Abstract:
The invention relates to an energy transfer circuit. The energy transfer circuit has a first electromagnetic induction device, electrically connected to a first power supply node; a first switch circuit for connecting the first electromagnetic induction device and a second power supply node according to a first control signal; a snubber electrically connected between the first electromagnetic induction device and the second power supply node; a second electromagnetic induction device, coupled to the first electromagnetic induction device and electrically connected to the snubber and the second power supply node; and a third electromagnetic induction device coupled to the first and second electromagnetic induction devices and electrically connected to an output port of the energy transfer circuit.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to an energy transfer circuit, and more particularly, to an energy transfer circuit capable of generating a wanted signal through utilizing a snubber to reduce power consumption and an electronic induction device to reuse energies stored inside the snubber. 
         [0003]    2. Description of the Prior Art 
         [0004]    A voltage converter is a necessary component in modern electronic products. Voltage converters are mainly utilized for adjusting the voltage inputted into an electronic product according to the required operational voltage of other components of the electronic product. For example, a normal hub operates with a 9V adapter. The 9V adapter is utilized to convert an AC voltage into a 9V DC voltage. Furthermore, because the operational voltage of an IC inside the hub is often 5V or 3V, a voltage converter should be set up inside the hub to convert the inputted 9V DC voltage into 5V or 3V voltage, which can then be utilized by the IC. 
         [0005]    Please refer to  FIG. 1 , which is a diagram of a conventional voltage converter  10 . As shown in  FIG. 1 , the voltage converter  10  is a flyback converter. The voltage converter  10  includes: a voltage source  12 ; two electronic induction devices  14 ,  16 ; a switch device  18 ; two diodes  28 ,  22 ; a capacitor  24 ; and a resistor  26 . The switch device  18  is turned on according to a control signal Sc. As the control signal Sc is a periodical signal, the switch device  18  is also turned on periodically. When the switch device  18  is turned on, the voltage source  12 , the electronic induction device  14 , and the switch device  18  form a loop. At this time, one end (the node A) of the electronic induction device  14  is electrically connected to the voltage source, and the other end (the node B) is electrically connected to ground through the switch device  18 . For the electronic induction devices  14  and  16 , the node A and the node D correspond to the same polarization, and the node B and the node C correspond to the same polarization. Therefore, the voltage level of the node D is higher than that of the node C. The current cannot pass through the diode  28  because the diode  28  is not forward biased. In other words, when the switch device  18  is turned on, the power provided by the voltage source  12  is stored in the electronic induction device  14 . When the switch device  18  is turned off, the current passing through the switch device  18  is reduced to zero. This means that the current passing through the electronic induction device  14  is similarly reduced to zero. Therefore, according to the theory of electronic induction reaction, the voltage level of the node D is lower than that of the node C such that the diode  28  becomes conductive. The electronic induction device  16  releases the power, which is previously provided by the voltage source  12 , through the diode  18  to the load between nodes E and F. From the above, it can be seen that if the switch device  18  is repeatedly and periodically turned on and off, a steady output voltage between the node E and F can be provided. Furthermore, in the prior art, the electronic induction devices  14  and  16  are two induction coils of a transformer. The voltage converter  10  can therefore change the duty cycle of the switch device  18  and the ratio of turns of the electronic induction devices  14 ,  16  such that the output voltage Vo can be adjusted. 
         [0006]    In an actual application, however, the switch device  18  is not an ideal device, and the electronic induction devices  14  and  16  have leakage inductance. At the time of switching the switch device  18  (this means the procedure where the switch device  18  is switched from a conductive state into a non-conductive state) and before the diode  28  is completely conductive, the above-mentioned leakage inductance generates a huge inducted voltage because the current reduces spontaneously. Furthermore, the inducted voltage generated by the leakage inductance, the inducted voltage generated by the electronic induction device  14 , and the voltage V in  provided by the voltage source  12  are series-connected such that an extreme voltage difference is formed on two ends of the switch device  18 . The above-mentioned extreme voltage difference and the current, which reduces during the switching procedure of the switch device  18 , consume a huge power, known as a turn off loss shown as the slope line region of  FIG. 2 . Please note that, in  FIG. 2 , I Q  represents the current passing through the switch device  18 , V Q  represents the voltage difference on the two ends of the switch device  18 , and the area of the slope line region is equal to the product of I Q  and V Q . Therefore, the conventional voltage converter  10  further includes a diode  22 , a capacitor  24 , and a resistor  26 . In the procedure of switching the switch device  18  from the conductive state into the non-conductive state, the voltage difference on the two ends of the switch device  18  turns on the diode  22 . Therefore, the diode  22  and the capacitor  24  form another current path to obtain currents such that the capacitor  24  is charged. In other words, the capacitor  24  can reduce the variance of the voltage difference V Q  on the two ends of the switch device  18 , decreasing the turn off loss. In addition, after the switch device  18  is turned on, the diode  22  cannot be forward biased. At this time, the energies stored in the capacitor  24  are consumed by the resistor  26 . 
         [0007]    From the above disclosure, for the conventional voltage converter  10 , the power stored inside the capacitor  24  is consumed by the resistor instead of being utilized. Therefore, the utilization rate of the power of the conventional voltage converter  10  is not good. 
       SUMMARY OF THE INVENTION 
       [0008]    It is therefore one of the primary objectives of the claimed invention to provide a energy transfer circuit capable of generating a wanted signal through utilizing a snubber to reduce power consumption and utilizing an electronic induction device to reuse energies stored inside the snubber, to solve the above-mentioned problem. 
         [0009]    According to an exemplary embodiment of the claimed invention, an energy transfer circuit is disclosed. The energy transfer circuit comprises: a first electronic induction device comprising a first end and a second end, wherein the first end of the first electronic induction device is electrically connected to a first power supply node; a first switch device, electrically connected to the second end of the first electronic induction device, for selectively establishing an electrical connection between the second end of the first electronic induction device and a second power supply node according to a first control signal; a snubber, electrically connected between the second end of the first electronic induction device and the second power supply node; a second electronic induction device, coupled to the first electronic induction device, the second electronic induction device comprising a first end and a second end, wherein the first end of the second electronic induction device is electrically connected to the snubber, and the second end of the second electronic induction device is electrically connected to the second power supply node; and a third electronic induction device, coupled to the first electronic induction device and the second electronic induction device, the third electronic induction device comprising a first end and a second end, wherein the second end of the third electronic induction device is electrically connected to an output port of the energy transfer circuit. 
         [0010]    According to another exemplary embodiment of the claimed invention, a energy transfer circuit is disclosed. The energy transfer circuit comprises: a first electronic induction device, comprising a first end and a second end, wherein the first end of the first electronic induction device is electrically connected to a first power supply node; a first switch device, electrically connected to the second end of the first electronic induction device, for selectively establishing an electrical connection between the second end of the first electronic induction device and a second power supply node according to a first control signal; a snubber, electrically connected between the second end of the first electronic induction device and the second power supply node; a second electronic induction device, comprising a first end and a second end, wherein the first end of the second electronic induction device is electrically connected to the snubber, and the second end of the second electronic induction device is electrically connected to the second power supply node; a third electronic induction device, coupled to the first electronic induction device, the third electronic induction device comprising a first end and a second end, wherein the second end of the third electronic induction device is electrically connected to a first output port of the energy transfer circuit; and a fourth electronic induction device, coupled to the second electronic induction device, the fourth electronic induction device comprising a first end and a second end, wherein the second end of the fourth electronic induction device is electrically connected to a second output port of the energy transfer circuit. 
         [0011]    The present invention power converter can utilize a snubber to reduce the turn off loss during the procedure of switching the switch devices, and feedback the energies stored in the snubber to another electronic induction device in order to generate wanted signals. Therefore, the present invention power converter can have a better power utilization rate. 
         [0012]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a diagram of a conventional voltage converter  10 . 
           [0014]      FIG. 2  is a diagram illustrating turn off loss according to the prior art. 
           [0015]      FIG. 3  is a diagram of a power converter of a first embodiment according to the present invention. 
           [0016]      FIG. 4  is a diagram of a snubber shown in  FIG. 3  of an embodiment according to the present invention. 
           [0017]      FIG. 5  is a diagram of an output module shown in  FIG. 3  of a first embodiment according to the present invention. 
           [0018]      FIG. 6  is a diagram of an output module shown in  FIG. 3  of a second embodiment according to the present invention. 
           [0019]      FIG. 7  is a diagram of an output module shown in  FIG. 3  of a third embodiment according to the present invention. 
           [0020]      FIG. 8  is a diagram illustrating the turn off loss of the power converter according to the present invention. 
           [0021]      FIG. 9  is a diagram of a power converter of a second embodiment according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Please refer to  FIG. 3 , which is a diagram of a power converter  100  of a first embodiment according to the present invention. In this embodiment, the power converter  100  includes a voltage source  102 , a plurality of electronic induction devices  104 ,  106 , and  122 , a plurality of switch devices  108  and  124 , a snubber  110 , and an output module  111 . The snubber  110  is utilized to reduce the power consumption (the turn off loss) of switching the switch device  108  from the conductive state into the non-conductive state. As shown in  FIG. 4 , in an embodiment, the snubber  1   10  can be formed by a diode  112  and a capacitor  114  (coupled between the node N 10  and N 11 ). Please note that the circuit of the snubber  110  is only utilized as an embodiment, not a limitation of the present invention. In this embodiment, the output module  111  is utilized to generate a wanted signal according to the voltage difference between the node N 3  and the node N 4 , which is established by the electronic device  106 . The output module  111  outputs the signal to the following circuit through the nodes N 5  and N 6 . Furthermore, the output module  111  can have different circuit structures according to different design demands (e.g. DC output or AC output) of the power converter  100 . As shown in  FIG. 5 , a first embodiment of the output module  111  can be formed by a diode  126 , which is used as a commuter to make the voltage level of the node N 5  always larger than the voltage level of the node N 6 . That is, the power converter  100  shown in  FIG. 5  can be utilized to output DC signals to the following circuits. In addition, as shown in  FIG. 6 , a second embodiment of the output module  111  can be formed by a capacitor  127  and a resistor  128 , for performing a waveform adjustment. For example, if the voltage between the nodes N 3  and N 4  corresponds to a square wave, the voltage between the nodes N 5  and N 6  corresponds to a sine wave. Moreover, as shown in  FIG. 7 , a third embodiment of the output module  111  can be formed by a resistor  129 . At this time, the output module  111  can be regarded as a loading, and have no waveform adjustment or current commutation functions. That is, if the voltage between the nodes N 3  and N 4  corresponds to a square wave, the voltage between the nodes N 5  and N 6  corresponds to a square wave too. Similarly, please note that the circuit structures of the output module  111  shown in  FIGS. 5-7  are only utilized as embodiments, and not limitations of the present invention. 
         [0023]    The electronic induction device  122  is utilized for reusing the energies stored inside the snubber, in order to raise the power utilization rate. In order to clearly illustrate the function and the operation of the electronic induction device  122 , the power converter  100  is utilized as an application of a flyback converter for an illustration. In addition, the output module  111  shown in  FIG. 3  is implemented as the circuit structure shown in  FIG. 5 . The snubber  110  shown in  FIG. 3  is implemented as the circuit structure shown in  FIG. 4 . The nodes N 1 , N 4 , and N 8  correspond to the same polarization, and the nodes N 2 , N 3 , and N 9  correspond to another polarization. 
         [0024]    The power converter  100  output a predetermined DC voltage through the nodes N 5  and N 6  for an external circuit (not shown) to use. As shown in  FIG. 3 , the control signal Sc is utilized to simultaneously control the switch devices  108  and  124 . When the switch device  108  is turned on to be conductive, the voltage source  102  provides a current from the power supply node n 1  into the electronic induction device  104  and the switch device  108 , and finally flows to ground through the power supply node n 2 . At this time, the two ends of the electronic induction device  104  have a voltage difference V 1 , which is almost equal to the input voltage V in  of the voltage source  102 . Because the switch device  108  connects one end of the electronic induction device  104  to ground, the diode  112  (shown in  FIG. 4 ) is not conductive because the diode is not forward biased. This means that there is no current passing through the diode  112 . Moreover, from the above illustration of the conventional voltage converter  10 , it is easily seen that there is no current passing thorough the diode  126  inside the output module  111 . 
         [0025]    Furthermore, from the above illustration of the conventional voltage converter  10 , during the procedure of switching the switch device  108  from the conductive state into the non-conductive state, when the diode  126  (shown in  FIG. 5 ) is not completely conductive, the current passing through the electronic induction device  104  is inputted to the capacitor  114  of the snubber  110  through the diode  112 . Therefore, the energies carried by the current are stored inside the capacitor  114 . Because the voltage between the node N 10  and N 11  of the capacitor  114  (the voltage between the nodes N 2  and N 7  of the switch device  108 ) rises slowly, the turn off loss caused by the switch device  108  can be reduced. Please note that, in  FIG. 8 , I ds  represents the current passing through the switch device  108 , V c  represents the voltage between the two ends of the capacitor  114 , and the area of the slope line region represents the product of I ds  and V c . 
         [0026]    When the switch devices  108  and  124  are tuned on again, the diode  112  becomes non-conductive. Therefore, the capacitor  114  and the electronic induction device  112  form a current path. At this time, the energies stored inside the capacitor  114  are transferred to the electronic induction device  122  such that a voltage is established between the two ends of the electronic induction device  122 . Because the electronic induction device  122  and the electronic induction devices  104  and  106  are coupled, when the diode  126  is conductive, the energies stored inside the electronic induction device  122  are also coupled to the electronic induction device  104 . That is, the electronic induction device  106  generates an inducted voltage according to the electronic induction devices  104  and  122 , and the amplitude of the inducted voltage is related to the turn ratio among the electronic induction devices (field inductors) and the duty cycle of the switch devices  108  and  124 . In other words, the present invention can control the output DC voltage through setting the turns of the electronic devices  104 ,  106 , and  122 , and the duty cycle of the control signal Sc. 
         [0027]    From the above disclosure, when the control signal Sc periodically changes its state, the voltage source  12  repeatedly charges the electronic induction device  104 , the snubber  110  also periodically absorbs the turn off loss of the switch device  108 , and the electronic induction device  122  further reuses the energy absorbed by the snubber  110  such that the efficiency of the voltage converter can be raised. Please note that, in this embodiment, the electronic induction devices  104 ,  106 , and  122  are composed of at least one induction coil. In order to have better efficiency, the electronic induction device  104 ,  106 , and  112  can share the same iron core (obviously, the core can be formed by other conductors). Therefore, the electronic induction devices  104 ,  106 , and  122  can be regarded as a voltage transformer. In addition, the present invention power converter  100  can be utilized not only in an application of a flyback converter, but also in a forward converter, an isolated converter, or other power converters in the form of a voltage transformer. For example, users can determine the corresponding relationships of the polarizations of the nodes N 1 , N 2 , N 3 , N 4 , N 8 , and N 9  such that the voltage converter can have different configurations. 
         [0028]    Please refer to  FIG. 9 , which is a diagram of a power converter  200  of a second embodiment according to the present invention. The power converter  200  shown in  FIG. 9  is similar to the power converter  100  shown in  FIG. 3 . The main difference between the power converter  100  and the power converter  200  is that the power converter  200  further includes an electronic induction device  222  and an output module  211 . Please note that the operation and the function of the other components inside the power converter  200  have been illustrated in the above disclosure, and are thus omitted here. In addition, the electronic induction device  122  is coupled with the electronic induction device  222  instead of the electronic induction devices  104  and  106  shown in  FIG. 3 . Therefore, the energies stored inside the electronic induction device  122  are transferred back to the electronic induction device  222  (in this embodiment, the electronic induction devices  122  and  222  form a voltage transformer, and the electronic induction devices  104  and  106  form another voltage transformer). The output module  211  then generates wanted signals according to the voltage difference between the nodes Ml and M 2  of the electronic induction device  222 , and outputs the signals to the following circuit. In this embodiment, the output module  211  can be implemented by the circuit structures shown in  FIGS. 5-7 . Please note that, in the power converter  200 , the circuit structure of the output module  211  is not limited to the circuit structures shown in  FIGS. 5-7 . In addition, because the energies stored inside the electronic induction device  122  are not transferred to the electronic induction device  106 , the power converter  200  can establish another output signal (an AC signal or a DC signal) through utilizing the electronic induction device  222 . For example, the output module  111  is utilized to provide a 5V DC voltage and the output module  211  can be utilized to provide a 3V DC voltage. 
         [0029]    In contrast to the prior art, the present invention power converter can utilize a snubber to reduce the turn off loss during the procedure of switching the switch devices, and feedback the energies stored in the snubber to another electronic induction device in order to generate wanted signals. Therefore, the present invention power converter can have a better power utilization rate. 
         [0030]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.