Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
2000-02-28
2001-05-08
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
C327S310000, C327S321000, C361S056000, C326S085000, C326S087000
Reexamination Certificate
active
06229355
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a switching device for controlling the supply of electric power from a power supply to a load. More particularly, the present invention relates to a switching device for controlling a rush current at the time of starting or stopping the driving of the load.
The present application is based on Japanese Patent Applications Nos. Hei. 11-49887 and 2000-16804, which are incorporated herein by reference.
2. Description of the Related Art
A switching device is used for controlling the supply of electric power from a power supply to each load in, for example, an automobile, and is comprised of a semiconductor switch for effecting a changeover between the supply and cutoff of electric power, a controlling device for effecting on/off control of the semiconductor switch, etc. In such a switching device, when the semiconductor switch is turned on and the current begins to flow, there are cases where a rush current which is larger than the normal current necessary for driving the load occurs in the manner of a pulse. This rush current constitutes causes of faults in the load such as by generating noise and shortening the service life.
To suppress such a rush current, the related switching device employs a controlling device such as a microcomputer to effect the duty control of the drive signal waveform during the starting and stopping of the load driving.
With the above-described switching circuit, however, the microcomputer and the like become necessary as the controlling device for suppressing the rush current, so that there is a problem in that the device becomes complex.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a switching device which is simplified, thereby overcoming the above-described drawback of the above related art.
To this end, in accordance with the present invention, there is provided a switching device which comprises a phase controlling device which shifts and outputs a phase of a command signal, and a plurality of switching units connected in parallel between a power supply and a load, each of the plurality of switching units including a driving device which outputs a drive signal in response to the command signal from the phase controlling device, a first semiconductor switch inserted in a power supply circuit connecting the power supply and the load, the first semiconductor switch being adapted to conduct in response to the drive signal and close the power supply circuit, a resistor connected to the power supply to form a shunt circuit, a second semiconductor switch inserted in the shunt circuit, the second semiconductor switch being adapted to conduct in response to the drive signal and close the shunt circuit, and a drive stopping device which compares an output voltage from the first semiconductor switch and an output voltage from the second semiconductor switch, and stops the driving device from outputting the drive signal when the output voltage from the second semiconductor switch is higher than the output voltage from the first semiconductor switch.
The resistor upon receiving the supply of current from the power supply generates an output voltage of the second semiconductor switch which is substantially equal to or lower than the output voltage from the first semiconductor switch persisting when all the plurality of semiconductor switches are supplying current to the load.
If the switching device is thus configured, the command signal is converted to command signals having different phases by the phase controlling device, and the respective switching units are consecutively turned on by the command signals having different phases, and begin to supply power to the load. The switching unit, which first received the drive command signal, begins to supply current from the power supply to the load when the driving device outputs the drive signal to the first semiconductor switch to set the first semiconductor switch in a conducting state. At this time, since the output voltage from the second semiconductor switch is higher than the output voltage from the first semiconductor, the drive stopping device stops the drive circuit from outputting the drive signal. As the output of the drive signal is stopped, the first semiconductor switch is set in a nonconducting state, so that the supply of current from the power supply to the load is stopped. Subsequently, when the output voltage from the first semiconductor switch and the output voltage from the second semiconductor switch drop to a substantially equal level, the drive stopping device causes the driving device to output the drive signal again, thereby allowing the first semiconductor switch to conduct and supplying the current to the load. As the outputting and stopping of the drive signal are repeated in the above-described manner, the first semiconductor switch periodically repeats conduction and nonconduction, so that the state becomes similar to that of duty control, and the current which is supplied at this time becomes smaller than the steady-state current. The respective switching units are consecutively made to conduct to effect similar operation. Subsequently, when the output voltage from the second semiconductor switch has become substantially equal to or lower than the output voltage from the first semiconductor switch, each switching unit stops the repetition of conduction and nonconduction of the first semiconductor switch, and is kept in the conducting state, so that the steady-state -current flows to the load. For this reason, the current increases in steps at the time of starting the driving of the load. On the other hand, when the driving of the load is stopped, since command signals for stopping the driving of the load are consecutively inputted to the respective switching units, when the first switching unit is set in the nonconducting state, the respective switching units are consecutively set in the nonconducting state while performing the repetition of the conduction and nonconduction of the first semiconductor switch in the same way as described above, so that the current at the time of stopping the load decreases in steps. In other words, the state becomes similar to that of duty control at the time of starting or stopping the driving of the load, and the current flowing across the load is increased or decreased in steps, so that it is possible to suppress the rush current. Thus, it is possible to suppress the rush current by hardware circuits alone without using a microcomputer as the controlling device. Further, most of the component elements such as the hardware circuits making up the switching device can be integrated on a single semiconductor chip. In short, the switching device can be simplified.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when read in conjunction with the accompanying drawings.
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Sughrue Mion Zinn Macpeak & Seas, PLLC
Wells Kenneth B.
Yazaki -Corporation
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