LNK6778K

LNK6778K is a high-performance AC-DC power conversion chip developed by Power Integrations for offline switcher applications. It is a highly integrated, precision single-channel primary-side controller chip with a large operating range designed for high switching frequency and low-cost, space-saving primary-side conversion. Its efficient and reliable design enables meeting worldwide energy-efficiency standards.

The LNK6778K controller offers a wide input voltage range of up to 350V AC, and its low current start-up strategy minimizes the space and components required for primary-side circuit design. The 95.5% peak efficiency of its power supply reduces heat dissipation and improves reliability. The minimum switch frequency of 280 kHz allows new designs to operate with a small external inductor and capacitor.

The LNK6778K integrates a variety of intelligent protection functions, including pulse-by-pulse current limiting, over-voltage protection, over-temperature protection and auto-restart protection. The built-in output current sensing Circuit allows designers to simply use a resistor to measure the output current (with only 10 μA quiescent current). In addition, it also has a steady-state overshoot current limitation and low standby power consumption.

Working principle of LNK6778K AC-DC power converter Controller

The LNK6778K is a single-channel primary-side controller employed for AC-DC power converter operations. It is designed to work with an externalrectifierto con ver t AC voltage in to DC voltage for the desired application. The chip comprises an adjustable input voltage range (up to 350V AC) and an adjustable switch frequency range (280kHz). It detects the input voltage and produces a fixed Pulse-Width Modulation (PWM) signal. This fixed PWM signal is then used to switch the power MOSFETs of the external rectifier circuit.

The LNK6778K also includes several protection features like pulse-by-pulse current limiting, over-voltage protection and over-temperature protection to ensure a safe and stable operation of the power supply. It features a built-in Output Current Sense (OCS) circuit which allows designers to measure the output current with a resistor. Upon start-up, it generates a stable 5V bias voltage for the rectifier circuit and subsequently adjusts the supply voltage in order to maintain stability.

The chip provides 95.5% peak efficiency and low standby power consumption. Its adaptive low current start-up strategy minimizes components to achieve a compact design and low cost. It also includes an auto-restart function to ensure a smooth and safe system operation in case of power interruption.

Conclusion

The LNK6778K AC/DC power converter is an integrated, highly precise, and versatile controller solution for offline switcher applications. With its wide input voltage and current range, precise switching frequency and various advanced protection features, it enables designers to build efficient, reliable and cost-effective power supplies that meet the global energy-efficiency standards. The LNK6778K is a versatile and efficient solution for power supply designs.