Discussion on Power Management Trends

　　In this article, the industry's leading power management chip suppliers explain their respective technical viewpoints and corresponding solutions from different levels.

As semiconductor terminal products develop towards the three major trends　　of being thin, light, short, digital and integrated with multiple functions , the status of power management ICs in the analog field can be said to be becoming more and more important, and the achievements are also very impressive. Under the prosperous market, the design trend of power management is also worthy of attention. In this regard, the industry's leading power management chip suppliers have elaborated on their respective technical viewpoints and corresponding solutions from different levels.

　　White LED driver becomes the design focus

　　The light source that provides backlight for LCD displays in portable products consumes the most power in the system, consuming more than ten times the power obtained by the display. The greater the backlight power, the stronger the light that the LCD of the portable device can emit. Due to increasingly stringent power restrictions, high brightness output cannot be pursued blindly, so white light LEDs with lower power consumption are still the most popular choice.

　　Currently, many manufacturers are developing white LED driver circuits with more compact structures and higher backlight efficiency. Peter Henry, vice president of the portable system power management products division of National Semiconductor, pointed out that as mobile phones continue to develop in the direction of multi-functional intelligence, the demand for LED drivers is expected to continue to increase. For example, ordinary mobile phones currently only use 2 to 4 LED drivers. However, dual-screen cameras with richer functions are more suitable for mobile phones.

A camera phone needs 7 to 9 LED drivers to meet the lighting requirements.

　　The LP3936 light management unit recently launched by NS has three groups of independently controllable drivers. One group is the main driver, responsible for driving 4 LEDs, mainly providing backlight for displays with a size of no more than 2.5 inches; another group is the auxiliary driver, responsible for driving 2 LEDs, mainly providing backlight for the secondary display or keypad; and another group is responsible for providing decorative lights or flashlights.

　　In addition, the application of the new generation of OLED displays in portable devices has also begun to heat up, and power IC suppliers are working hard to expand white light LED drivers in this area. Li Zijun, manager of the power management product technology marketing department of Sipex, said that 2.2-inch full-color PMOLED has been mass-produced and is gradually emerging in the mobile phone market where the demand for color screens has increased significantly. Because the entry threshold of PMOLED is lower than that of AMOLED, it has risen faster in today's market. Sipex has launched several driver chips in the SP6690/91 series for customers to choose from.

　　Generally speaking, the driving voltage required for PMOLED varies according to the screen size. For example, a 1-inch full-color PMOLED requires a voltage of about +11V. In mobile phone applications, since the standard voltage of lithium batteries is between +2.7V and +4.2V, a boost IC is needed to convert the voltage to drive this type of OLED.

　　As for AMOLED, the technical threshold is relatively high, so it is quite difficult to design a driver IC that meets the characteristics and can make the panel image uniform. In addition, facing competition from mainstream TFT LCD panels with stable yields and continuously declining prices, the future market prospects are still unclear.

　　LCD TV brings new demands

　　As the cost of LCD panels continues to drop and their performance continues to improve, another emerging application of LCD, LCD TV, has also entered the home, and market demand is steadily increasing. LCD TV manufacturers are increasingly relying on innovations in the field of power management as a key factor in differentiating themselves in the market.

　　Steve Mappus, an application engineer for TI's system power management business, said that LCDTVs are highly dependent on power management and require circuits such as AC power factor correction, isolated power conversion, non-isolated point-of-load power conversion, and various levels of power monitoring, sequencing, and monitoring protection. For current LCD TV designs, traditional analog power control ICs and microcontrollers with one or more monitoring functions are required.

　　TI has a well-established power supply portfolio in this area, with 300W to 400W power systems (most 40" LCD TVs fall into this category) using a switching power factor correction controller such as the UCC28050/1 to boost the AC line voltage to a very high voltage DC output after regulation. If an active clamp PWM controller such as the UCC2894 is then added, the overall efficiency of the LCD TV power system can be optimized, as a series of well-defined functions enable zero current switching for the power factor correction stage and zero voltage switching for the isolated DC/DC stage. For low voltage, non-isolated point-of-load conversion, TI offers a variety of DC/DC converters with integrated MOSFETs, such as TI's SWIFT DC/DC series or the TPS6xxx series of low voltage converters.

　　Specifically targeting the development of digitally controlled power supply systems, TI recently launched the UCD7K, UCD8K and UCD9K series of Fusion Digital Power products, which are equivalent to the sum of several high-speed analog control ICs. The microcontroller and LCD backlight display drive signals are unified into the same DSP-based controller. As LCD TV's requirements for power management become increasingly complex, digital power solutions will be more attractive in the future. However, Steve Mappus also pointed out that the speed of the popularization of digital power in LCD TVs will depend on the close cooperation between LCD TV manufacturers and power management semiconductor manufacturers. As for digital power itself, since a single scale cannot fit all types of equipment, the promotion of digital power will depend on whether all parties can fully understand each other's specific needs. Towards high integration

　　The development trend of power management technology is to integrate more functional features on smaller silicon chips, while achieving stronger system power performance with higher design flexibility without increasing costs. Li Qian, general manager of NS China, emphasized: This is especially true for portable applications with very limited board space. The combination of multiple single-function power management devices will gradually become unfeasible, and may be replaced by chips similar to PMU (power management unit).

　　For example, NS's multi-function power management unit LP3970 has 11 built-in low-voltage noise-reducing linear regulators, 8 of which are responsible for driving digital loads, and the other 3 are responsible for driving analog loads. LP3970 also has 2 inductive DC/DC step-down regulators, 1 backup battery charger and 4 general outputs to provide regulated power for application processors. Through the I 2 C interface, the application processor can digitally control the LP3970 and dynamically adjust the power supply voltage according to the load conditions to save power consumption.

　　Maxim introduced the MAX8621Y/MAX8621Z power management IC, which integrates two step-down DC/DC converters, four LDOs, a reset timer and a driver, occupying only 16mm2. If seven discrete SOT23 package components are used to achieve the same function, 75mm2 of circuit board area is required.

　　Reducing energy consumption is imperative

　　In order to meet the needs of energy saving and environmental protection, many governments and

Various new energy consumption standards have been issued by energy agencies. At the same time, more stringent regulations are also being formulated. Reducing energy consumption has become an important issue that cannot be avoided, and higher requirements have been placed on power management.

　　It is encouraging that there are already many new products that can play a role in reducing energy consumption. Taehoon Kim, vice president of the high power products division of Fairchild Semiconductor, said that household appliances usually account for about 20% of total energy consumption, and motors are the main source of energy consumption. In the low-power home appliance market, high-voltage brushless DC motors (BLDC) are replacing single-phase AC induction motors, which not only improves efficiency from less than 50% to 90%, but also reduces noise and vibration audible to the human ear.

　　Usually, white appliance motors with power less than 100W require the use of discrete MOSFET transistors and half-bridge integrated circuits, as well as noise filtering components, which occupy a large area and have no advantages in reliability and cost. Fairchild Semiconductor has developed a more effective smart power module (SPM), among which the newly launched smart motion power module (Motion SPM) (FSB50325\FSB50250H and FSB50450) is a multi-chip module that includes six fast recovery MOSFET transistors (FRFET) and three half-bridge high-voltage integrated circuits (HVIC). For BLDC motors in white appliances, this module can save 60% of energy costs.

　　For switching power supplies, it is very important to reduce standby energy consumption. ON Semiconductor has made a lot of efforts in this regard in recent years. Yu Hui, the company's senior engineer for market applications, said that most of ON Semiconductor's PWM control chips have a standby function. The chip itself can automatically realize the standby function under no-load or light-load conditions by detecting the working status of the circuit. In order to further reduce the standby energy consumption, from the perspective of system design, ON Semiconductor has also launched the PWM control chip NCP1230/1 with extremely low standby energy consumption. This series of products can turn off the power factor correction (PFC) when light load/no load, eliminating a power link and reducing the standby energy consumption of the entire system. This product is suitable for adapter power supplies such as laptops and monitors.

　　Particularly worth mentioning is the high-efficiency, ultra-low standby power solution NCP1603 with PFC level for adapters launched in the first quarter of this year. The chip has built-in discontinuous current type PFC control chip NCP1601 and current type PWM control chip NCP1230, integrating PFC and PWM chips into one, fully combining the advantages of the two chips, avoiding the common frequency synchronization problem of two-stage design and shutting down the PFC stage under light load/no load conditions, achieving ultra-low standby energy consumption.