脉冲电源开关设备 - 概述
By John Pasley
Copyright John Pasley 1996. This document may be freely distributed via. Any means in part or in whole, however the authors name must be included and correctly attributed.
The References Listed and The Disclaimer must also be included.
1。1Switching basics and terminology
The switch is possibly the most elementary device in the field of electronics. A switch controls the flow of current in a circuit in a manner such that either the current flows at a value determined by the other components in series with it, or does not flow at all, as the case may be. However this ideal behavior is actually never exactly what is seen in real life. A switch has it’s own parameters that determine how fast it can switch from open to closed, or how rapidly it can interrupt the flow of current once it is has been opened. Also of course there are more elementary considerations such as the current handling capacity of the switch and the peak voltage it can cope with before damage or other unwanted effects occur.
Electromagnetic relays and reed switches experience similar problems to those seen in the humble light switch. Long commutation and switch bounce are standard features of virtually all mechanical switching devices.
There are a great many different types of vacuum tube in existence, however it is possible to group tubes according to some fairly basic criteria. There are two primary distinguishing features, the source of free electrons within the device and the gaseous filling (or lack of it) within the tube envelope. The later of these two concepts we have already introduced by implication. A vacuum tube is a device with a vacuum (very low pressure gas) filling. And a gas filled device is, as the name would suggest, filled with gas that might be at a pressure somewhat above or below atmospheric. The type of gas used is also an important feature, particularly in switching tubes where a wide variety of fillings are encountered.
装置中的自由传导电子的源极可以是热的热丝，例如与装置的阴极物理相关 - 热阴极，或者可选地，在该装置上的高压梯度的简单后果，导致自动化阴极。采用该后一种方法的装置称为冷阴极装置。在高压切换的高电压下，因此设备内大电压梯度的可能性意味着冷阴极系统，在大多数其他类型的管中相当罕见，是规范而不是异常。
抖动is the variation of time delay from shot to shot given similar electrical stimulus.
The commutation time is the time taken for the conduction to reach maximum once it has commenced. (i.e. From the time from the end of the delay time to the time at which the maximum level of conduction occurs.)
It should be pointed out that none of the switching tubes we are about to consider look very much like the things in the back of an old radio set. Many are large, some exceptionally so. Also glass has largely given way to ceramic in the higher powered devices. Before you go down your local electronics shop or radio shack it should also be pointed out that many of these devices besides costing $100’s (often $1000’s) a piece, and are also largely unavailable to the general public due to their application in advanced missile and nuclear weapon technologies. Of these devices the most ‘everyday’ is the ignitron which finds much application in industrial welding situations.
The following devices are considered herein:
2.0 Vacuum and Gaseous State Switching devices
Most of the devices in this section switch by inducing an arcing process in a gaseous medium. I have included in the triggered spark gap section some mention of devices that actually use a liquid or solid substitute for the gaseous material that is the norm in triggered spark gaps.
The process of arc formation is actually quite complex physically, and it will not be gone into in any depth. Anyone who wishes to look more deeply into this aspect of device operation may contact the author for some suggestions as to suitable text books for use in such study.
冷阴极管触发身体小德vices designed to switch impulse currents and voltages of relatively small amplitude. Usually they are intended, as their name suggests, to trigger other larger devices.
- A trigger pulse of sufficient amplitude is present at the trigger electrode.
Cold cathode trigger tubes rely upon some external or internal source to ionize the gas suitably for conduction to commence (This is called priming). This means that in theory some of these tubes will only switch a minute or so after the application of a suitable triggering voltage to the appropriate terminal of the device when some natural source of ionizing radiation ionizes the gas (forming a plasma) and hence causes conduction to commence.
触发基本上是随机的 - 即使在显然相似的环境中，它也会受到巨大的统计变化。一些装置包括适当电离的源，以便在触发器施加时减少最大可能的时间延迟。该来源可以是某种形式或其他形式的电子，放射性或光子源。然而，即使是标准商业设备常常在阳光和黑暗中触发的设备之间经常显示大的变化（高达和高于不同的数量级），例如，标准商业管Z900T例如在日光下显示20US延迟和黑暗中的250us延迟。
2.2 The Krytron
The Krytron is designed to switch moderately high impulse currents (up to around 3kA) and voltages (Up to around 5kV) in an arc discharge mode, compare this with the usual glow discharge of the standard trigger tube. Also, and perhaps more importantly, the Krytron is able to turn on this arc discharge very rapidly, the reason being that it relies on an already present plasma to support the conduction, rather than waiting for the plasma to be formed as a result of priming etc. This plasma is created and sustained by a keep-alive current between the keep-alive electrode and the cathode of the device. When the trigger is applied under the conditions of a high anode to cathode voltage, this plasma forms an easy path for the main conduction between anode and cathode.
A Krytron contains a source of Beta radiation, Ni-63. The quantity in each device is less than 5 microcuries and presents no significant hazard. Usually the source is pulse welded to a piece of Nickel wire that is in turn welded to one of the electrode supports. The purpose of this source is to increase the reliability of the krytron by aiding the formation of the initial glow discharge between the keep alive and the cathode. This initial keep alive current is very much subject to environmental factors such as are seen in the formation of the glow discharge in standard trigger tubes. It is for this reason that a radioactive priming element is used, much as in the priming source employed in a standard trigger tube (which is also occasionally a radioactive source).
Krytrons typically come in a small glass envelope somewhat similar to a neon indicator bulb with more leads.
Krytrons require a high voltage pulse (500V to 2kV) to be applied to the trigger electrode to fire successfully. This pulse is almost always generated by a pulse transformer fired by a capacitor discharge in the primary (rather like a simple strobe tube firing circuit).
The krytron often has only a short life expectancy if used regularly (often is few as a couple of hundred shots) However when used within the appropriate parameters and well within the expected life time they are extremely reliable, requiring no warm up and being immune to many environmental factors to a large extent (e.g. vibration, temperature, acceleration).
These properties, combined with the small size make the krytron ideal for use in the detonating circuitry of certain types of missiles and smart bombs. The krytron may be used directly to fire a high precision exploding wire, or alternatively as part of the triggering circuitry for a triggered spark gap or similar ultra high current triggering device as used in exploding foil slapper type detonators and larger EBW circuits.
2.3 The Sprytron
The Sprytron, otherwise known as the Vacuum Krytron, is a device of very similar performance to the Krytron. Though it generally exhibits a somewhat lower time delay after triggering. The Sprytron is designed for use in environments were high levels of radiation are present. The sprytron is a hard vacuum ‘filled’ device unlike the krytron which, as noted above contains a low pressure gas.
The Sprytron requires a more powerful trigger pulse than the Krytron, as the device works by forming an arc directly between the trigger and the cathode, which causes the tube to breakdown (go into conduction) by disrupting the field between the anode and cathode.
A Sprytron is triggered in a similar fashion to Krytron, but as mentioned requires a higher energy trigger pulse and therefore a more powerful trigger transformer etc. EG&G makes trigger transformers optimized for use with their various tubes, and also make devices named Krytron-Pacs which incorporate a gas filled krytron and trigger transformer in a single housing.
Thyratrons come in several varieties. All work similarly to the emiconductor Thyristor, one difference being that in many designs (Hydrogen Thyratrons are a common exception) the gate must be biased highly negative in the off state and then biased positive to achieve switching. Like Thyristors, Thyratrons operate like a latching switch, ie. once you have turned them on you can only turn off by cutting the supply to the main circuit. Mercury filled Thyratrons are the slowest, least useful type and are much more restricted environmentally than other types due chiefly to problems with the mercury condensing . They are rarely used as they have few advantages of the thyristor. Hydrogen Thyratrons are *much* faster switching than Thyristors. Some can achieve commutation in under 20ns. Inert gas fillings tend to offer superior performance compared to mercury filled devices, without matching the speed of the Hydrogen filled devices.
The actual Physical construction/ operation of the thyratron is quite omplicated compared to the other devices we have looked at and no attempt will be made to explain it’s operation. The reader is advised to consult a wide range of books as devices employing different fillings, or electrode heating methods operate ifferently. It is not considered to be especially important to consider all these variations here as this is merely an overview of these devices and is not intended to be the final word on the subject. However, in order to differentiate the thyratron form other similar devices and to define it in at least some physical manner here follows Frungel’s (Ref.4) definition of the device:
‘By the term ‘thyratron’ there is meant a discharge chamber in which are arranged a cathode, one or several grids, and an anode, and which is filled with an inert gas or metal vapor.’
例如。E3213可以切换70kV（双间隙类型）。遇到具有陶瓷和金属体的专家Thyratrons。这些设计用于极端环境条件。在Thyratrons中有各种各样的网格配置，在这里考虑它们是不切实际的。Thyratrons的制造商包括Eg＆G，GEC，英式电动阀门有限公司M-O阀门有限公司。Ltd. Big Thyratrons经常要求您获得一个充满驱动程序/控制电路的大盒子。价格从几美元变为数千美元。遇到冷热阴极型器件。
Note these ratings are the exception rather than the rule in Thyratron devices, devices designed for sub kilovolt voltages and only capable of handling a few tens of amps pulsed are common enough.
2.5 The Over Voltage Spark Gap
The Over voltage spark gap is essentially just two electrodes with a gap between. When the voltage between the two electrodes exceeds the breakdown voltage of the gas, the device arcs over and a current is very rapidly established. The voltage at which arcing occurs in these devices is given by the Dynamic Breakdown Voltage, which is the voltage at which the device will breakdown for a fast rising impulse voltage. Note that this voltage may be as much as 1.5 times greater than the static breakdown voltage (breakdown voltage for a slowly rising voltage.) how much greater than the static breakdown voltage the actual breakdown voltage is will be depends almost entirely on how rapidly the voltage rise, a shorter rise time means a higher breakdown voltage. Commutation times for these devices are exceptionally low (sometimes less than 1nanosecond).
Overvoltage gaps are primarily used for protection. But in combination with the other devices mentioned here they are commonly used to sharpen the output pulses (decrease the rise times) of very high current pulses form triggered switching devices e.g. Thyratrons.
The size of these devices is almost entirely dependent upon how much current/voltage they are intended to switch, There is really no limit as to the size of these devices they can be as small as krytrons, however they can also be very big, and devices intended to switch MA will be just that.
2.6 Triggered spark gaps
The triggered spark gap is a simple device, a high voltage trigger pulse applied to a trigger electrode initiates an arc between anode and cathode. This trigger pulse may be utilized within the device in a variety of ways to initiate the main discharge. Different spark gaps are so designed to employ one particular method to create the main anode to cathode discharge. The different methods areas follows…
Triggered spark gap electrode configurations:
- Field distortion: three electrodes; employs the point discharge (actually sharp edge) effect in the creation a conducting path
- Irradiated: three electrodes; spark source creates an illuminating plasma that excites electrons between the anode and cathode.
- Swinging cascade: three electrodes; trigger electrode nearer to one of the main electrodes than the other.
- Mid plane: three electrodes; basic triggered spark gap with trigger electrode centrally positioned.
- Trigatron: trigger to one electrode current forms plasma that spreads to encompass a path between anode and cathode.
通常，气体填充的火花喘气在20-100kV / 20到100ka范围内运行，但可提供更高的功率设备。我有一个规格的麦克斯韦尔填充装置，可以处理3 ma - 这是300万安培！但那么这是一辆小型车的大小！更常见的气体填充装置具有几英寸的尺寸。套餐通常像大型冰冰盘，也可以看到类似结构的双管，管状和盒子。
Typical spark gap device no.’s are: TG7, TG113, TG 114 etc. etc.
Spark gaps are damaged by repeated heavy discharge. This is an inevitable consequence of such high discharge currents. Electrode pitting being the most common form of damage. Between 1 and 10 thousand shots per device is usually about what is permissible before damage begins to severely degrade performance.
Laser switching of spark gaps. The fastest way to switch a triggered spark gap is with an intense pulse of Laser light which creates a plasma between the electrodes with extreme rapidity. There have been quite a few designs employing this method, chiefly in the plasma research area.
Triggered spark gaps tend to have long delay times than Thyratrons (their chief competitor, at least at lower energies) However once conduction has started it reaches a peak value exceptionally rapidly (couple of nanoseconds commutation.)
The ignitron is mercury vapor rectifier in which an arc is switched between a (usually graphite) anode and a mercury pool cathode. The discharge is initiated by an ignitor electrode which dips into the mercury pool cathode.
Anode excitation: common in resistance welding applications here the anode bias is connected to the ignitor by means of a switch (thyristor, thyratron etc.) and a resistor/fuse network. The ignitor current drops rapidly on ignition as the anode-cathode voltage drops very low during conduction.
Separate excitation: as the name suggests, here the ignitor circuit is largely independent of the main circuit.
Ignitrons must often be cooled when used continuously (ie. Not single shot as in capacitor discharge) Water cooling is commonly employed. It is vital that Ignitrons must be used in the correct temperature range to hot or to cold can be very bad news for these devices- (cold leads to mercury vapor condensing on the anode.)
引燃管是非常有限的关于他们的物理ical orientation. This reason being simple that they rely upon a pool of liquid at one end of the device that must be correctly positioned for the ignitor to function correctly. Positioning the device so that it leans over at an angle of more than 2 or 3 degrees from the vertical is fatal.
Thyratrons and Krytrons are sometimes used in ignitron triggering circuits along with the familiar thyristor.
3.。0 Solid State Devices
expanded following further research by the author.)
A new class of devices is at present showing great promise in the R&D sector. These devices are optically (usually LASER) switched devices employing GaAs or Diamond film technologies. The reader is advised to
consult the appropriate reference below for more information relating to these devices.
Final note to the reader:
Some of the devices I have mentioned are subject to strict control due to their military applications. Non of the above information is however in any way restricted or controlled. For clarity switching devices that are restricted by dual use guidelines are as follows: (courtesy Oak Ridg National Laboratory)
- Anode peak voltage rating of 2500 V or more;
- Anode peak current rating of 100 A or more;
(b) Triggered spark-gaps having an anode delay time of 15 microsecond or less rated for a peak current of 500 A or more;
(c) Modules or assemblies with a fast switching function having all of the following characteristics:
- Anode peak voltage rating greater than 2000 V;
- turn-on time of 1 microsecond or less.
Carey Sublette for providing a great deal of help and encouragement.
Roy Schmaus for providing the original site for this information.
References: (in alphabetical order by title)
2) Exploding Wires Vol. 4, Proc. of 4th Conf. on the Exploding Wire Phenomena. Ed. Chace and Moore -Plenum Press (RE: EBW’s)
ed. Rosen And Zutavern- Artech House (RE: Solid state devices)
4.) High Speed Pulse Technology by Frank Frungel -Academic Press.(RE: EBW’s, FCG’s, components)
5) High Velocity Impact Phenomena by Ray Kinslow-Academic Press.(RE: Foil Slappers)
IEEE publications (please contact author for more details).
Maxwell Catalogues. (RE: spark gaps)
FURTHER INFORMATION PERTAINING TO THE SUBJECT MATTER WILL BE MUCH WELCOMED BY THE AUTHOR.
关于作者:我不是一个费用rt in any of the above technologies and I will welcome any corrections. However please could anyone providing information also provide references to either the material they present or as to themselves so that their contribution may be given due weight.
Anyone who would like to contact me (the author) for whatever reason should mail:
High voltages are generally exceptionally dangerous, and none of the above is intended or should be used to provide instruction in the correct procedures for building or constructing high voltage circuitry of any description. High voltage is used here to describe any voltage which may cause death i.e. anything above 50V.