What is a power supply?

What is a power supply?

A power supply is an electrical device that provides power to an electrical load. The main purpose of a power supply is to convert the current from the source to the correct voltage, frequency, and current to power the load. As a result, power supplies are sometimes known as electric power converters. Some power supplies are stand-alone units, while others are integrated into the load appliances they power. Power supplies seen in desktop computers and consumer electronics devices are examples of the latter. Other functions of power supplies include limiting the current drawn by the load to safe levels, shutting off the current in the event of an electrical fault, power conditioning to prevent electronic noise or voltage surges on the input from reaching the load, power-factor correction, and storing energy to continue powering the load in the event of a temporary interruption in the source power (uninterruptible power supply). You can check the power supply price in Pakistan.

All power supplies have a power input connection that receives energy from a source in the form of electric current and one or more power output or rail connections that distribute current to the load. The power supply could be the electric power grid, such as an outlet, energy storage devices like batteries or fuel cells, generators or alternators, solar power converters, or another power supplier. Although most power supplies have hardwired circuit connections for input and output, some use wireless energy transfer to power their loads without physical connections. Other sorts of inputs and outputs are available on some power supply for functions such as external monitoring and control.

Types of power supply

DC power supply

An AC-to-DC power supply takes an AC input voltage and produces a DC output voltage. Depending on the application, the output voltage may contain significant or minor quantities of AC frequency components known as ripple voltage, which are related to the frequency of the AC input voltage and the operation of the power supply. A DC-to-DC converter is a DC power supply that operates on a DC input voltage. This section focuses primarily on the AC-to-DC version.

Linear power supply

In a linear power supply, the AC input voltage is passed through a power transformer and then rectified and filtered to obtain a DC voltage. Filtering reduces the amplitude of the AC mains frequency present at the rectifier output and can be as simple as a single capacitor or as complex as a pi filter. The ripple tolerance of the electrical load dictates the minimum amount of filtering that must be provided by the power supply. In some applications, the ripple can be neglected entirely. For example, in some battery charging applications, the power supply consists of only a transformer and a diode, with a simple resistor placed at the power supply output to limit the charging current.

Switching power supply

In a switching power supply (SMPS), the AC mains input is directly rectified and then filtered to obtain a DC voltage. The resulting DC voltage is then switched on and off at high frequency by electronic switching circuitry, thereby producing an AC current that will pass through a high-frequency transformer or inductor. Switching takes place at a much higher frequency (typically 10 kHz - 1 MHz), thus enabling the use of transformers and filter capacitors that are much smaller, lighter, and lower than those found in mains-frequency linear power supplies. Are expensive. After the inductor or transformer secondary, the high-frequency AC is rectified and filtered to produce a DC output voltage. If the SMPS uses a properly insulated high-frequency transformer, the output will be electrically isolated from the mains. This feature is often required for security.

Switched-mode power supplies are usually regulated, and to keep the output voltage constant, the power supply uses a feedback controller that monitors the current drawn by the load. The switching duty cycle increases as power output requirements increase.

SMPSs often include safety features such as current limiting or a crowbar circuit to help protect the device and the user from damage. In the event that an abnormally high current power draw is detected, the switched-mode supply assumes It could be that it is a direct short and will shut itself off before damage is done. PC power supplies often provide a power-good signal to the motherboard. The absence of this signal prevents operation when abnormal supply voltages are present.

Some SMPSs have an absolute limit on the minimum current output. They are only able to output above a certain power level and cannot operate below that point. Under no-load conditions the frequency of the power slicing circuit increases too rapidly, causing the isolation transformer to act as a Tesla coil, resulting in losses due to high voltage power spikes. Switched-mode supplies with protection circuits may turn on briefly but then turn off when no load is detected. A very small low-power dummy load such as a ceramic power resistor or a 10-watt light bulb can be connected to the supply to allow it to operate without a primary load.

Switch-mode power supplies used in computers have historically had low power factors and have also been significant sources of line interference (due to induced power line harmonics and transients). In simple switch mode power supplies, the input stage can distort the line voltage waveform, which can adversely affect other loads (and result in poor power quality for other utility customers), and wires. And may cause unnecessary heating in distribution equipment. Additionally, consumers pay higher electricity bills for operating low power factor loads. To prevent these problems, some computer switch-mode power supplies optimize the power factor, and may use input filters or additional switching stages to reduce line interference.

Capacitive power supply

A capacitive power supply (transformerless power supply) uses the reactance of a capacitor to step down the mains voltage to a small AC voltage. Typically, the resulting reduced AC voltage is rectified, filtered, and regulated to produce a constant DC output voltage.

The output voltage is not isolated from the mains. Consequently, anything connected to a power supply must be reliably insulated, to avoid exposing people and equipment to dangerous high voltages.

The voltage-dropping capacitor must withstand the full mains voltage, and must also have sufficient capacitance to support the maximum load current at the rated output voltage. Taken together, these constraints limit the practical use of this type of supply to low-power applications.

Linear regulator

The function of a linear voltage regulator is to convert a varying DC voltage to a constant, often specified, low DC voltage. In addition, they often provide a current-limiting function to protect the power supply and load from overcurrent (excessive, potentially destructive current).

Many power supply applications require a constant output voltage, but the voltage supplied by many power sources will vary with changes in load impedance. Furthermore, when an unregulated DC power supply is the energy source, its output voltage will also vary with changing input voltage. To prevent this, some power supplies use a linear voltage regulator to maintain the output voltage at a constant value, independent of fluctuations in input voltage and load impedance. Linear regulators can also reduce the magnitude of ripple and noise on the output voltage.

AC power supply

An AC power supply usually takes voltage from a wall outlet (mains supply) and uses a transformer to step up or step down the voltage to the desired voltage. Some filtering may also occur. In some cases, the source voltage is equal to the output voltage. This is called an isolation transformer. Other AC power supply transformers do not provide mains isolation. These are called autotransformers. A variable output autotransformer is known as a variac. Other types of AC power supplies are designed to provide approximately constant current, and the output voltage may vary depending on the load impedance. In cases where the power source is direct current, (such as an automobile storage battery), an inverter and step-up transformer can be used to convert it to AC power. Portable AC power may be provided by a diesel or gasoline engine-driven alternator (for example, on a construction site, in an automobile or boat, or as backup power generation for emergency services), whose current is passed to a regulator circuit to provide a constant voltage at the output. Some types of AC power conversion do not use a transformer. If the output voltage and input voltage are the same, and the primary purpose of the device is to filter AC power, it may be called a line conditioner. If the device is designed to provide backup power, it may be called an uninterruptible power supply. A circuit can be designed with a voltage multiplier topology to directly amplify AC power. Previously, such an application was the vacuum tube AC/DC receiver.

In modern use, AC power supplies can be divided into single-phase and three-phase systems. AC power supplies can be used to change frequency as well as voltage, often used by manufacturers to test the suitability of their products for use in other countries. 230 V 50 Hz or 115 60 Hz or even 400 Hz for avionics testing.

AC adapter

An AC adapter is a power supply that is built into the AC mains power plug. AC adapters are also known by various other names such as "plug pack" or "plug-in adapter", or by slang terms such as "wall wart". AC adapters typically have a single AC or DC output that is routed to a connector via a hardwired cable, but some adapters have multiple outputs that can be routed over one or more cables. "Universal" AC adapters have interchangeable input connectors to accommodate different AC mains voltages.

Adapters with AC output may consist of only a passive transformer (plus a few diodes in the DC-output adapter), or they may use switch-mode circuitry. AC adapters consume electricity (and generate electric and magnetic fields) even when not connected to a load. For this reason, they are sometimes known as "electrical vampires", and can be plugged into power strips to allow them to be turned on and off easily.

Programmable power supply

A programmable power supply (PPS) is one that allows remote control of its operation via an analog input or a digital interface such as RS232 or GPIB. Controlled characteristics may include voltage, current, and frequency in the case of AC output power supplies. They are used in a wide variety of applications, including automated equipment testing, crystal growth monitoring, semiconductor fabrication, and X-ray generators.

Programmable power supplies typically use an integral microcomputer to control and monitor power supply operation. Power supplies equipped with a computer interface may use proprietary communication protocols or standard protocols and device control languages such as SCPI.

Uninterruptible power supply

An uninterruptible power supply (UPS) draws its power from two or more sources simultaneously. It is usually powered directly from the AC mains, while simultaneously charging the storage battery. If there is a mains dropout or failure, the battery takes over immediately so that the load never experiences an interruption. Instantaneous here should be defined as the speed of electricity inside the conductors which is close to the speed of light. This definition is important because the transmission of high-speed data and communication service should have continuity/non-interruption of the service. Some manufacturers use a semi-standard of 4 milliseconds. However, even 4ms is not fast enough to transfer from one source to another with high-speed data. A transition should be made before the procedure. A UPS that fulfills this requirement is called a True UPS or a Hybrid UPS. The amount of time a UPS will supply is often based on the batteries and generators combined. This time range can range from a minimum of 5 to 15 minutes to hours or days. In many computer installations, the batteries only have enough time to allow operators time to shut down the system in an orderly manner. Other UPS schemes may use an internal combustion engine or turbine to supply electricity during utility power outages and then the amount of battery time depends on how long it takes the generator to come online and the fragility of the goods being carried. Such schemes are found in hospitals, data centers, call centers, cell sites, and telephone central offices.

High voltage power supply

A high voltage power supply is one that outputs hundreds or thousands of volts. A special output connector is used which prevents arcing, insulation breakdown and accidental human contact. Federal standard connectors are generally used for applications above 20 kV, although other types of connectors (eg, SHV connectors) may be used at lower voltages. Some high-voltage power supplies provide an analog input or digital communication interface that can be used to control the output voltage. High-voltage power supplies are commonly used to accelerate and manipulate electron and ion beams in instruments such as X-ray generators, electron microscopes, and focused ion beam columns, and in a variety of other applications, including electrophoresis and electrostatics.

High-voltage power supplies typically put most of their input energy into a power inverter, which in turn uses a voltage multiplier or high-turns-ratio, high-voltage transformer, or both (usually a transformer followed by a multiplier) drives to produce a high. Voltage. The high voltage is taken out of the power supply through a special connector and is also applied to a voltage divider which converts it to a low-voltage metering signal compatible with the low-voltage circuitry. The metering signal is used by a closed-loop controller to control the high voltage by controlling the inverter input power, and it can also be fed out of the power supply to allow external circuitry to monitor the high-voltage output.

Bipolar power supply

A bipolar power supply operates in all four quadrants of the voltage/current Cartesian plane, meaning that it will produce the positive and negative voltages and currents required to maintain regulation. When its output is controlled by a low-level analog signal, it is effectively a low-bandwidth operational amplifier with high output power and seamless zero-crossing. This type of power supply is commonly used to power magnetic instruments in scientific applications.

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