Dc power supplies-Introduction

jojo September 8, 2009 3 Comments
General Introduction to DC power supplies: The electrical power is almost exclusively generated, transmitted and distributed in the form of ac because of economical consideration but for operation of most of the electronic devices and circuits, dc supply is required. Dry cells and batteries can be used for this purpose. No doubt, they have the advantages of being portable and ripple free but their voltages are low, they need frequent replacement and are expensive in comparison to conventional dc...
read more

Dual power supply using L165

john August 20, 2009 3 Comments
Description. This dual power supply is based on the L165 power operational amplifier from SGS-Thomson Micro electronics. The IC L165 can easily deliver up to 3.5A of current (internally limited). The IC is available in Pentawatt package and is very suitable for power supply applications like this. Here the L165 is wired as a voltage amplifier which amplifies the voltage available at the junction between R1 and R2.The output voltage will be always half of the input voltage (Vin).For...
read more

13V 5A adjustable regulator using LM338

john August 19, 2009 8 Comments
Description. This 13V/5A power supply is based on the famous LM338 IC from the ST Microelectronics. The IC has time dependent current limiting, thermal regulation and is available in 3 lead transistor package. The IC can easily supply well over 5A at an output voltage range between 1.2V and 30V. In this circuit the output voltage is determined by the two resistors R1 and R2.The output voltage can be varied by adjusting the R2.Diodes D2 and D3 are protection...
read more

3A adjustable regulator using LM350

john August 5, 2009 6 Comments
Description. This is the circuit diagram of a 3A adjustable power supply using IC LM350K.. LM350K is a very rugged voltage regulator IC with features like thermal regulation, short circuit protection etc. This circuit is designed as per the application notes in the data sheet and was found to be working very fine.This circuit has improved ripple rejection and better stability compared to the elementary voltage regulator using the same IC. The output voltage can be adjusted by using...
read more

Fuse with status indicator.

john August 4, 2009 No Comments
Description. Here is the circuit diagram of a fuse that has an automatic status indicator. This circuit can be added to circuit that operates from 12V DC. As long as the fuse is intact, the LED D3 will glow continuously and when the fuse blows off the LED will start and continue blinking. The first part of the circuit includes an astable multivibrator built around transistors Q1 and Q2.The output of the multivibrator is coupled to the base of...
read more

40V dual power supply

john July 30, 2009 78 Comments
Description. This 40V dual power supply circuit was designed in response to a request made by Michael from Philippines. His application is to power the 150 Watt amplifier circuit published here. I think this power supply design is adequate for the purpose. The transformer T1 steps down the mains voltage, bridge D1 performs the rectification, C1 and C2 does the job of filtering.C3 and C4 are decoupling capacitors. Circuit diagram with Parts list. Notes. The T1 must be a...
read more

Simple 10W audio amplifier

john November 2, 2011 11 Comments
Description. The circuit given below is of a simple audio amplifier that can deliver 12W to an 8 Ohm speaker. Op amp IC TL081 is used as the preamplifier here. Actually any opamp with matching power supply ratings can be used instead of TL081.Transistors Q1 and Q2 (TIP125 and TIP120) comprises the power amplifier stage. Output is taken from the collector junction of two transistors. Circuit diagram. Notes. The circuit can be assembled on a Vero board. Heat sinks...
read more

Regulated dual power supply circuit

john August 13, 2017 25 Comments
Dual Power Supply Circuit Description The circuit given here is of a regulated dual power supply that provides +12V and -12V from the AC mains. A power supply like this is a very essential tool on the work bench of an electronic hobbyist. The transformer T1 steps down the AC mains voltage and diodes D1, D2, D3 and D4 does the job of rectification. Capacitors C1 and C2 does the job of filtering.C3, C4, C7and C8 are decoupling capacitors....
read more

1.3V Power supply

john May 14, 2009 1 Comment
Description. This 1.3V power supply can be used as replacement for the 1.3V Mercury Cell in any circuit. When the input 5V is given to the circuit, the  voltage drop across  zener diode D1 will be around 2V.The diode D2 will drop a 0.7 V from the 2V volt and the remaining 1.3V will be available at the output. The Resistor R1 limits the current through Zener diode Circuit diagram with Parts list. Notes. The circuit can be assembled...
read more

Soft start power supply using L200

john May 13, 2009 1 Comment
Description. Here is the circuit diagram of a simple soft start power supply using the well known IC L200.The L200 is a monolithic IC that can be used for voltage and current regulation. The built-in features such as thermal shut down, over current protection and input over voltage protection makes this IC nearly indestructible. When the power supply to the circuit is switched ON, the capacitor C3 starts to charge through resistor R3.The internal comparator pin (pin2) of the...
read more