Patent Application
20050094337
The present invention relates to a signal switching apparatus and in particular, to a signal switching apparatus comprising multiple relays. Moreover, the present invention relates to an apparatus that drives multiple electrical devices. The present invention is ideal for a signal switching device having multiple relays, and the like.
Conventional semiconductor testers comprise many relays for switching signals. Mercury relays and mechanical relays such as reed relays are used in relays so that the signals will not degrade. Mechanical relays comprise coils and are relays with which the electrical circuit is switched by the electromagnetic effect of these coils.
A conventional signal switching apparatus that uses relays is shown in
The current output from control device 110 and the current that flows through coil 132 flow into the emitter of transistor array 120 and therefore, the ground to which control device 110 is connected and the ground to which transistor array 120 is connected must be a common ground. Consequently, the electrical source connected to coil 132 must be a positive electrical source.
Moreover, the electrical source connected to coil 132 must have a voltage that is at least the value that is obtained by adding the collector-emitter voltage during saturated operation of transistor array 120 to the operating voltage of relay 130. The collector-emitter voltage during saturated operation of a Darlington-pair transistor array is generally 1 V. Consequently, when the operating voltage of relay 130 is 5 V, the voltage of the electrical source connected to coil 132 must be 6 V or higher. A 6V electrical source is not commonly used for electronic devices in general.
Semiconductor testers comprise many signal switching apparatuses. A relay drive current of 30 milliamperes to 40 milliamperes is generally necessary. Consequently, in addition to the electrical source that supplies current to the electronic devices, semiconductor testers comprise large-capacity positive electric sources for relays. Moreover, a large current flows to the ground when the relay is being driven and therefore, the semiconductor tester has a ground pattern that becomes denser around the relay and it further comprises many parts intended to counter noise, such as large common mode choke coils.
The present invention provides a signal switching apparatus that does not require a special electrical source, dense ground pattern, or many parts intended to counter noise.
The present invention is a driving method for driving multiple electrical devices, comprising a step whereby current is supplied to each of these electrical devices from either a positive electrical source or a negative electrical source connected to a common reference potential, with the positive electrical source and the negative electrical source being divided to the devices and current being supplied to each of these electrical devices such that the difference between the total current supplied from this positive electrical source to these electrical devices and the total current supplied from this negative electrical source to these electrical devices is reduced; and a step whereby the current that flows to these electrical devices is allowed to continue or be interrupted in response to signals from an apparatus that is electrically isolated from this positive electrical source and this negative electrical source.
The present invention also provides for an electrical device driving apparatus, characterized in that it is an apparatus for driving multiple electrical devices; it comprises multiple switch means; these switch means comprise an input part and a switch part that are electrically isolated from one another and these switch parts work in response to signals input to this input part; and each switch part of these switch means is connected, with at least one of these electrical devices in between, to either a positive electrical source or a negative electrical source connected to a common reference potential and these switch parts are connected so that they are distributed between the positive electrical source and the negative electrical source such that the difference between the total current flowing to the switch parts connected to this positive electrical source and the total current flowing to the switch parts connected to this negative electrical source is reduced.
The switch parts connected to this positive electrical source and the switch parts connected to this negative electrical source are further virtually simultaneously brought to a state of conduction.
The present invention is also includes a signal switching apparatus that switches between multiple signals; it comprises multiple relays and multiple photocouplers; the output part of each of these photocouplers is connected to the coil of at least one of these relays; and each coil of these relays is connected to a positive electrical source or a negative electrical source having a common ground, with these coils being connected so that they are distributed between the positive electrical source and the negative electrical source such that the difference between the total current flowing to the coils connected to this positive electrical source and the total current flowing to the coils connected to this negative electrical source is reduced. The signal switching apparatus may further comprise a control device for controlling each of these photocouplers so that the coils connected to this positive electrical source and the coils connected to this negative electrical source are driven virtually simultaneously.
The photocouplers are transistor output photocouplers. Alternatively, the photocouplers are MOS-FET output photocouplers.
According to the present invention, multiple relays of a signal switching apparatus comprising multiple relays are driven by photocouplers and therefore, the relay drive electrical source is not limited to a positive electrical source. Moreover, according to the present invention, these multiple relays of a signal switching apparatus comprising multiple relays are driven by a MOS-FET output photocoupler with low resistance and therefore, selection of the relay drive electrical source is simple. Consequently, the signal switching apparatus comprising multiple relays according to the present invention does not require a special relay electrical source.
Furthermore, according to the present invention, these multiple relays of a signal switching apparatus comprising multiple relays are connected so that they are distributed between a positive electrical source and a negative electrical source and therefore, the current that flows into the ground when the relay is driven is controlled and many parts intended to counter noise, such as a large common mode choke coil, and a dense ground pattern are not necessary.
Based on the above-mentioned effects, for instance, the part of the semiconductor tester that is associated with the signal switching apparatus can be reduced in size without compromising function or performance.
The present invention will be described in detail based on the embodiments shown in the attached drawings. The first embodiment is a signal switching apparatus comprising multiple relays, and a block diagram thereof is shown in
By means of signal switching apparatus 200 with this type of structure, control device 210 outputs control signals such that output part 222 of photocoupler 220 and output part 232 of photocoupler 230 conduct a current virtually simultaneously, preferably perfectly simultaneously. Thus, reed relay 240 and reed relay 250 operate virtually simultaneously, preferably perfectly simultaneously, and the current that flows from positive electric source (+VR) through coil 242 to ground GNDR flows through coil 252 to negative electrical source (−VR) in unaltered form. As a result, signal switching apparatus 200 does not require many parts intended to counter noise such as a large common mode choke coil, or a dense ground pattern. Moreover, photocoupler 220 and photocoupler 230 are MOS-FET output photocouplers and therefore, the voltage drop caused by output part 222 and output part 232 is sufficiently small in comparison to the sensitivity voltage of reed relay 240 and reed relay 250. Consequently, the absolute output voltage of positive electrical source (+VR) and negative electrical source (−VR) can be the same as this sensitivity voltage. That is, selection of the electrical source that drives reed relay 240, and the like is simplified.
The MOS-FET output photocoupler of signal switching apparatus 200 can also be replaced by a transistor output photocoupler. A signal switching apparatus of this type is shown in
By means of signal switching apparatus 300 with this type of structure, control device 210 outputs control signals such that output part 322 of photocoupler 320 and output part 332 of photocoupler 330 conduct a current virtually simultaneously, preferably perfectly simultaneously. Thus, reed relay 240 and reed relay 250 operate virtually simultaneously, preferably perfectly simultaneously, and the current that flows from positive electrical source (+VR) through coil 242 to ground GNDR flows through coil 252 to negative electrical source (−VR) in unaltered form. As a result, signal switching apparatus 300 does not require many parts intended to counter noise such as a large common mode choke coil, or a dense ground pattern.
One requirement of the present invention is that the relay coils are connected to either a positive electrical source or a negative electrical source, with the coils being connected so that they are distributed between a positive electrical source and a negative electrical source such that the difference between the current that flows to the coils connected to the positive electrical source and the current flowing to the coils connected to the negative electrical source is reduced. For instance, 20 of 40 relays having the same properties are connected directly or indirectly to the positive electrical source and the other 20 are connected directly or indirectly to the negative power source. Moreover, if there are 39 relays having the same properties, 20 of these are directly or indirectly connected to the positive electrical source and the remaining 19 are directly or indirectly connected to the negative power source. Furthermore, when there is a mixture of relays having different properties, for instance, when there are coils with a rated current of 30 mA and coils with a rated current of 20 mA, 20 relays comprising coils with a rated current of 30 mA are connected to the positive electrical source and 30 relays comprising coils having a rated current of 20 mA are connected to the negative electrical source. These multiple relays can be divided into at least two groups and controlled together in each group, or they can all be controlled individually.
Consequently, the number of relays or photocouplers connected to the positive electrical source or the negative electrical source is not limited to only one as with the signal switching device shown in
Ground in the present text means the reference potential and is not restricted to ground potential. Moreover, ground GNDR and ground GNDD have independent potentials and these potentials can be the same or different.
The present invention is not limited to the driving of relays and is applicable to the driving of other types of electrical devices. For instance, the present invention is applicable to separately driving multiple high-luminance LEDs in large video display devices.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-371749 | Oct 2003 | JP | national |
