LEDs are an integral part of the electronics, allowing the status of devices to be indicated. Depending on the color and location on the case, light-emitting diodes signal the charging status, the gadget is connected to the network, etc. But there are situations when there is no standard alarm in the device, but a person needs it. Then the question arises of how to turn on the LED at 220 V without using voltage-reducing transformer devices.
Content
- Diode technical features
- Resistor connection
- Capacitor application
Diode technical features
An LED is a radio-technical element that transmits current, like a standard diode, in only one direction, but at the same time emits electromagnetic waves in the visible range. If we integrate such a diode into a DC network, then it is important not to confuse "plus" and "minus". The introduction of a light diode into an alternating network and the solution of the question of how to power the LED from a 220 V network, where periodically (with a frequency of 50 Hz) there is a change in the direction of the current and voltage, it will require additional calculations.
To determine the average value of the current and connect the LED to a 220 volt network, it is necessary to divide the voltage of the current network in half, that is, 220 V / 2 = 110 V. This value is taken as the basis for subsequent calculations.
The electrical resistance of an LED, like any semiconductor element, is not linear and depends on the magnitude of the potential difference applied to it. For a network with alternating current and voltage of 220 V, an average value of 1.7 ohms can be taken with acceptable accuracy. Then, according to Ohm's law, the amount of current that will pass through the semiconductor crystal of the diode, if connected directly to the network, will be approximately equal to 65 amperes (110 / 1.7).
Such an indicator will simply lead to the burning of the device. To reduce the amount of current passing through the semiconductor, it will be necessary to connect in series in the circuit next to the resistance light diode.
For this purpose, apply only resistors in constant voltage circuits, and with alternating current it is possible to use the so-called reactances - capacitors and inductors. They create resistance due to the accumulation of electromagnetic energy in the first half-cycle (the current flows in one direction) and its return to the network in the second half-period (with the reverse flow of electric current).
Resistor connection
A similar scheme is usually implemented to indicate the operation of electrical devices. It is used in the light signal indicating that the electric kettle is plugged in, in the backlight of the switch button, etc. The main advantages of this option for integrating a luminous diode into a network are considered to be relative cheapness, simplicity and reliability.
But there is one nuance in this scheme. It consists in the need to damp the reverse voltage, since its excess can lead to failure of the semiconductor device. Silicon diodes can easily cope with this task, which are capable of passing a current in magnitude no less than what passes in the network. You can connect them to the circuit in two ways:
- in series, that is, after the resistor and in front of the LED, but observing the polarity;
- in parallel with the luminous diode, but changing the polarity by 180 degrees.
Some experts believe that the use of quenching diodes is optional, but practice shows that reverse current in some cases causes thermal breakdown of the pn junction. Therefore, the additional costs for the purchase of silicon diodes are quite justified for the implementation of connecting the LED to a 220 V network, the circuit of which contains a damping resistor.
Capacitor application
The downside of using a resistor to reduce the current when a 220V LED is connected to the circuit is the rather significant power dissipation. This problem becomes noticeable with a load with a high current consumption. The solution is a circuit for connecting the LED to 220 V, where the integration of a non-polar capacitor is implemented instead of a resistor. The resistance of the capacitors is reactive, which eliminates power dissipation.
Connecting a capacitor to the LED circuit for the purpose of current limitation has one nuance, which can lead to failure of the light diode, - preservation of the accumulated charge after disconnecting the power supply networks. Because of this add to the circuit with a non-polar capacitor:
- two resistors;
- a diode connected in parallel to the LED, but in the opposite direction.
Resistors (one in parallel with the capacitor and the other in series) protect the entire circuit from surges voltage when supplying voltage from the network, and the diode is the protection of the LED against potential differences with reverse polarity.
These connection methods are applicable to low power LEDs that are used for indication or backlighting. The connection of powerful diode elements intended for LED lighting lamps is carried out by circuits using special power supplies (drivers).
