JP6605491B2 - Bi-directional AC switch - Google Patents

Description

  The present embodiment relates to a bidirectional AC switch.

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

  As one form of a bidirectional AC switch using silicon (Si) as a material so far, there is a configuration in which a circuit in which MOSFETs having antiparallel diodes are connected to face each other is used as a basic cell.

  The conventional electromagnetic switch was a non-voltage contact, but the response speed of the physical relay was slow and the life was inferior to the semiconductor bidirectional AC switch. Especially in the high voltage bidirectional AC switch used in the power system, Since it took several tens of milliseconds to reach a complete open state due to arc discharge when switching, a huge accident current could flow during that time. For this reason, the wiring and the electronic equipment connected to the system need to be designed to allow the fault current, which increases the wiring work cost.

  In addition, the conventional semiconductor bidirectional AC switch is superior to the electromagnetic bidirectional AC switch in that the response speed, long life, and no discharge at the time of switching, but the voltage drop caused by factors other than the contact contact resistance is expensive. It is difficult to use because it has a voltage contact point with a large amount of heat, and the heat generation increases, so the cooling mechanism must be improved and the heat generation must be dispersed.

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

  In addition, a bidirectional AC switch that uses SiC to achieve high withstand voltage, high temperature resistance, and downsizing is also disclosed.

JP 2012-54694 A JP-A-10-308510 JP 2007-135081 A

  The present embodiment provides a bidirectional AC switch having no voltage contact that is excellent in linearity of voltage-current characteristics, is small and inexpensive, has a long life, has a high withstand voltage, and has a large current capacity and a high-speed response.

  According to one aspect of the present embodiment, a first SiC-MOSFET having a first gate, a first source and a first drain, a second gate and a second short-circuited with the first gate and the first source, respectively. A cell comprising a second SiC-MOSFET having a source and a second drain, and a gate driving circuit for controlling a gate voltage applied to the first gate and the second gate that are short-circuited to each other, A bidirectional AC switch connected in series and n in parallel, wherein the rated current when energized between the switch output terminals of the bidirectional AC switch is the first when the positive voltage is applied to the first source side. Comparing the current flowing through the channel part of the 1 SiC-MOSFET and the body diode part of the first SiC-MOSEFT, the current flowing through the channel part side is Bidirectional AC switch which is set in the hear becomes current range is provided.

  According to the present embodiment, it is possible to provide a bidirectional AC switch having no voltage contact that is excellent in linearity of voltage-current characteristics, is small and inexpensive, has a long life, has a high withstand voltage, and has a large current capacity and can respond quickly. .

The typical circuit block diagram of the bidirectional | two-way AC switch which concerns on 1st Embodiment. The circuit representation figure of SiC-MOSFET applicable to the bidirectional | two-way AC switch which concerns on 1st Embodiment. Explanatory drawing of the forward direction and reverse direction current-voltage characteristic of SiC-MOSFET and Si-MOSFET applicable to the bidirectional | two-way AC switch which concerns on 1st Embodiment. 6 is a drain current-drain voltage characteristic example in the forward and reverse directions of the SiC-MOSFET applicable to the bidirectional AC switch according to the first embodiment. In the SiC-MOSFET applicable to the bidirectional AC switch according to the first embodiment, the forward current-voltage characteristic example of the MOS current I _MOS conducting the channel portion in the ON state, and the forward current of the body diode— Example of voltage characteristics. 4 is a current-voltage characteristic example of the bidirectional AC switch according to the first embodiment. Explanatory drawing of the rated current operation range on the current-voltage characteristic of the bidirectional | two-way AC switch which concerns on 1st Embodiment. The typical circuit block diagram of the bidirectional | two-way AC switch which concerns on 2nd Embodiment. The typical circuit block diagram of the bidirectional | two-way AC switch which concerns on 3rd Embodiment. The schematic circuit block diagram of the unit cell of a bidirectional | two-way AC switch in the bidirectional | two-way AC switch which concerns on 3rd Embodiment. The typical circuit block block diagram of the bidirectional | two-way AC switch which concerns on 4th Embodiment. FIG. 3 is a schematic cross-sectional structure diagram of a SiC DIMOSFET, which is an example of a semiconductor device applicable to the bidirectional AC switch according to the embodiment. FIG. 4 is a schematic cross-sectional structure diagram of a SiC TMOSFET, which is an example of a semiconductor device applicable to the bidirectional AC switch according to the embodiment.

  Next, embodiments will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted 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 planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  In addition, the embodiment described below exemplifies an apparatus and method for embodying the technical idea, and the embodiment describes the material, shape, structure, arrangement, etc. of the component parts as follows. It is not something specific. Various modifications can be made to the embodiments within the scope of the claims.

  In the following description, a non-voltage contact is a contact whose contact contact resistance value has a constant value regardless of the current value, and has a linearity in current-voltage characteristics at least in the vicinity of 0 V, and the positive and negative of the voltage. This refers to the characteristics without distortion at the time of switching voltage and current waveform.

[Comparative example]
In each cell of the bi-directional AC switch according to the comparative example using silicon as a material, the antiparallel diode applies a positive voltage to the source side of a metal-oxide-semiconductor field effect transistor (MOSFET). In this case, the connection is made not for the MOSFET part but for the purpose of flowing the current to the diode part having a lower on-resistance with respect to the operating current.

  In each cell of the bi-directional AC switch, when an AC voltage is applied between the switch output terminals with the MOSFET gate turned on, the barrier height of the anti-parallel diode is on the side on which the anti-parallel diode is forward-biased. In the voltage region below the voltage corresponding to, current flows only through the MOSFET, and in the voltage region above it, current flows through both the MOSFET and the antiparallel diode.

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

  Therefore, in the case of Si bidirectional AC switches, the linearity of the current-voltage characteristics is lost near zero voltage, and strictly speaking, there are characteristics and restrictions other than the contact switch characteristics. It can not be said. In addition, since the antiparallel diode is connected for the purpose of low resistance, the number of elements increases, leading to an increase in the size and cost of the entire system.

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

As shown in FIG. 1, the bidirectional AC switch 100 according to the first embodiment includes first gates G1 _ij (i = 1, 2,..., M, j = 1, 2,..., N, m and n are integers of 1 or more), a first SiC-MOSFET Q1 _ij having a first source S1 _ij and a first drain D1 _ij, and a second gate short-circuited to the first gate G1 _ij and the first source S1 _ij , respectively. A gate for applying a gate voltage to the second SiC-MOSFET Q2 _ij having G2 _ij and the second source S2 _ij and having the second drain D2 _ij and the first gate G1 _ij and the second gate G2 _ij short-circuited to each other A cell 110 _{ij including} a drive circuit 13 _ij is 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 _{When a} positive voltage is applied to the _ij side, the MOS current I _MOS flowing through the channel portion of the first SiC-MOSFET Q1 _ij is compared with the BD current I _BD flowing through the body diode (BD1 _ij ) portion of the first SiC-MOSEFT Q1 _ij. Thus, the MOS current I _MOS flowing through the channel side is set within a current range in which the MOS current I _MOS is larger. Here, the rated current will be described later with reference to FIG.

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. And a light emitting diode (LED) 8 _ij that can be controlled on and off. The gates G1 _ij and G2 _ij of the first SiC-MOSFET Q1 _ij and the second SiC-MOSFET Q2 _ij that are short-circuited with each other are connected to the light receiving element capable of receiving light from the light emitting diode (LED) 8 _ij and the light receiving element A photoelectric conversion circuit including 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 this 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 shown by short-circuiting G1 _ij and G2 _ij .

In the cell 110 _ij constituting the bidirectional AC switch 100 according to the first embodiment, two SiC-MOSFETs Q1 _ij and Q2 _ij of 1200 V 80 mΩ are connected face to face to receive the optical signal from the LED 8 _ij. A bidirectional AC switch having a contact rating of AC (700 × m) V / (5 × n) A that performs gate control with a light receiving element and a charge / discharge circuit can be configured.

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

As shown in FIG. 3, an explanatory diagram of the forward and reverse current-voltage characteristics of the SiC-MOSFET and the Si-MOSFET applicable to the cell 110 _ij constituting the bidirectional AC switch according to the first embodiment. expressed.

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

On the other hand, the SiC-MOSFET has a lower on-resistance than the Si-MOSFET, as shown by the solid line in FIG. 3, the forward MOS current I _MOS (SiC-MOS) in the on state (eg, Vgs = 18V). . In addition, since the pn junction diffusion potential of the SiC body diode BD is about 3 V or less in SiC, which is a wide gap semiconductor, the electrical characteristics of the body diode BD are, for example, the curve I _BD (SiC− in FIG. 3B). As shown in (MOS), it is almost non-conductive up to about 0.6V. Therefore, for example, the reverse characteristics follow the reverse MOS current I _MOS (SiC-MOS) characteristics up to about 0.6 V, and when a reverse voltage of about 0.6 V or more is further applied, As the current increases, the forward current of the body diode BD increases and the characteristic of I _MOS (SiC-MOS) + I _BD (SiC-MOS) is obtained as shown by the solid line in FIG.

An example of the 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 is expressed as shown in FIG. The In FIG. 4, a broken line RA indicates an example of a rated operation range when one SiC-MOSFET is air-cooled.

In FIG. 4, the forward MOS current I _MOS is not substantially conducted at the gate voltage Vgs = 0V, and the reverse current is the current I _BD conducted to the body diode BD. On the other hand, at the gate voltage Vgs = 18V, the SiC-MOSFET is turned on (conductive), and the forward and reverse MOS currents I _MOS both have current-voltage characteristics with good linearity within the range of the broken line RA. It has been.

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 that conducts the channel portion of the MOSFET in the ON state with 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. The broken line represents the ratio of current I _BD / (I _BD + 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 does not substantially operate in the region of ± 5 A or less, and the relationship reflects the electrical characteristics of the channel portion of the SiC-MOSFET. ing. That is, as shown in FIG. 5, since the drain-source on-voltage of the SiC-MOSFET at 5A is 0.68 V, the current _D flowing in the channel portion and the body diode when a positive voltage is applied to the source side. The ratio I _BD / (I _BD + I _MOS ) (%) is 0.002% or less, and the current flows almost completely only in the MOSFET portion. As for this tendency, at 25 ° C., the current ratio becomes 0.001% or less, and the same effect can be obtained.

  Since SiC is a wide band gap semiconductor, the diffusion potential when a pn junction is formed is very large compared to Si. For this reason, if SiC is used as a material, when a positive voltage is applied to the source side of the MOSFET in the gate-on state, the current flowing through the body diode can be suppressed, and the current can be selectively supplied only to the MOSFET portion. In other words, the pn junction diffusion potential of SiC is about 3V, and the body diode is difficult to conduct. Therefore, a bidirectional switch circuit is made only by SiC-MOSFET, and the operating current is limited to only the MOSFET without moving the body diode. It is possible to create an excellent bidirectional AC switch.

With the circuit configuration shown in FIG. 1, a cell 110 _ij constituting the bidirectional AC switch 100 in which SiC-MOSFETs Q1 _ij and Q2 _ij are connected face to face 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 formed from SiC, which is a wide band gap semiconductor, and is as high as about 3 V. On the other hand, since the dielectric breakdown electric field is high, the thickness of the drift layer can be thin, the carrier concentration can be set high, and the drain-source on-resistance of SiC-MOSFETs Q1 _ij and Q2 _ij can be set low. For example, 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 can be realized.

Therefore, when a positive voltage is applied to the sources S1 _ij and S2 _{ij of} the SiC-MOSFETs Q1 _ij and Q2 _ij , the on-resistance value of the channel-side current path is set as the on-resistance of the body diode BD1 _ij and BD2 _ij- side current path. The range that can be set lower can be dramatically expanded as compared with the Si-MOSFET, and current can be preferentially passed through the channel side. Even in Si-MOSFETs, if the number of parallels is increased in a large amount, the current range that can be supplied only to the channel portion can be increased. In this case, however, a control circuit corresponding to the number of MOSFET elements and the number thereof is required. The whole system becomes large and is not realistic.

  Here, if the rated current of the bidirectional AC switch is limited to a range where the current in the channel-side current path is mainly, 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, a sharp inflection point of the current-voltage characteristic does not appear. Further, the SiC-MOSFET has a low on-resistance, and there is almost no voltage drop even when a current flows only in the SiC-MOSFET. The contact output resistance of the switch output unit is only the on-resistance of the SiC-MOSFET, and a non-voltage contact bidirectional AC switch in which voltage drop due to 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 contact with low distortion and excellent linearity is configured. can do. Further, there is no diode other than the body diode connected in reverse parallel, and the number of parts is reduced. Therefore, the device can be manufactured in a small size and at low cost, and the reliability is improved.

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

In other words, if the on-resistance is designed so that the current I _BD flowing on the body diode BD side and the current I _MOS flowing on the channel side together with the current I _MOS is 1% or less, the current substantially flows only in the channel portion. Therefore, a bidirectional AC switch with less distortion of current-voltage characteristics and excellent linearity can be configured.

  Further, in the bidirectional AC switch 100 according to the first embodiment, as shown in FIG. 5, when a rated current flows, it is applied between the drain and source when 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 when the gate of the SiC-MOSFET is turned on within the rated current range of the bidirectional AC switch to 1.0 V or less, the current can flow substantially only through the channel portion. Therefore, a bidirectional AC switch having a low current-voltage characteristic distortion rate and excellent linearity can be configured.

  Since the body diode of the SiC-MOSFET does not operate substantially if the forward voltage is 1.0 V or less regardless of the chip area and the amount of integration, the current can be allowed to flow substantially only in the channel portion. Furthermore, in the minute voltage region of 1.0 V or less, only the linear region part of the current-voltage characteristic of the current path passing through the channel part of the MOSFET can be used, so that distortion of the output current waveform due to the influence of the saturation region property is also suppressed. Thus, a bidirectional AC switch having a very excellent linearity of current-voltage characteristics can be configured.

  FIG. 4 is an example of current-voltage characteristics of a 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 SiC-MOSFETs of 1200 V80 mΩ are shown in FIG. As shown in FIG. A broken line RA indicates a rated operation range of a unit cell constituting a 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 cells constituting the bidirectional AC switch according to the first embodiment is expressed as shown in FIG.

The rated current is the same in the SiC-MOSFET applied to the unit cell constituting the bidirectional AC switch according to the first embodiment and in the bidirectional AC switch in which two of these SiC-MOSFETs are connected in series. Can be defined. That is, the rated current depends on the calorific value, the thermal resistance, and the cooling method, and is defined as the maximum current value that is not _more than the rated junction temperature T _jMAX under a certain cooling condition.

The current value ID is expressed as a rated current in 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. 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 a constant air cooling condition, a rated current ID = 5 A is obtained at a rated junction 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, it is possible to apply an SiC-MOSFET in which the body diode does not operate in a desired current specification range, and therefore, the linearity of the current-voltage characteristic is kept good. A sagging no-voltage contact bidirectional AC switch can be realized.

  In addition, the number of series-parallel cells can take an arbitrary value of 1 or more. When a sequence is formed using this bidirectional AC switch, the design complexity can be suppressed because it is a non-voltage contact. . For example, simplification of design, shortening of the design period, and avoiding malfunction due to voltage drop of the switch unit can be realized.

  According to the bidirectional AC switch according to the first embodiment, the voltage-current characteristic is linear, and it is a small-sized, inexpensive, long-life, high withstand voltage, large-current capacity, high-speed response and non-voltage contact bidirectional An AC switch can be provided.

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

The surge killer circuit 26 _i may include a first avalanche breakdown diode (ABD) ABD1 _ij and a second avalanche breakdown diode ABD2 _ij having cathodes connected to each other.

In the bidirectional AC switch 102 according to the second embodiment, as shown in FIG. 8, a surge killer circuit 26 _i having ABD1 _ij and ABD2 _ij facing each other is connected between the output terminals of each stage. With this configuration, for example, the bidirectional AC switch 102 with the contact rated load AC (700 × m) V / (5 × n) A can be provided. Further, the voltage applied between the drain and source of the same i-th stage SiC-MOSFETs Q1 _ij and Q2 _ij can be limited by the surge killer circuit 26 _i connected to the i-th stage.

  Although SiC-MOSFET can make the thickness of the drift layer thin and carrier concentration high by utilizing the fact that SiC, which is a material, has a high breakdown electric field, there is a risk that strong electric field strength is applied to the gate insulating film. . On the other hand, because the drift layer conditions are set not for the avalanche breakdown voltage but for the purpose of reducing the electric field concentration on the gate insulating film, the device drain-source rated voltage and the avalanche breakdown voltage are greatly different. There are many.

  Here, if a SiC Schottky Barrier Diode (SiC-SBD) is connected in reverse parallel to the SiC-MOSFET, the voltage is limited by the avalanche breakdown of the SiC-SBD, but only the SiC-MOSFET. In the case where the bidirectional AC switch is configured, 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 avalanche breakdown.

  Here, by arranging an ABD (avalanche breakdown diode) connected face-to-face 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 prescribed.

  In addition, since the intermediate point of the ABD opposite to the intermediate point of the SiC-MOSFET is 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 removed from the device selection criteria, and the degree of design freedom is improved.

  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 the ABD, has excellent linearity of voltage-current characteristics, and is compact. Low voltage, long life, high withstand voltage, large current capacity, high speed response, non-voltage contact bidirectional AC switch with reduced risk of SiC-MOSFET breakdown due to large voltage and non-uniform voltage balance can do.

  One or more surge suppressor circuits may be connected to each stage of the bidirectional switch, or may be connected to each cell. Further, the number of ABDs in series may be increased for the purpose of securing the ABD withstand voltage.

  In addition, the series / parallel number of cells may take an arbitrary value of 1 or more. When a sequence is formed using this bidirectional AC switch, since it is a non-voltage contact, design complexity can be suppressed. 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]
A schematic circuit configuration of the bidirectional AC switch 104 according to the third embodiment is expressed as shown in FIG. 9, and a 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

Third bidirectional AC switch 104 according to the embodiment of, as shown in FIGS. 9 and 10, and two MOFET Q1 _ij · Q2 _ij connected to face each other, the drain D1 _ij and MOFET Q2 of MOFET Q1 _ij the configuration including the surge suppressor circuit 26 _i which was facing the two ABD1 _ij · ABD2 _ij between _ij drain D2 _ij as a unit cell 202 _ij, having the configuration of connecting the unit cells 202 _ij in m series × n parallel .

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 supplied with a DC voltage (DC + 24V), and an E / O converter. 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 _i and an FET driver 12 _i1 connected to the O / E converter 14 _i . A breakdown 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 with a contact rated load AC (700 × m) V / (5 × n) A can be provided.

  According to the third embodiment, the noise resistance on the control side is enhanced by securing a sufficient insulation distance by the optical fiber, and the current drop due to the gate voltage drop, the gate breakdown due to the gate overvoltage, and the deterioration of the switching characteristics are suppressed. The bidirectional AC switch can be configured.

  In addition, according to the third embodiment, it is difficult to break down by guaranteeing the applied voltage by the surge killer circuit, excellent in linearity of voltage-current characteristics, small and inexpensive, long life, high withstand voltage, large current capacity. Thus, 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 non-uniform balance of voltage division.

[Fourth embodiment]
As shown in FIG. 11, the schematic circuit block configuration of the bidirectional AC switch 106 according to the fourth embodiment is arranged in series outside the switch output terminal of the bidirectional AC switch 100 according to the first embodiment. A disconnect switch 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 performs an operation of supplying a trigger signal for turning off the disconnector 107 to the disconnector 107.

  Since the bi-directional AC switch 100 using a semiconductor does not physically cut the wiring, there is a slight leakage current. In order not to cause this problem, the bidirectional AC switch 100 is shut off at high speed, and then physically shuts off using the disconnector 107, so that power loss due to leakage current or the off-state bidirectional AC switch 100 can be reduced. Accidents can be prevented when an abnormality occurs.

  That is, in the bidirectional AC switch 100 using a semiconductor, the physical connection between the output terminals is not cut off, and it is difficult to make the leakage current completely zero. The disconnector 107 is connected in series to the output terminal of the bidirectional AC switch 100 using a semiconductor, and after the bidirectional AC switch 100 cuts off the current conduction, the voltage is turned off by the disconnector 107. While interrupting the electric current conducted to 108 while ensuring high safety, it is possible to suppress power consumption when the bidirectional AC switch 100 is turned off. Since the bidirectional AC switch can complete the current interruption in a short time within 1 μsec, it completely eliminates the delay of the interruption time due to the discharge phenomenon peculiar to the electromagnetic switch and the possibility of the occurrence of a huge accident current. This realizes simplification of the current allowable design of the wiring 108 and electronic equipment connected to the system.

  In addition, although the example which applies the bidirectional | two-way AC switch 100 which concerns on 1st Embodiment in the bidirectional | two-way AC switch 106 which concerns on 4th Embodiment was disclosed, the bidirectional | two-way AC which concerns on 1st Embodiment is disclosed. The switch 100 is not limited. That is, the present invention 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.

(Configuration example of semiconductor device)
―SiC-DIMOSFET―
12 is an example of the semiconductor device 200 applicable to the bidirectional AC switch according to the first to third embodiments, and a schematic cross-sectional structure of a SiC-DI (Double Implanted) MOSFET is represented as shown in FIG. Is done.

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

In FIG. 12, in the semiconductor device 200, a p body region 128 and an 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 ⁺ Connected to source electrode 134 connected to source region 130 and p body region 128. The gate pad electrode GP (not shown) is connected to the gate electrode 138 disposed on the gate insulating layer 132. Further, the source pad electrode SP / source electrode 134 and the gate pad electrode GP (not shown) are disposed on a passivation interlayer insulating film 144 that covers the surface of the semiconductor device 200, as shown in FIG.

―SiC-TMOSFET―
It is an example of the semiconductor device 200 applicable to the bidirectional | two-way AC switch which concerns on the 1st-3rd embodiment, Comprising: The typical cross-section of SiC-TMOSFET is represented as shown in FIG.

The SiC-TMOSFET applicable to the bidirectional AC switch according to the first to third embodiments includes an n ⁺ SiC substrate 124 and an n ⁻ epitaxially grown on the n ⁺ SiC substrate 124 as shown in FIG. Drift layer 126N, p body region 128 formed on the surface side of n ⁻ drift layer 126N, n ⁺ source region 130 formed on the surface of p body region 128, p body region 128, and n ⁻ Trench gate electrode 138TG formed through gate insulating layer 132 and interlayer insulating films 144U and 144B in the trench formed up to drift layer 126N, and source electrode 134 connected to source region 130 and p body region 128, , Drain electrode electrically connected to the surface of n ⁺ SiC substrate 124 opposite to n ⁻ drift layer 126N 136.

  In FIG. 13, in the semiconductor device 200, a trench gate electrode 138TG formed through a gate insulating layer 132 and interlayer insulating films 144U and 144B is formed in a trench penetrating the p body region 128 and extending 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 disposed on the gate insulating layer 132. Further, the source pad electrode SP / source electrode 134 and the gate pad electrode GP (not shown) are disposed on a passivation interlayer insulating film 144U that covers the surface of the semiconductor device 200, as shown in FIG.

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

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

  Since the SiC device has a high breakdown electric field (for example, about 3 MV / cm, about 3 times that of Si), the drift layer is made thinner and the carrier concentration is set higher than that of Si. Can withstand pressure. 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 necessary n ^- thin thickness of the drift layer 126 · 126N, by both the benefits of carrier concentration and thickness, n ^- reducing the resistance of the drift layer 126 · 126N, resistance R _on The chip area can be reduced (smaller chip). Furthermore, since it is possible to realize a breakdown voltage comparable to that of Si-IGBT with the MOSFET structure as a unipolar device, it is considered that high breakdown voltage and high-speed switching can be achieved, and a reduction in switching loss can be expected.

  As described above, according to the present embodiment, the voltage-current characteristic linearity is excellent, and it is a compact, inexpensive, long-life, high withstand voltage, high-current capacity, non-voltage contact bidirectional AC switch. Can be provided.

[Other embodiments]
As described above, the first to third embodiments have been described. However, it should be understood that the description and drawings constituting a part of this disclosure are exemplary and limit the present invention. Absent. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  As described above, this 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, and is a small, inexpensive, long life, high withstand voltage, high voltage capacity, non-voltage contact capable of high-speed response. As a bidirectional AC switch, it can be applied to a wide range of application fields including a switchgear for performing 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 ... EO converter 24 ... Loads 26 ₁ , 26 ₂ , ..., 26 _m , 26 ₁₁ , 26 ₁₂ , ..., 26 _mn ... Surge killer circuits 100, 102, 104, 106 ... Bidirectional AC switch 107 ... Disconnector 108 ... Wiring 109 ... Control circuit 110 ₁₁ , 110 ₁₂ , ..., 110 _mn , 111 ₁₁ , 111 ₁₂ , ..., 111 _mn , 202 ₁₁ , 202 ₁₂ , ..., 202 _mn ... cells (unit cells)
124 ... n ⁺ SiC substrates 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 electrodes 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 (9)

A first SiC-MOSFET having a first gate, a first source and a first drain;
A second SiC-MOSFET having a second gate and a second source that are short-circuited with the first gate and the first source, respectively, and having a second drain;
A gate driving circuit for controlling a gate voltage applied to the first gate and the second gate which are short-circuited to each other;
A bidirectional AC switch connected in m series × n parallel,
When a positive voltage is applied to the first source side when a rated current is applied between the switch output terminals of the bidirectional AC switch, the channel portion of the first SiC-MOSFET and the body diode portion of the first SiC-MOSEFT The bidirectional AC switch is set within a current range in which the current flowing through the channel portion side is larger than the current flowing through the channel portion.   The rated current is set within a current range in which a current flowing to the body diode portion side of the first SiC-MOSFET is 1% or less of the whole when a positive voltage is applied to the first source side. The bidirectional AC switch according to claim 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 AC switch according to claim 1, wherein the bidirectional AC switch is set as follows.   One or more surge suppressor circuits connected between the first drain and the second drain in each of the m stages of the m series × n parallel bidirectional AC switches are provided. The bidirectional AC switch according to any one of claims 1 to 3.   The surge suppressor circuit connected between the first drain and the second drain is provided for each cell of the bidirectional AC switch connected in m series × n parallel. 2. A bidirectional AC switch according to item 1.   6. The bidirectional AC switch according to claim 4, wherein the surge killer circuit includes a first avalanche breakdown diode and a second avalanche breakdown diode that have cathodes connected to each other.   The gate driving circuit includes a photoelectric conversion circuit including at least a light emitting element connected to an input, a light receiving element that receives light from the light emitting element, and a charge / discharge circuit connected to the light receiving element. The bidirectional AC switch according to any one of claims 1 to 6. The gate driving circuit includes:
An E / O converter connected to the input;
An isolated DC / DC converter supplied with a DC voltage;
An optical fiber connected to the E / O converter;
An O / E converter connected to the E / O converter via the optical fiber and connected to the isolated DC / DC converter;
The bidirectional AC switch according to any one of claims 1 to 6, further comprising: an FET driver connected to the O / E converter.   The bidirectional AC switch according to any one of claims 1 to 8, further comprising a disconnector connected in series outside a switch output terminal of the bidirectional AC switch.

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