View source for Diode bridge

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{{Short description|Circuit arrangement of four diodes}}
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{{Infobox electronic component
| name              = Diode bridge
| image             = Brueckengleichrichter IMGP5380.jpg
| caption           = Diode bridge in various packages
| type              = [[Semiconductor]]
| working_principle =
| invented          = [[Karol Pollak]] in 1895
| first_produced    = 
| pins              =
| symbol            = [[Image:Diode_bridge.svg|200px]]
| symbol_caption    = 2 [[alternating-current]] (AC) inputs converted into 2 [[direct-current]] (DC) outputs
}}
[[Image:Diode bridge Diodový mostík.jpg|thumb|right|A hand-made diode bridge. The silver band on the diodes indicates the [[cathode]] side of the diode.]]

A '''diode bridge''' is a [[bridge circuit|bridge]] rectifier circuit of four [[diode]]s that is used in the process of converting [[alternating current]] (AC) from the input terminals to direct current (DC, i.e. fixed [[Electrical polarity|polarity]]) on the output terminals. Its function is to convert the negative voltage portions of the AC waveform to positive voltage, after which a [[low-pass filter]] can be used to smooth the result into DC.<ref>{{Cite book |last1=Yazdani |first1=Amirnaser |title=Voltage-Sourced Converters in Power Systems Modeling, Control, and Applications |last2=Iravani |first2=Reza |date=15 February 2010 |publisher=Willey |isbn=9780470521564 |language=English}}</ref>

When used in its most common application, for conversion of an [[alternating-current]] (AC) input into a [[direct-current]] (DC) output, it is known as a '''bridge rectifier'''. A bridge [[rectifier]] provides [[Rectifier#Full-wave rectification|full-wave rectification]] from a two-wire AC input, resulting in lower cost and weight as compared to a rectifier with a three-wire input from a [[transformer]] with a [[Center tap|center-tapped]] secondary winding.<ref name=AOE>{{cite book |last1=Horowitz |first1=Paul |last2=Hill |first2=Winfield |title=The Art of Electronics |url=https://archive.org/details/artofelectronics00horo |url-access=registration |edition=Second |publisher=Cambridge University Press |year=1989 |pages=[https://archive.org/details/artofelectronics00horo/page/44 44–47] |isbn=0-521-37095-7}}</ref>

Prior to the availability of [[integrated circuit]]s, a bridge rectifier was constructed from separate diodes. Since about 1950, a single four-terminal component containing the four diodes connected in a bridge configuration has been available and is now available with various [[voltage]] and current ratings.

Diodes are also used in bridge topologies along with capacitors as [[voltage multiplier]]s.

== History ==
The diode bridge circuit was invented by [[Karol Pollak]] and patented in December 1895 in Great Britain<ref>[https://depatisnet.dpma.de/DepatisNet/depatisnet?action=bibdat&docid=GB000189524398A British patent 24398].</ref> and in January 1896 in Germany.<ref>[https://babel.hathitrust.org/cgi/pt?id=wu.89048352934;view=1up;seq=389 (Graetz, 1897), p. 327 footnote.]</ref><ref>{{cite journal |last1=(Editorial staff) |title=''Ein neues Gleichrichter-Verfahren'' |journal=Elektrotechnische Zeitschrift |date=24 June 1897 |volume=18 |issue=25 |page=359 and footnote |url=https://babel.hathitrust.org/cgi/pt?id=njp.32101050985074;view=1up;seq=381 |trans-title=A new method of rectification |language=de}}</ref> In 1897, [[Leo Graetz]] independently invented and published a similar circuit.<ref>See:
* {{cite journal |last1=Graetz |first1=L. |title=''Electrochemisches Verfahren, um Wechselströme in Gleichströme zu verwandeln'' |journal=Sitzungsberichte der Mathematisch-Physikalischen Classe der Königlich Bayerischen Akademie der Wissenschaften zu München (Transactions of the Mathematical-Physical Classes of the Royal Bavarian Academy of Sciences in Munich) |date=1 May 1897 |volume=27 |issue=10 |pages=223–228 |doi=10.1002/andp.18972981008 |bibcode=1897AnP...298..323G|url=https://babel.hathitrust.org/cgi/pt?id=hvd.32044092897610;view=1up;seq=1069 |trans-title=Electrochemical method of changing alternating into direct currents |language=de}}
* {{cite journal |last1=Graetz |first1=L. |title=''Electrochemisches Verfahren, um Wechselströme in Gleichströme zu verwandeln'' |journal=Annalen der Physik und Chemie |date=1897 |volume=62 |pages=323–327 |url=https://babel.hathitrust.org/cgi/pt?id=wu.89048352934;view=1up;seq=385 |series=3rd series |issue=10 |doi=10.1002/andp.18972981008 |bibcode=1897AnP...298..323G |trans-title=Electrochemical method of changing alternating into direct currents|language=de}}
* {{cite journal |last1=Graetz |first1=L. |title=''Electrochemisches Verfahren, um Wechselströme in Gleichströme zu verwandeln'' |journal=Elektrotechnische Zeitschrift|date=22 July 1897 |volume=18 |issue=29 |pages=423–424 |doi=10.1002/andp.18972981008 |bibcode=1897AnP...298..323G|url=https://babel.hathitrust.org/cgi/pt?id=njp.32101050985074;view=1up;seq=445 |trans-title=Electrochemical method of changing alternating into direct currents |language=de}}
</ref><ref>{{cite book |editor-last1=Strzelecki |editor-first1=Ryszard Michal |editor-last2=Benysek |editor-first2=Grzegorz  |url=https://books.google.com/books?id=LqWPPiSM5M0C&pg=PA57 |title=Power Electronics in Smart Electrical Energy Networks |isbn=9781848003187 |publisher=Springer |date=August 29, 2008 |page=57}}</ref> Today the circuit is sometimes referred to as a "Graetz circuit" or "Graetz bridge".<ref>{{cite web |url=http://www.mathworks.in/help/physmod/hydro/examples/graetz-flow-control-circuit.html |title=Graetz Flow Control Circuit |url-status=dead |archive-url=https://web.archive.org/web/20131104072407/http://www.mathworks.in/help/physmod/hydro/examples/graetz-flow-control-circuit.html |archive-date=2013-11-04 }}</ref>
 
== Current flow==
According to the [[conventional current|conventional model]] of [[Current (electricity)|current]] flow, originally established by [[Benjamin Franklin]] and still followed by most engineers today,<ref>Stutz, Michael (stutz@dsl.org), [http://www.allaboutcircuits.com/vol_1/chpt_1/7.html "Conventional versus electron flow"], ''All About Circuits'', Vol. 1, Chapter 1, 2000.</ref> current flows through [[electrical conductor]]s from the positive to the negative pole (defined as positive flow). In actuality, [[free electron model|free electrons]] in a conductor nearly always flow from the negative to the positive pole. In the vast majority of applications, however, the actual direction of current flow is irrelevant. Therefore, in the discussion below the conventional model is retained.

The fundamental characteristic of a diode is that current can flow only one way through it, which is defined as the forward direction.  A diode bridge uses diodes as series components to allow current to pass in the forward direction during the positive part of the AC cycle and as shunt components to redirect current flowing in the reverse direction during the negative part of the AC cycle to the opposite rails.

== Rectifier ==
In the diagrams below, when the input connected to the left corner of the diamond is positive, and the input connected to the right corner is negative, current flows from the upper supply terminal to the right along the red (positive) path to the output and returns to the lower supply terminal through the blue (negative) path.

[[Image:Diode bridge alt 1.svg]]

When the input connected to the left corner is negative, and the input connected to the right corner is positive, current flows from the lower supply terminal to the right along the red (positive) path to the output and returns to the upper supply terminal through the blue (negative) path.<ref name=SZY>{{cite book |editor-last1=Sears |editor-first1=Francis W. |editor-last2=Zemansky |editor-first2=Mark W. |editor-last3=Young |editor-first3=Hugh D. |title=University Physics |edition=6th |publisher=Addison-Wesely Publishing Co., Inc. |date=1982 |page=685 |isbn=0201071959}}</ref>

[[Image:Diode bridge alt 2.svg]]

[[File:Diodebridge-eng.gif|thumb|center|alt=An animated diagram of a diode bridge, where pulsing is meant to represent an electric current]]

In each case, the upper right output remains positive,<ref>{{cite web |url=https://www.thegeekpub.com/243767/bridge-rectifier-circuit-electronics-basics/ |title=Bridge Rectifier Circuit - Electronics Basics |website=The Geek Pub |date=15 August 2019 |access-date=3 September 2019}}</ref> and lower right output negative. Since this is true whether the input is AC or DC, this circuit not only produces a DC output from an AC input, it can also provide reverse-polarity protection;  that is, it permits normal functioning of DC-powered equipment when batteries have been installed backwards, or when the leads from a DC power source have been reversed, and protects the equipment from potential damage caused by reverse polarity.<ref>{{cite web |title=Reverse Polarity Protection |at=Bridge Rectifier for Reverse Polarity Protection |website=The Renewable Energy UK Website |url=http://www.reuk.co.uk/wordpress/electric-circuit/reverse-polarity-protection/ |access-date=18 December 2023 |archive-date=4 May 2023 |archive-url=https://web.archive.org/web/20230504095844/http://www.reuk.co.uk/wordpress/electric-circuit/reverse-polarity-protection/ |url-status=live }}</ref>

Alternatives to the diode-bridge full-wave rectifiers are the [[full-wave rectifier|center-tapped transformer and double-diode rectifier]], and [[Voltage doubler#Bridge circuit|voltage doubler]] rectifier using two diodes and two capacitors in a bridge topology.

[[Image:Rectification.svg|thumb|250px|AC, [[Rectifier#Half-wave rectification|half-wave]] and full-wave rectified signals<ref name="CEST">"Rectifier", ''Concise Encyclopedia of Science and Technology'', Third Edition, Sybil P. Parker, ed. McGraw-Hill, Inc., 1994, p. 1589.</ref>]]

== Smoothing circuits ==
{{unreferenced section|date=October 2017}}
{{See also|Rectifier#Rectifier output smoothing}}
With AC input, the output of a diode bridge (called a [[full-wave rectifier]] for this purpose; there is also [[half-wave rectification]], which does not use a diode bridge) is polarized pulsating [[non-sinusoidal waveform|non-sinusoidal]] voltage of the same amplitude but twice the frequency of the input.  It may be considered as DC voltage upon which is superimposed a very large [[ripple voltage]]. This kind of electric power is not very usable, because ripple is dissipated as [[waste heat]] in DC circuit components and may cause noise or distortion during circuit operation.  So nearly all rectifiers are followed by a series of [[bandpass]] or [[bandstop filter]]s and/or a [[voltage regulator]] to convert most or all of the ripple voltage into a smoother and possibly higher DC output. A filter may be as simple as a single sufficiently large [[capacitor]] or [[choke (electronics)|choke]], but most power-supply filters have multiple alternating series and shunt components.  When the ripple voltage rises, [[reactive power]] is stored in the filter components, reducing the voltage; when the ripple voltage falls, reactive power is discharged from the filter components, raising the voltage.  The final stage of rectification may consist of a [[zener diode]]-based voltage regulator, which almost completely eliminates any residual ripple.

== Polyphase diode bridges ==
{{See also|Rectifier#Three-phase rectifiers}}
The diode bridge can be generalized to rectify [[polyphase system|polyphase]] AC inputs. For example, for a three-phase AC input, a half-wave rectifier consists of three diodes, but a full-wave bridge rectifier consists of six diodes.{{Citation needed|date=April 2021}}

A half-wave rectifier may be considered a [[Three-phase_electric_power#Wye (or, star; Y)|wye connection]] (star connection), because it returns the current through the center (neutral) wire. A full-wave rectifier is more like a [[Three-phase_electric_power#Delta_(Δ)|delta connection]], although it can be connected to the three-phase source of either wye or delta and it does not use the center (neutral) wire.{{Citation needed|date=April 2021}}

[[Image:3 phase bridge rectifier.svg|thumb|left|260px|Three-phase full-wave bridge rectifier]] <!-- invisible in night mode on phone browsers -->
[[File:3 phase rectification 2.svg|thumb|right|260px|3-phase AC input waveform (top), half-wave rectified waveform (center), and full-wave rectified waveform (bottom)]]
[[Image:Tridge rectifier.jpg|thumb|left|260px|[[Three-phase electric power|Three-phase]] bridge rectifier for a [[wind turbine]]]]
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== See also ==
* [[1N400x general-purpose diodes]] also called rectifier diodes
* [[Active rectification]]
* [[HVDC converter]]

== References ==
{{reflist}}

== External links ==
{{Commons category|Bridge rectifiers}}

{{Bridge circuits}}

[[Category:Bridge circuits]]
[[Category:Rectifiers]]