A power supply is an electrical device that supplies power to the electrical load. The main function of the power supply is to change the electrical current from the source to the appropriate voltage, current, and frequency to drive the load. As a result, the power supply is sometimes referred to as an electric power converter. Some power supplies are separate separate equipment, while others are built into the load equipment they control. The latter example includes the power supplies found on desktop computers and consumer electronics devices. Other functions that can be used by the power supply include limiting the current drawn by the load to a safe level, switching off the current in case of electrical failure, power conditioning to prevent electronic interference or voltage spikes on input from the load, factor correction, and energy saving so it can continue to empower the burden if there is interruption while on a power source (uninterruptible power supply).
All power supplies have a power input connection, which receives energy in the form of an electric current from a source, and one or more power output connections that transmit current to the load. Power sources may come from power grids, such as electrical outlets, energy storage devices such as batteries or fuel cells, generators or alternators, solar power converters, or other power supplies. Inputs and outputs are usually circuit-connected connections, although some power supplies use wireless energy transfer to drive their loads without a wired connection. Some power supplies have other input and output types as well, for functions such as external monitoring and control.
Video Power supply
General classification
Functional
Power supplies are categorized in various ways, including by functional features. For example, a regulated power supply is set is one that maintains a constant output voltage or current despite variations of load current or input voltage. Conversely, the output of unregulated power supply can change significantly when the input voltage or load current changes. Adjustable power supplies allow output voltages or currents programmed by mechanical controls (eg buttons on the front panel of the power supply), or by using control inputs, or both. The adjustable power supply is adjustable and adjustable. The isolated power supply has power output that is electrically independent of its power input; this is different from other power supplies that share a common connection between input and power output.
Packaging
Power supplies are packed in different ways and are classified accordingly. Bench power supply is a stand-alone desktop unit used in applications such as circuit testing and development. Open frame power supply has only a partial mechanical cover, sometimes only consisting of a mounting base; this is usually built into a machine or other equipment. Rack mount power supplies are designed to be secured to a standard electronic equipment rack. Integrated power is a power supply that shares a common printed circuit board with its cargo. The external power , AC adapter or electric brick , is a power supply located on a loaded AC power cord connected to a wall outlet; wall wart is an external supply that integrates with the output outlet itself. It's popular in consumer electronics because of its security; a dangerous 120 or 240 volt voltage current is converted to a safer voltage before entering the appliance.
Power conversion method
The power supply can be broadly divided into linear and linear types. The linear power converter processes the input power directly, with all active power conversion components operating in its linear operating region. In switching power converters, input power is converted to AC or to DC pulses before being processed, by components that operate predominantly in non-linear mode (for example, transistors that spend most of their time in cutoff or saturation). Power is "lost" (converted to heat) when components operate in their linear region and, consequently, switching converters are usually more efficient than linear converters because their components spend less time in linear operating areas. Maps Power supply
Type
DC power supply
The DC power supply is one that supplies a constant DC voltage to its load. Depending on the design, DC power supplies can be powered from a DC source or from an AC source such as a power source.
AC-to-DC supply
DC power supplies use AC power as an energy source. Such power supply will use a transformer to convert the input voltage to a higher or lower AC voltage. A rectifier is used to convert the transformer output voltage to a varying DC voltage, which in turn is passed through an electronic filter to convert it into an unregulated DC voltage.
Filters eliminate most, but not all variations of AC voltage; the remaining AC voltage is known as ripple . The electrical load tolerance of the ripple determines the minimum amount of filtering that should be provided by the power supply. In some applications, high ripple is tolerated and therefore no filtering is required. For example, in some battery charging applications it is possible to implement an electric powered DC power supply with nothing more than a single rectifier transformer and diode, with a resistor in series with the output to limit the charging current.
Switch mode power supply
In a switched-mode power supply (SMPS), the AC power input is directly fixed and then filtered to obtain DC voltage. The resulting DC voltage is then switched on and off at high frequencies by an electronic switching circuit, resulting in an AC current that will pass through a high frequency transformer or inductor. Switches occur at very high frequencies (typically 10 kHz - 1 MHz), allowing the use of transformers and filter capacitors much smaller, lighter, and cheaper than those found in linear power supplies operating at the main frequency. After the inductor or secondary transformer, high frequency AC is repaired and filtered to produce DC output voltage. If SMPS uses a fairly isolated high-frequency transformer, the output will be electrically isolated from the parent; This feature is often important for security.
Switch mode power supply is usually set, and to keep the output voltage constant, the power supply uses a feedback controller that monitors the current drawn by the load. Switching switching cycle increases when power output requirements increase.
SMPSs often include safety features such as current limiting or crowbar circuitry to help protect devices and users from harm. If any abnormal high current withdrawal is detected, the switched-mode supply may assume this is a short direct and will die on its own before the damage is complete. PC power supplies often signal power to the motherboard; the absence of this signal prevents operation when an abnormal supply voltage is present.
Some SMPs have an absolute limit on their minimum current output. They can only produce output above a certain power level and can not work below that point. Under no-load conditions, the frequency of the power slicer circuit will increase to high speed, causing an isolated transformer to act as a Tesla coil, causing damage due to very high power surge. The mode storage connected to the protection circuit can briefly activate but then switch off when no loads detected. Very small low power dummy loads such as a ceramic power resistor or 10-watt light bulb can be attached to the supply to enable it to run without the main load installed.
Switch-mode power supplies used in computers have historically low power factor and are also a significant source of line noise (caused by electric and transient harmonization). In a simple switch-mode power supply, the input stage can distort the line voltage waves, which can affect other loads (and produce poor power quality for other utility customers), and lead to unnecessary heating in cables and distribution equipment. Furthermore, customers issue higher electricity bills when operating a lower power factor load. To solve this problem, some power-mode computer switches power factor correction, and can use input filters or additional switching stages to reduce channel interference.
Linear regulator
Linear voltage regulator function is to convert DC voltage into constant, often specific, and lower DC voltage. In addition, they often provide a current-limiting function to protect the power supply and load from more current (excessive, potentially destructive) currents.
The constant output voltage is required in many power supply applications, but the voltage supplied by many energy sources will vary with changes in load impedance. Furthermore, when an unregulated DC power supply is an energy source, the output voltage will also vary by changing the input voltage. To avoid this, some power supplies use linear voltage regulators to maintain the output voltage at a stable value, independent of input voltage fluctuations and load impedances. Linear regulators can also reduce the amount of ripple and noise at the output voltage.
AC power supply
The AC power supply usually takes the voltage out of the socket (power supply) and uses the transformer to increase or decrease the voltage to the desired voltage. Some filtering can be done as well. In some cases, the source voltage equals the output voltage; this is called an isolation transformer. Other AC power supply transformers do not provide parent isolation; this is called autotransformer; variable autotransformer output known as variac. Another type of AC power supply is designed to provide an almost constant current, and the output voltage may vary depending on the load impedance. In case when the power source is direct current (such as car storage battery), the inverter and step-up transformer can be used to convert it to AC power. Portable AC power can be provided by an alternator powered by a diesel engine or gasoline engine (for example, at a construction site, in a car or boat, or a backup power generator for emergency services) whose currents are forwarded to the regulatory circuit to provide a constant voltage to the output. Some types of AC power conversion do not use the transformer. If the output voltage and input voltage are the same, and the main purpose of this device is to filter AC power, it can be called line conditioner. If the device is designed to provide backup power, this can be called an uninterruptible power supply. A circuit can be designed with a voltage multiplier topology to directly increase AC power; previously, such an application is a vacuum tube AC ​​/DC receiver.
In modern usage, AC power supply can be divided into single phase and three phase system. "The main difference between a single phase and three-phase AC power is a delivery assignment." AC power supplies can also be used to change the frequency and voltage, they are often used by manufacturers to check the suitability of their products for use in other countries. 230V 50 Hz or 115 60 Hz or even 400 Hz for avionics testing.
Programmable power supply
A programmable power supply is one that allows remote control of its operation through analogue input or a digital interface such as RS232 or GPIB. The controlled properties may include voltage, current, and in terms of the AC power supply, frequency. They are used in a wide range of applications, including automated testing equipment, crystal growth monitoring, semiconductor fabrication, and x-ray generators.
Programmable power supplies typically use an integral microcomputer to control and monitor the operation of the power supply. Power supplies equipped with computer interfaces can use either proprietary communication protocols or standard protocols and control language devices such as SCPI.
Uninterruptible power supply
Uninterruptible power supply (UPS) takes power from two or more sources simultaneously. These are usually powered directly from AC power, while charging storage batteries. If there is a pause or power failure, the battery will immediately take over so that the load never has an interruption. In computer installations, it gives the operator time to shut down the system in a regular way. Other UPS schemes can use internal combustion engines or turbines to continuously supply power to the system in parallel with power coming from AC. Engine-driven generators will usually stop, but can reach full power in a matter of a few seconds to keep the vital equipment running without interruption. Such schemes can be found at the hospital or telephone headquarters.
High voltage power supply
A high voltage power supply is one that generates hundreds or thousands of volts. Special output connectors are used that prevent arcing, insulation damage and accidental human contact. Federal Standard Connectors are typically used for applications over 20 kV, although other connector types (eg SHV connectors) can be used at lower voltages. Some high voltage power supplies provide analog input or digital communication interfaces that can be used to control the output voltage. High voltage power supplies are commonly used to accelerate and manipulate electrons and beam ions in equipment such as x-ray generators, electron microscopes, and focused beam ion columns, and in various other applications, including electrophoresis and electrostatic.
The high-voltage power supply usually applies most of their input energy to the power inverter, which in turn drives a voltage multiplier or high rotation ratio, a high voltage transformer, or both (usually a transformer followed by a multiplier) to produce a high voltage. The high voltage is passed from the power supply through a special connector and is also applied to the voltage divider which converts it into a low voltage meter signal compatible with the low voltage circuit. The metering signal is used by a closed-loop controller that regulates the high voltage by controlling the input power of the inverter, and it can also be delivered from the power supply to allow external circuits to monitor high-voltage output.
Specifications
The suitability of a particular power supply for an application is determined by the various power supply attributes, which are usually listed in the power supply specification . The attributes typically specified for the power supply include:
- The type of input voltage (AC or DC) and range
- Power conversion efficiency
- The amount of voltage and current that can be supplied to its charge
- How stable is the voltage or output current under various channel conditions and loads
- How long can supply energy without refueling or refilling (applicable to power supplies using portable energy sources)
- Operating and storage temperature range
Power supply app
The power supply is a fundamental component of many electronic devices and is therefore used in a variety of diverse applications. This list is a small example of many applications of power supplies.
Power supply computer
The modern computer power supply is a switch-mode power supply that changes the AC power from the mains supply, to some DC voltage. Switch-mode inventory replaces linear supplies due to cost, weight, and size increase. A diverse set of output voltages also has widely diverse current withdrawal requirements.
Vehicle power supply
Electric vehicles are those that rely on energy created through power generation. The power supply unit is part of the design required to change the battery power of a high voltage vehicle.
Welding power supply
Arc welding uses electricity to join the metal by melting it. Electricity is provided by welding power supplies , and can be either AC or DC. Arc welding requires high currents usually between 100 and 350 amperes. Some types of welding can use at least 10 amperes, while some point welding applications use currents as high as 60,000 amperes for a very short time. The welding supply consists of a transformer or engine that drives the generator; Modern welding equipment uses semiconductors and may include microprocessor controls.
Aircraft power supplies
Both commercial and military avion systems require DC-DC or AC/DC power supplies to convert energy into usable voltage. It may often operate at 400Hz for the sake of heavy savings.
AC adapter
The AC adapter is a power supply that is plugged into an AC power socket. The AC adapter is also known by various other names such as "plug pack" or "plug-in adapter", or with slang terms like "wall wart". The AC adapter usually has a single AC or DC output delivered through a cable connected to the connector, but some adapters have multiple outputs that can be delivered via one or more cables. The "Universal" AC Adapter has an interchangeable input connector to accommodate different AC power voltages.
Adapters with AC output can only consist of passive transformers (plus some diodes in the DC output adapter), or they can use switch-mode circuits. The AC adapter consumes power (and generates an electric and magnetic field) even when it is not connected to the load; for this reason they are sometimes known as "electric vampires", and can be plugged into an extension socket for easy shutdown and power on.
Thermal Management
The power supply of the electrical system tends to generate a lot of heat. The higher the efficiency, the more heat is drawn away from the unit. There are many ways to manage the heat from the power supply unit. The types of cooling are generally divided into two categories - convection and conduction. Common convection methods for cooling electronic power supplies include natural airflow, forced airflow, or other liquid streams above the unit. Common conduction cooling methods include heat sinks, cold plates, and thermal compounds.
Overload protection
The power supply often has protection from short circuit or overload which can damage supply or cause fire. Fuses and circuit breakers are two commonly used mechanisms for overload protection.
A fuse contains a piece of short wire that melts if too much current flows. This effectively disconnects the power supply from its load, and the equipment stops working until the problem causing the overload is identified and the fuse is replaced. Some power supplies use very thin wire connections that are soldered as axis. The fuses in the power supply unit may be replaced by an end user, but fuses in consumer equipment may require tools to access and change.
The circuit breaker contains elements that heat, flex and trigger the spring that shuts down the circuit. After the element cools down, and problems are identified, the breaker can be reset and power recovered.
Some PSUs use thermal cuts buried in the transformer rather than the fuse. The advantage is allowing larger currents to be drawn for a limited time rather than continuously supplied. Some clippings like that self reset, some only used once.
Current restrictions
Some inventories use current limitation instead of power cut if overloaded. Two types of current limitation are electronic limitation and impedance restriction. The first is common on the laboratory bench PSU, the latter is common on the inventory of less than 3 watts of output.
The folding current limiter reduces the output current to far less than the maximum non-interference current.
Terminology
- SCP - Short circuit protection
- OPP - Overpower Protection (overloaded)
- OCP - Overflow protection
- OTP - Temperature protection protection
- OVP - Overvoltage Protection
- UVP - Undervoltage Protection
- UPS - Uninterruptible Power Supply
- PSU - Power Supply Unit
- SMPSU - Switch Mode Power Supply Unit
See also
- AC Adapter
- Capacitive power supply
- Power plant
- High voltage
- Primary electricity by country
- Generator-motor
- Power cord
- Sense (electronics)
- Voltage
References
External links
- Introduction to Bench Power Supplies - B & amp; K Precision
- Understanding Linear Power Operations
- Load Resources for Peak Efficiency, James Colotti, EDN 1979 5 October
Source of the article : Wikipedia
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