Electric lamp and discharge devices: systems – Current and/or voltage regulation
Reexamination Certificate
2000-06-15
2001-04-24
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
C315S244000, C315S2090SC, C315SDIG007
Reexamination Certificate
active
06222327
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a lighting device for a discharge tube.
In recent days, a discharge tube (for example, a fluorescent lamp) is more likely to employ a system arranged to convert a DC voltage into a high-frequency AC voltage through the effect of a lighting circuit composed of an inverter and to apply the high-frequency AC voltage into a resonant load circuit containing the discharge tube itself. The resonant load circuit also contains a resonant inductor and a resonant capacitor for setting a resonant frequency. This type of lighting circuit includes an inverter circuit composed of two power semiconductor switching elements connected between a positive and a negative polarities in a half-bridge structure, which is operated to apply the high-frequency AC voltage onto both ends of the resonant load circuit. The waveform of the current flowing through the resonant load circuit (referred to as resonant current) is resonated into a sinusoidal waveform through the effect of the inductor and the capacitor. This resonant current is controlled by changing an operation frequency of the inverter.
As a prior art for stabilizing the driving frequency of a switching element, there has been proposed a stabilizing circuit disclosed in JP-A-8-45685. This circuit provides a half-bridge circuit for supplying an AC voltage to the resonant load circuit containing the discharge lamp and is operated to divide part of the resonant current into a capacitor and a feedback transformer and apply a control signal to the switching element between a high side and a low side of the half-bridge circuit according to a voltage on the secondary side of the feedback transformer. Unlike the normal fluorescent lamp, this prior art discusses the lighting device for an electrodeless fluorescent lamp for generating plasma through magnetic lines of force emitted from an exciting coil. The electrodeless lamp operates to supply high-frequency current of several megahertz to a solenoid type exciting coil and thereby emit magnetic lines of force for generating ions inside of a bulb through the inductive discharge and form those ions as discharge current in a closed loop (plasma) through the effect of electromagnetic coupling applied by the force of magnetization. Mercury vapor in the plasma is excited by the inductive electric field so as to fire ultraviolet rays onto a fluorescent material coated on the inside of the tube on which the ultraviolet rays are converted into visible rays.
SUMMARY OF THE INVENTION
The foregoing prior art is arranged to supply a control signal having the same frequency as the resonant current to the half-bridge circuit through the feedback transformer. That is, this prior art is a self-excited circuit that keeps the half-bridge circuit in operation without any signal supplied from the external and thus is suitable to the high-frequency operation. However, the feedback transformer has self-inductance, which brings about a phase difference between the control signal and the resonant current and furthermore a slip of the frequency of the control signal from a suitable value. The phase difference and the slip of the frequency may allow pass current to flow through the half-bridge circuit, thereby disadvantageously increasing the loss. Hence, a first problem to be solved by the present invention is to provide lighting circuit means which stabilizes at high frequency.
The electrodeless fluorescent lamp to be controlled by the prior art provides an exciting coil. The use of the exciting coil as a resonant inductor may be effective in reducing the cost of parts and the circuit in size. However, the plasma may given an influence onto an equivalent inductance of the exciting coil, which means that the equivalent inductance is varied depending on the luminescent state of the lamp. Hence, a second problem to be solved by the present invention is to implement the lighting circuit that may use the exciting coil of the electrodeless fluorescent lamp as the resonant inductor.
As described above, an object of the present invention is to provide a lighting device which stably operates at a high frequency and is small in size and cost.
The foregoing object may be achieved by a lighting device for illumination for applying an AC voltage to resonating means having an inductor and a capacitor according to the switching operation of two power semiconductor elements connected in bridge and supplying AC current to a discharge tube connected to any one of the inductor and the capacitor, comprising first and second voltage drop means and said resonating means connected in series with an I/O terminal of the bridge, the voltages of the first and the second voltage drop means being applied to each control terminal of the two power semiconductor elements as a signal of an opposite phase.
The object of utilizing the exciting coil of the electrodeless fluorescent lamp may be achieved by comprising a bridge circuit having two power semiconductor elements, a capacitor, the exciting coil, and the first and the second voltage drop means connected in series between I/O terminals of the bridge circuit, wherein the voltages of the first and the second voltage drop means may be applied to each control terminal of the two power semiconductor elements as a signal of an opposite phase through first and second phase shift means.
REFERENCES:
patent: 4316243 (1982-02-01), Archer
patent: 4631449 (1986-12-01), Peters, Jr.
patent: 4686428 (1987-08-01), Kuhnei et al.
patent: 4749914 (1988-06-01), Feher et al.
patent: 4952849 (1990-08-01), Fellows et al.
patent: 5138236 (1992-08-01), Bobel et al.
patent: 5446350 (1995-08-01), El-Hamamsy
patent: 5559394 (1996-09-01), Wood
patent: 5614810 (1997-03-01), Nostwick
patent: 5671128 (1997-09-01), Nakamura
patent: 5739645 (1998-04-01), Xia
patent: 5796214 (1998-08-01), Nerone
patent: 5925984 (1999-07-01), Fischer et al.
patent: 37 11 814 A1 (1987-11-01), None
patent: 197 29 768 A1 (1998-01-01), None
patent: 0 806 888 A1 (1997-11-01), None
patent: 8-9655 (1996-01-01), None
patent: 8-37092 (1996-02-01), None
patent: 9-238474 (1997-09-01), None
Miyazaki Hideki
Namura Yuuichi
Shoji Hiroyuki
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Philogene Haissa
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