This Simple switching power supply for 15 Watt can be used to power any load up to 15 … 20 watts and has smaller dimensions than a similar, but with the step-down transformer, operating at a frequency of 50 Hz.
In the secondary circuit after the rectifier bridge is an ordinary linear regulator on the chip, which allows the output voltage is fixed, regardless of changes in the input network (187 … 242 V).
In the Simple switching power supply for 15 Watt scheme used capacitors C1 and C2 type K73-16 for 630 V, W – K50-29 440; C4 – K73-17V, 400; C5 – K10-17, C6 – K53-4A at 16; C7 and C8-type K53-18 to 20 V. The resistors can be arbitrary. Zener diode can be replaced by VD6 KS147A.
Pulse transformer T1 is performed on the ferrite core M2500NMS-2 or M2000NM9 Sh5h5 size (cross-section of the magnetic coils at the location of 5×5 mm with a gap in the center). Winding wire is made brand PEL-2. Winding 1.2 turns of wire contains 600 0.1 mm in diameter, 3-4 – 44 turns of 0.25 mm diameter, 5-6 – 10 turns in the same wire as the primary winding.
If necessary, the secondary windings may be several (in the diagram shows only one), and for the oscillator to observe the polarity phase windings 5-6 in accordance with the scheme.
Setting the converter is to obtain a steady excitation oscillator when the input voltage from 187 to 242 B. Elements requiring the selection, followed by an asterisk “*”. Resistor R2 can be par 150 … 300 ohms, and capacitor C5 – 6800 pF … 15000. To reduce the size converter for less withdrawn in the secondary circuit of power ratings electrolytic filter capacitors (NW, C7 and C8) can be reduced. Their value is related to load capacity ratio:
P : power to the load circuit, W;
Um -: the amplitude of the rectified voltage (acting for the incident on the input line voltage amplitude is 242 342);
Fc : frequency, to calculate the SP it takes 50 Hz;
ΔU : maximum ripple of rectified voltage range allowed by the applicable type of capacitor (taken from the handbook: the case for C50-29 he is 10 … 14% [L16], ie 34 V).
The design of the Simple switching power supply for 15 Watt device should include the installation of the transistor D1 and stabilizer on the radiators, as well as shielding the entire circuit to reduce the radiated noise.