KR101905305B1 - An Apparatus For Lighting Cold Cathode Fluorescent Lamps - Google Patents

Abstract

The present invention relates to a cold cathode device having a circuit protection part 1, a surge current and over current protection part 2, an EMI filter 3, a rectification and PFC part 4, an inverter part 5 and a resonance tank 6, The inverter 5 includes a first switch element Q1 and a second switch element Q2 of a half bridge type so as to generate a high frequency AC power source for driving the lamp from a DC power source from the rectifier circuit Wherein the first and second switch elements each include a body diode and when the first switch element Q1 is turned on, the second switch element Q2 is turned off and the first switch element Q1 is turned off The second switch element Q2 is turned on to convert the DC rectified in the rectifying part to AC and supply the AC to the primary winding of the transformer T2 so that a plurality of cold cathode fluorescent lamps connected in parallel to the secondary winding of the transformer So that the power of one ballast Cathode fluorescent lamps can be easily turned on, so that not only the power saving effect but also the durability of the lamp is prolonged and the durability is improved. Further, the lamps are uniformly activated by the same brightness as the conventional circuit, The simpler transformer and the smaller power supply have the effect of reducing the production cost of the product.

Description

TECHNICAL FIELD [0001] The present invention relates to a cold cathode fluorescent lamp,

More particularly, the present invention relates to a lighting apparatus for a cold-cathode fluorescent lamp, and more particularly, to a lighting apparatus for a cold-cathode fluorescent lamp which is improved to easily light a plurality of cold-cathode fluorescent lamps using one ballast, And a lighting apparatus for a cold cathode fluorescent lamp.

In lighting fixtures that have been developed continuously since electricity and incandescent lamps were discovered and invented, lighting fixtures are not common enough to oppose the brightness and energy of fluorescent lamps in modern times.

Fluorescent lamps developed by replacing incandescent lamps have been developed into bendable fluorescent lamps, which are often referred to as three-wavelength lamps, and they are now widely used. Recently, LEDs (light emitting diodes) have been widely used for lighting due to the development of technologies for developing semiconductor devices and the like.

The above LED has a lower energy consumption than a conventional incandescent lamp or a fluorescent lamp in contrast to brightness. However, since the LED emits blue light at a temperature of 7500K due to the nature of the light, The brightness of the eyes of the user is too bright.

In addition, there is a problem that the color of the object is changed by the refraction of the wavelength of the light, and the application range is not as wide as the fluorescent lamp due to the heat dissipation structure due to the heat generation.

Conventionally, a fluorescent lamp is limited to activate one fluorescent lamp with one ballast. Recently, a circuit for activating a plurality of fluorescent lamps in a single circuit has been introduced. However, in reality, a single input device and a plurality of output devices It is a product that can reduce the cost by unifying the input device as one circuit.

A cold cathode fluorescent lamp has been developed for such a conventional fluorescent lamp as disclosed in Korean Patent Laid-Open Publication No. 2003-0057323 (July 7, 2003) as a cold cathode fluorescent lamp (CCFL) Cold cathode fluorescent lamps have advantages of low power consumption, low heat generation, high brightness and long life by operating with low current, and they can be used for backlight of monitor such as liquid crystal display (TFT-LCD), copier, fax, And the like. In addition, the CCFL is advantageous in that full color can be easily used as a light source using cold cathode emission phenomenon, and its use is increasing.

Conventionally, a fluorescent lamp is limited to activate one fluorescent lamp with one ballast. Recently, a circuit for activating a plurality of fluorescent lamps in a single circuit has been introduced. However, in reality, a single input device and a plurality of output devices It is a product that can reduce the cost by unifying the input device as one circuit.

Accordingly, a plurality of cold-cathode fluorescent lamps can be activated with a single ballast, and an improved cold-cathode fluorescent lamp lighting device is required to improve its durability.

Korean Patent Publication No. 2003-0057323 (July 7, 2003)

SUMMARY OF THE INVENTION It is an object of the present invention to improve at least one pair of cold-cathode fluorescent lamps in one circuit in order to solve the problems of the prior art and to easily light a plurality of cold-cathode fluorescent lamps using a single ballast The present invention provides a lighting apparatus for a cold cathode fluorescent lamp which is improved not only in power saving effect but also in durability because the life of the lamp is prolonged, the cost of the ballast is reduced, and the energy consumed by the circuit is minimized to save electricity.

According to an aspect of the present invention, there is provided an apparatus for lighting a cold cathode fluorescent lamp, comprising: at least two cold cathode fluorescent lamps each having a breakdown voltage and connected in series and a primary winding for applying an alternating current; And a shunt capacitor connected in parallel to the one cold cathode fluorescent lamp, wherein the shunt capacitor is generated by the secondary winding And the voltage applied to the two or more cold cathode fluorescent lamps connected in series is much smaller than the sum of the respective breakdown voltages of the two or more cold cathode fluorescent lamps.

The cold cathode fluorescent lamp lighting apparatus of the present invention is a cold cathode fluorescent lamp lighting apparatus including a circuit protection unit, a surge current and an overcurrent protection unit, an EMI filter, a rectification and PFC unit, an inverter unit and a resonance tank, Bridge type first switch element Q1 and a second switch element Q2 so as to generate a high frequency AC power source for driving a lamp, and the first and second switch elements are respectively connected to a body diode When the first switch element Q1 is turned on, the second switch element Q2 is turned off. When the first switch element Q1 is turned off, the second switch element Q2 is turned on, And supplies the DC power to a plurality of cold cathode fluorescent lamps connected in parallel to the secondary side winding of the transformer.

And a shunt capacitor C14 connected in series between the cathode fluorescent lamp and a secondary winding of a transformer T2 of the resonant tank, wherein a junction between the terminals of the cold cathode fluorescent lamp and the shunt capacitor is connected to the ground of the circuit do.

 The surge current and over current protection unit includes a varistor connected in parallel to the terminals of the AC power input terminal to prevent external surge noise and a thermistor connected to the terminal to lower the inrush current.

The EMI filter is connected in parallel to the terminals of the first and second coils LF1 and LF2 and the AC power input terminal in order to remove noise in a low frequency band and a high frequency band to suppress noise in a low frequency band in a differential mode The second capacitor C2 and the third capacitor C3 are connected in parallel to the first capacitor C1 and the terminals of the power input terminal in order to suppress noise in a common mode of the high frequency band, And a fourth capacitor C4 connected in parallel to the terminals of the second capacitor C4.

The rectifying and PFC unit rectifies and receives a commercial AC in a circuit including bridge diodes D1, D2, D3 and D4 and a capacitor C5 to output a direct current and receives a direct current outputted from the rectifying unit In order to correct the power factor in the PFC part, the PFC part is connected in parallel with the diodes D5 and D6 connected in parallel with a coil L1 connected in series to a line connected to a terminal, and capacitors C6 and C7 ), Capacitors (C15, C16), and capacitors (C8, C9).

The rectifying and PFC unit includes a bridge switch circuit for branching the output of the bridge rectifier and converting the alternating current into direct current, and a link switch circuit for controlling the input current according to the voltage and the input voltage according to the load, And a variable switching frequency control PFC circuit for noise elimination.

 According to the present invention, since a plurality of cold cathode fluorescent lamps can be easily turned on by using one ballast, not only the power saving effect but also the durability of the lamp is prolonged.

In particular, it is an object of the present invention to provide an improved electric circuit for simultaneously activating at least one or more pairs of cold cathode fluorescent lamps with electric energy provided from a single transformer. In addition to providing uniform brightness of the lamps, A simplified transformer and a smaller power supply have the effect of reducing the production cost of the product.

1 is a circuit diagram of a lighting device for activating the operation of two or more cold-cathode fluorescent lamps.
Fig. 2 is a specific circuit diagram of the circuit protection portion, the surge current, the overcurrent protection portion, and the EMI filter portion of Fig. 1;
3 is a specific circuit diagram of the inverter unit of FIG.
Figure 4 is a rectification and PFC circuit diagram of Figure 3;
5 is a specific circuit diagram of the inverter unit and the resonance tank of FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to electrical apparatus for providing electrical energy for activating cold-cathode fluorescent lamps (CCFLs), and more particularly, to at least one pair of CCFLs with electrical energy provided from a single transformer. And is an electric device for activating simultaneously.

1, the lighting apparatus for a cold cathode fluorescent lamp according to the present invention includes a circuit protection unit 1, a surge current and overcurrent protection unit 2, an EMI filter 3, a rectification and PFC unit 4, (5) and a resonance tank (6).

This will be described with reference to a circuit diagram specifically shown in Figs. 2 to 5. Fig. The surge current and the overcurrent protection unit 2 are configured such that the current does not flow at a preset low voltage and the current rapidly flows at a voltage higher than the set voltage, A varistor is connected in parallel to the terminal 111 and the terminal 112 of the AC power input terminal to prevent surge noise by clipping the part of 250 V or more when the external surge current such as the power is supplied, And a thermistor 22 connected to the thermistor 22.

The EMI filter 3 is connected in parallel to the first coil LF1 for suppressing noise in a common mode of a low frequency band and the terminals 111 and 112 of an AC power input terminal to generate a low frequency differential The first capacitor C1 is connected in parallel to the terminals of the power input terminal in order to remove noise in the high frequency band. The common mode noise of the high frequency band is connected to the terminals of the first capacitor C1, The fourth capacitor C4 connected in parallel to the terminals of the power input terminal and the terminals 111 and 112 of the power input terminal are connected in parallel to control the differential mode of the high frequency band (Noise) of an alternating current power source can be attenuated by effectively reducing the common mode noise in the high-frequency region and the low-frequency region, respectively, by including the second coil LF2 for suppressing noise in the differential mode To protect the circuit from surge voltage.

The rectifying and PFC unit 4 rectifies and receives a commercial AC to output a DC current, receives a DC current output from the rectifying unit, and corrects the power factor in the PFC unit. To this end, a bridge rectifier 7 for converting an alternating current into a direct current and a link switch circuit 8 and a variable switching frequency control PFC circuit 9 for branching the output of the bridge rectifier are connected.

In Fig. 4, the link switch element 8 includes a diode D1, an output choke L2, and a capacitor C9. The power supply operates in mostly discontinuous mode, while the diode (D1) is a reverse-recovery time and ultra-fast diode of approximately 75 nanoseconds that can be accommodated for MDCM operation. For continuous conduction mode (CCM), the diode is preferably a diode with a recovery time (trr) of less than 35 nanoseconds. The inductor L2 has an RMS current rate and an acceptable temperature rise rate. Capacitor C9 has the function of limiting the output voltage ripple as an output filter capacitor.

First, since the forward voltage drop of the diodes D1 and D2 is the same, the voltage difference of the capacitor C8 tracks the output voltage. The voltage difference developed in the capacitor C8 is sensed and adjusted through the resistors R12, 14 and 15 connected to the feedback pin FB. The values of the resistors R12, 14, and 15 are selected so that the voltage of the feedback pin at the required output voltage is 1.65V.

Adjustment is performed by skipping the switching cycle, and when the output voltage rises, the current to the feedback pin rises. If this exceeds the IFB, the subsequent cycle is skipped until the current is reduced below the IFB. Thereby, more cycles will be skipped as the output load is reduced, and smaller cycles are skipped when the load is increased. If the cycle is not skipped during the 40ms period to prevent overload, the link switch circuit is auto-restarted to limit the average output power to approximately 6% of the maximum load power. To track the error between the output voltage and the capacitor C9 at light load or no load, a resistor R16 is provided to provide a small preload.

 The variable switching frequency control PFC circuit 9 controls the input rush current to be outputted according to the input voltage with the averaged current so as to improve the power factor and remove the harmonic noise. The boost converter stage includes an inductor L1 and a PFS element U2. This stage operates as a boost converter and regulates the output DC voltage while controlling the input current of the power supply. Diode D1 bypasses inductor L1 and charges output capacitor C25 to prevent resonance build-up of the output voltage at start-up. Capacitor C20 provides bypassing and decoupling to filter the supply voltage and maintain stable operation of PFS element U2 while diode D1 provides reverse polarity protection.

The resistor R22 causes the output voltage level to be lower than the level at which the PG (POWER GOOD) pin enters the high impedance state through the PGT (Power Good Threshold) pin of the PFS element U2, and the capacitor C21 is connected to the PGT pin To provide noise immunity. The PFS element U2 is configured in the maximum power mode according to the capacitor C19 connected to the REF pin. The rectified AC input voltage of the power supply is sensed in a PFS element U2 using resistors R17 to R20, and such a resistance value is formed to be large in order to minimize power consumption. A capacitor C20 connected in parallel with the bottom resistor R20 filters the noise coupled to the VOLTAGE MONITOR pin. An output voltage distribution network consisting of resistors R24 to R27 is used to adjust the output voltage and provide feedback to the PFS element U2. The capacitor C24 connected in parallel with the resistor R27 reduces the high frequency noise.

It is used to regulate the output voltage and form the input current to comply with harmonic current limit (high power factor) regulation. By integrating the switch current and controlling amp-sec constant during the switch-on time, the average input current can follow the input voltage. By integrating the difference between the output voltage and the input voltage, the output voltage and power are regulated by keeping the Volt-sec balance constant depending on the electromagnetic characteristics of the boost inductor.

In particular, for this adjustment, a constant Volt-sec for off-time (tOFF) is set. The off-time is controlled as follows.

The constant volt-sec (tOFF) control during off time is defined as (Vo-Vin) x toff = K1 and the constant volt-sec (tON) control during on time is defined as Vin x ton = K1, And ton time. Since on-time volt-sec must be equal to off-time volt-sec, on-time (tON) is controlled as follows to maintain magnetic flux balance in PFC choke.

If the current charging is constant with various switching frequency according to the load change, Iin = Vin x (K2 / K1) can be obtained by calculating the Iin current equation by defining Iin x ton = K2. .

The PFC unit includes capacitors C6 and C7 connected in series to the diodes D5 and D6 connected in parallel with a coil L1 connected in series to a line connected to the terminal 111 and being a link capacitor for current smoothing, C15, and C16, and capacitors C8 and C9.

The PFC unit improves a power factor with respect to a voltage to convert an input voltage into a predetermined high voltage, and can realize a DC / DC conversion operation with a frequency and a fixed duty. And the operation can be performed at the optimum operating point, thereby improving efficiency and performance. In addition, between the terminals of the PFC unit, the output voltage of the PFC unit is resistively coupled to the coil L1 and the capacitors by using the voltage dividing resistors R1 and R2 in order to make the phases of the input voltage and the input current match, And the diodes D7 and D8 receive the feedback voltage from the connection point of the voltage dividing resistors R1 and R2 to detect an error between the actual output voltage of the output terminal of the PFC unit and the target voltage, And generates a predetermined PWM switching signal.

An inverter 5 is connected to the PFC unit to generate a high frequency AC power source for driving the DC power from the rectifier circuit through the inverter. For this purpose, the inverter 5 is an inverter system implemented in a half-bridge manner, and is a method for controlling a lamp current to a desired value while converting an input DC voltage to an AC voltage of several hundred V or more in order to drive a CCFL lamp. Width Modulation) control method.

The inverter 5 includes a first switch element Q1 and a second switch element Q2, and the first and second switch elements each include a body diode. The first and second switching elements Q1 and Q2 are formed of N-type MOSFETs.

The first switch element Q1 is connected to the input end of the first switch element Q1 via the voltage dividing resistors R1 and R2 and the diode D9 to apply the output voltage of the voltage dividing resistor and the first output terminal is connected to the output terminal of the PFC section .

The collector side of the transistor Q3 is connected to the output end of the voltage-dividing resistors R1 and R2 and the diode D9. The base side of the transistor Q3 is connected to the divided voltage line through the resistor, Line. And a second output terminal of the switch element Q1 is connected to a line connected to the base of the transistor Q3.

The input terminal of the second switch element Q2 is connected to the output terminal of the voltage-dividing resistor, and the first output terminal of the second switch element is connected to the emitter side of the transistor Q3 and the line connected to the divided voltage line of the voltage- And the second output terminal is connected to the base side of the transistor Q4 via a resistor R10 connected in series and the voltage dividing line is also connected to the transistor D10 via the diode D10 and the resistor R8, And the emitter side is connected to the output terminal of the rectifying and PFC unit 4 and the collector side is connected to the voltage dividing line of the voltage divider and connected to the emitter side of the resistor R12 through the parasitic capacitor C11 Is connected to the primary windings (5, 6) of the transformer (T2) of the resonance tank (6). The collector side of the transistor Q3 is connected to the primary windings 1 and 3 of the transformer T2 of the resonance tank 6 through a resistor R6 and a parasitic capacitor C10. The windings 2 of the windings 2 and 4 of the transformer T2 are connected to the outputs of the capacitors C6 and C7 and the capacitors C15 and C16 through the blocking diode BD2. The blocking diodes BD1 and BD2 connect the current flow when the voltage drops below a predetermined voltage but blocks the current flow to prevent overdischarge when the voltage is greater than a predetermined voltage.

When the first switch element Q1 is turned on, the second switch element Q2 is turned off, and when the first switch element Q1 is turned off, the second switch element Q2 is turned on. The secondary winding 7, 8, and the secondary winding 7, 8 are wound so that the DC is rectified and supplied to the transformer T2, and the current is supplied to the transformer T2 of the resonance tank, 9 and 10 so that a high output voltage is supplied to the output terminals 211 and 212. The secondary windings of the transformer T2 of the resonance tank are connected to the output terminals 211 and 212, and at least one or more cold-cathode fluorescent lamps not shown in the figure are connected in parallel to the output terminals.

In the present invention, in order to activate the operation of a single cold cathode fluorescent lamp, the lamp is connected in series with both the secondary winding of the transformer and the separation capacitor, which disconnects the direct current, .

According to the present invention, it is possible to easily light a plurality of cold-cathode fluorescent lamps using one inverter, and more particularly to an improved electric circuit for simultaneously activating at least one pair of cold-cathode fluorescent lamps L with electric energy provided from a single transformer The lifespan of the lamp is prolonged and the durability of the lamp is improved. Thus, it is possible to reduce the manufacturing cost of the lighting apparatus for a plurality of cold cathode fluorescent lamps.

Background of the Invention In a typical cold cathode lamp used in a computer LCD, the isolation capacitor typically has a capacitance of about 10 picofarads to 68 picofarads. When the lamp is turned off, i.e., when no light is emitted, the AC voltage applied to the cold cathode lamp initially rises to a break-down voltage of about 1,000 volts to 1,600 volts. Thus, before the voltage across the lamp reaches the breakdown voltage, the lamp is in a nonconductive state, i.e., the current flowing through the lamp is essentially zero and only the leakage current flows through the secondary winding and the isolation capacitor. When the lamp is surrendered, a considerable current flows through the lamp to a conductive state, the lamp starts to emit light, and the voltage across the lamp drops to a holding voltage of about 350 volts to 600 volts.

After the lamp becomes conductive and begins to emit light, the voltage across the isolation capacitor remains essentially constant during the interval that lasts until the AC voltage across the secondary winding falls below the sustaining voltage for some time interval.

Since relatively high frequency AC energy is provided to the primary winding of the transformer, to return the lamp to its non-conducting state, the voltage across the lamp must be kept below the sustain voltage for a time interval much longer than one period of the AC voltage across the lamp .

When the AC voltage across the secondary winding drops below the holding voltage for a sufficiently long time interval, the lamp becomes nonconductive again and stops emitting light.

For each period of the AC voltage after the breakdown first occurs, the lamp conducts the current through the lamp twice in one direction for the first hold voltage interval and then in the opposite direction for the second hold voltage interval .

Further, the electric circuit according to the present invention includes a shunt capacitor connected in parallel to the first ramp, and by connecting the capacitor with the shunt, the secondary winding is supplied through the first and the N lamps connected in series The voltage to be applied is considerably reduced. That is, the voltage is significantly smaller than the sum of the breakdown voltages of the first and Nth CCFLs.

A particularly preferred embodiment of the electric circuit according to the present invention also comprises a first and an Nth cold cathode fluorescent lamps connected in series and a separation capacitor connected in series between the secondary windings of the transformer, The secondary winding of the transformer and the DC between the lamps and electrically disconnects them.

According to another aspect of the present invention, there is provided a cold cathode fluorescent lamp further comprising a shunt capacitor C14 connected in series between the cold cathode fluorescent lamp and a secondary winding of the transformer, wherein a junction between the cold cathode fluorescent lamp and the terminals of the shunt capacitor is connected to the circuit As shown in FIG.

And an energy providing means for supplying electric energy to the primary winding of the transformer, wherein the energy providing means applies electric energy converted from a frequency of 20 KHz to 150 KHz and a voltage of 200 to several thousand volts .

It is to be understood that the present invention is not limited to the lighting apparatus of the power saving cold cathode tube lamp according to the embodiments described above and that various modifications and variations can be made without departing from the spirit and scope of the present invention, It is clear to the person. It is therefore intended that such variations and modifications fall within the scope of the appended claims.

INDUSTRIAL APPLICABILITY The present invention can be applied to a power supply device of a cold cathode fluorescent lamp.

1: Circuit protection
2: Surge current and overcurrent protection
3: EMI filter
4: rectification and PFC section
5: Inverter section
6: Resonant tank
7: Bridge stop
8: Link switch circuit
9: Variable Switching Frequency Control PFC Circuit
111, 112: (power input terminal) terminal
211, 212: (output side) terminal

Claims (6)

A cold cathode fluorescent lamp lighting device including a circuit protection unit 1, a surge current and over current protection unit 2, an EMI filter 3, a rectification and PFC unit 4, an inverter unit 5, and a resonance tank 6 as,
The inverter section (5)
The first output terminal is connected to the output terminal of the rectifying and PFC unit 4 and the second output terminal is connected to the input terminal of the rectifier and the output terminal of the PFC unit 4, The first switch element Q1,
The collector side is connected to the output terminals of the voltage-dividing resistors R1 and R2 and the diode D9. The base side is connected to the voltage dividing line and the second output terminal of the first switch element Q1 is connected through the resistor R4 A third transistor Q3 connected to the primary winding of the transformer T2 of the resonance tank 6 through a resistor R6 and a parasitic capacitor C10,
And a first output terminal is connected to the emitter side of the third transistor Q3 and a line connected to the partial pressure line of the voltage dividing resistor. The blocking diode is connected to the output terminal of the voltage dividing resistors R1 and R2. A second switch element Q2 connected through the first node BD1,
The partial pressure line is connected to the emitter side through a diode D10 and a resistor R8. The emitter side is connected to the rectification and the output terminal of the PFC unit 4, and the base side is connected to the emitter side via a resistor R10 connected in series. The collector side of the transformer T2 is connected to the second output terminal of the second switch element Q2 and the collector side of the transformer T2 is connected to the divided voltage line via the resistor R12 and the parasitic capacitor C11. And a fourth transistor (Q4)
When the first switch element Q1 is turned on, the second switch element Q2 is turned off, and when the first switch element Q1 is turned off, the second switch element Q2 is turned on The DC rectified in the rectifying section is converted into AC and supplied to the primary winding of the transformer T2 of the resonance tank 6 to supply power to a plurality of cold cathode fluorescent lamps connected in parallel to the secondary winding of the transformer Characterized by cold cathode fluorescent lamp lighting device.
The method according to claim 1,
The surge current and over current protection unit 2 includes a varistor 21 connected in parallel with a terminal 111 and an input terminal 112 of an AC power input terminal to prevent external surge noise, And a thermistor (22) connected to the cathode fluorescent lamp (112).
The method according to claim 1,
The EMI filter 3 is connected in parallel to the first and second coils LF1 and LF2 and the terminals 111 and 112 of the AC power input terminal for eliminating noise in a low frequency band and a high frequency band, The first and second capacitors C1 and C2 are connected in parallel to the first and second capacitors C1 and C2 in order to suppress noise in a common mode of the high frequency band. (C3), and a fourth capacitor (C4) connected in parallel to the terminals of the power input terminal.
The method according to claim 1,
The rectifying and PFC unit 4 rectifies and receives a commercial AC in a circuit including a bridge diode and a capacitor C5 to output a DC current and receives a DC current output from the rectifying unit to correct a power factor in the PFC unit The PFC unit includes capacitors C6 and C7 connected in series to the diodes D5 and D6 connected in parallel with a coil L1 connected in series to a line connected to the terminal 111 and being a link capacitor for current smoothing, C15, and C16, and capacitors (C8, C9).
The method according to claim 1,
Cathode fluorescent lamp and a shunt capacitor C14 connected in series between a secondary winding of a transformer T2 of the resonance tank 6 and a junction between the terminals of the cold cathode fluorescent lamp and the shunt capacitor, Wherein the cold cathode fluorescent lamp lighting device is connected to the ground.
The method according to claim 1,
The rectifying and PFC unit 4 includes a bridge rectifier 7 for converting an alternating current into a direct current and a bridge rectifier connected to the output of the bridge rectifier. A switch circuit (8) and a variable switching frequency control PFC circuit (9) for power factor correction and harmonic noise elimination.

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