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

MOS power IC full range

KKST patch plug-in active passive crystal oscillator hot sale 24.576000MHZ

This article delves into the critical considerations for designing power supplies in portable embedded systems and outlines the guidelines that should be followed in the process. These principles are invaluable for anyone working on the power supply design of a powerful, portable system that relies on battery power. By examining the building blocks discussed here, readers can choose the right components and strategies tailored to their specific design needs.

Specifying functional and architectural modules for the power supply circuit is far from trivial. These decisions directly impact the operational duration of a battery-powered system. The architecture of the power system varies based on the embedded product and its intended application area. The figure below illustrates a typical power scheme for a portable embedded system.

In the diagram, each component plays a crucial role. Let’s define these roles. Assume the product is powered either by a battery pack or an external power source. The power path controller ensures seamless switching between available power sources, which may include emerging methods like USB or Power over Ethernet (PoE).

The battery protection circuit safeguards the battery against overvoltage, undervoltage, overheating, overcurrent, and other anomalies. A dedicated battery charging circuit should activate whenever an alternative power source becomes available. Additionally, the fuel gauge circuit continuously monitors the battery's state and provides users and power management software with real-time battery status updates.

A portable embedded system may require multiple DC-DC power converters, including switching power supplies (SMPS), low-dropout (LDO) regulators, and charge pumps. These converters cater to diverse input power sources and varying voltage requirements within the product design.

The digital interface or hardware button controller manages the system's on/off functionality—sometimes referred to as soft start. Some modern power converters allow for precise adjustments to output voltages via the digital interface, a necessity in energy-efficient power supply designs.

Efficient Power Supply Standards

In embedded applications, power efficiency goes beyond the conventional ratio of system output power to input power. An efficient power supply solution for embedded systems should meet the following criteria: 1) Enable long operation time when using battery power; 2) Extend battery lifespan (charge-discharge cycles); 3) Minimize component and battery temperature rise; 4) Offer integrated software intelligence to optimize efficiency.

While there’s no universal guideline to maximize power solution efficiency, designers typically consider several factors during development. Battery life depends on its charging characteristics. For lithium-ion batteries, manufacturers usually recommend following the optimal charging current (constant current mode) and termination/precharge current values. Adhering to these specifications is essential in charger circuit design.

Battery Management

For consumer electronics, battery protection is a fundamental feature due to its direct link to user safety. Overvoltage, undervoltage, and temperature monitoring must be implemented effectively. Devices like thermally sensitive resistors ensure automatic current limiting under abnormal conditions. A fuel gauge is also critical, providing not only battery detection but also ensuring safety. Many fuel gauges are installed on the battery itself and can monitor temperature, discharge current, and more.

One overlooked issue with power path controllers is the potential for gaps in power supply loops when switching between sources, even briefly. This might necessitate additional reverse connection diodes or switches. Furthermore, when one power supply is in use, its voltage should not backfeed into the other power supply’s input.