DISCONTINUOUS AC POWER BALLAST FOR DISCHARGE LAMP

Technical Field The present invention relates to a discontinuous AC ballast for a discharge lamp comprising DC or a rectifier circuit converting AC to DC, a controller circuit generating discontinuous AC power control signals, and an electric power circuit supplying discontinuous AC to the discharge lamp with control signals generated by the controller circuit, that prevents undesirable power loss by stopping current supply to the discharge lamp for a predetermined period at a transition point of AC (+) and (-), when current is supplied to a conventional discharge lamp.

Background Art

Conventional discharge lamps such as a fluorescent lamp, mercury lamp, and neon lamp are illuminated with AC supply, and built-in ballasts are used to extend the lifetime of the lamps and to maintain a continuous illumination state.

FIG. 4 is a conceptual view showing the relationship of continuous AC and plasma in a conventional discharge lamp and FIG 5 is a wave diagram of the continuous AC in the conventional discharge lamp. Firstly, referring to FIG. 4, the relationship between continuous AC and plasma having electrons and positive ions in the discharge lamp will be described as follows, wherein the continuous AC is supplied from a conventional ballast to the discharge lamp.

As shown in step (a) of FIG 4, if AC (+) and (-) is respectively applied to the first and second electrodes of a discharge lamp 4, electrons © are accelerated and move towards an anode (+) and positive ions ® are accelerated and move towards a cathode (-) by an electric field.

Subsequently, as shown in step (b), if AC (+) and (-) is applied in the reverse direction of step (a) to both electrodes of the discharge lamp 4, electrons ® are accelerated and move towards the reversed anode (+), and positive ions © are accelerated and move towards the reversed cathode (-) by the electric field formed in the direction opposite to the electric field in step (a).

Accordingly, if the AC is continuously applied to the discharge lamp 4, a power loss region 11 is formed at a transition point of the electric field as shown in FIG. 5.

That is, the power loss region 11 is a region in which movement direction of the accelerated electrons © and positive ions © is reversed to the opposite direction as the anode (+) and cathode (-) of the discharge lamp 4 are reversed.

However, in the power loss region 11, power is required both to illuminate the discharge lamp and to change the movement directions of electrons © and positive ions ©, and thereby more power should be supplied to compensate the energy loss caused from the transition point of the electric field so that electrons © of the reversed direction can be accelerated to an extent to have enough energy for illumination. Therefore, substantial power loss is caused.

As described above, the conventional ballast applied with the continuous AC does not fully utilize the supplied current for the illumination of the discharge lamp because it loses a large amount of the power at the transition point of the electric field, and thereby has a disadvantage of low energy efficiency due to undesirable power consumption.

Disclosure of the Invention Technical Problem

An object of the present invention is to provide a discontinuous AC ballast for a discharge lamp that prevents power loss caused from a transition point of an electric field by installing a controller circuit to control discontinuous AC supply in an electric power circuit of

the discharge lamp using AC.

Technical Solution

In order to achieve the above object, the present invention comprises a rectifier circuit converting AC to DC, a controller circuit controlling control signals to generate discontinuous

AC, and an electric power circuit supplying the discontinuous AC to a discharge lamp with the control signals generated by the controller circuit, which provides a pause period of current supply at a transition point of an electric field applied to the discharge lamp.

Advantageous Effects

With the discontinuous AC ballast according to the present invention, energy efficiency may be improved by saving 30 - 50% of power consumed to change the acceleration direction of electrons and positive ions at the transition point of the electric field. Additionally, the lifetime of the discharge lamp may be extended by restraining damages of electrodes due to heat generated by unnecessary power consumption at the transition point of the electric field.

Description of the Drawings

FIG. 1 is a conceptual view showing the relationship of discontinuous AC and plasma in ballast according to the present invention. FIG 2 is a schematic block diagram of a ballast circuit according to the present invention.

FIG 3 is a circuit diagram of a ballast according to an example embodiment of the present invention.

FIG. 4 is a conceptual view showing the relationship of continuous AC and plasma in a conventional discharge lamp.

FIG. 5 is a wave diagram of the continuous AC in a conventional discharge lamp.

Best Mode

Hereinafter, preferred example embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a conceptual view showing the relationship of discontinuous AC and plasma in a ballast according to the present invention. Referring to FIG. 1, the relationship between discontinuous AC and plasma having electrons and positive ions in a discharge lamp will be described in detail as follows, wherein the discontinuous AC is supplied by the ballast according to the present invention. As shown in FIG 1 , if current is applied to both ends of a discharge lamp 4, plasma is generated in the discharge lamp 4. That is, if AC (+) and (-) is selectively applied to both electrodes of the discharge lamp as shown in step (c), electrons © are accelerated and move towards an anode (+), and positive ions © are accelerated and move towards a cathode (-) by an electric field, and thereby the discharge lamp 4 illuminates. Subsequently, before applying a reversed AC (+) and (-) to the discharge lamp 4, if current is not applied to both electrodes of the discharge lamp 4 as shown in step (d), electrons © and positive ions © respectively accelerated towards the anode and cathode by the electric field in step (c) freely move and collide with each other as the electric field is released, and thereby their movement directions are scattered and their energy is gradually lost. At this point, as shown in step (e), if AC (-) and (+) is applied to both electrodes of the discharge lamp 4 in the direction opposite to that of step (c), electrons © are accelerated towards the reversed anode (+) from step (c) and positive ions © are accelerated towards the reversed cathode (-) from step (c) by the electric field formed in the direction opposite to that of step (c). As a result, positive ions and negative ions are accelerated and move in the direction opposite to that of step (c), and thereby the discharge lamp illuminates again.

In this state, if power is not applied to both electrodes of the discharge lamp 4 as

shown in step (f), electrons © and positive ions © respectively accelerated towards the reversed anode (+) from step (c) and the reversed cathode (-) from step (c) by the electric field in step (e) freely move and collide with each other as the electric field is released, and thereby their movement directions are scattered and their energy is gradually lost. As a result, at the transition point, namely at a shift point of AC (+) and (-), electrons

© and positive ions © accelerated in a given directions do not consume power required for their direction change and movement, and thereby waste of the power may be prevented and energy efficiency of illumination may be improved.

Here, the duration of applying no current in steps (d) and (f) is preferably maintained shorter than the time at which energy of electrons © of plasma in the discharge lamp 4 is kept above the energy level required for illumination.

That is, electrons © illuminated with enough energy supplied by an electric field lose their direction and energy at the same time with the direction change of the electric field, and finally stop illuminating at a certain point in the energy reduction procedure. Accordingly, a pause period of current supply is preferably designed to be shorter than the time from the transition point of the electric field to the point at which electrons © stop illuminating, so that the discharge lamp 4 can maintain the illumination state with AC supplied discontinuously. The pause period differs according to the composition of gas in the discharge lamp 4, and an optimum period may be found out through repeated experiments with regards to the compositions.

FIG. 2 is a schematic block diagram of a ballast circuit according to the present invention. Referring to FIG. 2, a circuit according to the present invention comprises a rectifier circuit 1 converting commercial AC 10 to DC, a controller circuit 2 generating control signals, an electric power circuit 3 generating discontinuous AC with the control signals generated by the controller circuit 2, and a discharge lamp 4 illuminated by the discontinuous AC supplied from the electric power circuit 3. Here, the rectifier circuit 1 may

be omitted, if DC is directly supplied to the controller circuit 2 and electric power circuit 3.

With the technical concept of the above description, a configuration of a circuit according to the present invention may be designed in more detail as shown in FIG 3.

Mode for carrying out the Invention

FIG. 3 is a circuit diagram of a ballast according to an example embodiment of the present invention. FIG. 3 is the circuit diagram showing an example embodiment of the present invention, which supplies discontinuous AC so that current is not applied to a discharge lamp 4 at a transition point of an electric field. However, the present invention should not be limited to the illustrated example.

Referring to FIG. 3, the circuit according to the present invention comprises a rectifier circuit 1 converting AC 10 to DC so that discontinuous AC is supplied to the discharge lamp 4, a controller circuit 2 generating control signals, and an electric power circuit 3 converting DC to discontinuous AC and supplying it to the discharge lamp 4. The rectifier circuit 1 is a conventional circuit for converting commercial AC to DC, which stably supplies drive voltage VCC2 required for the controller circuit 2 and drive voltage VCCl required for the electric power circuit 3. In the case that DC is directly supplied, the rectifier circuit 1 may be omitted as described above.

The controller circuit 2 receiving the DC from the rectifier circuit 1 generates control signals to control the current supplied to the discharge lamp 4, and controls FETl, FET2, FET3, FET4, and condenser C7 of the electric power circuit 3.

In more detail, an oscillator 5 generates high-frequency signals and supplies them to a shift resistor 7, and the shift resistor 7 receiving the high-frequency signals from the oscillator 5 sequentially supplies discontinuous signals to drivers 8 and 9. Additionally, two drivers 8,9 receiving the discontinuous signals from the shift resistor

7 supplies control signals to the electric power circuit 3 which switches on/off field-effect

transistors FETl and FET4 in a pair, and FET2 and FET3 in a pair.

In the meantime, a timer 6 installed in the controller circuit 2 supplies high voltage required for starting the illumination of the discharge lamp 4 and, after a predetermined time elapse, transfers control signals to the electric power circuit 3 for supplying normal voltage to the discharge lamp 4.

As described above, the electric power circuit 3 receiving control signals from the controller circuit 2 and drive voltage VCCl from the rectifier circuit 1 supplies discontinuous AC for illumination to the discharge lamp 4.

That is, FETl, FET2, FET3, and FET4 receiving the control signals from the drivers 8,9 of the controller circuit 2 convert DC drive voltage VCCl supplied from the rectifier circuit 1 to discontinuous AC, and supply it to the discharge lamp 4.

Additionally, because starting voltage is generally higher than the illumination-maintaining voltage in the case of a discharge lamp, high voltage for starting the illumination of the discharge lamp 4 is supplied to the discharge lamp 4 by utilizing transformer Tl and condenser C7 in the initial state of illumination, and the illumination-maintaining voltage is supplied to the discharge lamp 4 by switching off the condenser C7 with a signal transferred from the timer 6 of the controller circuit 2 right after the illumination of the discharge lamp 4.

Industrial Applicability

As described above, with a discontinuous AC ballast according to the present invention, energy efficiency may be improved by saving 30 - 50% of power consumed to change the acceleration direction of electrons and positive ions at a transition point of an electric field. Additionally, the lifetime of the discharge lamp may be extended by restraining electrode damages due to heat generated by unnecessary power consumption at the transition point of the electric field. As a result, power consumption of the discharge lamp may be saved.