Power supply of a fluorescent lamp with direct current. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Power supply of a fluorescent lamp with direct current. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Lighting

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The problem of powering fluorescent lamps still attracts the attention of readers of our magazine. And such interest is not surprising, since fluorescent lamps are economical, have a variety of color shades of the emitted light flux, and have a long service life.

Issues of operational reliability of fluorescent lamps (LDS), their "resuscitation" were repeatedly covered on the pages of the journal "Radio" [1-3]. To improve the reliability of the LDS in [1, 5], it is recommended to feed them with a rectified current of the network using a starterless starter device. The filaments of the lamp are not used for their intended purpose, each of them is shunted by a jumper and acts as an electrode, which is supplied with the voltage necessary to turn on the lamp. In fact, instantaneous "cold ignition" is proposed by a sharp increase in voltage at the LDS during start-up without preheating its electrodes.

Daylight lamp supply with direct current

However, we note that ignition with cold electrodes of serial LDS, designed to work with heating by filaments, is a more difficult mode for electrodes than switching on in the usual way [4]. The lamps wear out quickly, and in this case, of course, it is not possible to talk about the operating time of the average LDS service life guaranteed by the manufacturer.

Another feature of the operation of LDS on direct current is the occurrence of the phenomenon of cataphoresis [6] due to the movement of mercury ions in the lamp to the cathode. As a result, the lamp is dimmed from the anode side, which reduces its luminous flux. It is possible to reduce the influence of this phenomenon if periodically (once or twice a month), according to the recommendation in [b], change the polarity of the LDS connection, and this complicates the operation of the lamps.

To the above, it should be added that the ignition of an LDS with cold electrodes requires an increase in voltage to 400 ... 750 V. Such a voltage, despite its short duration, is unsafe in operation, especially in everyday life.

Therefore, the advice given in [1, 5] is more suitable for LDS, which cannot operate on AC power, which happens when the filaments are broken or destroyed, emission is lost by one of the lamp electrodes.

To improve general or local lighting, in [1] it is proposed to supplement an ordinary luminaire with an incandescent lamp with a luminaire with an LDS switched on for direct current, with the incandescent lamp acting as a ballast resistor. So, for incandescent lamps with a power of 75 or 100 W, it is necessary to install a lamp with a 20 W LDS, and for 200 or 250 W, an 80-watt LDS.

However, the use of an incandescent lamp instead of a choke significantly reduces the efficiency of such a combined lamp. An incandescent lamp with a power of 100 W and a voltage of 220 ... 235 V creates a luminous flux of 1000 lm. During the operation of such a lamp, which acts as a ballast resistor, together with a 20 W LDS, the voltage on it is about 180 V (according to the measurement results), which is 80% of the nominal value. The power consumed by the incandescent lamp in this case is 70% of the nominal value (approximately 70 W), and the luminous flux is only 45% (450 lm). With an LDS luminous flux of 1200 lm, the total luminous flux of the combined lamp will be 1650 lm, and the power consumption will be 90 watts. At the same time, a 30 W LDS creates a luminous flux of 2100 lm, 27% more with three times less power consumption. Obviously, instead of a combined lamp, it is much more economical to use a conventional one with a 30 W LDS, eliminating additional costs for installation work to connect the lamps to each other.

A similar analysis of the operation of a combined luminaire with a 200 W incandescent lamp and an 80 W LDS, whose operating voltage is 102 V, in contrast to the LDS - 20 W, shows that the luminous flux of the incandescent lamp is only 5,4% (280 lm) from the LDS luminous flux (5220 lm), and the total power consumption is 160 W (80 W incandescent lamp and 80 W LDS). In terms of the generated luminous flux, a "dvuhsotka" lamp in a combined lamp will be equivalent to a "magpie" incandescent lamp (300 lm). In fact, in such a lamp, an incandescent lamp only "warms up", consuming a power of 80 W, but does not shine (5,4%), and, naturally, there is no need for such a lamp.

It is possible to increase the luminous flux of a combined lamp with an LDS with a power of 30, 40, 65, 80 W if you use incandescent lamps for a voltage of 127 V. However, in this case, when the diodes of the bridge from which the LDS is powered, the incandescent lamp is energized by 220 V , and its thread burns out [1]. To exclude the failure of an incandescent lamp, it must be connected to the DC circuit in series with the LDS (see diagram). A similar method is described in [b]. When the SA1 switch is turned on, the device operates as a voltage doubler, the output voltage of which is applied to the cathode-anode gap of the EL2 lamp. After the lamp is ignited, the device enters the full-wave rectification mode with a resistive load. The rectified voltage is approximately equally distributed between the EL1 and EL2 lamps, which is true for LDS with a power of 30, 40, 65, 80 W, which have an average operating voltage of about 100 V.

For an 80 W LDS, it is advisable to use two 127 V incandescent lamps of 60 W each, turning them on in parallel. With this inclusion, the luminous flux of incandescent lamps will be approximately 24% of the LDS flux.

For a 65 W LDS, the most suitable incandescent lamp is 100 W, 127 V. The luminous flux of this lamp in a combined lamp is approximately 20% of the LDS flux. Accordingly, for an LDS with a power of 40 W, an incandescent lamp of 60 W, 127 V is required. Its luminous flux will be 20% of the LDS flux. And finally, for a 30 W LDS, you can use two 127 V incandescent lamps of 25 W each, turning them on in parallel. The luminous flux of these two incandescent lamps is about 17% of the LDS luminous flux. Such an increase in the luminous flux of an incandescent lamp in a combined luminaire is explained by the fact that they operate at a voltage close to the nominal when their luminous flux approaches 100%. At the same time, when the voltage on the incandescent lamp is about 50% of the nominal, their luminous flux is only 6,5%, and the power consumption is 34% of the nominal [7].

To power the LDS with a power of 30, 40, 65 W, it is best to use the KTs404A diode assembly, which has a fuse holder. LDS with a power of 80 W (operating current 0,86 A) will require more powerful diodes, for example, KD202R, KD203G, D248B.

Literature

1. Kavyev A. Supply of a fluorescent lamp with direct current. -Radio, 1997, No. 5, p. 36.
2. Khovaiko O. Restoration of fluorescent lamps. - Radio, 1997, Ms 7, p. 37.
3. Yeserkenov Zh. Method of resuscitation of fluorescent lamps. - Radio, 1998, No. 2, p. 61.
4. Reference book on ionic devices. Ed. D. S. Gurleva. - Kyiv: Tehzhka, 1970.
5. Danilov V. Chokeless power supply of fluorescent lamps: Sat: "To help the radio amateur", vol. 114. - M.: Patriot, 1992.
6. Borovsky V., Partala O. On the use of fluorescent lamps with burnt out filaments. - RadioAmator, 1993, No. 1, p. 36.
7. Tarnizhevsky M. V., Afanas’eva E. I. Energy saving in electrical installations of housing and communal services enterprises. - M.: Stroyizdat, 1989.

Author: K. Kolomoytsev, Ivano-Frankivsk; Publication: N. Bolshakov, rf.atnn.ru

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Comments on the article:

V.Semenov
This scheme does NOT work (although it was once published in the Radio magazine). To ignite EL2, you need twice the mains voltage, but it is not in the circuit. In order for the circuit to work, it is necessary to tear off the lower terminal of the diode bridge from the common point C1, C2 and the network. Then on the top plate C2 will be +300V, and on the top C1 - minus 300V. And the diode bridge is not needed here - two upper diodes are enough.

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