CA2218295A1 - Simplified switch driver for inductive ignition - Google Patents

Abstract

A simple form of ignition driver and control circuit for the coil power switches of an inductive ignition system for setting and controlling the primary current Ipo in the coil primary windings (@ 3) of igniti on coils (@ 2a, 2b) of a multi-cylinder engine with "n" powerswitchess S1 through Sn, the driver circuit being comprised of "n" isolatio n diodes with only one common control switch, a comparator (@ 10) and a common input trigger circuit working in conjunction a current sense circuit with partial temperature compensation and the comparator to set the power switch on-time duration, Tdw for sequentially en ergizing and de-energizing the ignition coils as dictated by an ignition spark firing and sequencing system.

Description

CA 022l8295 l997- lO- l5 SIMPLIFIED SWITCH DRIVER FOR INDUCTIVE IC~NITION

l;l~LD OF THE INVENTION
This invention relates to control ci~ y for inductive ignition systems for in~rn~l combustion engines, and more particularly for simplifying the driverS ~ ;uilly of the ignition coil power switches for coil energizing and spark hring, and for partially temperature ccs~ .s~ g simple current sensor means used to set and control the peak coil charging current and power converter current.

BACKGROUND OF THE INVENTION AND PRIOR ART
There is a move in the ~u~ o~ive industry to distributorless ignition 10 systems of one coil per spark plug, and particularly towards plug-mounted coils.
Motivations for this are more compact ignition, elimin~tion of electrom~gnetic L~L~lr~r~lce, and higher ignition efflciency (no distributor or spark plug wires), as well as other reasons.
Such distributorless ignition ~y~ s require one power switch per 15 i nition coil, typically from four to eight for four to eight cylinder engines. Each swiech must have a driver circuit to turn the switch on and off to build up the required primary current and energy in the ignition coil and deliver it as an i~nition spark at the spark plug in the engine cylinder. Such multiple driver circuits can be more complex and costly than required. Furthermore, the ignition20 triggering and cylinder ph~in~ (se~uellcing~ circuits may also be complex, especially for retrofit applications where a more universal but simple fo~m of tri~çnng and ph~ing is required. Thelerol~;, circuits that can simplify the multiple driver aspects of such distributorless ignitions, or more generally i~nition circuits with multiple coils and power switches, and simplify the trigger 25 and phase input requirements, are desirable. Partially temperature compensating simple forms of current sensing means associated with the power switches, and power supply switching if used, is also desirable.

CA 0221829S 1997-10- lS

SUMMARY OF THE INVENTION
The invention comprises a simple form of ignition power switch driver circuit based on the principle of keeping the gates of the ignition power switches Si (~sllmçcl to be Insulated Gate Bipolar Transistors, IGBTs) in the low or 5 disabled condition by means of one driver transistor per power switch, or one driver diode per power switch with only one driver control transistor shared among the multiple power switches and driver diodes, and firing the ignition system by energizing tran~r~ lnel- coil Ti by disab}ing the driver transistor (or tr~n~ tors) and applying a signal to the gate of the a~L~,pliate switch Si to turn 10 it on, which is then turned off when the coil set peak plin~aly current Ipo has been attained by turning on the driver tr~n~istQr(s) which disable, i.e. pull to a low or ground level, the gates of the power switches, to turn off all the power switches including the one that was turned on irrespective of whether it still has a drive signal being applied to its gate. A co~ alor is preferably used with the15 driver circuit to define the on-time (dwell-tilne) of the power switch by turning off the disabling driver switch during the coil energizing time (dwell-time).
A pl erel ~ed automotive driver circuit for a 4-cylinder engine with one coil and power switch per cylinder, the reference engine and ignition for the presentdisclosure, has four diodes, one driver switch which pulls all four gates of the20 power switches to ground, or sufficiently close to ground to disable them when the coils are not being energized, and a coil charging duration controller whichis preferably a ~onlpdl~lor which senses the coil peak primary current Ipo and swltches states when Ipo has reached a set point or ,~îelellce voltage level. The gates of switches Si are driven by any of a number of ways, one way employing 25 an octal coul~Lel for an engine with up to eight ignition coils switches Si whose outputs are connected to the gates of the power switches Si through resistors.
For the pler~.ed simple forms of current sensor means using the base-emitter voltage Vbe of a transistor as the sense voltage, simple diode means aredisclosed to partially compensate the negative teml,eralule coefficient of Vbe.

CA 022l8295 l997- lO- l5 BRIEF DESCRIPTlON OF THE DRAWINGS
FIG. 1 is a partial circuit drawing of an embodiment of the invention, in which one driver switch QDi is used per power switch Si of a l~ ro~ er i~nition coil Ti of a multi-cylinder engine using a conventional inductive ignition 5 system with current sensors at the emitters of the power transistors Si, and also including a simplified ignition trigger input circuit.
FI~. 2 is a partial block diagram, partial eircuit drawing of a ~leÇ~Lled embodiment of ~ne invention, applied to an advanced ~orm of inductive ignition system, called Hybrid Inductive Ignition, HBI, disclosed elsewhere, wherein one 10 driver switch QD is used for multiple ignition coils Ti and gate diodes Di, and wherein both a prc~r~l~d simplified trigger input circuit and phase circuit are shown for use in conjunction with an octal counter for operating an engine with up to eight ignition coil switches Si.
FIG. 3 depicts a l,lef~-led form of HBI ignition circuit which uses diodes 15 in place of, or in addition to, resistors in the current sensing circuits to partially compensate the negative tempel~lule variation of the base-emitter voltage Vbe of the current sense transistor.
FIGS. 4a and 4b are graphs of typical diode current versus diode voltage Vd with temperature as a parameter showing the diode's negative lelllperature 20 variation of voltage Vd which is used to partially compensate the negative telllpt;ralule variation of the base-emitter voltage Vbe of the sense transistor.
FIG. 5 depicts the use of diodes for partial temperature compensation of base-emitter voltages Vbe of two sense transistors where a single sense point isused, as is preferred with the boost converter powered HBI type ignition system.

DESCRIPTION OF PRl~;ERRED EMBODIMENTS r FIG. 1 is a partial circuit drawing on an embodiment of the invention applied to a standard automotive inductive ignition system including an input triggering and ~ ling circuit. The ignition assumes operation from a standard 512 volt car battery 1 (voltage Vb) with two ignition coils 2a and 2b of severalpossible shown (also designated as T1, T2, or more generally Ti, where the subscript "i" designates the "ith" transformer coil). Each coil has primary winding 3 of turns Np and inductance Lp and coil primary le~ ge infl~lct~n~e Lpe, and secondary win-ling~ 4 of in.l,lc~lce Ls. The coils each have a main or 10 coil power switch 5a, 5b, , (Sl and S2 shown), and spark gap 6. All the switches have a comlllull emitter connection (Tn.~ul~terl Gate Bipolar Tr~nsistors, IBGT's, shown for switches Si) with current sensor resistor 7 to ground.
In operation, switch Si is turned on by a controller and switch driver for the "dwell" period Tdw to build up a prescribed peak or "break" current Ipo developing a voltage Vsense across sensor resistor 7, and then opened to deliverthe energy El stored in the m~neticc core to the secondary coil circuit, where:
El = 1/2-Lp-Ipo2, where "-" denotes multiplication.
An embodiment of the controller and switch driver comprises an optional gate resistor Ri (8a, 8b for switches 5a, Sb) of switch Si, drive NPN tr:ln~istors QDi (9a/QD1, 9b/QD2 for switches 5a, 5b) or other switch type with collectors connected to the resistors Ri and their emitters grounded. Drivers QDi have their bases connected through optional current limitin~ resistor 11 to open collector output of comparator 10 which is normally high through pull~up resistor 12 co~ c~e-l to switched battery voltage Vcc. The non-inverting input of con~c-tor 10 is at a re~erence voltage V'ref, e.g. 2.5 volts, and the inverting input is connected to the output point 10a of a trigger and control circuit, which is normally low, setting the conlpal~lor ~0 output high, all the drive switches DQi on, and all the coil power switches Si off.

CA 02218295 1997- lO- 15 The gate of each switch Si is connected to trigger points Tri (Trl and Tr2 for gate switches S1, S2) through resistors 13a, 13b, ..., ~for switches S1, S2 respectively) which are sequentially turned on to energize each coil Ti in turn.In this design, it is assumed that one of the tngger points Tri is high at all times S (and the others are held low) designating which switch Si should be operating,and ~ nlp~tor 10 provides the dwell time duration control by turning o~f all thedrive switches QDl, Qn2,..., QDn, which enables all the power switches S1, S2, ..., Sn, allowing switch Si to be turned on from trigger Tri. Once coil Ti is energized, i.e. set or peak current Ipo flows through sensor resistor 7, comparator 10 10 hlvelLillg input is pulled low (by transistor 14), its output goes high, all driver switched QD1, QD2, ..., QDn, are turned on, thereby turning off all the power switches including switch Sj which was on.
In ~is trigger input design, tum-off of the power swiLches is accom-plished by sensor NPN tr~n~i~tor 14 (or other switch or cheuill~r) whose base isconnected to the sense point 7a of current sensor 7 and its emitter to ground.
The trigger input circuit shown comprises differenti~ing input circuit made of up of capacitor 15 in series with the trigger input Tr and shunt resistor 16, ofvalues, ~or example, 0.05 microfarads (uF) and 22 kilohms (22K) respectively, followed by series time delay resistor 17, e.g. 2.2K value, shunted by voltage setting zener 18, e.g. 6.2 volt zener, and series isolating diode 19 through which timing capacitor 20 ~of value, e.g. 0.010 uF) is charged, across which is override discharge resistor 21. Turn-off transistor 14 is across the capacitor with its collector connected to the inverting input 10a of the comparator 10 (representing the control point 10a) and its emitter grounded.

2~ When a positive trigger signal is received at the trigger input Tr it is differentiated (if it is a square wave versus pulse) and clipped by zener 18, rapidly charging dwell-time capacitor 20 with a time delay due to (time delay) resistor 17, malcing control node point 10a high and enabling all the power switches. Capacitor 20 remains charged (slowly discharging through discharge -CA 0221829~ 1997-10-1~

resistor 21) and is discharged when control transistor 14 is turned on, to in turn disable all the power switches (including switch Si which was on). The value of the discharge resistor 21 is preferably selected to discharge dwell-time capacitor 20 to the reference voltage V'ref in a time longer than the normal dwell time but 5 not much longer to provide a protective override function.
A simplification of the driver circuit is shown in FIG. 2 wherein one driver switch QD, 22, is used in place of the multiple driver switches QD1, QD2, ..., QDn, with associated isolating diodes D1, D2, ..., ~n (22a, 22b for switches Sa, Sb). Like numerals represent like parts with respect to FIG. 1.
In this figure is also shown a l~rer~lled embodiment power converter and isolation circuit for raising the battery voltage to a higher voltage Vc, which is disclosed elsewhere and shown here as block 23. At its output it includes energystorage capacitor 24 with diode 25 across it which is charged to a voltage Vc from the power converter 23, and includes the current sensor resistor 7 between 15 it and ground and the sensor transistor 14a whose base is grounded in this case and emitter connected to the sense point 7b since the sense voltage is negative in this case (versus positive in the case of FIG. 1) and equal to transistors 14/14a base-emitter voltage ~of typically approximately 0.6 volts).
In this drawing is also shown optional saturating inductor 26 with 20 optional diode 26a across it to reduce the coil output voltage on power switch Si closure as disclosed elsewhere. Also shown is snubber circuit comprised of isolation diodes 27a, 27b,...., connected to each collector of the IGBT power switches Si with their cathodes interconn~cte(l to a snubber capacitor 28 with series resistors 29a and 29b ~hllntecl across it to allow capacitor 28 to discharge 2~ and to provide low control voltage at node point 30. Node point 30 is connected to the base of trigger input (lis~hlin~ transistor 31 (which in FIG. 1 played the role of the control transistor 14~. Snubber circuit plays the usual role of storing and dissipating the high frequency energy associated with both the coil leakage in(lllct~n~e Lpe and optionally saturating inductor 26 inductance.

CA 02218295 1997- lO- 15 WO 97t30287 PCT/US97/02410 The input trigger circuit is the same as that as shown in FIG. 1 except that transis~or 31 across the dwell time capacitor 20 is a disabling switch which m~int~in~ capacitor 20 grounded for a period of time following power switch Si opening (versus switch 14a which actually controls and turns off switch Si). Also 5 shown is an alternate trigger input, designated TrQ, which is a pull-to-groundtrigger (usually an open collector connection point). This trigger input has a pull-up resistor 32 to Vcc and an optional isolating diode 33 in series to the trigger input TrQ. To resistor 32 is connected debounce and isolating circuit made up of paralleled resistor 34 and isolation diode 35, in turn connectecl to isolation 10 capacitor 36 which blocks Vcc from i~telre~ g with the trigger input.
Operation of trigger point TrQ occurs by it being pulled low by an open collector or ignition points and then allowed to go high. When it goes high, a signal passes through isolation diode 35 and capacitor 36 to provide a pulse at input of resistor 17 as with the other trigger circuit Tr, to charge up dwell-time 15 capacitor 20 to enable the power switches Si7 as already described, with turn-off as already described.
In this ple~l-ed embodiment is shown a circuit for sequencing the coil fiAngs ~versus in FIG. 1 where it was assumed that properly sequenced signals Trl, Tr2, ..., Trn, were already provided). This circuit requires a coil ~lring ph~ing input and the use o~ a sequencer, such as an octal counter 37 which is the ~lerelled device shown.
The phasing circuit is modelled after the trigger circuit so that components that play similar roles as in the trigger circuit are given the same numerals with the suffix "a". The PhsQ input is a pull-down phase input and employs pull-up resistor 32a, paralleled resistor 34a and diode 35a and isolating ca~aci~ol 36a. The positive signal phase input Phs uses dirrt;~ ting ca~aci~ol 15a and resistor 16a. H~w~vel, beyond that point ~e circuit differs from the trigger circuit in that it uses an emitter-follower NPN transistor 38 to provide a high impedance to the two phase inputs, with its base connected to input base resistor 17a, its collector connected to a l~r~l~nce voltage, e.g. 5 volts, and its emitter to capacitor 20a and discharge resistor 21 a. The base-emitter diode of the transistor plays the isolating role of diode 19, and the reference voltage Vref provides the limiting l~r~,~;nce voltage for the non-inverting input of c<~ ar~lol 10a (so diode 18a can be a simple diode versus a zener in the case of diode 18).In this case (versus for the case of the trigger circuit), conlydl~tor output isnorm~lly low, with its inverting input connected to a reference voltage V'ref well below Vref, e.g. 2.5 volts. This voltage (already proposed) is ~tt:lin~ble by m~kin~ a resistive divider with two resistors 39 and 40 and Vref. The output of the col~ ualcJl 10a has pull-up resistor 12a to a voltage Vx, preferably higher than 12 volts to be able to drive industrial type IGBT's which re~luire higher gate drive than more conventional clamped ignition IGBTs. Likewise, supply of cc"~ tor io, clock (CLK) input and VCC input of octal counter 37 are connected to Vx. By connecting output of trigger comparator 10 to the enable (ENA) input, and output of phase compdralor 10a to the reset (RST) input, as disclosed in U.S. patent # 5,558,071, proper ~h~ing and actuation of the octal counter 37 outputs connected to the trigger resistors 13a, 13b can be obtained.
That is, with the clock (CLK) input kept high, the outputs of the octal counter will shift when sequential low signals (G0) are received at the enable (ENA) input. Operation of the circuit is known to those versed in the art.
While in the examples of applications of the switch driver it is assumed that one switch is activated at each ignition firing, a number of switches can be sim~llt~nçously activated, e.g. two switches at a time as in an ignition with two spark plugs with per cylinder and one coil and switch per spark plug, and so on.Moreover, while a ~rere"~d embodiment of the switch driver circuit is the use of one diode Di per switch, one control switch QD, and one c~ alator, other co~hin~tions are possible, including using a different c~,nl~ ol or other kind of duration control device or scheme, the main feature of the siln~lired switch driver circuit being the enabling and disabling of all the switches during WO 97t~0287 PCT/US97/02410 ~e ignition coil energizing, on-time, and off-time respectively, and then s~alalely selecting the al~r~liate switch to be turned on, m~king for a very simple and effective design. It is also noted that the resistors 13a, 13b ....
through which is conducted the turn-on current for the gates of the power 5 switches Si, can be large, e.g. in the kilo-ohm range, while the tum-off resistors 8a, 8b, ..., FIG. 1, will be much lower (or absent as shown in FIG. 2, although a small resistor may be included in series with switch 22 (QD)).
A feature of the present invention is simplicity and low cost of the control ci~:uil-~y. In the embodiment of FIG. 2 the current sensing circuit is very simple, compAsed of one tr~n~istor 14a and resistor 7, as is also disclosed in U.S. patent 5,558,071. In that patent is disclosed use of a negative te~ elalulecoefficient resistor (with a resistor in series with it) across the sense resistor to compensate, over a teln~ ul~ range, the negat;ve l~ )elalui~ coeffi~ient of the base-emitter voltage Vbe (~ tely minus 2 millivolts per ~C) of the sense tr~n~i~tor. However, in the present case sense resistor 7 is about one order Of m~gnitllde smaller so the coll.pensation may be more difficult and expensive.FIG. 3 depicts a simple and low cost way of partially compPn~fing the reduction of the sense transistor base-emitter voltage Vbe with temperature, by par~llelin~ the resistors in the current sensing circuits with diodes which carry some or essenti~lly all of the current to be sensed. Only partial c~ ellsation is required since it is desirable to have lower peak currents at higher temperatures, and vice versa. Diode 41 (Dc) is placed across sense resistor 7 to partially compensate the telllpc;l~ture variation of Vbe of sense transistor 14a. A secondcurrent sense circuit for the flyback version of power converter 23 ~FIG. 2) is shown, comprising sense tr:~n.ci~tor 14b and resistor 42 with diode 43 (Ds) across it for contro!ling the current in a flyback converter. Like numerals represent like parts with respect to the earlier figures. The flyback converter, disclosed elsewhere, has a transformer 44, FET switch 45, and output diode 46 to raise battery voltage to a ple~lled voltage Vc of 30 to ~0 volts.
-CA 022l8295 l997- lO- l5 In the case of the power converter sensor, one can select a diode 43, as depicted in FIG. 4a, to have a signi~lc~nt diode voltage Vd red~ction with t~ eld~ at the sense current Isl, shown as 6 amps at 25~C tfor Vsense of 0.6 volts~, so that at 125~C the sense current Is2 is higher than it might otherwise be, i.e. Is3 (shown as 4 amps) had ~e diode 43 not been used. Resistor 42 is included to allow for flexibility of design and for holding the sense point 7b close to ground for shorting out any reverse current. Diode 43 is preferably a Schollky diode to provide low rO.vv~ drop (although a standard diode may be used if higher sense voltage ;s used, i.e. by rn~king transistor 14b a Darlington 10 In this application, the sense circuit is used in conjunction with a timing resistor 47 as disclosed elsewhere.
The current sense circuit for sensing the peak ignition current Ipo works similarly, with curves of FIG. 4b depicting the characteristics of the diode 41 (Dc) which must handle much higher cull~.lls. Two or more diodes may be used 15 in parallel, and the sense voltage Vsense may be made larger as described, i.e.
by ~n~kin~ transistor 14a a D~rlingtcn, or using other means to increase the sense voltage (values are not inflis~ted in FIG. 4b to indicate this variability). In this case, as shown in FIG. 4b, the peak current Ipl is lowered ~rom 30 amps to a peak current Ip2 of 26 amps, versus an overly low current Ip3 of 21 amps 20 ~tt~in~od without the partial co~ )e~ ting effect of the diode 41.
A particularly simple case of the use of compe~e~tin~ sense diodes is when the same sense point is used, as shown in FIG. 5, which depicts for power supply 23 a boost converter with inductor 50, switch 45, and output diode 46.
Like numerals represent like parts with respect to the earlier figures. In this case, 25 sense point 7c is ~he same point for both current sense circuits, although sense transistor 14b has its base connected to the sense point 7c and emitter to ground since it is sensing a power converter positive, versus negative, current. Note that in this figure saturating inductor 26 is shown, which is not essential in some applications.

..
wo 97/30287 PCT/US97102410 In the simplest form OlC a common sense point 7c ~for two sense ci}cuits), resistor 7 can be used as the sense resistor for tr~n~i~tor 14b (not requiring sense diode 43) since the sense current is much smaller, e.g. 3 to 15 amps versus about 30 amps for the peak coil charging current. Resistor 7 is typically between 0.04and 0.2 ohms, depending on the power output of the power converter and type and design, i.e. boost or flyback. Resistor 7 preferably has negative tell~el~t~lre coefficient as is achievable with carbon resistors, or special design resistors, or paralleled resistors as aiready discussed, to provide some temperature comr~n.~tion. Since typically ferrite core material is used for the cores o~ the10 magnetic components 44, 50 of the power converters, and core saturation flux density drops by about 30% for a 100 ~C increase in core temperature, only small ~ pelature compensation may be required for the power converter sense circuit. Therefore, a simple sense circuit for c~)mmon sense point sensing is achievable with a total o~ only four main components, two sense transistors, one15 diode, and one resistor (with parallel resistor components as discussed). If one uses sense transistors with differing base-emitter voltages Vbe, e.g. 0.6 volts for 14b and 1.2 volts for 14a, and the two sense c~u~ ls differ by a factor of only two to three, then the sense resistor can carry the dominant current even for the higher current sense circuit (transistor 14a) and the single sense diode may be 20 either elimin~ted or be a lower cost, lower current diode. Clearly, wi~ comrnon point sensing, both cullt;nts cannot be flowing simultaneously, i.e. the power converter must be turned off during coil charging, as is the ~ler~ d case.
By using the various simplifying control features, circuits, and components disclosed herein, one achieves the benefits of an ignition system 2~ with olltst~n~ing spark characteristics and acceptable cost and relatively simple design. Since certain changes may be made in the above circuits and method without departing from the scope of the invention herein disclosed, it is intended that all matter cont~inecl in the above description, or shown in the accompanying drawings, shall be inl~ eted in an illustrative and not limiting sense.

Claims (38)

What is claimed is:

1 An ignition driver and control system for driving and controlling the power switches of an inductive ignition system with voltage source and with one or more ignition coils Ti and associated power switches Si, each having a controlling element or gate, where the range of selection of j=1,2, ...n, where each coil Ti has a primary winding and secondary winding, and wherein one end of the primary windings of each coil Ti is connected to the high end of said voltage source and the other ends to the separate power switches Si, wherein thelow side of switches Si are returned, through a low resistance sense resistor means, to the low side of said voltage source, wherein said voltage source, eachof the primary windings of said coils Ti, the corresponding switches Si, and thesense resistor means form a set of series circuits, and wherein upon turning on,or closure, of each of switches Si a peak current Ipo is produced within the primary winding of the corresponding coil Ti to energize the coil within a time duration, or dwell-time Tdw, and upon switch Si opening, discharge of said coil energy takes place, the ignition driver being constructed and arranged such that two connections are made to the controlling elements or gates of all switches Si, a first set of common connections from said controlling elements or gates to a switch control circuit which keeps all the switches of a group simultaneously disabled or in the off state for the entire ignition operating time except for the dwell-times Tdw when all the power switches Si of the group are enabled and capable of being turned on, and a second set of connections comprised of separate conductors connecting to each gate of each switch Si of the group, wherein at all times one conductor is in the turn-on-state able to turn on a switch Si and all the other conductors are in turn-off-state to keep the remaining switches off, such that when an ignition firing trigger signal is received, the first connections enable all the switches of the group for the time duration Tdw, but only that switch Si whose gate is connected to the second connection and is in the turn-on state will be turned on for the duration Tdw dictated by the first connection with enabling time Tdw, and all the other switches of the group will be off.

2. The ignition system as defined in claim 1 wherein said switch control circuitcomprises a set of control switches QDi, first set of connections comprise conductors from each gate of said power switches Si to one side of control switches QDi which disable the power switches Si when switches QDi are turned on, and wherein the control element of each of said switches QDi are interconnected so they are all turned on and off together, and wherein they are turned off for a period Tdw when an ignition firing trigger is received, simultaneously enabling all the switches Si for the duration Tdw.

3. The ignition system as defined in claim 2 wherein said control switches QDi are NPN transistors with grounded emitters and with interconnected bases.

4. The ignition system as defined in claim 3 wherein the interconnected bases of said control transistors QDi are constructed and arranged to be kept high at all times except when an ignition firing trigger is received when they are takenlow for a duration Tdw, keeping the transistors QDi in the off state for said time duration Tdw.

5. The ignition system as defined in claim 4 wherein the switches Si are of the class of bipolar transistors with interconnected emitters connected to said sense resistor, the interconnection point defined as the sense point with the other side of the sense resistor grounded, wherein voltage Vsense on said sense point is used to determine the peak current Ipo and hence dwell-time Tdw.

6. The ignition system as defined in claim 5 wherein said interconnected bases of said control transistors QDi are connected to the output of a comparator.

7. The ignition system as defined in claim 6 wherein said sense point is connected to the control point of a sense transistor which returns the output ofsaid comparator to a high level when a sense trip voltage Vsense is attained.

8. The ignition system as defined in claim 7 constructed and arranged so that the non-inverting input of said comparator is at some reference voltage V'ref and the inverting input is normally low except when an ignition firing trigger signal isreceived and it goes high and stays high until pulled low by said sense transistor in time Tdw.

9. The ignition system as defined in claim 8 wherein the ignition firing triggerinput circuit includes a capacitor with shunt resistor across it which is rapidly charged to voltage Vref above V'ref and stays charged above V'ref for at least a time duration Tdw and is discharged after a time Tdw by said sense transistor connected across said capacitor.

10. The ignition system as defined in claim 9 wherein said trigger input circuitincludes a differentiating capacitor and resistor network at its input for reducing a positive going trigger input signal to a duration much less than Tdw, and further including a zener diode for setting the capacitor reference voltage Vref, and an isolation diode which prevents the capacitor from being discharged when the differentiated input trigger signal decays to below Vref.

11. The ignition system as defined in claim 1 wherein said first set of connections comprise connections from each gate of said power switches Si to the anodes of isolation diodes Di whose cathodes are interconnected to one side of a control switch QD which disables the power switches Si when switch QD
is turned on, and wherein said switch QD is turned off for a period Tdw when an ignition firing trigger is received, simultaneously enabling all the switches Si for the duration Tdw.

12. The ignition system as defined in claim 11 wherein said control switch QD
has its other side grounded and its control point kept high at all times except when an ignition firing trigger is received when it is taken low for a duration Tdw, keeping switch QD in the off state for said duration Tdw.

13. The ignition system as defined in claim 12 wherein the switches Si are of the class of bipolar transistors comprised of IGBT switches with interconnected emitters connected to ground, and wherein said low resistance sense resistor is connected at the low side of said voltage source point of voltage Vc, said low side defined as the sense point and the other side of sense resistor grounded, and constructed and arranged so that voltage Vsense on said sense point is usable todetermine the peak current Ipo and hence dwell-time Tdw.

14. The ignition system as defined in claim 13 wherein said sense point is connected to the emitter of a sense NPN transistor whose base is grounded and which is turned on when the negative sense voltage, due to coil primary current flow, equals the sense transistor base-emitter voltage Vbe.

15. The ignition system as defined in claim 14 wherein the collector of said sense transistor is connected to the inverting input of a comparator whose output is connected to the control point of said control switch QD which is normally kept high, and wherein the non-inverting input of the comparator is kept at a reference voltage V'ref, such that when an ignition firing trigger signal is received the inverting input which is normally low goes high to a voltage Vref above V'ref, flipping the comparator output low, turning off switch QD, and enabling the power switches Si, one of which is turned on through said second connection point and kept on for a period Tdw until the sense transistor begins to conduct.

16. The ignition system as defined in claim 15 wherein the ignition firing trigger input circuit includes a timing capacitor with shunt resistor, which upon receipt of a trigger signal is rapidly charged to a voltage Vref above V'ref and stays charged above V'ref for at least time duration Tdw and discharged after time Tdw by said sense transistor whose collector is connected to said timing capacitor, wherein said trigger input signal at a terminal Tr is either a positive pulse or positive step in voltage of a value at least equal to said reference voltage Vref.

17. The ignition system as defined in claim 16 wherein said trigger input circuit comprises a differentiating capacitor and resistor network at its input for reducing the trigger input signal of terminal Tr to a duration much less than Tdw, and further comprising a zener diode for setting the capacitor reference voltage Vref, and an isolation diode which prevents the timing capacitor from being discharged when the differentiated input trigger signal decays to below Vref, and which further includes a snubber controlled switch across said timing capacitor which is turned on and keeps the capacitor discharged after an energized power switch Si has been turned off and charges a snubber capacitor to a high voltage, a portion of which voltage is used to turn on said snubber controlled switch and keep the timing capacitor discharged for a period of time dictated by a time constant set by the snubber capacitor and one or more resistors shunting the snubber capacitor.

18. The ignition system as defined in claim 17 wherein said ignition controller includes a phase input circuit and octal counter whose outputs provide said second connections to the gates of said power switches Si, the clock (CLK) inputof said octal counter being kept at a high supply voltage, the enable (ENA) input connected to the output of said comparator, and the reset input (RST), which is normally low, being connected through a circuit to the phase input and taken high when a signal is received at the phase input, the phase input providing theproper beginning of the coil firing sequence and the octal counter providing theactual sequence of ignition coil Ti firing signals.

19. The ignition system as defined in claim 18 wherein the phase input circuit shares some common features with the trigger input circuit, (a) a differentiating capacitor and resistor network at its input for reducing a positive input phase signal to a suitable duration, (b) a phase NPN transistor whose base receives the differentiated signal and whose collector is taken to the reference voltage Vref for setting a phase timing capacitor reference voltage close to Vref as is done with the zener diodein the trigger input circuit, the base-emitter junction of the transistor providing isolation to prevent a phase timing capacitor connected to the emitter of the phase transistor from being discharged when the differentiated input phase signal decays as is done with the isolation diode in the trigger input circuit, (c) a discharge resistor across the phase capacitor, and (d) the emitter of the phase transistor being connected to the non-inverting input of said phase comparator whose inverting input is at the reference voltage V'ref and whose output, is connected to the reset pin, RST, of the octal counter.

20. The ignition system as defined in claim 19 constructed and arranged for automotive use or the like wherein said voltage source point is an energy storage capacitor C charged to said voltage Vc above the normal automotive battery voltage of 13 volts.

21. The ignition system as defined in claim 20 wherein said voltage Vc is in therange of 24 to 80 volts and wherein said coils Ti store a high energy above 100 millijoules during coil Ti primary winding charging to peak current Ipo for delivery to a spark gap.

22. The ignition system as defined in claim 17 wherein an alternative trigger input TrQ is available for the case of an open collector trigger connection point or ignition points, input of TrQ comprised of a pull-up resistor to a supply voltage Vcc, a paralleled resistor and diode acting also as a points debounce circuit, followed by a capacitor which blocks the supply voltage Vcc from interfering with the positive trigger differentiating input of the trigger inputterminal Tr.

23. The ignition system as defined in claim 22 wherein the output of said alternate trigger input TrQ, comprised of a capacitor, is connected to said differentiating resistor whose other side is grounded.

24. An inductive ignition system with voltage source and with at least one groupof one or more ignition coils Ti and associated power switches Si, each having a controlling element or gate, where the range of selection of i=1,2, ...n, with an ignition driver and control system for driving and controlling said power switches, each coil Ti having a primary and secondary winding, and comprising (a) means for interconnecting one end of the primary windings of each coil Ti to a common voltage source point connected to the high end of said voltage source and the other ends to the separate power switches Si, (b) means for interconnecting and electrically returning low sides of switches Si through means for a low resistance sensing to the low side of said voltage source, (c) wherein said voltage source, each of the primary windings of said coils Ti, the corresponding switches Si, and the means for sensing form a set ofseries circuits, and wherein upon turning on, or closure, of each of switches Sia peak current Ipo is produced within the primary winding of the corresponding coil Ti to energize the coil within a time duration, or dwell-time Tdw, and uponswitch Si opening, discharge of said coil energy takes place, (d) the said ignition driver and control system being constructed and arranged such that two connections are made to the controlling elements or gatesof all switches Si, using the following:
(i) means for establishing a first set of common connections from said controlling elements or gates to a circuit which keeps all the switches of a group simultaneously disabled or in the off state for the entire ignition operating time except for the dwell-times Tdw when all the power switches Si of the group are enabled and capable of being turned on, (ii) means for establishing a second set of connections comprised of separate conductors connecting to each gate of each switch Si of the group, wherein at all times one conductor is in the turn-on-state able to turn on a switch Si and all the other conductors are in turn-off-state to keep the remaining switches off, and (iii) the said means (i) and (ii) being constructed and arranged such that when an ignition firing trigger signal is received, the said means for establishing the first connections enable all the switches of the group for the time durationTdw, but only that switch Si whose gate is connected to the second connection established by said means (ii) for second connections and is in the turn-on state will be turned on for the duration Tdw dictated by the first connection with enabling time Tdw, and all the other switches of the group will be off.

25. The system of claim 24 with "i" equal to 2 or greater.

26. The ignition system as defined in claim 5 wherein a diode means is placed across said sense resistor to carry part or essentially all of the current and provide a voltage which is sensed by a sensor to provide partial temperature compensation of the reference sensor voltage.

27. The ignition system as defined in claim 7 wherein a diode means is placed across said sense resistor to partially compensate the base-emitter voltage Vbe reduction with temperature of said sense transistor.

28. The ignition system as defined in claim 14 wherein a diode means is placed across said sense resistor to partially compensate the base-emitter voltage Vbe reduction with temperature of said sense transistor.

29. The ignition system as defined in claim 1 wherein said voltage source is a battery of voltage Vb with a power converter for raising said battery voltage Vbto a higher voltage Vc, wherein said power converter includes a current sensing circuit for setting the peak power converter current, said sensing circuit comprised of a parallel combination of sense resistor and sense diode means, through which flow the power converter current, and a sense transistor whose base-emitter voltage Vbe defines the reference sense voltage.

30. The ignition system as defined in claim 29 wherein said sense diode means comprises Schottky diode means.

31. The ignition system as defined in claim 29 wherein said power converter comprises capacitor means and is constructed and arranged to charge up capacitor means to the voltage Vc and wherein an in-parallel sensor resistor anddiode is placed at the ground side of said capacitor means for sensing the peak ignition coil charging current Ipo.

32. The ignition system as defined in claim 1 wherein said voltage source is a battery of voltage Vb with a power converter for raising said battery voltage Vbto a higher voltage Vc and charging a capacitor means, and wherein at least one sense resistor and sense diode means are connected in parallel to the low side of said capacitor means and their other points to ground, the connection point to the capacitor defined as a common sense point having two sense transistors connected to it, a power converter current sense transistor with base connected to the sense point and its emitter to ground, and a peak ignition coil charging current Ipo sense transistor with its emitter connected to the same sense point and its base to ground.

33. The ignition system as defined in claim 32 wherein said one or more diode means are used also for partially compensating the temperature variation of the reference sense voltage of one or both of the sense transistors.

34. The ignition system as defined in claim 33 wherein said sense resistor is used to provide the main sense control voltage of the power converter current control and said diode to provide the main sense control voltage of the peak ignition coil charging current Ipo.

35. The ignition system as defined in claim 34 wherein the sense voltage Vbe of the power converter sense transistor is lower than that of the sense voltage of the sense transistor of the ignition current Ipo.

36. The ignition system as defined in claim 35 wherein the sense resistor carries the main current for both the power converter and the ignition coil charging in at least one temperature range and wherein said sense resistor has some temperature compensating feature.

37. The ignition system as defined in claim 32 wherein said power converter is a flyback converter.

38. The ignition system as defined in claim 32 wherein said power converter is a boost converter.