3W LED driver. Homemade Driver for Powerful LEDs. What differences between the driver for LEDs and the power supply for LED tape

Recently, consumers are increasingly interested in LED lighting. The popularity of LED lamps is quite substantiated - the new technology of lighting does not allocate ultraviolet studies, economical, and the life of such lamps is more than 10 years. In addition, with LED elements in domestic and office interiors, it's easy to create original light textures on the street.

If you decide to purchase such devices for your home or office, then you should know that they are very demanding to the parameters of the power grid. For optimal lighting operation, you will need a LED driver. Since the construction market is filled with devices of both different quality and pricing policies, before purchasing LED devices and a power supply to them, will not be superfluous with the main advice that specialists give in this matter.

To begin with, consider what such a device is needed as a driver.

What is the purpose of the drivers?

The driver (power supply) is a device that performs the functions of the current stabilization flowing through the LED circuit, and is responsible for the device you purchased to work out the number of hours. When selecting a power unit, it is necessary to begin to thoroughly examine its output characteristics, among which the current, voltage, power, efficiency (efficiency), as well as the degree of it to protect the effect of external factors.

For example, the brightness of the LED depends on the passage characteristics of the current. The digital stress designation reflects the range in which the driver functions with possible voltage jumps. And of course, the higher the efficiency, the more effectively the device will work, and its life will be more.

Where are the LED drivers apply?

The electronic device - the driver - is usually powered by a 220V electrical network, but is designed to work with very low voltage B10, 12 and 24V. The range of working output voltage, in most cases, is from 3B to several dozen volts. For example, you need to connect seven LEDs with voltage 3B. In this case, the driver is required with an output voltage from 9 to 24V, which is designed for 780 mA. Please note that despite the versatility, such a driver will have a small efficiency, if you give it a minimum load.

If you need to install lighting in a car, insert a lamp into a bike head, a motorcycle, one or two small street lamps or a manual flashlight, nutrition from 9 to 36V will be quite enough.

LED - Powerfuls will need to choose if you intend to connect the LED system consisting of three or more devices, on the street, chose it to design your interior, or you have desktop office lamps that work at least 8 hours a day .

How does the driver work?

As we have already told, LED - the driver acts as a source of current. The voltage source creates some voltage at its output, ideally independent of the load.

For example, connect to a voltage of 12 to the resistor 40 Ohm. Through it will go the current of 300mma.

Now we will turn on two resistors at once. The total current will be already 600mA.

The power supply supports the specified current at its output. Voltage can change. Connect the same resistor 40 to the 300mA driver.

The power supply will create a 12V voltage drop on the resistor.

If you connect parallel to two resistors, the current will also be 300mA, and the voltage will fall twice.

What are the main characteristics LED - Drivers?

When selecting the driver, be sure to pay attention to parameters such as output voltage, power consumed power (current).

- the voltage at the outlet depends on the voltage drop on the LED; the number of LEDs; From the method of connection.

- The current at the output of the power supply is determined by the characteristics of the LED and depends on their power and brightness, quantity and color solutions.

Let us dwell on the color characteristics of LED - lamps. From this, the load power depends on the word. For example, the average power consumption of a red LED varies within 740 MW. In green, the average power will be about 1.20 W. Based on this data, you can calculate in advance which power you will need the driver.

P \u003d PLED X N

where PLED is the power of LED, N is the number of connected diodes.

Another important rule. D.in a stable operation of the power supply of power, the power supply should be at least 25%. That is, the following ratio should be performed:

PMAX ≥ (1.2 ... 1.3) XP

where Pmax is the maximum power supply power.

How to connect LED-LED?

Connect LEDs in several ways.

The first method is a consistent introduction. Here you will need a driver with voltage of 12V and a current of 300mA. With this method, the LEDs in the lamp or on the tape are in the same way bright, but if you decide to connect a larger number of LEDs, you will need a driver with a very large voltage.

The second method is a parallel connection. We will fit the power supply to 6B, and the current will be consumed approximately twice as much as with a sequential connection. There is a disadvantage - one chain can shine brighter than the other.

Consecutive-parallel compound - occurs in spotlights and other powerful luminaires, and from constant, and from alternating voltage.

Fourth way - the driver is connected sequentially two. It is the least preferable.

There is also a hybrid option. He combined the dignity from the serial and parallel connection of the LEDs.

Specialists advise the driver to choose before you buy LEDs, and it is also desirable to pre-determine the circuit of their connection. So the power supply will work to work more effectively.

Linear and impulse drivers. What are their principles of work?

Today for LED lamps and tapes produce linear and pulse drivers.
The linear output serves as a current generator that provides stabilization of the voltage without creating electromagnetic interference. Such drivers are easy to use and not expensive, but the low efficiency limits their scope.

Pulse drivers, on the contrary, have a high efficiency (about 96%), and even compact. The driver with such characteristics is preferable to use for portable lighting devices, which allows you to increase the power supply time. But there is a minus - due to the high level of electromagnetic interference, it is less attractive.

Do you need a LED driver for 220v?

To turn on the 220V network, linear and pulse drivers are available. In this case, if the power supplies have galvanic junction (power transmission or signal between electrical circuits without electrical contact between it), they demonstrate a high efficiency, reliability and safety in operation.

Without electroplating, the power supply will cost you cheaper, but it will not be so reliable, it will take care when connecting due to the danger of impact shock.

When selecting power parameters, experts recommend to stop their choice on LED drivers with a power exceeding the required minimum by 25%. Such a power supply will not give an electronic device and a supply device to quickly fail.

Should I buy Chinese drivers?

Made in China - Today you can meet hundreds of drivers of various characteristics produced in China. What do they imagine? These are mainly devices with a pulse source of current by 350-700mA. The low price and the presence of galvanic junction allow such drivers to be in demand from buyers. But there are disadvantages of the Chinese assembly. Often they do not have the case, the use of cheap elements reduces the driver's reliability, and there is also no protection against overheating and oscillations in the power grid.

Chinese drivers, like many products manufactured in Middle Kingdom, are short-lived. Therefore, if you want to set a high-quality lighting system that will serve you for one year, it is best to buy a transducer for LEDs from a proven manufacturer.

What is the service life of the LED driver?

Drivers, like any electronics, have their own service life. The warranty service life of the LED - driver is 30,000 hours. But do not forget that the operation time of the device will depend on the instability of the network voltage, the level of humidity and temperature drop, the effect on it by external factors.

Incomplete loading driver also reduces the life of the device. For example, if the LED is designed for 200W, and runs on the load 90W, half of its power returns to the electrical network, causing it overload. It provokes frequent power failures and the device can overcome, losing you just a year.

Follow our tips and then you do not have to change the LED devices.

The standard RT4115 LED driver diagram is shown in the figure below:

The supply voltage must be at least 1.5-2 volts are higher than the total voltage on the LEDs. Accordingly, in the range of supply voltages from 6 to 30 volts, from 1 to 7-8 LEDs can be connected to the drive.

Maximum microcircuit voltage 45 VBut the work in this mode is not guaranteed (better pay attention to the similar chip).

The current through the LEDs has a triangular shape with a maximum deviation from the mean value of ± 15%. The average current through the LEDs is defined by the resistor and is calculated by the formula:

I LED \u003d 0.1 / R

The minimum allowable value r \u003d 0.082 ohms, which corresponds to the maximum current 1.2 A.

The deviation of the current through the LED from the calculated does not exceed 5%, subject to the installation of the resistor R with a maximum deviation from the nominal value of 1%.

So, to turn on the LED to a constant brightness, the output of DIM leave hanging in the air (it inside PT4115 is pulled up to the level of 5V). At the same time, the current at the outlet is determined exclusively by the resistance of R.

If there is a capacitor between the derivation of DIM and the "Earth", we get the effect of smooth ignition of LEDs. The maximum brightness time will depend on the capacitance of the capacitor than it is more, the longer the lamp will flare up.

For reference: Each nanofarade of the capacitance increases the inclusion time by 0.8 ms.

If you want to make a dimmable driver for LEDs with brightness adjustment from 0 to 100%, then you can resort to one of two ways:

1. First method It assumes the submission of a DIM voltage in the range in the range from 0 to 6B. In this case, the brightness adjustment from 0 to 100% is carried out at a voltage at the DIM output from 0.5 to 2.5 volts. The increase in voltage above 2.5 V (and up to 6 V) does not affect the current through the LEDs (the brightness does not change). On the contrary, a decrease in voltage to the level of 0.3B or below leads to a disconnection of the circuit and translating it into standby mode (current consumption current drops to 95 μA). Thus, you can effectively manage the driver without removing the supply voltage.
2. Second way It implies the signal from the latitude-pulse converter with an output frequency of 100-20000 Hz, the brightness will be determined by the filling coefficient (pulse duty). For example, if a high level is kept 1/4 part of the period, and a low level, respectively, 3/4, then it will correspond to a brightness level of 25% of the maximum. It is necessary to understand that the driver's frequency is determined by the inductance of the throttle and in any way depends on the dimming frequency.

PT4115 LED driver diagram with a permanent voltage brightness regulator is shown below:

Such a diagram of adjusting the brightness of the LED works perfectly due to the fact that inside the chip output DIM "tighten" to the bus 5B through the resistance resistor 200 com. Therefore, when the potentiometer slider is in the extreme lower position, the voltage divider 200 + 200 kΩ is formed and the DIM output is formed by the potential 5/2 \u003d 2.5V, which corresponds to a 100% brightness.

How the scheme works

At first point, when the input voltage is applied, the current via R and L is zero and the output key built into the chip in the chip is open. The current through the LEDs begins to grow smoothly. The rate of increasing current depends on the value of inductance and supply voltage. The intrahemum comparator compares the potentials before and after the resistor R and, as soon as the difference is 115 mV, a low level appears at its output, which closes the output key.

Due to the energy stored in the inductance, the current through the LEDs does not disappear instantly, but begins to decrease smoothly. Gradually decreases the voltage drop on the R Resistor. As soon as it reaches a value of 85 mV, the comparator will again display a signal to open the output key. And the whole cycle is repeated first.

If you need to reduce the scope of current ripples through LEDs, it is allowed to connect the capacitor parallel to LEDs. The more its capacity will be, the stronger the triangular shape of the current will be smoothed through the LEDs and the more it will become similar to the sinusoidal. The capacitor does not affect the operating frequency or the efficiency of the driver, but increases the time of setting the specified current through the LED.

Important assembly nuances

An important element of the scheme is C1 condenser. It does not just smooth the pulsation, but also compensates for the energy accumulated in the inductance coil at the time of closing the output key. Without C1 stored in the throttle, energy will go through the Schottky diode on the power supply and can trigger the microcircuit. Therefore, if you enable the driver without a capacitor feeding, the microcircuit is almost guaranteed. And the greater the inductance of the choke, the greater the chance to burn Mikruch.

The minimum capacitance of the capacitor C1 is 4.7 of the ICF (and when powering the circuit with a pulsating voltage after a diode bridge - at least 100 μF).

The capacitor should be located as close as possible to the chip and have as low as possible ESR (i.e., tantalum clubs are welcome).

It is also very important to accommodately approach the choice of the diode. It must have a small direct voltage drop, a short recovery time during switching and stability of parameters with an increase in the temperature of the P-N of the transition to prevent the leakage current to increase.

In principle, it is possible to take an ordinary diode, but best for these requirements are suitable Schottky diodes. For example, STPS2H100A in SMD version (direct voltage 0.65V, reverse - 100V, current in the pulse up to 75a, operating temperature up to 156 ° C) or FR103 in the DO-41 case (reverse voltage up to 200V, current to 30a, temperature up to 150 ° C). The common SS34 was well shown very well, which can be pushed from old boards or buy a whole pack for 90 rubles.

The inductance of the throttle depends on the output current (see the table below). The incorrectly selected value of inductance can lead to an increase in power dissipated on the microcircuit and output beyond the working temperature mode.

When overheating above 160 ° C, the chip will automatically turn off and will be in the off state until it cools up to 140 ° C, after which it starts automatically.

Despite the available tabular data, the installation of the coil with the deviation of the inductance is allowed to a large side of the nominal. This changes the efficiency of the whole scheme, but it remains workable.

The throttle can be taken by the factory, but you can make it yourself from the ferrite ring from the burnt motherboard and the wires of PAL-0.35.

If the maximum autonomy of the device is important (portable lamps, lights), then, in order to increase the efficiency of the scheme, it makes sense to spend time on careful selection of choke. At small currents, inductance should be greater to minimize current control errors arising due to delay when switching transistor.

The throttle should be located as close as possible to the output SW, ideally - is connected directly to it.

And, finally, the most precise element of the LED driver circuit - Resistor R. As already mentioned, its minimum value is 0.082 ohms, which corresponds to 1.2 A.

Unfortunately, it is not always possible to find a resistor of a suitable nominal value, so it's time to recall the formulas for calculating the equivalent resistance with a sequential and parallel inclusion of resistors:

• R Ambulance \u003d R 1 + R 2 + ... + R n;
• R pairs \u003d (R 1 xr 2) / (R 1 + R 2).

Combining various ways to inclusion, you can get the required resistance from several existing resistors.

It is important to breed a fee so that the Schottky diode current does not proceed along the path between R and VIN, as this can lead to the errors of the load current measurement.

Low cost, high reliability and stability of the driver characteristics on the RT4115 contributes to its widespread use in LED lamps. Almost every second 12-volt LED lamp with the MR16 base is collected on PT4115 (or CL6808).

Resistance to the current resistor (in Omach) is calculated exactly according to the same formula:

R \u003d 0.1 / I LED [A]

Typical inclusion scheme looks like this:

As you can see, everything is very similar to the LED lamp diagram on the RT4515. Description of work, signal levels, features of the elements used and the printed circuit board layouts are exactly the same as y, therefore it does not make sense to repeat.

CL6807 Sell on 12 rubles / pcs, you just need to look, so that you do not slip soldering (I recommend to take).

SN3350.

SN3350 - another inexpensive microcircuit for LED drivers (13 rubles / thing). It is almost a complete analogue of PT4115 with the only difference that the supply voltage can lie in the range from 6 to 40 volts, and the maximum output current is limited to 750 millias (long current should not exceed 700 mA).

Like all of the above chips, SN3350 is a pulsed step-down converter with the output current stabilization function. As usual, the current in the load (and in our case, one or several LEDs protrudes in the role of load) is set by the resistor resistance R:

R \u003d 0.1 / I LED

In order not to exceed the maximum output current value, the resistance R should not be below 0.15 ohms.

The chip is produced in two housings: SOT23-5 (maximum 350 mA) and Sot89-5 (700 mA).

As usual, feeding a constant voltage to the ADJ output, we turn the circuit to the simplest adjustable driver for LEDs.

A feature of this microcircuit is a slightly different adjustment range: from 25% (0.3B) to 100% (1.2V). When the potential decreases at the output of ADJ to 0.2V, the microcircuit goes into sleep mode with consumption in the area of \u200b\u200b60 μA.

Typical inclusion scheme:

For details, see the specification on the chip (PDF file).

ZXLD1350.

Despite the fact that this chip is another clone, some differences in technical specifications do not allow them to replace them with each other.

Here are the main differences:

• the microcircuit starts at 4.8V, but the normal mode of operation is released only at a supply voltage from 7 to 30 volts (half a second is allowed to be supplied to 40V);
• maximum load current - 350 mA;
• the resistance of the output key in the open state - 1.5 - 2 Ohm;
• by changing the potential on the output of ADJ from 0.3 to 2.5V, the output current (brightness of the LED) can be changed in the range from 25 to 200%. At a voltage of 0.2V for at least 100 μs, the driver goes into sleep mode with low power consumption (about 15-20 μA);
• if the adjustment is carried out by the PWM signal, then at the frequency of the pulses below 500 Hz, the range of brightness change is 1-100%. If the frequency is above 10 kHz, then from 25% to 100%;

The maximum voltage that can be supplied to the brightness adjustment (ADJ) input is 6B. At the same time in the range from 2.5 to 6V, the driver issues the maximum current, which is set by a current-limitary resistor. Resistance to the resistor is calculated in the same way as in all of the above chips:

R \u003d 0.1 / I LED

The minimum resistance of the resistor is 0.27 ohms.

The type of inclusion scheme does not differ from their fellow:

Without a C1 capacitor, it is impossible to feed food !!! At best, the microcircuit will overheat and issue unstable characteristics. In the worst case - instantly fails.

More detailed characteristics of ZXLD1350 can be found in the datashitis on this chip.

The cost of the chip is unreasonably high (), though the output current is quite small. In general, strongly on an amateur. I would not bind.

QX5241.

QX5241 is a Chinese analogue MAX16819 (MAX16820), but in a more convenient building. Also available under the names KF5241, 5241B. It has labeling "5241a" (see photo).

In one famous store they sell them almost on the weight (10 pieces for 90 rubles).

The driver works at exactly the same principle as all of the above (reduced continuous converter), but does not contain an output key, so the external field transistor is required to connect.

You can take any N-channel MOSFET with a suitable flow current and voltage of stock source. For example, such as: SQ2310ES (up to 20V !!!), 40N06, IRF7413, IPD090N03L, IRF7201. In general, the lower the discovery voltage, the better.

Here are some key characteristics of the LED drivers for QX5241:

• maximum output current - 2.5 A;
• Efficiency up to 96%;
• the maximum dimming frequency is 5 kHz;
• maximum operating frequency of the converter - 1 MHz;
• accuracy of current stabilization through LEDs - 1%;
• supply voltage - 5.5 - 36 volts (normally works at 38!);
• the output current is calculated by the formula: R \u003d 0.2 / I LED

Read more in the specification (on ingle).

The LED driver on QX5241 contains little details and is always assembled by such a scheme:

The chip 5241 is only in the SOT23-6 housing, so that with a soldering iron for soldering the saucepan, it is better not to fit. After installation, the fee should be thicker to rinse from flux, any incomprehensible contamination can adversely affect the microcircuit mode.

The difference between the power supply voltage and the total voltage drop on diodes should be volt 4 (or more). If less, there are some glitches in the work (current instability and throttle whistling). So take with a margin. Moreover, the larger the output current, the greater the supply of voltage. Although, perhaps, I just got an unsuccessful copy of the microcircuit.

If the input voltage is less than the overall drop on the LEDs, the generation is broken. At the same time, the yield is fully open and the LEDs are glowing (naturally, not at full power, as the voltages are not enough).

Al9910.

Diodes Incorporated has created one very interesting LED driver chip: AL9910. It is curious that its working voltage range allows you to connect it directly to the 220V network (through a simple diode rectifier).

Here is its main characteristics:

• input voltage - up to 500V (up to 277V for a change);
• built-in voltage stabilizer for nutritional nutrition that does not require a quenching resistor;
• the ability to adjust brightness by changing the potential on the control foot from 0.045 to 0.25V;
• built-in overheating protection (operations at 150 ° C);
• the operating frequency (25-300 kHz) is set by an external resistor;
• to work, an external field transistor is needed;
• available in the eight hundred SO-8 and SO-8EP housings.

The driver assembled on the Al9910 chip does not have a galvanic junction with the network, so it should be used only where it is impossible to directly touch the elements of the circuit.

Each diode, in turn, is indicated in the description of the voltage drop at different currents. For example, for a red diode 660 nm at a current of 600 mA it will be 2.5 V:

The number of diodes that can be connected to the driver, the total drop in voltage should be laid at the driver's output voltage. That is, a 50W 600 mA driver with an output voltage of 60-83 V can be connected from 24 to 33 red diodes 660 nm. (I.e. 2.5 * 24 \u003d 60, 2.5 * 33 \u003d 82.5).

Another example:
We want to collect a bicolor lamp red + blue. Chose the ratio of red to blue 3: 1 and we want to calculate which driver you need to take for 42 red and 14 blue diodes. We believe: 42 * 2.5 + 14 * 3.5 \u003d 154 V. It means that we will need two drivers of 50 W 600 mA, each will have 21 red and 7 blue diodes, the total voltage drop on each will turn out to be 77 in that It falls into its output voltage.

Now a few important explanations:

1) Do not look for a driver with a power of more than 50 W: they are, but they are less effective than a similar set of less power drivers. Moreover, they will warmly warm, which will require additional costs of more powerful cooling. In addition to the TGU, the driver with a power of more than 50W is usually strongly more expensive, for example, a 100W driver can be more expensive than 2 drivers 50W. Therefore, it is not necessary to chase them. Yes, and more reliable when the circuits of the LED are divided into sections, if suddenly there is something overrigent - then it burns not all but only to do. Therefore, it is beneficial to divide into several drivers, and not strive to hang everything for one. Conclusion: 50W - the optimal option, no more.

2) The current drivers are different: 300 mA, 600 mA, 750 mA is the running. There are quite a lot of other options.
By and large, more efficient from the point of view of the efficiency on 1 W will be the use of a 300 mA driver, it will also not heat the LEDs strongly, and they will warm up less and last longer. But the main minus of such drivers that the diodes will work "crawled", and therefore they will be required about two times more than for analogue from 600 mA.
The driver with a current of 750 mA will feed the diodes at the limit of opportunities, so the diodes will warm very much, and they will need very powerful, well-thought-out cooling. But even despite this, in any case they degrade from overheating before the average life of the LED LED lamps, for example, 500-600 mA.
Therefore, we recommend using drivers with a current of 600 mA. They are obtained by the most optimal solution in terms of the ratio of price-efficiency-service life.

3) the power of the diodes is indicated nominal, that is, the maximum possible. But they are never powered at maximum (why - see clause 2). The real power of the diode is easy to calculate: you need a current of the driver used to multiply the diode voltage drop. For example, when connecting a driver by 600 mA to a red diode 660 nm we obtain the actual voltage on the diode: 0.6 (a) * 2.5 (B) \u003d 1.5 W.

The advantages of LED paws were considered repeatedly. The abundance of positive feedback of users of LED lighting will causes them to think about the own bulbs of Ilyich. Everything would be nice, but when it comes to the calculation of the re-equipment of the apartment on the LED lighting, the numbers are slightly "strained."

To replace an ordinary lamp on 75W, there is a LED light bulb for 15W, and such lamps need to be changed a dozen. With an average cost of about 10 dollars per lamp, the budget is decent, and it is also impossible to exclude the risk of acquiring the Chinese "clone" with a life cycle of 2-3 years. In the light of this, many consider the possibility of independent manufacture of these devices.

220V LED Power Theory

The most budget option can be collected with your own hands from these LEDs. A dozen such baby costs less than a dollar, and in brightness corresponds to the incandescent lamp by 75W. It is not a problem to collect all together, that's just you can not connect them directly - burned. The heart of any LED lamp is the power driver. It depends on how long the light bulb will shine.

To collect the LED lamp with their own 220 volts, we will understand in the power driver diagram.

Network parameters greatly exceed the needs of the LED. Whatever the LED can work from the network, it is necessary to reduce the amplitude of the voltage, current strength and convert the variable voltage of the network to constant.

For these purposes, a voltage divider with resistor or capacitive load and stabilizers are used.

Components of a diode lamp

The 220 volt LED lamp circuit will require a minimum amount of available components.

• LEDs 3.3V 1W - 12 pcs.;
• ceramic condenser 0.27MKF 400-500V - 1 pc.;
• 500Kom resistor - 1m 0.5 - 1W - 1 sh.
• 100V diode - 4 pcs.;
• electrolytic capacitors for 330MKF and 100MKF 16V 1 pcs.;
• voltage stabilizer to 12V L7812 or similar - 1pc.

Manufacture of LED drivers for 220V do-it-yourself

The layout of the ice driver for 220 volts is nothing but a pulse power supply.

As a homemade LED driver from a 220V network, we consider the simplest pulse power supply without galvanic junction. The main advantage of such schemes is simplicity and reliability. But be careful when assembling, since this scheme has no limit on the current current. The LEDs will select their last amps of the ampere, but if you are touched by the curtain wires with your hand, the current will reach a dozen amp, and such a current is very tangible.

The circuit of the simplest driver for 220V LEDs consists of three main cascades:

• Voltage divider on the capacitance resistance;
• diode bridge;
• tension stabilization cascade.

First Cascade - Capacitive resistance on the C1 condenser with a resistor. The resistor is necessary for self-discharge of the capacitor and does not affect the operation of the diagram itself. Its nominal is not particularly critical and can be from 100 to 1m with a capacity of 0.5-1 W. The capacitor is necessarily not electrolytic at 400-500V (efficient amplitude voltage of the network).

With the passage of the half-wave voltage through the capacitor, it skips the current until the hoist charge occurs. The smaller its capacity, the faster the full charge occurs. With a capacity of 0.3-0.4 mpq. Charging time is 1/10 of the network voltage half-wave period. In simple language, only a tenth of the incoming voltage will pass through the condenser.

Second Cascade - diode bridge. It converts alternating voltage to constant. After cutting off most of the half-wave voltage by the capacitor, at the outlet of the diode bridge we get about 20-24V DC.

Third Cascade - smoothing stabilizing filter.

The capacitor with a diode bridge perform a voltage divider function. When the voltage changes in the network, the amplitude will also change at the outlet of the diode bridge.

To smooth the voltage pulsation parallel to the circuit, connect the electrolytic capacitor. Its container depends on the power of our load.

In the driver diagrater, the supply voltage for LEDs should not exceed 12V. As a stabilizer, you can use the distributed element L7812.

The collected scheme of the LED lamp by 220 volts starts to work immediately, but before turning onto the network, it is thoroughly insulating all the bare wires and places of the soldering of the schema elements.

Driver Option without current stabilizer

There is a huge number of drivers for LED drivers from a 220V network, which do not have current stabilizers.

The problem of any non-versionable driver is the pulsation of the output voltage, therefore, the brightness of the LEDs. The capacitor installed after the diode bridge partially copes with this problem, but it decides not completely.

On diodes there will be a pulsation with an amplitude of 2-3B. When we set the stabilizer to 12V into the scheme, even taking into account the pulsation of the amplitude of the incoming voltage will be higher than the clipping range.

Voltage diagram in scheme without stabilizer

Diagram in a scheme with a stabilizer

Therefore, the driver for diode lamps, even assembled with her own hands, in the level of ripples will not give up similar nodes of expensive lamps of factory production.

As you can see, collect the driver with your own hands does not represent much difficulty. By changing the parameters of the schema elements, we can vary the output values \u200b\u200bwidely.

If you have a desire based on such a scheme to assemble a 220 volt LED scheme, it is better to remake the output cascade of 24V voltage with the corresponding stabilizer, since the output current in L7812 1,2A, it limits the load capacity of 10W. For more powerful sources of lighting, it is required to either increase the number of output cascades, or use a more powerful stabilizer with output current to 5a and install it on the radiator.

POWTECH microcircuit PT4115 continues to earn positive feedback among Russian radio amateurs. A little-known Chinese manufacturer managed to accommodate several control units in the compact package with a powerful transistor at the output. The chip is designed to stabilize current and power LEDs with a capacity of more than 1 W. The PT4115-based driver has a minimal strapping and high efficiency. Make sure this article will help to know about the intricacies of the selection of elements of the concept of the concept.

Short description chip PT4115

According to the official documentation, the LED driver with the function of dimming based on PT4115 has the following technical characteristics:

• range of working input voltage: 6-30V;
• adjustable output current up to 1,2A;
• the error of the stabilization of the output current of 5%;
• there is protection against load cliff;
• there is an output for adjusting brightness and turn on / off using DC or PWM;
• switching frequency up to 1 MHz;
• Efficiency up to 97%;
• it has an efficient body, in terms of power dissipation.

Put4115 conclusions:

1. SW. Output switch (MOS transistor), which is connected directly to its drain.
2. GND. The total output of the signal and power supply of the scheme.
3. Dim. Login to task the dimming.
4. CSN. Entry from the current sensor.
5. Vin. Power voltage output.

The PT4115 chip has a separate output to control the on and off of LEDs, as well as the possibility of adjusting the brightness by changing the voltage level or PWM on the DIM output.

Concept of Driver

The figure shows two software schemas for 3W LED based on PT4115. The first circuit is powered by a direct current source of 6 to 30 volts. The second scheme complements the diode bridge, it feeds it with a source of alternating current with a voltage of 12-18V.

An important element of both schemes is a C-in capacitor. It is not easy smoothes ripples, but also compensates for energy accumulated in inductance coil at the time of closing the key (MOS transistor). Without with in in inductive energy through the Schottki Diode D will go out on the VIN output and provokes a breakdown of nutrition chip. Therefore, the turning on the driver without the input capacitor is strictly prohibited.

The inductance L is selected based on the number of LEDs and current in the load.

According to the documentation, the driver for 3 cotton LEDs is recommended to use inductance by 68-220 μH.

Despite the available tabular data, it is allowed to install the coil with the deviation of the nominal inductance in the large direction. This reduces the efficiency of the whole scheme, but the scheme remains operational. At small currents, inductance should be greater to compensate for pulsations arising due to a delay when switching transistor.

The R S resistor performs the function of the current sensor. At first point in time, when the input voltage is applied through R S and L is zero. Then the intrahemny CS compararator compares the potentials before and after the resistor R S and a high level appears at its output. Current in the load, due to the presence of inductance, it begins to grow smoothly to the value determined by R s. The speed of increasing current depends not only on the value of inductance, but also on the size of the supply voltage.

The driver operation is based on switching the comparator inside the chip, which constantly compares the voltage levels on In and CSN outputs. The deviation of the current through the LED from the calculated does not exceed 5%, subject to the installation of the resistor R S with a maximum deviation from the nominal value of 1%.

To turn on the LED on a permanent brightness, the output of the DIM remains not involved, and the output current is determined exclusively with the value of R s. Dimmation control (brightness) can be carried out by one of two options.
The first method assumes the flow of a constant voltage DIM in the range from 0.5 to 2.5V. At the same time, the current will change in proportion to the level of the potential at the derivation of the DIM. Further voltage growth, up to 5V, does not affect the brightness and corresponds to 100% current in the load. Reduced potential below 0.3V leads to a trip to the entire scheme. Thus, you can effectively manage the driver without removing the supply voltage. The second method implies the flow of the signal from the pulse transducer with an output frequency of 100-20000 Hz.

Build construction and details

The choice of elements located in the PT4115 chip strapping should be performed on the basis of the manufacturer's recommendations. As C In, it is recommended to use a low ESR capacitor (equivalent sequential resistance). This parameter is harmful and negatively affects the efficiency. When powered from a stabilized source, one input capacitor is suspicious of a capacity of at least 4.7 μF, which must be placed in the immediate vicinity of the chip. When powering from an AC source, Powtech indicates the need to install a tantalum capacitor with a capacity of more than 100 μF.

The Typical PT4115 Turning Scheme for 3W LED implies the installation of an inductance coil at 68 μH, it should be placed as close as possible to the output SW PT4115.

The inductor coil can be made with their own hands using the ring from the old computer and the wire PAL-0.35.

Special requirements are put forward to the Diode D: a small direct voltage drop, a small recovery time during switching and stability of parameters with the increase in the temperature of the P-N of the transition to prevent the leakage current to increase. These conditions correspond to Schottinka FR103, capable of withstanding current pulses up to 30a at temperatures up to 150 ° C.

Finally, the most precise element of the driver for 3W LED is a resistor R s. The minimum value of R s \u003d 0.082 ohms, which corresponds to current 1.2 A. It is calculated, based on the required current supply of the LED, according to the formula:

R s \u003d 0.1 / i LED, where I LED is the nominal value of the LED current, A.

In the inclusion scheme PT4115 for 3W LED, the value of R S is 0.13 ohms, which corresponds to the current of 780 mA. In stores it is not always possible to find a resistor of such a nominal. Therefore, we will have to recall the formulas for calculating the total resistance with a sequential and parallel inclusion of resistors:

• R Ambulance \u003d R1 + R2 + ... + R n;
• R pairs \u003d (R1xr2) / (R1 + R2).

Thus, it is possible to obtain the desired resistance of several low-level resistors with high accuracy.

In conclusion, I would like to once again emphasize the importance of current stabilization, and not the voltage to ensure the normal long-term operation of powerful LEDs. There are cases when in LEDs of Chinese origin, the current smoothly continues to grow for some time after switching on and stops at a value exceeding the passportal nominal value. This leads to overheating of the crystal and a gradual decrease in brightness. The driver for 3W LED on the PT4115 chip is a guarantee of stable light output in combination with high efficiency, subject to an effective heat removal from the crystal.

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