Most electronic devices need a 12 volt DC power supply. 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 tables. The step-down transformer is wound on a ferrite ring, the material grade is M200MN.
Transformer manufacturing
The primary winding consists of an insulated wire MGTF 0, 7, the secondary of the wire PEV-1, 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 microcircuit. Outside, the wires are closed with a double layer of PTFE tape.
Do-it-yourself switching power supplies are mounted on a printed circuit board made of single-sided fiberglass. Production technologysuch products is described in detail in the relevant literature and is beyond the scope of the article. The drawing of the current-carrying tracks for the printed circuit board was developed on the basis of the circuit diagram of the device. The transistors require heatsinks, which are made from an aluminum plate.
Required radio parts
It is rational to use ready-made chokes as an input choke, these are usually installed in power supplies for displays or personal computers. The capacitor is calculated based on the ratio of capacitance 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 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. The selection of triodes 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 ways to stabilize the output group, but the proven schemes are reliable. Looking for other solutions in this case will be a waste of time.
Assembly and setup
A high-quality do-it-yourself power supply is soldered on a prepared board. When performing 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 the current-carrying tracks. Solder residues are removed from the inner surface, which can lead to a short circuit.
Switching power supplies, assembled and prepared for launch with your own hands, are recommended to be loaded with a current-limiting resistor during testing. In this capacity, a 60 W incandescent lamp can be used, its short-term inclusion will serve as an indicator of the correct assembly.
