Selenium rectifier

Last updated
An 8-plate 160 V 450 mA Federal brand selenium rectifier Selenium Rectifier.jpg
An 8-plate 160 V 450 mA Federal brand selenium rectifier

A selenium rectifier is a type of metal rectifier, invented in 1933. [1] They were used in power supplies for electronic equipment and in high-current battery-charger applications until they were superseded by silicon diode rectifiers in the late 1960s. The arrival of the alternator in some automobiles was the result of compact, low-cost, high-current silicon rectifiers. These units were small enough to be inside the alternator case, unlike the selenium units that preceded silicon devices.

Contents

The rectifying properties of selenium, amongst other semiconductors, were observed by Braun, Schuster and Siemens between 1874 and 1883. [2] The photoelectric and rectifying properties of selenium were also observed by Adams and Day in 1876 [3] and C. E. Fitts around 1886, but practical rectifier devices were not manufactured routinely until the 1930s. Compared with the earlier copper-oxide rectifier, the selenium cell could withstand higher voltage, but at a lower current capacity per unit area. [4]

Construction

Typical structure of a selenium rectifier Structure selenium rectifier.svg
Typical structure of a selenium rectifier

Selenium rectifiers are made from stacks of aluminum or steel plates coated with about 1  μm of bismuth or nickel. A much thicker layer of selenium (50 to 60 μm) doped with a halogen is deposited on top of the thin metal plating. The selenium is then converted into polycrystalline gray (hexagonal) form by annealing. Cadmium selenide forms by reaction of the selenium with the tin-cadmium alloy and the CdSe-Se heterojunction is the active rectifying junction. Each plate is able to withstand about 20 volts in the reverse direction. The metal squares, or disks, also serve as heat sinks in addition to providing a mounting place for the selenium disks. Plates can be stacked indefinitely to withstand higher voltages. Stacks of thousands of miniature selenium disks have been used as high-voltage rectifiers in television sets and photocopy machines.

Use

Selenium rectifiers used in 1950s MADDIDA computer MADDIDA Selen Rectifier.JPG
Selenium rectifiers used in 1950s MADDIDA computer
Selenium rectifier from 1960s. Each plate is 1-inch square. Selenium rectifier.agr.jpg
Selenium rectifier from 1960s. Each plate is 1-inch square.

Selenium rectifiers are able to withstand repetitive significant overload without the need of special protective measures. It is commonly used in electroplating rectifier under 200,000 A and electrostatic precipitators operating between 30 and 100 kV [5]

Radio and television receivers used them from about 1947 to 1975 to provide up to a few hundred volts of plate voltage. Vacuum-tube rectifiers had efficiencies of only 60% compared to the 85% of selenium rectifiers, partially because vacuum-tube rectifiers required heating. Selenium rectifiers have no warm-up time, unlike high-vacuum rectifiers. Selenium rectifiers were also cheaper and simpler to specify and install than vacuum tubes. However, they were later replaced by silicon diodes with high efficiencies (close to 100% at high voltages). Selenium rectifiers had the capability to act as current limiters, which can temporarily protect the rectifier during a short circuit and provide stable current for charging batteries.[ citation needed ]

Properties

A selenium rectifier is about the same size as a copper-oxide rectifier, but is much larger than a silicon or germanium diode. Selenium rectifiers have a long but not indefinite service life of 60,000 to 100,000 hours, depending on rating and cooling. The rectifier can show some unforming of the rectifier characteristic after long storage. [6] Each cell can withstand a reverse voltage around 25 volts and has a forward voltage drop around 1 volt, which limits the efficiency at low voltages. Selenium rectifiers have an operating temperature limit of 130 °C and are not suitable for high-frequency circuits. [7]

Replacement

Selenium rectifiers had a shorter lifespan than desired. In the early stage of failure they produce a modest amount of sweet-smelling gas. Sometimes described as 'sickly-sweet'. At that point the rectification properties are almost totally gone, allowing reverse voltage to leak through the rectifier. During catastrophic failure they produced significant quantities of malodorous and highly toxic hydrogen selenide [8] [9] [10] that let the repair technician know what the problem was. By far the most common failure mode was a progressive increase in forward resistance, increasing forward voltage drop and reducing the rectifier's efficiency. During the 1960s they began to be superseded by silicon rectifiers, which exhibited lower forward voltage drop, lower cost, and higher reliability. [11]

Selenium diode computer logic

In 1961 IBM started developing a low-speed computer logic family [12] that used selenium diodes with similar characteristics to silicon but cost less than one cent. The terminal development departments were begging for low cost and did not need speed. It was possible to punch 1/8-inch discs from a sheet of selenium diode. GE claimed that they could make reliable selenium diodes. A design was achieved for a DDTL circuit with two levels of diode logic feeding one alloy transistor and no series input resistor or speed-up capacitor. The family was called SMAL [13] or SMALL, for "selenium matrix alloy logic". The alloy transistor proved to be too fast for the selenium diode recovery. To solve this problem, a selenium diode was connected around the base–emitter to slow it down. The two-level logic was similar to the programmable logic array (PLA) that would come on the market many years later. Nearly any static logic function that yielded one output could be achieved with one transistor and a handful of cheap diodes. Several years later the selenium diodes were found to be not reliable and were replaced by silicon diodes. The logic family was packaged on SMS cards. [13]

Further reading

Related Research Articles

<span class="mw-page-title-main">Diode</span> Two-terminal electronic component

A diode is a two-terminal electronic component that conducts current primarily in one direction. It has low resistance in one direction and high resistance in the other.

<span class="mw-page-title-main">Vacuum tube</span> Device that controls current between electrodes

A vacuum tube, electron tube, valve, or tube, is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.

<span class="mw-page-title-main">Rectifier</span> Electrical device that converts AC to DC

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 is performed by an inverter.

<span class="mw-page-title-main">Alternator</span> Device converting mechanical into electrical energy

An alternators is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature. Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used. In principle, any AC electrical generator can be called an alternator, but usually the term refers to small rotating machines driven by automotive and other internal combustion engines.

<span class="mw-page-title-main">Schottky diode</span> Semiconductor diode

The Schottky diode, also known as Schottky barrier diode or hot-carrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage drop and a very fast switching action. The cat's-whisker detectors used in the early days of wireless and metal rectifiers used in early power applications can be considered primitive Schottky diodes.

<span class="mw-page-title-main">Silicon controlled rectifier</span> Four-layer solid-state current-controlling device

A silicon controlled rectifier or semiconductor controlled rectifier is a four-layer solid-state current-controlling device. The name "silicon controlled rectifier" is General Electric's trade name for a type of thyristor. The principle of four-layer p–n–p–n switching was developed by Moll, Tanenbaum, Goldey, and Holonyak of Bell Laboratories in 1956. The practical demonstration of silicon controlled switching and detailed theoretical behavior of a device in agreement with the experimental results was presented by Dr Ian M. Mackintosh of Bell Laboratories in January 1958. The SCR was developed by a team of power engineers led by Gordon Hall and commercialized by Frank W. "Bill" Gutzwiller in 1957.

<span class="mw-page-title-main">Diode–transistor logic</span>

Diode–transistor logic (DTL) is a class of digital circuits that is the direct ancestor of transistor–transistor logic. It is called so because the logic gating functions AND and OR are performed by diode logic, while logical inversion (NOT) and amplification is performed by a transistor.

<span class="mw-page-title-main">Voltage multiplier</span> Electrical circuit power converter

A voltage multiplier is an electrical circuit that converts AC electrical power from a lower voltage to a higher DC voltage, typically using a network of capacitors and diodes.

<span class="mw-page-title-main">Metal rectifier</span>

A metal rectifier is an early type of semiconductor rectifier in which the semiconductor is copper oxide, germanium or selenium. They were used in power applications to convert alternating current to direct current in devices such as radios and battery chargers. Westinghouse Electric was a major manufacturer of these rectifiers since the late 1920s, under the trade name Westector.

<span class="mw-page-title-main">All American Five</span> American radio with 5 vacuum tubes

The term All American Five is a colloquial name for mass-produced, superheterodyne radio receivers that used five vacuum tubes in their design. These radio sets were designed to receive amplitude modulation (AM) broadcasts in the medium wave band, and were manufactured in the United States from the mid-1930s until the early 1960s. By eliminating a power transformer, cost of the units was kept low; the same principle was later applied to television receivers. Variations in the design for lower cost, shortwave bands, better performance or special power supplies existed, although many sets used an identical set of vacuum tubes.

<span class="mw-page-title-main">Breakdown voltage</span> Voltage at which insulator becomes conductive

The breakdown voltage of an insulator is the minimum voltage that causes a portion of an insulator to experience electrical breakdown and become electrically conductive.

Diode logic constructs AND and OR logic gates with diodes and resistors.

<span class="mw-page-title-main">Vibrator (electronic)</span> Electromechanical device

A vibrator is an electromechanical device that takes a DC electrical supply and converts it into pulses that can be fed into a transformer. It is similar in purpose to the solid-state power inverter.

<span class="mw-page-title-main">1N4148 signal diode</span> Standard silicon switching diode

The 1N4148 is a standard silicon switching signal diode. It is one of the most popular and long-lived switching diodes because of its dependable specifications and low cost. Its name follows the JEDEC nomenclature. The 1N4148 is useful in switching applications up to about 100 MHz with a reverse-recovery time of no more than 4 ns.

<span class="mw-page-title-main">Fleming valve</span> Type of vacuum tube; early radio detector

The Fleming valve, also called the Fleming oscillation valve, was a thermionic valve or vacuum tube invented in 1904 by English physicist John Ambrose Fleming as a detector for early radio receivers used in electromagnetic wireless telegraphy. It was the first practical vacuum tube and the first thermionic diode, a vacuum tube whose purpose is to conduct current in one direction and block current flowing in the opposite direction. The thermionic diode was later widely used as a rectifier — a device that converts alternating current (AC) into direct current (DC) — in the power supplies of a wide range of electronic devices, until beginning to be replaced by the selenium rectifier in the early 1930s and almost completely replaced by the semiconductor diode in the 1960s. The Fleming valve was the forerunner of all vacuum tubes, which dominated electronics for 50 years. The IEEE has described it as "one of the most important developments in the history of electronics", and it is on the List of IEEE Milestones for electrical engineering.

A mechanical rectifier is a device for converting alternating current (AC) to direct current (DC) by means of mechanically operated switches. The best-known type is the commutator, which is an integral part of a DC dynamo, but before solid-state devices became available, independent mechanical rectifiers were used for certain applications. Before the invention of semiconductors, rectification at high currents involved serious losses.

In solid-state physics, a metal–semiconductor (M–S) junction is a type of electrical junction in which a metal comes in close contact with a semiconductor material. It is the oldest practical semiconductor device. M–S junctions can either be rectifying or non-rectifying. The rectifying metal–semiconductor junction forms a Schottky barrier, making a device known as a Schottky diode, while the non-rectifying junction is called an ohmic contact.

<span class="mw-page-title-main">Active rectification</span>

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively controlled switches, usually power MOSFETs or power bipolar junction transistors (BJT). Whereas normal semiconductor diodes have a roughly fixed voltage drop of around 0.5 to 1 volts, active rectifiers behave as resistances, and can have arbitrarily low voltage drop.

<span class="mw-page-title-main">Joule thief</span> Voltage booster electronic circuit

A joule thief is a minimalist self-oscillating voltage booster that is small, low-cost, and easy to build, typically used for driving small loads, such as driving an LED using a 1.5 volt battery. This circuit is also known by other names such as blocking oscillator, joule ringer, or vampire torch. It can use nearly all of the energy in a single-cell electric battery, even far below the voltage where other circuits consider the battery fully discharged ; hence the name, which suggests the notion that the circuit is stealing energy or "joules" from the source – the term is a pun on "jewel thief". The circuit is a variant of the blocking oscillator that forms an unregulated voltage boost converter.

In vacuum tube technology, HT or high tension describes the main power supply to the circuit, which produces the current between anode and cathode. It is also known as the plate supply or voltage, B battery supply, or simply labeled →B on circuit diagrams, from the days of battery powered circuitry.

References

  1. Hempstead, Colin; Worthington, William (2005-08-08). Encyclopedia of 20th-Century Technology. Routledge. p. 669. ISBN   978-1-135-45551-4. selenium rectifiers, which were invented by Charles E. Fitts in 1933
  2. books.google.co.uk
  3. books.google.co.uk
  4. Peter Robin Morris. A history of the world semiconductor industry, IET, 1990, ISBN   0-86341-227-0, pages 13, 18.
  5. Reeves, E. A.; Heathcote, Martin (2013-06-17). Newnes Electrical Pocket Book. Taylor & Francis. p. 95. ISBN   978-1-136-37644-3.
  6. Ernst Bleule (ed.), Electronic methods, Academic Press, 1964, ISBN   0-12-475902-5, pages 206–207.
  7. H. P. Westman (ed), Reference Data for Radio Engineers Fifth Edition, Howard W. Sams & Co., Inc. 1968, chapter 13.
  8. Preston, J. S. (1950-08-22). "Constitution and mechanism of the selenium rectifier photocell". Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences. 202 (1071): 449–466. Bibcode:1950RSPSA.202..449P. doi:10.1098/rspa.1950.0112. ISSN   0080-4630. S2CID   93164294.
  9. "Occupational Health Guideline for Hydrogen Selenide" (PDF). cdc.gov. 1978. Retrieved 2022-10-01.
  10. PubChem. "Hydrogen selenide". pubchem.ncbi.nlm.nih.gov. Retrieved 2022-10-01.
  11. Selenium, U.S. Department of the Interior.
  12. US Patent 3218472: Transistor switch with noise rejection provided by variable capacitance feedback diode.
  13. 1 2 The 1060 Data Communications System (PDF). IBM. p. 2.