阅读说明：本技术 内燃机点火装置 (Ignition device for internal combustion engine ) 是由 北雅人 小林洋一郎 于 2019-01-08 设计创作，主要内容包括：提供一种内燃机点火装置,能够抑制专用部件等的成本,并且在从正常点火动作模式向保护动作模式转移时,能够使驱动电路的输出信号电平不会急剧变化。本发明的内燃机点火装置具备：第一差动电路,其输出第一模式时的驱动信号；以及第二差动电路,其输出第二模式时的驱动信号,所述第一差动电路和所述第二差动电路分别具备晶体管,并以供给所述驱动信号的驱动电流流过在所述第一模式和所述第二模式之间共用的所述晶体管的形式构成。(Provided is an internal combustion engine ignition device capable of preventing an output signal level of a drive circuit from changing abruptly when shifting from a normal ignition operation mode to a protection operation mode while suppressing the cost of dedicated parts and the like. An ignition device for an internal combustion engine according to the present invention includes: a first differential circuit that outputs a drive signal in a first mode; and a second differential circuit that outputs a drive signal in a second mode, wherein the first differential circuit and the second differential circuit each include a transistor, and are configured such that a drive current supplied to the drive signal flows through the transistor shared between the first mode and the second mode.)

1. An internal combustion engine ignition device that ignites an internal combustion engine by supplying a drive signal to a drive switch included in an ignition circuit, the internal combustion engine ignition device comprising:

a drive circuit that outputs the drive signal to the drive switch;

a first differential circuit that operates the drive circuit in a first mode by outputting a first differential signal to the drive circuit; and

a second differential circuit for operating the drive circuit in a second mode by outputting a second differential signal to the drive circuit,

the first differential circuit and the second differential circuit are each provided with a transistor, and are configured such that a drive current supplied with the drive signal flows through the transistor shared between the first mode and the second mode.

2. The internal combustion engine ignition device according to claim 1,

the first differential circuit is configured using a first transistor, a second transistor, and a first constant current source,

the second differential circuit is configured using the first transistor, a third transistor connected in parallel to the second transistor and the first constant current source,

the first differential circuit outputs the first differential signal by a current flowing through the first transistor, the second transistor, and the first constant current source when the driver circuit is operated in the first mode,

when the driver circuit is operated in the second mode, the second differential circuit outputs the second differential signal by a current flowing through the first transistor, the third transistor, and the first constant current source.

3. The internal combustion engine ignition device according to claim 1,

when the drive circuit is operated in the first mode, the first differential circuit outputs the first differential signal to the drive circuit for a predetermined time and then cuts off the first differential signal,

when the drive circuit is operated in the second mode, the second differential circuit forms a signal waveform of the second differential signal so that the drive switch is turned from an on state to an off state more slowly than in the first mode.

4. The internal combustion engine ignition device according to claim 2,

the internal combustion engine ignition device turns on the third transistor in a state where the first transistor and the second transistor are turned on, and then turns off the second transistor to make the drive circuit shift from the first mode to the second mode.

5. The internal combustion engine ignition device according to claim 1,

the internal combustion engine ignition device further includes a first feedback circuit that feeds back an output of the drive circuit,

the second differential circuit outputs the second differential signal by using as inputs an input signal to the second differential circuit and an output of the drive circuit fed back via the first feedback loop.

6. The internal combustion engine ignition device according to claim 1,

the ignition device for an internal combustion engine further comprises:

a power-on control circuit that controls the first differential circuit; and

an abnormal energization control circuit that controls the second differential circuit,

the abnormal power-on control circuit operates the second differential circuit to output the second differential signal when detecting that the drive switch is continuously on for a predetermined time or longer, and then outputs a signal instructing the power-on control circuit to cut off the first differential signal.

7. The internal combustion engine ignition device according to claim 1,

the drive circuit includes a first output transistor that forms a first current mirror circuit that mirrors a current flowing through the first differential circuit,

the first output transistor outputs a current having a current level corresponding to a current mirror ratio of the first current mirror circuit.

8. The internal combustion engine ignition device according to claim 1,

the internal combustion engine ignition device further includes a third differential circuit that operates the drive circuit in a third mode by outputting a third differential signal to the drive circuit,

the third differential circuit is configured using a fourth transistor, a fifth transistor, and a second constant current source,

when the driver circuit is operated in the first mode, the third differential circuit flows a first current via the fourth transistor and the second constant current source,

when the driver circuit is operated in the third mode, the third differential circuit flows the first current through the fourth transistor and the second constant current source, and flows the second current through the fifth transistor and the second constant current source.

9. The internal combustion engine ignition device of claim 8,

when the drive circuit is operated in the third mode, the third differential circuit gradually increases the ratio of the second current to the first current, thereby suppressing the output current of the drive switch to a predetermined current value or less.

10. The internal combustion engine ignition device of claim 8,

the ignition device of the internal combustion engine further includes a second feedback circuit that feeds back an output current of the drive switch,

the third differential circuit outputs the third differential signal by using as inputs an input signal to the third differential circuit and an output of the drive circuit fed back via the second feedback loop.

11. The internal combustion engine ignition device of claim 10,

the ignition device for an internal combustion engine further comprises:

a power-on control circuit that controls the first differential circuit; and

a threshold voltage generation circuit that outputs a threshold voltage to the third differential circuit,

the fourth transistor is configured to be turned on by receiving the threshold voltage,

the fifth transistor is configured to be turned on by receiving a voltage converted from an output current of the driving switch fed back through the second feedback loop,

the second constant current source keeps the sum of the first current and the second current constant.

12. The internal combustion engine ignition device of claim 8,

the drive circuit includes:

a first output transistor that forms a first current mirror circuit that mirrors a current flowing through the first differential circuit; and

a second output transistor forming a second current mirror circuit that mirrors a current flowing through the fifth transistor,

the first output transistor outputs a current having a current level corresponding to a current mirror ratio of the first current mirror circuit,

the second output transistor outputs a current having a current level corresponding to a current mirror ratio of the second current mirror circuit.

13. The internal combustion engine ignition device according to claim 1,

the first differential circuit is configured using a first transistor, a second transistor, and a first constant current source,

the second differential circuit is configured using the first transistor, a third transistor connected in parallel to the second transistor and the first constant current source,

the first differential circuit outputs the first differential signal by a current flowing through the first transistor, the second transistor, and the first constant current source when the driver circuit is operated in the first mode,

the second differential circuit outputs the second differential signal by a current flowing through the first transistor, the third transistor, and the first constant current source when the driver circuit is operated in the second mode,

the internal combustion engine ignition device further includes a first feedback circuit that feeds back an output of the drive circuit,

the second differential circuit outputs the second differential signal by using as inputs an input signal to the second differential circuit and an output of the drive circuit fed back via the first feedback loop,

the ignition device for an internal combustion engine further comprises:

a power-on control circuit that controls the first differential circuit; and

an abnormal energization control circuit that controls the second differential circuit,

the abnormal power-on control circuit outputs a signal for instructing the power-on control circuit to cut off the first differential signal after operating the second differential circuit to output the second differential signal when detecting that the drive switch is continuously in the on state for a predetermined time or longer,

the internal combustion engine ignition device further includes a third differential circuit that operates the drive circuit in a third mode by outputting a third differential signal to the drive circuit,

the third differential circuit is configured using a fourth transistor, a fifth transistor, and a second constant current source,

when the driver circuit is operated in the first mode, the third differential circuit flows a first current via the fourth transistor and the second constant current source,

when the driver circuit is operated in the third mode, the third differential circuit flows the first current via the fourth transistor and the second constant current source, and flows the second current via the fifth transistor and the second constant current source,

the ignition device for an internal combustion engine further comprises a second feedback circuit for feeding back an output current of the drive switch,

the third differential circuit outputs the third differential signal by using as inputs an input signal to the third differential circuit and an output of the drive circuit fed back via the second feedback loop,

the ignition device for an internal combustion engine further comprises:

a threshold voltage generation circuit that outputs a threshold voltage to the third differential circuit,

the fourth transistor is configured to be turned on by receiving the threshold voltage,

the fifth transistor is configured to be turned on by receiving an output of the driving switch fed back through the second feedback loop,

the second constant current source keeps the sum of the first current and the second current constant.

Technical Field

The present invention relates to an apparatus for igniting an internal combustion engine.

Background

An internal combustion engine ignition device is provided with a protection circuit for cutting off a current in order to prevent an ignition coil or a switching element of a primary current of the ignition coil from being destroyed by an overcurrent. The protection circuit generally has two modes of operation: (a) a soft-off mode in which the primary-side current of the coil is slowly reduced so that an abnormally high voltage is not generated on the secondary side of the ignition coil due to a cutoff operation after the primary-side current of the coil is electrified for a long time; (b) a current limiting mode which controls the switching element to reduce the coil primary side current.

Patent document 1 listed below discloses a technique related to the soft-off mode. In the technique described in this document, when the long energization time equal to or longer than a predetermined time is detected by the long energization detection circuit while the switching element is in the on state, the soft-off mode is realized by outputting a discharge current from the soft-off capacitor and gradually switching the switching element from the on state to the off state.

Disclosure of Invention

Problems to be solved by the invention

When the operation of the protection circuit is shifted from the normal ignition operation to the soft-off mode, the current limiting mode, or the like, it is preferable that the on state of the switching element be slowly changed so as to cause unexpected ignition. For example, if the switching element is an IGBT, the gate voltage needs to be made to transition slowly.

The technique described in patent document 1 uses a capacitive element for generating a waveform for soft-off. When the normal ignition operation is shifted to the soft-off operation, it is considered that the capacitor element absorbs the switching noise and suppresses a rapid change in the gate voltage of the switching element (IGBT). However, the following problems are considered: (a) a capacitor element dedicated for soft-off is required, which increases the cost, (b) the soft-off waveform is determined by the value of the capacitor element, the IGBT gate input resistance value, and the gate input capacitance value, which results in a large load dependence, and adjustment cost therefor is required.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an internal combustion engine ignition device capable of preventing an output signal level of a drive circuit from changing abruptly when a normal ignition operation mode is shifted to a protection operation mode while suppressing the cost of dedicated parts and the like.

Means for solving the problems

An ignition device for an internal combustion engine according to the present invention includes: a first differential circuit that outputs a drive signal in a first mode; and a second differential circuit that outputs a drive signal in a second mode, wherein the first differential circuit and the second differential circuit each include a transistor, and are configured such that a drive current supplied to the drive signal flows through the transistor shared between the first mode and the second mode.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the internal combustion engine ignition device of the present invention, when switching from the normal operation mode to the protection operation mode, the output signal level of the drive signal can be slowly switched. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

Drawings

Fig. 1 is a configuration diagram of an internal combustion engine ignition device according to embodiment 1.

Fig. 2 is a timing chart for explaining the operation of the ignition control apparatus 100.

Fig. 3A is a circuit diagram of the differential circuit 51, the differential circuit 52, and the drive circuit 61.

Fig. 3B is a diagram illustrating a smooth transition from the normal ignition mode to the soft-off mode.

Fig. 4 is a configuration diagram of an internal combustion engine ignition device according to embodiment 2.

Fig. 5 is a timing chart for explaining the operation of the ignition control apparatus 100 in embodiment 2.

Fig. 6A is a circuit diagram of the differential circuit 51, the differential circuit 53, and the drive circuit 61.

Fig. 6B is a diagram illustrating smooth transition from the normal ignition mode to the current limiting mode.

Fig. 7 is a configuration diagram of an internal combustion engine ignition device according to embodiment 3.

Fig. 8 is a timing chart for explaining the operation of the ignition control apparatus 100 according to embodiment 3.

FIG. 9A is a circuit diagram of the differential circuits 51 to 53 and the drive circuit 61.

Fig. 9B is a diagram illustrating the current flow when the normal ignition mode is shifted to the current limiting mode and then further shifted to the soft off mode.

Detailed Description

< embodiment 1>

Fig. 1 is a configuration diagram of an internal combustion engine ignition device according to embodiment 1 of the present invention. The internal combustion engine ignition device includes an ECU (Electronic Control Unit) 21, an ignition Control device 100, a battery 11, a switching element 71, an ignition coil 74 (a primary coil 72, a secondary coil 73), and an ignition plug 75. The ignition control device 100 further includes an input buffer circuit 31, an energization control circuit 41, an abnormal energization detection circuit 42, a differential circuit 51, a differential circuit 52, and a drive circuit 61.

The switching element 71 outputs a drive signal to the ignition coil 74 to ignite the internal combustion engine. The switching element 71 is driven by inputting a drive signal output from the ignition control device 100 to the gate terminal.

The ECU21 instructs the ignition control device 100 to ignite the internal combustion engine. The energization control circuit 41 is a circuit that outputs an energization control signal to the switching element 71 in the normal ignition mode. The abnormal energization detecting circuit 42 detects that the switching element 71 is energized longer than in the normal operation (abnormal energization). When abnormal energization is detected, the abnormal energization detecting circuit 42 notifies the energization controlling circuit 41 of the abnormal energization. The energization control circuit 41 stops the energization control signal, and thereafter the abnormal energization detection circuit 42 outputs the energization control signal to the switching element 71, thereby implementing the soft-off mode.

The differential circuit 51 and the differential circuit 52 are circuits that amplify a difference between two input signals. The differential circuit 51 outputs a drive signal in the normal ignition mode, and the differential circuit 52 outputs a drive signal in the soft-off mode. The differential circuit 51 amplifies the difference between the two energization control signals received from the energization control circuit 41. The differential circuit 52 amplifies a difference between the energization control signal received from the abnormal energization detecting circuit 42 and a signal fed back from the output of the drive circuit 61. Specific examples of the differential circuits 51 and 52 and the drive circuit 61 will be described later.

Fig. 2 is a timing chart for explaining the operation of the ignition control apparatus 100. Here, signal waveforms in the main signal lines are shown. Hereinafter, the operations in the normal ignition mode and the soft-off mode will be described with reference to signal waveforms in fig. 2.

In the normal ignition mode, an energization control signal is input from the ECU21 via the signal line 1. The energization control signal is output to the switching element 71 as a drive signal through the input buffer circuit 31, the energization control circuit 41, the differential circuit 51, the drive circuit 61, and the signal line 9. The switching element 71 operates in accordance with the drive signal.

In the differential circuit 51, a (+) terminal is connected to the signal line 4, and a (-) terminal is connected to the signal line 5. When the signal line 4 is a high-level signal and the signal line 5 is a low-level signal, the signal line 9 output from the drive circuit 61 is at a high level, and the switching element 71 is turned on. When the signal line 4 is a low-level signal and the signal line 5 is a high-level signal, the signal line 9 is at a low level and the switching element 71 is turned off. When the switching element 71 is turned on, a current flows to the primary coil 72 of the ignition coil 74. When the switching element 71 is turned off, a primary voltage is generated in the primary coil 72, and a secondary voltage corresponding to the turn ratio is generated in the secondary coil 73 by the mutual induction. The secondary voltage is supplied to the ignition plug 75, whereby the internal combustion engine is ignited.

The abnormal energization detecting circuit 42 detects an energization time of the switching element 71 as long as a predetermined time or longer (abnormal energization). When the abnormal energization is detected by the abnormal energization detecting circuit 42, the ignition control apparatus 100 shifts from the normal ignition mode to the soft-off mode. In the soft-off mode, the drive signal to the gate terminal of the switching element 71 is slowly changed from the high level to the low level. This causes the switching element 71 to gradually transition from the on state to the off state.

Before the transition to the soft-off mode, the switching element 71 is in the energized state, so that the signal line 4 is at a high level, the signal line 5 is at a low level, and the signal line 6 is at a low level, and a high-level signal is output from the signal line 9. When abnormal energization is detected, the abnormal energization detecting circuit 42 outputs a signal waveform in the soft-off mode from the signal line 6. The signal waveform in the soft-off mode is slowly changed from a high level to a low level.

The soft off signal from the signal line 6 is input to the (+) terminal of the differential circuit 52. The signal line 9 (output of the drive circuit 61) is negatively fed back to the (-) terminal of the differential circuit 52. That is, a waveform following the waveform of the signal line 6 is fed back to the differential circuit 52 via the signal line 9.

The energization control circuit 41 receives information of detection of abnormal energization from the abnormal energization detecting circuit 42 via the signal line 3. Upon receiving the signal, the energization control circuit 41 changes the signal line 4 from a high level to a low level, and keeps the signal line 5 at the low level. By setting the timing at which the signal line 4 changes from the high level to the low level after the signal line 6 changes to the high level (i.e., shifts to the soft-off mode), the signal line 9 remains at the high level. Thus, when the normal ignition mode is shifted to the soft-off mode, the driving signal level does not change rapidly, and the operation mode is smoothly shifted.

Fig. 3A is a circuit diagram of the differential circuit 51, the differential circuit 52, and the drive circuit 61. Next, the configuration of these circuits will be described with reference to fig. 3A.

The differential circuit 51 includes a constant current source I1, NMOS (MN1, MN2), and PMOS (MP20, MP 21). The differential circuit 52 is composed of a constant current source I1, NMOS (MN3, MN4), and PMOS (MP20, MP 21). The constant current source I1 and the PMOS (MP20, MP21) are shared between the differential circuit 51 and the differential circuit 52.

The drive circuit 61 is constituted by MP23 and MN 12. The output current from MP23 is obtained by mirroring the output current on the (+) terminal side of the differential circuit based on the current mirror ratio from MP21 to MP 23. The output current from MN12 is obtained by mirroring the output current on the differential circuit (-) terminal side based on the current mirror ratio from MP20 to MP22 and the current mirror ratio from MN10 to MN 12. The output of the drive circuit 61 (signal line 9) is negatively fed back to the (-) terminal of the differential circuit 52.

Fig. 3B is a diagram illustrating a smooth transition from the normal ignition mode to the soft-off mode. The thick dashed line of fig. 3B indicates that the output of the driver circuit 61 is formed by a current mirror between MP21 and MP 23. The dotted line of fig. 3B represents the current path in the normal ignition mode. The one-dot chain line of fig. 3B indicates a current path in the soft-off mode.

Before the transition to the soft-off mode, the signal line 4 to the (+) terminal of the differential circuit 51 is at a high level, the signal line 6 to the (+) terminal of the differential circuit 52 is at a low level, MN1 is on, and MN3 is off. The current flowing in MP21 flows through MN 1.

When shifting to the soft-off mode, first the signal line 6 becomes high level, so MN1 and MN3 become on-state, but the current flowing through MP21 does not change by the action of the constant current source I1. Then, MN1 turns off, and MN3 becomes an on state. The current flowing in MP21 flows through MN 3. During this period, the current flowing in the MP21 also does not change by the action of the constant current source I1. Since the output of the drive circuit 61 is formed by a current mirror between MP21 and MP23, if the current flowing through MP21 does not change, the current flowing through MP23 does not change either. Thus, the mode can be smoothly switched without rapidly changing the output current of the drive circuit 61 during the transition from the normal ignition mode to the soft-off mode.

< embodiment mode 1: summary >

When the internal combustion engine ignition device according to embodiment 1 is switched from the normal ignition mode to the soft-off mode, a current flows through the MP21 common to both modes. Since the driving current is generated by the current mirror between MP21 and MP23, the driving current does not change abruptly at the time of switching the mode. This enables smooth switching of the operation mode.

The internal combustion engine ignition device according to embodiment 1 feeds back the output of the drive circuit 61 as the negative terminal input of the differential circuit 52. This enables the output of the drive circuit 61 to be formed following the input signal to the differential circuit 52 in the soft-off mode. That is, the drive signal following the input signal to the differential circuit 52 can be output without depending on the load of the drive circuit 61.

In embodiment 1, since the conditions of the input terminals of the switching elements 71 are various, it is necessary to optimize the load driving capability of the driving circuit 61. In embodiment 1, since the drive signal is generated by current-mirroring the current flowing through the differential circuit 51 or the differential circuit 52, the drive circuit 61 can be optimized in accordance with the current-mirror ratio.

< embodiment 2>

In embodiment 1, a configuration example in which the normal ignition mode and the soft-off mode are smoothly switched is described. In embodiment 2 of the present invention, a configuration example in which the normal ignition mode and the limiter mode are smoothly switched will be described. The current limiting mode is an operation of lowering the gate voltage of the switching element 71 to balance the current flowing through the primary coil 72 so as not to exceed a set current limiting value.

Fig. 4 is a configuration diagram of an internal combustion engine ignition device according to embodiment 2. In fig. 4, a threshold voltage generation circuit 43 is disposed instead of the abnormal energization detection circuit 42 described in embodiment 1, and a differential circuit 53 is disposed instead of the differential circuit 52. The threshold voltage generation circuit 43 outputs a threshold voltage to the (+) terminal of the differential circuit 53 without depending on the energization control signal output from the ECU 21. The result of detecting the current flowing through the primary coil 72 by the detection resistor 76 is input to the (-) terminal of the differential circuit 53.

Fig. 5 is a timing chart for explaining the operation of the ignition control device 100 in embodiment 2. Next, the operation in the current limiter mode will be described with reference to signal waveforms in fig. 5. The operation in the normal ignition mode is the same as in embodiment 1.

The current limit mode is active during the conduction period of the primary coil 72, and thus the normal ignition signal is high. That is, the signal line 4 is at a high level, the signal line 5 is at a low level, and the signal line 9 is at a high level. When the current flowing through the primary coil 72 increases, the voltage of the signal line 10 rises.

The differential circuit 53 gradually increases the output current as the voltage of the signal line 10 approaches the voltage of the signal line 7, which is the threshold voltage. Thereby, the output of the drive circuit 61 is gradually lowered from the high level. When the output of the drive circuit 61 decreases, the gate voltage of the switching element 71 decreases, and thus the current flowing through the primary coil 72 decreases. The feedback loop balances the signals and limits the current flowing through the primary winding 72 so that it does not exceed a threshold voltage.

Fig. 6A is a circuit diagram of the differential circuit 51, the differential circuit 53, and the drive circuit 61. The differential circuit 53 includes a constant current source I2, NMOS (MN5, MN6), and PMOS (MP 20). The PMOS (MP20) is shared between the differential circuit 51 and the differential circuit 53. The (+) terminal of the differential circuit 53 is the gate terminal of MN5, and the threshold voltage is input via the signal line 7. The (-) terminal side of the differential circuit 53 is the gate terminal of MN6, and the result of detecting the current flowing through the primary coil 72 is input via the signal line 10.

Fig. 6B is a diagram illustrating smooth transition from the normal ignition mode to the current limiting mode. The thick dashed line of fig. 6B indicates that the output of the driver circuit 61 is formed by a current mirror between MP21 and MP 23. The dotted line of fig. 6B indicates the current path in the normal ignition mode. The two-dot chain line of fig. 6B indicates a current path in the current limiting mode.

In the normal ignition mode, the (+) terminal of the differential circuit 51 is at a high level, and a current flows to the MP21 side. In the differential circuit 53, since the value of the signal line 10 as the detection voltage is smaller than the value of the signal line 7 as the threshold voltage, a current flows to the MN5 side, and no current flows through a current path from MN6 to MP 20. In the drive circuit 61, a current flows only on the MP23 side, and a current does not flow on the MN12 side.

When the current of the primary coil 72 increases and the detection voltage rises, the voltage of the signal line 10 rises. As the voltage of the signal line 10 approaches the threshold voltage (signal line 7), the current flowing through MN5 decreases, and the current flowing in the current path from MN6 to MP20 increases. Then, a current determined by the current mirror ratio of MP20 to MP22 and the current mirror ratio of MN10 to MN12 flows to the MN12 side. Thereby, the output (signal line 9) level drops. When the output (signal line 9) falls, the gate voltage of the switching element 71 falls, and therefore the current of the primary coil 72 decreases, and the detection voltage (signal line 10) falls. The feedback loop balances the signals, and limits the current of the primary coil 72.

The current of MN6 increases due to the rise of the detection voltage, but by slowing the change in the current of MN6, the current flowing through MN12 also changes slowly, so the output (signal line 9) also changes slowly. Therefore, the transition from the normal ignition mode to the current limiter mode can be smoothly performed.

< embodiment mode 2: summary >

The internal combustion engine ignition device according to embodiment 2 gradually increases the current flowing through MN6 when switching from the normal ignition mode to the current limiter mode. The current through MN12 gradually increased due to the current mirror between MP20 and MP22 and the current mirror between MN10 and MN 12. As the current flowing through MN12 gradually increases, the output of the drive circuit 61 gradually decreases. Thus, the drive current does not change rapidly at the time of switching the mode, and the mode can be switched smoothly.

The internal combustion engine ignition device according to embodiment 2 feeds back the output of the switching element 71 (specifically, the current detection result of the detection resistor 76) to the negative input terminal of the differential circuit 53. Thus, as the current flowing through the primary coil 72 increases beyond the threshold voltage, the current flowing through MN12 gradually increases, and the drive current is adjusted to be in balance with the threshold voltage. Therefore, the current limiting mode can be smoothly implemented.

< embodiment 3>

Fig. 7 is a configuration diagram of an internal combustion engine ignition device according to embodiment 3 of the present invention. In embodiment 3, a configuration example in which embodiments 1 to 2 are combined will be described. The same configurations as those in embodiments 1 to 2 will be omitted as appropriate. The drive signals from the differential circuit 51, the differential circuit 52, and the differential circuit 53 are input to the drive circuit 61 in parallel.

Fig. 8 is a timing chart for explaining the operation of the ignition control device 100 according to embodiment 3. In embodiment 3, after the transition from the normal ignition mode to the current limiter mode, if the abnormal energization is continued, the transition is further made to the soft off mode. The operation procedure of each mode is the same as that of embodiments 1 to 2. When shifting to the soft-off mode in the current limiting mode, the output (signal line 9) changes slowly from the high level to the low level. As a result, the gate voltage of the switching element 71 gradually decreases, and the current of the primary coil 72 gradually decreases. Along with this, the voltage of the detection voltage (signal line 10) also gradually decreases, and thus the current limiting mode ends. The soft-off mode then ends.

Fig. 9A is a circuit diagram of the differential circuits 51 to 53 and the drive circuit 61. The configuration of each circuit is the same as that described in embodiments 1 to 2.

Fig. 9B is a diagram illustrating the flow of current when the normal ignition mode is shifted to the current limiting mode, and then the soft off mode is further shifted. In the normal ignition mode, the (+) terminal (signal line 4) of the differential circuit 51 is at a high level, and the driver circuit 61 outputs a current from the MP 23. When shifting to the current limiting mode, a current corresponding to the current value flowing from MN6 to MP20 flows to MN12, depressing the output (signal line 9) level. When shifting to the soft-off mode in this state, the current paths of the differential circuit 51 and the differential circuit 52 are switched from the MN1 side to the MN3 side. Since the current flowing through MP23 does not change, the output (signal line 9) does not change. When the signal level of the signal line 9 slowly falls following the soft-off signal waveform, the detection voltage also falls, and therefore the current flowing from MN6 to MP20 decreases, and the current flowing to MN12 also decreases. Finally, the current limiting mode is not implemented, and then the soft-off mode is ended.

< modification of the present invention >

The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above embodiments are described in detail to explain the present invention easily and understandably, and are not necessarily limited to all configurations described. Further, a part of the configuration of one embodiment may be replaced with the configuration of another embodiment, or the configuration of another embodiment may be added to the configuration of one embodiment. Further, a part of the configuration of each embodiment may be added, deleted, or replaced with another configuration.

Description of the symbols

1-10: signal line

11: battery with a battery cell

21：ECU

31: input buffer circuit

41: power-on control circuit

42: abnormal electrification detection circuit

43: threshold voltage generation circuit

51-53: differential circuit

61: driving circuit

71: switching element

72: primary side coil

73: secondary side coil

74: ignition coil

75: spark plug

76: detection resistor

I1-I2: constant current source

MN 1-6, 10, 12: NMOS transistor

MP 20-23: PMOS transistor

100: an ignition control device.