Abstract: A lighting device is capable of realizing a stable dimming control in a wide range of light output. The lighting device includes a DC power circuit for providing power to a switching element of the lighting device. A current controller switches the switching element to enable a current to flow from the DC power circuit through a solid state light source and maintain the current from the DC power circuit through the solid state light source current controller at a predetermined current. The current controller includes a first switching controller operable to change a width of an on-pulse provided to the switching element and a second switching controller operable to determine a burst-on time during which the on-pulses determined by the first switching controller are provided to the switching element. The burst-on time is longer than an on-pulse period of the first switching controller.

Abstract: A lighting device is capable of realizing a stable dimming control in a wide range of light output. The lighting device includes a DC power circuit for providing power to a switching element of the lighting device. A current controller switches the switching element to enable a current to flow from the DC power circuit through a solid state light source and maintain the current from the DC power circuit through the solid state light source current controller at a predetermined current. The current controller includes a first switching controller operable to change a width of an on-pulse provided to the switching element and a second switching controller operable to determine a burst-on time during which the on-pulses determined by the first switching controller are provided to the switching element. The burst-on time is longer than an on-pulse period of the first switching controller.

Abstract: An inverter controller dives an inverter to operate at a switching frequency selectively from one of a preheating frequency (f1), a starting frequency (f2), and a lighting frequency (f3) which are different from each other, thereby giving a preheating mode, a starting mode, and a lighting mode. A reset means is provided to make the starting mode upon lowering of a voltage supplied to the inverter below a first threshold, while an inverter stop means is provided to stop the inverter upon detection of abnormality of a discharge lamp. A timer generates a signal determining the start of the preheating, starting, and/or lighting modes, and generates a reset signal disable signal for disabling the reset means, an inverter stop disable signal for disabling the inverter stop means. The inverter controller includes a frequency sweep means for varying the switching frequency gradually from the starting frequency to the lighting frequency.

Abstract: An inverter controller dives an inverter to operate at a switching frequency selectively from one of a preheating frequency (f1), a starting frequency (f2), and a lighting frequency (f3) which are different from each other, thereby giving a preheating mode, a starting mode, and a lighting mode. A reset means is provided to make the starting mode upon lowering of a voltage supplied to the inverter below a first threshold, while an inverter stop means is provided to stop the inverter upon detection of abnormality of a discharge lamp. A timer generates a signal determining the start of the preheating, starting, and/or lighting modes, and generates a reset signal disable signal for disabling the reset means, an inverter stop disable signal for disabling the inverter stop means. The inverter controller includes a frequency sweep means for varying the switching frequency gradually from the starting frequency to the lighting frequency.

Abstract: A ballast circuit for a discharge lamp capable of protecting the circuit when the lamp reaches its end of life with a cost effective circuit arrangement. The circuit includes a DC voltage sensing network for sensing a DC voltage which appears as a consequence of the lamp reaching its end of life. Upon the sensed DC voltage exceeding a threshold, a control is made to limit or stop supplying an output power to the lamp for protecting the ballast circuit from an otherwise generating excessive current. The sensing network is composed of a DC sensing capacitor and a resistor which are connected in circuit outside of a resonant circuit responsible for generating a high frequency voltage to operate the lamp. Thus, the DC sensing capacitor can be kept free from the high voltage generated by the resonant circuit and be of less cost for reducing a manufacturing cost.

Abstract: A ballast circuit for a discharge lamp capable of protecting the circuit when the lamp reaches its end of life with a cost effective circuit arrangement. The circuit includes a DC voltage sensing network for sensing a DC voltage which appears as a consequence of the lamp reaching its end of life. Upon the sensed DC voltage exceeding a threshold, a control is made to limit or stop supplying an output power to the lamp for protecting the ballast circuit from an otherwise generating excessive current. The sensing network is composed of a DC sensing capacitor and a resistor which are connected in circuit outside of a resonant circuit responsible for generating a high frequency voltage to operate the lamp. Thus, the DC sensing capacitor can be kept free from the high voltage generated by the resonant circuit and be of less cost for reducing a manufacturing cost.

Abstract: A power supply with a full-wave rectifier and a chopper having an inductor and a transistor connected in series across the rectifier. The transistor is switched on and off providing an interrupted voltage which is applied across a smoothing capacitor, via a blocking diode, to produce a smoothed DC voltage for driving a load. When the transistor is turned on, current from the rectifier is drawn through the inductor. When the transistor is turned off, the current through the inductor is conducted, in a positive direction, to the smoothing capacitor. The inductor and parasitic capacitance inherently present in the chopper create oscillations which allow current to flow through the inductor in a negative direction.