Patent ID: 9585209
Date: 2017-02-28
CPC Classifications: H05B

Claim:
1. A lighting apparatus, comprising: a switching element connected to a DC power supply and controlled to be turned on and off; an inductor through which a current flows from the DC power supply when the switching element is turned on, said inductor being connected 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; and a control circuit adapted to receive a dimming signal corresponding to a dimmer setting corresponding to a brightness level of the light source load and to control an On and Off operation of the switching element, wherein the control circuit operates in 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 switching frequency and an On time so that a current flows through the inductor in continuous mode without a time interval during which value of the current is zero; (b), in the second control mode, to change the On time of the switching element while maintaining the switching frequency of the switching element fixed; and (c), in the third control mode, to change the switching frequency of the switching element while maintaining the On time of the switching element fixed, wherein the control circuit operates in the second control mode at least for a first dimming interval in a dimming range between a dimmer setting corresponding to a minimum brightness level of the light source load and a dimmer setting corresponding to a maximum brightness level of the light source load, wherein the control circuit operates in the third control mode at least for a second dimming interval, different from the first dimming interval, in the dimming range between the dimmer setting corresponding to the minimum brightness level of the light source load and the dimmer setting corresponding to the maximum brightness level of the light source load, and wherein the control circuit is adapted: (i), if the dimming signal corresponds to the dimmer setting corresponding to the maximum brightness level of the light source load, to operate in the first control mode to light the light source load to the maximum brightness level of the light source load; and (ii), if the dimming signal corresponds to a dimmer setting between the dimmer setting corresponding to a minimum brightness level of the light source load and the dimmer setting corresponding to a maximum brightness level of the light source load, to operate in one of the second and third control modes , the control circuit operating in the second control mode when the dimming signal corresponds to a dimmer setting in the second dimming interval and the control circuit operating in the third control mode when the dimming signal corresponds to a dimmer setting in the second dimming interval.