Because of the great interest in this construction I created a very simple non-regulated switching symmetric power supply with
high power 350W. It is a Half Bridge without regulation. The power supply can
be used as a replacement for the standard power supplies for audio amplifiers, because
transformers and as electrolytic capacitors for power amplifiers are very expensive
and bulky. Transformers are also very heavy and not suitable for portable devices. Price for simplicity is
the fact that the short circuit or overload destroys MOSFETs and other components. MOSFETs may be stressed on power up,
because they have to charge the output capacitors. For more reliable solutions use
Regulated switching supply with protection.
The switching power supply is utilizing two N MOSFETs driven by integrated circuit IR2153. This switching power supply is
not stabilized, but for the purposes of the audio amplifiers (the output voltage is still harder and less ripple
than in classic power supply). Ripple at full load is less than 2V.
IR2153 circuit is powered via a power resistor 27k 6W. Stabilisation of the voltage
ensures its built-in 15V Zener diode. Operating frequency is about 50kHz. At the input is a thermistor
to limit the peak current during charging of capacitors. It can be found in broken AT or ATX PC power supply. The core of
the transformer is also from any PC supply. First the half of the primary is wound (20 turns), the secondaries and finally
the rest of the primary. This method ensures low leakage inductance and thus the hard output voltage. Between
primary and secondary there must be sufficient insulation. For increased safety, the output (ie center tap
0V) should be connected to the earth. Chokes are intended to remove RF output ripple from the supply. Number of turns is not critical, as well as
used core. Even this core can be found in the PC supplies. 6k8 resistor on the output is used to discharge capacitors after switching off and
prevents the increase of woltage when working with no load. In series with it can be connected LED. MOSFETs are mounted on
a small heatsink eg from PC supply.
