When installing LED lamps in place of halogen lamps, it is often necessary to replace the old power source. Halogen lamps are connected to 12V electric transformers, LED lamps require the installation of special power supplies with a similar output voltage. In this regard, it is important to figure out whether the old transformer can be used or whether it should be replaced.
What is an electronic transformer
An electronic transformer is a switching power supply circuit based on a high-frequency generator operating on semiconductor switches and the transformer itself. The power supply of such a circuit is provided by a standard 220V AC mains, but at the output the effective value is in the 12V region. First, power from the mains is supplied to the rectifier, and then the already rectified voltage is sent to the generator and power switches unit.
The standard implementation of such a scheme is the use of an autogenerating push-pull type, the key feature of which is that there is no need to use any special switching power supplies like PWM controllers. The automatic generator in this case switches the transistor under the influence of voltages that are induced on the transformer windings, and also provides positive feedback.
To ensure proper operation of LED lamps, you will need any source that provides a stable voltage of 12V on a constant basis and minimizes ripple. For this, the ICs mentioned above are most often used.
Both schemes provide for the use of an integrated PWM controller, which regulates the operation of bipolar or field-effect transistors. In addition, the output stage of the circuit includes a rectifier, as well as capacitors that smooth out ripple - they act as a kind of filter.
As a result, a stabilized power supply is obtained, the ripple of which corresponds to the current load, as well as the capacitance of the filtering capacitors. If necessary, it can be implemented on an autogenerator circuit by analogy with an electronic transformer, using additional feedback circuits to provide the necessary stabilization of the output voltage.
Why can't ET be used with LED lamps?
- LED lamps provide for the need for constant voltage, which is due to their nonlinear current-voltage characteristic and sensitivity to any deviations from the nominal voltage. At the slightest excess, such lamps can eventually fail quickly.
- Electronic transformers are sources of alternating voltage with high frequency, and the indicators of bursts and peaks in some situations reach 40V, which ultimately often leads to complete breakdown of LEDs or drivers used in the construction of modern LED lamps. In addition, such an approach is fraught with their unstable work.
- Electronic transformers are distinguished by the presence of a minimum load. Thus, if the load of the connected lamp does not reach the level indicated on the power supply, the transformer may not start working at all, or it will work with increased ripple, turn off. This is a critical point, since the power consumption of halogen lamps is much higher than that of LED lamps.
- Power supplies designed to power LED lamps provide a stabilized and constant voltage.
- Halogen lamps are not picky about whether they go through the network with direct or alternating current. Only his tension plays a role. In this regard, they can be connected to any power source.
Classic electronic transformers cannot be used as a power source for any LED luminaires. When replacing lamps, it will be necessary to select a special unit that provides a stabilized voltage. If you ignore this, you can face the premature failure of all lamps.
A step-down transformer
The typical LED lamp life is 4000 operating hours according to the manufacturer's specifications. If you do not use specialized step-down transformers in the operation of such devices, leaving the diode as the basis for operation, the operating period is reduced to 1200 hours of uninterrupted operation.
If the lamps are installed in rooms with a high concentration of moisture or constant temperature fluctuations (saunas, swimming pools), you need to use a special step-down transformer equipped with protection against water. It is also important to ensure that the total LED lamp load is within 60%.
How to choose
There is nothing difficult in choosing a step-down transformer for LED lamps. If you have any difficulties, you can always consult with the managers of the companies that sell such equipment. The most important thing is to correctly calculate the power.
The sum of all LED lamps installed in the room is calculated, 20% is added to the result, since in the majority of cases only one transformer is used.
For example, there will be six 12V lamps in the room, their sum is 72V. Devices rated 60V can no longer be used. You need to purchase equipment for 100V or reduce the number of light sources. If you put in a powerful transformer, you can add another lamp.
The savings do not depend on the power of the light sources used, but on the voltage. It is provided through the use of a transformer, which significantly increases the life of the LED lamps.
Installation features
Ideally, the devices are anchored to a concrete slab. To provide easy access to them, a small hatch is made in the surface of the wall or ceiling. It should be borne in mind that over time, the device will need to be changed, so the cut-in hole must correspond to its dimensions.
The decision to hide the transformer in the closet is not always advisable, especially if several devices are to be installed. There should be no more than 2 meters of wire to the load source, so it will not work to place the transformer far from the luminaire. To avoid all these problems, it is recommended to buy luminaires with a built-in transformer.
The transformer heats up during operation
If you bought a new transformer, which, after connecting and turning on, began to get very hot, you need to carry out several operations:
- Check the load of the energy consumption in the room and the correspondence of the permissible rating of the transformer to the number of lamps connected to it.
- Check the wiring of outlets and lighting by groups.
- Check if there is a load on the device.
- View reviews on the Internet for the purchased device. It is quite possible that a poor-quality transformer was purchased.
If a transformer that has been in use for several years heats up, this is an indicator of equipment wear. Change it to a new one. It is better not to ignore these signals, as you may encounter a melting of the case, and this creates a risk of a fire hazard.
