Protective device for a tripping circuit for a personal protection device for a vehicle and tripping circuit

Abstract

Protective device (104) for a tripping circuit for a personal protective device (102) for a vehicle (100), wherein the tripping circuit comprises an ignition device (110), a high-side output stage (112) for connecting a high-side terminal (116) of the ignition device (110) to a first voltage potential (120) and a low-side output stage (114) for connecting a low-side terminal (118) of the ignition device (110) to a second voltage potential (122), and wherein the protective device (104) has the following features: a highside interface (130) for contacting the protective device with the highside terminal (116) of the ignition device (110) and a lowside interface (132) for contacting the protective device with the lowside terminal (118) of the ignition device (110); a suppressor diode (134) connected between the high-side interface (130) and the second voltage potential (122), the anode of the suppressor diode (134) being connected to the second voltage potential (122); and a first diode (136) connected between the low-side interface (132) and the second voltage potential (122), wherein the anode of the first diode (136) is connected to the second voltage potential (122); a second diode (336) connected between the low-side interface (132) and the second voltage potential (122), the anode of the second diode (336) being connected to the second voltage potential (122); and wherein the first diode (136) and the second diode (336) are arranged as a switching diode pair on a die (351).

Description

State of the art

[0001] The invention is based on a protective device for a triggering circuit for a personal protection device for a vehicle and a triggering circuit for a personal protection device according to the class of the independent claims.

[0002] Airbag systems have high-side and low-side output stages that must meet specific ESD (electrostatic discharge) requirements. These primarily serve to ensure the safe processing of the components during the control unit manufacturing process. These must meet the requirements of the Human Body Model (HBM) with a 100pF discharge resistor, a 1500 ohm discharge resistor, and a charging voltage of + / -2000V or + / -4000V, depending on the test class, without damage.

[0003] DE 199 34 559 C1 discloses a switching output stage for an igniter of an occupant protection device.

[0004] US 2005 / 0200203 A1 discloses a noise protection circuit with three Zener diodes, one of which is connected in parallel to a squib and the others between a terminal of the squib and a body of a vehicle.

[0005] To meet the significantly higher ESD requirements resulting from the installation of the airbag control unit in a vehicle, additional external measures, usually capacitances on the high-side firing circuit and the low-side firing circuit of an airbag power amplifier ASIC, must be provided.

[0006] The requirements typically specify contact discharges on the control unit pins in the passive state corresponding to HBM models with 330pF, 2000 Ohm, + / -8000V (IS01 0605).

[0007] Static short circuits to vehicle ground or vehicle supply voltage are also tolerated. All of these requirements specifically cover faults in the vehicle not involved in the crash.

[0008] DE 10 2013 211 421 A1 describes a device for operating a cold gas generator. Disclosure of the invention

[0009] Against this background, the approach presented here proposes a protective device for a triggering circuit for a personal protection device for a vehicle and a triggering circuit according to the main claims. The measures listed in the dependent claims allow advantageous further developments and improvements of the device specified in the independent claim.

[0010] By using the protective device, the trigger circuit can be protected from damage and malfunctions, for example in the event of a collision of the vehicle, hereinafter also referred to as a crash, which could be triggered, for example, by an accident-related short circuit to a consumer installed in the vehicle.

[0011] A trigger circuit for a personal protection device for a vehicle has an ignition device, a high-side output stage for connecting a high-side terminal of the ignition device to a first voltage potential and a low-side output stage for connecting a low-side terminal of the ignition device to a second voltage potential.

[0012] The personal protection device can, for example, be an occupant protection device or a pedestrian protection device, for example in the form of an airbag. The personal protection device can be activated using the trigger circuit. The ignition device is also referred to below as the ignition circuit and can, for example, comprise an igniter with an ignition charge in addition to the forward and return lines. The high-side output stage can have a high-side switch via which a high-side terminal of the ignition device can be electrically connected to the first voltage potential, for example to a conductor or terminal carrying the first voltage potential. The first voltage potential can, for example, correspond to an ignition voltage for igniting the ignition device.The low-side output stage can have a low-side switch, via which a low-side terminal of the ignition device can be electrically connected to the second voltage potential, for example, to a conductor or terminal carrying the second voltage potential. The second voltage potential can, for example, correspond to a ground potential. The protective device can improve the robustness of the trigger circuit against injection currents.

[0013] The protective device for the trigger circuit has a high-side interface for contacting the protective device with the high-side terminal of the ignition device and a low-side interface for contacting the protective device with the low-side terminal of the ignition device, a suppressor diode connected between the high-side interface and the second voltage potential, and at least one first diode connected between the low-side interface and the second voltage potential.

[0014] The high-side interface and the low-side interface may each comprise one or more terminals or lines via which the protective device can be electrically connected to the terminals of the ignition device.

[0015] The anode of the suppressor diode and, correspondingly or alternatively, the anode of the first diode can be connected to the second voltage potential. Injection currents, for example, can be diverted via these diodes.

[0016] The protection device can include a second diode connected between the low-side interface and the second voltage potential. This allows two diodes to be connected in parallel. The two diodes allow the current load of the low-side output stage diodes to be reduced.

[0017] The first diode and the second diode can be arranged on a die. A die can be understood as a piece of semiconductor substrate. Arranging them together on a die enables a cost-effective and space-saving implementation.

[0018] The protection device may include an additional suppressor diode connected between the high-side and low-side interfaces. This allows an injection current to be bypassed by the ignition device.

[0019] Both suppressor diodes can be arranged on one die. This can be the one already mentioned or a separate die.

[0020] According to one embodiment, the ignition device can be embodied as an airbag ignition circuit. Advantageously, the described approach can be used in conjunction with ignition devices installed in areas of a vehicle that may be deformed in a collision.

[0021] A trigger circuit for a personal protection device for a vehicle has the following features: an ignition device; a high-side output stage for connecting a high-side terminal of the ignition device to a first voltage potential; a low-side output stage for connecting a low-side terminal of the ignition device to a second voltage potential; and a protective device which contacts the high-side terminal of the ignition device via the high-side interface and the low-side terminal of the ignition device via the low-side interface.

[0022] Furthermore, a method for protecting a trigger circuit for a personal protection device for a vehicle from the effects of an induction current injected into the trigger circuit is presented. The trigger circuit comprises an ignition device, a high-side output stage for connecting a high-side terminal of the ignition device to a first voltage potential, and a low-side output stage for connecting a low-side terminal of the ignition device to a second voltage potential. The method comprises the following steps: Dissipating at least a portion of the injection current via a suppressor diode connected between the high-side terminal and the second voltage potential; and

[0023] Diverting at least a portion of the injection current via at least one first diode connected between the low-side terminal and the second voltage potential.

[0024] The injection current can be a negative or positive current. By diverting the injection current, malfunctions and damage to the trigger circuit can be prevented. The steps of the method can be implemented, for example, using devices of the aforementioned protective device.

[0025] According to one embodiment, at least a portion of the injection current, in particular a portion of the injection current that could flow through the ignition device, can be diverted through a parallel path formed by a suppressor diode connected between the low-side terminal and the high-side terminal. The suppressor diode connected in parallel with the ignition device can provide further protection for the ignition device.

[0026] Examples of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows: Fig. 1 a schematic representation of a vehicle with a protective device for a trigger circuit for a personal protection device according to an embodiment; Fig. 2 is a flowchart of a method for protecting a trigger circuit for a personal protection device according to an embodiment; Fig. 3 shows a protective device for a trigger circuit for a personal protection device according to an embodiment; Fig. 4 a schematic representation of a vehicle with an ignition circuit protection circuit for a trigger circuit for a personal protection device; Fig. 5 a schematic representation of possible injection flows with respect to the Fig. 4 shown trigger circuit; Fig. 6 is a schematic representation of a vehicle with a protective device for a trigger circuit for a personal protection device according to an embodiment; Fig. 7 a schematic representation of possible injection flows with respect to the Fig. 6 shown trigger circuit according to an embodiment; Fig. 8 a model of an effect of an injection current with respect to the Fig. 6 shown trigger circuit according to an embodiment; Fig. 9 a graphical representation of injection flows with respect to the Fig. 6 shown trigger circuit according to an embodiment; Fig. 10 a model of an effect of an injection current with respect to the Fig. 6 shown trigger circuit according to an embodiment; Fig. 11 a model of an effect of an injection current with respect to the Fig. 6 shown trigger circuit according to an embodiment; and Fig. 12 a schematic representation of possible injection flows with respect to the Fig. 6 shown trigger circuit according to an embodiment.

[0027] In the following description of advantageous embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted.

[0028] Fig. 1 shows a schematic representation of a vehicle 100 with a personal protection device 102 and a protection device 104 for a trigger circuit of the personal protection device 102 according to one exemplary embodiment. For example, the personal protection device 102 is an airbag that can be activated in the event of a collision of the vehicle using the trigger circuit, for example, to protect a driver of the vehicle 100 from the consequences of the collision.

[0029] The trigger circuit comprises an ignition device 110, a high-side output stage 112, and a low-side output stage 114. The ignition device 110 is connected to the high-side output stage 112 via a high-side terminal 116 and to the low-side output stage 114 via a low-side terminal 118. By appropriately controlling the high-side output stage 112, the high-side terminal 116 of the ignition device 110 can be connected to a first voltage potential 120, which corresponds, for example, to an ignition voltage for igniting the ignition device 110. By appropriately controlling the low-side output stage 114, the low-side terminal 118 of the ignition device 110 can be connected to a second voltage potential 122, which corresponds, for example, to a ground potential.If the output stages 112, 114 are connected accordingly, the terminals 116, 118 of the ignition device 110 are connected to the potentials 120, 122, resulting in an ignition current flowing through the ignition device 110 and activating the ignition device.

[0030] The protective device 104 has a high-side interface 130 and a low-side interface 132. In the installed state, the protective device 104 is electrically conductively connected to the high-side terminal 116 of the ignition device 110 via the high-side interface 130. In the installed state, the protective device 104 is electrically conductively connected to the low-side terminal 118 of the ignition device 110 via the low-side interface 132.

[0031] A suppressor diode 134 of the protective device 104 is connected between the high-side interface 130 and a terminal carrying the second voltage potential 122 in the operational state of the protective device 104. At least one first diode 136 is connected between the low-side interface 132 and a terminal carrying the second voltage potential 122 in the operational state of the protective device 104.

[0032] The protective device 104 can protect the trigger circuit from undesirable effects of an injection current 138, which may be injected into a line section of the trigger circuit in the event of a collision of the vehicle 100 and a resulting deformation of the vehicle 100.

[0033] The approach described is not about protective components that enable safe activation of pyrotechnic ignition circuits 110, but rather it is about the “vehicle crash case” and the dangers that other devices can pose to them, in particular when using ignition circuits 110 in the crash zone.

[0034] This is explained below using an example. A pyrotechnic ignition circuit 110 is used in the engine compartment to interrupt the vehicle's battery-generator connection.

[0035] In an assumed crash situation, the engine compartment is deformed and the wiring (forward and return lines) of the ignition circuit 110 in the engine compartment is short-circuited with an electrical consumer and the supply to this consumer is cut off.

[0036] The airbag control unit is now exposed to the dangers this consumer can pose to the connected airbag electronics via the ignition cables. The danger is particularly high with inductive consumers such as motors, ignition coils, or horns.

[0037] According to one embodiment, the protective device is designed to match the properties of the airbag electronics and prevents the above-described process from affecting the airbag electronics to such an extent that a RESET detection in the system ASIC caused by substrate currents could occur or that the ASIC could be destroyed. This can prevent the airbag system from failing in the event of a crash, from partially failing, depending on the timing of the fault, or from unintentionally activating firing circuits 110 at the wrong time. Thus, the protective device enables protective measures on the airbag firing circuit 100 against external influences, in particular inductive external influences.

[0038] Fig. 2 shows a flowchart of a method for protecting a trigger circuit for a personal protection device according to an embodiment. This can be the Fig. 1 shown trigger circuit.

[0039] The method is carried out according to one embodiment when at least one injection current is injected into the trigger circuit. In this case, at least a portion of the injection current is diverted via a suppressor diode 201, as described with reference to Fig. 1 and additionally or alternatively at least a part of the injection current is diverted 203 via at least one first diode, as described in Fig. 1. Accordingly, steps 201, 203 can be executed simultaneously, staggered in time, or individually.

[0040] Furthermore, in one of the diversion steps 201, 203 or in a further diversion step, a portion of the injection current that could flow through the ignition device can be diverted via a parallel path. According to one embodiment, the parallel path is formed by a suppressor diode connected between the low-side terminal and the high-side terminal, and thus in parallel with the ignition device.

[0041] Fig. 3 shows a protective device 104 for a trigger circuit for a personal protection device according to an embodiment. This can be an embodiment of the device described with reference to Fig. 1 described protective device 104 and trigger circuit.

[0042] The high-side terminal 116 is also referred to here and below as "ZK+x," and the low-side terminal 118 is also referred to as "ZK-x." According to this exemplary embodiment, the cathode of the suppressor diode 134 is connected to the high-side terminal 116 of the ignition device 110 via the high-side interface 130. The suppressor diode 134 is also referred to here and below as "ZD_1."

[0043] According to this exemplary embodiment, the cathode of the first diode 136 is connected to the low-side terminal 118 of the ignition device 110 via the low-side interface 132. The first diode 136 is also referred to here and below as "D_1."

[0044] A connection connecting the high-side connection 116 to the high-side power amplifier is referred to here and below as “IGHx” and a connection connecting the low-side connection 118 to the low-side power amplifier is referred to here and below as “IGLx”.

[0045] Optionally, the protection device 104 has a second diode 336 which is connected in parallel to the first diode 136 and is also referred to here and below as “D_2”.

[0046] Optionally, the protection device 104 includes a further suppressor diode 337 connected between the interfaces 130, 132. According to this exemplary embodiment, the cathode of the further suppressor diode 337 is connected to the high-side interface 130. The further suppressor diode 337 is also referred to here and below as "ZD_2."

[0047] Line sections located between the interfaces 130, 132 and the terminals 116, 118 are each coupled to the second voltage potential 122, here ground, via a capacitor.

[0048] According to one embodiment, the protective device 104 is a protective circuit of an ignition device 110 designed as an ignition circuit, in particular as an airbag ignition circuit. In the following, the protective device 104 is also referred to as protective circuit 104 and the ignition device 110 is also referred to as ignition circuit 110.

[0049] The protective device 104 makes it possible to ensure the robustness of special ignition circuits 110 of the airbag control unit located in the crumple zone of vehicles, such as disconnecting the battery from the generator, triggering the hood lift, activating extinguishing devices, etc., against short circuits to inductive loads. In particular, it makes it possible to prevent the overall function of the control unit from being compromised in a crash if massive electrical loads occur on external ignition circuits 110 in the crumple zone.

[0050] The robustness of the ignition circuit 110 in the crumple zone against current injection is compared to the following using the Fig. 4 and Fig. 5 designs shown have been increased many times over.

[0051] Specifically, the approach described here can reduce the risk of false triggering due to injection current. Peak values, also referred to below as peak values, between 4A and 8A can be achieved.

[0052] Furthermore, the destruction of the ignition circuit output stages and subsequent phenomena such as RESET can be prevented up to very high injection current levels (>20A).

[0053] Advantageously, a uniform ASIC ignition triple output stage design can be made usable for up to n ignition circuit connections with uniform requirements for the vehicle interior (driver airbag, ...) by the protection circuit 104 for the vehicle crumple zone.

[0054] According to the Fig. In the embodiment shown in Figure 3, the protection circuit 104 comprises two suppressor diodes ZD_1, ZD_2. According to one embodiment, the suppressor diodes ZD_1, ZD_2 are implemented as a suppressor diode pair on a die 350 in a package.

[0055] Furthermore, the protective circuit comprises the Fig. 3, the two diodes D_1, D_2. According to one embodiment, the two diodes D_1, D_2 are implemented as fast switching diodes and, according to one embodiment, as a switching diode pair on a die 351 in a package. According to one embodiment, the suppressor diodes ZD_1, ZD_2 and the diodes D_1, D_2 are arranged on separate dies enclosed in separate packages.

[0056] Fig. 4 shows a schematic representation of a vehicle 100 with an ignition circuit protection circuit for a trigger circuit for a personal protection device.

[0057] The trigger circuit has an ignition device 110, here in the form of an ignition circuit with a squib, a high-side output stage 112 and a low-side output stage 114.

[0058] The high-side output stage 112 has the functionalities of a driver, a regulator, and a logic-implementing device 440, via which a switch, here a transistor TH of the high-side output stage 112, is controlled. The device 440 is configured to receive, on the input side, in addition to signals µC_CTL and SCON_CTL, auxiliary voltages as well as references regarding current and voltage. The high-side output stage 112 further has a diode D_th_d, a shunt resistor RsH, and a diode D_th_sd of the transistor TH, with respect to which Fig. 4, a voltage Uth is shown. On the input side, a switched ignition voltage is supplied to the high-side output stage 112 via a diode D_H and a terminal VHx. A line connecting the high-side output stage 112 to the high-side terminal ZK+x is coupled to ground via a capacitor in the form of an EMC / ESD MLCC.

[0059] The low-side output stage 114 has the functionalities of a driver, a regulator, and a logic-implementing device 442, via which a switch, here a transistor TL of the low-side output stage 114, is controlled. The device 442 is configured to receive, in addition to other signals, auxiliary voltages and references regarding current and voltage on the input side. The low-side output stage 114 further has a diode D_th_d, a shunt resistor RsL, and a diode D_th_sd of the transistor TL. Furthermore, a shunt resistor RsL connected to ground is shown. A line connecting the low-side output stage 114 to the low-side terminal ZK-x is coupled to ground via a diode D_ESD of a negative IGL-ESD-P circuit and via a capacitor in the form of an EMC / ESD MLCC.

[0060] The output stages 112, 114 are implemented in a system ASIC 444 together with the diode D_ESD, further diodes D_HK, D_LK and a positive IGH / IGL_ESD-P circuit 443, which comprises a transistor T_ESD with a diode D_tesd_sd, a further Zener diode ZD_ESD and a resistor RG.

[0061] The system ASIC 444 is arranged on a circuit board 446 which is designed as an airbag ECU PCB.

[0062] Fig. 5 shows a schematic representation of possible short circuit variants 501, 502, 503, 504 with respect to the Fig. 4 shown trigger circuit.

[0063] In addition, Fig. 5 shows a voltage potential 520, which represents the vehicle plus potential (6 ... 20V) 520, as well as the vehicle chassis ground 522. Furthermore, a current Iv is shown, which flows between the potentials 520, 522 via a resistor Rv and an inductance Lv.

[0064] According to this embodiment, the ignition device 110 has a resistance Rsq of 1.7 to 2.5 ohms.

[0065] In the following, the ignition circuit performance of the Fig. 4 and Fig. 5 described circuit is considered using different DC short circuit variants 501, 502, 503, 504.

[0066] The ignition circuit output stages (high-side, low-side) 112, 114 and the ignition circuit wiring are designed so that a static short circuit on the ignition circuit plus (ZK+) / minus (ZK-) side to vehicle plus (6V ... 20V) 520, as shown by the variants 501, 502, cannot cause any currents via the ignition device 110 in the form of an igniter (squib), which could cause an unwanted triggering.

[0067] For this purpose, the EMC capacitors at the terminals ZK+x, ZK-x are dimensioned so that the charging current caused does not exceed the “no fire” requirements (e.g. 5A@4µs) of the igniter 110.

[0068] All transistor structures TH, TL and the Pos. IGH / IGL ESD element 443 do not conduct before 36V, depending on the process of the ASIC 444.

[0069] The ignition circuit output stages (high-side, low-side) 112, 114 and the ignition circuit wiring are designed so that a static short circuit on the ignition circuit plus (ZK+) / minus (ZK-) side to vehicle ground (chassis) 522, as shown by variants 503, 504, cannot cause currents via the ignition element 110, which could cause an unwanted triggering.

[0070] For this purpose, there must not be a quasi-static ground offset of approximately 1.5V between the airbag control unit ground and the vehicle chassis ground 522, otherwise the "No fire" requirement (e.g. 0.4A@10s) of the igniter 110 cannot be met in the event of error 503, since the low-side ESD diodes D_ESD are conducting.

[0071] Likewise, in error case 504, there must not be a quasi-static ground offset of approximately 4V (Uth=2.5V+1.5V) between the airbag SG ground and the vehicle chassis ground 522, otherwise the "No fire" requirement (e.g. 0.4A@10s) of the igniter 110 cannot be met, since the diode D_th_d and the H-side transistor TH are conducting when the ignition voltage VHx is switched off.

[0072] Fig. Figure 6 shows a schematic representation of a vehicle 100 with a protective device 104 for a trigger circuit for a personal protection device according to an exemplary embodiment. The trigger circuit corresponds to the one described with reference to Fig. 4, which is supplemented by the protective device 104. According to one embodiment, the protective device 104 is the circuit described with reference to Fig. 3 described protective device.

[0073] Furthermore, a case 501 of a possible injection current is shown. For this purpose, Fig. 5 shows the voltage potential 520, which represents the vehicle plus potential (6 ... 20V), as well as the vehicle chassis ground 522 and possible current profiles of a current Iv flowing via the resistor Rv and the inductance Lv between the potentials 520, 522.

[0074] According to one embodiment, the protection device 104 is designed as an ignition circuit protection circuit for the crash zone of the vehicle 100.

[0075] The protective device 104 provides sufficiently effective protection measures if short circuits occur on the ignition circuit 110 against inductive loads in the crash zone, whose supply is sheared off under load, which is equivalent to an electrical disconnection. Such a case 501 is described in Fig. 6. In the crash zone, the ignition circuit 110 is pressed against the supply line 656 of an inductive consumer Lv, for example the horn or an electric motor of the vehicle 100, and the consumer supply line 656 is sheared off, as is the case with the switch 658 in Fig. 6 is indicated.

[0076] In this case 501 the current Iv in the consumer commutates into the ignition circuit short circuit as injection current.

[0077] On the one hand, this current must be kept away from the igniter 110, and on the other hand, it must not overload the ESD and input structures of the high-side and low-side output stages 112, 114 or damage them to such an extent that a RESET monitor in the system ASIC 444 could respond.

[0078] Fig. Figure 7 shows a schematic representation of possible injection currents with respect to the Fig. 6 according to an embodiment. In particular, a current distribution at the short-circuited trigger circuit 110 after a current commutation is shown, as can be seen from Fig. 6. This scenario is described below using the example shown in Fig. Case 701 shown in Figure 7.

[0079] By means of the protection circuit 104, which is also referred to as “ZK-PC_CZ” (ignition circuit protection circuit crash zone), the injection current caused by the commutation of the load current Iv into the ignition circuit 110 is theoretically split at the injection point, indicated by the arrow representing case 701, into two partial currents Iv_p, Iv_m.

[0080] The partial flow Iv_m via the igniter 110 shall not violate the “No Fire” condition in a first load case.

[0081] For this purpose, the current Iv_m should be kept below 0.4A for relevant times > 4µs.

[0082] For this purpose, the suppressor diode ZD_1 is connected between the control unit ground 122 (anode) and the ZKx+ terminal (cathode). According to one embodiment, the suppressor diode ZD_1 has a small rd_zdf (diff. resistance, forward) to divert as much injection current as possible to ground 122.

[0083] A fast switching diode pair D_1, D_2 is connected to the ZKx- terminal between control unit ground 122 (anode) and ZKx- (cathode).

[0084] According to one embodiment, this is done to reduce the current load on the ASIC low-side diodes and prevent the risk of destruction or reset detection. According to one embodiment, a switching diode pair D_1, D_2 with a medium rd_df is selected.

[0085] Depending on the location of the short-circuit point, an additional suppressor diode ZD_2, in particular as the second diode of a cathode-coupled suppressor diode pair ZD_1, ZD_2 between the terminals ZKx- (anode) and ZKx+ (cathode) may prove to be an optimization in order to avoid having to conduct part of the injection current via the igniter 110.

[0086] The following assumptions are made: To easily consider high current injection at the ignition circuit 110, all diodes can be set to the same forward voltage (small differences do not matter, the differential resistance is crucial), resulting in a voltage Uf=0.8V.

[0087] All ZK EMV / ESD capacitances are irrelevant in the time range >4µs.

[0088] Fig. Figure 8 shows a model of an effect of an injection current with respect to the Fig. 6 according to one embodiment. In particular, an ignition circuit model for the effect of the injection current Iv on the igniter 110 is shown. The suppressor diode of the protection circuit 104 is modeled by a resistor rd_zdf, the further suppressor diode by a resistor rd_zdf, and a switch S2, which is closed when the voltage UZK between the terminals ZK+x, ZK-x is > 0.8V. The first and second diodes are modeled by the resistor rd_df. The ignition device 110 is modeled by the forward and return line resistances Rltg_p, Rltg_m, and the igniter (squib) resistor R_SQUIB.

[0089] The following values ​​are assumed as examples: R_SQUIB=2.15 ohms Rltg_p=0.175 Ohm;(5m;Cu) Rltg_m=0.175 Ohm;(5m;Cu) Rtm=0.2 Ohm;(Track,Bonds) rd_zdf=0.2 Ohm rd_df=0.5 Ohm rd_LSf=0.33Ohm lv=Peak consumer current Lv=1mH

[0090] From the Fig. The ignition circuit model shown in Figure 8 for the effect of the injection current Iv on the igniter 110 results in the following values ​​when the switch S2 is open: Rp=Rltg_p+rd_zdf=0.375 Ohm Rm=R_SQUIB+Rtlg_m+rd_df*(Rtm+rd_LSf) / (rd_df+Rtm+rd_LSf)=2.15Ohm+0.175Ohm+0.5Ohm*(0.2 Ohm+0.33Ohm) / (0.5Ohm+0.2Ohm+0.33Ohm)=2.325Ohm+0.275Ohm=2.582OhmRg=Rp*Rm / (Rp+Rm)=0.327 Ohm lv_m / Lv=Rg / Rm→lv_m=lv*(Rg / Rm)=lv*0.127 lv_m_nofire=0.4A→lv_nofire=0.4A / 0.127=3.15A lv_p_nofire=lv_nofire−lv_n_nofire=2.75A UZK_nofire=lv_m_nofire*(Rltg_m+R_SQUIB)−Rltg_p*lv_p_nofire=0.4A*(0.175+2.15)Ohm−0.175Ohm*2.75A=0.448V→Assumption S2=open is true

[0091] The ignition circuit wiring for the crash zone increases the robustness of the affected igniter 110 against injection currents, especially decaying inductive ones, by approximately 10 times.

[0092] If the short-circuit point is closer to the control unit, the closed switch S2, which means that the additional suppressor diode ZD_2 is conducting, results in a further increase in the robustness of the affected igniter against injection currents by up to 20 times compared to the standard (0.4A).

[0093] Fig. Figure 9 shows a graphical representation of injection currents Iv, Iv_m, Izd_2 and the power drop P_squib at the ignition device with respect to the Fig. 6 shown trigger circuit according to an embodiment.

[0094] The current Iv drops from a value of approximately 8A to 4.4A in a period of 0.0ms to 1.0ms.

[0095] The current Iv_m drops from approximately 0.45 A to 0.35 A between 0.0 ms and 1.0 ms. The current Izd_2 drops from approximately 0.9 A to 0.1 A between 0.0 ms and 1.0 ms.

[0096] The power P_squib drops from a value of approximately 460mW to 260mW in the period from 0.0ms to 1.0ms.

[0097] Out of Fig. Figure 9 shows that the "no fire" injection current curve is 20 times higher than the standard of 0.4 A. The parameter is: Iv(peak)=8 A@4 mH@2 Ohm

[0098] The igniter current Iv_m averages approximately 400mA, which is close to the "no fire" limit. At least a portion of the injection current Iv is also conducted as current Izd_2 in the curve shown via diode ZD_2 (S2 closed).

[0099] Fig. 10 shows a model of an effect of an injection current with respect to the Fig. 4 according to an embodiment. In particular, a firing time model for the effect of the injection current Iv on the output stages is shown. The trigger circuit is not represented by the Fig. 6 described protective device.

[0100] In addition to the igniter 110 of a system ASIC affected by injection current Iv, dangers from the system ASIC itself must be averted so that no subsequent errors (reset, damage spreading to neighboring functions) occur.

[0101] If the overload limit of an airbag high-side / low-side power amplifier is assumed to be approximately 6A@2ms injection current Iv, the improvement factor caused by the new protective circuit can be determined.

[0102] According to the Fig. For the model described in section 8, the following values ​​are assumed as examples: R_SQUIB=2.15 ohms Rltg_p=0.175 Ohm; (5m;Cu) Rltg_m=0.175 Ohm;(5m;Cu) Rtm=0.2 Ohm; (Track, Bonds) rd_LSf=0.33Ohm rd_THf=0.5 Ohm rdson_TH=0.5 Ohm Rtp=0.2 Ohm; (Track, Bonds) lv=Peak consumer current Lv=1mH

[0103] The switch S3 is closed when the voltage UZK+ is < - 3.3V.

[0104] From the Fig. The ignition circuit model shown in Figure 10 for the effect of the injection current Iv of the injection current Iv results in the following values ​​without a protective device and in the case that the switch S3 is closed: Rp=Rltg_p+Rtp+rdson_TH+rd_THf=1.375Ohm Rm=R_SQIUB+Rltg_m+Rtm+rd_LSf=2.855Ohm Rg=Rp*Rm / (Rp+Rm)=0.928 Ohm lv_m / lv=Rg / Rm→lv_m=lv*(Rg / Rm)=lv*0.325 lv_m_max=6A→lv_max=6A / 0.325=18.5A lv_p=HIS@lv_m_max→12.5A

[0105] However, this robust state only lasts for about 30 to 70µs, then the igniter is activated and creates an interruption.

[0106] This results in the following with regard to the Fig. 4 shown design is not an improvement factor.

[0107] The injection current Iv cannot exceed the overload limit of the high-side / low-side power stage (e.g. 6A)

[0108] Fig. 11 shows a model of an effect of an injection current Iv with respect to the Fig. 6 shows a trigger circuit with a protective device according to one embodiment. In particular, a trigger time model for the effect of the injection current Iv on the output stages 110 is shown.

[0109] The following values ​​are assumed as examples: R_SQUIB=2.15 ohms Rltg_p=0.175 Ohm;(5m;Cu) Rltg_m=0.175 Ohm;(5m;Cu) Rtm=0.2 Ohm;(Track,Bonds) rd_zdf=0.2 Ohm rd_df=0.5 Ohm rd_LSf=0.33 Ohm rd_THf=0.5 Ohm rdson_TH=0.5 Ohm Rtp=0.2 Ohm;(Track,Bonds) lv=Peak consumer current Lv=1mH

[0110] From the Fig. The ignition circuit model shown in Figure 8 for the effect of the injection current Iv on the igniter 110 results in improvements due to the protective device for the case of the already activated igniter 110 (open).

[0111] Switch S2 is closed when the voltage UZK is > 0.8V. Switch S3 is closed when the voltage UZK is >- 3.3V.

[0112] When switches S2, S3 are closed, the following applies: lv=lv_p and lv_m=0 Rg=Rp*Rm / (Rp+Rm) Rp=[rd_zdf*(Rtp+rdson_TH+rd_THf) / (rd_zdf+Rtp+rdson_TH+rd_THf)]=0.171 ohms Rm=[rd_zdf+rd_df∗(Rtm+rdLSf) / (rd_df+Rtm+rdLSf)]=0.457Ohm Rg=0.1244 Ohm lv_p / lv=Rg / Rp→lv_p=lv*Rg / Rp=lv*0.727 R_HS=Rtp+rdson_TH+rd_THf=1.2Ohm lHS / lv_p=Rp / R_HS=0.1425; lHS=lv_p*0.1425=lv*0.727*0.1425=lv*0.1036 For lHSmax=6A→lvmax=58A lv_m=0.273*lv lLS / lv_m=(Rm−rd_zdf) / (Rtm+rd_LSf)=0.257 / 0.533=0.482 lLS=lv*0.273*0.482=lv*0.132 For lLSmax=6A→lvmax=46A

[0113] The ignition circuit with the crash zone protection device theoretically increases the robustness of the high-side power amplifier against damage by approximately 10 times compared to a standard design. However, since damage to the low-side power amplifier is also not permitted, the achievable value is lower, at approximately 7 to 8 times.

[0114] Thanks to the new crash zone protective circuit, short-term injection current peaks of approximately 40A ... 50A can be handled without destroying the ignition circuit output stages and / or RESET of the system ASICS.

[0115] The time load limit is approximately 100µs but can also be adjusted by changing the diode selection.

[0116] The required injection current limit of 20A@1mH@0.8Ohm is reached without problems.

[0117] Fig. 12 shows a schematic representation of possible injection currents with respect to the Fig. 6 shows a trigger circuit according to one embodiment. In particular, positive injection currents of small consumers are shown.

[0118] In addition to the risks of negative injection currents of an ignition circuit 110 in the crash zone presented so far, positive injection currents Iv of small consumers can also arise if they are not screwed to chassis GND 552 but have a ground cable.

[0119] Protection circuit 104 is also effective in this case. The suppressor diode pair ZD_1, ZD_2 clamps when the VBR voltage (27V) is exceeded, thus relieving the load on the central ASIC ESD clamp element 443 (position IGH / IGL ESD-P), which opens at approximately 38V ignition circuit voltage and can absorb approximately 4A at an internal resistance of approximately 20Ω, including coupling diodes D_LK, D_HK, without damage or reset. This increases the total clamping power to approximately 6A.

[0120] In Fig. Figure 12 illustrates the generation and effect of positive injection currents. At high injection currents, only a "no fire" current is conducted through the igniter 110. The suppressor diode ZD_2, which is connected in parallel, conducts a portion of up to 2 A of the injection current toward the suppressor diode ZD_1.

[0121] The voltage at ZK+ is thus clamped to approximately 47V (rd_zdr=10 ohms). Since the ZD_1 clamp voltage is higher than the ASIC's central clamp voltage of 38V, it also consumes a large portion of the injection current (4A) with an internal resistance of approximately 2 ohms.

[0122] Likewise, current injection at ZK+ is possible without exceeding the “no-fire” current of the igniter 220 and corresponding distribution of the clamp power between ZD_1 and the ASIC clamp element.

[0123] If an embodiment comprises an “and / or” link between a first feature and a second feature, this is to be read as meaning that the embodiment according to one embodiment has both the first feature and the second feature and according to another embodiment has either only the first feature or only the second feature.

Claims

[1] A protective device (104) for a triggering circuit for a personal protection device (102) for a vehicle (100), wherein the triggering circuit comprises an ignition device (110), a high-side output stage (112) for connecting a high-side terminal (116) of the ignition device (110) to a first voltage potential (120), and a low-side output stage (114) for connecting a low-side terminal (118) of the ignition device (110) to a second voltage potential (122), and wherein the protective device (104) has the following features: a high-side interface (130) for contacting the protective device with the high-side terminal (116) of the ignition device (110) and a low-side interface (132) for contacting the protective device with the low-side terminal (118) of the ignition device (110); a suppressor diode (134) connected between the high-side interface (130) and the second voltage potential (122), the anode of the suppressor diode (134) being connected to the second voltage potential (122); and a first diode (136) connected between the low-side interface (132) and the second voltage potential (122), the anode of the first diode (136) being connected to the second voltage potential (122); a second diode (336) connected between the low-side interface (132) and the second voltage potential (122), the anode of the second diode (336) being connected to the second voltage potential (122); and wherein the first diode (136) and the second diode (336) are arranged as a switching diode pair on a die (351). [2] Protection device (104) according to claim 1, comprising a further suppressor diode (337) connected between the high-side interface (130) and the low-side interface (132). [3] Protection device (104) according to claim 2, wherein the suppressor diodes (134; 337) are arranged as a suppressor diode pair on a further die (350). [4] Protection device (104) according to one of the preceding claims, wherein the ignition device (110) is designed as an airbag ignition circuit. [5] Trigger circuit for a personal protection device (102) for a vehicle (100), the trigger circuit having the following features: an ignition device (110); a high-side output stage (112) for connecting a high-side terminal (116) of the ignition device (110) to a first voltage potential (120); a low-side output stage (114) for connecting a low-side terminal (118) of the ignition device (110) to a second voltage potential (122); and a protective device (104) according to one of the preceding claims, wherein the protective device contacts the high-side terminal (116) of the ignition device (110) via the high-side interface (130) and the low-side terminal (118) of the ignition device (110) via the low-side interface (132). [6] Method for protecting a triggering circuit for a personal protection device (102) for a vehicle (100) from the effect of an injection current injected into the triggering circuit, wherein the triggering circuit comprises an ignition device (110), a high-side output stage (112) for connecting a high-side terminal (116) of the ignition device (110) to a first voltage potential (120) and a low-side output stage (114) for connecting a low-side terminal (118) of the ignition device (110) to a second voltage potential (122), and wherein the method comprises the following steps: diverting (201) at least a portion of the injection current via a suppressor diode (134) connected between the high-side terminal (116) and the second voltage potential (122); and Diverting (203) at least a portion of the injection current via a first diode (136) and a second diode (336) arranged as a switching diode pair on a die (351) and connected between the low-side terminal (118) and the second voltage potential (122). [7] Method according to claim 6, wherein in at least one of the steps of diverting (201, 203) at least a part of the injection current is diverted through a parallel path formed by a suppressor diode (337) connected between the low-side terminal (118) and the high-side terminal (116).

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