Current regulating circuit for an electric consumer
AssigneeRobert Bosch GmbH
InventorsWinfried Arnold, Johannes Locher, Bernd Schelling
Life of this patent
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Abstract
A so-called current-regulated end stage for electromagnetic consumers such as magnetic valves or electromagnetic final control elements is provided, in which a field effect transistor takes over the functions of the switch and of the current measuring resistor. When the field effect transistor is conductive, the voltage over a capacitor is made to follow the current flowing through the consumer, and when the field effect transistor is blocked, the flow of current through the free-running circuit is simulated via the capacitor discharge. Both a singlefold and a multiple realization are disclosed, the latter using multiple examples of an RC member and a threshold switch.
Claims16
In an electrical circuit in combination with a motor vehicle control unit having an electrical consumer and a switch means for supplying current to the consumer, the improvement which comprises:
- current regulating means for regulating the consumer current;
- a field effect transistor (FET) which is connected in the circuit to serve as said switching means and to also serve as a current measuring device for said current regulating means;
- and
- the field effect transistor having a current measuring pick-up means connected thereto.
A circuit for regulating current supplied to an inductive consumer from a direct current source, which comprises:
- a free-running diode connected in parallel with the consumer;
- a field effect transistor, or FET, having a source-drain path connected in series with the consumer and having a gate terminal for receiving a FET control signal which controls the conductivity of the FET source-drain path;
- FET control means for generating and switching the FET control signal between a first value at which the FET source-drain path is rendered conductive and a second value at which the FET source-drain path is rendered nonconductive in accordance with a signal corresponding to current flowing in the consumer, the FET control means switching the FET control signal to its first value whenever the value of the signal corresponding to the consumer current is less than a predetermined low threshold value, and the FET control means switching the FET control signal to its second value whenever the signal corresponding to the consumer current rises above a predetermined high threshold value;
- and
- signal generating means for generating the signal corresponding to the consumer current, which comprises:
- a capacitor,
- a capacitor charging circuit including the FET source-drain path,
- a capacitor discharging circuit including a discharge resistor, and
- a capacitor switching means, controlled at least indirectly by the FET control means, for switching the capacitor between the charging circuit and the discharging circuit, the capacitor switching means switching the capacitor into the charging circuit in parallel arrangement to the FET source-drain path whenever the FET source-drain path is rendered conductive by the FET control means wherein the voltage across the capacitor increases as the consumer current increases and is a measure of the consumer current, and the capacitor switching means switching the capacitor into the capacitor discharging circuit whenever the FET source-drain path is rendered nonconductive by the FET control means wherein the discharge resistor through which the capacitor discharges has a resistance value such that the voltage across the capacitor when it is being discharged simulates the consumer current, wherein the voltage across the capacitor constitutes the signal corresponding to the consumer current for controlling the FET control means.
Dependencies are inferred from the claim text.