Electric power conversion systems – Current conversion – Having plural converters for single conversion
Reexamination Certificate
1999-11-17
2001-10-23
Berhane, Adolf Deneke (Department: 2838)
Electric power conversion systems
Current conversion
Having plural converters for single conversion
C363S070000
Reexamination Certificate
active
06307761
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a technique for suppressing harmonics current in power supply apparatuses such as AC-DC converters and inverter-type power supplies for lighting equipment, i.e. a technique for improving the power factor thereof, without causing an aggravation of power transferring efficiency. According to the invention, the size of power supply apparatuses is made compact, the reliability is improved, and the cost for manufacture is reduced. Further, the present invention relates to a power supply apparatus where the holding time for a power failure can be kept longer and a ripple in an output voltage can be reduced as occasion demands.
Furthermore, the present invention relates to a power supply apparatus where both the character of a flyback type converter, which is easy to control, and the advantage of a forward type converter, i.e. a high efficiency, are provided.
BACKGROUND OF THE INVENTION
In order to reduce the amount of harmonics current in power supply apparatuses, in other words, in order to improve the power factor thereof, it is considered to use a so-called active harmonics filter or a so-called capacitance-less converter, which does not have a smoothing capacitor at an input side thereof. In such an active harmonics filter or a capacitance-less converter, a smoothing capacitor is not provided after the rectifying section, and a rectified line current is directly switched by a switching element, so that a necessary and sufficient power factor can be obtained and the construction thereof is very simple. However, they also have disadvantages such that a significant amount of output ripple occurs or a holding time is not apt to be sufficiently kept for an instant power failure of about 0.02 sec. Therefore, a so-called two-stage converter type power supply apparatus is used, in which a DC-DC converter is provided after the active harmonics filter. In such an apparatus, an electric current must go through two-stage converters, so that a switching loss is caused twice and then the efficiency becomes low.
On the other hand, some single switching element type converters are suggested in which a holding time can be kept and the output ripple can be reduced so as to overcome the disadvantage of the conventional capacitance-less converter type apparatus while a power factor there is also improved. However, almost all of these apparatuses are designed as an energy circulating type converter or a resonance type converter; therefore an electric current is circulated at the primary side of the apparatus. In addition to this, when an electric current goes through diodes or inductors a loss of electric current is caused so that efficiency becomes low.
Further, in case of applying a forward type circuit to a capacitance-less converter having a single switching element, it is not so easy to combine a forward type circuit with the capacitance-less converter. Because dealing with a reset current is difficult and a more complicated contrivance is required to realize the combination.
The object of the present invention is to provide a single-stage converter type power supply apparatus where the energy loss, caused by two-stage switching operations in a two-stage converter type power supply apparatus, is reduced to improve the efficiency of the apparatus.
Another object of the present invention is to provide a single stage converter type power supply apparatus where a power factor is improved without reducing the efficiency, and the holding time can be kept long and also the ripple characteristic can be improved.
As stated above, if it is tried to keep a sufficient holding time and to improve a ripple characteristic while improving a power factor in a single stage converter type power supply apparatus, one cannot avoid making to make the switching loss large. There are two types of circuit system for a single stage converter type switching power supply system, one of which is the flyback type circuit system and the other one is a forward type. The former has an advantage that is easy to control while having a disadvantage in that the efficiency is somewhat low and the size of the transformer must be large. On the other hand, the latter has an advantage in that the efficiency is high and the size of the transformer can be made smaller; however, it is required to give a reset current in order to prevent a saturation of the cores and therefore it is difficult to control the system because of the limitation for dealing with the reset current. For this reason, almost all of the capacitance-less converters use the flyback type circuit system.
In addition to this, capacitance-less converters have disadvantages in that a sufficient holding time cannot be obtained under a power failure condition because energy cannot be stored at the primary side of a transformer and a great amount of output ripple occurs.
The present invention has solved these problems by means explained below.
DISCLOSURE OF THE INVENTION
In a power supply apparatus according to the first invention of the present application, a switching transformer or a switching choke coil, which has no current smoothing function, i.e. which is for use in a rectified line current power supply, and a switching transformer or a switching choke coil, which has a current smoothing function, i.e. which is for use in a direct current power supply, are provided in a parallel manner; the transformer and the choke coil are arranged to be switched by only one switching element; the transformer output and the choke coil output are added. In accordance with such a construction, a power factor, a holding time and a ripple characteristic can be sufficiently obtained, while the efficiency is well improved. That is to say, since an electric current goes through both the rectified line current route and the direct current route in a parallel manner, only one switching loss is caused and thus the efficiency of the apparatus is increased. Naturally, after the electric current passes through these routes, how to add the outputs thereof can be freely selected, i.e. in a series manner or a parallel manner, so as to make it suitable for the circuit to which the power supply apparatus is applied.
The second invention of the present application is to provide a power supply apparatus where power is directly supplied to a load through a converter for switching a rectified line current route; and a DC-DC converter for switching a direct current route, which is provided in a different route from the rectified line current switching route but in a parallel manner. According to the second invention, the disadvantage of the output ripple or the holding time for power failure is compensated. In such a construction, electric current passes the rectified line current switching route and the direct current switching route in a parallel manner and the efficiency is increased because the switching loss is caused only once. The second invention is preferably used when a higher performance is required.
The third invention of the present application is a more simplified power supply apparatus in comparison to the second invention. That is to say, the direct current route is simplified where no switching circuit is used. The third invention is preferably used in a case that the output voltage becomes route 2 times, i.e. 1.41 times, or 2 route 2 times, i.e. 2.82 times as stated in the attached claims
3
to
5
, and no line regulating circuit is required.
The fourth invention according to the present application has a construction such that a ripple component contained in a commercial power supply is added to a signal for controlling a switching operation adequately so that the ripple of an output voltage is reduced and the power factor is improved.
The fifth invention according to the present application is to provide a power supply apparatus where amounts of electric current between the rectified line current side and the direct current side are well balanced. More concretely, a suitable ratio of the amount of electric current between the rect
Berhane Adolf Deneke
Fidelix Y.K.
Norris McLaughlin & Marcus P.A.
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