Description

HYBRID BALLAST FOR DRIVING TRIODE CARBON NANO

TUBE LAMP

Technical Field

[1] The present invention relates to a hybrid ballast for driving a triode carbon nanotube

(CNT) lamp, and more particularly to a hybrid ballast for driving a triode CNT lamp, which is capable of applying a high DC voltage to an anode terminal and applying a bipolar pulse to a gate terminal in a state in which a cathode terminal is grounded. Background Art

[2] Fluorescent lamps which are currently being used have been widely used as light sources in a home and an industrial field, together with incandescent lamps. However, in recent research into a light source, the development of a product which emits light similar to solar light with high energy efficiency is further required. In addition, as importance of environment conservation is emphasized, the development of an environment-friendly light source which discharges a small amount of mercury (a fluorescent lamp averagely contains 25 mg of mercury) is further required.

[3] Research into a product capable of providing maximum efficiency has been continuously conducted in the past, and advanced enterprises have focused on the development of a technology for preoccupying a future large market.

[4] In the development of the technology, a light-emitting diode (LED), a plasma display panel (PDP), and an electroluminescence (EL) device have attempted to be used for illumination in some field, but are inferior to the existing fluorescent lamp in view of efficiency, life span, brightness, power consumption, and price.

[5] However, a field emission display (FED) using field emission, which is reported as a representative next-generation light-emitting device recently, can theoretically implement a fluorescent display device having a high response speed and low power consumption and is being expected as an environment-friendly device which has high energy efficiency and does not use harmful gas such as mercury.

[6] As an electron emission source of a field emission light-emitting device, a carbon nanotube (CNT) is most excellent. A field emission lamp using a CNT includes a diode field emission lamp and a triode field emission lamp. In view of life span, the triode field emission lamp is advantageous.

[7] The triode field emission device is obtained by coating a fluorescent material on an anode using transparent electrode glass, vertically arranging a CNT on a cathode and a gate electrode using a suitable method, and maintaining two substrates at a predetermined gap, and performing vacuum packaging.

[8] In order to induce field emission of the CNT lamp, a high DC voltage of about 10 kV should be applied. In order to allow a ballast to output a high voltage, a device having a high internal voltage (e.g., a capacitor, a diode, or a transformer) should be used. The device having the high internal voltage is not widely used in an industrial field and is difficult to be used in an economical or technical viewpoint. Disclosure of Invention Technical Problem

[9] Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a hybrid ballast for driving a triode CNT lamp, which is capable of applying a high DC voltage to an anode terminal and applying a bipolar pulse to a gate terminal in a state in which a cathode terminal is grounded. Technical Solution

[10] In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a hybrid ballast for driving a triode carbon nanotube (CNT) lamp including: a high DC power supply source which supplies a high DC voltage to an anode terminal of the triode in a state in which a cathode terminal is grounded; and a bipolar pulse power supply source which supplies a bipolar pulse voltage to a gate terminal of the triode in a state in which the cathode terminal is grounded.

[11] The high DC power supply source may include a filter which eliminates noise included in an input AC voltage; a rectifier which converts the AC voltage input through the filter into a DC voltage and outputs the DC voltage; an active power factor compensator which compensates for a power factor of the DC voltage output from the rectifier, amplifies the DC voltage, and outputs the amplified DC voltage; an inverter which converts the DC voltage output from the active power factor compensator into a rectangular wave AC voltage having a high frequency; a resonance circuit which boosts the rectangular wave AC voltage output from the inverter to a high sinusoidal wave AC voltage; and a double voltage circuit which rectifies the AC voltage having the high frequency, which is output from the resonance circuit, and outputs a high DC voltage.

[12] The hybrid ballast for driving the triode CNT lamp may further include an output voltage controller which controls a driving frequency of the inverter in order to maintain the high DC voltage output from the double voltage circuit at a constant value.

[13] The bipolar pulse power supply source may include a bipolar pulse driving voltage generator which generates a driving voltage of a bipolar pulse using an AC voltage

across an inductor included in the active power factor compensator; and a bipolar pulse generator which outputs the bipolar pulse using the DC voltage output from the bipolar pulse driving voltage generator. Brief Description of the Drawings

[14] FIG. 1 is a block diagram showing a hybrid ballast for driving a triode CNT lamp according to an embodiment of the present invention; and

[15] FIG. 2 is a circuit diagram showing in detail the hybrid ballast for driving the triode

CNT lamp according to the embodiment of the present invention. Best Mode for Carrying Out the Invention

[16] Hereinafter, a hybrid ballast for driving a triode CNT lamp according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[17] FIG. 1 is a block diagram showing a hybrid ballast for driving a triode CNT lamp according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing in detail the hybrid ballast for driving the triode CNT lamp according to the embodiment of the present invention.

[18] As shown in FIG. 1, the hybrid ballast for driving the triode CNT lamp according to the present invention includes a high DC power supply source 10 which supplies a high DC voltage to an anode terminal of the triode of the triode CNT lamp 30 in a state in which a cathode terminal is grounded and a bipolar pulse power supply source 20 which supplies a bipolar pulse voltage to a gate terminal of the triode of the triode CNT lamp 30 in a state in which the cathode terminal is grounded. That is, the present invention is characterized in that the high DC voltage supplied to the anode terminal and the bipolar pulse supplied to the gate terminal are simultaneously generated in one ballast.

[19] As shown in FIG. 1, the high DC power supply source 10 for generating the high DC voltage supplied to the anode terminal includes a filter 12 for eliminating noise included in an input AC voltage generated by an AC power supply source 11 , a rectifier 13 for converting an AC voltage from which noise is eliminated by the filter 12 into a DC voltage and outputting the DC voltage, an active power factor compensator 14 for compensating for a power factor of the DC voltage, an inverter 15 for converting the DC voltage having the compensated power factor into a rectangular wave voltage, a resonance circuit 16 for boosting the rectangular wave voltage to a sinusoidal wave AC voltage, and a double voltage circuit 17 for rectifying the AC voltage and outputting a high DC voltage.

[20] The high DC power supply source 10 having the above-described configuration generates and applies the high DC voltage to the anode terminal of the field emission

lamp using the CNT.

[21] The filter 12 eliminates a surge component from the AC power supply source 11 or filters noise included in an AC component and outputs the AC voltage. The filter 12 is used to prevent the device from being damaged due to the surge component and to prevent an undesired voltage from being generated due to noise. The filter 12 may be a surge ballast, a Electromagnetic Interference (EMI) filter or an electromagnetic compatibility (EMC) filter.

[22] The AC voltage from which noise is eliminated by the filter 12 is input to the rectifier 13. The rectifier 13 converts the AC voltage into the DC voltage. In the present invention, the rectifier 13 is a bridge type rectifying circuit obtained by connecting four diodes in a bridge shape, as shown in FIG. 2. In the DC voltage output from the rectifier 13, the shape of a current waveform is distorted and thus a phase difference between voltage and current is generated. Accordingly, reactive power needs to be reduced by equalizing the phase and the shape of the current waveform and the phase and the shape of the voltage waveform.

[23] Since the DC voltage output from the rectifier 13 includes a large amount of reactive power, a power factor is low and efficiency deteriorates. The DC voltage output from the rectifier 13 is input to the active power factor compensator 14 such that the power factor is improved.

[24] That is, the active power factor compensator 14 which receives the DC voltage output from the rectifier 13 minimizes the reactive power to improve the power factor, amplifies the DC voltage, and outputs the amplified voltage. The active power factor compensator 14 may be implemented by a variety of circuits for compensating for the power factor. In the present invention, as shown in FIG. 2, a field effect transistor (FET), a diode and an inductor configure the active power factor compensator 14. The driving of the FET is controlled by a power factor compensator (PFC) control circuit.

[25] The active power factor compensator 14 uses an active control integrated circuit (IC) and a boost converter circuit and can control a high power factor and a constant voltage.

[26] In the basic operation principle of the PFC control circuit, the input current waveform is controlled to follow the input voltage waveform under a feedforward control such that the input current waveform is converted into a sinusoidal waveform to improve the power factor and to cope with the restriction of harmonics.

[27] The DC voltage of which the power factor is compensated by the active power factor compensator 14 is input to the inverter 15. The inverter 15 converts the DC voltage having the compensated power factor into a rectangular wave AC voltage having a high frequency and outputs the rectangular wave AC voltage. The inverter 15 is a half- bridge inverter as shown in FIG. 2. Two FETs configuring the inverter 15 are

frequency-controlled and driven by a pulse width modulation (PWM) control circuit. [28] That is, the inverter 15 includes two MOSFETs and at least two capacitors for dividing the DC voltage in a half-bridge structure and generates the rectangular wave

AC voltage having the high frequency. [29] The rectangular wave AC voltage output from the inverter 15 is input to the resonance circuit 16. The resonance circuit 16 boosts the rectangular wave AC voltage to the high sinusoidal wave AC voltage and outputs the high sinusoidal wave AC voltage. [30] The resonance circuit 16 LC-resonates to convert the rectangular wave AC voltage having the high frequency, which is output from the inverter 15, into the sinusoidal wave AC voltage. The sinusoidal wave AC voltage output from the resonance circuit

16 can adjust a peak value of the output sinusoidal wave AC voltage by a variation in resonance gain according to a variation in operational frequency.

[31] The AC voltage having the high frequency, which is output from the resonance circuit 16, is input to the double voltage circuit 17. The double voltage circuit 17 rectifies the AC voltage having the high frequency and outputs the high DC voltage. That is, the double voltage circuit 17 rectifies the high sinusoidal wave voltage output from the resonance circuit 16 and boosts the voltage in proportion to a double voltage value. The high DC voltage output from the double voltage circuit 17 is applied to the anode terminal of the triode CNT lamp.

[32] The high DC voltage output from the double voltage circuit 17 should be applied to the anode terminal of the triode CNT lamp while being maintained at a constant value. Accordingly, in order to control the high voltage output from the double voltage circuit

17 to be maintained at the constant value, an output voltage controller 18 is further included. The output voltage controller 18 controls a driving frequency of the inverter 15.

[33] The output voltage controller 18 controls the PWM control circuit in order to increase the driving frequency of the inverter 15 if the high DC voltage output from the double voltage circuit 17 is higher than a normal output value and controls the PWM control circuit in order to decrease the driving frequency of the inverter 15 if the high DC voltage output from the double voltage circuit 17 is lower than the normal output value.

[34] That is, a resonance type half-bridge converter has a characteristic in which a resonance gain is decreased if a switching frequency is increased and is increased if the switching frequency is decreased in a specific frequency range. Accordingly, when the output voltage is increased, the switching frequency of the PWM control circuit of the inverter is increased and, when the output voltage is decreased, the switching frequency of the PWM control circuit of the inverter is decreased. Thus, the output

voltage is constantly maintained.

[35] The high DC voltage generated by the high DC power supply source 10 having the above-described configuration is applied to the anode terminal of the triode CNT lamp such that the lamp can be smoothly turned on.

[36] Meanwhile, a bipolar pulse applied to the gate terminal of the triode CNT lamp is not generated by applying a separate driving voltage and is generated using the AC voltage across the inductor included in the active power factor compensator 14 of the high DC power supply source 10.

[37] That is, as shown in FIGS. 1 and 2, the bipolar pulse power supply source 2 uses the

AC voltage across the inductor of the active power factor compensator 14 included in the high DC power supply source 10.

[38] A bipolar pulse driving voltage generator 21 generates a DC driving voltage of a bipolar pulse using the AC voltage across the inductor of the active power factor compensator 14. The bipolar pulse driving voltage generator 21 rectifies the voltage across the inductor of the active power factor compensator 14 and generates the driving voltage without ripple using only a transistor, a zener diode and a resistor.

[39] The driving voltage generated by the bipolar pulse driving voltage generator 21 is applied to a bipolar pulse generator 22. The bipolar pulse generator 22 receives the driving voltage and generates a bipolar pulse. The bipolar pulse generator 22 generates the bipolar pulse having a high frequency and a pulse width of several microseconds or less using the driving voltage output from the bipolar pulse driving voltage generator 21. This bipolar pulse is applied to the gate terminal of the triode CNT lamp such that the lamp can be smoothly turned on.

[40] According to the present invention, it is possible to implement a hybrid ballast in which the outputs of the double voltage circuit 17 and the bipolar pulse generator 22 are connected to the field emission lamp using the CNT through respective output lines. Industrial Applicability

[41] According to a hybrid ballast for driving a triode CNT lamp of the present invention, since, in one ballast, a high DC voltage applied to an anode terminal can be generated and a bipolar pulse applied to a gate terminal can be generated in a state in which a cathode terminal is grounded, it is possible to smoothly drive a field emission lamp using a CNT.