Abstract:
The proposed voltage regulator has a power converter, a switch, a transformer, and a switching control device. The power converter is electrically connected to a power source for providing a voltage to compensate the output voltage of the voltage regulator when the output voltage is higher or lower than a predetermined level. The transformer is electrically connected to the switch for being used as a variable voltage source and the connecting configuration of the switch is determined by the input voltage. Also, the switching control device is electrically connected to the power converter for causing the voltage to have a phase shift with the input voltage and the inner product of the voltage and the input current being a positive value. The proposed control method is employed for generating a compensation voltage to stabilize the output voltage of the voltage regulator.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to the field of voltage regulators, and especially relates to an uninterruptible power supply. 
     BACKGROUND OF THE INVENTION 
     Please refer to FIG.  1 ( a ) which is a schematic diagram illustrating an isolated type of a mechanical regulator according to the prior art. As shown in FIG.  1 ( a ), the isolated type of a mechanical voltage regulator  100  includes an isolated transformer  101 , a relay  102 , and an input voltage sensor  103 . The input voltage sensor  103  is used to sense the input voltage V in , and then a trigger signal is generated thereby in order to actuate the relay  102 . Accordingly, the turn ratio of the isolated transformer  101  can be adjusted by turning on and off the relay  102 . By the adjustment of the turn ratio, the output voltage V out  can be stabilized at a predetermined level. 
     Please refer to FIG.  1 ( b ) is a schematic diagram illustrating a non-isolated type of a mechanical voltage regulator according to the prior art. As shown in FIG.  1 ( b ), the non-isolated type of a mechanical regulator  200  includes a non-isolated transformer  201 , a relay  202 , and an input voltage sensor  203 . The input voltage sensor  203  is used to sense the input voltage V in , and then a trigger signal is generated thereby in order to actuate the relay  202 . Accordingly, the turn ratio of the isolated transformer  201  can be adjusted by turning on and off the relay  202 . By the adjustment of the turn ratio, the output voltage V out  can be stabilized at a predetermined level. 
     According to the aforementioned art, the employment of the tap-changing transformers  100 ,  200  was often adopted in stabilizing the system voltage at a customer side. By tuning the transformer taps to reach the expected turn ratio, the input voltage can be boosted or reduced to meet the application need while the load voltage is maintained at a certain level. This strategy seems feasible, yet their speed response and voltage regulation are restricted to the use of mechanical tap changers. Moreover, the bulk volume of the transformer may deteriorate the system encasement, thereby affecting the cost of the system. 
     Please refer to FIG.  2 ( a ). FIG.  2 ( a ) is a schematic diagram illustrating an electronic voltage regulator according to the prior art. As shown in FIG.  2 ( a ), the electronic voltage regulator  300  consists of at least one electronic switch  301 , at least one resistor  302 , at least one capacitor  303 , and at least one inductor  304 . Also a high frequency electrical switching technique is employed in the electronic voltage regulator  300  to stabilize the output voltage V out . 
     Please refer to FIG.  2 ( b ). FIG.  2 ( b ) is a schematic diagram illustrating an electronic voltage regulator according to the prior art. As shown in FIG.  2 ( b ), the electronic voltage regulator  400  consists of at least one electronic switch  401 , at least one resistors  402 , at least one capacitors  403 , and at least one inductor  404 . Also a high frequency electrical switching technique is employed in the electronic voltage regulator  300  to stabilize the output voltage V out . 
     The conventional electronic voltage regulators employ the power transistors and inductors to regulate input energy and increase the circuit ability to stabilize the output voltage. However, in these cases there exist large voltage phase differences between the system input and output. An additional safety design for an I/O bypass circuit becomes difficult and may degrade the operational reliability of the system. Besides, it is also hard to expand the voltage regulators with the function of Uninterruptible Power Supplier (UPS) due to less possibility of embedding DC batteries in these systems. It is therefore attempted by the applicant to deal with the above situation encountered with the prior art. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to propose an electronic voltage regulator and a control method thereof. Especially, when the electronic voltage regulator further includes an energy storage device, the inventive voltage regulator can be used as an uninterruptible power supply. 
     According to an aspect of the present invention, the electronic voltage regulator includes input terminals electrically connected to an power source which provides an input voltage, output terminals for providing a stable output voltage, a power converter electrically connected to the power source for generating a DC voltage and then converting the DC voltage to generate a compensation voltage to compensate the output voltage when the output voltage is different from a predetermined value, a switch with a first terminal electrically connected to the power source, a transformer with a primary winding and a secondary winding, wherein a first terminal of the primary winding electrically connected to an output terminal of the power converter, a second terminal of the primary winding electrically connected to a second terminal of the output terminals, a first terminal of the secondary winding electrically connected to a first terminal of the output terminals, a second terminal of the secondary winding electrically connected to a second terminal of the switch, and a third terminal of the switch electrically connected to the first terminal of the primary winding, and a switching control device electrically connected to the power converter for controlling the power converter to stabilize the output voltage. 
     Preferably, the power source is an AC power. 
     Preferably, the electronic voltage regulator further includes a DC-DC converter electrically connected to the DC voltage for providing a transformation of the DC voltage. 
     Preferably, the electronic voltage regulator further comprises a energy storage device electrically connected to the DC-DC converter in which the electric energy of the DC voltage charges the energy storage device through the DC-DC converter when the input voltage is within a specific range, and the electric energy of the energy storage device is transformed to compensate the DC voltage when the input voltage is out of the specific range. 
     Preferably, the energy storage device is a battery. 
     Preferably, the electronic voltage regulator is an uninterruptible power supply (UPS). 
     Preferably, the DC voltage is a DC-Bus voltage. 
     Preferably, the transformer is a variable voltage source depending on a connection configuration of the switch. 
     Preferably, the switching control device controls the compensation voltage having a phase difference with the input voltage and thereby keep the compensating power to be a positive value. 
     Preferably, the connection configuration of the switch includes a first connection configuration in which the second terminal of the switch is electrically connected to the first terminal of the switch to form a conducting path when the input voltage is within a specific range, and a second connection configuration in which, the second terminal of the switch is electrically connected to the third terminal of the switch to form a conducting path when the input voltage is out of the specific range. 
     Preferably, the power converter further includes an output switch assembly electrically connected to the DC voltage for converting the DC voltage to provide the compensation voltage to stabilize the output voltage. 
     Preferably, the switching control device obtains one group of voltages and one group of phases by feedback of the input voltage, the output voltage, and the DC voltage and thereby a pulse width modulation (PWM) signal is generated through the output switch assembly to stabilize the output voltage. 
     Preferably, the switching control device includes a DC voltage sensor unit electrically connected to the DC voltage for sensing the DC voltage to generate a first signal according to a magnitude of the DC voltage, a first voltage compensator unit electrically connected to the DC voltage sensor for transforming the first signal to a second signal, an input voltage sensor unit electrically connected to the power source for sensing the input voltage to generate a third signal, a phase lock loop unit electrically connected to the input voltage sensor unit for sensing a phase of the third signal to generate a first phase signal, a phase shift unit electrically connected to the phase lock loop unit for processing 90° phase shift of the first phase signal to generate a second phase signal, a multiplier unit electrically connected to the an output terminal of the first voltage compensator unit and the phase shift unit for multiplying the second signal by the second phase signal to generate a fourth signal, an output voltage sensor unit electrically connected to the output voltage for sensing the output voltage to generate a fifth signal having a magnitude and a phase, a AC-to-DC converter unit electrically connected to the output voltage sensor unit for transforming the fifth signal to a sixth signal, a second DC voltage compensator unit electrically connected to the AC-to-DC converter unit for transforming the sixth signal to generate a seventh signal, a second multiplier unit electrically connected to the second DC voltage compensator unit for multiplying the seventh signal by the first phase signal to generate an eighth signal, an adder unit electrically connected to an output terminal of the first multiplier unit and an output terminal of the second multiplier unit for adding the fourth signal and the eighth signal to generate a command tracking signal, an AC command tracking control unit electrically connected to an output terminal of the adder unit and an output terminal of the output voltage sensor unit to compare the command tracking signal with the fifth signal to generate a trigger signal, and a PWM generator electrically connected to the AC command tracking control unit for transforming the trigger signal to a PWM signal, thereby driving the output switch assembly to provide the compensation voltage to stabilize the output voltage. 
     Preferably, the first signal, the second signal, the third signal, the sixth signal, and the seventh signal are DC signals. 
     Preferably, the fourth signal, the fifth signal, the eighth signal, and the command tracking signal are AC signals. 
     According another aspect of the invention, the control method applying an electronic voltage regulator which comprises input terminals electrically connected to an power source which provides an input voltage, output terminals for providing a stable output voltage, a power converter electrically connected to the power source for generating a DC voltage and providing a transformation of the DC voltage to generate a compensation voltage, a switch, a transformer electrically connected between the power converter, the switch, and output terminals, wherein the transformer is a variable voltage source to stabilize the output voltage depending on a connection configuration of the switch, including the steps of judging whether the output voltage is within a specific range, determining a connection configuration of the switch, generating the compensation voltage through the power converter and the transformer, controlling the compensation voltage having a phase difference with the input voltage and keeping the compensating power to be a positive value, and thereby utilizing the compensation voltage to stabilize the output voltage. 
     Preferably, the electronic voltage regulator further comprises a DC-DC converter electrically connected to the DC voltage for providing a transformation of the DC voltage. 
     Preferably, the electronic voltage regulator further comprises a energy storage device electrically connected to the DC-DC converter in which the electric energy of the DC voltage charges the energy storage device through the DC-DC converter when the input voltage is within a specific range, and the electric energy of the energy storage device is transformed to compensate the DC voltage when the input voltage is out of the specific range. 
     Preferably, the energy storage device is a battery. 
     Preferably, the electronic voltage regulator is an uninterruptible power supply (UPS). 
     Preferably, the connection configuration of the switch includes a first connection configuration in which the second terminal of the switch is electrically connected to the first terminal of the switch to form a conducting path when the output voltage is within a specific range, and a second connection configuration in which the second terminal of the switch is electrically connected to the third terminal of the switch to form a conducting path when the output voltage is out of the specific range. 
     According a further aspect of the invention, the electronic voltage regulator includes input terminals electrically connected to an power source which provides an input voltage, output terminals for providing a stable output voltage, a power converter electrically connected to the power source for generating a DC voltage and then converting the DC voltage to generate a compensation voltage to compensate the input voltage when the input voltage is different from a predetermined value, a switch with a first terminal electrically connected to the power source, a transformer with a primary winding and a secondary winding, wherein a first terminal of the primary winding electrically connected to an output terminal of the power converter, a second terminal of the primary winding electrically connected to a second terminal of the output terminals, a first terminal of the secondary winding electrically connected to a first terminal of the output terminals, a second terminal of the secondary winding electrically connected to a second terminal of the switch, and a third terminal of the switch electrically connected to the first terminal of the primary winding, and a switching control device electrically connected to the power converter for controlling the power converter to stabilize the output voltage. 
     Preferably, the electronic voltage regulator ether comprises a DC-DC converter electrically connected to the DC voltage for providing a transformation of the DC voltage. 
     Preferably, the electronic voltage regulator further includes a energy storage device electrically connected to the DC-DC converter in which the electric energy of the DC voltage charges the energy storage device through the DC-DC converter when the input voltage is within a specific range, and the electric energy of the energy storage device is transformed to compensate the DC voltage when the input voltage is out of the specific range. 
     Preferably, the energy storage device is a battery. 
     Preferably, the electronic voltage regulator is an uninterruptible power supply (UPS). 
     Preferably, the transformer is a variable voltage source depending on a connection configuration of the switch. 
     Preferably, the switching control device controls the compensation voltage having a phase difference with the input voltage and thereby keeps the compensating power to be a positive value. 
     Preferably, the connection configuration of the switch includes a first connection configuration in which the second terminal of the switch is electrically connected to the first terminal of the switch to form a conducting path when the input voltage is within the specific range, and a second connection configuration in which the second terminal of the switch is electrically connected to the third terminal of the switch to form a conducting path when the input voltage is out of the specific range. 
     Preferably, the power converter further comprises an output switch assembly electrically connected to the DC voltage for converting the DC voltage to provide the compensation voltage to stabilize the output voltage. 
     Preferably, the switching control device obtains one group of voltages and one group of phases by feedback of the input voltage, the output voltage, and the DC voltage and thereby a pulse width modulation (PWM) signal is generated through the output switch assembly to stabilize the output voltage. 
     The present invention may best be understood through the following description with reference to the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG.  1 ( a ) is a schematic diagram illustrating an isolated type of a mechanical regulator according to the prior art; 
     FIG.  1 ( b ) is a schematic diagram illustrating a non-isolated type of a mechanical regulator according to the prior art; 
     FIG.  2 ( a ) is a schematic diagram illustrating in electronic voltage regulator according to the prior art; 
     FIG.  2 ( b ) is a schematic diagram illustrating another electronic voltage regulator according to the prior art; 
     FIG. 3 is a schematic diagram illustrating an electronic voltage regulator according to a preferred embodiment of the present invention; 
     FIG.  4 ( a ) is a schematic diagram illustrating an UPS when the input voltage is within a specific range according to a preferred embodiment of the present invention; 
     FIG.  4 ( b ) is a schematic diagram illustrating the UPS when the input voltage is out of the specific range according to a preferred embodiment of the present invention; and 
     FIG. 5 is a block diagram illustrating the switching control device of the UPS according to a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Please refer to FIG.  3 . It is a schematic diagram illustrating an electronic voltage regulator according to a preferred embodiment of the present invention. As shown in FIG. 3, the electronic voltage regulator  500  includes input terminals  501 ,  502 , output terminals  504 ,  505  for providing a stable output voltage V out , a power converter  506 , a switch, a transformer  508 , and a switching control device  514 . Input terminals  501 ,  502  are electrically connected to a power source  503  which provides an input voltage V in . The power converter  506  are electrically connected to the power source  503  for generating a DC voltage V dc-bus  and then converting the DC voltage V dc-bus  to generate a compensation voltage to compensate the output voltage V out  when the output voltage V out  is different from a predetermined value. The switch has a first terminal  507  being electrically connected to the power source  503 . The transformer  508  has a primary winding  510  and a secondary winding  509 . Meanwhile, a first terminal of the primary winding  510  is electrically connected to an output terminal of the power converter  506 . A second terminal of the primary winding  510  is, electrically connected to the second terminal  505  of the output terminals. A first terminal of the secondary winding  509  is electrically connected to a first terminal  504  of the output terminals. A second terminal of the secondary winding  509  is electrically connected to a second terminal  511  of the switch. And, a third terminal  512  of the switch is electrically connected to the first terminal of the primary winding  510 . In addition, a switching control device  514  is electrically connected to the power converter  506  for controlling the power converter to stabilize the output voltage. Preferably, the power source is an AC power. 
     Please refer to FIGS.  4 ( a ) and  4 ( b ). FIG.  4 ( a ) is a schematic diagram illustrating an UPS when the input voltage is within a specific range according to a preferred embodiment of the present invention. As shown in FIG.  4 ( a ), the major difference between FIG.  4  and FIG. 3 is that there exist a DC-DC converter  515  and a battery  516  employed in the electronic voltage regulator  500  in FIG.  4 . Preferably, the electronic voltage regulator  500  can be an UPS in FIG.  4 . For the architecture shown in FIG. 4, the DC-DC converter  515  is electrically connected to the DC voltage V dc-bus  for providing a transformation of the DC voltage V dc-bus . The electric energy of the DC voltage V dc-bus  charges the battery  516  through the DC-DC converter  515  when the input voltage is within a specific range. Under this operation, the first terminal  507  of the switch SW 1  is directly connected to the second terminal  511  of the switch SW 1 , thereby forming a conducting path through the first terminal  507  of the switch SW 1  to the second terminal  511  of the switch SW 1 . At this time, the transformer  508  can be a variable voltage source to compensate the variation of the output voltage V out . Even though the input voltage V in  is varied, the transformer  508  can be a variable voltage source to compensate the variation of input voltage V in  to stabilize the output voltage V out . Consequently, the output voltage V out  can be stabilized at a predetermined value, which is independent of the variation of the input voltage V in  and the output voltage V out . 
     However, the major characteristic of the present invention is to utilize the switching control device  514  to control the compensation voltage having a phase difference with the input voltage V in  and keep the compensating power to be a positive value, wherein the compensating power is always drained from the power converter  506  via the transformer  508  to the load. 
     On the other hand, FIG.  4 ( b ) is a schematic diagram illustrating the UPS when the input voltage is out of the specific range according to a preferred embodiment of the present invention. The second terminal  511  of the switch SW 1  is electrically connected to the third terminal  512  of the switch SW 1  to form a conducting path when the input voltage V in  is out of the specific range. At the same time, the electric energy of the battery  516  is transformed to maintain the DC voltage V dc-bus  at a predetermined value. 
     Please refer to FIGS. 3 and 4. The power converter further includes an output switch assembly  513  which is electrically connected to the DC voltage V dc-bus  for converting the DC voltage V dc-bus  to provide the compensation voltage to stabilize the output voltage V out . In addition, the switching control device  514  obtains one group of voltages and one group of phases by feedback of the input voltage, the output voltage, and the DC voltage, thereby generating a pulse width modulation (PWM) signal through the output switch assembly  513  to stabilize the output voltage V out . 
     Please refer to FIG.  5 . FIG. 5 is a block diagram illustrating the switching control device of the UPS according to a preferred embodiment of the present invention. As shown in FIG. 5, the switching control device  514  includes a DC voltage sensor unit  601 , a first voltage compensator unit  602 , an input voltage sensor unit  603 , a phase lock loop unit  604 , a phase shift unit  605 , a multiplier unit  606 , an output voltage sensor unit  607 , a AC-to-DC converter unit  608 , a second DC voltage compensator unit  609 , a second multiplier unit  610 , a adder unit  611 , an AC command tracking control unit  612 , a PWM generator  613 . The DC voltage sensor unit  601  is electrically connected to the DC voltage for sensing the DC voltage to generate a first signal S 1  according to a magnitude of the DC voltage. The first voltage compensator unit  602  is electrically connected to the DC voltage sensor  601  for transforming the first signal S 2  to a second signal S 2 . The input voltage sensor unit  603  is electrically connected to the power source for sensing the input voltage V in  to generate a third signal S 3 . The phase lock loop unit  604  is electrically connected to the input voltage sensor unit  603  for sensing a phase of the third signal S 3  to generate a first phase signal θ 1 . The phase shift unit  605  is electrically connected to the phase lock loop unit  604  for processing 90° phase shift of the first phase signal θ 1  to generate a second phase signal θ 2 . The multiplier unit  606  is electrically connected to the an output terminal of the first voltage compensator unit  602  and the phase shift unit  605  for multiplying the second signal S 2  by the second phase signal θ 2  to generate a fourth signal S 4 . The output voltage sensor unit  607  is electrically connected to the output voltage V out  for sensing the output voltage V out  to generate a fifth signal S 5  having a magnitude and a phase. The AC-to-DC converter unit  608  is electrically connected to the output voltage sensor unit  607  for transforming the fifth signal S 5  to a sixth signal S 6  The second DC voltage compensator unit  609  is electrically connected to the AC-to-DC converter unit  608  for transforming the sixth signal S 6  to general a seventh signal S 7 . The second multiplier unit  610  is electrically connected to the second DC voltage compensator unit  609  for multiplying the seventh signal S 7  by the first phase signal θ 1  to generate an eighth signal S 8 . The adder unit  611  is electrically connected to an output terminal of the first multiplier unit  606  and an output terminal of the second multiplier unit  610  for adding the fourth signal S 4  and the eighth signal S 8  to generate a command tracking signal S 9 . The AC command tracking control unit  612  is electrically connected to an output terminal of the adder unit  611  and an output terminal of the output voltage sensor unit  607  to compare the command tracking signal S 9  with the fifth signal S 5  to generate a trigger signal S 10 . And, the PWM generator  613  is electrically connected to the AC command tracking control unit  612  for transforming the trigger signal S 10  to a PWM signal S 11 , thereby driving the output switch assembly to provide the compensation voltage to stabilize the output voltage V out . 
     In conclusion, the following are some of the important advantages of the invention. (1) According to the design of the present invention, the present invention may reduce the voltage stress suspended at the primary transformer winding so as to save the required rating and volume of the transformer. This is can be further explained by the following numerical example. As concerned a system with the utility voltage of 120 volt and the ±20% of the utility voltage design range of the power electronic regulator, the voltage across the primary winding of the transformer is 24 volt, which is much less than input voltage level. (3) The present invention utilizes the high frequency switching technique to stabilize the output voltage, thereby increasing the precision of the output voltage regulation. (4) The present voltage regulator can be capable of an uninterruptible power supplier, thereby increasing the reliability of the system. 
     While the invention has been described in terms of what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.