DC-DC converter is the core of modern electronic power supply. It provides conversion from one voltage level to multiple other voltage levels. The DC DC converter can be used not only as a core IC designed by yourself, but also as a module and building block (see "what is a building block?") at the end of this article. The latter two types eliminate a large number of original designs by providing products that can be integrated into larger power supplies.
Over the years, DC DC converters have become the main components to set and maintain operating voltage, improve efficiency and increase power density. A summary update of the old device shows how it can be changed to meet a variety of drivers.
Today‘s power systems use two main types of architectures: distributed architecture and intermediate bus architecture. Fig. 1A shows a distributed arrangement. Traditional AC-DC power supply will generate a main DC bus, which has been allocated to all parts of the equipment. The DC voltage required by IC and other equipment is generated by the load point (POL) DC-DC converter / regulator.
A distributed bus architecture (a) and an intermediate bus architecture (b) are shown.
The layout of the intermediate bus is shown in Figure 1b. The main DC distribution bus of the AC power supply is connected to each main subsystem or the DC-DC converter in the printed circuit board (PCB) that generates the intermediate bus. From there, the pol DC-DC converter takes over and creates a separate supply voltage for the load.
Trends and goals
DC DC converter specifications and functions have several main drivers. These drivers are the trends affecting power design today:
Low power supply voltage: large MPUs, FPGAs and ASICs increasingly use extremely low core power supply voltage. The voltage range is 0.6 to 1.8V. At the same time, the current drawn from these devices has increased sharply from tens of amperes to hundreds of amperes. Some new devices operate at a voltage of 1 V or less and consume more than 500A of current.
Greater efficiency: efforts to reduce energy consumption and reduce heat levels have pushed efficiency to the top of their priorities.
Transition to 48 V: the power bus voltage is usually 12 V, but 5, 24, 28 and 36 V buses have been used. A major trend is standardization at 48 v. This higher voltage has several advantages, including improved efficiency and reduced I 2R loss. A higher voltage will reduce the current at the same power level. The result is a 16 fold reduction in power consumption. Many new products and systems are transitioning to 48 V, such as power tools, industrial equipment (such as robots) and forklifts. Data center is the main user of 48V system. And, of course, the car is gradually transitioning to the 48V system to supplement the existing 12V system.
Increased power density: all designers seem to want to achieve these functions in smaller packages. However, it is difficult to improve the power density. A common method is to use a higher switching frequency to reduce the size of inductors and capacitors. Placing all these components and modules in a small space will cause heat dissipation problems. Ingenious mechanical packaging can greatly reduce this problem.
Improving reliability: all these goals should be achieved, but maintaining or improving the reliability of equipment is another key challenge for designers.
A good example of current power design is the rapid and huge growth of cloud storage and computing business. This has led to the addition of more rack servers to the data centers of major participants (Amazon, IBM, Microsoft, etc.). This growth has added thousands of new servers and, in some cases, a million more.
Due to the high energy consumption, it is also necessary to reduce the cost of electrical services to reduce the heat level of the data center and reduce the cost of air conditioning. Higher efficiency will help control energy costs, while smaller packaging can provide more space for data centers to expand in the future.
Other trends and goals are:
Increase the use of broadband gap devices such as Gan transistors to improve efficiency.
Improved packaging through more 3D design.
Power factor correction (PFC) is increasingly used.
Reduce no-load power consumption.
Increasing use of power management.
energy management
Power management refers to the use of digital control of DC-DC converter to optimize power transmission and provide protection in products or systems. Power management IC or subsystem regulates, controls and distributes product power. Some power management chips include two or more DC DC converters and perhaps some LDOS. The converter may also include a driver for using an external MOSFET power device at a higher voltage and / or higher current.
Another function is the power monitoring and control circuit. These circuits measure and digitize input and output voltages, currents, and internal and external temperatures. Other controls may involve the ability to set the output voltage from an external power source. Overvoltage and overcurrent detection provides signals to shut down the equipment to prevent damage.
Most power management ICs include a pmbus communication port to provide external programming and monitoring and control functions. Pmbus is a variant of the popular I2C serial interface.
Some of the most widely used power management chips are those in mobile phones that monitor status and provide feedback. Such chips also include battery chargers and other battery related circuits.
Special purpose DC-DC converter
DC-DC converters can realize various applications. Almost every electronic product produced today has one or more of them. However, they appear in some very unusual products, devices and systems.
One of these special cases is the system used to grow corals. The researchers created a system in which a precise 1.2 to 4 V DC voltage was applied between the two electrodes while immersing the two electrodes in seawater, resulting in the growth of calcium carbonate (limestone). This limestone supports coral growth and speeds up the process.
Large systems can be deployed in offshore areas where corals are completely or partially depleted. This large-scale system for offshore deployment requires heavy-duty, high output DC-DC converters. Driven by the action of sun, wind or wave, DC-DC converter will feed high current into seawater to produce limestone.
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