Semiconductor Devices

Abstract

The purpose of the present invention is to provide a semiconductor device capable of inhibiting switching element loss during high temperatures without increasing the radiation noise of the switching element. This semiconductor device (2a) comprises: an IGBT (21) having a gate (G) to which a gate signal is input; a temperature detection element (23) that detects the temperature of the IGBT (21); and a capacitance adjustment unit (11) that is disposed between the gate (G) of the IGBT (21) and a reference potential terminal (41), and adjusts the capacitance between the gate (G) and an emitter (E) of the IGBT (21) in accordance with the detected temperature detected by the temperature detection element (23).

Description

[Technical field]

[0001] The present invention relates to a semiconductor device that is applied to a power conversion device or the like. [Background technology]

[0002] Insulated gate bipolar transistors (IGBTs), bipolar transistors, and metal-oxide-semiconductor field-effect transistors (MOSFETs) are widely used as switching elements. These switching elements are generally used in the form of a power module in which a plurality of pairs of a switching element and a free wheeling diode (FWD) connected in anti-parallel to the switching element are assembled in one package. In addition, intelligent power modules (IPMs) that add a drive circuit and a protection function to such power modules are being actively developed.

[0003] Power modules and IPMs have a gate capacitor connected to the control signal input terminal of a switching element (for example, the gate of an IGBT). The gate capacitor is used to reduce the instantaneous voltage change (recovery voltage change rate (dv / dt)) caused by reverse recovery of the freewheeling diode when the switching element switches from the off state to the on state (i.e., when turned on), thereby suppressing the radiation noise that occurs when the element is turned on. The gate capacitor is mounted in the control circuit section provided on the control board (printed circuit board). The gate capacitor is added by the user of the power module or IPM.

[0004] Generally, power modules and IPMs are equipped with an overheat protection function to protect the IGBT from overheating. To protect the IGBT from overheating, a temperature detection diode built into the IGBT chip is used along with the IGBT. IGBT modules and IPMs use the negative temperature characteristics of the diode to detect whether the IGBT chip is overheating. If the IGBT module or IPM detects overheating of the IGBT chip, it stops the operation of the IGBT.

[0005] Patent Document 1 discloses an IGBT drive circuit that enables an IGBT to be easily switched between a normal mode with high dv / dt and a low dv / dt mode, and facilitates suppression of high-frequency leakage current. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-313570 Summary of the Invention [Problem to be solved by the invention]

[0007] Generally, the larger the recovery voltage change rate of an IGBT, the greater the radiation noise accompanying the operation of a switching element (e.g., an IGBT), but the lower the loss (generated loss) that occurs in the switching element. On the other hand, the smaller the recovery voltage change rate, the lower the radiation noise accompanying the operation of the switching element, but the higher the generated loss of the switching element. In other words, in a switching element, there is a trade-off between the recovery voltage change rate and radiation noise, and the generated loss.

[0008] Furthermore, the recovery voltage change rate tends to decrease as the temperature of a semiconductor chip incorporating a switching element such as an IGBT increases. Therefore, the recovery voltage change rate of a switching element is greater at room temperature than at high temperature. The radiation noise of a switching element is adjusted by the capacitance value of a gate capacitor so that it is smaller than a predetermined value within the operable temperature range of the switching element. The capacitance value of the gate capacitor is determined by the recovery voltage change rate of the switching element at room temperature. Therefore, when a switching element such as an IGBT becomes hot, the recovery voltage change rate becomes smaller than necessary, resulting in a problem of increased loss generated by the switching element.

[0009] An object of the present invention is to provide a semiconductor device capable of suppressing loss in a switching element at high temperatures without increasing radiation noise from the switching element. [Means for solving the problem]

[0010] In order to achieve the above object, the semiconductor device comprises a switching element having a control signal input terminal to which a switching control signal is input, a temperature detection element that detects the temperature of the switching element, and a capacitance adjustment unit that is arranged between the control signal input terminal and a reference potential terminal and adjusts the capacitance between the gate and emitter of the switching element in accordance with the detected temperature detected by the temperature detection element. Effect of the Invention

[0011] According to one aspect of the present invention, it is possible to suppress loss in a switching element at high temperatures without increasing radiation noise from the switching element. [Brief description of the drawings]

[0012] [Figure 1] 1 is a circuit block diagram showing a schematic configuration of a power conversion device including a semiconductor device according to each embodiment of the present invention. [Diagram 2]1 is a circuit block diagram showing a schematic configuration of a semiconductor device according to a first embodiment of the present invention. [Diagram 3] 4 is a diagram showing an example of the relationship between the detected temperature and the detected voltage in the temperature detection element provided in the semiconductor device according to the first embodiment of the present invention. FIG. [Figure 4] 5A to 5C are diagrams illustrating an example of an operation of a capacitance adjusting section provided in the semiconductor device according to the first embodiment of the present invention. [Diagram 5] FIG. 4 is a diagram showing an example of the relationship between the reflux current and the recovery voltage change rate in the semiconductor device according to the first embodiment of the present invention. [Figure 6] 4 is a diagram showing an example of the relationship between the collector current and switching loss in the IGBT provided in the semiconductor device according to the first embodiment of the present invention. FIG. [Figure 7] FIG. 11 is a circuit block diagram showing a schematic configuration of a semiconductor device according to a second embodiment of the present invention. [Figure 8] FIG. 11 is a circuit block diagram showing a schematic configuration of a semiconductor device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Each embodiment of the present invention is an example of an apparatus or method for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not specify the material, shape, structure, arrangement, etc. of the components to those described below. The technical idea of ​​the present invention can be modified in various ways within the technical scope defined by the claims.

[0014] [First embodiment] (Configuration of power conversion device) A power conversion device 1 including semiconductor devices 2a, 2b, 2c, 2d, 2e, and 2f (hereinafter, "semiconductor devices 2a, 2b, 2c, 2d, 2e, and 2f" may be abbreviated as "semiconductor devices 2a to 2f") according to a first embodiment of the present invention will be described with reference to Fig. 1. Hereinafter, an inverter circuit will be taken as an example of the power conversion device 1 including the semiconductor devices 2a to 2f according to this embodiment, but the semiconductor devices 2a to 2f are not limited to inverter circuits and can also be applied to power conversion devices such as converter circuits and full-bridge circuits.

[0015] As shown in Fig. 1, the power conversion device 1 is connected to a three-phase AC power source 3. The power conversion device 1 has a rectifier circuit 4 that full-wave rectifies the three-phase AC power input from the three-phase AC power source 3, and a smoothing capacitor 5 that smoothes the power rectified by the rectifier circuit 4. Although a specific configuration of the rectifier circuit 4 is not shown in the figure, it is configured by connecting six diodes in a full bridge configuration or by connecting six switching elements in a full bridge configuration.

[0016] A positive line Lp is connected to the positive output terminal of the rectifier circuit 4, and a negative line Ln is connected to the negative output terminal. A smoothing capacitor 5 is connected between the positive line Lp and the negative line Ln. The power conversion device 1 also includes an inverter circuit 2 that converts a DC voltage applied between the positive line Lp and the negative line Ln into a three-phase AC voltage. The inverter circuit 2 includes semiconductor devices 2a, 2c, and 2e each having an insulated gate bipolar transistor (one example of a switching element) 21 as a voltage-controlled switching element that constitutes an upper arm portion connected to the positive line Lp, and semiconductor devices 2b, 2d, and 2f each having an insulated gate bipolar transistor 21 that constitutes a lower arm portion connected to the negative line Ln. Hereinafter, the insulated gate bipolar transistor is abbreviated as "IGBT".

[0017] The IGBT 21 provided in the semiconductor device 2a and the IGBT 21 provided in the semiconductor device 2b are connected in series between the positive line Lp and the negative line Ln to form a U-phase output arm 2U. The IGBT 21 provided in the semiconductor device 2c and the IGBT 21 provided in the semiconductor device 2d are connected in series between the positive line Lp and the negative line Ln to form a V-phase output arm 2V. The IGBT 21 provided in the semiconductor device 2e and the IGBT 21 provided in the semiconductor device 2f are connected in series between the positive line Lp and the negative line Ln to form a W-phase output arm 2W.

[0018] The IGBTs 21 provided in each of the semiconductor devices 2a to 2f are connected in anti-parallel to a free wheel diode 22. The IGBTs 21 and the free wheel diode 22 will be described in detail later.

[0019] The connection portions of the IGBT 21 provided in the semiconductor device 2a and the IGBT 21 provided in the semiconductor device 2b, the connection portions of the IGBT 21 provided in the semiconductor device 2c and the IGBT 21 provided in the semiconductor device 2d, and the connection portions of the IGBT 21 provided in the semiconductor device 2e and the IGBT 21 provided in the semiconductor device 2f are each connected to a load, such as a motor 7.

[0020] Each of the semiconductor devices 2a to 2f includes a gate drive circuit 10 that individually controls the switching operation of the IGBT 21. In FIG. 1, the gate drive circuit 10 is indicated as "GDU." In each of the semiconductor devices 2a to 2f, an output terminal of the gate drive circuit 10 is connected to a gate (an example of a control signal input terminal) G of the IGBT 21. Each of the semiconductor devices 2a to 2f also includes a gate capacitor (an example of a capacitor) 30 connected to the gate drive circuit 10. Details of the gate drive circuit 10 and the gate capacitor 30 will be described later.

[0021] The inverter circuit 2 has a three-phase full-bridge circuit in which a U-phase output arm 2U, a V-phase output arm 2V, and a W-phase output arm 2W are connected in parallel, semiconductor devices 2a and 2b that control the switching operation of the U-phase output arm 2U, semiconductor devices 2c and 2d that control the switching operation of the V-phase output arm 2V, and semiconductor devices 2e and 2f that control the switching operation of the W-phase output arm 2W.

[0022] The power conversion device 1 has a control device 6 that controls the gate drive circuits 10 provided in each of the semiconductor devices 2a to 2f. The control device 6 is configured to output, for example, a pulse-shaped input signal Vin to each of the gate drive circuits 10 provided in each of the semiconductor devices 2a to 2f. As a result, the control device 6 controls the gate drive circuits 10 provided in each of the semiconductor devices 2a to 2f to drive the IGBTs 21 provided in each of the semiconductor devices 2a to 2f by, for example, pulse width modulation (PWM).

[0023] <Semiconductor device> Next, the semiconductor device according to the present embodiment will be described with reference to Fig. 1 and Fig. 2 to Fig. 6. The semiconductor devices 2a to 2f provided in the power conversion device 1 have the same configuration and operate in the same manner. Therefore, the semiconductor devices 2a to 2f will be described below by taking the semiconductor device 2a as an example.

[0024] (Configuration of Semiconductor Device) The schematic configuration of a semiconductor device 2a according to the present embodiment will be described with reference to FIG. As shown in FIG. 2, the semiconductor device 2a includes an IGBT (an example of a switching element) 21 having a gate (an example of a control signal input terminal) G to which a gate signal (an example of a switching control signal) is input, and a current detection terminal S used to detect at least one of an overcurrent and a short-circuit current. The semiconductor device 2a includes a temperature detection element 23 that detects the temperature of the IGBT 21. The semiconductor device 2a includes a capacitance adjustment unit 11 that is disposed between the gate G of the IGBT 21 and a reference potential terminal 41 and adjusts the capacitance between the gate G and the emitter E of the IGBT 21 in accordance with the detected temperature detected by the temperature detection element 23. A gate capacitor (an example of a capacitor) 30 is disposed between the capacitance adjustment unit 11 and the reference potential terminal 41. The gate capacitor 30 is provided to reduce the rate of change in recovery voltage during switching of the IGBT 21.

[0025] The reference potential terminal 41 is connected to the output terminal of the inverter circuit 2 in the semiconductor devices 2a, 2c, and 2e that constitute the upper arm portion of the inverter circuit 2 (see Figure 1), and is connected to the ground terminal (earth terminal) in the semiconductor devices 2b, 2d, and 2f that constitute the lower arm portion of the inverter circuit 2.

[0026] The semiconductor device 2a includes a current detection circuit 13 that detects a detection current output from a current detection terminal S as a voltage. The semiconductor device 2a includes a gate signal generation circuit 12 that generates a gate signal to be input to a gate G. The semiconductor device 2a includes a temperature detection circuit 15 that detects the temperature of the IGBT 21 based on a voltage input from a temperature detection element 23. The semiconductor device 2a includes a protection circuit 14 that protects the IGBT 21 from abnormal operation based on the voltage input from the current detection circuit 13 and the voltage input from the temperature detection circuit 15.

[0027] The semiconductor device 2a includes a semiconductor substrate (not shown) and a gate drive circuit 10 that has a capacitance adjustment unit 11, a gate signal generation circuit 12, a current detection circuit 13, a protection circuit 14, and a temperature detection circuit 15 formed on the semiconductor substrate and controls the IGBT 21. The gate capacitor 30 is connected to the gate drive circuit 10. The semiconductor device 2a includes a printed circuit board (not shown) on which the gate drive circuit 10 and the gate capacitor 30 are mounted. The reference potential terminal 41 is formed on the printed circuit board, for example.

[0028] The semiconductor device 2a includes a semiconductor element 20 having an IGBT 21, a free wheel diode 22 connected in anti-parallel to the IGBT 21, and a temperature detection element 23. The cathode of the free wheel diode 22 is connected to the collector C of the IGBT 21, and the anode of the free wheel diode 22 is connected to the emitter E of the IGBT 21. For example, the semiconductor element 20 and the printed circuit board have a module configuration in which they are packaged together.

[0029] The IGBT 21 is a composite element having a main IGBT through which a main current, which is a current supplied to the motor 7, flows, and a sense IGBT through which a detection current for detecting the current flowing through the main IGBT flows. The gate of the main IGBT and the gate of the sense IGBT are connected to each other, forming the gate G of the IGBT 21. The collector of the main IGBT and the collector of the sense IGBT are connected to each other, forming the collector C of the IGBT 21. The emitter of the main IGBT is the emitter E of the IGBT 21. The emitter of the sense IGBT is the current detection terminal S of the IGBT 21. The detection current is much smaller than the main current, for example, about 1 / 10,000 of the main current.

[0030] The collector C of the IGBT 21 provided in each of the semiconductor devices 2a, 2c, and 2e (see FIG. 1) is connected to the positive line Lp (see FIG. 1). The emitter E of the IGBT 21 provided in the semiconductor device 2a is connected to the collector C of the IGBT 21 provided in the semiconductor device 2b (see FIG. 1). The emitter E of the IGBT 21 provided in the semiconductor device 2c is connected to the collector C of the IGBT 21 provided in the semiconductor device 2d (see FIG. 1). The emitter E of the IGBT 21 provided in the semiconductor device 2e is connected to the collector C of the IGBT 21 provided in the semiconductor device 2f (see FIG. 1). The emitter E of the IGBT 21 provided in each of the semiconductor devices 2b, 2d, and 2f is connected to the negative line Ln (see FIG. 1).

[0031] 2, the gate signal generating circuit 12 is connected to a signal input terminal Ti provided in the semiconductor device 2a. An input signal Vin output from the control device 6 is input to the gate signal generating circuit 12 via the signal input terminal Ti. Although a detailed description is omitted, the gate signal generating circuit 12 generates a gate signal (e.g., a pulse signal) having a signal level capable of controlling the IGBT 21 to an on state (conductive state) or an off state (non-conductive state) based on the signal level of the input signal Vin input from the signal input terminal Ti.

[0032] Further, an output signal output by the protection circuit 14 is input to the gate signal generation circuit 12. When an output signal indicating abnormal operation of the IGBT 21 is input from the protection circuit 14, the gate signal generation circuit 12 generates a gate signal of a signal level capable of controlling the IGBT 21 to an off state regardless of the signal level of the input signal Vin, and outputs the gate signal to the IGBT 21. Here, abnormal operation of the IGBT 21 means operation in a state in which at least one of the current flowing through the IGBT 21 and the operating temperature of the IGBT 21 exceeds the absolute maximum rating.

[0033] As shown in FIG. 2, the input of the current detection circuit 13 is connected to the output of the current detection terminal S of the IGBT 21, and the output of the current detection circuit 13 is connected to the input of the protection circuit 14. When the detection current input from the current detection terminal S of the IGBT 21 is smaller than the absolute maximum rated current of the IGBT 21, the current detection circuit 13 outputs, for example, an output signal having a low level signal level to the protection circuit 14. On the other hand, when the detection current input from the current detection terminal S of the IGBT 21 is equal to or larger than the absolute maximum rated current of the IGBT 21, the current detection circuit 13 outputs, for example, an output signal having a high level signal level to the protection circuit 14. For example, the current detection circuit 13 compares a detection voltage obtained by converting the detection current input from the current detection terminal S of the IGBT 21 into a voltage with a voltage (for example, 1.5 to 2 times) larger than a voltage corresponding to the absolute maximum rated current of the IGBT 21 that is set in advance. In this way, the current detection circuit 13 detects whether or not the current (for example, collector current) flowing through the IGBT 21 exceeds an amount of current that allows operation.

[0034] As shown in FIG. 2, the input of the temperature detection circuit 15 is connected to the output of the temperature detection element 23. The output of the temperature detection circuit 15 is connected to the input of the protection circuit 14, which is different from the output of the current detection circuit 13. The output of the constant current circuit 16 provided in the gate drive circuit 10 is connected to the connection between the input of the temperature detection circuit 15 and the output of the temperature detection element 23. The constant current circuit 16 operates with a power supply voltage Vcc applied to a power supply terminal Tvd provided in the semiconductor device 2a, and outputs a constant current of a predetermined value to the temperature detection element 23. The output of the constant current circuit 16 is connected to the input of the temperature detection circuit 15 as well as to the inverting input terminal (-) of a comparator 112 (details will be described later) provided in the switch circuit 111. The input impedance of the temperature detection circuit 15 and the input impedance of the comparator 112 are high impedance. Therefore, the constant current output from the constant current circuit 16 flows to the temperature detection element 23 without flowing almost to the temperature detection circuit 15 and the comparator 112.

[0035] As shown in FIG. 2, the temperature detection element 23 is composed of a plurality of diodes (three in this embodiment) connected in series. The diodes are made of, for example, silicon. The temperature detection element 23 is arranged between the temperature detection circuit 15, the constant current circuit 16, and the comparator 112 and the reference potential terminal 41. The temperature detection element 23 is arranged in a forward direction from the constant current circuit 16 side to the reference potential terminal 41 side. Therefore, among the plurality of diodes constituting the temperature detection element 23, the anode of the diode arranged on the constant current circuit 16 side is connected to the input of the temperature detection circuit 15, the output of the constant current circuit 16, and the input of the comparator 112. Among the plurality of diodes constituting the temperature detection element 23, the cathode of the diode arranged on the reference potential terminal 41 side is connected to the reference potential terminal 41.

[0036] Generally, the forward voltage of a silicon diode is lower when the ambient temperature is high than when it is low. Therefore, when a constant current is input from the constant current circuit 16 to the temperature detection element 23, if the temperature of the IGBT 21 rises, the voltage drop at the temperature detection element 23 becomes smaller. As a result, the voltage input from the temperature detection element 23 to the temperature detection circuit 15 decreases as the temperature of the IGBT 21 increases. Therefore, the temperature detection circuit 15 can detect whether the temperature of the IGBT 21 exceeds the absolute maximum rating by using the voltage input from the temperature detection element 23 and which changes according to the temperature of the IGBT 21.

[0037] When the temperature detected by the temperature detection element 23 is lower than a value set based on the absolute maximum rated temperature of the IGBT 21, the temperature detection circuit 15 outputs, for example, an output signal with a low level signal level to the protection circuit 14. On the other hand, when the temperature detected by the temperature detection element 23 is equal to or higher than a value set based on the absolute maximum rated temperature of the IGBT 21, the temperature detection circuit 15 outputs, for example, an output signal with a high level signal level to the protection circuit 14. For example, the temperature detection circuit 15 compares the value input from the temperature detection element 23 with a value that is preset and set based on the absolute maximum rated temperature of the IGBT 21. In this way, the temperature detection circuit 15 detects whether the temperature of the IGBT 21 is an operable temperature or not.

[0038] 2, the protection circuit 14 has two outputs. One output of the protection circuit 14 is connected to an input of the gate signal generation circuit 12 that is different from the input signal Vin. The other output of the protection circuit 14 is connected to a signal output terminal To provided in the semiconductor device 2a.

[0039] The protection circuit 14 outputs a signal indicating an abnormal state of the IGBT 21 to the gate signal generation circuit 12 when an output signal indicating that a current exceeding an operable range is flowing through the IGBT 21 (hereinafter, sometimes referred to as a "current abnormality signal") is input from the current detection circuit 13. When the current abnormality signal is input from the current detection circuit 13, the gate signal generation circuit 12 outputs a gate signal capable of turning the IGBT 21 off to the gate G of the IGBT 21 in order to stop the operation of the IGBT 21 at a current exceeding the operable range. In addition, when the current abnormality signal is input from the current detection circuit 13, the protection circuit 14 outputs an alarm signal ALM (for example, a signal with a high level) to the signal output terminal To. This allows the semiconductor device 2a to output an alarm signal ALM indicating that the IGBT 21 is in an abnormal state to the control device 6 (see FIG. 1).

[0040] The protection circuit 14 outputs a signal indicating an abnormal state of the IGBT 21 to the gate signal generation circuit 12 when an output signal indicating that the IGBT 21 is operating at a temperature exceeding the operable temperature (hereinafter, sometimes referred to as an "abnormal temperature signal") is input from the temperature detection circuit 15. When the abnormal temperature signal is input from the temperature detection circuit 15, the gate signal generation circuit 12 outputs a gate signal capable of turning the IGBT 21 off to the gate G of the IGBT 21 in order to stop the operation of the IGBT 21 at a temperature exceeding the operable range. In addition, when the abnormal temperature signal is input from the temperature detection circuit 15, the protection circuit 14 outputs an alarm signal ALM (for example, a signal with a high level) to the signal output terminal To. This allows the semiconductor device 2a to output an alarm signal ALM indicating that the IGBT 21 is in an abnormal state to the control device 6 (see FIG. 1).

[0041] The protection circuit 14 may be configured to output different alarm signals ALM to the signal output terminal To depending on whether a current abnormality signal is input from the current detection circuit 13 or a temperature abnormality signal is input from the temperature detection circuit 15. When a current abnormality signal is input from the current detection circuit 13, the protection circuit 14 may output, for example, an alarm signal ALM having a high signal level to the signal output terminal To. On the other hand, when a temperature abnormality signal is input from the temperature detection circuit 15, the protection circuit 14 may output, for example, a pulse-shaped alarm signal ALM to the signal output terminal To. Note that when neither a current abnormality signal nor a temperature abnormality signal is input (i.e., when the IGBT 21 is in a normal operating state), the protection circuit 14 outputs, for example, an alarm signal ALM having a low signal level to the signal output terminal To. This allows the control device 6 to determine the operating state of the IGBT 21 based on the alarm signal ALM input from the semiconductor device 2a.

[0042] As shown in FIG. 2, the capacitance adjustment unit 11 has a switch circuit 111 that cuts off the connection between the gate G of the IGBT 21 and the gate capacitor 30 when the detected temperature detected by the temperature detection element 23 is equal to or higher than a predetermined comparison temperature, and connects the gate G of the IGBT 21 and the gate capacitor 30 when the detected temperature is lower than the comparison temperature. In this embodiment, the comparison temperature is set to, for example, a temperature based on the absolute maximum rated temperature as the operable temperature of the IGBT 21 (a temperature equal to or lower than the absolute maximum rated temperature). The capacitance adjustment unit 11 has a comparator (an example of a comparison unit) 112 that compares a detection voltage corresponding to the detection temperature input from the temperature detection element 23 and detected by the temperature detection element 23 with a comparison voltage V1 corresponding to the comparison temperature. The capacitance adjustment unit 11 has a voltage generation unit 113 that generates the comparison voltage V1.

[0043] The switch circuit 111 has, for example, a P-type MOS transistor 111a (an example of an interrupting switch) that is provided so as to be able to interrupt the connection between the gate G of the IGBT 21 and the gate capacitor 30. The switch circuit 111 has, for example, an N-type MOS transistor 111b (an example of a connecting switch) that is provided so as to be able to discharge the charge of the gate capacitor 30.

[0044] The MOS transistor 111a and the MOS transistor 111b have a complementary configuration in which they are connected in series between the gate G of the IGBT 21 and the reference potential terminal 41. Therefore, the switch circuit 111 is a complementary switch circuit composed of the MOS transistor 111a and the MOS transistor 111b. Therefore, the capacitance adjustment unit 11 has a complementary switch circuit.

[0045] The source of the MOS transistor 111a is connected to the gate G of the IGBT 21. The drain of the MOS transistor 111a is connected to the drain of the MOS transistor 111b. The source of the MOS transistor 111b is connected to the reference potential terminal 41.

[0046] The gate of the MOS transistor 111a and the gate of the MOS transistor 111b are connected to each other. The gate of the MOS transistor 111a and the gate of the MOS transistor 111b are connected to an output terminal of a comparator 112 provided in the capacitance adjustment unit 11. The drain of the MOS transistor 111a and the drain of the MOS transistor 111b are connected to a gate capacitor 30. The connection point of the gate of the MOS transistor 111a and the gate of the MOS transistor 111b becomes an input terminal of the switch circuit 111. For this reason, the comparator 112 is arranged on the input side of the switch circuit 111. The connection point of the drain of the MOS transistor 111a and the drain of the MOS transistor 111b becomes an output terminal of the switch circuit 111. For this reason, the gate capacitor 30 is arranged on the output side of the switch circuit 111.

[0047] One electrode of the gate capacitor 30 is connected to the drain of the MOS transistor 111a and the drain of the MOS transistor 111b. The other electrode of the gate capacitor 30 is connected to the reference potential terminal 41. Therefore, the gate capacitor 30 is disposed between the output terminal of the switch circuit 111 and the reference potential terminal 41, with one electrode of the gate capacitor 30 connected to the output terminal of the switch circuit 111.

[0048] Fig. 3 is a diagram showing an example of the relationship between the detected temperature and the detected voltage in temperature detection element 23. The horizontal axis of the graph shown in Fig. 3 represents the detected temperature detected by temperature detection element 23. The vertical axis of the graph shown in Fig. 3 represents the detected voltage corresponding to the detected temperature detected by temperature detection element 23. "TV" shown in Fig. 3 indicates the characteristic of the detected voltage with respect to the detected temperature of temperature detection element 23 (temperature voltage characteristic).

[0049] As described above, the temperature detection element 23 has a characteristic that the detection voltage decreases, for example, linearly, as the detection temperature increases. Therefore, as shown in FIG. 3, the temperature detection element 23 has a temperature-voltage characteristic TV that slopes downward. In the semiconductor device 2a, a comparison temperature Tc based on the absolute maximum rated temperature of the IGBT 21 is set in the temperature-voltage characteristic TV. Therefore, when the detection temperature detected by the temperature detection element 23 is lower than the comparison temperature Tc, the detection voltage is higher than the comparison voltage V1. On the other hand, when the detection temperature detected by the temperature detection element 23 is equal to or higher than the comparison temperature Tc, the detection voltage is equal to or lower than the comparison voltage V1.

[0050] In this embodiment, the comparison temperature Tc is set based on the maximum operable temperature (absolute maximum rated temperature) of the IGBT 21. Therefore, when the detected temperature detected by the temperature detection element 23 is lower than the comparison temperature Tc set based on the absolute maximum rated temperature of the IGBT 21, the detection voltage is higher than the comparison voltage V1. On the other hand, when the detected temperature detected by the temperature detection element 23 is equal to or higher than the comparison temperature Tc, the detection voltage is equal to or lower than the comparison voltage V1.

[0051] 2, the voltage generating unit 113 is configured by, for example, a DC power supply. The negative electrode side of the voltage generating unit 113 is connected to the reference potential terminal 41. The comparison voltage V1 is set based on a voltage corresponding to the absolute maximum rated temperature of the IGBT 21.

[0052] 2, the comparator 112 is, for example, a hysteresis comparator configured with an operational amplifier and a resistor element (not shown). The temperature detection element 23 is connected to an inverting input terminal (-) of the comparator 112. The positive electrode side of the voltage generation unit 113 is connected to a non-inverting input terminal (+) of the comparator 112. The output terminal of the comparator 112 is connected to the gates of the MOS transistor 111a and the MOS transistor 111b provided in the switch circuit 111.

[0053] The comparator 112 outputs an output signal having a signal level, for example, a low level, to the switch circuit 111 when the detection voltage input from the temperature detection element 23 and corresponding to the detection temperature is higher than the comparison voltage V1 generated by the voltage generation unit 113. Also, the comparator 112 outputs an output signal having a signal level, for example, a high level, to the switch circuit 111 when the detection voltage input from the temperature detection element 23 is the same as or lower than the comparison voltage V1 (i.e., when it is equal to or lower than the comparison voltage V1). Therefore, the comparator 112 outputs a high level output signal when the detection temperature detected by the temperature detection element 23 is the same as or higher than the comparison temperature Tc. On the other hand, the comparator 112 outputs a low level output signal when the detection temperature detected by the temperature detection element 23 is lower than the comparison temperature Tc.

[0054] Since the MOS transistor 111a is composed of a P-type MOS, it is turned off (non-conductive) when the output signal output by the comparator 112 is at a high level, and turned on (conductive) when the output signal is at a low level. Therefore, the MOS transistor 111a cuts off the connection between the gate G of the IGBT 21 and the gate capacitor 30 (more specifically, the electrical connection with one electrode of the gate capacitor 30) when the detected temperature detected by the temperature detection element 23 is equal to or higher than the comparison temperature Tc (when the output signal of the comparator 112 is at a high level). On the other hand, the MOS transistor 111a connects the gate G of the IGBT 21 and the gate capacitor 30 (more specifically, electrically connects the gate G and one electrode of the gate capacitor 30) when the detected temperature detected by the temperature detection element 23 is lower than the comparison temperature Tc (when the output signal of the comparator 112 is at a low level).

[0055] Since the MOS transistor 111b is composed of an N-type MOS, it is turned on (conductive) when the output signal output by the comparator 112 is at a high level, and is turned off (non-conductive) when the output signal is at a low level. Therefore, the MOS transistor 111b connects the reference potential terminal 41 to the gate capacitor 30 (more specifically, electrically connects the reference potential terminal 41 to one electrode of the gate capacitor 30) when the detected temperature detected by the temperature detection element 23 is equal to or higher than the comparison temperature Tc (when the output signal of the comparator 112 is at a high level). In addition, the MOS transistor 111b disconnects the reference potential terminal 41 from the gate capacitor 30 (more specifically, electrically disconnects the reference potential terminal 41 from one electrode of the gate capacitor 30) when the detected temperature detected by the temperature detection element 23 is lower than the comparison temperature Tc (when the output signal of the comparator 112 is at a low level).

[0056] In other words, when the comparator 112 outputs a signal indicating that the detection voltage corresponding to the detection temperature detected by the temperature detection element 23 is equal to or lower than the comparison voltage V1 corresponding to the comparison temperature, the MOS transistor 111a cuts off the connection between the gate capacitor 30 and the gate G of the IGBT 21 (more specifically, the electrical connection between one electrode of the gate capacitor 30 and the gate G of the IGBT 21), and the MOS transistor 111b connects the gate capacitor 30 to the reference potential terminal 41 (more specifically, the electrical connection between one electrode of the gate capacitor 30 and the reference potential terminal 41). On the other hand, when the comparator 112 outputs a signal indicating that the detection voltage detected by the temperature detection element 23 is higher than the comparison voltage V1, the MOS transistor 111a does not cut off the connection between the gate capacitor 30 and the gate G (more specifically, the electrical connection between one electrode of the gate capacitor 30 and the gate G of the IGBT 21), and the MOS transistor 111b disconnects the gate capacitor 30 from the reference potential terminal 41 (more specifically, electrically disconnects one electrode of the gate capacitor 30 from the reference potential terminal 41).

[0057] Therefore, the switch circuit 111 has a function of switching to a circuit configuration that discharges the charge of the gate capacitor 30 when the detected temperature detected by the temperature detection element 23 is equal to or higher than the comparison temperature (when the detected voltage corresponding to the detected temperature is equal to or lower than the comparison voltage V1 corresponding to the comparison temperature). That is, the switch circuit 111 connects the gate capacitor 30 to the reference potential terminal 41 when the detected temperature detected by the temperature detection element 23 is equal to or higher than the comparison temperature. The comparison temperature is set based on, for example, the maximum operable temperature (absolute maximum rated temperature) of the IGBT 21 (for example, set to be equal to or lower than the absolute maximum rated temperature). In this case, the switch circuit 111 also cuts off the connection between the gate G of the IGBT 21 and the gate capacitor 30 (more specifically, the electrical connection between the gate G of the IGBT 21 and one electrode of the gate capacitor 30). Furthermore, when the detected temperature detected by the temperature detection element 23 is lower than the comparison temperature (when the detected voltage is higher than the comparison voltage V1), the switch circuit 111 disconnects the gate capacitor 30 from the reference potential terminal 41 (more specifically, electrically disconnects one electrode of the gate capacitor 30 from the reference potential terminal 41). In this case, the switch circuit 111 also connects the gate G of the IGBT 21 to the gate capacitor 30 (more specifically, electrically connects the gate G of the IGBT 21 to one electrode of the gate capacitor 30).

[0058] As will be described in more detail later, the semiconductor devices 2a to 2f control the switch circuit 111 in accordance with the temperature of the IGBT 21, and when the IGBT 21 is higher than the comparison temperature, the connection between the gate G of the IGBT 21 and the gate capacitor 30 is cut off, thereby suppressing losses in the IGBT 21 at high temperatures without increasing the radiation noise of the IGBT 21.

[0059] [Operation of the Semiconductor Device] The operation of the semiconductor device 2a according to this embodiment will be described using FIG. 4 with reference to FIG. 1 to FIG. 3. FIG. 4 is a diagram for explaining the operation of the capacitance adjustment unit 11. In FIG. 4, the MOS transistors 111a and 111b are illustrated with the circuit symbol of a switch to facilitate understanding of the open / closed state. FIG. 4(a) is a circuit diagram of the capacitance adjustment unit 11 and the like in which the MOS transistor 111a is in the on state (conductive state) and the MOS transistor 111b is in the off state (non-conductive state). FIG. 4(b) is a circuit diagram of the capacitance adjustment unit 11 and the like in which the MOS transistor 111a is in the off state and the MOS transistor 111b is in the on state.

[0060] (normal operation) Assume that no overcurrent or short-circuit current flows between the collector C and emitter E (see FIG. 2) of the IGBT 21 and the IGBT 21 operates within an operable temperature range (hereinafter, sometimes referred to as a "normal state"), and an input signal Vin having a high level, for example, is input from the control device 6 (see FIG. 1). In this case, the gate signal generating circuit 12 (see FIG. 2) provided in the semiconductor device 2a is in an inoperative state and does not output a gate signal to the gate G of the IGBT 21. Therefore, the IGBT 21 is in an off state. As a result, no current flows between the collector and emitter of the IGBT 21, and no detection current flows from the current detection terminal S (see FIG. 2). Furthermore, since the temperature of the IGBT 21 remains, for example, at room temperature, the temperature detection element 23 detects a temperature lower than the comparison temperature Tc.

[0061] When the IGBT 21 is in a normal state and the gate signal generating circuit 12 does not output a gate signal to the gate G of the IGBT 21, no detection current is output from the current detection terminal S of the IGBT 21. For this reason, the current detection circuit 13 (see FIG. 2) outputs an output signal indicating that the IGBT 21 is in a normal operating state to the gate signal generating circuit 12.

[0062] When the temperature of the IGBT 21 is at room temperature, the detection voltage output from the temperature detection element 23 is a voltage corresponding to a temperature lower than the absolute maximum rated temperature of the IGBT 21. Therefore, the temperature detection circuit 15 (see FIG. 2) outputs an output signal indicating that the IGBT 21 is in a normal operating state to the gate signal generation circuit 12.

[0063] When the temperature of the IGBT 21 is at room temperature, the detection voltage output from the temperature detection element 23 is a voltage corresponding to a temperature lower than the comparison temperature Tc and higher than the comparison voltage V1. Therefore, the comparator 112 provided in the capacitance adjustment unit 11 outputs an output signal having a low level to the switch circuit 111 (see FIG. 2). As a result, the switch circuit 111 electrically connects the gate G of the IGBT 21 and one of the electrodes of the gate capacitor 30, and electrically disconnects the reference potential terminal 41 and one of the electrodes of the gate capacitor 30.

[0064] When no overcurrent or short-circuit current flows between the collector C and emitter E of the IGBT 21 and the IGBT 21 is in a normal state operating within an operable temperature range, if an input signal Vin with a low signal level is input from the control device 6, the gate signal generating circuit 12 enters an operating state and outputs, for example, a gate signal with a high signal level to the IGBT 21. This switches the IGBT 21 from an off state to an on state, and a collector-emitter current flows between the collector C and the emitter E. Furthermore, a detection current of a predetermined amount based on the collector-emitter current flows from the current detection terminal S of the IGBT 21 to the current detection circuit 13.

[0065] Since this is a normal state in which no overcurrent or short-circuit current flows between the collector C and emitter E of the IGBT 21, the detection current output from the current detection terminal S of the IGBT 21 in this case has a current amount based on the current flowing through the IGBT 21 in the normal state. Therefore, the current detection circuit 13 outputs an output signal indicating that the IGBT 21 is in a normal operating state to the gate signal generation circuit 12.

[0066] The ambient temperature of the IGBT 21 is almost the same as or higher than room temperature because a current flows through the IGBT 21. However, when the IGBT 21 is operating normally, the ambient temperature of the IGBT 21 does not rise to the absolute maximum rated temperature of the IGBT 21. Therefore, the temperature detection element 23 detects a temperature lower than the comparison temperature Tc. As a result, the temperature detection circuit 15 outputs an output signal indicating that the IGBT 21 is operating normally to the gate signal generation circuit 12.

[0067] When the IGBT 21 is in a normal state, the current detection circuit 13 and the temperature detection circuit 15 output an output signal indicating that the IGBT 21 is in a normal state to the gate signal generation circuit 12. Therefore, the gate signal generation circuit 12 continues to output a gate signal to the gate G of the IGBT 21 for transitioning the IGBT 21 from an off state to an on state or for maintaining the on state.

[0068] The temperature of the IGBT 21 during normal operation (i.e., the ambient temperature) is lower than the absolute maximum rated temperature. Therefore, the detection voltage output from the temperature detection element 23 is a voltage corresponding to a temperature lower than the comparison temperature Tc and higher than the comparison voltage V1. As a result, the comparator 112 provided in the capacitance adjustment unit 11 outputs an output signal having a low level to the switch circuit 111. As a result, as shown in FIG. 4(a), the MOS transistor 111a is turned on and the MOS transistor 111b is turned off. As a result, the switch circuit 111 connects the gate G of the IGBT 21 to the gate capacitor 30 and disconnects the reference potential terminal 41 from the gate capacitor 30.

[0069] The gate signal generating circuit 12 outputs a gate current to the gate G when the IGBT 21 is changed from an OFF state to an ON state. By connecting the gate G of the IGBT 21 to the gate capacitor 30, a part of the gate current flows from the gate signal generating circuit 12 as shown by the dashed arrow in Fig. 4(a) and the gate capacitor 30 is charged. As a result, the IGBT 21 is maintained at a predetermined potential even after it changes from an OFF state to an ON state, so that the IGBT 21 can maintain the ON state.

[0070] In this way, the semiconductor devices 2a to 2f can connect the gate G of the IGBT 21 to the gate capacitor 30 when the temperature of the IGBT 21 is lower than the absolute maximum rated temperature and the IGBT 21 transitions from an off state to an on state (turns on). This allows the semiconductor devices 2a to 2f to reduce the rate of change of the recovery voltage of the IGBT 21 when the IGBT 21 is turned on, thereby suppressing the radiation noise emitted by the IGBT 21.

[0071] (Operation at high temperatures) When the IGBT 21 transitions from an off state to an on state (turns on) at a temperature equal to or higher than the comparison temperature, the temperature detection element 23 detects a temperature equal to or higher than the comparison temperature Tc. Therefore, the temperature detection element 23 outputs a detection voltage based on the detection temperature to the non-inverting input terminal (+) of the comparator 112 provided in the capacitance adjustment unit 11. The detection voltage input to the comparator 112 is a voltage lower than the comparison voltage V1. Therefore, the comparator 112 outputs an output signal with a high signal level to the switch circuit 111. As a result, as shown in FIG. 4(b), the MOS transistor 111a is turned off and the MOS transistor 111b is turned on. As a result, the switch circuit 111 cuts off the electrical connection between the gate G of the IGBT 21 and the gate capacitor 30 and electrically connects the reference potential terminal 41 and the gate capacitor 30. When the gate capacitor 30 is charged, the charge stored in the gate capacitor 30 is discharged to the reference potential terminal 41 via the MOS transistor 111b, as indicated by the dashed arrow in FIG. 4(b).

[0072] In this way, the semiconductor devices 2a to 2f cut off the electrical connection between the gate G of the IGBT 21 and the gate capacitor 30 when the temperature of the IGBT 21 is equal to or higher than the comparison temperature. As a result, the semiconductor devices 2a to 2f can reduce the loss of the IGBT 21 when the IGBT 21 is turned on, as will be described in detail later.

[0073] <Effects of semiconductor device> Next, the effect of the semiconductor device according to the present embodiment will be described with reference to FIGS. 2 to 4, taking the semiconductor device 2a as an example, and using FIGS. 5 and 6. FIG. 5 is a diagram showing the relationship between the freewheeling current flowing through a freewheeling diode connected in antiparallel to an IGBT and the voltage change rate when the freewheeling diode (FWD) performs a reverse recovery operation. For example, when focusing on the semiconductor device 2a and the semiconductor device 2b, the graph shown in FIG. 5 is obtained from the actual measurement value of the freewheeling current flowing through the freewheeling diode 22 provided in the semiconductor device 2b when the IGBT 21 provided in the semiconductor device 2a is turned on, and the actual measurement value of the voltage change rate. However, the semiconductor device used to obtain the graph shown in FIG. 5 does not have the capacitance adjustment unit 11 provided in the semiconductor devices 2a to 2f.

[0074] The horizontal axis of the graph shown in FIG. 5 represents the reflux current, and the vertical axis of the graph shown in FIG. 5 represents the recovery voltage change rate. In FIG. 5, "Cn25" shown by connecting white triangles with a dashed line indicates the characteristics of the recovery voltage change rate with respect to the reflux current when there is no gate capacitor and the IGBT temperature is 25°C. In FIG. 5, "Ce25" shown by connecting white circles with a solid line indicates the characteristics of the recovery voltage change rate with respect to the reflux current when there is a gate capacitor and the IGBT temperature is 25°C. In FIG. 5, "Cn125" shown by connecting shaded triangles with a dashed line indicates the characteristics of the recovery voltage change rate with respect to the reflux current when there is no gate capacitor and the IGBT temperature is 125°C. In FIG. 5, "Ce125" shown by connecting shaded circles with a solid line indicates the characteristics of the recovery voltage change rate with respect to the reflux current when there is a gate capacitor and the IGBT temperature is 125°C. In the characteristics Ce25 and Ce125, the semiconductor device is provided with gate capacitors having the same capacitance value.

[0075] The horizontal axis of the graph shown in FIG. 5 indicates that the return current increases from left to right. The vertical axis of the graph shown in FIG. 5 indicates that the recovery voltage change rate increases from bottom to top. Here, a configuration "without a gate capacitor" refers to a configuration in which a gate capacitor is not connected to the gate of the IGBT. Also, a configuration "with a gate capacitor" refers to a configuration in which a gate capacitor is connected between the gate of the IGBT and the reference potential terminal.

[0076] FIG. 6 is a diagram showing the relationship between the collector current flowing through an IGBT at a temperature of 125° C. and the switching loss of the IGBT. FIG. 6 shows a graph obtained from the measured values ​​of the collector current and switching loss of the IGBT. The horizontal axis of the graph shown in FIG. 6 represents the collector current flowing through the IGBT. The vertical axis of the graph shown in FIG. 6 represents the switching loss of the IGBT. The switching loss of the IGBT shown here is a combination of the loss when the IGBT transitions from an off state to an on state and the loss during reverse recovery of the free wheel diode (FWD). The characteristic Cn125 shows the same content as the characteristic Cn125 in FIG. 5, and the characteristic Ce125 shows the same content as the characteristic Ce125 in FIG. 5. The horizontal axis of the graph shown in FIG. 6 indicates the collector current increasing from left to right. The vertical axis of the graph shown in FIG. 6 indicates the switching loss increasing from bottom to top.

[0077] As shown in FIG. 5, by comparing the characteristics Cn25 and Cn125 or by comparing the characteristics Ce25 and Ce125, it is found that the recovery voltage change rate of the IGBT is higher when the temperature of the IGBT is low than when the temperature of the IGBT is high. Also, by comparing the characteristics Cn25 and Ce25 or by comparing the characteristics Cn125 and Ce125, it is found that the recovery voltage change rate of the IGBT is higher when the semiconductor device has a gate capacitor than when the semiconductor device does not have a gate capacitor. Therefore, the recovery voltage change rate of the IGBT is maximum when the semiconductor device does not have a gate capacitor and the temperature of the IGBT is the lowest (25° C. in FIG. 5). The radiation noise generated from the IGBT becomes larger as the recovery voltage change rate of the IGBT becomes higher. Therefore, the radiation noise generated from the IGBT is maximum when the semiconductor device does not have a gate capacitor and the temperature of the IGBT is the lowest (25° C. in FIG. 5).

[0078] Furthermore, a comparison between the characteristics Cn25 and Ce25 or a comparison between the characteristics Cn125 and Ce125 shows that the gate capacitor has the effect of reducing the recovery voltage change rate of the IGBT. Therefore, the gate capacitor has the effect of suppressing the radiation noise of the IGBT. Therefore, the radiation noise of the IGBT is larger when the IGBT is at a low temperature than when it is at a high temperature.

[0079] As shown in Fig. 6, the switching loss of the IGBT is 3% to 8% lower when the gate capacitor is not provided than when the gate capacitor is provided. Although not shown in the figures, the switching loss of the IGBT is also lower when the gate capacitor is not provided than when the gate capacitor is provided at other temperatures.

[0080] Incidentally, the radiation noise of the IGBT may cause malfunction of other electronic components constituting the semiconductor device or devices arranged around the semiconductor device. For this reason, in a semiconductor device having an IGBT, it is necessary to reduce the radiation noise of the IGBT in the temperature range in which the IGBT can operate. For this reason, it is desirable for the semiconductor device to include a gate capacitor that can reduce the radiation noise of the IGBT even when the IGBT is at a low temperature (25°C in FIG. 5).

[0081] However, when a semiconductor device has a gate capacitor capable of effectively reducing radiation noise generated when the IGBT is at a low temperature, the loss generally increases compared to when the semiconductor device has a gate capacitor capable of effectively reducing radiation noise generated when the IGBT is at a high temperature. Furthermore, regardless of the temperature of the IGBT, when a semiconductor device has a gate capacitor, the loss of the IGBT generally increases compared to when the semiconductor device does not have a gate capacitor. Therefore, when a semiconductor device has a gate capacitor capable of effectively reducing radiation noise generated when the IGBT is at a low temperature, there is a problem that the noise and loss of the IGBT cannot be effectively reduced when the IGBT is in a high temperature state.

[0082] In contrast, the semiconductor devices 2a to 2f according to this embodiment include a capacitance adjustment unit 11. Therefore, even if the semiconductor devices 2a to 2f include a gate capacitor 30 whose capacitance value is adjusted so as to effectively reduce radiation noise generated when the IGBT 21 is at a low temperature, when the IGBT 21 is in a high temperature state, the electrical connection between the gate capacitor 30 and the gate G of the IGBT can be cut off. As a result, the semiconductor devices 2a to 2f can obtain the effect of reducing radiation noise from the IGBT 21 (i.e., the effect of reducing the recovery voltage change rate of the IGBT 21) and can suppress losses (generated losses) generated from the IGBT at high temperatures.

[0083] As described above, the semiconductor devices 2a to 2f according to this embodiment include an IGBT 21 having a gate G to which a gate signal is input, a temperature detection element 23 that detects the temperature of the IGBT 21, and a capacitance adjustment unit 11 that is disposed between the gate G of the IGBT 21 and a reference potential terminal 41 and adjusts the capacitance between the gate G and the emitter E of the IGBT 21 in accordance with the detected temperature detected by the temperature detection element 23. As a result, the semiconductor devices 2a to 2f can suppress loss of the IGBT 21 at high temperatures without increasing radiation noise of the IGBT 21.

[0084] Second Embodiment A semiconductor device according to a second embodiment of the present invention will be described with reference to FIG. 7. The semiconductor device according to this embodiment is characterized in that the capacitance between the control signal input terminal and the reference potential terminal of the switching element can be adjusted stepwise according to the temperature of the IGBT. Since the power conversion device including the semiconductor device according to this embodiment is similar to the power conversion device 1 including the semiconductor device according to the first embodiment, FIG. 1 will be referred to as necessary below, and a description thereof will be omitted. In addition, in describing the semiconductor device according to this embodiment, components that have the same actions and functions as those of the semiconductor device according to the first embodiment will be denoted by the same reference numerals, and a description thereof will be omitted.

[0085] The semiconductor devices 2a to 2f (see FIG. 1) provided in the power converter in this embodiment have the same configuration and operate in the same manner, so the semiconductor devices 2a to 2f will be described below by taking the semiconductor device 2a as an example.

[0086] 7 is a circuit block diagram showing a schematic configuration of a semiconductor device 2a according to this embodiment. In order to facilitate understanding, in FIG. 7, of the capacitance adjustment unit provided in the semiconductor device 2a, only a voltage generation unit is shown.

[0087] 7, the semiconductor device 2a according to the present embodiment includes an IGBT (an example of a switching element) 21 having a gate (an example of a control signal input terminal) G to which a gate signal (an example of a switching control signal) is input, and a current detection terminal S used to detect at least one of an overcurrent and a short-circuit current. The semiconductor device 2a includes a temperature detection element 23 that detects the temperature of the IGBT 21.

[0088] The semiconductor device 2a includes a plurality of (three in this embodiment) capacitance adjustment units 11-1, 11-2, and 11-3. The capacitance adjustment units 11-1, 11-2, and 11-3 are arranged between the gate G of the IGBT 21 and the reference potential terminal 41, and are configured to adjust the capacitance between the gate G and the emitter E of the IGBT 21 according to the detected temperature detected by the temperature detection element 23. The semiconductor device 2a includes a plurality of (three in this embodiment) gate capacitors 30-1, 30-2, and 30-3 (one example of a capacitor) each corresponding to one of the plurality of capacitance adjustment units 11-1, 11-2, and 11-3, which are different from each other. The gate capacitor 30-1 corresponds to the capacitance adjustment unit 11-1. The gate capacitor 30-2 corresponds to the capacitance adjustment unit 11-2. The gate capacitor 30-3 corresponds to the capacitance adjustment unit 11-3.

[0089] The capacitance adjustment units 11-1, 11-2, and 11-3 have the same configuration as the capacitance adjustment unit 11 (see FIG. 2) in the first embodiment. The gate capacitor 30-1 is connected to a switch circuit 111 (see FIG. 2) provided in the capacitance adjustment unit 11-1. The gate capacitor 30-2 is connected to a switch circuit 111 provided in the capacitance adjustment unit 11-2. The gate capacitor 30-3 is connected to a switch circuit 111 provided in the capacitance adjustment unit 11-3.

[0090] The plurality of capacitance adjustment units 11-1, 11-2, and 11-3 compare different comparison temperatures with a detected temperature detected by a temperature detection element 23 (see FIG. 2) to control the switch circuit 111. As shown in FIG. 7, the voltage generation unit 113 provided in the capacitance adjustment unit 11-1 is configured to generate a comparison voltage V1, the voltage generation unit 113 provided in the capacitance adjustment unit 11-2 is configured to generate a comparison voltage V2, and the voltage generation unit 113 provided in the capacitance adjustment unit 11-3 is configured to generate a comparison voltage V3.

[0091] The comparison voltage V1 is set to a temperature equal to or lower than the absolute maximum rated temperature of the IGBT 21 (hereinafter referred to as "comparison temperature T1"). The comparison voltage V2 is set to a voltage higher than the comparison voltage V1. Therefore, the voltage value of the comparison voltage V1 is set to the same voltage value as the detection voltage output when the temperature detection element 23 detects the comparison temperature T1 as the temperature of the IGBT 21. The voltage value of the comparison voltage V2 is set to the same voltage value as the detection voltage output when the temperature detection element 23 detects a temperature (hereinafter referred to as "comparison temperature T2") that is a predetermined amount lower than the comparison temperature T1. The voltage value of the comparison voltage V3 is set to the same voltage value as the detection voltage output when the temperature detection element 23 detects a temperature (hereinafter referred to as "comparison temperature T3") that is a predetermined amount lower than the comparison temperature T2 and a predetermined amount higher than room temperature.

[0092] Therefore, the capacitance adjustment unit 11-3 cuts off the electrical connection between one electrode of the gate capacitor 30-3 and the gate G of the IGBT 21 at a detection temperature (comparison temperature T3) lower than those of the capacitance adjustment units 11-1 and 11-2, and electrically connects one electrode of the gate capacitor 30-3 to the reference potential terminal 41. The capacitance adjustment unit 11-2 cuts off the electrical connection between one electrode of the gate capacitor 30-2 and the gate G of the IGBT 21 at a detection temperature (comparison temperature T2) lower than those of the capacitance adjustment unit 11-1, and electrically connects one electrode of the gate capacitor 30-2 to the reference potential terminal 41. Similar to the capacitance adjustment unit 11 in the first embodiment described above, the capacitance adjustment unit 11-1 cuts off the electrical connection between one electrode of the gate capacitor 30-1 and the gate G of the IGBT 21 at a detection temperature (comparison temperature T1) that is the same as or a predetermined amount lower than the absolute maximum rated temperature of the IGBT 21, and electrically connects one electrode of the gate capacitor 30-1 to the reference potential terminal 41.

[0093] More specifically, when the temperature detection element 23 detects a temperature lower than the comparison temperature T3, the detection voltage is higher than the comparison voltages V1 to V3. In this case, the comparators 112 provided in each of the capacitance adjustment units 11-1, 11-2, and 11-3 output an output signal having a low signal level to the switch circuit 111. Therefore, the MOS transistors 111a provided in the switch circuits 111 of the capacitance adjustment units 11-1, 11-2, and 11-3 are all turned on, and the MOS transistors 111b provided in the switch circuits 111 are all turned off. As a result, the gate capacitors 30-1, 30-2, and 30-3 are all electrically connected to the gate G of the IGBT 21 and electrically disconnected from the reference potential terminal 41. As a result, the gate capacitors 30-1, 30-2, and 30-3 are connected in parallel between the gate G of the IGBT 21 and the reference potential terminal 41. If the capacitance value of the gate capacitor 30-1 is C1, the capacitance value of the gate capacitor 30-2 is C2, and the capacitance value of the gate capacitor 30-3 is C3, then the capacitance value between the gate G of the IGBT 21 and the reference potential terminal 41 is "C1+C2+C3" (excluding the parasitic capacitance Cge between the gate G of the IGBT 21 and the reference potential terminal 41). When the capacitance value of "C1+C2+C3" is the same as the capacitance value of the gate capacitor 30 in the first embodiment, the semiconductor devices 2a to 2f according to this embodiment can obtain the same radiation noise reduction effect and switching loss reduction effect as the semiconductor devices 2a to 2f according to the first embodiment at room temperature.

[0094] When the temperature detection element 23 detects a temperature equal to the comparison temperature T3 or lower than the comparison temperature T2 (i.e., a temperature higher than room temperature by a predetermined amount), the detection voltage is a voltage in the range from the comparison voltage V3 to higher than the comparison voltage V2. In this case, the comparator 112 provided in the capacitance adjustment unit 11-3 outputs an output signal having a high signal level to the switch circuit 111. On the other hand, the comparators 112 provided in the capacitance adjustment units 11-1 and 11-2 each output a signal having a low signal level to the switch circuit 111. Therefore, the MOS transistor 111a provided in the switch circuit 111 of the capacitance adjustment unit 11-3 is turned off, and the MOS transistor 111b provided in the switch circuit 111 is turned on. On the other hand, the MOS transistors 111a provided in the switch circuits 111 of the capacitance adjustment units 11-1 and 11-2 are both turned on, and the MOS transistors 111b provided in the switch circuits 111 are both turned off.

[0095] As a result, one electrode of the gate capacitor 30-3 is electrically disconnected from the gate G of the IGBT 21 and electrically connected to the reference potential terminal 41. On the other hand, one electrode of each of the gate capacitors 30-1, 30-2 is electrically connected to the gate G of the IGBT 21 and electrically disconnected from the reference potential terminal 41. As a result, the gate capacitors 30-1, 30-2 are connected in parallel between the gate G of the IGBT 21 and the reference potential terminal 41, and the capacitance value between the gate G of the IGBT 21 and the reference potential terminal 41 becomes "C1+C2" (excluding the parasitic capacitance Cge between the gate G of the IGBT 21 and the reference potential terminal 41).

[0096] In this way, when the semiconductor devices 2a to 2f detect a comparison temperature T3 that is a predetermined amount higher than the room temperature of the IGBT 21, they can reduce the capacitance value of the gate capacitor connected between the gate G of the IGBT 21 and the reference potential terminal 41.

[0097] When the temperature detection element 23 detects a temperature equal to the comparison temperature T2 or lower than the comparison temperature T1, the detection voltage is in the range from the comparison voltage V2 to a voltage higher than the comparison voltage V1. In this case, the comparator 112 provided in the capacitance adjustment unit 11-2 outputs an output signal having a high signal level to the switch circuit 111 provided in the capacitance adjustment unit 11-2. Similarly, the comparator 112 provided in the capacitance adjustment unit 11-3 outputs an output signal having a high signal level to the switch circuit 111 provided in the capacitance adjustment unit 11-3. On the other hand, each comparator 112 provided in the capacitance adjustment unit 11-1 outputs an output signal having a low signal level to the switch circuit 111. Therefore, the MOS transistors 111a provided in the switch circuits 111 of the capacitance adjustment units 11-2 and 11-3 are turned off, and the MOS transistors 111b provided in these switch circuits 111 are turned on. On the other hand, the MOS transistor 111a provided in the switch circuit 111 of the capacitance adjustment unit 11-1 is turned on, and the MOS transistor 111b provided in the switch circuit 111 is turned off.

[0098] As a result, one electrode of each of the gate capacitors 30-2, 30-3 is electrically disconnected from the gate G of the IGBT 21 and electrically connected to the reference potential terminal 41. On the other hand, one electrode of the gate capacitor 30-1 is electrically connected to the gate G of the IGBT 21 and electrically disconnected from the reference potential terminal 41. As a result, the gate capacitor 30-1 is connected between the gate G of the IGBT 21 and the reference potential terminal 41, and the capacitance value between the gate G of the IGBT 21 and the reference potential terminal 41 becomes "C1" (excluding the parasitic capacitance Cge between the gate G of the IGBT 21 and the reference potential terminal 41).

[0099] In this way, when the semiconductor devices 2a to 2f detect a temperature in the range from comparison temperature T2 to lower than comparison temperature T1, the capacitance value of the gate capacitor connected between the gate G of the IGBT 21 and the reference potential terminal 41 can be reduced compared to when the semiconductor devices 2a to 2f detect a temperature in the range from comparison temperature T3 to lower than comparison temperature T2.

[0100] When the temperature detection element 23 detects a temperature equal to or higher than the comparison temperature T1, the detection voltage is equal to or lower than the comparison voltage V1. In this case, the comparator 112 provided in the capacitance adjustment unit 11-2 outputs an output signal having a high signal level to the switch circuit 111 provided in the capacitance adjustment unit 11-2. Similarly, the comparator 112 provided in the capacitance adjustment unit 11-3 outputs an output signal having a high signal level to the switch circuit 111 provided in the capacitance adjustment unit 11-3. Furthermore, the comparator 112 provided in the capacitance adjustment unit 11-1 outputs an output signal having a high signal level to the switch circuit 111. Therefore, the MOS transistors 111a provided in the switch circuits 111 of the capacitance adjustment units 11-1, 11-2, and 11-3 are turned off, and the MOS transistors 111b provided in these switch circuits 111 are turned on.

[0101] As a result, one electrode of each of the gate capacitors 30-1, 30-2, and 30-3 is electrically disconnected from the gate G of the IGBT 21 and is electrically connected to the reference potential terminal 41. As a result, none of the gate capacitors 30-1, 30-2, and 30-3 is connected between the gate G of the IGBT 21 and the reference potential terminal 41, and therefore the capacitance value between the gate G of the IGBT 21 and the reference potential terminal 41 becomes "0" (excluding the parasitic capacitance Cge between the gate G of the IGBT 21 and the reference potential terminal 41).

[0102] In this way, when the semiconductor devices 2a to 2f detect a temperature equal to or higher than the comparison temperature T3, the capacitance value of the gate capacitor connected between the gate G of the IGBT 21 and the reference potential terminal 41 can be reduced compared to when the semiconductor devices 2a to 2f detect a temperature in the range from the comparison temperature T3 to a temperature lower than the comparison temperature T1.

[0103] In this way, the semiconductor devices 2a to 2f according to the present embodiment can adjust the capacitance between the gate G of the IGBT 21 and the reference potential terminal 41 in a stepwise manner in accordance with the temperature detected by the temperature detection element 23. As a result, the semiconductor devices 2a to 2f according to the present embodiment can more effectively reduce the radiation noise and switching loss of the IGBT 21 in accordance with the temperature of the IGBT 21 than the semiconductor devices 2a to 2f according to the first embodiment.

[0104] As described above, the semiconductor device 2a to 2f according to the present embodiment includes a plurality of capacitance adjusters 11-1, 11-2, and 11-3, and a plurality of gate capacitors 30-1, 30-2, and 30-3 each associated with one of the plurality of capacitance adjusters 11-1, 11-2, and 11-3 that are different from each other. The plurality of capacitance adjusters 11-1, 11-2, and 11-3 are configured to compare different comparison temperatures with a detection temperature detected by the temperature detection element 23 to control the switch circuit 111.

[0105] As a result, the semiconductor devices 2a to 2f according to this embodiment can adjust the capacitance between the gate G of the IGBT 21 and the reference potential terminal 41 in a stepwise manner in accordance with the detected temperature detected by the temperature detection element 23. As a result, the semiconductor devices 2a to 2f according to this embodiment can suppress the loss of the IGBT 21 in accordance with the temperature of the IGBT 21 without increasing the radiation noise of the IGBT 21, in addition to the effects of the semiconductor devices 2a to 2f according to the first embodiment.

[0106] Third Embodiment A semiconductor device according to a third embodiment of the present invention will be described with reference to FIG. 8. The semiconductor device according to this embodiment is characterized in that the capacitance between the control signal input terminal and the reference potential terminal of the switching element can be continuously adjusted according to the temperature of the IGBT. Since the power conversion device including the semiconductor device according to this embodiment is similar to the power conversion device 1 including the semiconductor device according to the first embodiment, FIG. 1 will be referred to as necessary below, and a description thereof will be omitted. In addition, in describing the semiconductor device according to this embodiment, components having the same actions and functions as those of the semiconductor device according to the first embodiment will be denoted by the same reference numerals, and a description thereof will be omitted.

[0107] The semiconductor devices 2a to 2f (see FIG. 1) provided in the power converter in this embodiment have the same configuration and operate in the same manner, so the semiconductor devices 2a to 2f will be described below by taking the semiconductor device 2a as an example.

[0108] FIG. 8 is a circuit block diagram showing a schematic configuration of a semiconductor device 2a according to the present embodiment. 8, the gate capacitor 31 included in the semiconductor device 2a according to this embodiment is a variable capacitance capacitor, the capacitance of which is variable depending on the voltage input to the control terminal.

[0109] The semiconductor device 2a according to the present embodiment has a non-inverting amplifier circuit 114 in addition to the capacitance adjustment unit 11 provided in the semiconductor device 2a according to the first embodiment. The output of the non-inverting amplifier circuit 114 is connected to the control terminal of the gate capacitor 31.

[0110] More specifically, the non-inverting amplifier circuit 114 has a non-inverting input terminal (+) connected to the output of the temperature detection element 23 and an amplifier 114a configured by, for example, an operational amplifier. The output terminal of the amplifier 114a is connected to the control terminal of the gate capacitor 31. The non-inverting amplifier circuit 114 has a resistor element 114b having one terminal connected to the inverting input terminal (-) of the amplifier 114a and the other terminal connected to the reference potential terminal 41. The non-inverting amplifier circuit 114 has a resistor element 114c connected between the inverting input terminal (-) of the amplifier 114a and the output terminal of the amplifier 114a. The resistor element 114c has one terminal connected to the output terminal of the amplifier 114a and the other terminal connected to the inverting input terminal (-) of the amplifier 114a and one terminal of the resistor element 114b. The resistor element 114b and the resistor element 114c form a feedback circuit.

[0111] The non-inverting amplifier circuit 114 is configured to amplify the detection voltage input from the temperature detection element 23 with an amplification factor based on the ratio of the resistance value of the resistor element 114b and the resistance value of the resistor element 114c, and output the amplified voltage to the control terminal of the gate capacitor 31. The temperature detection element 23 outputs a lower detection voltage as the temperature of the IGBT 21 is higher (the detection temperature is higher). Therefore, the non-inverting amplifier circuit 114 outputs a lower output voltage to the control terminal of the gate capacitor 31 as the detection temperature detected by the temperature detection element 23 is higher. The gate capacitor 31 has a characteristic that, for example, the capacitance value becomes smaller as the voltage input to the control terminal is lower. Therefore, the semiconductor device 2a according to this embodiment can reduce the capacitance value of the gate capacitor 31 as the detection temperature detected by the temperature detection element 23 becomes higher.

[0112] Furthermore, the capacitance adjustment unit 11 in this embodiment has a switch circuit 111. Therefore, the semiconductor device 2a can cut off the connection between the gate capacitor 31 and the gate G of the IGBT 21 when the temperature detected by the temperature detection element 23 becomes equal to or higher than a comparison temperature set based on the absolute maximum rated temperature of the IGBT 21.

[0113] As described above, the semiconductor devices 2a to 2f according to this embodiment include the capacitance adjustment unit 11. As a result, the semiconductor devices 2a to 2f according to this embodiment can achieve the same effects as the semiconductor devices 2a to 2f according to the first embodiment. Furthermore, the semiconductor devices 2a to 2f according to this embodiment include a variable capacitance gate capacitor 31. As a result, the semiconductor devices 2a to 2f according to this embodiment can adjust the capacitance between the IGBT 21 and the reference potential terminal 41 in accordance with the temperature detected by the temperature detection element 23. As a result, the semiconductor devices 2a to 2f according to this embodiment can suppress the loss of the IGBT 21 in accordance with the temperature of the IGBT 21 without increasing the radiation noise of the IGBT 21.

[0114] The present invention is not limited to the above-described embodiment, and various modifications are possible. Although the semiconductor devices 2a to 2f according to the above-mentioned embodiments include an IGBT 21 as a switching element, the present invention is not limited thereto. The switching element included in the semiconductor device may be any of an IGBT, a bipolar transistor, and a MOS transistor. The switching element may also be a wide band gap semiconductor element including SiC, GaN, diamond, a gallium nitride-based material, a gallium oxide-based material, AlN, AlGaN, or ZnO.

[0115] In the above embodiment, the MOS transistor 111a and the MOS transistor 111b have a complementary configuration connected in series between the gate G of the IGBT 21 and the reference potential terminal 41, but the present invention is not limited to this. The switches provided in the capacitance adjustment units 11, 11-1, 11-2, and 11-3 do not need to have a complementary configuration as long as they operate in the same manner as a complementary switch circuit. For example, a plurality of (e.g., two) switches (e.g., MOS transistors) provided in the capacitance adjustment units 11, 11-1, 11-2, and 11-3 may be configured to be individually controlled by different signals.

[0116] The scope of the present invention is not limited to the exemplary embodiments shown and described, but includes all embodiments that achieve the same effect as the object of the present invention. Furthermore, the scope of the present invention is not limited to the combination of the features of the invention defined by the claims, but may be defined by any desired combination of specific features among all the respective features disclosed. [Explanation of symbols]

[0117] 1 Power conversion device 2. Inverter circuit 2a,2b,2c,2d,2e,2f Semiconductor device 2U U-phase output arm 2V V-phase output arm 2W W-phase output arm 3 Three-phase AC power supply 4 Rectifier circuit 5 Smoothing capacitor 6. Control device 7 Motor 10 Gate drive circuit 11, 11-1, 11-2, 11-3 Capacitance adjustment section 12 Gate signal generation circuit 13 Current detection circuit 14 Protection circuit 15 Temperature detection circuit 16 Constant current circuit 20 Semiconductor elements 21 IGBT 22 Freewheeling diode 23 Temperature detection element 30, 30-1, 30-2, 30-3, 31 Gate capacitor 41 Reference potential terminal 111 Switch Circuit 111a, 111b MOS transistor 112 Comparator 113 Voltage Generation Unit 114 Non-inverting amplifier circuit 114a Amplifier 114b, 114c Resistance element ALM Alarm signal C Collector E emitter G Gate Ln Negative line Lp Positive electrode line S Current detection terminal T1,T2,T3,Tc comparison temperature Ti signal input terminal To signal output terminal Tvd power terminal V1, V2, V3 comparison voltage Vcc power supply voltage Vin Input signal

Claims

1. a switching element having a control signal input terminal to which a switching control signal is input; a temperature detection element for detecting a temperature of the switching element; a capacitance adjusting section arranged between the control signal input terminal and a reference potential terminal, the capacitance adjusting section adjusting a capacitance between the gate and the emitter of the switching element in response to a temperature detected by the temperature detecting element; a capacitor disposed between the capacitance adjustment unit and the reference potential terminal; Equipped with the capacitance adjustment unit has a switch circuit between the control signal input terminal and the capacitor, the switch circuit includes a first switching element having one end connected to the control signal input terminal, and a second switching element having one end connected to the other end of the first switching element and the other end connected to the reference potential terminal; the capacitor is connected to a connection point between the first switching element and the second switching element, When the detected temperature is equal to or higher than a predetermined comparison temperature, the switch circuit turns off the first switching element and turns on the second switching element to interrupt the connection between the control signal input terminal and the capacitor, and when the detected temperature is lower than the comparison temperature, turns on the first switching element and turns off the second switching element to connect the control signal input terminal and the capacitor. Semiconductor device.

2. The switch circuit has a function of switching to a circuit configuration that discharges the charge of the capacitor when the detected temperature is equal to or higher than the comparison temperature. The semiconductor device according to claim 1 .

3. The switch circuit has a cutoff switch that is provided so as to be able to cut off the connection between the control signal input terminal and the capacitor. The semiconductor device according to claim 1 .

4. The cutoff switch cuts off a connection between the control signal input terminal and the capacitor when the detected temperature is equal to or higher than the comparison temperature, and connects the control signal input terminal and the capacitor when the detected temperature is lower than the comparison temperature. The semiconductor device according to claim 3 .

5. The switch circuit has a connection switch that is provided so as to be able to discharge the charge of the capacitor. The semiconductor device according to claim 3 .

6. The connection switch connects the reference potential terminal and the capacitor when the detected temperature is equal to or higher than the comparison temperature, and disconnects the reference potential terminal and the capacitor when the detected temperature is lower than the comparison temperature. The semiconductor device according to claim 5 .

7. The cutoff switch and the connect switch have a complementary configuration in which they are connected in series between the control signal input terminal and the reference potential terminal. The semiconductor device according to claim 5 .

8. the capacitance adjustment unit has a comparison unit that compares a detection voltage that is input from the temperature detection element and corresponds to the detection temperature with a comparison voltage that corresponds to the comparison temperature; when the comparator outputs a signal indicating that the detection voltage is equal to or lower than the comparison voltage, the cutoff switch cuts off the connection between the capacitor and the control signal input terminal, and the connection switch connects the capacitor to the reference potential terminal; When the comparator outputs a signal indicating that the detection voltage is higher than the comparison voltage, the cutoff switch does not cut off the connection between the capacitor and the control signal input terminal, and The connection switch disconnects the capacitor from the reference potential terminal. The semiconductor device according to claim 5 .

9. A plurality of the capacitance adjustment units; a plurality of the capacitors each corresponding to one of the plurality of capacitance adjustment units, the plurality of capacitors being respectively associated with different capacitance adjustment units; Equipped with The capacitance adjustment units control the switch circuit by comparing the comparison temperature and the detected temperature, which are different from each other. The semiconductor device according to claim 1 .

10. The capacitor is a variable capacitance capacitor. The semiconductor device according to claim 1 .

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