Power switches designing


All power supply engineers follow a general pattern of steps in the design of power supplies. If the pattern is followed, each step actually sets the foundation for subsequent design steps and will guide the designer through a path of least resistance to the desired result. This text presents an approach that consists of two facets first it breaks the power supply into distinct blocks that can be designed in a modular fashion secondly, it prescribes the order in which the blocks are to be designed in order to ease their pasting together. The reader is further helped by the inclusion of typical industry design approaches for each block of various applications used by power supply designers in the field. Each block includes the associated design equations from which the component values can be quickly calculated. The result is a coherent, logical design flow in which the unknowns are minimized. The approach is organized such that the typical inexperienced designer can produce a professional grade power supply schematic in under 8 working hours, which is about 40 percent of the entire design process. The physical design, such as breadboarding techniques, low-noise printed circuit board (PCB) layouts, transformer winding techniques, etc., are shown through example. The physical factors always present a problem, not only to the inexperienced designer, but to the experienced designer as well. It is hoped that these practical examples will keep the problems to a minimum. All power supplies, regardless of whether they are linear or switching, follow a general design flow. The linear power supplies, though, because of the maturity of the technology and the level of integration offered by the semiconductor manufacturers, will be presented mainly via examples. The design flow of the switching power supplies, which are much more complicated, will be covered in more detail in the respective chapters dealing with the selected power supply technology. The generalized approach is as follows.  [c.8]

There is an abundance of software-based power supply design tools, particularly for PWM switching power supply designs. Many of these software packages were written by the semiconductor manufacturers for their own highly integrated switching power supply integrated circuits (ICs). Many of these ICs include the power devices as well as the control circuitry. These types of software packages should only be used with the targeted products and not for general power supply designs. The designs presented by these manufacturers are optimized for minimum cost, weight, and design time, and the arrangements of any external components are unique to that IC.  [c.9]

The disadvantage of the quasi-resonant converter compared to the newer lossless snubber and active clamp techniques in addition to the basic PWM converters, is the voltage or current stresses placed upon the power components. The peak voltage or current values that exist within quasi-resonant converters can be two to three times higher than in PWM converters. This forces the designer to use higher-rated power switches and rectifiers which may not have as good conduction characteristics.  [c.151]

Pumps, compressors, turbines, drivers, and auxiliary machinery should be designed to provide reliable, rugged performance. Pump selection and performance depend on the capacity required and tlie nature of Uie fluids involved. Remotely controlled power switches and shutoff valves are necessary to control fluid flow during an emergency. The inlets for air compressors should be strategically located to prevent the intake of hazardous materials.  [c.495]

RCT are designed to successfully solve a whole number of tasks in nuclear power when testing fuel elements, in aviation and space industry when testing construction materials, nozzles and engine units, turbine blades and parts, in electromechanical industry-cables switching elements, electric motors in defense sphere- charges, equipment in prospecting for research of rock distribution and detection of precious stones in samples.  [c.598]

Thus to design a system protected through HRC fuses or a current limiting device for a higher fault level than necessary will only lead to overprotection and the extra cost of the current-carrying system, switching equipment and power cables. An individual device or component and its connecting links in such cases may therefore be designed for a size commensurate to its current rating. See also Section 13.5.1.  [c.864]

The trends within the industry are away from linear regulators (except for board-level regulators) towards PWM switching power supplies. Resonant and quasi-resonant switching power supplies are emerging slowly as the technology matures and their designs are made easier. To help in the selection, Table f-f summarizes some of the trade-offs made during the selection process.  [c.4]

There are several generalized switching power supply design software packages available primarily from circuit simulator companies. Caution should be practiced in reviewing all software-based switching power supply design tools. Designers should compare the results from the software to those obtained manually by executing the appropriate design equations. Such a comparison will enable designers to determine whether the programmer and his or her company really understands the issues surrounding switching power supply design. Remember, most of the digital world thinks that designing switching power supplies is just a matter of copying schematics.  [c.9]

Power supplies, especially switching power supplies, require the designer to view parameters not commonly encountered in the other fields of electronics. Aside  [c.9]

The relative losses among the various sections within a PWM switching power supply are somewhat predictable from experience. These loss proportions are of course affected by the design paths pursued by the designer, but at this stage only a good guess estimate is desired. Table 3-3 shows the typical efficiency for each major topology and the percentage of loss that occurs between the power switch stage and the output rectifier stage.  [c.35]

In the initial breadboard, the voltage and current waveforms associated with the power transistor must be carefully scrutinized and it must be verified that they do not exceed the SOA limits. This is also the time to modify any values that enhance its switching characteristics, since it represents about 40 percent of the supply s entire losses. The drive schemes shown in Figures 3-33 and 3-34 are the common approaches to driving the bipolar transistor and will give the designer a very good staring point.  [c.66]

The final stage in the design of any switching power supply is the physical design of the printed circuit board (PCB). If it is designed improperly, the PCB could contribute to the supply s instability, and radiate excessive electromagnetic interference (EMI). The role of the designer is to insure a good PCB design by understanding the physical operation of the circuit.  [c.93]

A PWM switching power supply that is designed with no extraordinary loss-control methods will exliibit efficiencies as seen in Table 3-3. For switching power supplies that have no problem in getting rid of the heat, such as some off-line applications, the aforementioned efficiencies may be satisfactory. For portable applications and equipment that must be small in size much better efficiencies must be sought. To improve the overall efficiency of a power supply, several techniques can be used.  [c.143]

Selecting the core material and style for a switching power supply application is often viewed as a dart board type of selection process by a designer starting his or her first transformer design. Although almost every core material and  [c.236]

Selecting the core material is the first issue to be addressed. All core materials are alloys based on ferrite. The major factor in a material s worthiness is its loss at the frequency of operation and the flux density of the application. A good place to start is with the materials the core manufacturer s themselves recommend for PWM switching power supplies and those that are commonly used by the designers in the field (see Table D-f).  [c.237]

To design a filter for the input of a switching power supply, the designer first needs to know which of the regulatory specifications is appropriate for the product. The specifications dictate the conducted and radiated EMI/RFI limits the product must meet to be sold into the particular market. A company s marketing department should know which areas of the world the product will be sold and hence the designers can determine the requirements that are appropriate. It is always a good idea to design for the most stringent specification that is applicable to your market.  [c.245]

Circuit breakers are switches that are operated by a signal, from a relay or from an operator. The circuit breaker is designed to interrupt the very large currents that may occur when the system experiences a fault, such as a lightning strike or arc to ground (e.g., a tree falling on a line, or a line falling to the ground). Because these extremely large currents can cause severe damage to equipment such as transformers or generators, and because these faults can disrupt the proper operation of the entire power system, the circuit breakers are designed to operate rapidly enough to prevent damage to equipment, often in 100 milliseconds or less.  [c.430]

Electrical connectors are mechanical devices that connect wires, cables, printed circuit boards, and electronic components to each other and to related equipment. Connector designs include miniature units for microelectronic applications specialized cable tack and panel designs for incorporating combinations of a-c, d-c, and radio-frequency conducting contacts and high current connectors for industrial application and for transmission and distribution of electrical power in overhead and underground networks. Further categorization of connectors can be made according to application, whether connectors permanently join conductors and components or permit separation and rejoining the means used to effect connection, whether by fusion (welding, soldering) or by pressure, the values of which can be small or great enough to severely deform metal the distribution type, whether of power or of low (signal) levels of current and the conductor size. The term electrical contact describes the junction between two or mote curtent-carrying members that provide electrical continuity at their interfaces. Connector contacts ordinarily remain stationary in active circuits, eg, they ate not mated or separated. Components having electrical contacts other than connectors include circuit breakers, switches, relays, and contactors that ate designed to intermpt or to establish current flow in active circuits, and slip rings and bmshes that transmit current from a stationary to a moving frame of reference.  [c.23]

Solids-level controls are important for determining the level of materials in bins and hoppers and can also protect conveyors from damage due to jamming if placed in transfer and discharge chutes. They may simply activate an audio or visual warning signal, or they may be electrically tied into the conveying system to start or stop conveyors automaticmly. Many designs are available, based on principles such as ultrasonics, lasers, radar, and switches operated by diaphragms or paddles. The two designs shown in Fig. 21-25 depend on hmit switches, with activation from a pendant cone on one and from a stain-less-steel diaphragm on the other. In either case, the presence of material resting against the cone or diaphragm opens or closes the switch, activating a warning signal in the latter case and turning off power to the conveyor in the former.  [c.1939]

During a high-frequency (FOW) surge, the inductive impedance of the windings becomes very high and offers an open circuit to the arriving surge, and there is no inductive transference of voltage surges to the secondary. But at lower frequencies, such as during overvoltages, long-duration switching surges (250/2500 /J.s). and even during lightning surges, the windings acquire enough inductive continuity to transfer a part of these voltages to the secondary, depending upon theyj, of the arriving surge, in the ratio of their transformation (V2/V,), It is generally noticed that such transferences hardly exceed the power frequency withstand level of the windings and are thus less critical. Nevertheless they must be counter-checked while designing the surge protection scheme for the whole system. If it is higher, then  [c.601]

If the input voltage of the switching power supply is greater than 40 V at the peak, then the power supply comes under the regulation of one or more international safety regulatory agencies. Many of these agencies mirror each other s safety limits, but the designer should still review the requirements for the markets into which his or her company s products are being sold. The International Engineering Consortium (lEC) is the main standard-writing body, whose standards have been adopted by all of the European Community safety agencies. The remaining safety agencies, such as Underwriters Laboratories (UL) in the U.S., Canadian Standards Agency (CSA) in Canada, and VCCI in Japan, are working together to adopt a uniform set of safety standards based upon the lEC standard. This will allow one set of standards to be utilized all over the world. Until the harmonized standards are adopted, there will be differences among countries around the world.  [c.52]

First, the designer should choose the type of rectification technology that is most appropriate for the application. The choice is whether to use passive rectification in which semiconductor rectifiers are used or synchronous recification in which power MOSFE B are placed in parallel with a smaller passive rectifier. Synchronous rectifiers are typically used in battery operated portable products where the added efficiency, usually an added two to eight percent, is important to extend the operating life of the battery or in applications where heat is important. In today s switching power supplies, passive rectifiers can dissipate 40 to 60 percent of the total losses within the power supply. Synchronous rectifiers affect only the conduction loss, which can be reduced by as much as 90 percent.  [c.57]

Much research and work has been done in the past two decades to improve the efficiency of the basic PWM switching power supply. During the f980s, the improvements largely took the form of improved semiconductor devices and ferrite materials. Their contributions allowed the switching frequencies to rise and their efficiency to improve about another +5 to +10 percent over the bipolar transistor-based designs. The most recent techniques include the use of resonant and charge redirection techniques. These modifications along with the use of synchronous rectifiers (where applicable), allowed switching power supplies to routinely exceed 90 percent efficiency.  [c.135]

Power Supply C/)okbook, Second Edition is organized in a rather unique manner and, if followed correctly, can greatly shorten the amount of time needed to design a power supply. By presenting intuitive descriptions of the power supply system s operation along with commonly used circuit approaches, it is designed to help anyone with a working electronics knowledge to design a very complex switching power supply quickly.  [c.268]

Inverters are designed with various power semiconductor arrangements. Power semiconductor elements of the inverter operate like switches by synthesizing the motor voltage waveform from segments of the DC bus voltage. For power ranges up to about 5 hp, convertors can use power transistors to synthesize six-step (per cycle), three-phase voltage for frequency ranges from 10 to 120 Hz for standard motors and from 240 to 1,200 Hz for high-frequency motors. For the conventional drive range from 5 to 500 hp, thyristor inverters are used to develop either six-step per cycle, twelve-step per cycle, or pulse-width modulated (pwm) voltages over typical frecjnency ranges from 10 to 120 Hz.  [c.417]


See pages that mention the term Power switches designing : [c.182]    [c.810]    [c.811]    [c.196]    [c.612]   
Power supply cookbook (2001) -- [ c.63 , c.64 , c.65 , c.66 , c.67 , c.68 , c.69 ]