Diy power supply filter circuit

Diy power supply filter circuit Diy power supply filter circuit

The surge protector is an electrical circuit that will implement the functionality low-pass filter for power supply circuits by means of 220 V AC (available as a network for household tasks).

The essence of the operation of such a device will be reduced to cutting off incidental electromagnetic radiation, in order to cut off such electromagnetic radiation, as well as interference (PEMIN) that arise as a result of irradiation of an electric wire of a household power supply network with unnecessary devices that study radiation (repeaters, radio stations,

… basic stations for wireless Internet, etc.) or powerful household appliances without the required degree of protection for the power circuit (refrigerators, air conditioners, split systems, etc.). You can make a power supply filter yourself.

General information. What you need is the selection of circuits and inventory

PEMINs appearing in the power supply network can have a negative impact on the operation of other low-current devices (TVs, digital technology, radio receivers, etc.) or cause interference in the reception of various signals ...

In addition, PEMIN can become a source of leakage of all confidential information, for example, during the operation of special equipment (information can be intercepted through grounding or power circuits).

It is the line filter that helps to protect the devices, which will perform two functions at once:

Most people very often come across power filters that are already built into an electrical type extension cord. But, manufacturers or traders are often misleading.

Certain filter models will not actually perform the declared filter functions, and they only provide protection against short-term overload in the event of an increase in voltage or current strength (short circuit).

As part of the mains filters there is only one varistor (this is an element of the electrical circuit that will implement the function of a variable resistor, which increases the resistance when the applied voltage is increased) and a self-acting type of switch (a fuse that is triggered when the current force). Such a device can only help, for example, from interference that is created by a lightning discharge during a thunderstorm. Devices that 100% implement the list of filter capabilities cost much more than their adapted counterparts.

So, network-type filters can be called products from the Pilot company (the series starts with Pilot L, Pilot GL, etc.

, the exception is Pilot S), and prices for it start from 1,000 rubles, or analogs from ARS, IPRON, BURO and others.For this reason, there is a completely natural desire to make an inexpensive, but at the same time no less active surge protector with his own hand. First of all, the purchased inexpensive filter with varistor protection can be converted for high-frequency filtering.

To modify it, you will need:

  • Ferrite Filter.
  • Resistors.

  • Capacitors.
  • Varistor (you can leave the existing one in the extension cord, if it is there).
  • Inductors or chokes.

Next, let's talk about schemes.


220 V power filter circuit

A typical varistor filter looks like this.

Two common variations are possible. The first is on the RLC filter. Next, consider the second diagram. Such circuits and elements were not chosen at all randomly, because all components can be placed in a used case from an extension cord without the need to install a separate case on a wire and other things. The principle of operation, like all low-frequency LC filters, is simple:

  • High-frequency oscillations, falling on the inductor, increase its degree of resistance and therefore will not pass further (induction resistance is proportional to the frequency) .


  • Hits on the contacts on the capacitor will extinguish high frequencies with the correct choice of capacitance (the capacitance resistance with a similar connection method is inversely proportional to the frequency of current oscillations).

Diy power supply filter circuit In the two circuits, a resistor with a huge resistance will be connected in parallel to the capacitor. It will act as a load for an element such as a capacitor when the power is turned off (a free type of charge may begin to accumulate on the capacitor, which is dangerous even after 100% disconnection of the filter from the AC mains).

The simplest surge protector can be made by hand. By the way, it is best to buy a ferrite filter in the form of an extension cable that is split in diameter. Its purpose in the operation of the circuit is to suppress high-frequency interference along the power supply circuit by increasing the conductive inductance, and also absorbing radiation directly by the ferrite. This is a great solution for connecting to the power supply of your home appliances. Other implementations of the mains electric filter are also possible.

As an example, you can cite the schemes that are used in the Pilot technique.

We provide you with instructions on the assembly process of a conventional filter for a network with our own hands. It is quite simple to assemble a filter from the proposed schemes, and this does not require printed circuit boards or a single case on an extension cord. With a good choice of element size and arrangement, they can be housed in a low cost varistor mains filter housing. The circuit that is available must be cut (contacts from the varistor to the sockets, and the varistor itself is left), and the elements will be placed in accordance with the diagram and soldered.

Everything should work out as in the scheme.

Only the inductors need to be placed orthogonally to each other. Regarding the resistance circuit R 1 and R 2 , it is important to select based on the load that is expected. For example, with an actual power consumption of up to 250 W, resistors of 0.82 Ohm are suitable, up to 380 W is 0.

36 Ohm, up to 500 W it will be 0.22 Ohm. If you plan to use more power, resistors can be excluded from the circuit, but the operation of the chokes will deteriorate. Chokes L 1 and L 2 must be equipped with a ferrite core, and the maximum permissible current must be no less than the planned load current, and the inductance from 10 μH to 10 mH (it is better to choose in the larger side, it turns out that the more, the better, though up to 10 mH).

Capacitors C 1 and C 2 can be combined into one if there are the necessary indicators and free space.

Or, on the contrary, to dial with several connections of a parallel type, if free space allows. It is best to use film capacities from 0.22 to 1 μF. It is better to take the maximum allowable voltage with a margin (in case of interference with sudden voltage changes), for example, up to 680 V. Resistance R 3 should be from 0.

5 to 1.5 MΩ. It is also better to take power with a margin for better thermal output of 0.5 W. In circuit number 3, the coils and capacitor will be changed, and it is the coils that have the most optimal inductance values ​​for small sizes and the tasks they face.

It turns out that you will use much fewer parts for soldering.

Precautions - what is important to consider

A 220 V power filter made by ourselves is a complex technical device. Its assembly process is impossible without knowledge of electrical engineering. All work must be performed in compliance with all safety measures. Otherwise, there is a risk of electric shock.

As stated earlier, the capacitors were rated for high voltage ratings.

They are capable of accumulating residual charge. An electric shock will be possible even after a complete filter disconnection from the current (AC) mains. For this reason, a parallel connected resistor is mandatory.

Before soldering, you need to make sure that all the elements are in good working order (it is important to measure the basic parameters with a tester and compare with the declared one).

Do not allow the crossing of wires, and even more so in places of potential heating (on bare contacts and resistors). Before connecting to the network, it is imperative to make sure (that is, "ring" through the tester) if there is no short circuit.

( 5 marks, average 2. 2 from 5 )