Future development of the switching power supply

Article Source：   Published：2015/03/02

Switching power electronics industry has been a very popular technology, but it also is a trend we must always pay attention to the problem, or an inattentive will not keep pace with technological development. Electronic Components Technology Network made a key focus of the switching power supply technology survey, get out of the following ten popular concerns.
Switching Power Density
Increase the power density switching power supply, making it smaller and lighter, is that people continue to strive for the goal. The high frequency power supply is one of the hotspots of international power electronics industry research. Power miniaturization, weight reduction of portable electronic devices (such as mobile phones, digital cameras, etc.) is particularly important. Switching power supply miniaturization specific measures are:
First, the high frequency. In order to achieve high power density the power necessary to increase the operating frequency of the PWM converter, thereby reducing the circuit size of the weight energy storage elements.
Second, the application of the piezoelectric transformer. Application of high-frequency power converter allows piezoelectric transformer light, small, thin and achieve high power density. A piezoelectric transformer utilizing a piezoelectric ceramic material-specific "voltage - vibration" Transformation and - Properties "vibration voltage" transformation transferred energy, the equivalent circuit as a series-parallel resonant circuit is one of the hotspots in the field of power conversion.
Third, using the new capacitor. To reduce the power electronic equipment size and weight, must try to improve the performance of the capacitor, increase energy density, and research and development suitable for power electronics and power systems with new capacitors, requiring large capacity, small equivalent series resistance ESR, volume and small.
High-frequency magnetic synchronous rectification
Power system with plenty of magnetic components, materials high frequency magnetic components, structure and performance are different from the power-frequency magnetic components, there are many issues need to be studied. High frequency magnetic components used in magnetic materials have the following requirements: loss, good thermal performance, superior magnetic properties. Applicable megahertz frequency magnetic materials of concern for people, nanocrystalline soft magnetic materials have also been developed applications.
After the high-frequency, in order to improve the efficiency of the switching power supply, must be developed and applied soft-switch technology. It is a hot topic in the past few decades the international power sector.
For low voltage, high current output soft-switching converters to further improve the efficiency of the measures is to try to reduce the switching-state losses. SR technologies such as synchronous rectification, that power MOS reverse as rectifier switching diodes, Schottky diodes instead (SBD), can reduce the pressure drop, thereby improving the efficiency of the circuit.
Distributed power structure
Distributed power systems suitable for use as ultra-high-speed integrated circuits consisting of a large workstation (such as image processing station), the power of large digital electronic switching systems, and its advantages are: to achieve DC / DC converter module modular; easy to achieve N + 1 power redundancy, easy to amplify the load capacity; can reduce the current and the voltage drop on the 48V bus; easy to achieve uniform heat distribution, ease of thermal design; transient response; available online to replace failed modules.
Now distributed power supply system, there are two types of structures, one two-stage structure, and the other is tertiary structure.
PFC converter
Because AC / DC converter circuit inputs rectifying element and filter capacitor, when sinusoidal voltage input, single-phase rectifier power supply electronic equipment, power side (AC input) power factor of 0.6 to 0.65. Using PFC (Power Factor Correction) converter, line power factor can be increased to 0.95 to 0.99, the input current THD is less than 10%. Both control the harmonic pollution, and improve the overall efficiency of the power supply. This technique is called active power factor correction of single-phase APFC APFC early development at home and abroad, technology has become more mature; APFC topology of three-phase type and control strategy Although there are many, but there continue to be research and development.
Generally high power factor AC / DC switching power supply, consisting of a two-stage topology for low power AC / DC switching power supply, the use of low levels, the overall efficiency of the topological structure of the high cost.
If the input of the power factor requirements are not particularly high, it will be a combination of post-stage PFC converter and a DC / DC converter into a topological form a single-stage high power factor AC / DC switching power supply, with only one main switch, can Power factor correction to 0.8 above, and the output DC voltage is adjustable, this topology is called a single-stage single tube that S4PFC converter.
VRM Voltage Regulator Module
Voltage regulator module is a class of low voltage, high current output DC-DC converter module, to provide power to the microprocessor.
Now the speed and efficiency of data processing systems increasing, microprocessor IC to reduce the electric field intensity and power consumption must be reduced logic voltage, logic voltage has decreased to a new generation microprocessor 1V, and the current is as high as 50A ~ 100A, so the VRM requirements are: very low output voltage, output current, the current change rate, fast response and so on.
Digital control
Control power has been controlled by the analog, analog-digital hybrid control, into full digital control phase. Full digital control is a new trend, has been applied in many power conversion devices.
But control over digital DC / DC converter used in less. The past two years, the power of high-performance digital control chip has been developed, the cost has dropped to a more reasonable level, there are many companies in Europe and America to develop and manufacture digital switching converter control chip and software.
Advantages of digital control are: digital and mixed-signal analog to digital signals can be compared to a smaller amount of calibration, chip prices are cheaper; for current detection error can be accurate digital correction voltage detection and more accurate; can achieve rapid, flexible control design.
Electromagnetic Compatibility
Electromagnetic Compatibility (EMC) high-frequency switching power supply problem has its particularity. Power semiconductor switches in the switching process generated di / dt and dv / dt, conducted electromagnetic interference caused by the powerful and harmonic interference. Some cases can also cause strong electromagnetic field (usually near-field) radiation. Only serious pollution to the surrounding electromagnetic environment, to nearby electrical equipment causing electromagnetic interference, but also may endanger the safety of operating personnel in the vicinity. Meanwhile, the power electronic circuits (such as switching converter) internal control circuit must be able to withstand electromagnetic interference (EMI) and application site switching noise generated. Particularity above, plus EMI measurements on specific difficulties in the field of electromagnetic compatibility in power electronics, there are many cross * scientific research topics at the forefront of people yet. Many universities at home and abroad have carried out a study of electromagnetic interference power electronic circuits and electromagnetic compatibility issues, and made a lot of encouraging results. In recent years, research shows that the voltage, current changes in the switching converter electromagnetic noise sources, mainly from the main switching device switching action arising. The faster rate of change, the larger the electromagnetic noise.
Design and testing technology
Modeling, simulation and CAD is a new design tool. For power system simulation, we must first build simulation models, including power electronics converter circuits, digital and analog control circuitry and magnetic components and magnetic field distribution models, but also consider the thermal model of the switch, you can model and EMC model * . Various models vary greatly, the development direction of the modeling are: digital - analog mixed modeling, mixed-level modeling, and various models of the formation of a unified multi-level model.
Power systems CAD, including the main circuit and control circuit design, component selection, parameter optimization, magnetic design, thermal design, EMI design and printed circuit board design, can be * estimates, computer-aided design, synthesis and optimization. Used for power system simulation expert system based CAD, design enables optimum system performance, reduce design and manufacturing costs and do manufacturability analysis, is one of the 21st century, the development direction of simulation and CAD technology. In addition, development, research and application of thermal power system testing, EMI testing, testing and other technology can * also should vigorously develop.
System Integration Technology
Power Equipment Manufacturing characteristics are: non-standard parts and more labor-intensive, long design cycle, high cost and low availability *, and user requirements factory production of power products more practical, can * higher performance, smaller and lighter lower cost. These circumstances make the power supply manufacturers under great pressure, the urgent need for research and development of integrated power modules, enabling power products standardization, modularity, manufacturability, scale production, lower costs and other objectives are achieved. In fact, the power of integrated technology development process, and has gone through a modular power semiconductor devices, power and control circuit integration, integrated passive components (including magnetic integration technology) and other stages of development. Direction of development in recent years is the small power supply system integrated on a chip, you can make a more compact power supply products, smaller, but also reduces the wire length, thus reducing the parasitic parameters. On this basis, the integration can be achieved, together with the control and protection of all components integrated in a single module.