L4981AD

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PMIC - PFC (Power Factor Correction) is an important technology for maximizing both power supply efficiency and power delivery efficiency. L4981AD is a high performance power factor correction (PFC) controller from STMicroelectronics, which operating voltage range is from 3V to 20V and offering a very high peak current capability. The L4981AD meets the applicable requirements of international body, in particular those related to harmonic content of input current.

Application Field of L4981AD

The L4981AD is mainly used in standby power supply applications. Commonly found application fields are LED drivers, Uninterruptible Power Supply (UPS), and Power Inverters. It is also used in a variety of other power supply designs, including those used in industrial and medical applications.

Working Principle of L4981AD

The L4981AD uses a technique called “Pulse Width Modulation” (PWM) to control the current drawn from the AC line. This control is achieved by shortening or lengthening (modulating) the width of the incoming AC signal to adjust the amount of current drawn from the line. This is done so that the desired input power factor is obtained across the entire input voltage range.

The controller has a built-in peak current control (PCC) loop that monitors the primary inductor current and adjusts the pulse width of the input AC waveform as required to keep the current to the desired level. This adjusts the harmonic content of the input current. The controller also has an active valley fill feature that minimizes further the generated harmonic distortion. In addition, the L4981AD also offers digital protection features, such as over-current protection, over-voltage protection, under-voltage protection, and thermal shutdown.

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