Electronic Project

adjustable voltage and current regulator circuit - Electronic Project

Introduction:

A voltage regulator is a system designed to automatically maintain a constant of the voltage. It may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism or electronic components. Depending on the design, it may be used to regulate one or more AC and DC voltage. Electronic voltage regulators are found in devices such as computer power supplies where they stabilize the DC voltages used by the processor or other elements. In automobile alternators and central power supply station generator plants, voltage regulators control the output of the plant. In an electric power supply distribution system, voltage regulators may be installed at a substation or along distribution lines so that all customers receive steady voltage independent of how much power supply is drawn from the line.

Linear regulators are simple voltage regulator circuit diagrams commonly used in electronics. This paper briefly discusses how linear regulators work, their advantages or disadvantages, variations on the linear regulator, and important datasheet parameters. Linear regulators use a closed feedback loop to bias a pass element to maintain a constant voltage across its output of the terminals. In Figure 1, the op-amp drives the base of Q1 to ensure that the voltage at its inverting input will be equal to the voltage of the reference at its non-inverting input. The op-amp in this circuit has a small load, the base current flow, and minimal capacitive loading. Consequently, it could respond to changes in load very quickly.

Batteries are often shown on a schematic circuit diagram as the source of DC voltage but usually, the actual DC voltage source is a power supply. There are many types of power supply. Most are designed to convert high-voltage AC mains electricity to a suitable low-voltage supply for electronic circuit diagrams and other devices. A more reliable method of obtaining a DC power supply is to transform, rectify, filter, or regulate an AC line voltage. A power supply could be broken down into a series of blocks, each of which performs a particular function.

Diagram of 7805 Voltage Regulator Pinout:

Hardware Required for this Project:

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Working Principle of 0-30V 20A High current adjustable voltage:

The purpose of a current flow regulator is to provide a constant current regardless of changes in the input of the voltage or load current. The schematic shown in Figure 4-42 is that of a circuit diagram designed to provide a constant current of 400 milliamperes. Voltmeters are shown in the schematic to emphasize the voltage drops across the specific components. These voltages will help you understand how the current flow regulator operates. The voltage drop across the base emitter of the junction of Q1 is 0.6 volts. This voltage is the difference between the Zener of the voltage and the voltage drop across R1. The 0.6-volt forward bias of Q1 permits the proper operation of the transistor. The output of the voltage across RL is 6 volts as shown by the voltmeter. With a regulated current flow output of 400 milliamperes, the transistor resistance (RQ1) is 9 ohms. This could be proved by using Ohm's law and the values shown on the schematic.

You should now know how voltage regulators work to provide constant output of the voltages. In some circuits, it may be necessary to regulate the current flow output. The circuitry that provides a constant current flow output is called a constant current regulator or just a CURRENT REGULATOR. The schematic shown in Figure 4-40 is a simplified schematic for a current flow regulator. The variable resistor shown in the schematic is used to illustrate the concept of current flow regulation. You should know from your study of voltage regulators that a variable of the resistor does not respond quickly enough to compensate for the changes. Notice that an ammeter has been included in this circuit diagram to indicate that the circuit shown is that of a current regulator. When the circuit diagram functions properly, the current reading of the ammeter remains constant. In this case, the variable resistor (RV) compensates for changes in the load or DC input of the voltage. Adequate current flow regulation results in the loss of voltage regulation. Studying the schematic shown, you should recall that any increase in load resistance causes a drop in current flow. To maintain a constant current flow, the resistance of RV must be reduced whenever the load of the resistance increases. This causes the total of the resistance to remain constant. An increase in the input of the voltage must be compensated for by an increase in the resistance of RV, thereby maintaining a constant current flow. The operation of a current flow regulator is similar to that of a voltage regulator. The basic difference is that one regulates current flow and the other regulates voltage.

Refer to the schematic shown in Figure 4-43. Remember a decrease in load of the resistance causes a corresponding increase in current flow. In the example shown, the load of the resistance RL has dropped from 15 ohms to 10 ohms. This results in a larger voltage drop across R1 because of the increased current flow. The voltage of the drop has increased from 2.4 volts to 2.5 volts. Of course, the voltage drop across CR1 remains constant at 9 volts due to its regulating ability. Because of the increased voltage drop across R1, the forward bias on Q1 is now 0.5 volts. Since the forward bias of Q1 has decreased when the resistance of the transistor increases from 9 ohms to 14 ohms. Notice that the 5-ohm increase in the resistance across the transistor corresponds to the 5-ohm decrease in the load of the resistance. Thus, the total resistance around the outside loop of the circuit diagram remains constant. Since the circuit is a current flow regulator, you know that output voltages will vary as the regulator maintains a constant current flow output.

A simple voltage/current flow regulator can be made from a resistor in series with a diode (or series of diodes). Due to the logarithmic shape of diode V-I curves, the voltage across the diode changes only slightly due to changes in the current flow drawn or changes in the input. When precise voltage control or efficiency is not important, this design may be fine. Since the forward of the voltage of a diode is small, this kind of voltage regulator is only suitable for low voltage-regulated output. When higher voltage output is needed, a zener diode and series of zener diodes may be employed. Zener diode regulators make use of the zener diode's fixed reverse of the voltage, which can be quite large.

Feedback voltage regulators operate by comparing the actual output voltage to some fixed reference of the voltage. Any difference is amplified and used to control the regulation element in such a way as to reduce the voltage of the error. This forms a negative feedback control loop; increasing the open-loop gain tends to increase regulation accuracy but reduces the stability. (Stability is avoidance of oscillation, and ringing, during step changes.) There will also be a trade-off between stability and the speed of the response to changes. If the output of the voltage is too low (perhaps due to input voltage reducing or load current flow increasing), the regulation element is commanded, up to a point, to produce a higher output of the voltage–by dropping less of the input voltage (for linear series regulators and buck switching regulators).

Frequently Asked Questions

What is voltage regulation and current regulation?

In voltage regulators, the current flow is varied to achieve the required voltage level, while current flow regulators usually involve variations in voltage/resistance to achieve the required current flow output. As such, while it is possible, it is usually difficult to regulate voltage and current at the same time in a circuit diagram.

What is the current regulator in a circuit?

A current flow regulator is a crucial component in electronics engineering. It serves to regulate and maintain a constant electrical current flowing through a circuit, despite variations in load resistance or input of the voltage. In essence, it prevents the electrical of the devices from getting damaged due to inconsistent power supply.

What is an adjustable voltage source?

AVS Voltage Source is an AC Power supply whose Output of the Voltage can be adjusted. In AVS produced with thyristor technology, the voltage of the changes is made without interruption. Voltage switching could be done under full load.

What is the importance of voltage regulation?

Voltage regulators help control fluctuating voltages and power supply that could otherwise be detrimental to electrical machinery. Disturbances such as power supply and surges affect sensitive electronic devices found in vehicles, computers, and batteries of the charging systems to name a few.

What is the current regulation?

Current flow regulation (Creg/ACC) is a weld control procedure for controlling the output to the workpiece. Rather than phase-shifting the SCRs strictly on a time domain basis (for example 50% of sine wave), the control determines the phase angle based on the programmed secondary current flow (Is).

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