Abstract: A lighting device of a discharge lamp, the lighting device includes: a DC voltage generating circuit including: a switching element that is controlled by a first controlling signal; and a coil that has one end portion, to which a first DC voltage is input, and the other end portion of the coil outputs a second DC voltage, and an AC voltage generating circuit that converts into an AC voltage and supplies to the discharge lamp; and a control circuit unit, which receives a polarity-inversion instructing signal, which generates a second controlling signal to determine a timing of polarity-inversion after a predetermined first period is elapsed, which sets a latest ON period, wherein the latest ON period is set based on both an elapsed time and the duty ratio, and which generates the first controlling signal to restart the ON/OFF control at a timing after a second period is elapsed.

Abstract: In a pulse width modulation circuit, which generates an output whose pulse width is modulated by controlling a duty ratio of an oscillation circuit adapted to generate an oscillation at a frequency determined by a resistor and a capacitor to be electrically charged via the resistor, there is provided a resistance value varying means to vary a value of the resistor. The value of the resistor is varied by shorting the both ends of the resistor with a transistor, whereby the capacitor is charged in a reduced amount of time realizing a high-speed pulse width modulation circuit.

Abstract: In a pulse width modulation circuit, which generates an output whose pulse width is modulated by controlling a duty ratio of an oscillation circuit adapted to generate an oscillation at a frequency determined by a resistor and a capacitor to be electrically charged via the resistor, there is provided a resistance value varying means to vary a value of the resistor. The value of the resistor is varied by shorting the both ends of the resistor with a transistor, whereby the capacitor is charged in a reduced amount of time realizing a high-speed pulse width modulation circuit.

Abstract: A discharge lamp lighting circuit includes an open-circuit protection means to protect a driving means when a discharge lamp is not lighted. The open-circuit protection means is adapted to send out to a control means a signal for limiting a current flowing in the driving means to or below a predetermined value when the tube current is equal to or lower than a first value predetermined, and a signal for sequentially increasing a current flowing in the driving means up to a rated current when the tube current is higher than the first value and also is equal to or lower than a second value predetermined, and to stop a driving signal sent from the control means when a tube current flowing in the discharge lamp has a value equal to or lower than the first value after a predetermined time.

Abstract: A discharge lamp lighting circuit includes an open-circuit protection means to protect a driving means when a discharge lamp is not lighted. The open-circuit protection means is adapted to send out to a control means a signal for limiting a current flowing in the driving means to or below a predetermined value when the tube current is equal to or lower than a first value predetermined, and a signal for sequentially increasing a current flowing in the driving means up to a rated current when the tube current is higher than the first value and also is equal to or lower than a second value predetermined, and to stop a driving signal sent from the control means when a tube current flowing in the discharge lamp has a value equal to or lower than the first value after a predetermined time.

Abstract: In a pulse width modulation circuit, which generates an output whose pulse width is modulated by controlling a duty ratio of an oscillation circuit adapted to generate an oscillation at a frequency determined by a resistor and a capacitor to be electrically charged via the resistor, there is provided a resistance value varying means to vary a value of the resistor. The value of the resistor is varied by shorting the both ends of the resistor with a transistor, whereby the capacitor is charged in a reduced amount of time realizing a high-speed pulse width modulation circuit.

Abstract: An image input device includes a turn-on circuit and a converting circuit for receiving light reflected at an object and converting it into an electrical signal. The image input device is connected to a laser device as an output device. The turn-on circuit includes a triangular wave generating circuit, an error amplifier, a pulse width modulator, a lamp turn-on circuit, a xenon lamp and a protection circuit. The converting circuit includes an oscillator, a system control unit having a microprocessor to control the whole image input device, and image sensors. A same clock having a certain frequency from the oscillator is supplied to the turn-on circuit and the system control unit in the converting circuit thereby controlling the turn-on circuit to synchronize with driving signals of the image sensors.

Abstract: An image input device includes a turn-on circuit and a converting circuit for receiving light reflected at an object and converting it into an electrical signal. The image input device is connected to a laser device as an output device. The turn-on circuit includes a triangular wave generating circuit, an error amplifier, a pulse width modulator, a lamp turn-on circuit, a xenon lamp and a protection circuit. The converting circuit includes an oscillator, a system control unit having a microprocessor to control the whole image input device, and image sensors. A same clock having a certain frequency from the oscillator is supplied to the turn-on circuit and the system control unit in the converting circuit thereby controlling the turn-on circuit to synchronize with driving signals of the image sensors.