The bulk of electronic devices needs a DC power supply with a voltage of 12 volts. Do-it-yourself switching power supplies are assembled on the basis of a microcircuit with the necessary parameters. Its selection is carried out according to radio engineering tables. The winding step-down transformer is made on a ferrite ring, material grade - M200MN.
The primary winding consists of an insulated MGTF 0.7 wire , the secondary of PEV-1 wire folded in half. Between them there should be an insulating layer, which is made of fluoroplastic tape. The secondary winding in the middle part has an additional branch for powering the control chip. Outside, the wires are closed with a double layer of fluoroplastic tape.
Do-it-yourself switching power supplies are mounted on a printed circuit board made of single-sided fiberglass. The production technology of such products is described in detail in the relevant literature and is beyond the scope of the article. The drawing of current-carrying tracks for a printed circuit board was developed based on the circuit diagram of the device. For transistors, radiators are needed that are made from an aluminum plate.
Required Radio Parts
It is rational to use ready-made chokes as an input choke, such are usually installed in power supplies for displays or personal computers. The capacitor is calculated based on the ratio of capacity and power one to one. The rectifier is made on the basis of a diode bridge with a low operating frequency. Such a device is capable of providing a current strength of up to 3 amperes at the output.
Switching power supplies used in radio electronics , the circuit of which has been worked out and tested for a long time, have transistor switches. Triode selection is carried out according to the specified parameters, the IRF 840 or VT 1 and VT3 series have proven themselves well. To ensure the required temperature conditions, transistors must have cooling radiators to remove excess heat.
Do-it-yourself switching power supplies are assembled with the output part of the circuit, represented by chokes based on ferrite cylinders about 40 mm long with a diameter of 3 mm. Tight winding is made from the same wire as the secondary winding of the transformer. It is possible to use other methods of stabilizing the output group, but the proven circuits are reliable. Finding other solutions in this case would be a waste of time.
Assembly and configuration
A high-quality power supply unit is soldered on a prepared board with its own hands. During installation, it is necessary to ensure normal lighting of the workplace and ventilation. After soldering, it is recommended to check the reliability of the installation of radio components and the contact between them and live tracks. Solder residues that may cause a short circuit are removed from the inner surface.
Switching power supplies, assembled and prepared for start-up, are recommended to be loaded with a current-limiting resistor during testing. As such, an incandescent lamp with a power of 60 W can be used, its short-term inclusion will serve as an indicator of the correct assembly.