KR100278071B1 - Lighting circuit of gas discharge lamp - Google Patents

Abstract

The present invention relates to a lighting device for a gas discharge lamp used in a headlight of an automobile, and the circuit according to the present invention converts an output voltage of a battery into a DC voltage of a predetermined level and provides the igniter and the DC-AC converter with DC-DC. A converter; The DC-AC converter converting a DC voltage output from the DC-DC converter into a square wave AC voltage and outputting the converted DC voltage; A power supply unit for converting the output voltage of the variable battery to provide a control voltage of a constant level to each part of the lighting circuit; A PWM control unit for outputting a DC voltage of a predetermined level from the DC-DC converter and a DC voltage of a level varying according to an ignition state of a lamp; A power control unit controlling the amount of light of the lamp constantly; The gate driver providing a gating signal as a control signal to output a square wave AC voltage from the DC-AC converter; And an igniter that receives the high voltage output from the DC-DC converter and the square wave AC voltage output from the DC-AC converter and outputs a starting voltage of the lamp.

As described above, the present invention provides stable light output even when the input voltage fluctuates, extends the life of the lamp by limiting the initial overcurrent, reduces the size and weight, and at the same time improves the reliability by simplifying the circuit. have.

Description

A circuit for lighting a gas discharge lamp

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a high brightness gas discharge lamp, and more particularly to a lighting device for a gas discharge lamp used for a headlight of an automobile.

In general, a gas discharge lamp uses a phenomenon of emitting light corresponding to an energy difference when an atom in an excited state transitions to a ground state during a gas discharge, and is divided into a high pressure gas discharge lamp and a low pressure gas discharge lamp. Here, a high intensity discharge lamp applies relatively high-density power to a light emitting lamp injecting a gas having a high pressure to obtain light therefrom. In this case, there is a local thermal equilibrium state in which the temperatures of electrons, ions, and gas atoms are almost the same. On the other hand, a low pressure gas discharge lamp has a relatively small gas density and a power density, and only electrons have a high average energy.

High pressure gas discharge (HID) lamps include high pressure sodium lamps, mercury lamps, metal halide lamps, and project lamps. Since high pressure sodium lamps have the highest efficiency among other white high pressure gas discharge lamps, they have more luminous flux than unit power consumption. to provide. This high pressure sodium lamp uses a special starting circuit and the arc tube is made of alumina. Xenon gas is used as the amalgam of mercury between the starting gas and sodium for the main arc. This ballast, such as high pressure sodium, contains a special starting circuit for ionizing xenon gas to low energy, high voltage pulses. That is, the high voltage pulse is supplied superimposed on the 60 Hz voltage until the xenon gas is ionized so that the voltage of the ballast can establish and maintain the xenon arc. Normally, after the xenon arc has taken place, the start pulse stops.

The mercury lamp consists of an external bulb filled with inert gas that forms a protective layer around the inner arc tube, and the arc tube is filled with high-purity mercury, which has a low vapor pressure at room temperature, making argon gas easier to start. do. When a starting voltage is applied between the gap between the main electrode and the starting electrode, it forms an argon arc that forms a heat that vaporizes mercury, and these ionized argon particles reduce the resistance between the main electrodes so that the ballast is the main arc. Causes When all mercury in the arc pipe vaporizes, the lamp is in steady state. The starting arc stops because the main arc resistance is less than the resistance of the starting circuit. Warm-up times of up to 80% of the light output require three to five minutes.

In metal halides, other metals are added to mercury in the arc tube to improve color characteristics and efficiency. That is, mercury is present in the arc tube and other metals are added in the form of halide salts (usually iodide). This, together with the iodide, forms mercury amalgam. However, as in mercury lamps, argon generates the first arc in metal halide lamps and generates initial heat, the temperature of the arc tube gradually rises, the main arc occurs, various iodides evaporate, separated from the base iodine and the added metals. Enter

Project lamps, D1 and D2S lamps, are expected to be used as next-generation headlamps. The D2S lamp is a D1 lamp with an external protection valve made of quartz and a touch protection device. The external protection valve absorbs a large amount of ultraviolet light. At room temperature, the D1 and D2S lamps contain mercury and various metal salts xenon. When switched on, the xenon immediately glows and heats to vaporize metals and metal salts. The project lamps achieve high luminous efficiency of the lamps by means of a metal vapor mixture, and the production of light is caused by mercury, while metal salts affect the color of the spectrum. D1 and D2S lamps have higher light efficiency than halogen lamps used as headlamps in automobiles.

Therefore, if the project lamp can be applied to a vehicle, a head lamp with excellent light efficiency can be obtained. To this end, a suitable starting current, a voltage for causing arc discharge, a voltage for stabilizing arc and operating a lamp, and There is a need for a ballast that controls the flow of current through arc discharge, i.e., a lighting circuit.

Accordingly, an object of the present invention is to provide a lighting circuit of a gas discharge lamp for driving a project lamp used for a head lamp of an automobile, which is devised to satisfy the above needs.

In the circuit of the present invention for achieving the above object, the output voltage of the battery is converted into a DC voltage of a predetermined level and provided to the igniter, and the output voltage of the battery is a DC voltage of a level that varies according to the ignition state of the lamp DC-DC converter to convert to provide a DC-AC converter;

The DC-AC converter converts a variable level DC voltage output from the DC-DC converter into a square wave AC voltage and outputs the DC voltage, and protects the lamp from overcurrent when the lamp is initially turned on.

A power supply unit for converting the output voltage of the variable battery to provide a control voltage of a constant level to each part of the lighting circuit;

The DC-DC converter is controlled by receiving the output voltage and the output current of the battery, so that a DC voltage of a predetermined level and a DC voltage varying according to an ignition state of a lamp are output from the DC-DC converter. PWM control unit;

A power controller configured to control the light amount of the lamp by receiving the output voltage of the battery, which is varied, and maintaining the output power at a constant level;

The gate driver providing a gating signal as a control signal to output a square wave AC voltage from the DC-AC converter; And

And an igniter for receiving the high voltage output from the DC-DC converter and the square wave AC voltage output from the DC-AC converter and outputting a starting voltage of the lamp.

1 is a circuit diagram showing a lighting circuit of a gas discharge lamp according to the present invention;

2 is a circuit diagram showing a power supply unit according to the present invention;

3 is a circuit diagram showing a PWM control unit according to the present invention;

4 is a circuit diagram showing a power control unit according to the present invention;

5 is a circuit diagram illustrating a gate driver according to the present invention;

6 is a circuit diagram illustrating an igniter according to the present invention.

* Explanation of symbols for the main parts of the drawings *

110: flyback converter 120: full-bridge converter

130: power supply unit 140: PWM control unit

150: power control unit 160: gate driver

170: lighter

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

1 is a block diagram illustrating a lighting circuit of a gas discharge lamp according to the present invention, which is a flyback converter 110 as a DC-DC converter, a full-bridge converter 120 as a DC-AC converter, and a power supply 130. , A PWM controller 140, a power controller 150, a gate driver 160, and an igniter 170.

Here, the flyback converter 110 converts the output voltages V + and V− of the battery into a DC voltage V15 of a predetermined level and provides the igniter 170 with the output voltages V + and V− of the battery. ) Is converted into a DC voltage of a level variable according to the ignition state of the lamp and provided to the full-bridge converter 120, which is switched on / off by a gating signal of the PWM controller as shown in FIG. When the transistors Q5 and Q6 and the switching transistors Q5 and Q6 are turned on / off, a transformer T2 for boosting and outputting the output voltages V + and V− of the battery, and an output from the transformer T2. Diodes (D7, D8, D9, D10) rectifying the high voltage (1500V) to be provided to the igniter 17, and rectifying the DC voltage output from the transformer (T2), which varies according to the ignition state of the lamp, Diodes D2 and D1 provided to the bridge converter 120 are configured. In addition, resistors R5 and R10, resistors R4 and R9, and electrolytic capacitors C6 are connected in parallel between the cathode and ground terminals of the diodes D2 and D1.

The full-bridge converter 120 converts a DC voltage of a variable level output from the flyback converter 110 into a square wave AC voltage and outputs the voltage, and protects the lamp from overcurrent when the lamp is initially turned on. 1, an overcurrent protection unit configured to include a diode D11, a resistor R7, and an inductor L4 to protect the lamp from overcurrent during initial lighting, and the overcurrent protection units D11 and R7. Switching transistors Q1, Q2 and Q3 connected in parallel by snubber circuits R8 and C7 for removing high frequency noise and driving signals G0, G1, G2 and G3 output from the gate driver 160. Q4).

The power supply unit 130 converts the output voltages of the storage batteries V + and V−, which vary according to the driving state of the vehicle, to provide a predetermined level of control voltage to each part of the lighting circuit, as shown in FIG. 2. A voltage controller U2 for sensing the output voltage of the battery and outputting a PWM control signal having a variable on-time, transistors Q7, Q8, and Q9 switched according to the PWM control signal output from the voltage controller U2; A transformer T3 for converting the output voltages V + and V- of the battery according to the switching operation of the transistors Q7, Q8 and Q9 to output a DC voltage V15 of a predetermined level, and the DC voltage V15. Rectification diode (D12) and a smoothing electrolytic capacitor (C11) for rectifying and smoothing. Of course, the DC voltage is divided through the division resistors R11 and R18 and then fed back to the voltage controller U2 to maintain the DC voltage V15 of the transformer T3 at a constant level. The voltage controller is connected with capacitors C8 and C9 and resistors R16, R12, R13, R14, R15 and R17 to control the period, frequency and duty ratio of the PWM control signal.

The PWM controller 140 receives the output voltage V _OUT and the output current I _in of the battery and outputs a gate driving signal GATE for controlling the flyback converter 110 to thereby output the flyback converter 110. The DC voltage of a predetermined level and the DC voltage of a level varying according to the ignition state of the lamp can be respectively output from the bar. As shown in FIG. 3, the voltage controller and the current controller are configured.

The voltage controller is used to control the initial voltage to 550V, and the current controller is used to obtain a constant power by using the current command value provided by the power controller 150. The output current of the battery is input to the voltage controller U3 through the resistor R28, and the current command value I _COM of the power controller 150 is input to the voltage controller U3 through the resistor R29. A capacitor C15 is connected between the R28 and the resistor R29. In order to determine the period, frequency and duty ratio of the PWM control signal output from the voltage controller U3, the resistors R20, R21, R26, R30 and capacitors C12, C16, C17 are connected, and the voltage controller U3 The PWM control signal output from) is applied to the flyback converter 110 through the buffers (Q10, Q11). When the lighting switch S1 of the lamp is turned on / off, chattering is removed by the NAND gates U4A and U4B. When the lighting switch S1 is turned on, a signal is applied to the voltage controller U3 through the diode D13. Then, the PWM control signal for driving the flyback converter 110 is output from the voltage controller U3.

The power control unit 150 receives the fluctuating output voltage V + of the battery and maintains the output power at a constant level to control the light quantity of the lamp constantly, which is illustrated in FIG. 4. Depressurize (V +) and apply it to the non-inverting terminal of the operational amplifier U5A, and connect the inverting terminal and the output terminal of the operational amplifier. The op amp U5A is a buffer for reducing the output impedance of the diodes D16, D17, and D18 when there is no input signal. The output signal of the operational amplifier U5A is applied to the inverting terminal of the operational amplifier U5B used as the subtraction circuit, and the inverting terminal and the output terminal of the operational amplifier U5B are connected.

The resistors R48 and R49 connected between the output terminal of the operational amplifier U5B and the ground terminal GND to determine the steady state current command value I _COM2 , and the output terminal and the ground terminal of the operational amplifier U5B. Resistor R40, R41 connected between the circuits to determine the initial current command value I _COM1 is included. The current command value I _COM passing through the resistors R40 and R48 is provided to the PWM controller 140 through the diodes D14 and D15. The output voltage Vo of the flyback converter 110 is 50V or more when the lamp is sufficiently warmed up and is lower than 50V when the lamp is initially driven. The output voltage Vo is the NAND gates U4C and U4D and the resistor R47. ) Is applied to the base end of the CMOS transistor Q12. The transistor Q12 is turned off during initial driving and turned on when the lamp is sufficiently warmed up.

The gate driver 160 provides a gating signal that is a control signal to output a square wave AC voltage from the full-bridge converter 120. The gate driver 160 includes a multivibrator part and a gate driver part as shown in FIG. The multivibrator portion includes NAND gates U6A and U6B, and its output frequency can be adjusted by changing the resistor R56, the capacitor C23, the resistor R57, and the capacitor C24. In addition, by adjusting the ratio of the resistor and the capacitor, it is possible to adjust the duty ratio of the pulse. The outputs of the NAND gates U6A and U6B are applied to the inverters U7A to U7B in the gate driving portion through the diodes D20 and D21 and the NAND gates U6D and U6C. In addition, an output signal of the NAND gate U6C is applied to an input terminal of the switching transistors Q2 and Q4 of the full-bridge converter 120, and an output signal of the NAND gate U6D is switched of the full-bridge converter 120. It is applied to the input terminals of the transistors Q1 and Q3.

The gate driving part is a circuit for driving a full-bridge converter without a separate power source, which includes a plurality of inverters (U7A to U7B) and a plurality of capacitors (C25, C27, C26, and C28) to accumulate Vcc voltages. And a plurality of resistors R59 to R67 and buffers Q14 to Q17 and Q19 to Q22.

The igniter 170 receives the high voltage output from the flyback converter and the square wave AC voltage output from the full-bridge converter and outputs a starting voltage of the lamp, as shown in FIG. 6, the capacitors C32 and C31. And a discharge element 171 and a transformer T4. The transformer T4 is for boosting and high voltage of 12000V to 30000V is induced on the secondary side.

The operation of the present invention configured as described above will be described.

Before explaining the detailed operation of each component, briefly look at the startup phase of the project lamp as follows. First, there is an ignition stage that supplies energy to cause gas discharge of the project lamp. In this ignition step, the igniter 170 must be controlled to supply high voltage, and when not ignited at a time, continuous ignition must occur. In addition, once the lamp is ignited, continuous conduction of current can occur, where the full-bridge converter blocks overcurrent flowing through the lamp because the lamp has a negative resistance characteristic and the current increases rapidly.

In the next step, the temperature in the lamp rises rapidly, causing pressure to rise as the gases in the lamp begin to vaporize. In order to accelerate this process and keep the lamp on fire, the wattage must be increased. As this step progresses, the light from the bulb moves from blue to white light.

The final stage is the stabilization stage, which is the stage where the amount of light in the lamp reaches its maximum and consumes steady state power. In this step, control to maintain a constant amount of watts must be made, which is controlled by the power control unit 150.

Hereinafter, the detailed operation of each component constituting the lighting circuit of the gas discharge lamp according to the present invention will be described. The operation of the flyback converter 110, which is a DC-DC converter, will be described with reference to FIG. 1. The output voltages V + and V- of the battery input to the flyback converter 110 are 9 to 32V. The output terminal of the back converter 110 outputs a DC voltage of 1500V supplied to the igniter 170 and 0 to 600V provided to the full-bridge converter 120. Here, a DC voltage of 1500 V is supplied to the igniter 170 to be used to obtain a high voltage necessary for the initial ignition of the lamp, and a DC voltage of 0 to 600 V is maintained at a voltage of 550 V when the lamp is not initially ignited from the moment of ignition. The voltage varies depending on the state of the lamp.

The flyback converter 110 stores energy in the transformer T2 when the switching transistors Q5 and Q6 are turned on, and then transfers this energy to the output side when the switching transistors Q5 and Q6 are turned on. The dot side of the transformer T2 that is turned on has a lower voltage than the opposite side. At this time, the reverse voltage is applied to the diodes D2, D1, D7 to D10 of the output terminal of the transformer T2, and the current flowing to the primary side of the transformer T2 increases linearly at the same ratio as in Equation (1).

here, L _P Is the magnetizing inductance on the primary side of transformer T2.

In addition, at this time, the energy stored in the primary side of the transformer (T2) is the same as the equation (2).

In this state, when the switching transistors Q5 and Q6 are turned off, the primary side current of the transformer T2 is transferred to the secondary side of the transformer T2 in the magnitude of Equation 3.

When the current having the same magnitude is transmitted to the secondary side of the transformer T2, the dot side of the transformer T2 has a positive voltage, and the diodes D2, D1, D7 to D10 connected to the output side of the transformer are turned on. As a result, the current induced in the secondary side decreases at the same ratio as in Equation 4.

As such, when the secondary current of the transformer decreases to zero, all the energy stored in the primary inductance is applied to the secondary side. The power supplied from the output voltage (V +) of the battery for one period T time is expressed by Equation 5, The output voltage of the transformer is shown in Equation 6.

here, Is the minimum input voltage, Is the maximum conduction time.

In other words, V + or R5 + R10 Goes up T _on By reducing the output voltage can be made constant.

Here, the resistors R5 and R10 supply the output current of the transformer to the PWM controller so that the duty ratio of the PWM control signal output from the PWM controller is varied so that the output voltage of the transformer can maintain a constant voltage. R9) senses the output voltage 50V and applies it to the power control unit. In addition, the input capacitor C5 filters the input current that is discontinuous so that a uniform input current can be provided to the transformer, and the resistor R6 senses the current to control the input power, thereby minimizing power consumption. Use a resistor with a very small resistance.

Next, the operation of the full-bridge converter 120 will be described with reference to FIG. 1. The full-bridge converter 120 receives a DC voltage of 0 to 600 V output from the flyback converter 110 and receives 500 to 600 Hz. It converts into square wave AC voltage and has overcurrent protection function. That is, during a very short moment when the lamp is ignited, the lamp may appear to be short-circuited, so that overcurrent flows into the lamp so that continuous ignition cannot occur. In this case, the current of the inductor L4 has a large impedance so that the current is connected with the diode D11. Flowing through (R7) prevents overcurrent. On the other hand, when the ignition of the lamp is completed, the inductor L4 has a very low impedance, so that current flows through the inductor L4.

If the full-bridge converter 120 does not have an overcurrent protection function, a current pulse of about 20A and 100μsec flows when the lamp is turned on, and the lamp is shocked, resulting in a shortened life and no continuous lighting. These problems are solved by the over-current protection of the bridge converter, which limits the maximum peak value of the current to 8 A or less at the initial lighting of the lamp. The resistor R8 and the capacitor C7 are snubber circuits to remove harmonic noise.

Next, referring to FIG. 2, the operation of the power supply unit 130 is a part for supplying a constant voltage of 15 V to each circuit part of the lighting circuit even if the output voltages V + and V− of the battery change. Implement using The voltage controller U2 of this flyback converter is implemented using a method having a positive output sensing technique.

That is, the transistor Q9 is switched by the PWM control signal output from the voltage controller U2, and a desired 15V DC voltage is output through the transformer T3. The DC voltage of 15V is sensed resistors R11 and R18. Is sensed and fed back to the voltage controller U2 to control the duty ratio of the PWM control signal.

Here, the switching frequency of the PWM control signal is determined by the capacitor C8 and the resistor R15, which is expressed by Equation 7.

After the PWM control signal output from the voltage controller TL494 is applied to the transistors Q7 and Q8, the gates of the transistors Q9 are driven by these transistors. As described above, when the transistor Q9 is switched by the PWM control signal output from the voltage controller U2, a desired DC voltage of 15 V can be obtained to the secondary side of the transformer T3.

Next, the operation of the PWM controller 140 will be described with reference to FIG. 3. The PWM controller includes a voltage controller and a current controller. The voltage controller is implemented by a positive output voltage sensing method. The gain is shown in equation (8).

Here, the resistors R5 and R10 are voltage sense resistors shown in the flyback converter 110 of FIG. 1. On the other hand, the current control unit is implemented using a negative output sensing method, the gain of the input current versus the output current is expressed by Equation 9.

Here, the resistors R28 and R29 are current sensing resistors, and 0.01 is a current sensing resistance value. In addition, the switching frequency of the PWM control signal is determined by the capacitor C12 and the resistor R21 and can be obtained as shown in Equation 10.

The PWM control signal generated at the frequency f is applied to the gate terminal of the switching transistors Q5 and Q6 of the flyback converter 110 through the buffers Q10 and Q11 to drive the switching transistors Q5 and Q6. Done.

Next, the operation of the power controller 150 will be described with reference to FIG. 4, which simplifies the inverse characteristic curve using a diode to control the power to be constant even if the input voltage changes. Looking at the basic operation principle from the input V + to the front end of the operational amplifier (U5A) first, the voltage (V1) of both ends of the resistor (R33), the voltage of both ends (V2) of the resistor (R35) and the voltage of both ends (V3) of the resistor (R38). ) Defines the voltage at which the slope of the characteristic curve varies, and the resistors R32 to R38, R44 to R46 change the slope of the curve by changing the equivalent resistance when the diodes D16, D17, and D18 are conducted. That is, this part has a function of simplifying the secondary characteristic curve.

The op amp U5A is used as a buffer to lower the output impedance of the diode circuit, and the op amp U5B is a subtraction circuit to invert the characteristic curve made using the diode to obtain a characteristic curve of the input voltage versus the input current. That is, when the lamp is ignited, the voltage applied to the output side of the lamp increases while the power applied from the input side remains constant.

If the lamp is turned on for a long time and then turned off immediately, when the lamp is turned on again, since the lamp is sufficiently heated and the ionization of the gas in the lamp is in progress, the voltage drop does not occur much because no current is required for the ionization of the gas. . In other words, the warm-up operation of the lamp is not required, and the power enters the stabilization stage to reduce the magnitude of current.

However, when the lamp is completely cooled, a lot of current flows for gas ionization in the lamp, and a lot of energy is required for warming up the lamp, thereby performing a warm-up operation to maintain a constant voltage without reducing the current command value.

At this time, whether the warm-up operation is performed is determined based on whether the input voltage of the lamp is higher or lower than 50V. The resistors R40, R41, R48, and R49 change the value of the current command value with respect to the input voltage of the lamp. That is, the resistors R48 and R49 are current command values in a steady state ( I _com2 ) And resistors R40 and R41 are initial current command values ( I _com1 Is determined.

In the initial state, the initial current command value is charged to the capacitor C19 through the diode D14. When the lamp is turned on and the lamp needs warm-up operation, when the lamp output voltage (V _O ) is lower than 50V, the current command value is changed because the transistor Q12 is turned off because the final output of the NAND gates U4C and U4D is low level. Keep the initial value. After that, when the lamp warms up sufficiently and the lamp output voltage _VO becomes higher than 50V, the final output of the NAND gates U4C and U4D becomes high and the transistor Q12 is turned on so that the diode D14 is turned on. The passage of the current through is cut off and the voltage charged in the capacitor C19 starts to discharge through the resistors R28 and R29. When the current command value reaches the final command value by the resistors R48 and R49, the diode D15 does not discharge any more and maintains the current command value in a steady state.

Next, the operation of the gate driver 160 will be described with reference to FIG. 5, which generates a gating signal of 500 to 600 Hz to the full-bridge converter 120. The gate driver 160 is divided into a multivibrator portion and a gate driver portion. The multivibrator portion is implemented using NAND gates U6A and U6B, and the output frequency can be adjusted by changing the resistor R56, the capacitor C23, the resistor R57 and the capacitor C24. In addition, the duty ratio of the output pulse can be adjusted by appropriately adjusting the ratio of the resistors R56-capacitor C23 and the resistors R57-capacitor C24.

The outputs of the NAND gates U6D and U6C are changed by the pulses output from the multivibrator section. When the NAND gate U6D is at a high level, the NAND gate U6C is at a low level. The transistors Q1 and Q3 are turned on when the NAND gate U6D is at a high level, and the transistors Q2 and Q4 are turned off when the NAND gate U6C is at a low level.

When the transistor Q1 is turned on, the capacitor C25 is charged to the power supply voltage V _CC through the power supply voltage V _CC , the diode D26, the capacitor C25, the transistor Q1, and the ground GND. This charged voltage is then used to conduct MOSFET Q4 for the next period. When the MOSFET Q4 conducts, most of the voltage difference between the source and the power supply V _CC is applied to the diode D26, so that the diode uses a sufficiently large reverse voltage that can be tolerated.

Next, the operation of the igniter 170 will be described with reference to FIG. 6. Unlike other high-pressure gas discharge lamps, the D1 lamp or the D2S lamp, which is a project lamp, has a characteristic that a voltage causing gas discharge at startup reaches tens of thousands of volts. This high voltage is obtained through a two-step process, which is achieved through the flyback converter 110 and the igniter 170. That is, the igniter 170 first obtains a DC voltage of about 1500 to 1800 V from the flyback converter 110, and discharges it instantaneously using the discharge device 170 to the second side through the transformer T4. A voltage up to volts is applied to the lamp to cause discharge.

In detail, when a DC voltage of 1500 to 1800 V is applied between the black terminal and the blue terminal of the igniter 170, most of the voltage is applied to the discharge element 171, whereby the discharge element 171 discharges. Cause an instantaneous current to flow. At this time, the voltage boosting function of the transformer T4 generates a high voltage of 22,000 V up to 30000 V on the secondary side, and the high voltage is applied to the lamp to start discharging the lamp. Here, the characteristic of the transformer T4 is to induce high voltage on the secondary side using an air core and minimize the influence of its inductance. In addition, since high voltage is applied and induced on the primary side and the secondary side of the transformer T4, thorough insulation is required.

In the present invention, the DC-DC converter uses a flyback converter, but in addition, a push-pull converter, a forward converter, and the like can be used, and the DC-AC converter is a full-bridge converter ( In addition to a full-bridge converter, a half-bridge converter may be used.

As described above, the present invention provides a lighting device such as a gas discharge lamp for smoothly lighting the project lamp when the project lamp having excellent light efficiency is applied to the headlamp of an automobile, thereby providing stable light output even when the input voltage is changed. It extends the life span of the lamp by limiting the initial overcurrent, achieves miniaturization and light weight, and improves reliability by simplifying the circuit.

Claims (3)

DC-DC converter that converts the output voltage of the battery into a DC voltage of a predetermined level and provides it to the igniter, and converts the output voltage of the battery into a DC voltage of a level that varies according to the ignition state of the lamp and provides the DC-AC converter. ; The DC-AC converter converts a variable level DC voltage output from the DC-DC converter into a square wave AC voltage and outputs the DC voltage, and protects the lamp from overcurrent when the lamp is initially turned on. A power supply unit for converting the output voltage of the variable battery to provide a control voltage of a constant level to each part of the lighting circuit; The DC-DC converter is controlled by receiving the output voltage and the output current of the battery, so that a DC voltage of a predetermined level and a DC voltage varying according to an ignition state of a lamp are output from the DC-DC converter. PWM control unit; A power controller configured to control the light amount of the lamp by receiving the output voltage of the battery, which is varied, and maintaining the output power at a constant level; The gate driver providing a gating signal as a control signal to output a square wave AC voltage from the DC-AC converter; And And a igniter configured to receive a high voltage output from the DC-DC converter and a square wave AC voltage output from the DC-AC converter to output a starting voltage of the lamp. 2. The lighting circuit of a gas discharge lamp according to claim 1, wherein the DC-DC converter is a flyback converter. The lighting circuit of a gas discharge lamp according to claim 1, wherein the DC-AC converter is a full-bridge converter.