control signal generating unit inverts the levels of the plurality of control signals.

7. The power conversion device according to any one of claims 1 to 5, wherein: Each of the plurality of conversion units includes a carrier signal generating unit for generating a carrier signal synchronized with the synchronization signal. The control signal generating unit generates the plurality of control signals synchronized with the carrier signal.

8. The power conversion device according to claim 7, wherein: The synchronization signal includes a first pulse having a pulse width greater than a first predetermined value, The carrier signal generating unit detects the first pulse at least once and generates the sawtooth or triangular wave carrier signal.

9. The power conversion device according to claim 7, wherein: The synchronization signal includes a first pulse having a pulse width greater than a first predetermined value, When the carrier signal generating unit detects the first pulse, the carrier signal generating unit initializes the carrier signal and then monotonically increases or decreases the carrier signal over time.

10. The power conversion device according to claim 7, wherein: The synchronization signal includes a first pulse having a pulse width greater than a first predetermined value, When the carrier signal generating unit detects the first pulse, it generates the carrier signal that repeats monotonically increasing and monotonically decreasing with the passage of time.

11. The power conversion device according to claim 7, wherein: The control signal generating unit generates the plurality of control signals by detecting a reversal of the magnitude relationship between the amplitude of the carrier signal and a median value of the amplitude of the carrier signal.

12. The power conversion device according to claim 7, wherein: The control signal generating unit generates a plurality of control signals by detecting the peaks or troughs of the carrier signal.

13. The power conversion device according to any one of claims 1 to 5, wherein: The plurality of switching elements driven by the first driving circuit are switching elements included in at least one half-bridge circuit of the first conversion circuit. The control signal generating unit provides a dead time for preventing a short circuit of the half-bridge circuit to the plurality of control signals.

14. The power conversion device according to any one of claims 1 to 5, wherein: Each of the plurality of conversion units includes a determination unit that determines whether to stop the first conversion circuit based on the synchronization signal.

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

16. The power conversion device according to claim 14, wherein: The synchronization signal includes a first pulse having a pulse width greater than a first predetermined value, and a second pulse having a pulse width greater than a second predetermined value, which is longer than the first predetermined value. When the determination unit detects the second pulse, the determination unit stops the first conversion circuit.

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

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

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

20. The power conversion device according to claim 14, wherein: The synchronization signal includes a first pulse having a pulse width greater than a first predetermined value, and a pulse train each having a pulse width shorter than the first predetermined value. The determination unit determines whether the operation of the first conversion circuit is permitted based on the array pattern of the pulse train.

21. The power conversion device according to any one of claims 1 to 5, wherein: The synchronization signal is a signal shared by the plurality of conversion units.

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

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