Patent Publication Number: US-2023139257-A1

Title: Power Conversion Device

Description:
BACKGROUND 
     Field 
     This invention relates to a power conversion device that supplies AC power to a motor. 
     Related Art 
     Power conversion device for motor drives receives several hundred volts of system voltage and output several hundred watts to several hundred kW of power, depending on the application. For this reason, it has a circuit section of a high-power system capable of withstanding these voltages and currents (hereinafter referred to as a high-power section). On the other hand, commands to run or stop the power conversion device are given from outside the power conversion device by the user of the conversion device by an external device such as a programmable logic controller (PLC). Therefore, the power conversion device for motor drive has a low-power circuit section (hereinafter referred to as the low-power section) as an interface between the user of the device and the high-power section, and various signals are exchanged between the high-power section and the low-power section to achieve the operation intended by the user. 
     Here, it is necessary for motor drive power conversion devices to take measures to ensure the safety of people involved in the operation of such devices. Various safety standards (e.g., IEC and UL standards) require, as part of electrical safety, measures to prevent electric shock between the high voltage parts, such as the system voltage and motor voltage, and the low voltage parts, which may come into contact with people. The requirements for electrical insulation, called reinforced insulation, are defined as a measure to prevent electric shock between the strong electric parts, such as system voltage and motor voltage, and the low electric parts, which may come into contact with people. In order to realize reinforced insulation, it is necessary to provide a specified insulation distance on the mounting board as defined in each standard, which causes the board area to increase. Therefore, it is effective to reduce the area of the reinforced insulation boundary as much as possible and to configure the power conversion device to save space on the board area and reduce the size of the device. 
     Patent document 1 describes a method of taking reinforced isolation in a power conversion device with two types of microcomputers: a current control microcomputer and a main control microcomputer. According to  FIG.  1    of the Patent Document 1, the power supply circuit for control is located in the drive section, and the power supply voltage generated by the power supply circuit is supplied to the current control microcomputer and the main control microcomputer. The current control microcomputer and the main control microcomputer are reinforced and insulated with a photocoupler or other insulating element in the communication circuit.
     Patent document 1: JP2007-300694A   

     SUMMARY 
     Two types of microcomputers are mounted in Patent Document 1. The current control microcomputer is located in the high-power section and the main control microcomputer is located in the low-power section, which are reinforced and insulated from each other. The power supply circuit is mounted in the drive section. Here, both the power supply line for the high-power section (current control microcomputer) and the power supply line for the low-power section (main control microcomputer) are located at the output of the power supply circuit, and the reinforced insulation boundary is located across the drive section, current control section, and multiple boards. As mentioned earlier, it is desirable to make the reinforced insulation boundary as small as possible, and the configuration in which the reinforced insulation boundary straddles the boards has the problem of causing the circuit boards to become larger. 
     Therefore, the purpose of the present invention is to provide a power conversion device in which the reinforced insulation boundary portion avoids a configuration in which it straddles multiple boards, thereby achieving a downsizing of the circuit board. 
     To solve the above problem, the power conversion device described in this invention has a main circuit board, a first board, and a second board. The main circuit board has a rectifier circuit that rectifies AC voltage and outputs DC voltage, and an inverter circuit that inversely converts DC voltage and outputs AC power in the high-power section. The second board has a second circuit arranged in the low-power section. The first board is connected to the main circuit board and the second board, and has a first circuit arranged in the high-power section, a reinforced insulation area for reinforcing insulation between the high-power section and the low-power section, and a second circuit arranged in the reinforced insulation area that receives DC voltage and outputs AC power. An isolation transformer, which is a component of a power supply circuit that supplies power to the first and second circuits, and an insulating element, which is disposed in the reinforced insulation area and causes signals to be exchanged between the first and second circuits. 
     According to the present invention, it is possible to avoid a configuration in which the reinforced insulation boundary straddles multiple boards and to achieve a smaller circuit board. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a block diagram of the power conversion device in Example 1. 
         FIG.  2    is a block diagram of another power conversion device in Example 1. 
         FIG.  3    is a block diagram of other power conversion devices in Example 1. 
         FIG.  4    is a diagram of the power conversion device in Example 1. 
         FIG.  5    is a bottom view of the power conversion device in Example 1. 
         FIG.  6    is a diagram of the power conversion device in Example 2. 
         FIG.  7    is a diagram of another power conversion device in Example 2. 
         FIG.  8    is a diagram of the power conversion device in Example 3. 
         FIG.  9    is a bottom view of the power conversion device in Example 3. 
         FIG.  10    is a block diagram of the power conversion device in Example 4. 
         FIG.  11    is a diagram of the power conversion device with an additional fourth board. 
         FIG.  12    is a bottom view of the power conversion device when a fourth board is added. 
         FIG.  13    is a diagonal view of the power conversion device. 
         FIG.  14    shows the heat radiation fins and the module case. 
         FIG.  15    shows the main body case. 
         FIG.  16    shows the front cover. 
         FIG.  17    is a block diagram of a conventional power conversion device. 
         FIG.  18    shows a circuit diagram of a flyback converter used in a power circuit. 
     
    
    
     DETAILED DESCRIPTION 
     The following is a detailed description of examples of the invention with reference to the drawings. 
       FIG.  17    is a block diagram of the power conversion device described in the patent document. As shown in  FIG.  17   , a conventional power conversion device comprises of three pieces: a main circuit board  101 , a first circuit board  102 , and a second circuit board  103 . The main circuit board  101  contains the main circuit boards, such as the rectifier circuit  111 , the smoothing capacitor  112 , inverter circuit  113 , and power supply circuit  123  are mounted on the main circuit board  101 , and the terminal block  114  to supply drive current to the motor. The first board  102  is mounted with a drive circuit  125  that detects the current of the inverter circuit  113  and outputs a drive signal to the inverter circuit  113 . The second board  103  is mounted with a communication circuit  131  that is responsible for communication between the external device and the power conversion device. 
     The drive circuit  125  and the communication circuit  131  are reinforced and insulated from each other (dotted line area in the figure), and the insulating elements, photocouplers  121  and  122 , which pass signals to each other through the insulating elements. The power supply circuit  123  receives the voltage Vdc 1  at both ends of the smoothing capacitor  112  and supplies the power supply voltage Vdc 2  to the drive circuit  125  and the power supply voltage Vdc 3  to the communication circuit  131 . 
       FIG.  18    shows a circuit diagram of a flyback converter commonly used as a power circuit  123 . As shown in  FIG.  18   , the power circuit  123  comprises of an isolation transformer  124 , rectifier diodes  201 ,  202 , smoothing capacitors  203  and  204 , MOSFET  205 . In the isolation transformer  124 , a voltage Vdc 1  is connected to one terminal of the primary winding  1241 , and the drain terminal of MOSFET  205  is connected to the other terminal. Pulse voltage is input to the primary winding  1241  of the isolation transformer  124  by switching MOSFET  205 , and voltage corresponding to the turn ratio of the isolation transformer  124  is output from the secondary windings  1242  and  1243 . The power is converted to voltage by the voltage conversion circuit as needed and consumed by loads such as drive circuit  125  and communication circuit  131 . The primary windings  1241  and the secondary windings  1242  located in the high-power section and the secondary windings  1243  located in the low-power section are reinforced and insulated from each other. 
     In the power conversion device described in Patent Document 1, the photocouplers  121  and  122  are mounted on the first board  102 , while the power circuit  123  is mounted on the main circuit board  101 , so the reinforced insulation boundary is placed across the main circuit board  101  and first board  102 , as shown in  FIG.  17   . Therefore, it is necessary to arrange the reinforced insulation boundary in a complex manner, which leads to larger circuit boards. 
     Example 1 
       FIG.  1    is a block diagram of the power conversion device in Example 1. As shown in  FIG.  1   , the power conversion device described in Example 1 comprises of three pieces: main circuit board  101 , first board  102 , and a second board  103 . The main circuit board  101  comprises of three main circuit boards, including a rectifier circuit  111 , a smoothing capacitor  112 , and inverter circuit  113  are mounted on the main circuit board  101 . In other words, the main circuit components are located in the high-power section. The first board  102  is mounted with a drive circuit  125  that outputs drive signals to the inverter circuit  113  and an isolation transformer  124  that is a component of the power circuit  123 . Details of the power circuit  123  are described in  FIG.  18   , and an isolation transformer  124  is a component of the power circuit  123 . The second board  103  is mounted with a communication circuit  131  that is responsible for communication between the external device and the drive circuit. In other words, the communication circuit  131  is placed in the lowly insulated area. The first board  102  has a reinforced insulation area (dotted line area in  FIG.  1   ), and in this reinforced insulation area, the components of the power circuit that receives DC voltage and supplies power to various loads are mounted. The reinforced insulated area is used to receive signals between the isolation transformer  124 , which is a component, the drive circuit  125 , and the communication circuit  131 . And photocouplers  121  and  122 , which are insulating elements that transfer signals between the drive circuit  125  and the communication circuit  131 . The reinforced isolation area is formed on the first board  102  by taking the high power section and the low power section at a predetermined distance defined by each standard. 
     This completes the reinforced insulation within the first board  102 , since the insulating elements for configuring the reinforced insulation, the isolation transformer  124  and the photocouplers  121  and  122 , are all mounted on the same board. 
     It is desirable for either the drive circuit  125  or the communication circuit  131  to include a microcontroller. For example, a microcontroller should be mounted in drive circuit  125 , communication signals with external devices should be processed by communication circuit  131 , and photocouplers  121 ,  122 , and communicate with the microcontroller mounted in the drive circuit  125  via the photocouplers. The microcontroller mounted in the drive circuit  125  may communicate with the microcontroller mounted in the drive circuit  125  via photocouplers  121  and  122 . A microcontroller can be mounted in the communication circuit  131 , and after the current of the inverter circuit is calculated by the drive circuit  125 , it can be transmitted to the microcontroller mounted in the communication circuit  131  via photocouplers  121  and  122 , and the microcontroller can output drive signals to the inverter circuit via photocouplers  121  and  122 . As in Patent Document 1, a microcontroller may be implemented in both the drive circuit  125  and the communication circuit  131 . 
     In addition, if the features of Example 1, namely the isolation transformer  124  and photocouplers  121  and  122  are provided on the first board, the drive circuit  125  can be mounted anywhere in the high-power section, not only on the first board  102 . For example, as shown in  FIG.  2   , it can be mounted on the main circuit board  101 , and as shown in  FIG.  3   , the communication circuit  131 , which is not shown in the figure, is similarly not limited to the second board  103 , but can be mounted anywhere in the low-power section. 
     As described above, according to Example 1, the isolation transformer  124 , photocouplers  121 ,  122  are all mounted on the same board, reinforced insulation is completed within the first board  102 , and the board can be downsized. Therefore, the reinforced insulation is completed in the first board  102 , and the board can be downsized. 
     Example 2 
     Next, Example 2 is described. The basic board configuration is the same as in Example 1 described in  FIG.  1    to  FIG.  3   . In this example, specific examples of the connection between the main circuit board  101  and the first board  102  are described using  FIG.  4    through  FIG.  7   . 
       FIG.  4    and  FIG.  5    show the basic configuration of the power conversion device in this example.  FIG.  4    is a diagonal view and  FIG.  5    is a bottom view in the board configuration shown in  FIG.  1   . As in Example 1, the main circuit board  101  mainly performs the power conversion function of receiving system voltage and outputting AC power for motor drive, receiving system voltage at the terminal block  114  on the main circuit board  101  and outputting AC power to the motor from the terminal block  114  through the rectifier circuit  111  (see  FIG.  5   ), smoothing capacitor  112  and inverter circuit  113 . The terminal block  114  and smoothing capacitor  112  are located on the front side of the power conversion device on the main circuit board  101  (forward in  FIG.  4   ). A diagram of the power conversion device is shown in  FIG.  13   , where the display panel with display  141  or operation units  142  is the front of the power conversion device. The rectifier circuit  111  and inverter circuit  113  are located on the rear side of the power conversion device and are joined to the heat dissipation fins described below. The first board  102  contains the drive circuit  125 , photocouplers  121 ,  122 , and the components of the power circuit  123 , an isolation transformer  124  are mounted. 
     In the power conversion device described in this example, the main circuit board  101  and the first board  102  are erected generally vertically. The first board  102  is mounted on the opposite side of the main circuit board  101  from the side on which the rectifier circuit  111  and inverter circuit  113  are mounted. In other words, the first board  102  is mounted on the product side of the main circuit board  101  so as to secure a space on the front side of the power conversion device where the rectifier circuit  111  and inverter circuit  113  are mounted. The first board  102  is positioned so that it faces the side of the terminal block  114  of the main circuit board  101 . This allows airflow by natural convection to be secured in the space on the front side of the product on the main circuit board  101 , compared to the case where the first board  102  is mounted parallel to the main circuit board  101  so that the cooling performance of the rectifier circuit  111  and inverter circuit  113  can be secured. 
     The isolation transformer  124  is located on the inside side of the power conversion device on the first board  102  and is cooled by the previously mentioned natural convection. If the mounting area of the first board  102  is to be enlarged, the first board  102  may also be provided at a location facing the side of the terminal block  114 . 
     In addition, between the main circuit board  101  and the first board  102 , the smoothing capacitor  112  voltage Vdc 1  (several hundred V) and the drive circuit  125  to the inverter circuit  113  (about several V), and drive signals, etc. (about several V) output from the drive circuit  113  must be transmitted simultaneously. If these wirings are in close proximity, there is concern about circuit malfunction due to noise superimposed on the low-voltage lines. For this reason, as shown in  FIG.  4   , a connector  115  for low-voltage transmission and a connector  116  for high-voltage transmission should be provided. As a connector, multiple connectors may be arranged according to the type of signal. 
     In  FIG.  4    and  FIG.  5   , the main circuit board  101  and the first board  102  are connected by board-to-board connectors ( 115 ,  116 ). As a result, the power conversion device can be configured by inserting the first board  102  into the main circuit board  101  from the front side of the power conversion device. This allows the power conversion device to be configured by inserting the first board  102  from the front side of the power conversion device into the main circuit board  101 , which eliminates the soldering process and allows for easy assembly. However, as long as the main circuit board  101  and the first board  102  are electrically connected, any configuration is possible. For example, a pin header can be used for soldering, or the main circuit board  101  and the first board  102  can be connected directly by soldering. The main circuit board  101  and the first board  102  may be connected directly by soldering. 
     As shown in  FIG.  4    and  FIG.  5   , the first board  102  is physically connected to the main circuit board  101  with board-to-board connectors  115  and  116 , but for further earthquake resistance, board-to-board fixation sections  117  and  118  may be provided. Specifically, the board-to-board fixing sections  117  and  118  are fixed to the main circuit board  101  by screwing or soldering, and are fixed in contact with the first board  102  by soldering or by clipping the board between the clips provided on the board-to-board fixing sections  117  and  118 , or by other methods. 
       FIG.  6    and  FIG.  7    show the basic configuration of the power conversion device in Example 2.  FIG.  6    is a diagrammatic view of the board configuration shown in  FIG.  2   , and  FIG.  7    is a diagrammatic view of the board configuration shown in  FIG.  3   . As shown in  FIG.  6   , in the board configuration shown in  FIG.  2   , as in the configurations shown in  FIG.  4    and  FIG.  5   , the first board  102  is erected against the main circuit board  101 , and the drive circuit  125  is mounted on the main circuit board  101 . The drive circuit  125  is mounted on the main circuit board  101 . As shown in  FIG.  7   , in the board configuration shown in  FIG.  3   , as in the configurations shown in  FIG.  4    to  FIG.  6   , the first board  102  is erected against the main circuit board  101 , and furthermore, the third circuit board  104  is mounted on the board-to-board connector  119 . Board connector  119  allows the third board  104  to be erected against the main circuit board  101 . This allows the drive circuit  125  to be mounted in the high-power section without reducing the space for airflow due to natural convection on the front side of the product in the inverter circuit  113 . 
     The board-to-board connector  119  can be made of any configuration as long as it is electrically connected, for example, it can be soldered using a pin header, or it can be directly soldered between the main circuit board  101  and the third board  104 . 
     According to Example 2, the isolation transformer  124  and photocouplers  121  and  122 , which are the isolation elements to constitute the reinforced insulation, are all mounted on the same board, so the reinforced insulation is completed in the first board  102 , and the board can be made smaller. 
     According to Example 2, the first board  102  is connected perpendicularly to the main circuit board  101 , which allows convection of heat from the rectifier circuit  111  and inverter circuit mounted on the main circuit board  101 , thereby improving cooling efficiency. cooling efficiency can be improved. 
     Example 3 
     Next, Example 3 is described. The basic board configuration is the same as in Example 1 described in  FIG.  1    to  FIG.  3   . In this example, specific examples of the connection between the first board  102  and the second board  103  are described using  FIG.  8    and  FIG.  9   . 
       FIG.  8    and  FIG.  9    show the basic configuration of the power conversion device in Example 3.  FIG.  8    is a diagonal view and  FIG.  9    is a bottom view. As shown in  FIG.  8    and  FIG.  9   , the power conversion device described in this example has the second board  103  positioned generally parallel to the main circuit board  101 . The first board  102  is placed between the main circuit board  101  and the second board  103 , and placed generally perpendicular to both the main circuit board  101  and the second board  103 . 
     The second board  103  has a communication circuit  131 , which is responsible for communication between the external device and the power conversion device, and a terminal block  132 , which is the interface between the external device and the power conversion device. The user connects the external device and the terminal block  132  with wires to construct the desired communication system. 
     Here, since both the main circuit board  101  and the second board  103  are equipped with terminal blocks ( 114 ,  132 ), it is desirable that both boards be placed parallel to the front of the product (front of the power conversion device) for ease of operation by the user. In addition, since the first board  102  is responsible for signal transfer between the main circuit board  101  and the second board  103 , the signal transmission means between the main circuit board  101  and the second board  103  can be simplified, making it possible to configure a compact power conversion device as a whole. 
     In addition, when the user connects the wires to the terminal block  132 , an external force is applied from the front of the product toward the rear. If the main circuit board  101  and the first board  102  are fixed using the method described in Example 2, and the first board  102  and the second board  103  are fixed by soldering, pin headers, board-to-board connectors, etc., the external force is transmitted to the first board  102  and the main circuit board  101  via the second board  103 , and there is concern that the connection between the boards may be damaged or the boards may be damaged. 
     Therefore, as shown in  FIG.  9   , signals between the first board  102  and the second board  103  are transmitted using board-to-cable connectors  126  and  133  and cable  127 . As a result, external forces applied to the second board  103  do not affect the first board  102 , making it possible to configure a power conversion device with superior durability compared to a case where the first board  102  and second board  103  are fixed between them. 
     Note that the connection between the first board  102  and the second board  103  does not need to use a cable if it is configured to escape external forces, for example, a board-to-board movable (floating) connector may be applied. 
     In addition, the board configuration shown in  FIG.  1   , the third board  103  based on main circuit board  101  and the first board shown in  FIG.  4   , however, even if the third board  104  is installed on the board configurations shown in  FIGS.  2  and  3    and the basic configurations shown in  FIGS.  5  and  6   , the third substrate  104  can still be installed on the first substrate  102 . Thereby the same effect can be obtained by placing the third substrate  104  generally perpendicular to the first substrate  102 . 
     Example 4 
     Next, Example 4 is described using  FIG.  10    through  FIG.  12   . 
       FIG.  10    is a block diagram of the power conversion device in this example. In the power conversion device described in Example 4, in contrast to the power conversion device described in Examples 1 to 3, a fourth circuit board  105  with a display  141  or an operation unit  142  is added. 
     The display  141  comprises of a 7-segment LED that displays data such as frequency and setting values, and an operating lamp that lights up when the inverter is running. The operation unit  142  comprises of the RUN key to operate the inverter, the STOP key to decelerate/stop the inverter, and so on. The display section  141  and the operation unit  142  improve the workability of the user of the equipment. 
       FIG.  11    and  FIG.  12    show the basic configuration of the power conversion device when a fourth board is added to the configuration shown in  FIGS.  1 ,  4 ,  5 ,  8 , and  9   .  FIG.  11    is a diagonal view and  FIG.  12    is a bottom view. Considering the user&#39;s workability, it is desirable to place the display  141  and operation unit  142  parallel to the front of the product as well as the main circuit board  101  and the second board  103 , so the fourth board  105  is generally connected to the second board  103  in parallel via board-to-board connector  134  as shown in  FIG.  11    and  FIG.  12   . 
     Example 5 
     Next, Example 5 is described using  FIG.  13    through  FIG.  16   . 
       FIG.  13    is a configuration diagram of the power conversion device in Example 5. In the power conversion device described in this example, cases  206 - 208  and heat dissipating fins  209  that protect each of the boards  101 - 105  are added to the power conversion device described in Example 4. 
       FIG.  14    depicts the heat dissipating fins  209  and module case  208  from  FIG.  13   . The heat-dissipating fins  209  are arranged for the purpose of dissipating heat generated from the rectifier circuit  111  and inverter circuit  113  mounted on the main circuit board  101 . In addition, the module case  208  has an opening in the part where the rectifier circuit  111  and inverter circuit  113  are mounted in advance and is fixed to the heat radiation fin  209  so that the mounting position can be easily determined when the rectifier circuit  111  and inverter circuit  113  are mounted on the heat radiation fin  209 . 
     Here, when the module case  208 -heat dissipating fin  209  is fixed with screws, it is also possible to co-tighten with other components with the screws. For example, in the case of fastening the board-to-board fixing sections  117  and  118  and the first board as described in Example 2 with screws, the number of screws can be reduced by using the same screws to fasten the board-to-board fixing sections  117  and  118 , the first board  102 , the module case  208 , and the heat radiation fin  209 . 
     Although not shown in  FIG.  13    and  FIG.  14   , a cooling fan may be added to the fins  209  to further improve the heat dissipation performance of the power conversion device. 
       FIG.  15    shows the main body case  207  extracted from  FIG.  13   . The main body case  207  protects each of the boards  101 - 103  from the outside and is configured to be joined with the module case  208  or the heat dissipation fins  209 . 
     As mentioned earlier, the first board  102  is fixed to the main circuit board  101  by board-to-board connectors  115  and  116  or board-to-board fixation sections  117  and  118 . To further reinforce earthquake resistance, the main case  207  may be provided with a  2071  fixing section for fixing the first board  102 . Specifically, the first board  102  is secured to the main case  207  by contacting it, such as by screwing it to the main case  207  or by pinching it into the gap provided in the fixing section  2071 . The second board  103  is fixed to the main case  207  by screwing or by pinching it into the gap provided in the fixing section  2072 . 
       FIG.  16    shows the front cover  206  extracted from  FIG.  13   . The front cover  206  protects the fourth board  105 , the display  14   1 , and operation unit  142  from the outside, and is configured to be joined to the main case  207 . The fourth board  105  is fixed in contact with the front cover  206 , and the front cover, when the  206  is joined to the main body cover  207 , the connector  13   4  is configured to mate with it when the front cover  206  is joined to the main unit cover  207 .
       101 ,  102 ,  103 ,  104 ,  105 : Board     111 : Rectifier circuit     112 : Smoothing capacitor     113 : Inverter circuit     114 ,  132 : Terminal block     115 ,  116 ,  119 ,  126 ,  133 ,  134 : Board-to-board connections     117 ,  118 : Board-to-board fixing section     121 ,  122 : Photocouplers     123 : Power supply circuit     124 : Isolation transformer     1241 : Primary winding     1242 ,  1243 : Secondary winding     125 : Drive circuit     127 : Cable     131 : Communication circuit     141 : Display section     142 : Operation unit     201 ,  202 : Rectifier diodes     203 ,  204 : Smoothing capacitor     206 ,  207 ,  208 : Case     209 : Heat dissipation fins     2071 ,  2072 : fixing section in