What Do All These Power Supply Terminologies Mean?
Power supply solutions are essential for the successful operation of electrical devices in any installation, whether in industries or at homes. This is because the characteristics of power being supplied often differ from those of the power that devices require. For example, electricity is usually transmitted over long distances in the form of alternating current. It’s easier to transmit it that way. As a result, mains current is usually in alternating current.
However, a number of home appliances use electricity in the form of direct current. For the mains electricity to be used to power a device such as a desktop computer, it has to be converted into direct current.
Similarly, if a homestead uses solar power, which stores electricity in batteries, it may be necessary to convert direct current into alternating current.
Power supply solutions take care of such conversions. They are built differently, depending on their intended use. The power supply built for a weapons system on a ship will be different from that built for an industrial-grade printer.
As such, there are different types of power supplies.
You’ll encounter numerous terms, all associated with power supplies. These include ruggedized power supply, medical power supply, uninterruptible power supply, switching power supplies, and linear power supplies.
There are several classifications of power supply products.
Classification By Current
Power supplies can be classified as either ac or dc power supplies depending on the type of current that they handle.
Ac power supplies supply alternating current to electric loads. The source of alternating current can be mains electricity or other sources like an alternator. Such power supplies are used to power home appliances like fans, air conditioners, and refrigerators, in addition to devices like motors and pumps.
Dc power supplies deliver direct current to electronic devices. They are commonly used for electrical devices like computers. A dc power supply can draw power from sources of direct current like a solar panel or a battery.
Classification By Function
Power supply products perform a wide range of power conversion functions. In addition, various power supplies achieve their functions differently. Here are some classifications of power supplies according to the function they perform.
Uninterruptible Power Supplies
You might have heard of the term uninterruptible power supply (UPS). This refers to a power supply that has an internal battery for storing power. It takes power from mains electricity while transmitting it to the load and – at the same time – storing some of the power in its internal battery.
This way, if a problem occurs with the mains power supply, the battery instantly takes over as a source of power for the device.
Uninterrupted power is crucial for installations such as call centers, data centers, and hospitals.
Linear Power Supplies
Linear power supplies first use a transformer to step the input voltage either up or down, in accordance with the required output voltage. The current is then rectified and filtered. For cases where constant voltage is required, a linear regulator is used. These power supplies have low noise and are commonly used in communication installations. The typical medical power supply will also be a linear power supply.
Switching Power Supplies
Switching power supplies were meant to overcome shortcomings of linear power supplies like inefficiency and bulkiness. They use the pulse-width modulation technique, which is highly efficient in power regulation. Their main disadvantage is that they have high noise and are thus unsuitable for low-noise applications, for example in some military use-cases.
AC Adapters
The part of an AC power plug that deals with power conversion is called an AC adapter, a plug pack, or a wall wart. An AC adapter can have one or multiple outputs. If it has several outputs, it is called a universal adapter, which has a range of connectors to accommodate devices with different power requirements.
Adapters typically use a combination of transformers, diodes, and switch-mode circuitry to perform their function.
High-Voltage Power Supplies
These are used in applications that need thousands of volts, for example in electron manipulation for x-ray machines, electron microscopes, and focused ion beam columns. Other applications that need high voltage include electrophoresis and electrostatics.
Such power supplies have an inbuilt power inverter. A huge amount of energy is applied to the inverter, which uses a high-voltage transformer or a voltage multiplier to produce high-voltage for the load.
Insulation breakdown, arcing, and accidental human contact are problems that come with high voltage. To deal with them, high-voltage power supplies are usually equipped with a special output connector.
In some high-voltage power supplies, output power characteristics can be controlled either through an analog or digital interface.
Programmable Power Supplies
Programmable power supplies allow arbitrary determination of power output characteristics. Such characteristics include current, voltage, and frequency. This is as opposed to non-programmable supplies which allow less freedom in controlling the output characteristics. Such supplies usually have an interface through which output power is controlled. The interface can be analog, consisting of a knob, or digital, consisting of USB or RS232 interfaces.
A programmable power supply will also have additional features such as overvoltage compensation and short-circuit protection.
Regulated Power Supplies
Regulated power supplies deliver a constant output, regardless of whether the input is constant. In unregulated power supplies, power output can vary depending on variations in input.
Regulated power supplies usually contain multiple components to help them regulate power output. These include a rectifier, a regulator, a filter, and a transformer.
Ruggedized Power Supplies
These are power supplies that are made specially for use in harsh environmental conditions for prolonged periods. Such conditions include high and low temperatures, and high-moisture environments.
Normal power supplies would not last long in such conditions and would therefore prove unreliable.
Military Power Supplies
These are made specially for the defense industry. They are ruggedized, to ensure that they can withstand harsh conditions not only like high moisture but also battlefield conditions such as heavy artillery fire.
In addition, they comply with a set of strict military standards on multiple parameters. Compliance with military standards ensures that they are highly reliable. For example, during testing, they are subjected to a replica of the field conditions that they are expected to operate in. They may be subjected to heavy rainfall or to drop-tests.
This way, any issues are dealt with before the power supply ever gets to the market.
Bipolar Power Supplies
Bipolar power supplies generate voltages and currents of both a negative and positive nature. They operate in all quadrants of the voltage-current cartesian plane. They are commonly used to power magnetic devices in scientific applications.
Classification By Packaging
Power supplies can also be classified according to packaging. They can be bench, open-frame, external, integrated, or rack-mounted.
A rack-mounted power supply is meant to be securely placed in normal electronic equipment racks.
An integrated power supply shares a printed circuit board with the load that it’s powering.
An external power supply is located on the load’s power cord, which is plugged into a wall outlet, while a wall wart is integrated into the outlet itself.
Open frame power supplies are built into other equipment and usually have a partial mechanical enclosure.
Bench power supplies are desktop units typically used in circuit testing and development.
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