New ideas of power management for portable multimedia equipment

All electrical and electronic equipment requires some form of power management, from simple switches to advanced power management units. The progress of power management is obvious to all. It has become a practical technology that will provide exciting innovations for tomorrow's device performance and functions. Effective power management can not only realize new technologies, but also personalize the final equipment, and legislation and standards have made the power supply issue an important issue in the concept stage of product development.

The portable multimedia player (PMP) market is one of the fastest growing mobile entertainment markets. According to a 2005 IDC report, as of 2009, PMP market sales will reach $ 2.4 billion. By launching some innovative PMP products with rich multimedia functions, OEM manufacturers are ambitiously competing for this market share, and the market situation is exciting.

New progress in power management

Each PMP has power supply problems, so the battery life and replaceable concept are of great significance for its future development. Although power system performance is usually not the primary factor for consumers to choose portable products, the performance of the power supply is sufficient to affect the quality of the entire system. At present, system designers widely use some design techniques to reduce system power consumption, such as: reducing the operating voltage, optimizing the system and CPU clock frequency, avoiding large current pulses during power-up; effectively managing the system battery and managing the system working mode May reduce bus activity, bus capacitance and transition noise.

We believe that PMP is mainly faced with the following aspects when dealing with power management issues: improving device conversion efficiency and reducing power consumption; making device packages smaller; improving the integration of power management chips and systems and reducing overall system power consumption; Environmental protection requirements, with extremely high energy efficiency. Below we will interpret the current new methods of power management for portable electronic products from four levels: advanced semiconductor technology and packaging technology, system consideration of power demand, management of load power consumption, digital management and control.

Power management IC suppliers currently use advanced semiconductor processes to improve conversion efficiency. For example, National Semiconductor uses a low-voltage low-power CMOS process to reduce quiescent current and improve conversion efficiency. In terms of reducing the size of the device, it is mainly to further improve integration and adopt more advanced packaging technologies, such as CSP, LLP and Micro SMD. Nowadays, the development of packaging technology focuses on three aspects: the packaging is getting smaller and smaller, the packaged chip is basically close to the size of the bare chip; the thickness of the package is continuously reduced; and the I / O density is continuously improved.

Another trend in power management technology for portable products is toward power management and system integration. For a long time, processor suppliers and power management chip manufacturers have developed their own technologies, but the improvement of traditional technologies has always had its limitations. The efficiency of battery energy utilization has almost reached the limit, and the future improvement is not large. To seek new breakthroughs in efficiency, we must change the traditional way of thinking, adopt new methods, comprehensively consider the power requirements of the entire system, and use intelligent power management chips to manage system performance and power consumption.

People usually think that the so-called power management is to use the most efficient and cost-effective method to feed the power supply to the relevant load. In fact, the development of power management technology in the future will gradually shift to managing load power consumption. That is, the characteristics of the load are divided, and the electronic system is regarded as a signal path. The circuits (whether discrete or built-in) are responsible for different tasks, such as signal amplification, conversion, and processing. In this process, different circuits have different power requirements. For example, although some circuits perform different tasks, the power consumed by them is the same; while in other circuits, the power consumption of different operations is different. These different requirements provide semiconductor products with an excellent opportunity to fully utilize their strengths, and power management chips have therefore become one of the most important components of electronic products. Therefore, the use of "dynamic power supply" technology, that is, to adjust the power supply according to changes in system load, can minimize power consumption in different states. The realization of "dynamic power supply" requires the cooperation of the processor and the power management device.

Digital management and control is a new idea of ​​power management. Because there are several complex loads in the distributed power supply structure, and it is increasing in high-end consumer products, the demand for advanced power management technology is increasingly strong. Complex loads such as DSPs, FPGAs, and microcontrollers often have more than one power channel. Driven by Moore's Law, the central core or DSP has been chasing down the voltage. I / O circuits or communication interfaces require standard higher voltage channels to operate. When the core voltage drops below 1V, the leakage current of the device will increase. In order to reduce the leakage current, advanced graphics and DSP generally use an underlying bias circuit that adds a negative voltage bias. Once the system has more than 6 power channels, you must pay attention to the timing and control issues that these channels require for reliable operation.

Digital power control, also known as the "processor inside the loop" is a completely different issue. It must compare two digital strings to generate a pulse width to drive the power switch, instead of using the traditional analog PWM comparator method. This applicable technology can be used in applications with constant load time to make the power supply run below 100kHz, such as power factor correction, non-interruptible power supply, multiple chemical battery charging and motor control; it can also be used to adopt several configurable PWM cores and control , Diagnostic and interface circuits for mobile phones and PDA PMU and other applications. The sub-circuits or peripherals in the running time control circuit can provide the most suitable operating voltage for its current state to save energy, and digital power control can make the regulator more sensitive and flexible.

Digitally controlled power management case

At present, the more common functions of PMP include: MPEG4 playback, TV program recording, MP3 / WMA audio playback, recording, picture display, game and storage functions (HDD / CF / SD), etc. The power supply is the root cause of the stability of the entire system, and power consumption is a sensitive issue of PMP, so this must be considered when choosing a chip. Over the past few years, power management device suppliers have been developing monolithic solutions that can meet multiple needs. This not only reduces the number of ICs, but also eliminates the need for discrete devices that support these ICs, reducing product cost and product volume.

National Semiconductor introduced the industry's first PowerWise Power Management Unit (EMU) LP5550 chip controlled by digital technology, which not only supports adaptive voltage regulation, helps to extend battery life, but also supports more new functions. As long as this highly integrated power management chip is used for battery-powered portable products, the power consumption of digital processors can be reduced. The chip can be used in conjunction with National Semiconductor's advanced power controller and ARM's Intelligent Power Management (IEM) technology to reduce the power consumption of the digital processor core by 70%. Its advanced power controller can also support the open PowerWise Interface (PWI) standard developed by the two companies for the industry.

In addition to considering power consumption in hardware design, it is also required in software design. After the hardware is designed, the power consumption is generally fixed, but the programmability of the chip can reduce the system power consumption as much as possible. While providing the best results, the software can be used to obtain the longest standby and playback time. . One method is to put the chip into a low-power mode during standby.