Integrated Circuits

Abstract

To provide an integrated circuit that makes it possible to properly control the on and off of a transistor.SOLUTION: An integrated circuit includes a transistor configured to control a current flowing through the coil, a control circuit configured to control on and off of the transistor based on a voltage level of a first line that is coupled to a control electrode of the transistor, and a Zener diode having a cathode coupled to the first line and an anode coupled to a second line that is coupled to an electrode of the transistor on the ground side thereof. The Zener diode has such a predetermined capacitance that, when a first signal for controlling the transistor and a second signal of a predetermined frequency higher than the frequency of the first signal are inputted to the first line, the control circuit can control the on and off of the transistor in response to the first signal irrespective of the second signal.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to integrated circuits. [Background technology]

[0002] There are integrated circuits used in ignition devices for internal combustion engines (see, for example, Patent Documents 1 to 8). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-153012 A [Patent Document 2] JP 2002-371945 A [Patent Document 3] JP 2008-045514 A [Patent Document 4] JP 2006-037822 A [Patent Document 5] JP 2014-013796 A [Patent Document 6] JP 2016-035220 A [Patent Document 7] Patent No. 5181834 [Patent Document 8] JP 2018-007539 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, some integrated circuits include an IGBT (Insulated Gate Bipolar Transistor) and a control circuit that controls the on / off of the IGBT within a single chip. Some control circuits operate using the voltage of a line connected to the gate electrode of the IGBT as the power supply voltage. In such control circuits, if noise is superimposed on the line and the voltage level of the line fluctuates, the control circuit may malfunction and the IGBT may not be turned on and off properly.

[0005] The present invention has been made in consideration of the above-mentioned problems in the conventional technology, and has an object to provide an integrated circuit capable of appropriately turning on and off transistors. [Means for solving the problem]

[0006] The integrated circuit of the present invention, which solves the above-mentioned problems, comprises a transistor that controls a current flowing through a coil, a control circuit that controls the on / off of the transistor based on the voltage level of a first line connected to a control electrode of the transistor, and a Zener diode having a cathode connected to the first line and an anode connected to a second line connected to the ground side electrode of the transistor, wherein the Zener diode has a predetermined capacitance so that when a first signal for controlling the transistor and a second signal having a predetermined frequency higher than the frequency of the first signal are input to the first line, the control circuit can control the on / off of the transistor based on the first signal regardless of the second signal. Effect of the Invention

[0007] According to the present invention, it is possible to provide an integrated circuit capable of appropriately turning on and off transistors. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of an igniter 10. [Diagram 2] FIG. 2 is a diagram for explaining details of the integrated circuit 11. [Diagram 3] FIG. 13 is a diagram showing an example of a wiring diagram when noise is superimposed on a drive signal Vdr. [Figure 4] FIG. 13 is a diagram illustrating an example of noise attenuated by a low-pass filter. [Diagram 5] 11 is a diagram showing an example of an input voltage Vin applied to a first line LN1 when noise is superimposed on a low-level drive signal Vdr. FIG. [Figure 6] 11 is a diagram showing an example of an input voltage Vin applied to a first line LN1 when noise is superimposed on a high-level drive signal Vdr. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] At least the following points will become apparent from the description of this specification and the accompanying drawings. =====This embodiment===== <<<One-chip igniter>>> 1 is a diagram showing an example of an igniter 10 according to an embodiment of the present invention. The igniter 10 is a semiconductor module used in an ignition device 20 described below. The igniter 10 is a one-chip igniter having a gate (G) terminal, a collector (C) terminal, and an emitter (E) terminal (hereinafter referred to as the “G terminal”, the “C terminal”, and the “E terminal”, respectively), and including an integrated circuit 11.

[0010] The G terminal is connected by wire 12 to a gate electrode of an IGBT (described later) formed on the front surface of the integrated circuit 11, and the E terminal is connected by wire 13 to an emitter electrode of the IGBT also formed on the front surface of the integrated circuit 11. The C terminal is connected to a collector electrode (not shown) of the IGBT formed on the back surface of the integrated circuit 11. The relationship between the integrated circuit 11 and the G terminal, C terminal, and E terminal will be described in detail later. The gate electrode to which the G terminal is connected corresponds to a "control electrode."

[0011] <<<An example of the configuration of the integrated circuit 11>>> 2 is a diagram for explaining details of the integrated circuit 11. The integrated circuit 11 controls the on / off of an IGBT 33, which will be described later, based on a drive signal Vdr from an ECU (Electronic Control Unit) 21, which will be described later.

[0012] The integrated circuit 11 includes a Zener diode 30, a control circuit 31, NMOS transistors 32, 35, and 38, an IGBT 33, a protection circuit 34, a limiting circuit 36, and a resistor 37. The Zener diode 30 is provided between the G terminal and the E terminal of the igniter 10.

[0013] The cathode of the Zener diode 30 is connected to the first line LN1 to which the G terminal is connected, and the anode of the Zener diode 30 is connected to the second line LN2 to which the emitter electrode (i.e., the electrode on the ground side) of the IGBT 33 is connected. Furthermore, when the input voltage Vin input to the first line LN1 exceeds the breakdown voltage Vzd (e.g., 7 V) of the Zener diode 30, the Zener diode 30 clamps the input voltage Vin to the breakdown voltage Vzd.

[0014] On the other hand, when the input voltage Vin exceeds the forward voltage Vf of the Zener diode 30 and becomes a negative voltage, the Zener diode 30 turns on and sets the input voltage Vin to a negative voltage that is reduced by the forward voltage Vf of the Zener diode 30. In addition, the Zener diode 30 has a junction capacitance Cb, which will be described in detail later.

[0015] <<Control circuit 31>> The control circuit 31 is a circuit that controls the on / off of the IGBT 33 based on the voltage level of the input voltage Vin input to the first line LN1. Specifically, the control circuit 31 turns off the NMOS transistor 32 when the input voltage Vin exceeds a threshold voltage VthH (e.g., 2.8 V). When the NMOS transistor 32 is turned off, the gate voltage Vg becomes the input voltage Vin, and the IGBT 33 is turned on. The threshold voltage VthH is higher than the threshold voltage Vth of the IGBT 33 (e.g., 1.5 V).

[0016] Furthermore, when the input voltage Vin falls below a threshold voltage VthL (e.g., 2.5 V) that is lower than the threshold voltage VthH, the control circuit 31 turns on the NMOS transistor 32. When the NMOS transistor 32 turns on, the gate voltage Vg becomes the ground voltage, and the IGBT 33 turns off. In this way, the control circuit 31 controls the state of the IGBT 33 by turning on and off the NMOS transistor 32 based on the level of the input voltage Vin.

[0017] In this embodiment, the control circuit 31 includes, for example, an inverter (not shown) having a threshold voltage VthH as a threshold voltage, an inverter (not shown) having a threshold voltage VthL as a threshold voltage, and other circuit elements. The threshold voltage VthH corresponds to a "first level", and the threshold voltage VthL corresponds to a "second level".

[0018] < <igbt33>> The IGBT 33 is a switching element that controls a current flowing through an ignition coil 22, which will be described later. The IGBT 33 of this embodiment includes a sense IGBT for current detection. The current flowing through the sense IGBT corresponds to a collector current Ic flowing through the IGBT 33, and flows to an E terminal of the igniter 10 via a resistor 37, which will be described later.

[0019] <<Protection circuit 34>> The protection circuit 34 is a circuit that prevents the IGBT 33 from being destroyed by heat. Specifically, the protection circuit 34 is formed in the integrated circuit 11, detects the temperature of the IGBT 33 based on the output of a diode (not shown) that functions as a temperature sensor, and turns off the IGBT 33 when the temperature of the IGBT 33 is higher than a predetermined temperature.

[0020] Incidentally, the temperature of the IGBT 33 rises when the IGBT 33 is turned on and a current flows through the IGBT 33. Therefore, the protection circuit 34 needs to operate before the IGBT 33 is turned on. Therefore, the protection circuit 34 of this embodiment detects whether the temperature of the IGBT 33 is equal to or higher than a predetermined temperature when the voltage level of the input voltage Vin becomes a predetermined level lower than the threshold voltage VthH.

[0021] Then, when the input voltage Vin exceeds the threshold voltage VthH and the temperature of the IGBT 33 exceeds a predetermined temperature, the protection circuit 34 outputs a voltage Vp which is the gate voltage Vg, and turns on the NMOS transistor 35. When the NMOS transistor 35 is turned on, the gate voltage Vg becomes the ground voltage, and the IGBT 33 is turned off. As a result, the current flowing through the IGBT 33 becomes zero, and the protection circuit 34 can suppress the temperature rise of the IGBT 33. In this way, when the IGBT 33 is on and the temperature of the IGBT 33 exceeds a predetermined temperature, the protection circuit 34 can turn off the IGBT 33. As a result, the protection circuit 34 can reliably prevent the IGBT 33 from being destroyed by heat.

[0022] <<Limiting circuit 36>> The limiting circuit 36 ​​is a circuit that limits the current flowing through the IGBT 33. Specifically, the limiting circuit 36 ​​detects whether the collector current flowing through the IGBT 33 is equal to or greater than a predetermined value (for example, 13 A), and limits the collector current flowing through the IGBT 33 so that it does not exceed the predetermined value.

[0023] Incidentally, in order to limit the collector current flowing through the IGBT 33, the limiting circuit 36 ​​needs to operate before the IGBT 33 is turned on. Therefore, the limiting circuit 36 ​​of this embodiment detects the collector current flowing through the IGBT 33 based on the voltage generated across the resistor 37 when the voltage level of the input voltage Vin becomes a predetermined level lower than the threshold voltage VthH.

[0024] When the collector current becomes equal to or exceeds a predetermined value, the limiting circuit 36 ​​outputs the voltage Vr to control the NMOS transistor 38 in order to lower the gate voltage Vg of the IGBT 33 so as to reduce the collector current. In this way, the limiting circuit 36 ​​limits the collector current to a predetermined current. As a result, the limiting circuit 36 ​​can limit the collector current so that the collector current does not become equal to or exceeds a predetermined current when the IGBT 33 is on.

[0025] <<<Details of Ignition Device 20>>> The ignition device 20 is a device for igniting the combustion gas in the cylinder of the internal combustion engine, and is configured to include an igniter 10, an ignition coil 22, a DC power supply 23, and an ignition plug 24.

[0026] The ignition device 20 receives a drive signal Vdr from the ECU 21 at a G terminal of the igniter 10 and discharges the spark plug 24 .

[0027] First, when the ECU 21 outputs a high-level (hereinafter referred to as "H" level, e.g., 5 V) drive signal Vdr, the voltage level of the first line LN1 connected to the G terminal rises, and the IGBT 33 turns on. Then, the voltage of the C terminal of the igniter 10 drops. As a result, a DC voltage Vdc (e.g., 14 V) from the DC power supply 23 is applied to the primary coil L1 of the ignition coil 22, and a current flows through the primary coil L1. Note that the IGBT 33 corresponds to a "transistor", and the primary coil L1 corresponds to a "coil".

[0028] Next, when the ECU 21 outputs a low-level (hereinafter referred to as "L" level, e.g., ground voltage) drive signal Vdr, the voltage level of the first line LN1 drops and the IGBT 33 turns off. Then, the current flowing through the coil L1 decreases abruptly, and the voltage across the primary coil L1 increases abruptly. The voltage across the secondary coil L2 of the ignition coil 22 also increases to several tens of kV (e.g., 30 kV), and the voltage across the secondary coil L2 is applied to the spark plug 24. Since the spark plug 24 discharges when a voltage of approximately 10 kV or more is applied to it, when the ECU 21 outputs an "L" level drive signal Vdr after outputting an "H" level drive signal Vdr, the spark plug 24 discharges.

[0029] The igniter 10 is mounted on a vehicle and used to ignite the combustion gas in the cylinder of an internal combustion engine. In addition to the igniter 10, the vehicle is also equipped with a microcomputer and various electronic circuits. Therefore, noise emitted from the electronic circuits may be superimposed on the drive signal Vdr, causing the voltage level of the G terminal to fluctuate. If the level of noise superimposed on the drive signal Vdr is very high, the control circuit 31 in the integrated circuit 11 of the igniter 10 may malfunction and erroneously control the on / off of the IGBT 33 because it operates based on the voltage level of the G terminal or the gate voltage Vg.

[0030] <<<Example of noise superimposed on drive signal Vdr>>> 3 is a diagram showing an example of a wiring diagram when noise is superimposed on the drive signal Vdr. For example, a current that becomes noise is injected into the drive signal Vdr from the ECU 21 (not shown) at node A. Then, the input voltage Vin with the noise superimposed on the drive signal Vdr is input to the first line LN1 via the G terminal. The drive signal Vdr corresponds to the "first signal" and the noise corresponds to the "second signal."

[0031] The igniter 10 receives an input voltage Vin and operates based on the voltage level of the input voltage Vin. An ignition coil 22 and the like are connected to a terminal C of the igniter 10 as shown in Fig. 2. In addition, a terminal E of the igniter 10 is grounded.

[0032] In FIG. 3, the distance of the wiring 40 between the node A and the igniter 10 is set as distance La. Here, the wiring 40 through which noise is transmitted from the node A to the cathode of the Zener diode 30 has a parasitic resistance Rp and a parasitic inductance Lp. The distance from the G terminal of the igniter 10 to the cathode of the Zener diode 30 is sufficiently shorter than the distance La. For this reason, in this embodiment, the parasitic component of the wiring from the G terminal to the cathode of the Zener diode 30 is ignored. The wiring 40 corresponds to a "line."

[0033] Furthermore, when the junction capacitance Cb of the Zener diode 30 is taken into consideration, the junction capacitance Cb constitutes a low-pass filter together with the parasitic resistance Rp of the wiring and the parasitic inductance Lp. Furthermore, since the parasitic resistance Rp is sufficiently small, if its influence is ignored, the cutoff frequency fc of the low-pass filter for removing noise is fc=1 / (2π√LpCb), where Lp is the inductance value of the parasitic inductance Lp and Cb is the capacitance value of the junction capacitance Cb. Note that the capacitance value Cb corresponds to the "predetermined capacitance value."

[0034] In addition, the "junction capacitance Cb" refers to the capacitance caused by the depletion layer generated in the PN junction portion of the Zener diode 30. The larger the reverse voltage applied to the Zener diode 30, the larger the depletion layer becomes, and therefore the smaller the capacitance value Cb of the junction capacitance Cb becomes.

[0035] In this embodiment, the frequency of the drive signal Vdr is, for example, 60 Hz, and the frequency band of the noise is, for example, 30 MHz to 400 MHz. Therefore, the cutoff frequency fc for attenuating the noise may be set to a frequency lower than 30 MHz, which is the lowest frequency of the noise frequency band. Here, if the inductance value Lp is 0.22 micro H, the capacitance value Cb when the cutoff frequency fc is a frequency lower than 30 MHz is 128 pF.

[0036] Furthermore, the maximum value of the voltage applied to the first line LN1 is the breakdown voltage Vzd of the Zener diode 30. Therefore, in order for the control circuit 31 to be able to control the on / off of the IGBT 33 based on the drive signal Vdr regardless of noise, it is sufficient that the junction capacitance Cb of the Zener diode 30 is 130 pF or more when the input voltage Vin becomes equal to or greater than the breakdown voltage Vzd. The frequency of the noise corresponds to the "predetermined frequency."

[0037] Fig. 4 is a diagram showing an example of noise attenuated by a low-pass filter. In Fig. 4, the noise is assumed to be a sine wave having a predetermined frequency and amplitude as shown by the dotted line. The voltage level of the drive signal Vdr is assumed to be a voltage Voffset as shown by the dashed line. When noise is superimposed on the drive signal Vdr at node A in Fig. 3, in the absence of the Zener diode 30, the input voltage Vin fluctuates around the voltage Voffset as shown by the dotted line in Fig. 4.

[0038] Furthermore, the noise components superimposed at node A are attenuated by a low-pass filter consisting of a parasitic resistance Rp, a parasitic inductance Lp, and a junction capacitance Cb. If the junction capacitance Cb of the Zener diode 30 is taken into consideration but the breakdown voltage Vzd and the forward voltage Vf are not taken into consideration, the input voltage Vin will be as shown by the solid line. Therefore, by appropriately setting the capacitance value Cb of the junction capacitance Cb, the effect of the noise superimposed on the drive signal Vdr can be reduced.

[0039] 2, the Zener diode 30 maintains the input voltage Vin between the breakdown voltage Vzd and a negative voltage lowered by the forward voltage Vf. Therefore, the input voltage Vin with the noise components attenuated is limited to a voltage range restricted by the Zener diode 30, so that the effect of noise on the operation of the control circuit 31 is reduced. To operate in this way, the breakdown voltage Vzd of the Zener diode 30 is determined to be higher than the voltage level of the "H" level drive signal Vdr and lower than the amplitude of the noise.

[0040] <<<Voltage of the first line LN1 when noise is superimposed on the drive signal Vdr>>> FIG. 5 is a diagram showing an example of the voltage applied to the first line LN1 when noise is superimposed on the "L" level drive signal Vdr. In FIG. 5, the dotted line drawn in a sine wave shape represents noise, and the dashed line represents the drive signal Vdr. The other dotted lines represent, from the top, the breakdown voltage "Vzd", the voltage of the "H" level drive signal Vdr "5V", the threshold voltage "VthH", the voltage of the "L" level drive signal Vdr "0V (ground voltage)", and the negative voltage side voltage "-Vf". The solid line represents the voltage of the first line LN1, and the dashed dotted line represents the average value "Vm" of the voltage of the first line LN1.

[0041] Before time ta, the input voltage Vin with noise attenuated fluctuates sinusoidally around 0V. Then, when the input voltage Vin rises from 0V and reaches the breakdown voltage Vzd of the Zener diode 30, the voltage applied to the first line LN1 is clamped to the breakdown voltage Vzd. Therefore, the input voltage Vin that exceeds the breakdown voltage Vzd is not applied to the first line LN1. Then, when the input voltage Vin drops and falls below the breakdown voltage Vzd, the voltage applied to the first line LN1 becomes the input voltage Vin.

[0042] Then, when the input voltage Vin drops and the Zener diode 30 turns on, the voltage applied to the first line LN1 becomes negative by the forward voltage Vf of the Zener diode 30. Therefore, the input voltage Vin, which has become even more negative than the forward voltage Vf, is not applied to the first line LN1. Furthermore, when the input voltage Vin rises and exceeds the negative voltage of the forward voltage Vf, the voltage applied to the first line LN1 becomes the input voltage Vin.

[0043] Therefore, the average value "Vm" of the voltage level of the first line LN1 is within the voltage range limited by the Zener diode 30, and does not exceed the threshold voltage VthH of the control circuit 31. Therefore, even if noise is superimposed on the "L" level drive signal Vdr, the breakdown voltage Vzd of the Zener diode 30 and the junction capacitance Cb act to prevent the IGBT 33 from being erroneously turned on.

[0044] After time ta, the ECU 21 outputs the drive signal Vdr at the "H" level. After time ta, noise is also superimposed on the drive signal Vdr, but this is omitted here for convenience. The operation after time ta will be described with reference to FIG. 6.

[0045] Fig. 6 is a diagram showing an example of a voltage applied to the first line LN1 when noise is superimposed on the "H" level drive signal Vdr. Each line in Fig. 6 is the same as each line in Fig. 5, except for the threshold voltage "VthL" indicated by a dotted line.

[0046] Before time tb, the input voltage Vin with noise attenuated fluctuates sinusoidally around 5V. Then, when the input voltage Vin rises from 5V to the breakdown voltage Vzd of the Zener diode 30, the voltage applied to the first line LN1 is clamped to the breakdown voltage Vzd. Therefore, the input voltage Vin that exceeds the breakdown voltage Vzd is not applied to the first line LN1. Then, when the input voltage Vin drops and falls below the breakdown voltage Vzd, the voltage applied to the first line LN1 becomes the input voltage Vin.

[0047] Then, when the input voltage Vin drops and the Zener diode 30 turns on, the voltage applied to the first line LN1 becomes negative by the forward voltage Vf of the Zener diode 30. Therefore, the input voltage Vin, which has become even more negative than the forward voltage Vf, is not applied to the first line LN1. Furthermore, when the input voltage Vin rises and exceeds the negative voltage of the forward voltage Vf, the voltage applied to the first line LN1 becomes the input voltage Vin.

[0048] Therefore, the average value "Vm" of the voltage level of the first line LN1 is within the voltage range limited by the Zener diode 30, and does not fall below the threshold voltage VthL of the control circuit 31. Therefore, even if noise is superimposed on the "H" level drive signal Vdr, the action of the breakdown voltage Vzd of the Zener diode 30 and the junction capacitance Cb prevents the IGBT 32 from being erroneously turned off.

[0049] After time tb, the ECU 21 outputs the drive signal Vdr at the "L" level. After time tb, noise is superimposed on the drive signal Vdr, as in FIG. 5, but is omitted here for convenience. The operation after time tb is as described in FIG. 5.

[0050] Moreover, if the breakdown voltage Vzd of the Zener diode 30 is high, the average value "Vm" of the voltage of the first line LN1 described above will be high, and the IGBT 33 will be erroneously turned on even if the ECU 21 outputs the drive signal Vdr of the ground voltage. Therefore, in order to keep the average value "Vm" low and to prevent the drive signal Vdr of 5V output by the ECU 21 of this embodiment from being clamped by the breakdown voltage Vzd, in this embodiment, it is preferable that the breakdown voltage Vzd is set to 6 to 8V. Furthermore, if the Zener diode 30 is configured with multiple Zener diodes, the capacitance value Cb of the Zener diode 30 will be small, so it is preferable that the Zener diode 30 is configured with a single Zener diode.

[0051] ===Summary=== The igniter 10 of this embodiment has been described above. The integrated circuit 11 of the igniter 10 includes a Zener diode 30, a control circuit 31, and an IGBT 33. The Zener diode 30 has a capacitance Cb so that the IGBT 33 can be turned on and off based on the drive signal Vdr when the input voltage Vin, which is a drive signal Vdr with noise superimposed thereon, is input to the G terminal. Due to the action of the breakdown voltage Vzd and the junction capacitance Cb of the Zener diode 30, the integrated circuit 11 can suppress erroneous turning on and off of the IGBT 33 even when the input voltage Vin, which is a drive signal Vdr with noise superimposed thereon, is input. Therefore, an integrated circuit that can appropriately turn on and off a transistor can be provided.

[0052] In addition, the cutoff frequency fc of the low-pass filter formed by the parasitic resistance Rp, the parasitic inductance Lp, and the junction capacitance Cb is lower than the noise frequency. Therefore, by appropriately setting the capacitance value Cb of the junction capacitance Cb of the Zener diode 30, the noise components superimposed on the input voltage Vin can be reduced.

[0053] In addition, the capacitance value Cb of the junction capacitance Cb is 130 pF or more. As a result, the low-pass filter formed of the parasitic resistance Rp calculated from the wiring distance La from the ECU 21 to the igniter 10 in the vehicle, the parasitic inductance Lp, and the junction capacitance Cb of the Zener diode 30 can sufficiently reduce the noise components of the input voltage Vin.

[0054] Furthermore, the breakdown voltage Vzd of the Zener diode 30 is higher than the voltage level of the "H" level drive signal Vdr and lower than the amplitude of noise. As a result, the input voltage Vin that exceeds the voltage range limited by the Zener diode 30 is not input to the first line LN1, so that malfunction of the IGBT 33 can be suppressed more effectively than if the noise were only attenuated by the junction capacitance Cb.

[0055] Furthermore, the control circuit 31 turns on the IGBT 33 when the voltage level of the first line LN1 becomes higher than the threshold voltage VthH, and turns off the IGBT 33 when the voltage level becomes lower than the threshold voltage VthL. As a result, the control circuit 31 prevents, for example, the protection circuit 34 and the limiting circuit 36 ​​from starting to operate when the input voltage Vin becomes a predetermined level lower than the threshold voltage VthH.

[0056] Furthermore, the limiting circuit 36 ​​limits the collector current flowing through the IGBT 33. In this way, the limiting circuit 36 ​​can limit the collector current, which increases at a predetermined gradient when the IGBT 33 is turned on, to a predetermined value.

[0057] Furthermore, when the temperature of the IGBT 33 rises, the protection circuit 34 turns off the IGBT 33. This makes it possible to prevent not only the IGBT 33 but also the igniter 10 from becoming too hot.

[0058] The above-mentioned embodiment is for the purpose of facilitating understanding of the present invention, and is not intended to limit the present invention. Furthermore, the present invention can be modified or improved without departing from the spirit of the present invention, and it goes without saying that the present invention includes equivalents thereof. [Explanation of symbols]

[0059] 10 Igniter 11 Integrated Circuits 12,13 Wire 20 Ignition system 22 Ignition coil 23 DC power supply 24 Spark plug 30 Zener Diode 31 Control circuit 34 Protection circuit 35,38 NMOS transistors 36 Limiting Circuit 37 Resistance

Claims

1. A transistor that controls the current flowing through the coil; a control circuit for controlling the on / off of the transistor based on a voltage level of a first line connected to a control electrode of the transistor; a Zener diode having a cathode connected to the first line and an anode connected to a second line connected to a ground side electrode of the transistor; a protection circuit that detects whether a temperature of the transistor is equal to or higher than a predetermined level when the voltage level of the first line becomes a predetermined level lower than a first level, and turns off the transistor when the temperature of the transistor becomes equal to or higher than the predetermined level; Equipped with the Zener diode has a predetermined capacitance so that, when a first signal for controlling the transistor and a second signal having a predetermined frequency higher than a frequency of the first signal are input to the first line, the control circuit can control on / off of the transistor based on the first signal regardless of the second signal; The control circuit turns on the transistor when the voltage level of the first line becomes higher than the first level, and turns off the transistor when the voltage level of the first line becomes lower than the second level. Integrated circuits.

2. 2. The integrated circuit of claim 1, a cutoff frequency based on the line through which the second signal is transmitted to the cathode and the predetermined capacitance is lower than the predetermined frequency; Integrated circuits.

3. 3. An integrated circuit according to claim 1 or 2, The predetermined capacitance is 130 pF or more. Integrated circuits.

4. An integrated circuit according to any one of claims 1 to 3, a breakdown voltage of the Zener diode is higher than a level of the first signal when the transistor is turned on and is lower than an amplitude of the second signal; Integrated circuits.

5. 2. The integrated circuit of claim 1, a limiting circuit for detecting whether a current of the transistor is equal to or greater than a predetermined level when the voltage level of the first line becomes a predetermined level lower than the first level, and for controlling the transistor so as to reduce the current of the transistor when the current of the transistor becomes equal to or greater than the predetermined level; Integrated circuits.

6. An integrated circuit according to any one of claims 1 to 5, the integrated circuit is an igniter; Integrated circuits.

Images