Abstract:
A full bridge oscillation resonance high power factor invertor being connected between a power source and a Load has a first inductor and a second inductor. The first and second inductors are respectively connected to a full bridge inverting circuit. The full bridge inverting circuit is connected parallelly to an energy storing capacitor. The present invention integrals conventional multiple stages invertor/convertors as a signal stage which is low cost and provides a very high transforming efficiency. The two inductors share current Loaded of the invertor, the invertor is able to provide a high power transforming performance. Switches of the full bridge inverting circuit all switch under zero voltage to reduce switching loss of the full bridge inverting circuit.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    The present invention relates to a full bridge oscillation resonance high power factor invertor. 
         [0003]    2. Description of the Related Art 
         [0004]    Power factor correction circuit has been studied and lots of programs/devices have been realized recently. One of the most commonly used circuits is two-stage hard-switching high power factor invertor that is shown as  FIG. 12 . In the prior art, the said “hard-switching” means that two ends of a switching circuit in the invertor kept a non-zero voltage drop during a switching process which generates a significant loss during the switching process. Conventional two-stage high power factor invertor regularly required two stages circuit. One of the two stages circuit is used for power factor correction and the other one is used for DC/AC conversion. On the other hand, heat dissipation problems of the switches are also one of the key issues to limits the performance outcome of the conventional invertor. Furthermore, an output power of the conventional invertor is limited since there has normally only one inductor is used and is very easy saturated under a high power operation, a limited average current waveform of the inductor is shown as  FIG. 13 . 
       SUMMARY OF THE INVENTION 
       [0005]    The primary objective of the present invention is to provide a full bridge oscillation resonance high power factor invertor to obviate and overcome short comings of the prior art and to achieve a high performance invertor. To solve the aforementioned problems or shortcomings in the prior art, a full bridge oscillation resonance high power factor invertor is provided in the present invention. The full bridge oscillation resonance high power factor invertor is connected between a power source and a Load, the invertor comprising a first inductor, a second inductor, a full bridge inverting circuit, a resonant circuit, and an energy storing capacitor, wherein the first and second inductors are respectively connected between the full bridge inverting circuit and the power source. The full bridge inverting circuit has four active switching units for being switched under a zero voltage. The energy storing capacitor and the full bridge inverting circuit are parallelly connected. The resonant circuit is connected to the Load in series and is connected to the full bridge inverting circuit. 
         [0006]    The invertor further comprises a power rectifying circuit for filtering the current from the power source. The power rectifying circuit includes a rectifying capacitor parallelly connected to the power source and a rectifying inductor being connected in serial between the rectifying capacitor. 
         [0007]    The advantages of the present invention are described as below. 
         [0008]    (1). The present invention is a single-stage high power factor correction circuit having simplified circuit structure and resolves the problem of conventional inefficient two-stage circuit. 
         [0009]    (2). The four active switching units of the full bridge inverting circuit is also provide a single state power factor correction, improves the problem of power factor, and makes the energy storing capacitor not easy to be saturated by using two inductors to share the current inputted to the converter and capable to be used in high power output circuit. 
         [0010]    (3). The switch element of the present invention functions zero voltage switching to decrease switch loss, improve circuit efficiency, and reduce heat generated from the switch element. 
         [0011]    (4). The circuit scheme of the present invention functions to convert the low frequency power to high frequency power and decrease the interference of high order harmonic generation; and the circuit scheme of the present invention functions to DC/AC and further adds two inductors to perform high power factor power input operation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a circuit schematic diagram of a first embodiment of a full bridge oscillation resonance high power factor invertor in accordance with the present invention; 
           [0013]      FIG. 2  is a circuit diagram of the first embodiment of the full bridge oscillation resonance high power factor invertor in accordance with the present invention; 
           [0014]      FIG. 3  is a voltage and current waveforms of some circuit elements in accordance with the present invention; 
           [0015]      FIG. 4  is a current waveform and composition waveform diagram of the two inductors in accordance with the present invention; 
           [0016]      FIG. 5  a voltage or current waveform diagram of main elements of the circuit in accordance with the present invention; 
           [0017]      FIGS. 6 and 7  are respectively an operation schematic drawing of the switches S 1  and S 4  of the circuit while switching ON in accordance with the present invention; 
           [0018]      FIG. 8  is an operation schematic drawing of the switches S 1  and S 4  of the circuit while switching OFF in accordance with the present invention; 
           [0019]      FIG. 9  and  FIG. 10  are respectively an operation schematic drawing of the switches S 2  and S 3  of the circuit while switching ON in accordance with the present invention; 
           [0020]      FIG. 11  is an operation schematic drawing of the switches S 2  and S 3  of the circuit while switching OFF in accordance with the present invention; 
           [0021]      FIG. 12  is a conventional two-stage hard-switching high power factor invertor of the prior art; and 
           [0022]      FIG. 13  is a current waveform of the prior art. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
         [0024]    With reference to  FIG. 1 , a circuit schematic diagram of a first prefer embodiment of a full bridge oscillation resonance high power factor invertor in accordance with the present invention comprises a switching converter and current converter being integrally connected and having two inductors to share a input current of the invertor to solving a current saturation problem which leading to a output power limitation caused by using one inductor in the prior art. A higher power output was achieved in the present embodiment by using two inductors in the invertor. 
         [0025]    With reference to  FIG. 2 , the single-stage high power factor invertor in the present embodiment is connected with a power source (AC) and a Load (Load). The single-stage high power factor invertor comprises a first inductor L 1 , a second inductor L 2 , a full bridge inverting circuit S 1 ˜S 4  and D 1 ˜D 4 , a resonant circuit C 3  and L 4 , and an energy storing capacitor C 1 . The first inductor L 1  and the second inductor L 2  are respectively connected between the full bridge inverting circuit S 1 ˜S 4  and D 1 ˜D 4  and a power rectifying circuit. The full bridge inverting circuit is parallelly connected to the energy storing capacitor C 1  and the energy storing capacitor C 1  is used to store/discharge energy in the circuit. 
         [0026]    The power rectifying circuit is connected in parallel between the power source and the single-stage high power factor invertor and is used for initially rectifying AC power outputted from the power source. The power rectifying circuit comprises a rectifying capacitor C 2  being parallelly connected to the power source, a rectifying inductor L 2  being serially connected to the power source and a bridge rectified diode D 5 . The bridge rectified diode D 5  is used for initially rectifying an AC power from the power source (AC) for the single-stage high power factor invertor. The rectifying circuit is not limited thereto and those who skilled in the art are able to select any one of elementary rectifying circuit to perform the filtering, rectifying, and protecting the circuit. 
         [0027]    The full bridge inverting circuit has four active switching units in full-bridge connection, and each active switching unit comprises a switch element and a diode being parallelly connected to each other. The parallelly connected diode and the switch element may be performed by a MOSFET with an embedded diode, or a FET without the embedding diode (such as BJT) connecting parallelly to an external diode. In other words, each active switching unit is equivalently comprising parallelly connected the diode and the switch element, which means the equivalent circuit of the four switch elements in full-bridge connection is including a first diode D 1 , a second diode D 2 , a third diode D 3 , and a fourth diode D 4  connected in turn. Cathodes and anodes of the first diode D 1  and the second diode D 2  are respectively connected with each other. Cathodes and anodes of the third diode D 3  and the fourth diode are respectively connected with each other. The first diode D 1  and the third diode D 3  are connected in series, and the second diode D 2  and the fourth diode D 4  are connected in series. Each diode D 1 ˜D 4  is parallelly connected one of the witch element S 1 ˜S 4  respectively. The first diode D 1  and the switch element S 1  are connected in parallel, the second diode D 2  and the switch element S 2  are connected in parallel, the third diode D 3  and the switch element S 3  are connected in parallel, and the fourth diode D 4  and the switch element S 4  are connected in parallel. 
         [0028]    The first inductor L 1  has a first end and a second end. The first end of the first inductor L 1  is connected to a connecting node of the first diode D 1  and the third diode D 3 . The second end of the first inductor L 1  is connected to the rectified diode D 5 . The second inductor L 2  has two ends. The two ends of the second inductor L 2  are respectively connected to a connecting node of the second diode D 2  and the fourth diode D 4  and the rectified diode D 5 . Two end of the energy storing capacitor C 1  are respectively connected to a connecting node of the third diode D 3  and the fourth diode D 4  and a node of the anodes of the first diode D 1  and the second diode D 2 . 
         [0029]    In the present embodiment of the present invention, the Load is serially connected to the resonant circuit L 4 , C 3 . The serially connected Load and the resonant circuit L 4 , C 3  is connected between nodes of the first diode D 1  and the third diode D 3  and the second diode D 2  and the fourth diode D 4 . The resonant circuit of the present embodiment is designed to operate in inductive Load characteristics to make each switch element S 1 ˜S 4  of the full bridge inverting circuit worked under zero-voltage switching and thus to reduce the loss during switching process. 
         [0030]    In the embodiment of the present invention, the four switch elements S 1 ˜S 4  of the full bridge inverting circuit works as a DC/AC conversion to the Load. The switch elements S 1 ˜S 4  are triggered symmetrically, that is, the switch elements S 1  and S 4  are switched ON synchronously and the switch elements S 2  and S 3  are switched ON synchronously. The switch elements S 1  and S 2  (or S 3  and S 4 ) are alternatively switched ON. Trigger waveforms to the switch elements S 1 □S 4  are shown in  FIG. 3 . V gs1 , V gs2 , V gs3 , and V gs4  are respectively trigger signals to switch the switch elements S 1 ˜S 4  ON and OFF. The current flowed through the first inductor L 1 , L 2  are respectively noted as i L1  and i L2 . With refer to  FIG. 3 , the switch elements S 1  and S 2  is alternatively switched ON with a dead time period (or delay time) and lead the first and second inductor L 1  and L 2  respectively to operate discontinuously. The dead time period is set for preventing the switch elements S 1  and S 4  (or switching elements S 2  and S 3 ) being switched on simultaneously. Besides, the diodes D 2 , D 3  and diodes D 1 , D 4  are switching ON first before switching ON the switch elements S 2 , S 3  and switch elements S 1 , S 4 ,. The switch elements S 2 , S 3  and switch elements S 1 , S 4  work under zero voltage switching to reduce the heat generation of the switch elements. 
         [0031]    With further reference to  FIGS. 4 and 5 , an output current i RO  and an output peak current i ROP  of the present embodiment is achieved by the arrangement of alternatively switching ON. Since inductive currents (i L1  and i L2 ) of the first inductor L 1  and the second inductor L 2  have a phase difference therein and are compensate in waveform to each other (the inductive current i L1  of the first inductor L 1  is indicated by a solid line, and the inductive current i L2  of the second inductor L 2  is indicated by a dashed line), the sum of the inductive currents, i.e. the output current i RO , is then very close to a sine wave without any processing. Therefore, a high-frequency noise in the output current i RO  may be very easy to be removed which is reducing complexity of circuit design in the present embodiment.  FIG. 5  shows the voltage or current waveforms of the key elements of the circuit. V AC  is referred to the voltage between two ends of the power source. V RO  and i RO  are respectively referred to the voltage and the current of the output side of the rectifying circuit. i S  is referred to the input current of the AC power source after being filtered. i AC  is referred to the input current of the AC power source before filtering. The operation sequence of the single-stage high power factor invertor in the present embodiment is illustrated as  FIGS. 6 to 11  and is described as below. 
         [0032]    (1) With reference to  FIG. 6 , the switch elements S 1  and S 4  are switched ON, the first inductor L 1  is start to storing energy, the second inductor L 2  may charge the energy storing capacitor C 1  via the switch element S 2  or the fourth diode D 4  or discharge energy via the resonant circuit, and current going through Voltage VL is passed through the switch elements S 4  and S 1 , where VL=VC. 
         [0033]    (2) With reference to  FIG. 7 , the switch elements S 1  and S 4  keep being switched ON, the first inductor L 1  keeps storing energy, the inductive current of the second inductor L 2  is discharging energy though the switch element S 4 , and the current going through voltage VL is passed through diodes D 3  and D 2 , where VL=−VC. 
         [0034]    (3) With reference to  FIG. 8 , the switch elements S 1  and S 4  are switched OFF, the circuit is in a dead time, the current is discharging the energy storing capacitor C 1  via the first inductor L 1  and third diode D 3  in turn, and the current is flowed through diodes D 3  and D 2  via Load VL, where VLVC. 
         [0035]    (4) With further reference to  FIG. 9 , the switch elements S 2  and S 3  are switched OFF, the second inductor L 2  is storing energy, the current is charging the energy storing capacitor C 1  via the first inductor L 1  and switch element S 3  or third diode D 3  or discharging energy via connecting to the resonant circuit in series, and the current of VL is flowed through the switch elements S 3  and S 2 , where VL=−VC. 
         [0036]    (5) With further reference to  FIG. 10 , the switch elements S 2  and S 3  keep switching ON, the second inductor L 2  keeps storing energy, the current is charging the energy storing capacitor C 1  via the first inductor L 1  and the switch element S 3 , and the current of the Load VL is flowed through the switch element S 2  and diode D 1 , where VL=VC. 
         [0037]    (6) With further reference to  FIG. 11 , the switch elements S 2  and S 3  are switching OFF, the second inductor L 2  is charging the energy storing capacitor C 1  through the diode D 4 , and the current of the Load VL is flowed through diodes D 4  and D 1 , where VL=VC. 
         [0038]    Thus, achievement of the present invention is described as below. 
         [0039]    1. The present invention is a single-stage high power factor correction circuit having simplified structure and resolves the problem of conventional inefficient two-stage circuit. 
         [0040]    2. Two inductors provide a very high output power and solves the saturation problem of the prior art that using signal inductor. 
         [0041]    3. A full bridge inverting circuit working under zero voltage switching is provided. The full bridge inverting circuit is a power factor corrector and a converter simultaneously through controlling switch elements and the resonant circuit to achieve a power factor performance and a signal stage conversion. 
         [0042]    4. The output current of the present invention before filtering process is already very close to a sine wave. Therefore, it a simplified filtering can be used in the present invention to achieve a perfect and stable output compared to prior art. 
         [0043]    The disclosure in the foregoing description is illustrative only. Changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.