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AC to DC Converters: Features, Design & Applications

Electrical circuits that convert alternating current (AC) input to direct current (DC) output are known as AC-DC converters. They’re employed in power electronic applications when the power input is a sine-wave AC voltage of 50 Hz or 60 Hz that needs to be converted to a DC output.

One of the most significant components in power electronics is the AC to DC Converter. This is due to the fact that these conversions are used in a variety of real-world applications. Rectification is the process of converting alternating electricity to direct current. The rectifier transforms the AC supply to DC at the load end connection. Similarly, transformers are commonly employed to reduce the voltage level of an AC source in order to improve the operating range of a DC supply.

Concept of Alternating current (AC) & Direct current (DC)

  • Alternating Current

The current changes direction and flows forward and backward in alternating current. An alternating current is a current whose direction changes on a regular basis (AC). It has a frequency that is not zero. AC generators, dynamos, and other devices produce it.

Simple AC Circuit Fig: Simple AC Circuit

  • Direct Current

The current in direct current does not fluctuate in amplitude or polarity. Direct current is when the current in a conductor always flows in the same direction. It has a frequency of zero. Cells, batteries, and DC generators, among other things, create it.

Simple DC Circuit Fig: Simple DC Circuit

Types

  • Linear devices are simple and low-cost, but they’re also big and inefficient. They convert excess electricity to heat, which can be problematic for applications that are temperature-sensitive.
  • Switching devices are AC to DC converters with a switched-mode power supply that are more complicated (SMPS). A switching regulator switches between full-on and full-off states quickly, reducing energy consumption. Switching converters are more efficient, smaller, and lighter than linear converters, but they are also more complex. If not thoroughly suppressed, they can produce electrical noise problems, and simple designs may have a low power factor.

Specifications

  • Allowable AC input can be set (e.g., 115, 208, or 230 VAC only) or a range (e.g., 85-264 VAC).
  • DC output is measured in watts (e.g., 3 to 1,000), volts (e.g., 3 to 380), and amps (positive or negative; 1.6 to 6,000).
  • Operating temperature ranges (e.g., -20 to 70 C) are also given for AC DC converters.

Features

Overcurrent, overvoltage, and short circuit protection may be included in AC-DC converters with multiple outputs. Ruggedized electronics are utilized in military applications because they are durable and shock-resistant. To counteract distortion and raise the power factor, certain switching converters have active or passive power factor correction. It’s possible that a remote on/off switch is provided.

Simple Steps to change AC into DC

Let’s talk about AC to DC converters now. Consider the 230V AC to 5V DC converter, which is a commonly used converter in the power supply circuit.

1. Stepping down the Voltage Levels

When delivering power across long distances, voltages may need to be increased. Similarly, for equipment that requires less power, voltages must be reduced. Step-up transformers are used to raise voltage levels, while step-down transformers are used to lower voltage levels.

Take a look at a transformer with a 12V output. By employing a step-down transformer, the 230V AC power source is transformed to 12V AC. The product of the square root of two and the RMS value gives the RMS value and its peak value, which is nearly equivalent to 17V, which is the output of the step-down transformer.

2. AC to DC Power Converter Circuit

At the load end connection, the rectifier transforms the AC supply to DC. Rectifiers come in a variety of shapes and sizes, including half-wave, full-wave, and bridge rectifiers.

AC to DC Converter Circuit

A full bridge rectifier is made up of four diodes coupled in a bridge configuration. During forward bias, the diode only conducts in one direction. In the opposite direction, i.e. during reverse bias, it remains in an off state.

The diodes D2 and D4 in the above circuit conduct during the positive half cycle. Diodes D1 and D3 conduct during the negative half cycle of the power supply. As a result, input AC power is rectified into output DC power in this manner. The issue is that DC output power contains pulses and is not pure DC.

3. Obtaining Pure DC Waveform

The pulsating DC must be converted to pure DC. Capacitors are used in the majority of the circuit to accomplish this. While the input voltage rises from zero to its maximum value, the capacitor is employed to store energy. While the input voltage is dropping from its highest value to zero, the capacitor’s energy can be discharged.

Using this charging and discharging operation of the capacitor, we may turn the pulsing DC into pure DC.

4. Regulating Fixed DC Voltage

Finally, we use the voltage regulator IC to fix the output voltage to the desired value. The 78XX is the name of the DC voltage regulators IC. The output voltage value is represented by the last two numbers XX. The 7805 Voltage Regulator IC, for example, is used to limit the output voltage to 5V. A 7809 voltage regulator IC is used to limit the voltage to 9V.

Applications

Almost all electronics and electrical devices need AC to DC converters. They are utilized in household applications such as vacuum cleaners, washing machines, refrigerators, and electric rice cookers as power supply circuits. Usable devices such as computers, televisions, cell phone chargers, and other AC-to-DC Converters serve a critical part in daily life.

Most electronic sensors and modules require a DC source, hence AC to DC Converters are required. Medical devices, factory automation, building automation, process control systems, signs displays, and telecommunications all employ them.

Renewable energy management, test, and measurement equipment, defense, aerospace, and transportation systems are some of the additional uses for AC to DC Converters.

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