Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
2001-12-21
2004-08-10
Zweizig, Jeffrey (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
Reexamination Certificate
active
06774682
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention lies in the field of semiconductor circuits. The invention relates to a circuit configuration for driving a semiconductor switching element, in particular, a semiconductor switching element that is connected up in a device for generating an ignition spark in an automobile.
Such a device for generating an ignition spark with a semiconductor switching element is illustrated in FIG.
1
. The device has a transformer TR with a primary coil L
1
, a power transistor T, and a spark plug Z. The power transistor T is constructed, in particular, as an Insulated Gate Bipolar Transistor (IGBT) or as a so-called power Darlington bipolar stage and is connected in series with the primary coil L
1
between two supply potentials V+, GND. The spark plug Z is connected in series with the secondary coil L
2
of the transformer TR. Two diodes D
1
, D
2
that are connected in series between the collector terminal and the gate terminal of the power transistor, configured as an IGBT in the example, serve for limiting the collector-emitter voltage of the transistor T by virtue of the transistor T being driven into the on state through these two diodes D
1
, D
2
if the potential at the collector K rises above a predetermined amount.
If the power transistor T is driven into the on state by the application of a suitable drive potential at its gate electrode G, a current flows through the primary coil L
1
, as a result of which the primary coil L
1
takes up energy. If the power transistor T is subsequently turned off, the primary coil induces a high voltage in the electric circuit of the primary coil, the high voltage, or the energy stored in the primary coil, being transmitted to the secondary side, where it leads to the generation of an ignition spark in the spark plug z.
In such devices, disturbance situations can occur in which the generation of an ignition spark is to be prevented under all circumstances, even when the power transistor T is already in the on state and the primary coil L
1
has already taken up energy. In such a case, simply switching off the power transistor T would lead to the generation of an ignition spark.
To avoid an ignition spark in such disturbance situations, the prior art includes changing over the collector of the power transistor by suitable circuit measures and, thereby, put at a potential value at which no ignition spark is generated.
In the case of so-called intelligent power transistors fabricated using chip-on-chip technology, a problem arises that the collector of the power transistor is not accessible. In such technology, the power transistor is realized in one semiconductor body and a drive circuit, protective circuits of the transistor, and the like are realized in a second semiconductor body, which is fixed on the first semiconductor body.
Due to the diverse additional functions, in particular, due to integrated protective circuits that deploy in the event of a short circuit of the load, to protect the power transistor, endeavors are being made to be able to use intelligent power transistors, so-called smart FETS or smart IGBTs, also for devices for generating ignition sparks.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a circuit configuration for driving a semiconductor switching element, preferably, a power transistor, in particular, a power transistor in a device for generating an ignition spark that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that ensures no ignition spark is generated when a disturbance situation occurs.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a circuit configuration for driving a semiconductor switching element, including an output terminal to be connected to the semiconductor switching element, a capacitive charge storage configuration coupled to the output terminal, a charging and discharging circuit having at least one input receiving at least one drive signal and an output connected to the capacitive charge storage configuration, the charging and discharging circuit providing, at the output, one of the group consisting of a charging current and a first discharging current for the capacitive charge storage configuration depending on the at least one drive signal, a discharging circuit having a connecting terminal connected to the capacitive charge storage configuration, and the connecting terminal providing a second discharging current for the charge storage configuration.
The capacitive charge storage configuration, which is connected to the output, serves for providing a drive potential for a semiconductor switching element, in particular, a power transistor, which can be connected to the output terminal. In such a case, the voltage across the charge storage configuration or the drive potential rises if the charge storage configuration takes up current from the charging and discharging circuit, and the voltage, or the drive potential, falls if the charge storage configuration is discharged.
In such a case, the charging and discharging circuit is configured such that it is able to charge the capacitive charge storage configuration comparatively quickly and also discharge it comparatively quickly. A power transistor connected to the output terminal is in the on state if the charge storage configuration is charged and it is in the off state if the charge storage configuration is discharged. In disturbance-free operation, the capacitive charge storage configuration is, therefore, charged rapidly through the charging and discharging circuit to drive the connected power transistor into the on state, and the capacitive charge storage configuration is discharged rapidly through the charging and discharging circuit to turn off the connected power transistor. In such a case, the time duration within which the charge storage configuration is discharged through the charging and discharging circuit, or within which the power transistor undergoes a transition from the on state to the off state, can be coordinated with the further connections of the power transistor and can be set to such a short time duration that when the power transistor is switched off, a sufficient voltage is induced in a connected primary coil of a transformer, so that an ignition spark is generated in an ignition coil connected to the secondary side of the transformer.
Preferably, in accordance with another feature of the invention, the discharging circuit provides a constant discharging current for the charge storage configuration, the discharging current being significantly lower than a discharging current of the charging and discharging circuit and also significantly lower than a charging current of the charging and discharging circuit. The discharging circuit, which draws current from the charge storage configuration, preferably, permanently, does not influence the functioning of the circuit configuration in disturbance-free operation, in which the charge storage configuration is alternately charged and discharged through the charging and discharging circuit.
When a disturbance situation occurs, the charging and discharging circuit can be driven by the drive signal such that it provides no current at its output terminal. In such a case, only the discharging circuit acts, which continuously draws current from the charge storage configuration until the latter is completely discharged. The discharging current is coordinated with the capacitance of the charge storage configuration such that the voltage change brought about by the discharging current across the charge storage configuration is so small that the power transistor connected to the output terminal undergoes a transition from an on state to an off state so slowly that an ignition spark is not generated in a spark plug connected on the secondary side.
By the circuit configuration according to the invention, the generation of an ignition spark can be prevented exclusively by dri
Leipold Ludwig
Leipold Stefan-Michael
Theobald Thomas
Greenberg Laurence A.
Infineon - Technologies AG
Leipold Stefan-Michael
Locher Ralph E.
Stemer Werner H.
LandOfFree
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