Patent Publication Number: US-2019173372-A1

Title: Switching power supply circuit structure

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a switching power supply circuit structure, particularly to a switching power supply circuit structure capable of reducing the inductor magnetizing current and output ripple effectively. 
     2. Description of the Related Art 
     Nowadays, two kinds of power supplies, the linear power supply and the switching power supply, have been developed. The linear power supply features a simple structure, low cost, less damage and less output noise, but it is easily affected by the input voltage. Also, its volume increases with the output voltage or current, and the energy conversion efficiency is not greater than that of the switching power supply. Conversely, the switching power supply has a complex structure, high cost, and more output power noise, but it is smaller than the linear power supply at the same output power, and the conversion efficiency is relatively high. 
     There are three types of switching power supplies in the prior art: buck converters, boost converters, and buck-boost converters. Among them, the input current of boost converters will not be interrupted and has a good power factor correction in the AC/DC conversion application, and the inductor magnetizing current is relatively small. However, when the field effect transistor is turn on, the inductors are not connected in series or in parallel with the output terminal, resulting in a larger output ripple. The boost converter can only be applied to occasions where the output voltage is higher than the input voltage. The inductor of the buck converter is always connected in series or in parallel with the output terminal, and it has a smaller output ripple. However, the input current will be interrupted, resulting in a large magnetizing current of the inductor, which can only be applied to occasions where the output voltage is lower than the input voltage. In addition, the buck-boost converter can be applied to occasions where the output voltage is lower or higher than the input voltage. The input current will be interrupted, resulting in a larger magnetizing current of the inductor. Also, when the field effect transistor is turn on, the inductor is not connected in series or in parallel with the output, resulting in a larger output ripple, which is its shortcoming. 
     Accordingly, it is necessary to devise a new switching power supply circuit structure to solve the problem in the prior art. 
     SUMMARY OF THE INVENTION 
     It is a major objective of the present invention to provide a switching power supply circuit structure which has the effect of reducing the inductor magnetizing current and output ripple effectively. 
     It is another major objective of the present invention to provide another switching power supply circuit structure. 
     To achieve the above objectives, one switching power supply circuit structure of the present invention includes an input terminal, an output terminal, an energy storage capacitor, a boost circuit, and a second inductor. The input terminal is connected in parallel with an input capacitor. The output terminal has a positive terminal and a negative terminal. The energy storage capacitor is electrically connected between the positive terminal and the ground terminal. The boost circuit comprises a first inductor, a switch component, and a diode. One end of the first inductor, the switch component, and the diode are electrically connected to each other to form a common point. The switch component is electrically connected between the common point and the ground terminal. The second inductor is electrically connected between the negative terminal and the common point, wherein the negative terminal is not connected to the ground terminal. 
     The other switching power supply circuit structure of the present invention includes an input terminal, an output terminal, a boost circuit, and a second inductor. The input terminal is connected in parallel with the input capacitor. The output terminal has a positive terminal and a negative terminal. The boost circuit comprises a first inductor, a switch component, and a diode. One end of the first inductor, the switch component, and the diode are electrically connected to each other to form a common point. The switch component is electrically connected between the common point and the ground terminal. One end of the second inductor is electrically connected to the positive terminal, and the other end thereof is electrically connected to the diode and the energy storage capacitor. The other end of the energy storage capacitor is electrically connected to the ground terminal, wherein the negative terminal is connected to the common point. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a switching power supply circuit structure according to a first embodiment of the present invention; 
         FIGS. 2A-2B  are schematic diagrams showing the current path of operating the switching power supply circuit structure according to a first embodiment of the present invention; 
         FIG. 3  is a schematic diagram of a switching power supply circuit structure according to a second embodiment of the present invention; 
         FIGS. 4A-4B  are schematic diagrams showing the current path of operating the switching power supply circuit structure according to a second embodiment of the present invention; 
         FIG. 5A  is a waveform diagram showing the performance of a buck-boost converter of the prior art; and 
         FIG. 5B  is a waveform diagram showing the performance of the switching power supply circuit structure of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereafter, the technical content of the present invention will be better understood with reference to preferred embodiments. 
     Hereafter, please first refer to  FIG. 1 , which is a schematic diagram of a switching power supply circuit structure according to a first embodiment of the present invention. 
     In the first embodiment of the present invention, the switching power supply circuit structure  1   a  includes an input terminal  10 , an output terminal  20 , an input capacitor C 1 , an energy storage capacitor C 2 , a boost circuit  30 , and a second inductor L 2 . The input terminal  10  is configured to input an original power source having an input current Iin and is connected in parallel with an input capacitor C 1  for suppressing a voltage change of the input terminal  10 . The output terminal  20  has a positive terminal  21  and a negative terminal  22  for electrically connecting an external load (not shown) for outputting the processed power. The processed power has output current Io and output voltage Vo. The energy storage capacitor C 2  is electrically connected between the positive terminal  21  and the ground terminal G. The boost circuit  30  includes a first inductor L 1 , a switch component  40 , and a diode D. The switch component  40  is an active power element. In the first embodiment of the present invention, the switch component  40  is a MOSFET, but the present invention is not limited thereto. Specifically, one end of the first inductor L 1 , the switch component  40 , and the diode D are electrically connected to each other to form a common point  50 , and the switch component  40  is electrically connected between the common point  50  and the ground terminal G. The second inductor L 2  is electrically connected between the negative terminal  22  and the common point  50 , wherein the negative terminal  22  is not connected to the ground terminal G. The first inductor L 1  has an inductor magnetizing current IL  1 , and the second inductor L 2  has an inductor magnetizing current IL 2 . The switching power supply circuit structure  1   a  further includes an output capacitor C 3 , which has a function of stabilizing output voltage. 
     Next, please refer to  FIGS. 2A-2B , which are schematic diagrams showing the current path of operating the switching power supply circuit structure according to a first embodiment of the present invention. 
     In the first embodiment of the present invention, when the switch component  40  is turn on, as shown in  FIG. 2A , the diode D will be reverse bias to form turn off, and the first inductor L 1 , the switch component  40 , and the ground terminal G form a first series circuit S 1 , such that the power of the input terminal  10  flows through the first inductor L 1 , the switch component  40 , and the ground terminal G in sequence to charge the first inductor L 1 . Meanwhile, through the output terminal  20  and the switch component  40 , the energy storage capacitor C 2  forms a second series circuit S 2  such that the energy of the energy storage capacitor C 2  flows through the positive terminal  21 , the load and output capacitor C 3 , the negative terminal  22 , the second inductor L 2 , the switch component  40 , and the ground terminal G in sequence to charge the second inductor L 2 . 
     When the switch component  40  is turn off, as shown in  FIG. 2B , the diode D will be forward biased, and the first inductor L 1 , the diode D, the energy storage capacitor C 2 , and the ground terminal G form a third series circuit S 3 , such that the power of the input terminal  10  flows through the first inductor L 1 , the diode D, the energy storage capacitor C 2 , and the ground terminal G to discharge energy of the first inductor L 1  to the energy storage capacitor C 2 . Meanwhile, the second inductor L 2 , the diode D, and the output terminal  20  form a fourth series circuit S 4 , such that the second inductor L 2  through the diode D discharges energy to the output terminal  20 , output capacitor C 3  and the load. 
     Please refer to  FIG. 3 , which is a schematic diagram of a switching power supply circuit structure according to a second embodiment of the present invention. 
     In the second embodiment of the present invention, the switching power supply circuit structure  1   b  also includes an output terminal  20 , an input terminal  10 , an input capacitor C 1 , an energy storage capacitor C 2 , a boost circuit  30 , and a second inductor L 2 . The output terminal  20  has a positive terminal  21  and a negative terminal  22 . The input terminal  10  is connected in parallel with the input capacitor C 1 . Similarly, the boost circuit  30  includes a first inductor L 1 , a switch component  40 , and a diode D. One end of the first inductor L 1 , the switch component  40 , and the diode D are electrically connected to each other to form a common point  50 , and the switch component  40  is electrically connected between the common point  50  and the ground terminal G. However, one end of the second inductor L 2  in the second embodiment of the present invention is electrically connected to the positive terminal  21 , and the other end of the second inductor L 2  is electrically connected to the diode D and the energy storage capacitor C 2 ; the other end of the energy storage capacitor C 2  is electrically connected to the ground terminal G, wherein the negative terminal  22  is electrically connected to the common point  50 . The switching power supply circuit structure  1   b  also includes an output capacitor C 3 , which has a function of stabilizing output voltage. 
     Next, please refer to  FIGS. 4A-4B , which are schematic diagrams showing the current path of operating the switching power supply circuit structure according to a second embodiment of the present invention. 
     In the second embodiment of the present invention, when the switch component  40  is turn on, as shown in  FIG. 4A , the diode D will be reverse bias to form turn off, and the first inductor L 1 , the switch component  40 , and the ground terminal G form a first series circuit S 1 ′, such that the power of the input terminal  10  flows through the first inductor L 1 , the switch component  40 , and the ground terminal G to charge the first inductor L 1  . Meanwhile, the energy storage capacitor C 2  forms a second series circuit S 2 ′ through the output terminal  20  and the switch component  40 , such that the energy of the energy storage capacitor C 2  flows through the second inductor L 2 , the load, the output the capacitor C 3 , the switch component  40 , and the ground terminal G in sequence to charge the second inductor L 2 . 
     When the switch component  40  is turn off, as shown in  FIG. 4B , the diode D will be forward biased, and the first inductor L 1 , the diode D, the energy storage capacitor C 2 , and the ground terminal G form a third series circuit S 3 ′. Consequently, the power of the input terminal  10  flows through the first inductor L 1 , the diode D, the energy storage capacitor C 2  and the ground terminal G in sequence, such that the first inductor L 1  discharges energy to the energy storage capacitor C 2 . Meanwhile, the second inductor L 2 , the diode D, and the output terminal  20  form a fourth series circuit S 4 ′, such that the second inductor L 2  through diode D discharges energy to the output terminal  20 , output capacitor C 3  and the load. 
     Accordingly, regardless of the switching power supply circuit structure  1   a  or  1   b , when the switch component  40  is in an on or off state, the flow of current through the first inductor L 1  is maintained and the magnetizing current of the first inductor L 1  can be reduced. Also, when the switch component  40  is in an on or off state, the second inductor L 2  and the output capacitor C 3  are always connected in series or in parallel with the output terminal  20  to reduce the ripple current of the output terminal  20 . 
     For comparison with the prior art, wherein the input and output are the same, all parts are the same, and the switching frequency is the same, the input current Iin, the inductor magnetizing current IL, ILL IL 2 , the output current Io, and the output voltage Vo of the switching power supply circuit structure  1   a  or  1   b  of the present invention and that of the buck-boost converter of the prior art are shown in  FIGS. 5A and 5B . Now please refer to  FIGS. 5A-5B , which are waveform diagrams showing the related performances, wherein  FIG. 5A  is a waveform diagram showing the performance of a buck-boost converter in the prior art and  FIG. 5B  is a waveform diagram showing the performance of the switching power supply circuit structure of the present invention. 
     As can be seen from the comparison of the waveform diagrams in  FIGS. 5A-5B , the performance of the switching power supply circuit structure  1   a  or  1   b  of the present invention is superior to that of the prior art. For example, the input current Iin is not interrupted, and both the inductor magnetizing current IL 1  of the first inductor L 1  and the inductor magnetizing current IL 2  of the second inductor L 2  are smaller than the inductor magnetizing current IL of the prior art, thereby reducing the copper loss. The ripple of the output current Io in the present invention is smaller than that of the prior art, and a smaller output capacitor can be used under the same design specification to reduce the size of the output capacitor. 
     It should be noted that the embodiments of the present invention described above are only illustrative. To avoid unnecessary redundancy, not all of the possible combinations of changes are documented. However, it shall be understood by those skilled in the art that each of the modules or elements described above may not be necessary. For the implementation of the present invention, the present invention may also contain other detailed conventional modules or elements. Each module or component is likely to be omitted or modified depending on need. Other modules or elements may be included or excluded between any two modules without departing from the scope of the invention defined solely by the appended claims.