Module power supply environment: module power supply application

Module Power supply

Modular power supply is a power supply module that can be directly installed on a printed circuit board. It can be used for power supply applications of digital or analog loads. Power supply modularization is the development trend of switching power supply . It can improve the working reliability, availability, and ease of use of the power supply system, shorten the repair and maintenance time of the power supply, and has been widely used. The technologies related to modular power supply include integrated circuit manufacturing and packaging , high-frequency power conversion, digital control, full-resonance high-frequency soft switching , synchronous rectification, intelligent control, electromagnetic compatibility, power factor correction, power protection control, parallel current control, pulse width modulation and other technologies.

With the improvement of semiconductor process and packaging technology, and the extensive application of high-frequency soft switching technology, the power density of module power supplies is getting higher and higher, the power conversion efficiency of module power supplies is getting higher and higher, and the size is getting smaller and smaller, and chip- level module power supplies have appeared .

Distribution of the World Power Supply Market

1 By brand

According to the data given by the APEC (Applied Power Electronics Conference) held in the United States in 2007 , the global power supply market is divided by brand as shown in Figure 1 (Source: Data given by IMS Research Institute at the 2007 APEC Conference (Global power supply market divided by brand market share in 2005 %)).

Figure 1: Division of the global power supply market by brand

① Six Taiwanese companies, two Japanese companies (including TDK-Lambda), two American companies, and one European company ranked at the top;

② The annual revenue of the 15th largest power supply company is about 200M$;

③ Currently, there is no power supply company in mainland China with annual revenue greater than 50M$.

2. Market distribution of power semiconductor devices

The global power semiconductor device market distribution (Source: 2007-APEC-IMS) (Global market distribution in 2005 (discrete components + modules) %) is shown in Figure 2.

Figure 2 Global power semiconductor device market distribution

① Figure 2 shows that four American manufacturers are at the top of the list;

②There are no Taiwanese or Chinese mainland companies among the top 20 companies;

③ From a global perspective, the scale of Taiwanese companies (such as Lite-On, Panjit, Taiwan Semi, DC Components) is still relatively small;

④Currently, the scale of enterprises in mainland China is still relatively small.

Challenges in modular switching power supply design

1. Improve the working efficiency of switching power supply

① Reduce the switching loss of the power switch tube ;

② Minimize the power loss of magnetic components (for example, core loss, proximity effect loss, coil loss, and eddy current loss of the switching transformer).

2. Improve the working reliability of modular switching power supply system

3 Reduce the cost of modular switching power supply system

4. Higher power density

To improve the power density of modular switching power supply products, we can start from the following three aspects. First, adopt advanced circuit topology and power conversion technology to improve the working efficiency of modular switching power supply products and reduce the loss of modular switching power supply products; second, reduce the volume of each component of modular switching power supply products and adopt compact process structure; third, improve the thermal design of modular switching power supply products so that modular switching power supply products can dissipate heat well under high power density conditions.

5 Faster control loop response, etc.

Advantages and main technical indicators of modular switching power supply

(1) The module switching power supply has the following advantages

①Flexible, simple and convenient to use;

②Shortened the development cycle of power supply;

③ Since the modular switching power supply adopts fully automated production and high-tech production technology, the quality of the modular switching power supply is stable and the operation is reliable;

④ The modular switching power supply has a wide range of applications and can be widely used in telecommunications, automatic control, instrumentation, power generation and distribution, household appliances, metallurgy and mining, locomotives, ships, military weapons, aerospace and scientific experiments, etc., especially in the fields of high reliability and high technology, the modular switching power supply plays an important role.

(2) Common technical indicators of modular switching power supplies

Common technical indicators of modular switching power supplies include maximum output power, output voltage accuracy, source voltage effect, load effect, temperature coefficient, output ripple and noise, input reflected ripple current , input common mode noise current, output voltage adjustment range, protection characteristics and working efficiency.

Challenges in today's module switching power supply designs

1 Power density and heat dissipation of module switching power supply

2 Low voltage , high current output

3 More complex power management requirements

① Power supply sequencing/tracking;

②Output voltage range;

③Power supply monitoring;

④Fault monitoring, response and protection of power supply system.

The main factors leading to low efficiency of module switching power supply

(1) Loss of module switching power supply

The losses of high-power module switching power supply mainly include high-frequency switching loss, high-frequency transformer loss, rectification loss and line conduction loss. In the application of low voltage and high current output, rectification loss and line conduction loss account for a large proportion. The lower the output voltage and the greater the output current, the greater the proportion of rectification loss and line conduction loss in the total loss of the module switching power supply.

(2) Rectification diode losses and synchronous rectification

Diode rectification is used in traditional rectification, while Schottky diode rectification is generally used under low voltage output conditions. Compared with other rectifier diodes, Schottky diodes have the advantages of fast switching speed and reduced forward voltage. However, the forward voltage drop of the Schottky diode is related to the size of the rectifier output current. The larger the rectifier output current, the larger the forward voltage drop, which may be as high as 0.5-0.6V or more, and the reverse leakage current of the Schottky diode is large.

The synchronous rectification technology uses a field effect transistor ( MOSFET ) with low on-resistance and low withstand voltage to replace the ordinary rectifier diode. Since the synchronous rectification MOSFET has the characteristics of low on- resistance (usually only a few mΩ), small leakage current when blocked, and high switching frequency, it can greatly reduce the power consumption of the power rectification part and significantly improve the working efficiency of the power supply system. However, in specific applications, the implementation of synchronous rectification is more complicated than diode rectification. In the low-voltage and high-current output applications of switching power supplies, synchronous rectification technology has a good application prospect.

(3) Loss of magnetic components

Transformer loss is also an important part of the module switching power supply loss. Transformer loss mainly includes iron loss and copper loss. Iron loss refers to the high-frequency loss caused by the material, shape, process structure and other related factors of the transformer, and copper loss refers to the conduction loss caused by the transformer winding line. In order to reduce the iron loss of the transformer, a core material with good high-frequency characteristics, small high-frequency loss, reasonable core structure shape and compact structure should be selected.

At the same time, in order to reduce the size of the module switching power supply, the switching operating frequency of the module switching power supply should be increased as much as possible. For example, if it is to be increased to about 500kHz or higher, the loss of ordinary magnetic core materials is very large, and the magnetic core is easy to overheat and magnetically saturate, so that it cannot work normally. Therefore, high-frequency magnetic core materials with excellent magnetic properties must be selected in the module switching power supply.

The size of magnetic components is closely related to the switching operating frequency. Within the allowable operating frequency range of magnetic components, the size of magnetic components is inversely proportional to the switching operating frequency. In order to reduce the volume of magnetic components such as high-frequency switching transformers and inductors in module switching power supplies, the switching operating frequency needs to be increased.

At the same time, the design of the high-frequency switching transformer windings in the modular switching power supply is also very important. The windings of the high-frequency switching transformer not only affect the copper loss, but also are related to the coupling between the windings of the high-frequency switching transformer, and also affect the iron loss of the high-frequency switching transformer. The design and production of the high-frequency switching transformer have a great influence on the working performance of the modular switching power supply.

The development trend of modular switching power supply

The following development trends of modular switching power supplies are worth noting.

● The power density is getting higher and higher, with low voltage (for example, output voltage is lower than 3.3V or lower) and high current output. At the same time, the transient load dynamic response characteristics of the module switching power supply should be fast;

● High reliability in use and increasingly higher requirements for work safety;

● Work efficiency is getting higher and higher (such as the requirements of the US Energy Star);

The US Energy Star's requirements for the power supply's efficiency under loaded and no-load working modes and the 80 Plus efficiency requirements developed by Ecos Consulting are shown in Table 1, Table 2, and Table 3, respectively.

It can be seen that the requirements for power supply efficiency are getting higher and higher. To achieve the above technical requirements, it is necessary to improve the circuit topology, components with better performance, packaging , heat dissipation, related control integrated circuit production and circuit processing and manufacturing technology.

● The design of modular switching power supplies is becoming more standardized, and control circuits are increasingly using digital control methods;

● The switching frequency is getting higher and higher, so that the dynamic response of the module switching power supply can be faster, which is also an important way to reduce the size of the module switching power supply. For example, the switching frequency of the small power module switching power supply has been increased from the current 200-500kHz to more than 1MHz. However, the high frequency of the module switching power supply will produce new problems such as increased switching loss and loss of passive components, high-frequency parasitic parameters and high-frequency EMI.

The general PWM switch control mode of the switching power supply is hard switching. The dv/dt and di/dt generated during the PWM hard switching process are relatively large, resulting in large switching losses and impacts, high junction temperature of the power switch tube , and short service life. The use of ZVS (zero voltage switching) or ZCS (zero current switching) switches can make the power switching process smoother, with less loss and impact, thereby reducing the junction temperature of the power switch tube and greatly improving the service life of the switching power supply. In addition, high-frequency switching itself is also a major source of noise in the modular switching power supply. Large dv/dt and di/dt will generate large noise. After using soft switching technology, dv/dt and di/dt are greatly reduced, and the modular switching power supply itself also obtains better electromagnetic compatibility (EMC).

In order to improve the power density of modular switching power supplies, soft switching and synchronous rectification technologies have attracted widespread attention. The industry has successively proposed a variety of soft switching technologies such as resonant converters, quasi-resonant converters, zero-switching PWM converters, and zero-conversion PWM converters. The zero-switching PWM converter uses resonance to achieve phase switching, and still uses the PWM working mode after the phase switching is completed, thereby overcoming the defects of hard-switching PWM in the switching process, and retaining the advantages of low steady-state loss and low steady-state stress of hard-switching PWM converters, greatly reducing the switching loss on the power switch tube. At the same time, due to the development of power devices, the switching operating frequency of modular switching power supplies has been greatly improved. Generally, PWM switching technology can also work above 500kHz, which greatly reduces the volume of magnetic components and improves the power density of modular switching power supplies.

Currently, the world's better module power suppliers include VICOR, ASTEC, LAMBDA, ERICCSON and POWER-ONE.