Igniter circuit having adjustable over-dwell time

Abstract

To provide ignition systems and methods for sensing a voltage of a battery and adjusting the duration of an over-dwell time automatically.SOLUTION: An ignition system may include an igniter circuit to control the current in a coil supplied by a battery based on an input signal from an engine control unit. To prevent overheating, the igniter circuit may be configured to shut down the current in the coil when the input signal is held high for an over-dwell period. The disclosed igniter circuit is configured with circuitry to automatically adjust the over-dwell period used based on a condition of the battery to prevent overheating without prematurely shutting down. The automatic adjustment includes indirectly monitoring the battery condition based on a current or voltage of a switching device coupled to the coil.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 18 / 338,278, filed June 20, 2023.

[0002] The present disclosure relates to power electronics for switching, and more particularly, to igniter circuits for automotive applications. [Background technology]

[0003] The automotive ignition system may include a battery, an induction coil, and an igniter circuit. The igniter circuit may include a switching device in series with the battery and the induction coil. When the switching device is shorted, current may flow from the battery through the induction coil. After a charging period, the current in the induction coil may be abruptly stopped by opening the switching device. The abrupt cessation of the current may cause a large voltage across the coil, which may be used to generate a spark for ignition. The igniter circuit may monitor the charging period to ensure that it does not exceed a maximum limit (i.e., an overdwell time) that may cause overheating and / or damage to the ignition system. Summary of the Invention

[0004] After the dwell time (i.e., dwell period), the current conducted by the coil in the ignition system may be gradually reduced by the igniter circuit to prevent damage (e.g., overheating). This disclosure describes ignition systems and methods for sensing battery voltage and automatically adjusting the duration of the dwell time.

[0005] In some aspects, the technology described herein relates to a method for shutting down current in an ignition system, the method including receiving an input signal to configure a switching device coupled in series with a coil to an on state, starting a timer, sensing a current in the coil after the switching device is configured to the on state, measuring a rise time corresponding to a time at which the current meets a criterion based on the timer, calculating a soft shutdown delay based on the rise time, waiting for the soft shutdown delay, and initiating a soft shutdown to reduce (i.e., shut down) the current in the coil after the soft shutdown delay.

[0006] In some aspects, the technology described herein relates to an ignition system including a coil coupled on a first side to a battery; an igniter circuit including a switching device coupled to a second side of the coil, a current controller configured to control a current state of the switching device, and an overdue circuit configured to measure a rise time of a current conducted by the switching device after being configured to an on state and to trigger the current controller to initiate a soft shutdown of the current after a soft shutdown delay based on the rise time of the current.

[0007] In some aspects, the technology described herein relates to a method for shutting down current in an ignition system, the method including receiving an input signal to configure a switching device coupled in series with a coil to an on state, delaying the input signal by a delay period before configuring the switching device to the on state and holding the switching device in an off state during the delay period, sensing a voltage of the switching device during the delay period, calculating an overdwell time based on the voltage of the switching device, and initiating a soft shutdown to shut down the current after the overdwell time based on the voltage of the switching device.

[0008] In some aspects, the technology described herein relates to an ignition system including a coil coupled to a battery on a first side; and an igniter circuit including a switching device coupled to a second side of the coil, a current controller configured to control a current state of the switching device, an overdwell circuit configured to delay an input signal coupled to a control terminal of the switching device such that the current state of the switching device is held in an off state for a delay period before being configured to an on state, sense a voltage of the switching device during the delay period, and trigger the current controller to initiate a soft shutdown of the current state after a overdwell time based on the voltage of the switching device during the delay period.

[0009] The foregoing illustrative summary, as well as other illustrative objects and / or advantages of the present disclosure, and the manner in which they are accomplished, are further described in the following detailed description and its accompanying drawings. [Brief description of the drawings]

[0010] [Figure 1] 1 includes a graph illustrating the power dissipated by a switching device in an ignition system for a battery under high and low voltage conditions, in accordance with a possible implementation of the present disclosure. [Diagram 2] FIG. 1 is a schematic block diagram of an ignition system according to a possible implementation of the present disclosure. [Diagram 3] 1 is a method for shutting down current in an ignition system according to a first possible implementation of the present disclosure. [Figure 4] 4 includes graphs illustrating possible signals in an ignition system configured to perform the method of FIG. 3. [Diagram 5] FIG. 1 is a schematic block diagram of an ignition system according to a first possible implementation form of the present disclosure. [Figure 6] 1 is a method for shutting down electrical current in an ignition system according to a second possible implementation of the present disclosure. [Figure 7]7 includes graphs illustrating possible signals in an ignition system configured to perform the method of FIG. 6. [Figure 8] FIG. 1 is a schematic block diagram of an ignition system according to a second possible implementation form of the present disclosure.

[0011] The elements of the drawings are not necessarily to scale relative to each other. Like reference numbers indicate corresponding parts throughout the several views. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An igniter circuit in an automotive system can monitor the duration of charging of the induction coil to ensure that it does not exceed a maximum limit (i.e., dwell time) that could cause overheating and / or damage to the ignition system. For example, if a switching device is controlled by an input signal to conduct current at the end of the dwell time, the igniter circuit can be configured to initiate a soft shutdown to reduce the current.

[0013] Soft shutdown (i.e., SSD) may include controlling a switching device in series with the battery and coil to gradually increase its resistance from a short circuit state (i.e., ON state) to an open circuit state (i.e., OFF state) over an SSD period to reduce the current in the induction coil. The gradual reduction in coil current can limit the voltage across the induction coil caused by back electromotive force (EMF), and limiting the voltage can prevent undesired sparks in ignition systems. One technical problem with this fixed dwell time approach is that because battery voltages can vary over a wide range, a dwell time suitable for a lower battery voltage may be too long for a higher battery voltage, and vice versa.

[0014] 1 includes a graph showing the power dissipated by a switching device (e.g., an insulated gate bipolar transistor (IGBT)) in an ignition system. The graph shows the difference that exists between battery conditions.

[0015] A first graph 110 in Fig. 1 illustrates an input (IN) signal for controlling a switching device of an ignition system. A first level (e.g., low) of the input signal can correspond to a current state in which the switching device is off (i.e., not conducting), and a second level (e.g., high) of the input signal can correspond to a current state in which the switching device is on (i.e., conducting). As shown, at the end of the dwell time (i.e., dwell period 111), the input signal is high. Thus, the current controller can intervene to discharge the coil.

[0016] The coil is in series with the switching device such that the collector current of the switching device corresponds to the current in the coil. In particular, the coil can be coupled between a battery and a terminal of the switching device. For example, a first side (i.e., the first terminal) of the coil can be coupled to the battery and a second side (i.e., the second terminal) of the coil can be coupled to the collector terminal of the IGBT. The battery can have a battery voltage that can charge (i.e., increase) the coil current while the IGBT is conducting, and the coil current can increase until it reaches a current limit (ICL) that corresponds to the conductivity of the switching device.

[0017] 1 includes a second graph 120 illustrating the current conducted by the switching device. As shown, at a first time 101 when an input signal sets the switching device on, the collector current (i.e., the current in the coil) begins to increase as the coil is charged by the battery. As shown, the rate at which the collector current (i.e., the coil current) increases depends on the voltage state of the battery. A high voltage state corresponds to a higher battery voltage than a low voltage state. In a high voltage state 121, the current increases to its maximum value (i.e., current limit (ICL)) faster than in a low voltage state 122.

[0018] If the input signal (in) is still high at the end of the overdwell time (i.e., overdwell period 111), soft shutdown can reduce the current. As shown in FIG. 1, at a second time 102, the collector current (i.e., the current in the coil) is reduced from its maximum value according to a soft shutdown profile. In practice, a current controller triggered for soft shutdown can, for example, linearly reduce the current limit of the switching device over the soft shutdown period 103 until the collector current is near zero.

[0019] 1 includes a third graph 130 corresponding to the power dissipated in a switching device (e.g., an IGBT) in a high-voltage state 131 (i.e., a relatively high battery voltage) and a low-voltage state 132 (i.e., a relatively low battery voltage). The power dissipated by the switching device in the high-voltage state is higher than the power dissipated by the switching device in the low-voltage state because the current through the switching device in the high-voltage state reaches its current limit (ICL) faster than in the low-voltage state. Therefore, a shorter overdwell time (i.e., overdwell period 111) may be necessary in the high-voltage state 131 to prevent overheating due to higher power dissipation.

[0020] Using a fixed (shorter) dwell time to trigger the SSD in both high and low voltage conditions can be problematic because it may be too short for the low voltage condition. In the low voltage condition, the current through the switching device takes longer to reach its limit. As a result, a soft shutdown may be triggered prematurely. Therefore, it may be desirable to control the dwell time (i.e., dwell period) based on the voltage of the battery (i.e., battery voltage). In particular, a relatively high battery voltage may correspond to a shorter dwell period than a relatively low battery voltage.

[0021] Controlling the dwell time based on the battery voltage can be problematic when the size and complexity of the igniter circuit is limited. The battery voltage may be in a higher voltage domain than that used by the igniter circuit. Thus, coupling the battery to the igniter circuit may require additional circuitry required to receive the higher voltage domain and transition to the voltage domain used by the igniter circuit. Furthermore, the timing circuitry required to handle typical dwell periods (e.g., milliseconds) may require a device (or devices) that is unreasonably large for a size-constrained igniter circuit. For example, the timing circuitry may require a capacitor on the order of microfarads (e.g., C=0.1 μF), which is too large for some implementations.

[0022] The present disclosure describes an igniter circuit to address at least the above-mentioned technical problems. The igniter circuit has an dwell time that is controlled based on the voltage of the battery without requiring a direct connection to the battery (i.e., without requiring terminals for the battery). The disclosed igniter circuit includes an adjustable dwell time feature with a small and low complexity circuit so that the igniter circuit can be made smaller and more cost-effectively (e.g., as an integrated circuit) compared to other dwell timer approaches.

[0023] 2 is a schematic block diagram of an ignition system 200 according to a possible implementation of the present disclosure. As shown, a coil 201 is coupled (e.g., directly connected) between a battery and a terminal of an igniter circuit 210.

[0024] The igniter circuit 210 may be implemented as an integrated circuit having at least an input terminal (IN), a collector terminal (COLLECT), and a ground terminal (GND). The igniter circuit 210 may not require a battery terminal or other circuitry to directly monitor the battery voltage (VB) of the battery 220. The igniter circuit 210 may include a switching device 211 (e.g., an IGBT) coupled between the coil 201 and ground 202. For example, the switching device may be an IGBT coupled to the coil 201 at a collector terminal, to a current sense resistor 212 at an emitter terminal, and to an input via a gate resistor 215 at a gate terminal. An input signal 231 to the igniter circuit 210 may be from an engine control unit 230 (ECU). The ignition system 200 may further include an ignition coil 240 magnetically coupled to the coil 201 in a transformer, which may step up the voltage of the coil 201 to a voltage sufficient to generate a spark at the gap 250.

[0025] The igniter circuit 210 may include a current controller 213 configured to control the current of the switching device 211 in a soft shutdown. For example, the current controller 213 may be configured to output an SSD signal when triggered to gradually reduce the current limit of the switching device 211 so that it gradually changes from an ON state to an OFF state. In other words, the current controller 213 may be configured to output a voltage that decreases linearly at an SSD rate over an SSD period. The SSD rate and SSD period (i.e., the SSD profile) may be preset to prevent sufficient voltage to generate a spark from being induced in the coil 201 during shutdown.

[0026] The igniter circuit 210 further includes an overdwell circuit 214. The overdwell circuit 214 may be configured to time the time that the input signal (IN) is held at an on level (e.g., high level). If the input signal is still on after the overdwell time (i.e., overdwell period) has expired, the overdwell circuit 214 can trigger the current controller 213 to initiate a soft shutdown.

[0027] Instead of directly sensing the voltage of the battery 220 itself, the igniter circuit 210 can adjust the dwell time (i.e., dwell period 111) based on sensing (i.e., measuring) the signal of the switching device 211. In a first implementation, the sensed signal is the current of the switching device 211, and in a second implementation, the sensed signal is the voltage of the switching device 211.

[0028] 3 is a method for shutting down a current in an ignition system according to a first possible implementation of the present disclosure. The method 300 includes receiving 310 an input signal (i.e., in an igniter circuit) to configure a switching device (e.g., an IGBT) to an on state. The switching device is coupled in series with a coil (e.g., a primary coil), such that in the on state, the current in the switching device may be equal to the current in the coil.

[0029] The method 300 further includes starting 320 a timer. For example, the timer may be started simultaneously with the input signal transitioning to a level (e.g., high) that turns on the switching device. The method 300 further includes sensing 330 a current of the switching device after the switching device is configured to an on state. For example, a collector current of an IGBT in series with a coil may be sensed as the current in the coil when the IGBT is conducting (e.g., in an on state). The method 300 further includes measuring 340 a rise time that corresponds to the time required for the current to meet a criterion. For example, starting from an initial time (T0) when the IGBT is turned on, the collector current may be sensed and compared to a threshold current (i.e., ICT). Then, once the collector current is equal to or greater than the threshold, a rise time may be determined based on the time (T1) of the (running) timer.

[0030] Method 300 further includes calculating 350 a soft shutdown delay (i.e., SSD delay) based on the rise time (e.g., T1-T0). The SSD delay may be an amount of time to wait before triggering a soft shutdown (if necessary). Thus, method 300 further includes waiting 360 for the SSD delay (e.g., based on a timer).

[0031] After waiting the SSD delay, the method 300 may include determining 365 whether a soft shutdown is required. For example, if the input signal (IN) is at an on level (e.g., high), a soft shutdown of the current may be required. If this is the case (i.e., yes), the method 300 includes initiating 370 a soft shutdown to shut down the current in the ignition system (i.e., the coil and the switching devices). If not, the method 300 may reset 375 until another input signal occurs to turn on the switching devices, at which point the method 300 may be repeated.

[0032] FIG. 4 includes graphs illustrating possible signals in an ignition system configured to perform the method of FIG. 3. A first graph 410 illustrates an input signal (e.g., at a gate of a switching device) transitioning to ON (i.e., high) at an initial time (T0). At this level, the input signal can configure the switching device to an ON state. A second graph 420 illustrates a current (i.e., collector current) of the switching device. As shown, the current begins to increase when the ON state begins at the initial time (T0). At a first time (T1), the current reaches a threshold level (ICT). A rise time 411 can be determined as the difference between the first time and the initial time (i.e., rise time=T1-T0). A soft shutdown delay (SSD delay 412) can be calculated based on the rise time 411. For example, the SSD delay 412 can be the rise time 411 multiplied by a fixed value (i.e., SSD delay=(rise time)···(A)). As a result, a relatively short rise time may result in a shorter SSD delay compared to the longer SSD delay of a relatively long rise time (i.e., short rise time<long rise time). The shorter SSD delay may reduce the power dissipated over the dwell period 413.

[0033] 4, the dwell period 413 may be the sum of the rise time 411 and the SSD delay 412. At a second time (T2) after the SSD delay 412, a soft shutdown 415 occurs to reduce the current in the switching device (i.e., the current in the coil). The soft shutdown 415 may be triggered by the input signal (IN) going to an on state (i.e., high) at the end of the SSD delay 412 (i.e., at the end of the dwell period 413).

[0034] 5 is a schematic block diagram of an ignition system according to a first possible implementation of the present disclosure. The ignition system 500 includes a coil 560 coupled on a first side to a battery voltage 561 (VB) of a battery and coupled on a second side to a switching device 550 (e.g., an IGBT) of an igniter circuit 530. The switching device 550 can receive an input signal at a gate terminal that configures the switching device to an on state such that the switching device conducts a current (I) between a collector terminal and an emitter terminal. The current (I) may be sensed to adjust the dwell period based on the battery voltage 561 instead of directly sensing the battery voltage.

[0035] The igniter circuit 530 includes an overdwell circuit 531 configured to measure the rise time of the current (I) from an initial time (T0) when the current is initiated to a first time (T1) when the current meets a criterion. The overdwell circuit 531 is further configured to wait for a soft-shutdown delay to expire at a second time (T2) before triggering a soft-shutdown of the current. For these time measurements, the overdwell circuit 531 includes (i) a first timer implemented using a clock generator 501 and a first counter 511, and (ii) a second timer implemented using a clock generator 501 and a second counter 521. The first counter 511 and the second counter 521 may be initialized (e.g., reset, started) by an enable signal 533 based on an input signal 532. For example, at the initial time (T0), the first counter 511 and the second counter 521 may be set to 0.

[0036] The overdwell circuit 531 may further include a current detector 509. In a possible implementation, the current detector 509 may be configured to compare the current (I) with a threshold (ICT) and output a signal to a first counter 511 when the current is equal to or greater than the threshold (ICT). The signal from the current detector 509 may trigger the first counter 511 to output a rise time count 510 corresponding to the number of cycles counted when the current is equal to or greater than the threshold.

[0037] The dwell circuit 531 may further include a multiplier 513. The multiplier 513 may be configured to multiply the rise time count 510 by a fixed value (A) to generate a delay count 520 corresponding to the SSD delay. In other words, the delay count 520 may be based on the rise time count. The fixed value (A) may be based on a target over the dwell period (e.g., 10 milliseconds) for the switching device 550. The delay count 520 may be coupled to a second counter 521, which may be configured to output an SSD trigger signal 522 when the count of the second counter 521 reaches the delay count 520.

[0038] The igniter circuit 530 further includes a current controller 540 coupled to a gate of the switching device to control a current state of the switching device. The current controller 540 may receive an SSD trigger signal 522 from the second counter 521 at a second time (T2) after the SSD delay. The SSD trigger signal 522 may trigger the current controller 540 to initiate a soft shutdown to reduce the current (I) in the switching device (i.e., the coil).

[0039] 6 is a method for shutting down a current in an ignition system according to a second possible implementation of the present disclosure. The method 600 includes receiving 610 an input signal for turning on a switching device of an igniter circuit and starting 620 (e.g., starting simultaneously) a timer. The method 600 further includes delaying 630 the input signal so that the switching device remains off. In other words, the input signal for configuring the switching device to an on state is delayed by a delay period so that the switching device is held in an off state for the delay period. In other words, the input signal is delayed to hold the switching device in an off state for the delay period before configuring the switching device to an on state. While the switching device is in an off state, no current flows and the voltage at the collector terminal of the switching device may correspond to (e.g., be equal to) the voltage of the battery (VB). Thus, the method 600 includes sensing 640 a collector voltage of the switching device and adjusting the overdwell period based on the voltage of the switching device. In particular, the method 600 includes calculating 650 an overdwell period based on the collector voltage. The method 600 further includes waiting 660 the overdwell time before determining 665 whether a soft shutdown is required. For example, if the input signal (IN) is at an on level (e.g., high), a soft shutdown of the current may be required. If this is the case (i.e., yes), the method 600 includes initiating 670 a soft shutdown to shut down the current in the ignition system (i.e., the coil and the switching device). If not, the method 600 may be reset 675 until another input signal occurs to turn on the switching device, at which point the method 600 may be repeated.

[0040] FIG. 7 includes graphs illustrating possible signals in an ignition system configured to perform the method of FIG. 6. A first graph 710 illustrates an input signal (e.g., at a gate terminal of a switching device) transitioning to ON (i.e., high) at an initial time (T0). A second graph 720 illustrates the input signal delayed by a delay period 725. The delay period 725 may begin at the initial time (T0) and end at a first time (T1). A third graph 730 illustrates the current (i.e., collector current) of the switching device. As shown, the current remains zero throughout the delay period 725 because the switching device is in an OFF state. A fourth graph 740 illustrates the collector voltage of the switching device. As shown, the collector voltage may be equal to the battery voltage (VB) during the delay period. The battery voltage (VB) may be measured during the delay period 725 by sensing the collector voltage of the switching device. This sensing may be enabled by a voltage monitor enable signal (VM_ENABLE), as shown in the fifth graph 750. After sensing the battery voltage, an overdwell time 713 may be calculated. For example, a high collector voltage sensed during the delay period may result in a shorter overdwell time compared to a longer overdwell time of a relatively low collector voltage measured during the delay period. A shorter dwell time may reduce the power dissipated for a higher battery voltage. After waiting for the overdwell time 713, a soft shutdown may be triggered by the input signal (IN) going to an on state (i.e., high) at the end of the overdwell time 713 (i.e., T2).

[0041] 8 is a schematic block diagram of an ignition system according to a second possible implementation of the present disclosure. The ignition system 800 includes a coil 860 coupled on a first side to a battery voltage 861 (VB) of a battery and coupled on a second side to a switching device 850 (e.g., an IGBT) of an igniter circuit 830. The switching device 850 can receive an input signal at a gate terminal that configures the switching device in an off state or an on state. In an on state, the switching device 850 conducts a current (I) between a collector terminal and an emitter terminal, and in an off state, a voltage at the collector terminal of the switching device (i.e., a collector voltage) can be equal to the battery voltage 861.

[0042] The igniter circuit 830 includes an overdose circuit configured to sense (i.e., measure) the collector voltage while the switching device 850 is in an off state. The overdose circuit of the igniter circuit 830 includes a delay 831 and an inverter 832 to generate a delayed and inverted version 834 of an input signal 833. The input signal 833 and the delayed inverted input signal 834 are input to a logic gate (e.g., AND gate 835) configured to compare the signals to generate a voltage monitor enable signal 836 (i.e., VM_ENABLE). In other words, the igniter circuit 830 includes a logic gate configured to compare the delayed input signal to the input signal to create (i.e., generate) an enable signal to configure the overdose circuit to sense the voltage of the switching device. The delayed version of the input signal may also be coupled to a control terminal (e.g., gate terminal) of the switching device 850 such that the switching device 850 is held in an off state for a delay period corresponding to the delay 831. As a result, during the delay period, switching device 850 is in an off state and the voltage monitor enable signal is active (eg, high).

[0043] The overdwell circuit further includes a voltage divider 810 configured to reduce a battery voltage 861 measured at the collector terminal while the switching device 850 is in an off state. The voltage divider 810 is coupled to a voltage monitor 811 configured to generate a dwell time voltage 812 corresponding to the battery voltage 861 while the voltage monitor enable signal 836 is active (e.g., high). The overdwell circuit further includes an analog-to-digital converter (i.e., digitizer 813) configured to convert the dwell time voltage 812 to a dwell time count 820. For example, the voltage of the switching device may be digitized by an analog-to-digital converter (A / D) to obtain (e.g., generate, create) the dwell time count. The dwell time count 820 corresponds to the voltage of the switching device 850, which corresponds to the voltage of the battery (VB) while the switching device 850 is in an off state. For example, a higher battery voltage may generate a smaller dwell time count than a lower battery voltage.

[0044] The dwell circuit is configured to wait for the dwell time before sending an SSD trigger signal 822 to the current controller 840 for soft shutdown of the current (I). The wait may be performed using a timer. Thus, the dwell circuit of the igniter circuit 830 may include a timer implemented using a clock generator 801 to generate a periodic clock signal (CLK) and a counter 821 configured to count cycles of the periodic clock signal. The counter 821 may be triggered to start counting based on the input signal 833 and may count until the dwell time count 820 is reached. Upon (e.g., in response to) reaching the dwell time count 820, the counter 821 may output the SSD trigger signal 822.

[0045] Below, some examples of the present disclosure are described.

[0046] Example 1. A method for shutting down current in an ignition system, the method including: receiving an input signal to configure a switching device coupled in series with a coil to an on state, starting a timer, sensing a current in the coil after the switching device is configured to an on state, measuring a rise time corresponding to a time when the current meets a criterion based on the timer, calculating a soft shutdown delay based on the rise time, and initiating a soft shutdown to reduce the current in the coil after the soft shutdown delay.

[0047] Example 2. The method of example 1, wherein the timer is a clock generator, and measuring the rise time includes counting cycles of the clock generator, comparing the current to a threshold, and outputting a rise time count corresponding to the rise time, the rise time count being the number of cycles counted when the current is greater than or equal to the threshold.

[0048] Example 3. The method of example 2, wherein calculating the soft-shutdown delay based on the time the current meets the criterion includes multiplying the rise time count by a fixed value to generate the delay count.

[0049] Example 4. The method of example 3, further comprising triggering a soft shutdown of the current in response to counting to the delay count.

[0050] Example 5. The method of example 1, wherein the sum of the rise time and the soft shutdown delay corresponds to an overdwell period, the overdwell period corresponding to a battery voltage coupled to the coil such that a relatively high battery voltage corresponds to a shorter overdwell period than a relatively low battery voltage.

[0051] Example 6. An ignition system including: a coil coupled on a first side to a battery; an igniter circuit including a switching device coupled to a second side of the coil, a current controller configured to control a current state of the switching device, and an overdwell circuit configured to measure a rise time of a current conducted by the switching device after being configured to an on state and to trigger the current controller to initiate a soft shutdown of the current after a soft shutdown delay based on the rise time of the current.

[0052] Example 7. The ignition system of example 6, wherein the overdwell circuit includes a clock generator, a first counter that counts cycles of the clock generator, and a current detector configured to output a signal to the first counter in response to determining that a current conducted by the switching device is greater than or equal to a threshold, the signal triggering the first counter to output a rise time count of cycles of the clock generator.

[0053] Example 8. The ignition system of example 7, wherein the dwell circuit further comprises a multiplier configured to multiply the rise time count by a fixed value corresponding to the dwell period to generate a delay count.

[0054] Example 9. The ignition system of example 8, further comprising a second counter configured to receive the delay count from the multiplier and output a soft shutdown trigger signal to the current controller after counting to the delay count.

[0055] Example 10. The ignition system of example 6, wherein the sum of the rise time and the soft shutdown delay corresponds to an overdwell period, the overdwell period corresponding to a battery voltage of the battery such that a relatively high battery voltage corresponds to a shorter overdwell period than a relatively low battery voltage.

[0056] Example 11. A method for shutting down current in an ignition system, the method including: receiving an input signal to configure a switching device coupled in series with a coil to an on state, delaying the input signal by a delay period before configuring the switching device to an on state to hold the switching device in an off state during the delay period, sensing a voltage of the switching device during the delay period, calculating an overdwell time based on the voltage of the switching device, and initiating a soft shutdown to shut down the current after the overdwell time based on the voltage of the switching device.

[0057] Example 12. The method of example 11, wherein the voltage at the switching device is a collector voltage at a collector terminal of the switching device, the collector terminal is connected to a first side of the coil and a battery is connected to a second side of the coil, and the voltage at the collector terminal corresponds to a battery voltage of the battery while the switching device is in an off state.

[0058] Example 13. The method of example 12, wherein sensing the voltage of the switching device while the switching device is in an off state includes generating an enable signal corresponding to a delay period, and enabling a voltage monitoring circuit based on the enable signal, the voltage monitoring circuit being configured to generate a dwell time voltage based on the collector voltage.

[0059] Example 14. The method of example 13, wherein calculating the overdwell time based on the voltage of the switching device includes digitizing the dwell time voltage to obtain a dwell time count.

[0060] Example 15. The method of example 14, further comprising configuring a counter to output a soft shutdown trigger signal after counting to a dwell time count, the dwell time count corresponding to a battery voltage such that a relatively high battery voltage corresponds to a shorter dwell time count than a relatively low battery voltage.

[0061] Example 16. An ignition system comprising: a coil coupled to a battery on a first side; an igniter circuit comprising a switching device coupled to a second side of the coil; a current controller configured to control a current state of the switching device; an overdwell circuit configured to delay an input signal coupled to a control terminal of the switching device such that the current state of the switching device is held in an off state for a delay period before being configured to an on state; sense a voltage of the switching device during the delay period; and trigger the current controller to initiate a soft shutdown of the current state after a overdwell time based on the voltage of the switching device during the delay period.

[0062] Example 17. The ignition system of example 16, wherein the lag circuit includes a delay configured to output a delayed input signal, and a logic gate configured to compare the delayed input signal to the input signal to generate an enable signal that configures the lag circuit to sense a voltage of the switching device.

[0063] Example 18. The ignition system of example 16, wherein the switching device is an insulated gate bipolar transistor coupled at a collector terminal to the second side of the coil, and a collector voltage of the insulated gate bipolar transistor corresponds to a battery voltage of the battery while the insulated gate bipolar transistor is in an off state.

[0064] Example 19. The ignition system of example 18, wherein the over dwell circuit further comprises: a voltage divider coupled to the collector terminal and configured to generate a dwell time voltage corresponding to a battery voltage; and a digitizer configured to output a dwell time count based on the dwell time voltage.

[0065] Example 20. The ignition system of example 19, wherein the overdwell circuit includes a counter configured to count cycles of the clock generator, receive a dwell time count from the digitizer, and, after counting up to the dwell time count, output a soft shutdown trigger signal to the current controller to trigger the current controller to initiate the soft shutdown of the current state.

[0066] Although certain features of the described implementations have been illustrated as described herein, those skilled in the art will now conceive many modifications, substitutions, changes, and equivalents. It will therefore be understood that the appended claims are intended to cover all such modifications and changes as fall within the scope of the implementations. It will be understood that these are presented by way of example only, not limitation, and that various changes in form and details may be made. Any part of the apparatus and / or method described herein may be combined in any combination, except mutually exclusive combinations. The implementations described herein may include various combinations and / or subcombinations of features, components and / or features of the different implementations described.

[0067] In the above specification, when an element is referred to as being on, connected to, electrically connected to, coupled to, or electrically coupled with another element, it will be understood that the element may be directly on, connected to, or coupled with the other element, or there may be one or more intervening elements. On the other hand, when an element is referred to as being directly on, directly connected to, or directly coupled with another element, there are no intervening elements present. Throughout the detailed description of the present invention, the terms directly on, directly connected to, or directly coupled may not be used, but elements shown as being directly on, directly connected to, or directly coupled may be referred to as such. The claims of this application (if included) may be amended to describe the exemplary relationships described herein or shown in the drawings.

[0068] As used herein, the singular can include the plural, unless in view of the context the specific instance clearly indicates. Spatially relative terms (e.g., throughout, above, above, below, lower, below, underneath, etc.) are intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the drawings. In some implementations, the relative terms above and below can include vertically above and vertically below, respectively. In some implementations, the term adjacent can include laterally adjacent or horizontally adjacent.

[0069] Some implementations may be implemented using various semiconductor processing and / or packaging technologies. Some implementations may be implemented using various types of semiconductor processing technologies associated with semiconductor substrates including, but not limited to, silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), silicon carbide (SiC), and / or the like.

Claims

1. 1. A method for shutting down electrical current in an ignition system, comprising: receiving an input signal to configure a switching device coupled in series with the coil to an on state; starting a timer; sensing the current in the coil after the switching device is configured to the on state; measuring a rise time corresponding to a time when the current meets a criterion based on the timer; calculating a soft shutdown delay based on the rise time; initiating a soft shutdown to reduce the current in the coil after the soft shutdown delay.

2. counting cycles of the timer generating a clock; comparing the current to a threshold; outputting a rise time count corresponding to the rise time, the rise time count being the number of cycles counted when the current is greater than or equal to the threshold; multiplying the rise time count by a fixed value to generate a delay count; triggering the soft shutdown of the current in response to counting the delay count; The method of claim 1 further comprising:

3. 2. The method of claim 1 , wherein the sum of the rise time and the soft shutdown delay corresponds to an overdwell period, the overdwell period corresponding to a battery voltage coupled to the coil such that a relatively high battery voltage corresponds to a shorter overdwell period than a relatively low battery voltage.

4. 1. An ignition system comprising: a coil coupled on a first side to the battery; 1. An igniter circuit comprising: a switching device coupled to a second side of the coil; a current controller configured to control a current state of the switching device; An overdwell circuit, comprising: measuring a rise time of a current conducted by the switching device after being configured to an on state; an overdwell circuit configured to trigger the current controller to initiate a soft shutdown of the current based on the rise time of the current after a soft shutdown delay.

5. The overdwell circuit includes: A clock generator; a first counter configured to count cycles of the clock generator; a current detector configured to output a signal to the first counter in response to determining that the current conducted by the switching device is greater than or equal to a threshold, the signal triggering the first counter to output a rise time count of the cycle of the clock generator; a multiplier configured to multiply the rise time count by a fixed value to generate a delay count, the fixed value corresponding to a dwell period; a second counter configured to receive the delay count from the multiplier and output a soft shutdown trigger signal to the current controller after counting the delay count.

6. 5. The ignition system of claim 4, wherein the sum of the rise time and the soft shutdown delay corresponds to an overdwell period, the overdwell period corresponding to a battery voltage of the battery such that a relatively high battery voltage corresponds to a shorter overdwell period than a relatively low battery voltage.

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