What is the difference between a power supply and an electronic transformer?

  • Dec 16, 2020
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In connection with the transition of most consumers to modern lighting equipment, it is increasingly important to obtain a modified voltage for their power supply. Various converters can be used for this. However, the output parameters of such devices, as well as the principle of their operation, have some differences. To understand the principles of separation in this article, we will consider the difference between a power supply and an electronic transformer.

Power Supply

A power supply means a fairly wide range of electronic devices designed to transfer reduced rectified voltage from an external network to low-current consumers. As a rule, the power supply consists of a step-down transformer that reduces the usual 230 V to the required rating. Then it is transmitted to the rectifier unit, which converts the alternating voltage into direct voltage.

An example of power supply operation is shown in the figure below:

How the power supply works
How the power supply works

Modern models contain additional blocks that increase the efficiency of the unit, they are used to power:

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  1. all constituent computer blocks from the power filter;
  2. recharging devices from the mains power supply unit;
  3. organization of safe power supply through the power supply in rooms where the use of 220V is unacceptable for safety reasons;
  4. connecting a tape with LEDs from the unit;
  5. for power supply of household and industrial appliances.

In theory, a power supply is a versatile device that can be used for several purposes at once. However, in practice, there is also a narrow specialization, for example, computer power supplies are equipped with a forced cooling system, so power supplies without a cooler will not be suitable for these purposes.

In each specific case, the power supply unit is selected not only for the purpose, but also must take into account the nominal supply voltage and the power of the supplied load. The voltage of the power supply must exactly correspond to the nominal value of the supplied device, and the power must be no less, it is even desirable to have a certain margin.

Electronic transformer and its distinctive features

The principle of operation of an electronic transformer is similar to the classical one - when an alternating voltage is applied to the primary winding, an alternating voltage is also removed from its secondary, but of a different value. The difference is that the undervoltage has a completely different frequency and curve shape, since it is artificially created by a pulse generator.

An example of an electronic transformer circuit and the principle of operation is shown in the figure below:

Figure: 2. Electronic transformer

As you can see, the supply voltage from the 230 V network is not supplied to the transformer windings, but uses a diode bridge as the main converter with a variable electrical quantity in constant. Then the signal is fed to the output transistors, which act as an electronic switch, which generate pulses of a certain number and frequency. It should be noted that the frequency from the pulse generator can reach several tens of kHz, but then it is fed to a pulse converter, which is represented by a power transformer.

Pulse transformers or, as they are also called, pulse power supplies have found wide application in powering fluorescent lamps. However, its location in relation to powered lighting fixtures should be in close proximity to reduce losses, stress in the mains wires and heat.

In comparison with a transformer power supply, a pulsed one has a number of significant advantages:

  1. Smaller dimensions for the same power, which reduces the cost of the device;
  2. It has the best parameters in regulating the supplied voltage;
  3. Differs in higher efficiency.

But along with the advantages, the pulse unit also has some disadvantages. An electronic transformer has a much more complex circuit, which entails a decrease in reliability. If you bargain with a transformer model, then the output current will give out a lot of impulse noise to the network that can affect the operation of adjacent equipment.