KR20030004636A - Electronic lamp invertor - Google Patents

Abstract

PURPOSE: An electronic ballast is provided to prevent the loss of switching by detecting a lamp voltage and a current to control a driving frequency of a switching device. CONSTITUTION: A lamp voltage and current detecting unit(100) detects a current flowing through a lamp(60) and a voltage applied to the lamp(60) to convert them into a first DC(Direct Current) voltage(V1) and a second DC voltage(V2). The lamp voltage and current detecting unit(100) linearly combines the first and second DC voltage(V1,V2) to output a third DC voltage(V3). A voltage controlled oscillator(200) receives the third DC voltage(V3) to output an oscillating signal(Fosc) having a variable frequency according to the third DC voltage(V3). The voltage controlled oscillator(200) varies driving frequencies of first, second, third, and fourth driving control signals(G1,G2,G3,G4) from first and second driving units(40,50) by using the oscillating signal(Fosc).

Description

Electronic ballast {Electronic lamp invertor}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic ballast, and in particular, to change a driving frequency of a driving unit for driving a lamp to detect a lamp voltage change and a lamp current change to maintain a lamp output at a rated value, and to operate in a high frequency band where acoustic resonance does not occur. It relates to an electronic ballast for high brightness discharge lamp.

In general, electronic ballasts for high intensity discharge lamps are important issues such as the elimination of acoustic resonance, the elimination of heat generation of the output switch element, the constant output control of lamps with variable negative resistance, and the control during ignition.

In the related art, various methods have been used for removing acoustic resonance, removing heat from an output switch element, controlling a constant output of a lamp having a variable negative resistance, and controlling at ignition.

According to US Patent No. US 6,020,691, registered on February 1, 2000, the acoustic resonance phenomenon was eliminated by containing 16% of high frequency of 50Hz in the spherical low frequency of 200Hz and using zero current switching method to reduce switching loss. It was. However, this method requires a lot of inductors and capacitors because of the circuit configuration, and the circuit configuration is complicated, and due to the capacity reduction of the capacitor, there is a problem in terms of durability.

According to Japanese Patent No. JP0341596, registered on January 3, 2001, a method of adjusting the duty ratio of a square wave according to the output power is used, but this has a problem in that heat generation of a switching device occurs in the case of a high output lamp.

The electronic ballast for the metal halide lamp of Korean Patent No. 87990, registered on August 17, 1995, controls the output power of the lamp by adjusting the frequency. Capacitors, resistors, and diodes configured in parallel with the switch element for removal have a problem of degrading efficiency.

An object of the present invention is to detect the lamp voltage and the lamp current to control the drive frequency of the switching element according to the detected lamp voltage and lamp current to maintain a constant output of the lamp at the nominal value, when the lamp overvoltage and overcurrent It is to provide an electronic ballast to protect the ballast and the lamp.

Another object of the present invention is to separately set a high-pressure generating circuit for the initial lighting of the lamp to generate a voltage of a high-pressure pulse of a size suitable for the initial lighting of the lamp, the high-voltage generating circuit is operated in the normal operation of the lamp or at the end of the lamp life To provide an electronic ballast that can extend the life of the lamp.

Another object of the present invention is to operate the switching device in a high frequency band in which acoustic resonance does not occur by using the zero voltage switching and zero current switching method, and to remove the heat generation phenomenon of the switching device when operating the switching device in the high frequency band. To provide an electronic ballast that can be.

1 is a block diagram of an electronic ballast of the present invention,

2 is a configuration diagram of a lamp current voltage detector for detecting a lamp voltage and a lamp current of FIG. 1;

3 is a configuration diagram of the high voltage pulse voltage generator of FIG. 1;

FIG. 4 is an equivalent circuit diagram of a lamp, a resonant coil, a second capacitor, a third capacitor, and a fourth capacitor positioned at output terminals of the switching transistors.

In order to achieve the above object, the electronic ballast of the present invention receives an AC input power, an electromagnetic wave removing unit for removing high frequency components and noise including the AC input power, an AC input with high frequency components and noise removed by the electromagnetic wave removing unit. Full-wave rectification unit for full-wave rectification and outputting full-wave rectification, Power factor improving unit for receiving full-wave rectification and outputting the first supply voltage, which is a DC voltage with improved power factor so that current and voltage of AC input power have the same phase. A first driving unit for outputting a drive control signal and a first drive control signal and a second drive control signal inverted; a third drive control signal and a third drive control signal and a fourth drive control signal inverted; The second driver, using the first supply voltage as a driving power source, is turned on or off depending on the driving frequency of the first drive control signal, the second drive control signal, the third drive control signal, and the fourth drive control signal. An electronic ballast having switching transistors for lighting a lamp, the electronic ballast comprising: detecting a current flowing through the lamp and a voltage applied to the lamp when the lamp is turned on, and converting the current into a first DC voltage and a second DC voltage, A lamp voltage current detection unit for linearly combining the second DC voltage to output a third DC voltage; And receiving a linearly-coupled third DC voltage, which is an output of the lamp voltage current detector, to output an oscillation signal having a frequency varying according to the third DC voltage, and outputting the oscillation signal to the first driver and the second driver. The drive control signal, the second drive control signal, the third drive control signal and the fourth drive control signal by varying the drive frequency characterized in that the lamp is provided with a voltage controlled oscillator having a nominal output within a certain range.

The lamp voltage current detector detects a current flowing through the lamp when the lamp is turned on and outputs a first DC voltage converted to the DC voltage; and detects a voltage applied to the lamp when the lamp is turned on and converts it into a DC voltage. A lamp voltage detector configured to output a second DC voltage; And an adder configured to receive the first DC voltage and the second DC voltage, add the second DC voltage, and output the third DC voltage.

The electronic ballast may further include protection means for receiving the first DC voltage and the second DC voltage to stop the operation of the switching transistors when an overcurrent or overvoltage occurs in the lamp to protect the ballast and the lamp.

The electronic ballast further comprises a high voltage pulse voltage generator for outputting a high voltage pulse voltage necessary for initial lighting of the lamp and not outputting the high voltage pulse voltage during normal operation of the lamp after the lamp is turned on.

The electronic ballast consists of a second capacitor connected in series across the output terminal of the switching transistors and third and fourth capacitors connected between the output terminal of the switching transistors and the ground voltage, respectively, so that voltage and current are in phase at the driving frequency of the switching transistors. It characterized by having a.

Hereinafter, with reference to the accompanying drawings will be described in detail the electronic ballast of the present invention.

1 is a block diagram showing an electronic ballast of the present invention.

The electronic ballast of the present invention of Figure 1 receives the AC input power (AC) by the electromagnetic wave removal unit 10, the electromagnetic wave removal unit 10, the electromagnetic wave removal unit 10 for removing the high frequency components and noise including the AC input power (AC) A full-wave rectifier 20 for outputting full-wave rectification by full-wave rectifying the AC input power from which components and noise have been removed, and a direct current voltage having improved power factor such that the current and voltage of the AC input power AC have the same phase. A power factor improving unit 30 for outputting a first supply voltage Vdc and a second drive control signal G2 that is an inverted signal from the first drive control signal G1 and the first drive control signal G1. The second driving unit 50 and the first driving unit 40 for outputting the fourth driving control signal G4, which is an inverted signal, to the first driving unit 40, the third driving control signal G3, and the third driving control signal G3. The first drive control signal G1, the second drive control signal G2, the third drive control signal G3 and the fourth drive control signal using the supply voltage Vdc as the drive power source. Switching transistors STR1 to STR4 that turn on or off the lamp 60 by turning on or off according to the driving frequency of the arc G4, and detect the current flowing through the lamp 60 and the voltage applied to the lamp 60 when the lamp is turned on. Converting it to the first DC voltage and the second DC voltage V2 and linearly combining the first DC voltage and the second DC voltage V2 to output the third DC voltage V3. An oscillation signal Fosc having a frequency varying according to the third DC voltage V3 by receiving the linearly coupled third DC voltage V3 output from the lamp voltage current detector 100 and the lamp voltage current detector 100. The first drive control signal G1, the second drive control signal G2, and the third drive control signal, which are outputs of the first drive unit 40 and the second drive unit 50, by the oscillation signal Fosc. The drive frequency of the G3) and the fourth drive control signal G4 is varied so that the lamp 60 is constituted by the voltage controlled oscillator 200 having a nominal output within a certain range.

2 is a configuration diagram of a lamp current voltage detector for detecting a lamp voltage and a lamp current of FIG. 1, wherein the lamp voltage current detector 100 detects a current flowing in the lamp 60 when the lamp is turned on, and converts it into a DC voltage. Lamp current detection unit 110 for outputting one DC voltage (V1), Lamp voltage detection unit for detecting the voltage applied to the lamp 60 when the lamp is turned on and outputs a second DC voltage (V2) converted to DC voltage ( 120 and an adder 130 which receives the first DC voltage V1 and the second DC voltage V2, adds the same, and outputs the third DC voltage V3.

The lamp voltage detector 120 includes a first resistor R1 connected to one side of the lamp 60, one terminal connected to the other terminal of the first resistor R1, and the other terminal connected to the other side of the lamp 60. A first rectifier 121 for receiving an AC signal applied to both ends of the second resistor (R2) and the second resistor (R2) connected to the terminal, and rectifying the wave to output a rectified signal. The first DC voltage converting unit 123 and the DC voltage Va, which is an output of the first DC voltage converting unit 123, are amplified to output the first DC voltage V1 to the first amplifier 125. It is composed.

The lamp current detector 110 includes a primary coil L1 and a secondary coil L2 to induce a lamp current induced in the primary coil L1 to the secondary coil L2. The second rectifying unit 111 receives the AC signal induced in the secondary coil L2 of the first transformer T1, and rectifies and propagates the RF signal to the DC voltage Vb. To a second amplifying unit 115 that amplifies the DC voltage Vb, which is an output of the second DC voltage converting unit 113 and the second DC voltage converting unit 113, and outputs a second DC voltage V2. It is composed.

As shown in FIG. 1, the electronic ballast receives the first DC voltage V1 and the second DC voltage V2 to operate the switching transistors STR1 to STR4 when an overcurrent or overvoltage is generated in the lamp 60. It may be further provided with a protection means 300 to protect the ballast and the lamp by stopping.

The protection unit 300 receives the first DC voltage V1 and the second DC voltage V2 and compares the DC voltage added with the DC voltage added by comparing the reference voltage set when an overcurrent or overvoltage is generated to the lamp. If exceeded, the first switching Q1 turned on or off according to the comparing unit 310 outputting the activated first switching control signal SC1 and the first switching control signal SC1 output from the comparing unit 310. When the first switching control signal SC1 is activated, the first switching Q1 is turned on so that the third DC voltage V3 which is an input of the voltage controlled oscillator 200 becomes the ground voltage Vss.

In addition, the protection means 300 receives a first DC voltage (V1) and a second DC voltage (V2) and adds the DC voltage added by comparing the reference voltage set when the overcurrent or overvoltage to the lamp is added as a reference When the voltage is exceeded, the second switching unit Q2 is turned on or off according to the comparison unit 310 outputting the activated first switching control signal SC1 and the first switching control signal SC1 output from the comparison unit 310. When the first switching control signal SC1 is activated, the second switching Q2 may be turned on so that the oscillation signal Fos, which is the output of the voltage controlled oscillator 200, may be set to the ground voltage Vss. .

The electronic ballast further includes a high voltage pulse voltage generator 400 for outputting a high voltage pulse voltage necessary for initial lighting of the lamp 60 and not outputting a high voltage pulse voltage during normal operation of the lamp after the lamp 60 is turned on. can do.

3 is a configuration diagram of the high voltage pulse voltage generator, and the high voltage pulse voltage generator 400 controls the discharge of the first timer 410 and the first timer 410 to output a discharge control signal DIS that is activated every predetermined period. The charging / discharging unit 420 and the initial lighting of the lamp 60 which initially charge the lamp 60 by outputting a high voltage pulse voltage to the lamp 60 by charging and discharging the first supply voltage Vdc according to the signal DIS. The switching control unit 430 for outputting the second switching control signal SC2 by full-wave rectifying the AC signal generated by the current induced by the second switch and the second switching control signal SC2 which is the output of the switching control unit 430 are activated. When the first timer 410 is turned on, the third timer switch Q3 stops the charging and discharging of the charging and discharging unit 420 so that a high voltage pulse voltage is not generated in the lamp 60.

The charging and discharging unit 420 has a third resistor R3 connected to one terminal of the first supply voltage Vdc, one terminal connected to the other terminal of the third resistor R3, and the other terminal to the ground voltage Vss. When the first capacitor C1 and the first timer 410 are connected, the voltage is turned on by the activated discharge control signal DIS, which is an output of the first timer 410, to discharge the voltage charged in the first capacitor C1. The fourth switch Q4 and one terminal are connected to the other terminal of the third resistor R3, and the other terminal is connected to the fourth switch Q4 so that the current is induced when the fourth switch Q4 is turned off. The lamp 60 is composed of an ignition coil L3 for generating a high voltage pulse voltage.

The high-voltage pulse voltage generator 400 outputs the second timer 440 for outputting the lamp end-of-life control signal LT activated every predetermined period and the third switch Q3 during the deactivation time of the lamp end-of-life control signal LT. If it is not turned on, when the end of lamp control signal LT of the second timer 440 becomes active, the silicon control rectifier SCR for stopping the operation of the first timer 410 and the second timer 440 is turned on. It may be further provided.

The electronic ballast is provided with a second capacitor C2 connected in series across the output terminals A and B of the switching transistors STR1 to STR4 and output terminals A and B of the switching transistors STR1 to STR4 and a ground voltage. And third and fourth capacitors C3 and C4 connected between Vss, respectively, so that voltage and current are in phase at the driving frequencies of the switching transistors STR1 to STR4.

The operation of the electronic ballast of the present invention according to the above configuration is as follows.

As shown in FIG. 1, in the electronic ballast of the present invention, an electromagnetic wave removing unit 10, a full-wave rectifying unit 20, a power factor improving unit 30, a first driving unit 40, a second driving unit 50, and a pool are provided. Switching transistors STR1 to STR4 that turn on or off the lamp 60 by turning on or off according to the driving frequency using a bridge method, and switch transistors STR1 to STR4 to operate normally after the lamp 60 is turned on. Capacitors C5, transformers T2, and capacitors C6 and C7 and the resonant coil Lr, which cause LCC resonance, are the same as those of the conventional electronic ballast. The operation of the lamp voltage current detection unit 100, the voltage controlled oscillation unit 200, the protection means 300 against overcurrent and overvoltage of the lamp 60 and the high voltage pulse voltage generator 400, which are features of the present invention, are omitted. The explanation is as follows.

In order to initially light the lamp 60, the electronic ballast of the present invention is provided with a separate high-voltage pulse voltage generator 400.

As shown in FIG. 3, the first capacitor C is formed by the third resistor R3 and the first capacitor C1 connected in series between the first supply voltage Vdc and the ground voltage Vss of the charge / discharge unit 420. C1) is charged to the first supply voltage Vdc, and when the fourth switching Q4 is turned on by the activated discharge control signal DIS, which is an output of the first timer 410, the first capacitor C1. The voltage charged in the is discharged. When the discharge control signal DIS of the first timer 410 is deactivated again, the fourth switching Q4 is turned off. When the fourth switching Q4 is turned off, an instantaneous current is induced in the ignition coil L3. As a result, a high voltage pulse voltage is instantaneously induced in the resonance coil Lr connected to the lamp 60 to light the lamp 60. Let's do it. When the high voltage pulse voltage is induced in the resonant coil Lr, the switching controller 430 is activated by the coil L4 and the rectifier 431 of the switching controller 430 after the lamp 60 is turned on. ) The third switching Q3 is turned on by the activated second switching control signal SC2 to turn the supply power Vd of the first timer 410 into the ground voltage Vss for operating the first timer 410. Since the first timer 410 does not operate, the high voltage pulse voltage is not applied to the lamp 60 after the lamp 60 is turned on. That is, the high voltage pulse voltage generator 400 outputs the high voltage pulse voltage necessary for the initial lighting of the lamp 60, and does not output the high voltage pulse voltage during the normal operation of the lamp after the lamp 60 is turned on.

In addition, as shown in FIG. 3, the high-voltage pulse voltage generator 400 sets a predetermined time to the second timer 440 at the end of the life of the lamp 60 or when the lamp 60 is detached, thereby controlling the silicon control rectifier ( SCR) is turned on to make the supply voltage Vd of the first timer 410 and the second timer 440 the ground voltage Vss to stop the operation of the first timer 410 and the second timer 440. The high voltage pulse voltage generator 400 does not operate to prevent damage to the electronic ballast.

In the normal operation of the lamp 60 after the lamp 60 is turned on by the high voltage pulse voltage generator 400, the lamp current detector 110 and the lamp voltage detector 120 of the lamp voltage current detector 100 are operated. The lamp current and lamp voltage applied to the lamp 60 are detected. That is, as shown in FIG. 1 and FIG. 2, the lamp voltage detector 120 detects a lamp voltage during the normal operation of the lamp 60 by the first resistor R1 and the second resistor R2. The lamp voltage detected by the rectifier 121 and the first DC voltage converter 123 is rectified to output a DC voltage Va, and the first amplifier 125 amplifies the DC voltage Va to generate a first voltage. Output 1 DC voltage (V1). As described above, the lamp current detection unit 110 detects the lamp current during the normal operation of the lamp 60 by the first transformer T1 including the primary side coil L1 and the secondary side coil L2, and thus the second direct current. Output the voltage V2. The adder 130 linearly combines the first DC voltage V1 and the second DC voltage V2 and outputs the third DC voltage V3. At this time, as shown in FIG. 2, the third DC voltage V3 is determined according to the values of the resistors Ra, Rb, and Rf of the adder 130. For example, if a and b are constants, the third DC voltage V3 has a value of a x V1 + b x V2. The voltage controlled oscillator 200 outputs an oscillation signal Fosc having a frequency varying according to the linearly coupled third DC voltage V3 to output the oscillation signal Fosc by the first driver 40 and the second driver. The driving frequency of the first driving control signal G1, the second driving control signal G2, the third driving control signal G3, and the fourth driving control signal G4, which are the outputs of 50, is varied. Can have nominal output within a certain range. That is, the electronic ballast of the present invention may vary in the lamp current and the lamp voltage in the normal operation of the lamp, so that the first drive control signal for turning on or off the switching transistors STR1 to STR4 according to the lamp current and the lamp voltage. G1), the drive frequency of the second drive control signal G2, the third drive control signal G3 and the fourth drive control signal G4 are varied so that the output of the lamp 60 is within ± 5% of the nominal value. Can be controlled.

In addition, as shown in FIG. 1, the electronic ballast of the present invention receives the first DC voltage V1 and the second DC voltage V2 and compares the DC voltage obtained by adding the DC voltage with the reference voltage set when the overcurrent or overvoltage is generated in the lamp. When the added DC voltage exceeds the reference voltage, the ON voltage is turned on according to the comparator 310 outputting the activated first switching control signal SC1 and the first switching control signal SC1 output from the comparator 310. The third direct current voltage V3, which is the input of the voltage controlled oscillator 200, is made to the ground voltage Vss by the protection means 300 configured as the first switching Q1 or the second switching Q2 which is turned off. The oscillation signal Fos, which is the output of the control oscillator 200, is made the ground voltage Vss to stop the operation of the switching transistors STR1 to STR4 when an overcurrent or an overvoltage is generated in the lamp 60 to stabilize the ballast and the lamp. Can protect.

As shown in FIG. 1, the electronic ballast of the present invention has a second capacitor C2 and an output terminal of the switching transistors STR1 to STR4 connected in series between the output terminals A and B of the switching transistors STR1 to STR4. The voltage and current are driven at the driving frequencies of the switching transistors STR1 to STR4 by snubber capacitors, which are the third and fourth capacitors C3 and C4 connected between the both ends of (A and B) and the ground voltage Vss, respectively. By having a phase, the switching transistors STR1 to STR4 are set to zero voltage switching and zero current switching, thereby preventing degradation of durability and efficiency due to heat generation of the switching element. .

4 illustrates a lamp 60, a resonant coil Lr, a second capacitor C2, a third capacitor C3, and a fourth capacitor positioned at both ends of the output terminals A and B of the switching transistors STR1 to STR4. The equivalent circuit diagram for C4) is shown in which the lamp 60 replaces the second capacitor C2, the third capacitor C3, and the fourth capacitor C4 with the snubber capacitor Cs. Can be.

Impedance (Zab) between the output terminals (A, B) of Figure 4 (Rl + jwLr) / {( 1-w 2 LrCs) + jwRlCs} This is an impedance (Zab) a pure resistance component between the output terminals (A, B) The driving condition (f) = (1 / 2π) × {(Lr-Rl ² Cs) / (Lr ² Cs)} ^1/2 becomes the condition that voltage and current are in phase at this driving frequency (f). Since switching transistors STR1 to STR4 are capable of zero voltage switching and zero current switching, the switching loss is small. For example, if the resistor Rl is set to 40 Hz, the resonance coil Lr is 200 uH, and the snubber capacitor Cs is set to 22 Hz, the driving frequency f becomes about 69 Hz, and the driving frequency f is 69 Hz. There is little switching loss at.

The electronic ballast of the present invention can prevent switching loss by adding a snubber capacitor for removing the heat generation of the switching element in order to drive at a high frequency that does not generate an acoustic resonance phenomenon, the lamp current and the lamp during normal operation of the lamp By detecting the voltage and changing the driving frequency to turn on or off the switching transistors according to the lamp current and the lamp voltage, the output of the lamp can be controlled within ± 5% of the nominal value. Separately, a voltage of a high voltage pulse suitable for initial lighting of the lamp is generated, and the high voltage generating circuit can stop the operation at the time of normal operation of the lamp or at the end of the lamp life to extend the life of the lamp.

Claims (12)

Electromagnetic wave removal unit for removing high frequency components and noise including AC input power by receiving AC input power, Full wave rectifying unit for outputting full wave rectification by full-wave rectifying AC input power from which high frequency components and noise are removed by electromagnetic wave removing unit; A power factor improving unit for receiving a full-wave rectification and outputting a first supply voltage, which is a direct current voltage having improved power factor, so that the current and voltage of the AC input power have the same phase, the first drive control signal and the first drive control signal and the inverted signal. A first driving unit for outputting a second driving control signal, a second driving unit for outputting a fourth driving control signal which is an inverted signal with a third driving control signal, and a third driving control signal, and a first supply voltage as a driving power source And switching transistors which turn on or off the lamps according to the driving frequencies of the first drive control signal, the second drive control signal, the third drive control signal and the fourth drive control signal. In the child ballast, When the lamp is turned on, it detects the current flowing through the lamp and the voltage applied to the lamp, converts it into a first DC voltage and a second DC voltage, and outputs a third DC voltage by linearly combining the first DC voltage and the second DC voltage. Lamp voltage current detection means; And Receiving a linear combination of the third DC voltage, the output of the lamp voltage current detection means, and outputs an oscillation signal having a frequency variable according to the third DC voltage and outputs the first driver and the second driver by the oscillation signal. Characterized in that the ramp is provided with a voltage controlled oscillation means having a nominal output within a predetermined range by varying the drive frequencies of the first drive control signal, the second drive control signal, the third drive control signal and the fourth drive control signal. Electronic ballast made with. The method of claim 1, wherein the lamp voltage current detection means Lamp current detection means for detecting a current flowing in the lamp when the lamp is turned on and outputting a first DC voltage converted into the DC voltage; Lamp voltage detection means for detecting a voltage applied to the lamp when the lamp is turned on and outputting a second DC voltage converted to the DC voltage; And And an adding means for receiving the first DC voltage and the second DC voltage, adding the same, and outputting a third DC voltage. The method of claim 1, wherein the lamp voltage detection means A first resistor having one terminal connected to one side of the lamp; A second resistor having one terminal connected to the other terminal of the first resistor and the other terminal connected to the other side of the lamp; First rectifying means for receiving an AC signal applied to both ends of the second resistor, and rectifying the wave to output a rectified signal; First DC voltage converting means for receiving a rectified signal and converting the DC signal into a DC voltage; And And a first amplifying means for amplifying a DC voltage which is an output of said first DC voltage converting means and outputting a first DC voltage. The method of claim 1, wherein the lamp current detecting means A first transformer composed of a primary side coil and a secondary side coil to induce a lamp current induced in the primary side coil to the secondary side coil; Second rectifying means for receiving an AC signal induced in the secondary coil of the first transformer, and rectifying the wave to output a rectified signal; Second DC voltage converting means for receiving a rectified signal and converting the DC signal into a DC voltage; And And a second amplifying means for amplifying a DC voltage which is an output of said second DC voltage converting means and outputting a second DC voltage. The electronic ballast of claim 1, further comprising protection means for receiving the first DC voltage and the second DC voltage to stop the operation of the switching transistors when an overcurrent or overvoltage occurs in the lamp to protect the ballast and the lamp. Electronic ballast characterized in that. The method of claim 5, wherein the protective means Receives the first DC voltage and the second DC voltage and compares the DC voltage added with the reference voltage set in the occurrence of overcurrent or overvoltage to the lamp and outputs the activated first switching control signal when the DC voltage added exceeds the reference voltage. Comparative means for doing; And A first switching means turned on or off in accordance with a first switching control signal output from the comparison means, and when the first switching control signal is activated, the first switching means is turned on to be the input of the voltage controlled oscillation means; Electronic ballast characterized in that the DC voltage to the ground voltage. The method of claim 5, wherein the protective means Receives the first DC voltage and the second DC voltage and compares the DC voltage added with the reference voltage set in the occurrence of overcurrent or overvoltage to the lamp and outputs the activated first switching control signal when the DC voltage added exceeds the reference voltage. Comparative means for doing; And And a second switching means turned on or off according to the first switching control signal which is the output of the comparing means. When the first switching control signal is activated, the second switching means is turned on and the oscillation signal which is the output of the voltage controlled oscillation means. Electronic ballast characterized in that the ground voltage. The method of claim 1, wherein the electronic ballast further comprises a high voltage pulse voltage generating means for outputting a high voltage pulse voltage required for the initial lighting of the lamp, and does not output a high voltage pulse voltage during normal operation of the lamp after the lamp is turned on. Electronic ballast characterized by the above-mentioned. The method of claim 8, wherein the high voltage pulse voltage generating means A first timer for outputting a discharge control signal that is activated every predetermined period; Charging and discharging means for initially charging the lamp by charging and discharging the first DC voltage according to the discharge control signal of the first timer and outputting a high voltage pulse voltage to the lamp; Switching control means for full-wave rectifying the AC signal generated by the current induced by the initial lighting of the lamp and outputting a second switching control signal; And A third switching control signal, which is an output of the switching control means, is turned on to stop the operation of the first timer to stop charging and discharging of the charging / discharging means so that a high voltage pulse voltage is not generated in the lamp; An electronic ballast comprising a switching means. The method of claim 9, wherein the charging and discharging means A third resistor having one terminal connected to the first supply voltage; A first capacitor having one terminal connected to the other terminal of the third resistor and the other terminal connected to the ground voltage; Fourth switching means for discharging a voltage charged in the first capacitor by being turned on by an activated discharge control signal which is an output of the first timer during the operation of the first timer; And An ignition coil having one terminal connected to the other terminal of the third resistor and the other terminal connected to the fourth switching means such that current is induced to generate a high voltage pulse voltage to the lamp when the fourth switching means is turned off. Electronic ballast, characterized in that provided. The method of claim 9, wherein the high voltage pulse voltage generating means A second timer configured to output a lamp end-of-life control signal activated every predetermined period; And If the third switching means is not turned on during the deactivation time of the lamp end-of-life control signal, when the lamp end-of-life control signal of the second timer becomes active, the silicon control to stop the operation of the first timer and the second timer. An electronic ballast, further comprising a rectifying means. The electronic ballast of claim 1, wherein the electronic ballast A second capacitor connected in series across the output terminal of the switching transistors; And a third and a fourth capacitor connected between the output terminal of the switching transistors and the ground voltage, respectively, so that the voltage and the current are in phase at the driving frequency of the switching transistors.