JP2006080560A - Optical coupling power semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical coupling power semiconductor device suitable for constituting a power semiconductor device circuit which is small, lightweight, high speed and low loss. <P>SOLUTION: The optical coupling power semiconductor device comprises a bipolar type power semiconductor device, in which a plurality of a p-type layer 34 and n-type layers 33, 35 which consist of a wide-gap semiconductor material having substantially same band gap, are laminated in at least three-layers alternately, and a light receiving element. The power semiconductor device is equipped with a control terminal 16A which controls current flowing through the intermediate layer 34 among a plurality of layers 33, 34, 35. A recombination center which generates light according to the fed current, is included in at least one layer, for example the layer 34, of a plurality of layers 33, 34, 35. The light generated in the recombination center is emitted to the outside. The light receiving element generates the output according to the fed current of the power semiconductor device, when the light is received. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optically coupled power semiconductor element including a power semiconductor element and a light receiving element. Such an optically coupled power semiconductor element is used to detect a change in energization current flowing through the power semiconductor element by the light receiving element and control the energization current.

  A power semiconductor element circuit that detects a change in energization current and controls the energization current includes a detection circuit that detects a change such as an increase or decrease in the energization current flowing through the power semiconductor element and outputs a detection signal. Using this detection signal, control is performed such as suppressing an abnormal increase or decrease in the energization current, or interrupting the current in order to protect the load or the power semiconductor element circuit itself when an abnormality such as a short circuit occurs.

  In the above control, it is necessary to detect the energization current with high sensitivity. Two conventional examples of the detection circuit will be described with reference to the circuit diagrams of FIGS. In the first conventional example shown in FIG. 9A, a load 52 is connected to a DC power source 50 such as a solar cell or a fuel cell via an IGBT (Insulated gate bipolar transistor) 51 as a control element. A detection coil 53 such as CT is provided in the electric circuit 59 between the IGBT 51 and the power supply 50, and the voltage V1 induced in the detection coil 53 due to a change in the current flowing through the electric circuit 59 is input to the drive circuit 55 as a detection signal. The drive circuit 55 controls the IGBT 51 based on the voltage V1. For example, when a short circuit accident occurs in the load 52, the current flowing through the electric circuit 59 increases rapidly, and the voltage V1 also increases rapidly due to the rapid increase in current. When the voltage V1 exceeds a predetermined value, the drive circuit 55 controls the gate voltage of the IGBT 51 to turn off the IGBT 51. This prevents damage to the power supply 50, the IGBT 51, and the load 52 when an abnormality occurs.

FIG. 9B shows a circuit diagram of a second conventional example. In the figure, a load 52 is connected to a DC power source 50 via an IGBT 51 and a resistor 54 as control elements. The current flowing through the load 52 is detected by the resistor 54, and a voltage V2 as a detection signal is obtained. The voltage V2 is input to the drive circuit 55, and controls the IGBT 51 as in the first conventional example.
JP 2000-233449 A

  The detection circuit using the detection coil 53 of the first conventional example has the following problems. In the case of a power semiconductor element circuit with a large energization current, the electric wire of the electric circuit 59 needs to be thick. For example, the diameter of a 500 A class polyethylene insulated vinyl sheath cable (commonly called CV cable) is about 35 mm. The diameter of the 1500A class CV cable is about 65 mm. The diameter of the detection coil 53 formed so as to surround these CV cables becomes a large one of about 70 mm to 100 mm, and the weight also increases.

  The detection response time of such a large detection coil 53 is relatively long as about 1 to 10 microseconds, and the control of the current of the IGBT 51 is also delayed by this amount. Due to this control delay, when a short-circuit accident occurs, a large current may flow through the load 52 and the IGBT 51, which may cause a failure. When the current change rate is slow, the detection output level of the detection coil 53 is extremely low. Therefore, even if there is a large current change, it may not be detected.

  In the detection circuit using the resistor 54 of the second conventional example, a change in the energization current can be easily detected even when the change in the energization current is moderate. However, when the energization current is large, a large power loss occurs in the detection resistor 54 and heat is generated.

  For example, in a power semiconductor element circuit with a normal energization current of 500 A, a power loss of 500 W occurs when a resistance of 0.002 ohm is used. For example, when a short circuit accident or the like occurs in the load 52 and the energizing current increases to 1000 A, the power loss reaches 2 kW. As described above, the problem is that the power loss at the resistor 54 is large. Even if the detection response time is as fast as 1 millisecond, it is relatively long as 1 microsecond, and this delay occurs in the control of the IGBT 51. Therefore, when a short circuit accident occurs, a large current flows, which may cause damage to the resistor 54 and damage to the IGBT 51 and the load 52. Furthermore, in order to prevent damage to the resistor 54 due to heat generation, it is necessary to use a large resistance element having a large heat capacity or a resistance element having a cooling means such as water cooling. There was a problem.

  Accordingly, an object of the present invention is to provide an optically coupled power semiconductor element suitable for constructing a small, lightweight, high-speed and low-loss power semiconductor element circuit that detects an energization current without using a detection coil or a detection resistor. Is to provide.

In order to solve the above problems, the optically coupled power semiconductor element of the present invention is:
A bipolar power semiconductor element in which a plurality of p-type layers and n-type layers made of a wide gap semiconductor material having substantially the same band gap are alternately stacked;
The power semiconductor element is
A control terminal that is electrically connected to a layer sandwiched between the plurality of layers and controls an energization current flowing through the element;
At least one of the plurality of layers includes a recombination center that generates light according to the energization current,
The light generated at the recombination center is radiated to the outside,
A light receiving element that receives the light emitted from the power semiconductor element to the outside and generates an output corresponding to the energization current of the power semiconductor element is provided.

  In the optically coupled power semiconductor element of the present invention, the power semiconductor element generates light in response to an energizing current flowing through the element by the recombination center, and the light is emitted to the outside. The light receiving element receives the light emitted from the power semiconductor element to the outside, and generates an output corresponding to the energization current of the power semiconductor element. Therefore, the power semiconductor element circuit to which the optically coupled power semiconductor element is applied may control the energization current through the control terminal of the power semiconductor element by the output generated by the light receiving element. As a result, the power semiconductor element circuit can be reduced in size, weight, speed, and loss.

  An optically coupled power semiconductor element according to an embodiment includes an optical fiber that transmits the light emitted from the power semiconductor element to the outside to the light receiving element.

  In one embodiment of the optically coupled power semiconductor device, the recombination center includes an acceptor / donor pair.

  In one embodiment of the optically coupled power semiconductor element, the power semiconductor element radiates light generated at the recombination center to a position corresponding to the layer including the recombination center on the surface side of the element. A light emission window is provided.

  In the optically coupled power semiconductor device according to one embodiment, the acceptor and the donor are made of doped aluminum atoms and nitrogen atoms, respectively.

In the optically coupled power semiconductor device of one embodiment, the concentration of the aluminum atom and the nitrogen atom is in the range of 1 × 10 ¹⁵ atoms / cm ^{3 to} 1 × 10 ¹⁹ atoms / cm ³ .

  In the optically coupled power semiconductor device of one embodiment, the recombination center is included only in a portion of the layer including the recombination center that faces the light emission window.

  In one embodiment of the optically coupled power semiconductor device, the layer including the recombination center is a p-type layer, and the aluminum atoms are more doped than the nitrogen atoms.

  In one embodiment of the optically coupled power semiconductor device, the layer including the recombination center is an n-type layer, and the nitrogen atoms are more doped than the aluminum atoms.

In one embodiment, the concentration of the aluminum atom is about 1 × 10 ²¹ atoms / cm ³ and the concentration of the nitrogen atoms is 1 × 10 ¹⁵ atoms / cm ^{3 to} 1 × 10 ¹⁹ atoms / cm. It is characterized by being in the range of cm ³ .

In the optically coupled power semiconductor device according to one embodiment, the concentration of the nitrogen atoms is about 1 × 10 ²¹ atoms / cm ³ and the concentration of the aluminum atoms is 1 × 10 ¹⁵ atoms / cm ^{3 to} 1 × 10 ¹⁹ atoms / cm. It is characterized by being in the range of cm ³ .

  The optically coupled power semiconductor element is preferably an insulated gate bipolar transistor having a gate as the control terminal.

  The optically coupled power semiconductor element is preferably a P-channel insulated gate bipolar transistor having a P-channel gate as the control terminal and a P-type buffer layer as the layer including the recombination center.

  The optically coupled power semiconductor element is preferably a gate turn-off thyristor having a gate as the control terminal.

  The optically coupled power semiconductor device is preferably a gate turn-off thyristor having an anode gate structure having an anode gate as the control terminal.

  The power semiconductor element circuit of the present invention is formed of a light-emitting wide gap semiconductor material that is provided in an electric circuit connecting a power source and a load and controls the electric current of the electric circuit, and emits radiated light that changes in accordance with the electric current. A semiconductor control element, a light receiving element that detects radiated light of the semiconductor control element and outputs a detection signal, and the detection signal of the light receiving element is input, and a control signal corresponding to the detection signal is input to the gate of the semiconductor control element A gate drive circuit for applying and controlling a current applied to the semiconductor control element;

  According to this power semiconductor element circuit, since the light receiving element detects the radiated light that changes according to the energization current of the semiconductor control element, and controls the semiconductor control element based on the detection signal of the light receiving element, The control response time, which is the time until control of the semiconductor control element, is short. Moreover, since it detects using light, it is hard to receive the influence of an electrical noise.

  A power semiconductor element circuit according to another aspect of the present invention is formed of a light-emitting wide gap semiconductor material that is provided in an electric circuit connecting a power source and a load and controls the electric current of the electric circuit, and changes according to the electric current. A semiconductor control element provided on a silicon substrate that emits radiated light, a light receiving element that detects radiated light of the semiconductor control element and outputs a detection signal, and the detection signal of the light receiving element is input, and according to the detection signal And a gate driving circuit for applying a control signal to the gate of the semiconductor control element to control the energization current of the semiconductor control element.

  According to another aspect of the present invention, there is provided a power semiconductor element circuit in which at least one of semiconductor layers formed of a wide gap semiconductor material, which is provided in an electric circuit connecting a power source and a load and controls the electric current of the electric circuit, is regenerated. A semiconductor bipolar control element that has a coupling center and emits radiated light that changes in accordance with an energization current, a light receiving element that detects the radiated light of the semiconductor bipolar control element and outputs a detection signal, and the detection signal of the light receiving element And a gate driving circuit configured to apply a control signal corresponding to the detection signal to the gate of the semiconductor control element to control an energization current of the semiconductor bipolar control element.

  In the power semiconductor element circuit, it is preferable that the recombination center is provided in a part of the at least one layer.

  In the power semiconductor element circuit, the power source is preferably a DC power source.

  In the power semiconductor element circuit, the light receiving element is preferably incorporated in a package of the semiconductor control element.

  The power semiconductor element circuit preferably further includes an optical fiber that transmits the radiated light of the semiconductor control element to the light receiving element.

  In the power semiconductor element circuit, the gate drive circuit has a determination control circuit that determines that the energization current exceeds a predetermined value, and applies the determination output of the determination control circuit to the gate to It is desirable to control the control element.

  In the power semiconductor element circuit, the semiconductor control element is preferably formed of silicon carbide as a wide gap semiconductor material.

  In the power semiconductor element circuit, the semiconductor control element has a p-type layer and an n-type layer using silicon carbide as a semiconductor material, and at least one of the p-type layer and the n-type layer is a predetermined layer. It preferably contains a number of aluminum and nitrogen atoms.

  In the power semiconductor element circuit, the semiconductor control element is preferably an insulated gate bipolar transistor formed of a light-emitting wide gap semiconductor material.

  In the power semiconductor element circuit, the semiconductor control element is preferably a gate turn-off thyristor formed of a light-emitting wide gap semiconductor material.

  In the power semiconductor device circuit, the semiconductor control device is preferably a gate turn-off thyristor having an anode gate structure.

  In the power semiconductor element circuit, the semiconductor control element is preferably formed of gallium nitride, which is a wide gap semiconductor material.

  In the power semiconductor element circuit, the semiconductor control element has a p-type layer and an n-type layer made of gallium nitride as a semiconductor material, and the n-type layer has a recombination center by a predetermined number of silicon atoms. Is desirable.

  In the power semiconductor element circuit, it is preferable that the recombination center is provided in a part of the n-type layer.

  An inverter device according to the present invention includes a semiconductor control element that is formed of a light-emitting wide gap semiconductor material connected between both positive and negative terminals of a DC power source, and emits radiated light that changes in accordance with an energization current. A light-receiving element that detects radiation of the element and outputs a detection signal; and the detection signal of the light-receiving element is input, and a control signal corresponding to the detection signal is applied to a gate of the semiconductor control element A plurality of series connection bodies of a power semiconductor element circuit and a semiconductor control element having a gate drive circuit for controlling the energization current of the load, a load connected to a connection point of the series connection body, a control circuit for controlling the semiconductor control element, And a flywheel diode connected to the semiconductor control element of the power semiconductor element circuit and the semiconductor control element in antiparallel.

An inverter device according to another aspect of the present invention includes:
A series connection body in which a plurality of two semiconductor control elements connected in series between the positive and negative terminals of the DC power supply are connected in series;
A load connected to a connection point of the series connection body;
In a control circuit for controlling the semiconductor control element, and an inverter device having flywheel diodes connected in antiparallel to the semiconductor control element,
At least one of the two semiconductor control elements of the serial connection body is formed of a light-emitting wide gap semiconductor material, a semiconductor control element that emits radiated light that changes in accordance with an energization current, and detects and detects the radiated light of the semiconductor control element A light receiving element that outputs a signal, and a gate drive that receives the detection signal of the light receiving element and applies a control signal corresponding to the detection signal to the gate of the semiconductor control element to control the energization current of the semiconductor control element A power semiconductor element circuit having a circuit.

  Embodiments of the optically coupled power semiconductor device of the present invention will be described below.

  Examples of suitable materials for power semiconductor elements used in power semiconductor element circuits (hereinafter referred to as “semiconductor control elements” or “bipolar semiconductor control elements”) include silicon carbide (SiC), gallium nitride (GaN), and diamond. Wide gap semiconductor materials are known. Wide-gap semiconductor materials have superior physical properties that they have a higher dielectric breakdown field and higher thermal conductivity than silicon (Si) semiconductor materials and operate at high temperatures. For this reason, a wide gap semiconductor element formed of a wide gap semiconductor material has a high withstand voltage and low loss, and the loss generated in the semiconductor element is small. Further, since the generated heat can be easily dissipated and the current can be increased to a considerably high temperature, it is suitable for a semiconductor element of a power semiconductor element circuit for controlling a large current.

  In a wide-gap semiconductor material, either a n-type layer or a p-type layer forming a junction has a carrier recombination center (impurity atoms or a plurality By forming a region where a complex of impurity atoms is present, a light-emitting wide gap semiconductor element that emits light when a current is passed through the junction can be obtained. When a light emitting wide gap bipolar semiconductor control element is formed using a wide gap semiconductor material and a light emitting portion is provided in a part of the element, light can be emitted therefrom. This light is detected by the light receiving element, and the value of the energizing current and its change can be detected from the obtained detection output. The intensity of the emitted light is approximately proportional to the current flowing through the bipolar semiconductor control element. When a light receiving element having photoelectric conversion characteristics with good linearity is used, the detection output of the light receiving element is proportional to the current flowing through the bipolar semiconductor control element. Therefore, when the drive circuit of the bipolar semiconductor control element is operated by the detection output of the light receiving element, the energization current of the bipolar semiconductor control element can be controlled. Note that if the number of recombination centers is too large, the on-voltage of the semiconductor element becomes higher and the power loss becomes larger in order to recombine electrons and holes than securing the required radiated light. For this reason, it is desirable to optimize the doping amount of impurity atoms or the like forming the recombination center, or to localize the doped region in a part of the semiconductor layer. For example, it is also possible to limit to a region of the semiconductor layer facing the light emitting portion.

As the light receiving element, a Si semiconductor light receiving element, a wide gap semiconductor light receiving element, a photoconductive element, or the like is used. The light receiving element is, for example, a substantially square flat plate having a side of several mm and a thickness of about 1 mm, and is provided in a package of a light emitting wide gap bipolar semiconductor control element. This configuration makes an optical bipolar semiconductor control element. In the optical bipolar semiconductor control element, the light receiving element and the bipolar semiconductor control element are electrically insulated, and the light receiving surface of the light receiving element faces the light emitting portion of the bipolar semiconductor control element. The increase in the volume of the package due to the incorporation of the light receiving element in the package of the bipolar semiconductor control element is about 3 cm ³ for a 6 kV class device, and the increase in weight is about 100 grams. The total transmission efficiency of the optical bipolar semiconductor control element is the light emission efficiency of the bipolar semiconductor control element, the light collection efficiency at which the light is collected on the light receiving element, and the photoelectric conversion efficiency at which the light collected on the light receiving element is converted into electricity. However, it is about 0.005 to 2%. For example, when 0.1%, the photocurrent generated in the light receiving element is about 0.5 A when the current flowing through the bipolar semiconductor control element is 500 A. Even if the current increases to, for example, 1000 A due to a short circuit accident or the like, the photocurrent generated in the light receiving element is about 1 A. Since a voltage of 20 to 30 V or less is normally applied to the light receiving element, the power loss generated in the light receiving element is about 20 to 30 W.

  Since the photocurrent of the light receiving element increases or decreases in proportion to the current flowing through the bipolar semiconductor control element, it can be detected even when the current changes slowly.

  As another preferred embodiment of the present invention, there is a method of detecting light of a bipolar semiconductor control element using a light-emitting wide gap semiconductor material by a light receiving element through an optical fiber. For example, the optical fiber is attached to the package of the bipolar semiconductor control element so that the incident end faces the light emitting portion of the bipolar semiconductor control element. A light receiving element is attached to the exit end of the optical fiber. In this configuration, in addition to the above effect, the withstand voltage between the bipolar semiconductor control element and the light receiving element can be easily increased.

A preferred embodiment of the present invention will be described below with reference to FIGS.
<< First Example >>
A power semiconductor device circuit including an optically coupled power semiconductor device according to a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a circuit diagram of the power semiconductor element circuit of this embodiment. In the figure, a load 14 is connected to a DC power source 13 such as a solar cell or a fuel cell via a gate turn-off thyristor (GTO) 1 as a semiconductor control element of a power semiconductor element circuit. The direct current power source 13 may be a direct current power source obtained by rectifying and smoothing alternating current from an alternating current power source using a rectifier. GTO1 is a luminescent wide-gap bipolar semiconductor control element manufactured using SiC, which is a luminescent wide-gap semiconductor material, and emits light whose intensity is approximately proportional to the current flowing through GTO1. The emitted light indicated by the arrow 1A is received by the light receiving element 2 provided in the package of the GTO 1, which will be described in detail later with reference to FIG. The cathode 9B of the light receiving element 2 is connected to the negative electrode G of the power source 13 via the power source 9c, and the anode 2A is connected to the input terminal 10 of the determination control circuit 7. A turn-on circuit 3 and a turn-off circuit 5 are connected to a gate 16 as a control terminal of the GTO 1. The turn-on circuit 3 includes a power source 3A, a transistor 3B, and a resistor 3C connected in series between the gate of the GTO 1 and the negative electrode G. A positive pulse signal for turning on the GTO 1 is applied to the gate terminal 4 of the transistor 3B. The OFF circuit 5 includes a DC power source 5A having a positive electrode connected to the negative electrode G of the power source 13, and a resistor 5B and an FET 5C connected in series between the negative electrode of the DC power source 5A and the gate of the GTO 1. A capacitor 5D is connected between the source of the FET 5C and the negative electrode G. A positive pulse signal for turning off the GTO 1 is applied to the gate 6 of the FET 5C. The determination control circuit 7 has a comparator 8 whose output end is connected to the gate 6. One input terminal 11 of the comparator 8 is connected to a reference power source 9 that generates a reference voltage, and the other input terminal 10 is connected to the anode 2 A of the light receiving element 2. A resistor 12 is connected between the input terminal 10 and the negative electrode G.

  Next, the operation of the power semiconductor element circuit of this embodiment will be described.

  The GTO 1 is, for example, a SiC-GTO thyristor having a withstand voltage of 6 kV and a current capacity of 200 A, and the light receiving element 2 uses a silicon photodiode. When the GTO 1 is turned on, a positive pulse signal is given to the input terminal 4 of the turn-on circuit 3. As a result, when the transistor 3B is turned on, the GTO 1 is turned on and a predetermined current (for example, 100 A) flows from the power supply 13 to the load 14. When turning off the GTO 1 in the on state, a positive pulse signal is applied to the input terminal 6 of the turn-off circuit 5 to turn on the FET 5C. As a result, the current is bypassed from the gate 16 of the GTO 1 to the DC power source 5A, the energization current of the GTO 1 is cut off, and the operation of the load 14 is stopped. The radiated light of the GTO 1 being energized is detected by the light receiving element 2, and the generated photocurrent 2C flows from the input terminal 10 of the determination control circuit 7 to the negative electrode G through the resistor 12. The voltage generated at the input terminal 10 is compared with the voltage of the reference power supply 9 by the comparator 8. When an abnormality such as a short circuit occurs in the load 14, a large current exceeding the normal value flows through the GTO 1 and the intensity of the emitted light increases. As a result, the photocurrent of the light receiving element 2 increases and the voltage at the detection terminal 10 of the comparator 8 also increases. When the voltage of the detection terminal 10 becomes higher than the reference voltage of the input terminal 11 of the comparator 8, the output of the comparator 8 becomes high level, the FET 5C of the turn-off circuit 5 is turned on, and the GTO 1 is turned off. For example, when a current of about 150 A flows, if the voltage of the input terminal 10 of the comparator 8 is set to exceed the reference voltage of the input terminal 11, the GTO 1 is turned off when a current exceeding 150 A flows and the power supply 13 and the load 14 are connected. Shut off. This can prevent the load 14 from being damaged and the power semiconductor element circuit from being damaged.

  It is desirable to connect a known snubber circuit between the cathode 13A and the anode 14A of GTO1. The snubber circuit is preferably a combination of resistors, capacitors, diodes, and the like.

  FIG. 2 is a cross-sectional view of an optical GTO element 100 having a withstand voltage of 6 kV and a current capacity of 200 A, in which the GTO 1 and the light receiving element 2 are housed in one package. In the figure, GTO 1 is fixed to the central portion of metal base 3 connected to anode electrode 14A. A light emission window 19 that emits light when a current flows through the GTO 1 is provided on the surface of the GTO 1. A metal cap 4 is fixed to the metal base 3. A photodiode 2 is attached to the inner surface of the cap 4 via an insulating plate 2D with the light receiving portion 2B facing the light emission window 19 of the GTO 1. The metal base 3 has two holes 17 and 18. A cathode electrode 13 A is led out from the hole 17, and a gate electrode 16 is led out from the hole 18. The cap 4 has two holes 10 and 11. The anode electrode 2A of the light receiving element 2 is led out from the hole 10, and the cathode electrode 9B is led out from the hole 11. The holes 10, 11, 17, 18 are all hermetically sealed with a known hermetic sealant. The optical GTO element 100, the turn-on circuit 3, the turn-off circuit 5, and the determination control circuit 7 constitute a power semiconductor element circuit.

  In the package of the optical GTO element 100, the cathode 20 of the GTO 1 is connected to the cathode electrode 13A by two conducting wires 14B and 14C. The gate 16 A of GTO 1 is connected to the gate electrode 16 by a conducting wire 15. What is necessary is just to increase / decrease the number of conducting wire 14B, 14C, 15 according to electric current amount. The anode 7 </ b> A of the light receiving element 2 is connected to the anode electrode 2 </ b> A by a conducting wire 6, and the cathode 9 </ b> A is connected to the cathode electrode 9 </ b> B by a conducting wire 28. The GTO 1 and the light receiving element 2 are electrically insulated. The distance between the light emission window 19 of the GTO 1 and the light receiving part 2B of the light receiving element 2 is about 1 cm. The silicon photodiode of the light receiving element 2 has a substantially square shape with a side of 3 mm and a thickness of about 0.5 mm. The anode electrode 14A, the gate electrode 16 and the cathode electrode 13A are all about 3 cm in length. As described above, since the silicon photodiode is small, the size of the optical GTO 100 is small. When this optical GTO 100 was compared with a SiC-GTO thyristor having a withstand voltage of 6 kV and a current capacity of 200 A, the optical GTO 100 increased in weight by about 100 grams and increased in volume by several percent. As shown in FIG. 2, in the optical GTO 1, the light emission window 19 is provided by removing a part of the pad for attaching the conductor of the anode 20, so that the light emission efficiency is relatively low. In addition, the light collection efficiency is lowered by separating the light emission window 19 and the light receiving portion 2B of the light receiving element 2 by about 1 cm. Therefore, even when the energization current instantaneously increases from 200 A to 1000 A at the time of abnormality, the photocurrent of the light receiving element 2 is about 120 mA. When the applied voltage of the light receiving element 2 is 10 V, for example, the power loss is about 1.2 W, which is an extremely low value.

  The detection response time from when the current suddenly increases due to a short circuit accident or the like in the load 14 until the light receiving element 2 detects the rapid increase in current is 0.1 microsecond or less. The time from the detection of the light receiving element 2 until the GTO 1 is turned off by the operation of the determination control circuit 7 and the drive circuit 23 is 2 to 3 microseconds, which is an extremely short time. The inventor conducted an experiment to set a voltage of the reference power supply 9 of the determination control circuit 7 and generate a short circuit so that the GTO 1 is turned off when the energization current of the GTO 1 exceeds 200 A. As a result, when the short circuit occurred and the current increased by about 40% to reach about 280 A, the control worked and GTO 1 was turned off. From this experimental result, it was found that the short-circuit current can be greatly suppressed. Since the short-circuit current does not increase, each component of the power semiconductor element circuit may have a small power capacity, and the power semiconductor element circuit can be reduced in size, weight, and loss. As described above, according to the present embodiment, the power semiconductor element circuit can be reduced in size and weight, and at the same time, high speed and low loss can be realized.

  The light-emitting wide gap bipolar semiconductor control element will be described in detail below.

In a conventional bipolar semiconductor control element such as GTO, recombination of carriers does not occur as much as possible in a p-type or n-type semiconductor layer forming a junction in order to lower the on-voltage and reduce the loss. It is configured. That is, the recombination center is not included in each semiconductor layer as much as possible. On the other hand, in the light-emitting wide gap bipolar semiconductor control element of the present invention, contrary to the conventional bipolar semiconductor control element, a certain amount of re-growth is performed on at least one of the semiconductor layers forming the bipolar semiconductor control element. The connection center is configured to exist. The recombination center is obtained by doping at least one SiC semiconductor layer with atoms of aluminum as an acceptor and nitrogen as a donor. In this case, light is generated by recombination of holes captured at the impurity level formed by aluminum atoms and electrons captured at the impurity level formed by nitrogen atoms. When the semiconductor layer is doped with a large number of aluminum atoms and nitrogen atoms to form a large number of recombination centers, the intensity of the emitted light increases. However, since recombination inhibits the flow of electrons and holes, the on-resistance of the bipolar control element is increased, and thus the on-voltage is increased. As a result, the power loss of the bipolar control element increases. Therefore, it is necessary to set the intensity of the emitted light and the magnitude of the on-resistance to desirable values in consideration of practicality. In the light-emitting wide gap bipolar semiconductor material of this embodiment, that is, SiC, it is desirable that the numbers of aluminum atoms and nitrogen atoms are in the range of 1 × 10 ¹⁵ to 1 × 10 ¹⁹ atoms / cm ³ , respectively. In the case of SiC, aluminum serves as a p-type impurity and nitrogen serves as an n-type impurity. Therefore, when the semiconductor layer having a recombination center is p-type, it is necessary to dope aluminum more than nitrogen. For example, aluminum may be increased to about 1 × 10 ²¹ atoms / cm ³ . Further, when the semiconductor layer having a recombination center is n-type, it is necessary to dope nitrogen more than aluminum. For example, nitrogen may be increased to about 1 × 10 ²¹ atoms / cm ³ .

  A detailed structure of the light-emitting wide gap GTO 1 used in this embodiment will be described with reference to FIGS. FIG. 3 is a plan view of the GTO 1, and FIG. 4 is a sectional view taken along the line IV-IV in FIG. GTO1 of FIG. 2 has shown II-II sectional drawing of FIG.

3 and 4, the GTO 1 has a p-type layer 32 having a thickness of about 100 μm formed on the cathode electrode 31 and an n-type layer 33 having a thickness of about 70 μm formed thereon as shown in the cross-sectional view of FIG. Forming. A p-type layer 34 having a recombination center and having a thickness of about 3 μm is formed on the n-type layer 33. In the figure of the p-type layer 34, gate electrodes 16A are formed at both ends. In the figure of the p-type layer 34, an n-type layer 35 having a thickness of about 2 μm is formed at the center, and the anode electrode 20 is formed on the n-type layer 35. The p-type layer 34 is doped with aluminum atoms at a concentration of 3.5 × 10 ¹⁷ atoms / cm ³ and nitrogen atoms at a concentration of 8 × 10 ¹⁶ atoms / cm ³ . Thus, for example, when the current was supplied at a current density of 100 A / cm ² , the on-voltage was a relatively low value of 5.2V. The intensity of the emitted light in this energized state was about 16 milliwatts (mW), and the wavelength of the emitted light was about 470 nanometers (nm). As shown in FIGS. 2 and 3, a known termination region 37 for relaxing the electric field is formed in the outer peripheral region of the GTO 1. The periphery of the light emission window is surrounded by the cathode electrode 20 so that a sufficient current flows through the p-type layer without the cathode electrode facing the light emission window. Although an experiment was conducted in the case where only aluminum other than the portion of the p-type layer 34 substantially facing the light emission window was doped and nitrogen was not doped, there was an effect in reducing the on-voltage.
<< Second Embodiment >>
FIG. 5 is a circuit diagram of a power semiconductor device circuit including the optically coupled power semiconductor device according to the second embodiment of the present invention. In the figure, a load 14 is connected to a DC power source 13 via an optical IGBT 101 as a power semiconductor element. The optical IGBT 101 includes a p-channel SiC insulated gate bipolar transistor (IGBT) 21 as a bipolar semiconductor control element made of a light-emitting wide gap semiconductor material and a silicon photodiode as a light receiving element 22 in one package (not shown). It is stored in. The configuration in the package is similar to the configuration of the optical GTO 100 shown in FIG. 2, and the radiated light indicated by the arrow 21 </ b> A of the SiC-IGBT 21 enters the light receiving portion of the light receiving element 22. A DC power source 103 is connected between the cathode of the light receiving element 22 and the negative electrode of the power source 13 so that the positive electrode is connected to the cathode. The output terminal 23 </ b> A of the drive circuit 23 that controls energization of the SiC-IGBT 21 is connected to the gate of the SiC-IGBT 21. A control signal for controlling the SiC-IGBT 21 from an external device is input to the input terminal 24 of the drive circuit 23. The anode of the light receiving element 22 is connected to the input terminal 10 through the resistor 12 of the determination control circuit 7. Since the circuit configuration of the determination control circuit 7 is the same as that of FIG. 1, the same operation is performed. The output terminal 7A of the determination control circuit 7 is connected to the input terminal 23B of the drive circuit 23. The optical IGBT 101, the drive circuit 23, and the determination control circuit 7 constitute a power semiconductor element circuit.

When the current flowing through the SiC-IGBT 21 increases due to fluctuations in the load 14 or the like, the photocurrent indicated by the arrow 22C flowing through the light receiving element 22 increases, and the voltage at the input terminal 10 of the determination control circuit 7 increases. When the voltage of the input terminal 10 becomes higher than the voltage of the reference power supply 9, the output terminal 7A of the comparator 8 becomes high level. As a result, the drive circuit 23 controls to reduce the current flowing through the SiC-IGBT 21 by lowering the level of the output end 23A. When the current flowing through the load 14 decreases below a predetermined value, the current flowing through the SiC-IGBT 21 is increased by performing the reverse operation. As a result, the current flowing through the load 14 can be kept in a substantially constant range. When an abnormality such as a short circuit accident occurs in the load 14 and a large current flows, the current of the SiC-IGBT 21 is significantly reduced or the SiC-IGBT 21 is turned off to prevent damage due to the accident. Although the detailed configuration of the SiC-IGBT 21 of this embodiment is not shown, the p-type buffer semiconductor layer has aluminum atoms of 1.6 × 10 ¹⁷ atoms / cm ³ and nitrogen atoms of 6 × 10 ¹⁶ atoms / cm ³ . Doped by concentration. Accordingly, for example, when the current was supplied at a current density of 100 A / cm ² , the on-voltage was a relatively low value of 4.6V. The intensity of the emitted light in this energized state was about 8 mW, and the wavelength was about 470 nm.

  In a specific example of the present embodiment, a SiC-p channel IGBT having a withstand voltage of 6 kV and a current capacity of 100 A is used as the IGBT 21, and a silicon photodiode is used as the light receiving element 22. In a normal use state, a drive signal is input to the input terminal 24 of the drive circuit 23. As a result, a negative voltage is applied to the gate of the IGBT 21, and the IGBT 21 is turned on. When the IGBT 21 is turned off, the level of the drive signal is set to zero, or a drive signal having a reverse polarity is applied depending on the case. As a result, the current flowing through the load 14 can be cut off by turning off the IGBT 21. In the specific example, even if a short circuit accident occurs in the load 14 and the current increases to, for example, 800 A, the current flowing through the light receiving element 22 is about 90 mA. If the voltage of the DC power supply 103 is 10 V, the power loss of the light receiving element 22 is extremely low at about 0.9 W, and there is no problem even if it is housed in the same package as the IGBT 21.

The detection response time from when the current suddenly increases due to a short circuit accident or the like in the load 14 until the light receiving element 22 detects the rapid increase in current is 0.1 microsecond or less. The time from detection of the light receiving element 22 until the IGBT 21 is turned off by the operation of the determination control circuit 7 and the drive circuit 23 is about 1 microsecond, which is an extremely short time. The inventor conducted an experiment in which the voltage of the reference power supply 9 of the determination control circuit 7 is set and a short circuit is generated at the load 14 so that the IGBT 21 is turned off when the energization current of the IGBT 21 exceeds 100A. As a result, when the short circuit occurred and the current increased by about 50% to about 150 A, the control was activated and the IGBT 21 was turned off. From this experimental result, it was found that the short-circuit current can be greatly suppressed. Since the short-circuit current does not increase, each component of the power semiconductor element circuit may have a small power capacity, and the power semiconductor element circuit can be reduced in size, weight, speed and loss.
<< Third embodiment >>
FIG. 6 is a circuit diagram of a 9 kV power semiconductor device circuit 40 including the optically coupled power semiconductor device of the third embodiment. In the figure, the anode electrode 49A of the GTO 41 as the power semiconductor element is connected to one input terminal of the load 14 and the determination control circuit 48, and the cathode electrode 49B is connected to the negative electrode of the power source 13. A load 14 is connected to the DC power source 13 via the GTO 41. The GTO 41 used in this embodiment is a gate turn-off thyristor (GTO) using SiC, which is a light-emitting wide gap semiconductor material. As shown in the cross-sectional view of FIG. 7, the GTO 41 is an SiC-GTO having an anode gate structure in which an n-type substrate is used and a gate is provided in an n-type base region. In FIG. 7, a p-type layer 37 having a thickness of about 95 μm is formed on the other surface of an n-type SiC substrate 36 having a thickness of about 250 μm having a cathode electrode 49B on one side. An n-type layer 38 having a recombination center and having a thickness of about 3 μm is formed on the p-type layer 37. A p-type layer having a thickness of about 2 μm is formed at the center of the n-type layer 38, and an anode electrode 49A is provided thereon. Gate electrodes 49C as control terminals are provided at both ends of the n-type layer 38.

In this SiC-GTO, the n-type layer 38 which is a base region is doped with aluminum atoms at a concentration of 8 × 10 ¹⁶ atoms / cm ³ and nitrogen atoms at a concentration of 2.8 × 10 ¹⁷ atoms / cm ³ . The on-state voltage when energized at a current density of 100 A / cm ² was a relatively low value of 4.1V. The intensity of the emitted light in this energized state was 13 mW, and the wavelength of the emitted light was about 470 nm.

  In the present embodiment, one end of the optical fiber 43 is disposed at the light emitting portion of the GTO 41, and a light receiving element 42 such as a photodiode is disposed at the other end of the optical fiber. Thereby, the radiated light of the GTO 41 enters the light receiving element 42 through the optical fiber 43. Since the GTO 41 and the light receiving element 42 are electrically isolated by the optical fiber 43, the light receiving element 42 and the determination control circuit 48 are not connected to the high power even if the circuit including the power supply 13, the load 14, and the GTO 41 is at a high voltage. The influence of voltage can be reduced. Further, since the light receiving element 42 can be provided away from the GTO 41, the degree of freedom in manufacturing the apparatus is increased. When the GTO 41 is turned on from an external device, a positive pulse voltage is applied to the input terminal 45 of the turn-on circuit 44, and when the GTO 41 is turned off, a positive pulse is similarly applied to the input terminal 47 of the turn-off circuit 46. Apply. When the current flowing through the GTO 41 increases and the intensity of radiated light increases, the intensity of incident light incident on the light receiving element 42 via the optical fiber 43 also increases. The detection current of the light receiving element 42 that is substantially proportional to the intensity of the incident light is applied to the determination control circuit 48 and compared with the output current of the reference power supply 9. When the intensity of the incident light of the light receiving element 42 increases and the current flowing through the light receiving element 42 exceeds a predetermined current value, the output signal of the output terminal 48A of the determination control circuit 48 is applied to the turn-off circuit 46 to turn off the GTO 41. To do. The output current of the reference power supply 9 can be arbitrarily changed, and the predetermined current value can be set to a desired value by adjusting the output current. Thereby, the current of GTO 41 can be controlled. This embodiment is more suitable for a power semiconductor circuit in which the voltage of the power supply 13 is 9 kV or higher and the current flowing through the load 14 is 200 A or higher. Further, since the GTO thyristor having an anode gate structure uses a SiC n-type substrate, the on-resistance is reduced to 1/5 or less as compared with the first embodiment using a SiC p-type substrate. Therefore, the power loss of the GTO 41 during energization is very small. The heat sink of GTO 41 may be small, and a small and light power semiconductor element circuit can be realized.

The detection response time from when the current suddenly increases due to a short circuit accident or the like in the load 14 until the light receiving element 42 detects the rapid increase in current is 0.1 microsecond or less. The time from the detection of the light receiving element 42 until the GTO 41 is turned off by the operation of the determination control circuit 7 and the drive circuit 23 is 2 to 3 microseconds, which is an extremely short time. The inventor conducted an experiment to set a voltage of the reference power supply 9 of the determination control circuit 7 and generate a short circuit so that the GTO 41 is turned off when the energization current of the GTO 41 exceeds 400A. As a result, when the short circuit occurred and the current increased by about 40% to about 560 A, the control was activated and the GTO 41 was turned off. From this experimental result, it was found that the short-circuit current can be greatly suppressed. Since the short-circuit current does not increase, each component of the power semiconductor element circuit may have a small power capacity, and the power semiconductor element circuit can be reduced in size, weight, speed and loss. In the n-type base layer, only the portion facing the light emission window (38A in FIG. 7) is doped with aluminum and nitrogen, and the other is doped with nitrogen alone to secure the emitted light intensity and further increase the on-resistance. It was effective in reducing.
<< 4th Example >>
FIG. 8 is a block diagram of an inverter device using the power semiconductor element circuit. In this embodiment, for example, the power semiconductor element circuit 40 of the third embodiment is used as a part of the control circuit of the inverter device. Instead of the power semiconductor element circuit 40, the power semiconductor element circuit of the first or second embodiment may be used. In FIG. 8, for example, the control circuit connected to the positive side of the DC power supply 13 is the power semiconductor element circuit 40 of the third embodiment, and each GTO 41 includes a control circuit 74 including a known PWM control circuit, A flywheel diode 41A is connected. When the voltage of the DC power supply 13 is not so high, the optical fiber 43 is not used for the transmission of light between the GTO 41 and the silicon photodiode 42, and both are arranged close to each other, and the light of the GTO 41 is directly incident on the photodiode 42. Also good. A non-luminous anode gate GTO 72 is used for the semiconductor control element on the negative electrode side of the DC power supply 13. The same power semiconductor element circuit 40 as that on the positive electrode side may be used in place of the anode gate GTO 72. However, since the light emitting GTO 41 has a higher on-voltage than the anode gate GTO 72, the power loss is increased accordingly. It is disadvantageous in terms of high cost. The control device 73 may be the same as a known PWM control circuit of the switching element of the inverter.

  According to the present embodiment, the photodiode 42 receives the radiated light substantially proportional to the energizing current flowing through the GTO 41 to detect the energizing current, and superimposes the detected current on the current of the reference power source 9 to the determination control circuit 48. Apply. Thereby, the energization pulse width of the GTO 41 can be controlled via the PWM control circuit, the energization current of the GTO 41 can be controlled, and a small, light and low-loss inverter device can be obtained. Further, by using the detection current of the photodiode to control not only the width of the energization pulse but also the height of the energization pulse, it is possible to obtain a small, light, and low loss inverter device that can increase or decrease the supply current.

  Although the four embodiments of the power semiconductor device circuit including the optically coupled power semiconductor device of the present invention have been described above, the present invention covers more application ranges or derivative structures. For example, GTO-thyristors and IGBTs using wide gap semiconductor materials may be other wide gap semiconductor bipolar control elements such as emitter switch thyristors and electrostatic induction thyristors, and a plurality of wide gap semiconductors stacked on a Si substrate. It may be a bipolar control element formed of layers. The GTO-thyristor and IGBT may be a hybrid element in which a unipolar element such as a MOSFET formed of Si or a wide gap semiconductor material and a bipolar control element formed of a wide gap semiconductor material are combined. For example, an element having a hybrid structure in which a Si-MOSFET is connected between an emitter and a collector of a bipolar transistor using a wide gap semiconductor material may be used.

The wide gap semiconductor GTO thyristor may be formed using gallium nitride (GaN), which is a wide gap semiconductor material. The gallium nitride GTO thyristor (GaN-GTO) preferably has an anode gate structure as shown in FIG. 7 of the third embodiment, and the thickness and impurity concentration of each of the n-type and p-type semiconductor layers are as shown in FIG. Should be almost the same. In GaN-GTO, zinc (Zn) is suitable as the p-type impurity, and silicon (Si) is suitable as the n-type impurity. When the n-type base (n-type layer 38 in FIG. 7) is doped with Si atoms at a concentration of 2.8 × 10 ¹⁷ atoms / cm ^3, a recombination center is formed by Si atoms, and a luminescent GaN-GTO is obtained. . The wavelength of the emitted light is about 470 nm, and the intensity of the emitted light at the same energizing current is stronger than that of SiC-GTO. The withstand voltage of GaN-GTO is 1200V (current 75A), which is lower than that of SiC-GTO. In the power semiconductor element circuit 40 of FIG. 6, by using GaN-GTO instead of SiC GTO 41, the power semiconductor element circuit 2 having the same effect as the third embodiment can be obtained.

  The light receiving element may be a phototransistor, a CdS photoconductive element, or the like other than the Si photodiode, or a light receiving element using a wide gap semiconductor material such as a SiC photodiode.

1 is a circuit diagram of a power semiconductor element circuit including an optically coupled power semiconductor element according to a first embodiment of the present invention. It is sectional drawing of the package containing a power semiconductor element and a light receiving element used for the power semiconductor element circuit of 1st Example. It is a top view of GTO1 as an optical coupling power semiconductor element of 1st Example. It is IV-IV sectional drawing of GTO1 of FIG. It is a circuit diagram of the power semiconductor element circuit provided with the optical coupling power semiconductor element of 2nd Example of this invention. It is a circuit diagram of the power semiconductor element circuit provided with the optical coupling power semiconductor element of 3rd Example of this invention. It is sectional drawing of SiC-GTO as an optical coupling power semiconductor element of 3rd Example. It is a circuit diagram of the inverter apparatus provided with the said power semiconductor element circuit. (A) is a circuit diagram of a power semiconductor element circuit of a first conventional example, and (b) is a circuit diagram of a power semiconductor element circuit of a second conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor control element 2 Light receiving element 2A Anode electrode 3 Turn-on circuit 5 Turn-off circuit 7 Judgment circuit 8 Comparator 9 Reference power supply 9A Cathode 9B Cathode electrode 13 DC power supply 13A Cathode 14 Load 14A Anode electrode 16 Gate electrode 19 Light emission window 21 Insulated gate bipolar Transistor (IGBT)
22 Photodetector 23 Drive circuit 31 Cathode electrode 32, 34 n-type layer 33, 35 p-type layer 37 termination region 41 optical GTO
42 Photodetector 43 Optical fiber 44 Turn-on circuit 46 Turn-off circuit 48 Judgment circuit 72 Anode gate GTO
73 Control Device 100 Optical GTO Element 101 Optical IGBT

Claims (15)

A bipolar power semiconductor element in which a plurality of p-type layers and n-type layers made of a wide gap semiconductor material having substantially the same band gap are alternately stacked;
The power semiconductor element is
A control terminal that is electrically connected to a layer sandwiched between the plurality of layers and controls an energization current flowing through the element;
At least one of the plurality of layers includes a recombination center that generates light according to the energization current,
The light generated at the recombination center is radiated to the outside,
An optically coupled power semiconductor element, comprising: a light receiving element that receives the light radiated to the outside by the power semiconductor element and generates an output corresponding to the energization current of the power semiconductor element. The optically coupled power semiconductor device according to claim 1,
An optically coupled power semiconductor element comprising an optical fiber that transmits the light emitted from the power semiconductor element to the outside to the light receiving element. The optically coupled power semiconductor device according to claim 1,
The recombination center includes a pair of an acceptor and a donor. The optically coupled power semiconductor device according to claim 3,
The power semiconductor element includes a light emission window that radiates light generated at the recombination center to the outside at a position corresponding to the layer including the recombination center on the surface side of the element. Optically coupled power semiconductor element. The optically coupled power semiconductor device according to claim 3,
The acceptor and donor are made of doped aluminum atom and nitrogen atom, respectively. The optically coupled power semiconductor device according to claim 5,
The concentration of the aluminum atom and nitrogen atom is in the range of 1 × 10 ¹⁵ atoms / cm ^{3 to} 1 × 10 ¹⁹ atoms / cm ³ , respectively. The optically coupled power semiconductor device according to claim 4,
The optical coupling power semiconductor element, wherein the recombination center is included only in a portion of the layer including the recombination center facing the light emission window. The optically coupled power semiconductor device according to claim 5,
The optically coupled power semiconductor device, wherein the layer including the recombination center is a p-type layer, and the aluminum atoms are more doped than the nitrogen atoms. The optically coupled power semiconductor device according to claim 5,
The optically coupled power semiconductor device, wherein the layer including the recombination center is an n-type layer, and the nitrogen atoms are more doped than the aluminum atoms. The optically coupled power semiconductor device according to claim 8,
The concentration of the aluminum atoms is about 1 × 10 ²¹ atoms / cm ³ , and the concentration of the nitrogen atoms is in a range of 1 × 10 ¹⁵ atoms / cm ^{3 to} 1 × 10 ¹⁹ atoms / cm ^3. Optically coupled power semiconductor element. The optically coupled power semiconductor device according to claim 9,
The nitrogen atom concentration is about 1 × 10 ²¹ atoms / cm ³ , and the aluminum atom concentration is in the range of 1 × 10 ¹⁵ atoms / cm ^{3 to} 1 × 10 ¹⁹ atoms / cm ^3. Optically coupled power semiconductor element.   2. The optically coupled power semiconductor device according to claim 1, wherein the optically coupled power semiconductor device is an insulated gate bipolar transistor having a gate as the control terminal.   2. The optically coupled power semiconductor device according to claim 1, which is a P-channel insulated gate bipolar transistor having a P-channel gate as the control terminal and a P-type buffer layer as the layer including the recombination center. .   2. The optically coupled power semiconductor device according to claim 1, which is a gate turn-off thyristor having a gate as the control terminal. 2. The optically coupled power semiconductor element according to claim 1, wherein the optically coupled power semiconductor element is a gate turn-off thyristor having an anode gate structure having an anode gate as the control terminal.

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