Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Patent
1989-03-15
1991-02-12
Wojciechowicz, Edward J.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
357 2313, 357 34, 357 41, 357 234, 361111, H01L 2990
Patent
active
049928368
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for controlling the electrical supply to a load in a "smart" power integrated circuit, and more particularly to such a device controlling the supply through an inductive load.
The name of "smart power integrated circuits" covers integrated circuits combining on the same chip logic functions executed in MOS or bipolar technology, for example, and at least one DMOS or bipolar power component, for example. Various technologies for the construction of such integrated circuits have been developed, and these have led to products such as the SMARTMOS circuits of the United States company MOTOROLA, the S2P2 or VIP technology products of the Italian company SGS MICROELECTTRONICA or the SMART SIPMOS products of the company SIEMENS AG of the Federal Republic of Germany.
Such "smart" power integrated circuits prove, in particular, to be well suited to the resolution of problems which arise in automobile electronics. In fact, functions such as the ignition, the control of the injection time, the modulation of the pressure in the braking circuits rely upon inductive loads, the supply to which must be controlled by power transistors. These power transistors are themselves controlled by low-current logic circuits which can be integrated, by virtue of these new "smart" circuits, on the same chip as the power transistor which controls the supply to the inductive load. As an example of such inductive loads, it is possible to mention the coil of an injector or that of a solenoid valve modulating a pressure of a brake fluid in a wheel antilock device. Again, it is possible to mention the coil of an inductive ignition primary circuit.
The circuits controlling such inductive loads in an automobile environment are frequently equipped with diagnosis means permitting the detection, for example, of a disconnection or an accidental short-circuit of the inductive load rendering the latter inoperative, this taking place for safety reasons, for example. These means comprise electronics circuits which monitor the voltage prevailing at the terminals of the load in order to detect, for example, the possible appearance of a short-circuit and to trigger appropriate alarm or corrective action.
The high negative voltages which appear at the terminals of the inductive load when the supply circuit of this load is opened by the power transistor placed in series with this load are then liable to impair the components of the diagnostic circuit. If the latter comprises, for example, an amplifier constructed in MOS technology, the maximum gate-source or gate-drain voltages which can be accepted by the transistors of this amplifier are approximately 20 volts.
In an automibile environment, the opening of the circuit of the inductive load currently causes the appearance, at the terminals of the latter, of negative voltages in the order of 20 to 30 volts, to discharge rapidly the energy stored in the load, these being voltages which are liable to impair the MOS transistors of the diagnostic circuit. Accordingly, it is necessary to intercalate between the output of the load and the input of the amplifier a component to protect this amplifier.
The object of the present invention is to incorporate such a protective component in a device for controlling an inductive load, which device is constructed as a "smart" power integrated circuit.
The object of the present invention is also to construct such a device in which the protective component is associated with means for the diagnosis of the condition of an inductive load in order to protect them from the voltages generated by the opening of a supply circuit of this load.
These objects of the invention, as well as others which will become apparent in the text which follows, are achieved with a device for controlling electrical supply to a load, in a "smart" power integrated circuit, comprising a circuit sensitive to the voltage at the terminals of the load, a supply circuit of the load and a protective component installed between a terminal of the load and an input of
REFERENCES:
patent: 4595966 (1986-06-01), Huber et al.
patent: 4750078, Ganger et al.
Boller George L.
Crane Sara W.
Siemens Aktiengesellschaft
Wells Russel C.
Wojciechowicz Edward J.
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