Patent Application
20190190238
An ignition coil typically used in ignition systems may be electrically controlled. Specifically, an electronic control unit (ECU) generally controls the dwell time of the ignition coil. The dwell time is the period of time that the coil is turned ON and is usually predetermined based on the system application. In some cases, however, malfunctions of the ECU may result in the ignition coil being turned on longer than it should (this condition may be referred to as “over dwell”), which may cause damage (e.g., melting and/or burning) to the ignition coil. In such a case, many conventional systems have a timeout function which activates a shutdown operation. In the shutdown operation, the coil current is turned off in either a manner of a “hard shutdown” or a “soft shutdown”. The “hard shutdown” quickly turns off the coil current through the ignition coil regardless of the crank position if the ignition coil operation time goes into over dwell. The “soft shutdown” slowly reduces the current through the ignition coil if the ignition coil operation time goes into over dwell. In cases where the ignition coil current is limited only by the resistance of the coil, and not an intentionally limited current, a time-lag exists between the intended start time of the soft shutdown period and the actual start time of the soft shutdown period. This time-lag effectively increases the length of time that the ignition coil is ON and is a function of the supply voltage. For example, the time-lag is greater in cases where the supply voltage is relatively low, which increases the likelihood that the ignition coil will be damaged due to overheating.
Various embodiments of the present technology comprise a method and apparatus for an ignition system. In various embodiments, the ignition system activates a soft shutdown of an ignition coil in the event of an over dwell condition. The apparatus comprises a first counter and a second counter that are selectively activated at predetermined events. An output of the second counter controls the value of a reference current that decreases linearly over time and wherein a rate of change of the reference current may be adjusted according to a frequency of a clock signal. In various embodiments, the soft shutdown operates independent of the supply voltage and temperature.
A more complete understanding of the present technology may be derived by referring to the detailed description when considered in connection with the following illustrative figures. In the following figures, like reference numbers refer to similar elements and steps throughout the figures.
The present technology may be described in terms of functional block components and various processing steps. Such functional blocks may be realized by any number of components configured to perform the specified functions and achieve the various results. For example, the present technology may employ various current limiters, digital-to-analog converters, ignition coils, switching circuits, counters, current sensors, and the like, which may carry out a variety of functions. In addition, the present technology may be practiced in conjunction with any number of systems, such as automotive, marine, and aerospace, and the systems described are merely exemplary applications for the technology. Further, the present technology may employ any number of conventional techniques for providing a control signal, sensing a current, signal conversion, generating a clock signal, and the like.
Methods and apparatus for an ignition system according to various aspects of the present technology may operate in conjunction with any suitable automotive system, such as an automobile with an internal combustion engine, and the like. Referring to
The power source 120 acts as a power supply to the ignition system 100. For example, the power source 120 may generate a DC (direct current) supply voltage VDD. The power source 120 may comprise any suitable device and/or system for generating power. For example, the power source 120 may comprise a 12-volt lead-acid battery commonly used in automotive applications. In an exemplary embodiment, the power source 120 may be coupled to the ignition coil 105. In various embodiments, the power source 120 may also be coupled to other components, such as the ECU 125, to facilitate operation.
The ECU 125 may control various operations of one or more components in the ignition system 100. For example, the ECU 125 may be configured to transmit various control signals representing an ON/OFF mode, a particular operating state, and the like. In an exemplary embodiment, the ECU 125 may be coupled to the igniter 130 and configured to transmit an ECU signal to operate the igniter 130. For example, the ECU signal may represent the ON/OFF mode of the igniter 130, which in turn controls operation of the ignition coil 105. In the event of a failure or malfunction of the ECU 125, the igniter 130 and ignition coil 105 may operate in an unintended manner and create an over dwell situation.
In general, the ECU 125 may be programmed with a predetermined dwell time, which is the preferred amount of time that the ignition coil 130 should be in the ON mode to achieve normal operation. The dwell time may be selected according to the particular application, the rated size of the power source 120, and/or transformation capabilities of the ignition coil 105. In a case where the ECU 125 does not turn off the igniter 130 at the desired time, the igniter 130 and ignition coil 105 will continue to operate in the ON mode. Most ignition systems 100, however, have a built-in function to turn off the ignition coil 105 if the igniter 130 remains in the ON mode longer than expected.
The ignition coil 105 transforms the DC voltage of the power source 120 to a higher voltage needed to create an electric spark in the spark plug 135, which in turn ignites the fuel-air mixture fed to the engine. For example, the ignition coil 105 may be electrically coupled to a positive terminal of the power source 120 and the spark plug 135. The ignition system 100 may comprise any suitable coil, for example, an induction coil. In various embodiments, the ignition coil 105 may comprise a primary coil 110 with a primary voltage VC1 and a secondary coil 115 with a secondary voltage VC2. In an exemplary embodiment, the primary coil 110 comprises a wire with relatively few turns and the secondary coil 115 comprises a wire thinner than that used in the primary coil 110 with many more turns. The ignition coil 105 may be described according to a turn ratio (N=N2/N1), which is the number of turns of the secondary coil 115 (N2) to the number of turns of the primary coil 110 (N1). In general, the secondary voltage VC2 is equal to the primary voltage VC1 multiplied by the turn ratio (i.e., VC2=VC1×N). Accordingly, the secondary voltage VC2 is higher than the primary voltage VC1. In an exemplary embodiment, the primary coil 110 may be coupled to the igniter 130 and the secondary coil 115 may be coupled to the spark plug 135.
According to various embodiments, the igniter 130 controls and/or measures (or detect or sense) a coil current ICOIL through ignition coil 105. In an exemplary embodiment, the igniter 130 may also be configured to perform a soft shutdown operation to turn off the ignition coil 105 if a malfunction or operational error has occurred and dwell time exceeded a predetermined timeout period. In an exemplary embodiment, the igniter 130 may be coupled to the primary coil 110 and the coil current ICOIL may be a current through the primary coil 110. The igniter 130 may comprise various circuit devices and/or systems for providing a count value, current sensing, signal amplification, controlling a reference voltage, signal conversion, controlling and/or limiting a current, and the like. For example, and referring to
According to various embodiments, the igniter 130 may further comprise a current source (not shown) configured to provide a bias current to the current limiter circuit 215, current sensor circuit 225, and/or other circuits within the igniter 130. The current source may comprise any suitable circuit and/or system configured to generate a predetermined current.
The protection circuit 250 operates in conjunction with the switch element 245 to gradually reduce a current through the primary coil 110 (i.e., a coil current ICOIL) until the ignition coil 105 is fully shutdown (i.e., the coil current equals zero) and no longer providing a voltage to the spark plug 135. The protection circuit 250 may be configured to convert a voltage to a current, provide a difference current of multiple currents, amplify a signal, and/or facilitate limiting and/or stopping the coil current ICOIL. For example, the protection circuit 250 may comprise a first counter 200, a second counter 205, a shutdown controller 220, a current limiter circuit 215, and a current sense circuit 225. The protection circuit 250 may further comprise a signal converter, such as a digital-to-analog (D/A) converter 235. The protection circuit 250 may operate in conjunction with the switch element 245 to generate a desired coil current ICOIL during the soft shutdown operation. The particular magnitude of the coil current ICOIL during the soft shutdown may be selected according to the rated size of the power source 120, the particular application, and/or transformation capabilities of the ignition coil 105.
The first and second counters 200, 205 may be configured to generate a digital output that incrementally increases/decreases. The first and second counters 200, 205 may be coupled to the clock generator circuit 230 to receive the clock signal CLK. For example, the first counter 200 may generate a first count output COUT1 according to the clock signal CLK, and similarly, the second counter 205 may generate a second count output COUT2 according to the clock signal CLK. The first and second counters 200, 205 may comprise any circuit and/or device suitable for generating a predefined state based on a clock pulse, such as a circuit constructed of flip-flops. In an exemplary embodiment, the first and second count outputs COUT1, COUT2 are digital signals. In alternative embodiments, the first and second count outputs COUT1, COUT2 may be any signal suitable for indicating a count value.
In an exemplary embodiment, a first output terminal of the first counter 200 may be coupled to the shutdown controller 220 and/or the second counter 205. Alternatively, a second output terminal of the first counter 200 may be coupled to the second counter 205 and configured to transmit a flag signal to the second counter 205 to start/stop operation of the second counter 205. In an exemplary embodiment, the second counter 205 may be responsive to the first count output COUT1 and/or the flag signal transmitted from the first counter 200. An output terminal of the second counter 205 may be coupled to the digital-to-analog converter 235, wherein the digital-to-analog converter 235 converts the second count output to a reference current IREF. The digital-to-analog converter 235 may then transmit the reference current IREF to the current limiter circuit 215.
In an exemplary embodiment, the first counter 200 may be programmed to count for a predetermined number of counts and/or a predetermined period of time, such as for 256 counts, 512 counts, or 1024 counts. The number of counts may be based on the particular specifications and/or desired shutdown operation of the ignition system 100 (
The shutdown controller 220 may be configured to control the operation of various circuits within the igniter 130. For example, the shutdown controller 220 may be coupled to the second counter 205 and may generate a controller output signal COUT3 to stop/start operation of the second counter 205. In an exemplary embodiment, the shutdown controller 220 may be coupled to the gate terminal of the switch element 245 and configured to detect a gate voltage VGATE of the switch element 245. The shutdown controller 220 may further be configured to detect a change in the gate voltage VGATE, such as a decrease in the gate voltage VGATE. In general, when the gate voltage VGATE starts to decrease, this indicates that the coil current ICOIL is about to start decreasing as well. In an exemplary embodiment, the shutdown controller 220 transmits the controller output signal COUT3 to stop the second counter 205 when the first counter output COUT1 reaches a predetermined value and/or to resume operation of the second counter 205 when the shutdown controller 220 detects a decrease in the gate voltage VGATE. The shutdown controller 220 may comprise any circuit and/or system configured to process data and transmit data according to predetermined events. For example, the shutdown controller 220 may comprise various logic circuits, a memory, an operational amplifier, and the like. The shutdown controller 220 may also be electrically connected to and receive power from the power source 120.
The current limiter circuit 215 is configured to control operation of the switch element 245. For example, an output terminal of the current limiter circuit 215 may be directly coupled to an input of the switch element 245 or may be coupled to the input of the switch element via the driver circuit 210. The current limiter circuit 215 may also be configured to compare and/or amplify a signal. For example, the current limiter circuit 215 may comprise an operational amplifier or any other suitable amplifier with variable gain. The current limiter circuit 215 may generate a reference voltage VREF at the output terminal according to the reference IREF and a sensed current ISENSE, where the sensed current ISENSE is generated according to the coil current ICOIL, which in turn controls the gate voltage VGATE. For example, the current limiter circuit 215 may compare the reference current IREF to the sensed current ISENSE. The current limiter circuit 215 may maintain the level of the reference voltage VREF, and in turn, the gate voltage VGATE, until the reference current IREF reaches a particular value, in which case the current limiter circuit 215 may start to decrease the reference voltage VREF, which in turn also decreases the gate voltage VGATE. In an exemplary embodiment, the output terminal is coupled to the switch element 245, wherein the switch element 245 is responsive to the gate voltage VGATE. The current limiter circuit 215 may comprise any suitable circuit for amplifying and/or attenuating an input signal and/or comparing two signals. In an exemplary embodiment, the current limiter circuit 215 may further be coupled to a current sense circuit 225 that senses/detects the coil current ICOIL.
The current sense circuit 225 senses and/or detects a current. In an exemplary embodiment, the current sense circuit 225 operates in conjunction with a sense resistor 240 to detect the magnitude of the coil current ICOIL. For example, the current sense circuit 225 may be connected at a first point between a terminal of the switch element 245 and the sense resistor 225, and at a second point between the sense resistor 240 and a ground GND. The current sense circuit 225 may be configured to sense the coil current ICOIL by indirectly sensing a voltage across the sense resistor 240. The current sense circuit 225 may convert the sensed voltage to the sensed current ISENSE value which corresponds to coil current ICOIL. The current sense circuit 225 may comprise any circuit and/or system suitable for sensing and/or measuring a current, either directly or indirectly.
The current limiter circuit 215 may be responsive to the magnitude of the sensed current ISENSE. For example, the current limiter circuit 215 may utilize information related to the coil current ICOIL and/or the sensed current ISENSE to adjust its output signal. For example, the current limiter circuit 215 may increase or decrease the magnitude of the reference voltage VREF according to a comparison between the sensed current ISENSE and the reference current IREF.
The switch element 245 is configured to control operation of the ignition coil 105. For example, in an exemplary embodiment, the switch element 245 is coupled to the primary coil 110 and controls the coil current ICOIL. The switch element 245 may comprise any circuit and/or system suitable capable of controlling a current flow.
In an exemplary embodiment, the switch element 245 comprises an insulated-gate bipolar transistor (IGBT) having a gate terminal, an emitter terminal, and a collector terminal. In the present embodiment, the collector terminal is coupled to the primary coil 110, the emitter terminal is coupled to the sense resistor 240 and current sense circuit 225, and the gate terminal is coupled to an output of the current limiter circuit 215 and/or the driver circuit 210. Accordingly, the switch element 245 is responsive to the current limiter circuit 215 and/or the driver circuit 210, and as a voltage to the gate terminal (i.e., the gate voltage VGATE) increases, the coil current ICOIL also increases.
In an alternative embodiment, the protection circuit 250 may be implemented using analog technology. For example, and referring to
In various alternative embodiments, the protection circuit 250 may be implemented with a combination of both digital and analog devices. For example, in one embodiment, the protection circuit 250 may comprise the first counter 200, the second ramp generator 705, and the voltage-to-current converter 710. In an alternative embodiment, the protection circuit 250 may comprise the first ramp generator 700, the second counter 205, and the D/A converter 235.
According to various embodiments, the igniter 130 operates to provide quick and stable activation of the shutdown function, as well as to ensure that a total time that the ignition coil is ON is not extended due to the level of the supply voltage. In operation, the igniter 130 activates the soft shutdown operation of the ignition coil 105 in a case of a malfunction, such as a malfunction of the ECU 125, which results in current flowing through the ignition coil 105 for an extended, or otherwise unintended period of time. To prevent damage to the ignition coil 105 and ensure that a soft shutdown period TSSD starts as soon as reasonably possible to reduce a total amount of time that the ignition coil 105 is ON (e.g., TON), and ends as quickly as possible, but long enough to reduce an inductive kickback that may occur during the soft shutdown period TSSD. Extending the soft shutdown period may help prevent an unintentional spark of the spark plug 135.
Referring to
The second counter 205 continues to count until the shutdown controller 220 detects a decrease in the gate voltage VGATE. When this occurs, the shutdown controller 220 transmits the controller output signal COUT3 to the second counter 205 to pause the second counter 205. When the first counter 200 reaches the end of the first predetermined period TON, the first counter 200 may transmit a second flag signal to the second counter 205 to resume operation of the second counter 205 and shutdown period TSSD starts.
The switch element 245 controls the coil current ICOIL and is responsive to the gate voltage VGATE. Accordingly, as the reference voltage VREF decreases, the gate voltage VGATE decreases, and the coil current ICOIL also decreases. Therefore, during the soft shutdown period TSSD, the second counter output COUT2 increases, the reference current IREF decreases, and the reference voltage decreases, which decreases the coil current ICOIL. The second counter 205 continues to count until the coil current ICOIL reaches zero.
In an exemplary embodiment, the igniter 130 controls the coil current ICOIL such that during the soft shutdown period TSSD, the coil current ICOIL decreases in a linear manner. In other embodiments, however, the coil current ICOIL may first decrease in a non-linear manner and then continue to decrease in a linear manner. A rate of change of the coil current ICOIL may be adjusted according to the frequency of the clock signal CLK.
Referring to
It may also be noted that the period in which the ignition coil 105 is ON (i.e., the first predetermined period TON) is independent of the supply voltage VDD and the temperature of the ignition coil 105 as long as the rate of clock signal CLK is constant. Further, a total second count output is a function of the supply voltage VDD. For example, the higher the supply voltage VDD, the longer the second counter 205 will count before the coil current ICOIL reaches zero. Overall, the operation described above shortens the total time that the ignition coil 105 is ON (i.e., TON) compared to conventional systems where the end of the ON period (and the beginning of the soft shutdown period TSSD) is a function of the supply voltage VDD.
In an alternative operation, and referring to
In the foregoing description, the technology has been described with reference to specific exemplary embodiments. The particular implementations shown and described are illustrative of the technology and its best mode and are not intended to otherwise limit the scope of the present technology in any way. Indeed, for the sake of brevity, conventional manufacturing, connection, preparation, and other functional aspects of the method and system may not be described in detail. Furthermore, the connecting lines shown in the various figures are intended to represent exemplary functional relationships and/or steps between the various elements. Many alternative or additional functional relationships or physical connections may be present in a practical system.
The technology has been described with reference to specific exemplary embodiments. Various modifications and changes, however, may be made without departing from the scope of the present technology. The description and figures are to be regarded in an illustrative manner, rather than a restrictive one and all such modifications are intended to be included within the scope of the present technology. Accordingly, the scope of the technology should be determined by the generic embodiments described and their legal equivalents rather than by merely the specific examples described above. For example, the steps recited in any method or process embodiment may be executed in any order, unless otherwise expressly specified, and are not limited to the explicit order presented in the specific examples. Additionally, the components and/or elements recited in any apparatus embodiment may be assembled or otherwise operationally configured in a variety of permutations to produce substantially the same result as the present technology and are accordingly not limited to the specific configuration recited in the specific examples.
Benefits, other advantages and solutions to problems have been described above with regard to particular embodiments. Any benefit, advantage, solution to problems or any element that may cause any particular benefit, advantage or solution to occur or to become more pronounced, however, is not to be construed as a critical, required or essential feature or component.
The terms “comprises”, “comprising”, or any variation thereof, are intended to reference a non-exclusive inclusion, such that a process, method, article, composition or apparatus that comprises a list of elements does not include only those elements recited, but may also include other elements not expressly listed or inherent to such process, method, article, composition or apparatus. Other combinations and/or modifications of the above-described structures, arrangements, applications, proportions, elements, materials or components used in the practice of the present technology, in addition to those not specifically recited, may be varied or otherwise particularly adapted to specific environments, manufacturing specifications, design parameters or other operating requirements without departing from the general principles of the same.
The present technology has been described above with reference to an exemplary embodiment. However, changes and modifications may be made to the exemplary embodiment without departing from the scope of the present technology.
These and other changes or modifications are intended to be included within the scope of the present technology, as expressed in the following claims.
