Interpret the development trend of AC/DC power supply from MPS products
“The operation of all Electronic devices is inseparable from the power supply. There are two main ways of power supply, namely battery power supply and AC power supply. Among them, AC power is the most widely used way, with power ranging from several watts to several kilowatts, with various applications, covering from From household appliances to industry, AC power supply includes two modes of AC direct power supply and AC to DC (AC/DC) power supply.
The operation of all electronic devices is inseparable from the power supply. There are two main ways of power supply, namely battery power supply and AC power supply. Among them, AC power is the most widely used way, with power ranging from several watts to several kilowatts, with various applications, covering from From household appliances to industry, AC power supply includes two modes of AC direct power supply and AC to DC (AC/DC) power supply.
After AC/DC converters evolved from the earliest linear components to MOSFET-based switching power supplies, efficiency, size and price have been significantly improved, but the requirements for controller ICs are also gradually increasing, and various regulations and requirements need to improve the power supply. Standby power and improve integration. It is precisely because of the different needs that few semiconductor companies can cover a broad product portfolio from consumer to industrial to IT infrastructure. MPS has been deeply involved in the ACDC field for many years, and has industry-leading products, covering the product range of 1~1000W on the market, and its customers are all over the world.
MPS AC/DC product layout, you can see that AC/DC applications are everywhere.
Recently, MPS AC/DC product director Huang Wannian introduced the AC/DC industry development trend in detail based on the product features of MPS.
The biggest difference between AC/DC and DC/DC is that the AC high-voltage side will cause harm to the human body. Therefore, the safety standard is also the most important for AC/DC power supply. This includes safety distance limitations and insulation limitations for high-voltage power supplies, thus making it difficult to increase the power density of AC/DC power supplies.
Secondly, the AC end is directly connected to the power grid, so it is necessary to ensure the EMC quality of the product, including anti-surge, anti-static, anti-pulse interference, harmonic distortion and other factors.
The third is to ensure EMI compliance. Since the AC/DC power supply is connected to the load or the downstream DC/DC conversion, it is necessary to ensure that it does not interfere with downstream equipment.
Fourth, it is the requirements of energy efficiency standards. As people’s awareness of environmental protection increases, more and more organizations have proposed new energy efficiency requirements, including the European Union, the U.S. Department of Energy, Energy Star and other organizations have successively proposed different energy efficiency certification indicators. , including average efficiency, light load efficiency, full load efficiency, standby power consumption, etc., and the standard is also improving year by year. As the first stage of power conversion, AC/DC directly affects the overall efficiency.
AC/DC Conversion Architecture
Huang Wannian introduced that compared with DC/DC, AC/DC has the following differences. First of all, in the AC/DC conversion scenario, the voltage of 220V after rectification often reaches more than 400V, and the withstand voltage requirements of the device are relatively high. Secondly, the high-voltage device characteristics of AC/DC make it difficult to greatly increase the switching frequency, usually only below 200kHz. Third, since the AC operating frequency is around 50Hz, it is difficult to reduce the size of discrete components such as capacitors. In addition, the transformer needs to have isolation requirements, and it is difficult to further reduce the size of the insulation isolation. This series of constraints also brings a lot of troubles to the AC/DC conversion design.
AC/DC conversion can be roughly divided into two structures: single-stage conversion and two-stage conversion. Among them, single-stage conversion is mainly used in low-power (<75W) scenarios. Similar to DC/DC, it mainly includes buck conversion and Flyback. Architecture.
For high-power (>75W) applications, the two-stage structure of PFC+LLC is mainly used. Among them, PFC is used to meet the power factor correction, improve the utilization rate of power and reduce the backflow pollution to the power grid, while LLC is to improve the power conversion efficiency and density, reducing switching losses. Huang Wannian said that with the popularity of LED street lighting, some places have stipulated that LED lights larger than 25W require PFC circuits.
Viewing the development of AC/DC power supply from the evolution of mobile phone chargers and IT infrastructure
Taking mobile phone chargers and server power supplies as examples, Huang Wannian combined low-power and high-power markets to summarize the four major trends in the development of AC/DC switching power supplies, namely miniaturization, high efficiency, low standby power consumption and the third Three generations of semiconductors.
Taking the mobile phone charger as an example, in 2005, because the mobile phone was still in the era of functional phones, there were not many functions and the battery capacity was not large, so the charger was still at the level of 3.5W, and the efficiency requirements were not high, and it was even used. Triodes are not MOSFETs, and with the popularity of smartphones, charging efficiency, size, charging power, and standby power consumption have been significantly improved. The latest charging heads have begun to use wide bandgap GaN materials to improve frequency and conversion efficiency.
For the server power supply, as shown in the data, the continuous upgrading of the 80PLUS standard for more than ten years has been enough to prove that the pursuit of efficiency is constantly improving.
Huang Wannian explained the current requirements for the four major developments of AC/DC with specific figures. (as shown in the table)
The evolution of each technology requires to overcome many technical challenges. In terms of miniaturization of the power supply, only by improving the efficiency and reducing the heat dissipation structure can the miniaturization be better achieved. The industry is improving efficiency through newer topologies, lower switching losses, reducing discrete components such as capacitors and inductors through higher switching frequencies, reducing bead size through better EMI characteristics, and reducing Overall space occupied.
Huang Wannian said that power supply design is a compromise engineering problem, and the frequency, efficiency and heat dissipation issues are not completely linear. “In the past, the operating frequency of silicon MOSFETs was at most around 100kHz, and the device itself could not withstand heat, so the problem of high frequency and thermal effects could be solved by choosing wide-bandgap semiconductors.”
Interpreting the MPS Product Portfolio
MPS’ products can cover AC/DC applications from 100mW to 1000W, and the broad solution portfolio includes controllers, voltage regulators, synchronous rectifiers and LDOs. These advanced devices are packaged in a compact package for high efficiency, reliability and longevity, and help engineers simplify the design process and speed time-to-market by reducing cost and BOM.
Huang Wannian said that the product development direction of MPS AC/DC has four major elements, which is consistent with the development direction of power supply demand.
The first is to use a variety of new topologies to improve efficiency. With the evolution of different topologies, MPS is actively developing, for example, using the hybrid topology of PFC + LLC and ACF + ZVS to achieve zero turn-on loss, while recycling the leakage inductance, which can achieve a high efficiency of more than 93%. For the totem pole topology that is currently the focus of IT infrastructure power supplies, MPS also hopes to launch corresponding fully digital integrated products to replace today’s discrete controller solutions.
Introduction to the development direction of MPS topology control
Secondly, it adopts a fully integrated design to simplify the design and reduce the cost.
The third is to develop high-frequency controllers to support wide-bandgap power semiconductors.
The fourth is to achieve better performance and more convenient design through the digital power control chip.
Huang Wannian took two new products of MPS as examples to explain the four development strategies of MPS AC/DC products.
The fully integrated flyback controller MPX2002/3 integrates the primary side controller, secondary side controller, isolation and protection functions into a single chip. The MPX2002 can operate in CCM at heavy loads, then switch to Quasi-Resonant (QR) operation when the load is reduced. If the load is further reduced, the MPX2002 will operate in frequency hopping (PFM) mode. When it enters burst mode, the switching frequency is fixed at 20kHz, which reduces noise. With this feature, the MPX2002 can achieve high efficiency under all load conditions while having excellent electromagnetic interference (EMI) performance. The traditional solution requires four ICs of flyback controller, optocoupler, voltage reference and synchronous rectification controller, while the MPX2002 single IC solution is used, which integrates the primary controller and the synchronous rectification controller. It simplifies design, improves efficiency, reduces board area, reduces standby power consumption, enhances reliability, and does not require optocoupler feedback to prevent optocoupler aging in a high-reliability environment. Especially in the CCM operation mode, higher precision synchronous rectification control can be achieved. The operating frequency of MPX2003 is 130kHz or even 300kHz, which can meet the requirements of miniaturization.
According to the data given by Huang Wannian, the MPX2002/3 is applied to the mobile phone fast charging adapter, and the total amount of the MPX2002/3 and the PD controller is only 30mW, which is far lower than the current industry-wide 75mW.
“Discrete devices need to consider complex settings such as loop design and synchronous rectification adjustment. Under the current fully integrated solution, the best efficiency solution can be obtained by designing a few resistors, which can greatly simplify the engineer’s design.” Huang Wannian concluded.
Compared with discrete solutions, MPX2002/3 solutions have multiple advantages such as high integration, low power consumption, high reliability, and convenient design.
HR1211 is a two-in-one controller integrating multi-mode PFC and current-mode LLC, mainly used in IT infrastructure power supplies of hundreds of watts. The chip integrates a high-voltage current source, a safety-certified X capacitor discharge circuit, and a high-voltage drive circuit for PFC and LLC, thus realizing a very simple peripheral circuit.
The HR1211’s digital control core combined with a re-editable memory unit gives the entire solution great flexibility. The cooperation between the two-stage circuits of PFC and LLC; the switching between different control modes; the switching frequency of key operating points; the threshold value, time and recovery method of the protection function; all these main functions can be freely performed through the UART communication port The configuration can be completed on the graphical operation interface, which makes the power supply design based on HR1211 flexibly adapt to the performance requirements of different applications in different designs.
Huang Wannian said that there are various power supply applications over 75W, such as notebook, desktop, electric vehicle charging, USB-PD charging and other forms. Each product has different needs. Through the fully digital controller, it can quickly respond to multiple power sources. Platform design, and can also achieve IP protection through encryption.
Conclusion – MPS will continue to meet the challenges of the power supply field
Huang Wannian concluded that due to its characteristics, the improvement of integration and efficiency of AC/DC is slower than that of DC/DC, and due to the existence of safety regulations, EMI, heat dissipation and other issues, it has brought great trouble to engineers’ design optimization. Despite the difficulties, the AC/DC market is indispensable in power management. As an MPS that has been deeply involved in the AC/DC field for more than ten years, it is continuously meeting the industry’s challenges for high efficiency through four major development directions, and helping the power supply industry continue to move towards The goal of green energy-saving development.
“The operation of all Electronic devices is inseparable from the power supply. There are two main ways of power supply, namely battery power supply and AC power supply. Among them, AC power is the most widely used way, with power ranging from several watts to several kilowatts, with various applications, covering from From household appliances…