JP7222270B2 - Semiconductor device and snubber device - Google Patents

Description

The present invention relates to semiconductor devices and snubber devices.

Conventionally, in fields such as power electronics, various technologies have been developed, such as technology to prevent element destruction due to surge voltage, technology to prevent element destruction due to short-circuit current, and technology to reduce wiring inductance ( For example, see Patent Documents 1 to 4).
Patent Document 1: JP-A-2016-144340 Patent Document 2: JP-A-2008-206348 Patent Document 3: JP-A-2012-110099 Patent Document 4: JP-A-2016-66974

However, the conventional technology may not be able to prevent element breakdown due to short-circuit current and surge voltage.

In order to solve the above problems, a first aspect of the present invention provides a semiconductor device. The semiconductor device may comprise a semiconductor module. The semiconductor device may comprise a snubber device mounted between the positive terminal and the negative terminal of the semiconductor module. A semiconductor device has a capacitor connected to a positive terminal and a negative terminal through a wiring longer than the wiring length between the snubber device and the positive terminal and the wiring length between the snubber device and the negative terminal. may be provided. The semiconductor device may include a current sensor that measures the current flowing through the wiring.

The snubber device may have a capacitor connected between the positive and negative terminals. The snubber device may have a charging path that charges the capacitor from the positive and negative terminals. The snubber device may have a discharge path that is at least partially different from the charge path that discharges from the capacitor to the positive and negative terminals.

The snubber device has a positive capacitor, a first diode, and a negative capacitor connected in series between a positive terminal and a negative terminal, respectively, and conducts current from the positive terminal to the negative terminal. It may have n (where n is an integer equal to or greater than 1) charging paths in parallel. The snubber device includes a negative capacitor at a negative terminal or an N-th charging path (where N is an integer of 0≦N≦n) among n charging paths, and a N+1-th charging path among n charging paths. and the positive side capacitor or the positive side terminal of each of the positive side capacitors, and current flows from the negative side terminal side to the positive side terminal side via at least one of the negative side capacitor and the positive side capacitor. There may be n+1 parallel discharge paths flowing.

The wiring inductance of each charging path may be less than the wiring inductance of each discharging path. The wire length of each charge path may be shorter than the wire length of each discharge path.

The semiconductor device may further include a short circuit detector that detects a short circuit in the semiconductor module based on the detected value of the current sensor. The wiring may be an electric wire.

A semiconductor device may comprise a plurality of semiconductor modules. The semiconductor device may include laminated bus bars that connect positive terminals and negative terminals of a plurality of semiconductor modules. A snubber device may be mounted between the positive and negative terminals via a laminated busbar.

A second aspect of the present invention provides a snubber device connected between a positive terminal and a negative terminal of a semiconductor module. The snubber device may comprise a capacitor connected between the positive and negative terminals. The snubber device may comprise a charging path that charges the capacitor from the positive and negative terminals. The snubber device may comprise a discharge path, at least partially different from the charge path, discharging from the capacitor to the positive and negative terminals. The snubber device may comprise a current sensor that measures the current flowing in the discharge path.

The current sensor may be provided at a location in the discharge path that is different from the charge path.

The snubber device has a positive capacitor, a first diode, and a negative capacitor connected in series between a positive terminal and a negative terminal, respectively, and conducts current from the positive terminal to the negative terminal. There may be provided n parallel charging paths (where n is an integer equal to or greater than 1). The snubber device includes a negative capacitor at a negative terminal or an N-th charging path (where N is an integer of 0≦N≦n) among n charging paths, and a N+1-th charging path among n charging paths. and the positive side capacitor or the positive side terminal of each of the positive side capacitors, and current flows from the negative side terminal side to the positive side terminal side via at least one of the negative side capacitor and the positive side capacitor. There may be n+1 parallel discharge paths to flow.

The wiring inductance of each charging path may be smaller than the wiring inductance of each discharging path. The wiring length of each charging path may be shorter than the wiring length of each discharging path.

A third aspect of the present invention provides a semiconductor device. The semiconductor device may comprise a semiconductor module. A semiconductor device may comprise the snubber device of the second aspect.

It should be noted that the above summary of the invention does not list all the necessary features of the invention. Subcombinations of these feature groups can also be inventions.

1 shows a semiconductor device 1 according to this embodiment. 1 shows a circuit diagram of a semiconductor device 1 according to this embodiment. FIG. It shows the current flow when the switching element 11 is turned off. It shows the current flow when the switching element 11 is turned on. Shows the current flow when a short circuit occurs. Indicates the amount of current that will flow if a short circuit occurs. A semiconductor device 1A according to a modification is shown. 2 shows an external configuration of the snubber device 7A.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential for the solution of the invention.

[1. Appearance Configuration of Semiconductor Device]
FIG. 1 shows a semiconductor device 1 according to this embodiment. It should be noted that the upper and lower portions of the figure show the external configuration of the semiconductor device 1 viewed from different directions. A dashed frame B in the figure shows a partially enlarged view of a part of the semiconductor device 1 surrounded by the dashed frame A viewed from another direction. A semiconductor device 1 includes a semiconductor module 5 , a heat sink 6 , a snubber device 7 , a capacitor 10 and a current sensor 9 .

The semiconductor module 5 incorporates one or more semiconductor elements. For example, the semiconductor module 5 may incorporate one or more switching elements to perform switching. The semiconductor module 5 has a positive terminal 51 , a negative terminal 52 and an output terminal 19 . The semiconductor module 5 may further have one or more control terminals (not shown), and may be connected to the control device of the semiconductor module 5 via the control terminals.

The heat sink 6 absorbs at least heat generated in the semiconductor module 5 . The heat sink 6 may have radiation fins (not shown) on the surface opposite to the semiconductor module. The heat sink 6 may be attached to the semiconductor module 5 to form a semiconductor stack 50 (also called composite). Note that the heat sink 6 may not be provided in the semiconductor device 6 .

The snubber device 7 is mounted between the positive terminal 51 and the negative terminal 52 of the semiconductor module 5 . The snubber device 7 may absorb an instantaneous surge voltage that occurs during switching operation of the semiconductor module 5 . The snubber device 7 may be configured by providing a capacitor or the like for absorbing surge voltage on the printed wiring board 70 .

The printed wiring board 70 may internally have planar positive wiring and negative wiring (not shown) connected to the positive terminal 51 and the negative terminal 52 of the semiconductor module 5 via terminals 700 . These positive wiring and negative wiring may be stacked with an insulating layer interposed therebetween so that they act differentially on each other to cancel out the magnetic field. This reduces the inductance of the positive wiring and the negative wiring. Moreover, when the snubber device 7 is provided with a plurality of parallel capacitors, each capacitor can be uniformly charged and discharged.

Capacitor 10 is connected to positive terminal 51 and negative terminal 52 of semiconductor module 5 via wiring 100 . The wiring 100 is longer than the wiring length between the snubber device 7 and the positive terminal 51 and the wiring length between the snubber device 7 and the negative terminal 52 .

Note that the capacitor 10 may be a DC capacitor that functions as a DC power source for the semiconductor module 5 or a smoothing capacitor that smoothes the voltage between the positive terminal 51 and the negative terminal 52 of the semiconductor module 5 . If capacitor 10 is a smoothing capacitor, a power supply (not shown) may be connected to positive terminal 51 and negative terminal 52 of semiconductor module 5 .

A current sensor 9 measures the current flowing through the wiring 100 . The current sensor 9 includes a short-circuit detector 8 (see FIG. 2) for detecting a short-circuit in the semiconductor module 5, that is, a short-circuit between the positive terminal 51 and the negative terminal 52, and a controller for the semiconductor module 5. , may supply the measurement results.

In the present embodiment, as an example, the current sensor 9 is formed in a ring shape with the wiring 100 inserted therein, as shown in the dashed frame B in the figure, but the wiring 100 may be sandwiched. The current sensor 9 may measure current by any method such as a CT method, a Hall element method, a Rogowski method, or a zero flux method.

According to the semiconductor device 1 described above, by detecting a short circuit from a change in current using the current sensor 9, it is possible to prevent element destruction due to a short circuit current. The positive terminal 51 and the negative terminal 52 are connected to the capacitor by the wiring 100 longer than the wiring length between the snubber device 7 and the positive terminal 51 and the wiring length between the snubber device 7 and the negative terminal 52 . 10 are connected, the wiring inductance between the semiconductor module 5 and the capacitor 10 is increased. Therefore, when a short circuit occurs between the positive terminal 51 and the negative terminal 52 due to breakage of the semiconductor module 5 or the like, the change in current is suppressed and the time until element breakdown is increased. Element destruction can be reliably prevented. Further, since the current sensor 9 is provided on the wiring 100 between the semiconductor module 5 and the capacitor 10, unlike the case where it is provided on the wiring between the semiconductor module 5 and the snubber device 7, the semiconductor module 5 and the snubber device 7 are connected. The wiring between can be shortened. Therefore, it is possible to reduce the surge voltage when the semiconductor module 5 is driven to cut off the current, and to reliably absorb the surge voltage by the snubber device 7, thereby preventing element destruction due to the surge voltage.

[2. Circuit Configuration of Semiconductor Device 1]
FIG. 2 is a circuit diagram of the semiconductor device 1 according to this embodiment. In the figure, a semiconductor device 1 is for one phase of a semiconductor device that converts DC power into multiphase AC power. The semiconductor device 1 outputs a converted voltage from the power output terminal 19 by switching the connection between each electrode of the power supply capacitor 10 and the power output terminal 19 . Note that the return path of the alternating current to be output may be the power supply output terminal 19 of another phase. An inductive load (not shown) may be connected to the power output terminal 19 . A semiconductor device 1 includes a capacitor 10 , a current sensor 9 , a short circuit detector 8 , a semiconductor module 5 and a snubber device 7 . Note that the semiconductor device 1 may convert DC power into single-phase AC power. In this case, the semiconductor device 1 may include two capacitors 10 connected in series, and the return path of the alternating current output from the power supply output terminal 19 may be the middle point of the capacitors 10 .

The capacitor 10 has a positive side connected to the positive terminal 51 of the semiconductor module 5 via a positive wiring 101 and a negative side connected to a negative terminal 52 via a negative wiring 102 .

The positive wiring 101 and the negative wiring 102 are examples of the wiring 100, and can have wiring inductance 1011 according to the wiring length. Although the wiring 100 is an electric wire as an example in this embodiment, it may not be an electric wire as long as the current sensor 9 can be provided. For example, the wiring 100 may be a wiring member such as a busbar.

The current sensor 9 is provided on the positive wiring 101 as an example in this embodiment. The current sensor 9 supplies the measurement result to the short circuit detector 9 .

The short circuit detector 8 detects a short circuit of the semiconductor module 5 based on the detected value of the current sensor 9 . The short-circuit detection unit 8 may detect the presence or absence of a short-circuit based on whether the measurement result (in this embodiment, as an example, a detected value of the current flowing through the positive wiring 101) exceeds a threshold. However, as long as the short-circuit detector 8 detects a short-circuit based on the current amount of the positive wiring 101, the short-circuit may be detected by other methods. The short-circuit detector 8 may supply the detection result to a control device (not shown).

The semiconductor module 5 has switching elements 11 and 12 and freewheeling diodes 13 and 14 . Switching elements 11 and 12 are sequentially connected in series between negative wiring 102 and positive wiring 101 . The switching elements 11 and 12 may constitute an upper arm and a lower arm in the power converter.

The switching elements 11 and 12 each have a drain terminal connected to the positive terminal 51 side and a source terminal connected to the negative terminal 52 side. A control device (not shown) is connected to gate terminals of the switching elements 11 and 12 to control ON/OFF of the switching elements 11 and 12 . For example, the switching elements 11 and 12 may be controlled to alternatively be in the connected state with a dead time in which both are turned off. The switching elements 11 and 12 may be controlled by PWM. A power supply output terminal 19 is connected to the middle point of the switching element 11 and the switching element 12 .

The switching elements 11 and 12 may be silicon semiconductor elements based on silicon, or may be wide bandgap semiconductor elements. A wide bandgap semiconductor device is a semiconductor device having a bandgap larger than that of a silicon semiconductor device, and includes, for example, SiC, GaN, diamond, gallium nitride-based materials, gallium oxide-based materials, AlN, AlGaN, or ZnO. element. The switching elements 11 and 12 may be MOSFETs, or semiconductor elements having other structures such as IGBTs and bipolar transistors.

Freewheeling diodes 13 and 14 are connected in anti-parallel to switching elements 11 and 12 so that the positive wiring 101 side serves as a cathode. Freewheeling diodes 13 and 14 may be Schottky barrier diodes. Freewheeling diodes 13 and 14 may be silicon semiconductor devices or wide bandgap semiconductor devices.

[2.1. snubber device 7]
The snubber device 7 protects each element of the semiconductor device 1 by absorbing a surge voltage generated when the switching elements 11 and 12 cut off the current. The snubber device 7 has a snubber circuit 2 . Snubber circuit 2 includes one or more capacitors 211 and 213 connected (directly or indirectly) between positive terminal 51 and negative terminal 52 and capacitor 10 from positive terminal 51 and negative terminal 52 . and one or more discharge paths 22 discharging from the capacitor 10 to the positive terminal 51 and the negative terminal 52, the discharging path 22 being the charging path 21 and the negative terminal 52. may be at least partially different.

In this embodiment, as an example, the snubber circuit 2 has n parallel charging paths 21 and n+1 parallel discharging paths 22 . Note that the number n is an integer of 1 or more, and is 3 as an example in this embodiment. In this embodiment, as an example, the three charging paths 21 are designated as a first charging path 21(1), a second charging path 21(2), and a third charging path 21(3) in order from the left side of the drawing. explain. In addition, the four discharge paths 22 are arranged in order from the left side of the drawing as a first discharge path 22(1), a second discharge path 22(2), a third discharge path 22(3), and a fourth discharge path 22( 4).

Each charging path 21 has a positive capacitor 211 , a first diode 212 and a negative capacitor 213 connected in series between a positive terminal 51 and a negative terminal 52 in order. The positive side capacitor 211 and the negative side capacitor 213 function as snubber capacitors, respectively, and an instantaneous surge voltage generated when the switching elements 11 and 12 are driven (for example, applied to the elements for a period greater than 10 ns and less than 10 μs). surge voltage). For example, positive side capacitor 211 and negative side capacitor 213 may suppress vibrations greater than 100 kHz and less than 100 MHz. Positive side capacitor 211 and negative side capacitor 213 may be, for example, film capacitors or laminated ceramic capacitors.

The first diode 212 is arranged with its anode facing the positive terminal 51 side and its cathode facing the negative terminal 52 side. As a result, each charging path 21 causes current to flow from the positive terminal 51 side to the negative terminal 52 side.

Each discharge path 22 has a second diode 221 . The second diode 221 connects the negative capacitor 213 at the negative terminal 52 or the Nth charging path 21 (where N is an integer of 0≦N≦n) among the n charging paths 21 and the n charging paths 21 . and the positive side capacitor 211 or the positive side terminal 51 in the N+1-th charging path 21 among the charging paths 21 . For example, the second diode 221 of the first discharge path 22(1) is connected between the negative terminal 52 and the positive capacitor 211 of the first charge path 21(1). A second diode 221 of the second discharge path 22(2) is between the negative capacitor 213 of the first charge path 21(1) and the positive capacitor 211 of the second charge path 21(2). Connected. The second diode 221 of the third discharge path 22(3) is between the negative capacitor 213 of the second charge path 21(2) and the positive capacitor 211 of the third charge path 21(3). Connected. A second diode 221 of the fourth discharge path 22 ( 4 ) is connected between the negative capacitor 213 of the third charge path 21 ( 3 ) and the positive terminal 51 . The second diode 221 is disposed with its anode facing the Nth charging path 21 (N) or the negative terminal 52 side and with its cathode facing the N+1th charging path 21 (N+1) or the positive terminal 51 side. be done. As a result, each discharge path 22 causes current to flow from the negative terminal 52 side to the positive terminal 51 side via at least one of the negative capacitor 213 and the positive capacitor 211 .

Here, the wiring inductance of each of the n charging paths 21 (three as an example in this embodiment) may be smaller than the wiring inductance of each of the discharging paths 22 . Also, the wiring length of each charging path 21 may be shorter than the wiring length of each discharging path 22 . For example, the wiring length of each charging path 21 connecting the positive terminal 51 and the negative terminal 52 may be shorter than the wiring length of each discharging path 22 connecting the positive terminal 51 and the negative terminal 52 . Also, the wiring length of each wiring portion between the positive side capacitor 211 and the negative side capacitor 213 in the three charging paths 21 is equal to the length of the wiring connecting the negative side capacitor 213 and the positive side capacitor 211 in each discharging path 22 . It may be shorter than the wiring length of the part. In this embodiment, as an example, each charging path 21 is physically arranged linearly between the positive terminal 51 and the negative terminal 52 .

[2.1.1. Operation of snubber circuit 2]
First, the operation when the switching element 11 is turned off from the state where the switching element 11 is on and the switching element 12 is off will be described. When the switching element 11 is on and the switching element 12 is off, the output current flows through the capacitor 10 , the positive wiring 101 , the switching element 11 , and the power output terminal 19 . At this time, an output current flows through the wiring inductance 1011 and energy is accumulated.

FIG. 3 shows the current flow when the switching element 11 is turned off from this state. In the figure, broken line arrows indicate current flow, and solid line arrows indicate voltages of capacitor 10, positive side capacitor 211 and negative side capacitor 213. FIG. Further, illustration of the current sensor 9 is omitted in FIG. 3 and FIG. 4 described later.

When the switching element 11 is turned off, the output current is commutated and flows from the capacitor 10 and the positive wiring 101 to the positive capacitor 211, the first diode 212 and the negative capacitor 213 of each charging path 21, and flows through the freewheeling diode 14. It is output from the power supply output terminal 19 via. As a result, the current energy of the wiring inductance 1011 is absorbed by charging the positive side capacitor 211 and the negative side capacitor 213 of the charging path 21 . Then, the output current is finally commutated to the capacitor 10 , the negative wiring 102 , the freewheeling diode 14 and the power supply output terminal 19 . This completes the commutation accompanying the turn-off operation of the switching element 11 .

FIG. 4 shows the current flow when the switching element 11 is turned on again after the turn-off operation of the switching element 11 is completed.

When the switching element 11 is turned on again, the output current flowing through the path of the capacitor 10, the negative wiring 102, the freewheeling diode 14, and the power supply output terminal 19 changes to the capacitor 10, the negative wiring 102, and each discharge path 22. of the second diode 221, the switching element 11, and the path of the power supply output terminal 19. At this time, it is stored in the positive side capacitor 211 and/or the negative side capacitor 213 on the anode side/cathode side of the second diode 221. Energy is released during the turn-off operation. Then, the output current is finally commutated to the capacitor 10 , the positive wiring 101 , the switching element 11 and the power supply output terminal 19 . This completes the commutation accompanying the turn-on operation of the switching element 11 .

Here, the voltages of the positive side capacitor 211 and the negative side capacitor 213 when the switching element 11 is turned off and turned on will be described. The relationship between the voltages of the positive side capacitor 211 and the negative side capacitor 213 of each charging path 21 during turn-off operation is represented by the following equation (1). However, in the formula, E is the voltage of the capacitor 10, and V _dc-off is the inter-terminal voltage between the positive terminal 51 and the negative terminal 52 during turn-off operation. V _p(1) to V _p(3) are the voltages of the positive capacitor 211 in the first charging path 21(1) to the third charging path 21(3). V _n(1) to V _n(3) are the voltages of the negative capacitor 213 in the first charging path 21(1) to the third charging path 21(3).

E≦( _Vp (1)+ _Vn (1))
=( _Vp (2)+ _Vn (2))
=( _Vp (3)+ _Vn (3))
=V _dc-off (1)

Also, the relationship between the voltages of the positive side capacitor 211 and the negative side capacitor 213 of each discharge path 22 during turn-on operation is represented by the following equation (2). However, in the formula, V _dc-on is the inter-terminal voltage between the positive terminal 51 and the negative terminal 52 during turn-on operation.

E≧V _p (1)
=( _Vn (1)+ _Vp (2))
=( _Vn (2)+ _Vp (3))
= V _n (3)
= _Vdc-on (2)

From equations (1) and (2), the relationship between the voltages of each positive capacitor 211 and each negative capacitor 213 is expressed by the following equation (3) (see also the voltages shown in FIGS. 3 and 4). . However, in the formula, Vdc is the inter-terminal voltage between the positive terminal 51 and the negative terminal 52 during normal operation.

E=V _dc ≈V _p (1)
= V _n (3)
= 1.5 x _Vp (2)
= 1.5 x _Vn (2)
= 3 x _Vn (1)
=3×V _p (3) (3)

From equation (3), the charging voltage in each charging path 21 when the capacitor current is cut off (4E/3 as an example in FIG. 4) is obtained from the discharging voltage in each discharging path 22 (E as an example in FIG. 4). is also found to be high. The same effect can be obtained from the symmetry of the circuit in the turn-on and turn-off operations of the switching element 12 when the output current is reversed, so detailed description will be omitted.

According to the snubber circuit 2 in the semiconductor device 1 described above, when the current is cut off by the semiconductor module 5 , the positive and negative capacitors 211 and 213 are supplied from the positive terminal 51 and the negative terminal 52 through the charging path 21 . Therefore, the energy accumulated in the wiring inductance of the wiring 100 between the semiconductor module 5 and the capacitors 211 and 213 passes through the charging path 21 and the capacitors 211 and 213 to the positive terminal 51 and the negative terminal 52. to a voltage higher than the voltage between This prevents element breakdown due to surge voltage.

In addition, since the discharge path 22 discharges from the positive side and negative side capacitors 211 or 213 to the positive side terminal 51 and the negative side terminal 52, when a current is supplied by the semiconductor module 5, it is accumulated in the capacitors 211 and 213. The energy is discharged, and the discharge voltage of each discharge path 22 drops to the voltage between the positive terminal 51 and the negative terminal 52 .

At least part of the discharge path 22 is different from the charge path 21, so that when the current is cut off by the semiconductor module 5, the energy for charging the capacitors 211 and 213 through the charge path 21 is transferred through the discharge path 22. Resonance operation such as discharging and charging the capacitors 211 and 213 is prevented. The snubber circuit 2 also includes n parallel charging paths 21 each having a positive capacitor 211 and a negative capacitor 213 , and a positive charge from the negative terminal 52 through at least one of the negative capacitor 213 and the positive capacitor 211 . Since n+1 discharge paths 22 are provided for flowing a current to the side terminal 51 side, the charging voltage in each of the n charging paths 21 when the current is interrupted is the discharge voltage in each of the discharge paths 22. higher than Therefore, the energy that charges the charging path 21 when the current is interrupted cannot further charge the charging path 21 even if it is discharged by the discharging path 22 . Therefore, the energy charged in the positive side capacitor 211 and the negative side capacitor 213 when the current is interrupted is charged and discharged by the resonance operation of the wiring inductance 1011 and the positive side capacitor 211 and the negative side capacitor 213, and is consumed as circuit loss. It is stored in the positive side capacitor 211 and the negative side capacitor 213 and regenerated. As a result, circuit loss due to resonance operation can be reliably reduced.

In this way, it is possible to prevent element destruction due to surge voltage when current is interrupted and reduce circuit loss. In addition, the flexibility of the length of the wiring 100 between the semiconductor module 5 and the capacitor 10 can be increased. Therefore, even if the wiring 100 is longer than the wiring length between the snubber device 7 and the semiconductor module 5, it is possible to prevent element breakdown due to surge voltage and reduce circuit loss. Also, the arrangement of the current sensor 9 can be facilitated.

Also, the wiring length of each charging path 21 is shorter than the wiring length of each discharging path 22 , and the wiring inductance of the charging path 21 is smaller than the wiring inductance of the discharging path 22 . Therefore, it is possible to reduce the surge voltage that occurs when the current is interrupted by the semiconductor module 5, and suppress the peak of the discharge current when the semiconductor module 5 allows the current to flow.

[3. Operation at short circuit]
FIG. 5 shows the current flow when a short circuit occurs. When the switching elements 11 and 12 are turned on and a short circuit occurs between the positive terminal 51 and the negative terminal 52, the capacitor 10, the positive wiring 101, the switching element 101, and the switching elements 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, and 101 are connected as indicated by broken arrows in the figure. Current flows through the elements 11 and 12, the negative wiring 102, and the capacitor 10 in this order.

Here, in the semiconductor device 1 according to the present embodiment, since the wiring lengths of the positive wiring 101 and the negative wiring 102 are longer than the wiring length between the snubber device 7 and the semiconductor module 5, a rapid change in current is prevented. suppressed. Therefore, by detecting a short circuit with the current sensor 9 and turning off the switching elements 11 and 12 respectively, element destruction can be prevented.

FIG. 6 shows the amount of current that flows when a short circuit occurs. The vertical axis in the figure is the amount of current, and the horizontal axis is time.

In the figure, the solid line graph G1 shows the waveform when the switching elements 11 and 12 are turned off when a short circuit is detected in the semiconductor device 1 according to this embodiment. A dashed line graph G2 shows a waveform when the switching elements 11 and 12 are not turned off when a short circuit is detected in the semiconductor device 1 according to this embodiment. A graph G3 of a two-dot chain line shows a conventional semiconductor in which the capacitor 10 and the semiconductor module 5 are connected by a wiring not longer than the wiring length between the semiconductor module 5 and the snubber device 7 and in which the current sensor 9 is not provided. Fig. 4 shows waveforms when a short circuit occurs in the device; As shown in this figure, according to the semiconductor device 1 according to the present embodiment, it is possible to reliably prevent element destruction by turning off the switching elements 11 and 12 when a short circuit is detected.

[4. Modification]
FIG. 7 shows a semiconductor device 1A according to a modification. The semiconductor device 1A includes a snubber device 7A instead of the snubber device 7. FIG. Snubber circuit 2A of snubber device 7A differs from snubber circuit 2 in that it has one or more current sensors 9A.

Current sensor 9A measures the current flowing through discharge path 22 . The current sensor 9</b>A may be provided at a location different from the charge path 21 in the discharge path 22 . The current sensor 9A may supply the measurement result to the control device of the semiconductor module 5 . The control device includes a discharge path 22 provided with the current sensor 9A and a path through which substantially the entire short-circuit current flows (for example, the capacitor 10, the positive wiring 101, the switching elements 11 and 12, the negative wiring 102, and the capacitor 10). A short-circuit path may be stored in advance, or the current ratio between the two when a short circuit occurs, and the amount of current on the short-circuit path is calculated based on the value of the ratio to detect a short circuit. you can

In addition, in this modification, the semiconductor device 1A does not need to include the wiring 100 between the capacitor 10 and the semiconductor module 5 and the current sensor 9 provided on the wiring 100 . In this case, the capacitor 10 may be connected to the semiconductor module 5 with a wiring that is not longer than the wiring length between the semiconductor module 5 and the snubber device 7 .

According to the snubber device 7A described above, since the current sensor 9 is provided, by detecting a short circuit from a change in current using the current sensor 9, it is possible to reliably prevent element breakdown due to a short circuit current. Moreover, since the current sensor 9 is provided on the discharge path 22, the charge path 21 can be shortened unlike the case where the current sensor 9 is provided on the charge path 21. FIG. Therefore, it is possible to reduce the surge voltage when the semiconductor module is driven and cut off the current, and to reliably absorb the surge voltage by the capacitors 211 and 213 on the positive and negative sides, thereby preventing element destruction due to the surge voltage. Further, since the current sensor 9A is provided in the discharge path 22, the current sensor 9A can be a low-capacity sensor compared to the case where the current sensor 9A is provided in the short-circuit path.

In addition, since the current sensor 9 is provided in a portion of the discharge path 22 different from the charge path 21, a portion shared with the charge path 21 (for example, between the positive side capacitor 211 and the positive side wiring 101, or between the negative side capacitor 213 and the negative wiring 102), the charging path 21 can be shortened. Therefore, since the wiring inductance of the charging path 21 can be made smaller than the wiring inductance of the discharging path 22, the surge voltage generated when the current is interrupted by the semiconductor module 5 can be reduced, and the current can be prevented from flowing by the semiconductor module 5. The peak of the discharge current can be suppressed when the

FIG. 8 shows the external configuration of the snubber device 7A. In each of the n+1 discharging paths 22, the wiring portion connecting the negative capacitor 213 of the Nth charging path 21 and the positive capacitor 211 of the N+1 charging path 21 may be pulled out of the printed wiring board 70. good. For example, this wiring portion may have two lands 705 of the printed wiring board 70 and a looped wiring 701 connected between the two lands 705 . The current sensor 9A may be provided on the wiring 701 concerned.

The wirings 701 provided in separate discharge paths 22 may be arranged close to each other. As a result, the adjacent portions of one wiring 701 and the adjacent portions of the plurality of wirings 701 may act in a synergistic manner to strengthen the magnetic field, and the inductance of the wiring 701 may be increased. In this case, the peak of the discharge current when the current is caused to flow by the semiconductor module 5 can be suppressed more reliably.

Also, the wiring 701 may include two regions that overlap each other. In this figure, as an example, the wiring 701 has a region extending in the horizontal direction on the upper side in the drawing and a region extending in the horizontal direction on the lower side, and these two regions overlap each other. As a result, the overlapping regions may act synergistically to strengthen the magnetic field, and the inductance of the wiring 701 may increase. In this case, the peak of the discharge current when the current is caused to flow by the semiconductor module 5 can be suppressed more reliably.

In FIG. 8, the wiring 701 is shown separated from the printed wiring board 70 for simplification of illustration. 8, two lands 705 and wiring 701 are provided between the second diode 221 and the positive side capacitor 211, but instead/in addition to this, the second diode 221 and the negative side capacitor 213 may be provided in between.

[5. Other Modifications]
In the above embodiments and modifications, the semiconductor device 1 has been described as a power conversion device from DC power to AC power, but it may be a power conversion device from AC power to DC power. It may be a power conversion device that converts voltage, the number of phases, and the like. In addition, the semiconductor device 1 does not need to perform power conversion as long as the semiconductor module 5 performs switching.

Also, although the semiconductor module 5, the snubber device 7, the capacitor 10, and the current sensor 9 have each been described as one in number, they may be provided independently in other numbers. When semiconductor devices 1 and 1A include a plurality of semiconductor modules 5, these semiconductor modules 5 may be connected in series or in parallel. Similarly, when semiconductor devices 1 and 1A include a plurality of capacitors 10, these capacitors 10 may be connected in series or in parallel. Also, the number of snubber devices 7 and 7A may be less than the number of semiconductor modules 5 . In this case, one snubber device 7 may be attached to a plurality of semiconductor modules 5 that generate AC power of one or more phases. Also, the number of snubber devices 7 may be greater than the number of semiconductor modules 5 . In this case, a plurality of semiconductor modules 5 may be attached to one semiconductor module 5 .

When the semiconductor devices 1 and 1A include a plurality of semiconductor modules 5, the positive terminals 51 and the negative terminals 52 of the semiconductor modules 5 may be connected to each other by laminated busbars (not shown). Also, in this case, the snubber device 7 may be mounted between the positive side terminal 51 and the negative side terminal 52 via the laminated bus bar. The laminated bus bar has a structure in which planar wiring layers are laminated with an insulating layer sandwiched therebetween. , the wiring inductance between the semiconductor module 5 and the snubber device 7 is reduced. Therefore, it is possible to reduce the surge voltage that occurs when the current is interrupted by the semiconductor module 5 . Even when the laminated busbar is used in this manner, the current can be reliably detected because the current sensors 9 and 9A are provided in the wirings 100 and 705 .

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the description of the scope of claims that forms with such modifications or improvements can also be included in the technical scope of the present invention.

The execution order of each process such as actions, procedures, steps, and stages in the devices, systems, programs, and methods shown in the claims, the specification, and the drawings is particularly "before", "before etc., and it should be noted that they can be implemented in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the specification, and the drawings, even if the description is made using "first," "next," etc. for the sake of convenience, it means that it is essential to carry out in this order. not a thing

REFERENCE SIGNS LIST 1 semiconductor device 2 snubber circuit 5 semiconductor module 7 snubber device 8 short circuit detector 9 current sensor 10 capacitor 11 switching element 12 switching element 13 freewheeling diode 14 freewheeling diode 19 output terminal 21 charge path 22 discharge path 51 positive terminal 52 negative terminal 70 printed circuit board 100 wiring 101 positive wiring 102 negative wiring 211 positive capacitor 212 first diode 213 negative capacitor 221 2nd diode, 700 terminal, 701 wiring, 705 land, 1011 wiring inductance

Claims (6)

A snubber device connected between a positive terminal and a negative terminal of a semiconductor module,
a capacitor connected between the positive terminal and the negative terminal;
a charging path that charges the capacitor from the positive terminal and the negative terminal;
a discharge path, at least partially distinct from the charge path, discharging from the capacitor to the positive terminal and the negative terminal;
A snubber device comprising: a current sensor that measures the current flowing in the discharge path. 2. The snubber device according to claim 1 , wherein said current sensor is provided at a location in said discharge path different from said charge path. The snubber device is
each having a positive side capacitor, a first diode, and a negative side capacitor connected in series between the positive side terminal and the negative side terminal, and conducting current from the positive side terminal side to the negative side terminal side; n parallel charging paths (where n is an integer equal to or greater than 1) to flow;
the negative capacitor at the negative terminal or the Nth charging path (where N is an integer of 0≦N≦n) among the n charging paths, and the N+1th charging path among the n charging paths and the positive side capacitor or the positive side terminal of the positive side capacitor, and from the negative side terminal side to the positive side via at least one of the negative side capacitor and the positive side capacitor. n+1 parallel discharge paths that pass current to the terminal side;
3. The snubber device of claim 1 or 2 , comprising: 4. A snubber device according to any one of claims 1 to 3 , wherein the wiring inductance of each charging path is smaller than the wiring inductance of each discharging path. 5. The snubber device of claim 4 , wherein the wire length of each charge path is shorter than the wire length of each discharge path. a semiconductor module;
a snubber device according to any one of claims 1 to 5 ;
A semiconductor device comprising

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