Power Electronics

Primary-Side-Controlled Offline Switch

Power Integrations expanded its popular LinkSwitch-II product family with the introduction of LNK632DG. Designed for applications with up to 3.1 W of output, the new device enables manufacturers to meet all worldwide energy-efficiency and no-load regulations for low-power chargers and adapters, such as ENERGY STAR EPS v2.0. Further, the LNK632DG enables the industry's lowest BOM cost for cellphone chargers designed to achieve a five-star efficiency rating with no-load power consumption of 30 mW or less. It also cuts the cost of USB chargers and LED light bulb designs by eliminating the need for clamping circuitry, therefore reducing component count.

Introduced in 2008, LinkSwitch-II simplifies the design of accurate-output CV/CC converters by eliminating the need for optocouplers and all secondary-side CV/CC control circuitry, as well as all control-loop compensation circuitry. The original LinkSwitch-II devices achieve output CV and CC tolerances of +/-5% and +/-10%, respectively. The newer LNK632 part relaxes the CC specification to +/-18% while increasing the system power output by operating in continuous conduction mode. Accuracies are achieved over a 0-100degC temperature range by incorporating precision-enhancing features that compensate for transformer inductance tolerances, input line variations and external component temperature variations. All LinkSwitch-II devices offer frequency jittering to greatly reduce EMI filter costs.

The star-rating system was recently launched by top cellphone makers: Nokia, Samsung, Sony Ericsson, Motorola and LG Electronics. Ratings for no-load energy consumption range from five stars for the most advanced chargers consuming just 30mW in no load mode down to zero stars for units consuming the most energy, making it easy for consumers to compare and choose the most energy-efficient chargers.

The LNK632DG includes sophisticated protection and safety features including auto-restart, output short-circuit protection, and hysteretic thermal shutdown. IEC 60950-1 HV creepage requirements are met between the drain pin and other pins, and all single-point failures are safely handled.

Housed in a simple 8-pin surface mount package, LNK632DG devices are available immediately from $0.42 each in 100,000-unit quantities.

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