Development of the capacitor block for the life of LEDs. Yak rozrahuvati transformer-less living unit

20.06.2023

Sometimes in electrical engineering it is necessary to assemble life blocks as a transformer. This is due to the recent decrease in input voltage. For example, reducing the alternating voltage of the circuit (220) at a frequency of 50 hertz to the required voltage value. An alternative to a transformer can be a capacitor, which is switched on in series to the voltage level (additional information about the installation of capacitors in the section “). Such a capacitor is called extinguishing.
Carry out a refurbishment of the capacitor to extinguish - this means finding out the capacitance of such a capacitor, which in the described case is connected to the lancet, reduce the input voltage to the required voltage. Now we can find the formula for the expansion of the capacitance of the capacitor to be extinguished. The capacitor, which operates in the lancus of the alternating stream, has an emnestic basis (), which is related to the frequency of the alternating stream and the moisture content () (and), more precisely:

Behind the washroom, they turned on a capacitor in the lancet of the alternating stream (actively navantazhenya ()). The final operation of the system () can be calculated as follows:

The fragments united sequentially, vikorista, we write:

de - Podіnnya voltage on the navantazhennі (voltage life of the device); - Voltage voltage, - Voltage drop on the capacitor. Vikorist suggested more formulas, perhaps:

If the voltage is small, then changing the capacitor, turning it on in series, is the simplest way to change the voltage. In this case, if the voltage at the output is less than 10-20 volts, then the capacitance of the capacitor to be extinguished is calculated using the following formula:

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The light indicator is an unknown part of electronics that people can easily understand with its help. In consumer electronic devices, the role of the indicator is the light-emitting diode, which is installed in the secondary life light, at the output of the transformer or stabilizer. However, you will have to rely on simple electronic designs that do not change the indicator of any obvious additions. For example, installing a light-emitting diode on the wall-mounted switchboard would become an important reference point for moving the switch at night. And the LED in the casing of the device with sockets signals the presence of its inclusion before the 220 V power supply.

Below is a number of simple circuits that will help people with a minimal amount of knowledge of electrical engineering to connect the LED to the alternating power supply.

Connection diagrams

The light-emitting diode is a variety of conductor diodes with a voltage and a much smaller current flow than that of everyday electricity. When directly connected to 220 volts, the mitt will work fine. Therefore, the light-transmitting diode is easily connected through the flow-interchange element. The cheapest and simplest are folded circuits with a step-down element in the form of a resistor or capacitor.

There is an important point that you need to pay attention to when connecting the LED to the extent of the alternating current - without exchanging the return voltage. These tasks can be easily dealt with by any silicon diode, with no less than a minimum of insurance costs. The LED is connected in series after the resistor or with reverse polarity in parallel with the LED.

The main idea is that it is possible to do without exchanging the return voltage, since the electrical breakdown does not cause damage to the LED. However, the gate current can cause overheating of the p-n junction, resulting in thermal breakdown and destruction of the LED crystal.

Instead of a silicon diode, another light-emitting diode can be combined with a similar direct stream, which is connected with reverse polarity in parallel to the first light-emitting diode.

The negative side of circuits with a flow-interchange resistor is the need for great power. This problem becomes especially relevant when the economy is connected to a great economic growth. This problem arises by replacing the resistor with a non-polar capacitor, which in such circuits is called ballast or suppressed.

A non-polar capacitor is switched on in the middle of the exchangeable stream, which is used as a support, but does not dissipate the tension in the appearance of heat.

In these circuits, when the voltage is turned on, the capacitor becomes undischarged, which creates the risk of an electrical shock. This problem can easily be solved by connecting a shunt resistor of 0.5 watt with a support of at least 240 kOhm to the capacitor.

Design of resistor for LED

In all the most commonly presented circuits with a flow-exchange resistor, the support is based on Ohm’s law: R = U/I, where U is the life voltage, I is the working flow of the LED. The resistor is used for the same tension as P = U * I. This data can be obtained for assistance.

Important. If you plan to install the circuit in a housing with low convection, it is recommended to increase the maximum voltage value that the resistor dissipates by 30%.

The capacitor needs to be extinguished for the LED.

The capacity of the capacitor to be quenched (in uF) is determined by the following formula: C = 3200 * I / U, where I is the voltage, U is the voltage. This formula is simple, but its accuracy is sufficient for the sequential connection of 1-5 low-current LEDs.

Important. To protect the circuit from voltage drops and pulse transients, the capacitor to be extinguished must be selected from an operating voltage of at least 400 V.

The capacitor is better than a ceramic ceramic type K73-17 with an operating voltage of over 400 V or an imported analogue. It is not possible to use electrolytic (polar) capacitors.

It is necessary to know

Golovne – don’t remember about safety equipment. Submitted schemes to live in 220 In the middle of a changeable strum, they are given special respect at the hour of collection.

The LED connections may be in clear accordance with the circuit diagram. Changes in circuits or inconsistencies can lead to short circuits or failure of operation of other parts.

It is important to remember to collect transformer-free life-saving devices so that the stench does not disturb the galvanic isolation from the circuit. The finished circuit can be reliably isolated from all metal parts and protected from the vault. It can only be dismantled if the voltage is applied.

A small experiment

To lighten up the tedious schemes a little, it is worthwhile to get acquainted with a small experiment that will be useful both for radio amateurs and advanced masters.

Rozrakhunok emnіsnogo support

The table shows the appropriate support X from the capacitor C extinguishes at a frequency of 50 Hz and the average value of the stream I medium, which is passed by the capacitor C extinguishing, calculated for the same time, if R n = 0, then in case of a short circuit the voltage is applied. (Even under this anomalous regime, the BTBP robot is not sensitive, and this is another great advantage over transformer life units.)

Other values of the amnesic support X s (in klomah) and the average value of the struma I avg (in milliamps) can be calculated using the formulas:

Extinguish - the capacity of the capacitor to be extinguished, in microfarads.

If you turn on the zener diode VD2, then the voltage U n on the vantage and the string I n through it is dependent on the vantage R n. It’s easy to figure out these parameters using the formulas:

U n - in volts, R n i X n - in kiloohms, I n - in milliamperes, C gas - in microfarads. (Following on, the formulas are based on the units themselves.)

With changes in the support, the voltage on it also changes, and at a non-linear level. And the axis of the strum, which passes through the navantazhenya, is growing, although not significantly. So, for example, a change in R n from 1 to 0.1 kOhm (exactly 10 times) leads to the fact that U n decreases by 9.53 times, and the flow through the vantage increases by 1.05 times. This “automatic” stabilization of the struma clearly improves the TBBP. type of transformer cores.

The tightness of Pn on the avantage, which is calculated using the formula:

With changes, R n decreases as intensely as i U n. For the same butt, the increased tension changes by 9.1 times.

The fragments of the strum I n are attracted at relatively small values, the support R n and the stress U n on it changes very little, it is practically entirely permissible to use the following formulas:

By updating the VD2 zener diode, we see voltage stabilization U n equal to U st - a value that is practically constant for the skin specific zener diode. І with a small avantage (great support R n) the equality U n = U art.

Rozrakhunok support navantazhennya

To what extent can R n be changed so that the equality of U n = U st is fair? Until then, until the unrest ends:

Also, if the pressure on the vantage appears to be less than the cost of Rn, the voltage on the vantage will no longer be equal to the stabilization voltage, but will appear less, the fragments of the streams through the zener diode VD2 will fall.

Disruption of permissible flow through a zener diode

And now it is important, which strum I flows through the direction of R n and which strum - through the zener diode VD2. I realized that

In the world, the support of the vantagement has changed and the tension P n = I n U n = U 2 st / R n increases. And the middle axis is compressed by the BPTP, the tension is equal

becomes unchangeable. This is explained by the fact that the strum I medium is divided into two - I n and I st - i, along with the vantage support, is redistributed between R n and the zener diode VD2, and so, the fewer the vantage supports R n, the smaller the strum goes through a zener diode, And by chance. This means that since the demand is small (or all day), the VD2 zener diode is used in the most important minds. However, it is not recommended to remove the pressure from the BPTP, otherwise the entire flow will go through the zener diode, which can lead to it going out of tune.

The amplitude of the voltage at the edge is 220 · 2 = 311 (V). An impulse of a higher value stream into the lanzyug, if you can mentally equip a capacitor with f can reach

Apparently, the zener diode VD2 is responsible for reliably venturing this pulse stream in the event of a sudden surge. Do not forget about the possible voltage changes in the lightening range, so that it becomes 20...25% of the nominal value, and dissolve the flow, so that it passes through the zener diode when the voltage is turned on with the corrections corrected. new coefficient 1.2...1.25.

There is no pressure zener diode

If there is no zener diode of the required voltage, it can always be replaced with a diode-transistor analogue. Ale todi BTBP will follow the circuit shown in Fig. 2. Here the stream that flows through the zener diode VD2 changes proportionally to the static transmission coefficient of the stream of the base of the pressurized n-p-n transistor VT1. The voltage of the UCT analogue will be approximately 0.7V higher than the U st of the smallest voltage zener diode VD2, if the transistor VT1 is silicon, and by 0.3V if it is germanium.

Here you can install a transistor with a p-n-p structure. However, you can also use the circuit shown in Fig. 3.

Layout of a single-phase block

The order with double-phase rectifier in BTBP is different from stagnation and the simplest single-phase (Fig. 4). In this case, it is necessary for R not to live on the positive aspects of the alternating stream, and the negative ones pass through the VD3 diode, bypassing the influence. Therefore, the average flow I medium through the diode VD1 will be twice as small. This means that when expanding the block, replace X with the trace of the double-larger support that is more expensive

and the middle stream with a closed short avantage is 9.9·πС extinguishment = 31.1 С extinguishing. Further development of this version of the BPTP is carried out in absolutely the same way until the forward phases.

Voltage loss on the capacitor, what to extinguish

It is taken into account that with a voltage of 220V, the nominal voltage of the capacitor must be extinguished, but not less than 400V, then with approximately a 30-hundred-hundredth margin in relation to the amplitude of the edge, leaving 1.3 311 = 404(B). However, in the most common cases, the nominal voltage ranges between 500 and 600 V.

I still. When selecting a secondary capacitor, it is not possible to install capacitors of the type MBM, MBPO, MBGP, MBGC-1, MBGC-2 in the BTBP, as the remains of the stench are not insured for work in lancets. amplitude voltage values exceeding 150V.

It is most reliable for BTBP to operate capacitors MBGCh-1, MBGCh-2 at a nominal voltage of 500V (such as old power machines, fluorescent lamps, etc.) or KBG-MN, KBG-MP, or at a nominal voltage of 1 000V.

Filter capacitor

Capacity of the filter condenser It is important to open the analytical solution. Therefore, they are selected experimentally. It is important to note that per milliampere of average compressed current it is necessary to take at least 3...10 µF of the capacitance, since the BTBP rectifier is double-current, or 10... 30 µF, as it is single-phase.

The nominal voltage of the vicorized oxide capacitor C f must be no less than U st. And since there is no zener diode in the BTBP, and the voltage is switched on continuously, the nominal voltage of the capacitor that filters must exceed the values:

Since the vanation cannot be switched on continuously, and the zener diode, the nominal voltage of the capacitor that filters, must become more than 450V, which is hardly acceptable due to the large dimensions of the capacitor C f. Before the speech, in which case it would be possible to reconnect the trace after disconnecting the BTBP from the border.

And that's not all

Regardless of the possible options, the BTBP must be supplemented with two additional resistors. One of them, which can be in the range of 300 kOhm...1 MOhm, is connected in parallel with the capacitor 3. This resistor is required to accelerate the discharge of the capacitor C after the device is turned off. The second one - ballast - with a support of 10...51 Ohm is switched on at the opening of one of the edge wires, for example, in series with the capacitor. This resistor is interconnected through the diode bridge VD1 at the moment of connecting the BTBP to the junction. The voltage of both resistors must be at least 0.5 W, which is required to guarantee against possible surface breakdowns of these resistors at high voltage. For the balance of the ballast resistor, the zener diode will have a little less pressure, but in the middle of the BTBP the pressure will increase significantly.

How to take it

The function of the double-phase rectifier BTBP is shown in the diagrams in Fig. 1...3 can be combined with the same assemblies of the KTs405 or KTs402 series with letter indices J or I, since the middle flow does not exceed 600 mA, or with indices A, B, since the mean flow reaches 1 A .Attached also to the adjacent diodes included in bridge circuit, for example the KD105 series with indexes B, V abo R, D226 B abo V - up to 300 mA, KD209 A, B abo V - up to 500 ... 700 mA, KD226 V, G abo D - up to 1.7 A .

Diode VD1 and VD3 for BTBP according to the diagram in Fig. 4 can buti be what they are because of the overinsurance of the property. It is also permissible to use two separate assemblies KD205K V, G or D for distribution to the strum up to 300 mA or KD205 A, V, J or I - up to 500 mA.

I will stay. The transformerless life block, as well as the equipment, is connected to the new one, connected directly to the limit of the changeable flow! The reason for the stink is the reliably insulated bells, say, placed in a plastic case. In addition, it is strictly forbidden to “ground” any of their pins, as well as open the housing when the device is closed.

The proposed method for dissolving the BPTP was tested by the author over a number of years. The whole process is carried out based on the fact that the BPTP is essentially a parametric voltage stabilizer, in which the role of intermediary is played by the capacitor, which is extinguished.

Magazine "SAM" No. 5, 1998

In the case of built-in edge blocks, the radio amplifiers use capacitors instead of step-down transformers Balastovikh, extinguishing excess voltage (Fig. 1).

A non-polar capacitor, switched on at the edge of the exchangeable structure, acts as a support, but instead of a resistor, does not dissipate the tension that disappears in the form of heat, which allows you to design a compact power supply unit, lightweight and cheap. The oscillatory operation of a capacitor at frequency f is described by the expression:

The value of the capacitance of the ballast capacitor Cb is calculated with sufficient accuracy using the following formula:

de U c - voltage limits;

I N - Strum navantazhennya, A;

U H - voltage at the front, V. If U H is in the range of 10 to 20 V, then for decomposition it is a very pleasant expression:

Substituting the values of U c = 220 and U H = 15 V, with I n = 0.5 A, we obtain the values Sb = 7.28 μF (1) і Sb = 7.27 μF (2). For both varieties, you can get a decent amount, especially if you boil it so that the capacity must be rounded to the nearest value. It is best to select capacitors from the K73-17 series with an operating voltage not lower than 300 V.

When using this circuit, you first need to remember that it is galvanically connected to the circuit, and you risk being hit by an electric shock with voltage potential. In addition, before installing a transformer-free device, be sure to carefully connect the vibrating equipment or any additional devices, otherwise you may end up with fireworks that are not at all Yuletide.

To liven up low-voltage devices, it is better to install step-down transformers. If the voltage of the secondary winding does not correspond to the necessary voltage (overextends), then it is safe to completely insert the capacitor, which is to be extinguished, into the lance of the primary winding of the transformer to reduce the voltage or to turn on the transformer with a low-voltage primary winding in to the measure (Fig. 2) The ballast capacitor is selected in this form from the design, so that at maximum pressure the output voltage of the transformer matches the specified one.

Literature

1. Biryukov S.A. Microcircuit devices. - M., 2000.

I. SEMENOV,

m. Dubna, Moscow region.

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