Introduction to power principle (I)

A key component of a DC power management system is a DC-powered power supply for the relevant system. The specific type of DC power management depends on its power input, including:

AC input - accepts AC power input, then rectifies and filters it, and the resulting DC voltage is connected to a voltage regulator circuit that provides a constant DC output voltage. There are a variety of AC DC power supplies with output voltages from less than 1 volt to several thousand volts. This DC power management system typically uses a switching power supply, and some linear power supplies are available.

DC Input - Receives a DC voltage input, typically 5 volts, 12V, 24V, or 48 volts, and produces a DC output voltage. At the low end, this type of power supply can produce less than 1 VDC, while other DC-DC power supplies can generate thousands of volts of DC. Here, power management usually uses a switched mode power supply.

Battery Input (for Portable Devices) - Due to the size and weight limitations of portable devices, this power management feature is often integrated with the rest of the electronic system. Some of these systems also include an AC adapter, which is a small power unit that plugs into the AC wall outlet and provides a DC output voltage. Typically, an AC adapter is used to power the unit and to charge the system battery.

Ultra Low Voltage Input (Energy Harvest) - Energy harvesting provides the energy to charge, replenish or replace the battery. A key component in the energy harvester is a power converter that can operate with ultra-low voltage inputs. In operation, the power converter captures a small amount of energy, accumulates it, stores it, and then maintains the stored energy as a power source. Low voltage inputs can come from solar, thermal, wind or kinetic energy.

Linear and switching power supplies:

There are two basic power configurations with a DC power management subsystem: linear and switch mode. The linear power supply always turns on the current. Switch mode converts DC to a switching signal and then rectifies it to produce a DC output. The differences between these two configurations include size and weight, power handling capabilities, electromagnetic interference and regulation.

The main components of the linear regulator are through the transistor, error amplifier and voltage reference, as shown in Figure 1-1. The linear regulator maintains a constant output voltage by using an error amplifier to compare a portion of the output voltage to a stable voltage reference. If the output voltage tends to increase, the feedback causes the output voltage to be reduced by the transistor and vice versa. OEM linear power supplies can handle several amps of current. They are usually bulky desktop or racking supplies.