Analysis and Applications of Modular Power Supply Market

Current Mainstream Modular Power Supply Technologies and Developments

Modular power supplies are widely used in switching devices, access devices, mobile communications, microwave communications, optical transmission, and defense military research. In communication fields such as routers and automotive electronics, aerospace, etc. The use of modular power supply systems has characteristics such as short design cycles, high reliability, and easy system upgrades, leading to an increasing application of modular power supplies. Especially in recent years, due to the rapid development of data services and the continuous promotion of distributed power supply systems, the growth rate of modular power supplies has exceeded that of traditional power supplies. With the extensive use of semiconductor processes, packaging technology, and high-frequency soft switching, the power density of modular power supplies is increasing, conversion efficiency is improving, and applications are becoming simpler.

Trends in Modular Power Supply Development

Several trends in modular power supply development are noteworthy:

1)High power density, low voltage output(below3.3V).The demand for rapid dynamic response drives the development of modular power supplies.

2)Non-isolatedDC-DCconverters(includingVRM)are growing faster than isolated ones.

3)Distributed power supplies are developing faster than centralized power supplies, but centralized power supply systems will still exist.

4)The proportion of standardizedDC-DCconverters will increase.

5)The design of modular power supplies is becoming increasingly standardized, with control circuits tending towards digital control methods.

Key Technologies of Modular Power Supplies

Currently, the main suppliers of modular power supplies in the domestic market include VICOR, ASTEC, LAMBDA, ERICSSON, COSEL, and POWER-ONE. To achieve high power density, early techniques employed quasi-resonant and multi-resonant technologies, but these techniques put high stress on components and used frequency modulation control, which was not conducive to optimizing magnetic components. Later, this technology evolved into high-frequency soft switching and synchronous rectification. By employing zero-voltage and zero-current switching, switching losses were significantly reduced, and with the development of components, the switching frequency of modules increased significantly, generally reaching over 500kHz for PWM. This greatly reduced the size of magnetic components and improved power density.

Trends in Circuit Topology Development

The main trends in the development of DC-DC converter circuit topology are as follows:

High frequency: To reduce the size of switching converters, improve their power density, and enhance dynamic response, the switching frequency of small powerDC-DCconverters will increase from the current200-500kHzto above1MHz, but high frequency will also introduce new issues, such as increased switching losses and losses in passive components, as well as challenges related to high-frequency parasitic parameters and high-frequency EMI.

Soft switching: Various soft switching technologies are employed to improve efficiency, including passive lossless(snubber networks)soft switching technologies and active soft switching technologies, such as:ZVS/ZCSresonant, quasi-resonant, and constant frequency zero switching technologies, to reduce switching losses and switching stress, achieving high efficiency in high-frequency operations. For instance, the AmericanVICORcompany developed aDC-DChigh-frequency soft switch converter,48/600Woutput, with an efficiency of90%,and a power density of120W/in3,while Japan’sLAMBDAcompany uses active clampZVS-PWMflyback combination conversion and synchronous rectification technology to achieve90%efficiency in theDC-DCconversion module.

Low voltage output: For example, the voltage of modern microprocessorVRMis1.1-1.8V,and the output voltage ofDC-DCconverters for portable electronic devices is1.2V,characterized by large load variations, and most operate below standby mode for long periods. This requiresDC-DCconverters to have the following features:a)High efficiency across the entire range of load variations.b)Low output voltage(the losses of CMOScircuits are proportional to the square of the voltage, so lower supply voltage results in lower circuit losses).c)High power density. This type of module adopts integrated chip packaging.

Development Directions of Modular Power Supply Technology

Reducing thermal resistance and improving heat dissipation—To enhance heat dissipation and increase power density, most medium and high power modular power supplies adopt multi-layer printed circuit board stacking packaging technology, placing the control circuit on the top layer and the power circuit on a substrate with excellent thermal conductivity at the bottom. Early medium and high power modular power supplies used ceramic substrates to improve heat dissipation, but this technology has evolved into Direct Copper Bonding (DCB) technology to meet high power needs. However, ceramic substrates are fragile, making it difficult to install heat sinks, and power ratings cannot be made very large. Later, this technology evolved into using Insulated Metal Substrate (IMS) with direct etched circuits. The most common substrate is aluminum substrate, which directly coats an insulating polymer on the aluminum heat sink, and then coats copper on the polymer, which is etched, allowing power devices to be directly soldered to the copper. To avoid thermal mismatch caused by directly mounting components on IMS, aluminum plates can also be used as substrates, with control circuits and power devices soldered separately onto multi-layer (greater than four layers for transformer winding) FR-4 printed boards, and then the side with power devices is fixed to a formed aluminum plate using thermal adhesive. Many modular power supplies have been compressed and sealed to enhance thermal conductivity, moisture resistance, and shock resistance. The most common sealing materials are silicone resin, but polyurethane rubber or epoxy resin materials are also used. The latter two methods have good insulation properties, high mechanical strength, and good thermal conductivity, becoming one of the key technologies for improving module power density in recent years.

Secondary integration and packaging technology—To increase power density, modular power supplies developed in recent years have all adopted surface mount technology. Due to the significant heat generated by modular power supplies, it is crucial to ensure thermal matching between surface-mounted devices and substrates. To simplify these issues, MLP (Multilayer Polymer) capacitors have recently emerged, as their thermal expansion coefficients are very close to those of copper, epoxy resin fillers, and FR4 PCB boards, reducing the likelihood of capacitor failure due to rapid temperature changes, as seen with tantalum and ceramic capacitors. Additionally, secondary integration technology is developing rapidly to further reduce size, which involves directly purchasing bare chips, assembling functional modules, and then packaging and soldering them onto printed boards, followed by wire bonding. This approach achieves higher power density and smaller parasitic parameters, and since it uses substrates of the same material, thermal matching among different devices is improved, enhancing the module’s resistance to thermal and cold shocks. Professor Li Zeyuan’s team at CPES is researching IPEM (Integrated Power Electronics Module), which is a three-dimensional packaging structure mainly aimed at power circuits, replacing wire bonding technology.

Flat transformers and magnetic integration technology—Magnetic components are often the largest and highest volume devices in power supplies, and reducing the size of magnetic components improves power density. In medium and high power modular power supplies, to meet standard height requirements, most specialized manufacturers customize magnetic cores. Currently, only Philips can provide universal flat magnetic cores, and the winding of these transformers poses certain difficulties. Using this type of magnetic core can further reduce size, shorten lead lengths, and decrease parasitic parameters.CPEShas been researching magnetic integration technology, and Professor Chen Wei from Fuzhou University studied magnetic integration technology atCPESthree years ago. They developed a prototype of a half-bridge circuit, using doubling rectification technology for output rectification, and integrating the two inductors at the output with the main transformer in one core, achieving a power density of300W/in3. Doubling rectification technology is suitable for scenarios with large output currents and high requirements for di/dt, such as in circuits implementing VRM.

Overview of Common Modular Power Supply Brands in Domestic and International Markets

VICOR

The core of the modular circuit technology of the AmericanVICORcompany is zero current switching. The process extensively uses secondary integration and customized devices, enablingVICORconverters to operate at frequencies exceeding1MHz,with efficiencies exceeding90%,and power densities that are 10 times higher than ordinary converters, reaching120Wper cubic inch.Once the module is powered on, it delivers a quantized energy block from the input source to an LC resonant circuit composed of inherent leakage inductance and capacitive elements of the transformer primary coil. At the same time, a current approximating half a sine wave flows through the power MOSFET switch, turning on when the current is zero, and turning off when the current returns to zero after half a sine wave.VICORmodules use this zero current switching principle to reduce switching losses and lower conduction and radiation noise levels. To ensure system stability under different loads,VICORmodules employ frequency modulation technology to track changes in load current, ensuring that the module operates optimally under all conditions.

NEMIC-LAMBDA, POWER-ONE and ASTEC, TYCO

Japan’sLAMBDA company COSEL power modules, America’sPOWER-ONE power modules, andASTEC(Yada) belong to the PWM part resonant zero voltage switch. Under the conditions of pulse width modulation constant frequency converters, the power MOSFET generates resonance at the moment of turning on and off, achieving zero voltage switching, thus significantly reducing switching losses and radiation interference, increasing operating frequencies to200-500kHz,and improving efficiency to80%-90%. Because the frequency is generally constant and not too high, the requirements for components are not very strict, and the circuit is not very complex, thus the cost is not very high. Compared to fully resonant converters, this type of converter has a lower price and achieves a better performance-to-price ratio in computing and communications fields.

ERICSSON

Sweden’sERICSSON power modules are mainly low-voltage input modules, with power ranging from5-200W.The characteristics of these modules mainly adopt push-pull and half-bridge pulse width modulation MOSFET circuits, with operating frequencies reaching300kHz.They employ patented circuits for driving and control. The process utilizes DCB and wire bonding technology, significantly reducing parasitic parameters, lowering ripple, and improving heat dissipation.

Domestic Modules

With the advancement of domestic production, particularly the demands of the defense industry for localization, domestic power supply manufacturers have also developed rapidly. Major suppliers include Chaoyang Power Supply, Chengli Power Supply, Xinleineng, China Electric Huaxing, Disai, 24th Institute, Beijing Mingdianlong, etc. Among them, Xinleineng and Disai source from the same place, so their products are generally similar. Most modules adopt a mix of surface mount and through-hole assembly processes, with early developed modules largely using aluminum electrolytic capacitors and self-made potting glue, which is low-cost but has poor craftsmanship and reliability.

Domestic power supplies began developing modular power supplies in the 1990s, and currently, they have completed and are developing a total of five major series and 31 varieties of modules, with power ratings ranging from1.5Wto 2000W.The classification of modular power supply series is as follows:

G: General series modular power supplies, used in situations with high cost requirements, ensuring reliability while having general performance requirements.

H: High-efficiency high power density series, mainly used in situations with strict requirements for size and efficiency.

D: Mainly used in situations with high size requirements.

N: Non-isolated series, mainly used for low voltage output and fast dynamic response situations.

R: Ring current series, used to power telephone ringing.

The development of domestic manufacturers’ modular power supplies is based on careful analysis of the failure modes of similar modular power supplies, absorbing the research and development experience of alternative modules. In terms of circuit topology,DC/DCmodular power supplies employ patented active clampZVSconversion technology, achieving zero voltage switching at the moment of turning on and off the main power tube, reducing switching losses and radiation interference. Low voltage modules use synchronous rectification to improve conversion efficiency. In terms of craftsmanship, medium and high power modules adopt aluminum substrate technology, forming a complete set of patented process solutions that greatly reduce coupling between circuits and thermal damage to components caused by different expansion coefficients.DC/ACring current modules achieve zero voltage conversion at low frequency switching moments, greatly improving the efficiency and reliability of the modules.

Most domestic manufacturers’ modular power supplies mainly have the following characteristics:a.FullSMTprocess, high reliability. During the product development phase, strict adherence to reliability design guidelines is followed, with a total of4reliability tests conducted during the testing and pilot production phases. After completing trial production,MTBFtests are conducted. All modules’ basic reliability indicators have been experimentally verified to be200,000 hours.The design reliability index exceeds2,000,000 hours.

b.Normal operation across the entire load range without the need for dummy loads.

c.Strong capacitive load capability, all modules pass tests with10000μFcapacitors under various experimental conditions.

Semi-conductor integration. The advancement of modular power supply packaging and circuit topology has brought modular power supplies into a whole new field, gradually moving towards device-level development. With the promotion of modular power supply integration and consistent design, the applications of modules are becoming increasingly standardized, and the application circuits are becoming simpler, making selection relatively easy. Various modular power supply manufacturers have begun integrating devices and circuits to minimize costs and enhance competitiveness. We hope everyone trusts and supports domestic modular power supplies!

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