Abstract:
A full-wave rectifying device includes a first rectification module and a second rectification module. The first rectification module includes one or a plurality of first rectification units. The second rectification module includes one or a plurality of second rectification units. In each of a plurality of transistors, the substrate is connected to the source so as to reduce the body effect of the rectifying circuit efficiently and enable generation of a dc voltage signal through rectification by a plurality of capacitors. A multistage rectifying circuit architecture including a plurality of first rectification units and second rectification units is provided, so as to reduce the body effect of transistors of a conventional rectifier and significantly stabilize the voltage output level, thereby allowing the rectifying circuit to generate a dc voltage level of designed value.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a full-wave rectifying device. More specifically this invention relates to a transistor full-wave rectifying device. 
         [0003]    2. Description of Related Art 
         [0004]    Radio-Frequency Identification (RFID) System is an automatic identification method that involves affixing a small electronic tag to a product which may be checked and monitored by a device known as “reader” which in turn transmits the data stored in the electronic tag back to the system via a wireless RF means, thus achieving remote authentication, tracking, control, management and handling. 
         [0005]    The electronic tags are categorized into two general varieties, passive and active. In particular, passive RFID tags have no internal power supply. The minute electrical current induced in the antenna by the incoming radio-frequency (RF) signal provides just enough power for the CMOS integrated circuit in the tag to power up and transmit a response. 
         [0006]    Generally, the amplitude of the RF signal is approximately 200 mV or lower, and it is not easy to power up passive RFID tags with such a weak signal. Moreover, current leakage or parasitic effect often occurs in electrical circuits, thereby causing the RF signal energy to be further dissipated. 
         [0007]    Consequently, a rectifier is designed such that, upon receiving the RF signal by the antenna of passive RFID tags, the capacitors are charged repeatedly, thereby converting the RF signal to a sufficient dc voltage level for the next stage of circuit operation. 
         [0008]    Referring to  FIG. 1 , the first conventional full-wave rectifying circuit structure is shown. The full-wave rectifying circuit has eight transistors, P 1 -P 6 , N 1  and N 2 . Such a circuit structure lowers the transistor body effect, thus improving the efficiency of converting the RF signal to a dc voltage. 
         [0009]    However, such a circuit structure is only a single-stage rectifying circuit, which produces the dc voltage output that is approximately the amplitude of the RF signal only. Even under the circumstance of 100% conversion efficiency, such a circuit structure usually fails to provide a sufficient dc voltage level. 
         [0010]    Referring to  FIG. 2 , another conventional full wave rectifying circuit structure is illustrated. Diode-connected transistor instead of Schottky diode is used in the cascade of a multistage rectifying circuit, thereby deriving a sufficient dc voltage level given a specified input power. 
         [0011]    However, the chip manufacturing process of such a circuit structure does not take into account the importance of separate bulk connection which suppresses the body effect. Hence, such a circuit may be affected by the body effect, thus causing a significant difference in the threshold voltage of the transistor at each stage. Consequently, the output voltage level is lowered and the circuit fails to output a dc voltage level that matches the designed value. 
         [0012]    In summary, it has become an urgent issue to designers of the RF circuit design field to propose a multistage full-wave rectifying circuit that not only provides a sufficient dc voltage level, but also avoids or lowers the body effect such that the difference in the threshold voltage of the transistor at each stage is reduced to minimum, in order for the circuit successfully to output a dc voltage level that matches the designed value. 
       SUMMARY OF THE INVENTION 
       [0013]    In view of the above disadvantages of the conventional techniques, it is a primary objective of the present invention to provide a full-wave rectifying device that supplies a sufficient dc voltage level and avoids or lowers the body effect such that the difference in the threshold voltage of the transistor at each stage is reduced to minimum, in order for the circuit successfully to output a dc voltage level that matches the designed value. 
         [0014]    In order to achieve the above-mentioned objective, the present invention provides a full-wave rectifying device that has a first rectification unit having a first transistor and a second transistor, a second rectification unit having a third transistor and a fourth transistor, and a plurality of capacitors. In particular, the source of each transistor is connected to the substrate and the drain is connected to the gate; by connecting the source of the transistor to the substrate, the body effect in the rectifying circuit is effectively lowered. 
         [0015]    In addition, the first transistor is connected in series with the second transistor, between which a capacitor is connected. The third transistor is connected in series with the fourth transistor, between which a capacitor is connected. Furthermore, the first rectification unit is connected to the second rectification unit to form a symmetrical full-wave rectifying circuit. 
         [0016]    Finally, the symmetrical full-wave rectifying circuit is connected to a signal input unit, a ground terminal and a load, thereby allowing the signal input unit to receive the RF signal fed from the external environment. The first rectification unit and the second rectification unit in turn convert the RF signal to a rectified dc voltage level. 
         [0017]    In order to achieve the aforementioned objective, the present invention provides another full-wave rectification device, which has a first rectification module, a second rectification module and a plurality of capacitors. In particular, the first rectification module includes two first rectification units, and each of the first rectification unit further includes a first transistor and a second transistor. As well, the second rectification module has two second rectification units, and each of the second rectification units further includes a third transistor and a fourth transistor. In addition, the source of each of the transistors is connected to the substrate, and the drain is connected to the gate. Hence, the body effect in the rectifying circuit is effectively lowered by employing the method of connecting the source of the transistor to its substrate. 
         [0018]    Also, the first transistor of each of the first rectification units is cascaded with the second transistor between which a capacitor is connected. As well, the third transistor of each of the second rectification units is cascaded with the fourth transistor between which a capacitor is connected. 
         [0019]    Subsequently, the first first rectification unit is connected to the second first rectification unit to form a first rectification module; similarly, the first second rectification unit is connected to the second second rectification unit to form a second rectification module. Furthermore, the first rectification module is connected to the second rectification module to form a symmetrical two-stage full-wave rectifying circuit. 
         [0020]    Finally, the symmetrical two-stage full wave rectifying circuit is connected to a signal input unit, a ground terminal and a load, thereby allowing the signal input unit to receive the RF signal fed from the external environment. The first rectification module and the second rectification module in turn convert the RF signal to a rectified dc voltage level. 
         [0021]    In order to achieve the above-mentioned objective, the present invention also provides another full-wave rectifier, which includes a first rectification module, a second rectification module and a plurality of capacitors. In particular, the first rectification module has a plurality of first rectification units, and each of the first rectification unit further includes a first transistor and a second transistor. As well, the second rectification module has a plurality of second rectification units, and each of the second rectification units further includes a third transistor and a fourth transistor. In addition, the source of each of the transistors is connected to the substrate and the drain is connected to the gate. The body effect in the rectifying circuit is effectively lowered by employing the method of connecting the source of the transistor to its substrate. 
         [0022]    Also, the first transistor of each of the first rectification units is cascaded with the second transistor between which a capacitor is connected. As well, the third transistor of each of the second rectification units is cascaded with the fourth transistor between which a capacitor is connected. 
         [0023]    Subsequently, the (N-1) st  first rectification unit is connected to the N th  first rectification unit to form a first rectification module; similarly, the (N-1) st  second rectification unit is connected to the N th  second rectification unit to form a second rectification module. Furthermore, the first rectification module is connected to the second rectification module to form a symmetrical N-stage full-wave rectifying circuit. 
         [0024]    Finally, the symmetrical N-stage full-wave rectifying circuit is connected to a signal input unit, a ground terminal and a load, thereby allowing the signal input unit to receive the RF signal fed from the external environment. The first rectification module and the second rectification module in turn convert the RF signal to a rectified dc voltage level. 
         [0025]    In summary, the full-wave rectifying device of the present invention employs the method of connecting the source of each transistor to the substrate in order to effectively lower the body effect in the rectifying circuit. Next, a plurality of capacitors are used to generate a rectified dc voltage level. Besides the present invention also discloses a multistage rectifying circuit design that employs a plurality of first rectification units and a plurality of second rectification units, so as to increase the rectified dc voltage level to a sufficient level. 
         [0026]    As a result, the above-mentioned multistage full-wave rectifying circuit designed using transistors not only lowers the body effect of transistors in the conventional rectifier, but also significantly increases the rectified dc voltage level to a level that matches the designed value. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0027]      FIG. 1  illustrates a first conventional full-wave rectifying circuit structure; 
           [0028]      FIG. 2  illustrates a second conventional full-wave rectifying circuit structure; 
           [0029]      FIG. 3   a  is a circuit schematic according to a first embodiment of the present invention; 
           [0030]      FIG. 3   b  is a diagram showing a connection of the source of a transistor and the substrate; 
           [0031]      FIG. 4  is a circuit schematic according to a second embodiment of the present invention; 
           [0032]      FIG. 5  is a circuit schematic according to a third embodiment of the present invention; and 
           [0033]      FIG. 6  is a circuit schematic of a symmetrical N-stage full-wave rectifying device according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0034]    The following illustrative embodiments are provided to illustrate the disclosure of the present invention, these and other advantages and effects can be apparently understood by those in the art after reading the disclosure of this specification. The present invention can also be performed or applied by other different embodiments. The details of the specification may be on the basis of different points and applications, and numerous modifications and variations can be devised without departing from the spirit of the present invention. 
         [0035]    The following embodiments further illustrate the points of the present invention in detail, however the scope of the invention is not limited to any points. 
       First Embodiment  
       [0036]      FIG. 3   a  illustrates a circuit according to a first embodiment of the present invention. As shown in the diagram, a full-wave rectifying device  10  of the present invention includes a first rectification unit  11  and a second rectification unit  12 . 
         [0037]    In particular, the first rectification unit  11  further has a first transistor  111  having a first drain  1111 , a first source  1112 , a first gate  1113 , and a first substrate  1114 ; a second transistor  112  having a second drain  1121 , a second source  1122 , a second gate  1123  and a second substrate  1124 ; the first source  1112  is connected to the first substrate  1114  to form a first connection node  191 ; the second drain  1121  is connected to the second gate  1123  to form a second connection node  192 ; the first drain  1111 , the first gate  1113 , the second source  1122  and the second substrate  1124  are connected to one another to form a third connection node  193 . 
         [0038]    The second rectification unit  12  further includes a third transistor  121  having a third drain  1211 , a third source  1212 , a third gate  1213 , and a third substrate  1214 ; a fourth transistor  122  having a fourth drain  1221 , a fourth source  1222 , a fourth gate  1223  and a fourth substrate  1224 ; the third source  1212  is connected to the third substrate  1214  to form a fourth connection node  194 ; the fourth drain  1221  is connected to the fourth gate  1223  to form a fifth connection node  195 ; the third drain  1211 , the third gate  1213 , the fourth source  1222  and the fourth substrate  1224  are connected to one another to form a sixth connection node  196 . 
         [0039]    It is to be noted that the present invention adopts the transistor symbol of source-to-substrate connection in the TSMC twin-well process as shown in  FIG. 3   b.    
         [0040]    The first rectification unit  11  further includes a first capacitor  113  having a first capacitor terminal  1131  and a second capacitor terminal  1132 , and a second capacitor  114  having a third capacitor terminal  1141  and a fourth capacitor terminal  1142 ; the second rectification unit  12  further includes a third capacitor  123  having a fifth capacitor terminal  1231  and a sixth capacitor terminal  1232 , and a fourth capacitor  124  having a seventh capacitor terminal  1241  and an eighth capacitor terminal  1242 . The second capacitor terminal  1132  is connected to the third connection node  193 ; the third capacitor terminal  1141  is connected to the first connection node  191 ; the sixth capacitor terminal  1232  is connected to the sixth connection node  196 ; the seventh capacitor terminal  1241  is connected to the fifth connection node  195 . 
         [0041]    The full-wave rectifying device  10  also includes a signal input unit  13 , a load  14 , and a ground terminal  15 . In particular, the signal input unit  13  is connected to the first capacitor terminal  1131  and the fifth capacitor terminal  1231 . The load  14  is connected in series between the first connection node  191  and the fifth connection node  195 . In addition, the second connection node  192 , the fourth connection node  194 , the fourth capacitor terminal  1142  and the eighth capacitor terminal  1242  are connected to the ground terminal  15 . 
         [0042]    Such an arrangement allows the signal input unit  13  to receive the RF signal, wherein a stable rectified dc voltage level is generated by the first rectification unit  11  and the second rectification unit  12 . The rectified dc voltage is then presented between the first connection node  191  and the fifth connection node  195  as an output signal. 
       Second Embodiment  
       [0043]      FIG. 4  illustrates a circuit schematic according to a second embodiment of the present invention. The present embodiment and the first embodiment have the same basic rectifying circuit concept. The only difference is that a rectification module composed of two rectification units is employed in the present embodiment in place of a single rectification unit. 
         [0044]    As shown in the diagram, the full-wave rectifying device  20  of the present invention includes a first rectification module  21 , a second rectification module  22 , a signal input unit  23 , a load  24  and a ground terminal  25 , wherein the first rectification module  21  further includes a first first rectification unit  211  and a second first rectification unit  212 ; the second rectification module  22  has a first second rectification unit  221  and a second second rectification unit  222 . 
         [0045]    In particular, each of the first rectification units and each of the second rectification units according to the present invention have the same circuit structure as the first rectification unit  11  and the second rectification unit  12 , respectively, described in the first embodiment. Besides, in the present embodiment, the first first rectification unit  211  has a first connection node  2111  and a second connection node  2112 . The second first rectification unit  212  includes a first connection node  2121  and a second connection node  2122 . Also the first second rectification unit  221  includes a fourth connection node  2211  and a fifth connection node  2212 . The second second rectification unit  222  has a fourth connection node  2221  and a fifth connection node  2222 . 
         [0046]    In the present embodiment, the first first rectification unit  211  has a first capacitor terminal  2113  and a fourth capacitor terminal  2114 ; the second first rectification unit  212  includes a first capacitor terminal  2123  and a fourth capacitor terminal  2124 . Also, the first second rectification unit  221  has a fifth capacitor terminal  2213  and an eighth capacitor terminal  2214 ; the second second rectification unit  222  includes a fifth capacitor terminal  2223  and an eighth capacitor terminal  2224 . 
         [0047]    In terms of the circuit structure, the second connection node  2122  of the second first rectification unit  212  is connected to the first connection node  2111  of the first first rectification unit  211 . The fourth connection node  2221  of the second second rectification unit  222  is connected to the fifth connection node  2212  of the first second rectification unit  221 . Subsequently, the second connection node  2112  of the first first rectification unit  211  and the fourth connection node  2211  of the first second rectification unit  221  are grounded. 
         [0048]    Next, the first capacitor terminal  2113 , the first capacitor terminal  2123 , the fifth capacitor terminal  2213 , and the fifth capacitor terminal  2223  are connected to the signal input unit  23 ; the fourth capacitor terminal  2114 , the fourth capacitor terminal  2124 , the eighth capacitor terminal  2214  and the eighth capacitor  2224  are connected to the ground terminal  25 . 
         [0049]    Finally, the first connection node  2121  of the second first rectification unit  212  and the fifth connection node  2222  of the second second rectification unit  222  are connected to the load  24 , thereby forming a two-stage rectifying circuit structure. 
         [0050]    Such an arrangement allows the signal input unit  23  to receive the RF signal, wherein a stable, rectified dc voltage level is generated by the first rectification module  21  and the second rectification module  22 . The rectified dc voltage is increased to a sufficient level and then presented at the first connection node  2121  of the second first rectification unit  212  and the fifth connection node  2222  of the second second rectification unit  222  as an output signal. 
       Third Embodiment  
       [0051]      FIG. 5  illustrates a circuit schematic according to a third embodiment of the present invention. The present embodiment has the same basic rectifying circuit concept as that of the first and the second embodiments. The only difference is that the present embodiment discloses a full-wave rectifying device that is allowed to be expanded arbitrarily, thereby forming an N-stage rectification module composed of N rectification units. In the present embodiment, N is a whole number that is greater than 2. 
         [0052]    However, it is too complicated to list all N rectification units of the rectification module, thus the present embodiment describes the concept of the rectification module composed of N rectification units using the rectification module made up of 4 rectification units as an example. In situations where N is greater than 4, the rectification structure is expanded accordingly. 
         [0053]    As shown in  FIG. 5 , the full-wave rectifying device  30  of the present invention includes a first rectification module  31 , a second rectification module  32 , a signal input unit  33 , a load  34  and a ground terminal  35 , wherein the first rectification module  31  further includes a first first rectification unit  311 , a second first rectification unit  312 , a third first rectification unit  313 , and a fourth first rectification unit  314 ; the second rectification module  32  includes a first second rectification unit  321 , a second second rectification unit  322 , a third second rectification unit  323  and a fourth second rectification unit  324 . 
         [0054]    In particular, each of the first rectification units and each of the second rectification units according to the present invention have the same circuit structure as the first rectification unit  11  and the second rectification unit  12  described in the first embodiment. Besides, in the present embodiment, the first first rectification unit  311  has a first connection node  3111  and a second connection node  3112 . The second first rectification unit  312  includes a first connection node  3121  and a second connection node  3122 . The third first rectification unit  313  has a first connection node  3131  and a second connection node  3132 . The fourth first rectification unit  314  includes a first connection node  3141  and a second connection node  3142 . 
         [0055]    The first first rectification unit  311  has a first capacitor terminal  3113  and a fourth capacitor  3114 ; the second first rectification unit  312  includes a first capacitor terminal  3123  and a fourth capacitor terminal  3124 ; the third first rectification unit  313  has a first capacitor terminal  3133  and a fourth capacitor terminal  3134 ; the fourth first rectification unit  314  includes a first capacitor terminal  3143  and a fourth capacitor terminal  3144 . 
         [0056]    The first second rectification unit  321  has a fourth connection node  3211  and a fifth connection node  3212 ; the second second rectification unit  322  includes a fourth connection node  3221  and a fifth connection node  3222 ; the third second rectification unit  323  has a fourth connection node  3231  and a fifth connection node  3232 ; the fourth second rectification unit  324  has a fourth connection node  3241  and a fifth connection node  3242   
         [0057]    The first second rectification unit  321  has a fifth capacitor terminal  3213  and an eighth capacitor terminal  3214 ; the second second rectification unit  322  includes a fifth capacitor terminal  3223  and an eighth capacitor terminal  3224 . Also, the third second rectification unit  323  has a fifth capacitor terminal  3233  and an eighth capacitor terminal  3234 ; the fourth second rectification unit  324  includes a fifth capacitor terminal  3243  and an eighth capacitor terminal  3244 . 
         [0058]    In terms of the circuit structure, the second connection node  3122  of the second first rectification unit  312  is connected to the first connection node  3111  of the first first rectification unit  311 . The second connection node  3132  of the third first rectification unit  313  is connected to the first connection node  3121  of the second first rectification unit  312 . The second connection node  3142  of the fourth first rectification unit  314  is connected to the first connection node  3131  of the third first rectification unit  313 . 
         [0059]    The fourth connection node  3221  of the second second rectification unit  322  is connected to the fifth connection node  3212  of the first second rectification unit  321 . The fourth connection node  3231  of the third second rectification unit  323  is connected to the fifth connection node  3222  of the second second rectification unit  322 . The fourth connection node  3241  of the fourth second rectification unit  324  is connected to the fifth connection node  3232  of the third second rectification unit  323 . 
         [0060]    Finally, the second connection node  3112  of the first first rectification unit  311  and the fourth connection node  3211  of the first second rectification unit  321  are grounded to form a symmetrical four-stage full-wave rectifying circuit structure. 
         [0061]    Based on the same concept and in the event that N rectification units are employed, it is concluded that the basic concept of such circuit connection involves connecting the second node of N th  first rectification unit to the first node of the (N-1) st  first rectification unit. In addition, the fourth connection node of the N th  second rectification unit is connected to the fifth connection node of the (N-1) st  second rectification unit. Finally, the second connection node of the first first rectification unit and the fourth connection node of the first second rectification unit are grounded, thereby forming a symmetrical N-stage full-wave rectifying circuit structure. 
         [0062]    Next, the first capacitor terminal  3113 , the first capacitor terminal  3123 , the first capacitor terminal  3133 , and the first capacitor terminal  3143  as well as the fifth capacitor terminal  3213 , the fifth capacitor terminal  3223 , the fifth capacitor terminal  3233  and the fifth capacitor terminal  3243  are connected to the signal input unit  33 . Subsequently, the fourth capacitor terminal  3114 , the fourth capacitor terminal  3124 , the fourth capacitor terminal  3134 , and the fourth capacitor terminal  3144  as well as the eighth capacitor terminal  3214 , the eighth capacitor terminal  3224 , the eighth capacitor terminal  3234  and the eighth capacitor terminal  3244  are connected to the ground terminal  35 . Finally, the first connection node  3141  of the fourth first rectification unit  314  and the fifth connection node  3242  of the fourth second rectification unit  324  are connected to the load  34 . 
         [0063]    Such an arrangement allows the signal input unit  33  to receive the RF signal, wherein a stable, rectified dc voltage level is generated by the four-stage full-wave rectifying circuit composed of the first rectification module  31  and the second rectification module  32 . The rectified dc voltage is increased to a sufficient level and then presented between the first connection node  3141  of the fourth first rectification unit  314  and the fifth connection node  3242  of the fourth second rectification unit  324  as an output signal. 
         [0064]    Hence, based on the same concept and in the event that N rectification units are employed, the basic concept of such circuit connection is concluded as follows. The RF signal, after received by the signal input unit, is converted to a stable, rectified dc voltage by the N-stage full-wave rectifying circuit composed of the first rectification module and the second rectification module. The voltage is also increased to a sufficient level and then presented between the first connection node of the N th  first rectification unit and the fifth connection node of the N th  second rectification unit as an output signal. 
         [0065]    In summary, the full-wave rectifying device of the present invention employs the method of connecting the source of each transistor to the substrate in order to effectively lower the body effect in the rectifying circuit. Next, a plurality of capacitors are used to generate a rectified dc voltage. Besides, the full-wave rectifying device of the present invention also discloses a multistage rectifying circuit design that employs a plurality of first rectification units and a plurality of second rectification units, so as to increase the rectified dc voltage to a sufficient level. 
         [0066]    While the invention has been particularly shown and described with reference to preferred embodiments for purposes of illustration, it will be understood that variations and modifications can be effected thereto by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.