LNK305DN

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The LNK305DN is a high-performance, integrated-power PWM controller optimized for Flyback, Boost, and SEPIC power-converter designs. With its multiple topologies, it supports a wide range of AC/DC converters and offline switchers applications. Its unique design provides minimal external components, and is specifically tailored to reduce system components and cost.

The LNK305DN offers a wide variety of features to simplify the design of offline power supplies for both AC and DC input voltage sources. It combines a powerful system controller with advanced control functions, and a high-voltage start-up circuit integrated onto a single chip.

Some of the key features of the LNK305DN are its high-voltage start-up circuit which is capable of up to 800V peak-to-peak start-up voltage, an overvoltage detection circuit, adjustable Dead Time and cycle-by-cycle current limit, and an integrated PWM controller. All of these features make it ideal for offline, power-supply applications.

The LNK305DN’s operating principle is relatively simple. It has three primary components: the power-control circuit, the feedback circuit, and the logic circuit. The power-control circuit is responsible for controlling the power-converter stage, while the feedback circuit monitors the output voltage and adjusts the power-control current accordingly. The logic circuit is responsible for adjusting the dead time, current-limit, and soft-start functions, as well as other input/output operations.

The power-control circuit consists of a Pulse-Width Modulator (PWM) circuit, a Buck–Boost converter, and a pair of output MOSFETs. In the PWM circuit, two high-power MOSFETs act as switches to control the output voltage. The Buck–Boost converter provides the voltage regulation of the output voltage, while the two output MOSFETs are responsible for controlling the current flow and converting the high-frequency AC voltage into a direct-current voltage.

The feedback circuit monitors the output voltage and adjusts the power-control current accordingly. It consists of a current-sense resistor and a voltage-feedback divider, which senses the voltage level of the output. This measurement is then compared to the reference voltage, and the output current is adjusted so that the output voltage matches the reference voltage.

The logic circuit is responsible for controlling the power-converter stage. It contains logic gates for performing the control functions and for configuring the power-controller. Additionally, it contains a SPI configuration port for programming the controller parameters, such as dead time, soft start, and current limit.

The LNK305DN is optimized for Flyback, Boost, and SEPIC converter topologies and provides an excellent solution for offline switchers applications. It has advanced protection functions, such as integrated overvoltage protection, and provides high efficiency and superior performance. With its small size and low external component count, it is ideal for low-cost, high-performance power supplies.

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