Design Support Device, Design Support System, Electrical Device, Design Support Method, and Storage Medium

Abstract

A design support apparatus, a design support system, an electrical device, a design support method, and a storage medium that can search for control values more efficiently are provided. The design support apparatus executes a first process. In the first process, the design support apparatus sets a control value group including a first time difference between a first timing at which a voltage is applied to a first gate and a second timing at which a voltage is applied to a second gate for a semiconductor element provided with a plurality of gates including the first gate and the second gate. In the first process, the design support apparatus calculates a characteristic value representing the characteristics of the semiconductor element based on an output result when an electric signal corresponding to the control value group is input to the semiconductor element. In the first process, the design support apparatus calculates a first function based on historical data including one or more data sets of a score based on the characteristic value and the control value group. The design support apparatus uses the first function to set a new control value group.

Description

[0001] This application is based on and claims priority from Japanese Patent Application No. 2021-004501 (filed on January 14, 2021). This application incorporates by reference the entire contents of that application. Technical Field

[0002] Embodiments of the present invention generally relate to a design support device, a design support system, an electrical device, a design support method, and a storage medium. Background Art

[0003] Regarding semiconductor elements including a plurality of gates, a technique capable of more efficiently searching for control values related to the gates is required. Summary of the Invention

[0004] Embodiments of the present invention provide a design support device, a design support system, an electrical device, a design support method, and a storage medium capable of more efficiently searching for control values.

[0005] According to an embodiment of the present invention, a design support device executes a first process. In the first process, the design support device sets a control value group including a first time difference between a first timing at which a voltage is applied to a first gate and a second timing at which a voltage is applied to a second gate for a semiconductor element provided with a plurality of gates including the first gate and the second gate. In the first process, the design support device calculates a characteristic value representing the characteristics of the semiconductor element based on an output result when an electric signal corresponding to the control value group is input to the semiconductor element. In the first process, the design support device calculates a first function based on historical data including one or more data sets of scores based on the characteristic values and the control value groups. The design support device uses the first function to set a new control value group.

[0006] According to the above embodiment, it is possible to provide a design support device, a design support system, an electrical device, a design support method, and a storage medium capable of more efficiently searching for control values. Brief Description of the Drawings

[0007] Figure 1 It is a block diagram showing the functional structure of a design support system according to an embodiment.

[0008] Figure 2 It is a flowchart showing a design support method according to an embodiment.

[0009] Figure 3 It is a flowchart showing a design support method according to an embodiment.

[0010] Figure 4 It is a schematic cross-sectional view showing an example of a semiconductor element.

[0011] Figure 5 is a schematic cross-sectional view showing an example of a semiconductor element.

[0012] Figure 6 is a schematic cross-sectional view showing an example of a semiconductor element.

[0013] Figure 7 is a schematic cross-sectional view showing an example of a semiconductor element.

[0014] Figure 8 is a schematic cross-sectional view showing an example of a semiconductor element.

[0015] Figure 9 is a schematic cross-sectional view showing an example of a semiconductor element.

[0016] Figure 10 is a schematic cross-sectional view showing an example of a semiconductor element.

[0017] Figure 11 is a schematic diagram illustrating a hardware structure.

[0018] Figure 12 is a flowchart showing a design support method according to a first modification of an embodiment.

[0019] Figure 13 is a block diagram showing a functional structure of a design support system according to a second modification of an embodiment.

[0020] Figure 14 is a block diagram showing a functional structure of an electrical device according to a third modification of an embodiment.

[0021] Figure 15 is a flowchart showing an operation of an electrical device according to a third modification of an embodiment.

[0022] Figure 16 is a block diagram showing a functional structure of an electrical device according to a fourth modification of an embodiment.

[0023] Symbol Explanation

[0024] 1, 1b: Design support system; 2, 2a, 2b: Electrical device; 10: Design support device; 10a, 10b: Control circuit; 11: Setting unit; 12: Characteristic value calculation unit; 13: Score calculation unit; 14: Function calculation unit; 15: Storage unit; 18: Input unit; 19: Output unit; 20: Drive circuit; 21: Pulse generation unit; 22: Driver; 30: Semiconductor element; 31: Electrical component; 40: Detection circuit; 90: Processing device; 91: CPU; 92: ROM; 93: RAM; 94: Storage device; 95: Input interface; 95a: Input device; 96: Output interface; 96a: Output device; 97: Communication interface; 97a: Server; 98: System bus; 100, 100a - 100f: Semiconductor element; 101: First semiconductor region; 101a: First sub-region; 101b: Second sub-region; 102: Second semiconductor region; 103: Third semiconductor region; 104: Fourth semiconductor region; 105 - 107: Semiconductor region; 111: Collector; 112: Emitter; 121: First gate; 121a: First insulating layer; 121t: First gate terminal; 122: Second gate; 122a: Second insulating layer; 122t: Second gate terminal; 123: Third gate; 123a: Third insulating layer; 123t: Third gate terminal; 124: Fourth gate; 124a: Fourth insulating layer; 124t: Fourth gate terminal; 125: Fifth gate; 125a: Fifth insulating layer; 125t: Fifth gate terminal; DM0, DM1, DM1a: Design support method Detailed implementation manners

[0025] Hereinafter, each embodiment of the present invention will be described with reference to the accompanying drawings. In the specification of this application and each figure, the same reference numerals are attached to the same elements as those already described, and the detailed description is appropriately omitted.

[0026] Figure 1 It is a block diagram showing the functional structure of the design support system according to the embodiment.

[0027] As Figure 1 shown, the design support system 1 includes a design support device 10, a drive circuit 20, a semiconductor element 30, and a detection circuit 40.

[0028] The design support system 1 and the design support device 10 are used to set a control value group related to the semiconductor element 30. In the semiconductor element 30, a plurality of gates including a first gate and a second gate are provided. The semiconductor element 30 includes an Insulated Gate Bipolar Transistor (IGBT). The semiconductor element 30 may also include a Reverse-Conducting IGBT (RC-IGBT) having a diode and an IGBT. The control value group includes a first time difference between a first timing of applying a voltage to the first gate and a second timing of applying a voltage to the second gate. The design support device 10 searches for the control value group.

[0029] The design support device 10 sets the control value group. The drive circuit 20 inputs an electric signal corresponding to the control value group to the semiconductor element 30. The detection circuit 40 detects the output of the semiconductor element 30 when the electric signal is input to the semiconductor element 30. The detection circuit 40 sends the detected output result to the design support device 10. The design support device 10 sets a new control value group based on the output result.

[0030] Describe the specific operation of the design support system 1.

[0031] The design support device 10 includes a setting unit 11, a characteristic value calculation unit 12, a score calculation unit 13, a function calculation unit 14, a storage unit 15, an input unit 18, and an output unit 19.

[0032] The setting unit 11 sets the control value group and sends it to the drive circuit 20. When the design support device 10 receives the output result sent from the detection circuit 40, the characteristic value calculation unit 12 calculates a characteristic value representing the characteristics of the semiconductor element 30 based on the output result. For example, the output result includes the change of current with respect to time and the change of voltage with respect to time. The characteristic value includes at least one selected from the group consisting of power loss, switching speed of current, switching speed of voltage, and switching time. As the power loss, it is also possible to calculate the switching loss when turning on or off the semiconductor element 30 and the conduction loss when the semiconductor element 30 is in the on state. The switching speed of current is the change (di / dt) of current (i) with respect to time (t). The switching speed of voltage is the change (dV / dt) of voltage (V) with respect to time (t). The characteristic value may also include a value calculated using at least one selected from the group. For example, the characteristic value may include the magnitude of the power loss and the switching speed of voltage in a vector space including the power loss and the switching speed of voltage. The characteristic value calculation unit 12 sends the characteristic value to the score calculation unit 13.

[0033] The score calculation unit 13 calculates a score based on the characteristic values. The score represents an evaluation of the control value group on which the characteristic values are based. A high evaluation indicates that preferable characteristic values for the user can be obtained through the control value group. The score calculation unit 13 calculates the score by inputting the characteristic values into an objective function. The objective function is a function for calculating the score based on the characteristic values and is preset by the user. For example, the objective function is set such that the more preferable the characteristic values, the higher the calculated score. The score calculation unit 13 sends the score to the function calculation unit 14. The score calculation unit 13 associates the calculated score with the characteristic values input into the objective function and the control value group on which the characteristic values are based and stores them in the storage unit 15.

[0034] The storage unit 15 stores historical data. The historical data includes one or more data sets. Each data set includes a combination of a control value group and a score. When a new data set is stored in the storage unit 15, the function calculation unit 14 accesses the storage unit 15 and obtains the previously obtained historical data. The function calculation unit 14 calculates a first function based on the historical data. The first function is used for setting a new control value group.

[0035] For the calculation of the first function, an optimization method can be applied. As the optimization method, at least one selected from the group consisting of Bayesian optimization, response surface method, and simulated annealing method can be used. For example, in the case of using the response surface method, a response surface is calculated as the first function. In the case of using Bayesian optimization, an acquisition function is calculated as the first function. The function calculation unit 14 sends the first function to the setting unit 11. The function calculation unit 14 stores the first function in the storage unit 15.

[0036] When receiving the first function, the setting unit 11 sets a new control value group. For example, the setting unit 11 adopts a first time difference that is expected to obtain the best characteristic values in the first function. The setting unit 11 sets a new control value group including the adopted first time difference.

[0037] The design support device 10 executes a first process including the setting of the above control value group, the calculation of characteristic values, the calculation of scores, and the calculation of the first function. The design support device 10 repeats the first process. Thereby, a more preferable control value group is searched for.

[0038] The input unit 18 is used for the user to input data. The user uses the input unit 18 to store the data required for the processing of the design support device 10 in the storage unit 15.

[0039] The output unit 19 outputs the data obtained through the processing of the design support device 10 to the user. For example, the output unit 19 outputs the best characteristic values obtained by repeating the first process. The output unit 19 may also output the control value group that obtains the best score. The output unit 19 may also output the relationship between the number of repetitions of the first process and the characteristic values.

[0040] The drive circuit 20 includes a pulse generation unit 21 and a driver 22. The pulse generation unit 21 generates a pulse signal corresponding to a control value group and sends the pulse signal to the driver 22. The pulse generation unit 21 may also generate a pulse signal corresponding to the control value group and other control signals. For example, the pulse generation unit 21 receives data indicating a first timing sent from another circuit. The pulse generation unit 21 generates a first pulse for applying a voltage to a first gate of the semiconductor element 30 according to the first timing. The pulse generation unit 21 generates a second pulse for applying a voltage to a second gate of the semiconductor element 30 according to the first timing and a first time difference included in the control value group. The driver 22 is electrically connected to a plurality of gates. The driver 22 generates an electrical signal corresponding to the pulse signal and sends the electrical signal to the plurality of gates.

[0041] For example, the pulse generation unit 21 includes a pulse generator and a level converter. The pulse generation unit 21 may also include an integrated circuit. The driver 22 includes an integrated circuit. The functions of the pulse generation unit 21 and the driver 22 may also be implemented by one integrated circuit.

[0042] The detection circuit 40 is electrically connected to, for example, a collector 111 and an emitter 112 of the semiconductor element 30. The detection circuit 40 detects the voltage between the collector 111 and the emitter 112 and the current flowing between the collector 111 and the emitter 112.

[0043] Figure 2 It is a flowchart showing a design support method according to an embodiment.

[0044] For example, the design support device 10 executes Figure 2 the design support method DM0 shown. The setting unit 11 sets a control value group (step S1). The characteristic value calculation unit 12 calculates a characteristic value based on the output result of the semiconductor element 30 (step S2). The score calculation unit 13 calculates a score based on the characteristic value (step S3). The function calculation unit 14 calculates a first function based on historical data (step S4). The design support device 10 repeats steps S1 to S4. Steps S1 to S4 correspond to the first process.

[0045] Figure 3 It is a flowchart showing a design support method according to an embodiment.

[0046] For example, the design support system 1 executes Figure 3The design support method DM1 shown. Initial sampling is performed (step S11). In the initial sampling, the setting unit 11 randomly sets a control value group. The characteristic value calculation unit 12 calculates characteristic values based on the output results. The score calculation unit 13 calculates scores based on the characteristic values. In the initial sampling, the setting of the control value group, the calculation of the characteristic values, and the calculation of the scores are repeated. For example, the initial sampling is repeated 2 to 5 times. Through the repetition of the initial sampling, the data sets of the control value group and the scores are repeatedly stored in the storage unit 15.

[0047] The function calculation unit 14 calculates a first function based on the multiple data sets stored in the storage unit 15 (step S12). The setting unit 11 generates a new control value group based on the first function (step S13). The drive circuit 20 inputs an electric signal corresponding to the control value group to the semiconductor element 30 (step S14). The detection circuit 40 detects the output from the semiconductor element 30 (step S15). The characteristic value calculation unit 12 calculates characteristic values based on the output results of the semiconductor element 30 (step S16). The score calculation unit 13 calculates scores based on the characteristic values (step S17). Steps S13, S16, S17, and S12 correspond to the first process.

[0048] The function calculation unit 14 determines whether an end condition is satisfied (step S18). Before the end condition is satisfied, steps S12 to S17 are repeated. As an example of the end condition, a condition that the number of repetitions of steps S12 to S17 reaches a specified number or a condition that the score reaches a preset target value is set. Through the repetition of steps S12 to S17, a preferable control value group related to the semiconductor element is searched for.

[0049] Figures 4 to 10 It is a schematic cross-sectional view showing an example of a semiconductor element.

[0050] For example, it is possible to Figures 4 to 10 use any of the semiconductor elements 100 and 100a to 100f shown as the semiconductor element 30.

[0051] Figure 4 The semiconductor element 100 shown includes a first semiconductor region 101, a second semiconductor region 102, a third semiconductor region 103, a fourth semiconductor region 104, a semiconductor region 105, a collector 111, an emitter 112, a first gate 121, a first insulating layer 121a, a second gate 122, and a second insulating layer 122a. The semiconductor element 100 includes an IGBT. The conductivity types of the semiconductor regions described below can also be reversed.

[0052] The direction from the collector 111 toward the emitter 112 is defined as the Z direction. The first semiconductor region 101 is disposed between the collector 111 and the emitter 112 in the Z direction. The conductivity type of the first semiconductor region 101 is p-type. The first semiconductor region 101 is electrically connected to the collector 111. The second semiconductor region 102 is disposed between the first semiconductor region 101 and the emitter 112 in the Z direction. The conductivity type of the second semiconductor region 102 is n-type. The third semiconductor region 103 is disposed between a part of the second semiconductor region 102 and the emitter 112 in the Z direction. The conductivity type of the third semiconductor region 103 is p-type. The fourth semiconductor region 104 is disposed between a part of the third semiconductor region 103 and the emitter 112 in the Z direction. The conductivity type of the fourth semiconductor region 104 is n-type. The third semiconductor region 103 and the fourth semiconductor region 104 are electrically connected to the emitter 112.

[0053] A semiconductor region 105 may be disposed between the first semiconductor region 101 and the second semiconductor region 102. The conductivity type of the semiconductor region 105 is n-type. The n-type impurity concentration in the semiconductor region 105 is higher than the n-type impurity concentration in the second semiconductor region 102.

[0054] The first gate 121 and the second gate 122 are disposed between another part of the second semiconductor region 102 and the emitter 112 in the Z direction. A plurality of first gates 121 are arranged along the X direction intersecting the Z direction. A plurality of second gates 122 are arranged along the X direction. The X direction is perpendicular to the Z direction, for example. In Figure 4 the example shown, the plurality of first gates 121 and the plurality of second gates 122 are alternately arranged in the X direction.

[0055] A first insulating layer 121a is disposed between each first gate 121 and the second semiconductor region 102. A second insulating layer 122a is disposed between each second gate 122 and the second semiconductor region 102. The first gate 121 and the second gate 122 are electrically isolated from the emitter 112.

[0056] A first gate terminal 121t is electrically connected to the first gate 121. A second gate terminal 122t is electrically connected to the second gate 122. The drive circuit 20 is electrically connected to the first gate terminal 121t and the second gate terminal 122t.

[0057] In a state where a positive voltage with respect to the emitter 112 is applied to the collector 111, a voltage above the threshold is applied to one or both of the first gate 121 and the second gate 122. As a result, a channel (inversion layer) is formed in the third semiconductor region 103. Electrons are injected from the emitter 112 into the second semiconductor region 102 via the channel. When the potential difference between the collector 111 and the second semiconductor region 102 becomes small due to the injection of electrons, holes are injected from the collector 111 into the second semiconductor region 102 via the first semiconductor region 101. Conductance modulation occurs in the second semiconductor region 102, and the resistance of the second semiconductor region 102 decreases. As a result, the semiconductor element 100 switches to the on state.

[0058] After that, when the voltages applied to both the first gate 121 and the second gate 122 are lower than the threshold, the injection of electrons from the emitter into the second semiconductor region 102 stops. As a result, the injection of holes from the collector 111 into the second semiconductor region 102 also stops. As a result, the semiconductor element 100 switches to the off state.

[0059] When the semiconductor element 100 switches from the off state to the on state, switching losses are generated during the period until carriers (electrons and holes) are accumulated in the second semiconductor region 102. In addition, when the semiconductor element 100 switches from the on state to the off state, the electrons and holes accumulated in the second semiconductor region 102 are respectively discharged to the collector 111 and the emitter 112. Switching losses are generated during the period until the carriers are discharged from the second semiconductor region 102. Conduction loss is the power loss during the period when the semiconductor element 100 is in the on state.

[0060] Figure 5 The semiconductor element 100a shown differs from the semiconductor element 100 in the structure of the first semiconductor region 101. The semiconductor element 100a includes an RC-IGBT.

[0061] The first semiconductor region 101 includes a first sub-region 101a and a second sub-region 101b. The conductivity type of the first sub-region 101a is p-type. The conductivity type of the second sub-region 101b is n-type. In Figure 5 In the example shown, a plurality of first sub-regions 101a and a plurality of second sub-regions 101b are alternately arranged in the X direction.

[0062] The semiconductor element 100a includes an IGBT including the first sub-region 101a, the second semiconductor region 102, the third semiconductor region 103, the fourth semiconductor region 104, the first gate 121, and the second gate 122. The semiconductor element 100a includes a diode including the second sub-region 101b, the second semiconductor region 102, and the third semiconductor region 103.

[0063] When a positive voltage with respect to the collector 111 is applied to the emitter 112 by using an induced electromotive force or the like, the diode of the semiconductor element 100a operates. Current flows from the third semiconductor region 103 to the second semiconductor region 102 and the second sub-region 101b.

[0064] Figure 6 The semiconductor element 100b shown also includes a third gate 123. The third gate 123 is disposed between the second semiconductor region 102 and the emitter 112 in the Z direction. A plurality of third gates 123 are arranged along the X direction. In Figure 6 the example shown, one first gate 121, one second gate 122, and one third gate 123 are alternately disposed in the X direction.

[0065] A third insulating layer 123a is disposed between each third gate 123 and the second semiconductor region 102. The third gate 123 is electrically isolated from the emitter 112. The third gate terminal 123t is electrically connected to the third gate 123. The drive circuit 20 is electrically connected to the third gate terminal 123t.

[0066] Figure 7 The semiconductor element 100c shown includes a first semiconductor region 101, a second semiconductor region 102, a third semiconductor region 103, a fourth semiconductor region 104, semiconductor regions 105 to 107, a collector 111, an emitter 112, a first gate 121, a first insulating layer 121a, a second gate 122, and a second insulating layer 122a.

[0067] The direction from the collector 111 to the second gate 122 is along the X direction. The second gate 122 is separated from and electrically isolated from the collector 111. The first semiconductor region 101 is disposed between the collector 111 and the emitter 112 in the Z direction. The semiconductor region 107 is disposed between the second gate 122 and the emitter 112 in the Z direction. The direction from the first semiconductor region 101 to the semiconductor region 107 is along the X direction. The conductivity types of the semiconductor regions 106 and 107 are n-type.

[0068] The semiconductor region 106 is separated from the semiconductor region 107 in the X direction. The direction from a part of the collector 111 to the semiconductor region 106 is along the Z direction. The direction from a part of the second gate 122 to the semiconductor region 106 is along the Z direction. The second insulating layer 122a is disposed between the second gate 122 and the first semiconductor region 101, between the second gate 122 and the semiconductor region 106, and between the second gate 122 and the semiconductor region 107.

[0069] The second semiconductor region 102 is disposed between the first semiconductor region 101 and the emitter 112 and between the semiconductor region 107 and the emitter 112 in the Z direction. The third semiconductor region 103 is disposed between a part of the second semiconductor region 102 and the emitter 112 in the Z direction. The fourth semiconductor region 104 is disposed between a part of the third semiconductor region 103 and the emitter 112 in the Z direction.

[0070] The first gate 121 is disposed between another part of the second semiconductor region 102 and the emitter 112 in the Z direction. A plurality of first gates 121 are arranged along the X direction intersecting the Z direction.

[0071] In a state where a positive voltage with respect to the emitter 112 is applied to the collector 111, a voltage above the threshold is applied to the first gate 121. As a result, the semiconductor element 100c switches to the on state. When the voltage applied to the first gate 121 is greater than the threshold, a voltage above the threshold is applied to the second gate 122. A channel is formed in the semiconductor region 107, and electrons are discharged from the second semiconductor region 102 to the collector 111 via this channel. In a state where a voltage above the threshold is applied to the second gate 122, when the voltage applied to the first gate 121 drops below the threshold, the discharge of electrons from the second semiconductor region 102 can be accelerated. Thereby, the switching loss during turn-off can be reduced.

[0072] Figure 8 The semiconductor element 100d shown further includes a semiconductor region 107, a third gate 123, a third insulating layer 123a, a fourth gate 124, and a fourth insulating layer 124a as compared with the semiconductor element 100.

[0073] The first semiconductor region 101, the third gate 123, and the fourth gate 124 are disposed between the collector 111 and the second semiconductor region 102 in the Z direction. The third gate terminal 123t is electrically connected to the third gate 123. The fourth gate terminal 124t is electrically connected to the fourth gate 124. The drive circuit 20 is electrically connected to the third gate terminal 123t and the fourth gate terminal 124t. A plurality of third gates 123 are arranged along the X direction. A plurality of fourth gates 124 are arranged along the X direction. In Figure 8 the example shown, a plurality of third gates 123 and a plurality of fourth gates 124 are alternately arranged in the X direction.

[0074] The third insulating layer 123a is disposed between each third gate 123 and the second semiconductor region 102. The fourth insulating layer 124a is disposed between each fourth gate 124 and the second semiconductor region 102. The third gate 123 and the fourth gate 124 are electrically isolated from the collector 111.

[0075] The first semiconductor region 101 and the semiconductor region 107 are disposed between the third gate 123 and the fourth gate 124 adjacent to each other in the X direction. The conductivity type of the semiconductor region 107 is n-type. A plurality of mutually separated semiconductor regions 107 may also be disposed between the third gate 123 and the fourth gate 124 adjacent to each other in the X direction. The semiconductor region 107 is disposed between the collector 111 and a part of the first semiconductor region 101 in the Z direction.

[0076] In a state where a positive voltage with respect to the emitter 112 is applied to the collector 111, a voltage above the threshold is applied to the first gate 121. As a result, electrons are injected from the emitter 112 into the second semiconductor region 102. In addition, a voltage above the threshold is applied to the second gate 122. As a result, holes are injected from the collector 111 into the second semiconductor region 102. By injecting electrons and holes into the second semiconductor region 102, the semiconductor element 100d is switched to the on state.

[0077] Before the semiconductor element 100d is turned off, a voltage above the threshold is applied to the second gate 122. As a result, holes on the emitter 112 side in the second semiconductor region 102 are discharged to the emitter 112. In addition, a voltage above the threshold is applied to the fourth gate 124. As a result, electrons on the collector 111 side in the second semiconductor region 102 are discharged to the collector 111. Before turning off, carriers accumulated in the second semiconductor region 102 are discharged, thereby reducing the switching loss during turn-off.

[0078] Figure 9 The shown semiconductor element 100e further includes a fifth gate 125 as compared with the semiconductor element 100d. The first gate 121, the second gate 122, and the fifth gate 125 are disposed between the second semiconductor region 102 and the emitter 112 in the Z direction. A fifth insulating layer 125a is disposed between the fifth gate 125 and the second semiconductor region 102. The fifth gate terminal 125t is electrically connected to the fifth gate 125. The drive circuit 20 is electrically connected to the first gate terminal 121t and the second gate terminal 122t. In Figure 9 In the shown example, one first gate 121, one second gate 122, and one fifth gate 125 are alternately disposed in the X direction.

[0079] The operations of the first gate 121 to the fourth gate 124 are the same as those of the semiconductor element 100d. In the semiconductor element 100e, when turned on, a voltage above the threshold is applied to the fifth gate 125. Thereby, the injection of electrons into the second semiconductor region 102 is promoted, and the switching loss at turn-on is reduced. In addition, when the semiconductor element 100e is in the on state, the voltage applied to the fifth gate 125 is less than the threshold. The discharge of holes from the second semiconductor region 102 to the emitter 112 is suppressed, and the carrier density in the second semiconductor region 102 can be increased. Thereby, the conduction loss in the semiconductor element 100e can be reduced.

[0080] Figure 10 The semiconductor element 100f shown is different from the semiconductor element 100d in that the first semiconductor region 101 includes a first sub-region 101a and a second sub-region 101b. The semiconductor element 100f includes an RC-IGBT.

[0081] The operation of the semiconductor element 100f as an IGBT is the same as that of the semiconductor element 100d. When the semiconductor element 100f operates as a diode, before the end of the diode operation, a voltage above the threshold is applied to at least one of the first gate 121 and the second gate 122. Thereby, the discharge of electrons to the emitter 112 is promoted. In addition, a voltage above the threshold is applied to at least one of the third gate 123 and the fourth gate 124. Thereby, the discharge of holes to the collector 111 is promoted. As a result, the reverse recovery loss during diode operation is reduced.

[0082] When the semiconductor element 100b is used, the control value group may further include a second time difference between the first timing of applying a voltage to the first gate and the third timing of applying a voltage to the third gate. The control value group may include at least one selected from the group consisting of a third voltage value applied to the third gate 123 and a third resistance of the third gate 123.

[0083] When the semiconductor element 100d is used, the control value group may further include the second time difference. The control value group may further include a third time difference between the first timing of applying a voltage to the first gate and the fourth timing of applying a voltage to the fourth gate. The control value group may include at least one selected from the group consisting of a third voltage value applied to the third gate 123, a third resistance of the third gate 123, a fourth voltage value applied to the fourth gate 124, and a fourth resistance of the fourth gate 124.

[0084] Figure 11 It is a schematic diagram illustrating a hardware configuration.

[0085] The design support device 10 according to the embodiment can pass through Figure 11It is implemented by the hardware structure shown below. Figure 11 The processing device 90 shown in the figure includes a CPU 91, a ROM 92, a RAM 93, a storage device 94, an input interface 95, an output interface 96, and a communication interface 97.

[0086] The ROM 92 stores a program for controlling the operation of the computer. In the ROM 92, programs required for the computer to implement the above-mentioned various processes are stored. The RAM 93 functions as a storage area where the programs stored in the ROM 92 are expanded.

[0087] The CPU 91 includes a processing circuit. The CPU 91 uses the RAM 93 as a working memory and executes the program stored in at least any one of the ROM 92 or the storage device 94. During the execution of the program, the CPU 91 controls each structure via the system bus 98 and executes various processes.

[0088] The storage device 94 stores data required for the execution of the program and data obtained through the execution of the program.

[0089] The input interface (I / F) 95 connects the processing device 90 to the input device 95a. The input I / F 95 is, for example, a serial bus interface such as USB. The CPU 91 can read various data from the input device 95a via the input I / F 95.

[0090] The output interface (I / F) 96 connects the processing device 90 to the output device 96a. The output I / F 96 is, for example, an image output interface such as a Digital Visual Interface (DVI) or a High-Definition Multimedia Interface (HDMI: registered trademark). The CPU 91 sends data to the output device 96a via the output I / F 96. The output device 96a outputs the data.

[0091] The communication interface (I / F) 97 connects the server 97a outside the processing device 90 to the processing device 90. The communication I / F 97 is, for example, a network card such as a LAN card. The CPU 91 can read various data from the server 97a via the communication I / F 97.

[0092] The storage device 94 includes one or more selected from a hard disk drive (HDD) and a solid state drive (SSD). The input device 95a includes one or more selected from a mouse, a keyboard, a microphone (voice input), and a touchpad. The output device 96a includes one or more selected from a monitor, a printer, a speaker, and a projector. A device having the functions of both the input device 95a and the output device 96a, such as a touch panel, may also be used.

[0093] The processing device 90 functions as a setting unit 11, a characteristic value calculation unit 12, a score calculation unit 13, and a function calculation unit 14. The functions of the setting unit 11, the characteristic value calculation unit 12, the score calculation unit 13, and the function calculation unit 14 may also be realized by the cooperation of multiple processing devices. When realizing the functions of the setting unit 11, the characteristic value calculation unit 12, the score calculation unit 13, and the function calculation unit 14, a processing device different from a part of the processing devices may be connected via a network. For example, a part of the functions of the setting unit 11, the characteristic value calculation unit 12, the score calculation unit 13, and the function calculation unit 14 may be provided by a cloud server.

[0094] The storage device 94 functions as a storage unit 15. The input device 95a functions as an input unit 18. The output device 96a functions as an output unit 19.

[0095] Describe the advantages of the embodiment.

[0096] Regarding a semiconductor element including a plurality of gates, there is a method of staggering the timing of applying a voltage to the gates between the gates. Thereby, the characteristics of the semiconductor element can be improved. For example, power loss can be reduced. In order to effectively improve the characteristics, it is desirable to set the time difference of the voltage application between the gates according to the structure of the semiconductor element. Conventionally, a person has changed the time difference while confirming the characteristics of the semiconductor element to search for the time difference.

[0097] According to the embodiment, a control value group including a first time difference is set using a first function calculated from historical data. For example, compared with the case where a person sets the control value group based on experience, intuition, etc., a better control value group can be searched efficiently. According to the design support device 10 according to the embodiment, the control value group is automatically searched. There is no need for a person to search for the control value group, and the design efficiency can be improved.

[0098] The first function is preferably calculated by Bayesian inference. For example, in Figure 3In step S12 of the design support method DM1 shown, the function calculation unit 14 infers a surrogate model of the score based on historical data. The function calculation unit 14 calculates an acquisition function as the first function based on the surrogate model of the score. The setting unit 11 sets a new control value group using the acquisition function.

[0099] According to Bayesian inference, compared with the response surface method, there is a high possibility of obtaining a preferable control value group with less processing time. Or, according to Bayesian inference, compared with the response surface method, the possibility of searching for a more preferable control value group can be improved. A more preferable control value group refers to a control value group that can obtain better characteristic values.

[0100] The control value group set using the first function may also include at least one selected from the group consisting of the first voltage value applied to the first gate 121, the second voltage value applied to the second gate 122, the first resistance of the first gate 121, and the second resistance of the second gate 122 instead of including the first time difference. The control value group may also include at least one selected from the group in addition to including the first time difference.

[0101] For example, the first gate 121 and the second gate 122 each include a gate resistance connected in series with an electrode portion provided in the second semiconductor region 102. The first gate resistance and the second gate resistance include variable resistors. The first gate resistance of the first gate 121 and the second gate resistance of the second gate 122 can be independently adjusted respectively.

[0102] Regarding at least one control value selected from the group, a more preferable value can be obtained through search. For example, a control value with lower power consumption can be obtained through search.

[0103] (First modification example)

[0104] Figure 12 It is a flowchart showing a design support method according to the first modification example of the embodiment.

[0105] The design support device 10 may also execute the second sub - process during the execution of the first sub - process. The first sub - process includes step S12. The second sub - process includes Figure 3 Steps S13 to S17 of the shown flowchart. That is, in one first process, the first sub - process and the second sub - process are executed.

[0106] In Figure 12In the design support method DM1a according to the first modification example shown, initial sampling is performed (step S11). The function calculation unit 14 calculates the first function (step S12). In the calculation of the first function, the setting unit 11 sets a control value group (step S13). The drive circuit 20 inputs an electrical signal to the semiconductor element 30 (step S14). The detection circuit 40 detects the output from the semiconductor element 30 (step S15). The characteristic value calculation unit 12 calculates characteristic values (step S16). The score calculation unit 13 calculates a score (step S17). During the execution of step S12 for the first time, the control value group is set randomly.

[0107] After step S17, the setting unit 11 determines whether the end condition of the second sub - process is satisfied (step S21). As the end condition, the condition that the calculation of the first function is completed is set. As the end condition, the condition that the number of repetitions of steps S12 to S17 reaches a specified number can also be set.

[0108] After step S12 is completed and it is determined in step S21 that the end condition is satisfied, the setting unit 11 determines whether the end condition for the repetition of the first sub - process and the second sub - process is satisfied (step S18). If the end condition is not satisfied, steps S12 and S13 are executed again. At this time, in step S13, the control value group is set using the first function obtained in the immediately preceding step S12.

[0109] The time required for the calculation of the first function is longer than the time required for the detection of the output from the semiconductor element 30, the calculation of characteristic values, the calculation of scores, etc. By executing the second sub - process during the execution of the first sub - process, the processing time required for searching the control value group can be shortened. By stopping the repetition of the second sub - process corresponding to the completion of the first sub - process, the time for one execution of the first process can be shortened. According to the design support method DM1a, compared with the design support method DM1, the number of executions of the second sub - process in the same time can be increased. The possibility of more quickly searching for an optimal control value group can be improved.

[0110] (Second Modification Example)

[0111] Figure 13 It is a block diagram showing the functional structure of the design support system according to the second modification example of the embodiment.

[0112] As Figure 13 shown, the design support system 1b according to the second modification example includes an electrical device 2, a design support device 10, and a detection circuit 40. The electrical device 2 includes a control circuit 10a, a drive circuit 20, and a semiconductor element 30.

[0113] The setting unit 11 sends the set control value group to the control circuit 10a. The control circuit 10a controls the drive circuit 20 in such a way as to send an electric signal corresponding to the control value group to the semiconductor element 30.

[0114] The control circuit 10a includes a storage unit. The control value group obtained by the search is stored in the storage unit. For example, in the design support system 1b according to the second modification, before the electrical device 2 is assembled into another product, the search for the control value group is executed. After the electrical device 2 is assembled into another product, the control circuit 10a operates the drive circuit 20 according to the control value group stored in the storage unit.

[0115] According to the second modification, it is possible to provide the electrical device 2 that exhibits more preferable characteristics.

[0116] (Third Modification)

[0117] Figure 14 It is a block diagram showing the functional structure of the electrical device according to the third modification of the embodiment.

[0118] As Figure 14 shown, the electrical device 2a according to the third modification includes a control circuit 10b, a drive circuit 20, a semiconductor element 30, and a detection circuit 40.

[0119] The control circuit 10b functions as the design support device 10 in the design support system 1. The control circuit 10b sets the control value group. The control circuit 10b controls the drive circuit 20 in such a way as to send an electric signal corresponding to the control value group to the semiconductor element 30. For example, the electrical device 2a according to the third modification searches for the control value group after being assembled into another product.

[0120] For example, the electrical device 2a executes Figure 3 the design support method DM1 shown. Whenever the electrical device 2a obtains the output result from the semiconductor element 30, it executes the calculation of the first function, the setting of a new control value group, etc. Thus, during the operation of the electrical device 2a, it is possible to improve the control value group in real time.

[0121] Figure 15 It is a flowchart showing other operations of the electrical device according to the third modification of the embodiment.

[0122] The electrical device 2a may also execute Figure 15The design support method DM2 shown. In the design support method DM2, initial sampling is performed (step S11). The function calculation unit 14 calculates the first function (step S12). The setting unit 11 sets a control value group based on the calculated first function (step S13). The electrical device 2a performs sampling using the set control value group (step S31). During sampling, the input to the semiconductor element 30, detection, calculation of characteristic values, and calculation of scores are repeated. The data set of the control value group and scores is repeatedly saved to the storage unit 15.

[0123] The electrical device 2a accumulates the data set until the end condition is satisfied. For example, the end condition is the condition that the operation time of the electrical device 2a has elapsed. When the end condition is satisfied, the function calculation unit 14 calculates the first function based on the historical data.

[0124] For example, according to the design support method DM2, during the operation period of the electrical device 2a, the data set is accumulated without changing the design value group. During the non-operation period of the electrical device 2a, the design value group is changed. According to the design support method DM2, for example, the operation of the electrical device 2a can be made more stable.

[0125] (Fourth modification example)

[0126] Figure 16 It is a block diagram showing the functional structure of the electrical device according to the fourth modification example of the embodiment.

[0127] The electrical device 2b according to the fourth modification example is different from the electrical device 2a in that it includes an electrical component 31. The electrical component 31 includes a semiconductor element 30. The electrical component 31 is, for example, a motor.

[0128] The detection circuit 40 detects the output of the electrical component 31. The characteristic value calculation unit 12 calculates a characteristic value representing the characteristic of the electrical component 31 based on the output result. When the electrical component 31 is a motor, the detection circuit 40 detects the current value flowing through the motor. In this case, the detection circuit 40 includes, for example, a current detection resistor (shunt resistor). Alternatively, the detection circuit 40 may detect the position (angle) of the motor. In this case, the detection circuit 40 includes a rotation angle sensor (e.g., a Hall sensor or a resolver). The characteristic value calculation unit 12 calculates a characteristic value representing the characteristic of the electrical component 31 based on the output result. In any case, the characteristic value is, for example, the rotational speed of the motor.

[0129] According to the design support system 1, the operating conditions of the semiconductor element 30 when searching for the control value group may be different from the operating conditions when actually using the semiconductor element 30. That is, the characteristics obtained during the search may be different from the characteristics obtained when actually using the semiconductor element 30. According to the third modification example, the control value group can be set based on the output when actually using the semiconductor element 30. Therefore, the characteristics obtained when actually using the semiconductor element 30 can be set to more preferable values.

[0130] The processing of the above various data can also be recorded on a magnetic disk (such as a floppy disk and a hard disk), an optical disk (such as a CD-ROM, CD-R, CD-RW, DVD-ROM, DVD±R, DVD±RW, etc.), a semiconductor memory, or other non-transitory computer-readable recording media as a program that can be executed by a computer.

[0131] For example, the information recorded on the recording medium can be read by a computer (or an embedded system). In the recording medium, the recording format (storage format) is arbitrary. For example, the computer reads the program from the recording medium, and the CPU executes the instructions described in the program according to the program. In the computer, the acquisition (or reading) of the program can also be performed via a network.

[0132] The embodiments may also include the following technical solutions.

[0133] (Technical solution 1)

[0134] A design support device that executes a first process, in which:

[0135] For a semiconductor element provided with a plurality of gates including a first gate and a second gate, a control value group including a first time difference between a first timing for applying a voltage to the first gate and a second timing for applying a voltage to the second gate is set.

[0136] Based on the output result when an electric signal corresponding to the control value group is input to the semiconductor element, a characteristic value representing the characteristics of the semiconductor element is calculated.

[0137] Based on historical data including one or more data sets of a score based on the characteristic value and the control value group, a first function is calculated.

[0138] The design support device uses the first function to set a new control value group.

[0139] (Technical solution 2)

[0140] According to the design support device described in Technical solution 1, wherein

[0141] Repeat the execution of the first process.

[0142] (Technical solution 3)

[0143] The design support device according to Technical solution 2, wherein

[0144] One execution of the first process includes:

[0145] A first sub-process, including the calculation of the first function; and

[0146] A second sub-process, including the setting of the control value group and the calculation of the characteristic value,

[0147] The design support device executes the second sub-process during the execution of the first sub-process.

[0148] (Technical solution 4)

[0149] The design support device according to Technical solution 3, wherein

[0150] In one execution of the first process, the second sub-process is repeatedly performed during the execution of the first sub-process, and the repetition of the second sub-process is stopped corresponding to the completion of the first sub-process.

[0151] (Technical solution 5)

[0152] The design support device according to any one of Technical solutions 1 to 4, wherein

[0153] The score is calculated by inputting the characteristic value into an objective function,

[0154] The first function is calculated by Bayesian inference based on the historical data,

[0155] The new control value group is set according to the first function.

[0156] (Technical solution 6)

[0157] The design support device according to any one of Technical solutions 1 to 5, wherein

[0158] The control value group further includes at least one selected from the group consisting of a first voltage value applied to the first gate, a second voltage value applied to the second gate, a first resistance of the first gate, and a second resistance of the second gate.

[0159] (Technical solution 7)

[0160] The design support device according to any one of Technical solutions 1 to 6, wherein

[0161] The output result includes the change of current with respect to time and the change of voltage with respect to time.

[0162] The characteristic value includes power loss.

[0163] (Technical solution 8)

[0164] The design support device according to any one of technical solutions 1 to 7, wherein

[0165] The plurality of gates further includes a third gate.

[0166] The control value group further includes a second time difference between the first timing and the third timing for applying a voltage to the third gate.

[0167] (Technical solution 9)

[0168] The design support device according to any one of technical solutions 1 to 8, wherein

[0169] The semiconductor element includes an IGBT.

[0170] (Technical solution 10)

[0171] A design support system includes:

[0172] The design support device according to any one of technical solutions 1 to 9;

[0173] A drive circuit that inputs the electrical signal to the semiconductor element; and

[0174] A detection circuit that detects the output from the semiconductor element and generates the output result.

[0175] (Technical solution 11)

[0176] An electrical device includes:

[0177] A semiconductor element provided with a plurality of gates including a first gate and a second gate; and

[0178] A control circuit electrically connected to the plurality of gates, the control circuit:

[0179] Sets a control value group including a first time difference between a first timing for applying a voltage to the first gate and a second timing for applying a voltage to the second gate,

[0180] Calculates a characteristic value representing the characteristics of an electrical component including the semiconductor element based on the output result when an electrical signal corresponding to the control value group is input to the semiconductor element.

[0181] Calculate a first function based on historical data including one or more data sets of scores based on the characteristic values and the control value group, and set the new control value group using the first function.

[0182] (Technical solution 12)

[0183] A design support method, in which a first process is performed, and in this first process:

[0184] For a semiconductor element provided with a plurality of gates including a first gate and a second gate, set a control value group including a first time difference between a first timing of applying a voltage to the first gate and a second timing of applying a voltage to the second gate,

[0185] Calculate a characteristic value representing the characteristics of the semiconductor element according to the output result when an electric signal corresponding to the control value group is input to the semiconductor element,

[0186] Calculate a first function based on historical data including one or more data sets of scores based on the characteristic values and the control value group,

[0187] In the design support method, use the first function to set the new control value group.

[0188] (Technical solution 13)

[0189] According to the design support method described in Technical solution 12, wherein,

[0190] Repeat the execution of the first process.

[0191] (Technical solution 14)

[0192] According to the design support method described in Technical solution 13, wherein,

[0193] One execution of the first process includes:

[0194] A first sub-process including the calculation of the first function; and

[0195] A second sub-process including the setting of the control value group and the calculation of the characteristic value,

[0196] During the execution of the first sub-process, execute the second sub-process.

[0197] (Technical solution 15)

[0198] According to the design support method described in Technical solution 14, wherein,

[0199] In the 1st first process, the 2nd second process is repeated during the execution of the 1st first sub-process, and the repetition of the 2nd second process is stopped corresponding to the completion of the 1st first sub-process.

[0200] (Technical solution 16)

[0201] A program that causes a processing device to execute a 1st first process, in which:

[0202] For a semiconductor element provided with a plurality of gates including a 1st first gate and a 2nd second gate, a control value group including a 1st first time difference between a 1st first timing for applying a voltage to the 1st first gate and a 2nd second timing for applying a voltage to the 2nd second gate is set.

[0203] Based on the output result when an electric signal corresponding to the control value group is input to the semiconductor element, a characteristic value representing the characteristics of the semiconductor element is calculated.

[0204] Based on historical data including one or more data sets of scores based on the characteristic value and the control value group, a 1st first function is calculated.

[0205] The program causes the processing device to set a new control value group using the 1st first function.

[0206] (Technical solution 17)

[0207] According to the program described in Technical solution 16, wherein,

[0208] The processing device is caused to repeatedly execute the 1st first process.

[0209] (Technical solution 18)

[0210] According to the program described in Technical solution 17, wherein,

[0211] One 1st first process includes:

[0212] A 1st first sub-process including the calculation of the 1st first function; and

[0213] A 2nd second sub-process including the setting of the control value group and the calculation of the characteristic value.

[0214] The program causes the processing device to execute the 2nd second sub-process during the execution of the 1st first sub-process.

[0215] (Technical solution 19)

[0216] According to the program described in Technical solution 18, wherein,

[0217] Cause the processing device to repeat the second sub - process during the execution of the first sub - process in the first process, and stop the repetition of the second sub - process corresponding to the completion of the first sub - process.

[0218] (Technical solution 20)

[0219] A storage medium stores the program described in any one of Technical solutions 16 to 19.

[0220] According to the embodiments described above, it is possible to provide a design support device, a design support system, an electrical device, a design support method, a program, and a storage medium that can search for a control value group more efficiently.

[0221] In the specification of this application, "vertical" is not strictly vertical. For example, it includes deviations in the manufacturing process, etc., as long as it is substantially vertical.

[0222] Above, the embodiments of the present invention have been described with reference to specific examples. However, the embodiments of the present invention are not limited to these specific examples. For example, in terms of the specific structures of each element such as the design support device, the control circuit, the drive circuit, the semiconductor element, and the detection circuit, those skilled in the art appropriately select from the known range and thus implement the present invention in the same way. As long as the same effects can be obtained, they are included in the scope of the present invention.

[0223] In addition, examples of combining any two or more elements in the specific examples within the technically possible range are also included in the scope of the present invention as long as they include the gist of the present invention.

[0224] In addition, based on the design support device, the design support system, the electrical device, the design support method, the program, and the storage medium described above as embodiments of the present invention, all design support devices, design support systems, electrical devices, design support methods, programs, and storage media that those skilled in the art can appropriately modify the design and implement also belong to the scope of the present invention as long as they include the gist of the present invention.

[0225] In addition, it should be understood that within the scope of the idea of the present invention, those skilled in the art can think of various modification examples and correction examples, and these modification examples and correction examples also belong to the scope of the present invention.

[0226] Several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their variations are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Claims

1. A design support device that performs a first process, in which: For a semiconductor element provided with a plurality of gates including a first gate and a second gate, a control value group including a first time difference between a first timing of applying a voltage to the first gate and a second timing of applying a voltage to the second gate is set; Based on the output result when an electrical signal corresponding to the control value group is input to the semiconductor element, a characteristic value representing the characteristics of the semiconductor element is calculated; Based on historical data including one or more data sets of scores based on the characteristic values and the control value group, a first function is calculated; The design support device uses the first function to set a new control value group.

2. The design support device according to claim 1, wherein, The first process is repeatedly executed.

3. The design support device according to claim 2, wherein, One first process includes: A first sub-process including the calculation of the first function; and A second sub-process including the setting of the control value group and the calculation of the characteristic value, During the execution of the first sub-process, the second sub-process is executed.

4. The design support device according to claim 3, wherein, In one first process, during the execution of the first sub-process, the second sub-process is repeatedly performed, and the repetition of the second sub-process is stopped corresponding to the completion of the first sub-process.

5. A design support system, comprising: The design support device according to any one of claims 1 to 4; A drive circuit that inputs the electrical signal to the semiconductor element; and A detection circuit that detects the output from the semiconductor element and generates the output result.

6. An electrical device, comprising: A semiconductor element provided with a plurality of gates including a first gate and a second gate; and A control circuit electrically connected to the plurality of gates, the control circuit: Sets a control value group including a first time difference between a first timing of applying a voltage to the first gate and a second timing of applying a voltage to the second gate; Based on the output result when an electrical signal corresponding to the control value group is input to the semiconductor element, calculates a characteristic value representing the characteristics of an electrical component including the semiconductor element; Calculates a first function based on historical data including one or more data sets of scores based on the characteristic value and the control value group, and sets a new control value group using the first function.

7. A design support method, in which a first process is executed, in which: For a semiconductor element provided with a plurality of gates including a first gate and a second gate, a control value group including a first time difference between a first timing of applying a voltage to the first gate and a second timing of applying a voltage to the second gate is set; Based on the output result when an electrical signal corresponding to the control value group is input to the semiconductor element, a characteristic value representing the characteristics of the semiconductor element is calculated; Based on historical data including one or more data sets of scores based on the characteristic value and the control value group, a first function is calculated; In the design support method, the first function is used to set a new control value group.

8. The design support method according to claim 7, wherein, the first process is repeatedly executed.

9. A storage medium storing a program that causes a processing device to execute a first process, in which: For a semiconductor element provided with a plurality of gates including a first gate and a second gate, a control value group including a first time difference between a first timing for applying a voltage to the first gate and a second timing for applying a voltage to the second gate is set, Based on the output result when an electric signal corresponding to the control value group is input to the semiconductor element, a characteristic value representing the characteristics of the semiconductor element is calculated, A first function is calculated based on historical data including one or more data sets of a score based on the characteristic value and the control value group, The program causes the processing device to use the first function to set a new control value group.

10. The storage medium according to claim 9, wherein, the processing device is caused to repeatedly execute the first process.

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