Home About Kali Products News Instructions Contact Us
Switching Mode Power Supply中文版
The development direction of switching power supply technology
2018-11-09      Browse times: 4021

1. High performance silicon carbide (SiC) power semiconductor device
        It is foreseeable that silicon carbide will be the newest power semiconductor device material that is most likely to be 
successfully applied in the 21st century. Its advantages are: forbidden bandwidth, high operating temperature (up to 600 ° C), 
low on-state resistance, good thermal conductivity, and leakage current Small, PN junction withstand voltage and so on.
2. High frequency magnetic technology
        A variety of magnetic components are used in high frequency switching converters, and there are many basic problems 
to be studied.
       (1) With the high frequency of the switching power supply, some parasitic parameters that can be ignored at low 
frequencies will have an important influence on certain circuit performance (such as switching peak energy, noise level, etc.) 
at high frequencies. In particular, the eddy current, leakage inductance, winding AC resistance Rac, and distributed 
capacitance of the magnetic element are very different in performance at low frequency and high frequency. As the frontier 
of the discipline, high-frequency magnetic technology theory is still widely concerned, such as: mathematical modeling of 
core loss, simulation modeling of hysteresis loop, computer simulation modeling of high-frequency magnetic components 
and CAD, high-frequency transformer One-dimensional and two-dimensional simulation models, etc. The problems to be 
studied are: the design of high-frequency magnetic components determines the performance, loss distribution and waveform 
of high-efficiency switching power supplies. It is hoped that the dependence of design criteria, methods, magnetic parameters 
and structural parameters on circuit performance will be given. Design freedom and constraints, etc.

       (2) The following requirements are applied to high-frequency magnetic materials: low loss, good heat dissipation 
performance, and superior magnetic properties. Magnetic materials suitable for megahertz frequency are of interest, such as 
5~6μm ultra-thin cobalt-based amorphous magnetic tape. When 1MHz (Bm=0.1T), the loss is only 0.7~1W/cm3, which is 
MnZn high-frequency ferrite. 1/3 to 1/4 of the body. Nanocrystalline soft magnetic films are also being studied.
       (3) Research on the high density integration of ferrite or other thin film materials on silicon wafers. Or the silicon 
material is integrated on the ferrite, which is a hybrid technology of magnetoelectricity. The magnetoelectric hybrid 
integration also includes the use of the inductive foil winding interlayer distributed capacitance to realize the hybrid 
integration of the magnetic component and the capacitor.

3. New capacitors
        Research and develop new capacitors and super capacitors suitable for power supply systems. It requires a large 
capacitance, a small equivalent resistance (ESR), and a small volume. According to reports, in the late 1990s, the United 
States has developed a new 330μF solid tantalum capacitor with a significant drop in ESR.
4. Power Factor Correction AC-DC Switching Technology
        The general high power factor AC-DC power supply consists of two stages: a first stage pre-power factor corrector 
is added in front of the DC-DC converter, and at least two main switch tubes and two sets of control drive circuits are required. 
This means that for low-power switching power supplies, the overall efficiency is low and the cost is high.For the case where 
the power factor requirement of the input terminal is not particularly high, the PFC and converter combination circuit is used to 
form a low-power AC-DC switching power supply. Only one main switch tube can be used to correct the PF to 0.8 or more, 
which is called single-tube single-stage PF. Correction of the AC-DC converter, referred to as S4. For example, an isolated 
S4PF-corrected AC/DC converter, a pre-power factor corrector using a Boost converter operated by a DCM, a post-voltage 
regulator main circuit being a flyback converter, operating in CCM or DCM; a two-stage circuit combining one Main switch tube.
5. Electromagnetic compatibility study of high frequency switching power supply

          The electromagnetic compatibility problem of high frequency switching power supplies is special. Usually, it 

involves di/dt and dv/dt generated by the switching process, causing strong conducted electromagnetic interference and 

harmonic interference. In some cases, it also causes strong electromagnetic field radiation. It not only seriously pollutes 

the surrounding electromagnetic environment, but also causes electromagnetic interference to nearby electrical equipment, 

and may also endanger the safety of nearby operators. At the same time, the control circuit inside the switching power supply

must also withstand the electromagnetic interference of the main circuit and industrial applications. Due to the above 

specificities and specific difficulties in measurement, research work on electromagnetic compatibility of switching power 

supplies is still in its infancy. Obviously, in the field of electromagnetic compatibility, there are many cutting-edge topics in 

cross-science that need to be studied. Such as: typical field and system near field, conducted interference and radiation 

interference modeling; printed circuit board and switching power supply EMC optimization design software; low intermediate 

frequency, super audio and high frequency strong magnetic field on human health; high power switching power supply EMC 

measurement Methodological research, etc.

6. Switching power supply design, testing technology

           Modeling, simulation, and CAD are new, convenient, and cost-effective design tools. In order to simulate a switching 

power supply, simulation modeling is first required. The simulation model should include power electronics, converter circuits, 

digital and analog control circuits, as well as magnetic components and magnetic field distribution models, circuit distribution 

parameter models, etc., as well as the thermal model, reliability model and EMC modeling of the switch. The various models 

vary widely, so the direction of modeling should be: digital-analog hybrid modeling; hybrid hierarchical modeling; and the 

formation of a unified multi-level model of various models (similar to a circuit model, with a block diagram, etc. ); automatically 

generate models to enable simulation software with automatic modeling to save user time. Based on this, a model library can 

be built.The switching power supply CAD, including main circuit and control circuit design, device selection, parameter 

optimization, magnetic design, thermal design, EMI design and printed circuit board design, reliability estimation, computer-

aided synthesis and optimization design. The simulation-based expert system for the switching power supply CAD can 

optimize the designed system performance, reduce the design and manufacturing costs, and can do manufacturability 

analysis. It is one of the development directions of 21st century simulation and CAD technology. Expert systems for 

designing DC-DC switching converters and MATSPICE software for simulation have been developed abroad.

           In addition, the development, research and application of thermal testing, EMI testing, and reliability testing of 

switching power supplies should be vigorously developed.

7. Low-voltage, high-current switching power supply development

(1) Requirements for low-voltage, high-current switching converters

           The speed and efficiency of data processing systems are increasing. The logic voltage of the new generation 

microprocessor is as low as 1.1~1.8V, and the current is 50~100A. The power supply is low voltage, high current output 

DC-DC converter module. Also known as the voltage regulator module (VRM). The requirements of the new generation 

of microprocessors for VRM are: low output voltage, large output current, high current rate of change, fast response, etc.

            1 In order to reduce the electric field strength and power consumption of the IC, the microprocessor supply 

voltage must be reduced, so the output voltage of the VRM should be reduced from the conventional 3V to less than 

2V or even 1V.

            2 When running, the power input current is >100A. Due to parasitic L and C parameters, the voltage disturbance 

is large, and L should be minimized.

            3 The microprocessor starts and stops frequently, continuously starts from the sleep state, works, and then goes to 

sleep state. Therefore, the VRM current is required to be abruptly changed from 0 to 50A, and then dropped to 0, and the 

current change rate is 5 A/ns.

            4 The design should control the disturbance voltage ≤10%, and allow the output voltage to vary by ±2%.

(2) Using waveform interleaving technology

            The parasitic impedance of the line, the ESR of the capacitor, and the ESL have a large effect on the voltage 

regulation of the VRM during load changes. High frequency, high power density and fast new VRM must be developed.

 A variety of topologies have emerged, such as: synchronous rectification Buck converter (using a power MOS transistor 

instead of a switching diode); to prevent output voltage disturbances due to high frequency parasitic parameters when the 

current is greatly changed, there are literatures that use multiple input channels or The multiphase DC-DC converter, 

called the Interleaving technique, is used to ensure that the VRM output ripple is small, the output transient response is 

improved, and the output filter inductance and capacitance are reduced.

(3) Voltage ripple and impulse voltage problems

             1 voltage ripple and ESR. For a load with a voltage below 1V and a current of 100A or more, the load resistance 

is 10mΩ or less, which is lower than the internal equivalent series resistance of the filter capacitor, and a voltage ripple 

problem occurs. Now, suppose that this power supply can be realized by a buck-boost or boost converter, but the ripple 

current flowing through the capacitor is above 100A, and the efficiency is less than 50%. In this regard, the buck converter 

includes a series filter inductor to suppress ripple current. However, the load resistance is equivalent to ESR, and the ripple 

current flows through the capacitor and the load, respectively, and its operation mode is different from the current filter circuit.

In order to explore the ripple voltage operation mode, the equivalent circuit is first simulated. In the simulation, according to 

the value of Crc, there are four operating modes of ripple voltage. There are four modes of operation for the relationship 

between the voltage ripple value and rc/R. The larger the C, the smaller the ripple rate. In order to further reduce the 

low-voltage and high-current output voltage ripple, that is, to reduce the ESR value of the filter capacitor, certain methods 

and strategies must be adopted.

              2 Shock voltage caused by load mutation. For the load of digital circuits, in order to respond quickly to various 

modes of conversion, it is very important that the output voltage corresponds to the transient response characteristics of 

the load change. At this time, if the rate of change of the current is large and the impact generation time is shorter than the 

switching period Ts, it is difficult to expect an output voltage stabilization effect by feedback. At present, there is no way for 

technology, and it is in the stage of simulation research.

(4) Exploring the possibility of omitting the filter capacitor

              If the output voltage fluctuates due to sudden load changes and the fluctuation duration exceeds the switching period, 

the feedback can be adjusted to some extent. The LC filter circuit plays a decisive role in this voltage adjustment effect. In 

order to achieve the purpose of voltage regulation, it is necessary to increase the switching frequency, reduce the L and C 

values, and extend the cutoff frequency as far as possible to the high end. Some people consider using two asymmetric 

inverters (with transformers) to output two-phase square waves. The output voltage of each inverter is connected to a common 

load through half-wave rectification, and the cutoff frequency is extended to the high end.

              The switching frequency is determined by the switching time of the MOSFET. In order to improve the switching 

efficiency and exceed its limit value, a multi-phase switching method can be used in practice to increase the switching 

frequency equivalently. However, there are limits to the number of phases. In addition, the reason for the change is only 

on the load side, and it is very effective to keep the cutoff frequency as low as possible. To achieve this, the use of electrical 

double-layer capacitor filters may be the future direction. Of course, it is necessary to consider how to simultaneously 

reduce the equivalent series resistance and equivalent series inductance of the double layer capacitor.

(5) Portable equipment and fuel cells

               For portable appliances such as laptops, cell phones, and digital cameras, power is the most problematic part. 

The power of portable devices has always been the world of traditional batteries, and the traditional batteries can not fully 

meet the requirements of users in terms of light weight and long-term use. For this reason, fuel cells composed of solid 

polymer materials have recently attracted attention. The fuel cell uses methanol as a fuel and platinum as a catalyst. 

The structure is an electrolyte membrane sandwiched between electrodes, and the energy density can be 10 times that of 

a lithium battery. The operating temperature below 100 °C includes power generation at room temperature, and the 

single-cell voltage is about 1~2V. Hydrogen is the most desirable fuel, but from a practical point of view, it is convenient to 

use a combination of methanol and platinum catalyst. However, it has problems with the followability of the load change, 

so in order to protect the electrode, it needs to be used in combination with the capacitor.

               The fuel cell has the advantage of being easy to maintain and can be used for a long time. When the power is 

insufficient, only the fuel can be replenished, and it is not necessary to charge for a long time.Above, the low-voltage, 

high-current switching power supply is the center, and the future development direction of the switching power supply is 

discussed. According to Moore's Law, IC integration will increase by a factor of two every 18 months, so it is difficult to 

determine how much the voltage will be reduced. If this trend continues unrestricted, it can be expected that the requirements 

for power supply will be higher and higher. To meet these requirements, the first is to develop new semiconductors and 

capacitors. In addition, building a micro-structure model of components from a circuit perspective may also become a key 

point to solve the problem. Therefore, the need to break the boundaries of disciplines for collaborative research at various 

levels will become more and more important in the future.

8. Low voltage, high current DC-DC converter module

                 According to IEEE Spectrum, the large-scale integrated circuits used in data processors in 2005 will have a 

transistor density of 100 million/cm2 and a clock frequency of 1 GHz.In order to meet the needs of the next generation of fast 

microprocessors, portable communication devices, servers, etc., it is necessary to develop VRMs with high current (50~100A), 

low output voltage (less than 1V), and high current rate of change (5A/ns). . Research new topologies, apply high-performance 

components, research new structures and packaging technologies, and make equivalent microprocessors and integrated 

packages with VRM. Figure 2 shows an idea of a microprocessor integrated with a VRM.