Free technical library

Electronic ballasts. Electronic ballast that allows you to adjust the brightness of the lamp. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Ballasts for fluorescent lamps

 Comments on the article

This single-ended converter allows adjust lamp brightness and install it in such a way that battery power is used more economically. On fig. 3.78 shows its scheme.

The converter consists of a master oscillator and a single-cycle power amplifier. The generator is made on the elements DD1.1-DD1.3. Such a generator allows you to change the duty cycle of the pulses (i.e., the ratio of the pulse repetition period to their duration) with a variable resistor R1, which determines the brightness of the LL. A buffer element DD1.4 is connected to the generator.

The signal from DDI.4 is fed to a power amplifier made on transistors VT1, VT2. Amplifier load - LL (ELI), connected through a step-up transformer T1. It is permissible to connect the lamp both with closed filament terminals (shown in the diagram) and with open ones. In other words, the integrity of the filaments of the lamp does not matter.

Rice. 3.78. Schematic of a single-ended dimmable converter

The converter is powered by a DC source with a voltage of 6-12 V, capable of delivering current up to several amperes to the load (depending on the lamp power and the set brightness). Power is supplied to the microcircuit through a parametric stabilizer, in which a ballast resistor R4 and a zener diode VD3 work. With a minimum supply voltage, the stabilizer practically does not work, but this does not affect the operation of the converter.

In addition to those indicated in the diagram, it is permissible to use transistors KT3117A, KT630B, KT603B (VT1), KT926A, KT903B (VT2), diodes of the KD503 series (VD1, VD2), Zener diode D814A (VD3). Capacitor C1 - KG, KM, K10-17, the rest - K50-16, K52-1, K53-1. Variable resistor - any design (for example, SP2, SDR), constant - OMLT-OD25. Lamp - power from 6 to 20 watts.

The transformer is wound on an armored magnetic core made of 2000NM1 ferrite with an outer diameter of 30 mm. Winding I contains 35 turns of PEV-2 wire with a diameter of 0,45 mm, winding II contains 1000 turns of PEV-2 with a diameter of 0,16 mm. The windings are separated by several layers of varnished fabric.

To increase the reliability, the winding II must be divided into several layers, laying a varnished cloth between them. The cups of the magnetic circuit are assembled with a gap of 0,2 mm and tightened with a screw and a nut made of non-magnetic material. With somewhat worse results (the ratio "brightness - current consumption"), a transformer made on a magnetic circuit from a horizontal transformer of the TV will work.

Setting up the converter start by checking the master oscillator with the amplifier output stage turned off. An oscilloscope is connected to pin 11 of the microcircuit and the pulses shown in the upper diagram of Fig. 3.79.

Rice. 3.79. Voltage waveform at test points

Then set the variable resistor slider to the left according to the diagram position "RESISTANCE INTRODUCED". Measure the duration of the pulses and the period of their repetition. By selecting resistor R3, a pulse duration of approximately 20 μs is achieved, and by selecting resistor R2, a repetition period of approximately 50 μs is achieved. After moving the engine from one extreme position to another, they are convinced of the change in the pulse repetition period with their duration unchanged.

Next, the output stage is connected, the oscilloscope is connected to the collector of its transistor, and an ammeter with a scale of 2-3 A is included in the power circuit. resistor. Observe the shape of the pulses on the collector of the transistor VT2 - in fig. 3.79 below.

This form was obtained when the converter was working with an LB 18 lamp. You may have to select resistors R2, R7 more accurately, and in some cases install a variable resistor of a different value in order to achieve the necessary limits for changing brightness and acceptable current consumption.

In the minimum brightness mode, which corresponds to a current of 250-400 mA depending on the supply voltage and lamp power, it is more convenient to start the generator, and therefore turn on the lamp, by pressing the SB1 button. Sometimes it is useful to try to change the polarity of the lamp and check the reliability of its ignition in this mode.

Evaluate the efficiency of the converter with different transistors, transformers, mode changes, etc., you can do this. At a distance of about 0,5 m from the lamp, a photodiode or photoresistor is strengthened and an ohmmeter is connected to it. Measure its resistance with a burning lamp and a fixed current consumption of the converter. Next, the part is replaced, the previous current is set with resistor R1 and the resistance of the photocell is measured. If it has decreased, then the brightness of the lamp has increased; the result of the experiment can be considered the best.

master oscillator can also be implemented on the widely used timer KR1006VI1 (LM555). On fig. 3.80 shows such a scheme.

Here, the timing resistors R2, R3 are variables, as a result of which the pulse parameters and frequency can be changed over a wide range (Fig. 3.30, a), and the connection option shown in Fig. 3.80, b, allows you to change the pulse width of the generator at a constant frequency. The frequency in this case is determined by the formula

The duty cycle adjustment range depends on the ratio of resistors R1, R2.

Rice. 3.80. Master oscillator circuit on the timer KR1006VI1 (LM555)

Instead of a power amplifier made on transistors VT1, VT2, R7, R7 (see Fig. 3.78), you can use a field effect transistor KP743, IRF510, BUZ21L, SPP21N10, etc. in the power amplifier (reduce R5 to 100 ohms). Schemes of this option are shown in Fig. 3.81.

It will not be superfluous to protect with the help of a special protective zener diode - a suppressor (TRANSIL, TVS, TRISIL) VD1, VD2. Diode VD3 - high-speed with a short recovery time.

Rice. 3.81. FET power amplifier circuit

Author: Koryakin-Chernyak S.L.

See other articles Section Ballasts for fluorescent lamps.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Alcohol content of warm beer 07.05.2024

Beer, as one of the most common alcoholic drinks, has its own unique taste, which can change depending on the temperature of consumption. A new study by an international team of scientists has found that beer temperature has a significant impact on the perception of alcoholic taste. The study, led by materials scientist Lei Jiang, found that at different temperatures, ethanol and water molecules form different types of clusters, which affects the perception of alcoholic taste. At low temperatures, more pyramid-like clusters form, which reduces the pungency of the "ethanol" taste and makes the drink taste less alcoholic. On the contrary, as the temperature increases, the clusters become more chain-like, resulting in a more pronounced alcoholic taste. This explains why the taste of some alcoholic drinks, such as baijiu, can change depending on temperature. The data obtained opens up new prospects for beverage manufacturers, ... >>

Major risk factor for gambling addiction 07.05.2024

Computer games are becoming an increasingly popular form of entertainment among teenagers, but the associated risk of gaming addiction remains a significant problem. American scientists conducted a study to determine the main factors contributing to this addiction and offer recommendations for its prevention. Over the course of six years, 385 teenagers were followed to find out what factors may predispose them to gambling addiction. The results showed that 90% of study participants were not at risk of addiction, while 10% became gambling addicts. It turned out that the key factor in the onset of gambling addiction is a low level of prosocial behavior. Teenagers with a low level of prosocial behavior do not show interest in the help and support of others, which can lead to a loss of contact with the real world and a deepening dependence on virtual reality offered by computer games. Based on these results, scientists ... >>

Traffic noise delays the growth of chicks 06.05.2024

The sounds that surround us in modern cities are becoming increasingly piercing. However, few people think about how this noise affects the animal world, especially such delicate creatures as chicks that have not yet hatched from their eggs. Recent research is shedding light on this issue, indicating serious consequences for their development and survival. Scientists have found that exposure of zebra diamondback chicks to traffic noise can cause serious disruption to their development. Experiments have shown that noise pollution can significantly delay their hatching, and those chicks that do emerge face a number of health-promoting problems. The researchers also found that the negative effects of noise pollution extend into the adult birds. Reduced chances of reproduction and decreased fertility indicate the long-term effects that traffic noise has on wildlife. The study results highlight the need ... >>

Random news from the Archive Automation against pirates 01.08.2010 The German company Platter, which manufactures fire-fighting equipment, offers an automatic system that, having noticed a small boat approaching a tanker or bulk carrier, raises the alarm when it notices a small vessel approaching a tanker or dry cargo ship using radar and infrared video cameras operating day and night. When outside boats, yachts or boats appear within a radius of 500 meters, loudspeakers turn on with a request to move away. If this appeal did not work and the boat continues to approach, at a distance of 90 meters, the automation launches numerous water cannons that eject up to 5000 liters of water per minute. This flow simply drives the pirates away. Automation can be turned off and the process can be controlled manually. Several major shipowners have already shown interest in the system. However, a representative of the well-known insurance company Lloyd expressed concern that such a shower would only irritate the pirates and they would use more serious weapons, usually available on their boats.

Other interesting news:

▪ Logitech G CLOUD Gaming Handheld Console

▪ Device for fighting pornography

▪ Garmin Forerunner 620 and 220 Sports Watches

▪ 5G on Everest

▪ Traffic light for colorblind people

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Field strength detectors. Article selection

▪ article Take / take on a pencil something. Popular expression

▪ article What was the first mammal? Detailed answer

▪ article Mechanic. Standard instruction on labor protection

▪ article Fittings for shoes. Simple recipes and tips

▪ article Source for automotive electrical repair and battery charging. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024