A regulated power supply is an embedded circuit; it converts unregulated AC (Alternating Current) into a constant DC. With the help of a rectifier it converts AC supply into DC. Its function is to supply a stable voltage (or less often current), to a circuit or device that must be operated within certain power supply limits. The output from the regulated power supply may be alternating or unidirectional, but is nearly always DC (
Direct Current
Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or eve ...
).
The type of stabilization used may be restricted to ensuring that the output remains within certain limits under various load conditions, or it may also include compensation for variations in its own supply source. The latter is much more common today.
Applications
D.C. variable bench supply
A bench power supply usually refers to a
power supply
A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a ...
capable of supplying a variety of output voltages useful for BE (
bench testing
Bench or The Bench can refer to:
Furniture
*Bench (furniture), a long seat
*Workbench, a table at which manual work is done
*Countertop or benchtop
Arts
*The Bench (2000 film), ''The Bench'' (2000 film), a Danish film
*The Bench (TV series), ''Th ...
) electronic circuits, possibly with continuous variation of the output voltage, or just some preset voltages. Some have multiple selectable ranges of current/voltage limits which tend to be
anti-proportional.
A laboratory ("lab") power supply normally implies an accurate bench power supply, while a balanced or tracking power supply refers to twin supplies for use when a circuit requires both positive and negative supply rails).
Types
Variable bench power supplies exist both as
linear
Linearity is the property of a mathematical relationship ('' function'') that can be graphically represented as a straight line. Linearity is closely related to '' proportionality''. Examples in physics include rectilinear motion, the linear ...
(transformer first) and
switched-mode power supply (full-bridge rectifier first), each with a different set of benefits and disadvantages:
=Linear
=
The linear type produces only very little noise (or "ripple voltage") and is less prone to external electromagnetic and radio frequency interference (EMI, RFI), making it preferable for
audio equipment and
radio
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transm ...
-related applications and for powering delicate circuitry. Linear power supplies also have fewer failable parts which increases longevity, and have a quicker
transient response
In electrical engineering and mechanical engineering, a transient response is the response of a system to a change from an equilibrium or a steady state. The transient response is not necessarily tied to abrupt events but to any event that aff ...
. Linear variable bench power supplies have existed since longer ago, dating back at least to the 1980s.
Linear power supplies typically make clicking sounds while adjusting the voltage, caused by adjustment between transformer taps. This is done to reduce energy wasted to heat by widening or narrowing the selected section of the secondary side of the transformer to be as close above the user-selected output voltage as possible.
=Switching
=
Switching-mode power supplies are more lightweight, efficient, and more compact at a similar power rating, making them suitable for high-power applications. The higher efficiency means less heat production at the same output power, thus less wasted energy and needed cooling. Additionally, they may be able to operate on a wider
MAINS input voltage range, typically around 110 to 240 volts rather than a section of approximately twenty volts on only end of the range, to be able to operate internationally. Similar switching technology is used in
AC adapters that charge battery-powered devices including
mobile phone
A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive telephone call, calls over a radio freq ...
s,
laptop computer
A laptop, laptop computer, or notebook computer is a small, portable personal computer (PC) with a screen and alphanumeric keyboard. Laptops typically have a clam shell form factor with the screen mounted on the inside of the upper l ...
s, and
electric bicycle
An electric bicycle (e-bike, eBike, etc.) is a motorized bicycle with an integrated electric motor used to assist propulsion. Many kinds of e-bikes are available worldwide, but they generally fall into two broad categories: bikes that assis ...
s.
=Other
=
Some high-current power supplies have a rear-sided output for high-current operation. Its poles are larger to support such currents and are usually initially covered by plastic caps. The poles can be connected to accordingly-sized
crocodile clamp
Alligator clip
A crocodile clip or alligator clip is a plier-like spring-tensioned metal clip with elongated, serrated jaws that is used for creating a temporary electrical connection. This simple mechanical device gets its name from the re ...
s.
Functionality and controls
The front panel typically has
LED indicators for "C.V." ("
constant voltage") and "C.C." ("
constant current A constant current (steady current, time-independent current, stationary current) is a type of direct current (DC) that does not change its intensity with time.
Sources
If the load is constant, a steady current can be obtained via a constant vo ...
"). When the current demanded by the load exceeds the limit set by the user, the power supply automatically switches to the latter mode by regulating the voltage down so much as to prevent the current limit from being exceeded.
Controls vary between power supply models. Many have rotary knobs for setting voltage and current, each usually with a "coarse" and "fine" knob, the former of which adjusts the parameter throughout the entire range, whereas the latter facilitates adjustment within a small surrounding range. Some models lack the "fine" knob for current, as drawn electrical current is decided by the load at a given voltage, thus less important to be throttled precisely.
Some, typically higher-end models, are equipped with additional features such as a button for toggling output power without having to switch the whole device on/off, a memory for shortcuts to voltage/current combinations, an option to automatically cut out power when reaching a current limit specified by the user ("over-current protection"), likewise over-voltage protection that cuts out power if the external voltage exceeds output, indicator displays with more digits (four or five instead of three), digital rather than analogue voltage control, and the ability to lock the power setting to prevent accidental adjustment. In addition to output voltage/current meters, few are equipped with a
wattage (power) meter which indicates the product of both in real time, and a
USB charging port.
Many models have a handle at the top for carrying. For cooling, a
heat sink
A heat sink (also commonly spelled heatsink) is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is dissipated away from the device, t ...
,
fan, or both may be used. Heat sinks may be mounted externally or internally. Heat sinks are silent, whereas fans are more effective in cooling. Fan speed may adjust
based on temperature or output current, the former of which cools faster while idle or low throughout intermittent power output, whereas the latter provides acoustic feedback of how much current is output.
Some power supplies have two output channels. These may be used at schools, as a multi-channel unit tends to cost less than two separate units due to shared hardware. High-end ones might allow internally connecting two channels to a series circuit to double the voltage limit. Few power supplies have a third auxiliary output channel that is typically less powerful. It is typically located near the right edge or at the center.
Bench power supply units equipped with an integrated
voltmeter
A voltmeter is an instrument used for measuring electric potential difference between two points in an electric circuit. It is connected in parallel. It usually has a high resistance so that it takes negligible current from the circuit.
An ...
panel to measure external voltages have existed in the 1990s and possibly earlier, but portable
multimeter
A multimeter is a measuring instrument that can measure multiple electrical properties. A typical multimeter can measure voltage, resistance, and current, in which case it is also known as a volt-ohm-milliammeter (VOM), as the unit is equipped w ...
s have made that feature obsolete.
Other applications
*
Mobile phone power adaptors
* Regulated power supplies in appliances
* Various amplifiers and oscillators
Topology & Technology
Many topologies have been used since the regulated supply was invented. Early technologies included
iron-hydrogen resistors, resonant transformers, nonlinear resistors, loading resistors, neon stabiliser tubes, vibrating contact regulators etc.
Modern regulated supplies mostly use a transformer, silicon diode bridge rectifier,
reservoir capacitor
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation (converting DC to AC) is performed by an in ...
and voltage regulator IC. There are variations on this theme, such as supplies with multiple voltage lines, variable regulators, power control lines, discrete circuits and so on. Switched mode regulator supplies also include an inductor.
At times regulated supplies can be much more complex. An example supply from a 1980s TV which used bidirectional interaction between the main supply and the line output stage to operate, generating a range of output voltages with varying amounts of stabilisation. Since neither stage could start without the other running, the supply also included a kickstart system to pulse the system into operation. The supply also monitored voltages in the TV power circuitry, shutting down if these voltages went out of spec. For special applications, supplies can become even more complex.
See also
*
Power supply
A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a ...
*
Voltage regulator
A voltage regulator is a system designed to automatically maintain a constant voltage. A voltage regulator may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism, or electronic components ...
References
{{DEFAULTSORT:Regulated Power Supply
Electrical power control