Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Patent
1995-12-26
1998-03-24
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
361187, 361190, H01H 4732
Patent
active
057319464
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device for driving a load, in particular an electromagnetic load.
BACKGROUND INFORMATION
German Published Patent Application No. 38 05 031 describes a device for driving a load, in particular an electromagnetic load. An actual-current measurement is used to measure the current flowing through the load and to adjust it to a setpoint value. In dependence upon the current flowing through the load, a switch connected in series to the load is triggered.
As switches, power transistors are preferably used. If the current is adjusted by means of an analog control loop, then very high power losses occur in the power transistor. The power consumption of transistors is essentially dependent upon the maximum permissible temperature and upon their thermal coupling to the surroundings. If the power loss exceeds the maximum power consumption of the transistor, then usually a transistor with a higher maximum power loss is used and/or the power loss is divided up among several transistors. These measures are often too expensive or do not suffice.
SUMMARY OF THE INVENTION
The present invention provides a device for driving a load, in particular an electromagnetic load, comprising means for detecting the current flowing through the load, a control means, such as a power transistor, connected in series to the load which is triggered in dependence upon the current flowing through the load, and a circuit component, such as a field-effect transistor, arranged parallel to the control means.
An object of the present invention is to reduce the power loss of the power transistor.
When working with the device according to the invention, it is possible to use power transistors having a considerably smaller maximum power consumption, thus less expensive transistors.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 schematically depicts the elements of a device in accordance with the present invention.
FIG. 2 shows various signals in the device of FIG. 1.
DETAILED DESCRIPTION
In the exemplary embodiment, the load is the coil of a solenoid valve which influences the metering of fuel into an internal combustion engine. By applying activation signals to this solenoid valve, the beginning of injection, the end of injection, and thus also the injected fuel quantity can be controlled. For this purpose, the solenoid valve must open and/or close at a defined instant. Furthermore, the solenoid valve must reach its new end position as quickly as possible after the driving signal is output.
FIG. 1 schematically depicts the elements of an embodiment of a device according to the present invention. An electromagnetic load 100 is coupled at its first terminal to a battery voltage and at its second terminal to a control means 110.
The control means 110 is preferably a transistor, in particular, a field-effect transistor. Here, the second connection of the load is linked to the drain connection of the field-effect transistor 110. The source connection of the transistor 110 communicates with a current-measuring means 120 for detecting the current flowing through the load. The second connection of the current-measuring means 120 is connected to ground.
The configuration of these three elements is merely shown for illustrative purposes. It is equally possible to arrange these elements in a different sequence. Thus, for example, one could interchange the ground and the battery terminals.
The connection point between the second connection of the load 100 and the control means 110 is linked to the first connection of a resistor 150. The second connection of the resistor 150 is linked to a circuit component 140. As circuit component 140, preferably a transistor, in particular, a field-effect transistor is used. In this case, the second connection of the resistor 150 is linked to the drain connection of the transistor 140. The source connection of the transistor 140 is in contact with the connection point between the control means 110 and the current-measuring means 120.
A control unit 130 applies d
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patent: 5568349 (1996-10-01), Kowalewski
patent: 5590013 (1996-12-01), Harasawa
Gaffin Jeffrey A.
Huynh Thuy-Trang N.
Robert & Bosch GmbH
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