JPH09148077A - Fluorescent lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a starting device for fluorescent lamp of excellent reliability and versatility using a low-cost circuit configuration, which can certainly start the lamp with one run of pulse voltage feed and is applicable even to a ballast or fluorescent lamp of different power rating. SOLUTION: Through a ballast 2 an AC power supply 1 is connected to between the power supply side terminals of the electrodes 4, 5 of a fluorescent lamp 3 fitted with a pre-heat electrode, and a starter circuit 6 is connected to between the non-power supply side terminals, and thus a fluorescent lamp lighting device is constructed. The starter circuit 6 consists of a series connection of a semiconductor switching element 7 having control terminal, the first diode 8, and a current sensing means 9 to sense the current flowing through the switching element 7. The sensing means 9 has the first resistance 10, and also a second resistance 11 and third resistance 12 which form a series circuitry and is connected parallel with the first resistance 10, and the voltage divided by the second and third resistances 11 and 12 is used as the sensing value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent lamp lighting device and, more particularly, to a starting device using a semiconductor switching element for a fluorescent lamp having a preheating electrode.

[0002]

2. Description of the Related Art Heretofore, a glow starter has been mainly used as a starting device for a fluorescent lamp, but it has drawbacks such as a long starting time and a short life. Recently, a starter using a semiconductor switch element has been developed, but its use is limited because it is more expensive than a glow starter. Therefore, in order to realize a starter having a relatively inexpensive circuit configuration using a semiconductor switching element, a circuit as shown in FIG. 5 in which an inexpensive transistor is used as a semiconductor switching element has been proposed (Japanese Patent Laid-Open No. 6-1401).
No. 64). The conventional circuit will be described below.

In FIG. 5, 1 is an AC power source, 2 is a ballast, 3 is a fluorescent lamp, 24 is a noise preventing capacitor, 2
7 is an electrolytic capacitor, 29 is a Zener diode, 30
Is a thyristor, 33 is a transistor, and 36 is a surge absorber. The series circuit of the resistor 26 and the electrolytic capacitor 27 constitutes a CR timer circuit.

Before the fluorescent lamp 3 is started, the base current is supplied to the base of the transistor 33 via the resistor 31 and the diode 34 while the power supply voltage is positive (the diode 25 is forward biased). 33
Is turned on, and a preheating current flows from the power supply to the fluorescent lamp 3 through the transistor 33, the diodes 25 and 34, and the resistor 32. Further, when the power supply voltage is in the negative cycle, the diode 25 cuts off the current, and the preheating current does not flow in the fluorescent lamp 3. Therefore, the preheating current of the fluorescent lamp 3 has a half-wave rectified waveform.

When the collector current is flowing, the resistance 26
The power supply voltage of the CR timer circuit including the capacitor 27 and the capacitor 27 is substantially equal to the collector-emitter voltage of the transistor 33. At this time, a half-wave rectified waveform, which is a voltage drop caused by the preheating current, is generated across the resistor 32, which is a current detection element inserted between the capacitor 27 of the timer circuit and the cathode of the thyristor 30. The voltage generated in the resistor 32 becomes a positive voltage between the gate and cathode of the thyristor 30, and the voltage obtained by adding this voltage and the voltage of the capacitor 27 is output as the output voltage of the timer circuit via the resistor 28 and the Zener diode 29. Is applied between the gate and cathode of the thyristor 30.

Further, since the voltage waveform of the capacitor 27 rises slowly every preheating half-wave cycle, the thyristor 3
The output voltage waveform of the timer circuit for the cathode of 0 is the voltage of the capacitor 27 superposed with the preheating current waveform for each half-wave cycle. As a result, when the slowly rising capacitor voltage approaches the predetermined voltage Vt for turning on the thyristor, the peak of the voltage ripple superimposed on the voltage of the capacitor every half-wave cycle causes the thyristor to turn on. Therefore, the pulse voltage is generated near the peak of the voltage / current phase at both ends of the fluorescent lamp.

That is, when the time set by the CR timer circuit has passed and the current / voltage phase is near the peak, the timer circuit of the resistor 26 and the electrolytic capacitor 27 causes the electrolytic capacitor 27 and the power source to connect to the gate terminal of the thyristor 30. Charges flow through the resistor 28 and the Zener diode 29, and the thyristor 30 is turned on. as a result,
Since the transistor 33 is turned off and the collector current is suddenly cut off near the peak value, a kick voltage (back electromotive force) is generated by the inductance 2 of the ballast 2. This kick voltage starts the discharge between the electrodes 4 and 5 of the fluorescent lamp 3, and the fluorescent lamp 3 is turned on.

When the fluorescent lamp 3 is turned on, the voltage between the preheating electrode terminals 4 and 5 drops to the lamp voltage at the time of lighting. In the half cycle in which the power supply voltage is positive, a charging current flows through the electrolytic capacitor 27 through the resistor 26 and the thyristor 30 is kept on, so that the transistor 33 is kept off. Therefore, the fluorescent lamp 3 is stably turned on.

[0009]

However, in such a conventional lighting device, the phase for generating the pulse voltage is always near the peak of the preheating current, and the peak value of the preheating current is large when the power supply voltage is high. Therefore, switching loss is large when the transistor 33 is turned off in this phase. As a result, it is easy to cause the breakdown of the transistor,
It is difficult to secure the reliability of the lighting device. By increasing the resistance value of the resistor 32, it is possible to reduce the preheating current and reduce the switching loss. However, if the resistance value of the resistor 32 is too large, the voltage drop of the resistor 32 causes the voltage value of the capacitor 27 to decrease. Since it becomes too large as compared with the above, malfunctions are likely to occur.

It is conceivable to connect the current detecting resistor and the current limiting resistor in series, but in this case, a resistor having a low resistance value of several hundred mΩ is required as the current detecting resistor. Such resistors are more expensive than ordinary ones. It is also conceivable to use a transistor that can withstand a large switching loss, but such a transistor has a large shape and is expensive. In addition, the timer circuit resistor 26
The voltage applied to the capacitor 27 is the transistor 3
Since it is almost equal to the collector-emitter voltage of 3 and the preheating time depends on the preheating current value, it cannot be applied to ballasts and fluorescent lamps having different rated powers.

The present invention has been made in order to solve the above-mentioned conventional problems, and can be applied to ballasts and fluorescent lamps having different rated powers, an appropriate preheating time, and An object of the present invention is to provide a reliable and inexpensive fluorescent lamp lighting device capable of reliably starting a fluorescent lamp by generating a pulse voltage at an appropriate phase and reducing stress of a transistor when a pulse is generated. And

[0012]

In the fluorescent lamp lighting device of the present invention, an AC power source is connected via a ballast between power source side terminals of a pair of electrodes of a fluorescent lamp with a preheating electrode, and the non-power source side of the electrodes. A starting circuit is connected between the terminals, and the characteristic is that the starting circuit includes a semiconductor switching element having a control terminal, a first diode, and a current detection means for detecting a current flowing through the semiconductor switching element. And are connected in series. Preferably,
The current detection means has a configuration in which a series circuit of a second resistor and a third resistor is connected in parallel with the first resistor.

According to the above structure, the preheating current flowing through the semiconductor switching element flows through the current detecting means in which the first resistor and the series circuit of the second resistor and the third resistor are connected in parallel. At this time, the peak value of the preheating current is lowered by the combined resistance of the current detecting means, and the switching current value at the time of turning off the semiconductor switching element is suppressed to be low, so that the energy of the kick voltage generated in the ballast can be reduced. As a result, the stress on the semiconductor switching element is reduced.

The starting circuit controls the switching control means for controlling the switching of the semiconductor switching element and the switching control means in the vicinity of the preheating current peak according to the output signal of the current detecting means with the elapse of a predetermined preheating time. It is preferable to include a timer means for outputting a signal. The cathode of the first diode is connected to the non-power supply side terminal of one electrode of the fluorescent lamp with a preheating electrode, the anode of the second diode is connected to the cathode of the first diode, and the second diode is connected to the cathode of the second diode. The cathode of the diode is connected to the timer means.

According to such a configuration, even when the present lighting device is used in a ballast or a fluorescent lamp having different rated powers, the pulse for starting the fluorescent lamp is given a predetermined preheat by the function of the timer means. Over time,
Further, it can be appropriately generated when the preheating current is near the peak.

Further, by housing the starting circuit in a container having a shape compatible with the glow starter of the fluorescent lamp fixture, it becomes easy to use the present lighting device in an existing lighting fixture.

Further, by using a field effect transistor as the semiconductor switching element, it is not necessary to separately provide a voltage suppressing element for preventing breakdown of the semiconductor switching element due to a kick voltage generated in the ballast. The diode included in the field-effect transistor prevents the semiconductor switching element itself from breakdown due to breakdown voltage.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. As shown in the circuit diagram of FIG. 1, in the fluorescent lamp lighting device of the present embodiment, an AC power source 1 is connected via a ballast 2 between power source side terminals of electrodes 4 and 5 of a fluorescent lamp 3 with a preheating electrode, A starting circuit 6 is connected between the non-power source side terminals of the electrodes 4 and 5. The starting circuit 6 includes a circuit in which a semiconductor switching element 7 having a control terminal, a first diode 8 and a current detecting means 9 for detecting a current flowing through the semiconductor switching element 7 are connected in series. The semiconductor switching element 7 is a field effect transistor having avalanche resistance. The current detection means 9 is arranged in parallel with the first resistor 10 and the second resistor 1
It has a configuration in which a series circuit of 1 and the third resistor 12 is connected.

The starting circuit 6 further includes a switching control means 13 for controlling the switching of the semiconductor switching element 7 and the switching control means in a phase near the preheating current peak according to the output signal of the current detection means 9 during a predetermined preheating time. 13 and a timer means 14 for outputting a signal. The Zener diode 16 of the switching control means 13 is between the gate and the source of the semiconductor switching element 7, and the resistor 17 is the drain of the semiconductor switching element 7.
It is connected between the gates. The cathode of the thyristor 18 is connected to the fluorescent lamp 3 side of the current detecting means 9, and the anode thereof is connected to the gate of the semiconductor switching element 7. The gate of the thyristor 18 is a timer means 14
It is connected to the.

The cathode of the first diode 8 is connected to the non-power supply side terminal of the electrode 5 of the fluorescent lamp 3, the anode of the second diode 15 is connected to the cathode of the first diode 8, and the second diode 15 is connected. The cathode of is connected to the timer means 14. The resistor 19 is connected between the non-power supply side terminal of the electrode 4 and the cathode of the diode 15,
The resistor 20 is connected between the connection point of the resistor 19 and the diode 15 and the positive terminal of the electrolytic capacitor 21, and the negative terminal of the capacitor 21 is connected to the connection point of the resistors 11 and 12. The cathode of the Zener diode 22 is connected to the positive terminal of the capacitor 21, and the anode is connected to the gate of the semiconductor switching element 7. The resistor 23 is connected between the cathode of the second diode 15 and the anode of the diode 8. The capacitor 24 connected in parallel with the starting circuit 6 between the non-power source side terminals of the electrodes 4 and 5 of the fluorescent lamp 3 is a noise preventing capacitor.

The starting circuit 6 of the fluorescent lamp lighting device as described above can be housed in a container having a shape compatible with the glow starter of the fluorescent lamp fixture as shown in FIG. 2, for example. This facilitates the use of the fluorescent lamp lighting device of the present embodiment in existing lighting equipment.

Next, the operation of the lighting device having the above structure will be described. During a half cycle of the AC power supply 1 in the positive period (the period in which the electrode 4 of the fluorescent lamp 3 has a positive voltage with respect to the electrode 5), the gate of the semiconductor switching element 7
A positive voltage is applied between the sources via the resistor 17, and the semiconductor switching element 7 is turned on. As a result, a drain current flows from the AC power source 1 through the ballast 2, preheating the preheating electrodes 4, 5 (filament) of the fluorescent lamp 3.
At this time, the Zener diode 16 serves to protect the semiconductor switching element 7 by absorbing the overvoltage between the gate and the source of the semiconductor switching element 7. The drain current, that is, the preheating current, flows through the current detecting means 9.

Three resistors 1 constituting the current detecting means 9
The resistance values of 0, 11, and 12 are set so that the resistance 10 is sufficiently smaller than the resistance 11 and the resistance 11 is sufficiently smaller than the resistance 12. As an example, the resistor 10 is set to 4.7.
Ω, the resistance 11 is 220 Ω, and the resistance 12 is 6.8 kΩ. At this time, most of the preheating current flows through the resistor 10. An added voltage of the voltage across the resistor 10 and the drain-source voltage of the semiconductor switching element 7 is applied to the timer means 14, and the electrolytic capacitor 21 is connected via the resistor 19 and the resistor 20.
A charging current flows through the capacitor and the voltage of the electrolytic capacitor 21 rises.

On the other hand, in the half cycle in which the AC power source is negative, the diode 15, the resistor 20, the electrolytic capacitor 21, and the resistor 1
The current from the power supply flows through a path that passes through the parasitic diode between the resistor 1, the resistor 10, and the source / drain of the semiconductor switching element 7. Therefore, even in this negative half cycle, the charging current of the same polarity as in the positive half cycle flows through the capacitor 21, and the voltage of the capacitor 21 rises.

The current waveform (a) shown in FIG. 3A is a current flowing through the semiconductor switching element 7, that is, a half-wave preheating current. The voltage waveform (a) in FIG. 3B shows the voltage across the electrodes of the fluorescent lamp 3. This voltage waveform is
The voltage waveform between the drain and source of the semiconductor switching element 7 is approximated during the positive period, and the power supply voltage waveform is approximated during the negative period.

The voltage waveform (c) in FIG. 3C shows how the capacitor 21 is charged. The voltage across the resistor 10 when the preheating current is flowing is divided by the resistors 11 and 12. When the resistors 11 and 12 have the above-mentioned values, the voltage across the resistor 11 is 1 / the voltage across the resistor 9.
The size is about 30.

The voltage waveform (d) in FIG. 3D shows the voltage obtained by adding the voltage of the electrolytic capacitor 21 and the voltage of the resistor 11. When this voltage exceeds a certain voltage (e) obtained by adding the gate-cathode voltage of the thyristor 18 and the Zener voltage of the Zener diode 22, a current flows through the Zener diode 22 to the gate of the thyristor 18, and the thyristor 18 is turned on. . As a result, the gate-source voltage of the semiconductor switching element 7 becomes zero and the semiconductor switching element 7 is turned off. At this time, the preheating current flowing through the ballast 2 is cut off, and the counter electromotive force (kick voltage) generated in the ballast 2 starts the discharge between the electrodes 4 and 5 of the fluorescent lamp 3 to turn on the fluorescent lamp 3. To do.

The kick voltage generated in the ballast 2 is clamped to a predetermined voltage determined by the avalanche withstand capability of the semiconductor switching element 7, so that the voltage destruction of the semiconductor switching element 7 is self-prevented. Therefore, it is not necessary to connect the voltage suppressing element in parallel to the semiconductor switching element 7. When the fluorescent lamp 3 is turned on, the electrolytic capacitor 21 is always charged by the voltage across the fluorescent lamp 3, and the charged voltage of the electrolytic capacitor 21 is the Zener diode 2.
Since the gate current of the thyristor 18 continues to flow via 2, the thyristor 18 maintains the ON state. As a result, the semiconductor switching element 7 remains off and the fluorescent lamp 3 remains lit.

When the power source is cut off, the fluorescent lamp 3 is turned off and the electric charge of the capacitor 21 is changed to the resistance 20 and the resistance 2.
3, the discharge is performed through the resistor 11, and the starting circuit 6 is reset. The preheating time is substantially determined by the constant setting of the resistor 20 and the electrolytic capacitor 21 of the timer means 14.

The voltage applied to the timer means 14 is as shown in FIG.
As shown in (b), the absolute value of the negative period is considerably larger than that of the positive period. Therefore, the charging of the capacitor 21 has a strong dependence on the power supply voltage in the negative period, and has a very small dependence on the voltage of the positive cycle, that is, the magnitude of the preheating current. In the present embodiment, both the 20 W fluorescent lamp and the 30 W fluorescent lamp can be set to a preheating time of about 1.2 seconds, and an appropriate preheating condition is realized.

Regarding the pulse generation phase, the voltage value of the resistor 11 which is the output signal of the current detecting means 9 is set to the capacitor 21.
3D, the phase can always be set near the peak of the preheating current as shown in FIG. As a result, it is possible to obtain a kick voltage of sufficient energy to surely cause dielectric breakdown of the fluorescent lamp 3 with one pulse voltage.

FIG. 4A shows a drain-source voltage waveform (f) and a drain current waveform (v) when the semiconductor switching element 7 is turned off when the resistance 10 is 4.7Ω. It can be seen that the drain-source voltage waveform (f) is clamped at the voltage value Vd, and energy is absorbed by the avalanche withstand capability of the semiconductor switching element 7. This amount of energy (corresponding to the area of the overlapped portion with diagonal lines in the figure) is a value obtained by integrating the product of the drain-source voltage and the drain current over the decay time T1 of the current. On the other hand, FIG.
Semiconductor switching element 7 when 0 is several hundred mΩ
Shows the drain-source voltage waveform (K) and the drain current waveform (K) at the time of turn-off.

Comparing (a) and (b) of FIG.
It can be seen that the drain current at the time of turn-off is smaller and the current decay time is shorter in (a) than in (b), so that the energy amount (area of the shaded portion) during this period is significantly reduced. By making this amount of energy smaller than the absolute constant values of the avalanche withstand capability of the semiconductor switching element 7 with a margin, the reliability against avalanche withstand capability breakdown can be greatly improved. In the case of the above example, the reliability could be significantly improved by setting the resistance 10 to 4.7Ω. In this case, the resistance 10
Since the voltage drop due to V is several tens of V, which is too large to use as it is as a current detection signal, a voltage is divided by the resistors 11 and 12 to have an appropriate voltage value.

As described above, the fluorescent lamp lighting device of this embodiment can realize an appropriate preheating time of about 1.2 seconds for both the 20 W fluorescent lamp and the 30 W fluorescent lamp. Further, the fluorescent lamp 3 is operated by the function of the current detecting means 9.
The semiconductor switching element 7 can be turned off at a phase near the current peak so as to reliably turn on. Moreover, by suppressing the current peak value and making the energy at the time of pulse generation smaller than the absolute constant values of the avalanche withstand capability of the semiconductor switching element 7 with a margin,
The reliability can be greatly improved. Furthermore, by storing the starting circuit in a container having a shape compatible with the glow starter of the fluorescent lamp fixture, it can be easily used in existing lighting fixtures.

[0035]

INDUSTRIAL APPLICABILITY According to the present invention, the fluorescent lamp can be used for ballasts and fluorescent lamps having different rated powers, and the pulse voltage is generated at an appropriate preheating time and at an appropriate phase to reliably start the fluorescent lamp. Further, it is possible to provide a highly reliable and inexpensive fluorescent lamp lighting device in which stress on the semiconductor switching element is reduced when a pulse is generated.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a fluorescent lamp lighting device according to an embodiment of the present invention.

FIG. 2 is a side view showing the outer appearance of a container accommodating a starting circuit of the fluorescent lamp lighting device of FIG.

FIG. 3 is an operation waveform diagram of preheating current, inter-electrode voltage, capacitor voltage, and added voltage of the capacitor voltage and the resistance voltage of the fluorescent lamp lighting device of FIG.

FIG. 4 is a diagram for explaining the operation of the fluorescent lamp lighting device of FIG. 1 when the semiconductor switching element is turned off.

FIG. 5 is a circuit diagram of a conventional fluorescent lamp lighting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Ballast 3 Fluorescent lamp 4,5 Preheating electrode 6 Starting device 7 Semiconductor switching element 8,15 Diode 9 Current detection means 13 Switching control means 14 Timer means

Claims (6)

[Claims] 1. A fluorescent lamp lighting device in which an AC power source is connected through a ballast between power source side terminals of a pair of electrodes of a fluorescent lamp with a preheating electrode, and a starting circuit is connected between non-power source side terminals of the electrodes. The fluorescent substance is characterized in that the starting circuit has a configuration in which a semiconductor switching element having a control terminal, a first diode, and a current detection means for detecting a current flowing through the semiconductor switching element are connected in series. Lamp lighting device. 2. The fluorescent lamp according to claim 1, wherein the current detecting means has a configuration in which a series circuit of a second resistor and a third resistor is connected in parallel with the first resistor. Lighting device. 3. The starting circuit comprises switching control means for controlling switching of the semiconductor switching element, and the switching control means near a preheating current peak in response to an output signal of the current detecting means with a lapse of a predetermined preheating time. 2. The fluorescent lamp lighting device according to claim 1, further comprising timer means for outputting a signal to the. 4. The cathode of the first diode is connected to a non-power supply side terminal of one electrode of the fluorescent lamp with a preheating electrode, and the anode of the second diode is connected to the cathode of the first diode, The fluorescent lamp lighting device according to claim 3, wherein the cathode of the second diode is connected to the timer means. 5. The fluorescent lamp lighting device according to claim 1, 2, 3, or 4, wherein the starting circuit is housed in a container having a shape compatible with a glow starter of a fluorescent lamp fixture. 6. The fluorescent lamp lighting device according to claim 1, wherein the semiconductor switching element is a field effect transistor.