We determine the optimal circuit for switching on fluorescent lamps. The principle of operation and connection diagram of a fluorescent lamp How to light a fluorescent lamp with a burnt filament

Despite the emergence of more “advanced” LED lamps, daylight fixtures continue to be in demand due to their affordable price. But there's a catch: you can't just plug them in and light them without adding a couple of extra elements. The electrical circuit for connecting fluorescent lamps, which includes these parts, is quite simple and serves to start lamps of this type. You can easily assemble it yourself after reading our material.

Design and operating features of the lamp

The question arises: why do you need to assemble some kind of circuit to turn on such light bulbs? To answer it, it is worth analyzing their operating principle. So, fluorescent (otherwise known as gas-discharge) lamps consist of the following elements:

A glass flask whose walls are coated on the inside with a phosphorus-based substance. This layer emits a uniform white glow when exposed to ultraviolet radiation and is called a phosphor.
On the sides of the flask there are sealed end caps with two electrodes each. Inside, the contacts are connected by a tungsten filament coated with a special protective paste.
The daylight source is filled with an inert gas mixed with mercury vapor.

Reference. Glass flasks can be straight or curved in the shape of a Latin “U”. The bend is made in order to group the connected contacts on one side and thus achieve greater compactness (an example is the widely used housekeeper light bulbs).

The glow of the phosphor is caused by a flow of electrons passing through mercury vapor in an argon environment. But first, a stable glow discharge must arise between the two filaments. This requires a short-term high voltage pulse (up to 600 V). To create it when the lamp is turned on, the above-mentioned parts are needed, connected according to a certain circuit. The technical name of the device is ballast or ballast.

In housekeepers, the ballast is already built into the base

Traditional circuit with electromagnetic ballast

In this case, the key role is played by a coil with a core - a choke, which, thanks to the phenomenon of self-induction, is capable of providing a pulse of the required magnitude to create a glow discharge in a fluorescent lamp. How to connect it to power via a choke is shown in the diagram:

The second element of the ballast is the starter, which is a cylindrical box with a capacitor and a small neon light bulb inside. The latter is equipped with a bimetallic strip and acts as a circuit breaker. Connection via electromagnetic ballast works according to the following algorithm:

After the main switch contacts close, the current passes through the inductor, the first filament of the lamp and the starter, and returns through the second tungsten filament.
The bimetallic plate in the starter heats up and closes the circuit directly. The current increases, causing the tungsten filaments to heat up.
After cooling, the plate returns to its original shape and opens the contacts again. At this moment, a high voltage pulse is formed in the inductor, causing a discharge in the lamp. Then, to maintain the glow, 220 V coming from the mains is enough.

This is what the starter filling looks like - only 2 parts

Reference. The principle of connection with a choke and a capacitor is similar to a car ignition system, where a powerful spark on the candles jumps when the high-voltage coil circuit breaks.

A capacitor installed in the starter and connected in parallel to the bimetallic breaker performs 2 functions: it prolongs the action of the high-voltage pulse and serves as protection against radio interference. If you need to connect 2 fluorescent lamps, then one coil will be enough, but you will need two starters, as shown in the diagram.

More details about the operation of gas-discharge light bulbs with ballasts are described in the video:

Electronic activation system

Electromagnetic ballast is gradually being replaced by a new electronic ballast system, devoid of such disadvantages:

long lamp startup (up to 3 seconds);
crackling or clicking noises when turned on;
unstable operation at air temperatures below +10 °C;
low-frequency flickering, which has a detrimental effect on human vision (the so-called strobe effect).

Reference. The installation of daylight sources is prohibited on production equipment with rotating parts precisely because of the strobe effect. With such lighting, an optical illusion occurs: it seems to the worker that the machine spindle is motionless, but in fact it is spinning. Hence - industrial accidents.

The electronic ballast is a single block with contacts for connecting wires. Inside there is an electronic frequency converter board with a transformer, replacing the outdated electromagnetic type control gear. Connection diagrams for fluorescent lamps with electronic ballast are usually depicted on the unit body. Everything is simple here: on the terminals there are indications where to connect the phase, neutral and ground, as well as the wires from the lamp.

Starting light bulbs without a starter

This part of the electromagnetic ballast fails quite often, and there is not always a new one in stock. To continue to use the daylight source, you can replace the starter with a manual breaker - a button, as shown in the diagram:

The point is to manually simulate the operation of a bimetallic plate: first close the circuit, wait 3 seconds until the lamp filaments warm up, and then open it. Here it is important to choose the right button for 220 V voltage so that you do not get an electric shock (suitable for a regular doorbell).

During the operation of a fluorescent lamp, the coating of the tungsten filaments gradually crumbles, which is why they can burn. The phenomenon is characterized by blackening of the edge zones near the electrodes and indicates that the lamp will soon fail. But even with burnt-out spirals, the product remains operational, it just needs to be connected to the electrical network according to the following diagram:

If desired, a gas-discharge light source can be ignited without chokes and capacitors, using a ready-made mini-board from a burnt-out energy-saving light bulb, operating on the same principle. How to do this is shown in the following video.

Well of course about " eternal lamp"This is a loud word, but here's how to "revive" a fluorescent lamp with burnt-out filaments quite possible...

In general, everyone has probably already understood that we are not talking about an ordinary incandescent light bulb, but about gas-discharge light bulbs (as they were previously called “fluorescent lamps”), which looks like this:

The operating principle of such a lamp: due to a high-voltage discharge, a gas (usually argon mixed with mercury vapor) begins to glow inside the lamp. In order to light such a lamp, a fairly high voltage is required, which is obtained through a special converter (ballast) located inside the housing.

useful links for general development : self-repair of energy-saving lamps, energy-saving lamps - advantages and disadvantages

The standard fluorescent lamps used are not without drawbacks: during their operation, the buzzing of the choke can be heard, the power system has a starter that is unreliable in operation, and most importantly, the lamp has a filament that can burn out, which is why the lamp has to be replaced with a new one.

But there is an alternative option: the gas in the lamp can be ignited even with broken filaments - to do this, simply increase the voltage at the terminals.
Moreover, this use case also has its advantages: the lamp lights up almost instantly, there is no buzzing during operation, and a starter is not needed.

To light a fluorescent lamp with broken filaments (by the way, not necessarily with broken filaments...), we need a small circuit:

Capacitors C1, C4 must be paper, with an operating voltage of 1.5 times the supply voltage. Capacitors C2, SZ should preferably be mica. Resistor R1 must be wirewound, according to the lamp power indicated in the table

Power lamps, W	C1 -C4 µF	C2 - NW pF	D1 - D4	Ohm
		3300	D226B
		6800	D226B
		6800	D205
		6800	D231

Diodes D2, DZ and capacitors C1, C4 represent a full-wave rectifier with doubling the voltage. The values of capacitances C1, C4 determine the operating voltage of lamp L1 (the larger the capacitance, the greater the voltage on the electrodes of lamp L1). At the moment of switching on, the voltage at points a and b reaches 600 V, which is applied to the electrodes of lamp L1. At the moment of ignition of lamp L1, the voltage at points a and b decreases and ensures normal operation of lamp L1, designed for a voltage of 220 V.

The use of diodes D1, D4 and capacitors C2, SZ increases the voltage to 900 V, which ensures reliable ignition of the lamp at the moment of switching on. Capacitors C2, SZ simultaneously help suppress radio interference.
Lamp L1 can work without D1, D4, C2, C3, but in this case the reliability of inclusion decreases.

Data for circuit elements depending on the power of fluorescent lamps are given in the table.

Dear visitors!!!

This method of connecting a fluorescent lamp should be familiar to everyone, in particular to professional electricians. With such a scheme for switching on a fluorescent lamp, there is one characteristic feature of the method of such connection, which you will have to familiarize yourself with. The information presented in this topic takes place in training students in the profession of “Electrician of electrical networks and electrical equipment,” which I am currently teaching.

How to turn on a fluorescent lamp - without a choke

The figure shows two ways to connect fluorescent lamps:

schematic diagram for switching on a fluorescent lamp with starter ignition (Fig. 1, a) and switching on a fluorescent lamp without a choke (Fig. 1, b).

For both schemes for switching on fluorescent lamps, the increased voltage pulse that promotes the formation of an arc discharge in the lamps (necessary for their ignition) is the inductor LL and the incandescent lamp EL2.

The second diagram (Fig. 1, b) shows a circuit for switching on a fluorescent lamp using an incandescent lamp (instead of a choke). In this circuit there is a current-carrying wire, one end of which is connected to one of the terminals of the electrodes of the fluorescent lamp. Instead of a live wire, you can use a wide strip of foil, which has the same electrical connection as the wire. Accordingly, both the piece of wire itself and the strip of foil must be secured at the ends of the bulb with metal clamps corresponding to the diameter of the bulb (fluorescent lamp).

That's all for now. Follow the section.

When choosing a modern method of lighting a room, you need to know how to connect a fluorescent lamp yourself.

The large surface area of the glow helps to obtain even and diffuse illumination.

Therefore, this option has become very popular and in demand in recent years.

Fluorescent lamps belong to gas-discharge lighting sources, characterized by the formation of ultraviolet radiation under the influence of an electrical discharge in mercury vapor with subsequent conversion into high visible light output.

The appearance of light is due to the presence on the inner surface of the lamp of a special substance called phosphor, which absorbs UV radiation. Changing the composition of the phosphor allows you to change the tint range of the glow. The phosphor can be represented by calcium halophosphates and calcium-zinc orthophosphates.

The principle of operation of a fluorescent light bulb

The arc discharge is supported by thermionic emission of electrons on the surface of the cathodes, which are heated by passing a current limited by the ballast.

The disadvantage of fluorescent lamps is represented by the inability to make a direct connection to the electrical network, which is due to the physical nature of the lamp glow.

A significant part of luminaires intended for installation of fluorescent lamps have built-in glow mechanisms or chokes.

Connecting a fluorescent lamp

To correctly carry out independent connection, you need to choose the right fluorescent lamp.

Such products are marked with a three-digit code containing all the information about the quality of light or color rendering index and color temperature.

The first number of the marking indicates the level of color rendering, and the higher these indicators are, the more reliable color rendering can be obtained during the lighting process.

The designation of the lamp glow temperature is represented by digital indicators of the second and third order.

The most widely used is an economical and highly efficient connection based on an electromagnetic ballast, supplemented by a neon starter, as well as a circuit with a standard electronic ballast.

Connection diagrams for a fluorescent lamp with a starter

Connecting an incandescent lamp yourself is quite simple, due to the presence of all the necessary elements and a standard assembly diagram in the kit.

Two tubes and two chokes

The technology and features of independent serial connection in this way are as follows:

supply of phase wire to the ballast input;
connecting the choke output to the first contact group of the lamp;
connecting the second contact group to the first starter;
connection from the first starter to the second lamp contact group;
connecting the free contact to the wire to zero.

The second tube is connected in a similar way. The ballast is connected to the first lamp contact, after which the second contact from this group goes to the second starter. Then the starter output is connected to the second lamp pair of contacts and the free contact group is connected to the neutral input wire.

This connection method, according to experts, is optimal if there are a pair of lighting sources and a pair of connecting kits.

Connection diagram for two lamps from one choke

Independent connection from one choke is a less common, but completely uncomplicated option. This two-lamp series connection is economical and requires the purchase of an induction choke, as well as a pair of starters:

a starter is connected to the lamps through a parallel connection to the pin output at the ends;
sequential connection of free contacts to the electrical network using a choke;
connecting capacitors in parallel to the contact group of the lighting device.

Two lamps and one choke

Standard switches belonging to the category of budget models are often characterized by sticking contacts as a result of increased starting currents, so it is advisable to use special high-quality versions of contact switching devices.

How to connect a fluorescent lamp without a choke?

Let's look at how fluorescent fluorescent lamps are connected. The simplest chokeless connection scheme is used even on burnt-out fluorescent lamp tubes and is distinguished by the absence of the use of an incandescent filament.

In this case, the power supply to the lighting device tube is due to the presence of an increased DC voltage through a diode bridge.

Switching on a lamp without a choke

This circuit is characterized by the presence of a conductive wire or a wide strip of foil paper, one side connected to the terminal of the lamp electrodes. For fixation at the ends of the bulb, metal clamps of the same diameter as the lamp are used.

Electronic ballast

The operating principle of a lighting fixture with electronic ballast is that electric current passes through a rectifier and then enters the buffer zone of the capacitor.

In electronic ballast, along with classic starting control devices, starting and stabilization occurs through a throttle. Power depends on high frequency current.

Electronic ballast

The natural complexity of the circuit is accompanied by a number of advantages compared to the low-frequency version:

increasing efficiency indicators;
elimination of flickering effect;
reduction in weight and dimensions;
absence of noise during operation;
increasing reliability;
long service life.

In any case, one should take into account the fact that electronic ballasts belong to the category of pulsed devices, so turning them on without sufficient load is the main cause of failure.

Checking the performance of an energy-saving lamp

Simple testing allows you to timely identify a breakdown and correctly determine the main cause of the malfunction, and sometimes even perform the simplest repair work yourself:

Dismantling the diffuser and carefully examining the fluorescent tube in order to detect areas of pronounced blackening. Very rapid blackening of the ends of the flask indicates burnout of the spiral.
Checking the filaments for breaks using a standard multimeter. If there is no damage to the threads, the resistance values can vary within 9.5-9.2Om.

If checking the lamp does not show malfunctions, then the lack of operation may be due to the breakdown of additional elements, including the electronic ballast and the contact group, which quite often undergoes oxidation and needs to be cleaned.

Checking the performance of the throttle is carried out by disconnecting the starter and shorting it to the cartridge. After this, you need to short-circuit the lamp sockets and measure the throttle resistance. If replacing the starter fails to achieve the desired result, then the main fault, as a rule, lies in the capacitor.

What causes danger in an energy-saving lamp?

Various energy-saving lighting devices, which have recently become very popular and fashionable, according to some scientists, can cause quite serious harm not only to the environment, but also to human health:

poisoning with mercury-containing vapors;
lesions of the skin with the formation of a severe allergic reaction;
increased risk of developing malignant tumors.

Flickering lamps often cause insomnia, chronic fatigue, decreased immunity and the development of neurotic conditions.

It is important to know that mercury is released from a broken fluorescent lamp bulb, so operation and further disposal must be carried out in compliance with all rules and precautions.

A significant reduction in the service life of a fluorescent lamp, as a rule, is caused by voltage instability or malfunctions of the ballast resistance, therefore, if the electrical network is of insufficient quality, it is suggested to use conventional incandescent lamps.

Video on the topic

I have already said more than once that many things that surround us could have been realized much earlier, but for some reason they entered our everyday life quite recently. We have all encountered fluorescent lamps - those white tubes with two pins at the ends. Remember how they used to turn on? You press a key, the lamp begins to blink and finally enters its normal mode. This was really annoying, so they didn’t install such things at home. They were installed in public places, in production, in offices, in factory workshops - they are really economical compared to conventional incandescent lamps. But they blinked at a frequency of 100 times per second, and many people noticed this blinking, which was even more annoying. Well, to start each lamp there was a ballast choke, like a piece of iron weighing about a kilogram. If it was not assembled well enough, it would buzz rather disgustingly, also at a frequency of 100 hertz. What if there are dozens of such lamps in the room where you work? Or hundreds? And all these dozens turn on and off in phase 100 times per second and the throttles hum, although not all of them. Did it really have no effect?

But, in our time, we can say that the era of buzzing chokes and blinking lamps (both at start and during operation) is over. Now they turn on immediately and to the human eye their operation looks completely static. The reason is that instead of heavy chokes and periodically sticking starters, electronic ballasts (electronic ballasts) came into use. Small and light. However, just looking at their electrical diagram, the question arises: what prevented their mass production back in the late 70s and early 80s? After all, the entire element base was already there then. Actually, in addition to two high-voltage transistors, it uses the simplest parts, literally of a pittance cost, which were available in the 40s. Well, okay, the USSR, here production responded poorly to technological progress (for example, tube TVs were discontinued only in the late 80s), but in the West?

So, in order...

The standard circuit for switching on a fluorescent lamp was, like almost everything in the twentieth century, invented by the Americans on the eve of the Second World War and included, in addition to the lamp, the choke and starter we have already mentioned. Yes, a capacitor was also hung parallel to the network to compensate for the phase shift introduced by the inductor or, in even simpler terms, to correct the power factor.

Chokes and starters

The principle of operation of the entire system is quite tricky. At the moment the power button is closed, a weak current begins to flow through the circuit network-button-throttle-first spiral-starter-second spiral-mains - approximately 40-50 mA. Weak because at the initial moment the resistance of the gap between the starter contacts is quite large. However, this weak current causes ionization of the gas between the contacts and begins to increase sharply. This causes the starter electrodes to heat up, and since one of them is bimetallic, that is, it consists of two metals with different dependences of changes in geometric parameters on temperature (different coefficients of thermal expansion - CTE), when heated, the bimetal plate bends towards the metal with a lower CTE and closes with another electrode. The current in the circuit increases sharply (up to 500-600 mA), but still its growth rate and final value are limited by the inductance of the inductor; inductance itself is the property of preventing the instantaneous inductance of current. Therefore, the choke in this circuit is officially called a “ballast control device”. This high current heats up the coils of the lamp, which begin to emit electrons and heat the gas mixture inside the cylinder. The lamp itself is filled with argon and mercury vapor - this is an important condition for the occurrence of a stable discharge. It goes without saying that when the contacts in the starter close, the discharge in it stops. The entire process described actually takes a fraction of a second.

Now the fun begins. The cooled contacts of the starter open. But the inductor has already stored energy equal to half the product of its inductance and the square of the current. It cannot instantly disappear (see above about inductance), and therefore causes the appearance of a self-induction EMF in the inductor (in other words, a voltage pulse of approximately 800-1000 volts for a 36-watt lamp 120 cm long). Added to the amplitude mains voltage (310 V), it creates a voltage on the electrodes of the lamp sufficient for breakdown - that is, for a discharge to occur. The discharge in the lamp creates an ultraviolet glow of mercury vapor, which in turn affects the phosphor and makes it glow in the visible spectrum. At the same time, let us remind you once again that the choke, having an inductive reactance, prevents an unlimited increase in the current in the lamp, which would lead to its destruction or tripping of the circuit breaker in your home or other place where similar lamps are used. Note that the lamp does not always light up the first time; sometimes it takes several attempts for it to enter a stable glow mode, that is, the processes that we described are repeated 4-5-6 times. Which is really quite unpleasant. After the lamp has entered the glow mode, its resistance becomes significantly less than the resistance of the starter, so it can be pulled out, the lamp will continue to glow. Well, also, if you disassemble the starter, you will see that a capacitor is connected in parallel to its terminals. It is needed to reduce radio interference generated by contact.

So, very briefly and without delving into the theory, let’s say that a fluorescent lamp is turned on with a high voltage, and is kept in a luminous state by much less (for example, it turns on at 900 volts, glows at 150). That is, any device for switching on a fluorescent lamp is a device that creates a high switch-on voltage at its ends, and after lighting the lamp, reduces it to a certain operating value.

This American switching scheme was actually the only one, and only 10 years ago its monopoly began to rapidly collapse - Electronic ballasts (EPG) entered the market en masse. They made it possible not only to replace heavy buzzing chokes, to ensure instantaneous switching on of the lamp, but also to introduce a lot of other useful things such as:

- soft start of the llama - pre-heating of the coils, which dramatically increases the life of the lamp

— overcoming flicker (lamp power frequency is significantly higher than 50 Hz)

— Wide input voltage range 100…250 V;

— reduction in energy consumption (up to 30%) with a constant luminous flux;

— increase in the average service life of lamps (by 50%);

— protection against power surges;

— ensure the absence of electromagnetic interference;

- O no switching current surges (important when many lamps turn on simultaneously)

— automatic shutdown of defective lamps (this is important, devices are often afraid of idling)

— Efficiency of high-quality electronic ballasts — up to 97%

— lamp brightness control

But! All these goodies are sold only in expensive electronic ballasts. And in general, not everything is so rosy. More precisely, maybe everything would be cloudless if the EPR circuits were made truly reliable. After all, it seems obvious that electronic ballast (EPG) should in any case be no less reliable than a choke, especially if it costs 2-3 times more. In the “former” circuit consisting of a choke, a starter and the lamp itself, it was the choke (starter control element) that was the most reliable and, in general, with high-quality assembly could work almost forever. Soviet chokes from the 60s still work, they are large and wound with a fairly thick wire. Imported chokes with similar parameters, even from well-known companies such as Philips, do not work as reliably. Why? The very thin wire with which they are wound raises suspicion. Well, the core itself is much smaller in volume than the first Soviet chokes, which is why these chokes get very hot, which probably also affects reliability.

Yes, so, as it seems to me, electronic ballasts, at least cheap ones - that is, costing up to 5-7 dollars apiece (which is higher than that of a throttle), are made deliberately unreliable. No, they can work for years and may even work forever, but it’s like in a lottery - the probability of losing is much higher than winning. Expensive electronic ballasts are made to be conditionally reliable. We will tell you why “conditionally” a little later. Let's start our little review with the cheap ones. As for me, they make up 95% of purchased ballasts. Or maybe almost 100%.

Let's consider several such schemes. By the way, all “cheap” circuits are almost identical in design, although there are nuances.

Cheap electronic ballasts (EPG). 95% of sales.

These types of ballasts cost 3-5-7 dollars and simply turn on the lamp. This is their only function. They don't have any other useful bells and whistles. I drew a couple of diagrams to explain how this newfangled miracle works, although as we said above, the principle of operation is the same as in the “classic” throttle version - we ignite with a high voltage, keep it low. It's just implemented differently.

All the circuits of electronic ballasts (EPG) that I held in my hands - both cheap and expensive - were half-bridges - only the control options and the “piping” differed. So, an alternating voltage of 220 volts is rectified by the diode bridge VD4-VD7 and smoothed out by capacitor C1. In the input filters of cheap electronic ballasts, due to saving price and space, small capacitors are used, on which the magnitude of voltage ripple with a frequency of 100 Hz depends, despite the fact that the calculation is approximately as follows: 1 watt of lamp - 1 µF of filter capacitance. In this circuit there are 5.6 uF per 18 watts, that is, clearly less than necessary. This is why (although not only this), by the way, the lamp glows visually dimmer than from an expensive ballast of the same power.

Then, through the high-resistance resistor R1 (1.6 MOhm), capacitor C4 begins to charge. When the voltage on it exceeds the operating threshold of the bidirectional dinistor CD1 (approximately 30 volts), it breaks through and a voltage pulse appears at the base of transistor T2. Opening the transistor starts the operation of a half-bridge self-oscillator formed by transistors T1 and T2 and transformer TR1 with control windings connected in antiphase. Typically these windings contain 2 turns, and the output winding contains 8-10 turns of wire.

Diodes VD2-VD3 dampen negative emissions occurring on the windings of the control transformer.

So, the generator starts at a frequency close to the resonant frequency of the series circuit formed by capacitors C2, C3 and inductor C1. This frequency may be equal to 45-50 kHz, in any case, I was unable to measure it more accurately; I did not have a storage oscilloscope at hand. Please note that the capacitance of capacitor C3 connected between the electrodes of the lamp is approximately 8 times less than the capacitance of capacitor C2, therefore, the voltage surge across it is the same times higher (since the capacitance is 8 times greater - the higher the frequency, the greater the capacitance on a smaller capacity). That is why the voltage of such a capacitor is always chosen to be at least 1000 volts. At the same time, a current flows through the same circuit, heating the electrodes. When the voltage on capacitor C3 reaches a certain value, breakdown occurs and the lamp lights up. After ignition, its resistance becomes significantly less than the resistance of capacitor C3 and it does not have any effect on further operation. The generator frequency also decreases. Choke L1, as in the case of the “classic” choke, now performs the function of limiting the current, but since the lamp operates at a high frequency (25-30 kHz), its dimensions are many times smaller.

Appearance of ballast. It can be seen that some elements are not soldered into the board. For example, where I soldered a current-limiting resistor after the repair, there is a wire jumper.

One more product. Unknown manufacturer. Here they did not sacrifice 2 diodes to make an “artificial zero”.

"Sevastopol scheme"

There is an opinion that no one will do it cheaper than the Chinese. I was sure of it too. I am sure until I got my hands on electronic ballasts from a certain “Sevastopol plant” - at least the person who sold them said so. They were designed for a 58 W lamp, that is, 150 cm in length. No, I won’t say that they didn’t work or worked worse than the Chinese ones. They worked. The lamps glowed from them. But…

Even the cheapest Chinese ballasts (electronic ballasts) consist of a plastic case, a board with holes, a mask on the board on the printed circuit side, and a designation indicating which part is which on the mounting side. The “Sevastopol version” was devoid of all these redundancies. There, the board was also the cover of the case, there were no holes in the board (for this reason), there were no masks, no markings, the parts were placed on the side of the printed conductors and everything that could be made of SMD elements, which I never I haven’t seen it even in the cheapest Chinese devices. Well, the scheme itself! I've watched a lot of them, but I've never seen anything like it. No, everything seems to be like the Chinese: an ordinary half-bridge. It’s just that the purpose of elements D2-D7 and the strange connection of the base winding of the lower transistor is completely unclear to me. And further! The creators of this miracle device combined a half-bridge generator transformer with a choke! They simply wound the windings on an W-shaped core. No one has thought of this, not even the Chinese. In general, this scheme was designed either by geniuses or alternatively gifted people. On the other hand, if they are so ingenious, why not sacrifice a couple of cents to introduce a current-limiting resistor to prevent current surge through the filter capacitor? Yes, and for a varistor for smooth heating of the electrodes (also cents) - they could go broke.

IN THE USSR

The above “American circuit” (choke + starter + fluorescent lamp) operates from an alternating current network with a frequency of 50 hertz. What if the current is constant? Well, for example, the lamp must be powered from batteries. Here you won’t be able to get by with the electromechanical option. You need to “make a diagram.” Electronic. And there were such schemes, for example, on trains. We all traveled in Soviet carriages of varying degrees of comfort and saw these fluorescent tubes there. But they were powered by a direct current of 80 volts, the voltage produced by the carriage battery. For power supply, “that same” circuit was developed - a half-bridge generator with a series resonant circuit, and to prevent current surges through the spirals of the lamps, a direct heating thermistor TRP-27 with a positive temperature coefficient of resistance was introduced. The circuit, it must be said, was exceptionally reliable, and in order to convert it into ballast for an AC network and use it in everyday life, it was necessary to essentially add a diode bridge, a smoothing capacitor and slightly recalculate the parameters of some parts and the transformer. The only "but". Such a thing would be quite expensive. I think its cost would be no less than 60-70 Soviet rubles, with the cost of the throttle being 3 rubles. Mainly due to the high cost of powerful high-voltage transistors in the USSR. And this circuit also produced a rather unpleasant high-frequency squeak, not always, but sometimes it could be heard; perhaps, over time, the parameters of the elements changed (the capacitors dried out) and the frequency of the generator decreased.

Power supply diagram for fluorescent lamps in trains in good resolution

Expensive electronic ballasts (EPG)

An example of a simple “expensive” ballast is a product from TOUVE. It worked in the aquarium lighting system; in other words, it powered two green llamas of 36 watts each. The owner of the ballast told me that this thing is something special, specially designed for lighting aquariums and terrariums. "Eco-friendly". I still don’t understand what is environmentally friendly; another thing is that this “ecological ballast” did not work. Opening and analyzing the circuit showed that, compared to cheap ones, it is significantly more complicated, although the principle - half-bridge + triggering through the same DB3 dinistor + series resonant circuit - is retained in full. Since there are two lamps, we see two resonant circuits T4C22C2 and T3C23C5. The cold coils of the lamps are protected from surge current by thermistors PTS1, PTS2.

Rule! If you buy an economical lamp or an electronic ballast, check how this same lamp turns on. If it’s instant, the ballast is cheap, no matter what they tell you about it. In more or less normal conditions, the lamp should turn on after pressing the button in about 0.5 seconds.

Further. The RV input varistor protects the power filter capacitors from surge current. The circuit is equipped with a power filter (circled in red) - it prevents high-frequency interference from entering the network. The Power Factor Correction is outlined in green, but in this circuit it is assembled using passive elements, which distinguishes it from the most expensive and sophisticated ones, where the correction is controlled by a special microcircuit. We will talk about this important problem (power factor correction) in one of the following articles. Well, a protection unit has also been added in abnormal modes - in this case, generation is stopped by shorting the SCR base Q1 to ground with the SCR thyristor.

For example, deactivation of the electrodes or a violation of the tightness of the tube leads to the appearance of an “open circuit” (the lamp does not light up), which is accompanied by a significant increase in the voltage across the starting capacitor and an increase in the ballast current at the resonance frequency, limited only by the quality factor of the circuit. Long-term operation in this mode leads to damage to the ballast due to overheating of the transistors. In this case, the protection should work - the SCR thyristor closes the Q1 base to ground, stopping generation.

It can be seen that this device is much larger in size than cheap ballasts, but after repair (one of the transistors flew out) and restoration, it turned out that these same transistors heat up, as it seemed to me, more than necessary, up to about 70 degrees. Why not install small radiators? I am not saying that the transistor failed due to overheating, but perhaps operation at elevated temperatures (in a closed case) was a provoking factor. In general, I installed small radiators, since there was room.