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autho r: Santa Cruz (Nickname - Bob) - Zagreb, Croatia Regulated DC power supply, short circuit safe, and with current limiter This PSU has been especially designed for current-hungry ham radio transceivers. It delivers safely around 20Amps at 13.8V. For lower currents, a separate current limiting output, capable of 15ma up to a total of 20A has been added. Let us see what we have got here. The power transformer should be capable to deliver at least 25A at 17.5 to 20V. The lower the voltage, the lower power dissipation. The rectified current will be “ironed” by the C1, whose capacity should not be less than 40.000uF, (a golden rule of around 2000uF/A), but we recommend up to 50.000uF. This capacity can be built up by several smaller capacitors in parallel. The base of this design is a simple 12V regulator (7812). The output voltage can be brought to desired value (here 13.8V) by two external resistors (R5 and R6) using this formula: U= 12(1+R5/R6) The low currents (here 15mA...

Here this circuit diagram is for +12V regulated (fixed voltage) DC power supply. These power supply circuit diagram is ideal for an average current requirement of  1Amp. This  circuit is based on IC LM7812. It is a 3-terminal (+ve) voltage regulator IC. It has short circuit  protection , thermal overload protection.  LM7812 IC is from LM78XX series. The LM78XX series IC is  positive voltage regulator IC for different voltage requirements, for example LM7805 IC is made for 5 volt fixed output voltage . There is LM79XX IC series for negative voltage . Circuit diagram of 12V fixed voltage power supply   A transformer(Tx=Primary 230 Volt, Secondary 12 Volt , 1Amp step down transformer) is used to covert 230V to 12V from mains. Here used a bridge rectifier made by four  1N4007 or 1N4003 diode to convert AC to DC . The filtering capacitor 1000uF,25V is used to reduce the ripple and  get a smooth DC voltage. This circuit is very easy to build. For good p...