In order for LED lamps to work as brightly and efficiently as possible, special modules are used - drivers. Everyone can assemble a driver circuit for LEDs on their own, if, of course, there is knowledge in electrical engineering. The meaning of the device is to convert an alternating voltage flowing in the network into a constant (reduced) voltage. But before proceeding with the assembly, you need to determine what requirements are imposed on the device - analyze the characteristics and types of devices.
What are drivers for?
The main purpose of the drivers is to stabilize the current that passes through the LED. Moreover, it must be taken into account that the current flowing through the semiconductor crystal must be exactly the same as that of the LED on the passport. This ensures stable lighting. The crystal in the LED will last much longer. To find out the voltage required to power the LEDs, you need to use the current-voltage characteristic. This is a graph showing the relationship between supply voltage and current.
If you plan to carry out lighting with LED lamps in a residential or office building, then the driver must be powered from a household AC network with a voltage of 220 V. If the LEDs are used in automotive or motor vehicles, you need to use drivers powered by a constant voltage, the value is 9-36 V. In some cases (if the LED lamp is of low power and is powered by a 220 V network), it is allowed to remove the LED driver circuit. From the network, if the device is powered, it is enough to include a constant resistor in the circuit.
Driver options
Before you purchase a device or make it yourself, you need to familiarize yourself with what it has the main characteristics:
- Rated current consumption.
- Power.
- Output voltage.
The voltage at the output of the converter directly depends on which method of connecting the light source, the number of LEDs, is selected. The current is directly dependent on the brightness and power of the elements.
The converter must provide a current at which the LEDs will work with the same brightness. On the PT4115, the LED driver circuit is implemented quite simply - it is the most common voltage converter for use with LED elements. To make a device based on it can literally "on the knee".
Driver power
The power of the device is the most important characteristic. The more powerful the driver, the greater the number of LEDs you can connect to it (of course, you will have to carry out simple calculations). A prerequisite is that the driver power should be greater than all the LEDs in total. This is expressed by the following formula:
P = P (sv) x N,
where P, W - driver power;
P (sv), W - power of one LED;
N is the number of LEDs.
For example, when assembling a driver circuit for a 10W LED, you can safely connect LED elements with a power of up to 10 watts as a load. Be sure to have a small margin of power - about 25%. Therefore, if you plan to connect a 10 W LED, the driver must provide a power of at least 12.5-13 watts.
LED colors
Be sure to consider what color the LED emits. It depends on what kind of voltage drop they will have at the same current strength. For example, with a supply current of 0.35 A, the voltage drop of the red LED elements is about 1.9-2.4 V. The average power is 0.75 watts. A similar model with green will already have a drop in the range of 3.3-3.9 V, and a power of 1.25 watts. Therefore, if you use a 220V LED driver driver circuit with conversion to 12 V, you can connect a maximum of 9 elements with green or 16 with red to it.
Types of drivers
In total, two types of drivers for LEDs can be distinguished:
- Impulse. Using such devices, high-frequency pulses are generated in the output part of the device. The operation is based on the principles of PWM modulation. The average current value depends on the duty cycle (the ratio of the duration of one pulse to the frequency of its repetition). The output current changes due to the fact that the duty cycle varies in the range of 10-80%, and the frequency remains constant.
- Linear - a typical circuit and structure are made in the form of a current generator on transistors with a p-channel. With their help, it is possible to ensure the most smooth stabilization of the supply current in case the input voltage is unstable. They are cheap, but they have low efficiency. During operation, a large amount of heat is generated, so it can only be used for low-power LEDs.
Pulse are more widespread, since their efficiency is much higher (can reach 95%). The devices are compact, the input voltage range is wide enough. But there is one big drawback - the high influence of various kinds of electromagnetic interference.
What to look for when buying?
A driver must be purchased when choosing LEDs. On the PT4115, the LED driver circuitry allows for the proper functioning of the lighting system. Devices using PWM modulators built on single-chip circuits are used mostly in automotive technology. In particular, for connecting backlights and headlights. But the quality of such simple devices is rather low - they are not suitable for use in household systems.
Dimmable driver
Almost all converter designs allow you to adjust the brightness of the LED elements. Using these devices, you can do the following:
- Reduce daylight intensity.
- Hide or emphasize certain elements of the interior.
- Zoning the room.
Thanks to these qualities, you can significantly save on electricity, increase the resource of elements.
Varieties of Dimmable Drivers
Types of Dimmable Drivers:
- They are connected between the PSU and the light source. They allow you to control the energy that is supplied to the LED elements. The design is based on PWM modulators with microcontroller control. All energy goes to the LEDs in pulses. The energy that goes to the LEDs directly depends on the length of the pulses. Such driver designs are mainly used for operation of modules with stabilized power supply. For example, for ribbons or creeping lines.
- The second type of device allows you to control the power supply. Control is performed using a PWM modulator. Also changes the amount of current that flows through the LEDs. Typically, such designs are used to power those devices that need a stabilized current.
It is necessary to take into account the fact that PWM regulation has a bad effect on vision. It is best to use driver circuits to power the LEDs, in which the current is regulated. But here is one caveat - depending on the magnitude of the current, the glow will be different. With a low value, the elements will emit light with a yellow tint, with an increase - with a bluish tint.
Which chip to choose?
If you donβt want to look for a finished device, you can make it yourself. Moreover, to calculate for specific LEDs. There are a lot of chips for making drivers. You only need the ability to read electrical circuits and work with a soldering iron. For the simplest devices (up to 3 W), you can use the PT4115 chip. It is cheap and easy to get. Element characteristics are as follows:
- Brightness control.
- Supply voltage - 6-30 V.
- The output current is 1.2 A.
- Permissible error during current stabilization is not more than 5%.
- Load shedding protection.
- Conclusions for dimming.
- Efficiency - 97%.
Chip pin designation:
- SW - connect the output switch.
- GND - negative output of power sources and signal.
- DIM - brightness control.
- CSN - input current sensor.
- VIN is the positive terminal connected to the power source.
Driver schematic options
Device options:
- If there is a power supply with a constant voltage of 6-30 V.
- Powered by an alternating voltage of 12-18 V. A diode bridge and an electrolytic capacitor are introduced into the circuit. In fact, the "classical" circuit of a bridge rectifier with a cutoff of a variable component.
It should be noted that the electrolytic capacitor does not smooth out voltage ripples, but allows you to get rid of the variable component in it. In equivalent circuits (according to the Kirchhoff theorem), an electrolytic capacitor in an alternating current circuit is a conductor. But in the DC circuit, it is replaced by a gap (there is no element).
Do-it-yourself assembly of the LED driver 220 circuit is possible only if you use an additional power supply. It necessarily involves a transformer, which lowers the voltage to the required value of 12-18 V. Note that you cannot connect drivers to LEDs without an electrolytic capacitor in the power supply. If it is necessary to install the inductance, it is necessary to calculate it. Typically, the value is 70-220 ΞΌH.
Assembly process
All elements that are used in the circuit must be selected based on the datasheet (technical documentation). Usually it even gives practical schemes for using devices. Be sure to use low impedance capacitors in the rectifier circuit (ESR must be low). The use of other analogues reduces the effectiveness of the regulator. The capacitance must be at least 4.7 microfarads (in the case of using a direct current circuit) and from 100 microfarads (for operation in an alternating current circuit).
You can assemble the driver for LEDs by your own hands in just a few minutes, only the presence of elements is required. But you need to know the features of the installation. The inductor should preferably be located near the output of the SW chip. You can make it yourself, for this you need only a few elements:
- Ferrite ring - can be used with old computer power supplies.
- PEL-0.35 type wire in varnish insulation.
Try to place all elements as close as possible to the microcircuit, this will eliminate the appearance of interference. Never connect elements with long wires. They not only create a lot of interference, but also are able to receive them. As a result, the microcircuit, unstable to these interferences, will work incorrectly, the current regulation will be disturbed.
Layout option
All elements can be placed in the housing from an old fluorescent lamp. It already has everything - a case, a cartridge, a board (which can be reused). Inside, you can arrange all the elements of the power supply and the chip without much difficulty. And from the outside, install the LED that you plan to power from the device. Driver circuits for 220 V LEDs can be used almost any, the main thing is to lower the voltage. To make this easy is the simplest transformer.
It is advisable to use a circuit board with a new one. And itβs better to do without it at all. The design is very simple, it is permissible to use a hinged installation. Be sure to make sure that the output voltage of the rectifier is within acceptable limits, otherwise the microcircuit will burn. After assembly and connection, measure the current consumption. Note that in the event of a decrease in the supply current, the life of the LED element will increase.
Carefully select the driver circuit for powering the LEDs, calculate each component of the structure - the service life and reliability depend on this. With the right selection of drivers, the characteristics of the LEDs will remain as high as possible, and the resource will not suffer. Driver schemes for high-power LEDs differ in that they have a larger number of elements. Often PWM modulation is used, but at home, as they say, "on the knee", such devices are already difficult to assemble.