In many applications, cheap stabilizers 78xx family of imperfect. When a large difference between input and output voltage, and a heavy load they lost a lot of energy, It is forcing you to use expensive and occupies a lot of space radiator. Switching Converters 78Rxx conclusions, compatible with 78xx, commercially available, but they are relatively expensive. The proposed solution is almost 3 such times cheaper analog converter.The design is based on the stabilizer Application Note switching regulator ST1S10. Chip improvement requires no external diode. His role is played by a field effect transistor, located in the chip structure ST1S10.
When current load is not more 3 The outer heat sink is not required – quite a small area on the surface of the board. For the reason that, that the surface of the wafer was limited to a minimum, maximum continuous current of the stabilizer in the solution proposed here makes 1,5 BUT. The maximum allowable input voltage is 18 AT. Manufacturer ST1S applied in relation to a high switching frequency (900 kHz), that allows the use of tiny inductors and small filter capacitors. On the other hand, Throttle quality and capacitor C2 has a decisive influence on the stability of the output voltage. The output voltage can be determined by the formula:However, it is more convenient to use the formula:The output voltage can be varied within 0,8 … 18 AT. Output voltage stability over the entire load range of 0,2%. If the result is worse, the reason for this is, choke or capacitor C2. Also, be aware, that the output voltage may be different from the nominal voltage without load. The values of the elements in the diagram set voltage inverter 5 AT. Since the minimum capacitance at the output of the stabilizer is 22 mF, as C2 used two ceramic capacitors 10 mF / 16 AT, soldered close. Capacitors can also be soldered to each other.