Main conversion circuit, power conversion device and moving body

Abstract

Main conversion circuit (201), comprising: a plurality of semiconductor devices (1) connected in parallel; a gate driver (13) that provides a gate voltage to the gates of the plurality of semiconductor devices (1); and a gate wire (14, 16) which is sequentially connected from the gate driver (13) to the gates of the plurality of semiconductor devices (1), wherein an excitation capacity of each of the semiconductor devices (1) indicates how easily a collector current flows in response to the provided gate voltage, and the multitude of semiconductor devices (1) with a lower excitation capability is connected closer to the gate driver (13).

Description

Area

[0001] The present invention relates to a main conversion circuit, a power conversion device and a moving body. background

[0002] With each new generation of main conversion circuits, increasing the available current capacity becomes essential. One method for increasing current capacity utilizes parallel-connected semiconductor devices. Since a certain amount of current can be determined during circuit design, independent of a range of products, the use of parallel-connected semiconductor devices has increased in recent years. When one of the parallel-connected semiconductor devices reaches the end of its lifetime, this also marks the end of the main conversion circuit's lifetime. If the loads (such as currents) applied to the semiconductor devices are unbalanced, their lifetimes will also become unbalanced, raising concerns that the main conversion circuit's lifetime will be shortened.

[0003] To ensure isolation, a multitude of semiconductor devices are aligned in the same direction, with a gate driver placed at either the right or left end of each aligned device. Therefore, when the multitude of semiconductor devices are driven by a single gate driver, a difference in distance and wire length is created between each device and the gate driver. Devices with a smaller or closer wiring distance to the gate driver receive a higher applied gate voltage and conduct current more readily. Since large loads are applied to the more readily conducting devices, there is concern that their lifetime will be reduced.

[0004] Accordingly, it is proposed to prepare gate drivers for the respective parallel-connected semiconductor devices and to individually adjust the gate drivers so that a higher gate voltage is applied to a device with a higher gate threshold voltage in order to suppress the imbalance of loads applied to the devices (see, for example, patent reference 1). It is also proposed to add a collector current detection function to the semiconductor devices to detect a current imbalance and to apply a positive offset to a gate threshold voltage of the semiconductor devices exhibiting a low current in order to suppress the current imbalance (see, for example, patent reference 2). List of citations from patent literature [PTL 1] JP 2008-178248 A [PTL 2] JP 2004-229382 A Summary Technical Problem

[0005] However, conventional technologies require the preparation of a large number of gate drivers or the connection of an additional circuit with transistors, which creates a problem of increasing the size and complexity of the devices.

[0006] The present invention was made to solve the problems described above, and it is an object of the present invention to provide a main conversion circuit, a power conversion device and a moving body which are able to increase electrical performance and reliability while avoiding an increase in the size and complexity of devices. Solution to the problem

[0007] A main conversion circuit according to the present invention comprises: a plurality of semiconductor devices connected in parallel; a gate driver providing a gate voltage to the gates of the plurality of semiconductor devices; and a gate wire sequentially connected from the gate driver to the gates of the plurality of semiconductor devices, wherein an excitation level of each of the semiconductor devices indicates how readily a collector current flows in response to the provided gate voltage, and the plurality of semiconductor devices with a lower excitation level is connected closer to the gate driver. Advantageous effects of the invention

[0008] In the present invention, the plurality of semiconductor devices exhibiting lower excitation capability are connected closer to the gate driver. As a result, it is possible to increase electrical performance and reliability while avoiding the increase in device size and complexity. Brief description of the drawings Fig. Figure 1 is a top view showing a semiconductor device according to embodiment 1 of the present invention. Fig. Figure 2 is a top view showing a main conversion circuit according to embodiment 1 of the present invention. Fig. Figure 3 is a circuit diagram representing the main conversion circuit according to embodiment 1 of the present invention. Fig. Figure 4 is a block diagram illustrating a configuration of an electrical power conversion system for which the electrical power conversion device according to the embodiment is used. Description of embodiments

[0009] With reference to the drawings, a main conversion circuit, a power conversion device, and a moving body according to embodiments of the present invention are described. The same components are designated by the same symbols, and their repeated description can be omitted. Design 1

[0010] Fig. Figure 1 is a top view depicting a semiconductor device according to embodiment 1 of the present invention. The semiconductor device 1 contains a MOS transistor. An AC output terminal 2 is provided at one end of the semiconductor device 1 in a longitudinal direction along a housing, and a positive voltage input terminal 3 and a negative voltage input terminal 4 are provided at the other end. The positive voltage input terminal 3 is a main terminal of the high-voltage side, and the negative voltage input terminal 4 is a main terminal of the ground side. Between these terminals are a gate terminal 5 of the high-voltage side, an emitter auxiliary terminal 6 of the high-voltage side, a gate terminal 7 of the low-voltage side, and an emitter auxiliary terminal 8 of the low-voltage side.

[0011] Fig. Figure 2 is a top view showing a main conversion circuit according to embodiment 1 of the present invention. Fig. Figure 3 is a circuit diagram illustrating the main conversion circuit according to embodiment 1 of the present invention. Due to spatial isolation distance and surface isolation distance limitations, a plurality of semiconductor devices 1 are aligned in the same direction. Each of the semiconductor devices 1 comprises transistors 9 and 10 and reflux diodes 11 and 12. The transistors 9 of the plurality of semiconductor devices 1 are connected in parallel. Similarly, the transistors 10 of the plurality of semiconductor devices 1 are also connected in parallel.

[0012] A gate driver 13 provides a gate voltage to the gates of the plurality of semiconductor devices 1. The gate driver 13 is positioned at the end of either the right or left side of the aligned semiconductor devices 1. A gate wire 14 of the high-voltage side is sequentially connected from the gate driver 13 to the gate terminals 5 of the high-voltage side of the plurality of semiconductor devices 1. An emitter wire 15 of the high-voltage side is sequentially connected to the emitter auxiliary terminals 6 of the high-voltage side of the plurality of semiconductor devices 1. A gate wire 16 of the low-voltage side is sequentially connected to the gate terminals 7 of the low-voltage side of the plurality of semiconductor devices 1. An emitter wire 17 of the low-voltage side is sequentially connected to the emitter auxiliary terminals 8 of the low-voltage side of the plurality of semiconductor devices 1.The gate wire 14 of the high-voltage side has an inductor L1 and a resistor R1 between the gate driver 13 and the semiconductor devices 1, and between adjacent semiconductor devices 1. The gate wire 16 of the low-voltage side has an inductor L2 and a resistor R2 between the gate driver 13 and the semiconductor devices 1, and between adjacent semiconductor devices 1.

[0013] The multitude of semiconductor devices 1 with a lower excitation capability is more closely connected to the gate driver 13. The excitation capability of each of the transistors 9 indicates how readily a collector current flows in response to an applied gate voltage. Of course, one can consider the characteristics of either transistor 9 or 10 contained in each of the semiconductor devices 1. Since the transistors 9 and 10 contained in the same semiconductor device 1 generally exhibit similar characteristics, the same effect can be achieved regardless of which characteristics are considered. Attention can also be paid to the average of the characteristics of the two transistors 9 and 10.

[0014] In the present embodiment, the plurality of semiconductor devices 1 with a lower excitation capability is connected closer to the gate driver 13. Therefore, the wiring distance of the transistors 9 with the lower excitation capability from the gate driver 13 is shorter, resulting in a smaller resistance between the gate driver 13 and the gates. Consequently, a higher gate voltage is provided to the transistors 9 with the lower excitation capability. Therefore, it is possible to suppress the imbalance of the current flowing into the plurality of parallel-connected semiconductor devices 1 without adding any further circuitry. This measure to shift the imbalance suppresses deviations in the lifetime of the plurality of parallel-connected semiconductor devices 1, and the lifetime of the main conversion circuit is extended compared to that of a conventional configuration.As a result, it is possible to increase electrical performance and reliability while avoiding the enlargement and complication of the devices.

[0015] For example, a collector-emitter saturation voltage VCE(sat) can be used as the excitation potential. The VCE(sat) is the voltage between a collector and an emitter when a rated current is applied to transistor 9. In this case, the multitude of semiconductor devices 1 with a higher VCE(sat) are connected closer to the gate driver 13. Accordingly, a higher gate voltage is provided to the transistors with a higher VCE(sat). Therefore, the VCE(sat) of the multitude of parallel-connected semiconductor devices 1 is balanced, so that the current imbalance can be suppressed. In the case of a main conversion circuit for electric railways, the VCE(sat) can often be obtained for all devices, and therefore an arrangement of the devices can be determined relatively easily. Utilizing the VCE(sat) is most effective for suppressing a current imbalance during regular operation.If the goal is to increase the reliability of the main conversion circuit, it is desirable to use this parameter.

[0016] The excitation capability can also be a gate threshold voltage VGE(th). VGE(th) is the gate voltage required to supply 1 / 10000 of a rated current when a specified voltage is applied across the collector and emitter. In this case, the multitude of semiconductor devices 1 with a higher VGE(th) are connected closer to the gate driver 13. Consequently, a higher gate voltage is provided to the transistors with a higher VGE(th). Therefore, a difference between VGE(th) and VGE is balanced among the multitude of parallel-connected semiconductor devices 1, making it possible to suppress the imbalance of the current and saturation current quantities. By taking this parameter into account, the imbalance of the saturation current quantity is suppressed, and therefore, the imbalance of short-circuit tolerance is also suppressed.This makes it possible to increase the reliability of the device at the time of a circuit malfunction. Therefore, this parameter is suitable for consumer electronics in railways.

[0017] The excitation capability can also be achieved by utilizing a time delay tdon of a line start. tdon is the delay time after a prescribed gate voltage is applied to the transistors until a prescribed amount of current begins to flow. In this case, the multitude of semiconductor devices 1 with a higher tdon is connected closer to the gate driver 13. Accordingly, a higher gate voltage is provided to the transistors with a higher tdon. Therefore, the imbalance of tdon in the multitude of parallel-connected semiconductor devices 1 can be suppressed, making it possible to prevent the current from concentrating on some of the transistors at the time of line start. It is also possible to suppress an imbalance of the dead time among the semiconductor devices.Accordingly, this parameter is suitable for conversion circuits (such as SIV) that are assumed to perform a high-speed operation.

[0018] The wide variety of semiconductor devices 1 is not limited to those made of silicon, but can be made of wide-bandgap semiconductors that have a larger bandgap than silicon. Examples of wide-bandgap semiconductors include silicon carbide, gallium nitride-based materials, and diamond.

[0019] Since silicon carbide devices have a faster switching speed than silicon devices, current imbalance and electromagnetic noise are more likely to occur. Therefore, conventional techniques, which require multiple gate drivers or additional circuitry, necessitate a noise countermeasure that is more stringent than that provided by silicon devices. However, in the present embodiment, even when using silicon carbide devices, a single gate driver is sufficient, thus eliminating the need for additional circuitry.

[0020] A power semiconductor device formed from such a wide-bandgap semiconductor exhibits high dielectric strength and high permissible current density, and can therefore be miniaturized. The use of such a miniaturized device enables the miniaturization and high integration of the semiconductor module in which the device is incorporated. Furthermore, since the device has high thermal resistance, a heat sink's heat sink fin can be miniaturized, and a water-cooled component can be air-cooled, leading to further miniaturization of the semiconductor module. Because the device exhibits low power loss and high efficiency, a highly efficient semiconductor module can also be achieved. Second embodiment

[0021] In this embodiment, the main conversion circuit according to the first embodiment described above is used for an electrical power conversion device. Although the present invention is not limited to a specific electrical power conversion device, a case in which the present invention is used for a three-phase inverter is described below as a second embodiment.

[0022] Fig.Figure 4 is a block diagram illustrating a configuration of an electrical power conversion system for which the electrical power conversion device according to the embodiment is used. This electrical power conversion system comprises a power supply 100, an electrical power conversion device 200, and a load 300. The power supply 100 is a DC power supply and provides DC power to the electrical power conversion device 200. The power supply 100 can consist of various components. For example, the power supply 100 can consist of a DC system, a solar cell, or a storage battery, or it can consist of a rectifier or an AC / DC converter connected to an AC system. Alternatively, the power supply 100 can consist of a DC / DC converter that converts DC power supplied by a DC system into a predetermined power output.

[0023] The electrical power conversion device 200 is a three-phase inverter connected at a node between the power supply 100 and the load 300. It converts DC power supplied by the power supply 100 into AC power and supplies the AC power to the load 300. The electrical power conversion device 200 includes a main conversion circuit 201, which converts DC power into AC power and supplies the AC power, and a control circuit 202, which outputs a control signal to the main conversion circuit 201 for controlling the main conversion circuit 201.

[0024] The Last 300 is a three-phase electric motor driven by AC power supplied by the electrical power conversion device 200. The Last 300 is not limited to a specific application. It can be used as an electric motor mounted on various electrical devices, such as a hybrid vehicle, an electric vehicle, a rail vehicle, a lift, or an air conditioner.

[0025] The electrical power conversion device 200 is described in detail below. The main conversion circuit 201 includes a switching device and a reflux diode (not illustrated). When the switching device is switched, the main conversion circuit 201 converts DC power supplied by the power supply 100 into AC power and supplies the AC power to the load 300. The main conversion circuit 201 can have various types of specific circuit configurations. The main conversion circuit 201 according to this embodiment is a three-phase, two-level full-bridge circuit, which can consist of six switching devices and six reflux diodes connected antiparallel to the respective switching devices. Each switching device of the main conversion circuit 201 consists of transistors 9 and 10 corresponding to the first embodiment described above.Two of the six switching devices are connected in series to form a vertical arm. Each vertical arm forms one phase (U-phase, V-phase, W-phase) of the full bridge circuit. The output terminals of each vertical arm, i.e., the three output terminals of the main conversion circuit 201, are connected to the load 300.

[0026] Furthermore, the main conversion circuit 201 includes a (not illustrated) control circuit that controls each switching device. The control circuit corresponds to the gate driver 13 according to the first embodiment described above and generates a control signal for controlling each switching device of the main conversion circuit 201 and provides the generated control signal to a control electrode of each switching device of the main conversion circuit 201. Specifically, the control circuit outputs to the control electrode of each switching device a control signal to turn on each switching device and a control signal to turn off each switching device according to the control signal output by the control circuit 202, which is described later. When the ON state of each switching device is maintained, the control signal is a voltage signal (ON signal) with a voltage equal to or higher than a threshold voltage of the switching device.If the OFF state of each switching device is maintained, the control signal is a voltage signal (OFF signal) with a voltage equal to or lower than the threshold voltage of the switching device.

[0027] The control circuit 202 controls each switching device of the main conversion circuit 201 to supply the desired power to the load 300. Specifically, the control circuit 202 calculates a period (ON period) during which each switching device of the main conversion circuit 201 is in the ON state, based on the power to be supplied to the load 300. For example, the main conversion circuit 201 can be controlled by means of a PWM controller to modulate the ON period of each switching device depending on the voltage to be supplied. The control circuit 202 also sends a control command (control signal) to the drive circuit so that at any given time, the ON signal is sent to each switching device to be switched on and an OFF signal is sent to each switching device to be switched off. The drive circuit sends the ON signal or OFF signal as the drive signal to the control electrode of each switching device according to the control signal.

[0028] In the electrical power conversion device according to this embodiment, the main conversion circuit according to the first embodiment is used as the main conversion circuit 201. Therefore, the electrical performance and reliability of the transistor are improved, and consequently, it is possible to improve the reliability and lifetime of the main conversion circuit.

[0029] Although this embodiment illustrates an example in which the present invention is used for a two-level three-phase inverter, the present invention is not limited to this and can be used for various power conversion devices. While this embodiment illustrates a two-level electrical power conversion device, the present invention can also be used for an electrical power conversion device with three or more levels. When electrical power is supplied to a single-phase load, the present invention can be used for a single-phase inverter. The present invention can also be used for a DC / DC converter or an AC / DC converter when electrical power is supplied to a DC load or the like.

[0030] Furthermore, in the electrical power conversion device for which the present invention is used, the aforementioned load is not limited to an electric motor. For example, the load can also be used as a power supply device for an electrical discharge machine, a laser beam machine, a cooking appliance with induction heating, or a system for wirelessly supplying device power. Alternatively, the electrical power conversion device can also be used as a power conditioner for a photovoltaic power generation system, an electricity storage system, or the like.

[0031] A power conversion device, for which the present invention is used, can be used for a moving body. Since the present invention can increase the reliability and service life of the power conversion device, it is possible to achieve an increase in the reliability and service life of the moving body. Reference symbol list

[0032] 1 Semiconductor device; 13 Gate driver; 14 High-voltage gate wire; 16 Low-voltage gate wire; 200 Electrical power conversion device; 201 Main conversion circuit; 202 Control circuit

Claims

[1] Main conversion circuit (201) comprising: a plurality of semiconductor devices (1) connected in parallel to each other; a gate driver (13) that provides a gate voltage to gates of the plurality of semiconductor devices (1); and a gate wire (14, 16) sequentially connected from the gate driver (13) to the gates of the plurality of semiconductor devices (1), wherein an excitation capability of each of the semiconductor devices (1) indicates how easily a collector current flows in response to the provided gate voltage, and the plurality of semiconductor devices (1) having a lower excitation capability are connected closer to the gate driver (13). [2] The main conversion circuit (201) according to claim 1, wherein the plurality of semiconductor devices (1) having a larger collector-emitter saturation voltage are connected closer to the gate driver (13). [3] The main conversion circuit (201) according to claim 1, wherein the plurality of semiconductor devices (1) having a larger gate threshold voltage are connected closer to the gate driver (13). [4] The main conversion circuit (201) according to claim 1, wherein the plurality of semiconductor devices (1) are connected with a larger time delay of a conduction start closer to the gate driver (13). [5] The main conversion circuit (201) according to any one of claims 1 to 4, wherein the plurality of semiconductor devices (1) are made of a wide band gap semiconductor. [6] The main conversion circuit (201) according to any one of claims 1 to 5, wherein in the plurality of semiconductor devices (1), an AC output terminal (2) is provided in one end in a longitudinal direction of a package, a positive voltage input terminal (3) and a negative voltage input terminal (4) are provided in the other end of the package, and the gate is provided between the AC output terminal and the positive voltage input terminal or the negative voltage input terminal. [7] An electrical power conversion device (200) comprising: the main conversion circuit (201) according to any one of claims 1 to 6, which converts input power and outputs converted power; and a control circuit (202) which outputs a control signal for controlling the main conversion circuit (201) to the main conversion circuit (201). [8] A moving body comprising the electric power conversion device (200) according to claim 7.

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