DE102007002339A1 - Trigger circuit for ignition tablets, released by electric ignition pulse of passenger protection system, comprises integrated switching circuits, which are provided with integrated switch and external output switching element - Google Patents

Abstract

The trigger circuit comprises integrated switching circuits (4.x,4.y), which are provided with an integrated switch (4.0) and an external output switching element (2.0). The external output switching element is arranged beyond the switching circuit for receiving power loss. A suitable external output switching element is provided for a part of the ignition tablets (3.x,3.y), particularly each ignition tablet. An external output switching element is operated as a controllable power source.

Description

The The invention relates to a drive circuit for squibs an occupant protection system according to the preamble of claim 1.

Such a drive circuit is for example from the DE 10255115 B3 refer to. Today's occupant protection systems have a plurality of squibs, which are required for the different occupant protection means or in multi-stage construction of this occupant protection means for the triggering of the individual stages. This plurality of squibs is driven by an integrated circuit, each with at least one integrated switch per squib, which is usually arranged next to a high-side switch between the supply voltage and the squib to hedge against single fault also a low-side switch between the squib and the reference potential ,

The Process technology for ASICs or semiconductor circuits is constantly evolving, so the structural widths are getting smaller, and as a result, one constantly increasing packing density of logic elements can be achieved.

at Occupant restraint systems are used to activate the occupant protection means the corresponding actuators for belt tensioners and / or airbags controlled by electrical switching means, wherein the output stage switch mostly located in an ASIC. As in the case of activation of the actuators the (controlled) drive current provided by the output stages with the current being in the ampere range, is a corresponding energy implemented in the circuit breakers, which almost independent of the process technology a certain Minimum area of silicon is required, hence the energy flow to no punctual thermal destruction of the semiconductor (ASIC) leads.

Therefore applies in the realization of such occupant protection devices to ensure that the final stage concept is implemented in such a way that as little energy as possible in the expensive integrated semiconductor Switches is implemented in order to size these as small as possible to be able to.

From the Scriptures DE 102 55 115 B3 a drive circuit for a vehicle restraint system is known, which is activated by a DC electrical ignition pulse, this is added by means of another external circuit breaker element in series with the semiconductor switches integrated in the ASIC, the power generated during an ignition power loss, so that the two power switches (high-side & Low-Side) per ignition circuit in the ASIC can be dimensioned as small as possible. This external circuit breaker element is operated jointly as a stabilized voltage source for all squibs, ie the voltage provided at the output controlled or regulated independently of the voltage applied on the input side to a default value.

When Disadvantage of this solution can be considered that no optimal performance adjustment using this solution can be achieved because by the supply of several parallel switched ignition circuits at the output of the additional switch a certain minimum voltage must be present, resulting from the maximum Ignition circuit resistance (including switch resistors) multiplied by the required current. This to be provided minimum voltage at the output of the additional Schalters, however, means that when an ignition circuit, in this the maximum ignition circuit resistance is not given is, the resulting / remaining differential voltage and Thus, the resulting power loss in the two ASIC internal Circuit breakers remains. This applies in particular when the ignition times the individual squibs can vary and Thus, the actual power consumption can vary significantly. The drive circuit must therefore be designed for the maximum load and the power loss remaining at lower load integrated circuit can be added.

task The invention is therefore the known drive circuit such educate that regardless of size the actual Zündkreiswiderstandes only each Minimal power dissipation occurs at the ASIC internal circuit breakers.

These The object is achieved by the features of the independent claims solved. Advantageous developments of the invention result are from the subclaims, including combinations and further developments of individual features are conceivable with each other.

One essential idea of the invention is that per ignition circuit an additional ASIC external switch is used, which is designed as a power source.

So is at least for each from an application perspective special important, preferably all squib (s) have their own external Power switching element provided and is the external power switching element each operated as a controllable power source.

By means of this measure, two advantages are achieved. On the one hand, an optimal performance adjustment can be achieved, in the sense of that the ASIC-integrated circuit breakers regardless of the actual Zündkreiswiderstandes only a minimum of energy is supplied. The voltage difference between the voltage actually required and the voltage present in the energy store drops off at the additional switch designed as a current source. The safe voltage drop at the additional switch is in this case achieved, for example, that it is structurally ensured that the set current of the working as a current source additional switch is lower than the current capability of the power amplifier for activating the actuator output stages.

One Another advantage is that if there is ever one additional ASIC-external switch per ignition circuit, required according to the prior art High-side circuit breakers in the ASIC can account for as required Decoupling of the ignition circuits with each other, as well as the demand for a separate silicon of the power amp switch on the low side and the high-side of the ignition, already with an ASIC-internal low-side switch and an external extra switch on the high side given each ignition circuit.

The 1 shows an implementation example ( 1 ) of the proposed concept, in which the ignition element ( 3.x ) for activating the actuator (not shown) in series between the low-side switch ( 4.x . 4.0 ) and the high-side switch ( 2.x . 2.0 ) is arranged.

In the case of an ignition request, the required current flow for activation of the ignition means ( 3.x ) from the energy store ( 5 ) via the current-source ASIC-external high-side switch ( 2.x . 2.0 ) to the ignition means ( 3.x ) and continue via the low-side switch ( 4 ) against mass. The one for the ignition element ( 3.x ) required / required current flow is in this case by a simple resistance-sense circuit ( 2.1 ) by means of the voltage drop across the sense resistor ( 2.1 ) the current in the switch ( 2.0 ) by means of a regulation ( 2.2 ) is regulated.

Next The x-th ignition circuit shown in detail has more Ignition circuits y, as indicated sketchy.

Just like the switches built into the integrated circuit 4.x . 4.y in a common circuit 4 The external circuit-breaker elements can also be integrated 2.x . 2.y .. together in a circuit breaker module 2 be summarized, so that only this must be designed for the corresponding power loss, but still integration and thus cost reduction is possible.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10255115 B3 [0002, 0006]

Claims (2)

Control circuit for triggerable by an electric ignition pulse squibs ( 3.x . 3.y ) of an occupant protection system, wherein an integrated circuit ( 4.x . 4.y , ...) each with at least one integrated switch ( 4.0 ) per squib ( 3.x . 3.y ) as well as at least one external, outside of the circuit power switching element ( 2.0 ) is provided for absorbing power loss, characterized in that for at least a portion of the squibs ( 3.x . 3.y ), preferably each squib, each having its own external power switching element ( 2.x . 2.y ) is provided and the external power switching element ( 2.x . 2.y ) is operated in each case as a controllable current source. Drive circuit according to Claim 1, characterized in that the external power switching element ( 2.x . 2.y ) each on the supply voltage ( 5 ) facing side of the squib ( 3.x . 3.y ) and the integrated circuit ( 4 ) only exactly one integrated switch ( 4.0.x . 4.0.y ) per squib ( 3.x . 3.y ) on the supply voltage ( 5 ) side facing away from the squib ( 3.x . 3.y ) having.