Semiconductor devices

Abstract

This invention provides a semiconductor device that reliably maintains conduction control even when the voltage of the control signal during power semiconductor element conduction control drops sharply due to noise interference. The threshold setting unit, which sets the threshold value of the power semiconductor element, is configured to supply charge stored in the gate capacitance of the power semiconductor element to the connection between a resistor and the power supply terminal of a cut-off signal generation unit via a diode. The resistor reduces the voltage of the control signal Vin input to the input terminal to a voltage signal Vs, and the cut-off signal generation unit uses the voltage signal Vs as its operating power source. Even when the voltage of the control signal Vin drops sharply during power semiconductor element conduction control, the voltage signal Vs receives the charge stored in the gate capacitance of the power semiconductor element, thereby preventing voltage drops and preventing malfunction of the cut-off signal generation unit.

Description

Technical Field

[0001] This invention relates to semiconductor devices. Background Technology

[0002] In the ignition system of an internal combustion engine in an automobile, a semiconductor device is used as an igniter to control the energization and de-energization of the ignition coil. Such a semiconductor device is known to include a power semiconductor element capable of handling large electrical currents and an integrated circuit having a function for reliably switching the power semiconductor element on and off (see, for example, Patent Document 1). Hereinafter, a conventional semiconductor device constructed based on the semiconductor device described in Patent Document 1 will be described.

[0003] Figure 8 This is a circuit diagram illustrating an example of the configuration of an ignition system using a conventional semiconductor device. Figure 9 This is a timing diagram illustrating an example of the operation of an ignition system using a conventional semiconductor device. Figure 9 (A) represents the action example during normal operation. Figure 9 (B) represents an example of an action when noise is mixed in.

[0004] The ignition system of an internal combustion engine in a vehicle includes a semiconductor device 100, an ignition coil 110, a spark plug 120, a battery 130, and an engine control unit (ECU) 140. The semiconductor device 100 has an input terminal 101 for receiving a control signal Vin from the engine control unit 140, an output terminal 102 connected to one terminal of the primary coil 111 of the ignition coil 110, and a ground terminal 103 connected to the negative terminal of the battery 130. The other terminal of the primary coil 111 of the ignition coil 110 is connected to the positive terminal of the battery 130. One terminal of the secondary coil 112 of the ignition coil 110 is connected to one electrode of the spark plug 120, and the other electrode of the spark plug 120 is grounded. The other terminal of the secondary coil 112 of the ignition coil 110 is connected to the positive terminal of the battery 130. It should be noted that the negative terminal of the battery 130 serves as the reference potential for the ignition system.

[0005] Semiconductor device 100 includes a power semiconductor element 104, a resistor 105, a threshold setting unit 106, and a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) 107. In this example, the power semiconductor element 104 is an IGBT (Insulated Gate Bipolar Transistor). The collector terminal of the power semiconductor element 104 is connected to the output terminal 102 of the semiconductor device 100, and the emitter terminal of the power semiconductor element 104 is connected to the ground terminal 103 of the semiconductor device 100. The gate terminal of the power semiconductor element 104 is connected to one terminal of the resistor 105, and the other terminal of the resistor 105 is connected to the input terminal 101 of the semiconductor device 100.

[0006] The threshold setting unit 106 includes a resistor 106a, a capacitor 106b, and a cutoff signal generation unit 106c. One terminal of the resistor 106a is connected to the input terminal 101 of the semiconductor device 100, and the other terminal of the resistor 106a is connected to one terminal of the capacitor 106b. The other terminal of the capacitor 106b is connected to the ground terminal 103 of the semiconductor device 100. The resistor 106a and the capacitor 106b constitute a low-pass filter, and the connection terminal of the resistor 106a and the capacitor 106b is connected to the power supply terminal of the cutoff signal generation unit 106c. The output terminal of the cutoff signal generation unit 106c is connected to the gate terminal of the MOSFET 107, and the ground terminal of the cutoff signal generation unit 106c is connected to the ground terminal 103 of the semiconductor device 100. The drain terminal of the MOSFET 107 is connected to the gate terminal of the power semiconductor element 104, and the source terminal of the MOSFET 107 is connected to the ground terminal 103 of the semiconductor device 100.

[0007] Next, refer to Figure 9 The timing diagram shown in (A) illustrates the operation of the ignition system when the engine control unit 140 outputs the control signal Vin. It should be noted that... Figure 9 In (A), from top to bottom, the control signal Vin, the voltage signal Vs which is the power supply for the cut-off signal generation unit 106c, the gate voltage Vg and collector current Ic of the power semiconductor element 104, and the change in the voltage Vp of the spark plug 120 are represented in sequence.

[0008] First, when the control signal Vin outputs a reference potential turn-off signal, the gate voltage Vg applied to the gate terminal of the power semiconductor element 104 is also a turn-off signal, so the power semiconductor element 104 is in the off state. At this time, the collector current Ic of the power semiconductor element 104 is not flowing. In addition, the voltage Vp of the spark plug 120 is maintained at the voltage of the battery 130.

[0009] If a control signal Vin, representing a conduction signal, is input to the input terminal 101 of the semiconductor device 100 at time t0, this conduction signal is first input to the threshold setting unit 106 as a power supply voltage. In the threshold setting unit 106, the control signal Vin is converted into a voltage signal Vs of the cut-off signal generation unit 106c via a low-pass filter composed of a resistor 106a and a capacitor 106b. When the voltage signal Vs rises, the cut-off signal generation unit 106c outputs a cut-off signal of the conduction signal until a predetermined threshold Vthin is reached, thereby turning on the MOSFET 107 and pulling down the gate voltage Vg of the power semiconductor element 104 to a reference potential.

[0010] If the voltage signal Vs reaches a predetermined threshold Vthin at time t1, the MOSFET 107 becomes off. At this time, the gate voltage Vg of the power semiconductor element 104 becomes a voltage higher than the threshold that turns the power semiconductor element 104 on, so that the power semiconductor element 104 becomes on at the moment when the MOSFET 107 becomes off.

[0011] If the power semiconductor element 104 becomes conductive, current begins to flow in the primary coil 111 of the ignition coil 110, and therefore, the collector current Ic of the power semiconductor element 104 gradually increases. If the collector current Ic of the power semiconductor element 104 saturates at time t2, then the collector current Ic remains at a constant value.

[0012] If the control signal Vin becomes an off signal at time t3, the cut-off signal generation unit 106c of the threshold setting unit 106 determines that the control signal Vin has decreased. That is, if the voltage signal Vs drops to a predetermined threshold Vthin, the cut-off signal generation unit 106c outputs a cut-off signal of the conduction signal to turn on the MOSFET 107 and pull down the gate voltage Vg of the power semiconductor element 104 to the reference potential. As a result, the collector current Ic of the power semiconductor element 104 is cut off because it becomes off. If the current flowing through the primary coil 111 of the ignition coil 110 is cut off, the magnetic field changes, and a voltage is generated in the primary coil 111 due to self-induction, and a high voltage is generated in the secondary coil 112 due to mutual induction. This high voltage is supplied to the spark plug 120, and a discharge is generated between the spark plugs 120 through this voltage Vp to generate a spark.

[0013] In automobiles, a number of semiconductor devices 100 serving as igniters, corresponding to the number of cylinders in the internal combustion engine, are installed. These devices generate noise when they produce sparks. Furthermore, automobiles contain numerous electrical devices, which also contribute to noise generation. In particular, the semiconductor devices 100 are designed to be noise-resistant; if they malfunction due to noise, not only will proper ignition timing not be achieved, but the internal combustion engine may also be damaged.

[0014] Figure 9 Example (B) illustrates a situation where, when the power semiconductor element 104 is in the ON state, at time t2a, a large external noise (negative surge voltage) is introduced in the negative direction, causing the control signal Vin to drop sharply. In such a case, the voltage signal Vs supplied to the cut-off signal generation unit 106c also drops, sometimes falling below the threshold Vthin, causing the cut-off signal generation unit 106c to output a cut-off signal. If the cut-off signal generation unit 106c outputs a cut-off signal, the MOSFET 107 becomes ON, so the gate voltage Vg of the power semiconductor element 104 is forcibly reduced instantaneously. In particular, if the noise lasts for a long time, the gate voltage Vg may be pulled down completely to the reference potential, causing the semiconductor device 100 to erroneously turn off despite receiving the control signal Vin that turns the power semiconductor element 104 ON. Even if the gate voltage Vg does not reach the voltage required to turn off the power semiconductor element 104, the collector current Ic drops sharply due to the decrease in gate voltage Vg, resulting in a negative voltage Vp in the secondary coil 112 of the ignition coil 110. If this voltage Vp exceeds the discharge voltage, a discharge will occur at a time other than the target ignition period.

[0015] To prevent such malfunctions, the time constant of the low-pass filter in the threshold setting unit 106 can be increased. Therefore, even if the control signal Vin drops sharply due to external noise, the voltage signal Vs is suppressed by resistor 106a or capacitor 106b, thus preventing malfunctions such as accidental ignition.

[0016] Existing technical documents

[0017] Patent documents

[0018] Patent Document 1: Japanese Patent Application Publication No. 2009-284420 (paragraphs

[0002] to

[0005] ), Figure 6 ) Summary of the Invention

[0019] Technical issues

[0020] However, while increasing the time constant of the low-pass filter is necessary to improve noise tolerance, increasing the chip size is necessary to implement large-capacity capacitors in integrated circuits, which leads to increased costs.

[0021] The present invention was made in view of the above-mentioned problems, and its object is to provide a semiconductor device that improves noise immunity without increasing chip size.

[0022] Technical solution

[0023] In order to solve the above-mentioned problems, one aspect of the present invention provides a semiconductor device comprising: a power semiconductor element connected between an output terminal and a ground terminal of the semiconductor device, and controlled to be turned on or off according to a gate potential; a threshold setting unit that uses a control signal supplied to an input terminal of the semiconductor device as an operating power source, and outputs a cut-off signal when the voltage of the control signal is lower than a predetermined voltage set as a threshold of the power semiconductor element; and a cut-off circuit connected between the gate terminal and the ground terminal of the power semiconductor element, which becomes on upon receiving the cut-off signal, thereby turning off the power semiconductor element. Here, the threshold setting unit includes a power supply circuit that, when the voltage of the control signal drops sharply, supplies power to the threshold setting unit using the charge stored in the gate capacitance of the power semiconductor element as an auxiliary power source.

[0024] Technical effect

[0025] When the power semiconductor element is turned on, the voltage of the control signal drops sharply. The voltage of the operating power supply of the threshold setting unit generated according to the control signal can be replenished by the charge stored in the gate capacitance of the power semiconductor element. Therefore, the threshold setting unit will not malfunction. Attached Figure Description

[0026] Figure 1 This is a circuit diagram illustrating an example of the configuration of an ignition system using the semiconductor device of the first embodiment.

[0027] Figure 2 This is a circuit diagram illustrating an example of the configuration of the cut-off signal generation unit.

[0028] Figure 3 This is a diagram showing the input-output characteristics of the cut-off signal generation unit.

[0029] Figure 4 This is a timing diagram illustrating an example of the operation of the ignition system of the semiconductor device according to the first embodiment. Figure 4 (A) represents the action example during normal operation. Figure 4 (B) represents the action example when noise is mixed in.

[0030] Figure 5 This is a circuit diagram illustrating an example of the configuration of an ignition system using the semiconductor device of the second embodiment.

[0031] Figure 6 This is a circuit diagram illustrating an example of the configuration of an ignition system using a semiconductor device according to the third embodiment.

[0032] Figure 7 This is a circuit diagram illustrating an example of the configuration of an ignition system using the semiconductor device of the fourth embodiment.

[0033] Figure 8 This is a circuit diagram illustrating an example of the configuration of an ignition system using a conventional semiconductor device.

[0034] Figure 9 This is a timing diagram illustrating an example of the operation of an ignition system using a conventional semiconductor device. Figure 9 (A) represents the action example during normal operation. Figure 9 (B) represents the action example when noise is mixed in.

[0035] Symbol Explanation

[0036] 10, 10a, 10b, 10c Semiconductor devices

[0037] 11 Input Terminals

[0038] 12 Output Terminals

[0039] 13 Grounding terminal

[0040] 14 Power Semiconductor Components

[0041] 15. Resistor (Gate Resistor)

[0042] 16 Threshold Setting Section

[0043] 16A resistor

[0044] 16b Cut-off signal generation unit

[0045] 16C diode (power supply circuit)

[0046] 16d capacitor

[0047] 16e MOSFET (Power Supply Circuit)

[0048] 17 MOSFET (Disconnect Circuit)

[0049] 18 MOSFETs (Disconnect Circuit)

[0050] 19 Resistors

[0051] 20 Ignition Coils

[0052] 21 Primary coil

[0053] 22 secondary coils

[0054] 30 Spark plugs

[0055] 40 batteries

[0056] 50 Engine Control Unit

[0057] 61 Power Terminal

[0058] 62 Grounding terminal

[0059] 63 Output terminals

[0060] 64 and 65 resistors (voltage divider circuit)

[0061] 66 Inverter Detailed Implementation

[0062] Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail using an ignition system for an internal combustion engine in an automobile as an example. It should be noted that in the drawings, portions indicated by the same reference numerals represent the same constituent elements. Furthermore, multiple embodiments can be implemented by partially combining them without contradiction.

[0063] Figure 1 This is a circuit diagram illustrating an example of the configuration of an ignition system using the semiconductor device of the first embodiment. Figure 2 This is a circuit diagram illustrating an example of the configuration of the cut-off signal generation unit. Figure 3 This is a diagram showing the input-output characteristics of the cut-off signal generation unit. Figure 4 This is a timing diagram illustrating an example of the operation of the ignition system of the semiconductor device according to the first embodiment. Figure 4 (A) represents the action example during normal operation. Figure 4 (B) represents the action example when noise is mixed in.

[0064] Figure 1The ignition system described herein includes a semiconductor device 10, an ignition coil 20, a spark plug 30, a battery 40, and an engine control unit 50. The semiconductor device 10 has: an input terminal 11 for receiving a control signal Vin from the engine control unit 50; an output terminal 12 connected to one terminal of the primary coil 21 of the ignition coil 20; and a ground terminal 13 connected to the negative terminal of the battery 40. The other terminal of the primary coil 21 of the ignition coil 20 is connected to the positive terminal of the battery 40, and the negative terminal of the battery 40 is connected to the chassis of the vehicle, which serves as the reference potential for the ignition system. One terminal of the secondary coil 22 of the ignition coil 20 is connected to the center electrode of the spark plug 30, and the ground electrode of the spark plug 30 is connected to the negative terminal of the battery 40. The other terminal of the secondary coil 22 of the ignition coil 20 is connected to the positive terminal of the battery 40.

[0065] The semiconductor device 10 includes a power semiconductor element 14, a resistor (gate resistor) 15, a threshold setting unit 16, and a MOSFET (shutdown circuit) 17. Here, the resistor 15, the threshold setting unit 16, and the MOSFET 17 are integrated circuits.

[0066] The power semiconductor element 14 here uses an IGBT, which, for example, has a voltage withstand capability of several hundred volts (V). The power semiconductor element 14 is, for example, a vertically oriented device with a collector formed on a first side of the substrate and a gate electrode and an emitter formed on a second side opposite to the first side. It should be noted that the power semiconductor element 14 can be replaced by other voltage-controlled power semiconductor elements such as a vertically oriented power MOSFET instead of an IGBT.

[0067] The collector terminal of the power semiconductor element 14 is connected to the output terminal 12 of the semiconductor device 10, and the emitter terminal of the power semiconductor element 14 is connected to the ground terminal 13 of the semiconductor device 10. The gate terminal of the power semiconductor element 14 is connected to one terminal of the resistor 15, and the other terminal of the resistor 15 is connected to the input terminal 11 of the semiconductor device 10. The resistor 15 serves as a potential difference generating section, creating a potential difference between the gate voltage Vg and the voltage of the control signal Vin between the gate terminal of the power semiconductor element 14 and the input terminal 11 of the semiconductor device 10. The resistance value of the potential difference generating section formed by the resistor 15 is preferably about 1 to 10 kΩ.

[0068] The threshold setting unit 16 includes a resistor 16a for reducing the voltage of the control signal Vin, a cutoff signal generating unit 16b for generating a cutoff signal, and a diode 16c constituting a power supply circuit. One terminal of the resistor 16a is connected to the input terminal 11 of the semiconductor device 10, and the other terminal of the resistor 16a is connected to the power supply terminal of the cutoff signal generating unit 16b. The output terminal of the cutoff signal generating unit 16b is connected to the gate terminal of an n-channel MOSFET 17, and the ground terminal of the cutoff signal generating unit 16b is connected to the ground terminal 13 of the semiconductor device 10. The drain terminal of the MOSFET 17 is connected to the gate terminal of the power semiconductor element 14, and the source terminal of the MOSFET 17 is connected to the ground terminal 13 of the semiconductor device 10. The anode terminal of the diode 16c is connected to the gate terminal of the power semiconductor element 14, and the cathode terminal of the diode 16c is connected to the power supply terminal of the cutoff signal generating unit 16b. The diode 16c can be any diode capable of supplying power on the order of microamps (μA).

[0069] like Figure 2 As shown, the cut-off signal generation unit 16b has a power supply terminal 61, a ground terminal 62, an output terminal 63, resistors 64 and 65 forming a voltage divider circuit, and an inverter 66. The power supply terminal 61 is connected to the other terminal of resistor 16a and the cathode of diode 16c, the ground terminal 62 is connected to the ground terminal 13 of semiconductor device 10, and the output terminal 63 is connected to the gate terminal of MOSFET 17.

[0070] In the cutoff signal generation unit 16b, power supply terminal 61 is connected to one terminal of resistor 64 and the power supply terminal of inverter 66. The other terminal of resistor 64 is connected to one terminal of resistor 65 and the input terminal of inverter 66. The other terminal of resistor 65 is connected to the ground terminal 62 of the cutoff signal generation unit 16b and the ground terminal of inverter 66. The output terminal of inverter 66 is connected to the output terminal 63 of the cutoff signal generation unit 16b. Inverter 66 uses the voltage signal Vs obtained by dividing the control signal Vin using resistor 16a and the series circuit of resistors 64 and 65 as its operating power supply. It should be noted that the resistance value of resistor 16a is set such that the voltage drop (Vin-Vs) across resistor 16a, generated by the voltage division ratio between resistor 16a and the series circuit of resistors 64 and 65, is less than the forward voltage of diode 16c.

[0071] The cut-off signal generation unit 16b has Figure 3The input / output characteristics are shown. Specifically, the cut-off signal generation unit 16b uses the voltage signal Vs obtained by reducing the voltage of the control signal Vin as the operating power supply. Therefore, during the instantaneous rise of the control signal Vin, an output voltage Vout is output at approximately the same potential as the control signal Vin, until the voltage obtained by dividing the voltage signal Vs using the voltage divider circuit composed of resistors 64 and 65 reaches the threshold voltage Vthin of the inverter 66. This output voltage Vout acts as a cut-off signal. If it exceeds the threshold voltage of MOSFET 17, MOSFET 17 is turned on, and the gate voltage Vg of the power semiconductor element 14 drops to near ground potential. Thus, the power semiconductor element 14 remains off even though it is being turned on by the input control signal Vin.

[0072] If, during the rise of the control signal Vin, the voltage obtained by dividing the voltage signal Vs using resistors 64 and 65 exceeds the threshold Vthin that turns off the inverter 66, then the inverter 66 outputs a low potential, and the MOSFET 17 is in the off state. At this instant, the control signal Vin is applied to the gate terminal of the power semiconductor element 14 via resistor 15, so the power semiconductor element 14 is turned on and becomes the on state.

[0073] Next, midway through the decrease of the control signal Vin, if the input voltage of inverter 66 is lower than its threshold Vthin, inverter 66 outputs a high potential, and MOSFET 17 is in the on state. At this instant, the gate voltage Vg of power semiconductor element 14 decreases, so power semiconductor element 14 is turned off and becomes non-conducting.

[0074] Subsequently, the output voltage Vout of inverter 66 decreases in accordance with the voltage of control signal Vin. If the output voltage Vout is lower than the threshold of MOSFET 17, MOSFET 17 is turned off.

[0075] Therefore, the threshold setting unit 16 does not use the threshold value of the power semiconductor element 14 with large characteristic deviation for the time of turning the power semiconductor element 14 on and off, but instead uses the threshold value Vthin of the inverter 66 with small characteristic deviation. It should be noted that, in order to easily understand the transient changes in the control signal Vin and the output voltage Vout, Figure 3 The diagram shown is enlarged to represent the timeline.

[0076] Reference Figure 4 (A) and Figure 4 (B) will explain the operation of the ignition system using the semiconductor device 10 configured as described above. Figure 4 (A) and Figure 4In (B), the horizontal axis represents time, and the vertical axis represents voltage or current value. From top to bottom, they represent control signal Vin, voltage signal Vs, gate voltage Vg of power semiconductor element 14, collector current Ic of power semiconductor element 14, and voltage Vp of spark plug 30.

[0077] First, during normal movements, such as Figure 4 As shown in (A), at time t10, if the control signal Vin supplied from the engine control unit 50 rises from a low potential of 0V to a high potential (e.g., 5V), the voltage signal Vs of the threshold setting unit 16 also rises. If the voltage obtained by dividing the voltage signal Vs exceeds the threshold Vthin of the inverter 66, the MOSFET 17 of the cut-off circuit is turned off. As a result, the gate voltage Vg of the power semiconductor element 14 rises, the gate-emitter capacitance (gate capacitance) of the power semiconductor element 14 is charged, and the power semiconductor element 14 is turned on.

[0078] Therefore, a collector current Ic flows from the battery 40 through the primary coil 21 of the ignition coil 20 to the power semiconductor element 14. It should be noted that the time variation dI / dt of the collector current Ic depends on the inductance of the primary coil 21 and the supply voltage of the battery 40, and increases until it reaches a predetermined current value at time t11. Afterward, the collector current Ic remains constant.

[0079] At time t12, if the control signal Vin drops from a high potential to a low potential, the power semiconductor element 14 is turned off, and the collector current Ic decreases sharply. Because the collector current Ic decreases sharply, the voltage across the primary coil 21 increases sharply due to the self-induced electromotive force, generating an induced electromotive force of tens of kV across the secondary coil 22. The voltage Vp of this secondary coil 22 is supplied to the spark plug 30, generating a spark in the gap of the spark plug 30.

[0080] Therefore, if the voltage of the control signal Vin does not drop sharply during the conduction control of the power semiconductor element, the diode 16c does not function because no potential difference exceeding the forward voltage of the diode 16c is generated between the gate voltage Vg and the voltage signal Vs.

[0081] Next, as Figure 4 As shown in (B), the case in which the control signal Vin drops sharply (e.g., several μ seconds) due to the influence of a negative surge voltage at time t11a when the power semiconductor element 14 is in the on state is explained.

[0082] At time t11a, if a negative surge voltage is applied to input terminal 11, the negative surge voltage is attenuated by resistor 16a, thus becoming a voltage signal Vs, which is input to the cutoff signal generation unit 16b. At this time, even if the voltage signal Vs is attenuated in order to attenuate the negative surge voltage, if the voltage of inverter 66 input to cutoff signal generation unit 16b is lower than the threshold voltage Vthin of inverter 66, MOSFET 17 becomes turned on, so the gate voltage Vg will also drop sharply.

[0083] When the collector current Ic before the negative surge voltage is applied is Ic > 1 / 2 × gm × (Vga - Vthi), the collector current Ic decreases sharply due to the negative surge voltage. Here, Vga is the gate voltage of the power semiconductor device 14 immediately after the surge voltage is generated, Vthi is the threshold voltage of the power semiconductor device 14, and gm is the transconductance of the power semiconductor device 14.

[0084] As can be seen from the above, even if the control signal Vin meets the conduction conditions of the power semiconductor element 14, the collector current Ic of the power semiconductor element 14 may decrease sharply due to the negative surge voltage. In this case, the spark plug 30, which should not ignite until time t12, will ignite prematurely at time t11a.

[0085] However, in this semiconductor device 10, when the control signal Vin is at a high potential, even if the control signal Vin drops sharply due to a negative surge voltage, the voltage signal Vs will not fall below the threshold Vthin of the inverter 66. That is, if the control signal Vin drops sharply and the potential difference between the control signal Vin and the voltage signal Vs is greater than the forward voltage of the diode 16c, the diode 16c becomes conductive. As a result, the diode 16c supplies the charge stored in the gate capacitor of the power semiconductor element 14 to the power supply terminal 61 of the cut-off signal generation unit 16b. Thus, the charge of the gate capacitor is used as an auxiliary power supply in emergency situations when the control signal Vin drops sharply, and the diode 16c supplies power to the power supply terminal 61 of the cut-off signal generation unit 16b, thereby suppressing the drop in the voltage signal Vs. As a result, it is possible to prevent malfunction of the threshold setting unit 16 and accidental ignition of the spark plug 30 caused by a negative surge voltage.

[0086] Figure 5 This is a circuit diagram illustrating an example of the configuration of an ignition system using the semiconductor device of the second embodiment. Figure 5 In the middle, to and Figure 1 Components that are identical or equivalent are marked with the same symbol and their detailed descriptions are omitted.

[0087] In the second embodiment, the semiconductor device 10a has a capacitor 16d connected to the power supply terminal and the ground terminal of the cutoff signal generation unit 16b. Thus, the resistor 16a and the capacitor 16d form a low-pass filter, which attenuates high-frequency noise entering the cutoff signal generation unit 16b.

[0088] The capacitor 16d added to the threshold setting unit 16, being formed together with the resistor 16a, the cutoff signal generation unit 16b, and the diode 16c, has a capacitance value on the order of picofarads (pF). In contrast, the gate capacitance of the power semiconductor element 14 has a capacitance value on the order of nanofarads (nF), which is about three orders of magnitude larger than the capacitance value of the capacitor 16d. Therefore, when charge is supplied from the gate capacitance of the power semiconductor element 14 when the control signal Vin drops sharply, the charging of the capacitor 16d occurs rapidly, so the voltage signal Vs does not substantially decrease. Therefore, the semiconductor device 10a of the second embodiment performs substantially the same operation as the semiconductor device 10 of the first embodiment.

[0089] Figure 6 This is a circuit diagram illustrating an example of the configuration of an ignition system using the semiconductor device of the third embodiment. Figure 6 In the middle, to and Figure 5 Components that are identical or equivalent are marked with the same symbol and their detailed descriptions are omitted.

[0090] In the semiconductor device 10b of the third embodiment, an n-channel MOSFET 16e is used to replace the diode 16c of the first and second embodiments to form a power supply circuit that provides charge to the gate capacitor. That is, the drain terminal of the MOSFET 16e is connected to the gate terminal of the power semiconductor element 14, and the source terminal of the MOSFET 16e is connected to the power supply terminal of the cut-off signal generation unit 16b. Furthermore, the MOSFET 16e connects its gate terminal to its own drain terminal to form a diode.

[0091] In this semiconductor device 10b, when the control signal Vin drops sharply, the charge stored in the gate capacitance of the power semiconductor element 14 is supplied to the power supply terminal of the cut-off signal generation unit 16b via the MOSFET 16e that constitutes the diode. Therefore, even if the control signal Vin drops sharply, the voltage signal Vs at the power supply terminal of the cut-off signal generation unit 16b will not drop, thus preventing malfunction of the inverter 66 and consequently preventing accidental ignition of the spark plug 30.

[0092] Alternatively, the semiconductor device 10b may be configured such that, similar to the semiconductor device 10 of the first embodiment, the capacitor 16d is not connected to the power supply terminal and the ground terminal of the cutoff signal generation unit 16b.

[0093] Figure 7 This is a circuit diagram illustrating an example of the configuration of an ignition system using the semiconductor device of the fourth embodiment. Figure 7 In the middle, to and Figure 5 Components that are identical or equivalent are marked with the same symbol and their detailed descriptions are omitted.

[0094] In the semiconductor device 10c of the fourth embodiment, a p-channel MOSFET 18 is connected between the gate terminal of the power semiconductor element 14 and the input terminal 11 of the semiconductor device 10c as a circuit for cutting off the power semiconductor element 14. Specifically, the drain terminal of the MOSFET 18 is connected to the gate terminal of the power semiconductor element 14, the source terminal of the MOSFET 18 is connected to the input terminal 11 of the semiconductor device 10c, and the gate terminal of the MOSFET 18 is connected to the output terminal of the cutoff signal generation unit 16b. Thus, the MOSFET 18 becomes a potential difference generation unit that generates a potential difference between the gate voltage Vg and the voltage of the control signal Vin when a control signal Vin that turns on the power semiconductor element 14 is input. Therefore, the on-resistance value of the MOSFET 18 when it is turned on is set to approximately 1 to 10 kΩ. The MOSFET 18 also receives a cutoff signal from the cutoff signal generation unit 16b to perform a turn-off operation and turns off the power semiconductor element 14. Therefore, the MOSFET 18 replaces the MOSFET 17, which functions as a cutoff circuit in the first to third embodiments.

[0095] In the semiconductor device 10c of the fourth embodiment, a resistor 19 is also connected between the gate terminal of the power semiconductor element 14 and the ground terminal 13 of the semiconductor device 10c. The resistor 19 is used to pull down the potential of the gate terminal of the power semiconductor element 14 when the MOSFET 18 receives a cut-off signal from the cut-off signal generation unit 16b and performs a turn-off operation.

[0096] According to the semiconductor device 10c of the fourth embodiment, if a control signal Vin for shutdown control is input, the cut-off signal generation unit 16b and MOSFET 18 become off, and the gate terminal of the power semiconductor element 14 is reduced to near the ground potential by the resistor 19.

[0097] If the control signal Vin, which is controlled by the input conduction control, cuts off the low-potential signal output by the signal generation unit 16b, then the MOSFET 18 becomes on and the power semiconductor element 14 is turned on.

[0098] When a high-potential control signal Vin is input, if a negative surge voltage is introduced, causing the control signal Vin to drop sharply, the charge accumulated in the gate capacitance of the power semiconductor element 14 is supplied to the power supply terminal of the cut-off signal generation section 16b via the diode 16c. Therefore, even if the control signal Vin drops sharply, the voltage signal Vs at the power supply terminal of the cut-off signal generation section 16b will not drop, thus preventing malfunction of the inverter 66 and consequently preventing accidental ignition of the spark plug 30.

[0099] The semiconductor device 10c can also be configured, similar to the semiconductor device 10 of the first embodiment, without connecting the capacitor 16d to the power supply terminal and the ground terminal of the cutoff signal generation unit 16b. Furthermore, the diode 16c constituting the power supply circuit can also be configured as a MOSFET, similar to the semiconductor device 10b of the third embodiment.

Claims

1. A semiconductor device, characterized by comprising: Possessing: a power semiconductor element connected between an output terminal and a ground terminal of a semiconductor device, and controlled to be on or off according to a gate potential; a threshold value setting portion which takes a control signal supplied to an input terminal of the semiconductor device as an operation power source, and outputs an off signal when a voltage of the control signal is lower than a predetermined voltage set as a threshold value of the power semiconductor element; and an off circuit connected between a gate terminal of the power semiconductor element and the ground terminal, and made to be in an on state by receiving the off signal, thereby making the power semiconductor element off, the threshold value setting portion has: a resistor which lowers the voltage of the control signal to be a voltage signal; an off signal generating portion which monitors the voltage signal and outputs the off signal when the control signal is lower than the predetermined voltage; a power supply circuit which is a diode, whose anode terminal is directly connected to the gate terminal of the power semiconductor element, whose cathode terminal is directly connected to a power source terminal of the off signal generating portion and connected to the input terminal via the resistor, and which is made to be in an on state if a potential difference between the control signal and the voltage signal becomes larger than a forward voltage of the diode when the control signal is in a state of a high potential, if the control signal sharply falls, and if the control signal is supplied to the resistor and the off signal generating portion as an auxiliary power source with the charge stored in a gate capacitor of the power semiconductor element, thereby suppressing a fall of the voltage signal. Possessing:

2. A semiconductor device, characterized by comprising: a power semiconductor element connected between an output terminal and a ground terminal of a semiconductor device, and controlled to be on or off according to a gate potential; a threshold value setting portion which takes a control signal supplied to an input terminal of the semiconductor device as an operation power source, and outputs an off signal when a voltage of the control signal is lower than a predetermined voltage set as a threshold value of the power semiconductor element; and an off circuit connected between a gate terminal of the power semiconductor element and the ground terminal, and made to be in an on state by receiving the off signal, thereby making the power semiconductor element off, the threshold value setting portion has: a resistor which lowers the voltage of the control signal to be a voltage signal; an off signal generating portion which monitors the voltage signal and outputs the off signal when the control signal is lower than the predetermined voltage; a power supply circuit which is an n-channel MOSFET, whose drain terminal is directly connected to the gate terminal of the power semiconductor element, whose source terminal is directly connected to a power source terminal of the off signal generating portion and connected to the input terminal via the resistor, and whose gate terminal is connected to the drain terminal thereof, which is made to be in an on state if a potential difference between the control signal and the voltage signal becomes larger than a predetermined value when the control signal is in a state of a high potential, if the control signal sharply falls, and if the control signal is supplied to the resistor and the off signal generating portion as an auxiliary power source with the charge stored in a gate capacitor of the power semiconductor element, thereby suppressing a fall of the voltage signal. ​ ​ 3. The semiconductor device according to claim 1 or 2, wherein the cutoff signal generating section has a voltage dividing circuit that divides the voltage signal, and an inverter that uses the voltage signal as a power supply and outputs a high potential when a voltage divided by the voltage dividing circuit is lower than a threshold of the inverter, and outputs a low potential when the voltage divided by the voltage dividing circuit is equal to or higher than the threshold of the inverter.

4. The semiconductor device according to claim 1, wherein the cutoff circuit is an n-channel MOSFET whose drain terminal is connected to a gate terminal of the power semiconductor element, whose source terminal is connected to the ground terminal, and whose gate terminal is connected to an output terminal of the threshold setting section.

5. The semiconductor device according to claim 1 or 2, wherein the threshold setting section has a capacitor connected between a connection portion between the resistor and a power supply terminal of the cutoff signal generating section and the ground terminal.

6. The semiconductor device according to claim 1 or 2, wherein the power semiconductor element is an insulated gate bipolar transistor or a vertical MOSFET.

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