JP6884186B2 - Bidirectional switch - Google Patents

Description

This embodiment relates to a bidirectional switch.

A bidirectional AC switch using a semiconductor is known as a method excellent in high speed response and long life as compared with an electromagnetic bidirectional AC switch.

As one form of the conventional bidirectional AC switch made of silicon (Si: Silicon) as a material, there is a configuration in which a circuit in which MOSFETs having antiparallel diodes are connected facing each other is used as a basic cell.

Conventional electromagnetic switches are non-voltage contacts, but they are physically relays and have a slow response speed and are inferior to semiconductor bidirectional AC switches in terms of life. Especially in high voltage bidirectional AC switches used in power systems. Since it takes several tens of milliseconds to reach a completely open state due to the arc discharge at the time of switching, a huge accident current may flow during that time. For this reason, the wiring and electronic devices connected to the system must be designed to withstand the accident current, which increases the wiring construction cost.

In addition, the conventional semiconductor type bidirectional AC switch is superior to the electromagnetic type bidirectional AC switch in that it has a response speed, a long life, and does not discharge at the time of switching, but it is expensive and the voltage drop caused by factors other than contact contact resistance occurs. Since it is a voltage contact with a voltage, it is difficult to use and heat generation is large, so it is necessary to enhance the cooling mechanism and disperse the heat generation.

On the other hand, power devices using silicon carbide (SiC: Silicon Carbide) are supplied to the world by multiple companies. Features of power devices made using SiC, which is a wide bandgap semiconductor, include low on-resistance, high-speed switching, and high-temperature operation, which are superior to conventional Si power devices.

Further, a bidirectional AC switch aiming at high withstand voltage, high temperature resistance, and miniaturization using SiC is also disclosed.

Japanese Unexamined Patent Publication No. 2012-54694 Japanese Unexamined Patent Publication No. 10-30810 Japanese Unexamined Patent Publication No. 2007-135081

Here, in the conventional power module, the insulating layer and the lead frame (metal layer) are in contact with each other in a plane. When an external force is applied while the insulating layer and the metal layer are in contact with each other on a flat surface in this way, the insulating layer and the metal layer may be displaced from each other, resulting in poor insulation. Further, if the insulating layer and the metal layer are displaced and a gap is provided between them, the thermal resistance of the module increases. As a result, the semiconductor device cannot be cooled as designed, so that thermal runaway of the semiconductor device, thermal deterioration of the bonding layer such as the solder layer, and fusing of the bonding wire occur.

An object of the present invention is to provide a power module and a method for manufacturing the same, in which the insulating layer and the metal layer are less likely to be displaced even when an external force is applied, and the reliability is improved.

The present embodiment provides a bidirectional switch of a non-voltage contact that has excellent linearity of voltage-current characteristics, is compact and inexpensive, has a long life, has a high withstand voltage, and can respond at high speed with a large current capacity.

According to one aspect of this embodiment, the first gate being short-circuited and the SIC-MOSFET having a first source and a first drain, the first gate and the shorted second gate, and the first source The second SiC-MOSFET having a second source and a second drain, and the first gate and the second gate short-circuited with each other are electrically controlled by a signal input from the outside. A bidirectional switch including a gate drive circuit including an insulation circuit, wherein a plurality of cells including the first SiC-MOSFET, the second SiC-MOSFET, and the gate drive circuit are connected in series and parallel, and each cell is connected. Commonly controlled by the signal input to the gate drive circuit, the rated current when energized between the switch output terminals of the bidirectional switch is the first SiC- when a positive voltage is applied to the first source side. A bidirectional switch is provided in which the current flowing through the channel portion of the MOSFET and the body diode portion of the first SiC-MOSFET is compared, and the current flowing through the channel portion is set within a larger current range.

According to this embodiment, it is possible to provide a bidirectional switch of a non-voltage contact which is excellent in linearity of voltage-current characteristics, is compact and inexpensive, has a long life, has a high withstand voltage, and can respond at high speed with a large current capacity.

The schematic circuit block diagram of the bidirectional AC switch which concerns on 1st Embodiment. The circuit representation diagram of the SiC-MOSFET applicable to the bidirectional AC switch according to the first embodiment. The explanatory view of the forward-direction and reverse-direction current-voltage characteristics of a SiC-MOSFET and a Si-MOSFET that can be applied to the bidirectional AC switch according to the first embodiment. Example of forward and reverse drain current-drain voltage characteristics of SiC-MOSFET applicable to the bidirectional AC switch according to the first embodiment. In SiC-MOSFET can be applied to a bidirectional AC switch according to the first embodiment, MOS current I _MOS forward current to conduct channel section in the on state - voltage characteristic example, and the forward current of the body diode - Example of voltage characteristics. An example of the current-voltage characteristics of the bidirectional AC switch according to the first embodiment. The explanatory view of the rated current operating range on the current-voltage characteristic of the bidirectional AC switch which concerns on 1st Embodiment. The schematic circuit block diagram of the bidirectional AC switch which concerns on 2nd Embodiment. The schematic circuit block diagram of the bidirectional AC switch which concerns on 3rd Embodiment. In the bidirectional AC switch according to the third embodiment, a schematic circuit configuration diagram of a unit cell of the bidirectional AC switch. The schematic circuit block block diagram of the bidirectional AC switch which concerns on 4th Embodiment. FIG. 6 is a schematic cross-sectional structural view of a SiC DI MOSFET, which is an example of a semiconductor device applicable to the bidirectional AC switch according to the embodiment. FIG. 6 is a schematic cross-sectional structural view of a SiC TMOSFET, which is an example of a semiconductor device applicable to the bidirectional AC switch according to the embodiment.

Next, an embodiment will be described with reference to the drawings. In the description of the drawings below, the same or similar parts are designated by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the plane dimensions, the ratio of the thickness of each layer, etc. are different from the actual ones. Therefore, the specific thickness and dimensions should be determined in consideration of the following explanation. In addition, it goes without saying that the drawings include parts having different dimensional relationships and ratios from each other.

Further, the embodiments shown below exemplify devices and methods for embodying the technical idea, and the embodiments describe the materials, shapes, structures, arrangements, etc. of the components as follows. It is not specific to. Various modifications can be made to the embodiments within the scope of the claims.

In the following description, the non-voltage contact is a contact whose contact contact resistance value has a constant value regardless of the current value, and the current-voltage characteristic at least in the vicinity of 0V has linearity, and the positive and negative of the voltage. The characteristic that there is no voltage or current waveform distortion at the time of switching.

[Comparison example]
In the individual cells of the bidirectional AC switch according to the comparative example using silicon as the material, the antiparallel diode applies a positive voltage to the source side of the metal-Oxide-Semiconductor Field Effect Transistor (MOSFET). When this is done, the current is connected not to the MOSFET section but to the diode section having a lower on-resistance to the operating current for the purpose of passing the current.

In each cell of a bidirectional AC switch, when an AC voltage is applied between the switch output terminals with the MOSFET gate turned on, the barrier height of the antiparallel diode is on the side where the antiparallel diode is forward biased. In the voltage region below the voltage corresponding to, current flows through almost only the MOSFET, and in the voltage region above that, current flows through both the MOSFET and the antiparallel diode.

Here, the Si MOSFET generally has a high on-resistance due to the structure for ensuring the withstand voltage, and the pn junction diffusion potential of the Si antiparallel diode (or body diode) is about 1 V or less for the narrow band gap semiconductor Si. Therefore, since the on-resistance can be suppressed low, basically, the above two operation modes always exist within the rated current range of the Si bidirectional AC switch.

Therefore, in the Si bidirectional AC switch, the linearity of the current-voltage characteristic is broken near zero voltage, and strictly speaking, it is a non-voltage contact (dry contact) in that it has characteristics and restrictions other than the contact switch characteristic. It can not be said. In addition, since the antiparallel diode is connected for the purpose of low resistance, the number of elements increases, which leads to an increase in size and cost of the entire system.

[First Embodiment]
The schematic circuit configuration of the bidirectional AC switch 100 according to the first embodiment is shown as shown in FIG.

As shown in FIG. 1, the bidirectional AC switch 100 according to the first embodiment has a first gate G1 _ij (i = 1, 2, ..., M, j = 1, 2, ..., N. m and n are integers of 1 or more), the first SiC-MOSFET Q1 _{ij having the first source S1 ij} and the first drain D1 _ij , and the second gate short-circuited with the first gate G1 _ij and the first source S1 _{ij, respectively.} It has a G2 _ij and the second source S2 _ij, and a second 2SiC-MOSFET Q2 _ij having a second drain D2 _ij, gate for applying a gate voltage to the first gate G1 _ij · second gate G2 _ij which are shorted together The drive circuit 13 _ij and the cell 110 _ij provided with the drive circuit 13 ij are connected in m series × n parallel.

Here, the rated current during energization between the respective drains D1 _ij · D2 _ij is connected switch output terminal of the 1SiC-MOSFET Q1 _ij and the SIC-MOSFET Q2 _ij is the source of the 1SiC-MOSFET Q1 _ij S1 _{Compare the MOS current I MOS} flowing through the channel section _{of the 1st SiC-MOSFET Q1 ij and the BD current I BD} flowing through the body diode (BD1 _ij ) section of the 1st SiC- _{MOS EFT Q1 ij} when a positive voltage is applied to the _{ij side. Therefore, the MOS current I MOS} flowing on the channel portion side is set within the larger current range. Here, the rated current will be described later with reference to FIG. 7.

_{In the cell 110 ij} constituting the bidirectional AC switch 100 according to the first embodiment, the gate drive circuit 13 _ij operates the voltage applied between the input terminals 18A and 18B as shown in FIG. , Equipped with a light emitting diode (LED) 8 _{ij that can be turned on and off. The gates G1 ij} and G2 _ij of the first SiC-MOSFET Q1 _ij and the second SiC-MOSFET Q2 _ij , which are short-circuited to each other, are connected to a light receiving element capable of receiving light from the light emitting diode (LED) 8 _{ij and a light receiving element.} A photoelectric conversion circuit having at least a charge / discharge circuit may be connected, but the illustration is omitted. _{That is, in the cell 110 ij} constituting the bidirectional AC switch 100 according to the embodiment, if the light emitting diode (LED) 8 _ij is continuously operated and the operation is stopped, the operation of the cell 110 _ij is also stopped. In FIG. 1, the gate control unit of the _{cell 110 ij} is simply short-circuited between _{G1 ij} and G2 _ij.

_{In the cell 110 ij} constituting the bidirectional AC switch 100 according to the first embodiment, two 1200V 80mΩ SiC-MOSFETs Q1 _ij and Q2 _ij are connected facing each other to receive an optical signal from the _{LED8 ij.} A bidirectional AC switch with a contact rating of AC (700 × m) V / (5 × n) A that controls the gate with the light receiving element and the charge / discharge circuit can be configured.

The circuit representation of the SiC-MOSFET applicable _{to the cell 110 ij} constituting the bidirectional AC switch according to the first embodiment is shown as shown in FIG. The circuit representation of FIG. 2 is the same for Si-MOSFET.

An explanatory diagram of the forward and reverse current-voltage characteristics of the SiC-MOSFET and the Si-MOSFET, which can be applied _{to the cell 110 ij} constituting the bidirectional AC switch according to the first embodiment, is as shown in FIG. expressed.

Here, in the Si-MOSFET, the forward MOS current I _MOS (Si-MOS) generally has a high on-resistance even in the on state, as shown by the broken line in FIG. Moreover, since the pn junction diffusion potential of the Si antiparallel diode (or body diode) is about 1 V or less for Si, which is a narrow band gap semiconductor, the reverse characteristic is, for example, the MOS current in the reverse direction up to about 0.6 V. According to the I _MOS (Si-MOS) characteristics, when a reverse voltage of about 0.6 V or more is further applied, the forward current of the body diode BD is superimposed, and as shown by the broken line in FIG. 3, the I _BD ( The characteristics of Si-MOS) can be obtained.

On the other hand, in the SiC-MOSFET, the forward MOS current I _MOS (SiC-MOS) in the on state (for example, Vgs = 18V) has a lower on-resistance than the SiC-MOSFET, as shown by the solid line in FIG. .. And since pn junction diffusion potential of the SiC body diode BD is much less SiC at about 3V, which is a wide-gap semiconductor, the electrical characteristics of the body diode BD, for example, curve I _BD of (2) in FIG. 3 (SiC- As shown in MOS), it is almost non-conducting up to about 0.6V. Therefore, for example, the reverse direction characteristic follows the reverse direction MOS current _IMOS (SiC-MOS) characteristic up to about 0.6 V, and when a reverse voltage of about 0.6 V or more is further applied, the applied voltage is applied. The larger the value, the larger the forward current of the body diode BD is superimposed, and as shown by the solid line in FIG. 3 (1), the characteristics of I _MOS (SiC-MOS) + I _BD (SiC-MOS) are obtained.

Examples of forward and reverse drain current-drain voltage characteristics of the SiC-MOSFET applicable _{to the cell 110 ij} constituting the bidirectional AC switch 100 according to the first embodiment are shown as shown in FIG. To. In FIG. 4, the broken line RA shows an example of the rated operating range of one SiC-MOSFET when it is air-cooled.

In FIG. 4, when the gate voltage Vgs = 0V, the forward MOS current I _MOS is substantially non-conducting, and the reverse current is the current I _{BD which} is conductive to the body diode BD. On the other hand, when the gate voltage Vgs = 18V, the SiC-MOSFET is turned on (conducting), and the forward and reverse MOS currents I _MOS both obtain good linear current-voltage characteristics within the range of the broken line RA. Has been done.

_{In the SiC-MOSFET applicable to the cell 110 ij} constituting the bidirectional AC switch according to the first embodiment, the forward direction of _{the MOS current I MOS} conducting the channel portion of the MOSFET in the ON state of the gate voltage Vgs = 18V. current - forward voltage characteristic example, and BD current I _BD to conduct body diode BD - voltage characteristic example is expressed as shown in FIG. Further, the broken line represents the current ratio I _BD / ( _IBD + I _MOS ) (%) flowing through the body diode BD.

In the drain current-drain voltage characteristics (150 ° C: rated junction temperature) of the SiC-MOSFET, the body diode BD hardly operates in the region of ± 5A or less, and the relationship reflects the electrical characteristics of the channel part of the SiC-MOSFET. ing. That is, as shown in FIG. 5, since the drain-source on-voltage of the SiC-MOSFET at 5 A is 0.68 V, the current _{D flowing through the channel portion and the body diode when a positive voltage is applied to the source side.} The ratio of I _BD / ( _IBD + I _MOS ) (%) is 0.002% or less, and the current flows almost completely only in the MOSFET section. This tendency is that the current ratio is 0.001% or less at 25 ° C., and the same effect can be obtained.

Since SiC is a wide bandgap semiconductor, the diffusion potential when a pn junction is formed is much larger than that of Si. Therefore, if SiC is used as a material, the current flowing through the body diode when a positive voltage is applied to the source side of the MOSFET in the gate-on state can be suppressed, and the current can be selectively passed only to the MOSFET section. That is, since the pn junction diffusion potential of SiC is as large as about 3 V and the body diode is difficult to conduct, a bidirectional switch circuit is made only with SiC-MOSFET, and the operating current is limited to MOSFET without moving the body diode. It is possible to create an excellent bidirectional AC switch.

According to the circuit configuration shown in FIG. 1, _{a cell 110 ij} constituting a bidirectional AC switch 100 in which _{SiC-MOSFETs Q1 ij} and Q2 _ij are connected facing each other is formed. Here, the SiC-MOSFETs Q1 _ij and Q2 _ij have built-in body diodes BD1 _ij and BD2 _ij , but the diffusion potential of the pn junction is as high as about 3 V because it is formed from SiC, which is a wide bandgap semiconductor. On the other hand, since the insulation breakdown electric field is high, the thickness of the drift layer can be made thin, the carrier concentration can be set high, and the drain-source on-resistance of _{the SiC-MOSFET Q1 ij} and Q2 _{ij can be set low.} For example, the SiC-MOSFETs Q1 _ij and Q2 _ij have a withstand voltage of 1200 V, an input capacitance of 2080 pF, and a drain-source on-resistance of about 80 mΩ.

Therefore, when a positive voltage is applied to the source S1 _ij / S2 _ij side of the SiC-MOSFET Q1 _ij / Q2 _ij , the on-resistance value of the channel-side current path is changed to the on-resistance of the body diode BD1 _ij / BD2 _ij- side current path. The range that can be set lower can be dramatically expanded as compared with Si-MOSFET, and it becomes easier to preferentially flow current to the channel side. Even in Si-MOSFET, if the number of parallels is increased in large quantities, the current range that can be passed only in the channel section can be increased, but in that case, the number of MOSFET elements and the control circuit corresponding to the number are required, so the bidirectional AC switch. The whole system becomes large and unrealistic.

Here, if the rated current of the bidirectional AC switch is limited to the range in which the current of the channel side current path is the main, the current-voltage characteristic of the bidirectional AC switch is the current-voltage characteristic of the current passing through the channel portion of the SiC-MOSFET. Since the main current path does not change in the middle, the steep turning point of the current-voltage characteristic does not appear. Further, the SiC-MOSFET has a low on-resistance, and even when a current flows only through the SiC-MOSFET, there is almost no voltage drop. The contact contact resistance of the switch output unit is only the on-resistance of the SiC-MOSFET, and a bidirectional AC switch with no voltage contact in which a voltage drop other than the contact resistance hardly occurs can be configured.

Since the bidirectional AC switch 100 according to the first embodiment uses only the linear region characteristics of the SiC-MOSFET, a bidirectional AC switch with no voltage contacts having a low distortion factor and excellent linearity is configured. can do. In addition, since there is no diode separate from the body diode connected in antiparallel and the number of parts is reduced, it can be manufactured in a small size and at low cost, and the reliability is also improved.

In the bidirectional AC switch 100 according to the first embodiment, as shown in FIG. 5, the body of the first SiC-MOSFET Q1 has a rated current when a positive voltage is applied to the source side of the first SiC-MOSFET. The current flowing on the diode BD1 side may be set within the current range of 1% or less of the total.

_{That is, if the on-resistance is designed so that the current I BD} flowing on the body diode BD side is 1% or less of the total current value including the _{current I MOS} flowing on the channel side, the current is substantially applied only to the channel portion. Since the current-voltage characteristic can be flowed, a bidirectional AC switch having a low distortion rate of the current-voltage characteristic and excellent linearity can be configured.

Further, in the bidirectional AC switch 100 according to the first embodiment, as shown in FIG. 5, when the rated current flows, it is applied between the drain and the source in the state where the gate of the SiC-MOSFET is turned on. The absolute value of the voltage may be set to be 1.0 V or less.

That is, by setting the drain-source on-voltage at the time of gate-on of the SiC-MOSFET to 1.0 V or less within the rated current range of the bidirectional AC switch, the current can flow almost completely only to the channel portion. Therefore, it is possible to configure a bidirectional AC switch having a small distortion rate of the current-voltage characteristic and excellent linearity.

Since the body diode of the SiC-MOSFET does not operate if the forward voltage is 1.0 V or less regardless of the chip area and the integrated amount, the current can be substantially passed only in the channel portion. Further, in the minute voltage region of 1.0 V or less, only the linear region portion of the current-voltage characteristics of the current path passing through the channel portion of the MOSFET can be used, so that the distortion of the output current waveform due to the influence of the saturation region characteristics is suppressed. , A bidirectional AC switch with very good linearity of current-voltage characteristics can be constructed.

An example of the current-voltage characteristics of the unit cell constituting the bidirectional AC switch according to the first embodiment, and the current-voltage characteristics of the bidirectional AC switch composed of two 1200 V80 mΩ SiC-MOSFETs are shown in FIG. It is represented as shown in 6. The broken line RA indicates the rated operating range of the unit cell constituting the bidirectional AC switch composed of SiC-MOSFET × 2.

An explanatory diagram of the rated current operating range on the current-voltage characteristics of the unit cell constituting the bidirectional AC switch according to the first embodiment is shown as shown in FIG. 7.

The rated current is the same for both the SiC-MOSFET applied to the unit cell constituting the bidirectional AC switch according to the first embodiment and the bidirectional AC switch in which two of these SiC-MOSFETs are connected in series. Can be defined as. That is, the rated current depends on the calorific value, the thermal resistance, and the cooling method, and is defined by the maximum current value that becomes the _{rated junction temperature T jMAX or less under certain cooling conditions.}

Due to the current-voltage characteristics of the linear range of the unit cell constituting the bidirectional AC switch according to the first embodiment shown in FIG. 7, the current value ID is represented by the rated current. In the current range ΔI between + ID and −ID, the unit cells constituting the bidirectional AC switch according to the first embodiment exhibit linear current-voltage characteristics. For example, under constant air cooling conditions, the rated current ID = 5A is obtained at the _{rated bonding temperature T jMAX = 150 ° C.}

According to the bidirectional AC switch according to the first embodiment, it is possible to realize a non-voltage contact bidirectional AC switch in which each of the constituting MOSFETs does not have an antiparallel diode different from the body diode.

According to the bidirectional AC switch according to the first embodiment, since it is possible to apply a SiC-MOSFET in which the body diode does not operate in a desired current specification range, the linearity of the current-voltage characteristic is maintained well. It is possible to realize a non-voltage contact bidirectional AC switch.

Further, the number of series-parallel cells may take any value of 1 or more, and when a sequence is formed using this bidirectional AC switch, the complexity of the design can be suppressed because it is a non-voltage contact. .. For example, it is possible to simplify the design, shorten the design period, and avoid malfunction due to the voltage drop of the switch unit.

According to the bidirectional AC switch according to the first embodiment, the bidirectional AC switch is a non-voltage contact that has excellent linearity of voltage-current characteristics, is compact and inexpensive, has a long life, has a high withstand voltage, and can respond at high speed with a large current capacity. AC switches can be provided.

[Second Embodiment]
As shown in FIG. 8, the schematic circuit configuration of the bidirectional AC switch 102 according to the second embodiment is between the first drain D1 _ij and the second drain D2 _{ij of each cell 111 ij of the bidirectional AC switch 102.} It is provided with a surge killer circuit 26 _{ij connected to.}

The surge killer circuit 26 _i may include a first avalanche breakdown diode (ABD) ABD1 _ij and a second avalanche breakdown diode ABD2 _{ij in} which cathodes are connected to each other facing each other.

As shown in FIG. 8, the bidirectional AC switch 102 according to the second embodiment connects _{a surge killer circuit 26 i with ABD1 ij} and ABD2 _ij facing each other between the output terminals of each stage. With this configuration, for example, it is possible to provide a bidirectional AC switch 102 having a contact rated load AC (700 × m) V / (5 × n) A. Further, the connected surge suppressor circuit 26 _i in the i-th stage, the drain of the SiC-MOSFET Q1 _ij · Q2 _ij of the same i-th stage - it is possible to limit the voltage applied between the source.

In SiC-MOSFET, the thickness of the drift layer can be made thin and the carrier concentration can be set high by utilizing the fact that SiC, which is a material, has a high dielectric breakdown electric field, but there is a risk that a strong electric field strength will be applied to the gate insulating film. .. On the other hand, since the drift layer conditions are set for the purpose of relaxing the electric field concentration on the gate insulating film instead of the avalanche breakdown voltage, the rated voltage between the drain and source of the device and the avalanche breakdown voltage are significantly different from each other. Often.

Here, if a SiC Schottky barrier diode (SiC-SBD: Silicon Carbide Schottky Barrier Diode) is connected in antiparallel to the SiC-MOSFET, the voltage is limited by the avalanche breakdown of the SiC-SBD, but only the SiC-MOSFET. When a bidirectional AC switch is configured with the above, when an unintended huge voltage is applied, there is a risk that the applied voltage continuously exceeds the drain-source rated voltage of the device without yielding the avalanche.

Here, by arranging ABDs (avalanche breakdown diodes) connected facing each other between the output terminals of each stage of the bidirectional AC switch, the voltage applied to each cell of the bidirectional AC switch is determined by the avalanche breakdown voltage of the ABD. Can be specified.

Further, since the intermediate point of the SiC-MOSFET and the intermediate point of the ABD facing each other are not connected, the influence of the forward characteristic of the ABD on the current-voltage characteristic of the bidirectional AC switch can be eliminated. The forward characteristics can be excluded from the device selection criteria, increasing the degree of freedom in design.

According to the bidirectional AC switch according to the second embodiment, the voltage applied to each cell of the bidirectional AC switch can be defined by the Avalanche breakdown voltage of ABD, and the voltage-current characteristic is excellent in linearity and compact. Provides a bidirectional AC switch with non-voltage contacts that is inexpensive, has a long life, has a high withstand voltage, has a large current capacity, can respond at high speed, and reduces the risk of destruction of the SiC-MOSFET due to uneven voltage and voltage division balance. can do.

Further, one or more surge killer circuits may be connected to each stage of the bidirectional switch, or may be connected to each cell. Further, the number of series of ABDs may be increased for the purpose of ensuring the withstand voltage of ABDs.

Further, the number of series-parallel cells may take any value of 1 or more, and when forming a sequence using this bidirectional AC switch, the complexity of the design can be suppressed because it is a non-voltage contact. it can. For example, it is possible to simplify the design, shorten the design period, and avoid malfunction due to the voltage drop of the switch unit.

[Third Embodiment]
The schematic circuit configuration of the bidirectional AC switch 104 according to the third embodiment is shown as shown in FIG. 9, and the schematic circuit configuration of the unit cell 202 _ij constituting the bidirectional AC switch 104 is shown in FIG. It is expressed as shown in.

As shown in FIGS. 9 and 10, the bidirectional AC switch 104 according to the third embodiment has two MOFETs Q1 _ij and Q2 _ij connected to each other and drains D1 _ij and MOFET Q2 of MOFET Q1 _{ij. A configuration having a surge killer circuit 26 i in} which two ABD1 _ij and an ABD2 _ij are opposed to each other between drains D2 _{ij of} ij is defined as a unit cell 202 _ij , and the unit cell 202 _ij is connected in m series × n parallel. ..

Further, the gate drive circuit 15 _{i includes an E / O converter 22 i} connected to the input terminals 18A and 18B, _{an isolated DC / DC converter 16 i} to which a DC voltage (DC + 24V) is supplied, and an E / O. an optical fiber 17 _i connected to the transducer 22 _i, through an optical fiber 17 _i is connected to the E / O converter 22 _i, and the insulation type DC / DC converter 16 _i and connected the O / E converter 14 _{The i} and the FET driver 12 _i1 connected to the O / E converter 14 _i are provided. A withstand voltage equal to or higher than that of the insulated DC / DC converter 16 _i is secured between the E / O converter 22 _i and the O / E converter 14 _i. Similarly, the FET drivers 12 _i2 , 12 _i3 , ..., 12 _in of the other cells 202 _i2 , 202 _i3 , ..., 202 _in of the i-th stage are commonly connected to the O / E converter 14 _i.

According to the bidirectional AC switch 104 according to the third embodiment, for example, a bidirectional AC switch having a contact rated load AC (700 × m) V / (5 × n) A can be provided.

According to the third embodiment, by securing a sufficient insulation distance by the optical fiber, the noise immunity on the control side is strengthened, and the current decrease due to the gate voltage decrease, the gate destruction due to the gate overvoltage, and the deterioration of the switching characteristics are suppressed. A bidirectional AC switch can be configured.

Further, according to the third embodiment, the applied voltage is guaranteed by the surge killer circuit to prevent failure, excellent linearity of voltage-current characteristics, small size and low cost, long life, high withstand voltage, and large current capacity. It is possible to provide a bidirectional AC switch having a non-voltage contact that is capable of high-speed response and reduces the risk of destruction of the SiC-MOSFET due to a large voltage or uneven voltage division balance.

[Fourth Embodiment]
As shown in FIG. 11, the schematic circuit block configuration of the bidirectional AC switch 106 according to the fourth embodiment is serialized outside the switch output terminal of the bidirectional AC switch 100 according to the first embodiment. A connected disconnector 107 is further provided. Here, the disconnector 107 can be configured by an electromagnetic switch or the like. Further, a control circuit 109 may be provided between the bidirectional AC switch 100 and the disconnector 107. The control circuit 109 receives the current cutoff signal of the bidirectional AC switch 100 and supplies the trigger signal for the off operation of the disconnector 107 to the disconnector 107.

Since the bidirectional AC switch 100 using a semiconductor does not physically cut the wiring, a slight leakage current exists. To prevent this from becoming a problem, the bidirectional AC switch 100 cuts off at high speed and then physically cuts off using the disconnector 107 to prevent power loss due to leakage current and the bidirectional AC switch 100 in the off state. It is possible to prevent an accident when an abnormality occurs.

That is, in the bidirectional AC switch 100 using a semiconductor, the physical connection between the output terminals is not broken, and it is difficult to completely eliminate the leakage current. A disconnector 107 is connected in series to the output terminal of the bidirectional AC switch 100 using a semiconductor, and the bidirectional AC switch 100 cuts off the current conduction and then turns off the voltage by the disconnector 107. It is possible to cut off the current conducted to the 108 while ensuring high safety, and to suppress the power consumption when the bidirectional AC switch 100 is off. Since the bidirectional AC switch can complete the current cutoff in a short time of 1 μsec or less, the delay of the cutoff time due to the discharge phenomenon peculiar to the electromagnetic switch and the possibility of the occurrence of a huge accident current are completely eliminated. This simplifies the current tolerance design of the wiring 108 and electronic devices connected to the grid.

In the bidirectional AC switch 106 according to the fourth embodiment, an example in which the bidirectional AC switch 100 according to the first embodiment is applied has been disclosed, but the bidirectional AC according to the first embodiment has been disclosed. It is not limited to the switch 100. That is, it can be similarly applied to the bidirectional AC switch 102 according to the second embodiment and the bidirectional AC switch 104 according to the third embodiment.

(Semiconductor device configuration example)
-SiC-DIMOSFET-
An example of the semiconductor device 200 applicable to the bidirectional AC switch according to the first to third embodiments, the schematic cross-sectional structure of the SiC-DI (Double Implanted) MOSFET is shown in the table as shown in FIG. Will be done.

As shown in FIG. 12, the SiC-DIMOSFET applicable to the bidirectional AC switch according to the first to third embodiments is ^{n − obtainedly grown on the n +} SiC substrate 124 and the n ⁺ SiC substrate 124. a drift layer 126, n ^- and p-body region 128 formed on the surface side of the drift layer 126, an n ⁺ source region 130 formed on the surface of the p-body region 128, n between the p-body region 128 ^- drift layer A gate insulating layer 132 arranged on the surface of 126, a gate electrode 138 arranged on the gate insulating layer 132, and ^{a source electrode 134 electrically connected to the n +} source region 130 and the p body region 128. The n ⁺ SiC substrate 124 includes a drain electrode 136 electrically connected to the surface opposite to ^{the n-drift layer 126.}

In FIG. 12, in the semiconductor device 200, the p-body region 128 and the n ⁺ source region 130 formed on the surface of the p-body region 128 are formed by double ion implantation (DI), and the source pad electrode SP is n ^+. It is connected to the source electrode 134 connected to the source region 130 and the p-body region 128. The gate pad electrode GP (not shown) is connected to the gate electrode 138 arranged on the gate insulating layer 132. Further, the source pad electrode SP / source electrode 134 and the gate pad electrode GP (not shown) are arranged on the passivation interlayer insulating film 144 covering the surface of the semiconductor device 200, as shown in FIG.

-SiC-TMOSFET-
An example of the semiconductor device 200 applicable to the bidirectional AC switch according to the first to third embodiments, the schematic cross-sectional structure of the SiC-TMOSFET is shown as shown in FIG.

N SiC-TMOSFET applicable to bidirectional AC switch according to the first to third embodiments, as shown in FIG. 13, in which the n ⁺ SiC substrate 124, which is epitaxially grown on the n ⁺ SiC substrate 124 ^- and the drift layer 126N, n ^- and p-body region 128 formed on the surface side of the drift layer 126N, the n ⁺ source region 130 formed on the surface of the p-body region 128, through the p-body region 128, n ^- A trench gate electrode 138TG formed via a gate insulating layer 132 and an interlayer insulating film 144U / 144B in a trench formed up to the drift layer 126N, and a source electrode 134 connected to a source region 130 and a p-body region 128. , The drain electrode 136 electrically connected to the surface of ^{the n +} SiC substrate 124 ^{opposite to the n-drift layer 126N.}

In FIG. 13, the semiconductor device 200 penetrates the p-body region 128, and the trench gate electrode 138TG formed through the gate insulating layer 132 and the interlayer insulating films 144U / 144B is formed in the trench formed up to the semiconductor substrate 126N. The source pad electrode SP is connected to the source electrode 134 connected to the source region 130 and the p body region 128. The gate pad electrode GP (not shown) is connected to the gate electrode 138 arranged on the gate insulating layer 132. Further, as shown in FIG. 13, the source pad electrode SP / source electrode 134 and the gate pad electrode GP (not shown) are arranged on the passivation interlayer insulating film 144U covering the surface of the semiconductor device 200.

Since the SiC-TMOSFET does not have a junction resistor extending from the p-body region 128 in the drain current path, it is possible to provide an FET with a lower on-resistance as compared with the SiC-DIMOSFET, and 100 A or more per element. It is also possible to tolerate the drain pulse current of.

Further, a GaN-based FET or the like can be applied instead of the SiC-based MOSFET to the semiconductor device 200 applicable to the bidirectional AC switch according to the first to third embodiments.

Since the SiC device has a high dielectric breakdown electric field (for example, about 3 MV / cm, which is about 3 times that of Si), the thickness of the drift layer is made thinner and the carrier concentration is set higher than that of Si. Withstand voltage can be secured. Due to the difference in dielectric breakdown electric field, the peak electric field strength of the SiC-MOSFET can be set higher than the peak electric field strength of the Si-MOSFET.

In SiC-MOSFET, the required ^{film thickness of n- drift layer 126/126N is thin, and the resistance value of n-} drift layer 126 / 126N is reduced by the merits of both carrier concentration and film thickness, _{and the on-resistance R on.} Can be lowered, and the chip area can be reduced (smaller chips). Further, since it is possible to realize a withstand voltage comparable to that of the Si-IGBT with the MOSFET structure which is a unipolar device, it is said that high withstand voltage and high-speed switching can be performed, and reduction of switching loss can be expected.

As described above, according to the present embodiment, a bidirectional AC switch with a non-voltage contact that has excellent linearity of voltage-current characteristics, is compact and inexpensive, has a long life, has a high withstand voltage, and can respond at high speed with a large current capacity. Can be provided.

[Other embodiments]
As described above, although described by the first to third embodiments, the statements and drawings that form part of this disclosure are exemplary and should be understood to limit the invention. Absent. This disclosure will reveal to those skilled in the art various alternative embodiments, examples and operational techniques.

As described above, the present embodiment includes various embodiments not described here.

The bidirectional AC switch of the present embodiment uses a power SiC-MOSFET, has excellent linearity of voltage-current characteristics, is compact and inexpensive, has a long life, has a high withstand voltage, and has a large current capacity and can respond at high speed. As a bidirectional AC switch, it can be applied to a wide range of application fields, including a switch gear that performs an AC high voltage relay.

8 ₁₁ , 8 ₁₂ , ..., 8 _mn ... Light emitting diode (LED)
12 ₁₁ , 12 ₁₂ , ..., 12 _mn ... FET driver 13 ₁₁ , 13 ₁₂ , ..., 13 _mn , 15 ₁ , 15 ₂ , ..., 15 _m ... Gate drive circuit 14 ₁ , 14 ₂ , ..., 14 _m ... O / E converter _{16 1, 16 2, ...,} 16 m ... insulated type DC / DC converter _{17 1, 17 2, ...,} 17 m ... optical fiber 18A, 18B ... input terminal _{22 1, 22 2, ...,} 22 m ... E / O converter 24 ... Load 26 ₁ , 26 ₂ , ..., 26 _m , 26 ₁₁ , 26 ₁₂ , ..., 26 _mn ... Surge killer circuit 100, 102, 104, 106 ... Bidirectional AC switch 107 ... Breaker 108 … Wiring 109… Control circuit 110 ₁₁ , 110 ₁₂ ,…, 110 _mn , 111 ₁₁ , 111 ₁₂ ,…, 111 _mn , 202 ₁₁ , 202 ₁₂ ,…, 202 _mn … Cell (unit cell)
124 ... n ⁺ SiC substrate 126, 126N ... n ^- drift layer 128 ... p body region 130 ... source region 132 ... gate insulating film 134 ... source electrode 136 ... drain electrode 138, 138TG ... gate electrode 144, 144U, 144B ... interlayer insulation Film 200, Q1 ₁₁ , Q1 ₁₂ , ..., Q1 _mn , Q2 ₁₁ , Q2 ₁₂ , ..., Q2 _mn ... Semiconductor device (SiC-MOSFET)
S1 ₁₁ , S1 ₁₂ , ..., S1 _mn , S2 ₁₁ , S2 ₁₂ , ..., S2 _mn ... Source G1 ₁₁ , G1 ₁₂ , ..., G1 _mn , G2 ₁₁ , G2 ₁₂ , ..., G2 _mn ... Gate D1 ₁₁ , D1 ₁₂ , ..., D1 _mn , D2 ₁₁ , D2 ₁₂ , ..., D2 _mn ... Drain BD1 ₁₁ , BD1 ₁₂ , ..., BD1 _mn , BD2 ₁₁ , BD2 ₁₂ , ..., BD2 _mn ... Body diode T1, T2 ... Switch output terminal V _ac … AC voltage

Claims (10)

A first SiC-MOSFET having a first gate, a first source and a first drain,
A second gate short-circuited with the first gate , a second SiC-MOSFET having a second source short-circuited with the first source, and a second drain.
A bidirectional switch comprising a gate drive circuit with an electrically isolated circuit configured to control the first gate and the second gate short-circuited with each other by a signal input from the outside.
A plurality of cells including the first SiC-MOSFET, the second SiC-MOSFET, and the gate drive circuit are connected in series and parallel, and each cell is commonly controlled by the signal input to the gate drive circuit.
When a positive voltage is applied to the first source side, the rated current when energized between the switch output terminals of the bidirectional switch is applied to the channel portion of the first SiC-MOSFET and the body diode portion of the first SiC-MOSFET. A bidirectional switch set within a current range in which the current flowing on the channel portion side is larger than the flowing current. The claimed current is set within a current range in which the current flowing to the body diode portion side of the first SiC-MOSFET is 1% or less of the total when a positive voltage is applied to the first source side. The bidirectional switch according to 1. When the rated current flows, the absolute value of the voltage applied between the first drain and the first source when the first gate of the first SiC-MOSFET is turned on is 1.0 V or less. The bidirectional switch according to claim 1 or 2, which is set to. The bidirectional switch according to any one of claims 1 to 3, further comprising one or more surge killer circuits connected between the first drain and the second drain of the bidirectional switch. The bidirectional switch according to claim 4, wherein the surge killer circuit includes a first avalanche breakdown diode and a second avalanche breakdown diode in which cathodes are connected to each other so as to face each other. The first SiC-MOSFET and the second SiC-MOSFET are
The first conductive type SiC substrate and
The first conductive type drift layer formed on the SiC substrate and
A second conductive body region formed on the surface side of the drift layer and
The first conductive type source region formed on the surface of the body region and
A gate insulating layer arranged on the surface of the drift layer in the body region,
With the gate electrode arranged on the gate insulating layer,
With source electrodes electrically connected to the source region and the body region,
The bidirectional switch according to claim 1, further comprising a drain electrode electrically connected to a surface of the SiC substrate opposite to the drift layer. The first SiC-MOSFET and the second SiC-MOSFET are
The first conductive type SiC substrate and
The first conductive type drift layer formed on the SiC substrate and
A second conductive body region formed on the surface side of the drift layer and
The first conductive type source region formed on the surface of the body region and
A trench gate electrode formed through a gate insulating layer and an interlayer insulating film in a trench formed through the body region and up to the drift layer.
With the source electrode connected to the source region and the body region,
The bidirectional switch according to claim 1, further comprising a drain electrode electrically connected to a surface of the SiC substrate opposite to the drift layer. The bidirectional switch according to any one of claims 1 to 7, wherein the body diode portion of the first SiC-MOSFET is a body diode incorporated between the first source and the first drain. The bidirectional switch according to claim 6 or 7, wherein the body diode portion of the first SiC-MOSFET is a body diode incorporated between the body region and the drift layer. The electrical insulation circuit includes a photoelectric conversion circuit and has a photoelectric conversion circuit.
The bidirectional switch according to claim 1, wherein the first gate and the second gate are controlled by a signal obtained by converting the signal input to the gate drive circuit by the photoelectric conversion circuit.

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