Electricity: electrical systems and devices – Control circuits for electromagnetic devices – For relays or solenoids
Reexamination Certificate
1999-12-06
2001-04-03
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
For relays or solenoids
C361S160000, C361S115000
Reexamination Certificate
active
06212053
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a device for driving at least one capacitive actuator, in particular an actuator of a fuel injection valve of a motor vehicle internal combustion engine. The device drives the capacitive actuator(s) by means of a control circuit. A charging capacitor is connected between the positive pole and the negative pole of a voltage source. A series circuit, connected in parallel with the charging capacitor, comprises a ring-around coil and at least one actuator with an assigned selector switch. The device further includes a discharging switch. The invention also relates to a method for operating the device.
A device of this type is disclosed in U.S. Pat. No. 4,688,536, entitled “drive circuit for an electrostrictive actuator in a fuel injection valve.” There, use is made of thyristors for the charging or selector switch and a discharging switch. During the switch-on operation, thyristors must be triggered with a pulse, and are extinguished automatically when the power current flowing via them vanishes. The relatively long critical hold-off interval of the thyristors is problematical. This can be countered if the thyristors are replaced by MOSFET switches and diodes. However, a very complicated high-side drive circuit is required for N-MOSFET switches; it is certainly true that the drive circuit can be of simpler construction for P-MOSFET switches, but with these the losses are approximately twice as high as with N-MOSFET switches.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and device for driving one or more capacitive actuators, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and wherein the drive is as simple as possible. It is also the object of the invention to specify a method for operating the device.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for driving at least one capacitive actuator, comprising:
a control circuit;
a voltage source having a positive pole and a negative pole;
a charging capacitor connected between the positive pole and the negative pole of the voltage source;
a series circuit connected in parallel with the charging capacitor, the series circuit comprising a ring-around coil and at least one actuator with an assigned selector switch, at least one N-MOSFET selector switch having a source terminal connected to the negative pole of the voltage source and a drain terminal;
a discharging capacitor connected between the charging capacitor and the ring-around coil;
a measuring circuit connected to measure a voltage across the discharging capacitor and to relay the voltage to the control circuit;
a first diode having an anode connected to the positive pole and a cathode connected to the discharging capacitor for conducting current to the discharging capacitor;
a second diode having an anode connected to the cathode of the first diode and a cathode;
an N-MOSFET discharging switch having a drain terminal connected to the cathode of the second diode and a source terminal connected to the drain terminal of the selector switch via a decoupling diode; and
a bypass device connected between a node between the ring-around coil and the actuator and the source terminal of the discharging switch.
In accordance with the invention, therefore, high-side charging switches (thyristors or MOSFET) are dispensed with, and the charging operations are triggered by selector switches that are referred to ground. The discharging circuit is not led via the frame terminal GND, in order to prevent an internal short circuit of the voltage source as a consequence of the missing charging switch when the discharging switch is on.
In accordance with an added feature of the invention, the bypass device is an N-MOSFET bypass switch controlled by the control unit, the bypass switch having a drain terminal connected to a node between the ring-around coil and the actuator and a source terminal connected to the source terminal of the discharging switch.
In an alternative embodiment, the bypass switch may be replaced with a diode or a Zener diode having a cathode connected to the ring-around coil.
In accordance with an additional feature of the invention, the voltage source is a switched-mode power supply connected to and controlled by the control unit.
In accordance with another feature of the invention, a further diode is connected to conduct current from the negative pole to the source terminal of the discharging switch.
In accordance with a further feature of the invention, the at least one actuator is one of a plurality of actuators each connected to a respective selector switch.
With the above and other objects in view there is also provided, in accordance with the invention, a method of operating the above-outlined device. The method comprises turning on the discharging switch when none of the selector switches is turned on.
In accordance with again an added feature of the invention, before a first operation of an actuator and between two actuator operations whose temporal spacing overshoots a prescribed duration, the discharging capacitor is charged by a least once simultaneously turning on the bypass switch and one of the selector switches and subsequently turning it off, until a voltage prescribed by the control unit is present across the discharging capacitor.
In accordance with again an additional feature of the invention, an actuator is operated until the associated selector switch is turned on.
In accordance with again another feature of the invention, the method comprises, during an operation of the device, controlling or regulating the output voltage of the voltage source to a constant charging voltage.
In accordance with again a further feature of the invention, the output voltage of the voltage source is controlled or regulated to a constant actuator voltage during an operation of the device.
In accordance with yet an added feature of the invention, the output voltage of the voltage source is controlled or regulated such that a constant charge is supplied to the respectively operated actuator or such that a constant energy is fed to the respectively operated actuator.
In accordance with yet an additional feature of the invention, the bypass switch is turned on when the actuator voltage overshoots a prescribed threshold value or when a switch fault occurs.
In accordance with a concomitant feature of the invention, the discharging switch is turned off when a current flowing through the drain-source path of the discharging switch overhoots a predetermined threshold value or when a voltage across the discharging switch exceeds a predetermined value.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device and method for driving at least one capacitive actuator , it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
REFERENCES:
patent: 4688536 (1987-08-01), Mitsuyasu et al.
patent: 6060814 (2000-05-01), Hoffmann et al.
patent: 6081062 (2000-06-01), Hoffmann et al.
patent: 3621541A1 (1987-01-01), None
patent: 0464443A1 (1992-01-01), None
patent: 0611881A1 (1994-08-01), None
patent: 2533263 (1982-09-01), None
patent: 9-112735 (1997-05-01), None
Freudenberg Hellmut
Gerken Hartmut
Hecker Martin
Hoffmann Christian
Pirkl Richard
Greenberg Laurence A.
Jackson Stephen W.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
LandOfFree
Device and method for driving at least one capacitive actuator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device and method for driving at least one capacitive actuator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device and method for driving at least one capacitive actuator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2448749