Semiconductor devices

Abstract

The present invention relates to a semiconductor device. A detection circuit (110) has a current source (120) and a resistor (121) connected in series via a first node (N1) between a positive electrode and a negative electrode of a switch element (10a) turned on and off by a drive circuit (150). A voltage comparator (130) outputs a detection signal (Sab) indicating a comparison result between an input DC voltage (Vt) and a voltage at the first node (N1). The DC voltage (Vt) and a resistance value (R1) of the resistor (121) are set so that when the inter-electrode voltage between the positive electrode and the negative electrode is higher than a predetermined judgment voltage, the voltage at the first node is higher than the DC voltage (Vt). The detection circuit (110) and the voltage comparator (130) are mounted on the same integrated circuit constituting the semiconductor device (100A).

Description

Technical Field

[0001] The present invention relates to semiconductor devices. Background Art

[0002] In the case of an inverter, etc., a so-called bridge arm structure is used in which two semiconductor switching elements (hereinafter referred to as "switching elements") are connected between a high potential node and a low potential node via an intermediate potential node. Hereinafter, in the bridge arm structure, the switching element connected to the high potential side is also referred to as a switching element on the high potential side, and the switching element connected to the low potential side is also referred to as a switching element on the low potential side.

[0003] The following semiconductor device is described in Japanese Patent Publication No. 2019-4535, that is, in the above-mentioned bridge arm structure, there is a detection circuit for state information of the switching element on the high potential side. In Japanese Patent Publication No. 2019-4535, the detection circuit and the signal transmission circuit for monitoring the state information of the switching element on the high potential side are configured as circuit elements provided outside a semiconductor chip (IC: Integrated Circuit), and the semiconductor chip is equipped with an IGBT (Insulated Gate Bipolar Transistor), that is, a driving circuit for the switching elements on the high potential side and the low potential side.

[0004] In Japanese Patent Publication No. 2019-4535, the detection circuit outputs a voltage corresponding to the state information of the switch element on the high potential side. In addition, the signal transmission circuit includes a signal switch element and a diode, the signal switch element is turned on and off according to the output of the detection circuit, and is mounted on a semiconductor chip, and the diode is connected in series with respect to the signal switch element outside the semiconductor chip. Thus, the insulation sought between the low potential side and the high potential side can be ensured by the diode, and the output of the detection circuit can be monitored.

[0005] However, in the structure of Japanese Patent Publication No. 2019-4535, the insulation between the high potential side and the low potential side is ensured by a diode connected outside the IC, so the state information of the switching element is monitored by the element mounted on the IC and the element outside the IC. As a result, there is a concern about an increase in the number of components and an increase in the circuit scale.

[0006] On the other hand, it is known that, for a switching element, if an overcurrent occurs, an unsaturated state occurs, and a voltage abnormality occurs in which the voltage between the positive electrode and the negative electrode rises even though the switching element is in the on state. Therefore, in order to avoid a continuous overcurrent state of the switching element, the above-mentioned voltage abnormality detection is effective, but at this time, it is desired to avoid the complication of the circuit structure such as that of Japanese Patent Publication No. 2019-4535 and realize the abnormality detection function by a simple circuit structure. Summary of the invention

[0007] The present invention is proposed to solve such a problem, and an object of the present invention is to provide a semiconductor device with a simple structure capable of detecting voltage abnormality between a positive electrode and a negative electrode when a switching element is turned on while ensuring insulation.

[0008] In a certain embodiment of the present invention, a semiconductor device has a detection circuit and a voltage comparator, and the detection circuit is connected between a positive electrode and a negative electrode of a semiconductor switch element. The detection circuit includes a current source and a first resistor element having a first resistance value. The current source and the first resistor element are connected in series between the positive electrode and the negative electrode via a first node. The voltage comparator outputs a comparison result between a DC voltage input to a second node and a voltage at a first node. The DC voltage and the first resistance value are set so that when the inter-electrode voltage between the positive electrode and the negative electrode is higher than a predetermined judgment voltage, the voltage at the first node is higher than the DC voltage. The detection circuit and the voltage comparator are mounted on the same integrated circuit.

[0009] The above and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a first circuit diagram for explaining the structure of the semiconductor device according to the first embodiment.

[0011] Figure 2 This is a second circuit diagram for explaining the structure of the semiconductor device according to the first embodiment.

[0012] Figure 3 Yes means Figure 1 Conceptual diagram of the voltage-current characteristics of the detection circuit shown.

[0013] Figure 4 This is a first waveform diagram for explaining an operation example of the semiconductor device according to the first embodiment.

[0014] Figure 5 This is a second waveform diagram for explaining an operation example of the semiconductor device according to the first embodiment.

[0015] Figure 6 This is a first circuit diagram for explaining the structure of a semiconductor device according to the second embodiment.

[0016] Figure 7 This is a second circuit diagram for explaining the structure of the semiconductor device according to the second embodiment.

[0017] Figure 8 This is a circuit diagram for explaining the structure of a semiconductor device according to the third embodiment.

[0018] Fig. 9 Yes Figure 8 A circuit diagram for explaining a configuration example of a current mirror circuit shown in FIG.

[0019] Fig.10 This is a circuit diagram for explaining a configuration example of a protection circuit included in a semiconductor device according to a fourth embodiment.

[0020] Fig.11 This is a first waveform diagram for explaining an operation example of the semiconductor device according to the fourth embodiment.

[0021] Fig.12 This is a second waveform diagram for explaining an operation example of the semiconductor device according to the fourth embodiment. DETAILED DESCRIPTION

[0022] Hereinafter, the embodiment of the present invention will be described in detail with reference to the accompanying drawings. In addition, in the following, the same reference numerals are attached to the same or corresponding parts in the drawings, and the description thereof will not be repeated in principle.

[0023] Implementation method 1.

[0024] Figure 1 as well as Figure 2 This is a circuit diagram for explaining the structure of the semiconductor device according to the first embodiment.

[0025] Reference Figure 1 The semiconductor device 100A has the function of a driver IC of the switch element 10a. The switch element 10a turned on and off by the semiconductor device 100A is typically composed of an IGBT, and is connected between the intermediate potential node 23 and the low potential node 22 to which the low potential GND is supplied. That is, the switch element 10a is equivalent to a switch element on the low potential side.

[0026] Reference Figure 2 The semiconductor device 100A has the function of a driver IC of the switch element 10b. The switch element 10b that is turned on and off by the semiconductor device 100A is typically composed of an IGBT, and is connected to a high potential node 21 to which a high potential Vcc is supplied and Figure 1 between the common intermediate potential node 23. That is, the switching element 10b corresponds to a switching element on the high potential side.

[0027] according to Figure 1 as well as Figure 2 It can be seen that the semiconductor device 100A ( Figure 1) and a semiconductor device 100A ( Figure 2 ) are the same, and therefore, first, the structure of the semiconductor device 100A on the low potential side will be described in detail.

[0028] Refer again Figure 1 The semiconductor device 100A includes a driving circuit 150 for the switching element 10a, a detection circuit 110 for the collector-emitter voltage (Vce) of the switching element 10a, and a voltage comparator 130. Vce corresponds to the voltage between the positive electrode and the negative electrode of the switching element.

[0029] The drive circuit 150 receives the control signal SIN of the switch element 10a and outputs the gate signal SOUT to the gate (control electrode) of the switch element 10a. For example, during the high level (hereinafter referred to as "H level") of the binary signal, the control signal SIN, the gate signal SOUT is set to the H level, so that the switch element 10a is turned on. The H level voltage of the gate signal SOUT is set to be higher than the threshold voltage of the IGBT constituting the switch element 10a with respect to the negative electrode (emitter) of the switch element 10a.

[0030] On the other hand, during the low level (hereinafter referred to as "L level") of the control signal SIN, the switching element 10a is turned off by setting the gate signal SOUT to the L level. For example, the L level voltage of the gate signal SOUT is set to be equal to the negative electrode (emitter) of the switching element 10a, that is, the low potential GND.

[0031] The detection circuit 110 includes a current source 120 and a resistor 121 connected in series. The resistor 121 is preferably formed of a variable resistor. For example, the resistor 121 can be formed so that the resistance value R1 can be adjusted by digital trimming.

[0032] The current source 120 and the resistor 121 are connected in series via the node N1 between the intermediate potential node 23 and the low potential node 22 , that is, between the positive electrode (collector) and the negative electrode (emitter) of the switch element 10 a .

[0033] The voltage comparator 130 outputs a detection signal Sab based on a comparison result between a voltage V+ at a +-side input terminal and a voltage V- at a -side input terminal. The detection signal Sab is set to an H level when V+>V-, and is set to an L level when V+≤V-.

[0034] The input terminal on the + side of the voltage comparator 130 is connected to the node N1 of the detection circuit 110. That is, the voltage V+ is equivalent to the voltage of the node N1. On the other hand, between the input terminal on the - side of the voltage comparator 130 and the low potential node 22 (the emitter of the switching element 10a), a voltage source 135 that outputs a DC voltage Vt is electrically connected. Preferably, the voltage source 135 is configured in a manner that can variably adjust the DC voltage Vt. The node N1 corresponds to an embodiment of the "first node", and the output terminal on the - side of the voltage comparator 130 corresponds to an embodiment of the "second node". In addition, the Vce of the switching element corresponds to an embodiment of the "inter-electrode voltage", and the resistor element 121 of the detection circuit 110 corresponds to an embodiment of the "first resistor element".

[0035] The current source 120 can be formed by, for example, diode-connecting a transistor having a high withstand voltage formed on an IC constituting the semiconductor device 100A. Figure 1 In the configuration example, the current source 120 is connected between the intermediate potential node 23 (the collector of the switch element 10a) and the node N1. The resistor 121 is connected between the node N1 and the low potential node (the emitter of the switch element 10a). The resistor 121 is also formed on the IC constituting the semiconductor device 100A.

[0036] Any circuit configuration can be applied to the voltage comparator 130 . For example, the voltage comparator 130 is configured using transistors and resistors formed on an IC constituting the semiconductor device 100A. Thus, the voltage comparator 130 is mounted on the IC constituting the semiconductor device 100A, similarly to the detection circuit 110 .

[0037] On the other hand, the voltage source 135 may be arranged outside the semiconductor device 100A (IC). In this case, a DC voltage Vt is supplied from outside the semiconductor device 100A to a terminal (not shown) electrically connected to the input terminal on the negative side of the voltage comparator 130. Alternatively, as the voltage source 135, a circuit that generates a constant voltage by stepping down the high potential Vcc may be formed using transistors or the like on the semiconductor device 100A.

[0038] As described above, it can be seen that if the switching element (IGBT) in the on state falls into an overcurrent state, even if it is in the on state, it becomes an unsaturated state in which Vce has not dropped sufficiently. As for the semiconductor device involved in this embodiment, the detection circuit 110 and the voltage comparator 130 are configured in a manner to detect the unsaturated state of the switching element 10a (IGBT). Specifically, during the H level of the control signal SIN, when Vce is higher than the judgment voltage Vth, the voltage comparator 130 sets the detection signal Sab to the H level, thereby enabling the detection of the unsaturated state. According to the characteristics of the switching element 10a, the judgment voltage Vth is set to a voltage that is lower than the Vce when the unsaturated state occurs by a margin. Usually, the judgment voltage Vth is a level less than 10 (V).

[0039] exist Figure 3 . The voltage-current characteristics of the detection circuit 110 are shown in FIG.

[0040] Reference Figure 3 , the output current Ia of the current source 120 is Ia=0 in the region where the Vce of the switch element 10a is low, and on the other hand, it shows a saturated constant value (Ia=I1) in the region where the Vce is high. In the Vce region including the above-mentioned determination voltage Vth, the output current Ia changes in proportion to Vce at a slope corresponding to the inverse of the resistance value R1 (resistance element 121).

[0041] Here, if the voltage and current of the current source 120 when Vce=Vth are represented by Va1 and Ia1, the relationship represented by the following equation (1) holds between the determination voltage Vth and the voltage Va1 and the current Ia1.

[0042] Vth=Va1+R1×Ia1…(1)

[0043] Furthermore, if the DC voltage Vt is adjusted using the current Ia1 in the equation (1) so that the following equation (2) holds, the output (detection signal Sab) of the voltage comparator 130 can be set to the H level when Vce>Vth.

[0044] Vt=R1×Ia1…(2)

[0045] According to equations (1) and (2), the following equation (3) holds true for the determination voltage Vth.

[0046] Vth=Va1+Vt…(3)

[0047] According to equation (3), the determination voltage Vth can be adjusted by the resistance value R1 of the resistor 121 and the DC voltage Vt from the voltage source 135. That is, the determination voltage Vth can be adjusted in accordance with the characteristics of the switching element 10a to be monitored for voltage anomaly.

[0048] exist Figure 4 as well as Figure 5 An operation example of the semiconductor device according to Embodiment 1 is shown in FIG. Figure 4 2 shows a waveform diagram of the switching element 10a during normal operation.

[0049] Reference Figure 4 Before time t0, the control signal SIN is set to L level, so the switch element 10a on the low potential side is in the off state. At this time, usually, the switch element 10b on the high potential side is turned on, so Vce = Vcc, so Vce> Vth. In the detection circuit 110, as in Figure 3 As described in , Ia=I1. In the voltage comparator 130, V+>V- corresponds to Vce>Vth, and therefore, when the switch element 10a is turned off, the detection signal Sab is at the H level.

[0050] At time t0, when the control signal SIN changes from L level to H level, the switch element 10a is turned on. Specifically, the gate voltage of the switch element 10a rises in accordance with the change of the gate signal SOUT output by the drive circuit 150 to H level. As a result, Vce decreases in the switch element 10a, and the collector-emitter current starts to flow.

[0051] In the normal on state of the switching element 10a, an unsaturated state does not occur, Vce drops to a voltage close to zero, and a normal collector-emitter current is generated. That is, Vce drops below the determination voltage Vth.

[0052] In response to such a drop in Vce, in the detection circuit 110, the output current Ia of the current source 120 becomes 0, and V+<V- in the voltage comparator 130. As a result, the detection signal Sab changes to the L level.

[0053] At time t1, if the control signal SIN changes from the H level to the L level, the switch element 10a is turned off. As a result, Vce, Ia, V+ and the detection signal Sab return to the state before time t0. In this way, in the normal on state of the switch element 10a, if the control signal SIN changes to the H level, the detection signal Sab becomes the L level.

[0054] On the other hand, Figure 5FIG. 2 shows an operation example when the switching element 10a is in an unsaturated state. Figure 5 ,and Figure 4 Similarly, at time t0 , the control signal SIN changes from the L level to the H level, whereby the switching element 10 a turns on.

[0055] However, in Figure 5 In the present invention, the switch element 10a generates an unsaturated state caused by excessive collector-emitter current (overcurrent state), so that Vce is not as high as Figure 4 Because of this voltage abnormality, Vce>Vth, so according to Figure 3 The output current Ia corresponding to the characteristic maintains V+>V-. As a result, Figure 4 On the contrary, even if the control signal SIN changes to the H level, the detection signal Sab is maintained at the H level.

[0056] Therefore, the semiconductor device 100A according to the first embodiment can detect the occurrence of the unsaturated state during the on-period of the switching element 10 a based on the detection signal Sab generated by the detection circuit 110 and the voltage comparator 130 .

[0057] In addition, the detection circuit 110 can ensure insulation between the intermediate potential node 23 and the low potential node 22 in a state where the high potential Vcc is transmitted by the current source 120 (for example, a high-voltage field effect transistor connected by a diode) when the switch element 10a is turned off. That is, the insulation of the detection circuit 110 can be ensured by using an element (for example, the above-mentioned high-voltage field effect transistor) formed on the IC constituting the semiconductor device 100A including the drive circuit 150, without using an external element of the IC as in Japanese Patent Application Laid-Open No. 2019-4535.

[0058] Refer again Figure 2 , the semiconductor device 100A can be Figure 1 The same circuit structure is applied to the switch element 10b on the high potential side. Figure 2 The circuit structure is equivalent to Figure 1 The intermediate potential node 23 in the example is set as the high potential node 21 , and the low potential node 22 is set as the intermediate potential node 23 .

[0059] exist Figure 2 In the embodiment, the detection circuit 110 is connected between the high potential node 21 and the intermediate potential node 23, that is, between the collector and the emitter of the switch element 10b, so that the Vce of the switch element 10b on the high potential side can be detected. That is, the output current Ia of the current source 120 has the same value as the Vce of the switch element 10b. Figure 3 Same characteristics.

[0060] In the voltage comparator 130, the + side input terminal is connected to Figure 1 Similarly, it is connected to the node N1 of the detection circuit 110. On the other hand, the voltage source 135 is electrically connected between the intermediate potential node 23 and the negative input terminal of the voltage comparator 130. As described above, the voltage source 135 can also input a DC voltage Vt from outside the semiconductor device 100A.

[0061] about Figure 2 The semiconductor device 100A shown in FIG. 1 also changes with respect to the change of the control signal SIN used for on-off control of the switching element 10b, as in FIG. Figure 4 as well as Figure 5 That is, the semiconductor device 100A can be applied to both the switching element 10a on the low potential side and the switching element 10b on the high potential side with the same circuit configuration.

[0062] Implementation method 2.

[0063] In the second embodiment, a circuit configuration for easily adjusting a determination voltage for detecting an unsaturated state will be described.

[0064] Figure 6 This is a first circuit diagram for explaining the structure of a semiconductor device according to the second embodiment.

[0065] Reference Figure 6 The semiconductor device 100B according to the second embodiment is different from the semiconductor device 100A according to the first embodiment in that the structure of the detection circuit 110 is different. Specifically, in the second embodiment, Figure 1 Compared with the structure of the semiconductor device 100B, the detection circuit 110 further includes a resistor element 122 connected in series with the current source 120 between the intermediate potential node 23 and the node N1. It is also preferable that the resistor element 122 can be variably adjusted in resistance value R2 by trimming or the like. The structure of the other parts of the semiconductor device 100B is the same as that of the semiconductor device 100A. The resistor element 122 corresponds to an embodiment of the "second resistor element".

[0066] In the detection circuit 110 of the second embodiment, due to the addition of the resistance element 122 (resistance value R2), the above-mentioned equation (1) is transformed into the following equation (4).

[0067] Vth=Va1+(R1+R2)×Ia1…(4)

[0068] In the second embodiment, similarly, when Vt=R1×Ia1 is set as shown in equation (2) using the current Ia1 of the current source 120 when Vce=Vth, the following equation (5) holds true for the determination voltage Vth.

[0069] Vth=Va1+Vt·(R1+R2) / R1…(5)

[0070] In the second embodiment, for the determination voltage Vth shown in the formula (5), when Vce>Vth, Sab=H level, and on the other hand, when Vce≤Vth, Sab=L level. According to the formula (5), in the second embodiment, the determination voltage Vth can be adjusted by the DC voltage Vt of the voltage source 135 and the resistance values ​​R1 and R2 of the resistance elements 121 and 122.

[0071] The operation of the semiconductor device 100B according to the second embodiment is the same as that of the semiconductor device 100A except for the setting of the determination voltage Vth. Therefore, in addition to the effects of the semiconductor device 100A according to the first embodiment, the semiconductor device 100B according to the second embodiment can easily adjust the determination voltage Vth.

[0072] exist Figure 7 2 shows a circuit configuration in which the semiconductor device 100B according to the second embodiment is applied to the switching element 10 b on the high potential side.

[0073] Reference Figure 7 Regarding the semiconductor device 100B according to the second embodiment, it is also possible to Figure 6 The same circuit structure is applied to the switching element 10b on the high potential side. Figure 7 The circuit structure is equivalent to Figure 6 The intermediate potential node 23 in the example is set as the high potential node 21 , and the low potential node 22 is set as the intermediate potential node 23 .

[0074] exist Figure 7 In the embodiment, the unsaturated state of the switching element 10b can be detected by comparing the Vce of the switching element 10b on the high potential side with the determination voltage Vth. Figure 6 Similarly, adjustment is performed by the DC voltage Vt of the voltage source 135 and the resistance values ​​R1 and R2 of the resistor elements 121 and 122 .

[0075] That is, in the semiconductor device 100B, similarly, the same circuit configuration can be used for both the low potential side switch element 10a and the high potential side switch element 10b. Figure 6 as well as Figure 7In the embodiment, the connection order of the current source 120 and the resistance element 122 connected in series can also be exchanged.

[0076] Implementation method 3.

[0077] In the third embodiment, a preferred configuration example of the current source 120 of the detection circuit 110 will be described.

[0078] Figure 8 This is a circuit diagram for explaining the structure of a semiconductor device according to the third embodiment.

[0079] Reference Figure 8 The semiconductor device 100C according to the third embodiment shows a configuration example of the current source 120 included in the detection circuit 110 of the semiconductor device 100B according to the second embodiment.

[0080] Specifically, in the third embodiment, the current source 120 of the detection circuit 110 includes current mirror circuits 125 and 126 . Figure 8 Other structures and implementation modes 2 ( Figure 6 That is, the detection signal Sab of the semiconductor device 100C is generated in the same manner as the semiconductor device 100B according to the second embodiment, and thus, the occurrence of Vce>Vth, that is, the occurrence of the unsaturated state of the switching element 10a, can be detected in the same manner as in the second embodiment.

[0081] Furthermore, according to Embodiment 3, the current source 120 is configured using a current mirror circuit, so that the output current Ia is stabilized, thereby improving the detection accuracy of Vce>Vth. In addition, the structural elements (transistors and resistors) of the current mirror circuits 125 and 126 described below are also formed on the IC constituting the semiconductor device 100C, similarly to the voltage comparator 130 and the drive circuit 150.

[0082] exist Fig. 9 Shown in Figure 8 A preferred structural example of the current mirror circuits 125 and 126 is shown.

[0083] Reference Fig. 9 The current source 120 includes transistors T1 to T3 that constitute a current mirror circuit 125 , transistors T4 to T6 that constitute a current mirror circuit 126 , and a resistor 123 .

[0084] In the current mirror circuit 125, the transistor T1 is connected between the intermediate potential node 23 (the collector of the switch element 10a) and the node N2, and the transistor T2 is connected between the intermediate potential node 23 and the node N3. The transistor T3 is connected between the node N2 and the resistor 121. The gates of the transistors T1 and T2 are connected to the node N2, and the gate of the transistor T3 is connected to the node N3.

[0085] In the current mirror circuit 126, the transistor T4 is connected between the node N3 and the node N4, and the transistor T5 is connected between the node N4 and the low potential node 22. The transistor T5 is connected between the node N5 and the low potential node 22 (the emitter of the switch element 10a). The gates of the transistors T5 and T6 are connected to the node N4. The gate of the transistor T4 is connected to the node N5 connected to the high potential node 21 via the resistor element 123 (resistance value R3).

[0086] exist Fig. 9 In the configuration example, the current mirror circuits 125 and 126 are composed of Wilson-type current mirror circuits, thereby improving the accuracy of the output current Ia of the current source 120. As a result, the setting accuracy of the determination voltage Vth is improved, thereby improving the detection accuracy of Vce>Vth, that is, the unsaturated state of the switching element.

[0087] exist Fig. 9 In the configuration example, the transistors T3 and T4 are formed of high withstand voltage transistors, thereby ensuring the insulation of the detection circuit 110.

[0088] In addition, Figure 7 As for the semiconductor device 100B shown in FIG. Figure 8 as well as Fig. 9 That is, the semiconductor device 100C according to the third embodiment can be applied with the same circuit configuration to both the low potential side switch element 10a and the high potential side switch element 10b.

[0089] In addition, the semiconductor device according to the third embodiment can also be implemented by Figure 1 as well as Figure 2 ) is based on the semiconductor device 100A by Figure 8 as well as Fig. 9 The current mirror circuit described in the above is implemented by constituting the current source 120 .

[0090] Implementation method 4.

[0091] In the fourth embodiment, application of the protection circuit corresponding to the detection of the unsaturated state of the switching element described in the first to third embodiments will be described.

[0092] Fig.10 1 is a circuit diagram for explaining a configuration example of a protection circuit 180 included in a semiconductor device according to Embodiment 4. The semiconductor device according to Embodiment 4 has a configuration in which a control signal SIN is input to a drive circuit 150 via the protection circuit 180 in addition to the semiconductor devices 100A to 100C according to Embodiments 1 to 3.

[0093] Reference Fig.10 , the protection circuit 180 has a delay circuit 181, a NAND gate 182 and an AND gate 183.

[0094] The delay circuit 181 outputs a delay signal S1 after the delay time Td is given to the control signal SIN. The NAND gate 182 outputs a signal S2 that corresponds to the NAND operation result between the detection signal Sab output by the voltage comparator 130 and the delay signal S1. The delay circuit 181 can be composed of a plurality of (even number of) inverters (NOT gates) connected in series, for example.

[0095] The AND gate 183 generates a control signal S3 input to the drive circuit 150 according to the result of AND operation between the control signal SIN that has not passed through the delay circuit 181 and the signal S2. The drive circuit 150 generates a gate signal SOUT according to the control signal S3.

[0096] Next, use Fig.11 as well as Fig.12 , an operation example of the semiconductor device according to the fourth embodiment is described. Fig.11 In, with Figure 4 Likewise, a waveform diagram during normal operation is shown.

[0097] Reference Fig.11 , if with Figure 4 Similarly, at time t0, the control signal SIN changes from L level to H level, and Figure 4 Similarly, Vce, Ia, V+ and the detection signal Sab change. As described above, in normal operation, the detection signal Sab changes from the H level to the L level in response to the drop in Vce.

[0098] The delay signal S1 changes from L level to H level at time tx after a delay time Td given by the delay circuit 181 from time t0. The delay time Td is preset to be longer than the circuit operation time required from the start of conduction (time t0) to the change of the detection signal Sab to L level in normal operation.

[0099] During the period from time t0 to tx, the delay signal S1 remains at the L level, and the signal S2 outputted by the NAND gate 182 is maintained at the H level. Furthermore, during the period from time tx to t1, the detection signal Sab is set at the L level, and thus the signal S2 is maintained at the H level.

[0100] Therefore, during normal operation, the signal S2 input to the AND gate 183 is always maintained at the H level. Therefore, the control signal S3 input to the drive circuit 150 has the same waveform as the control signal SIN. As a result, the switch elements 10a and 10b are turned on and off according to the control signal SIN by the gate signal SOUT from the drive circuit 150 of the semiconductor device according to the fourth embodiment.

[0101] On the other hand, Fig.12 In, with Figure 5 Similarly, an operation example when the switching element 10 a is in an unsaturated state is shown.

[0102] Reference Fig.12 ,and Figure 5 as well as Fig.11 Similarly, at time t0, the control signal SIN changes from L level to H level. Fig.11 Therefore, the signal S2 is maintained at the L level until the time tx when the delay signal S1 changes to the H level.

[0103] Therefore, at least during the period until time tx, the control signal S3 input to the driving circuit 150 is the same as the control signal SIN, and thus Fig.11 Likewise, the switching elements 10a and 10b are turned on.

[0104] The behavior of Vce, Ia, V+ and the detection signal Sab when the switching elements 10a and 10b are in an unsaturated state is similar to Figure 5 That is, the detection signal Sab is maintained at the H level during the H level period of the control signal SIN.

[0105] As a result, at time tx and thereafter, the signal S2 output from the NAND gate 182 changes to an L level. Accordingly, by setting the control signal S3 output from the AND gate 183 to an L level, the switch elements 10a and 10b are forcibly cut off (disconnected) due to the detection of the unsaturated state. Thus, the switch elements 10a and 10b can be protected from damage by overcurrent.

[0106] As described above, according to the semiconductor device according to the fourth embodiment, in addition to the effects of the semiconductor devices according to the first to third embodiments, a protection function of automatically shutting off the switching element in response to the detection of an unsaturated state can be realized.

[0107] In addition, the protection circuit 180 can be formed by a logic circuit using transistors formed on the IC constituting the semiconductor devices 100A to 100C, for example, a CMOS (Complementary Metal Oxide Semiconductor) logic circuit. Thus, the protection circuit 180 can be mounted on the same integrated circuit as the detection circuit 110, the voltage comparator 130, and the drive circuit 150. Alternatively, a function equivalent to the protection circuit 180 can be provided outside the semiconductor device (IC), and a signal equivalent to the control signal S3 can be input to the drive circuit 150 from outside the semiconductor device.

[0108] In this embodiment, IGBTs are exemplified as the switching elements 10a and 10b. However, for switching elements other than IGBTs used on the high potential side and the low potential side of the bridge arm structure, the semiconductor devices involved in embodiments 1 to 4 can also be applied, thereby ensuring insulation and detecting abnormalities such as voltage generated between the positive electrode and the negative electrode when the device is turned on.

[0109] Although the embodiments of the present invention have been described, it should be understood that the embodiments disclosed this time are illustrative in all aspects and are not restrictive. The scope of the present invention is indicated by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims.

Claims

1. A semiconductor device comprising: A detection circuit is connected between the positive electrode and the negative electrode of the semiconductor switch element. The detection circuit includes a current source and a first resistor element having a first resistance value, which are connected in series between the positive electrode and the negative electrode via a first node. The current source operates in such a manner that the output current increases toward a saturated constant value as the voltage of the positive electrode becomes higher than that of the negative electrode. The semiconductor device further comprises: a voltage comparator, the output of which is a comparison result between the DC voltage input to the second node and the voltage of the first node, The DC voltage and the first resistance value are set so that when the inter-electrode voltage between the positive electrode and the negative electrode is higher than a predetermined determination voltage, the voltage at the first node is higher than the DC voltage. The detection circuit and the voltage comparator are mounted on the same integrated circuit.

2. The semiconductor device according to claim 1, wherein The detection circuit further comprises: a second resistor element connected in series with the current source between the positive electrode and the first node, The second resistor element has a second resistance value. The first and second resistance values ​​and the DC voltage are set so that, when the inter-electrode voltage is higher than the determination voltage, the voltage at the first node is higher than the DC voltage.

3. The semiconductor device according to claim 1, wherein The current source includes a diode-connected field effect transistor.

4. The semiconductor device according to claim 2, wherein: The current source includes a diode-connected field effect transistor.

5. The semiconductor device according to claim 1, wherein The current source has a plurality of field effect transistors forming a current mirror circuit.

6. The semiconductor device according to claim 2, wherein: The current source has a plurality of field effect transistors forming a current mirror circuit.

7. The semiconductor device according to any one of claims 1 to 6, wherein: It also has a drive circuit for driving the control electrode of the semiconductor switch element, The driving circuit is mounted on the same integrated circuit as the detection circuit and the voltage comparator.

8. The semiconductor device according to claim 7, wherein: The device further comprises a protection circuit which receives a first control signal for controlling the on and off of the semiconductor switch element and an output signal of the voltage comparator and outputs a second control signal to the drive circuit. The second control signal is generated in such a manner that, even if the first control signal changes from the first level indicating the disconnection of the semiconductor switch element to the second level indicating the connection, when the voltage between the electrodes is not lower than the judgment voltage, the drive circuit is instructed to disconnect the semiconductor switch element.

9. The semiconductor device according to claim 8, wherein: The protection circuit is mounted on the same integrated circuit as the drive circuit.

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