KR100866098B1 - Electronic ballast - Google Patents

Abstract

The present invention employs a thyristor (Q3) to shut down the lamp driving circuit in the event of an overvoltage of the lamp output of the prior art so that the IC chip is shut down in response to the application of the current at the gate side thereof. In order to provide an electronic ballast having a thyristor protection circuit to be made in accordance with the attachment of the lamp, in particular to provide an electronic ballast having a thyristor protection circuit to prevent a malfunction occurs when the lamp driving unit 200 ', A protection circuit 220 to protect the lamp driving circuit from an overvoltage of the lamp output by turning on the rectifier Q3 to shut down the IC chip U1 when the output of the unit 300 is an abnormal voltage; And controlling the operation of the IC chip U1 by cutting off the driving power applied to the IC chip U1 by sensing the lamp when the lamp unit 300 is incapable, and the protection circuit 220 according to the lamp attachment. And a feedback circuit unit 210 'for resetting the rectifier Q3 in the ON state. When the ballast is turned on and immediately turned off in the feedback circuit unit 210', the voltage of the soft start capacitor of the IC chip U1 is turned off. And means for delaying the drop so that no preheating time is required.

Ballast, Protection Circuit, Feedback Circuit, Soft-Start Capacitor, Preheating.

Description

Preheating-type electronic ballast which prevents malfunctions when lighting {ELECTRONIC BALLAST}

1 is a circuit diagram of an electronic ballast of the prior art.

2 is a circuit diagram of the protection circuit voltage of the electronic ballast of the prior art.

3 is a voltage and frequency waveform diagram according to the operation mode of the electronic ballast of the prior art.

4 is a circuit diagram of an electronic ballast in which a malfunction is prevented during lighting according to an embodiment of the present invention.

5 is a voltage waveform diagram according to the operation mode of the electronic ballast according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: rectification and smoothing part 200, 200 ': lamp driving part

210, 210 ': feedback circuit 220: protection circuit

300: lamp unit 310: lamp

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic ballast having a thyristor protection circuit, and more particularly, to effectively protect a ballast driving a lamp when an overvoltage is applied or a lamp failure such as a failure of a lamp. The present invention relates to a preheated-type electronic ballast in which a malfunction in lighting is prevented by adding a function of preventing a malfunction in lighting.

In general, the ballast makes a high voltage during discharge and plays a role of limiting the current after discharge. Until now, magnetic ballasts that operate at 50Hz to 60Hz have been widely used.

However, these magnetic ballasts are bulky and heavy, have flickering and audible noise, and low efficiency due to large power loss. Recently, the electronic ballast has been replaced by many magnetic ballasts. have.

Electronic ballasts contain a starting semiconductor element in the ballast, which preheats the electrode with its switching action or electrode heating winding and starts the lamp by the semiconductor switching action, while the lamp is heated by the lamp current and the electrode heating winding during lighting. As the ballast used in the circuit method, there are self-excited equations oscillated by its own LC resonant circuit, and the equations relating to the present invention using a separate oscillator.

Electronic ballasts have a number of advantages over conventional ballasts, but have weaknesses in voltage fluctuations and surge voltages, and therefore must have built-in protection circuits.

As one general conventional technique described above, an example of a strike-type electronic ballast employing an oscillating IC chip will be described with reference to FIG. 1.

As shown in Fig. 1, the conventional electronic ballast employs a thyristor Q3 to shut down the lamp driving circuit in the event of an overvoltage of the lamp output to shut down the IC chip according to the application of the current at the gate side thereof. On the other hand, it is an electronic ballast having a thyristor protection circuit such that the reset of the thyristor is made in accordance with the attachment of the lamp.

In more detail, the rectification and smoothing unit 100 is applied to the rectified and converted to a DC power by receiving a commercial AC voltage, and the lamp unit 300 is applied to the DC power output from the rectifying and smoothing unit 100 is applied. The lamp driver 200 for turning on the lamp of the lamp, the protection circuit 220 for shutting down the lamp driver 200 when the output of the lamp unit 300 is an abnormal voltage, and the lamp unit 300 when the lamp is disabled. And a feedback circuit unit 210 to prevent a driving DC voltage from being applied to the IC chip U1 of the lamp driver 200.

Referring to Figure 1 in more detail with respect to the electronic ballast having a conventional thyristor protection circuit,

The rectification and smoothing unit 100 is a fuse for blocking the application of an alternating voltage of the varistor (VA) and the overvoltage to remove the abnormal voltage generated from the power input through the input terminals (BK, WH) input the commercial AC voltage Low pass filter LF and ripple elimination capacitor C1-C3 are continuously connected to FUSE to stabilize the voltage of the applied AC power, and bridge diodes that convert commercial AC to DC voltage on the other side. (D1-D4) and a smoothing capacitor (C4) responsible for smoothing the voltage rectified from the bridge diodes (D1-D4).

The lamp driver 200 turns on the lamp of the lamp unit 300 by the DC power applied through the rectifying and smoothing part 100. The lamp driving part 200 is the rectifying and smoothing part 100. The smoothed DC power is applied through the current control resistors R1 and R2 connected to the other side of the IC chip and applied to the VCC terminal (No. 8 terminal) of the control IC chip U1 through the feedback circuit unit 210. The operating power of U1 is supplied. For example, the IC chip is FAN7544.

In addition, the soft start capacitor connection terminal of terminal 1 and the soft start resistor connection terminal of terminal 3 of the IC chip U1 are connected to the ground terminal through the sixteenth capacitor C16 and the fourteenth resistor R14, respectively. As described above, the parameter values of the sixteenth capacitor C16 and the fourteenth resistor R14 determine the initial frequency and phase so that a soft start occurs.

In addition, the timing capacitor connection terminal, which is terminal 2, is connected to the ground terminal through the seventeenth capacitor C17, and the seventeenth capacitor C17 is periodically charged and discharged to generate a sawtooth waveform that determines the oscillation frequency. Also, terminal 5 is a ground terminal, and terminals 7 and 6 are output terminals.

Terminal 7, which is an output terminal of the IC chip U1, is connected to the input side OSC-2 of the oscillator OSC through a coupling capacitor C12 and a coupling resistor R8, and the oscillator OSC. Output side OSC-1 is connected to the gate terminal of the first switching element Q1 through a sixth resistor R6. The sixth terminal, which is another output terminal of the IC chip U1, is connected to the gate of the second switching element Q2 through a coupling resistor R7, and eventually oscillates at a constant frequency by the oscillator OSC. As a result, the switching elements Q1 and Q2 are periodically switched.

At this time, one terminal of the first switching element Q1 is connected to the output side of the rectifying and smoothing unit 100, and one terminal of the second switching element Q2 is grounded.

Meanwhile, the other terminals of the first and second switching elements Q1 and Q2 are connected to each other, and the connection terminal is connected to the lamp 310 at the lamp unit 300 through one side winding PT-1 of the transformer. And the other winding PT-2 of the transformer is connected to the coupling resistor R9 to the VCC terminal of the IC chip U1 through the diode D10, respectively, while the protective circuit portion is connected through the diode D9. An input control resistor R10 of 220 is connected.

On the other hand, the input of the lamp driving unit 200 is connected to the choke coil (T2-1), one side of the choke coil (T2-1) through the fifth diode (D5) the first switching element (Q3) and The parallel circuits of the fifteenth resistor R15 and the eleventh capacitor C11 are connected to the contacts of the second switching element Q4, respectively. The cathode of the fifth diode D5 is connected to the current control resistor R2, the voltage divider resistors R1 and R3, and the electrolytic capacitors C5 and C6 at the input terminal of the lamp driver 200.

On the other hand, the lamp unit 300 is composed of a lamp 310 connected to one winding (PT-1) of the transformer, the BB terminal and BC terminal of the first lamp 310 is a capacitor for impedance and resonance control ( C10 and a sixteenth resistor R16 are interconnected, and both terminals BA, BB, BC, and BD of each filament of the lamp 310 are connected via capacitors C18, C19, respectively. In addition, the BD terminal of the lamp is connected to the current control resistor R2 at the input terminal of the lamp driver 200 ′ through the fifth resistor R5.

In addition, the BD terminal of the lamp 310 is connected to the output terminal and the ground terminal of the rectifying and smoothing unit 100 through the capacitors C7 and C8, respectively, and the choke coil and the ground through the diodes D7 and D8, respectively. It is connected to each terminal.

The feedback circuit unit 210 is inserted between the resistors R1 and R2 for supplying the output DC power of the rectifying and smoothing unit 100 and the IC chip U1 driven by the output DC power. The emitter terminal of transistor Q4, which is connected to the contacts of the resistors R1 and R2 and the collector terminal, is connected to the VCC terminal of the IC chip U1, and the base terminal of the transistor Q4 is The fifth resistor R5 is connected to the BD terminal of the lamp 310 in the lamp unit 300, and grounded through the third zener diode ZD3. Meanwhile, a fifteenth capacitor C15 and a first zener diode ZD1 are inserted between the emitter terminal and the ground of the transistor Q4, and electrolytic capacitors C5 and C6 are inserted between the choke coil and the ground, respectively. .

Therefore, when the lamp of the lamp unit 300 operates normally, the "high" signal is applied to the base terminal of the transistor Q4 so that the transistor Q4 is turned on to supply the driving voltage to the IC chip U1. do.

However, when the lamp is disabled, such as when the lamp is not connected to the socket, the base end of the transistor Q4 is in the "low" state, and the transistor Q4 is turned off to the off state, so that the rectifying and smoothing part 100 is turned off. ) Is not applied to the IC chip (U1), the operation of the chip is stopped.

Therefore, the feedback circuit unit 210 can sense whether the lamp unit 300 is attached to the lamp unit 300, thereby protecting the circuit of the lamp unit 300 and reducing power loss.

On the other hand, the protection circuit 220 is connected through the diode (D9, D10) and the resistor (R10) connected to the secondary terminal (PT2) of the transformer, this protection circuit 220 of the resistor (R10) While connected to the gate side of the rectifier Q3, which is a switching thyristor, through a second zener diode ZD2 connected in a reverse direction of the thirteenth capacitor C13 and the eleventh resistor R11 grounded at the other side, The gate holding current elements R12 and C14 connected to the gate side of Q3) are grounded.

At this time, the cathode side of the rectifier Q3 is grounded and the anode side is grounded through the fifteenth capacitor C15 and is also connected to terminal 8, the Vcc terminal of the IC chip U1.

Therefore, when the operating voltage of the lamp detected by the transformer is normal, the second zener diode ZD2 is connected in the reverse direction to the gate terminal of the rectifier Q3, which is a switching element of the protection circuit 220, so that no current flows. ) Is kept off, and therefore the Vcc voltage is applied to the Vcc terminal of the IC chip U1 so that the chip operates normally.

However, when the output voltage V1 of the lamp detected by the transformer is equal to or greater than a predetermined value (for example, 12V) as in the case of a bad lamp or a lamp miswiring, the second zener diode ZD2 of the protection circuit 220 is braked. This causes a down and thus a current is applied to the gate side of the rectifier Q3 to turn on the rectifier Q3.

Therefore, the Vcc terminal of the IC chip U1 is grounded to 0V, and as a result, the IC chip U1 is shut down, so that the protection circuit 220 protects the lamp driving circuit from the overvoltage of the lamp output.

On the other hand, since the on-state rectifier Q3 is maintained in the on state even when the current flowing through the gate is blocked, it is not connected to the socket in the lamp unit 300 to reset, that is, to restore. When the lamp in the lamp deactivated state is re-attached, the transistor Q4 of the feedback circuit unit 210 survives, causing the third zener diode ZD3 connected to the base side to break down, while the emitter side is connected to ground. The charging capacitor C15 connected to is charged so that the polarity of the voltage passing through the rectifier Q3 is reversed, so that the rectifier Q3 is automatically reset, that is, turned off.

That is, the feedback circuit unit 210 can sense the presence or absence of the lamp, and not only shut off the power applied to the IC chip U1 according to the presence or absence of the lamp, but also shut down the IC chip U1 when the overvoltage of the lamp output is applied. It is possible to perform a function to reset the rectifier (Q3) of the protection circuit 220.

However, the ballast of the prior art has the following problems.

That is, as shown in Fig. 2, when the ballast is 'on', the lamp output voltage (V1) increases (P0-P1), if the normal lighting, the output voltage drops at the point P1 (about 10V) 8 when the normal operation Maintain -9V (see dashed line).

However, if the output voltage V1 is falling (P1-P2) (it takes about 2-3 seconds until this time), the switch is turned off and then turned on again immediately, the output voltage V1 rises again at the point P2 before falling to 0V. (P2-P3).

However, if this is repeated (P3-P4-P5), the lamp output voltage V1 exceeds the breakdown voltage 12V of the second zener diode ZD2 even though the lamp is normal before the lamp is turned on. Since a phenomenon occurs and the protection circuit 220 is operated, the lamp is not turned on even when the ballast is turned on.

That is, in the preheating ballast, the IC chip U1 is driven only when the voltage Vc16 of the sixteenth capacitor C16 of the soft start capacitor connection terminal (pin 1) is charged above a predetermined voltage. As shown, the oscillation frequency and the voltage Vc16 of the capacitor C16 are different for each of the 'preheating step-lighting step-normal driving step'. In other words, the programmed ballast is set to maintain a constant preheat time tph for lamp preheating, which is generally the time until the capacitor C16 is charged to about 2.9V.

As a result, in the prior art, it is pointed out as a problem that the output voltage V1 rises before the capacitor C16 is sufficiently charged.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to adopt a thyristor (Q3) to shut down the lamp driving circuit in the event of overvoltage of the lamp output of the prior art. An electronic ballast having a thyristor protection circuit which allows the IC chip to be shut down while the reset of the thyristor is made in accordance with the lamp binding, but in particular an electronic ballast having a thyristor protection circuit which prevents malfunctions when turned on. To provide.

Electronic ballast which is prevented from malfunctioning when lighting in accordance with the present invention for achieving the above object, rectification and smoothing unit 100 for rectifying the applied commercial AC power to convert to DC power, and the rectifying and smoothing unit 100 A lamp driver 200 'for supplying driving power to the lamp by switching to a predetermined oscillation frequency according to a control operation of the internal IC chip U1 by receiving a DC power output from the lamp driver; and driving from the lamp driver 200'. As an electronic ballast comprising a lamp unit 300 is turned on by receiving power,
The lamp driving unit 200 ′ protects the lamp driving circuit from overvoltage of the lamp output by turning on the rectifier Q3 and shutting down the IC chip U1 when the output of the lamp unit 300 is an abnormal voltage. Protection circuit 220; And
The lamp unit 300 senses when the lamp is incapable and cuts off the driving power applied to the IC chip U1 to control the operation of the IC chip U1, and at the protection circuit 220 according to the lamp attachment. A feedback circuit unit 210 'for resetting rectifier Q3 in an on state,
When the ballast is turned on and off immediately in the feedback circuit unit 210 ', the voltage drop of the soft start capacitor of the IC chip U1 is delayed so that no preheating time is required. And a time constant increasing means connected between the soft start capacitor connection terminal and the capacitor C16 which is the time constant determining element.

Preferably, the time constant increasing means includes a fourth zener diode ZD4 and a resistor R4 connected between the soft start capacitor connection terminal of the IC chip U1 and the capacitor C16 which is the time constant determining element. It is characterized by the addition of a parallel circuit.

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

Figure 4 is a circuit diagram of an electronic ballast according to an embodiment of the present invention, the same components as the ballast circuit of the prior art of Figure 1 is given the same number and the corresponding components are given similar member numbers.

The difference between the ballast circuit according to the present invention of FIG. 4 and the ballast circuit of the prior art of FIG. 1 is that the soft start capacitor connection terminal (No. 1 pin) and the sixteenth capacitor of the IC chip U1 of the feedback circuit section 210 '. A parallel circuit of the fourth zener diode ZD4 and the fourth resistor R4 is inserted between the C16.

That is, the lamp driving unit 200 ′ of the ballast of the present invention turns on the lamp of the lamp unit 300 with a DC power applied through the rectifying and smoothing unit 100. The smoothed DC power is applied through the current control resistors R1 and R2 connected to the other side of the rectifying and smoothing unit 100, and the VCC terminal of the control IC chip U1 is connected through the feedback circuit unit 210 '. Terminal 8) to supply the operating power of the IC chip U1. For example, the IC chip is FAN7544.

In addition, the soft start capacitor connection terminal, which is the first terminal of the IC chip U1, is connected to the ground terminal through a parallel circuit of the fourth zener diode ZD4 and the resistor R4 and the sixteenth capacitor C16. The third soft start resistor connection terminal, which is a third terminal of the IC chip U1, is connected to a ground terminal through a fourteenth resistor R14, and thus parameters of the sixteenth capacitor C16 and the fourteenth resistor R14 are provided. The value determines the initial frequency and phase so that a soft start occurs.

In addition, the timing capacitor connection terminal, which is terminal 2, is connected to the ground terminal through the seventeenth capacitor C17, and the seventeenth capacitor C17 is periodically charged and discharged to generate a sawtooth waveform that determines the oscillation frequency. Also, terminal 5 is a ground terminal, and terminals 7 and 6 are output terminals.

Terminal 7, which is an output terminal of the IC chip U1, is connected to the input side OSC-2 of the oscillator OSC through a coupling capacitor C12 and a coupling resistor R8, and the oscillator OSC. Output side OSC-1 is connected to the gate terminal of the first switching element Q1 through a sixth resistor R6. The sixth terminal, which is another output terminal of the IC chip U1, is connected to the gate of the second switching element Q2 through a coupling resistor R7, and eventually oscillates at a constant frequency by the oscillator OSC. As a result, the switching elements Q1 and Q2 are periodically switched.

At this time, one terminal of the first switching element Q1 is connected to the output side of the rectifying and smoothing unit 100, and one terminal of the second switching element Q2 is grounded.

Meanwhile, the other terminals of the first and second switching elements Q1 and Q2 are connected to each other, and the connection terminal is connected to the lamp 310 at the lamp unit 300 through one side winding PT-1 of the transformer. And the other winding PT-2 of the transformer is connected to the coupling resistor R9 to the VCC terminal of the IC chip U1 through the diode D10, respectively, while the protective circuit portion is connected through the diode D9. An input control resistor R10 of 220 is connected.

The choke coil T2-1 is connected to an input terminal of the lamp driver 200 ′, and one side of the choke coil T2-1 is connected to the first switching element Q1 through a fifth diode D5. And a parallel circuit of the fifteenth resistor R15 and the eleventh capacitor C11 connected to the contact point of the second switching element Q2, respectively. The cathode of the fifth diode D5 is connected to the current control resistor R2, the voltage divider resistors R1 and R3, and the electrolytic capacitors C5 and C6 at the input terminal of the lamp driver 200 '.

On the other hand, the lamp unit 300 is composed of a lamp 310 connected to one winding (PT-1) of the transformer, the BB terminal and BC terminal of the first lamp 310 is a capacitor for impedance and resonance control ( C10) and a sixteenth resistor R16, and both terminals BA, BB, BC, and BD of each filament of the lamp 310 are connected through capacitors C18, C19, respectively. In addition, the BD terminal of the lamp is connected to the current control resistor R2 at the input terminal of the lamp driver 200 ′ through the fifth resistor R5.

In addition, the BD terminal of the lamp 310 is connected to the output terminal and the ground terminal of the rectifying and smoothing unit 100 through the capacitors C7 and C8, respectively, and the choke coil and the ground through the diodes D7 and D8, respectively. It is connected to each terminal.

Meanwhile, the feedback circuit unit 210 ′ is disposed between the resistors R1 and R2 for supplying the output DC power of the rectifying and smoothing unit 100 and the IC chip U1 driven by the output DC power. The emitter terminal of the transistor Q4, which is connected to the contacts of the resistors R1 and R2 and the collector terminal thereof, is connected to the VCC terminal of the IC chip U1, and also the base terminal of the transistor Q4. Is connected to the BD terminal of the lamp 310 in the lamp unit 300 through the fifth resistor R5, and is grounded through the third zener diode ZD3. Meanwhile, a fifteenth capacitor C15 and a first zener diode ZD1 are inserted between the emitter terminal and the ground of the transistor Q4, and electrolytic capacitors C5 and C6 are inserted between the choke coil and the ground, respectively. .

Therefore, when the lamp of the lamp unit 300 operates normally, the "high" signal is applied to the base terminal of the transistor Q4 so that the transistor Q4 is turned on to supply the driving voltage to the IC chip U1. do.

However, when the lamp is disabled, such as when the lamp is not connected to the socket, the base end of the transistor Q4 is in the "low" state, and the transistor Q4 is turned off to the off state, so that the rectifying and smoothing part 100 is turned off. ) Is not applied to the IC chip (U1), the operation of the chip is stopped.

Accordingly, through this, the feedback circuit unit 210 ′ can sense whether the lamp unit 300 is attached to the lamp, thereby protecting the circuit of the lamp unit 300 and reducing power loss.

On the other hand, the protection circuit 220 is connected through the diode (D9) and the resistor (R10) connected to the secondary terminal (PT2) of the transformer, this protection circuit 220 is the other side of the resistor (R10) The rectifier Q3 is connected to the gate side of the rectifier Q3, which is a switching thyristor, via a second zener diode ZD2 connected in a reverse direction of the grounded thirteenth capacitor C13 and the eleventh resistor R11. The gate holding current elements R12 and C14 connected to the gate side of the circuit are grounded.

At this time, the cathode side of the rectifier Q3 is grounded and the anode side is grounded through the fifteenth capacitor C15 and is also connected to terminal 8, the Vcc terminal of the IC chip U1.

Therefore, when the operating voltage of the lamp detected by the transformer is normal, the second zener diode ZD2 is connected in the reverse direction to the gate terminal of the rectifier Q3, which is a switching element of the protection circuit 220, so that no current flows. ) Is kept off, and therefore the Vcc voltage is applied to the Vcc terminal of the IC chip U1 so that the chip operates normally.

However, when the output voltage V1 of the lamp detected by the transformer is equal to or greater than a predetermined value (for example, 12V) as in the case of a bad lamp or a lamp miswiring, the second zener diode ZD2 of the protection circuit 220 is braked. This causes a down and thus a current is applied to the gate side of the rectifier Q3 to turn on the rectifier Q3.

Therefore, the Vcc terminal of the IC chip U1 is grounded to 0V, and as a result, the IC chip U1 is shut down, so that the protection circuit 220 protects the lamp driving circuit from the overvoltage of the lamp output.

On the other hand, since the on-state rectifier Q3 is maintained in the on state even when the current flowing through the gate is blocked, it is not connected to the socket in the lamp unit 300 to reset, that is, to restore. When the lamp of the lamp stop state is re-attached, the transistor Q4 of the feedback circuit unit 210 'is alive and the third zener diode ZD3 connected to the base side causes breakdown, while the emitter side and the ground The charging capacitor C15 connected therebetween is charged so that the polarity of the voltage passing through the rectifier Q3 is reversed, so that the rectifier Q3 is automatically reset, that is, turned off.

That is, the feedback circuit unit 210 ′ may sense the presence or absence of a lamp, and not only cut off the power applied to the IC chip U1 according to the presence or absence of the lamp, but also shut down the IC chip U1 when an overvoltage is applied to the lamp output. It is possible to perform the function to reset the rectifier (Q3) of the protection circuit 220.

Referring to the operation of the protection circuit of the ballast according to the present invention, in the case of an abnormal state of output overvoltage, breakdown of the zener diode ZD2 of the protection circuit 220 occurs and the rectifier Q3 is turned on. Therefore, pin 8 of the IC chip, which is the anode end of the thyristor, becomes 0V, and thus, the operation of the oscillation IC is stopped to protect the entire ballast.

On the other hand, in the ballast of the present invention, when the switch is turned off and immediately turned off, the fourth zener diode (connected between the soft start capacitor connection terminal (terminal 1) of the IC chip U1 and the sixteenth capacitor C16 ( Due to the parallel circuit of ZD4) and resistor R4, as shown by the member number '②' of FIG. 5, the voltage charged in the sixteenth capacitor C16 gradually drops (in the case of the prior art of FIG. As shown by the number '1', the voltage across the capacitor drops sharply), so when the switch is turned off and then turned on again immediately, the lamp is turned on immediately because the pre-heating time tph is not necessary because of the already charged voltage. In this case, since the lamp is already preheated, the lamp is not overwhelmed, and since the lamp output voltage does not exceed 12V, the overvoltage protection circuit 220 does not operate as long as it is a normal lamp, so that no malfunction occurs in lighting. do.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited to the drawing.

In other words, the purpose of the fourth Zener diode ZD1 and the fourth resistor R4 is to delay the voltage drop of the soft start capacitor of the IC chip U1 when the ballast is turned on and immediately turned off, thereby increasing the preheating time. It is a means not to be necessary, which may be composed of a time constant increasing means connected between the soft start capacitor connection terminal of the IC chip (U1) and the capacitor (C16) that is the time constant determining element, the means must be the zener It is not limited to the parallel circuit of the diode ZD4 and the resistor R4.

As described above, the electronic ballast having the thyristor protection circuit shown in the present invention is applied to the gate terminal of the rectifier (Q3) during the overvoltage of the lamp output detected through the transformer to turn the rectifier on and drive accordingly By providing a protection circuit for shutting down the IC chip, the stability problem of the driving circuit caused by the overvoltage applied to the lamp can be easily solved by using the protection circuit, and the reset operation of the rectifier can be facilitated. When the switch is turned off and then turned on again, the lamp is immediately turned on without requiring a preheating time (tph), and the overvoltage protection circuit 220 does not operate as long as it is a normal lamp, and thus there is an advantage that no malfunction occurs in the lighting.

Claims (3)

Rectification and smoothing unit 100 for rectifying and converting the commercial AC power supplied to the DC power, and the DC power output from the rectifying and smoothing unit 100 is applied according to the control operation of the internal IC chip (U1) An electronic ballast comprising a lamp driver 200 'for switching the oscillation frequency to supply driving power to a lamp and a lamp unit 300 that is turned on by receiving driving power from the lamp driver 200'. The lamp driving unit 200 ′ protects the lamp driving circuit from overvoltage of the lamp output by turning on the rectifier Q3 and shutting down the IC chip U1 when the output of the lamp unit 300 is an abnormal voltage. Protection circuit 220; And The lamp unit 300 senses when the lamp is incapable and cuts off the driving power applied to the IC chip U1 to control the operation of the IC chip U1, and at the protection circuit 220 according to the lamp attachment. A feedback circuit unit 210 'for resetting rectifier Q3 in an on state, When the ballast is turned on and off immediately in the feedback circuit unit 210 ', the voltage drop of the soft start capacitor of the IC chip U1 is delayed so that no preheating time is required. And a time constant increasing means connected between a soft start capacitor connection terminal and a capacitor (C16) that is the time constant determining element. delete The method of claim 1, The time constant increasing means, And a parallel circuit of a fourth zener diode ZD4 and a resistor R4 connected between the soft start capacitor connection terminal of the IC chip U1 and the capacitor C16 which is the time constant determining element. Preheating-type electronic ballast that prevents malfunctions when turned on.

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