How does a regulated power supply work

The output voltage changes by a great value due to the huge change in the current drawn from the supply. But this value may go higher in some countries volts. Temperature Variation — The use of semiconductor devices in electronic devices may cause variation in temperature. These variations in dc output voltage may cause an inaccurate or erratic operation or even malfunctioning of many electronic circuits. For instance, in oscillators the frequency will shift, in transmitters output will get distorted, and in amplifiers, the operating point will shift causing bias instability.

All the above-listed problems are overcome with the help of a voltage regulator which is employed in conjunction with an unregulated power supply. Thus, the ripple voltage is largely reduced. Thus, the supply becomes a regulated power supply. The internal circuitry of a regulated power supply also contains certain current limiting circuits which help the supply circuit from getting fried from inadvertent circuits.

Programmable power supplies are also available to allow remote operation that is useful in many settings. Regulated power supply is an electronic circuit that is designed to provide a constant dc voltage of predetermined value across load terminals irrespective of ac mains fluctuations or load variations.

A regulated power supply essentially consists of an ordinary power supply and a voltage regulating device, as illustrated in the figure. The output from an ordinary power supply is fed to the voltage regulating device that provides the final output. The output voltage remains constant irrespective of variations in the ac input voltage or variations in output or load current. Figure given below shows the complete circuit of a regulated power supply with a transistor series regulator as a regulating device.

Each part of the circuit is explained in detail. A step down transformer is used to step down the voltage from the input AC to the required voltage of the electronic device. This output voltage of the transformer is customized by changing the turns ratio of the transformer according the electronic device specs. The input of the transformer being Volts AC mains, the output is provided to a full bridge rectifier circuit. Know More: Transformers. The rectified DC output is given as input to the filter circuit.

Know More: Filter Circuits. The ac voltage, typically V rms is connected to a transformer which transforms that ac voltage to the level for the desired dc output.

Unregulated power supplies are designed to produce a certain voltage at a particular current. That is, to use the fancy electrical terms again, unregulated power supplies provide a constant amount of power voltage x current. The output voltage will decrease as the output current increases, and vice versa; thus, an unregulated power supply should always be matched as closely as possible to the voltage and current requirements of the device it is powering.

Unregulated power supplies by their nature do not produce a clean i. Without a regulator to stabilize the output voltage, any change in input voltage will be reflected on the output voltage. If the power supply and load requirements are closely matched, there is usually not a problem. However, if the ripple voltage is large enough in relation to the output voltage, it will impact the behavior of circuits and devices.

To reduce the impact of ripple voltage, a filter capacitor can be placed across the positive and negative outputs of the power supply. The capacitor, which resists changes to voltage, will act like a regulator, smoothing the output voltage and allowing for normal operation.

So which is the better choice? It depends on your needs. For instance, a step-down transformer is used in a transistor radio, and a step-up transformer is used in a CRT. Transformer gives separation from the power-line, and must be used even as any modify within voltage is not required. A rectifier is an electrical device used to convert alternating current into direct current. It can be a full wave rectifier as well as half wave rectifier with the help of a transformer by a bridge rectifier otherwise center tapped secondary winding.

A filter in the regulated power supply is mainly used for leveling the ac differences from the corrected voltage. A voltage regulator in the regulated power supply is essential for keeping a steady DC output voltage by supplying load regulation as well as line regulation. For this reason, we can employ regulators like a Zener, transistorized, otherwise 3-terminal integrated regulators. An SMPS-switched mode power supply can be used for supplying huge load current by small power dissipation within the series pass transistor.

Some of the factors are explained below. The load regulation is also known as a load effect. Much like the circuit breaker in a house, the overload protection shuts off the power supply so the load will not be damaged. Efficiency : Efficiency is the ratio of power being pulled from the power grid that is effectively being converted to DC power. An efficient system will reduce heat generation and can save energy. Noise and ripple are artifacts of the transformation of AC to DC and are the byproduct of rectification and switching.

During conversion, the alternating sine wave cannot be completely suppressed. These artifacts are typically combined into one specification, given in peak-to-peak voltage, showing the extent of the noise spikes that arise from switching, which can negatively affect sensitive instrumentation.

The small voltage variations are called ripple. Many times, the amount of fluctuation depends on how well the power supply is matched to the load. Noise is the unwanted additions that occur outside of the normal ripple. It comes from many other sources, including switching and electronic noise generated outside of the power supply, such as from nearby electronics. Noise usually occurs in conjunction with ripple and is much more variable and unpredictable. Switching noise typically occurs at very high frequencies.

Figure 7 is an example of noise created by switching and ripple in a medium quality power supply. Figure 8 illustrates the noise potential in a regulated linear power supply. While much less than the ripple of a regulated switched supply, it can still be significant enough to mask data.

If the noise and ripple are very high, small signals can be overwhelmed or the life of the hardware can be significantly shortened. However, with a high quality power supply it can be virtually eliminated.

At the advent of electrical distribution, the standard current in Europe was alternating current AC and in the US was direct current DC. The main load of electrical usage was the light bulb, which was designed by Thomas A. Edison to use direct current. The conflict was actually much larger, with American and European companies having a vested interest in the decline of one type or the other.

The drawback of alternating current at the time was that load on the system was affected when appliances were turned on and off, affecting others using the line. Direct current had the advantage of using only the current needed and not affecting the rest of the load on the line. Unfortunately for the DC proponents, the voltage drop across the wires from source to output was significant and different voltages could not be sent across the same wires. This meant that DC generation required generating plants to be located within about a few miles of their destination and multiple wires strung for each voltage needed, both of which were prohibitively expensive for rural communities.

A further disadvantage was that DC was really only feasible for small appliances, as the low voltages were too inefficient to be scaled up for technology that required large voltages. In contrast, high voltages of alternating current could be transmitted very long distances on a single line, for hundreds of miles and therefore required fewer generating plants.

Transmission of AC resulted in very little voltage drop, and the voltage could then be reduced through the use of transformers to the desired amount needed at its destination. Additionally, with increasing industrialization, the high voltages were desirable for large loads, such as railways and industrial motors. Competition remained between AC and DC proponents until a series of events, contract awards, and field trials proved that AC transmission lines were the most economical, although DC lines remained in use well into the 20th Century.

Since most appliances, developed by Edison, were DC devices, the need for direct current was strong. Wavelength Electronics solves problems for researchers and OEMs that use high precision laser diodes, quantum cascade lasers, and thermoelectrics.

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Introducing Power Supplies Power is the backbone of any electronic system and the power supply is what feeds the system. AC-DC Conversion Basics A power supply takes the AC from the wall outlet, converts it to unregulated DC, and reduces the voltage using an input power transformer, typically stepping it down to the voltage required by the load.

Figure 1: Alternating Current from Wall Outlet In the first step of the process, the voltage is rectified using a set of diodes. Figure 2: Full Wave Rectified Once the voltage has been rectified, there is still fluctuation in the waveform—the time between the peaks—that needs to be removed.