1. Field of the Invention
The present invention relates to an electronic ballast, and more particularly, to an electronic ballast for varying an inductor or a capacitor of a resonance circuit according to a selection of a user in order to adjust consumed power of a lamp.
2. Description of the Related Art
A fluorescent lamp is a kind of discharge tubes and requires a high voltage on an initial stage to discharge thermal electrons necessary for electric discharge. Also, the fluorescent lamp has a negative resistance characteristic in which a voltage applied thereto after the electric discharge decreases with an increase in a current flowing in the fluorescent lamp. Therefore, the fluorescent lamp is unstably lighted or broken down due to the negative resistance characteristic. An electronic ballast supplies a high voltage to the fluorescent lamp on the initial stage to light the fluorescent lamp and then controls the current flowing in the fluorescent lamp to keep the brightness of the fluorescent lamp constant.
Since a magnetic ballast uses a chock coil, a leakage transformer, and a high capacity condenser, the magnetic ballast loses a large amount of power of about 8 W due to light emitted from a fluorescent lamp and heat generated by an iron core and a copper wire. Thus, power of about 8 W or more is lost. Also, since the magnetic ballast lights the fluorescent lamp with commonly used power of 60 Hz, the fluorescent lamp flickers. When a power state is poor and the magnetic ballast is worn out, the fluorescent lamp may more seriously flicker and may not be lighted up at a low ambient temperature or a high percentage of humidity.
In order to solve these problems, the electronic ballast rectifies commonly used alternating current (AC) power of 60 Hz into direct current (DC) power using a semiconductor device. Also, an inverter circuit converts the DC power into high frequency power between 25 KHz and 50 KHz so as to stably light the fluorescent lamp through an output power controlling circuit. Since the electronic ballast lights the fluorescent lamp using the high frequency power, the electronic ballast improves luminous efficiency by about 15%, compared to the magnetic ballast. Also, since the electronic ballast uses the semiconductor device, the electronic ballast reduces loss of power caused by heat generated from the chock coil by about 25%. Thus, the electronic ballast a power saving effect of 35% or more, compared to the magnetic ballast.
Besides saving power, the electronic ballast lights the fluorescent lamp (which flickers 5 to 10 million times per second) using the high frequency power to supply high-quality light sensed by eyes so as to protect eyesight. In addition, the electronic ballast removes noise which is generated by vibrations of an electromagnetic force generated by the chock coil and the iron core of the magnetic ballast. The electronic ballast is lighter than the magnetic ballast and generates heat 10° lower than the magnetic ballast. Thus, the electronic ballast reduces a heating rate. Since the electronic ballast lights the fluorescent lamp even at a low voltage, the electronic ballast is appropriate in the summer in which a power state is poor or in a region in which a power state is poor. Also, the electronic ballast lights the fluorescent lamp at a low temperature and uses lamps without distinction.
The above contents have been described to help understanding of the present invention but do not mean the prior art widely well known in the art to which the present invention pertains.