Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Reexamination Certificate
2001-03-29
2001-10-30
Han, Jessica (Department: 2838)
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
C363S017000, C363S098000
Reexamination Certificate
active
06310787
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to electric power converters in general and, in particular, to a single- or multi-phase power converter capable of conversion from one alternating voltage to another in more ways than one; that is, the output voltage may be either equal to, or higher or lower than, the input voltage.
The a.c.-to-d.c.-to-a.c. power converter has been known which is constituted of a half-bridge a.c.-to-d.c. converter and a half-bridge d.c.-to-a.c. inverter. How to improve the efficiency of this type of power converter has also been known, as described and claimed by Japanese Unexamined Patent Publication No. 8-126352 filed by the assignee of the instant application. It suggests use of a high switching frequency, a frequency much higher than that of the input voltage, only for some of the switches included in the a.c.-to-d.c.-to-a.c. converter, and actuation of the other switches at the input voltage frequency for rectification purposes, rather than driving all the switches of the a.c.-to-d.c. converter and d.c.-to-a.c. inverter at the high frequency.
The noted prior art a.c.-to-d.c.-to-a.c. converter is capable of operation in either of three different modes depending upon the way the switches are controlled: (a) Nonconversion Mode in which the output voltage is approximately equal to the input; (b) Stepdown Mode in which the output is lower than the input; and (c) Stepup Mode in which the output is higher than the input. Such a multiway power converter can, in effect, transform one a.c. input voltage into several different a.c. output voltages, or several different a.c. input voltages into one a.c. output voltage.
Although the prior art device succeeds in reduction of switching frequencies, it has some offsetting drawbacks. Its power factor and current waveforms are still unsatisfactory. Additionally, it has very complex circuitry, with too many switches, in order to provide for selective operation in the three different modes.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to improve the power factor of a multiway power converter of the kind defined.
Another object of the invention is to simplify the circuit configuration of a multiway power converter of the kind defined.
Briefly, the invention may be summarized as a multiway power converter for converting an alternating input voltage from a power supply, connected between a first and a second input terminal, into two or more different alternating output voltages to be applied to a load connected between a first and a second output terminal. Included are a serial connection of a first and a second switch, with a junction therebetween connected to the first input terminal, another serial connection of a third and a fourth switch with a junction therebetween connected to interconnected second input terminal and second output terminal, and still another serial connection of a fifth and a sixth switch with a junction therebetween connected to the first output terminal. All the three serial switch connections are connected in parallel with one another. At least two inductors are connected in positions selected from among a first position between the first input terminal and the junction between the first and the second switch, a second position between the first output terminal and the junction between the fifth and the sixth switch, and a third position between the interconnected second input terminal and second output terminal and the junction between the third and the fourth switch.
Also included is a control circuit comprising at least any two of: (a) first control means for making on-off control of the first and the second and the fifth and the sixth switch at the frequency of the input voltage, and of the third and the fourth switch at a frequency higher than that of the input voltage, in Nonconversion Mode in which a first voltage between the first input terminal or the junction between the first and the second switch and the interconnected second input terminal and second output terminal is approximately equal to a second voltage between the first output terminal or the junction between the fifth and the sixth switch and the interconnected second input terminal and second output terminal; (b) second control means for making on-off control of the first and the second switch at the frequency of the input voltage, and of the third and the fourth and the fifth and the sixth switch at a frequency higher than that of the input voltage, in Stepdown Mode in which the second voltage is lower than the first voltage; and (c) third control means for making on-off control of the first and the second and the third and the fourth switch at a frequency higher than that of the input voltage, and of the fifth and the sixth switch at the frequency of the input voltage, in Stepup Mode in which the second output voltage is higher than the first voltage.
Thus, in each mode, one or two serially interconnected pairs of switches are driven at the input voltage frequency for less switchings per unit length of time and, in consequence, for less switching loss. It may also have been noted that the third and fourth switches are invariably operated at the high frequency in all the modes, affording improvement in power factor in each mode.
Preferably, for controlling the three pairs of switches as outlined above, there can be employed a rectangular wave generator connected to the pair of input terminals for generating a rectangular wave voltage at the same frequency as the input voltage. The rectangular wave voltage can be utilized for driving the one or two pairs of switches at the input voltage frequency in each mode, instead of at the high frequency. The rectangular wave generator and associated means for prevention of the high-frequency driving of the required switch pair or pairs are recommended for their simplicity in construction and reliability in operation.
In a preferred embodiment of the invention to be disclosed subsequently, the converter is so constructed as to provide a constant output voltage in the face of changes in input voltage, or several different output voltages from an unvarying input voltage. Either way, however, the converter operation in each case may be described as either Nonconversion, Stepdown, or Stepup Mode.
The above and other objects, features and advantages of this invention will become more apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference had to the attached drawings showing some preferred embodiments of the invention.
REFERENCES:
patent: 5291384 (1994-03-01), Mammano
patent: 5592368 (1997-01-01), Bidaud et al.
patent: 5949668 (1999-09-01), Schweighofer
patent: 08126352 A (1996-05-01), None
Ito Youichi
Nakajima Yasuhiro
Sato Sinji
Watanabe Toshihiko
Han Jessica
Sanken Electric Co. Ltd.
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
LandOfFree
Multiway power converter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multiway power converter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multiway power converter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2613847