How does the electronic fluorescent lamp. Modern electronic ballasts with your hands

If someone does not know how fluorescent lamps work, then the important point here is electricitybut not in terms of nutrition, but in terms of its appearance. Fluorescent lamps operate from direct currentthat's why in electrical circuit  the lamp is installed the so-called adjustable high-frequency inverter or otherwise electronic ballast. In fact, this is a regular rectifier, only it is distinguished from a standard device by its small size and, accordingly, its low weight. As a pleasant addition, the inverter does not emit noise during operation. Let's look at this article, what is electronic ballast - a scheme of its internal filling.

First of all it is necessary to note the fact that the device is responsible not only for straightening. alternating current, but also for starting the lamp itself. That is, it can be compared with a normal (standard) throttle contact. True, one must be completely frank and say that electronic ballast for fluorescent lamps is a capricious device, so its shelf life leaves much to be desired.

Varieties and Purpose

Currently, manufacturers offer two basic types:

• Single.
• Paired.

Everything is clear here. Single intended to turn on a single lamp, paired for several connected to a single network. Most importantly, when choosing an inverter, it is necessary to take into account the overall brightness of the lamp as a whole, because it is for this indicator that the ballast for fluorescent lamps is selected.

So, in addition to the above functions, which still requires electronic ballast.

1. The inverter installed in the circuit must provide a direct current supply, thereby providing the light source with uniform radiation without flickering.
2. With it, the lamp is quickly turned on. Without it, it will light up, too, but only after a few seconds and when it is working it will be necessary to buzz.
3. Power surges are the number one enemy for a lighting system. So the ballast smoothes these jumps due to the rectification of the current regardless of its amplitude.
4. The electronic ballast circuit has a special regulator. It fixes faults inside the lamp itself. If a breakdown is detected, the regulator immediately disconnects the light source from the supply of electric current.

Attention! Many manufacturers in the schemes use various parts and elements with the help of which it is possible to save the consumed electric power. In many models, this figure is 20%. Not a bad result.

How does ballast work

As mentioned above, the ballast for fluorescent lamps is practically a choke. Therefore, this device rectifies the electric current, and then heats the cathodes of fluorescent lamps. After that, they receive the amount of voltage that the lighting device quickly turns on. The voltage is set by a special regulator, which is installed in the inverter circuit, it is they who set the voltage range. That is why the flickering of the light source is absent.

The circuit also has its own starter. He is responsible for the transmission of voltage and ignition. When the lamp is turned on, the voltage on the ballast microcircuit drops, and the current decreases accordingly. This makes it possible to find the optimal mode of operation of the lamp.

Currently fluorescent lights  completed with two types of ballasts:

• Smooth start is the so-called cold version.
• Quick start - hot. These mainly include control gear chokes.

Lighting lamps daylight  has a significant advantage over incandescent bulbs: efficiency, longer service life, high efficiency, a small amount of heat dissipated by the lamp, the spectrum of light emitted by these lamps is closer to the natural, compared with the usual incandescent. And naturally they have the disadvantages of it: the complexity of turning on the lamps daytime lighting, the occurrence of stroboscopic effects on moving mechanisms, the relative high cost.
   Despite the strong development of modern electronic ballasts for powering fluorescent lamps (LDS), the circuit shown in the figure is considered to be the standard LDS switching circuit.

The principle of operation is simple, but still requires certain conditions for the normal exploitation of LDS. For ignition fluorescent lamp and its normal operation requires a starter (starting device), a throttle (control gear - control gear), capacitors. The starter serves to automatically turn on and off the pre-heating of the electrodes. It is a glass cylinder filled with an inert gas, in which there are metal and bimetallic electrodes, the findings of which are connected to the projections in the base for mounting in the lamp circuit. When the lamp is turned on according to the above scheme, the mains voltage is applied to the electrodes of the lamp and the starter, which is enough to form a glowing discharge between the starter electrodes. Therefore, a glow starter current flows in the circuit, approximately 0.01 ... 0.04 A. The heat generated by the flow of current through the starter heats the bimetallic electrode, which is bent towards the other electrode. After a period of glow discharge of 0.2 ... 0.4 s, the contacts of the starter close, and a starting current begins to flow through the circuit, the value of which is determined by the network voltage and the resistances of the choke and the electrodes of the lamp. This current is not enough to heat the starter electrodes, and the bimetallic starter electrode unbends, breaking the starting current circuit. Pre-start current heats the electrodes of the lamp. Due to the presence of an inductance in the circuit, when the starter contacts open, a voltage pulse arises in the circuit that ignites the lamp. The heating time of the lamp electrodes is 0.2 ... 0.8 seconds, which in most cases is not enough, and the lamp may not light up the first time, and the whole process may repeat. The total duration of the starting mode of the lamp is 5 ... 15 s. The duration of the starting pulse when opening the contacts of the starter is 1 ... 2 μs, which is not enough for reliable ignition of the lamp, therefore, in parallel with the contacts of the starter, include a capacitor of 5 ... 10 pF. The choke, which is a winding wound on a core of electrical steel sheet, facilitates the ignition of the lamp, and also limits the current and ensures its stable operation (sometimes the choke is replaced with a compensating capacitor, an incandescent light bulb of small power). Figure 1 shows simplest scheme starter ignition of a fluorescent lamp, included in the network 127-220 V. The problem of the scheme under consideration is that at the time of opening the starter does not always coincide with the half-wave voltage of the network, and the starter is idling. The scheme is certainly much simpler than those that will be described below. But all the same schemes considered further find their application in really high-quality and cost-effective lighting systems.
   So...

Electronic ballast on the chip IR2153

As for the specific circuit solutions, I will try to highlight the solutions on the basis of the microcircuits of the manufacturer International Rectifier.
   The circuit shown in the figure is a mains voltage converter 220 V, 50 Hz to 160 V 33 kHz. It is the obtained output parameters that are the factors that significantly increase the operational characteristics of light sources based on LDS.
First factor:  The indiscriminate flickering of the lamp at the time of the initial launch is completely eliminated.
Second:  The potential arising during the start is sufficient to guarantee arson of the lamp the first time. Startup time is approximately 0.5 seconds.
Third:  Due to the high-frequency switching, the gas in the lamp does not have time to deionize during periods of sine-wave supply current to zero, which means that the normal operation of the lamp requires less voltage. This is the main power saving.
Fourth:  The complete absence of a stroboscopic effect on a moving mechanism, due to the absence of 100 Hz (double network frequency) light pulsations.
Fifth:  Requires a choke with a lower inductance, and hence with smaller size, weight, heat, ohmic losses and cost.
   Before the above listed, you can safely put the sign "+"
   Well, where do we get away from the shortcomings, they are:
The first:  Relative complexity of the scheme.
Second:  The relatively high cost of manufacturing such a device (if we are talking about powering only one lamp).
Third:  High level of EMR.

The circuit consists of the main components: a power supply filter, a mains voltage rectifier, a generator-driver for controlling high-voltage MOSFET transistors, a half-bridge of keys, and a load in the role of which is a lamp with a ballast choke.
   The scheme does not contain anything particularly unusual and is not complicated.
The mains voltage is supplied through a line filter L1, C2. It enters the rectifier VD1, C3. Formed on the capacitor C3 310B directly feed the half-bridge of the transistors VT1, VT2 and through the quenching resistor R2 we obtain the necessary 9-10V chips for operation.
   After connecting to the network in about 0.5 seconds at the output of the circuit (the right side of the capacitor C8), a 165V square wave appears with a small “shelf” between the open states of the transistors. The voltage applied to the lamp for about 0.5 seconds. warms the cathodes. This manifests itself in the form of a short-dim orange glow of the cathodes, after sufficient ionization of the gas in the lamp bulb, due to high-voltage emissions from the L2 choke, the gas gap breaks through. And, as without consequences - the lamp is lit! Further work is accompanied by heating the lamp and inductance, as a result of which the brightness increases slightly.
   The “engine” of the circuit is a generator-driver chip. The contents of which can be sorted out on the basis of this picture:

The microcircuit contains a similarity of the 555th timer, phase-splitting trigger, shaper of the “dead” gap, which allows to avoid the through current in the output keys, the power supply circuit of the upper key driver, the undervoltage control circuit, the zener diode of the main power supply and the delay circuit, which allows to equalize the propagation time of the signals through the channels upper and lower key, as well as a few more nodes in which to understand it makes no sense.

About used components

| |

In this article, I will discuss the common failures of modern "ballasts" of fluorescent lamps, how to repair them, and give analogs of radio components that can be used for repairs. Since These lamps are still quite common in everyday life (for example, I use 5 such lamps daily), I think the topic is more than relevant.

If the fluorescent lamp stops shining, the first thing you need to do is replace the luminescent “flask” itself. It may have two faults: the failure of one of the channels (breakage of the filament spiral) or the banal effect of "aging".

If in the dark on the switched on lamp there is a barely noticeable glow of the filaments, then, most likely, the breakdown of the electronic "ballast" is in the breakdown of the capacitor connecting the filament (see Fig. 2). Its capacity is 4.7n, the operating voltage is 1.2kV. It is better to replace the same, only with an operating voltage of 2kV. In cheap ballasts there are 400 or even 250V capacitors. They are the first to fail.

When the actions from the previous paragraph did not help, you need to start checking the radio components with a fuse on the diagram. It is often available, but I do not have it on the board (see fig. P. 1).

The next thing you should pay attention to is the transistors (see fig. 1). They can fail due to power surges, for example, if there is a relay voltage regulator at home, or welding is often used by you or your neighbors. These replacement transistors can be found in the power supply of energy-saving lamps. Since Since such lamps often fail due to bulb failures, the circuit and, accordingly, the transistors remain working.

If there are no such llamas, then transistors can be replaced with analogs. The analogs of the transistors 13001, 13003, 13005, 13007, 13009 are shown in the table below. Popular substitutes themselves are such analogs as KT8164A and KT872A.

Sometimes you need to ring the rest of the radio components and replace them, in case the damaged ones are found. After each stage of repair of the ballast of fluorescent lamps, their first inclusion is recommended to be made through a series-on incandescent 40-watt bulb. By its glow you can see the presence of a short circuit.

It is important to remember that modern electronic ballasts are impulse devices that are switched on without a load (in our case, a fluorescent lamp) is strictly prohibited, since this will cause them to fail.

If you have tried everything, but nothing helped, or there is no desire to mess with the ballast, you can use pulse unit  supply from energy saving lamp. Its dimensions are so small that they fit easily in some housings for fluorescent lamps. In this case, the filament of a fluorescent lamp is connected to the contacts on the board where the contacts of the bulb of the energy-saving lamp were connected. The power supply should correspond approximately to the lamp power. Personally, my 36W fluorescent lamp is powered by a 32W lamp power supply.

Although incandescent bulbs are cheap, they consume a lot of electricity, so many countries refuse to produce them (USA, Western European countries). Instead, they come compact fluorescent fluorescent lamps (energy-saving), they are twisted in the same E27 cartridges as incandescent bulbs. However, they cost 15-30 times more expensive, but they serve 6-8 times longer and 4 times less electricity, which determines their fate. The market is filled with a variety of such lamps, mainly made in China. One of these lamps, the company DELUX, shown in the photo.

Its power is 26 W -220 V, and the power supply, also called electronic ballast, is located on the board with dimensions of 48x48 mm ( fig.1) and is located in the base of this lamp.

Its radio elements are placed on the circuit board by a mounted installation, without the use of chip elements. The schematic diagram is drawn by the author from the inspection of the circuit board and is shown in fig.2.

Schematic note: there is no point in the diagram denoting the connection of the dynistor, the diode D7 and the base of the transistor EN13003A

At first it is appropriate to recall the principle of ignition of fluorescent lamps, including when using electronic ballasts. To ignite a fluorescent lamp, it is necessary to heat its filaments and apply a voltage of 500 ... 1000 V, i.e. significantly more than the mains voltage. The magnitude of the ignition voltage is directly proportional to the length of the glass bulb of the fluorescent lamp. Naturally, it is smaller for short compact lamps, but smaller for long tubular lamps. After ignition, the lamp sharply reduces its resistance, which means that a current limiter should be used to prevent short circuits in the circuit. The electronic ballast circuit for a compact fluorescent lamp is a push-pull half-bridge voltage converter. initially mains voltage  using a 2-half-period bridge, it is rectified to a constant voltage of 300 ... 310 V. A converter is triggered by a symmetrical dinistor, indicated in the Z diagram, it opens when, when the power supply is turned on, the voltage at its connection points exceeds the threshold. When opened, a dynistor passes a pulse to the base of the lower transistor circuit, and the converter starts. Next, a push-pull half-bridge converter, the active elements of which are two npn transistor, converts a constant voltage of 300 ... 310 V to high-frequency voltage, which allows to significantly reduce the size of the power supply. The load of the converter and at the same time its control element is a toroidal transformer (indicated in the circuit L1) with its three windings, of which two control windings (each with two turns) and one working (9 turns). Transistor switches open out of phase from positive impulses from control windings. For this, the control windings are included in the transistor bases in antiphase (in Figure 2, the beginning of the windings are indicated by dots). Negative voltage surges from these windings are quenched with diodes D5, D7. Opening each key causes a tip-off of pulses in two opposite windings, including in the working winding. The alternating voltage from the working winding is supplied to the fluorescent lamp through a series circuit consisting of: L3 - lamp filament -С5 (3.3 nF 1200 V) - lamp filament - C7 (47 nF / 400 V). The values ​​of inductances and capacitances of this circuit are selected so that a voltage resonance occurs at a constant frequency of the converter. When the resonance voltage in serial circuit, inductive and capacitive impedances are equal, the current in the circuit is maximum, and the voltage on the reactive elements L and C can significantly exceed the applied voltage. The voltage drop on C5, in this series resonant circuit, is 14 times greater than on C7, since the capacitance of C5 is 14 times smaller and its capacitance is 14 times greater. Therefore, before igniting the fluorescent lamp, the maximum current in the resonant circuit heats both filaments, and the large resonant voltage on the C5 capacitor (3.3 nF / 1200 V), connected in parallel with the lamp, lights the lamp. Pay attention to the maximum allowable voltages on capacitors C5 = 1200 V and C7 = 400 V. These values ​​are chosen by chance. At resonance, the voltage at C5 reaches about 1 kV and it must withstand it. The lit lamp sharply reduces its resistance and blocks (short-circuits) the capacitor C5. The capacitance C5 is eliminated from the resonant circuit, and the voltage resonance in the circuit is stopped, but the already lit lamp continues to glow, and the inductor L2, with its inductance, limits the current in the lit lamp. In this case, the converter continues to operate in automatic mode, without changing its frequency since the start. The entire ignition process takes less than 1 s. It should be noted that the fluorescent lamp is always supplied aC voltage. This is better than permanent, as it ensures uniform wear of the emission capabilities of the filament and thus increases its service life. When the lamps are powered from DC, its service life is reduced by 50%, therefore constant voltage  on discharge lamps do not serve.

Purpose of the elements of the converter.
  The types of radio elements are indicated on schematic diagram  (Fig.2).
  1. EN13003A- transistor keys  (for some reason, the manufacturers did not identify them on the wiring diagram). These are bipolar high-voltage transistors of average power, conduction npn, TO-126 package, their MJE13003 or KT8170A1 analogs (400 V, 1.5 A; 3 A pulse), and KT872A (1500 V; 8 A; T26a), but in size they are larger. In any case, it is necessary to correctly determine the outputs of the BKE, since different manufacturers may have different sequences, even the same analogue.
  2. A toroidal ferrite transformer, designated by the manufacturer L1, ring sizes 11x6x4.5, probable magnetic permeability 2000, has 3 windings, two of them are 2 turns and one is 9 turns.
  3. All diodes D1-D7 are of the same type 1N4007 (1000 V, 1 A), of which diodes D1-D4 are a rectifier bridge, D5, D7 suppress negative emissions of the control pulse, and D6 separates the power supplies.
  4. Chain R1СЗ provides a delay in the start of the converter for the purpose of "soft start" and not allowing the inrush current.
  5. Symmetrical dynistor Z type DB3 Uс.max = 32 V; Uoc = 5 V; U neotp.i.max = 5 V) provides the initial start of the converter.
  6. R3, R4, R5, R6 - limiting resistors.
  7. C2, R2 - damping elements designed to dampen the emissions of the transistor switch at the time of its closure.
  8. L1 choke consists of two W-shaped ferrite halves glued together. Initially, the choke participates in the voltage resonance (together with C5 and C7) to ignite the lamp, and after ignition, with its inductance, it quenches the current in the fluorescent lamp circuit, since the lit lamp sharply decreases its resistance.
  9. C5 (3.3 nF / 1200 V), C7 (47 nF / 400 V) are capacitors in the fluorescent lamp circuit that participate in its ignition (through voltage resonance), and after ignition, C7 maintains luminescence.
  10. С1 - smoothing electrolytic capacitor.
  11. A choke with a ferrite core L4 and a capacitor C6 constitute a barrier filter that does not transmit impulse noise from the converter to the supply network.
  12. F1 - mini fuse in a 1 A glass case, located outside the circuit board.

Repairs.
Before repairing the electronic ballast, it is necessary to “get” to its circuit board, for this it is enough to separate the two components of the base with a knife. Be careful when repairing the board under voltage, as its radio elements are under phase voltage!

Burnout (break) of fluorescent lamp filamentswhile the electronic ballast remains intact. This is a typical malfunction. It is impossible to restore the spiral, and glass luminescent flasks for such lamps are not sold separately. What is the way out? Or adapt a serviceable ballast to a 20-watt lamp having a straight glass lamp, instead of its “native” choke (the lamp will work more reliably and without hum) or use board elements as spare parts. Hence the recommendation: buy compact compact fluorescent lamps of the same type - it will be easier to repair.

Cracks in the soldering of the circuit board.  The reason for their appearance is periodic heating and subsequent, after switching off, cooling of the place of soldering. The solder spot is heated from elements that are heated (fluorescent lamp spirals, transistor switches). Such cracks may appear after several years of operation, i.e. after repeated heating and cooling of the place of soldering. Eliminates the problem of re-soldering cracks.

Damage to individual radio elements.  Separate radio elements can be damaged both from cracks in the soldering and from voltage surges in the supply network. Although there is a fuse in the circuit, it will not protect radio elements from voltage surges, as a varistor could have done. The fuse will burn out the breakdown of radio elements. Of course, the weakest point of all the radio elements of this device are transistors.

Radioammat number 1, 2009.

List of radio elements