Simple DC power delay circuit

jacky May 25, 2010 7 Comments
Description. The circuit diagram shown here is of a simple DC power delay circuit that is based on an SCR. This circuit is a very handy one and can be employed in many applications. The working of this circuit is very simple. When the input power is applied the capacitor C2 charges through resistor R2 and when the voltage across the capacitor just exceeds the Zener diode D3’s breakdown voltage, it breaks down and the SCR H1 is triggered...
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12V boost regulator circuit.

jacky March 4, 2010 3 Comments
Description. Here is the circuit diagram of a 12V boost converter using IC LM2698 from National Semiconductors. The LM2698 is a general purpose boost converter with an 18V, 1.35A. 0.2 Ohm internal switch. This results in high efficiency power conversion to outputs ranging from 2.2V to 17V DC. The input supply voltage range is 2.2V to 17V DC. The IC has excellent line and load regulation and frequency compensation over the entire input voltage range. In the circuit diagram...
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5V buck regulator using LM2678

jacky March 4, 2010 8 Comments
Description. Here is the circuit diagram of a 5V buck switching regulator based on the IC LM2678 from National Semiconductors. LM2678 series of regulators are monolithic integrated circuits which provide all necessary functions required for a buck switching regulator and can drive up to 5A loads. The IC has more than 90% efficiency and has excellent load and line regulation. The LM2678 is available in three fixed output voltages (3.3V, 5V, 12V) and an adjustable output version. The IC...
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Battery eliminator circuit

john December 14, 2009 25 Comments
Description. Here is the circuit diagram of a battery eliminator circuit that can be used as a replacement for 9V PP3 batteries. The circuit given here can be used to power any device that operates from a 9V battery. The transformer T1 steps down the mains voltage and bridge D1 performs the job of rectification. Capacitor C1 is a filter. IC LM317T is the regulator here. The value of R1, R2 and R3 are so selected that the output...
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CVT-Constant Voltage Transformer

jojo January 23, 2018 12 Comments
  With the popularisation of PCs, the constant voltage transformers (CVTs) have also become equally popular. The CVT is simply a magnetic transformer of a special construction that has a capacitor connected across the secondary winding of the transformer. In an ordinary transformer, the primary and secondary windings are wound near each other so that whenever there is a change of voltage across the primary there is a corresponding change in the secondary voltage depending upon the ratio of the...
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Dual Voltage Supplies

jojo July 8, 2014 4 Comments
Dual Power Supply using LM 320 and LM 340 Bipolar or dual voltage supplies can be easily designed with the help of two 3-terminal regulators. This is shown in the figure above using the IC’s LM320 and LM 340. Opposite-phase ac is provided by the transformer’s secondary and a grounded center tap. The single full-wave bridge converts these into positive and negative dc voltages (with respect to the grounded center tap). The output of the rectifier circuit is filtered...
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IC Voltage Regulators

jojo July 7, 2014 7 Comments
A voltage regulator is one of the most widely used electronic circuitry in any device. A regulated voltage (without fluctuations & noise levels) is very important for the smooth functioning of many digital electronic devices. A common case is with micro controllers, where a smooth regulated input voltage must be supplied for the micro controller to function smoothly. You may also like this article on Regulated Power Supply Voltage regulators are of different types. In this article, our interest...
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Controlled Transistor Series Regulator With Overload and Short-Circuit Protection

john October 1, 2009 4 Comments
If the load resistance RL is reduced or load terminals are shorted acciden­tally, a very large load current will flow. It may destroy the pass transistor Q1, diode or possibly some other component. Fuse protection will not prove adequate because the transistor may get damaged in a very small fraction of a second To avoid this situation, a current limiting circuit is added to a series regulator, as illustrated in the figure. The current limit­ing circuit consists of a...
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Controlled Transistor Series Regulator

john October 1, 2009 1 Comment
Controlled Transistor Series Regulator A controlled transistor series regula­tor is shown in the figure. The circuit is quite similar to that of a simple transistor series voltage regulator except that an additional transistor Q2 is inserted in the circuit. The emitter terminal of this transistor Q2 is connected to the negative terminal of input supply through a Zener diode. The base of this additional transistor is connected to the variable tap of a potentiometer. This voltage regulator employs the...
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Zener Controlled Transistor Voltage Regulators

john July 2, 2014 10 Comments
The efficiency of Zener regulated power supply becomes very low when the load current is high. Under such conditions a Zener controlled transistor is always used for maintaining output voltage constant. Basically there are two types of Zener controlled transistor voltage regulators. They are Series Voltage Regulators Shunt Voltage Regulators You may also go through the following articles: Regulated Power Supply, Voltage Regulators, Discrete Transistor Voltage Regulators, and IC Voltage Regulators Transistor Series Voltage Regulator or Emitter Follower Voltage Regulator     A...
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