KR0168089B1 - Operating device for fluorescent lamp - Google Patents

Abstract

The present invention relates to a stable driving device of a fluorescent lamp for stably driving a fluorescent lamp, the apparatus comprising: an overvoltage detecting means for detecting an overvoltage of a fluorescent lamp driving means when a fluorescent lamp is defective, and a fluorescent lamp according to an overvoltage signal detected by the overvoltage detecting means. And control means for stably controlling the point and the like, and relay driving means for driving the relay to control the power applied to the fluorescent lamp in accordance with the overvoltage signal output from the overvoltage detection means.

Description

Stable Driving Device of Fluorescent Lamp

1 is a control block diagram of a conventional drive device for a fluorescent lamp.

2 is a control block diagram of a stable driving device of a fluorescent lamp according to an embodiment of the present invention.

3 is a detailed circuit diagram of a stable driving device of a fluorescent lamp according to an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

10: bridge rectification means 20: starting voltage means

30: fluorescent lamp driving means 40: overvoltage detection means

50: control means 60: fluorescent lamp

70: relay drive means 90: switch means

The present invention relates to a stable driving device of a fluorescent lamp to drive the fluorescent lamp stably.

In general, a conventional drive device for a fluorescent lamp includes a bridge rectifying means 10 for full-wave rectification by receiving a commercial AC input voltage output from the AC power input terminal 1 and the bridge as shown in FIG. A starting voltage means 20 for receiving a DC voltage output from the rectifying means 10 and outputting an initial starting voltage signal for preheating the filament of the fluorescent lamp 40, and a starting voltage output from the starting voltage means 20; Receiving a signal and outputting a driving signal for turning on the fluorescent lamp 60 to the fluorescent lamp 40 and shutting off the power of the AC power input terminal 1 according to a defective state of the fluorescent lamp 60; The switch means 90 is comprised.

In the conventional fluorescent lamp driving device configured as described above, the fluorescent lamp driving means 30 for supplying the phase controlled power so that the fluorescent lamp 60 is turned on when the fluorescent lamp 60 is defective or the end of life is not shown. An overcurrent flows through the uncontrolled power control switching element, and heat is generated. The heat generated by the overcurrent is released through a heat sink attached to the power control switching element.

When the heat dissipated through the heat sink attached to the power control switching element reaches a temperature of a predetermined level or more, the switch unit 90 cuts off the commercial AC input voltage from the AC power input terminal 1 to replace the fluorescent lamp 60. Turn off).

However, in such a configuration, since the overcurrent flows to the power control switching element during the time to reach the predetermined temperature set by the switch means 90, the switching element is damaged, and thus the performance of the device cannot be guaranteed. Irrespective of the defective state of the fluorescent lamp, the fluorescent lamp driving means 30 is operated so that other fluorescent lamps having a good state are subjected to overvoltage above the rated power, so that the illumination intensity of the fluorescent lamp is severe and a stable illumination output cannot be obtained.

Accordingly, the present invention has been made to solve the above-described conventional problems, and an object of the present invention is to detect the defective state of the fluorescent lamp by using the overvoltage detecting means and the control means so that the fluorescent lamp can be turned on at a constant resonance point. Therefore, to provide a stable illumination output of the fluorescent lamp, and to provide a stable driving device of the fluorescent lamp that can protect the eyesight of the user.

Another object of the present invention is to detect the defective state of the fluorescent lamp by using the over-voltage detection means and the relay driving means by turning on and off the fluorescent lamp at regular intervals to inform the user of the point of replacement of the fluorescent lamp while controlling the point of the fluorescent lamp, etc. It is to provide a stable driving device such as a fluorescent lamp that can prevent the destruction of the device.

In order to achieve the above object, a stable driving apparatus of a fluorescent lamp according to the present invention includes an overvoltage detecting means for detecting an overvoltage of a fluorescent lamp driving means in the event of a defective fluorescent lamp, a point of a fluorescent lamp according to an overvoltage signal detected by the overvoltage detecting means, and the like. It characterized in that it comprises a control means for controlling the stable and a relay drive means for driving a relay to control the power applied to the fluorescent lamp in accordance with the overvoltage signal output from the overvoltage detection means.

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

2 is a control block diagram of a stable driving device of a fluorescent lamp according to an embodiment of the present invention, Figure 3 is a detailed circuit diagram of a stable driving device of a fluorescent lamp according to an embodiment of the present invention.

As shown in Figs. 2 to 3, the bridge rectifying means 10 receives a commercial AC input voltage output from the AC power input terminal 1, and performs full-wave rectification by DC, and the starting voltage means 20 is connected to the bridge. By receiving the DC voltage output from the rectifying means 10 and outputting an initial starting voltage signal for preheating the filament of the fluorescent lamp 60, the starting voltage means 20 is output from the bridge rectifying means 10 A voltage divider resistor R1 and R2 for receiving a DC voltage to be divided to a predetermined voltage, a capacitor C1 charged and discharged to generate an initial starting voltage upon receiving a voltage divider signal from the voltage divider resistors R1 and R2; It is composed of the divider resistors R1 and R2 and the diac DIAC turned on / off by the starting voltage generated from the capacitor C1, and one side of the capacitor C1 is connected in parallel to the divider resistors R1 and R2. And the other side is bridge rectification means (10) Is connected to the output terminal.

The fluorescent lamp driving means 30 receives the starting voltage signal outputted from the starting voltage means 20 and outputs a driving signal for turning on the fluorescent lamp 60 to the fluorescent lamp 60, so that the fluorescent lamp driving means 30 ) Is a current transformer (CT) that operates by receiving a current signal output from the DIAC (DIAC) of the starting voltage means 20, and the secondary coil 32 in the primary coil (31) of the current transformer (CT). Transistors TR1 and TR2 that receive the voltage induced by the transistor 33 through the resistors R3 and R4 and alternate operation signals from the transistors TR1 and TR2 to drive the fluorescent lamp 60. Resonance circuit 31 composed of coils L1 and L2 and capacitors C2 and C3 generating high frequency resonance voltage, and a resonance circuit for maintaining the high frequency resonance voltage generated by the resonance circuit 31 at a constant level. Clamping diodes D5 and D6 connected in parallel to the furnace 31. .

A cathode terminal is connected to the base terminals of the transistors TR1 and TR2, and diodes D1 and D2 having anode terminals connected to one terminal of the secondary coils 32 and 33 of the current converter CT are connected, respectively. The diodes D3 and D4 are provided at collector and emitter terminals of the transistors TR1 and TR2 to bypass the counter electromotive force generated when the transistors TR1 and TR2 are turned off to protect the transistors TR1 and TR2. Connected.

One side of the coil (L1, L2) is connected to one terminal of the relay to be described later, the other side is connected to the primary coil 31 of the current transformer (CT), respectively, one side of the capacitor (C2, C3) It is connected to the filament connection terminal of the 1st and 2nd fluorescent lamps 61 and 62, and the other side is connected to the output terminal of the bridge rectification means 10, respectively.

The overvoltage detecting means 40 detects the overvoltage of the fluorescent lamp driving means 30 when the fluorescent lamp 60 is defective, so that the overvoltage detecting means 40 is the first fluorescent lamp of the fluorescent lamp 60. (61) The first overvoltage detecting means 41 for detecting the high voltage due to the bad state and the second overvoltage detecting means 42 for detecting the overvoltage due to the bad state of the second fluorescent lamp 62 of the fluorescent lamp 60. Consists of.

The control means 50 stably controls the lighting of the fluorescent lamp 60 according to the overvoltage signal detected by the overvoltage detection means 40, so that the control means 50 is the bridge rectifying means 10. A reference voltage generator 51 for receiving a DC voltage from the circuit and generating a constant reference voltage signal Vref, and a diode for half-wave rectifying the overvoltage signals from the first and second overvoltage detection means 41 and 41; D7 and D8 and the voltage half-wave rectified by the diodes D7 and D8 are inputted from the non-inverting terminal (+) through the resistor R7 and at the same time the constant reference voltage from the reference voltage generator 51 A comparator COM that receives Vref at the inverting terminal (-) through the voltage divider R5 and R6 and compares it, and a transistor TR3 that receives and operates a comparison signal from the comparator COM through the resistor R8. ) From the bridge rectifying means 10 when the transistor TR3 is turned on. It consists of a photocoupler (PC) operating by receiving a current voltage through a resistor (R9), one side of the resistor (R7) is connected to the cathode terminal of the diode (D7, D8), the other side of the capacitor (C6) Connected to a terminal to form a charging circuit composed of a resistor R7 and a capacitor C6, one end of which is connected to the output terminal of the comparator COM and the other end of which is connected to the base terminal of the transistor TR3. One end of the resistor R9 is connected to the output terminal of the bridge rectifying means 10, and the other end thereof is connected to the photocoupler PC.

In addition, in the drawing, the relay driving means 70 receives an overvoltage signal from the overvoltage detecting means 40 and receives a DC voltage from the bridge rectifying means 10 and is applied to the fluorescent lamp 60. The relay driving means 70 receives the overvoltage signal from the first overvoltage detecting means 41 of the overvoltage detecting means 40 and simultaneously the bridge rectifying means 10. First relay driving means (71) for outputting a first driving contact signal to control a power applied to the first fluorescent lamp (61) of the fluorescent lamp (60) by receiving a DC voltage from the overvoltage detecting means (40); Control the power applied to the second fluorescent lamp 62 of the fluorescent lamp 60 by receiving the overvoltage signal from the second overvoltage detecting means 42 of the controller and receiving the DC voltage from the bridge rectifying means 10 at the same time. The second relay drive means 72 outputs a second drive contact signal.

The first overvoltage detecting means 41 of the overvoltage detecting means 40 receives the voltage induced from the primary coil L1 of the fluorescent lamp driving means 30 to the secondary coil L1 'through the diode D9. It is parallel to the smoothing capacitor C7 for half-wave rectifying and filtering the mech component contained in the half-wave rectified voltage, and the smoothing capacitor C7 to discharge the DC voltage filtered by the smoothing capacitor C7. And a zener diode ZD1 connected to the connected resistor R10 and the DC voltage filtered by the smoothing capacitor C7 to bypass only a voltage higher than a breakdown voltage of a predetermined level, and the second overvoltage detection means 42 ) Half-wave rectifies the voltage induced from the primary coil L2 to the secondary coil L2 'of the fluorescent lamp driving means 30 through the diode D10, and includes the pulse wave component included in the half-wave rectified voltage. A smoothing capacitor C8 for filtering and the smoothing capacitor A resistor R16 connected in parallel with the smoothing capacitor C8 to discharge the DC voltage filtered at C8 and a DC voltage filtered by the smoothing capacitor C8 and receiving a voltage equal to or higher than a breakdown voltage of a predetermined level. Zener diode ZD2 bypasses the bay.

The reference voltage generator 51 of the control means 50 is connected in parallel to the bridge rectifying means 10 to receive a DC voltage from the bridge rectifying means 10 and generate a reference voltage signal Vref of a constant level. And a photocoupler PC, which is configured to operate when the transistor TR3 is turned on, and a phototriac that operates when the LED is turned on. (DT).

In addition, the first relay driving means 71 of the relay driving means 70 receives the overvoltage signal output from the first overvoltage detecting means 41 of the overvoltage detecting means 40 through the voltage divider R1 and R2. The transistor TR4 that is received and turned on, and the transistor TR5 that is turned on by receiving the DC voltage Vcc from the bridge rectifying means 10 through the voltage divider R13 and R14 when the transistor TR4 is turned off. And a relay RL1 which receives and drives the DC voltage Vcc from the bridge rectifying means 10 through the resistor R5 when the transistor TR5 is turned on. The transistor 72 receives the overvoltage signal output from the second overvoltage detection means 42 of the overvoltage detection means 40 through the voltage divider R17 and R18 and turns on the transistor TR6 and the turn of the transistor TR6. When off, the DC voltage Vcc from the bridge rectifying means 10 is divided. Transistor TR7 that is turned on by receiving resistors R19 and R20 and DC voltage Vcc from the bridge rectifying means 10 is driven through resistor R21 when the transistor TR7 is turned on. It consists of a relay coil RL2.

Hereinafter, the effect of the stable driving device of the fluorescent lamp configured as described above will be described.

First, a commercial AC input voltage output from the AC power input terminal 1 of a fluorescent lamp is received by the bridge rectifying means 10, and full-wave rectified by DC, and the full-wave rectified DC voltage is a starting voltage means 20, a fluorescent lamp driving means ( 30) and the reference voltage generator 51 of the control means 50.

The starting voltage means 20 receives the DC voltage output from the bridge rectifying means 10 and divides the voltage into a voltage of a predetermined level through the voltage dividing resistors R1 and R2, and the divided voltage is used to charge the capacitor C1. When the start-up voltage for preheating the filament of the fluorescent lamp 40 is charged to an appropriate voltage capable of driving the DIAC, the DIAC is turned on and the transistor TR2 is turned on through the resistor R4. A voltage is applied to the base terminal of the transistor TR2 to turn on.

When the transistor TR2 is turned on, current flows in the first and second fluorescent lamps 61 and 62 by the voltage charged in the capacitor C2, and is connected in parallel to the first and second fluorescent lamps 61 and 62. As the filaments of the first and second fluorescent lamps 61 and 62 are preheated by the capacitors C4 and C5, current flows in the primary coil 31 of the current transformer CT through the coils L1 and L2. An organic current is generated in the secondary coil 32, and the generated organic current is applied to the base terminal of the transistor TR1 through the resistor R3 to turn on the transistor TR1.

(At this time, the dot directions of the secondary coils 32 and 33 of the current transformer CT are symmetrical so that the transistor TR2 is in an off state.)

When the transistor TR1 is turned on, current flows through the inductances L1 and L2 to the first and second fluorescent lamps 61 and 62, and a capacitor connected in parallel to the first and second fluorescent lamps 61 and 62. As the filaments of the first and second fluorescent lamps 61 and 62 are preheated by C4 and C5, current flows in the capacitor C3.

When an organic current is generated in the secondary coil 33 of the current transistor CT, the transistor TR2 is turned on through the resistor R4 (at this time, the transistor TR1 is turned off) and the transistor ( TR1 and TR2 continuously light the first and second fluorescent lamps 41 and 42 by repeating the alternating operation.

In this case, when the current flows, the current flows from the transistor TR1 to the inductance L1 and L2 to the first and second fluorescent lamps 61 and 62 to the capacitor C2 when the transistor TR1 is turned on. When the transistor TR2 is turned on, current flows in the direction of the capacitors C1 to the first and second fluorescent lamps 61 and 62 to the inductance L1 and L2 to the transistor TR2.

If the first fluorescent lamp 61 of the fluorescent lamp 60 is in a defective state or at the end of its life, the induced current generated at the secondary side L1 ′ of the inductance L1 is a diode of the first overvoltage detecting means 41. Half-wave rectification through D9 and filtering the pulsating component contained in the half-wave rectified voltage in the smoothing capacitor C7 so that the filtered voltage is higher than the voltage VZD1 set in the zener diode ZD1. When the zener diode ZD1 is turned on, the filtered voltage is divided through the voltage divider R11 and R12 and applied to the base terminal of the transistor TR4 so that the transistor TR4 is turned on and the transistor TR4 is turned on. At this time, since the DC voltage from the bridge rectifying means 10 flows to the collector terminal of the transistor TR4 through the resistor R13, a bias voltage is not applied to the base terminal of the transistor TR5. Since TR5 is turned off so that no current is induced in the relay coil RL1 ', the relay RL1 is turned off and the first fluorescent lamp 61 is turned off.

When the voltage charged to the capacitor C7 continues to discharge when the first fluorescent lamp 61 is turned off, the discharge voltage of the zener diode ZD1 becomes less than the set voltage VZD1 of the zener diode ZD1. TR4 is turned off, and when the transistor TR4 is turned off, a direct current voltage from the bridge rectifying means 10 is applied to the base terminal of the transistor TR5 through the voltage divider R13 and R14, so that the transistor TR5 is turned off. Since the current is induced in the relay coil RL1 'while turning ON, the relay RL1 is turned on and the first fluorescent lamp 61 is turned on again.

That is, the first fluorescent lamp 61 periodically turns on and off so that the user knows when to replace the fluorescent lamp 60.

Of course, at this time, since the zener diode ZD2 of the second overvoltage detecting means 42 is in a non-conductive state, the transistor TR6 is turned off, and when the transistor TR6 is turned off, from the bridge rectifying means 10. Is applied to the base terminal of the transistor TR7 through the voltage divider R19 and R20 to turn on the transistor TR7 to induce a current in the relay coil RL2 ', so that the relay RL2 is turned on. The second fluorescent lamp 62 is kept lit.

In addition, the voltage filtered by the smoothing capacitor C7 is half-wave rectified by the diode D7, and the half-wave rectified voltage is charged by the resistor R7 and the capacitor C6 while being charged by the non-inverting terminal of the comparator COM. The constant reference voltage Vref applied to (+) and divided through the divided resistors R5 and R6 of the reference voltage generator 51 is input to the inverting terminal (−) of the comparator COM.

When the DC voltage input to the non-inverting terminal (+) of the comparator COM is higher than the reference voltage Vref input to the inverting terminal (−), a high level signal is output to the output terminal of the comparator COM. The output high level signal is applied to the base terminal of the transistor TR3 through the resistor R8 to turn on the transistor TR3.

When the transistor TR3 is turned on, the DC voltage from the bridge rectifying means 10 is applied to the anode terminal of the light emitting diode LED of the photocoupler PC through the resistor R9 to light the light emitting diode LED. As a result of this, the phototriac PT is turned on to connect the inductances L1 and L2 in parallel.

Accordingly, even when the first fluorescent lamp 61 of the fluorescent lamp 60 is defective or at the end of life, the second fluorescent lamp 62 is maintained by constantly connecting the inductances L1 and L2 in parallel to maintain the resonance frequency fo. It is possible to keep the illuminance of the light stable.

In addition, when the second fluorescent lamp 62 of the fluorescent lamp 60 is in a defective state or at the end of its life, the induced current generated in the secondary side L2 ′ of the inductance L2 is the diode of the second overvoltage detecting means 42. Half-wave rectification through the (D10), the pulsating component contained in the half-wave rectified voltage is filtered by the smoothing capacitor (C8) so that the filtered voltage is higher than the voltage (VZD2) set in the zener diode (ZD2) When the zener diode ZD2 is conducted, the filtered voltage is divided through the voltage divider resistors R17 and R18 and applied to the base terminal of the transistor TR6 to turn on the transistor TR6 and turn on the transistor TR6. At this time, since the DC voltage from the bridge rectifying means 10 flows through the resistor R19 to the collector terminal of the transistor TR6, a bias voltage is not applied to the base terminal of the transistor TR7, so that the transistor (TR7) is turned off due to the relay coil (RL2 ') because the current is not an organic relay (RL2) is turned off a second fluorescent lamp 62 is turned off.

When the voltage charged to the capacitor C8 when the second fluorescent lamp 62 is turned off continues to be discharged to be lower than or equal to the set voltage VZD2 of the zener diode ZD2, the zener diode ZD2 is not conducting and the transistor ( TR6 is turned off, and when the transistor TR6 is turned off, a direct current voltage from the bridge rectifying means 10 is applied to the base terminal of the transistor TR7 through the voltage divider R19 and R20 to make the transistor TR7. Since the current is induced in the relay coil RL2 'while turning ON), the relay RL2 is turned on and the second fluorescent lamp 61 is turned on again.

That is, the second fluorescent light 62 periodically turns on and off so that the user knows when to replace the fluorescent light 60.

Of course, at this time, since the zener diode ZD1 of the first overvoltage detecting means 41 is in a non-conductive state, the transistor TR4 is turned off, and when the transistor TR4 is turned off, from the bridge rectifying means 10. Is applied to the base terminal of the transistor TR5 through the voltage divider R13 and R14 to turn on the transistor TR5 to induce a current in the relay coil RL1 ', so that the relay RL1 is turned on. The first fluorescent lamp 61 is kept lit.

Then, the voltage filtered by the smoothing capacitor C8 is half-wave rectified at the diode D8, and the half-wave rectified voltage is charged by the resistor R7 and the capacitor C6 while being charged by the non-inverting terminal of the comparator COM. The constant reference voltage Vref applied to (+) and divided through the divided resistors R5 and R6 of the reference voltage generator 51 is input to the inverting terminal (−) of the comparator COM.

When the DC voltage input to the non-inverting terminal (+) of the comparator COM is higher than the reference voltage Vref input to the inverting terminal (−), a high level signal is output to the output terminal of the comparator COM. The output high level signal is applied to the base terminal of the transistor TR3 through the resistor R8 to turn on the transistor TR3.

When the transistor TR3 is turned on, the DC voltage from the bridge rectifying means 10 is applied to the anode terminal of the light emitting diode LED of the photocoupler PC through the resistor R9 to light the light emitting diode LED. As a result of this, the phototriac PT is turned on to connect the inductances L1 and L2 in parallel.

Accordingly, even when the second fluorescent lamp 62 is defective or at the end of life, the inductances L1 and L2 are always connected in parallel to maintain the resonant frequency fo to maintain the resonance frequency fo. It is possible to keep the illuminance of the light stable.

In addition, the same operation as in the above case is performed even when the first fluorescent lamps and the second fluorescent lamps 61 and 62 of the fluorescent lamp 60 are in a defective state or have reached the end of their service life.

As described above, according to the stable driving apparatus of the fluorescent lamp according to the present invention, since the fluorescent lamp can be turned on at a constant resonance point by detecting an inferior state of the fluorescent lamp by using the overvoltage detecting means and the control means, the stable illuminance output of the fluorescent lamp is output. In addition, it is possible to protect the eyesight of the user, and to detect the defective state of the fluorescent lamp by using the overvoltage detecting means and the relay driving means, by turning on and off the fluorescent lamp at regular cycles, thereby replacing the fluorescent lamp. While notifying the user, there is an excellent effect of preventing the destruction of the switching element for controlling the lighting of the fluorescent lamp.

Claims (8)

A fluorescent lamp driving device for turning on or off a plurality of fluorescent lamps, comprising: a plurality of overvoltage detection means for detecting an overvoltage of a fluorescent lamp driving means generated when a fluorescent lamp is defective for each of the plurality of fluorescent lamps and outputting an overvoltage signal; Control means for stably controlling the points of the fluorescent lamps in a steady state by connecting inductances of the respective fluorescent lamps in parallel when an overvoltage signal is input from at least one of the overvoltage detection means, and overvoltage from the plurality of overvoltage detection means. Safety input device of a fluorescent lamp comprising a relay driving means for driving a relay to turn on and off the corresponding fluorescent lamp when a signal is input. 2. The overvoltage detecting means of claim 1, wherein the overvoltage detecting means comprises: first overvoltage detecting means for detecting an overvoltage of the fluorescent lamp driving means generated when the first fluorescent lamp is defective and overvoltage of the fluorescent lamp driving means generated when the second fluorescent lamp is defective; And a second overvoltage detecting means for detecting the voltage. 3. The control means according to claim 2, wherein the control means comprises: a reference voltage generator for receiving a DC voltage from the bridge rectifying means and generating a constant reference voltage signal Vref, and from the first and second overvoltage detection means of the overvoltage detection means. A comparator (COM) for receiving and comparing the output overvoltage signal and receiving a half-wave rectified diode and a half-wave rectified voltage from the diodes (D7, D8) and a constant reference voltage (Vref) from the reference voltage generator. ), A transistor TR3 turned on when the comparison signal from the comparator COM is at a high level, and a DC voltage output from a bridge rectifying means when the transistor TR3 is turned on and applied to the fluorescent lamp. A stable driving device for a fluorescent lamp, characterized in that it comprises a photocoupler (PC) that operates to maintain a voltage. 3. The relay driving means according to claim 2, wherein the relay driving means comprises: first relay driving means for driving a relay to receive an overvoltage signal output from the first overvoltage detecting means and to control a power applied to the first fluorescent lamp; And a second relay driving means for driving a relay to control an electric power applied to the second fluorescent lamp by receiving an overvoltage signal output from the second fluorescent lamp. 3. The method of claim 2, wherein the first overvoltage detecting means half-wave rectifies the voltage induced from the primary coil L1 of the fluorescent lamp driving means to the secondary coil L1 'through the diode D9, and the half-wave rectification thereof. Smoothing capacitor (C7) for filtering the pulsating component contained in the voltage, and resistor (R10) connected in parallel to the smoothing capacitor (C7) to discharge the DC voltage filtered by the smoothing capacitor (C7) and And a zener diode (ZD1) for receiving only the DC voltage filtered by the smoothing capacitor (C7) and bypassing only a voltage higher than a breakdown voltage of a predetermined level. The method of claim 2, wherein the second overvoltage detection means, the half-wave rectification of the voltage induced from the primary coil (L2) to the secondary coil (L2 ') of the fluorescent lamp driving means through the diode (D10), the half-wave rectification A smoothing capacitor C8 for filtering the pulse flow component included in the supplied voltage, and a resistor R16 connected in parallel to the smoothing capacitor C8 to discharge the DC voltage filtered by the smoothing capacitor C8. And a zener diode (ZD2) for receiving only the DC voltage filtered by the smoothing capacitor (C8) and bypassing only a voltage higher than a breakdown voltage of a predetermined level. 5. The transistor of claim 4, wherein the first relay driving means comprises: a transistor TR4 which receives the overvoltage signal output from the first overvoltage detection means and is turned on; and a direct current from the bridge rectifying means when the transistor TR4 is turned off. And a transistor TR5 that is turned on by receiving the voltage Vcc and a relay RL1 that receives and drives the DC voltage Vcc from the bridge rectifying means when the transistor TR5 is turned on. Stable driving device for fluorescent lamps. 5. The second relay driving means according to claim 4, wherein the second relay driving means includes a transistor TR6 which is turned on by receiving an overvoltage signal output from the second overvoltage detection means, and a direct current from the bridge rectifying means at the time of turning off the transistor TR6. A transistor TR7 that receives the voltage Vcc and is turned on, and a relay RL2 that receives and drives the DC voltage Vcc from the bridge rectifying means 10 when the transistor TR7 is turned on. A stable driving device such as a fluorescent lamp.