Semiconductor device

Abstract

To provide a semiconductor device capable of improving overcurrent detection accuracy of a switching element.SOLUTION: A switching element 1 comprises a main part 2 and a current sense part 3 for detecting a current value of the main part 2. A control IC 4 includes a gate drive part 5 for driving the switching element 1. A sense resistor 7 is connected between an emitter of the main part 2 and an emitter of the current sense part 3 and formed inside of the control IC 4. A comparator 8 compares a sense voltage Vs applied to the sense resistor 7 with a reference voltage Vref. When the sense voltage Vs exceeds the reference voltage Vref, a cutoff circuit 9 cuts off electrification of the switching element 1. When the electrification of the switching element 1 is cut off, the sense voltage Vs is 1 V or higher.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to semiconductor devices. [Background technology]

[0002] For miniaturization, a semiconductor device has been proposed in which an overcurrent detection circuit for a switching element is built into a control IC (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-92907 Summary of the Invention [Problem to be solved by the invention]

[0004] The overcurrent detection circuit has a sense resistor that converts the current flowing through the current sensing section of the switching element into a voltage. Large manufacturing variations in the sense resistor built into this control IC result in large variations in the overcurrent detection value. As a result, there is a problem in that the accuracy of overcurrent detection of the switching element deteriorates.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its object is to provide a semiconductor device that can improve the accuracy of detecting overcurrent in a switching element. [Means for solving the problem]

[0006] The semiconductor device according to the present disclosure comprises a switching element having a main section and a current sense section for detecting a current value of the main section, a control IC having a gate drive section for driving the switching element, a sense resistor formed inside the control IC and connected between the emitter of the main section and the emitter of the current sense section, a comparator for comparing a sense voltage applied to the sense resistor with a reference voltage, and a shut-off circuit for cutting off the flow of electricity to the switching element when the sense voltage exceeds the reference voltage, wherein the sense voltage when cutting off the flow of electricity to the switching element is 1V or more. [Effects of the Invention]

[0007] In the present disclosure, the sense voltage when the current to the switching element is cut off is 1 V or more. This makes it possible to suppress variations in the sense voltage due to manufacturing variations in the sense resistor. As a result, the accuracy of overcurrent detection of the switching element 1 can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a semiconductor device according to a first embodiment; [Figure 2] FIG. 10 is a diagram showing the relationship between the resistance value of a sense resistor and a sense voltage. [Figure 3] FIG. 10 is a diagram showing the relationship between the resistance value of a sense resistor and a sense current. [Figure 4] FIG. 10 is a top view showing a switching element according to a second embodiment. [Figure 5] FIG. 10 is a diagram illustrating a semiconductor device according to a second embodiment. [Figure 6] FIG. 10 is a diagram illustrating a semiconductor device according to a third embodiment. [Figure 7] FIG. 10 is a diagram showing a modified example of the semiconductor device according to the third embodiment. [Figure 8] FIG. 10 is a diagram showing a semiconductor device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] A semiconductor device according to an embodiment will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repeated description may be omitted.

[0010] Embodiment 1 1 is a diagram showing a semiconductor device according to a first embodiment. A switching element 1 is an IGBT, and has a main section 2 and a current sense section 3 for detecting a current value of the main section 2. The current sense section 3 is formed inside the switching element 1. A control IC 4 has a gate drive section 5 for driving the switching element 1. A free wheel diode 6 is connected in parallel to the switching element 1.

[0011] The current sense unit 3 has an effective area, which is the area of ​​the cell through which current flows, that is very small, less than 1 / 3000 of the effective area of ​​the main unit 2. Therefore, when a main current Im flows through the main unit 2, a sense current Is according to the effective area ratio also flows through the current sense unit 3.

[0012] A sense resistor 7 is connected between the emitter of the main unit 2 and the emitter of the current sense unit 3, and is formed inside the control IC 4. The sense resistor 7 converts the sense current Is flowing through the current sense unit 3 into a sense voltage Vs. A comparator 8 compares the sense voltage Vs applied to the sense resistor 7 with a predetermined reference voltage Vref. If the sense voltage Vs is equal to or greater than the reference voltage Vref, the comparator 8 outputs a cutoff signal. The cutoff circuit 9 is a MOSFET, and when it receives a cutoff signal from the comparator 8, it connects the gate of the switching element 1 to GND, forcibly cutting off the current flowing through the switching element 1.

[0013] Figure 2 shows the relationship between the resistance value of the sense resistor and the sense voltage. Figure 3 shows the relationship between the resistance value of the sense resistor and the sense current. The gate voltage was fixed at 15 V and the collector current at 450 A, and the resistance value of the sense resistor 7 was changed. Note that the collector current of 450 A is three times the rated current and corresponds to an overcurrent at which the switching element 1 should be shut off. Increasing the resistance value of the sense resistor 7 increases the sense voltage Vs, but the sense current Is flowing through the current sense unit 3 gradually decreases.

[0014] As shown in Figure 2, when the sense voltage Vs is 1 V or higher, the change in the sense voltage Vs relative to the change in the resistance value of the sense resistor 7 becomes small. This critical value of 1 V is determined by the current density (rated current value per unit area) of the current sense section 3, but does not change significantly depending on the design values ​​of the semiconductor device. For example, it is not a value that would change if the chip area were reduced by about 10%.

[0015] Here, the higher the withstand voltage of a product, the thicker the semiconductor element is, and therefore the current density is designed to be lower. The current density of the current sense unit 3 is 240 to 420 A / cm for a 600 V withstand voltage element (AC200 V system). 2 , 120 to 240 A / cm for 1200 V withstand voltage elements (AC400 V system) 2 The resistance value of the sense resistor 7 at which the sense voltage Vs during an overcurrent becomes 1 V or more is 130 Ω or more for a 600 V withstand voltage element, and 180 Ω or more for a 1200 V withstand voltage element.

[0016] When the sense resistor 7 is built into the control IC 4, manufacturing variations in the resistance value of the sense resistor 7 become large. Therefore, in this embodiment, the sense resistor 7 is set so that the sense voltage Vs when the current to the switching element 1 is cut off is 1 V or more. This makes it possible to suppress variations in the sense voltage Vs due to manufacturing variations in the sense resistor 7. Therefore, the accuracy of overcurrent detection of the switching element 1 can be improved.

[0017] Furthermore, if the current passing through the switching element 1 becomes too large, there is a risk that the switching element 1 may be destroyed. To prevent this destruction, the switching element 1 is cut off when the sense voltage Vs exceeds the reference voltage Vref. As described above, if the sense voltage Vs at the time of cut-off is 1V or higher, the change in the sense voltage Vs relative to the change in the resistance value of the sense resistor 7 becomes small, so the reference voltage Vref is set to any voltage value equal to or higher than 1V.

[0018] Furthermore, due to the presence of the sense resistor 7, the emitter voltage of the current sense unit 3 becomes higher than the emitter voltage of the main unit 2. This reduces the gate voltage of the current sense unit 3, deteriorating the current-carrying capacity of the current sense unit 3. Therefore, the gate threshold voltage of the current sense unit 3 is made smaller than the gate threshold voltage of the main unit 2. This improves the current-carrying capacity of the current sense unit 3, making it possible to compensate for the decrease in current-carrying capacity caused by the sense resistor 7.

[0019] Generally, if the gate threshold voltage of a power semiconductor device drops by 0.1 V, the device's current carrying capacity increases by about 30% of the rated current. Therefore, the gate threshold voltage of the current sense unit 3 is set to be 0.1 V or more higher than the gate threshold voltage of the main unit 2. This increases the current carrying capacity by 30%, allowing the device to operate safely.

[0020] The switching element 1 may be an RC-IGBT in which an IGBT and a free wheel diode are integrated into one chip, or may be a MOSFET, etc. The sense resistor 7 may be made of polysilicon.

[0021] Embodiment 2 4 is a top view showing a switching element according to embodiment 2. A main section 2 and a current sense section 3 are provided on a semiconductor substrate 10 of the switching element 1, and a termination region 11 is provided on the periphery thereof. A gate pad 12 is connected to the gate of the main section 2. A gate pad 13 is connected to the gate of the current sense section 3. A current sense pad 14 is connected to the emitter of the current sense section 3. The gate pad 12 of the main section 2 and the gate pad 13 of the current sense section 3 are separated from each other. This allows the gate of the main section 2 of the switching element 1 and the gate of the current sense section 3 to be driven separately.

[0022] FIG. 5 is a diagram showing a semiconductor device according to a second embodiment. The gate of the main unit 2 and the gate of the current sense unit 3 are separated, with a first gate driver 5a driving the main unit 2 and a second gate driver 5b driving the current sense unit 3. This allows separate gate voltages to be applied to the main unit 2 and the current sense unit 3. Therefore, the first gate driver 5a and the second gate driver 5b are controlled at the same timing, and the output voltage of the second gate driver 5b is set to be greater than the output voltage of the first gate driver 5a. This improves the current-carrying capacity of the current sense unit 3, thereby compensating for the decrease in current-carrying capacity due to the sense resistor 7. The other configurations and effects are the same as those of the first embodiment.

[0023] Embodiment 3 FIG. 6 is a diagram showing a semiconductor device according to a third embodiment. The switching operation of the main unit 2 causes the voltage and current to rise or fall. This switching operation of the main unit 2 generates noise in the semiconductor device. Therefore, in this embodiment, a gate resistor 15 is provided between the control IC 4 and the gate of the main unit 2. The gate resistor 15 drops the gate voltage of the main unit 2, thereby slowing down the switching speed of the main unit 2 and reducing noise in the semiconductor device.

[0024] If a gate resistor is provided at the gate of the current sense unit 3, the gate voltage of the current sense unit 3 may be reduced by the voltage drop across the gate resistor in addition to the sense voltage. Therefore, no gate resistor is provided in the current sense unit 3. This makes it possible to adjust the switching speed of the main unit 2 while maintaining the current carrying capacity of the current sense unit 3. This allows for safe protection operation. Other configurations and effects are the same as those of the first or second embodiment.

[0025] 7 is a diagram showing a modification of the semiconductor device according to the third embodiment. The gate resistor 15 is built into the switching element 1. This allows the semiconductor device to be miniaturized.

[0026] Embodiment 4 FIG. 8 is a diagram showing a semiconductor device according to a fourth embodiment. An amplifier 16, which is a bipolar transistor, is provided between the control IC 4 and the gate of the main unit 2. The amplifier 16 amplifies the gate current of the main unit 2, thereby increasing the switching speed of the main unit 2. This reduces loss in the semiconductor device. The other configurations and effects are the same as those of the first embodiment.

[0027] The switching element 1 and the freewheel diode 6 are not limited to those made of silicon, but may also be made of a wide-bandgap semiconductor with a wider bandgap than silicon. Examples of wide-bandgap semiconductors include silicon carbide, gallium nitride, and diamond. Semiconductor chips made of such wide-bandgap semiconductors have high voltage resistance and allowable current density, allowing for miniaturization. By using such miniaturized semiconductor chips, semiconductor devices incorporating these chips can also be miniaturized and highly integrated. Furthermore, the high heat resistance of the semiconductor chip allows for miniaturization of the heat sink's heat dissipation fins, enabling air-cooling instead of water-cooling, thereby further miniaturizing the semiconductor device. Furthermore, the semiconductor chip has low power loss and high efficiency, allowing for high efficiency of the semiconductor device. While it is desirable for both the switching element 1 and the freewheel diode 6 to be made of wide-bandgap semiconductors, either one may be made of a wide-bandgap semiconductor, and the effects described in this embodiment can be obtained. [Explanation of symbols]

[0028] 1 switching element, 2 main section, 3 current sense section, 4 control IC, 5 gate drive section, 5a first gate drive section, 5b second gate drive section, 7 sense resistor, 8 comparator, 9 cutoff circuit, 12 gate pad, 13 gate pad, 15 gate resistor, 16 amplifier

Claims

1. a switching element having a main section and a current sense section for detecting a current value of the main section; a control IC having a gate driver that drives the switching element; a sense resistor connected between the emitter of the main section and the emitter of the current sense section and formed inside the control IC; a comparator that compares a sense voltage applied to the sense resistor with a reference voltage; a cutoff circuit that cuts off current flow to the switching element when the sense voltage exceeds the reference voltage; The semiconductor device is characterized in that the sense voltage when the current flow to the switching element is cut off is 1 V or more.

2. The current density of the current sensing section is 120 to 420 A / cm ２ 2. The semiconductor device according to claim 1, wherein:

3. 3. The semiconductor device according to claim 1, wherein a gate threshold voltage of the current sense section is lower than a gate threshold voltage of the main section.

4. the gate driver includes a first gate driver that drives the main unit and a second gate driver that drives the current sense unit; 3. The semiconductor device according to claim 1, wherein the output voltage of the second gate driver is greater than the output voltage of the first gate driver.

5. 3. The semiconductor device according to claim 1, further comprising a gate resistor for dropping a gate voltage of the main section.

6. 6. The semiconductor device according to claim 5, wherein the gate resistor is built into the switching element.

7. 7. The semiconductor device according to claim 5, wherein the current sense section is not provided with a gate resistor.

8. 3. The semiconductor device according to claim 1, further comprising an amplifier for amplifying the gate current of the main section.

9. 9. The semiconductor device according to claim 4, wherein the gate pad of the main section and the gate pad of the current sense section are separated from each other.

10. 10. The semiconductor device according to claim 1, wherein the switching element is formed of a wide bandgap semiconductor.

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