Device having galvanic optocoupling

The present disclosure relates to an architecture of a device with galvanic optocoupling of the type having at least one optical source and one optical detector, optically connected by means of an insulation layer that functions to transmission optical signals, and having at least one input terminal and one output terminal, the optical source and the optical detector connected to a respective first and second voltage reference. The optical source is realized by a structure integrated directly above the insulation layer in correspondence with the optical detector, the architecture thus completely realized inside a single integration island.

BACKGROUND

1. Technical Field

The present disclosure relates to the architecture of a device having a galvanic optocoupling and, more specifically, to the galvanic optocoupling of at least one light source and an optical detector, optically connected through a transmission means and having at least one input terminal and one output terminal, the light source and the optical detector connected to respective first and second voltage references.

2. Description of the Related Art

As is known, certain applications require the use of components able to ensure a certain galvanic insulation between two different ports of a system, without penalizing the passage of a signal that encodes or contains a piece of information in the system itself. To this purpose, the use of galvanic optocouplers is known, i.e., devices able to transfer the desired information by means of an optical signal with suitable insulation characteristics.

This solution, widely present on sale, is usually realized by suitably assembling a light source, such as for example a light emitting diode (LED), realized with direct-gap semiconductors (type III-V) and a detector, such as for example usually a photodiode or a phototransistor, typically realized by silicon.

In substance, a galvanic optocoupler is essentially a safety device that allows two different sections, in particular an input stage and an output stage, of a system to exchange commands and information in a unidirectional way while remaining separate from the electric point of view. In particular, the signal transmission through the galvanic optocoupler occurs by means of light pulses that pass through an insulation layer transparent to light but with high dielectric rigidity.

An optical coupling thus occurs between the two parts of the system connected by the galvanic optocoupler which, however, remain electrically insulated one from the other (in particular, they do not have ground terminals in common).

A galvanic optocoupler of the known type is schematically shown inFIG. 1, globally indicated with1. In particular, the galvanic optocoupler1connects a first circuit node, or input IN, to a second circuit node, or output OUT, ensuring the galvanic insulation of the respective voltage references GND1and GND2due to the conversion of an input electric signal into an optical signal.

The galvanic optocoupler1thus includes an input stage, in particular a light or optical source2connected, through an intermediate stage3realized by a transmission means, and in particular an insulation layer, to an output stage or optical detector4. In particular, the insulation layer of the intermediate stage3is a means suitable for transmitting an optical signal (indicated with Light in the figure).

More in particular, the input or transmitter optical source2or transmitter emits a power that is transferred to the optical detector4or output photodetector. In this way, if the transmission means3through which the transmitter and photodetector communicate shows a good transparency and a good degree of electric insulation, the galvanic optocoupler1completely realizes the transmission functionality and simultaneous insulation requested.

For realizing a galvanic optocoupler device an assembly technique must be used that provides a good optical coupling between source and detector, without penalizing the galvanic insulation between the input and output gates of the device itself.

Two assembly techniques are known and widely used in the optoelectronic field that obtain a galvanic optocoupler device having these characteristics, and in particular:

1) face to face assembly technique.

This technique, schematically shown inFIG. 2A, consists in facing an optical source2and an optical detector4, by means of respective self-aligned frames2aand3aelectrically separated between input and output. The optical coupling is ensured in that the optical detector4is directly lightened by the optical source2, while the galvanic insulation is obtained using an insulating, optically transparent resin inserted between the two components according to the transmission means3.

This technique, schematically shown inFIG. 2B, consists in the use of an optical reflector5(or dome) which concentrates and conveys part of the optical power emitted by the optical source2onto the optical detector4, both glued on a planar frame6with two islands that electrically separate the input from the output. An insulating, optically transparent resin incorporates the optical source2and the optical detector4and serves as support for the realization of the optical reflector5with function of transmission means3. Finally, the galvanic optocoupler device includes a containment package7.

The use of an insulator with magnetic transmission or i-coupler, as galvanic optocoupler device, as schematically shown inFIG. 2Cis also known.

In particular, the i-coupler structure there shown has been obtained in the so called “Coreless Transformer” technology, as described for example in the article by Munzer et al. entitled “Coreless transformer a new technology for half bridge driver IC's”, PCIM 2003 Conference, Nuremberg, 2003.

In this structure, a primary coil2aand a secondary coil4acomprise respective integrated circuits,2band4b, provided with respective active parts,2cand4c. In particular, the active part2cof the primary coil2ais realized above an insulation layer3aand magnetically communicates with the secondary coil4athrough its corresponding active part4c.

In particular, in the structure shown inFIG. 2C, the primary coil2ais connected to its active part2cby means of suitable conductive paths8while the secondary coil4ais connected to its active part4cby means of suitable bonding wires9.

Although advantageous under several aspects, these solutions are not however exempt from drawbacks. In particular, in the face to face assembly technique, the realization of two different support frames of optical source2and optical detector4as well as their alignment is problematic, in particular expensive. The step of gluing the respective elements to these support frames is as much difficult.

Similarly, the dielectric mirror assembly technique requires the use of at least two different molding compounds; in particular the compound realizing the optical reflector5is very expensive and difficult to be dispensed.

Finally, further difficulties can be found in the realization of the magnetically connected active parts of the primary and secondary coil in the case of the “Coreless Transformer” assembly technique.

One technical problem addressed by the present disclosure is that of devising an architecture of a device having galvanic optoinsulation suitable for being completely integrated by using integration process flows widely employed in the field of microelectronics, overcoming the limits and drawbacks still affecting the galvanic optocoupler devices realized according to prior designs and the related assembly techniques.

BRIEF SUMMARY

The present disclosure is directed to using an optical source directly integrated above the insulation source of the optical detector, the galvanic optocoupler thus being contained in a single island, simplifying the type of package to be used for the containment of the galvanic optocoupler.

On the basis of this approach, the technical problem is solved by an architecture of a device having a galvanic optocoupling of the type including at least one optical source and an optical detector, optically connected by means of an insulation layer with function of transmission means and having at least one input terminal and one output terminal, the optical source and the optical detector 4-connected to respective first and second voltage references. The optical source is realized by a structure directly integrated above the insulation layer, in correspondence with the optical detector, the architecture being thus completely realized inside a single integration island.

In accordance with one embodiment of the present disclosure, a galvanic optocoupler is provided, the optocoupler including a single integration island on a single die; an input stage coupled to a first ground potential; an optical source formed in the island and optically coupled to the input stage; an optically conductive electrical insulation layer formed in the island adjacent the optical source; an optical detector formed in the island adjacent to the insulation layer in optical communication with the optical source through the insulation layer; and an output stage optically coupled to the optical detector and electrically coupled to a second ground potential that is electrically insulated from the first ground potential.

In accordance with another aspect of the foregoing embodiment, the input stage and the output stage, at least one or both, are formed on a separate die than on the single die.

In accordance with another aspect of the foregoing embodiment, the optical source is formed by a directly integrated structure above the insulation layer.

In accordance with another embodiment of the present disclosure, a device is provided, the device includes a galvanic optocoupler that has a single integration island on a single die; an input stage coupled to a first ground potential; an optical source formed in the island and optically coupled to the input stage; an optically conductive electrical insulation layer formed in the island adjacent the optical source; an optical detector formed in the island adjacent to the insulation layer in optical communication with the optical source through the insulation layer; and an output stage optically coupled to the optical detector and electrically coupled to a second ground potential that is electrically insulated from the first ground potential.

In accordance with another aspect of the foregoing embodiment, at least one of the input stage and the output stage are formed on a separate die than the single die.

In accordance with another aspect of the foregoing embodiment, the optical source is formed in an integrated structure above the insulation layer.

In accordance with another aspect of the foregoing embodiment, the input stage and the output stage are both formed on the single integration island on the single die.

DETAILED DESCRIPTION

With reference to these figures, and in particular toFIG. 3A, reference numeral10globally and schematically indicates an architecture of a device having galvanic optocoupling realized according to the present disclosure.

As may be seen in connection with the known devices, the architecture10realizes a device equipped with a galvanic optocoupler having at least one optical source12and one optical detector14optically connected by means of an insulation layer13having the function of a transmission means. The optical source12and the optical detector14are connected to respective voltage references, in particular first and second ground references, GND1and GND2, respectively.

In particular, advantageously according to the disclosure, the optical source12is realized by a structure that is directly integrated above the insulation layer13in correspondence with the optical detector14. In this way, the architecture10is completely realized inside a single integration island11.

The optical source12is in particular connected to an input stage15, for example a driving device or driver, in turn connected to an input terminal IN and to the first ground reference, GND1, by means of suitable connections16, in particular bonding wires.

The input stage15can also be integrated in a separated die with respect to the one containing the first integration island11. Thus, the galvanic optocoupler would be formed by the optical source12, by the insulation layer13and by the optical detector14, as well as possibly the output stage18. This separated die being suitably glued on the insulation layer13.

It is further possible to integrate both the optical source12and the input stage15above the insulation layer13. In this case, the connections16will be realized by suitable metal tracks.

The input stage15is also connected to a supply terminal Ta receiving a supply voltage Vsource.

In the embodiment shown inFIG. 3A, the optical detector14is realized in the form of a phototransistor and is also connected to a possible output stage18of the device, in particular an amplification stage or a control logic, by means of suitable connections19such as metallization, vias, tracks, wires, or the like.

The output stage18is further connected to an output terminal OUT and to the second ground terminal, GND2.

In this way an architecture of a galvanic optocoupler device10integrated in an integration island11is obtained, considerably simplifying the realization of a containment package of the device itself, in practice allowing the use of a single island package of the standard type.

It is also to be noted that the presence of the insulation layer13ensures the desired galvanic insulation between the input stage15and the output stage18of the device thus obtained, as well as between the first and the second ground terminal, GND1and GND2.

Still advantageously according to the disclosure, the optical source12is realized above the optical detector14, thus ensuring the greatest optical coupling for the device thus obtained.

In a further embodiment, the architecture10includes at least one first and one second integration island,11A and11B, respectively, adapted for hosting distinct elements of the device.

More in particular, in the example shown inFIG. 3B, the first island11A includes the input stage15, for example a driving device or driver for the optical source12, suitably connected to the input terminal IN, to the supply terminal Ta and to the first ground terminal, GND1.

This first island11A is connected, by means of suitable connections16, in particular by means of bonding wires, to the optical source12, suitably realized above the optical detector14in the second island11B. Also in the embodiment shown inFIG. 3B, this optical detector14is realized in the form of a phototransistor.

The second island11B also includes the possible output stage18of the device, in particular an amplification stage or a control logic, in turn connected to the optical detector14by means of suitable connections19as described above.

The output stage18is further connected to the output terminal OUT and to the second ground terminal GND2.

It is immediately clear that the structures hosted in the integration islands11A and11B are very easy to integrate, making the architecture10usable in multiple fields of application.

It is also to be noted that the presence of these integration islands allows separation of the supply of at least the input stage15, enabling realization of devices having galvanic optocoupling compatible with already known circuits.

It is also important to note that the architecture10does not impose constraints of any type on the realization of the elements connected to the output terminal OUT. In particular, the optical detector14and the output stage18can be integrated on a same die (with connections19realized by means of metal tracks) or realized in two separate dies and connected to each other by bonding wires as connections19.

The architecture10according to the disclosure provides a device having galvanic optocoupling with a single unidirectional channel, i.e., a device wherein the information is transmitted from the input stage15to the output stage18and not vice versa.

It is also possible to realize a device having galvanic optocoupling of the bidirectional type by assembling, in a same package, two specular unidirectional architectures,10A and10B, as schematically shown inFIG. 4, globally indicated with20.

Although each of the architectures10A and10B shown inFIG. 4comprises two distinct integration islands of the type shown inFIG. 3B, the bidirectional device20can be obtained by means of two architectures each having one single integration island of the type shown inFIG. 3A.

In particular, in the bidirectional device20shown inFIG. 4the information travels from the left to the right on a first channel, indicated with A, and in the opposite direction on a second channel, indicated with B, between the respective input and output terminals INA-OUTA and INB-OUTB, relative to the first architecture and to the second architecture of the device having galvanic optocoupler device,10A and10B. It is not in fact possible to realize a bidirectional communication with a single channel.

Also in the case of the bidirectional device20, all the ground references are independent to ensure a correct galvanic insulation. In particular, the first architecture10A is connected to respective first and second ground terminals, GND1A and GND2A, and similarly the second architecture10B is connected to respective first and second ground terminals GND1B and GND2B.

In conclusion, advantageously according to the disclosure, an architecture has been proposed suitable for realizing a device having galvanic optocoupling in at least one first and one second integration island, suitably connected to respective ground terminals and hosting different elements of the device.

The main advantage of the architecture10according to the disclosure is that it can be integrated with processes compatible with mature and consolidated techniques, such as the silicon one, currently used in the field of the microelectronics. Moreover, the architecture10does not need particularly complex and expensive packages, any package with two islands of the known type being perfectly suitable for the purpose.