Koito Manufacturing Company, Ltd.

Soichi Yagi

Goichi Oda

Tomoyuki Ichikawa

Akihiro Matsumoto

Akiyoshi Ozaki

Masatoshi Sugasawa

Masaya Shidoh

Masayasu Ito

Hitoshi Takeda

Hiroki Shibata

Kotaro Matsui

Akihiro Mochizuki

Hiroki Ishibashi

Shuji Matsuura

Atsuhiko Murata

A discharge lamp lighting circuitincludes a direct current-alternating current converting circuit, a starting circuit, controlling meansfor controlling power, switching elementsH,L driven by the controlling meansand a series LC resonance circuit (). A frequency modulating circuit is provided for restraining acoustic resonance by modulating a frequency of driving the switching element. When a basic frequency related to the drive frequency is equal to or higher than 1 MHz, a modulation width is set to be equal to or higher than 20 kHz.

Discharge lamp lighting circuit

A lighting system provides an auxiliary lighting circuit for turning on an auxiliary light source in place of the discharge lamp if the abnormality in the lighting circuit is detected.

Lighting system for vehicle

A lighting circuit for a vehicular discharge lamp having a DC voltage booster circuit for boosting an input voltage from a DC voltage input terminal, comprises a current detector, a voltage detector, an abnormality judging circuit, and a power cutoff relay circuit. The current detector acquires a detection signal concerning an output current of the DC voltage booster circuit. The voltage detector acquires a detection signal concerning an output voltage of the DC voltage booster circuit. The abnormality judging circuit compares the levels of the detection signals from the current detector and the voltage detector with each other to determine whether or not the lighting circuit is in an abnormal status. The power cutoff circuit inhibits power supply to the discharge lamp upon reception of a signal from the abnormality judging circuit representing an abnormality in the lighting circuit.

Lighting circuit for vehicular discharge lamp

A lighting circuit for a vehicular discharge lamp for lighting a discharge lamp using a DC power supply, comprises an OFF state detector, a DC input voltage detector and a power cutoff means. The OFF state detector detects an OFF status of a discharge lamp. The DC input voltage detector detects if a DC input voltage is within a predetermined range. The power cutoff means inhibits power supply to the discharge lamp when the OFF status of the discharge lamp is detected by the OFF state detector and the DC input voltage lying off the predetermined range is detected by the DC input voltage detector, and permits power supply to the discharge lamp upon reception of a signal indicating that the DC input voltage has returned within that range.

A lighting circuit for high-pressure discharge lamp or high-pressure discharge lamp for vehicular use including a DC voltage booster circuit, a voltage detector, a current detector, an a control circuit. The booster circuit boosts the input voltage from a DC voltage input terminal to provide an output voltage that is converted into an AC voltage to be applied to a high-pressure discharge lamp. The voltage detector detects the output voltage of the booster circuit. The current detector detects an output current of the booster circuit. The control circuit applies a control signal corresponding to signals from the voltage detector and the current detector to control the output voltage of the booster circuit. The control circuit, the voltage detector and the current detector constitute a feedback system for the booster circuit. Also, in lighting the discharge lamp from a cool state, therefore, the operation of the timer circuit causes transition to constant power control using rated power after execution of control so as to supply power exceeding the rated power to the output voltage detector and the output current detector sequentially.

Lighting circuit for high-pressure discharge lamp for vehicles

A lighting circuit for a vehicular discharge lamp has a DC voltage booster circuit, a control circuit, and a voltage drop detector. The booster circuit boosts an input voltage from a DC voltage input terminal to provide an output voltage to be applied to the discharge lamp. The control circuit functions for varying the output voltage of the DC booster circuit to effect lighting control including constant power control of the discharge lamp. The voltage drop detector detects a DC input voltage applied to the booster circuit. In response to a signal received from the voltage drop detector in accordance with a drop of the DC input voltage, the control circuit performs voltage boosting control to set power supplied to the dicharge lamp lower than the rated power. It is therefore possible to suppress an increase in current consumption and a consequent increase in generated heat when the DC input voltage drops. Further, the lighting circuit for a vehicular discharge lamp has a protection circuit which cuts off the supply of the DC input voltage to the DC voltage booster circuit when it is detected that the DC input voltage has dropped too low to maintain the lighting of the discharge lamp, and allows the DC input voltage to be supplied again to the booster circuit when the DC input voltage has been restored to or greater than a predetermined value. It is therefore possible to prevent the circuit elements from being deteriorated or destroyed due to an abnormal reduction in DC input voltage.

A lighting circuit for a metallic halide lamp for vehicular headlight applications is disclosed. Included are a pair of input terminals between which a battery is connected for feeding the lamp via a normally open relay switch which is closed upon energization of an associated relay coil. The relay coil is connected in series with an operator actuated lamp switch and a protection switch, so that both lamp switch and protection switch must be closed to energize the relay coil and hence to close the relay switch. The protection switch is automatically opened to deenergize the relay coil when the battery develops overvoltage or when the lamp will not glow upon closure of the lamp switch. In an alternate embodiment, the protection switch is also opened in response to the development of overcurrent or overvoltage by a d.c. voltage booster circuit included in the lighting circuit.

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Shizuoka, Japan

Soichi Yagi