Patent Publication Number: US-2019189342-A1

Title: Variable inductor and integrated circuit using the variable inductor

Description:
FIELD OF THE INVENTION 
     The present disclosure relates to a variable inductor and, more particularly, to a variable inductor which can be formed on an integrated circuit. 
     BACKGROUND OF THE INVENTION 
     Referring to  FIG. 1A  and  FIG. 1B ,  FIG. 1A  and  FIG. 1B  shows a conventional variable inductor. The conventional variable inductor  1000  has a primary conductor  1100  and a secondary conductor  1200 , a switch  1300  and a current source  1400 . The secondary conductor  1200  forms a loop on the outside of the primary conductor  1100 . The switch  1300  couples in series with the secondary conductor  1200  and is turned on or off to make the loop close or open. The inductance of the conventional variable inductor  1000  is varied by closing and opening the loop with the switch  1300 . The current source  1400  is also coupled in series with the secondary conductor  1200  and used to control the current flow in the secondary conductor  1200  to either increase or decrease the inductance. 
     Referring to  FIG. 2 ,  FIG. 2  shows another one conventional variable inductor. The conventional variable inductor  2000  has a first conductor  2100 , a second conductor  2200 , a first switch  2300 , a second switch  2400  and a third switch  2500 . The first switch  2300 , the second switch  2400  and the third switch  2500  are disposed on three current paths connected between the first conductor  2100  and the second conductor  2200 , respectively. The inductance of the conventional variable inductor  2000  is varied by closing and opening the first switch  2300 , the second switch  2400  and the third switch  2500 . 
     The conventional variable inductor  1000  may have a limitedly adjustable inductance range and an insufficient inductance resolution. The conventional variable inductor  2000  may have a lower Q value, durability issues and bias concern. 
     Accordingly, it is imperative to provide a variable inductor and an integrated circuit using the variable inductor which can overcome the aforesaid drawbacks of the conventional variable inductors. 
     SUMMARY OF THE INVENTION 
     In view of the aforesaid drawbacks of the prior art, it is an objective of the present disclosure to provide a variable inductor and an integrated circuit using the variable inductor which can have a wider adjustable inductance range, a better inductance resolution, a higher Q value, fewer durability issues and no bias concern. 
     In order to achieve the above and other objectives, the present disclosure provides a variable inductor which comprises a primary conductor, a first secondary conductor and a first switch. The primary conductor has a first node and a second node, wherein the first node being used to connect a first external component and the second node being used to connect a second external component. The first secondary conductor magnetically couples to the primary conductor. The first switch has two sides connected to the first secondary conductor, respectively. The first secondary conductor is formed a single-loop structure with two changeable current paths which are operated by the states of the first switch. 
     Regarding the variable inductor, the variable inductor further comprises a second switch having two sides connected to the first secondary conductor, respectively, and the first secondary conductor is formed a single-loop structure with four changeable current paths which are operated by the states of the first and second switches. 
     Regarding the variable inductor, the variable inductor further comprises a third switch having two sides connected to the first secondary conductor, respectively, and the first secondary conductor is formed a single-loop structure with eight changeable current paths which are operated by the states of the first, second and third switches. 
     Regarding the variable inductor, the variable inductor further comprises a second secondary conductor magnetically coupling to the primary conductor and a fourth switch having two sides connected to the second secondary conductor, respectively. The second secondary conductor is formed a single-loop structure with two changeable current paths which are operated by the states of the fourth switch. 
     Regarding the variable inductor, the variable inductor further comprises a fifth switch having two sides connected to the second secondary conductor, respectively, and the second secondary conductor is formed a single-loop structure with four changeable current paths which are operated by the states of the fourth and fifth switches. 
     Regarding the variable inductor, the variable inductor further comprises a sixth switch having two sides connected to the second secondary conductor, respectively, and the second secondary conductor is formed a single-loop structure with eight changeable current paths which are operated by the states of the fourth, fifth and sixth switches. 
     Regarding the variable inductor, the first secondary conductor is disposed on one side of the primary conductor and the second secondary conductor is disposed on another side of the primary conductor. 
     Regarding the variable inductor, the first node is on one end of the primary conductor and the second node is on another end of the primary conductor. 
     Regarding the variable inductor, the variable inductor is integrated in a radio frequency integrated circuit. 
     Regarding the variable inductor, the first switch is implemented by a CMOS (complementary metal oxide semiconductor) or PCB (printed circuit board) lump component. 
     In order to achieve the above and other objectives, the present disclosure provides an integrated circuit. The integrated circuit comprises a first component, a second component and a variable inductor. The variable inductor comprises a primary conductor, a first secondary conductor and a first switch. The primary conductor has a first node and a second node. The first node is used to connect a first external component and the second node is used to connect a second external component. The first secondary conductor magnetically couples to the primary conductor. The first switch has two sides connected to the first secondary conductor, respectively. The first secondary conductor is formed a single-loop structure with two changeable current paths which are operated by the states of the first switch. 
     Regarding the integrated circuit, the variable inductor further comprises a second switch having two sides connected to the first secondary conductor, respectively, and the first secondary conductor is formed a single-loop structure with four changeable current paths which are operated by the states of the first and second switches. 
     Regarding the integrated circuit, the variable inductor further comprises a third switch having two sides connected to the first secondary conductor, respectively, and the first secondary conductor is formed a single-loop structure with eight changeable current paths which are operated by the states of the first, second and third switches. 
     Regarding the integrated circuit, the variable inductor further comprises a second secondary conductor magnetically coupling to the primary conductor and a fourth switch having two sides connected to the second secondary conductor, respectively. The second secondary conductor is formed a single-loop structure with two changeable current paths which are operated by the states of the fourth switch. 
     Regarding the integrated circuit, the variable inductor further comprises a fifth switch having two sides connected to the second secondary conductor, respectively, and the second secondary conductor is formed a single-loop structure with four changeable current paths which are operated by the states of the fourth and fifth switches. 
     Regarding the integrated circuit, the variable inductor further comprises a sixth switch having two sides connected to the second secondary conductor, respectively, and the second secondary conductor is formed a single-loop structure with eight changeable current paths which are operated by the states of the fourth, fifth and sixth switches. 
     Regarding the integrated circuit, the first secondary conductor is disposed on one side of the primary conductor and the second secondary conductor is disposed on another side of the primary conductor. 
     Regarding the integrated circuit, the first node is on one end of the primary conductor and the second node is on another end of the primary conductor. 
     Regarding the integrated circuit, the integrated circuit is used for radio frequency. 
     Regarding the integrated circuit, the first switch is implemented by a CMOS (complementary metal oxide semiconductor). 
     In conclusion, give the aforesaid variable inductor and integrated circuit, the present disclosure feature a wider adjustable inductance range, a better inductance resolution, a higher Q value, fewer durability issues and no bias concern. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Objectives, features, and advantages of the present disclosure are hereunder illustrated with specific embodiments in conjunction with the accompanying drawings. 
         FIG. 1A  shows a schematic diagram of a conventional variable inductor; 
         FIG. 1B  shows a schematic diagram of a conventional variable inductor; 
         FIG. 2  shows a schematic diagram of another one conventional variable inductor; 
         FIG. 3  is schematic diagrams of a variable inductor according to an embodiment of the present disclosure; 
         FIG. 4A  is a plan view of different current paths of a first secondary conductor of the variable inductor according to an embodiment of the present disclosure; 
         FIG. 4B  is a plan view of different current paths of a first secondary conductor of the variable inductor according to an embodiment of the present disclosure; 
         FIG. 4C  is a plan view of different current paths of a first secondary conductor of the variable inductor according to an embodiment of the present disclosure; 
         FIG. 4D  is a plan view of different current paths of a first secondary conductor of the variable inductor according to an embodiment of the present disclosure; 
         FIG. 4E  is a plan view of different current paths of a first secondary conductor of the variable inductor according to an embodiment of the present disclosure; 
         FIG. 4F  is a plan view of different current paths of a first secondary conductor of the variable inductor according to an embodiment of the present disclosure; 
         FIG. 4G  is a plan view of different current paths of a first secondary conductor of the variable inductor according to an embodiment of the present disclosure; 
         FIG. 4H  is a plan view of different current paths of a first secondary conductor of the variable inductor according to an embodiment of the present disclosure; 
         FIG. 5  shows an illustratively equivalent circuit of the variable inductor of  FIG. 3 ; 
         FIG. 6A  shows two different arrangements of a variable inductor according to another two embodiments of the present disclosure; 
         FIG. 6B  shows two different arrangements of a variable inductor according to another two embodiments of the present disclosure; 
         FIG. 7  is schematic diagrams of a variable inductor according to another one embodiment of the present disclosure; 
         FIG. 8  shows an illustratively equivalent circuit of the variable inductor of  FIG. 7 ; 
         FIG. 9A  shows two different arrangements of a variable inductor according to two embodiments of the present disclosure; 
         FIG. 9B  shows two different arrangements of a variable inductor according to two embodiments of the present disclosure; and 
         FIG. 10  shows a simulation result of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 3 ,  FIG. 3  is schematic diagrams of a variable inductor according to an embodiment of the present disclosure. The variable inductor  100  has a primary conductor  110 , a first secondary conductor  120 , a first switch S 1 , a second switch S 2  and a third switch S 3 , wherein the primary conductor  110  and the first secondary conductor  120  magnetically couple to each other to form a transformer structure. By controlling the first through third switches S 1  through S 3 , the equivalent inductance of the first secondary conductor  120  and coupling factor are changed due to magnetic coupling theory of the transformer structure. The inductance value of the primary conductor  110  is changed as the equivalent inductance of the first secondary conductor  120  and coupling factor are changed. Therefore, the primary conductor  110 , the first secondary conductor  120  and the first through third switches S 1  through S 3  can achieve the object of variable inductance. 
     In  FIG. 3 , the first secondary conductor  120  is disposed on the top of the primary conductor  110 . The first switch S 1 , the second switch S 2  and the third switch S 3  can be implemented on a substrate or printed circuit board  140 . The substrate or printed circuit board  140  can be disposed under the bottom of the primary conductor  110 . 
     The first switch S 1  has two sides connected to the first secondary conductor  120 , respectively. The second switch S 2  has two sides connected to the first secondary conductor  120 , respectively. The third switch S 3  has two sides connected to the first secondary conductor  120 , respectively. The first switch S 1 , the second switch S 2  and the third switch S 3  are formed on current paths P 1 -P 3 , respectively. 
     The first secondary conductor  120  is formed a single-loop structure. The current paths P 1 -P 3  are formed as three different bypaths of the single-loop structure. Therefore, if the state of anyone of the first switch S 1 , the second switch S 2  and the third switch S 3  are changed, then the current paths of the first secondary conductor  120  is changed. 
       FIGS. 4A through 4H  show eight different current paths of the first secondary conductor  120 . In  FIG. 4A , all of the first switch S 1 , the second switch S 2  and the third switch S 3  operated to be open. The first secondary conductor  120  is formed a single-loop structure with a main branch M. 
     In  FIG. 4B , only the first switch S 1  is operated to be closed. The first secondary conductor  120  is formed a single-loop structure with the main branch M and the current path P 1 . 
     In  FIG. 4C , only the second switch S 2  is operated to be closed. The first secondary conductor  120  is formed a single-loop structure with the main branch M and the current path P 2 . 
     In  FIG. 4D , only the third switch S 3  is operated to be closed. The first secondary conductor  120  is formed a single-loop structure with the main branch M and the current path P 3 . 
     In  FIG. 4E , the first switch S 1  and the second switch S 2  are operated to be closed. The first secondary conductor  120  is formed a single-loop structure with the main branch M, the current path P 1  and the current path P 2 . 
     In  FIG. 4F , the first switch S 1  and the third switch S 3  are operated to be closed. The first secondary conductor  120  is formed a single-loop structure with the main branch M, the current path P 1  and the current path P 3 . 
     In  FIG. 4G , the second switch S 2  and the third switch S 3  are operated to be closed. The first secondary conductor  120  is formed a single-loop structure with the main branch M, the current path P 2  and the current path P 3 . 
     In  FIG. 4H , all of the first switch S 1 , the second switch S 2  and the third switch S 3  operated to be closed. The first secondary conductor  120  is formed a single-loop structure with the main branch M, the current path P 1 , the current path P 2  and the current path P 3 . 
     The first secondary conductor  120  is formed a single-loop structure with eight changeable current paths which are determined by the state of the first switch S 1 , the second switch S 2  and third switch S 3 . The inductance of the variable inductor  100  is varied by closing and opening the first switch S 1 , the second switch S 2  and the third switch S 3 . Therefore, in this embodiment, the variable inductor  100  has an adjustable inductance range which includes eight different inductance values corresponding to eight different current paths (as shown as  FIG. 4A through 4H ), respectively.  FIG. 5  is an illustratively equivalent circuit of the variable inductor of  FIG. 3 . The inductance from the first node N 1  through the second node N 2  of the primary conductor  110  is changed according to the state of the switch S 1  through S 3  of the first secondary conductor  120 . 
       FIGS. 6A and 6B  show two different arrangements of a variable inductor according to two embodiments of the present disclosure. In  FIG. 6A , the first secondary conductor  120  is disposed on the top of the primary conductor  110 , and the substrate or printed circuit board  140  is disposed under the bottom of the primary conductor  110 . In  FIG. 6B , the first secondary conductor  120  is disposed under the bottom of the primary conductor  110 , and the substrate or printed circuit board  140  is disposed under the bottom of first secondary conductor  120 . 
     In other one embodiment, the third switch S 3  can be eliminated. In that embodiment, the first secondary conductor  120  is formed a single-loop structure with four changeable current paths which are operated by the states of the first switch S 1  and the second switch S 2 . 
     In the other one embodiment, both the second switch S 2  and the third switch S 3  can be eliminated. In that embodiment, the first secondary conductor  120  is formed a single-loop structure with two changeable current paths which are determined by the state of the first switch S 1 . 
     In still the other one embodiment, the number of the switches can be N 1  and the first secondary conductor  120  is formed a single-loop structure with M 1  changeable current paths which are determined by the state of the N 1  switches, wherein N 1  is more than 3 and M 1  is more than 8. 
     Referring to  FIG. 7 ,  FIG. 7  is schematic diagrams of a variable inductor according to another one embodiment of the present disclosure. The variable inductor  200  has a primary conductor  210 , a first secondary conductor  220 , a second secondary conductor  230 , a first switch S 1 , a second switch S 2 , a third switch S 3 , a fourth switch S 4 , a fifth switch S 5  and a sixth switch S 6 . 
     In  FIG. 7 , the second secondary conductor  230  is disposed under the bottom of the primary conductor  210 . The fourth switch S 4 , the fifth switch S 5  and the sixth switch S 6  can be implemented on a substrate or printed circuit board  240 . The printed circuit board  240  can be disposed under the bottom of the primary conductor  210 . 
     The fourth switch S 4  has two sides connected to the second secondary conductor  230 , respectively. The fifth switch S 5  has two sides connected to the second secondary conductor  230 , respectively. The sixth switch S 6  has two sides connected to the second secondary conductor  230 , respectively. The fourth switch S 4 , the fifth switch S 5  and the sixth switch S 6  are formed on another three current paths, respectively. 
     The second secondary conductor  230  is formed a single-loop structure. The three current paths are formed as three different bypaths of the single-loop structure. Therefore, if the state of anyone of the fourth switch S 4 , the fifth switch S 5  and the sixth switch S 6  are changed, then the current paths of the second secondary conductor is changed. 
     The structure of the first secondary conductor  220  and the second secondary conductor  230  are roughly the same as the structure of the first secondary conductor  120 . Therefore, the detailed description of the first secondary conductor  220  and the second secondary conductor  230  is omitted. 
     The first secondary conductor  220  is formed a single-loop structure with eight changeable current paths which are determined by the state of the first switch S 1 , the second switch S 2  and third switch S 3 . The second secondary conductor  230  is also formed a single-loop structure with eight changeable current paths which are determined by the state of the fourth switch S 4 , the fifth switch S 5  and the sixth switch S 6 . The inductance of the variable inductor  200  is varied by closing and opening the first switch S 1 , the second switch S 2 , the third switch S 3 , the fourth switch S 4 , the fifth switch S 5  and the sixth switch S 6 . Therefore, in this embodiment, the variable inductor  200  has an adjustable inductance range which includes 64 different inductance values corresponding to 8*8 different current paths, respectively.  FIG. 8  is an illustratively equivalent circuit of the variable inductor of  FIG. 7 . 
       FIGS. 9A and 9B  show two different arrangements of a variable inductor according to two embodiments of the present disclosure. In  FIG. 9A , the second secondary conductor  230  is disposed on the top of the primary conductor  210 , the first secondary conductor  220  is disposed under the bottom of the primary conductor  210 , and the printed circuit board  240  is disposed under the bottom of the first secondary conductor  220 . In  FIG. 9B , the first secondary conductor  220  is disposed on the top of the primary conductor  210 , the second secondary conductor  230  is disposed under the bottom of the primary conductor  210 , and the printed circuit board  240  is disposed under the bottom of the second secondary conductor  230 . 
     In other one embodiment, the sixth switch S 6  can be eliminated. In that embodiment, the second secondary conductor  230  is formed a single-loop structure with four changeable current paths which are operated by the states of the fourth switch S 4  and the fifth switch S 5 . 
     In the other one embodiment, both the fifth switch S 5  and the sixth switch S 6  can be eliminated. In that embodiment, the second secondary conductor  230  is formed a single-loop structure with two changeable current paths which are determined by the state of the fourth switch S 4 . 
     In still the other one embodiment, the number of the switches can be N 2  and the second secondary conductor  230  is formed a single-loop structure with M 2  changeable current paths which are determined by the state of the N 2  switches, wherein N 2  is more than 3 and M 2  is more than 8. 
     The variable inductor is suitable for being integrated in an integrated circuit, for example, a radio frequency integrated circuit. A first node N 1  of the variable inductor can be disposed on one end of the primary conductor of the variable inductor and a second node N 2  of the variable inductor can be disposed on another end of the primary conductor of the variable inductor. The first node N 1  can connect to a first external component, for example, a first component of the integrated circuit. The second node N 2  can connect to a second external component, for example, a second component of the integrated circuit. 
     Referring to  FIG. 10 ,  FIG. 10  shows a simulation result of  FIG. 3 . In  FIG. 10 , three switches are implemented by 28 nm CMOS (complementary metal oxide semiconductor). The adjustable inductance range is 187 pH-277 pH. 
     In conclusion, the aforesaid variable inductor and integrated circuit, the present disclosure feature a wider adjustable inductance range, a better inductance resolution, a higher Q value, fewer durability issues or no bias concern. 
     The present disclosure is disclosed above by preferred embodiments. However, persons skilled in the art should understand that the preferred embodiments are illustrative of the present disclosure only, but should not be interpreted as restrictive of the scope of the present disclosure. Hence, all equivalent modifications and replacements made to the aforesaid embodiments should fall within the scope of the present disclosure. Accordingly, the legal protection for the present disclosure should be defined by the appended claims.