JPH0351279B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is a method for lighting a low-pressure discharge lamp (hereinafter referred to as a lamp) such as a fluorescent lamp or a rare gas discharge lamp at a high frequency and with a pause period in each half cycle. The present invention relates to a high frequency lighting device.

[Prior art]

Conventionally, Japanese Utility Model Publication No. 51-8160 discloses that lamp efficiency is improved when a rectangular waveform alternating current with a rest period is passed through a fluorescent lamp. This is said to be because the electrons in the lamp, which have cooled during the rest period, are rapidly accelerated during the application period, and the density of high-temperature electrons becomes higher than when the lamp is lit with direct current or commercial frequency. In addition, as a result of various studies conducted by the present inventors on lighting low-pressure mercury vapor discharge lamps such as fluorescent lamps with high-frequency AC voltage having a rest period, it was found that It has become clear that lamp efficiency can be improved.

However, it was limited to Utility Model Publication No. 51-8160,
A device using an inverter that generates a rectangular waveform output voltage, such as a device in which a lamp is connected to the diagonal of a bridge circuit with transistors arranged on four sides, and a rest period is formed by another transistor provided at the input end of the bridge circuit. In this case, even if the lamp efficiency were improved, the overall efficiency of the entire device was insufficient, the capacity of the device tended to increase, or the radio noise was large.

The present inventors previously proposed a device as shown in FIG. 1 to improve these points. Next, this device will be briefly explained. In the figure, 11 is a DC power supply, AC power supply 12, and rectifier 1.
3 and a capacitor 14. Reference numeral 15 denotes a well-known self-excited push-pull type transistor inverter, which has a circuit coil 17, a transformer 18, a capacitor 20, transistors 21a, 21b, resistors 22a, 22b, and a circuit coil 23. A high frequency output voltage is generated. 16 is a fluorescent lamp which is a low pressure discharge lamp connected between the output terminals of the inverter 15; 18f and 18f are the electrodes 1 of the lamp 16;
These are preheating windings that preheat the lamps 6f and 16f, respectively, and the chiyoke coil 23 is a current limiting impedance for keeping the current of the lamp 16 at a predetermined value. Further, A is a switch device installed in parallel with the lamp 16,
It is composed of a full-wave rectifier circuit 24 whose AC end is connected in parallel with the lamp 16 and a transistor 25 arranged at the DC end of this rectifier circuit 24. A control device 19 controls the operation of the transistor 25. 33 is a current transformer that detects the output current of the inverter 15 and inputs it to the control device 19.

FIG. 2 shows the configuration of the control device 19, where 34 is the output resistance of the current transformer 33, 35 is a full-wave rectifier that rectifies the output of the current transformer 33, 31 is a constant voltage diode,
36 is a DC power source for driving, for example, the inverter 15
Rectifying the output of the auxiliary winding provided in the transformer 18,
It can be constructed by smoothing, etc. 29 is a transistor, and 30 and 32 are resistors. Also, FIG. 3A shows the output voltage of the full-wave rectifier 35, and FIG. .

In the above configuration, when the power supply 11 is turned on,
As is well known, the transistor 21 of the inverter 15
a and 21b are alternately opened and closed, and the inverter 15 starts self-excited oscillation and generates a high frequency voltage. When the lamp 16 starts discharging, the current transformer 33 generates an output voltage, and at this time, due to the action of the voltage regulator diode 31, the transistor 29 becomes conductive during the period T _1a of the output current of the inverter 15, as shown in FIG. , the transistor 25 is cut off. Therefore, this period
At T _1a , the discharge current of the lamp 16 flows as shown in the hatched area in FIG. 3C. When a current close to the maximum instantaneous value of the output current of the inverter 15 flows through the lamp 16 in this way, the capacity of the device can be reduced and the efficiency of the device can be improved compared to the case where this is not the case.

However, in the above device, if the lamp 16 does not light up normally for some reason, the switch device A
The disadvantage is that an excessive voltage is applied to the transistor 25. The reason for this is that the transistor 25 is conductive for _a period from θ ₁ to θ ₂ in FIG. Alternatively, if the lamp 16 is not connected, the current flowing through the switch coil 23 will be suddenly cut off, and a high back electromotive force will be applied to the switch device A. If this state continues, the transistor 2 There was a risk of damage.

[Summary of the invention]

The present invention aims to eliminate the above-mentioned drawbacks, and by cutting off the switch device when no current flows through the lamp, it reduces the back electromotive force of the choke coil that occurs when the switch device is cut off. The purpose is to prevent damage to the transistor.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 4, the transformer 18 of the inverter 15 is configured as a leakage transformer, and also functions as a current limiting impedance. Therefore, the secondary winding 18 of the transformer 18
The voltage at S will be equal to the terminal voltage of lamp 16,
The detection winding 18K also has a voltage similar to the terminal voltage of the lamp 16. 40 is a full wave rectifier, 41, 4
4 is a resistor, 42 is a constant voltage diode, 43 is a capacitor, 45 is a transistor, and the other components are the first
It is similar to FIG.

In the above configuration, when the lamp 16 is lit normally, the voltage of the detection winding 18K is low and is blocked by the constant voltage diode 42, and the voltage of the transistor 4
5 is a cut-off state, in which the switch device A is cut off at the hatched portion in FIG.

Next, if the lamp 16 does not light up or is not connected, the secondary winding 18
S becomes approximately its secondary no-load voltage _V2 . This secondary no-load voltage V ₂ is normally set to be at least twice the lamp voltage during lighting of the lamp 16 in order to start discharging the lamp 16 . Therefore, the detection winding 1
The output voltage of 8K is higher, and the voltage regulator diode 4
2, the capacitor 43 is charged. As a result, a base current flows through the transistor 45, making it conductive. Therefore, the base current no longer flows through the transistor 25 of the switch device A, resulting in a cutoff state, and it is possible to prevent a high voltage caused by a back electromotive voltage from being applied to the transistor 25 every half cycle of the output of the inverter 15. The cut-off state of the transistor 25 is made to last for one or more cycles of the output frequency of the inverter 15.

If the lamp 16 is initially in a non-discharging state in FIG. 4, the transistor 25 of the switch device A is turned on by the resistor 30, so that a current flows as shown in FIG. 3C. Therefore, the current transformer 33 generates an output even if the lamp 16 is not discharging, the transistor 25 is turned off between θ ₁ and _{θ 2} , and a current flows through the lamp 16 for a period of T _1a .

In the above embodiment, the detection winding 18K provided on the secondary side of the transformer 18 is used as a means for detecting whether the lamp 16 is not lit, but other means such as detecting the current of the lamp 16 may be used. .

Further, in the above embodiment, even if the lighting state of the lamp 16 becomes an asymmetric discharge state, this can be detected and the switch device A can be shut off. This asymmetrical discharge tends to occur when the electron emitting material of the electrode 16f is severely consumed, such as at the end of the life of the lamp 16, and in this state, the lamp 1
It can be detected because the voltage at terminal 6 becomes high. However, if the switch device A is maintained in the cut-off state in this state, the current limiting impedance of the inductive reactance may increase in comparison with normal times due to the DC component flowing through the lamp 16. Therefore, a thermally responsive protective device (generally referred to as a thermal protector) is provided near the output transformer 18 and the transistors 21a and 21b of the inverter 15, for example, to prevent heating when the lamp current increases and heats up. If the protection device detects this and stops the current supply to the lamp 16, safety can be further improved.

As is clear from the explanation up to this point, high voltage generation can be achieved by setting the voltage corresponding to the high voltage generation state, such as when there is no discharge at the start of startup or when asymmetric discharge is performed, as the second predetermined value. It is understood that this can be prevented.

In addition, the switch device A is the rectifier circuit 24 in the embodiment.
Although the transistor 25 is used, the same effect can be obtained using a field effect transistor or other switching element. Furthermore, the connection of the switch device A can be made in a manner other than the above-mentioned embodiments.
For example, an additional winding having a polarity opposite to that of the secondary winding 18S of the transformer may be provided and the switch device A may be connected through this, or the transformer 18 may be configured as a leakage transformer without using the chiyoke coil 23 as in the above embodiment. In such a case, the secondary winding 18S may be provided with an intermediate tap and connected to the low-voltage electric path formed by this intermediate tap, or another winding may be used as the low-voltage electric path. Furthermore, an impedance may be connected in series with the switch device A to reduce the current flowing through the switch device A. Alternatively, a switch device A may be connected in parallel with the lamp 16 via its electrodes 16f, 16f, and a preheating current may be applied when the switch device A is turned on. In addition, for the purpose of preheating the electrodes 16f, 16f when starting the lamp 16, and facilitating the start of discharge, the switch device A is turned on and off.
A means may be added to make the cutoff operation different from that during normal lighting.

In addition to using the rectified and smoothed power supply as in the above embodiment, the input DC voltage of the inverter 15 is
As shown in Figure A, the pulsating DC voltage or the
As shown in Figure C, a DC voltage configured in combination with a suitable auxiliary power source with a low peak value can also be used.
In addition, in the case of a voltage with many ripples like this, depending on the configuration of the control device, switch device A may remain in the cut-off state in cycles with a peak value lower than a certain current value A _L , as shown in Figure 5D. The present invention may be applied to a device in which the operation is performed only in cycles having a peak value greater than or equal to . Moreover, conversely, the present invention may be applied to a device in which the switch device A is operated only during a period lower than A _L. Furthermore, as the current limiting impedance for the lamp current, a chiyoke coil 23 may be used as in the device shown in FIG.
The inverter 15 may be, for example, a series inverter or a bridge type inverter provided with an output transformer 18.

Although the frequency of the inverter 15 is not specifically mentioned, as disclosed in Japanese Patent Application No. 110369/1982, in addition to improving lamp efficiency, it is possible to prevent audible noise and use a bipolar type as a switching transistor for the inverter. From the viewpoint of loss, noise, etc. when using transistors, 17KHz or more 100KHz
The following are preferred. Further, in the above embodiment, the lamp 1
Although No. 6 has been described for the case of one lamp, it can also be applied to the case of two or more lamps, and as a low-pressure discharge lamp, it can also be applied to rare gas discharge lamps containing neon, krypton, etc., in addition to fluorescent lamps. Furthermore, the present invention can also be applied to a device in which the operation of the switch device A is different from that during steady lighting when preheating the electrodes when starting the lamp 16 or when starting discharge.

In the description of the embodiment, the set voltages of the constant voltage diode 31 and the constant voltage diode 42 correspond to a first predetermined value and a second predetermined value, respectively.

〔Effect of the invention〕

As described above, in the present invention, the switch device is completely cut off when the discharge current does not flow through the discharge lamp, thereby preventing the generation of high voltage due to the interruption of continuity of the switch device. This has the advantage that it is possible to prevent damage to the switch device, and that if the discharge lamp is lit normally, it can automatically return to its original lighting state after a period of rest.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional device, Fig. 2 is a block diagram of a conventional control device, Fig. 3 is an operating waveform diagram of the conventional device, Fig. 4 is a block diagram of the device of the present invention, and Fig. 5 is a block diagram of the present invention. FIG. 3 is a waveform diagram of each example of a DC power supply applicable to the device. 11...DC power supply, 15...Inverter, 16
...Lamp, 18...Output transformer, 18K...
Detection winding, 33... Current transformer, 35, 40... Full wave rectifier, 31, 42... Constant voltage diode, 2
9,45...Transistor, A...Switch device. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An inverter that converts DC voltage into a nearly sinusoidal high-frequency output voltage and lights up a discharge lamp via the current limiting impedance of an inductive reactance, connected in parallel with the discharge lamp to the output of the inverter. When the voltage corresponding to the output electrode of the inverter is higher than a first predetermined value set for converting the sinusoidal waveform output of the inverter into a rectangular waveform, the switch device is cut off, and the output voltage of the inverter is A control device that cuts off the switch device for one or more cycles of the inverter's output frequency when the voltage exceeds a second predetermined value, which corresponds to a high voltage generation state such as when the low-pressure discharge lamp does not discharge at the start of startup or when an asymmetrical discharge is performed. A discharge lamp lighting device characterized by comprising: 2. Claim 1, characterized in that the output transformer of the inverter is constituted by a leakage transformer, and a detection winding is provided on the secondary side of the leakage transformer as a detection means for detecting the lighting state of the discharge lamp. The discharge lamp lighting device described.