(12) United States Patent
`Lepley et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 9.429,132 B1
`Aug. 30, 2016
`
`USOO94291.32B1
`
`(54) CAPACITIVE IGNITION SYSTEM WITH
`ON-SENSING AND SUPPRESSION OF AC
`RINGING
`(71) Applicant: Hoerbiger Kompressortechnik
`Holding GmbH, Vienna (AT)
`(72) Inventors: Joseph M. Lepley, Girard, OH (US);
`David Lepley, Girard, OH (US);
`Steven B Pirko, Lake Milton, OH
`(US); Arno Gschirr, Igls (AT)
`(73) Assignee: Hoerbiger Kompressortechnik
`Holding GmbH, Vienna (AT)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`(21) Appl. No.: 15/079,698
`
`(*) Notice:
`
`Mar. 24, 2016
`
`(22) Filed:
`(51) Int. Cl.
`F02P3/01
`F02P 3/09
`F02P 3/08
`F02P 3/12
`FO2P 3/04
`(52) U.S. Cl.
`CPC ................ F02P3/09 (2013.01); F02P3/0884
`(2013.01); F02P3/12 (2013.01); F02P3/0435
`(2013.01)
`
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`
`(58) Field of Classification Search
`CPC ........... H05B 41/00; F02P3/01; F02P 15/10;
`F02P 15/12: F02P1/086; F02P 9/002:
`F02P 17/12: F02P 3/12
`... 315/209 CD, 209 M, 209 T, 209 SC, 276,
`315/277,279
`See application file for complete search history.
`
`USPC
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,230,240 A
`5,777,216 A
`7,778,002 B2
`8,978,632 B2
`2004/0084.035 A1
`
`7/1993 Ohsawa et al.
`7/1998 Van Duyne et al.
`8, 2010 Skinner et al.
`3/2015 Steinrueck et al.
`5/2004 Newton ................. FO2M 26/O1
`123,630
`
`* cited by examiner
`Primary Examiner — Tuyet Vo
`(74) Attorney, Agent, or Firm — Dykema Gossett PLLC
`
`ABSTRACT
`(57)
`In order to reduce AC ringing of the secondary voltage after
`the spark event in a capacitive ignition system, which would
`influence ion-sensing, a secondary winding current (I)
`flowing through the secondary winding (4) after the spark
`event is forced to flow through a forward-biased muting
`diode (D1) that is connected across the secondary winding
`(4).
`
`4 Claims, 4 Drawing Sheets
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`
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`Exhibit 1008
`MOTORTECH v. Altronic - IPR2025-00398
`Page 1 of 9
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`U.S. Patent
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`Aug. 30, 2016
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`Sheet 1 of 4
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`US 9,429,132 B1
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`Fig. 1
`(Prior Art)
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`Exhibit 1008
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`Page 2 of 9
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`U.S. Patent
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`Aug. 30, 2016
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`Sheet 2 of 4
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`US 9,429,132 B1
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`U.S. Patent
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`Aug. 30, 2016
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`Sheet 3 of 4
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`US 9,429,132 B1
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`U.S. Patent
`U.S. Patent
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`Aug. 30, 2016
`Aug. 30, 2016
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`Sheet 4 of 4
`Sheet 4 of 4
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`US 9,429,132 B1
`US 9,429,132 B1
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`Exhibit 1008
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`Exhibit 1008
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`1.
`CAPACTIVE IGNITION SYSTEM WITH
`ON-SENSING AND SUPPRESSION OF AC
`RINGING
`
`BACKGROUND OF THE INVENTION
`
`The present invention pertains to a capacitive ignition
`system with ion-sensing comprising an ignition coil, with a
`primary winding that is connected to an energy source for
`providing the energy for a spark event and with a secondary
`winding having a first terminal connected to a spark plug so
`that a secondary voltage across the secondary winding is
`applied to the spark gap of the spark plug, an ionization
`current biasing and measurement circuitry on a secondary
`side of the ignition coil for providing a biasing Voltage to the
`spark gap after the spark event for ion-sensing and a diode
`that is connected across the secondary winding. The inven
`tion pertains also to a method for damping AC ringing after
`occurrence of a spark event in a capacitive ignition system
`with ion-sensing.
`It is well known that the combustion process of an internal
`combustion engine can be analysed using the ionization
`current across the spark gap of a spark plug. When the spark
`plug sparks the gas Surrounding the spark gap is ionized. If
`a Voltage is applied across the spark gap after the spark event
`has occurred, the ionized gas causes ionization current to
`flow across the spark gap that can be measured and analysed
`using Suitable detection circuits. Measuring and analysing
`the ionization current (the so called ion-sensing) allows
`detecting misfire, engine knock, peak pressure, a deteriorat
`ing spark plug (plug fouling) and other characteristics of the
`engine or the combustion process. Information from ion
`sensing enables also the correction or adjustment of ignition
`parameters in order to adapt to different load conditions or
`to improve the performance of the engine or to decrease
`emissions or fuel consumption, by influencing the air/fuel
`ratio, for example. There are many known methods and
`systems in the prior art for detecting, measuring and analy
`sing an ionization current.
`An ignition system usually uses an ignition coil having a
`primary and secondary winding. The energy required for
`sparking is Supplied from the primary winding to the sec
`ondary winding causing a secondary Voltage across the
`secondary winding that is applied to the spark gap. Depen
`dent on the energy source on the primary side for generating
`the primary Voltage across the primary winding, it is differed
`between inductive ignition systems and capacitive ignition
`systems.
`In an inductive ignition system the energy is stored in the
`primary winding which is released for sparking. To this end
`a primary Switch in series with the primary winding is turned
`on for loading the coil primary that is connected to a Supply
`Voltage. The spark occurs when the primary Switch is turned
`off. Inductive ignition, also with ion-sensing, is well known,
`e.g., from U.S. Pat. No. 5,230,240 A. In U.S. Pat. No.
`5,230,240A, a diode across the secondary winding is shown
`which prevents unwanted sparking when the primary Switch
`turns on to load the coil primary. This diode is forward
`biased when the switch is turned on, and reverse biased
`when the switch is turned off. Hence, the diode conducts
`before the desired spark breakdown across the spark plug
`electrodes occurs. The diode across the secondary winding
`would need to conduct significant current every time the
`primary Switch is turned on and would then need to dissipate
`the power again. This would significantly burden the diode,
`and a diode with high power rating would be required.
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`US 9,429,132 B1
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`2
`In a capacitive ignition system a storage capacitor on the
`primary side of the ignition coil stores the energy for
`sparking. The storage capacitor is discharged over the pri
`mary winding to generate the primary Voltage across the
`primary winding, e.g., by turning on a Switch that connects
`the capacitor with the primary winding. After the spark
`event, the capacitor is recharged for the next spark event.
`With capacitive ignition it is possible to generate short
`duration, high power sparks and, hence, is particularly
`Suitable for igniting lean mixtures, such as in gas engines.
`Capacitive ignition, also with ion-sensing, is well known,
`e.g., from WO 2013/045288 A1. In WO 2013/045288 A1 a
`resistor is connected in series with the spark plug for
`measuring the ionization current. The required bias Voltage
`across the spark plug electrodes for ion-sensing is generated
`by repeatedly discharging the storage capacitor on the pri
`mary side after the initial spark breakdown.
`A major challenge in combustion monitoring via ion
`sensing of the spark gap is minimization of the associated
`ringing of the secondary Voltage in the secondary winding of
`the ignition coil after the spark event. The coil secondary
`winding is an inductor with a DC current (direct current)
`flowing through it whenever the spark is created. When the
`spark goes out the secondary DC current drops to Zero
`momentarily and as a result the charged inductance of the
`coil secondary winding tries to maintain the previous current
`flow. But because the secondary path is now highly resistant
`to the flow of DC current at the available secondary voltage,
`the only current which can flow is an AC current (alternating
`current) through the parasitic capacitance of the spark plug
`gap. This AC current causes the ringing of the secondary
`voltage. This parasitic AC current is often much larger in
`magnitude than the DC ion current which is the signal of
`interest with ion-sensing, which makes ion-sensing difficult.
`This phenomenon has traditionally been managed by a
`number of different approaches, namely reduced coil imped
`ance and active “turn-off circuits on the primary side of the
`circuit. Reduced coil impedance can significantly impact
`ignition performance as the coil with reduced coil imped
`ance typically delivers very short duration sparks with
`limited output energy. Active “turn-off circuits on the
`primary side, on the other hand, can improve the ringing
`behaviour on the secondary winding, but are cumber-some
`to implement effectively and have limited benefit.
`From EP 1990 813 A1 an inductive ignition system with
`ion-sensing and an apparatus for reducing ringing of the
`secondary Voltage is known. For ion-sensing a capacitor on
`the secondary side of the ignition coil is charged during the
`flow of a spark current. After the spark breakdown occurred,
`the capacitor is discharged to generate the bias Voltage
`across the spark plug electrodes for detecting the ionization
`current that is measured. For reducing the ringing of the
`secondary Voltage, that would influence the measurement of
`the ionization current, an additional control winding in
`series with a diode are arranged on the primary side of the
`ignition coil. This diode is oriented so that it is forward
`biased only when a current opposite to the spark current,
`e.g., an ionization current, flows and, hence, does not
`conduct during the spark event. After the spark goes out, the
`control winding and the diode cooperate to dissipate residual
`electrical charge in the coil in order to limit the ringing.
`However, the diode introduces an incremental parasitic loss
`during charging of the ignition coil primary that will detri
`mental-ly increase the amount energy required for charging
`the coil primary.
`Another capacitive ignition system with ion-sensing is
`shown in EP 879 355 B1, which uses an additional energy
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`Exhibit 1008
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`Page 6 of 9
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`US 9,429,132 B1
`
`3
`Source on the secondary side for generating a high current
`spark arc and also for generating the required bias Voltage
`across the spark plug electrodes for ion-sensing. The energy
`Source of the primary side is used solely for creating a spark
`across the spark gap. To this end a high-voltage diode is
`connected across the secondary winding. If the capacitor on
`the primary side is discharged for sparking, a high Voltage is
`created on the secondary winding. This high Voltage is also
`applied across the spark gap and ionizes the matter Sur
`rounding the spark gap and creates the spark. Once the spark
`gap is ionized, the secondary side energy source connected
`to the coil secondary provides the required current, which
`flows over the ionized spark gap, to generate the arc for the
`spark event. This spark current flows also over the forward
`biased high-voltage diode, which ensures that the secondary
`side energy source is decoupled from the primary side of the
`ignition coil. The high-voltage diode is used to Supply the
`power to the spark. The energy for creating the spark which
`is Supplied by the secondary side energy source connected to
`the coil secondary is quickly dissipated in the secondary
`winding and the high-voltage diode. In addition, after the
`spark event, the secondary side energy source provides also
`the ionization current for ion sensing. This ionization current
`flows again over the forward-biased high-voltage diode and,
`during ion-sensing, the high-voltage secondary side is again
`decoupled from the primary side of the ignition coil to
`pre-vent undesired cross conduction or interaction of the two
`separate isolated energy sources. The additional energy
`Source increases the complexity of the ignition system with
`regard to hardware, as well as with regard to timing and
`control of the energy sources. The secondary winding and
`the high-voltage diode are significantly thermally burdened.
`Therefore, both the ignition coil and the high-voltage diode
`must be designed or chosen to withstand this high thermal
`load caused by the fact that the secondary side high-voltage
`diode conducts both the spark current and the ionization
`current. In EP 879 355 B1 a low pass filter is used to
`condition the ionization current signal. Because of the
`polarity of the secondary side energy source, the secondary
`ringing Voltages are not suppressed by the high-voltage
`diode which can be seen in the waveforms of FIGS. 5a and
`SE of EP 879 355 B1.
`It is an object of the present invention to provide a method
`and an apparatus for easily reducing AC ringing of the
`secondary Voltage after the spark event in a capacitive
`ignition system.
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`SUMMARY OF THE INVENTION
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`This objective is achieved in that the diode is connected
`across the secondary winding so that it is reverse-biased for
`a spark current flowing through the spark gap during the
`spark event of the spark plug and forward-biased for an AC
`ringing Voltage after the spark event. The forward-biased
`muting diode connected across the secondary winding forces
`a secondary current to flow through the secondary winding
`after the spark event. A secondary current flowing through
`the secondary winding caused by the secondary ringing
`Voltage when the spark ends is forced to flow through a
`forward-biased muting diode that is connected across the
`secondary winding because the muting diode shortens the
`secondary winding after the spark event. By the muting
`diode electrical energy that re-mains stored in the secondary
`winding of the ignition coil is rapidly dissipated in the
`resistance of the secondary winding because the current
`flowing in the secondary winding is forced to flow through
`the low-impedance path provided by the forward-biased
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`muting diode. In this way the secondary current is held away
`from the spark gap and thus, does not influence ion-sensing
`after the spark event. Therefore, the secondary AC current is
`prevented from flowing through the spark gap after the spark
`event and thereby does not influence the small DC ionization
`current that flows through the spark gap for ion-sensing.
`In an advantageous, easy to implement embodiment, the
`ionization current biasing and measurement circuitry is
`connected to a second terminal of the secondary winding
`and comprises a biasing capacitor that is connected to the
`second terminal and that is charged during the spark event
`by the spark current and that is discharged after the spark
`event for providing the biasing Voltage.
`It is especially advantageous to use a muting diode with
`an avalanche breakdown Voltage in the range of a maximum
`Voltage rating of the ignition coil. When the muting diode
`with Such an avalanche breakdown voltage is exposed to
`spark Voltages above the avalanche breakdown voltage, the
`spark Voltage is limited due to the occurring avalanche
`breakdown of the muting diode and the ignition coil is
`protected from damage due to high Voltages.
`The present invention is explained in greater detail below
`with reference to FIGS. 1 to 4, which schematically show
`advantageous embodiments of the invention by way of
`example and in a non-limiting manner.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows a capacitive ignition system according to the
`prior art,
`FIG. 2 shows a capacitive ignition system with a muting
`diode in accordance with the invention,
`FIG. 3A shows the secondary voltage and the current
`through the spark gap without the inventive muting diode,
`FIG. 3B shows the secondary voltage and the current
`through the spark gap with the inventive muting diode, and
`FIG. 4 shows a Zoomed in view of the tail-end part of the
`spark event.
`
`A capacitive ignition system 1 as known from prior art
`and as shown in FIG. 1 comprises an ignition coil 2 with a
`primary winding 3 and a secondary winding 4. A storage
`capacitor C1 is provided on the primary side of the ignition
`coil 2 that stores the required energy for the spark event. The
`storage capacitor C1 is charged by a supply voltage V. A
`switch SW, a semiconductor Switch like a transistor, for
`example, is connected in series to the primary winding 3.
`The storage capacitor C1 is advantageously (but not neces
`sarily) connected in parallel to the primary winding 3, as in
`FIG. 1. A first terminal T1 of the secondary winding 4 is
`connected in known manner with the grounded spark plug 5.
`so that a secondary voltage Vs across the secondary winding
`4 is applied to the spark gap 8.
`If the switch SW is turned on, e.g., under control of a
`control unit ECU, the storage capacitor C1 discharges via
`the primary winding 3, and an optionally possible resistor
`R1, causing a secondary Voltage Vs across the secondary
`winding 4. This secondary Voltage Vs is applied to the spark
`gap 8 of the spark plug 5. When the secondary voltage Vs
`is sufficiently high, a spark breakdown across the Spark gap
`8 occurs and a spark current I
`flows into the spark gap
`8 for maintaining the arc across the spark gap 8 (see also
`FIG. 3A). The electrical energy for the spark event, i.e., for
`creating a spark and for maintaining the arc, is provided by
`the energy source on the primary side of the ignition coil 2.
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`DETAILED DESCRIPTION OF THE DRAWINGS
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`Exhibit 1008
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`Page 7 of 9
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`US 9,429,132 B1
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`During the spark event, the first terminal T1 of the ignition
`coil 2 connected to the spark plug 5 goes negative and the
`Voltage across the spark gap 8 is essentially constant and the
`amplitude of spark current I
`gradually declines. At some
`time after the spark event, i.e., after the spark has extin
`guished, the ionization current I
`can be measured, as
`described in the following.
`The capacitive ignition system 1 further comprises an
`ionization current biasing and measurement circuitry 6 that
`measures a ionization current I, across the spark gap 8 and
`provides a measurement signal I proportional to the ion
`ization current I. The ionization current biasing and
`measurement circuitry 6 can be implemented in many dif
`ferent ways, for example as shown in FIG. 1. The ionization
`current I
`can be measured in many different ways known
`to those skilled in the art. The ionization current biasing and
`measurement circuitry 6 is connected to a second terminal
`T2 of the secondary winding 4, which is usually connected
`to ground. The measurement signal I can be further pro
`cessed in a signal conditioning unit 7, e.g., by filtering or by
`amplifying with current amplifier as in FIG. 1, and is output
`as ion signal IS.
`The ionization current biasing and measurement circuitry
`6 comprises for example a biasing capacitor C2 connected in
`parallel to a diode D2 that are connected to the second
`terminal T2 of the secondary winding 4. Biasing capacitor
`C2 and diode D2 are also connected to opposing oriented,
`parallel connected diodes D3, D4 that in turn are connected
`to ground via resistor R2. A measurement resistor RM is
`serially connected to the connection between the parallel
`connected biasing capacitor C2 and diode D2 and the
`parallel connected diodes D3, D4. The current flowing over
`the measurement resistor RM is the measurement signal I.
`It would of course also be possible to measure the ion
`current in many other ways.
`When a spark current I
`flows as result of a spark
`breakdown across the spark gap 8, the spark current I.
`charges also the biasing capacitor C2 via the resulting
`current path (secondary winding 4-biasing capacitor C2-di
`ode D4-(optional) resistor R2-ground-spark gap 8). After the
`spark went out, the biasing capacitor C2 discharges and
`provides the DC biasing voltage V, to the spark gap 8
`required for ion-sensing. This DC biasing Voltage V,
`causes the ionization current I, that flows in opposite
`direction of the spark current I.
`In FIG. 3A the resulting secondary Voltage Vs signal and
`the signal of the current I, flowing over the spark gap 8.
`i.e., the spark current I
`and the ionization current I,
`are
`shown. FIG. 3A depicts two subsequent spark events. At
`time t the Switch SW is turned on causing a high secondary
`Voltage Vs. As soon as the breakdown voltage is reached a
`spark breakdown across the spark gap 8 occurs and the spark
`current I
`flows. The spark current I
`decreases as the
`storage capacitor C1 discharges. After the spark went out at
`time t2, because the ignition coil 2 can no longer maintain
`the flow of spark current I
`over the spark gap 8 due to
`the limited energy available at the primary side, the biasing
`capacitor C2 provides a DC bias Voltage to the spark gap 8
`causing the ionization current I
`to flow. The typical open
`circuit AC ringing Voltage V of the ignition coil 2 after the
`spark went out is Superimposed to the DC bias Voltage of
`biasing capacitor C2. The resulting ionization current I
`(that is much lower in magnitude than the spark current
`I) flowing through the spark gap 8 consists of a small
`DC ionization current I, which creates a Small DC ioniza
`tion voltage of interest combined with the much larger
`amplitude AC ringing current caused by the coil secondary
`
`6
`AC ringing Voltage V (as indicated in FIG. 3A). This makes
`the measurement of the small DC ionization current difficult.
`To avoid that the open circuit AC ringing Voltage V
`influences the ionization current I, after the spark event a
`high-voltage muting diode D1, e.g., a 40 kV muting diode,
`is connected across the secondary winding 4., i.e., in parallel
`to the secondary winding 4 or in other words between the
`first terminal T1 and the second terminal T2 of the secondary
`winding 4, of the ignition coil 2 in accordance to the
`invention, as shown in FIG. 2. This muting diode D1 is
`connected in such way that it is reversed-biased for the
`flowing spark current I
`forcing the spark current I
`to flow over the spark gap 8 and the secondary winding 4.
`To this end, the cathode of the muting diode D1 is connected
`to the second terminal T2 of the secondary winding 4 of the
`ignition coil 2, to which also the ionization current biasing
`and measurement circuitry 6 is connected to in the shown
`embodiment.
`After the spark event, both before and during the time
`when the ionization current I, flows, the muting diode D1
`has the effect that the open circuit AC ringing Voltage V at
`the secondary winding 4 is at the first opposite polarity ring
`(voltage Swing) clamped to a simple forward-biased diode
`drop. Thereby, the local secondary winding current I is held
`away from the ionization current biasing and measurement
`circuitry 6 as the secondary winding current I (indicated in
`FIG. 2) is forced to flow through the secondary winding 4 by
`the forward-biased muting diode D1 which provides a very
`low impedance path for this current I. Given this low
`impedance path directly across the secondary winding 4 of
`the ignition coil 2, this secondary winding current I does
`not flow thru the capacitance of the spark gap 8, since the
`voltage potential exists only between the two terminals T1,
`T2 of the secondary winding 4 and is shorted by the muting
`diode D1. As a consequence, the inductive coil energy
`remaining after the spark event is rapidly consumed in the
`form of IR losses inside the coil secondary winding 4, with
`the current I flowing through the secondary winding 4 and
`the resistance R of the secondary winding 4. Thus, the
`unwanted AC ringing secondary winding current I is held
`away from the spark gap 8 and does not influence the
`measurement of the ionization current I, in the ionization
`current biasing and measurement circuitry 6. The muting
`diode D1 does not affect the normal operation of the
`capacitive ignition system 1, but only suppresses the unde
`sired coil ringing after the spark event. The effect of the
`muting diode D1 is depicted in FIG. 3B. It can clearly be
`seen that the AC ringing after the spark event has been
`eliminated.
`FIG. 4 shows a Zoomed in view of the tail-end part of the
`spark event. The AC ringing Voltage V has been eliminated
`and the Small DC biasing Voltage V, caused by the
`discharging biasing capacitor C2 is applied to the spark gap
`8 which in turn causes the Small (as compared to the spark
`current I) ionization current I.
`An additional benefit of the muting diode D1 is that the
`muting diode D1 can be selected in Such a way that
`avalanche breakdown occurs when the muting diode D1 is
`exposed to spark Voltages above the maximum voltage
`rating of the ignition coil 2, thereby limiting the spark
`Voltage and protecting the ignition coil 2. To this end the
`avalanche breakdown voltage of the muting diode D1 should
`be in the range of the maximum Voltage rating of the ignition
`coil 2, preferably in the range of 90% to 110% of the
`maximum Voltage rating of the ignition coil 2. The ava
`lanche breakdown voltage does preferably not exceed the
`maximum voltage rating of the ignition coil 2.
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`7
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`The invention claimed is:
`1. A capacitive ignition system (1) with ion-sensing
`comprising an ignition coil (2), with a primary winding (3)
`that is connected to an energy source for providing the
`energy for a spark event and with a secondary winding (4)
`having a first terminal (T1) connected to a spark plug (5) so
`that a secondary Voltage (Vs) across the secondary winding
`(4) is applied to the spark gap (8) of the spark plug (5), an
`ionization current biasing and measurement circuitry (6) on
`a secondary side of the ignition coil (2) for providing a
`biasing Voltage to the spark gap (8) after the spark event for
`ion-sensing and a diode (D1) that is connected across the
`secondary winding (4), wherein the diode (D1) is connected
`across the secondary winding (4) so that it is reverse-biased
`for a spark current flowing through the spark gap (8) during
`the spark event of the spark plug (5) and forward-biased for
`an AC ringing Voltage (V) after the spark event.
`2. A capacitive ignition system (1) according to claim 1,
`wherein the ionization current biasing and measurement
`circuitry (6) is connected to a second terminal (T2) of the
`Secondary winding (4) and comprises a biasing capacitor
`(C2) that is connected to the second terminal (T2) and that
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`5
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`10
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`15
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`US 9,429,132 B1
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`8
`is charged during the spark event by the spark current (I)
`and that is discharged after the spark event for providing the
`biasing Voltage.
`3. A capacitive ignition system (1) according to claim 1,
`wherein a muting diode (D1) with an avalanche breakdown
`Voltage in the range of a maximum voltage rating of the
`ignition coil (2), preferably equal to the maximum voltage
`rating of the ignition coil (2), is used.
`4. A method for damping AC ringing after occurrence of
`a spark event in a capacitive ignition system (1) with
`ion-sensing comprising a primary winding (3) that is con
`nected to an energy source that provides the energy for a
`spark event and a secondary winding (4) having a first
`terminal (T1) connected to a spark plug (5) so that a
`Secondary Voltage (Vs) across the secondary winding (4) is
`applied to a spark gap (8) of the spark plug (5), whereas a
`spark current (I) flows over the spark gap (8) during the
`spark event, wherein after the spark event a secondary
`winding current (I) through the secondary winding (4) is
`forced to flow through a forward-biased muting diode (D1)
`that is connected across the secondary winding (4).
`
`Exhibit 1008
`MOTORTECH v. Altronic - IPR2025-00398
`Page 9 of 9
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