document_title: Fist of the Blue Sky

question_text: fist of the blue sky regenesis opening song

text: Fist of the Blue Sky

text: Plot[edit]

text: The main protagonist of this story is Kenshiro Kasumi, better known as "Yan Wang" or "The King of Hell". Kenshiro is a laid back and chain-smoking Tokyo professor who is secretly the successor of the deadly Chinese assassin martial art Hokuto Shinken. He travels to Shanghai after hearing that his Triad friend Pan Guang-Lin and love interest Pan Yu-Ling are in trouble.

text: In Shanghai, Kenshiro fights the three Hokuto families, the Hokuto Sankaken (based on the royal families of Romance of the Three Kingdoms). At the same time he helps Pan's Qīng Bāng triad against their rivals, the immoral Hóng Huá Huì, in gaining territory and influence in Shanghai.

text: Production[edit]

text: Many of the plot points mentioned in the comic contain real historical facts, such as how Shanghai was controlled by the foreign concessions (the story focus mainly on the French settlement) during the 1930s. Also seen are Jewish refugees who escaped from Nazi persecution in Europe, and the invasion of China by the Japanese Army. Chiang Kai-shek and some historical Kuomintang figures appear in the story as well.

text: Tetsuo Hara wanted the fights in the manga to look more like traditional Chinese martial arts, so the action is somewhat faster and more detailed than those in Fist of the North Star. Hara went to Shanghai in person to get his inspiration. Tetsuo Hara describes the protagonist Kenshiro Kasumi as a combination of the strength of Kenshiro, the good nature of Keiji Maeda from Hana no Keiji and the sarcastic attitude of the title character of Nakabo Rintaro.

text: Media[edit]

text: Manga[edit]

text: Written and illustrated by Tetsuo Hara, Fist of the Blue Sky was serialized in Weekly Comic Bunch throughout the magazine's  entire history. Beginning in its first issue with the cover date of May 29, 2001,[1] the chapters were published irregularly until the final issue in August 2010. Publisher Shinchosha collected the chapters into 22 tankōbon volumes.

text: An English version of Fist of the Blue Sky was serialized in the now-defunct manga anthology Raijin Comics published by Gutsoon! Entertainment from 2002 to 2004. Four collected volumes were published by Gutsoon under their Raijin Graphic Novels imprint before the company went out of business and ceased publication of all their titles.

text: A continuation of the manga, titled Sōten no Ken: Re:Genesis (蒼天の拳 RE:GENESIS), began serialization in the December 2017 issue of Comic Zenon. It is written by Hiroyuki Yatsu and illustrated by Hideki Tsuji.[2]

text:
Vol.
Release date
show[3] ISBN

01
2001-10-09
ISBN 4-10-771000-9

02
2001-11-09
ISBN 4-10-771016-5

03
2002-05-09
ISBN 4-10-771036-X

04
2002-08-09
ISBN 4-10-771051-3

05
2003-01-09
ISBN 4-10-771073-4

06
2003-05-09
ISBN 4-10-771089-0

07
2003-09-09
ISBN 4-10-771112-9

08
2004-01-09
ISBN 4-10-771129-3

09
2004-05-09
ISBN 4-10-771151-X

10
2004-08-09
ISBN 4-10-771167-6

11
2004-12-09
ISBN 4-10-771189-7

12
2005-03-09
ISBN 4-10-771206-0

13
2005-07-09
ISBN 4-10-771225-7

14
2006-01-09
ISBN 4-10-771258-3

15
2006-07-09
ISBN 4-10-771281-8

16
2007-02-09
ISBN 978-4-10-771318-6

17
2007-09-08
ISBN 978-4-10-771356-8

18
2008-03-08
ISBN 978-4-10-771387-2

19
2008-10-09
ISBN 4-10-771421-7

20
2009-03-09
ISBN 978-4-10-771467-1

21
2009-12-09
ISBN 978-4-10-771535-7

22
2010-11-09
ISBN 978-4-10-771601-9

text:
Vol.
Release date
show[4] ISBN

01
2003-06-18
ISBN 0-9725037-8-1

02
2003-09-09
ISBN 1-932454-03-9

03
2003-11-18
ISBN 1-932454-09-8

04
2004-03-17
ISBN 1-932454-22-5

05
Unpublished
ISBN 1-932454-33-0

text: Anime[edit]

text: A weekly anime series based on Sōten no Ken aired on Japan's TV Asahi on Thursdays at 2:40am from October 4, 2006 to March 14, 2007. The series lasted only 26 episodes, but four of the episodes (16-18, and 21) did not air during the original run. The complete series has been released on DVD in Region 2 format by Universal Entertainment Japan, including unaired episodes and uncensored content. The series adapts the storyline from the beginning and up to vol. 8. The Opening theme is "Bara ga Saku, Bara ga Chiru" (薔薇が咲く 薔薇が散る, "Roses Bloom, Roses Scatter") by Rina Aiuchi while the ending themes are "Kokoro no Rhythm Tobichiru Butterfly (心のリズム飛び散るバタフライ, Kokoro no Rizumu Tobichiru Batafurai, lit. "The Rhythm of the Heart is a Fluttering Butterfly") by doa and "Kissing til i die" by Jun Manaka.

text: On October 24, 2017, it was announced that Sōten no Ken: Re:Genesis would receive an anime adaption that premiered on April 2, 2018 on Tokyo MX.[5][6] The opening is "Souten no Hate ni" by AK-69 while the ending theme is "Inori no Hoshizora" by Sumire Uesaka.[7]


document_title: Dating the Bible

question_text: when do we believe the new testament was first written down

root

text: Dating the Bible

text: Table I: Chronological overview[edit]

text: This table summarises the chronology of the main tables and serves as a guide to the historical periods mentioned. Much of the Hebrew Bible or the Protocanonical Old Testament may have been assembled in the 5th century BCE.[1] The New Testament books were composed largely in the second half of the 1st century CE.[2] The Deuterocanonical books fall largely in between.

tag: p

text:
Period

Books

Monarchic8th–7th centuries BCEc. 745–586 BCE

Late 8th-early 7th: Amos (initial composition of earliest layer);[3] "First Isaiah" (Isaiah 1–39),[4] Hosea,[5] Micah (second half).[6]
7th: Nahum (based on its assumption of the fall of Thebes and call for the destruction of Nineveh),[7] Zephaniah (in the reign of Josiah, c. 649–609 BCE),[8] Habakkuk (possibly shortly before the battle of Carchemish, 605 BCE);[9] first edition of the Deuteronomistic history (books of Joshua/Judges/Samuel/Kings) in the reign of Josiah;[10] Deuteronomy 5–26 in the reign of Josiah.[11]

Exilic6th century BCE586–539 BCE

Core of Obadiah around the fall of Jerusalem, 586 BCE.[12]
Completion of Deuteronomistic history (Joshua/Judges/Samuel/Kings).[13]
Deuteronomy expanded with addition of chapters 1–4 and 29–30 to serve as an introduction to the Deuteronomistic history.[11]
Jeremiah active in the last decade of the 7th century and first decades of the 6th;[14]
Ezekiel active in Babylon 592–571 BCE;[15]
"Second Isaiah" (author of Isaiah 40–55) active in Babylon around mid-century.[16]
Expansion and reshaping of Hosea, Amos, Micah and Zephaniah.[17]
Possible early Psalms collection (psalms "of David") ending with psalm 89.[17]

Post-exilicPersian5th–4th centuries BCE538–330 BCE

Torah (books of Genesis/Exodus/Leviticus/Numbers), with 250 BCE as terminus ad quem (last possible date) for the production of the final text on the basis of the extant manuscript evidence.[18][19]
Deuteronomy revised with expansions to chapters 19–25 and addition of chapter 27 and 31–34 to serve as conclusion to the Torah.[11]
"Third Isaiah" (Isaiah 56–66)[16]
Later version (the Masoretic Hebrew version) of Jeremiah[20]
Haggai (self-dated to the second year of the Persian king Darius 520 BCE),[21]
Zechariah (chapters 1–8 contemporary with Haggai, chapters 9–14 from the 5th century)[22]
Malachi (5th century BCE, contemporaneous or immediately prior to the missions of Nehemiah and Ezra)[23]
Chronicles (between 400–250 BC, probably in the period 350–300 BCE)[24]
Origins of Ezra-Nehemiah (may have reached its final form as late as the Ptolemaic period, c. 300–200 BCE).[25]

Post-exilicHellenistic3rd–2nd centuries BCE330–164 BCE

Job, Ecclesiastes and the Song of Songs (Could have been written in the 4th or even 5th centuries, but seem to reflect contact with Greek culture).[26]
Book of Jonah (Persian or Hellenistic, no later than 2nd century BCE).[27]
Most of the individual psalms making up the final third of the Book of Psalms.[28]

Maccabean/Hasmonean2nd–1st centuries BCE164–4 BCE

Daniel (164 BCE, combining newly-written visions, chapters 7–12, with the Persian and Hellenistic tales of chapters 1–6).[29]
1 Maccabees/2 Maccabees/3 Maccabees/possibly 4 Maccabees; Tobit, Judith, Additions to Daniel and Additions to Esther
Wisdom of Solomon late 1st century BCE or early to mid 1st century CE.[26]

Roman1st century CE onwardafter 4 BCE

4 Maccabees (after 63 BCE, probably mid-1st century CE).[30]
Wisdom of Solomon (late 1st century BCE or early to mid 1st century CE).[26]
New Testament (between c. 50–110 CE – see Table IV).

tag: table

text: Table II: Hebrew Bible/Protestant Old Testament[edit]

text:
Torah

Date or range of dates most widely held by scholars

Book of GenesisBook of ExodusBook of LeviticusBook of NumbersBook of Deuteronomy

The majority of modern biblical scholars believe that the Torah – the books of Genesis, Exodus, Leviticus, Numbers and Deuteronomy – reached its present form in the post-Exilic period.[19]
The five books are drawn from four "sources" (distinct schools of writers rather than individuals): the Priestly source, the Yahwist and the Elohist (these two are often referred to collectively as the "non-Priestly" source), and the Deuteronomist.[31] There is general agreement that the Priestly source is post-exilic, but there is no agreement over the non-Priestly source(s).[31]

Genesis is a post-exilic work combining "Priestly" and "non-Priestly" material.[32]
Exodus is an anthology drawn from nearly all periods of Israel's history.[33]
Leviticus is entirely Priestly and dates from the exilic/post-exilic period.[34]
Numbers is a Priestly redaction (i.e., editing) of a Yahwistic/non-Priestly original.[35]
Deuteronomy, now the last book of the Torah, began as the set of religious laws (these make up the bulk of the book), was extended in the early part of the 6th century to serve as the introduction to the Deuteronomistic history, and later still was detached from that history, extended yet again, and edited to conclude the Torah.[36]

Prophets

Date or range of dates most widely held by scholars

Former Prophets:
Book of JoshuaBook of JudgesBooks of SamuelBooks of Kings

This group of books, plus Deuteronomy, is called the "Deuteronomistic history" by scholars. The proposal that they made up a unified work was first advanced by Martin Noth in 1943, and has been widely accepted. Noth proposed that the entire history was the creation of a single individual working in the exilic period (6th century BCE); since then there has been wide recognition that the history appeared in two "editions", the first in the reign of Judah's King Josiah (late 7th century), the second during the exile (6th century).[10] Noth's dating was based on the assumption that the history was completed very soon after its last recorded event, the release of King Jehoiachin in Babylon c. 560 BCE; but some scholars have termed his reasoning inadequate, and the history may have been further extended in the post-exilic period.[37]

Three Major Prophets:
Book of IsaiahBook of JeremiahBook of Ezekiel

Scholars recognise three "sections" in the Book of Isaiah: Proto-Isaiah (the original 8th century Isaiah); Deutero-Isaiah (an anonymous prophet living in Babylon during the exile); and Trito-Isaiah (an anonymous author or authors in Jerusalem immediately after the exile).[38]
The Book of Jeremiah exists in two versions, Greek (the version used in Orthodox Christian Bibles) and Hebrew (Jewish, Catholic and Protestant Bibles), with the Greek representing the earlier version.[39] The Greek version was probably finalised in the early Persian period and translated into Greek in the 3rd century BCE, and the Hebrew version dates from some point between then and the 2nd century BCE.[40]
The Book of Ezekiel describes itself as the words of the Ezekiel ben-Buzi, a priest living in exile in the city of Babylon, and internal evidence dates the visions to between 593 and 571 BCE. While the book probably reflects much of the historic Ezekiel, it is the product of a long and complex history, with significant additions by a "school" of later followers.[41][42]

Twelve Minor Prophets

In the Hebrew Bible the Twelve Minor Prophets are a single collection edited in the Second Temple period, but the collection is broken up in Christian Bibles.[43] With the exception of Jonah, which is a fictional work, there exists an original core of prophetic tradition behind each book:[44][45]
Book of Hosea: second half of the 8th century BCE[5]
Book of Joel: late Persian or Hellenistic[46]
Book of Amos: first half of the 8th century[47]
Book of Obadiah: around the time of the fall of Jerusalem, 586 BCE[12]
Book of Jonah: Persian or Hellenistic, no later than 2nd century BCE[27]
Book of Micah: c. 750–700 BCE[48]
Book of Nahum: an "oracle concerning Nineveh", the Assyrian city destroyed in 612 BCE[49]
Book of Habakkuk: possibly shortly before the battle of Carchemish, 605 BCE[9]
Book of Zephaniah: reign of Josiah[8]
Book of Haggai: self-dated to the second year of the Persian king Darius (Darius the Great), 520 BCE[21]
Book of Zechariah: first eight chapters contemporary with Haggai; chapters 9–14 from the 5th century[22]
Book of Malachi: 5th century BCE, contemporaneous or immediately prior to the missions of Nehemiah and Ezra (which, however, are themselves difficult to date)[23]

Writings

Date or range of dates most widely held by scholars

Wisdom collection:Job, Ecclesiastes and Proverbs

The books of Job, Ecclesiastes and Proverbs share a similar outlook which they themselves call "wisdom".[50] It is generally agreed that Job comes from between the 7th and 4th centuries BCE, with the 6th century as the most likely.[51] Ecclesiastes can be no earlier than about 450 BCE, due to the presence of Persian loan-words and Aramaic idioms, and no later than 180 BCE, when the Jewish writer Ben Sira quotes from it.[52][53] Proverbs is a "collection of collections" relating to a pattern of life which lasted for more than a millennium, and impossible to date.[54]

Poetic works: Psalms and Lamentations

The psalms making up the first two-thirds of the psalter are predominantly pre-exilic and the last third predominantly post-exilic.[28] The collected book of Psalms was possibly given its modern shape and division into five parts in the post-exilic period, although it continued to be revised and expanded well into Hellenistic and even Roman times.[55] It is generally accepted that the destruction of Jerusalem by Babylon in 586 BCE forms the background to the Book of Lamentations.[56]

Histories: Chronicles and Ezra-Nehemiah

Chronicles was composed between 400–250 BCE, probably in the period 350–300 BCE;[24] Ezra-Nehemiah (two books in modern Bibles, but originally one) may have reached its final form as late as the Ptolemaic period, c. 300–200 BCE.[25]

Miscellaneous works: Book of Ruth, Book of Esther, Book of Daniel, Song of Songs

The Book of Ruth is commonly dated to the Persian period;[57] Esther to the 3rd or 4th centuries BCE; the Book of Daniel can be dated more precisely to 164 BCE thanks to its veiled prophecy of the death of a Greek king of Syria;[58] and the Song of Songs could have been composed at any time after the 6th century BCE.[59]

text: Table III: Deuterocanonical Old Testament[edit]

text:
Book

Date or range of dates most widely held by scholars

Tobit

225–175 BCE, on the basis of apparent use of language and references common to the post-exilic period, but lack of knowledge of the 2nd century BCE persecution of Jews.[60]

Judith

150–100 BCE, although estimates range from the 5th century BCE to the 2nd century CE.[61]

1 Maccabees

100 BCE[62]

2 Maccabees

c. 100 BCE[62]

3 Maccabees

100–75 BCE "very probable"[63]

4 Maccabees

mid-1st century CE[30]

Wisdom of Solomon

late 1st century BCE/early 1st century CE, on the basis of shared outlook with other works dating from this time.[64]

Sirach

196–175 BCE, as the author implies that Simon the high priest had died (196 BCE), but shows no knowledge of the persecution of the Jews that began after 175 BCE.[65]

Additions to Daniel

Prayer of Azariah (Song of the Three Holy Children); Bel and the Dragon: late 6th century;[66] Susanna and the Elders: possibly 95–80 BCE[67]

Baruch and Letter of Jeremiah

2nd century BCE, as Baruch uses Sirach (written c. 180 BCE) and is in turn used by the Psalms of Solomon (mid-1st century BCE). The Letter of Jeremiah, ch. 6:1–73 of the Book of Baruch, is sometimes considered a separate book.[68]

text: Table IV: New Testament[edit]

text:
Book

Date or range of dates most widely held by scholars

Earliest known fragment

Gospel of Matthew

80–90 CE.[69] This is based on three strands of evidence: (a) the setting of Matthew reflects the final separation of Church and Synagogue, about 85 CE; (b) it reflects the capture of Jerusalem and destruction of the Temple by the Romans in 70 CE; (c) it uses Mark, usually dated around 70 CE, as a source.[70]

P

{\displaystyle {\mathfrak {P}}}

104 (150–200 CE)

Gospel of Mark

68–70 CE.[71] References to persecution and to war in Judea suggest that its context was either Nero's persecution of the Christians in Rome or the Jewish revolt.[72]

P

{\displaystyle {\mathfrak {P}}}

45 (250 CE)

Gospel of Luke

80–90 CE, with some scholars suggesting 90–100.[73] There is evidence, both textual (the conflicts between Western and Alexandrian manuscript families) and from the Marcionite controversy (Marcion was a 2nd-century heretic who produced his own version of Christian scripture based on Luke's gospel and Paul's epistles) that Luke-Acts was still being substantially revised well into the 2nd century.[74]

P

{\displaystyle {\mathfrak {P}}}

4,

P

{\displaystyle {\mathfrak {P}}}

75 (175–250 CE)

Gospel of John

90–110 CE, the upper date based on textual evidence that the gospel was known in the early 2nd century, and the lower on an internal reference to the expulsion of Christians from the synagogues.[75]

P

{\displaystyle {\mathfrak {P}}}

52 (125–160 CE)

Acts

95–100 CE.[71] If Acts uses Josephus as a source, as has been proposed, then it must have been composed after 93 CE; the social situation is one in which the faithful need "shepherds" to protect them from heretical "wolves", which again reflects a late date.[76]

P

{\displaystyle {\mathfrak {P}}}

29,

P

{\displaystyle {\mathfrak {P}}}

45,

P

{\displaystyle {\mathfrak {P}}}

48,

P

{\displaystyle {\mathfrak {P}}}

53,

P

{\displaystyle {\mathfrak {P}}}

91 (250 CE)

Romans

c. 57 CE. One of the genuine Pauline letters, written to the Romans as Paul was about to leave Asia Minor and Greece, and expressing his hopes to continue his work in Spain.[71]

P

{\displaystyle {\mathfrak {P}}}

46 (late 2nd century or 3rd century CE)

Corinthians

c. 56 CE. Another of the Genuine Pauline letters. Paul expresses his intention to re-visit the church he founded in the city c. 50–52 CE.[71]

P

{\displaystyle {\mathfrak {P}}}

46 (late 2nd century or 3rd century CE)

Galatians

c. 55 CE. Paul does not express any wish to revisit the church in Galatia, which he founded, and so some scholars believe the letter dates from the end of his missionary work. The letter concerns the question of whether Gentile converts are required to adopt full Jewish customs.[71]

P

{\displaystyle {\mathfrak {P}}}

46 (late 2nd century or 3rd century CE)

Ephesians

c. 80–90 CE. The letter appears to have been written after Paul's death in Rome, by an author who uses his name.[71]

P

{\displaystyle {\mathfrak {P}}}

46 (late 2nd century or 3rd century CE)

Philippians

c. 54–55 CE. A genuine Pauline letter, it mentions "Caesar's household," leading some scholars to believe that it is written from Rome, but some of the news in it could not have come from Rome. It seems rather to date from an earlier imprisonment, perhaps in Ephesus, from which Paul hopes to be released.[71]

P

{\displaystyle {\mathfrak {P}}}

46 (late 2nd century or 3rd century CE)

Colossians

c. 62–70 CE. Some scholars believe Colossians dates from Paul's imprisonment in Ephesus around 55 CE, but differences in the theology suggest that it comes from much later in his career, around the time of his imprisonment in Rome.[71]

P

{\displaystyle {\mathfrak {P}}}

46 (late 2nd century or 3rd century CE)

1 Thessalonians

c. 51 CE. One of the earliest of the genuine Pauline epistles.[71]

P

{\displaystyle {\mathfrak {P}}}

46 (late 2nd century or 3rd century CE)

2 Thessalonians

c. 51 CE or post-70 CE. If this is a genuine Pauline epistle it follows closely on 1 Thessalonians. But some of the language and theology point to a much later date, from an unknown author using Paul's name.[71]

P

{\displaystyle {\mathfrak {P}}}

92 (300 CE)

1 Timothy, 2 Timothy, Epistle to Titus

c. 100 CE. The two Timothy epistles and Titus reflect a much more developed Church organisation than that reflected in the genuine Pauline epistles.[71]

Codex Sinaiticus (350 CE)

P

{\displaystyle {\mathfrak {P}}}

32 (200 CE)

Philemon

c. 54–55 CE. A genuine Pauline epistle, written from an imprisonment (probably in Ephesus) that Paul expects will soon be over.[71]

P

{\displaystyle {\mathfrak {P}}}

87 (3rd century CE)

Hebrews

c. 80–90 CE. The elegance of the Greek and the sophistication of the theology do not fit the genuine Pauline epistles, but the mention of Timothy in the conclusion led to its being included with the Pauline group from an early date.[71]

P

{\displaystyle {\mathfrak {P}}}

46 (late 2nd century or 3rd century CE)

James

c. 65–85 CE. Like Hebrews, James is not so much a letter as an exhortation; the style of the Greek makes it unlikely that it was actually written by James the brother of Jesus.[71]

P

{\displaystyle {\mathfrak {P}}}

20,

P

{\displaystyle {\mathfrak {P}}}

23 (early 3rd century CE)

First Peter

c. 75–90 CE[71]

P

{\displaystyle {\mathfrak {P}}}

72 (3rd/4th century CE)

Second Peter

c. 110 CE. This is apparently the latest writing in the New Testament, quoting from Jude, assuming a knowledge of the Pauline letters, and including a reference to the gospel story of the Transfiguration of Christ.[71]

P

{\displaystyle {\mathfrak {P}}}

72 (3rd/4th century CE)

Epistles of John

90–110 CE.[77] The letters give no clear indication, but scholars tend to place them about a decade after the Gospel of John.[77]

P

{\displaystyle {\mathfrak {P}}}

9, Uncial 0232, Codex Sinaiticus (3rd/4th century CE)

Jude

Uncertain. The references to "brother of James" and to "what the apostles of our Lord Jesus Christ foretold" suggest that it was written after the apostolic letters were in circulation, but before 2 Peter, which uses it.[71]

P

{\displaystyle {\mathfrak {P}}}

72 (3rd/4th century CE)

Revelation

c. 95 CE. The date is suggested by clues in the visions pointing to the reign of the emperor Domitian.[71]

P

{\displaystyle {\mathfrak {P}}}

98 (150–200 CE)


document_title: Switched-mode power supply

question_text: which circuit is the first stage of a dc power supply

text: Switched-mode power supply

text: History[edit]

text: Explanation[edit]

text: A linear regulator provides the desired output voltage by dissipating excess power in ohmic losses (e.g., in a resistor or in the collector–emitter region of a pass transistor in its active mode). A linear regulator regulates either output voltage or current by dissipating the excess electric power in the form of heat, and hence its maximum power efficiency is voltage-out/voltage-in since the volt difference is wasted.

text: In contrast, a switched-mode power supply changes output voltage and current by switching ideally lossless storage elements, such as inductors and capacitors, between different electrical configurations. Ideal switching elements (approximated by transistors operated outside of their active mode) have no resistance when "on" and carry no current when "off", and so converters with ideal components would operate with 100% efficiency (i.e., all input power is delivered to the load; no power is wasted as dissipated heat).

text: For example, if a DC source, an inductor, a switch, and the corresponding electrical ground are placed in series and the switch is driven by a square wave, the peak-to-peak voltage of the waveform measured across the switch can exceed the input voltage from the DC source. This is because the inductor responds to changes in current by inducing its own voltage to counter the change in current, and this voltage adds to the source voltage while the switch is open. If a diode-and-capacitor combination is placed in parallel to the switch, the peak voltage can be stored in the capacitor, and the capacitor can be used as a DC source with an output voltage greater than the DC voltage driving the circuit. This boost converter acts like a step-up transformer for DC signals. A buck–boost converter works in a similar manner, but yields an output voltage which is opposite in polarity to the input voltage. Other buck circuits exist to boost the average output current with a reduction of voltage.

text: In a SMPS, the output current flow depends on the input power signal, the storage elements and circuit topologies used, and also on the pattern used (e.g., pulse-width modulation with an adjustable duty cycle) to drive the switching elements. The spectral density of these switching waveforms has energy concentrated at relatively high frequencies. As such, switching transients and ripple introduced onto the output waveforms can be filtered with a small LC filter.

text: Advantages and disadvantages[edit]

text: The main advantage of the switching power supply is greater efficiency than linear regulators because the switching transistor dissipates little power when acting as a switch.

text: Other advantages include smaller size and lighter weight from the elimination of heavy line-frequency transformers, and comparable heat generation. Standby power loss is often much less than transformers.

text: Disadvantages include greater complexity, the generation of high-amplitude, high-frequency energy that the low-pass filter must block to avoid electromagnetic interference (EMI), a ripple voltage at the switching frequency and the harmonic frequencies thereof.

text: Very low cost SMPSs may couple electrical switching noise back onto the mains power line, causing interference with A/V equipment connected to the same phase. Non-power-factor-corrected SMPSs also cause harmonic distortion.

text: SMPS and linear power supply comparison[edit]

text: There are two main types of regulated power supplies available: SMPS and linear. The following table compares linear regulated and unregulated AC-to-DC supplies with switching regulators in general:

text:
Comparison of a linear power supply and a switched-mode power supply

Linear power supply
Switching power supply
Notes

Size and weight
Heatsinks for high power linear regulators add size and weight. Transformers, if used, are large due to low operating frequency (mains power frequency is at 50 or 60 Hz); otherwise can be compact due to low component count.
Smaller transformer (if used; else inductor) due to higher operating frequency (typically 50 kHz – 1 MHz). Size and weight of adequate RF shielding may be significant.
A transformer's power handling capacity of given size and weight increases with frequency provided that hysteresis losses can be kept down. Therefore, higher operating frequency means either a higher capacity or smaller transformer.

Output voltage
With transformer used, any voltages available; if transformerless, limited to what can be achieved with a voltage doubler. If unregulated, voltage varies significantly with load.
Any voltages available, limited only by transistor breakdown voltages in many circuits. Voltage varies little with load.
A SMPS can usually cope with wider variation of input before the output voltage changes.

Efficiency, heat, and power dissipation
If regulated: efficiency largely depends on voltage difference between input and output; output voltage is regulated by dissipating excess power as heat resulting in a typical efficiency of 30–40%.[18] If unregulated, transformer iron and copper losses may be the only significant sources of inefficiency.
Output is regulated using duty cycle control; the transistors are switched fully on or fully off, so very little resistive losses between input and the load. The only heat generated is in the non-ideal aspects of the components and quiescent current in the control circuitry.
Switching losses in the transistors (especially in the short part of each cycle when the device is partially on), on-resistance of the switching transistors, equivalent series resistance in the inductor and capacitors, and core losses in the inductor, and rectifier voltage drop contribute to a typical efficiency of 60–70%. However, by optimizing SMPS design (such as choosing the optimal switching frequency, avoiding saturation of inductors, and active rectification), the amount of power loss and heat can be minimized; a good design can have an efficiency of 95%.

Complexity
Unregulated may be simply a diode and capacitor; regulated has a voltage-regulating circuit and a noise-filtering capacitor; usually a simpler circuit (and simpler feedback loop stability criteria) than switched-mode circuits.
Consists of a controller IC, one or several power transistors and diodes as well as a power transformer, inductors, and filter capacitors. Some design complexities present (reducing noise/interference; extra limitations on maximum ratings of transistors at high switching speeds) not found in linear regulator circuits.
In switched-mode mains (AC-to-DC) supplies, multiple voltages can be generated by one transformer core, but that can introduce design/use complications: for example it may place minimum output current restrictions on one output. For this SMPSs have to use duty cycle control. One of the outputs has to be chosen to feed the voltage regulation feedback loop (usually 3.3 V or 5 V loads are more fussy about their supply voltages than the 12 V loads, so this drives the decision as to which feeds the feedback loop. The other outputs usually track the regulated one pretty well). Both need a careful selection of their transformers. Due to the high operating frequencies in SMPSs, the stray inductance and capacitance of the printed circuit board traces become important.

Radio frequency interference
Mild high-frequency interference may be generated by AC rectifier diodes under heavy current loading, while most other supply types produce no high-frequency interference. Some mains hum induction into unshielded cables, problematical for low-signal audio.
EMI/RFI produced due to the current being switched on and off sharply. Therefore, EMI filters and RF shielding are needed to reduce the disruptive interference.
Long wires between the components may reduce the high frequency filter efficiency provided by the capacitors at the inlet and outlet. Stable switching frequency may be important.

Electronic noise at the output terminals
Unregulated PSUs may have a little AC ripple superimposed upon the DC component at twice mains frequency (100–120 Hz). It can cause audible mains hum in audio equipment, brightness ripples or banded distortions in analog security cameras.
Noisier due to the switching frequency of the SMPS. An unfiltered output may cause glitches in digital circuits or noise in audio circuits.
This can be suppressed with capacitors and other filtering circuitry in the output stage. With a switched mode PSU the switching frequency can be chosen to keep the noise out of the circuits working frequency band (e.g., for audio systems above the range of human hearing)

Electronic noise at the input terminals
Causes harmonic distortion to the input AC, but relatively little or no high frequency noise.
Very low cost SMPS may couple electrical switching noise back onto the mains power line, causing interference with A/V equipment connected to the same phase. Non power-factor-corrected SMPSs also cause harmonic distortion.
This can be prevented if a (properly earthed) EMI/RFI filter is connected between the input terminals and the bridge rectifier.

Acoustic noise
Faint, usually inaudible mains hum, usually due to vibration of windings in the transformer or magnetostriction.
Usually inaudible to most humans, unless they have a fan or are unloaded/malfunctioning, or use a switching frequency within the audio range, or the laminations of the coil vibrate at a subharmonic of the operating frequency.
The operating frequency of an unloaded SMPS is sometimes in the audible human range, and may sound subjectively quite loud for people whose hearing is very sensitive to the relevant frequency range.

Power factor
Low for a regulated supply because current is drawn from the mains at the peaks of the voltage sinusoid, unless a choke-input or resistor-input circuit follows the rectifier (now rare).
Ranging from very low to medium since a simple SMPS without PFC draws current spikes at the peaks of the AC sinusoid.
Active/passive power factor correction in the SMPS can offset this problem and are even required by some electric regulation authorities, particularly in the EU. The internal resistance of low-power transformers in linear power supplies usually limits the peak current each cycle and thus gives a better power factor than many switched-mode power supplies that directly rectify the mains with little series resistance.

Inrush current
Large current when mains-powered linear power supply equipment is switched on until magnetic flux of transformer stabilises and capacitors charge completely, unless a slow-start circuit is used.
Extremely large peak "in-rush" surge current limited only by the impedance of the input supply and any series resistance to the filter capacitors.
Empty filter capacitors initially draw large amounts of current as they charge up, with larger capacitors drawing larger amounts of peak current. Being many times above the normal operating current, this greatly stresses components subject to the surge, complicates fuse selection to avoid nuisance blowing and may cause problems with equipment employing overcurrent protection such as uninterruptible power supplies. Mitigated by use of a suitable soft-start circuit or series resistor.

Risk of electric shock
Supplies with transformers isolate the incoming power supply from the powered device and so allow metalwork of the enclosure to be grounded safely. Dangerous if primary/secondary insulation breaks down, unlikely with reasonable design. Transformerless mains-operated supply dangerous. In both linear and switch-mode the mains, and possibly the output voltages, are hazardous and must be well-isolated.
Common rail of equipment (including casing) is energized to half the mains voltage, but at high impedance, unless equipment is earthed/grounded or doesn't contain EMI/RFI filtering at the input terminals.
Due to regulations concerning EMI/RFI radiation, many SMPS contain EMI/RFI filtering at the input stage consisting of capacitors and inductors before the bridge rectifier. Two capacitors are connected in series with the Live and Neutral rails with the Earth connection in between the two capacitors. This forms a capacitive divider that energizes the common rail at half mains voltage. Its high impedance current source can provide a tingling or a 'bite' to the operator or can be exploited to light an Earth Fault LED. However, this current may cause nuisance tripping on the most sensitive residual-current devices.

Risk of equipment damage
Very low, unless a short occurs between the primary and secondary windings or the regulator fails by shorting internally.
Can fail so as to make output voltage very high. Stress on capacitors may cause them to explode. Can in some cases destroy input stages in amplifiers if floating voltage exceeds transistor base-emitter breakdown voltage, causing the transistor's gain to drop and noise levels to increase.[19] Mitigated by good failsafe design. Failure of a component in the SMPS itself can cause further damage to other PSU components; can be difficult to troubleshoot.
The floating voltage is caused by capacitors bridging the primary and secondary sides of the power supply. Connection to earthed equipment will cause a momentary (and potentially destructive) spike in current at the connector as the voltage at the secondary side of the capacitor equalizes to earth potential.

text: Theory of operation[edit]

text: Input rectifier stage[edit]

text: If the SMPS has an AC input, then the first stage is to convert the input to DC. This is called rectification. A SMPS with a DC input does not require this stage. In some power supplies (mostly computer ATX power supplies), the rectifier circuit can be configured as a voltage doubler by the addition of a switch operated either manually or automatically. This feature permits operation from power sources that are normally at 115 V or at 230 V. The rectifier produces an unregulated DC voltage which is then sent to a large filter capacitor. The current drawn from the mains supply by this rectifier circuit occurs in short pulses around the AC voltage peaks. These pulses have significant high frequency energy which reduces the power factor. To correct for this, many newer SMPS will use a special PFC circuit to make the input current follow the sinusoidal shape of the AC input voltage, correcting the power factor. Power supplies that use active PFC usually are auto-ranging, supporting input voltages from ~100 VAC – 250 VAC, with no input voltage selector switch.

text: An SMPS designed for AC input can usually be run from a DC supply, because the DC would pass through the rectifier unchanged.[20] If the power supply is designed for 115 VAC and has no voltage selector switch, the required DC voltage would be 163 VDC (115 × √2). This type of use may be harmful to the rectifier stage, however, as it will only use half of diodes in the rectifier for the full load. This could possibly result in overheating of these components, causing them to fail prematurely. On the other hand, if the power supply has a voltage selector switch, based on the Delon circuit, for 115/230V (computer ATX power supplies typically are in this category), the selector switch would have to be put in the 230 V position, and the required voltage would be 325 VDC (230 × √2). The diodes in this type of power supply will handle the DC current just fine because they are rated to handle double the nominal input current when operated in the 115 V mode, due to the operation of the voltage doubler. This is because the doubler, when in operation, uses only half of the bridge rectifier and runs twice as much current through it.[21] It is uncertain how an Auto-ranging/Active-PFC type power supply would react to being powered by DC.

text: Inverter stage[edit]

text: The inverter stage converts DC, whether directly from the input or from the rectifier stage described above, to AC by running it through a power oscillator, whose output transformer is very small with few windings at a frequency of tens or hundreds of kilohertz. The frequency is usually chosen to be above 20 kHz, to make it inaudible to humans. The switching is implemented as a multistage (to achieve high gain) MOSFET amplifier. MOSFETs are a type of transistor with a low on-resistance and a high current-handling capacity.

text: Voltage converter and output rectifier[edit]

text: If the output is required to be isolated from the input, as is usually the case in mains power supplies, the inverted AC is used to drive the primary winding of a high-frequency transformer. This converts the voltage up or down to the required output level on its secondary winding. The output transformer in the block diagram serves this purpose.

text: If a DC output is required, the AC output from the transformer is rectified. For output voltages above ten volts or so, ordinary silicon diodes are commonly used. For lower voltages, Schottky diodes are commonly used as the rectifier elements; they have the advantages of faster recovery times than silicon diodes (allowing low-loss operation at higher frequencies) and a lower voltage drop when conducting. For even lower output voltages, MOSFETs may be used as synchronous rectifiers; compared to Schottky diodes, these have even lower conducting state voltage drops.

text: The rectified output is then smoothed by a filter consisting of inductors and capacitors. For higher switching frequencies, components with lower capacitance and inductance are needed.

text: Simpler, non-isolated power supplies contain an inductor instead of a transformer. This type includes boost converters, buck converters, and the buck-boost converters. These belong to the simplest class of single input, single output converters which use one inductor and one active switch. The buck converter reduces the input voltage in direct proportion to the ratio of conductive time to the total switching period, called the duty cycle. For example an ideal buck converter with a 10 V input operating at a 50% duty cycle will produce an average output voltage of 5 V. A feedback control loop is employed to regulate the output voltage by varying the duty cycle to compensate for variations in input voltage. The output voltage of a boost converter is always greater than the input voltage and the buck-boost output voltage is inverted but can be greater than, equal to, or less than the magnitude of its input voltage. There are many variations and extensions to this class of converters but these three form the basis of almost all isolated and non-isolated DC to DC converters. By adding a second inductor the Ćuk and SEPIC converters can be implemented, or, by adding additional active switches, various bridge converters can be realized.

text: Other types of SMPSs use a capacitor-diode voltage multiplier instead of inductors and transformers. These are mostly used for generating high voltages at low currents (Cockcroft-Walton generator). The low voltage variant is called charge pump.

text: Regulation[edit]

text: A feedback circuit monitors the output voltage and compares it with a reference voltage, as shown in the block diagram above. Depending on design and safety requirements, the controller may contain an isolation mechanism (such as an opto-coupler) to isolate it from the DC output. Switching supplies in computers, TVs and VCRs have these opto-couplers to tightly control the output voltage.

text: Open-loop regulators do not have a feedback circuit. Instead, they rely on feeding a constant voltage to the input of the transformer or inductor, and assume that the output will be correct. Regulated designs compensate for the impedance of the transformer or coil. Monopolar designs also compensate for the magnetic hysteresis of the core.

text: The feedback circuit needs power to run before it can generate power, so an additional non-switching power-supply for stand-by is added.

text: Transformer design[edit]

text: Any switched-mode power supply that gets its power from an AC power line (called an "off-line" converter[22]) requires a transformer for galvanic isolation. Some DC-to-DC converters may also include a transformer, although isolation may not be critical in these cases. SMPS transformers run at high frequency. Most of the cost savings (and space savings) in off-line power supplies result from the smaller size of the high frequency transformer compared to the 50/60 Hz transformers formerly used. There are additional design tradeoffs.

text: The terminal voltage of a transformer is proportional to the product of the core area, magnetic flux, and frequency. By using a much higher frequency, the core area (and so the mass of the core) can be greatly reduced. However, core losses increase at higher frequencies. Cores generally use ferrite material which has a low loss at the high frequencies and high flux densities used. The laminated iron cores of lower-frequency (<400 Hz) transformers would be unacceptably lossy at switching frequencies of a few kilohertz. Also, more energy is lost during transitions of the switching semiconductor at higher frequencies. Furthermore, more attention to the physical layout of the circuit board is required as parasitics become more significant, and the amount of electromagnetic interference will be more pronounced.

text: Copper loss[edit]

text: At low frequencies (such as the line frequency of 50 or 60 Hz), designers can usually ignore the skin effect. For these frequencies, the skin effect is only significant when the conductors are large, more than 0.3 inches (7.6 mm) in diameter.

text: Switching power supplies must pay more attention to the skin effect because it is a source of power loss. At 500 kHz, the skin depth in copper is about 0.003 inches (0.076 mm) – a dimension smaller than the typical wires used in a power supply. The effective resistance of conductors increases, because current concentrates near the surface of the conductor and the inner portion carries less current than at low frequencies.

text: The skin effect is exacerbated by the harmonics present in the high speed PWM switching waveforms. The appropriate skin depth is not just the depth at the fundamental, but also the skin depths at the harmonics.[23]

text: In addition to the skin effect, there is also a proximity effect, which is another source of power loss.

text: Power factor[edit]

text: Simple off-line switched mode power supplies incorporate a simple full-wave rectifier connected to a large energy storing capacitor. Such SMPSs draw current from the AC line in short pulses when the mains instantaneous voltage exceeds the voltage across this capacitor. During the remaining portion of the AC cycle the capacitor provides energy to the power supply.

text: As a result, the input current of such basic switched mode power supplies has high harmonic content and relatively low power factor. This creates extra load on utility lines, increases heating of building wiring, the utility transformers, and standard AC electric motors, and may cause stability problems in some applications such as in emergency generator systems or aircraft generators. Harmonics can be removed by filtering, but the filters are expensive. Unlike displacement power factor created by linear inductive or capacitive loads, this distortion cannot be corrected by addition of a single linear component. Additional circuits are required to counteract the effect of the brief current pulses. Putting a current regulated boost chopper stage after the off-line rectifier (to charge the storage capacitor) can correct the power factor, but increases the complexity and cost.

text: In 2001, the European Union put into effect the standard IEC/EN61000-3-2 to set limits on the harmonics of the AC input current up to the 40th harmonic for equipment above 75 W. The standard defines four classes of equipment depending on its type and current waveform. The most rigorous limits (class D) are established for personal computers, computer monitors, and TV receivers. To comply with these requirements, modern switched-mode power supplies normally include an additional power factor correction (PFC) stage.

text: Types[edit]

text: Switched-mode power supplies can be classified according to the circuit topology. The most important distinction is between isolated converters and non-isolated ones.

text: Non-isolated topologies[edit]

text: Non-isolated converters are simplest, with the three basic types using a single inductor for energy storage. In the voltage relation column, D is the duty cycle of the converter, and can vary from 0 to 1. The input voltage (V1) is assumed to be greater than zero; if it is negative, for consistency, negate the output voltage (V2).

text:
Type[24]
Typical Power [W]
Relative cost
Energy storage
Voltage relation
Features

Buck
0–1,000
1.0
Single inductor
0 ≤ Out ≤ In,

V

2

=
D

V

1

{\displaystyle \scriptstyle V_{2}=DV_{1}}

Current is continuous at output.

Boost
0–5,000
1.0
Single inductor
Out ≥ In,

V

2

=

1

1
−
D

V

1

{\displaystyle \scriptstyle V_{2}={\frac {1}{1-D}}V_{1}}

Current is continuous at input.

Buck-boost
0–150
1.0
Single inductor
Out ≤ 0,

V

2

=
−

D

1
−
D

V

1

{\displaystyle \scriptstyle V_{2}=-{\frac {D}{1-D}}V_{1}}

Current is dis-continuous at both input and output.

Split-pi (or, boost-buck)
0–4,500
>2.0
Two inductors and three capacitors
Up or down
Bidirectional power control; in or out

Ćuk

Capacitor and two inductors
Any inverted,

V

2

=
−

D

1
−
D

V

1

{\displaystyle \scriptstyle V_{2}=-{\frac {D}{1-D}}V_{1}}

Current is continuous at input and output

SEPIC

Capacitor and two inductors
Any,

V

2

=

D

1
−
D

V

1

{\displaystyle \scriptstyle V_{2}={\frac {D}{1-D}}V_{1}}

Current is continuous at input

Zeta

Capacitor and two inductors
Any,

V

2

=

D

1
−
D

V

1

{\displaystyle \scriptstyle V_{2}={\frac {D}{1-D}}V_{1}}

Current is continuous at output

Charge pump / switched capacitor

Capacitors only

No magnetic energy storage is needed to achieve conversion, however high efficiency power processing is normally limited to a discrete set of conversion ratios.

text: When equipment is human-accessible, voltage and power limits of <=42.4 V peak/60 V dc and 250 VA apply for safety certification (UL, CSA, VDE approval).

text: The buck, boost, and buck-boost topologies are all strongly related. Input, output and ground come together at one point. One of the three passes through an inductor on the way, while the other two pass through switches. One of the two switches must be active (e.g., a transistor), while the other can be a diode. Sometimes, the topology can be changed simply by re-labeling the connections. A 12 V input, 5 V output buck converter can be converted to a 7 V input, −5 V output buck-boost by grounding the output and taking the output from the ground pin.

text: Likewise, SEPIC and Zeta converters are both minor rearrangements of the Ćuk converter.

text: The neutral point clamped (NPC) topology is used in power supplies and active filters and is mentioned here for completeness.[25]

text: Switchers become less efficient as duty cycles become extremely short. For large voltage changes, a transformer (isolated) topology may be better.

text: Isolated topologies[edit]

text: All isolated topologies include a transformer, and thus can produce an output of higher or lower voltage than the input by adjusting the turns ratio.[26][27] For some topologies, multiple windings can be placed on the transformer to produce multiple output voltages.[28] Some converters use the transformer for energy storage, while others use a separate inductor.

text:
Type[24]
Power
[W]
Relative cost
Input range
[V]
Energy storage
Features

Flyback
0–250
1.0
5–600
Mutual Inductors
Isolated form of the buck-boost converter.1

Ringing choke converter (RCC)
0–150
1.0
5–600
Transformer
Low-cost self-oscillating flyback variant.[29]

Half-forward
0–250
1.2
5–500
Inductor

Forward2
100-200

60–200
Inductor
Isolated form of buck converter

Resonant forward
0–60
1.0
60–400
Inductor and capacitor
Single rail input, unregulated output, high efficiency, low EMI.[30]

Push-pull
100–1,000
1.75
50–1,000
Inductor

Half-bridge
0–2,000
1.9
50–1,000
Inductor

Full-bridge
400–5,000
>2.0
50–1,000
Inductor
Very efficient use of transformer, used for highest powers.

Resonant, zero voltage switched
>1,000
>2.0

Inductor and capacitor

Isolated Ćuk

Two capacitors and two inductors

text:
^1 Flyback converter logarithmic control loop behavior might be harder to control than other types.[31]
^2 The forward converter has several variants, varying in how the transformer is "reset" to zero magnetic flux every cycle.

tag: ul

text: Quasi-resonant zero-current/zero-voltage switch[edit]

text: In a quasi-resonant zero-current/zero-voltage switch (ZCS/ZVS) "each switch cycle delivers a quantized 'packet' of energy to the converter output, and switch turn-on and turn-off occurs at zero current and voltage, resulting in an essentially lossless switch."[32] Quasi-resonant switching, also known as valley switching, reduces EMI in the power supply by two methods:

text:
By switching the bipolar switch when the voltage is at a minimum (in the valley) to minimize the hard switching effect that causes EMI.
By switching when a valley is detected, rather than at a fixed frequency, introduces a natural frequency jitter that spreads the RF emissions spectrum and reduces overall EMI.

tag: ol

text: Efficiency and EMI[edit]

text: Higher input voltage and synchronous rectification mode makes the conversion process more efficient. The power consumption of the controller also has to be taken into account. Higher switching frequency allows component sizes to be shrunk, but can produce more RFI. A resonant forward converter produces the lowest EMI of any SMPS approach because it uses a soft-switching resonant waveform compared with conventional hard switching.

text: Failure modes[edit]

text: For failure in switching components, circuit board and so on read the failure modes of electronics article.

text: Power supplies which use capacitors suffering from the capacitor plague may experience premature failure when the capacitance drops to 4% of the original value.[not in citation given] This usually causes the switching semiconductor to fail in a conductive way. That may expose connected loads to the full input volt and current, and precipitate wild oscillations in output.[33]

text: Failure of the switching transistor is common. Due to the large switching voltages this transistor must handle (around 325 V for a 230 VAC mains supply), these transistors often short out, in turn immediately blowing the main internal power fuse.

text: Precautions[edit]

text: The main filter capacitor will often store up to 325 volts long after the power cord has been removed from the wall. Not all power supplies contain a small "bleeder" resistor to slowly discharge this capacitor. Any contact with this capacitor may result in a severe electrical shock.

text: The primary and secondary sides may be connected with a capacitor to reduce EMI and compensate for various capacitive couplings in the converter circuit, where the transformer is one. This may result in electric shock in some cases. The current flowing from line or neutral through a 2 kΩ resistor to any accessible part must, according to IEC 60950, be less than 250 μA for IT equipment.[34]

text: Applications[edit]

text: Switched-mode power supply units (PSUs) in domestic products such as personal computers often have universal inputs, meaning that they can accept power from mains supplies throughout the world, although a manual voltage range switch may be required. Switch-mode power supplies can tolerate a wide range of power frequencies and voltages.

text: Due to their high volumes mobile phone chargers have always been particularly cost sensitive. The first chargers were linear power supplies, but they quickly moved to the cost effective ringing choke converter (RCC) SMPS topology, when new levels of efficiency were required. Recently, the demand for even lower no-load power requirements in the application has meant that flyback topology is being used more widely; primary side sensing flyback controllers are also helping to cut the bill of materials (BOM) by removing secondary-side sensing components such as optocouplers.[citation needed]

text: Switched-mode power supplies are used for DC to DC conversion as well. In automobiles where heavy vehicles use a nominal 24 VDC cranking supply, 12V for accessories may be furnished through a DC/DC switch-mode supply. This has the advantage over tapping the battery at the 12V position (using half the cells) that all the 12V load is evenly divided over all cells of the 24V battery. In industrial settings such as telecommunications racks, bulk power may be distributed at a low DC voltage (from a battery back up system, for example) and individual equipment items will have DC/DC switched-mode converters to supply whatever voltages are needed.

text: A common use for switched-mode power supplies is as extra-low-voltage sources for lighting, and for this application they are often called "electronic transformers".

text: Terminology[edit]

text: The term switchmode was widely used until Motorola claimed ownership of the trademark SWITCHMODE, for products aimed at the switching-mode power supply market, and started to enforce their trademark.[22] Switching-mode power supply, switching power supply, and switching regulator refer to this type of power supply.[22]


document_title: Ethiopian eunuch

question_text: which book of prophecy was the ethiopian eunuch reading from

text: Ethiopian eunuch

text: Biblical narrative[edit]

text: Philip the Evangelist was told by an angel to go to the road from Jerusalem to Gaza, and there he met the Ethiopian eunuch. He had been to Jerusalem to worship (Acts 8:27), and was returning home. The eunuch was sitting in his chariot reading the Book of Isaiah, and had come to Isaiah 53:7-8. Philip asked the Ethiopian, "Do you understand what you are reading?" He said he did not ("How can I understand unless I have a teacher to teach me?"), and asked Philip to explain the text to him. Philip told him the Gospel of Jesus, and the Ethiopian asked to be baptized. They went down into some water and Philip baptized him.

text: In the King James Version and the Catholic Douay-Rheims Version, the Ethiopian says, "I believe that Jesus Christ is the Son of God" (verse 37), but this is omitted in most modern versions. Hubbard suggests that confession is "not supported in the better manuscripts [i.e. the Alexandrian text-type])", although the Ethiopian is still "one of the outstanding converts in Acts."[1]

text: After this, Philip was suddenly taken away by the Spirit of the Lord, and the eunuch "went on his way rejoicing" (verse 39).

text: Christian traditions[edit]

text: Church Father St. Irenaeus of Lyons in his book Adversus haereses (Against the Heresies, an early anti-Gnostic theological work) 3:12:8 (180 AD), wrote regarding the Ethiopian eunuch, "This man (Simeon Bachos the Eunuch) was also sent into the regions of Ethiopia, to preach what he had himself believed, that there was one God preached by the prophets, but that the Son of this (God) had already made (His) appearance in human flesh, and had been led as a sheep to the slaughter; and all the other statements which the prophets made regarding Him." In Ethiopian Orthodox Tewahedo tradition he was referred to as Bachos and in Eastern Orthodox tradition he is known as an Ethiopian Jew with the name Simeon also called the Black, the same name he is given in Acts 13:1.[2][3]

text: Assessment and interpretation[edit]

text: The Ethiopian is described as a eunuch and a treasury official at the court of Queen Candace (Acts 8:27). D. A. Hubbard suggests that he may have been a proselyte,[1] though Paul Mumo Kisau argues that he was a Godfearer instead.[4] Scott Shauf suggests that the "primary point of the story is about carrying the gospel to the end of the earth, not about establishing a mission to Gentiles," and thus Luke "does not bring the Gentile status of the Ethiopian into the foreground." However, "the suggestion that the eunuch is or at least might be a Gentile in the story, by both his ethnic and possibly physical description, serves to tantalize the reader with the mystery of the situation."[5] The eunuch may have been from Nubia or the Sudan: David Tuesday Adamo suggests that the word used here (Αίθίοψ, aithiops) is best translated simply as "African."[6]

text: Commentators generally suggest that the combination of "eunuch" together with the title "court official" indicates a literal eunuch, who would have been excluded from the Temple by the restriction in Deuteronomy 23:1.[7][8] Some scholars point out that eunuchs were excluded from Jewish worship and extend the New Testament's inclusion of these men to other sexual minorities; John J. McNeill, citing non-literal uses of "eunuch" in other New Testament passages such as Matthew 19:12,[9] suggests that this eunuch was "the first baptized gay Christian,"[10] while Jack Rogers writes that "the fact that the first Gentile convert to Christianity is from a sexual minority and a different race, ethnicity and nationality together"[11]:135 calls Christians to be radically inclusive and welcoming.

text: Other scholars have addressed the issue of the eunuch's race. Some, such as Frank M. Snowden, Jr., interpret the story as emphasizing that early Christian communities accepted members regardless of race: "Ethiopians were the yardstick by which antiquity measured colored peoples."[12][13] Others, such as Clarice Martin, write that it is a commentary on the religion rather than on its adherents, showing Christianity's geographical extent; Gay L. Byron goes further, saying, "The Ethiopian eunuch was used by Luke to indicate that salvation could extend even to Ethiopians and Blacks."[14]

text: C. K. Barrett contrasts the Ethiopian eunuch's story with that of Cornelius the Centurion, another convert. He notes that while the Ethiopian continues on his journey home and passes out of the narrative, Cornelius and his followers form another church in Judea, and speculates that this reflects a desire to focus on Peter rather than Philip.[15] Robert O'Toole argues that the way Philip is taken away parallels the way Jesus disappears after he has been talking to the disciples on the road to Emmaus in Luke 24.[16]

text: Wikimedia Commons has media related to The Ethiopian eunuch.


document_title: Scatter plot

question_text: in order to draw a scatter diagram we need interval data for

text: Scatter plot

text: Overview[edit]

text: A scatter plot can be used either when one continuous variable that is under the control of the experimenter and the other depends on it or when both continuous variables are independent. If a parameter exists that is systematically incremented and/or decremented by the other, it is called the control parameter or independent variable and is customarily plotted along the horizontal axis. The measured or dependent variable is customarily plotted along the vertical axis. If no dependent variable exists, either type of variable can be plotted on either axis and a scatter plot will illustrate only the degree of correlation (not causation) between two variables.

text: A scatter plot can suggest various kinds of correlations between variables with a certain confidence interval. For example, weight and height, weight would be on y axis and height would be on the x axis. Correlations may be positive (rising), negative (falling), or null (uncorrelated). If the pattern of dots slopes from lower left to upper right, it indicates a positive correlation between the variables being studied. If the pattern of dots slopes from upper left to lower right, it indicates a negative correlation. A line of best fit (alternatively called 'trendline') can be drawn in order to study the relationship between the variables. An equation for the correlation between the variables can be determined by established best-fit procedures. For a linear correlation, the best-fit procedure is known as linear regression and is guaranteed to generate a correct solution in a finite time. No universal best-fit procedure is guaranteed to generate a correct solution for arbitrary relationships. A scatter plot is also very useful when we wish to see how two comparable data sets agree to show nonlinear relationships between variables. The ability to do this can be enhanced by adding a smooth line such as LOESS.[5] Furthermore, if the data are represented by a mixture model of simple relationships, these relationships will be visually evident as superimposed patterns.

text: The scatter diagram is one of the seven basic tools of quality control.[6]

text: Scatter charts can be built in the form of bubble, marker, or/and line charts.[7]

text: Example[edit]

text: For example, to display a link between a person's lung capacity, and how long that person could hold his/her breath, a researcher would choose a group of people to study, then measure each one's lung capacity (first variable) and how long that person could hold his/her breath (second variable). The researcher would then plot the data in a scatter plot, assigning "lung capacity" to the horizontal axis, and "time holding breath" to the vertical axis.

text: A person with a lung capacity of 400 cl who held his/her breath for 21.7 seconds would be represented by a single dot on the scatter plot at the point (400, 21.7) in the Cartesian coordinates. The scatter plot of all the people in the study would enable the researcher to obtain a visual comparison of the two variables in the data set, and will help to determine what kind of relationship there might be between the two variables.

text: Scatterplot matrices[edit]

text: For a set of data variables (dimensions) X1, X2, ... , Xk, the scatter plot matrix shows all the pairwise scatter plots of the variables on a single view with multiple scatterplots in a matrix format. For k variables, the scatterplot matrix will contain k rows and k columns. A plot located on the intersection of i-th row and j-th column is a plot of variables Xi versus Xj.[8] This means that each row and column is one dimension, and each cell plots a scatterplot of two dimensions.

text: A generalized scatterplot matrix[9] offers a range of displays of paired combinations of categorical and quantitative variables. A mosaic plot, fluctuation diagram, or faceted bar chart may be used to display two categorical variables. Other plots are used for one categorical and one quantitative variables.