Toshiba Electric Equipment Corporation

Sanken Electric Co., Ltd.

Kabushiki Kaisha Toshiba

Toshiba Lighting & Technology Corporation

Toshiba Denzai Kabushiki Kaisha

Nanjou Aoike

Hisao Kobayashi

Kenichi Inui

Keiichi Shimizu

Masaki Kanazawa

Katsuyuki Ide

Hideki Nakamichi

Hironobu Sou

Yasunobu Koshimura

Yuji Takahashi

Noriyuki Kitamura

Tsutomu Kakitani

Fumihiko Nagasaki

Mitsuhiro Hamaguchi

Kouhei Yuhara

Fuminori Nakaya

Akihiro Ueda

A lighting system for a fluorescent lamp includes an inverter circuit to which is connected a load circuit including a resonant circuit of an inductor and a capacitor in serial connection, with a lamp connected in parallel with the capacitor. An inversely frequency dependent voltage is applied between the lamp electrodes according to a predefined resonance characteristic such that the resonance frequency is less than a discharge start frequency at which the lamp is to start glowing. For lighting up the lamp the frequency of the inverter output voltage is changed from a first frequency that is higher than the discharge start frequency to a second frequency that is less than the resonance frequency. If the lamp accidentally goes off, the current flowing through the load circuit will advance out of phase with the inverter output voltage, possibly resulting in the destruction of the inverter switch or switches due to overcurrent. This danger is precluded by constantly monitoring the phase of the load current and, in event the load current is found to be in phase advance, by making the inverter output frequency higher than the resonance frequency of the resonant circuit and thereby delaying the phase of the load current.

Discharge lamp lighting system with overcurrent protection for an

A rectification device rectifies an input voltage from an AC power source. First and second switching devices are arranged between a pair of output terminals of the rectification device and alternately turned on/off. A series circuit of a first capacitor and an inductor is arranged between the two terminals of one of the first and second switching devices so as to perform a smoothing operation with respect to the frequency of an output from the rectification device. A second capacitor serves to form a resonance circuit in cooperation with the inductor in accordance with the ON/OFF operations of the first and second switching devices. The capacitance of the second capacitor is smaller than that of the first capacitor.

Power supply apparatus having high power-factor and low

An inverter is made up of a parallel circuit as a voltage resonance circuit, and a first diode, which are connected in series between both ends of a power source. The parallel resonance circuit includes the primary winding of an output transformer of the leakage type, and a resonance capacitor. The first diode is connected at the cathode to the primary winding of the output transformer. The secondary winding of the output transformer is coupled with a load such as a discharge lamp. The cathode and anode of the first diode are respectively connected to the collector and emitter of a transistor. A series circuit of a second diode and capacitor is connected across the collector-emitter path of the transistor. The second diode is forwardly arranged with respect to the transistor. A voltage detector comprises the capacitor and two resistors which are connected in series, and connected across the capacitor. The output voltage is derived from the node of those resistors. An error amplifier compares the output voltage of the voltage detector and an output voltage from a reference voltage source. A VCO oscillates at a switching frequency based on the comparison result. The oscillation output signal is applied to the base of the transistor.

Inverter capable of controlling operating frequency

A discharge-lamp lighting device comprises a voltage generating circuit for generating a high-frequency voltage for lighting a discharge lamp, a self-oscillating device provided in the path of lamp current flowing through the discharge lamp for exciting the voltage generating circuit to self-oscillation, a direct current blocking element connected in series with the self-oscillating device for blocking the flow of a direct current in the self-oscillating device, and a bypass element connected in parallel with the direct current blocking element and the self-oscillating device for bypassing the direct current.

Discharge lamp lighting device

An apparatus for starting and operating a discharge lamp includes an inverter circuit. The inverter circuit comprises a parallel resonance circuit including an oscillation coil and capacitor, and which is connected to the discharge lamp, via a current-limiting coil, a switching transistor for triggering the parallel resonance circuit, and a feedback circuit connected to the switching transistor, for allowing a feedback signal for driving the switching transistor to be supplied to the base of the switching transistor, the feedback circuit being magnetically coupled to the current-limiting coil.

Apparatus for starting and operating a discharge lamp

A large image display apparatus comprises a plurality of discharge lamps each having an anode, a cathode and a light emitting tube, a display board having the plurality of discharge lamps thereon, a heating circuit for heating the cathodes of the plurality of discharge lamps, a power supply circuit for generating a rectified high frequency voltage and biasing the plurality of discharge lamps, an image signal generator for generating an image signal, and a control circuit for controlling the quantity of light emitted from each discharge lamp in response to the image signal.

Large image display apparatus

A large number of luminous display elements are arrayed on a board, and the quantity of light emitted by each display element is controlled in accordance with a video signal generated by a video signal generator. Each display element is constituted by a discharge lamp and a high frequency generator lighting the same.

Large size image display apparatus

An output transformer for an inverter driven by a pulsating voltage obtained through the full wave rectification of a low frequency alternating current voltage is provided with an auxiliary winding, and a high frequency voltage obtained from the auxiliary winding is rectified to obtain a voltage for charging a capacitor. The voltage across the capacitor is used as an auxiliary voltage together with the pulsating voltage for driving the inverter. The circuit for charging the capacitor includes a current limiting inductor having first and second coil sections, through which the charging current flows alternately in opposite directions depending upon the polarity of the high frequency voltage.

Power supply device

A low frequency AC voltage is rectified through a full-wave rectifier to obtain a pulsating voltage, which is superimposed with an auxiliary voltage of a predetermined level provided from an auxiliary power source, and the resultant composite pulsating voltage is inverted at an inverter to a high frequency voltage. The high frequency voltage thus obtained from the inverter is used to operate a discharge lamp. Minimum value V.sub.min of the resultant voltage is set to be 1/3 to 4/5 of the maximum value V.sub.max of the resultant voltage.

Apparatus for operating discharge lamps

An apparatus for operating a gaseous discharge lamp comprises a D.C. power source, a transistor inverter which is connected to the D.C. power source through a switch, provided with at least one inverter transistor and generates an output having a prescribed frequency, and a discharge lamp which is energized by an output from the transistor inverter and having a pair of electrodes heated by part of the output. The apparatus further comprises base current control means which holds the base current of the inverter transistor at a level lower than a first level during a prescribed length of time after the close of the switch, and holds the base current at the first level after the prescribed length of time. The discharge lamp has its electrodes preheated, but does not display discharge when the base current has a level lower than the first level, and commences discharge when the base current reaches the first level and thereafter continues discharge.

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Yokohama, Japan

Nanjou Aoike