Power Supply Adapter

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. 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 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) will keep the 7812 in its regular function. As soon as the current rises over 15ma, the voltage drop on R4 will “open” the Q3, actually handling the high output current. Thi...

Actually, this is ordinary regulated power supply , but the current expander using a transistor make this power supply become powerful. Based on the datasheet, the stabilizer IC’s can deliver up to 1A output current. For example 78xx series regulators are available in different voltage ratings, but in any case the current should not exceed 1A . The transistor Q1 (2N 29055) used here has 5A current capacity. The resistor R1 is used to keep the current through regulator IC below 300mA . When the current through R1 increases the base current of Q1 (2N 29055) also increases & the load required load current flows through this transistor. By this way a current greater than the capacity of the regulator IC can be delivered to the load. The C1 is used to filter the ripples off the rectifier output. Notes: Assemble the circuit on good quality PCB. T1 can be a 230V primary,15V/1A secondary, step down transformer. If 1 A bridge is not available, make one using four 1N 4007 diodes. The s...

Here is 9V Regulated Power Supply schematic diagram : You can use this power supply for your electronics project which only require electric current about 500mA. This is cheap circuit which will give you stabilized output voltage. If you want to change the output voltage, you should change the IC type. For example, you need 5V output, then change the IC from 7098 with 7805 dan change the output of transformer from 16V AC become 9VAC or 12V AC.

This simpl e circuit will protect the costly equipment from high as well as low voltages and the voltage surges (when power resumes). It also gives a melodious tune when mains power resumes. When mains voltage is normal, the DC voltage at the cathode of zener diode D4 is less then 5.6V. As a result transistor T1 is in ‘off’ state. The DC voltage at the cathode of zener diode D5 is greater than 5.6V and as a result transistor T2 is in ‘on’ state. Consequently, relay RL1 gets energised, which is indicated by lighting up of green LED . Under high mains voltage condition, transistor T1 switches to ‘on’ state because the voltage at cathode of zener diode D4 becomes greater than 5.6V. Consequently, transistor T2 switches to ‘off’ state, making the relay to de-energise Under low mains voltage condition, transistor T1 switches to ‘off’ state and as a result transistor T2 also switches to ‘off’ state, making the relay to de-energise. Read more explanation here

This circuit is not really simple, but will save your money :). This over/under voltage cut-out will save your costly electrical and electronic appliances from the adverse effects of very high and very low mains voltages. The circuit features auto reset and utilises easily available components . It makes use of the comparators available inside 555 timer ICs. Supply is tapped from different points of the power supply circuit for relay and control circuit operation to achieve reliability. The circuit utilises comparator 2 for control while comparator 1 output (connected to reset pin R) is kept low by shorting pins 5 and 6 of 555 IC. The positive input pin of comparator 2 is at 1/3rd of Vcc voltage. Read more explanation here

This is a simple low-cost 12 Volt 50W off-line switching power supply , which can be used for home projects or to learn operation of flyback converters. It can work over a universal AC line input range 90-264 VAC and provides a 12VDC output at more then 4A load. Line and load regulation is better then 0.5%. The unit has overcurrent, overtemperature and overvoltage protections as well as passive inrush current limiting. Output ripple are approximately 0.2 V. If you need to get lower ripple, you may put an additional output LC filter. Complete explanation, visit this site

This page come from my.integritynet.com.au , will show you about how to make a variable regulated power supply . This type of regulation is ideal for having a simple variable bench power supply . Actually I think this is quite important because one of the first projects a hobbyist should undertake is the construction of a bench supply. While a dedicated supply is quite handy e.g. 12V, it's much handier to have a variable supply on hand. There have been many times I have had to "smoke test" a project. This means I have started out at the minimum voltage on my supply (about 3V), seen nothing untoward happening and then slowly winding up the voltage to say 15V (this would only be where the project design called for 15V). By the way, this is the recommended way to test a project after having double checked parts placement against circuit drawings and parts placement guide (if any). Always start out at minimum voltage and look for signs of distress among components (usuall...