Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Silicon controlled rectifier ignition
Reexamination Certificate
2002-03-28
2003-04-15
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Silicon controlled rectifier ignition
C315S219000, C315S291000, C315S224000, C315S307000, C315SDIG007
Reexamination Certificate
active
06548964
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a discharge lamp lighting apparatus for lighting a discharge lamp at a high frequency using a single-transistor voltage resonance inverter. Moreover, the present invention relates to a luminaire using the discharge lamp lighting apparatus.
BACKGROUND OF THE INVENTION
A so-called electronic type discharge lamp lighting apparatus wherein a discharge lamp is lighted at a high frequency is now being propagated. Conventionally, a bipolar transistor which is a current drive type switching element has been used for a switching element of a high-frequency inverter which principally constitute the electronic type discharge lamp lighting apparatus. However, a MOSFET which is of a voltage drive type switching element is able to be used recently. Therefore, integrated circuits are widely used as a drive circuit of the switching element. By integrating the drive circuit in a chip, not only the installation of the discharge lamp becomes easy, but also it is able to miniaturize a wiring board and the discharge lamp lighting apparatus.
However, since the high voltage proof MOSFET has a high ON-state resistance, there is a characteristic problem such as a large conduction loss. Therefore, MOSFET is widely used in an inverter like a half-bridge type inverter which can be used at a relatively low voltage.
Accordingly, the bipolar transistor is used for a single-transistor voltage resonance inverter for which a high voltage proof is required. In this case, the switching operation of the bipolar transistor is performed by current feedback using a saturable transformer.
However, the saturable transformer has a drawback of a wide dispersion in characteristics. So, it is difficult to control the quality of the saturable transformer. Moreover, the saturable transformer has another drawback of a wide dispersion in temperature characteristics. Accordingly, a single-transistor voltage resonance inverter had a problem of difficult to design.
When a control circuit suitable for the single-transistor voltage resonance inverter using a bipolar transistor is constituted of an integrated circuit, sufficient base current have to be supplied to the bipolar transistor of the current drive type. Thus, the integrated circuit became upsizing, and the integration was difficult in fact.
SUMMARY OF THE INVENTION
The present invention has an object to provide a discharge lamp lighting apparatus principally constituted by a single-transistor voltage resonance inverter using a bipolar transistor, and further, the principal part of its control circuit is constituted by a small integrated circuit. Furthermore, the present invention has another object to provide a luminaire using the discharge lamp lighting apparatus.
In addition, the present invention has another object to provide a discharge lamp lighting apparatus and a luminaire using the lamp system which perform the turn-on operation of the bipolar transistor of the single-transistor voltage resonance inverter effectively.
Furthermore, the present invention has other object to provide a discharge lamp lighting apparatus and a luminaire using the lighting device which start a single-transistor voltage resonance inverter effectively.
To achieve an object of the present invention, a first aspect of the discharge lamp lighting apparatus includes a DC power supply, generating a direct current voltage, an inverter circuit, switching the direct current voltage at a high frequency, and including one bipolar transistor, which is turned on by a feedback signal of the high frequency voltage and turned off by an off-switching signal of a control circuit, and a resonance circuit resonated by the switching operations, a discharge lamp, operated by the high frequency voltage, and the control circuit, provided with a timer, which determines operation-durations including a preheating mode, a starting mode and a lighting mode of the discharge lamp, and an oscillator generating the off-switching signal according to the each mode.
In descriptions of the first aspect and other aspects of the discharge lamp lighting apparatus, some definitions and their technical meanings are presented for following specific terms, unless otherwise specified.
<First DC Power Supply>
A first DC power supply is a power source for supplying an electric energy to energizing at least a single-transistor voltage resonance inverter and a discharge lamp. The first DC power supply supplies electrical energy straightforwardly to the single-transistor voltage resonance inverter. The first DC power supply may be any one of a battery power source and a rectified DC power supply. In case of a rectified DC power supply, a voltage of a low-frequency AC power source, for instance, of a commercial AC power source is rectified in order to obtain a DC voltage.
Further, the rectified DC power supply can contain a smoothing circuit as needed. A smoothing circuit may be any of a passive filter containing a partial smoothing circuit wherein a smoothing capacitor is simply coupled across the DC output terminals, a partial smoothing circuit as described below and an active filter such as a chopper. In addition, the partial smoothing circuit is provided with at least a capacitor and a diode, and it outputs a DC output having a rectified waveform of half wave whose valley is filled with a DC voltage up to the middle level. By using an active filter, an input current is enhanced in its power-factor and suppressed in its harmonics. In addition, in order to enhance the power-factor and suppress harmonics of the input current, the single-transistor voltage resonance inverter may be used further to obtain a smoothing DC voltage by using a high-frequency switching operation of the bipolar transistor of the single-transistor voltage resonance inverter.
Furthermore, a first DC power supply can also supply the operating power to the control circuit.
<Single-Transistor Voltage Resonance Inverter>
A single-transistor voltage resonance inverter is provided with a single switching element and a resonance circuit where the switching element is coupled to the first DC power supply. The signal-transistor voltage resonance inverter performs the inverter operation for generating a sinusoidal wave AC voltage in the resonance circuit by the switching operation of the switching element turning on and off. Here, the “one switching transistor” means that it can be considered a single switching element functionally. Therefore, it may be provided with two or more switching elements coupled in parallel at the point of current capacity.
Further, the first aspect of the discharge lamp lighting apparatus is provided with a bipolar transistor as a switching element of the single-transistor voltage resonance inverter. The turn-on switching operation of the switching element is performed by the feedback control to flow a current to a base of the bipolar transistor. The feedback control is for performing a current feedback of any of a collector current and a resonance current or a lamp current flowing in the resonance circuit, or for performing a voltage feedback of a voltage drop of a current-limiting reactor. Here, the turn-off switching operation of the switching element is performed by using a control circuit. Further, in order to perform the turn-off switching operation easily, it can be provided with a base current cut-off device for short-circuiting between the base and emitter of the bipolar transistor.
Furthermore, a high frequency current can be took out of a secondary winding when the inductor of the resonance circuit is constituted by a primary winding for instance, or a it can lead the voltage drop of the inductor electrically. Here, in the description of the first aspect of the discharge lamp lighting apparatus, the term “high frequency” means the frequency of around 10 KHz, and more preferably, between 40 KHz to 500 KHz. If the frequency is 10 KHz or more, it realize a lighting device of the discharge lamp which is compact in size and light in weight, and improves the lamp efficiency.
Kamata Masahiko
Shimizu Keiichi
Alemu Ephrem
Pillsbury & Winthrop LLP
Toshiba Lighting & Technology Corporation
Wong Don
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