Semiconductor device

Abstract

Semiconductor device with: a transistor; a diode configured to be connected antiparallel to the transistor; a sensing transistor that is configured to have a current flowing in the sensing transistor dependent on a current flowing in the transistor; a sensing diode that is configured to have a current flowing in the sensing diode dependent on a current flowing in the diode; a resistor configured to have one terminal connected to an emitter of the sensing transistor and an anode of the sensing diode, and to have another terminal connected to an emitter of the transistor and an anode of the diode; and a current mirror configured to be connected in parallel with the resistor and to output a current dependent on a current flowing in the same direction as a forward direction of the sensing diode.

Description

Technical area

[0001] The disclosures herein generally relate to a semiconductor device. Background technology

[0002] Conventionally, a technique is known that detects a current flowing in a transistor and a current flowing in a diode connected in antiparallel with the transistor through a common sensing resistor (see, for example, Patent Document 1). State-of-the-art publications

[0003] The document US 8 072 241 B2 shows a semiconductor device with IGBT with built-in diode and a semiconductor device with DMOS with built-in diode. Patent documents

[0004] Patent Document 1: Japanese Patent Laid-Open No. 2009-268054 Summary of the inventionProblem to be solved by the invention

[0005] For example, to detect a relatively large current flowing in a transistor, the resistance of a sense resistor can be set low. However, the lower the resistance of the sense resistor, the lower the detection sensitivity of the current through the sense resistor. Therefore, for a sense resistor using the conventional technique described above, it is difficult to detect, for example, a current close to zero amperes flowing in the diode connected in antiparallel with the transistor with high accuracy.

[0006] Thereupon, an object of at least one embodiment is to provide a semiconductor device that increases the detection sensitivity of a current flowing in a diode connected in antiparallel to a transistor. Means to solve the problem

[0007] According to one embodiment, a semiconductor device comprises a transistor; a diode configured to be connected in anti-parallel with the transistor; a sensing transistor configured to have a current flowing in the sensing transistor depending on a current flowing in the transistor; a sensing diode configured to have a current flowing in the sensing diode depending on a current flowing in the diode; a resistor configured to have one terminal connected to an emitter of the sensing transistor and an anode of the sensing diode and another terminal connected to an emitter of the transistor and an anode of the diode; and a current mirror configured to be connected in parallel with the resistor and to output a current depending on a current flowing in a same direction as a forward direction of the sensing diode. Advantage of the invention

[0008] According to one embodiment, it is possible to increase the detection sensitivity of a current flowing in a diode connected in antiparallel with a transistor. Short description of the drawings Fig. 1 is a configuration diagram of a semiconductor device according to an embodiment; Fig. 2 is a timing chart illustrating an example of operation waveforms of a semiconductor device; Fig. 3 is a configuration diagram of a semiconductor device according to an embodiment; Fig. 4 is a configuration diagram of a semiconductor device according to an embodiment; Fig. 5 is a configuration diagram of a semiconductor device according to an embodiment; and Fig. 6 is a configuration diagram of a semiconductor device according to an embodiment. Mode for carrying out the invention

[0009] In the following, embodiments are described with reference to the drawings.

[0010] Fig. 1 is a diagram illustrating a configuration example of a drive device 1 serving as an example of a semiconductor device. The drive device 1 may be a semiconductor device having a configuration implemented by an integrated circuit or a semiconductor device having a configuration implemented by discrete elements.

[0011] The drive device 1 is a semiconductor circuit comprising a unit for driving an inductive load (e.g., an inductor or a motor) connected to a first conductive element 61 or a second conductive element 62 by controlling a main transistor 12 of a transistor element 11 on and off. Devices using one or more drive devices 1 include, for example, a converter that up-converts or down-converts DC power, an inverter that converts power between DC power and AC power, and the like.

[0012] For example, in a device using multiple drive devices 1, a switching circuit is configured in which switching elements 10 are connected in series. The switching elements 10 are provided on an upper side and a lower side with respect to an intermediate node to which an inductive load is connected. For example, a three-phase inverter using multiple drive devices 1 includes three such switching circuits in parallel.

[0013] The conductive element 61 is a current path that is conductively connected to a high-energy potential element, such as a positive electrode of a power source, or may be indirectly connected to the high-energy potential element via another switching element or a load. The conductive element 62 is a current path that is conductively connected to a low-energy potential element, such as a negative electrode of a power source (for example, a ground or earth potential element), or may be indirectly connected to the low-energy potential element via another switching element or a load.

[0014] The control device 1 includes the switching element 10. The switching element 10 is a voltage-controlled insulated-gate semiconductor element with a current sensing function. The switching element 10 includes the transistor element 11 and a diode element 14.

[0015] For example, if the transistor element 11 is an insulated gate bipolar transistor (IGBT), the switching element 10 is a built-in diode IGBT that has the transistor element 11 and the diode element 14 arranged on a common semiconductor substrate. The built-in diode IGBT has a structure that includes a common electrode for the anode electrode of the diode and the emitter electrode of the IGBT, and a common electrode for the cathode electrode of the diode and the collector electrode of the IGBT. The built-in diode IGBT is also called a "reverse conducting IGBT" (RC-IGBT).

[0016] As a specific example of the transistor element 11, one can consider a power transistor element such as an IGBT and a metal oxide semiconductor field effect transistor (MOSFET). Fig. Figure 1 illustrates an IGBT as an example of the transistor element 11. In the following description, for simplicity of explanation, it is assumed that the transistor element 11 is an IGBT. If it is a MOSFET, the wording can be changed to read "collector" as "drain" and "emitter" as "source."

[0017] The gate terminal G of the transistor element 11 is, for example, a control terminal connected to a drive circuit 43 of a control circuit 40 via a gate resistor connected in series with the gate terminal G. The collector terminal C of the transistor element 11 is a first main terminal connected, for example, to a connection point c and, via the connection point c, to the conductive element 61. The emitter terminal E of the transistor element 11 is a second main terminal connected, for example, to a connection point d and, via the connection point d, to the conductive element 62. The sense emitter terminal SE of the transistor element 11 is a sense terminal connected, for example, to a connection point b and, via the connection point b, to a terminal of a sense resistor 20.The sensing emitter terminal SE is connected to the conductive element 62 via the connection point d, which is connected to another terminal of the sensing resistor 20.

[0018] Transistor element 11 is configured to include main transistor 12 and a sense transistor 13. Main transistor 12 and sense transistor 13 are switching elements such as IGBTs. Sense transistor 13 is connected in parallel with main transistor 12. Main transistor 12 and sense transistor 13 may each be configured with multi-cell transistors.

[0019] Respective gate electrodes g of the main transistor 12 and the sensing transistor 13 are control electrodes commonly connected to the gate terminal G of the transistor element 11. Respective collector electrodes c of the main transistor 12 and the sensing transistor 13 are first main electrodes commonly connected to the collector terminal C of the transistor element 11. The emitter electrode e of the main transistor 12 is a second main electrode connected to the emitter terminal E of the transistor element 11. The sensing emitter electrode se of the sensing transistor 13 is the sensing electrode connected to the sensing emitter terminal SE of the transistor element 11.

[0020] The sensing transistor 13 is an example of a sensing transistor that generates a current depending on the current flowing in the main transistor 12, and is a sensing element in which a larger current flows when a larger current flows in the main transistor 12. The sensing transistor 13 outputs, for example, a sensing current Ise proportional to the main current Ie flowing in the main transistor 12.

[0021] For example, a collector current flowing from the collector terminal C into the transistor element 11 is divided into the main current Ie flowing in the main transistor 12 and the sense current Ise flowing in the sense transistor 13 by means of a sense ratio n. The sense current Ise is a current that flows depending on the main current Ie by means of the sense ratio n, and whose current value is made smaller than the main current Ie by means of the sense ratio n. The sense ratio n is determined, for example, depending on a ratio of the area of ​​the emitter electrode e of the main transistor 12 and the area of ​​the sense emitter electrode se of the sense transistor 13.

[0022] The main current Ie flows through the collector electrode c and the emitter electrode e of the main transistor 12 and is output from the emitter terminal E. The main current Ie output from the emitter terminal E flows into the conductive element 62 via the connection point d. The sense current Ise flows through the collector electrode c and the sense emitter electrode se of the sense transistor 13 and is output from the sense emitter terminal SE. The sense current Ise output from the sense emitter terminal SE flows into the conductive element 62 via the sense resistor 20 and the connection point d.

[0023] On the other hand, the diode element 14 is configured to include a main diode 15 and a sensing diode 16.

[0024] The main diode 15 is an example of a diode connected in antiparallel to the main transistor 12, has the anode connected to the emitter terminal E, and has the cathode connected to the collector terminal C. The anode electrode of the main diode 15 is a P-type electrode connected to the connection point d, which is connected to the emitter terminal E, and connected via the connection point d to the conductive element 62. The cathode electrode of the main diode 15 is an N-type electrode connected to the connection point c, which is connected to the collector terminal C, and connected via the connection point c to the conductive element 61.

[0025] The sensing diode 16 is an example of a sensing diode in which a current flows depending on the current flowing in the main diode 15, and is a sensing element in which a larger current flows when a larger current flows in the main diode 15. For example, the sensing diode 16 outputs a sensing diode current Isd that is proportional to the diode current Id flowing in the main diode 15.

[0026] The sensing diode current Isd is a current that flows depending on the diode current Id by means of a sensing ratio m, and whose current value is smaller than the diode current Id by means of the sensing ratio m.

[0027] The anode electrode of the sensing diode 16 is a P-type electrode connected to the junction point b, which is connected to the sensing emitter terminal SE, and connected to the conductive element 62 via the sensing resistor 20 and the junction point d. The cathode electrode of the sensing diode 16 is an N-type electrode connected to the junction point c, which is connected to the collector terminal C, and connected to the conductive element 61 via the junction point c.

[0028] The drive device 1 has the sensing resistor 20 arranged between the sensing emitter terminal SE and the emitter terminal E. The sensing resistor 20 is an example of a resistor having one terminal commonly connected to the sensing emitter electrode se of the sensing transistor 13 and the anode electrode of the sensing diode 16, and another terminal commonly connected to the emitter electrode e of the main transistor 12 and the anode electrode of the main diode 15.

[0029] The control device 1 includes a current mirror circuit 30. The current mirror circuit 30 is an example of a current mirror connected in parallel with the sensing resistor 20. The current mirror circuit 30 outputs an output current I3 depending on an input current I2 flowing in the same direction as the forward or conducting direction of the sensing diode 16.

[0030] By connecting the current mirror circuit 30 in parallel with the sensing resistor 20 in this way, the output current I3 can be generated, which flows depending on the magnitude of the diode current Id. Therefore, the magnitude of the diode current Id can be detected by the magnitude of the output current I3 of the current mirror circuit 30, which is a detection unit different from the sensing resistor 20. Therefore, the current mirror ratio k of the current mirror circuit 30 can be adjusted independently of the resistance value of the sensing resistor 20, and therefore, even when the resistance value of the sensing resistor 20 is low, the detection sensitivity of the diode current Id can be easily increased by adjusting the current mirror ratio k.

[0031] For example, the input current I2 also decreases while the diode current Id decreases. Even if the current value of the input current I2 assumes a value slightly greater than zero, an output current I3 whose current value is greater than the input current I2 can be easily generated by adjusting the current mirror ratio k of the output current I3 with respect to the input current I2. Therefore, it is possible to detect a diode current Id flowing in the main diode 15, which is slightly greater than zero, by the output current I3 with high accuracy.

[0032] When flowing into the current mirror circuit 30, the input current I2, which flows depending on the magnitude of the diode current Id, is converted into the output current I3, which is a current copied or mapped by the current mirror ratio k of the current mirror circuit 30. On the other hand, when flowing into the sensing resistor 20, the sensing current Ise, which flows depending on the magnitude of the main current Ie, is converted into a sensing voltage Vse generated between both terminals of the sensing resistor 20. In other words, the diode current Id can be detected by the current mirror circuit 30, and the main current Ie can be detected by the sensing resistor 30. Therefore, the detection sensitivity of the diode current Id by the current mirror circuit 30 and the detection sensitivity of the main current Ie by the sensing resistor 20 can be independently adjusted.

[0033] The current mirror circuit 30 includes, for example, an input transistor 31 and an output transistor 32. The input transistor 31 is connected in parallel with the sense resistor 20, into which the input current I2 flows, serving as an input. The output transistor 32 outputs the output current I3 depending on the input current I2 by means of the current mirror ratio k.

[0034] The input transistor 31 is a diode-connected transistor, for example, an NPN transistor, which has its emitter connected to one terminal of the sensing resistor 20 and its collector and base connected to the other terminal of the sensing resistor 20. The output transistor 32 is an NPN transistor which has its emitter connected to the emitter of the input transistor 31 and one terminal of the sensing resistor 20, its base connected to the base and collector of the input transistor 31, and its collector connected to one terminal of a resistor 41 of the control circuit 40. The NPN transistor can be replaced by another switching element, such as a MOSFET.

[0035] The input transistor 31 and the output transistor 32 each have a PN junction between the base and emitter and can therefore prevent the sense current Ise flowing in the sense transistor 13 from flowing into the current mirror circuit 30. In other words, the sense current Ise does not flow in the current mirror circuit, but rather flows in the sense transistor 20.

[0036] On the other hand, a current flowing depending on the diode current Id is divided to flow in the sensing resistor 20 and the current mirror circuit 30, and then combined to flow in the sensing diode 16. When the diode current Id flows, the resistance current I1 proportional to the diode current Id flows in the sensing resistor 20, the input current I2 proportional to the diode current Id flows, and the output current I3 proportional to the diode current Id (or the input current I2) flows. When the diode current Id flows, for example, the input current I2 is a current larger than the resistance current I1.

[0037] The drive device 1 includes the control circuit 40. The control circuit 40 is an example of a control unit for controlling a drive of the main transistor 12 and the sense transistor 13 based on the output of the current play circuit 30.

[0038] When the output current I3, which flows depending on the input current I2, is output from the current mirror circuit 30 depending on the flow of the diode current Id, the control circuit 40 turns off the main transistor 12 and the sense transistor 13. Thus, when the diode current Id flows, the main transistor 12 and the sense transistor 13 can be prevented from being turned on. When the diode current Id flows, the loss in the diode element 14 can also be prevented from increasing, which might occur when the main transistor 12 and the sense transistor 13 are turned on.

[0039] For example, the control circuit 40 turns off the main transistor 12 and the sense transistor 13 when it detects that the current value of the output current I3 is greater than or equal to a predetermined threshold (for example, a current value greater than or equal to zero).

[0040] The control circuit 40 comprises the resistor 41, an AND circuit 42 and the drive circuit 43.

[0041] Resistor 41 is an example of a conversion unit that converts output current I3 into a detection voltage Va. Resistor 41 has one terminal connected to the collector of output transistor 32 included in current mirror circuit 30, and the other terminal connected to a reference voltage element 44 that outputs a constant reference voltage VR1. A connection point a between one terminal of resistor 41 and the collector of output transistor 32 is connected to AND circuit 42. The detection voltage Va output from connection point a is input to AND circuit 42.

[0042] When the diode current Id flows, a voltage drop is generated across the resistor 41 by the output current I3 flowing in the resistor 41. Therefore, the detection voltage Va is a low-level signal that instructs the main transistor 12 and the sensing transistor 13 to turn off. On the other hand, when the diode current Id does not flow, a voltage drop is not generated across the resistor 41 because the output current I3 does not flow across the resistor 41. Therefore, the detection voltage Va is a high-level signal that instructs the main transistor 12 and the sensing transistor 13 to turn on.

[0043] The AND circuit 42 is an example of a determination unit that determines whether the main transistor 12 and the sensing transistor 13 should be turned on or off based on the voltage level of a command signal S1 and the voltage level of the detection voltage Va. The AND circuit 42 calculates the logical AND or the logical sum of the command signal S1 and the detection voltage Va and outputs a pre-drive signal S2. The command signal S1 is a signal that instructs turning the main transistor 12 and the sensing transistor 13 on or off, and is a signal supplied from an external device such as a microcomputer (for example, a pulse width modulation signal).

[0044] The AND circuit 42 outputs a low-level pre-drive signal S2 when the command signal S1 and / or the detection voltage Va is a low-level signal instructing turning off the main transistor 12 and the sense transistor 13. The low-level pre-drive signal S2 is a signal for turning off the main transistor 12 and the sense transistor 13. In other words, the AND circuit 42 outputs a low-level pre-drive signal S2 when the detection voltage Va becomes low, even if it receives a high-level command signal S1 instructing turning on the main transistor 12 and the sense transistor 13.

[0045] On the other hand, when both the command signal S1 and the detection voltage Va5 are high-level signals, the AND circuit 42 outputs a high-level pre-drive signal S2, which instructs the main transistor 12 and the sense transistor 13 to turn on. A high-level pre-drive signal S2 is a signal for turning on the main transistor 12 and the sense transistor 13.

[0046] The drive circuit 43 outputs a gate drive signal S3 having the same phase as the pre-drive signal S2 output from the AND circuit 42. The drive circuit 43 shifts the voltage level of the pre-drive signal S2 sufficiently high to drive the main transistor 12 and the sense transistor 13, and outputs the gate drive signal S3 whose voltage level is higher than the voltage level of the pre-drive signal S2.

[0047] Fig. 2 is a timing chart illustrating an example of operation waveforms of the drive device 1. The command signal S1 is a signal instructing the main transistor 12 and the sensing transistor 13 to turn on or off. A current Isw is a current flowing in the conductive element 62 and is practically equivalent to the sum of the main current Ie and the diode current Id. Note that the magnitude of the sensing current Ise and the sensing diode current Isd is negligible with respect to the current Isw because the sensing current Ise is sufficiently smaller than the main current Ie and the sensing diode current Isd is sufficiently smaller than the diode current Id.

[0048] A period during which the current Isw assumes a negative value represents that the current Isw flows in the same direction as the forward direction of the main diode 15 and the sensing diode 16. The forward direction of the main diode 15 and the sensing diode 16 is a direction from the anode electrode to the cathode electrode. On the other hand, a period during which the current Isw assumes a positive value represents that the current Isw flows in a direction opposite to the forward direction of the main diode 15 and the sensing diode 16. The direction opposite to the forward direction of the main diode 15 and the sensing diode 16 is a direction from the collector terminal C to the emitter terminal E or the sensing emitter terminal SE.

[0049] When the diode current Id flows, the detection voltage Va becomes a negative low-level voltage. Therefore, when the command signal S1 goes high and the detection voltage Va goes low, the gate drive signal S3 goes low, and both the main transistor 12 and the sense transistor 13 are turned off. By turning off both the main transistor 12 and the sense transistor 13, the flow of the main current Ie and the sense current Ise is cut off. Therefore, when the flow of the main current Ie and the sense current Ise is cut off, the current Isw is practically equivalent to the sum of the diode current Id, the resistor current I1, and the input current I2.

[0050] As the diode current Id decreases, the sense diode current Isd also decreases. The sense diode current Isd is practically equivalent to the sum of the resistor current I1, the input current I2, and the output current I3. When the diode current Id decreases to zero amperes, the current Isw also decreases to practically zero amperes. Near zero amperes, where the current Isw changes from negative to positive, the detection voltage Va changes from the low level to the high level (see times t1 and t2). Thus, the gate drive signal S3 goes high.

[0051] Therefore, when the command signal S1 goes high and the detection voltage Va goes high, the gate drive signal S3 goes high, and therefore both the main transistor 12 and the sense transistor 13 turn on. Because both the main transistor 12 and the sense transistor 13 turn on, the main current Ie and the sense current Ise gradually increase, and thereby the current Isw also gradually increases (see periods t1-t2 and periods t4-t5).

[0052] When the command signal S1 changes from high to low, the gate drive signal S3 changes from high to low (see times t2 and t5), and therefore both the main transistor 12 and the sense transistor 13 are turned off. By turning off both the main transistor 12 and the sense transistor 13, the flow of the main current Ie and the sense current Ise is cut off (see periods t2-t3).

[0053] In this way, it is possible to allow the output current I3 to flow to some extent, which is greater than or equal to a predetermined value, when the diode current Id, which is even slightly greater than zero, flows in the main diode 15 by adjusting the current mirror ratio k of the current mirror circuit 30. Thus, at a time when the diode current Id stops or starts to flow (in the case of Fig. 2 at time t1, t3 or t4, when the current Isw changes from negative to positive or from positive to negative), it is easy to implement a steep change in the detection voltage Va.

[0054] Also, the resistance value of resistor 41 and the resistance value of the sensing resistor 20 can be adjusted independently. Therefore, the resistance value of resistor 41 can be easily increased, so that the voltage drop of resistor 41 becomes larger. Thus, at a time when the diode current Id stops or starts to flow (in the case of Fig. 2 at time t1, t3 or t4, when the storm Isw changes from negative to positive or from positive to negative), it is easy to implement a steep change in the detection voltage Va.

[0055] Fig. 3 is a diagram illustrating a configuration example of a drive device 2 serving as an example of a semiconductor device. Description of the same elements and effects as in the configuration example of the above-described drive device is omitted here. The drive device 2 includes a control circuit 45 having an overcurrent detection circuit for turning off the main transistor 12 and the sense transistor 13 based on a sense voltage Vse generated by the resistance current I1 flowing in the sense resistor 20.

[0056] A comparator 46 is an example of the overcurrent detection circuit. The comparator 46 has an inverting input element connected to one terminal of the sense resistor 20 and a non-inverting input element connected to a reference voltage element 47 that outputs a constant reference voltage VR2. The reference voltage VR2 is a threshold voltage for determining whether the main current Ie is an overcurrent.

[0057] When the diode current Id flows, the comparator 46 outputs a high-level output signal S4 because the sense voltage Vse is smaller than the reference voltage VR2. When a normal main current Ie, which is smaller than an overcurrent, flows in the main transistor 12, the comparator 46 outputs a high-level output signal S4 because the sense voltage Vse is smaller than the reference voltage VR2. When an excessive main current Ie, which is greater than or equal to a predetermined value, flows into the main transistor 12, the comparator 46 outputs a low-level output signal S4 because the sense voltage Vse is greater than the reference voltage VR2.

[0058] The control circuit 45 includes an AND circuit 48 that receives the output signal S4 of the comparator 46 as its input. The AND circuit 48 is an example of a determination unit that determines whether the main transistor 12 and the sensing transistor 13 should be turned on or off based on the voltage level of the output signal S4 and the voltage level of the detection voltage Va. The AND circuit 48 calculates the logical AND or the logical sum of the output signal S4 and the detection voltage Va and outputs an output signal S5.

[0059] The AND circuit 42 is an example of a determination unit that determines whether the main transistor 12 and the sense transistor 13 should be turned on or off based on the voltage level of the command signal S1 and the voltage level of the output signal S5. The AND circuit 42 calculates the logical AND or the logical sum of the command signal S1 and the output signal S5 and outputs a pre-drive signal S2.

[0060] Thus, the control circuit 40 can turn off the main transistor 12 and the sense transistor 13 when it detects that the diode current Id is flowing in the main diode 15 and / or an excessive main current Ie is flowing in the main transistor 12. On the other hand, when it detects that a normal main current Ie is flowing in the main transistor 12, the control circuit 40 can turn on the main transistor 12 and the sense transistor 13.

[0061] Fig. 4 is a diagram illustrating a configuration example of a drive device 3 serving as an example of a semiconductor device. Descriptions of the same elements and effects as those in the configuration example of the drive device described above are omitted here. The drive device 3 includes a control circuit 51 having an output detection circuit for detecting whether the output current I3 is output.

[0062] A comparator 49 is an example of the output detection circuit. The comparator 49 has a non-inverting input element connected to the connection point a and an inverting input element connected to a reference voltage element 50 that outputs a constant reference voltage VR3. The reference voltage VR3 is a threshold voltage for determining whether the main current Ie or the output current I3 is flowing.

[0063] When the diode current Id flows, the comparator 49 outputs a low-level output signal S6 because the detection voltage Va is less than the reference voltage VR3. When the diode current Id does not flow, the comparator 49 outputs a high-level output signal S6 because the detection voltage Va is greater than the reference voltage VR3. The output signal S6 of the comparator 49 is input to the AND circuit 42.

[0064] As it is in Fig. 1, it is possible to detect whether the diode current Id is flowing without the comparator 49. If the comparator 49 is provided as shown in Fig. 4, however, the voltage value of the reference voltage VR3 can be adjusted, and therefore degrees of freedom for adjusting the detection sensitivity of the diode current Id can be increased.

[0065] Fig. 5 is a diagram illustrating a configuration example of a drive device 4 serving as an example of a semiconductor device. Description of the same elements and effects as in the configuration example of the above-described drive device will be omitted here. A current mirror circuit 35 includes emitter resistors 33 and 34. The emitter resistor 33 has one terminal connected to the emitter of the input transistor 31 and the other terminal connected to one terminal of the sense resistor 20. The emitter resistor 34 has one terminal connected to the emitter of the output transistor 32 and the other terminal connected to one terminal of the sense resistor 20.

[0066] By providing the emitter resistors 33 and 34, the ratio of respective currents flowing in the current mirror circuit 35 and the sensing transistor 20 can be adjusted, and therefore degrees of freedom for adjusting the detection sensitivity can be further increased.

[0067] Fig. 6 is a diagram illustrating a configuration example of a drive device 5 serving as an example of a semiconductor device. Description of the same elements and effects as in the configuration example of the above-described drive device is omitted here. The drive device 5 includes a control circuit 53 having a constant current source 52 for supplying a constant current IR1, generated based on the reference voltage VR1, to the output transistor 32 of the current mirror circuit 30. The constant current source 52 is an example of a conversion unit that converts the output current I3 into the detection voltage Va.

[0068] When the output current I3 of the current mirror circuit 30 becomes greater than the constant current IR1, the detection voltage Va is switched from the high level to the low level. When the output current I3 becomes smaller than the constant current IR1, the detection voltage Va is switched from the low level to the high level. By providing the constant current source 52 in this way, it is possible to prevent the detection voltage Va from fluctuating due to a fluctuation in the reference voltage VR1.

[0069] It should be noted that the comparator 49 and the reference voltage element 50 in Fig. 6 can be omitted, as in Fig. 1 is illustrated.

[0070] The semiconductor device has been described using the embodiments set forth above. It should be noted that the present invention is not limited to the above embodiments. Various modifications and improvements can be made within the scope of the present invention by combining and / or replacing some or all of the embodiments with the others.

[0071] For example, a switching element such as a transistor may be a switching element other than an IGBT, for example, an N-channel MOSFET or a P-channel MOSFET.

[0072] This application is based on Japanese priority application No. 2013-227678 filed on October 31, 2013, the entire contents of which are hereby incorporated by reference. Description of reference symbols 1, 2, 3, 4, 5 Control device (example of semiconductor device) 10 Switching element 11 Transistor element or part 12 Main transistor 13 sensing transistor 14 Diode element or part 15 Main diode 16 sensing diode 20 sensing resistor 30, 35 Current mirror circuit 31 Input transistor 32 Output transistor 40, 45, 51, 53 control circuit 44, 47, 50 Reference voltage element or part 52 constant current source 61, 62 conductive element or part

Claims

[1] Semiconductor device comprising: a transistor; a diode configured to be connected in antiparallel with the transistor; a sensing transistor configured to have a current flow in the sensing transistor depending on a current flowing in the transistor; a sensing diode configured to have a current flow in the sensing diode dependent on a current flowing in the diode; a resistor configured to have one terminal connected to an emitter of the sensing transistor and an anode of the sensing diode and another terminal connected to an emitter of the transistor and an anode of the diode; and a current mirror configured to be connected in parallel with the resistor and to output a current dependent on a current flowing in a same direction as a forward direction of the sensing diode. [2] A semiconductor device according to claim 1, wherein the current mirror comprises: an input transistor connected in parallel with the resistor and receiving as input the current flowing in the same direction, and an output transistor for outputting a current dependent on the current flowing in the same direction. [3] A semiconductor device according to claim 2, wherein the input transistor and the output transistor each have a PN junction that prevents the current flowing in the sensing transistor from flowing into the current mirror. [4] Semiconductor device according to claim 2 or 3, additionally comprising: a conversion unit configured to convert the output current of the output transistor into a voltage. [5] A semiconductor device according to any one of claims 1 to 4, further comprising: a control unit configured to control a drive of the transistor based on the output of the current mirror. [6] A semiconductor device according to claim 5, wherein the control unit turns off the transistor when the current flows in the diode. [7] A semiconductor device according to claim 6, wherein the control unit turns off the transistor when the current flows in the diode even if a command to turn on the transistor is received. [8] A semiconductor device according to any one of claims 5 to 7, wherein the control unit turns off the transistor when it is detected that the current flows in the diode and / or a current greater than or equal to a predetermined value flows in the transistor.

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