Abstract:
An integrated converter with single-ended control and power factor correction includes an input unit, a boost inductor, a voltage regulator, an energy-storing capacitor, a buck-boost converter, a single-ended switch and a control unit. The voltage regulator and the buck-boost converter share the single-ended switch and the control unit in order to correct power factor, reduce output ripple, simplify the complexity of circuit and decrease the number of components. The voltage regulator is utilized in reducing the frequency of switching and the conductive losses, thus improving overall performance. With the magnetic loop, the transformers of the boost inductor and the voltage regulator can be merged, and thus the efficiency of the whole spatial usage is increased and the noise interference is reduced.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a converter, and more particularly to an integrated converter with single-ended control, power factor correction (PFC), and low output ripple. 
       DESCRIPTION OF THE PRIOR ART 
       [0002]      FIG. 1  illustrates a traditional power-converting circuit, wherein the traditional power-converting circuit includes a rectifying circuit  91 , a PFC (power factor correction) circuit  92 , a DC (Direct Current) to DC converter  93 , an anterior controller  94 , and a posterior controller  95 . The PFC circuit  92  is coupled to and between the rectifying circuit  91  and the DC to DC converter  93 . 
         [0003]    The PFC circuit  92  is coupled to an AC (Alternating Current) source  90  through the rectifying circuit  91  so as to acquire an AC supply. The PFC circuit  92  includes a boost inductor  921 , a capacitor  922 , a diode  923 , and a switch  924 . 
         [0004]    The rectifying circuit  91  is coupled to an AC source  90 . The switch  924  is coupled to the output end of the rectifying circuit  91  through boost inductor. The capacitor  922  is connected in parallel to the switch  924 . The anterior controller  94  is coupled to the control end of the switch  924 , so as to control the conduction of the switch  924  and further control the storage voltage of the capacitor  922  by outputting a control signal. 
         [0005]    The converter  93  is coupled to the PFC circuit  92  and therefore gains a direct current. The converter  93  includes two windings  931 ,  932  located at the primary and secondary sides respectively and a switch  933 . The posterior controller  95  is coupled to the control end of the switch  933 , so as to control the conduction of the switch  933  by outputting a control signal. 
         [0006]    Therefore, the traditional circuit uses the anterior PFC circuit  92  to achieve the goal of boosting and modifying the power factor, while the posterior converter  93  uses the anterior circuit  92  to output voltage and proceed with voltage regulation so as to provide loading usage. Since the whole circuit needs to use two sets of transistor switches  924 ,  933  and controllers  94 ,  95 , the conductive losses will be greater. Furthermore, the voltage stress of the output capacitor  922  of the anterior circuit  92  increases with the boosting voltage. Hence, when considering the capacitor  922 , the capacitor with higher voltage must be chosen for safety purpose, which causing the increase of cost. Besides, also owning to generating higher output ripple, the output voltage will fluctuate more significantly, and the output voltage will be more unsteady, which may affect the posterior loading. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides an integrated converter, which merely utilizes a single controller at the posterior circuit (the buck-boost converter) without the need of the anterior-circuit controller (the voltage regulator). 
         [0008]    The present invention also provides an integrated converter with higher efficiency, more stable output voltage and lower cost. 
         [0009]    The present invention further provides an integrated converter which can lower the level of requirement concerning the voltage specification of the energy-storing capacitor of the anterior circuit. 
         [0010]    The integrated converter of the present invention includes an input unit, a boost inductor, a voltage regulator, an energy-storing capacitor, a buck-boost converter, a single-ended switch, and a control unit. The input unit receives the electric-power signal transmitted by a power source. The boost inductor is electrically coupled to the input unit. 
         [0011]    The voltage regulator includes a first diode, a second diode and a first transformer, wherein the voltage regulator is electrically coupled to the boost inductor through those diodes, and to the buck-boost converter through the first transformer. The first transformer includes a primary winding and a secondary winding. The secondary winding is electrically coupled to those diodes. The primary winding is electrically coupled to the buck-boost converter. The energy-storing capacity is electrically coupled to the boost inductor and the voltage regulator. 
         [0012]    The control unit is electrically coupled to the single-ended switch, while the single-ended switch is electrically coupled to the buck-boost converter, so as to optionally alter the induced electromotive force of the first transformer and further switch on the first diode or the second diode alternatively. 
         [0013]    In one preferred embodiment, the buck-boost converter includes a primary winding and a secondary winding. The primary winding of the buck-boost converter is electrically coupled to the primary winding of the voltage regulator. The integrated converter also satisfies the following relational expression: V + =V p1 +V c2 , wherein V +  denotes the input voltage of the buck-boost converter, V p1  denotes the induced voltage of the primary winding of the voltage regulator and V c2  denotes the divided voltage of the energy-storing capacitor. 
         [0014]    The induced electromotive force of the transformer of the voltage regulator can be altered by the single-ended switch, so as to switch on the diode components alternatively. Furthermore, the goal of exchanging the energy between the boost inductor and the energy-storing capacitor can be accomplished through switching on or off alternatively mentioned above. Owning to the fact that the voltage stress of the energy-storing capacitor varies with the input voltage, the capacitor components with lower voltage can be chosen and, therefore, cost can be saved. 
         [0015]    The buck-boost converter can further include a rectifying diode which is coupled to the secondary winding of the buck-boost converter. One end of the single-ended switch is coupled to the primary winding of the buck-boost converter. Another end of this is coupled to the control unit. The control unit can be a pulse-width-modulating controller, while the single-ended switch can be a transistor switch. The drain terminal of this is coupled to the primary winding of the buck-boost converter, the gate terminal of this is coupled to the control unit and the source terminal of this is grounded. 
         [0016]    In a preferred embodiment, the control unit can include a bridge rectifier, and can further include a filter capacitor. The filter capacitor is connected in parallel to the boost inductor. The input unit can further include an EMI (Electro-Magnetic Interference) filter, which is coupled to and between the power source and the bridge rectifier. 
         [0017]    In other preferred embodiments, the boost inductor and the first transformer of the voltage regulator are an integrated structure sharing common steel cores. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The primitive objectives and advantages of the present invention will become apparent upon reading the following description and upon reference to the accompanying drawings in which: 
           [0019]      FIG. 1  is a schematic diagram of a traditional power-converting circuit; 
           [0020]      FIG. 2  is a schematic diagram of an integrated converter with single-ended control possessing PFC in accordance with the present invention; 
           [0021]      FIG. 3  illustrates the circuit of an integrated converter with single-ended control possessing PFC in accordance with the first preferred embodiment of the present invention; and 
           [0022]      FIG. 4  is a schematic diagram of structural integration between the boost inductor and the transformer of the voltage regulator in accordance with the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    In order to fully understand the manner in which the above-recited details and other advantages and objects according to the invention are obtained, a more detailed description of the invention will be rendered by reference to the best-contemplated mode and specific embodiments thereof. The following description of the invention is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense; it is intended to illustrate various embodiments of the invention. As such, the specific modifications discussed are not to be construed as limitations on the scope of the invention. It will be apparent to one skilled in the art that various equivalents, changes, and modifications may be made without departing from the scope of the invention, and it is understood that such equivalent embodiments are to be included herein. The terminology used in the description presented below is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific embodiments of the invention. Certain terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this detailed description section. Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of items in the list. 
         [0024]    Preferred embodiments and aspects of the invention will be described to explain the scope, structures and procedures of the invention. In addition to the preferred embodiments of the specification, the present invention can be widely applied in other embodiments. 
         [0025]      FIG. 2  is the diagram of an integrated converter with single-ended control possessing PFC in accordance with the present invention. The FIG. illustrates that the integrated converter with single-ended control possessing PFC mainly includes an input unit  11 , a boost inductor  12 , a voltage regulator  13 , an energy-storing capacitor  14 , a buck-boost converter  15  and a control unit  161  along with a single-ended switch  162 . The input unit  11  is used to receive the electric-power signal transmitted by a power source  10 , for example, an alternating current supply. 
         [0026]    The input unit  11  is coupled to and between the power source  10  and the boost inductor  12 . The voltage regulator  13  is coupled to the boost inductor  12  on one hand, and also to the energy-storing capacitor  14  on the other hand. The buck-boost converter  15  is coupled to the output of the voltage regulator  13  in order to receive the regulated electrical-signals, and the control unit  161  is coupled to the buck-boost converter  15  through the single-ended switch  162  so as to control the energy exchange between the boost inductor  12  and the energy-storing capacitor  14 . 
         [0027]    Alternatively, the voltage regulator  13  includes a first diode  131 , a second diode  132  and a first transformer T 1 . The voltage regulator  13  uses those diodes  131 ,  132  to be electrically coupled to the boost inductor  12 , and uses the first transformer T 1  to be electrically coupled to the buck-boost converter  15 . The first transformer T 1  includes a primary winding  133  and a secondary winding  134 . The secondary winding  134  is electrically coupled to those diodes  131 ,  132 . The primary winding  133  is electrically coupled to the buck-boost converter  15 , wherein the two diodes  131 ,  132  is coupled in parallel. 
         [0028]    The state of the voltage regulator  13  can be switched by the operation of the control unit  16 . That is, the induced electromotive force of the first transformer T 1  can be altered, thus optionally causing one of the two situations as follows: the first diode  131  is in a conductive state when the second diode  132  is not, or the other way around. 
         [0029]      FIG. 3  illustrates the circuit of the first embodiment in accordance with the present invention.  FIG. 2  is also provided to more clearly and specifically demonstrate the circuit of the integrated converter with single-ended control and PFC of the present invention. 
         [0030]    In the embodiment, the input unit  11  includes an EMI filter  111 , a bridge rectifier  112  and a filter capacitor  113 . The EMI filter  111  is coupled to the input end of the bridge rectifier  112  on one hand, and to the power source  10  on the other hand so as to transmit electrical-signal energy to the bridge rectifier  112 . 
         [0031]    Both the filter capacitor  113  and the boost inductor  12  are connected in series to the bridge rectifier  112 , while the filter capacitor  113  is connected in parallel to the boost inductor  12 . One end of the filter capacitor  113  is grounded. The filter capacitor  113  can filter the alternating component of the current from the boost inductor  12  and eliminate high-frequency noise. 
         [0032]    One end of the boost inductor  12  is coupled to the input of the bridge rectifier  112 , when another end of this is coupled to the first diode  131  and the second diode  132 . One end of the energy-storing capacitor  14  is grounded, while another end of this is coupled to the first transformer T 1 . 
         [0033]    The buck-boost converter  15  includes a second transformer T 2 , a rectifying diode  153  and a capacitor  154 . The primary side of the second transformer T 2  is set with a primary winding  151 , and the secondary side with a secondary winding  152 . The primary winding  151  of the buck-boost converter  15  is electrically coupled to the primary winding  133  of the voltage regulator  13 . One end of the rectifying diode  153  is coupled to the secondary winding  152  of the buck-boost converter  15 , and another end of this is coupled in series to the capacitor  154 . 
         [0034]    One end of the single-ended switch  162  is coupled to the primary winding  151  of the buck-boost converter  15 , and another end of this is coupled to the control unit  161 . The control unit  161  can be a pulse-width-modulating controller. The single-ended switch  162  can be a transistor switch. The drain terminal of the single-ended switch  162  is coupled to the primary winding  151  of the buck-boost converter  15 , the gate terminal of this is coupled to the control unit  161  and the source terminal of this is grounded through a transistor  163 . 
         [0035]    The pulse-width-modulating controller will send a control signal so as to control the single-ended switch  162 . That is, when the single-ended switch  162  is in a conductive state, an electrical signal will pass through the boost inductor  12 , the first diode  131 , the first transformer T 1  and the second transformer T 2  in sequence. Energy will eventually be output from the buck-boost converter  15 . When the single-ended switch  162  is in a non-conductive state, instead of being transmitted from the first transformer T 1  to the second transformer T 2 , the electrical signal will be transmitted through the boost inductor  12 , the second diode  132  and the energy-storing capacitor  14 . The two operation modes are equivalent to the circumstance that the boost inductor  12  cooperates with the energy-storing capacitor  14  on energy-storing and energy-releasing. 
         [0036]    In another embodiment, the circuit possesses a relational expression as follows: V + =V p1 +V c2 , wherein V +  denotes the input voltage of the buck-boost converter  15 , V p1  denotes the output voltage of the primary winding  133  of the voltage regulator  13 , V c2  denotes the divided voltage of the energy-storing capacitor  14 . By adjusting the ratio of winding turns on the two sides of the first transformer T 1  of the voltage regulator  13 , the output voltage V p1  of the primary side thereof can be controlled, thus controlling the input voltage V +  of the buck-boost converter  15 . 
         [0037]    Therefore, the circuit structure of the present invention features the fact that the anterior and the posterior circuits (the voltage regulator and the buck-boost converter) share a single control unit while the function of PFC can exactly be performed and, in consequence, the complexity of circuit can be simplified while the number of required components can be reduced. Particularly as a consequence of this, the frequency of switching and the conductive losses of the anterior switch (the voltage regulator) can be reduced and, therefore, the whole efficiency of circuit can be increased. 
         [0038]    Further, more general switch components can be selected as the only single-ended switch in use by an appropriate adjustment to the output voltage of the voltage regulator. Under the specially corresponding relationship mentioned above, the voltage stress of the energy-storing capacitor varies with the increase of input voltage, instead of the discrepancy of transforming voltage (that is, the discrepancy between V p1  and V s1  in accordance with the ratio of winding turns) caused by the voltage regulator. Consequently, the options for the voltage specification of the energy-storing capacitor are more flexible in comparison with those in the prior art, that is, the lower-voltage specification can be selected. Besides, the output ripple with lower magnitude can be produced, so the fluctuation of output voltage will be smaller and steadier output voltage can thus be provided for the posterior loading. 
         [0039]    The voltage regulator and the buck-boost converter share a single switch and a control unit to achieve the goal of correcting power factor, simplifying the complexity of circuit and decreasing the number of components. 
         [0040]    In a preferred embodiment, those two magnetic components, the boost conductor  12  and the first transformer T 1  of the voltage regulator, can be considered to merge and share a set of steel cores, thus achieving structural integration as can be seen in  FIG. 4 . By this, the efficiency of spatial usage of applied products can be increased and, at the same time, the noise interference can be decreased. 
         [0041]    The foregoing description, for purposes of explanation, was set forth in specific details of the preferred embodiments to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that specific details are not required in order to practice the invention. Therefore, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description only and should not be construed in any way to limit the scope of the invention. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed; obviously, many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following Claims and their equivalents define the scope of the invention. 
         [0042]    The above-described embodiments of the present invention are intended to be illustrative only. Numerous alternative embodiments may be devised by those skilled in the art without departing from the scope of the following claims.