Mixing
Cuk topology patent
Clash Royale CLAN TAG#URR8PPP
up vote
1
down vote
favorite
While searching for a good inverting SMPS topology, I stumbled across the Cuk topology which suits me perfectly by all means. The only thing that worries me is that unlike more common SMPS topologies, like inverting buck-boost or flyback, Cuk topology seems to patented according to wikipedia and many other sources.
I am going to use the Cuk topology in a PSU for a eurorack synth I am working on and I was thinking about selling some PSUs made from leftover PCBs and parts.
So, my question is: realistically speaking, how safe is it to use the Cuk topology in commercial products today? What could be the effects of doing it? Both in case of niche, yet still commercial products and in case of more spreaded ones.
EDIT:
The wikipedia gives links to expired patents.
- https://patents.google.com/patent/US4257087
- https://patents.google.com/patent/US4274133
- https://patents.google.com/patent/US4184197
I am, however, pretty much sure that a number of other patents with slight changes could also be filed in more recent years (especially from IC manufacturers), but wasn't able to find any.
I am planning to sell the product mostly in Russian Federation, the patents are from the US. But still, theoretically speaking, what could happen in case if the product well be sold with worldwide shipping?
I do understand that this is more of a "lawyer" question than "electrical engineering" one, so the "electrical engineering" part of the question is "how do engineers deal with it".
switch-mode-power-supply dc-dc-converter
asked 3 hours ago
sx107
1018
add a comment |Â
up vote
1
down vote
favorite
While searching for a good inverting SMPS topology, I stumbled across the Cuk topology which suits me perfectly by all means. The only thing that worries me is that unlike more common SMPS topologies, like inverting buck-boost or flyback, Cuk topology seems to patented according to wikipedia and many other sources.
I am going to use the Cuk topology in a PSU for a eurorack synth I am working on and I was thinking about selling some PSUs made from leftover PCBs and parts.
So, my question is: realistically speaking, how safe is it to use the Cuk topology in commercial products today? What could be the effects of doing it? Both in case of niche, yet still commercial products and in case of more spreaded ones.
EDIT:
The wikipedia gives links to expired patents.
- https://patents.google.com/patent/US4257087
- https://patents.google.com/patent/US4274133
- https://patents.google.com/patent/US4184197
I am, however, pretty much sure that a number of other patents with slight changes could also be filed in more recent years (especially from IC manufacturers), but wasn't able to find any.
I am planning to sell the product mostly in Russian Federation, the patents are from the US. But still, theoretically speaking, what could happen in case if the product well be sold with worldwide shipping?
I do understand that this is more of a "lawyer" question than "electrical engineering" one, so the "electrical engineering" part of the question is "how do engineers deal with it".
switch-mode-power-supply dc-dc-converter
asked 3 hours ago
sx107
1018
1
Has the patent expired?
– Andy aka
3 hours ago
1
Check with a patent lawyer, chances are that such a patent won't hold since its an obvious extension of already existing technology.
– PlasmaHH
3 hours ago
1
In what countries do you want to make and sell the products? In which countries has the patent been filed?
– Jack B
3 hours ago
1
Given that a number of the major players in SMPS devices have application notes and reference designs in their datasheets implementing this topology without reference to any patents (which they normally do if such exists) I would be surprised if this is still covered (but IANAL).
– Peter Smith
3 hours ago
add a comment |Â
up vote
1
down vote
favorite
up vote
1
down vote
favorite
While searching for a good inverting SMPS topology, I stumbled across the Cuk topology which suits me perfectly by all means. The only thing that worries me is that unlike more common SMPS topologies, like inverting buck-boost or flyback, Cuk topology seems to patented according to wikipedia and many other sources.
I am going to use the Cuk topology in a PSU for a eurorack synth I am working on and I was thinking about selling some PSUs made from leftover PCBs and parts.
So, my question is: realistically speaking, how safe is it to use the Cuk topology in commercial products today? What could be the effects of doing it? Both in case of niche, yet still commercial products and in case of more spreaded ones.
EDIT:
The wikipedia gives links to expired patents.
- https://patents.google.com/patent/US4257087
- https://patents.google.com/patent/US4274133
- https://patents.google.com/patent/US4184197
I am, however, pretty much sure that a number of other patents with slight changes could also be filed in more recent years (especially from IC manufacturers), but wasn't able to find any.
I am planning to sell the product mostly in Russian Federation, the patents are from the US. But still, theoretically speaking, what could happen in case if the product well be sold with worldwide shipping?
I do understand that this is more of a "lawyer" question than "electrical engineering" one, so the "electrical engineering" part of the question is "how do engineers deal with it".
switch-mode-power-supply dc-dc-converter
asked 3 hours ago
sx107
1018
While searching for a good inverting SMPS topology, I stumbled across the Cuk topology which suits me perfectly by all means. The only thing that worries me is that unlike more common SMPS topologies, like inverting buck-boost or flyback, Cuk topology seems to patented according to wikipedia and many other sources.
I am going to use the Cuk topology in a PSU for a eurorack synth I am working on and I was thinking about selling some PSUs made from leftover PCBs and parts.
So, my question is: realistically speaking, how safe is it to use the Cuk topology in commercial products today? What could be the effects of doing it? Both in case of niche, yet still commercial products and in case of more spreaded ones.
EDIT:
The wikipedia gives links to expired patents.
- https://patents.google.com/patent/US4257087
- https://patents.google.com/patent/US4274133
- https://patents.google.com/patent/US4184197
I am, however, pretty much sure that a number of other patents with slight changes could also be filed in more recent years (especially from IC manufacturers), but wasn't able to find any.
I am planning to sell the product mostly in Russian Federation, the patents are from the US. But still, theoretically speaking, what could happen in case if the product well be sold with worldwide shipping?
I do understand that this is more of a "lawyer" question than "electrical engineering" one, so the "electrical engineering" part of the question is "how do engineers deal with it".
switch-mode-power-supply dc-dc-converter
switch-mode-power-supply dc-dc-converter
asked 3 hours ago
sx107
1018
asked 3 hours ago
sx107
1018
edited 3 hours ago
asked 3 hours ago
sx107
1018
asked 3 hours ago
sx107
1018
asked 3 hours ago
sx107
1018
1018
1
Has the patent expired?
– Andy aka
3 hours ago
1
Check with a patent lawyer, chances are that such a patent won't hold since its an obvious extension of already existing technology.
– PlasmaHH
3 hours ago
1
In what countries do you want to make and sell the products? In which countries has the patent been filed?
– Jack B
3 hours ago
1
Given that a number of the major players in SMPS devices have application notes and reference designs in their datasheets implementing this topology without reference to any patents (which they normally do if such exists) I would be surprised if this is still covered (but IANAL).
– Peter Smith
3 hours ago
add a comment |Â
1
Has the patent expired?
– Andy aka
3 hours ago
1
Check with a patent lawyer, chances are that such a patent won't hold since its an obvious extension of already existing technology.
– PlasmaHH
3 hours ago
1
In what countries do you want to make and sell the products? In which countries has the patent been filed?
– Jack B
3 hours ago
1
Given that a number of the major players in SMPS devices have application notes and reference designs in their datasheets implementing this topology without reference to any patents (which they normally do if such exists) I would be surprised if this is still covered (but IANAL).
– Peter Smith
3 hours ago
1
1
Has the patent expired?
– Andy aka
3 hours ago
Has the patent expired?
– Andy aka
3 hours ago
1
1
Check with a patent lawyer, chances are that such a patent won't hold since its an obvious extension of already existing technology.
– PlasmaHH
3 hours ago
Check with a patent lawyer, chances are that such a patent won't hold since its an obvious extension of already existing technology.
– PlasmaHH
3 hours ago
1
1
In what countries do you want to make and sell the products? In which countries has the patent been filed?
– Jack B
3 hours ago
In what countries do you want to make and sell the products? In which countries has the patent been filed?
– Jack B
3 hours ago
1
1
Given that a number of the major players in SMPS devices have application notes and reference designs in their datasheets implementing this topology without reference to any patents (which they normally do if such exists) I would be surprised if this is still covered (but IANAL).
– Peter Smith
3 hours ago
Given that a number of the major players in SMPS devices have application notes and reference designs in their datasheets implementing this topology without reference to any patents (which they normally do if such exists) I would be surprised if this is still covered (but IANAL).
– Peter Smith
3 hours ago
add a comment |Â
2 Answers
2
active
oldest
votes
up vote
3
down vote
Disclaimer: I am not a lawyer and patent law is complicated, especially because it differs greatly between jurisdictions.
The patents you linked to have long expired. This means you can duplicate the converters covered in the patent. After all, that’s the point of patents. The inventor discloses the invention in return for a 20 year monopoly right. After the end of the 20 years everyone can use the invention.
If you find any new patents, they will cover only improvements that have not been disclosed in the prior art (old patents). Read the claims of the patent. They limit what is protected. For example, suppose there is some new capacitor X that improves the performance of buck converters. A claim will look like this:
- A buck converter comprising at least one capacitor X.
According to the above claim you can still use buck converters, if you do not include capacitor X.
What can happen if you infringe on a patent is that the assignee (owner of the property rights) can ask you to stop selling, using, manufacturing, or importing the invention. If you refuse, they can get a court order for the same.
Keep in mind that patents are regional rights. The only patents valid in your jurisdiction are the patents issued by your local patent office.
answered 2 hours ago
user110971
2,8311715
Can you address the "maintenance" issue discussed by @JonRB in their answer? Are there ever situations where a patent issued in one jurisdiction is enforceable in another? What if the product is sold or exported to another jurisdiction?
– Elliot Alderson
1 hour ago
@ElliotAlderson In order to ensure that patents without commercial application are not kept going for the full 20 years the patent office requires escalating maintenance fees be paid. I believe the first fee is due at the 3.5 year mark and then every 4 years for a total of three times in the U.S. A patent expires after 20 years or when a maintenance fee is not paid.
– user110971
1 hour ago
@ElliotAlderson A patent is always a regional right. You can obtain patent protection in more than one jurisdiction by applying at multiple patent offices either within one year or through the PCT (patent cooperation treaty). The local patent office needs to approve patentability, e.g. software patents are not allowed in Europe. If you patent an invention in a list of jurisdictions, everyone not resident at one of the jurisdictions can take your disclosure in the patent and exploit the invention. A patent prevents sale, use, manufacture, and import. You cannot avoid it by importing.
– user110971
1 hour ago
add a comment |Â
up vote
2
down vote
The patents associated with the Cuk topology
US Patent 4257087 filed 1979 https://patents.google.com/patent/US4257087 expired but maintenance fee appears to have been made
US Patent 4274133 filed 1979 https://patents.google.com/patent/US4274133 expired but maintenance fee appears to have been made
US Patent 4184197 filed 1977 https://patents.google.com/patent/US4184197 expired but maintenance fee appears to have been made
So essentially the way to determine if a patent has expired is
http://piersonpatentlaw.com/how-can-i-tell-if-a-patent-is-expired/
1) Determine if the patent was filed, or claims priority to a
patent filed prior to 20 years before the date.
2) Determine if the maintenance fees have been paid.
20years have passed but checking the transaction history: http://portal.uspto.gov/external/portal/pair/ none have "Expired Patent"
What you will find is LT and other makers of Cuk based converter chips pay a licensing fee.
edited 2 hours ago
Neil_UK
70.7k273155
answered 2 hours ago
JonRB
12.3k21838
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
Disclaimer: I am not a lawyer and patent law is complicated, especially because it differs greatly between jurisdictions.
The patents you linked to have long expired. This means you can duplicate the converters covered in the patent. After all, that’s the point of patents. The inventor discloses the invention in return for a 20 year monopoly right. After the end of the 20 years everyone can use the invention.
If you find any new patents, they will cover only improvements that have not been disclosed in the prior art (old patents). Read the claims of the patent. They limit what is protected. For example, suppose there is some new capacitor X that improves the performance of buck converters. A claim will look like this:
- A buck converter comprising at least one capacitor X.
According to the above claim you can still use buck converters, if you do not include capacitor X.
What can happen if you infringe on a patent is that the assignee (owner of the property rights) can ask you to stop selling, using, manufacturing, or importing the invention. If you refuse, they can get a court order for the same.
Keep in mind that patents are regional rights. The only patents valid in your jurisdiction are the patents issued by your local patent office.
answered 2 hours ago
user110971
2,8311715
Can you address the "maintenance" issue discussed by @JonRB in their answer? Are there ever situations where a patent issued in one jurisdiction is enforceable in another? What if the product is sold or exported to another jurisdiction?
– Elliot Alderson
1 hour ago
@ElliotAlderson In order to ensure that patents without commercial application are not kept going for the full 20 years the patent office requires escalating maintenance fees be paid. I believe the first fee is due at the 3.5 year mark and then every 4 years for a total of three times in the U.S. A patent expires after 20 years or when a maintenance fee is not paid.
– user110971
1 hour ago
@ElliotAlderson A patent is always a regional right. You can obtain patent protection in more than one jurisdiction by applying at multiple patent offices either within one year or through the PCT (patent cooperation treaty). The local patent office needs to approve patentability, e.g. software patents are not allowed in Europe. If you patent an invention in a list of jurisdictions, everyone not resident at one of the jurisdictions can take your disclosure in the patent and exploit the invention. A patent prevents sale, use, manufacture, and import. You cannot avoid it by importing.
– user110971
1 hour ago
add a comment |Â
up vote
3
down vote
Disclaimer: I am not a lawyer and patent law is complicated, especially because it differs greatly between jurisdictions.
The patents you linked to have long expired. This means you can duplicate the converters covered in the patent. After all, that’s the point of patents. The inventor discloses the invention in return for a 20 year monopoly right. After the end of the 20 years everyone can use the invention.
If you find any new patents, they will cover only improvements that have not been disclosed in the prior art (old patents). Read the claims of the patent. They limit what is protected. For example, suppose there is some new capacitor X that improves the performance of buck converters. A claim will look like this:
- A buck converter comprising at least one capacitor X.
According to the above claim you can still use buck converters, if you do not include capacitor X.
What can happen if you infringe on a patent is that the assignee (owner of the property rights) can ask you to stop selling, using, manufacturing, or importing the invention. If you refuse, they can get a court order for the same.
Keep in mind that patents are regional rights. The only patents valid in your jurisdiction are the patents issued by your local patent office.
answered 2 hours ago
user110971
2,8311715
Can you address the "maintenance" issue discussed by @JonRB in their answer? Are there ever situations where a patent issued in one jurisdiction is enforceable in another? What if the product is sold or exported to another jurisdiction?
– Elliot Alderson
1 hour ago
@ElliotAlderson In order to ensure that patents without commercial application are not kept going for the full 20 years the patent office requires escalating maintenance fees be paid. I believe the first fee is due at the 3.5 year mark and then every 4 years for a total of three times in the U.S. A patent expires after 20 years or when a maintenance fee is not paid.
– user110971
1 hour ago
@ElliotAlderson A patent is always a regional right. You can obtain patent protection in more than one jurisdiction by applying at multiple patent offices either within one year or through the PCT (patent cooperation treaty). The local patent office needs to approve patentability, e.g. software patents are not allowed in Europe. If you patent an invention in a list of jurisdictions, everyone not resident at one of the jurisdictions can take your disclosure in the patent and exploit the invention. A patent prevents sale, use, manufacture, and import. You cannot avoid it by importing.
– user110971
1 hour ago
add a comment |Â
up vote
3
down vote
up vote
3
down vote
Disclaimer: I am not a lawyer and patent law is complicated, especially because it differs greatly between jurisdictions.
The patents you linked to have long expired. This means you can duplicate the converters covered in the patent. After all, that’s the point of patents. The inventor discloses the invention in return for a 20 year monopoly right. After the end of the 20 years everyone can use the invention.
If you find any new patents, they will cover only improvements that have not been disclosed in the prior art (old patents). Read the claims of the patent. They limit what is protected. For example, suppose there is some new capacitor X that improves the performance of buck converters. A claim will look like this:
- A buck converter comprising at least one capacitor X.
According to the above claim you can still use buck converters, if you do not include capacitor X.
What can happen if you infringe on a patent is that the assignee (owner of the property rights) can ask you to stop selling, using, manufacturing, or importing the invention. If you refuse, they can get a court order for the same.
Keep in mind that patents are regional rights. The only patents valid in your jurisdiction are the patents issued by your local patent office.
answered 2 hours ago
user110971
2,8311715
Disclaimer: I am not a lawyer and patent law is complicated, especially because it differs greatly between jurisdictions.
The patents you linked to have long expired. This means you can duplicate the converters covered in the patent. After all, that’s the point of patents. The inventor discloses the invention in return for a 20 year monopoly right. After the end of the 20 years everyone can use the invention.
If you find any new patents, they will cover only improvements that have not been disclosed in the prior art (old patents). Read the claims of the patent. They limit what is protected. For example, suppose there is some new capacitor X that improves the performance of buck converters. A claim will look like this:
- A buck converter comprising at least one capacitor X.
According to the above claim you can still use buck converters, if you do not include capacitor X.
What can happen if you infringe on a patent is that the assignee (owner of the property rights) can ask you to stop selling, using, manufacturing, or importing the invention. If you refuse, they can get a court order for the same.
Keep in mind that patents are regional rights. The only patents valid in your jurisdiction are the patents issued by your local patent office.
answered 2 hours ago
user110971
2,8311715
answered 2 hours ago
user110971
2,8311715
answered 2 hours ago
user110971
2,8311715
answered 2 hours ago
user110971
2,8311715
2,8311715
Can you address the "maintenance" issue discussed by @JonRB in their answer? Are there ever situations where a patent issued in one jurisdiction is enforceable in another? What if the product is sold or exported to another jurisdiction?
– Elliot Alderson
1 hour ago
@ElliotAlderson In order to ensure that patents without commercial application are not kept going for the full 20 years the patent office requires escalating maintenance fees be paid. I believe the first fee is due at the 3.5 year mark and then every 4 years for a total of three times in the U.S. A patent expires after 20 years or when a maintenance fee is not paid.
– user110971
1 hour ago
@ElliotAlderson A patent is always a regional right. You can obtain patent protection in more than one jurisdiction by applying at multiple patent offices either within one year or through the PCT (patent cooperation treaty). The local patent office needs to approve patentability, e.g. software patents are not allowed in Europe. If you patent an invention in a list of jurisdictions, everyone not resident at one of the jurisdictions can take your disclosure in the patent and exploit the invention. A patent prevents sale, use, manufacture, and import. You cannot avoid it by importing.
– user110971
1 hour ago
add a comment |Â
Can you address the "maintenance" issue discussed by @JonRB in their answer? Are there ever situations where a patent issued in one jurisdiction is enforceable in another? What if the product is sold or exported to another jurisdiction?
– Elliot Alderson
1 hour ago
@ElliotAlderson In order to ensure that patents without commercial application are not kept going for the full 20 years the patent office requires escalating maintenance fees be paid. I believe the first fee is due at the 3.5 year mark and then every 4 years for a total of three times in the U.S. A patent expires after 20 years or when a maintenance fee is not paid.
– user110971
1 hour ago
@ElliotAlderson A patent is always a regional right. You can obtain patent protection in more than one jurisdiction by applying at multiple patent offices either within one year or through the PCT (patent cooperation treaty). The local patent office needs to approve patentability, e.g. software patents are not allowed in Europe. If you patent an invention in a list of jurisdictions, everyone not resident at one of the jurisdictions can take your disclosure in the patent and exploit the invention. A patent prevents sale, use, manufacture, and import. You cannot avoid it by importing.
– user110971
1 hour ago
Can you address the "maintenance" issue discussed by @JonRB in their answer? Are there ever situations where a patent issued in one jurisdiction is enforceable in another? What if the product is sold or exported to another jurisdiction?
– Elliot Alderson
1 hour ago
Can you address the "maintenance" issue discussed by @JonRB in their answer? Are there ever situations where a patent issued in one jurisdiction is enforceable in another? What if the product is sold or exported to another jurisdiction?
– Elliot Alderson
1 hour ago
@ElliotAlderson In order to ensure that patents without commercial application are not kept going for the full 20 years the patent office requires escalating maintenance fees be paid. I believe the first fee is due at the 3.5 year mark and then every 4 years for a total of three times in the U.S. A patent expires after 20 years or when a maintenance fee is not paid.
– user110971
1 hour ago
@ElliotAlderson In order to ensure that patents without commercial application are not kept going for the full 20 years the patent office requires escalating maintenance fees be paid. I believe the first fee is due at the 3.5 year mark and then every 4 years for a total of three times in the U.S. A patent expires after 20 years or when a maintenance fee is not paid.
– user110971
1 hour ago
@ElliotAlderson A patent is always a regional right. You can obtain patent protection in more than one jurisdiction by applying at multiple patent offices either within one year or through the PCT (patent cooperation treaty). The local patent office needs to approve patentability, e.g. software patents are not allowed in Europe. If you patent an invention in a list of jurisdictions, everyone not resident at one of the jurisdictions can take your disclosure in the patent and exploit the invention. A patent prevents sale, use, manufacture, and import. You cannot avoid it by importing.
– user110971
1 hour ago
@ElliotAlderson A patent is always a regional right. You can obtain patent protection in more than one jurisdiction by applying at multiple patent offices either within one year or through the PCT (patent cooperation treaty). The local patent office needs to approve patentability, e.g. software patents are not allowed in Europe. If you patent an invention in a list of jurisdictions, everyone not resident at one of the jurisdictions can take your disclosure in the patent and exploit the invention. A patent prevents sale, use, manufacture, and import. You cannot avoid it by importing.
– user110971
1 hour ago
add a comment |Â
up vote
2
down vote
The patents associated with the Cuk topology
US Patent 4257087 filed 1979 https://patents.google.com/patent/US4257087 expired but maintenance fee appears to have been made
US Patent 4274133 filed 1979 https://patents.google.com/patent/US4274133 expired but maintenance fee appears to have been made
US Patent 4184197 filed 1977 https://patents.google.com/patent/US4184197 expired but maintenance fee appears to have been made
So essentially the way to determine if a patent has expired is
http://piersonpatentlaw.com/how-can-i-tell-if-a-patent-is-expired/
1) Determine if the patent was filed, or claims priority to a
patent filed prior to 20 years before the date.
2) Determine if the maintenance fees have been paid.
20years have passed but checking the transaction history: http://portal.uspto.gov/external/portal/pair/ none have "Expired Patent"
What you will find is LT and other makers of Cuk based converter chips pay a licensing fee.
edited 2 hours ago
Neil_UK
70.7k273155
answered 2 hours ago
JonRB
12.3k21838
add a comment |Â
up vote
2
down vote
The patents associated with the Cuk topology
US Patent 4257087 filed 1979 https://patents.google.com/patent/US4257087 expired but maintenance fee appears to have been made
US Patent 4274133 filed 1979 https://patents.google.com/patent/US4274133 expired but maintenance fee appears to have been made
US Patent 4184197 filed 1977 https://patents.google.com/patent/US4184197 expired but maintenance fee appears to have been made
So essentially the way to determine if a patent has expired is
http://piersonpatentlaw.com/how-can-i-tell-if-a-patent-is-expired/
1) Determine if the patent was filed, or claims priority to a
patent filed prior to 20 years before the date.
2) Determine if the maintenance fees have been paid.
20years have passed but checking the transaction history: http://portal.uspto.gov/external/portal/pair/ none have "Expired Patent"
What you will find is LT and other makers of Cuk based converter chips pay a licensing fee.
edited 2 hours ago
Neil_UK
70.7k273155
answered 2 hours ago
JonRB
12.3k21838
add a comment |Â
up vote
2
down vote
up vote
2
down vote
The patents associated with the Cuk topology
US Patent 4257087 filed 1979 https://patents.google.com/patent/US4257087 expired but maintenance fee appears to have been made
US Patent 4274133 filed 1979 https://patents.google.com/patent/US4274133 expired but maintenance fee appears to have been made
US Patent 4184197 filed 1977 https://patents.google.com/patent/US4184197 expired but maintenance fee appears to have been made
So essentially the way to determine if a patent has expired is
http://piersonpatentlaw.com/how-can-i-tell-if-a-patent-is-expired/
1) Determine if the patent was filed, or claims priority to a
patent filed prior to 20 years before the date.
2) Determine if the maintenance fees have been paid.
20years have passed but checking the transaction history: http://portal.uspto.gov/external/portal/pair/ none have "Expired Patent"
What you will find is LT and other makers of Cuk based converter chips pay a licensing fee.
edited 2 hours ago
Neil_UK
70.7k273155
answered 2 hours ago
JonRB
12.3k21838
The patents associated with the Cuk topology
US Patent 4257087 filed 1979 https://patents.google.com/patent/US4257087 expired but maintenance fee appears to have been made
US Patent 4274133 filed 1979 https://patents.google.com/patent/US4274133 expired but maintenance fee appears to have been made
US Patent 4184197 filed 1977 https://patents.google.com/patent/US4184197 expired but maintenance fee appears to have been made
So essentially the way to determine if a patent has expired is
http://piersonpatentlaw.com/how-can-i-tell-if-a-patent-is-expired/
1) Determine if the patent was filed, or claims priority to a
patent filed prior to 20 years before the date.
2) Determine if the maintenance fees have been paid.
20years have passed but checking the transaction history: http://portal.uspto.gov/external/portal/pair/ none have "Expired Patent"
What you will find is LT and other makers of Cuk based converter chips pay a licensing fee.
edited 2 hours ago
Neil_UK
70.7k273155
answered 2 hours ago
JonRB
12.3k21838
edited 2 hours ago
Neil_UK
70.7k273155
edited 2 hours ago
Neil_UK
70.7k273155
edited 2 hours ago
Neil_UK
70.7k273155
70.7k273155
answered 2 hours ago
JonRB
12.3k21838
answered 2 hours ago
JonRB
12.3k21838
answered 2 hours ago
JonRB
12.3k21838
12.3k21838
add a comment |Â
add a comment |Â
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1
Has the patent expired?
– Andy aka
3 hours ago
1
Check with a patent lawyer, chances are that such a patent won't hold since its an obvious extension of already existing technology.
– PlasmaHH
3 hours ago
1
In what countries do you want to make and sell the products? In which countries has the patent been filed?
– Jack B
3 hours ago
1
Given that a number of the major players in SMPS devices have application notes and reference designs in their datasheets implementing this topology without reference to any patents (which they normally do if such exists) I would be surprised if this is still covered (but IANAL).
– Peter Smith
3 hours ago