Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2000-10-23
2001-11-27
Wong, Peter S. (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S098000, C363S124000
Reexamination Certificate
active
06324078
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to power source devices for supplying a high frequency power from commercial power sources to loads.
DESCRIPTION OF RELATED ART
Examples of the power source device of the kind referred to have been described in U.S. Pat. No. 5,063,490 to Maehara et al., assignors to the same assignee as the present invention, Japanese Patent Publication No. 5-88067 and so on. Maehara et al. disclose a device comprising an inverter circuit of a full bridge arrangement of a plurality of pairs of such switching elements as power MOSFET's and a plurality of parasitic diodes respectively connected between drain and source of each switching element, and a resonance load circuit of an inductor, capacitor and discharge lamp and connected between a junction point of one of the pair of the switching elements and a junction point of another pair of the switching elements. One switching element is connected at the drain to the cathode of one diode which is connected at the anode to the cathode of another diode, and this another diode is connected at the anode to the source of the one switching element. The junction point of the plurality of the switching elements is connected to one end of a commercial power source, and the other end of this power source is connected through two inductors to a junction point of further diodes. A capacitor is connected between a junction point of these inductors and the one end of the power source, and an AC filter is formed by this capacitor and one of these inductors.
A driving signal of a square wave is input across the gate and source of one switching element in one of the pairs, and another square wave driving signal is input across the gate and source of the other switching element in the same pair, so that the switching elements in the pair will be alternately turned ON and OFF. Further, the same square wave driving signal as that to the other switching element of the one pair is input to one switching element in the other pair, and the same signal as that to the one switching element of the one pair is input to the other switching element of the other pair, so that the other switching element of the other pair will be turned ON and OFF simultaneously with the other element of the one pair and the one switching element of the other pair will be turned ON and OFF simultaneously with the one element of the one pair.
In this circuit according to Maehara et al., the switching elements of one of the pairs in the inverter circuit are acting in common as switching elements in a chopper so as to form the device with a fewer number of elements, and there arise advantages that power loss is reduced, and that required circuit structure can be also simplified. Further, as the respective switching elements of each pair are made to act alternately as the elements of the chopper and of the inverter in every half cycle of the commercial source voltage, there arises further advantage that any stress per each switching element can be reduced. As the respective switching elements in each pair are well balanced in the power loss, it is enabled to employ the same structure for heat radiation, for example, in respect of the respective elements. Since the respective switching elements in the one pair are operating commonly as the elements of the chopper and inverter, further, it is made unnecessary to provide a separate chopper driving circuit, while the required driving circuit itself can be simplified in the structure. The insertion of the AC filter comprising one of the two inductors and the capacitor between the commercial power source and the inductors renders the input current to be continuous so as to be able to reduce input current distortion factor and, as the input current can be made to be of a sinusoidal wave of the same phase as the input voltage, it is possible to render the input power factor substantially to be 1.
In addition, Maehara et al. are providing a system for intermittently stopping the switching elements capable of controlling the input, in correspondence to the power source polarity detected by a source polarity detecting means. In concrete, the operation of the one switching element in one pair is intermittently stopped when the polarity of the commercial power source is positive. When the source power polarity is negative, to the contrary, the operation of the other switching element in the one pair is intermittently stopped. With the operation of the switching elements in one pair capable of controlling the input stopped intermittently in this manner, the power supply from the commercial power source can be freely reduced, and the voltage of the smoothing capacitor can be prevented from increasing due to an excessive supply of power.
SUMMARY OF THE INVENTION
In the foregoing power source device according to Maehara etal., the provision of the power conversion circuit constituted by the inverter of full bridge arrangement with the switching frequency of the inverter made variable renders the output to the load to be controllable.
However, when the switching frequency is varied in the case when the DC power is prepared by rectifying and smoothing the commercial source power, there occurs a problem that the high frequency leaks on to the side of the commercial power source, upon which it becomes necessary to provide a filter for preventing the high frequency from leaking to, for example, input end of the diode bridge for rectifying the commercial source power. In performing the control of the output to load (hereinafter “the load output”) over a wide range, further, it is required to control the switching frequency of the switching element over a wide range, and there arises a problem that required design of the filter for restraining such harmonic distortion becomes complicated.
In recent years, further, there has been provided straight or circular tube lamps of T5 type made thin to be 16 mm in the tube diameter from the view point of resource saving and energy reduction, as well as a high output discharge lamp thin to be about 18 to 29 mm in the tube diameter and long to be 1400 to 2500 mm in light path length. When, for example, as shown in
FIGS. 33 and 34
, a plurality of circular light emitting tubes
1
having at one end a filament electrode
2
and closed at the other end
3
are arranged concentrically and these circular light emitting tubes
1
are joined at portions adjacent to the closed ends
3
by means of a junction point
4
, there is formed a single discharge path in their interior. At the same time, the coldest point
6
is formed at the closed ends, bases
5
are fitted to enclose both ends of the circular light emitting tubes
1
, and a double tube type fluorescent lamp is provided.
These discharge lamps of the type referred to are made thinner in the tube diameter in order to improve the lamp efficiency, and the lamp current is made smaller but the lamp voltage is made higher relatively to various general use fluorescent lamps. Further, as the highly efficient discharge lamps of this kind are smaller in the tube diameter than conventional discharge lamps, spatial allowance for disposing the filament electrode
2
is small. Consequently, the filament electrode
2
is minimized in size, while a high precision control of preheating current for preventing the filament from being damaged becomes necessary, and the filament current at lighting is also subjected to a control. In an event when a preheating system in which a capacitor is connected between non-source side ends of a pair of the filament electrodes is employed (preheating circuit using one capacitor), the filament current at lighting becomes larger as the lamp voltage increases with the capacitor made constant in the capacity and as the frequency of the filament current, that is, the switching frequency of the switching elements becomes higher. In the case where the load is the discharge lamp, the dimming increased causes the lamp voltage to increase, so that the filament current at lighting decreased renders the switching frequen
Hori Kazuhiro
Kanda Takashi
Naruo Masahiro
Ohnishi Masahito
Yoshida Kazuo
Burns Doane , Swecker, Mathis LLP
Matsushita Electric & Works Ltd.
Vu Bao Q.
Wong Peter S.
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