Patent ID: 9398648
Filing Date: 2016-07-19
CPC Classification: H05B

Claim Text:
1. A lighting device comprising: a lighting unit including a switching device and configured to output a direct current; a smoothing unit having a capacitor configured to smooth the direct current outputted from the lighting unit and supply the smoothed direct current to a light source; a signal processing unit configured to generate a PWM signal; and a control unit adapted to control the switching device to alternately repeat a turning on and off of the switching device during a first time period while the PWM signal is a high level and to maintain an off state of the switching device during a second time period while the PWM signal is a low level, wherein during the first time period, the smoothed direct current is increased and during the second time period, the smoothed direct current is decreased, wherein a product of a frequency of the PWM signal and a capacitance of the capacitor is equal to or greater than 0.05 in order to set a ripple factor in the smoothed direct current to be 15% or less, wherein the ripple factor is defined as: where I wherein a unit of the frequency is hertz and a unit of capacitance is farad.