Based on embedded system power supply design - Power Circuit - Circuit Diagram

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This article explores the considerations for power supply design for portable embedded systems and the guidelines to be followed in design. These principles are helpful for any powerful portable system power supply design that must be battery powered. Based on the construction blocks described herein, the reader can select the appropriate device and design strategy for a particular design.
It is not trivial to specify specific functional and architectural modules for the power supply circuit. These tasks directly affect the operating time of the battery-powered system. The power system architecture will vary depending on the embedded product and application area. The figure below shows the power scheme in a typical portable embedded system.

Below we define the requirements for each component in the diagram. Assume that the product is powered by a battery pack or an external power source. The function of the power path controller is to switch to the appropriate power source when there are multiple power supplies. In some designs it may be necessary to consider powering methods such as emerging USB and Power over Ethernet (PoE).

The battery protection circuit protects the battery from overvoltage, undervoltage, overheating, overcurrent and other abnormal conditions; the dedicated battery charging circuit should charge the battery once there are other sources of power; the fuel gauge circuit continuously monitors the battery Battery status and battery status information for users and power management software.

The system may require multiple DC-DC power converters. For example, switching power supply (SMPS), LDO regulator, charge pump, etc. These different converters are used for all possible input power supplies and the different voltages required in the product design.

The digital interface or hardware button controller is responsible for turning the system on and off - sometimes called soft start. In some recently introduced power converters, the digital interface can also be used to fine tune the output voltage produced by various converters. This fine tuning is required in power-conscious power supply designs.

Efficient power supply standard

In embedded applications, power efficiency is not limited to the traditional ratio of system output power to system input power. In embedded systems, the high-efficiency power supply solution should meet the following standards: 1. When using battery power, the equipment can work for a long time; 2. Extend battery life (charge and discharge times); 3. Limit the temperature rise of components and the battery itself; 4 Provide integrated software intelligence to maximize efficiency.

In fact, there is no single guideline to maximize the efficiency of your power solution. However, designers will consider the following points when developing a power system: battery life (number of charge and discharge) depends on the battery's charging characteristics; for lithium-ion batteries, manufacturers generally recommend following the optimal charging current (constant current mode). And termination/precharge current values. These specifications must be strictly adhered to when designing the charger circuit.

Battery management

For consumer electronics, battery protection must be considered a basic feature because it is closely related to the user's personal safety. Adequate measures must be taken to detect overvoltage, undervoltage, and temperature of the battery; suitable devices such as temperature-dependent resistors must be used to ensure that the current is automatically limited regardless of any abnormal conditions; a fuel gauge must be used. In addition to normal battery detection, it also ensures battery safety. Most fuel gauges are mounted on the battery and can be used to detect battery temperature, discharge current, and more.

A problem that is often overlooked for power path controllers is that when switching from one power supply to another, no matter how short the time is, there is no way to form a loop between the two. This may require additional reverse connection diodes or switches. Similarly, when one of the power supplies is used, the voltage of the power supply should not pass to the input of the other power supply.