JP5125899B2 - Ignition device for internal combustion engine - Google Patents

Description

  The present invention relates to a semiconductor device in which an electric current value is limited in an ignition device for an internal combustion engine.

  An example of a semiconductor device whose current value is limited is an internal combustion engine ignition device (igniter). An ignition device for an internal combustion engine is provided as a control device for a gasoline engine used in a car or the like, and ignites with a spark plug, for example, an air-fuel mixture of gasoline and air, which is fuel introduced into a combustion chamber. It is a device to start. FIG. 7 is a conceptual diagram showing an example of a conventional ignition device for an internal combustion engine. The ignition device for an internal combustion engine includes a primary side coil 111 and a secondary side coil 112 as ignition coils, a switching means 113 for intermittently connecting a low voltage current flowing through the primary side coil 111, a battery 114 for supplying power to the ignition coil, a primary The ignition plug 115 is configured to ignite the air-fuel mixture by discharging the high-voltage current generated in the secondary-side coil 112 by intermittently connecting the low-voltage current flowing through the side coil 111. The switching means 113 is connected to the primary coil 111 by the external collector terminal 102 and has an amplification function and a switching function. Bipolar transistors are used to realize this amplification function and switching function, but in recent years, IGBTs (insulated gate bipolar transistors) are being replaced.

  The switching means 113 is provided with an IGBT 103 that interrupts a low-voltage current flowing through the primary coil 111. A gate protection Zener diode 104 for protecting the gate of the IGBT 103 is connected between the gate of the IGBT 103 and the ground. A protective Zener diode 105 for protecting the IGBT 103 is connected between the gate and the collector of the IGBT 103. A gate resistor 106 for protecting the IGBT 103 is connected between the gate of the IGBT 103 and the external gate terminal 101. The emitter of the IGBT 103 is kept at the ground level.

  The following devices have been proposed as ignition devices for internal combustion engines using IGBTs. A DC power source and switching means are connected to the primary winding of the ignition coil, and a spark plug is connected to one end of the secondary winding of the ignition coil. A high voltage generated in the wire is supplied to the spark plug, and the switching means is a MOS gate structure transistor, and at least the coil current detection unit and the MOS gate are used to limit the coil current of the primary winding to a certain value. Generated by the current flowing from the main terminal to the gate terminal when the voltage of the main terminal on the higher voltage side of the MOS gate structure transistor is higher than the gate terminal voltage. In an internal combustion engine ignition semiconductor device having a current supply circuit for applying a voltage to a gate terminal , The current supply circuit is constructed by serially connecting at least a plurality of the constant current element. At this time, the constant current element is a depletion type IGBT or a depletion type MOSFET (MOS gate type field effect transistor) (for example, refer to Patent Document 1).

  Further, as another ignition device for an internal combustion engine, the following device has been proposed. A switching device connected in series with the ignition coil to control on / off of the current flowing through the ignition coil, a current limiting circuit for controlling the switching device to limit the current flowing through the ignition coil, and discharging from the ignition coil In an ignition semiconductor device equipped with a voltage limiting circuit for clamping a voltage to be applied, the operation starts in response to an input signal applied to the drive terminal of the switching device, and after a certain time has elapsed since the application of the input signal A timer circuit that outputs an output signal; and a main current gradual reduction circuit that reduces a current flowing through the switching device regardless of continuous application of the input signal in response to the output signal of the timer circuit. Yes. This ignition semiconductor device uses an IGBT as a switching device that is an output stage element (see, for example, Patent Document 2).

The electrical characteristics of the IGBT used as the switching means in the ignition device for an internal combustion engine as described above will be described. FIG. 8 is a characteristic diagram showing the switching waveform of the IGBT in the conventional internal combustion engine ignition device. In a state where the collector current I _ce flows in the IGBT 103, the gate voltage V _g supplied from the battery 114 is divided into the internal resistance of the ignition coil and the ON resistance of the IGBT 103 itself, and the current amount does not increase any more. The collector voltage V _ce applied to the IGBT 103 becomes the saturation voltage V _sat . From this state, when the gate voltage _Vg is turned off, L · dI / dt (L: primary side coil 111) according to the change amount dI / dt of the collector current _Ice, which attempts to cut off the collector current _Ice. Voltage on the primary side coil 111 is generated. A large voltage corresponding to the turn ratio between the primary side coil 111 and the secondary side coil 112 is induced in the secondary side coil 112 by the voltage generated in the primary side coil 111. Collector voltage V _ce becomes a voltage value above the increased base voltage V _b, a voltage value induced in the secondary coil 112 reaches a discharge voltage value L · I _ce ^2/2 of the spark plug 115. Then, generated sparks from the spark plug 115 by the voltage induced in the secondary coil 112 is discharged, the collector voltage V _ce is kept at the power supply voltage V _z2 decreases after the lapse of the discharge time t _spk It is.

However, when the voltage induced in the secondary coil 112 is not normally discharged due to the malfunction of the spark plug 115, the energy rebounds as it is to the primary side, and the collector voltage _Vce rapidly rises to a very high voltage. The IGBT 103 may be destroyed. In order to avoid this, generally, as shown in FIG. 7, a protection function called a dynamic clamp composed of a protection Zener diode 105 and a gate resistor 106 is provided.

FIG. 9 is a characteristic diagram showing a dynamic clamp waveform in a conventional internal combustion engine ignition device. If the collector voltage V _ce reaches the voltage value of more than the breakdown voltage V _z of the protection Zener diode 105, current flows through the protection Zener diode 105, the collector voltage V _ce is divided by a protective Zener diode 105 and the gate resistor 106. Then, this divided voltage is applied to the gate of the IGBT 103. As a result, a current flows through the IGBT 103 that was attempting to cut off the collector current I _ce , so that the collector voltage V _ce is clamped to the V _z (the voltage at this time is referred to as the clamp voltage V _z ), and Does not rise any more. The collector current I _ce is cut off with a gradual change amount dI / dt due to the clamp voltage V _z (= L · dI / dt). Then, the collector voltage V _ce decreases from the clamp voltage V _z to the base voltage V _b after the elapse of time t _p .

  As an ignition device for an internal combustion engine having a protection function by a dynamic clamp, the following device has been proposed. Used for an insulated gate type transistor in which a load is connected to the high voltage side or low voltage side terminal and a drive circuit is connected to the gate terminal, and the high voltage side or low voltage side terminal of the insulated gate type transistor is connected to the gate terminal. Connected between the first Zener diode that breaks down by applying a surge voltage from the high-voltage side terminal or the low-voltage side terminal, and connected between the gate terminal of the insulated gate transistor and the drive circuit, A resistor for preventing current from passing from the high-voltage side terminal or low-voltage side terminal of the insulated gate transistor to the drive circuit at the time of breakdown of the zener diode, and the low-voltage side or high-voltage side terminal of the insulated gate transistor Is connected between the gate terminal and a voltage that causes a breakdown. Lower than the gate breakdown voltage type transistor, and a second zener diode a plurality of stages of clamping the gate voltage during a breakdown of the first Zener diode (e.g., refer to Patent Document 3.).

  Further, as another ignition device for an internal combustion engine, the following device has been proposed. An overvoltage protection circuit comprising a MOS transistor and a Zener diode portion connected between one electrode and a control electrode of the MOS transistor and protecting the circuit to be protected from overvoltage. Is higher than the threshold voltage at which the protection operation is started when the circuit to be protected is in a non-operating state (see, for example, Patent Document 4).

  Further, as another ignition device for an internal combustion engine, the following device has been proposed. A DC power supply and switching means are connected to the primary winding of the ignition coil, a spark plug is connected to one end of the secondary winding of the ignition coil, and the secondary winding is changed by changing the primary current of the ignition coil by opening and closing the switching means. In the case of supplying a high voltage generated in the wire to the spark plug, the switching means is a MOS gate structure transistor, and in order to limit the coil current of the primary winding to a certain constant value, at least the coil current detector and the MOS gate structure transistor The main terminal voltage on the higher voltage side of the MOS gate structure transistor flows into the gate terminal from the main terminal on the higher voltage side. A current supply circuit is provided for applying a voltage generated by the current to the gate terminal. At this time, the main terminal voltage is equal to or lower than a predetermined voltage and below a voltage value set within a range higher than the gate terminal voltage, it is generated by a current flowing from the main terminal to the gate terminal. A voltage is applied to the gate terminal according to a constant value or a difference between the main terminal voltage and the gate terminal voltage. When the voltage is higher than the set voltage value, the voltage is generated by a current flowing from the main terminal to the gate terminal. A circuit that suppresses, decreases, or cuts off the increase in the voltage is provided (for example, see Patent Document 5).

  Further, as another ignition device for an internal combustion engine, the following device has been proposed. Ignition connected to a primary side of an ignition coil connected in series to a DC power source, an insulated gate semiconductor device, and a secondary side of the ignition coil, and applied with a high voltage generated on the secondary side by opening and closing the semiconductor device A plug, a current limiting circuit for limiting a main current of the semiconductor device to a predetermined value, and a current supply circuit for supplying current to a control electrode from a main terminal having a higher potential among a pair of main terminals of the semiconductor device The current supply circuit is configured to connect the main terminal having the higher potential to the control electrode through a series connection body of a resistor and a diode (for example, Patent Document 6). reference.).

  Further, as another ignition device for an internal combustion engine, the following device has been proposed. A power switching unit that controls energization / shut-off of the primary current flowing through the ignition coil in accordance with the input ignition control signal to generate a high voltage on the secondary side of the ignition coil, a current limiting circuit that limits the primary current, and The power switching unit has a connection circuit for connecting a collector and a gate and a feedback circuit for flowing a feedback current from the collector to the gate, and the power switching unit and the current limiting circuit are integrated on a monolithic silicon substrate of an insulated gate bipolar power transistor. The internal combustion engine ignition device includes a path through which a sneak current generated in the connection circuit flows to the emitter of the power switching unit. At this time, the connection circuit includes an impedance element, and the path includes a Zener diode that operates by a voltage drop of the impedance element (see, for example, Patent Document 7).

JP 2000-310173 A JP 2002-004991 A Japanese Patent No. 3255147 JP 2006-216651 A Japanese Patent No. 3186619 Japanese Patent No. 3740008 Japanese Patent No. 3917865

  In order to reduce the size and cost of the internal combustion engine ignition device as a whole, it is preferable to reduce the size of the IGBT used as the switching means as much as possible. In general, in an IGBT used for, for example, an inverter for switching purposes, a generated loss is reduced by realizing a low on-voltage, so that a semiconductor device can be downsized and cost can be reduced. However, in the internal combustion engine ignition device having the protection function by the dynamic clamp as described above, the energy that can be controlled by the IGBT (hereinafter referred to as controllable energy) is determined by the capability of the IGBT itself. In general, as the size of the IGBT is reduced, the current density increases accordingly, so that the controllable energy of the IGBT is reduced. This controllable energy may be determined by latch-up, which is a parasitic effect of the IGBT.

  However, as a result of extensive studies by the present inventors, it has been newly found that the controllable energy of the IGBT is determined by the allowable temperature of the material used for the semiconductor device. Due to the dynamic clamp, energy corresponding to the product of the collector voltage applied to the IGBT and the collector current is generated inside the semiconductor substrate constituting the IGBT. As a result, the temperature inside the semiconductor substrate rises, and when the temperature exceeds, for example, 300.degree. Thus, the size of the semiconductor device is limited by the minimum energy required for dynamic clamping. Therefore, even if it is attempted to reduce the chip size by realizing a low on-resistance, the temperature limit determined by the semiconductor does not necessarily lead to miniaturization of the semiconductor device. This is one of the factors that make it difficult to reduce costs in an internal combustion engine ignition device.

  An object of the present invention is to provide a semiconductor device capable of reducing the cost by reducing the size of the entire semiconductor device in order to eliminate the above-described problems caused by the prior art.

In order to solve the above-described problems and achieve the object, an ignition device for an internal combustion engine according to the invention of claim 1 is connected in series to a primary side coil of an ignition coil and intermittently flows an electric current flowing through the primary side coil. And an ignition plug for an internal combustion engine, which is connected in series to the secondary coil of the ignition coil and discharges a high voltage generated in the secondary coil by the intermittent connection of the IGBT. to a plurality of Zener diodes connected in series between the collector and the gate, a resistor connected in parallel with part of said Zener diode, and a capacitor connected in parallel to said resistor, characterized in that it comprises a .

An ignition device for an internal combustion engine according to a second aspect of the invention is the ignition device according to the first aspect, wherein the resistance and the capacity are a current flowing through the IGBT when no discharge of the spark plug occurs. the time required for the interruption and having respectively a resistance and capacitance such that more than 300 [mu] s.

  According to a third aspect of the present invention, there is provided an internal combustion engine ignition device according to the first or second aspect, wherein at least the IGBT, the Zener diode, and the resistor are formed and integrated on the same semiconductor substrate. It is characterized by.

  An ignition device for an internal combustion engine according to a fourth aspect of the invention is characterized in that, in the third aspect of the invention, the resistor is formed of polycrystalline silicon (p-Si: polysilicon). .

  According to the invention of each claim described above, when no discharge occurs, the clamp voltage decreases with time, and the collector current flowing through the IGBT gradually decreases gradually, whereby the gate voltage is turned off. The time until is extended. Therefore, it is possible to make the time during which the heat generated inside the IGBT is dissipated longer than before, and the heat dissipation effect of the IGBT is improved. Thereby, the controllable energy of the IGBT can be increased, and the IGBT can be downsized by an amount corresponding to the increase amount of the energy breakdown voltage of the IGBT.

  According to the inventions of claims 3 and 4 described above, the semiconductor switch as a whole can be made small by producing the protection function of the IGBT and IGBT on one semiconductor substrate.

  According to the ignition device for an internal combustion engine according to the present invention, it is possible to reduce the size of the entire ignition device for an internal combustion engine and to reduce the cost.

Exemplary embodiments of an ignition device for an internal combustion engine according to the present invention will be explained below in detail with reference to the accompanying drawings. Note that, in the following description of the embodiments and all the attached drawings, the same reference numerals are given to the same components, and duplicate descriptions are omitted. In this specification, a semiconductor having n or p means that electrons and holes are majority carriers, respectively. Further, “ ⁺ ” or “ ⁻ ” attached to n or p, such as n ⁺ or n ^−, is relatively higher or lower than the impurity concentration of the semiconductor to which they are not attached. Represents that. The measurement results described in the present invention are derived by a standard measurement method corresponding to the measurement results using the internal combustion engine ignition device.

(Embodiment 1)
FIG. 1 is a circuit diagram illustrating a semiconductor switch having a protection function according to the first embodiment. As shown in FIG. 1, the semiconductor device having a protection function according to the first embodiment includes a primary side coil 11 and a secondary side coil 12 as ignition coils, and switching means 13 for intermittently passing a low voltage current flowing through the primary side coil 11. A battery 14 for supplying electric power to the ignition coil, and an ignition plug 15 for igniting the air-fuel mixture.

  The switching means 13 includes an IGBT 3 that is connected to the primary side coil 11 by the external collector terminal 2 and intermittently connects the low-voltage current flowing through the primary side coil 11. A gate protection Zener diode 4 for protecting the gate of the IGBT 3 is connected between the gate of the IGBT 3 and the ground. A protective Zener diode 5 for protecting the IGBT 3 is connected between the gate and the collector of the IGBT 3. The protection Zener diode 5 is configured by connecting a plurality of Zener diodes in series. A bypass resistor 7 having a high resistance value is connected in parallel to at least a part of the protective Zener diode 5. A capacitor 8 is connected to the bypass resistor 7 in parallel. A gate resistor 6 for protecting the IGBT 3 is connected between the gate of the IGBT 3 and the external gate terminal 1. The emitter of the IGBT 3 is kept at the ground level.

  In the gate protection Zener diode 4, the cathode of the first Zener diode is connected to the gate of the IGBT 3. The anode of the first Zener diode and the anode of the second Zener diode are connected. The cathode of the second Zener diode is kept at the ground level.

  In the protective Zener diode 5, the cathode of the first Zener diode is connected to the collector of the IGBT 3. The anode of the first Zener diode and the cathode of the second Zener diode are connected. Similarly, the anode of the Zener diode and the cathode of the next Zener diode are connected and connected. Finally, in the illustrated example, the anode of the fifth Zener diode is connected to the gate of the IGBT 3.

  The bypass resistor 7 is connected in parallel to at least a part of the plurality of Zener diodes connected in series of the protective Zener diode 5. The bypass resistor 7 and the capacitor 8 have the effect of gradually reducing the collector current flowing through the IGBT 3 due to the time constant CR (C: capacitance of the capacitor 8 and R: electric resistance of the bypass resistor 7). By providing the bypass resistor 7, the effect of radiating the heat generated inside the IGBT 3 is improved. As the capacitor 8, the capacitance of the protective Zener diode 5 itself may be used.

  As the gate protection Zener diode 4 and the protection Zener diode 5, it is preferable to use a low breakdown voltage Zener diode. The reason is that the low withstand voltage Zener diode has a large current capacity, so that the effect of avoiding an overcurrent flowing through the IGBT can be enhanced. The resistance value of the bypass resistor 7 is preferably set so that the time during which the gate voltage is turned off is 300 to 400 μs or more. The reason will be described later.

  As described above, according to the first embodiment, the collector current flowing through the IGBT 3 gradually and gradually decreases, thereby extending the time until the gate voltage is turned off. Therefore, the time for radiating the heat generated in the IGBT 3 can be made longer than before, and the heat radiating effect of the IGBT 3 is improved. Thereby, the controllable energy of the IGBT 3 can be increased, and the IGBT 3 can be reduced in size by an amount corresponding to the increase amount of the energy breakdown voltage of the IGBT 3.

(Embodiment 2)
Next, a semiconductor switch in which the IGBT and the protection function of the IGBT are formed and integrated on one semiconductor substrate will be described. FIG. 2 is a plan view showing a planar layout of a monolithic semiconductor switch incorporating the IGBT and the protection function of the IGBT according to the second embodiment. FIG. 3 is a plan view showing a planar layout of a portion that realizes the protection function of the IGBT according to the second embodiment. The plan view shown in FIG. 2 is a planar layout of the IGBT emitter and gate electrodes and the protection function of the IGBT. As shown in FIG. 2, in the planar layout of the semiconductor switch, the emitter electrode 49 is formed in a substantially rectangular shape, for example. The gate electrode 47 has a track shape and surrounds the emitter electrode 49. Furthermore, a track-shaped electrode 54 is provided so as to surround the gate electrode 47. This electrode 54 is electrically connected to a collector electrode (see FIG. 4) on the back surface of the substrate in a region not shown in the figure. A Zener diode 30 is formed between the gate electrode 47 and the electrode 54 surrounding it.

  As shown in FIG. 3, the Zener diode 30 has a configuration in which n-type semiconductor regions (first conductivity type semiconductor regions) 32 and p-type semiconductor regions (second conductivity type semiconductor regions) 31 are alternately arranged. . This Zener diode 30 is the protection Zener diode 5 shown in the first embodiment. A bypass resistor 33 is formed in a part of the Zener diode 30 via an isolation region 34 formed using, for example, an oxide film. This bypass resistor 33 is the bypass resistor 7 shown in the first embodiment, and bypasses a part of the pn pair of the Zener diode 30.

4 is a cross-sectional view showing a cross-sectional structure taken along the cutting line AA ′ of FIG. In addition, the description of n or p of the Zener diode 30 is omitted except for a part. As shown in FIG. 4, in a semiconductor substrate in which an n ⁺ buffer layer 42 and an n drift layer 43 are formed on a high impurity concentration p-type silicon substrate to be a p ⁺ collector layer 41, an IGBT region 21 and a protection functional region 22 is provided. In IGBT region 21, p ⁻ base region 44 is provided in a part of the surface layer of n drift layer 43. An n ⁺ emitter region 45 is provided in a part of the surface layer of the p ⁻ base region 44. A gate insulating film 46 is formed from the surface of the n drift layer 43 where the p ⁻ base region 44 is not formed to a part of the adjacent n ⁺ emitter region 45. A gate electrode 47 is provided via the gate insulating film 46. An emitter electrode 49 is provided on the surface of the p ⁻ base region 44 and the n ⁺ emitter region 45 where the gate insulating film 46 is not formed. The emitter electrode 49 formed on the adjacent p ⁻ base region 44 is connected, and the emitter electrode 49 is insulated from the gate electrode 47 by the interlayer insulating film 48. A collector electrode 55 is provided on the back surface of the p ⁺ collector layer 41. An emitter terminal 56 and a gate terminal 57 are provided on the emitter side of the semiconductor substrate. A collector terminal 58 is provided on the collector side of the semiconductor substrate.

In the protective function region 22, a first p ⁺ high concentration region 50 is provided on a part of the surface layer of the n drift layer 43 so as to be in contact with the p ⁻ base region 44 near the boundary between the IGBT region 21 and the protective function region 22. It has been. A second p ⁺ high concentration region 51 is provided apart from the first p ⁺ high concentration region 50. Further, an n ⁺ region 52 is provided in a region opposite to the boundary with the IGBT region 21 apart from the second p ⁺ high concentration region 51. An insulating film 53 formed of, for example, an oxide film is provided from a part of the p ⁻ base region 44 in contact with the first p ⁺ high concentration region 50 to a part of the n ⁺ region 52. An electrode 54 is provided on a part of the surface of the insulating film 53 on the n ⁺ region 52 side so as to connect to the n ⁺ region 52. On the surface of the insulating film 53 where the emitter electrode 49 and the electrode 54 are not formed, the Zener diode 30 is provided so as to be away from the emitter electrode 49 and in contact with the electrode 54. Zener diode 30 is electrically connected to gate terminal 57. The electrode 54 is electrically connected to the collector electrode 55.

  Although not shown in FIG. 4, the bypass resistor 33 is preferably formed using polycrystalline silicon (p-Si: polysilicon). The reason is that the Zener diode is formed using polycrystalline silicon which is a material constituting the gate of the IGBT, and the bypass resistor 33 can be formed in a part of the Zener diode.

  As described above, according to the second embodiment, the same effect as in the first embodiment can be obtained. Further, by fabricating the IGBT and IGBT protection function on one semiconductor substrate, the entire semiconductor switch can be made small.

Then, when connecting the bypass resistor 7 and a capacitor 8 to the protection Zener diode 5, it is described with the voltage waveform of the collector voltage V _ce of IGBT 3. FIG. 5 is a characteristic diagram showing electrical characteristics of the IGBT of the semiconductor switch having a protection function according to the present invention. An internal combustion engine ignition device shown in FIG. 1 will be described as an example. Further, the breakdown voltage of the protective Zener diode 5 is set to the first breakdown voltage V _z . The breakdown voltage of the protection Zener diode 5 when a part of the protection Zener diode 5 is bypassed by the bypass resistor 7 is defined as a second breakdown voltage V _z1 . If the collector voltage V _ce reaches the voltage value of the above first breakdown voltage V _z, the collector voltage V _ce is clamped to the first breakdown voltage V _z (clamp voltage V _z). By providing the bypass resistor 7 and the capacitor 8, the collector voltage V _ce then gradually decreases to substantially the same voltage as the second breakdown voltage V _z1 . Then, after the elapse of time t _p , the voltage drops from substantially the same voltage as the second breakdown voltage V _z1 to the base voltage V _b .

Collector current I _ce between from happening dynamic clamp until time t _p is considering the time constant CR is the time axis, gradually change amount dI / dt of the right edge of the exponential curve convex downward Decrease gradually. Thus, it was found that the heat dissipation effect of the IGBT 3 can be improved by providing the bypass resistor 7 and the capacitor 8 as a protection function as compared with the related art. And it turned out that the controllable energy of IGBT can be increased because the heat dissipation effect improves.

  Next, the relationship between the clamp voltage and the maximum energy at which the IGBT to which the clamp voltage is applied is not destroyed (hereinafter referred to as clamp energy) will be described. FIG. 6 is a characteristic diagram showing the relationship between clamp voltage and clamp energy. In FIG. 6, the measurement result 62 is a measurement result when the bypass resistor 7 and the capacitor 8 are provided. The other measurement results are the measurement results when the bypass resistor 7 and the capacitor 8 are not provided. From the results shown in FIG. 6, it was found that the clamp energy increases when the clamp voltage is lowered and decreases when the clamp voltage is increased. This is because the heat generated inside the semiconductor substrate is transmitted to the heat sink via the circuit board by being lowered in the clamp voltage, and is released to the outside of the semiconductor. On the other hand, the OFF time of the gate voltage of the IGBT becomes longer when the clamp voltage is lowered and becomes shorter when the clamp voltage is raised. Therefore, in this measurement, it was found that the heat generated inside the semiconductor substrate is dissipated when the IGBT gate voltage OFF time is 300 to 400 μs or more. It is preferable to set the resistance value of the bypass resistor 7 so as to satisfy this condition.

In the measurement result 61 of the clamp energy described above when the clamp voltage is 410 V, the clamp energy when the bypass resistor 7 and the capacitor 8 are provided was measured. Note that when the first breakdown voltage V _z is 410 V, the second breakdown voltage V _z1 is set to 160 V by connecting the bypass resistor 7 and the capacitor 8. From the results shown in FIG. 6, it was found that the clamp energy in the measurement result 61 increased by about 30 to 40% and became the measurement result 62 indicated by an asterisk. Therefore, the controllable energy of the IGBT can be increased by the increase amount of the clamp energy. Thereby, all the increase amount of the energy tolerance of IGBT can be made into the element for size reduction of IGBT.

  In the above, the present invention can be applied not only to the internal combustion engine ignition device described above but also to a semiconductor device in which the current value is limited.

  As described above, the internal combustion engine ignition device according to the present invention is useful as an internal combustion engine ignition device using an IGBT.

1 is a circuit diagram showing a semiconductor switch having a protection function according to a first embodiment; FIG. 6 is a plan view showing a planar layout of a monolithic semiconductor switch incorporating an IGBT according to a second embodiment and an IGBT protection function. FIG. 10 is a plan view showing a planar layout of a part that realizes the IGBT protection function according to the second exemplary embodiment; FIG. 3 is a cross-sectional view showing a cross-sectional structure taken along a cutting line AA ′ in FIG. 2. It is a characteristic view shown about the electrical characteristic of IGBT of the semiconductor switch which has a protection function concerning the present invention. It is a characteristic view which shows the relationship between a clamp voltage and clamp energy. It is a conceptual diagram which shows an example of the ignition device for internal combustion engines of a prior art example. It is a characteristic view which shows the switching waveform of IGBT in the ignition device for internal combustion engines of a prior art example. It is a characteristic view which shows the dynamic clamp waveform in the ignition device for internal combustion engines of a prior art example.

Explanation of symbols

1 External gate terminal 2 External collector terminal 3 IGBT
4 IGBT gate protection Zener diode 5 IGBT protection Zener diode 6 Gate resistance 7 Bypass resistance 8 Capacity 11 Primary coil 12 Secondary coil 13 Switching means 14 Battery 15 Spark plug

Claims (4)

An IGBT connected in series to the primary coil of the ignition coil, and connected to the secondary coil of the ignition coil in series with the IGBT that interrupts the current flowing through the primary coil, and connected to the secondary coil by the intermittent of the IGBT. In an ignition device for an internal combustion engine comprising an ignition plug for discharging a generated high voltage,
A plurality of zener diodes connected in series between the collector and gate of the IGBT;
A resistor connected in parallel with part of the Zener diode,
A capacitor connected in parallel to the resistor;
An ignition device for an internal combustion engine comprising: The resistor and the capacitor have a resistance value and an electrostatic capacity , respectively, such that the time required to cut off the current flowing through the IGBT is 300 μs or more when no discharge of the spark plug occurs. The internal combustion engine ignition device according to claim 1.   3. The ignition device for an internal combustion engine according to claim 1, wherein at least the IGBT, the Zener diode, and the resistor are integrally formed on the same semiconductor substrate.   The ignition device for an internal combustion engine according to claim 3, wherein the resistor is formed of polycrystalline silicon.

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