Patent Publication Number: US-10770981-B2

Title: Voltage conversion module and bobbin

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 15/704,007, filed Sep. 14, 2017, which is a reissue application of U.S. Pat. No. 9,559,609 B2, issued Jan. 31, 2017, which are herein incorporated by reference in their entireties. This application is a continuation-in-part of U.S. application Ser. No. 15/073,319, filed Mar. 17, 2016, which claims priority to Taiwan Application Serial Number 104133388, filed Oct. 12, 2015, which are herein incorporated by reference in their entireties. This application claims priority to Provisional Application No. 62/466,383, filed Mar. 3, 2017, which is incorporated by reference herein in its entirety. The present application is a continuation application of U.S. application Ser. No. 15/706,785, filed Sep. 18, 2017, which is herein incorporated by reference. All of these applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     Field of Invention 
     The present invention relates to power conversion systems. 
     Description of Related Art 
     Since diode and Schottky diode have designated forward bias, the power loss of the power conversion system having the diode or Schottky diode to rectify power is large. Metal-oxide-semiconductor field-effect transistor (MOSFET) has advantages of low input resistance, short response time, and high input resistance, thus it replaces the diode and Schottky diode to be the main component of the rectifier. 
     In general, the power conversion system includes a plurality of synchronous rectifiers, which are driven at the same time rectify power entering thereto. Specifically, when an electronic device electrically connected to the power conversion system is activated, the synchronous rectifiers perform synchronous rectifying procedure, and the MOSFETs of the synchronous rectifiers are switched to rectify the power entering the synchronous rectifiers; however, when the electronic device is inactivated, the synchronous rectifiers does not perform synchronous rectifying procedure. Even if the operation manner of the synchronous rectifier mentioned above is easy, the power provides by the power conversion system is a constant no matter the electronic device during non-light load condition and light load condition, thus the power loss during the electronic device under light load condition is large. 
     SUMMARY 
     An embodiment of the present disclosure is related to a voltage conversion module. The voltage conversion module comprises a front side magneto-sensitive unit, at least one voltage conversion unit, a core group, and a bobbin. The bobbin comprises a first accommodating part, a second accommodating part, and a gap. The first accommodating part is used for accommodating the front side magneto-sensitive unit. The second accommodating part is used for accommodating the at least one voltage conversion unit. The gap is used for accommodating the core group. The second accommodating part comprises a first opening and a second opening. The first opening is disposed at one side of the second accommodating part. The second opening is disposed at another side of the second accommodating part. The first opening and the second opening are disposed opposite to each other, and the first opening, the second opening and the at least one voltage conversion unit form a heat dissipation channel. 
     Another embodiment of the present disclosure is related to a voltage conversion module. The voltage conversion module comprises a front side magneto-sensitive unit, a voltage conversion unit, a core group, and a bobbin. The voltage conversion unit has a circuit board having a base portion and an expending portion connected to the base portion, a rectifier, and a filter. A penetrating hole is formed on the expending portion, and a magnetic sensitive layer is disposed on the expending portion for interacting with the front side magneto-sensitive unit. The rectifier is disposed on the base portion. The filter is disposed on the base portion, wherein the filter and the rectifier are electrically connected. The bobbin comprises an accommodating part, a spacer, and a through channel. The accommodating part comprises a first opening, and a second opening. The first opening is disposed at one side of the accommodating part. The second opening is disposed at another side of the accommodating part. A winding part is formed between the spacer and the accommodating part. The through channel penetrates the accommodating part and the spacer. Part of the core group penetrates the through channel and the penetrating hole. 
     Still another embodiment of the present disclosure is related to a bobbin. The bobbin comprises an accommodating part, a spacer, and a through channel. The first opening is disposed at one side of the accommodating part. The second opening is disposed at another side of the accommodating part. A winding part is formed between the spacer and the accommodating part. The through channel penetrates the accommodating part and the spacer. The first opening and the second opening are disposed opposite to each other, and the first opening, the second opening and an inner wall of the accommodating part form a heat dissipation channel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG. 1  is a circuit block diagram of a power conversion system according to a first embodiment of the present disclosure; 
         FIG. 2  is a circuit diagram of the power conversion system according to the first embodiment of the present disclosure; 
         FIG. 3  is a timing chart indicating the operations of power switches and rectifying switches shown in  FIG. 2 ; 
         FIGS. 4 a  and 4 b    are timing charts indicating operations of the power conversion system during light load condition; 
         FIGS. 5 a  and 5 b    are timing charts indicating operations of the power conversion system during normal load condition; 
         FIGS. 6 a  and 6 b    are timing charts indicating operations of the power conversion system during heavy load condition; 
         FIG. 7  is a cross sectional view of an isolating transformer according to the first embodiment of the present disclosure; 
         FIG. 8  is a diagram showing the state of leakage inductance, the magnetic flux, and temperature distribution in the isolating transformer shown in the  FIG. 7 ; 
         FIG. 9  is a diagram showing the state of leakage inductance, the magnetic flux, and temperature distribution in the isolating transformer shown in the  FIG. 7 ; 
         FIG. 10  is a diagram showing the state of leakage inductance, the magnetic flux, and temperature distribution in the isolating transformer shown in the  FIG. 7 ; 
         FIG. 11  is a circuit diagram of a power conversion system according to a second embodiment of the present disclosure; 
         FIG. 12  is a circuit diagram of an integrated power-converting module according to the present invention; 
         FIG. 13  is an exploded view of the integrated power-converting module according to the present invention; 
         FIG. 14  is a partially assembled view of the integrated power-converting module according to the present invention; 
         FIG. 15  is an assembled view of the integrated power-converting module according to the present invention; 
         FIG. 16  is a sectional view of the integrated power-converting module along line  16 - 16  shown in  FIG. 14 ; 
         FIG. 17  is a sectional view of the integrated power-converting module along line  17 - 17  shown in  FIG. 14 ; 
         FIG. 18  to  FIG. 29  illustrate a power conversion system according to one embodiment of the present invention; 
         FIG. 30  to  FIG. 36  illustrate a voltage conversion module according to another embodiment of the present invention; and 
         FIG. 37  to  FIG. 43  illustrate a voltage conversion module according to yet another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     As used in the description herein and throughout the claims that follow, the meaning of “a”, “an”, and “the” includes reference to the plural unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the terms “comprise or comprising”, “include or including”, “have or having”, “contain or containing” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. As used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Reference is made to  FIG. 1 , which is a circuit block diagram of a power conversion system according to a first embodiment of the present disclosure. In  FIG. 1 , the power conversion system (its reference numeral is omitted) receives an input voltage Vi and is configured to provide an output voltages Vo. The power conversion system includes a primary side and a secondary side, which are separated by an isolating transformer  30 . The isolating transformer  30  includes a primary winding  310  and a plurality of secondary windings  320   a   ˜   320   d  magnetically coupled to the primary winding  310 . The power conversion system further includes a switching module  10 , a resonant module  20 , an output-controlling device  40 , and a current sense unit  50 . The switching module  10 , the resonant module  20 , and the primary winding  310  are arranged at the primary side of the power conversion system, and the secondary windings  320   a   ˜   320   d , the output-controlling device  40 , and the current sense unit  50  are arranged at the secondary side of the power conversion system. The output-controlling device  40  includes a plurality of output-controlling modules  400   a   ˜   400   d , and the controlling modules  400   a   ˜   400   d  include a plurality of synchronous rectifying units (details are described in the following paragraphs) and a plurality of output switches (details are described in the following paragraphs). The current sense unit  50  senses a current flowing through a sensing resistor Rs electrically connected to the output-controlling unit  40  and sends a current sensed signal to the controller  420  for controlling the operation of the output-controlling unit  40 . 
     Reference is made to  FIG. 2 , which is a circuit diagram of a power conversion system according to the first embodiment of the present disclosure. The switching module  10  is electrically connected to the input voltage Vi and includes a first power switch QA, a second power switch QB, a third power switch QC, and a fourth power switch QD. The first to fourth switches QA ˜ QD are, for example, metal-oxide-semiconductor field-effect transistors (MOSFETs). The drains of the first power switch QA and the third power switch QC are connected to the input voltage Vi, the source of the first power switch QA is connected to the drain of the second power switch QB, and the source of the third power switch QC is connected to the drain of the fourth power switch QD and the primary winding  310 . The sources of the second power switch QB and the fourth power switch QD are connected to the input voltage Vi. 
     The switching module  10  may further includes a plurality of diodes D and a plurality of capacitors C electrically connected to the first to fourth power switches QA ˜ QD. Specifically, the diodes D are, for example, the body diodes of the first to fourth power switches QA ˜ QD, and the capacitors C are, for example, parasitic capacitances of the first to fourth power switches QA ˜ QD; the cathode of each diode D is connected to the drain of one of the first to fourth power switches QA ˜ QD, the anode thereof is connected to the source of one of the first to fourth power switches QA ˜ QD, and each of the capacitors C is electrically connected to one of the diodes D in parallel. 
     The resonant module  20  includes a resonant inductor Lr, a direct-current (DC) isolating capacitor Cb, and a magnetizing inductor. In  FIG. 2 , the resonant inductor Lr and the isolating transformer  30  are shown integrally; nevertheless, they are able to be separated in the practical manufacturing process. The DC isolating capacitor Cb, the resonant inductor Lr, and the primary winding  310  are electrically connected in series. specifically, one terminal of the DC isolating capacitor Cb is connected to the sources of the first power switch QA and second power switch QB, and the other terminal of the DC isolating capacitor Cb is connected to one terminal of the resonant inductor Lr, and the other terminal of the resonant indictor Lr is connected to the primary winding  310 . 
     The first to fourth power switches QA ˜ QD of the resonant module  20  are controlled using a zero-voltage-switching (ZVS) scheme to reduce switching loss. 
     The output-controlling device  40  includes a first synchronous rectifying unit  410   a , a second synchronous rectifying unit  410   b , a third synchronous rectifying unit  410   s , a fourth synchronous rectifying unit  410   d , a first output switch SW 1 , a second output switch SW 2 , a third output switch SW 3 , and a fourth power switch SW 4 . The first synchronous rectifying unit  410   a  is connected to the secondary winding  320   a  and the first output switch SW 1 , the second synchronous rectifying unit  410   b  is electrically connected to the secondary winding  320   b  and the second output switch SW 2 , the third synchronous rectifying unit  410   c  is electrically connected to the secondary winding  320   c  and the third output switch SW 3 , and the fourth synchronous rectifying unit  410   d  is electrically connected to the secondary winding  320   d  and the fourth output switch SW 4 . 
     The first synchronous rectifying unit  410   a  includes rectifying switches Q 1  and Q 2 , the second synchronous rectifying unit  410   b  includes rectifying switches Q 3  and Q 4 , the third synchronous rectifying unit  410   c  includes rectifying switches Q 5  and Q 6 , and the fourth synchronous rectifying unit  410   d  includes rectifying switches Q 7  and Q 8 . The rectifying switches Q 1  to Q 8  are, for example, MOSFETs. 
     The source of the rectifying switch Q 1  is connected to the source of the rectifying switch Q 2 , and the drains of the rectifying switches Q 1  and Q 2  are respectively connected to the secondary winding  320   a  (the drain of the rectifying switch Q 1  is connected to one terminal of the secondary winding  320   a , and the drain of the rectifying switch Q 2  is connected to the other terminal of the secondary winding  320   a ). The source of the rectifying switch Q 3  is connected to the source of the rectifying switch Q 4 , and the drains of the rectifying switches Q 3  and Q 4  are respectively connected to the secondary winding  320   b . The source of the rectifying switch Q 5  is connected to the source of the rectifying switch Q 6 , and the drains of the rectifying switches Q 5  and Q 6  are respectively connected to the secondary winding  320   c . The source of the rectifying switch Q 7  is connected to the source of the rectifying switch Q 8 , and the drains of the rectifying switches Q 7  and Q 8  are respectively connected to the secondary winding  320   d . The gates SR 1   ˜ SR 8  of the rectifying switches Q 1   ˜ Q 8  are electrically connected to the controller  420 , and the rectifying switches Q 1   ˜ Q 8  are controlled by the controller  420  using a synchronous rectifying scheme. 
     The power conversion system further includes filters L 1   ˜ L 8 , which are, for example, chokes. The filters L 1  and L 2  are arranged between the secondary winging  320   a  and the first output switch SW 1 , the filter L 3  and L 4  are arranged between the secondary winding  320   b  and the second output switch SW 2 , the filter L 5  and L 6  are arranged between the secondary winding  320   c  and the third output switch SW 3 , and the filter L 7  and L 8  are arranged between the secondary winding  320   d  and the fourth output switch SW 4 . Specifically, each secondary winding  320   a   ˜   320   d  has two terminals, one terminal of the secondary winding  320   a  is connected to the filter L 1 , and the other terminal thereof is connected to the filter L 2 ; one terminal of the secondary winding  320   b  is connected to the filter L 3 , and the other terminal thereof is connected to the filter L 4 ; one terminal of the secondary winding  320   c  is connected to the filter L 5 , and the other terminal thereof is connected to the filter L 6 ; one terminal of the secondary winding  320   d  is connected to the filter L 7 , and the other terminal thereof is connected to the filter L 8 . 
     The power conversion system still further includes a plurality of output capacitors Co. One terminal of the output capacitor is connected to synchronous rectifying unit  410   a   ˜   410   d , and the other terminal thereof is connected to one of the first to fourth output switch SW 1   ˜ SW 4 . 
     It should be noted that the power conversion system is configured to provide different powers to meet the power required for the electronic device. Therefore, the controller  420  may measure the power required for the electronic device by the current sensed signal representing the current flowing through the sensing resistor Rs sent from the current sense unit  50  and place at least one of the synchronous rectifying units  410   a   ˜   410   d  or at least one of the first to fourth output switch SW 1   ˜ SW 4  in a conducting state to conduct the power required for the electronic device to the electronic device. It should be noted that when the synchronous rectifying  410   a   ˜   410   d  are in the conducting state, the powers coupled to the secondary winding  320   a   ˜   320   d  are conducted to the synchronous rectifying units  410   a   ˜   410   d , and a synchronous rectifying procedure is performed. On the contrary, when the synchronous rectifying units  410   a   ˜   410   d  are not in the conducting state (or called the synchronous rectifying units  410   a   ˜   410   d  are in a non-conducting state), the power transmitted to the primary winding  310  cannot conducted to the secondary windings  320   a   ˜   320   d , and the synchronous rectifying procedure is not performed. Besides, when the first to fourth output switches SW 1   ˜ SW 4  are in the conducting state, the first to fourth output switches SW 1   ˜ SW 4  turn on (close), the powers with synchronous rectification are conducted to the output capacitors Co and the output Vo. One the contrary, when the first to fourth output switches SW 1   ˜ SW 4  are in the non-conducting state, the first to fourth output switches SW 1   ˜ SW 4  turn off (open), the powers with synchronous rectification cannot be conducted to the output capacitors Co and the output Vo. 
     The isolating transformer  30  and the resonant inductor Lr (if exist) provide a leakage inductance. In order to achieve higher efficiencies and lower electromagnetic interferences (EMI), a zero voltage switching (ZVS) mode is operated. With ZVS mode, during operation, the first to fourth power switches QA ˜ QD in a switching stage of the power conversion system are activated at zero crossings of their main terminal voltage to minimize turn on losses. An amount of time is required by the first to fourth power switches QA ˜ QD to turn off (open) and on (close). The overlap between these transitions can be referred to as dead-time (as time points between t 2  and t 3  and the time points between t 4  and t 5  shown in the  FIG. 4 a   ). A minimum amount of dead-time is needed to avoid having the first power switch QA and second power switch QB (or the third power switch QC and the fourth power switch QD) closed (turned on) at the same time. If the first power switch QA and the second power switch QB (or the third power switch QC and the fourth power switch QD) are closed at the same time, potentially destructive shoot-through current that travels directly from input voltage Vi to electronic device may result. The period of the dead-time is rises gradually as leakage inductance is increased. The gates of the first to fourth power switches QA ˜ QD are electrically connected to a controlling circuit (not shown), and the first to fourth power switches QA ˜ QD are turned off and on according to signals sent from the controlling circuit. 
     Reference is made to  FIG. 2  and  FIG. 4 a   , wherein  FIG. 4 a    is a timing chart indicating operations of the power conversion system during light load condition. In order to clarify detailed operation of the power conversion system of the present disclosure, the following example is given. It should be noted that the values given in the example are only for clarity. The values can be changed to meet system requirements. During the heavy load condition, the power (including voltage and current) provided by the power conversion system is the largest. As the load lightens, the power is reduced. During the light load condition, the power provided by the power conversion system reduces to, for example, 20%; during the normal load condition, the power provided by the power conversion system reduces to, for example, 50%. 
     Seven time points t 1 -t 7  are shown in the  FIG. 4 a   . With the second power switch QB and the third power switch QC are closed (placed in conducting states) (wherein the first power switch QA and the fourth power switch QD are opened) to provide a conduction path between time points t 1  and t 2 , a primary current Ip from the input voltage Vi flows through the third power switch QC, the primary winding  310 , the resonant module  20 , the second power switch QB to the ground. During this time, energy is stored in the resonant inductor Lr, and the primary current (Ip) is raised. 
     The second power switch QB is then opened at time point t 2  (the third power switch QC is continuously closed), and then a short time duration later, the first power switch QA is closed (at time point t 3 ). During this short duration, the current supported by the energy stored in the isolating transformer&#39;s leakage inductance, and optionally in resonant inductor Lr, now flows out of the capacitances C associated with the first power switch QA and the second power switch QB and into the third power switch QC (which is still closed). Specifically, when the second power switch QB is opened, the primary current Ip freewheels through the diode D associate with the first power switch QA, and the capacitor C associated with the second power switch QB is charged, and the capacitor C associated with the first power switch QA is discharged until the potential of the capacitor C associates with the second power switch QB is equal to that of the input voltage Vi. 
     When a voltage across drain-source of the first power switch QA is lower than a voltage across the forward bias of the diode D associated with the first power switch QA, the diode D associate with the first power switch QA turns on (placed in conducting states). As such, the first power switch QA is closed under zero-voltage condition (i.e., zero voltage switching). Due to that the voltage across drain-source of the first power switch QA is lower than the voltage across the diode D associate with the first power switch QA, the conduction loss is low. At this time, the primary voltage Vp of the power conversion system is zero. 
     Between time points t 4  and t 5 , the third power switch QC is closed and the current freewheels through the diode D associated with the fourth power switch QD. During this short duration, the current supported by the energy stored in the isolating transformer&#39;s leakage inductance, and optionally in resonant inductor Lr, now flows out of the capacitances C associated with the third power switch QC and the fourth power switch QD and into the first power switch QA (which is still closed). Specifically, when the third power switch QC is opened, the primary current Ip freewheels through the diode D associate with the fourth power switch QD, and the capacitor C associated with the third power switch QC is charged, and the capacitor C associated with the fourth power switch QD is discharged until the potential of the capacitor C associates with the third power switch QC is equal to that of the input voltage Vi and a voltage across drain-source of the second power switch QD is dropped to zero (as curve VQ 4  shown). 
     When a voltage across drain-source of the fourth power switch QD is lower than a voltage across the forward bias of the diode D associated with the fourth power switch QD, the diode D associate with the fourth power switch QD turns on (placed in conducting states). As such, the fourth power switch QD is closed under zero-voltage condition. 
     Due to the voltage across the resonant inductor Lr is equal to the input voltage Vi, the primary current Ip is linearly decreased between time points t 5  and t 6 . In  FIG. 4 a   , a duty cycle loss appears between time points t 5  and t 6  since a primary voltage Vp does not drop to negative value at time point t 5 , which the fourth power switch QD is closed (wherein the fourth power switch QD is closed at time point t 6 ). The more the leakage inductance is, the more duty cycle loss is, and the duty cycle loss is given by
 
Lr*(Ip/Vp)
 
     wherein 
     Lr is the inductance of the resonant inductor; 
     Ip is the primary current of the power conversion system; and 
     Vp is the primary voltage of the power conversion system. 
       FIG. 5 a    is a timing chart indicating operations of the power conversion system during normal load condition.  FIG. 6 a    is a timing chart indicating operations of the power conversion system during heavy load condition. The function and relative description of the power conversion system during normal load condition and during heavy load condition are the same as that of during light load condition mentioned above and are not repeated here for brevity. It should be noted that the current provided by the power conversion system is increased while the power (current) required for the electronic device is increased, and the duty cycle loss of the power conversion system is increased while the current provided by the power conversion system is increased. As such, a hold-up time depends upon the duty cycle loss is then decreased, that result in lower efficiency. Specifically, if the input voltage Vi falls below the minimum permissible voltage and adversely affects the power conversion system operation, the electronic devices that rely on the power conversion system for power could experience critical failures such as the loss of data. The length of time that the power conversion system can continue to operate in the absence of line voltage is referred to as the hold-up time. 
     If power conversion system is to provide a better efficiency, then a lower duty cycle loss will be needed. As a result, a distinctive operation of the output-controlling device  40  is required to meet the duty cycle loss required to keep the efficiency of the power conversion system within acceptable limits. 
     In general, the power provided by the power conversion system depends upon the power required for the electronic device. More particularly, the power required for the electronic device during heavy load condition is higher than that of during the light load condition. Therefore, the power (such as current) provided by the power conversion system while the electronic device operated under heavy load condition will be higher than that of operated under light load condition. 
     The output-controlling device  40  of the present disclosure is controlled to make the current provided by the power conversion system to meet the power required for the electronic device. 
     The power conversion system may provide the power to meet the required for the electronic device depends upon the operation of the first to fourth synchronous rectifying units  410   a   ˜   410   d  of the output-controlling module  400   a   ˜   400   d . Reference is made back to  FIG. 2  and  FIG. 3 . In first operation state, when a first current I 1  is required for the electronic device, the controller  420  sends signals to gates SR 1   ˜ SR 8  of the rectifying switches Q 1   ˜ Q 8  according to the current sensed signal sent from the current sense unit  50  for indicating that the first current I 1  is required by the electronic device, and places one of the first to fourth rectifying unit  410   a   ˜   410   d  in the conducting state for performing synchronous rectifying procedure, thus the first current I 1  is provided by the power conversion system. Specifically, the controller  420  may send pulsating signals to drive the rectifying switches Q 1  and Q 2  to interleaved turn off and on (as time points between 0 ˜ t 1  shown in  FIG. 3 ), thus a power coupled to the secondary winding  320   a  is synchronous rectified by the first synchronous rectifying unit  410   a  and the rectified power is then conducted to the output terminal (connected to the electronic device) by passing through the filters L 1  and L 2 , the first output switch SW 1 , and the output capacitor Co connected to the first output switch SW 1 . 
     In second operation state, when a second current I 2  is required for the electronic device, the controller  420  receives the current signal sent from the current sense unit for indicating that the second current I 2  is required by the electronic device, and sends signals to the gates SR 1   ˜ SR 8  for placing two of the first to fourth synchronous rectifying units  410   a   ˜   410   d  in the conducting state for performing synchronous rectifying procedure, thus the second current I 2  is then provided by the power conversion system, the second current I 2  is larger than the first current I 1 . Specifically, the controller  420  may send pulsating signals to drive the rectifying switches Q 1   ˜ Q 4  to interleaved turn off and on (as time points between t 1  and t 2  shown in  FIG. 3 ), thus powers coupled to the secondary winding  320   a  and  320   b  are synchronous rectified by the first and second synchronous rectifying units  410   a  and the  410   b , respectively, and the rectified powers are then conducted to the output terminal (connected to the electronic device) by passing through the filters L 1   ˜ L 4 , the first power switch SW 1 , second output switch SW 2 , and the output capacitors Co connected to the first power switch SW 1  and the second output switch SW 2 . 
     In third operation state, when a third current I 3  is required for the electronic device, the controller  420  receives the current sensed signal sent from the current sense unit  50  for indicting that the third current is required for the electronic device, and sends signals the gates SR 1   ˜ SR 8  for placing three of the first to fourth synchronous rectifying unit  410   a   ˜   410   d  in the conducting state for performing synchronous rectifying procedure, thus the third current I 3  is then provided by the power conversion system, the third current I 3  is larger than the second current I 2 . Specifically, the controller  420  may send pulsating signals to drive the rectifying switches Q 1   ˜ Q 6  to interleaved turn off and on (as time points between t 2  and t 3  shown in  FIG. 3 ), thus powers coupled to the secondary windings  320   a   ˜   320   c  are synchronous rectified by the first to third synchronous rectifying units  410   a   ˜   410   c , respectively, and the rectified powers are then conducted to the output terminal (connected to the electronic device) by passing through the filters L 1   ˜ L 6 , the first to third output switch SW 1   ˜ SW 3 , and the output capacitors Co connected to the first to third output switch SW 1   ˜ SW 3 . 
     In fourth operation state, when a fourth current I 4  is required for the electronic device, the controller  420  receives the current sensed signal sent from the current sense unit for indicating that the third current is required for the electronic device, and sends signals to the gates SR 1   ˜ SR 8  for placing all of the first to fourth synchronous rectifying unit  410   a   ˜   410   d  in the conducting state for perform synchronous rectifying procedure, thus a fourth current I 4  is then provided by the power conversion system, the fourth current I 4  is larger than the third current I 3 . Specifically, the controller  420  may sent pulsating signals to drive the rectifying switches Q 1   ˜ Q 8  to interleaved turn on and off continuously (after time point t 3  shown in  FIG. 3 ), thus powers coupled to the secondary winding  320   a   ˜   320   d  are synchronous rectified by the first to fourth synchronous rectifying units, respectively, and the rectified power are then conducted to the output terminal (connected to the electronic device) by passing through the filters L 1   ˜ L 8 , the first to fourth output switch SW 1   ˜ SW 4  and the output capacitors Co. 
     As such, an effect of energy conservation is provided and the power loss while the electronic device operated under light load condition is reduced since the first to the fourth rectifying unit  410   a   ˜   410   d  are separately placed in the conducting state and driven to synchronous rectify the powers coupled to the secondary windings  320   a   ˜   320   d.    
     The controller  420  may selectively place the first to fourth switches SW 1   ˜ SW 4  in the conducting state for conducting power required for the electronic device to the output terminal. It should be noted when the controller  420  places at least one of the first to fourth synchronous rectifying units  410   a   ˜   410   d  in the conducting state for conducting power require for the electronic device to the output terminal, the first to fourth switches SW 1   ˜ SW 4  are always closed to make the rectified power(s) flowing therethrough; when the controller  420  places at least one of the first to fourth switch SW 1   ˜ SW 4  in the conducting state for conducting power required for the electronic device to the output terminal, the controller  420  sends the pulsating signals to the rectifying switches Q 1   ˜ Q 8  to makes the first to fourth synchronous rectifying units  410   a   ˜   410   d  perform synchronous rectifying procedure all the time. 
     Reference is made back to  FIG. 2  and  FIG. 3 . The controller  420  may place the first switch SW 1  in the conducting state for conduct a power coupled to the secondary winding  320   a  and rectified by the first synchronous rectifying unit  410   a  to the output terminal (connected to the electronic device) in first operation state, therefore the first current I 1  is provided to the electronic device (as the time points between 0 and t 1  shown in the  FIG. 3 ). 
     In second operation state, the controller  420  may place the first switch SW 1  and the second switch SW 2  in the conducting state for conducting powers coupled to the secondary windings  320   a  and  320   b  and rectified by the first synchronous rectifying unit  410   a  and the second synchronous rectifying unit  410   b  to the output terminal (connected to the electronic device), therefore the second current I 2  is provided to the electronic device (as the time points between t 1  and t 2  shown in the  FIG. 3 ), wherein the second current I 2  is larger than the first current I 1 . 
     In third operation state, the controller  420  may place the first to third switches SW 1   ˜ SW 3  in the conducting state for conducting powers coupled to the secondary windings  320   a   ˜   320   c  and rectified by the first to third synchronous rectifying units  410   a   ˜   410   c  to the output terminal (connected to the electronic device), therefore the third current I 3  is provided to the electronic device (as the time points between t 2  and t 3  shown in the  FIG. 3 ), wherein the third current I 3  is larger than the second current I 2 . 
     The controller  420  places the first to fourth switches SW 1   ˜ SW 4  in the conducting state for conducting powers coupled to the secondary windings  320   a   ˜   320   d  and rectified by the first to fourth synchronous rectifying units  410   a   ˜   410   d  to the output terminal (connected to the electronic device), therefore the fourth current I 4  is provided to the electronic device (as the time point t 3  shown in the  FIG. 3 ), wherein the fourth current I 4  is larger than the third current I 3 . 
     The arrangement of the primary winding  310  and the second windings  320   a   ˜   320   d  of the present disclosure is further controlled to lower the power loss of the power conversion system. 
     Reference is made to  FIG. 7 , which is a cross-sectional view of the isolating transformer according to the first embodiment of the present disclosure. The isolating transformer  30  further includes a bobbin  330  and a magnetic core  340 , and the magnetic core  340  is assembled with the bobbin  330 . The primary winding  310  and the secondary winding  320   a   ˜   320   d  are placed on the bobbin  330 . In  FIG. 7 , the isolating transformer  30  includes one primary winding  310  and four secondary windings  320   a   ˜   320   d , the secondary windings  320   a   ˜   320   d  are arranged at the bobbin  330  with equidistance intervals (such as inserted into slots preset on the bobbin  330  with equidistance intervals), the primary winding  310  is wound on the bobbin  330  (where the secondary windings  320   a   ˜   320   d  does not placed and across each of the secondary windings  320   a   ˜   320   d ). As a result, the primary winding  310  and the secondary windings  320   a   ˜   320   d  are arranged in a staggered manner in a side view direction, i.e., the primary winding  310  is placed at same side of each secondary winding  320   a   ˜   320   d  (wherein in  FIG. 7 , the primary winding  310  is wound on the bobbin  310  and placed at the left side of the secondary winding  320   a   ˜   320   d ). 
     Reference is made back to  FIG. 2  and  FIG. 7 , the power conversion system may provide power required for the electronic device by controlling the operation states of the output-controlling modules  400   a   ˜   400   d.    
     In one of the operation states, the controller  420  may send pulsating signals to drive the rectifying switches Q 1   ˜ Q 8  to perform synchronous rectifying procedure. As a result, the power coupled to the second windings  320   a   ˜   32   d  is synchronously rectified by the first to fourth synchronous rectifying units  410   a   ˜   410   d , and the rectified powers are then conducted to the output terminal (connected to the electronic device) by passing through the conducted first to fourth switches SW 1   ˜ SW 4 . Selectively, the controller  420  may drive the first to fourth switches SW 1   ˜ SW 4  to close and then conduct the power coupled to the second windings  320   a   ˜   320   d  and rectified by the first to fourth synchronous rectifying units  410   a   ˜   410   d  to the output terminal (connected to the electronic device). As a result, a leakage inductance based on the magnetic coupling between the primary winding  310 , the secondary windings  320   a   ˜   320   d , and optionally in resonant inductor Lr is generated. 
     Reference is made to  FIG. 8 , the lowest leakage inductance appears at the points that each of the second windings  320   a   ˜   320   d  is close to the primary winding  310 , and the leakage inductance is increased when the coupling distance between each of the secondary windings  320   a   ˜   320   d  and the primary winding  310  is increased. The leakage inductance varies in a fixed range since the primary winding  310  and the secondary windings  320   a   ˜   320   d  are arranged in the staggered manner. 
     In another operation state, the controller  420  may send pulsating signals to the rectifying switches Q 1   ˜ Q 2  to drive the first synchronous rectifying unit  410   a  perform synchronous rectifying procedure (wherein the rectifying switches Q 3   ˜ Q 8  are always opened). As a result, only the power coupled to the second windings  320   a  is synchronously rectified by the first synchronous rectifying units  410   a , and the rectified power is then conducted to the output terminal (connected to the electronic device) by passing through the conducted first to fourth switches SW 1   ˜ SW 4 . Selectively, the controller  420  may drive the first switch SW 1  to close and conduct the power coupled to the second windings  320   a  and rectified by the first synchronous rectifying units  410   a  to the output terminal (connected to the electronic device). Another leakage inductance based on the magnetic coupling between the primary winding  310 , the secondary windings  320   a , and optionally in resonant inductor Lr is generated. 
     Reference is made to  FIG. 9 , the lowest leakage inductance appears at the point between the second winding  320   a  and the primary winding  310 , and the leakage inductance is increased when the coupling distance between the secondary winding  320   a  and the primary winding  310  is increased. 
     In the other state, the controller  420  may send pulsating signals to the rectifying switches Q 3   ˜ Q 6  to drive the second synchronous rectifying unit  410   b  and the third synchronous rectifying unit  410   c  to perform synchronous rectifying procedure (wherein the rectifying switches Q 1 , Q 2 , Q 7 , and Q 8  are always opened). As a result, only the powers coupled to the second windings  320   b  and  320   c  are synchronously rectified by the second synchronous rectifying units  410   b  and the third synchronous rectifying units  410   c , and the rectified powers are then conducted to the output terminal (connected to the electronic device) by passing through the conducted first to fourth switches SW 1   ˜ SW 4 . Selectively, the controller  420  may drive the second switch SW 2  and the third switch SW 3  to close and conduct the powers coupled to the second windings  320   b  and  320   c  and rectified by the second synchronous rectifying unit  410   b  and the third synchronous rectifying units  410   c  to the output terminal (electrically connected to the electronic device). Still another leakage inductance based on the magnetic coupling between the primary winding  310 , the secondary windings  320   b  and  320   c , and optionally in resonant inductor Lr is generated. 
     Reference is made to  FIG. 10 , the lowest leakage inductance appears at the point between the second windings  320   b ,  320   c  and the primary winding  310 , and the leakage inductance is increased when the coupling distance between the secondary winding  320   b ,  320   c  and the primary winding  310  is increased. 
     In sum, the amount of the first to fourth synchronous rectifying units  410   a   ˜   410   d  performing synchronous rectifying procedure and the coupling distance between the secondary winding  320   a   ˜   320   d  performing synchronous rectifying and the primary windings  310  affects the leakage inductance of the power converting system. As such, by effectively controlling the amount of the first to fourth synchronous rectifying units  410   a   ˜   410   d  performing synchronous rectifying procedure and the coupling distance mentioned above, the power conversion system can accurately provide power required for the electronic device to the electronic device. 
     It should be noted that the power conversion system provides power to the electronic device only when the synchronous rectifying unit ( 410   a   ˜   410   d ) connected to the particular secondary winding ( 320   a   ˜   320   d ) performs synchronous rectifying procedure and the output switch (SW 1   ˜ SW 4 ) connected to the synchronous rectifying ( 410   a   ˜   410   d ) is close. For example, reference is made to  FIG. 2 , when the first synchronous rectifying unit  410   a  performs synchronous rectifying procedure and the first switch SW 1  is close, the power conducted to the primary winding  310  is coupled to the secondary winding  320   a  connected to the first synchronous rectifying unit  410   a , and then the rectified power is conducted to the electronic device by passing through the filters L 1  and L 2 . In the meanwhile, a leakage inductance based on the magnetic coupling between the primary winding  310  and the secondary windings  320   a   ˜   320   d  is generated. 
     The detail data of the leakage inductance in different operation states are shown in Table 1. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 1st 
                 2nd 
                 3rd 
                 4th 
                 Leakage 
               
               
                   
                 synchronous 
                 synchronous 
                 synchronous 
                 synchronous 
                 induc- 
               
               
                   
                 rectifying 
                 rectifying 
                 rectifying 
                 rectifying 
                 tance 
               
               
                   
                 unit 
                 unit 
                 unit 
                 unit 
                 (μH) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 1st 
                 non- 
                 non- 
                 non- 
                 conducting 
                 25.19 
               
               
                 state 
                 conducting 
                 conducting 
                 conducting 
                 state 
               
               
                   
                 state 
                 state 
                 state 
               
               
                 2nd 
                 conducting 
                 non- 
                 non- 
                 non- 
                 24.4 
               
               
                 state 
                 state 
                 conducting 
                 conducting 
                 conducting 
               
               
                   
                   
                 state 
                 state 
                 state 
               
               
                 3rd 
                 conducting 
                 non- 
                 non- 
                 conducting 
                 14.59 
               
               
                 state 
                 state 
                 conducting 
                 conducting 
                 state 
               
               
                   
                   
                 state 
                 state 
               
               
                 4th 
                 non- 
                 non- 
                 conducting 
                 non- 
                 12.3 
               
               
                 state 
                 conducting 
                 conducting 
                 state 
                 conducting 
               
               
                   
                 state 
                 state 
                   
                 state 
               
               
                 5th 
                 non- 
                 conducting 
                 non- 
                 non- 
                 12.2 
               
               
                 state 
                 conducting 
                 state 
                 conducting 
                 conducting 
               
               
                   
                 state 
                   
                 state 
                 state 
               
               
                 6th 
                 non- 
                 non- 
                 conducting 
                 conducting 
                 11.93 
               
               
                 state 
                 conducting 
                 conducting 
                 state 
                 state 
               
               
                   
                 state 
                 state 
               
               
                 7th 
                 conducting 
                 conducting 
                 non- 
                 non- 
                 10.13 
               
               
                 state 
                 state 
                 state 
                 conducting 
                 conducting 
               
               
                   
                   
                   
                 state 
                 state 
               
               
                 8th 
                 conducting 
                 non- 
                 conducting 
                 conducting 
                 9.95 
               
               
                 state 
                 state 
                 conducting 
                 state 
                 state 
               
               
                   
                   
                 state 
               
               
                 9th 
                 conducting 
                 non- 
                 conducting 
                 non- 
                 9.9 
               
               
                 state 
                 state 
                 conducting 
                 state 
                 conducting 
               
               
                   
                   
                 state 
                   
                 state 
               
               
                 10th 
                 non- 
                 conducting 
                 non- 
                 conducting 
                 9.89 
               
               
                 state 
                 conducting 
                 state 
                 conducting 
                 state 
               
               
                   
                 state 
                   
                 state 
               
               
                 11th 
                 conducting 
                 conducting 
                 non- 
                 conducting 
                 8.29 
               
               
                 state 
                 state 
                 state 
                 conducting 
                 state 
               
               
                   
                   
                   
                 state 
               
               
                 12th 
                 conducting 
                 conducting 
                 conducting 
                 non- 
                 8.2 
               
               
                 state 
                 state 
                 state 
                 state 
                 conducting 
               
               
                   
                   
                   
                   
                 state 
               
               
                 13th 
                 non- 
                 conducting 
                 conducting 
                 conducting 
                 8.12 
               
               
                 state 
                 conducting 
                 state 
                 state 
                 state 
               
               
                   
                 state 
               
               
                 14th 
                 conducting 
                 conducting 
                 conducting 
                 conducting 
                 8.02 
               
               
                 state 
                 state 
                 state 
                 state 
                 state 
               
               
                 15th 
                 non- 
                 conducting 
                 conducting 
                 non- 
                 8 
               
               
                 state 
                 conducting 
                 state 
                 state 
                 conducting 
               
               
                   
                 state 
                   
                   
                 state 
               
               
                   
               
            
           
         
       
     
     In Table 1, “conducting state” means that the synchronous rectifying unit ( 410   a   ˜   410   d ) is places in the conducting state and performs synchronous rectifying procedure, thus the power conducted to the primary winding  310  may be coupled to particular secondary winding ( 320   a   ˜   320   d ) connected to the synchronous rectifying unit ( 410   a   ˜   410   d ) placed in the conducting state, and a rectified power is then conducted to the electronic device; nevertheless, “non-conducting state” means that the synchronous rectifying unit  410   a   ˜   410   d  is places in the non-conducting state and does not perform synchronous rectifying procedure, and the power conducted to the primary winding  310  does not coupled to the secondary winding  320   a   ˜   320   d  connected to the synchronous rectifying unit  410   a   ˜   410   d  placed in the non-conducting state. 
     Reference is made to  FIG. 4 b   , which is another timing chart indicating operations of the power conversion system during light load condition. It should be noted that the timing chart shown in the  FIG. 4 b    indicates the power conversion system which the amount of the first to fourth synchronous rectifying units  410   a   ˜   410   d  performing synchronous rectifying procedure and the coupling distance between the secondary winding  320   a   ˜   320   d  connected to the first to fourth synchronous rectifying units  410   a   ˜   410   d  performing synchronous rectifying procedure and the primary windings  310  are controlled as mentioned above. In  FIG. 4 b   , a duty cycle loss appears between time points t 5  and t 6 ′ since a primary voltage Vp does not drop to negative value at time point t 5 , which the fourth power switch QD is closed. Comparing to the  FIG. 4 a    (the duty cycle loss appears between time points t 5  and t 6 ), the duty cycle loss shown in the  FIG. 4 b    is reduced (the period between time points t 6 ′ and t 6  shown in the  FIG. 4 b    indicates the duty cycle loss which is eliminated from  FIG. 4 a   ). 
       FIG. 5 b    is another timing chart indicating operations of the power conversion system during normal load condition.  FIG. 6 b    is another timing chart indicating operations of the power conversion system during heavy load condition. In  FIGS. 5 b  and 6 b   , the period between time points t 5  and t 6  indicates duty time loss of the power conversion system which the amount of the synchronous rectifying units performing synchronous rectifying procedure and the coupling distance between the secondary winding  320   a   ˜   320   d  and the primary windings  310  are not controlled (for example, the first to fourth synchronous rectifying units  410   a   ˜   410   d  perform synchronous rectifying procedure as the same time). On the contrary, the period between time points t 5  and t 6 ′ indicates duty time loss of the power conversion system which the amount of the synchronous rectifying units performing synchronous rectifying procedure and the coupling distance between the secondary winding  320   a   ˜   320   d  and the primary windings  310  are well controlled (wherein the period between time points t 6 ′ and t 6  shown in the  FIG. 5 b    and  FIG. 6 b    indicates the duty cycle loss which is eliminated from  FIGS. 5 a  and 6 a   ). 
     In order to prevent generated heat that arises at the time of driving from being stored, the first to fourth synchronous rectifying units  410   a   ˜   410   d  may perform synchronous rectifying procedure in sequence. For example, the controller  420  may progressively increase the amount of the synchronous rectifying units ( 410   a   ˜   410   d ) performing synchronous rectifying procedure when the power required for the electronic device is gradually increased. In addition, the controller  420  may drives the synchronous rectifying units ( 410   a   ˜   410   d ) in a convergence manner when only one of the synchronous rectifying units ( 410   a   ˜   410   d ) performs synchronous rectifying procedure. More particularly, the convergence manner may first make the synchronous rectifying unit ( 410   a   ˜   410   d ) far from a central axis of the isolating transformer  30  shown in the  FIG. 7  perform synchronous rectifying procedure, and next makes the synchronous rectifying units close to the central axis of the transformer shown in the  FIG. 7  to prevent generated heat that arises at the time of driving from being stored, i.e., the controller  420  may makes the first synchronous rectifying units  410   a , the fourth synchronous rectifying units  410   d , the second synchronous rectifying units  410   b , and the third synchronous rectifying units  410   c  shown in the  FIG. 7  perform synchronous rectifying procedure in sequence. It should be noted that if the distances between two synchronous rectifying units and the central axis are the same, the two synchronous rectifying units interleaved perform synchronous rectifying procedure. 
     Reference is made back to Table 1, in 1st and 2nd states, they are only one of the synchronous rectifying units is placed in the conducting state and performs synchronous rectifying procedure. As can be shown in  FIG. 7 , the distance between the synchronous rectifying unit performing synchronous rectifying procedure in 1st state and the central axis of the isolating transformer  30  is equal to that of in 2nd state, and the leakage inductance in 1st state is close to that of in 2nd state. Therefore, the controller  420  may interleaved drive the first synchronous rectifying unit  410   a  and the fourth synchronous rectifying unit  410   d  to conduct the power coupled to the secondary winding  320   a  and  320   d  to the electronic device while the electronic device is operated under the same condition (such as light load condition) to prevent generated heat that arises at the time of driving from being stored in particular synchronous rectifying unit ( 410   a   ˜   410   d ), which is placed in the conducting state and performs synchronous rectifying procedure all the time. 
     It should be noted that the synchronous rectifying units ( 410   a   ˜   410   d ) may be interleaved placed in the conducting state (i.e. the first to fourth synchronous rectifying units  410   a   ˜   410   d  may be driven to interleaved perform synchronous rectifying procedure) according to the distance between the central axis and the synchronous rectifying units ( 410   a   ˜   410   d ), for example, the synchronous rectifying units ( 410   a   ˜   410   d ) with same distance from the central axis may be interleaved driven to perform synchronous rectifying procedure. However, that the synchronous rectifying units ( 410   a   ˜   410   d ) may be driven to interleaved perform synchronous rectifying procedure according to inductance in different operation states of the synchronous rectifying units ( 410   a   ˜   410   d ). For example, the operation states with similar leakage inductance (such as the difference in leakage inductance between the operation states is less than 5 μH) may be interleaved driven to perform synchronous rectifying procedure. 
     In sum, the power conversion system of the present disclosure performs a power conversion procedure for powering the electronic device includes step as following first, the power conversion system including a primary winding  310 , a plurality of secondary windings  320   a   ˜   320   d , and a plurality of synchronous rectifying units  410   a   ˜   410   d  is provided. There are a plurality of coupling distances between the primary winding  310  and the secondary windings  320   a   ˜   320   d.    
     Next, the operation condition (such as light load condition, normal load condition, or heavy load condition) of the electronic device is measured by measuring a current required by the electronic device. Specifically, the current required for the electronic device during light load condition may be smaller than that of during normal load condition, and the current required for the electronic device during heavy load condition may be larger than that of during normal load condition. Thereafter, the synchronous rectifying units ( 410   a   ˜   410   d ) are selectively placed in a conducting state for varying a leakage inductance of the power conversion system, thus a output current of the power conversion system is modulated to meet the current requirement of the electronic device. The output current is only provided by the synchronous rectifying units  410   a   ˜   410   d  which is placed in the conducting state, and the power conversion system has a lowest leakage inductance when all of the output-controlling modules  400   a   ˜   400   d  are placed in the conducting state, therefore a largest output current is provided. 
     The power conversion system may vary the leakage inductance by selectively place one of the synchronous rectifying units  410   a   ˜   410   d  in the conducting state at a time; however, the power conversion system may further selectively place two or more synchronous rectifying units  410   a   ˜   410   d  at a time. Besides, the leakage inductance of the power conversion system is varied when an amount of the synchronous rectifying units  410   a   ˜   410   d  placed in the conducting state changes. 
     Reference is made to  FIG. 11 , which is a circuit diagram of a power conversion system according to a second embodiment of the present disclosure. In  FIG. 11 , the power conversion system includes a switching module  10 , a resonant module  20 , a transformer  30 , and an output-controlling device  40 . The transformer  30  includes a primary winding  310  and a plurality of secondary windings  320   a   ˜   320   d  coupled with the primary winding  310 . 
     The function and relative description of switching module  10  and the resonant module  20  of the power conversion system shown in the  FIG. 11  are the same as that of first embodiment (shown in the  FIG. 2 ) mentioned above and are not repeated here for brevity, and the switching module  10  and the resonant module  20  of the power conversion system shown in the  FIG. 11  can achieve the functions as power conversion system of the first embodiment does. It should be noted that the transformer  30  and the output-controlling device  40  shown in the  FIG. 11  is different from that of the first embodiment. 
     In  FIG. 11 , the transformer  30  is a center-tapped transformer, which has an advantage of compact. However, the isolating transformer shown in  FIG. 2  has an advantage of double-current. The output-controlling device  40  is electrically connected to the secondary winding  320   a   ˜   320   d  of the transformer and includes first to fourth synchronous rectifying units  410   a   ˜   410   d , controller  420 , and first to fourth output switch SW 1   ˜ SW 4 . The first synchronous rectifying unit  410   a  is connected to the secondary winding  320   a , the second synchronous rectifying unit  410   b  is connected to the secondary winding  320   b , the third synchronous rectifying unit  410   c  is connected to the secondary winding  320   c , and the fourth synchronous rectifying unit  410   d  is connected to the secondary winding  320   d.    
     The first synchronous rectifying unit  410   a  includes rectifying switches Q 1  and Q 2 , the second synchronous rectifying unit  410   b  includes rectifying switches Q 3  and Q 4 , the third synchronous rectifying unit  410   c  includes rectifying switches Q 5  and Q 6 , and the second synchronous rectifying unit  410   d  includes rectifying switches Q 7  and Q 8 . Specifically, the sources of the rectifying switch Q 1  and Q 2  are connected to ground, the drains thereof is connected to two taps of the second winding  320   a , and the filter L 1  is connected to the center-tap of the second winding  320   a ; the sources of the rectifying switch Q 3  and Q 4  are connected to ground, the drains thereof is connected to two taps of the second winding  320   b , and the filter L 2  is connected to the center-tap of the second winding  320   b ; the sources of the rectifying switch Q 5  and Q 6  are connected to ground, the drains thereof is connected to two taps of the second winding  320   c , and the filter L 3  is connected to the center-tap of the second winding  320   c ; the sources of the rectifying switch Q 7  and Q 8  are connected to ground, the drains thereof is connected to two taps of the second winding  320   d , and the filter L 4  is connected to the center-tap of the second winding  320   d . The gates SR 1   ˜ SR 8  of the rectifying switch Q 1   ˜ Q 8  and the first to fourth output switch SW 1   ˜ SW 4  are connected to the controller  420 . The controller  420  sends signals the rectifying switch Q 1   ˜ Q 8  to drive one of the first the fourth synchronous rectifying units  410   a   ˜   410   d  to perform synchronous rectifying procedure. The controller  420  further sent signals to the first to fourth output switch SW 1   ˜ SW 4  to makes one of the first to fourth output switch SW 1   ˜ SW 4  to turn off or on, wherein when the first to fourth output switch SW 1   ˜ SW 4  is turned on, the rectified power con be conducted to the electronic device. The center tap of the transformer  30  is further electrically connected to an output capacitor Co. 
     The function and relative description of other components of power conversion system of this embodiment are the same as that of first embodiment mentioned above and are not repeated here for brevity, and the power conversion of this embodiment can achieve the functions as the power conversion system of the first embodiment does. 
     Reference is made to  FIG. 12 , which is a circuit diagram of an integrated power-converting module according to the present invention. The integrated power-converting module having functions of changing voltage, rectification, and filtration, and includes a transformer  5 , a plurality of rectifiers  44 , and a plurality of filter  46 . The rectifier  44  and the filters  46  are electrically connected to a secondary side of the transformer  5 . The rectifier  44  receives the converted electric power outputted from the secondary side of the transformer  5  and converts the converted electric power from alternative current (AC), which periodically reverse direction, to direct current (DC), which flow in only one direction. The filter  46  is configured to remove the unwanted AC components (or called ripple) of the rectifier  44  output, thus the integrated power-converting module can output a smooth and steady DC. 
     Reference is made to  FIG. 13  and  FIG. 14 , which are respectively an exploded view and an assembled view of the integrated power-converting module according to the present invention. The integrated power-converting module includes a bobbin  10 ′, at least one primary coil  20 , a magnetic core assembly  30 ′, and a plurality of power-converting units  41   a   ˜   41   d.    
     The bobbin  10 ′ includes a main body  100 , a plurality of winding portions  102 , and a plurality of receiving portions  104   a   ˜   104   d . The main body  100  includes a first channel  101 . The amount of the receiving portions  104   a   ˜   104   b  is the same as that of the winding portions  102 . The receiving portions  104   a   ˜   104   d  are arranged in a parallel manner, and the winding portions  102  and the receiving portions  104   a   ˜   104   d  are arranged in a stagger manner. 
     The main body  100  further includes a second channel  109  communicating with the first channel  101  and substantially perpendicular thereto. 
     The bobbin  10 ′ of the present invention includes four receiving portions  104   a   ˜   104   d  arranged at two opposite sides of the second channel  109 . In particular, the receiving portions  104   a  and  104   b  are arranged at one side of the second channel  109 , and the receiving portions  104   c  and  104   d  are arranged at the other side thereof. The winding portions  102  also arranged at the opposite sides of the second channel  109 , and the winding portions  102  and the receiving portions  104   a   ˜   104   d  are arranged in staggered manner. 
     Each of the receiving portions  104   a   ˜   104   d  including a slot  106  communicating with the first channel  101  and a side-wall  110  disposed opposite to the power-converting units  41   a   ˜   41   d  and enclose the slot  106 . 
     Each of the receiving portions  104   a   ˜   104   d  further includes two protrusions  105  arranged on the bottom and far away from each other. An extending direction of the protrusions  105  is substantially perpendicular to the opening direction of the slots  106 . The power-converting module further includes a plurality of electrically conductive terminals  12  and a plurality of fixing members  13 , the electrically conductive terminals  12  are connected to the protrusions  105  far away from the power-converting units  41   a   ˜   41   b , and the fixing members  13  are connected to the protrusions  105  close to the power-converting units  41   a   ˜   41   d.    
     The primary coil  20  is electrically connected to the electrically conductive terminals  12  and is wound on the winding portions  102  in S-shaped, and initial end of the primary coil  20  is connected to one of the electrically connective terminal  12 , and a terminal end of the primary coil  20  is connected to the other electrically connected terminal  12 , as shown in  FIG. 14 . The primary coil  20  is a primary winding of the integrated power-converting module. 
     The main body  100  further includes a plurality of spacers  108  arranged between the second channel  109  and the receiving portions  104   b  and  104   c  close to the second channel  109  for spacing the second channel  109  and the receiving portions  104   b  and  104   c.    
     The magnetic core assembly  30 ′ is assembled with the bobbin  102  and partially inserted into the first channel  101 . The magnetic core  30 ′ can be assembled by two E-shaped magnetic cores, and each magnetic core includes a central led  300  and two lateral legs  302  and  304  arranged at two opposite sides of the central lag  300  and connected thereto. When the magnetic core assembly  30 ′ is assembled with the bobbin  102 , the top surfaces of the lateral leg  302  and  304  are contacted with each other, the central leg  300  is received within the first channel  101 , and an air gap  31  is formed between the top surface of the central legs  300  and within the second channel  109 , as shown in  FIG. 16 , and then an effect of energy storage is achieved. It should be noted that if the primary coil  20  does not wind on above the air gap  31 , an eddy current loss can then be effectively reduce. 
     Besides, when the magnetic core assembly  30 ′ is assembled with the bobbin  102 , there are air passages  50  allowing vapor flowing therethrough exist, and the air passages  50  are formed between the lateral lags  302  and  304  of each of the magnetic core and the main body  100 . Thus the integrated power-converting module has a good thermal dissipating effect. 
     The power-converting units  41   a   ˜   41   d  are arranged in a parallel manner and each of the power-converting units  41   a   ˜   41   d  includes a circuit board  42 , a rectifier  44 , and a filter  46 . 
     The circuit board  42  includes a base portion  420  and an extending portion  422  connected to the base portion  420 . The base portion  420  and the extending portion  422  are both placed with copper foil, and an electrically connected sheet  43  is placed on the extending portion  422  and attached to the copper foil formed thereon, thus the electrically conductive sheet  43 , the rectifier  44 , and the filter  46  can be electrically connected to each other. As shown in the  FIG. 13 , a profile of the base portion  420  is substantially of rectangular, and a plurality of connecting terminals  426  are connected to the bottom of each of the base portions  420 . 
     A penetrating hole  424  is formed on the extending portion  422  so that a profile of the extending portion  422  is ring shape and corresponding to that of the receiving portions  104   a   ˜   104   d , and when the extending portions  422  are inserted into the receiving portions  104   a   ˜   104   d , the penetrating hole  424  of each extending portion  422  is aligned with and communicating with the first channel  101 . The extending portions  422  are configured to transit alternative current to the rectifiers  44 . 
     The power-converting unit  41   a   ˜   41   d  can further includes the electrically conductive sheets  43  placed on each of the extending portions  423  and attached on the copper foil. A profile of the electrically conductive sheet  43  is corresponding to that of the extending portion  423  and has an opening  430 , thus the electrically conductive sheets  43  is of C-shaped. The electrically conductive sheets  43  configured to conduct current can be made of tinned copper for providing a good electrical conduction and thermal dissipation. 
     In the present invention, the primary coil  20  wound on the winding portion  102 , the magnetic core assembly  30 ′ assembled with the bobbin  10 ′, the extending portions  422  where placed with copper foil (and the electrically conductive sheet  43 ) and inserted into the slots  106  of the bobbin  10 ′, collectively construct the transformer  5  shown in  FIG. 12 . 
     The rectifier  44  is placed on one surface of the base portion  420  of the circuit boards  42 , and the filter  46  is placed on the other surface of the base portion  420  thereof. The rectifier  44  can be synchronous rectifier composed of four metal-oxide-semiconductor field-effect transistors (MOSFETs). Each of the power-converting units  41   a   ˜   41   d  further includes a electrically conductive plate  48  placed on the base portion  420 , and the electrically conductive plate  48  and the rectifier  44  are placed on the same surface. The filter  46  is, for example, choke. 
     The surface of the power-converting unit  41   b  placed with the filter  46  faces the surface of the power-converting unit  41   c  placed with the filter  46 , which means that the filters  46  of the two power-converting units  41   b  and  41   c  close to the second channel  109  face each other, and the length of two filters  46  aforementioned is substantially equal to the width of the second channel  109 . 
     Moreover, the surface of the circuit board  42  of the power-converting unit  41   a  placed with the rectifier  44  faces the surface of the circuit board  42  of the power-converting unit  41   b  placed with the rectifier  44 . In the other words, two power-converting units  41   a  and  41   b  (or  41   c  and  41   d ) arranged at the same side of the second channel  109  face each other. In such manner, the integrated power-converting module is compact since the power-converting units  41   a   ˜   41   d  are tightly arranged. 
     The integrated power-converting module of the present invention having circuit diagram shown in  FIG. 12  and arrangement shown in  FIG. 13  and  FIG. 17 , which has advantage of compact and eddy current loss and switching loss can be effectively reduced. 
     The integrated power-converting module can be mounted on a circuit main board, in the other words, the circuit main board is disposed below the integrated power-converting module. The fixing members  13  is inserted into the circuit main board, so that the integrated power-converting module can stand on the circuit main board to prevent the integrated power-converting module from tilt caused by heavy weight. It should be noted that if the integrated power-converting module includes both the fixing members  13  and the electrically conductive terminals  12 , the electrically conductive terminals  12  can be disposed at the bottom of the receiving portions  104   a   ˜   104   d , and the primary coil  30 ′ can be connected to the electrically connected terminals  12  and electrically connected to the circuit main board via the electrically connected terminals  12 . The fixing members  13  are disposed at the bottom of the receiving portions  104   a   ˜   104   d  where the electrically conductive terminal is not disposed, such that the integrated power-converting module can stand firmly on the circuit main board. If the integrated power-converting module only includes the fixing members  13 , the fixing members  13  are disposed at the bottom of the receiving portions  104   a   ˜   104   d , and the primary coil  20  wound on the bobbin  10 ′ is directly connected to the circuit main board (by fly line connection). In the practical application, the arrangement of the electrically connective terminals  12  and the mixing member  13  can be adjusted based on the different situations. 
     The integrated power-converting module of the present invention for outputting multiple direct current electric powers integrates secondary windings (the copper foil or electrically conductive sheet  43  formed on the extending portions  422 ), the rectifier  44 , and the filter  46  into one circuit board  42 , which is assembled with the bobbin  10 ′ by inserting the extending portions  422  into the receiving portions  104   a   ˜   104   d  respectively. Thus it is compact and easily to manufacture and assemble. 
     As shown in  FIG. 18 , the power conversion system  1000  includes a printed circuit board  1001 , a switching module  1002 , a resonance module  1003 , a voltage conversion module  1004 , and an output control device  1500 . As shown in  FIG. 18 , in structure, the resonant module  1003  is electrically connected between the switching module  1002  and the voltage conversion module  1004 , and the voltage conversion module  1004  is electrically connected to the output control device  1500 . For example, the switching module  1002  may be the full bridge switching module  10  described above, the resonant module  1003  may be the resonant module  20  described above, and the voltage conversion module  1004  may be the isolation transformer  30  described above, and the output control device  1500  may be the output-controlling device  40  as described above. The switching module  1002 , the resonant module  1003 , the voltage conversion module  1004 , and the output control device  1500  may be disposed on the printed circuit board  1001  or may be disposed on different printed circuit boards electrically connected to each other. Those with ordinary skill in the art may flexibly design depending on the desired application. 
     Refer to  FIG. 18  and  FIG. 19 , the voltage conversion module  1004  includes a front side magneto-sensitive unit  1100 , a first voltage conversion unit  1200 , and a second voltage conversion unit  1300 . The front-side magneto-sensitive unit  1100  is electrically connected the resonant module  1003 , and the front-side magneto-sensitive unit  1100  receives the electric energy transmitted from the resonant module  1003  to generate a magnetic energy signal and isolatedly transmits the magnetic energy signal. The first voltage conversion unit  1200  and the front side magneto-sensitive unit  1100  form a magnetic loop, and the first voltage conversion unit  1200  includes a first output portion  1213 . The first output portion  1213  is inserted into the printed circuit board  1001 . The second voltage conversion unit  1300  and the front side magneto-sensitive unit  1100  form a magnetic loop, and the second voltage conversion unit  1300  includes a second output portion  1313 . The second output portion  1313  is inserted into the printed circuit board  1001 . The first voltage conversion unit  1200  and/or the second voltage conversion unit  1300  receive the magnetic energy signal transmitted from the front side magneto-sensitive unit  1100  and process the magnetic energy signal into an energy signal. The first output portion  1213  and the second output portion  1313  conduct the processed energy signal to the printed circuit board  1001 . 
     The output control device  1500  includes a controller  1510 , a first output control switch  1511  and a second output control switch  1512 . The first output control switch  1511  is electrically connected to the first output portion  1213 , and the second output control switch  1512  is electrically connected to the second output portion  1313 . The output control device  1500  is mainly based on the energy demand of the load side to control the first output control switch  1511  and the second output control switch  1512 , so as to supply the processed energy signal from the first voltage conversion unit  1200  and/or the second voltage conversion unit  1300  to the load side. 
     In use, the switching module  1002  is used to pass the positive half-cycle or negative half-cycle of the input AC, or to convert the positive half-cycle or the negative half-cycle to another half-cycle, so that all half cycles are positive half cycle or negative half-cycle, and then output one-direction signal of all positive half-cycle or negative half-cycle. The resonant module  1003  is used to receive and process a one-direction signal, and output a first voltage. 
     The front side magneto-sensitive unit  1100  is used to receive the first voltage and generate magnetic energy. The first voltage conversion unit  1200  and the front side magneto-sensitive unit  1100  form a magnetic loop to magnetize each other to produce a first induced current and rectify the first induced current as a first current. The first output portion  1213  is used to conduct the first current to the printed circuit board  1001 . The second voltage conversion unit  1300  and the front side magneto-sensitive unit  1100  form a magnetic loop to magnetize each other to produce a second induced current and rectify the second induced current as a second current. The second output portion  1313  is used to conduct the second current to the printed circuit board  1001 . 
     The controller  1510  controls the first output control switch  1511  to be turned on or off or the second output control switch  1512  to be turned on or off. When the first output control switch  1511  is turned on and the second output control switch  1512  is turned off, the first current is outputted; when the first output control switch  1511  is turned off and the second output control switch  1512  is turned on, the second current is outputted; when the first output control switch  1511  and the second output control switch  1512  are all turned on, a third current is outputted, where the third current is the sum of the first current and the second current. 
     As shown in  FIG. 19  and  FIG. 20 , the front side magneto-sensitive unit  1100  has a first hollow portion  1101 . For example, the front side magneto-sensitive unit  1100  may be a copper wire winding, a copper piece winding, or a winding is formed by a copper foil of a printed circuit board, but is not limited thereto, or may be a primary winding  310  as described in  FIG. 2  or  FIG. 7 . 
     The first voltage conversion unit  1200  includes a second hollow portion  1214 , and the second voltage conversion unit  1300  includes a third hollow portion  1314 . The voltage conversion module  1004  further includes a core group  1400  having a centre leg  1410  installed in the second hollow portion  1214 , the third hollow portion  1314 , and the first hollow portion  1101 , as described above. 
     The bobbin  1110  is used to combine the front side magneto-sensitive unit  1100 , the first voltage conversion unit  1200 , the second voltage conversion unit  1300 , and the core group  1400  to form a voltage conversion module  1004 . The bobbin  1110  has a containment space that houses the front side magneto-sensitive unit  1100 , the first voltage conversion unit  1200 , and the second voltage conversion unit  1300 . The bobbin  1110  has a through hole  1111  for receiving the centre leg  1410 . 
     As shown in  FIG. 21  and  FIG. 22 , the first voltage conversion unit  1200  includes a first conductive substrate  1210 , a first rear side magnetic sensitive layer  1220 , a third rear side magnetic sensitive layer  1225 , and a first rectifying unit  1230 . 
     The first conductive substrate  1210  has a first conductive region  1212  and a first output portion  1213 , and two sides of the first conductive substrate  1210  have a first magnetic sensitive region  1211  and a third magnetic sensitive region  1215 , respectively. The first magnetic sensitive region  1211  and the third magnetic sensitive region  1215  have a second hollow portion  1214 . The first magnetic sensitive region  1211  and the third magnetic sensitive region  1215  are connected to or electrically connected to the first conductive region  1212 . The first conductive region  1212  and the first output portion  1213  are connected or electrically connected. 
     The first rear side magnetic sensitive layer  1220  is arranged on the first magnetic sensitive region  1211  in an annular manner, and the first rear side magnetic sensitive layer  1220  has a first open end  1221  and a second open end  1222  that are not connected to each other. The third rear side magnetic sensitive layer  1225  is arranged on the third magnetic sensitive region  1215  in an annular manner, and the third rear side magnetic sensitive layer  1225  has a third open end  1226  and a fourth open end  1227  that are not connected to each other. The first rear side magnetic sensitive layer  1220  is electrically connected to the third rear side magnetic sensitive layer  1225  through the first conductive substrate  1210 . The first rear side magnetic sensitive layer  1220  and third rear side magnetic sensitive layer  1225  for interacting with the front side magneto-sensitive unit  1100  to produce a first induced current. In other words, the first rear side magnetic sensitive layer  1220  of the first magnetic sensitive region  1211  and the third rear side magnetic sensitive layer  1225  of the third magnetic sensitive region  1215  receive the magnetic energy signal of the front side magneto-sensitive unit  1100  to generate an energy signal. The energy signal is conducted to the printed circuit board  1001  via the first conductive region  1212  and the first output portion  1213 . 
     The first rectifying unit  1230  is disposed on the first conductive region  1212  and is electrically connected to the first rear side magnetic sensitive layer  1220  and the third rear side magnetic sensitive layer  1225 , to rectify the first induced current to a first current. The first output portion  1213  is electrically connected to the first rectifying unit  1230 , and the first output portion  1213  outputs the first current. A filter unit composed of an inductor L and/or a capacitor C may be provided between the first output portion  1213  and the first rectifying unit  1230  to filter the first current. In one embodiment of the present invention, the first rectifying unit  1230  may comprise at least one switch for rectification in a switched manner. 
     The first magnetic sensitive region  1211  is provided with a metal sheet  1610 , and the metal sheet  1610  is bonded to the first rear side magnetic sensitive layer  1220  to increase the heat dissipation and current tolerance. The first magnetic sensitive region  1211  is provided with two first positioning holes  1701  which are diagonally to each other. The metal sheet  1610  includes a positioning structure  1611  for engaging with the first positioning hole  1701 . For example, the positioning structure  1611  may be a bump that is locally punched on the metal sheet  1610 . On the other hand, a metal sheet  1620  is disposed on one side of the first conductive region  1212 , and the metal sheet  1620  serves to increase the heat dissipation and current resistance. 
     The third magnetic sensitive region  1215  is provided with a metal sheet  1630 , and the metal sheet  1630  is bonded to the third rear side magnetic sensitive layer  1225  to increase the heat dissipation and current tolerance. The third magnetic sensitive region  1215  is provided with two third positioning holes  1703  which are diagonally to each other. The metal sheet  1630  includes a positioning structure  1631  for engaging with the third positioning hole  1703 . For example, the positioning structure  1631  may be a bump that is locally punched on the metal sheet  1630 . On the other hand, a metal sheet  1640  is disposed on the other side of the first conductive region  1212  for increasing the heat dissipation and current resistance. The first positioning hole  1701  and the third positioning hole  1703  are offset from each other, where the two first positioning holes  1701  and the two third positioning holes  1703  are respectively diagonally opposed to each other, so that the positioning structure  1611  is engaged with the positioning structure  1631 , and to enhance structural stability. 
     The first output portion  1213  is located in the first conductive region  1212 . It has a first angle Θ 1  between the first magnetic sensitive region  1211  and the first output portion  1213 , where the first angle Θ 1  is greater than 0 degrees and less than 180 degrees. 
     The structure and circuit characteristics of the second voltage conversion unit  1300  are substantially the same as those of the first voltage conversion unit  1200  and are not repeated herein. It is important to note that the first voltage conversion unit  1200  and the second voltage conversion unit  1300  may be identical or may be arranged on opposing side of the mirror manner, or are individually separate circuit layout designs, all of which fall within the scope of the present invention. 
     As shown in  FIG. 23  and  FIG. 24 , the bobbin  1110  has a first accommodating part  2510 , a second accommodating part  2520 , and a first opening  2521 , wherein the second accommodating part  2520  has a second opening  2522 . The first opening  2521  and the second opening  2522  are connected to each other, and the first opening  2521  is larger than the second opening  2522 . In use, the first accommodating part  2510  is used to accommodate the front side magneto-sensitive unit  1100 , and the second accommodating part  2520  accommodates the first voltage conversion unit  1200  and/or the second voltage conversion unit  1300 . And the second accommodating part  2520  improves heat dissipation via first opening  2521  and the second opening  2522 . 
     The upper and/or lower edges of the first opening  2521  have a stopper  2523  against the first voltage conversion unit  1200  or the second voltage conversion unit  1300 . 
     The upper and/or lower edges of the second opening  2522  have a stopper  2524 . The stopper  2524  of the upper and/or lower edge of the second opening  2522  is disposed against the magnetic sensitive regions of the first voltage conversion unit  1200  or the second voltage conversion unit  1300 . 
     The upper and/or lower edges of the second accommodating part  2520  are provided with divider blocks  2528  and  2529  which divide the second accommodating part  2520  into two slots  2525  and  2526 . The two slots  2525  and  2526  provide the first voltage conversion unit  1200  and the second voltage conversion unit  1300  to be inserted respectively. 
     Refer to  FIG. 20  and  FIG. 24 , a first height T 1  is between the upper edge of the through hole  1111  in  FIG. 20  and the upper wall of the second accommodating part  2520 . A second height T 2  is between the lower edge of the through hole  1111  and the lower wall of the second accommodating part  2520 . The divider block  2528  has a third height T 3 . The divider block  2529  has having a fourth height T 4 . The third height T 3  of the divider block  2528  is less than the first height T 1  so as to prevent the divider block  2528  from penetrating through the through hole  1111  and affecting the assembly of the core group  1400 . The fourth height T 4  of the divider block  2529  is less than the second height T 2 , thereby preventing the divider block  2529  from penetrating through the through hole  1111  and affecting the assembly of the core group  1400 . 
     The upper and/or lower edges of the first opening  2521  have a notch  2800  for positioning or fixing the first voltage conversion unit  1200  and the second voltage conversion unit  1300 . 
     As shown in  FIG. 25  and  FIG. 26 , the front side magneto-sensitive unit  1100 , the first voltage conversion unit  1200  and the second voltage conversion unit  1300  are assembled together with the bobbin  1110 . The front side magneto-sensitive unit  1100  is installed in the first accommodating part  2510 , the first voltage conversion unit  1200  is inserted in the slot  2525  of the second accommodating part  2520 , and the second voltage conversion unit  1300  is inserted in the slot  2526  of the second accommodating part  2520 . A gap  2530  is formed between the first voltage conversion unit  1200  and the second voltage conversion unit  1300 . The stopper  2523  of the first opening  2521  is disposed against the first voltage conversion unit  1200  and the second voltage conversion unit  1300 , and magnetic sensitive regions of the first voltage conversion unit  1200  and the second voltage conversion unit  1300  are disposed against the stopper  2524  of the second opening  2522 . 
     Referring to  FIG. 27 , there is a schematic cross-sectional view of the A-A′ section of the bobbin  1110  in  FIG. 20 , where the hatching line A-A′ corresponds to the position where the second accommodating part  2520  is located at the divider blocks  2528  and  2529 . As shown in  FIG. 27 , after the centre leg  1410  penetrates the through hole  1111 , it can block a portion of the gap  2530  (see  FIG. 26 ), but since the first height T 1  is greater than the third height T 3  and the second height T 2  is greater than the fourth height T 4 . The upper edge of the through hole  1111  with the lower edge of the divider block  2528 , and the lower edge of the through hole  1111  with the upper edge of the divider block  2529  form the upper and lower passages, respectively. There is a distance between the second opening  2522  and an end of the through hole  1111  close to the second opening  2522 , so that the air flow can flow between the first opening  2521  and the second opening  2522  via the upper or lower passages in the gap  2530  (see  FIG. 26 ) to increase the heat dissipation effect. 
     It should be understood that although the above-described embodiments have been described in terms of the first voltage conversion unit  1200  and the second voltage conversion unit  1300 , which are adjacent to the slots inserted into a space, but this does not limit the number of the voltage conversion units of the present invention. In other embodiments of the present invention, the voltage conversion unit  2200  is individually inserted in the slot  2525  or slot  2526  of the second accommodating part  2520  of the bobbin  1110 , as shown in  FIG. 28  and  FIG. 29 . Through this alone manner can also be used to achieve the same or similar efficacy. 
     In another embodiment of the present invention, as shown in  FIG. 30  and  FIG. 31 , the voltage conversion module  3000  includes a front side magneto-sensitive unit  3100 , a core group  3200 , a bobbin  3300 , and a voltage conversion unit  3400 . The front side magneto-sensitive unit  3100  receives the electric energy to generate a magnetic energy signal and isolatedly transmits the magnetic energy signal. The voltage conversion unit  3400  and the front side magneto-sensitive unit  3100  form a magnetic loop, and the voltage conversion unit  3400  includes an output portion  3420  inserted into the printed circuit board. The voltage conversion unit  3400  receives the magnetic energy signal sent by the front side magneto-sensitive unit  3100  and processes the magnetic energy signal as an energy signal. The output portion  3420  conducts the processed energy signal to the printed circuit board. 
     In use, the front side magneto-sensitive unit  3100  is used to receive the voltage and generate magnetic energy. The voltage conversion unit  3400  and the front side magneto-sensitive unit  3100  form a magnetic loop to magnetize each other to produce an induced current and rectify the induced current as a rectified current. The output portion  3420  is used to conduct the rectified current to the printed circuit board. 
     The front side magneto-sensitive unit  3100  has a first hollow portion  3110 . For example, the front side magneto-sensitive unit  3100  may be a copper wire winding, a copper piece winding, or a winding is formed by the copper foil of a printed circuit board, but is not limited thereto, or may be a primary winding  310  as described in  FIG. 2  or  FIG. 7 . 
     The voltage conversion unit  3400  includes a second hollow portion  3410 . The core group  3200  having a centre leg  3210  installed in the second hollow portion  3410 , and the first hollow portion  3110  as described above. 
     The bobbin  3300  is used to combine the front side magneto-sensitive unit  3100 , the voltage conversion unit  3400 , and the core group  3200  to form a voltage conversion module  3000 . The bobbin  3300  has a containment space that houses the front side magneto-sensitive unit  3100  and the voltage conversion unit  3400 . The bobbin  3300  has a through hole  3340  for receiving the centre leg  3210 . 
     The structure and circuit characteristics of the voltage conversion unit  3400  are substantially the same as those of the first voltage conversion unit  1200  and are not repeated herein. 
     As shown in  FIG. 32  and  FIG. 33 , the bobbin  3300  has a first accommodating part  3310 , a second accommodating part  3320 , and a first opening  3330 , wherein the second accommodating part  3320  has a second opening  3321 . The first opening  3330  and the second opening  3321  are connected to each other, and the first opening  3330  is larger than the second opening  3321 . In use, the first accommodating part  3310  is used to accommodate the front side magneto-sensitive unit  3100 , and the second accommodating part  3320  accommodates the voltage conversion unit  3400 . The heat generated from the voltage conversion unit  3400  is dissipated via the first opening  3330  and the second opening  3321 . 
     The upper and/or lower edges of the first opening  3330  have a stopper  3331  against the voltage conversion unit  3400 . 
     The upper and/or lower edges of the second opening  3321  have a stopper  3323 . The stopper  3323  of the upper and/or lower edge of the second opening  3321  is disposed against the magnetic sensitive regions of the voltage conversion unit  3400 . 
     The second accommodating part  3320  has a slot  3322 . The slot  3322  provides the voltage conversion unit  3400  to be inserted therein. 
     The upper and/or lower edges of the first opening  3330  have a notch  3332  for positioning or fixing the voltage conversion unit  3400 . 
     As shown in  FIG. 34  and  FIG. 35 , the front side magneto-sensitive unit  3100 , and the voltage conversion unit  3400  are assembled together with the bobbin  3300 . The front side magneto-sensitive unit  3100  is installed in the first accommodating part  3310 , and the voltage conversion unit  3400  is inserted in the slot  3322  of the second accommodating part  3320 . Wherein the stopper  3331  of the first opening  3330  is disposed against the voltage conversion unit  3400 , and the magnetic sensitive region of voltage conversion unit  3400  is disposed against the stopper  3323  of the second opening  3321 . 
     When the voltage conversion unit  3400  is inserted into the slot  3322 , a gap  3324  is formed between the inner wall of the second accommodating part  3320  and the voltage conversion unit  3400 . See  FIG. 36 , which is a schematic view of the A-A′ section of the bobbin  3300  in  FIG. 31 . In  FIG. 35  and  FIG. 36 , after the centre leg  3210  penetrates the through hole  3340 , it can partially block the gap  3324 , but the gap  3324  is not completely blocked by the centre leg  3210 . There is a distance between the second opening  3321  and an end of the through hole  3340  close to the second opening  3321 , so that the air flow can flow between the first opening  3330  and the second opening  3321  via the gap  3324  to increase the heat dissipation effect. 
     In another embodiment of the present invention, as shown in  FIG. 37  and  FIG. 38 , the voltage conversion module  5000  includes a front side magneto-sensitive unit  5100 , a core group  5200 , a bobbin  5300 , a first voltage conversion unit  5400 , a second voltage conversion unit  5500 , a third voltage conversion unit  5600  and a fourth voltage conversion unit  5700 . The core group  5200  has a centre leg  5210 . The front side magneto-sensitive unit  5100  receives the electric energy to generate a magnetic energy signal and isolatedly transmits the magnetic energy signal. The first voltage conversion unit  5400  and the front side magneto-sensitive unit  5100  form a magnetic loop, and the first voltage conversion unit  5400  includes a first output portion  5430  inserted into the printed circuit board. The second voltage conversion unit  5500  and the front side magneto-sensitive unit  5100  form a magnetic loop, and the second voltage conversion unit  5500  includes a second output portion  5530  inserted into the printed circuit board. The third voltage conversion unit  5600  and the front side magneto-sensitive unit  5100  form a magnetic loop, and the third voltage conversion unit  5600  includes a third output portion  5630  inserted into the printed circuit board. The fourth voltage conversion unit  5700  and the front side magneto-sensitive unit  5100  form a magnetic loop, and the third voltage conversion unit  5600  includes a fourth output portion  5730  inserted into the printed circuit board. The first voltage conversion unit  5400 , the second voltage conversion unit  5500 , the third voltage conversion unit  5600  and/or the fourth voltage conversion unit  5700  receives the magnetic energy signal sent by the front side magneto-sensitive unit  5100  and processes the magnetic energy signal as an energy signal. The first output portion  5430 , the second output portion  5530 , the third output portion  5630 , and the fourth output portion  5730  conduct the processed energy signal to the printed circuit board. 
     In use, the front side magneto-sensitive unit  5100  is used to receive the voltage and generate magnetic energy. The first voltage conversion unit  5400 , the second voltage conversion unit  5500 , the third voltage conversion unit  5600 , the fourth voltage conversion unit  5700  and the front side magneto-sensitive unit  5100  form a magnetic loop to magnetize each other to produce a induced current and rectify the induced current as a rectified current. The first output portion  5430 , the second output portion  5530 , the third output portion  5630 , and the fourth output portion  5730  are used to conduct the rectified current to the printed circuit board. 
     The front side magneto-sensitive unit  5100  has a first hollow portion  5110 . For example, the front side magneto-sensitive unit  5100  may be a copper wire winding, a copper piece winding, or a winding is formed by a copper foil of a printed circuit board, but is not limited thereto, or may be a primary winding  310  as described in  FIG. 2  or  FIG. 7 . 
     The first voltage conversion unit  5400  includes a second hollow portion  5411 . The second voltage conversion unit  5500  includes a third hollow portion  5511 . The third voltage conversion unit  5600  includes a fourth hollow portion  5611 . The fourth voltage conversion unit  5700  includes a fifth hollow portion  5711 . The core group  5200  having a centre leg  5210  installed in the second hollow portion  5411 , the third hollow portion  5511 , the fourth hollow portion  5611 , the fifth hollow portion  5711 , and the first hollow portion  5110  as described above. 
     The bobbin  5300  is used to combine the front side magneto-sensitive unit  5100 , the first voltage conversion unit  5400 , the second voltage conversion unit  5500 , the third voltage conversion unit  5600 , the fourth voltage conversion unit  5700  and the core group  5200  to form a voltage conversion module  5000 . The bobbin  5300  has a containment space that houses front side magneto-sensitive unit  5100 , the first voltage conversion unit  5400 , the second voltage conversion unit  5500 , the third voltage conversion unit  5600  and the fourth voltage conversion unit  5700 . The bobbin  5300  has a through hole  5340  for receiving the centre leg  5210 . 
     The structure and circuit characteristics of the first voltage conversion unit  5400 , the second voltage conversion unit  5500 , the third voltage conversion unit  5600  and the fourth voltage conversion unit  5700  are substantially the same as those of the first voltage conversion unit  1200  and are not repeated herein. It is important to note that the first voltage conversion unit  5400 , the second voltage conversion unit  5500 , the third voltage conversion unit  5600  and the fourth voltage conversion unit  5700  may be identical or may be arranged on opposing side of the mirror manner, or are individually separate circuit layout designs, all of which fall within the scope of the present invention. 
     As shown in  FIG. 39  and  FIG. 40 , the bobbin  5300  has a first accommodating part  5310 , a second accommodating part  5320 , and a third accommodating part  5330 . The second accommodating part  5320  has a first opening  5321  and a second opening  5322 . The first opening  5321  and the second opening  5322  are connected to each other, and the first opening  5321  is larger than the second opening  5322 . The third accommodating part  5330  has a third opening  5331  and a fourth opening  5332 . The third opening  5331  and the fourth opening  5332  are connected to each other, and the third opening  5331  is larger than the fourth opening  5332 . In use, the first accommodating part  5310  is used to accommodate the front side magneto-sensitive unit  5100 , and the second accommodating part  5320  accommodates the first voltage conversion unit  5400  and/or the second voltage conversion unit  5500 . And the second accommodating part  5320  improves heat dissipation via the first opening  5321  and the second opening  5322 . The third accommodating part  5330  accommodates the third voltage conversion unit  5600  and/or the fourth voltage conversion unit  5700 . And the third accommodating part  5330  improves heat dissipation via the third opening  5331  and the fourth opening  5332 . 
     The upper and/or lower walls of the first opening  5321  have divider blocks  5323  and  5324  which divide the second accommodating part  5320  into two slots  5325  and  5326 . The two slots  5325  and  5326  provide the first voltage conversion unit  5400  and the second voltage conversion unit  5500  to be inserted respectively. 
     The upper and/or lower walls of the third opening  5331  have divider blocks  5333  and  5334  which divide the third accommodating part  5330  into two slots  5335  and  5336 . The two slots  5335  and  5336  provide the third voltage conversion unit  5600  and the fourth voltage conversion unit  5700  to be inserted respectively. 
     The upper and/or lower edges of the first opening  5321  have a stopper  5327  against the first voltage conversion unit  5400  and/or the second voltage conversion unit  5500 . 
     The upper and/or lower edges of the second opening  5322  have a stopper  5328  against the first voltage conversion unit  5400  and/or the second voltage conversion unit  5500 . 
     The upper and/or lower edges of the third opening  5331  have a stopper  5337  against the third voltage conversion unit  5600  and/or the fourth voltage conversion unit  5700 . 
     The upper and/or lower edges of the fourth opening  5332  have a stopper  5338  against the third voltage conversion unit  5600  and/or the fourth voltage conversion unit  5700 . 
     Refer to  FIG. 38  and  FIG. 40 , a first height T 1  is between the upper edge of the through hole  5340  in  FIG. 40  and the upper wall of the second accommodating part  5320 . A second height T 2  is between the lower edge of the through hole  5340  and the lower wall of the second accommodating part  5320 . The divider block  5323  has a third height T 3 . The divider block  5324  has having a fourth height T 4 . The third height T 3  of the divider block  5323  is less than the first height T 1  so as to prevent the divider block  5323  from penetrating through the through hole  5340  and affecting the assembly of the core group  5200 . The fourth height T 4  of the divider block  5324  is less than the second height T 2 , thereby preventing the divider block  5324  from penetrating through the through hole  5340  and affecting the assembly of the core group  5200 . 
     The upper and/or lower edges of the first opening  5321  and the third opening  5331  have notches  5350  for positioning or fixing the first voltage conversion unit  5400 , the second voltage conversion unit  5500 , the third voltage conversion unit  5600  and the fourth voltage conversion unit  5700 . 
     As shown in  FIG. 41  and  FIG. 42 , the front side magneto-sensitive unit  5100 , the first voltage conversion unit  5400 , the second voltage conversion unit  5500 , the third voltage conversion unit  5600  and the fourth voltage conversion unit  5700  are assembled together with the bobbin  5300 . The front side magneto-sensitive unit  5100  is installed in the first accommodating part  5310 . The first voltage conversion unit  5400  and the second voltage conversion unit  5500  are inserted in the slots  5325  and  5326  of the second accommodating part  5320 . A gap  5329  is formed between the first voltage conversion unit  5400  and the second voltage conversion unit  5500 . The third voltage conversion unit  5600  and the fourth voltage conversion unit  5700  are inserted in the slots  5335  and  5336  of the third accommodating part  5330 . A gap  5339  is formed between the third voltage conversion unit  5600  and the fourth voltage conversion unit  5700 . The stopper  5327  of the first opening  5321  is disposed against the first voltage conversion unit  5400  and the second voltage conversion unit  5500 , and magnetic sensitive regions of the first voltage conversion unit  5400  and the second voltage conversion unit  5500  are disposed against the stopper  5328  of the second opening  5322 . The stopper  5337  of the third opening  5331  is disposed against the third voltage conversion unit  5600  and the fourth voltage conversion unit  5700 , and magnetic sensitive regions of the third voltage conversion unit  5600  and the fourth voltage conversion unit  5700  are disposed against the stopper  5338  of the fourth opening  5332 . 
     Referring to  FIG. 43 , there is a schematic cross-sectional view of the A-A′ section of the bobbin  5300  in  FIG. 38 , where the hatching line A-A′ corresponds to the position where the second accommodating part  5320  is located at the divider blocks  5323  and  5324 . As shown in  FIG. 43 , after the centre leg  5210  penetrates the through hole  5340 , it can block a portion of the gap  5329 , but since the first height T 1  is greater than the third height T 3  and the second height T 2  is greater than the fourth height T 4 , the upper edge of the through hole  5340  with the lower edge of the divider block  5323  and the lower edge of the through hole  5340  with the upper edge of the divider block  5324  form the upper and lower passages, respectively. There is a distance between the second opening  5322  and an end of the through hole  5340  close to the second opening  5322 , so that the air flow can flow between the first opening  5321  and the second opening  5322  via the upper or lower passages in the gap  5329  to increase the heat dissipation effect. 
     In the present embodiment, the structure of the third accommodating part  5330  is substantially similar to that of the second accommodative part  5320 . After the centre leg  5210  penetrates the through hole  5340 , the air flow can flow between the third opening  5331  and the fourth opening  5332  via the upper or lower passages in the gap  5339  to increase the heat dissipation effect. 
     It should be noted that the embodiments of the present invention can be combined with different amounts of voltage conversion units depending on the different requirements such as space, environment of use, output power, or so forth. For example, one voltage conversion unit is placed in a single accommodating space, three or four voltage conversion units are placed in two accommodating spaces, or more voltage conversion units are placed in more accommodating spaces. Those with ordinary skill in the art may flexibly design depending on the desired application. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.