Light-emitting diode driving device for reducing light off period
An LED driving apparatus is provided. The apparatus includes an LED Portion 10 , a charging/discharging capacitor 111 , a capacitor charging and discharging paths, and a capacitor charging constant current portion 110 . The LED driving portion 3 controls a current in the LED portion 10 . The capacitor 111 is connected in parallel to the LED portion 10 . The charging and discharging paths are connected to the capacitor whereby charging and discharging the capacitor, respectively. The constant current portion 110 is connected on the charging path and controls a charging current so that the capacitor is charged at a constant current. When rectified voltage applied to the LED portion becomes high, the capacitor is charged with the charging current through the charging path. When the voltage becomes low, the capacitor is discharged at a discharging current through the discharging path so that the discharging current is applied to the LED portion.
1. A light-emitting diode driving apparatus comprising:
a rectifying circuit that can be connected to AC power supply and rectifies an AC voltage of the AC power supply to provide a rectified voltage;
an LED portion that includes first and second LED sections serially connected to the output side of said rectifying circuit, each of the first and second LED sections including at least one LED device;
a third LED section that includes at least one LED device serially connected to said second LED section;
an LED driving portion that controls a current flowing in said LED portion;
a charging/discharging capacitor that is connected in parallel to said LED portion;
a capacitor charging path that is connected to said charging/discharging capacitor whereby charging said charging/discharging capacitor;
a capacitor discharging path that is connected to said charging/discharging capacitor whereby discharging said charging/discharging capacitor;
a capacitor charging constant current portion that is connected on said capacitor charging path and adjusts a capacitor charging current to a constant current;
a first portion that is connected in parallel to said second LED section, and controls the flowing current amount in said first LED section;
a second portion that is connected in parallel to said third LED section, and controls the flowing current amount in said first and second LED sections;
a fourth portion that is connected serially to said third LED section, and controls the flowing current amount in said first, second and third LED sections;
a first current control portion that controls said first portion;
a second current control portion that controls said second portion;
a fourth current control portion that controls said fourth portion; and
a current detection portion that detects a current detection signal based on the amount of a current flowing in an output line serially connected from said first LED section to said third LED section,
wherein when the rectified voltage applied to said LED portion becomes high, said charging/discharging capacitor is charged with the charging current through said charging path, and
when the rectified voltage applied to said LED portion becomes low, said charging/discharging capacitor is discharged at a discharging current through said discharging path so that the discharging current is applied to said LED portion.
2. The light-emitting diode driving apparatus according to claim 1 further comprising
a charging diode that is connected on said capacitor charging path and allows the charging current to flow whereby charging said charging/discharging capacitor, and
a discharging diode that is connected on said capacitor discharging path and allows the discharging current to flow whereby discharging said charging/discharging, capacitor.
3. The light-emitting diode driving apparatus according to claim 1 , wherein said capacitor charging constant current portion includes a plurality of transistors.
4. The light-emitting diode driving apparatus according to claim 1 further comprising a harmonic suppression signal providing portion that provides a harmonic suppression signal voltage based on the rectified voltage provided from said rectifying circuit, wherein said first, second and fourth current control portions compare the current detection signal detected by said current detection portion with the harmonic suppression signal voltage provided by said harmonic suppression signal providing portion, and control said first, second and fourth portions based on the comparison result whereby suppressing harmonic components.
5. The light-emitting diode driving apparatus according to claim 4 further comprising
a fourth LED section that includes at least one LED device serially connected to said third LED section,
a third portion that is connected in parallel said fourth LED section, and controls the flowing current amount in said first, second and third LED sections, and
a third current control portion that controls said third portion, wherein
said fourth portion controls the flowing current amount in said first, second, third and fourth LED sections.