Adjustable current regulator on LM317 for LEDs

The demand for voltage stabilizing systems has grown significantly in recent years. Particular interest is shown in devices working with artificial light sources and, in particular, with LEDs. The current stabilizer on the lm317 is a simple, inexpensive, but reliable device that you can purchase or assemble yourself. In the latter case, you need to know the basic rules of instrumentation, safety requirements when working with electricity and prepare a standard set of elements.

What is the stabilization of current and voltage for?

The number of electrical devices in homes is constantly growing. In recent years, the number of electrical appliances has increased several times. As a result, the need for voltage levels in electrical networks has increased. Moreover, most of the buildings (residential and industrial) and power plants were built more than 30-40 years ago.

Some modern devices are manufactured with built-in stabilizers - small circuits to prevent damage from power surges. But most of them do not contain additional devices and even a small drop in the network threatens to burn out. Large household appliances (not digital) are at high risk. In particular boilers and washing machines.

To avoid damage and ensure a stable voltage in the network, stabilizers are installed. This is optional in every home. If the building has a constant current supply without serious fluctuations (within 220 Volts with a maximum error of 10%), there is no point in additional devices. But when the surges are constant, installing a stabilizer will save equipment and provide electricity.

Types of stabilizing devices

Before purchasing a device, you should familiarize yourself with the main types and features. Each has advantages and disadvantages, designed for different voltage levels and number of devices. The principles of work are also different.

Relay

The best option for private and country houses, apartments. Several magnetic windings are installed on the transformer. At the moment of a voltage drop, switching occurs between them, which allows maintaining the voltage flow in the same mode. The disadvantages include:

• change in the energy flow in a stepwise mode (abruptly, intermittently);
• curvature of the sinusoid of the voltage flow;
• low power at the moment of recoil.

The cost of such devices is much lower than other models of stabilizers. The owners' reviews are good, the device turns out to be enough for home networks.

Electronic

There are two types of electronic "filling" stabilizers - triac and thyristor. In the first, switching between windings in automatic mode is carried out by a small mechanism - a triac. The efficiency of the device is high, it works quickly. A significant plus for domestic use is noiseless operation. The second type is not as effective, it is usually used to stabilize home networks without high voltage. The most notable drawback is cost.

Electromechanical

Other names are servo motor, servo motor. The principle of operation - with the help of an electric drive, the carbon electrode moves along the windings, creating an uninterrupted voltage. Often bought for household needs and small premises (home, summer cottage, office). Pros - price, compactness, smooth switching. Cons - noise, slow switching speed.

Ferroresonant

In recent years, it is rarely used due to the advent of more modern devices. The ferroresonance effect occurs in the system of interaction between a transformer and a capacitor. The devices are large-sized, noisy, do not work under sudden and significant overloads. Advantages - long service life, the ability to use in rooms with high humidity.

Inverter

Devices of this type are powerful and expensive. They are used in everyday life and large industrial premises. The main difference is a crystal oscillator and a controller, which convert the voltage at the input to direct current, and at the output to alternating current. Simultaneous dual shaping allows you to work with different current levels - from 115 to 300 volts. Advantages - no noise, small size, fast switching and regulation, other additional features (for example, protection of household appliances from overvoltage).

Linear device diagrams

The current stabilizer on the lm317 is a device that operates on a linear voltage switching circuit. Such microcircuits are used for networks where high efficiency and excessive power are not required. In particular, to support the operation of LEDs. Benefits:

• protection against sudden surges, excessive power levels;
• polarity reversal of the current at the input element;
• lack of additional parts and devices.

The disadvantages include lower efficiency - the voltage obtained in excess of the required is processed into heating, therefore additional cooling is necessary.

For stable operation, a positive difference in currents at the input and output is required - linear stabilizers stop functioning when a drop of 0.4V (even at 0.5V). Therefore, the power supply circuit on lm317 with current and voltage regulation is not used for large-sized devices and "heavy" networks.

Main characteristics

The voltage regulator on the lm317 operates within a certain range of power supply. The limits are 1.25V minimum, 37V maximum. At the output, the voltage power does not exceed 1.5 Amperes, the error with an unstable connection is up to 0.1%.

The voltage regulator on the lm317 microcircuit has additional internal protection systems: from short circuits, from thermal overvoltage, from excessive dissipation of "excess" voltage.

Thermal limitation is provided by special microsensors that guarantee the protection of equipment from exceeding the dissipated power - if this happens, the device will simply turn off and not suffer.

Power and input voltage

For the current regulator to work on the lm317 circuit, the voltage at the input part must not be higher than 40 volts. In this case, the minimum current difference at the inputs and outputs must exceed 2 Volts.

For the voltage regulator to work on the lm317, the circuit must not receive a load greater than 1.5A. If there is no additional cooling, the level will drop. The approximate power is calculated by multiplying two indicators - the power of the electricity at the output and the potential difference between the input and output.

At ambient temperatures up to 30 ° Celsius, a power dissipation of up to 1.5W is allowed (if there is no heat sink). At a normal level of heat dissipation, dissipation of up to 20W is allowed.

Device design

The lm317 stabilizer power supply circuit with current and voltage regulation with a minimum arrangement has two resistors, the difference in resistance of which regulates the voltage at the output and capacitors.The average current on the supporting elements is 1.25 V. The resistance should not exceed 240 ohms.

The body of the stabilizer in the lm317 diagram is made of plastic. Possible options: TO 220 and 220FP, SOT23 and D2PAK. Internal protection systems allow the device to operate if the control input is disconnected.

Pulse drivers

Drivers with an impulse system are the same voltage regulators. AC voltage allows you to regulate the operation of the device. If the level is less than 2-3 Amperes, no additional heat dissipation is required.

Pulse devices "cut" the input current to obtain the desired voltage level at the output. It can work with networks of high loads. Cons - you need a separate power source, cost, external "extra" electromagnetic field. Difficult to assemble at home.

Connection diagrams

The circuit for switching on the power supply unit on lm317 with current and voltage regulation allows the stabilizer to be used in networks with non-standard voltage. A minimum of two resistors are required for the device to work. The most important indicators are the voltage of the reference point, the level of the output current.

The simplest stabilized power supply

Voltage stabilizers are needed not only to protect household and industrial equipment. In the laboratory, the devices help to avoid excessive power flows and network burnouts. Therefore, beginners and professional technicians tend to use at least simple stabilizing blocks.

Main pluses:

• easy assembly;
• reliable work;
• inexpensive and affordable parts.

The disadvantages include low output efficiency, the use of large radiators, and the large size of the device.

For a standard device, several elements are required:

• lm317 circuit;
• transistor with a plastic case;
• diode;
• two resistors;
• two capacitors;
• diode bridge.

The minimum number of parts and simple design will allow you to quickly assemble the voltage regulator and use it for a small network.

The indicators of the elements are not critical. For example, the resistors on R1 can range from 30 to 50 ohms, and the diode is not installed.

Integrated stabilizer power supply

Devices with an integrated system of operation are used in voltage stabilizers, audio systems, amplifiers, power supplies and others. All parts of the structure are connected by means of a silicon crystal so that their sequence makes up a stabilizer. In electrical engineering, two types are used:

• using a semiconductor;
• with the use of film elements (hybrid).

The standard circuit includes several typical parts: a reference source, an amplifier, a regulator, and a protective mechanism for shutting down and preventing short circuits.

Integrated circuits are devices with a complete functional cycle. Each has an entry, exit and ground path.

You can use such circuits only with certain voltage indicators. Permissible limits are from 5 to 24V, for current - less than 1A.

Integrated circuits have an output voltage limiter. An additional overheating protection is also installed.

Stabilizer circuit with regulated power supply

A bridge rectifier in such devices allows you to convert an alternating current flow into a constant one. One of the capacitors filters the ripple energy, the other makes the voltage transition smoother. This type allows the regulator to operate at low DC frequencies.

The selection of the resistor is carried out according to the nominal value allowed for the stabilizer. The error should be minimal. The best option is an accurate calculation.

Application area

Stabilizers based on the LM317 microcircuit are used to stabilize the main indicators of technical devices. Such a device is easy to assemble by yourself, and a factory-made device is inexpensive. For this class, it has excellent operational data and service life, if there are no excessively strong power surges.

The disadvantage is the voltage limit - no more than 3V. The stabilizer based on the TO 220 case is the most affordable model that is used in several areas:

• household (home) networks;
• laboratory conditions;
• LED lighting (light emitting diodes).

Voltage stabilization systems based on the LM317 microcircuit are reliable, simple and convenient devices. The cost is small, but the characteristics are positive. These stabilizers are often used for LEDs in cars.