LIGHTING APPARATUS AND ILLUMINATING FIXTURE WITH THE SAME
First Claim
1. A lighting apparatus, comprising:
- a switching element connected in series to a DC power supply and controlled to be turned on and off at high frequency;
an inductor through which a current flows from the DC power supply when the switching element is turned on, said inductor being connected in series to the switching element;
a diode that discharges electromagnetic energy stored in the inductor, when the switching element is turned on, to a light source load comprising a semiconductor light emitting element when the switching element is turned off;
an output capacitor connected in parallel with the light source load and adapted to smooth a pulsation component of an output current supplied to the light source load, said pulsation component being caused by the turning on and off of the switching element; and
a control circuit adapted to control an On and Off operation of the switching element,wherein the control circuit comprises first, second and third control modes as control modes of the switching element, and is adapted;
(a), in the first control mode, to turn the switching element on and off at a predetermined oscillating frequency and an On time so that a current flows through the inductor in a critical mode or a discontinuous mode;
(b), in the second control mode, to fix the oscillating frequency of the switching element and change the On time of the switching element, and(c), in the third control mode, to fix the On time of the switching element and change the oscillating frequency of the switching element,wherein the second control mode and the third control mode are allocated for at least two intervals of intervals into which a dimming range between a minimum dimming ratio and a maximum dimming ratio is divided, andwherein the control circuit is adapted;
(i), if a full lighting mode is designated, to select the first control mode to fully light the light source load; and
(ii), if a dimming ratio is designated, to select one of the second and third control modes according to the interval, to which the dimming ratio corresponds, to dim the light source load at the dimming ratio.
3 Assignments
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Accused Products
Abstract
A control circuit selects a first control mode in which a switching element is turned on and off so that a current flows through an inductor in a critical or discontinuous mode, thereby fully lighting a light source load. The control circuit selects one of a second control mode in which On time of the switching element is changed and a third control mode in which an oscillating frequency is changed according to an interval, to which a designated dimming ratio corresponds, to dim the light source load. An output capacitor connected between output terminals of a step-down chopper circuit smoothes pulsation component of an output current supplied to the light source load and has capacity set so that a ripple ratio of the output current is less than 0.5 at full lighting of the light source load.
21 Citations
9 Claims
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1. A lighting apparatus, comprising:
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a switching element connected in series to a DC power supply and controlled to be turned on and off at high frequency; an inductor through which a current flows from the DC power supply when the switching element is turned on, said inductor being connected in series to the switching element; a diode that discharges electromagnetic energy stored in the inductor, when the switching element is turned on, to a light source load comprising a semiconductor light emitting element when the switching element is turned off; an output capacitor connected in parallel with the light source load and adapted to smooth a pulsation component of an output current supplied to the light source load, said pulsation component being caused by the turning on and off of the switching element; and a control circuit adapted to control an On and Off operation of the switching element, wherein the control circuit comprises first, second and third control modes as control modes of the switching element, and is adapted; (a), in the first control mode, to turn the switching element on and off at a predetermined oscillating frequency and an On time so that a current flows through the inductor in a critical mode or a discontinuous mode; (b), in the second control mode, to fix the oscillating frequency of the switching element and change the On time of the switching element, and (c), in the third control mode, to fix the On time of the switching element and change the oscillating frequency of the switching element, wherein the second control mode and the third control mode are allocated for at least two intervals of intervals into which a dimming range between a minimum dimming ratio and a maximum dimming ratio is divided, and wherein the control circuit is adapted; (i), if a full lighting mode is designated, to select the first control mode to fully light the light source load; and (ii), if a dimming ratio is designated, to select one of the second and third control modes according to the interval, to which the dimming ratio corresponds, to dim the light source load at the dimming ratio. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification