1. Field of the Invention
This invention relates to a floppy disc driving device (FDD), and more particularly relates to a floppy disc driving device (FDD) located near a diskette insertion drawer having a light emitting diode (LED) driving circuit for emitting light when a floppy disc is being rotatively driven to ensure driving of the light emitting diode and to save the driving circuit cost.
2. Description of the Related Art
Generally, a light emitting diode is located near a diskette insertion slot of a floppy disc driving device to light the light emitting diode when the floppy disc is rotatively driven for showing that the floppy disc is now being rotatively driven.
In the case of a floppy disc driving device described hereinabove, a diskette insertion slot and a light emitting diode are located on the front side of the floppy disc driving device whereas an interface connector to be connected to an external main control unit (computer) is located on the back side of the floppy disc driving device. An integrated circuit (IC) for controllably driving the floppy disc driving device is also located on the back side of the floppy disc driving device. As the result such a structure brings about a long distance and inevitably a long connection conductor between the light emitting diode and the integrated circuit.
FIG. 3 is a circuit diagram for showing a typical equivalent circuit of a light emitting diode driving circuit that has been used for a conventional floppy disc driving device.
As shown in FIG. 3, the light emitting diode driving circuit is provided with a light emitting diode 31, a flexible printed circuit (FPC) 32 that is a component of a connection conductor, a current limiting resistor 33, and a voltage driving power source 34 contained in the integrated circuit (not shown in the figure). In this case, because it is difficult to fix the connection conductor, which is served to connect between the light emitting diode 31 and the integrated circuit, in the internal of the floppy disc driving device, a connection conductor that is flat-shaped and has a flexible characteristic, typically a flexible printed circuit (FPC), is used. The flexible printed circuit 32 is provided with a flexible copper (Cu) first conductor 321 and a flexible copper (Cu) second conductor 322 that are located in parallel with insulation between them, and the flexible printed circuit 32 is flat and band-shaped as the whole.
The anode side of the light emitting diode 31 is connected to one end of the first conductor 321 of the flexible printed circuit 32, and on the other hand the cathode side is connected to one end of the second conductor 322 of the flexible printed circuit 32. One end of the current limiting resistor 33 is connected to the other end of the first conductor 321 of the flexible printed circuit 32, and on the other hand the other end of the current limiting resistor 33 is connected to the positive side terminal of the voltage driving power source 34. The negative side terminal of the voltage driving power source 34 is connected to the other end of the second conductor 322 of the flexible printed circuit 32.
When a diskette is inserted into the floppy disc driving device through the diskette insertion slot having the abovementioned configuration and a floppy disc in the inserted diskette is rotatively driven, the voltage driving power source 34 generates a driving voltage. The driving voltage causes a current flowing from the positive side terminal of the voltage driving power source 34 through the current limiting resistor 33, the first conductor 321 of the flexible printed circuit 32, the anode of the light emitting diode 31, the cathode of the light emitting diode 31, and the second conductor 322 of the flexible printed circuit 32 to the negative side terminal of the voltage driving power source 34, and the current activates the light emitting diode 31 and the light emitting diode 31 is lighted. At that time, because the intensity of the current that flows through the light emitting diode 31 is kept approximately at a constant value due to interposition of the current limiting resistor 33, and the light emitting diode 31 is lighted approximately at a constant brightness due to substantial current driving.
The abovementioned conventional floppy disc driving device is provided with the flexible printed circuit 32 for the light emitting diode driving circuit, and the flexible printed circuit 32 uses a conducting wire formed of copper (Cu) and the conductive wire is long. Such a structure results in relatively high cost of the light emitting diode driving circuit, and the manufacturing cost of a floppy disc driving device is resultantly high
In this case, a method in which a membrane conductor, which is generally more inexpensive than the flexible printed circuit 32, is used may be employed. However, a membrane conductor cannot be used instead of a flexible printed circuit 32 without any additional contrivance because the resistance value of the membrane conductor is considerably higher than that of the flexible printed circuit 32 and the resistance value of a membrane conductor changes significantly with temperature change and humidity change. It is difficult to maintain light emitting brightness of a light emitting diode at a constant value continuously, and the light emitting brightness of a light emitting diode cannot be stabilized.
The present invention has been accomplished in view of the abovementioned technical background, and it is an object of the present invention to provide a low-cost floppy disc driving device that maintains light emitting brightness of a light emitting diode at a constant value continuously in which a membrane conductor is used for connecting between a light emitting diode and an integrated circuit for current driving of the light emitting diode.
To achieve the abovementioned object, a floppy disc driving device in accordance with the present invention is provided with a circuit substrate formed on one side of a chassis on which at least an integrated circuit and an interface connector are mounted, a light emitting diode located near the diskette insertion slot that emits light when a floppy disc is rotatively driven, and a connection conductor that connects between the circuit substrate and the light emitting diode, wherein the connection conductor is a membrane conductor formed by spreading coating material on one side of the chassis, and the light emitting diode is driven with a current supplied from the integrated circuit through the membrane conductor.
According to the abovementioned configuration, because the membrane conductor formed by spreading coating material on one side of the chassis as the connection conductor for connection between the circuit substrate and the light emitting diode, the membrane connector is considerably more inexpensive than that of a flexible printed circuit, which has been used as the conventional connection conductor of this type, and furthermore because the light emitting diode is driven with a current supplied from the integrated circuit through the membrane conductor, a current that flows through the light emitting diode can be maintained approximately at a constant value to resultantly maintain light emitting brightness of the light emitting diode at a constant value continuously even though a relatively high resistance value of the membrane conductor is changed or a resistance value varies significantly due to an environmental temperature change or an environmental humidity change
The membrane conductor in the abovementioned means preferably contains carbon powder or silver paste as a main component.
By forming the membrane conductor as described hereinabove, the membrane conductor can be obtained by means of relatively simple means, and the membrane conductor is manufactured at a low cost.