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New LinkSwitch simplifies CV/CC charger designs

San Jose, Calif.—Power Integrations' LinkSwitch-II family, the newest generation of the company's LinkSwitch series of AC/DC switched-mode power conversion ICs, touts an output accuracy of ±5 percent over line and temperature variations. It includes line-drop compensation circuitry, and guarantees very low no-load dissipation to easily meet Energy Star 2.0 standards for external power supplies.

“LinkSwitch-II sets a new standard in the level of integration achievable in a switching power supply design,” said Doug Bailey, vice president of marketing, citiing new control circuitry to provide very tight output- voltage and current regulation that compensates for transformer and internal parameter tolerances along with input-voltage variations. “It uses primary side regulation to accurately control the output current and voltage, eliminating an expensive optocoupler and all of the secondary feedback and compensation components. A charger designed with LinkSwitch-II has nine fewer components compared to the previous generation of LinkSwitch and up to 15 fewer components when compared to discrete designs.” Overall, the new off-line switcher will reduce power supply component count by 30 percent, according to the company.

The chip, suited for cell phone chargers, high-brightness-LED drivers and other high-accuracy applications, integrates all control and protection circuitry plus a 700-volt MOSFET in an 8-pin halogen-free, RoHS-compliant package. Output constant-current, constant-voltage (CV/CC) tolerances of ±5 percent and ±10 percent, respectively, are guaranteed over the 0-100°C temperature range through the use of circuitry that compensates for transformer inductance tolerances, output cable voltage drop (LNK61x version only) and external component temperature variations. LinkSwitch-II also offers frequency jittering to greatly reduce EMI filter costs.

Protection and safety features include auto-restart, output short-circuit protection, and hysteretic thermal shutdown. The chip meets IEC 60950-1 HV creepage requirements between the drain and all other pins.

In an example cellphone 5-watt charger design (1 amp at 5 volts), LinkSwitch-II achieves an average efficiency of up to 75 percent at 25, 50, 75 percent and full-load across a 115 to 230 VAC input range, thanks largely to its on/off control scheme and elimination of secondary-side current sense resistor and control circuitry. “Lack of secondary feedback sensing components increases the efficiency of LinkSwitch-II-powered chargers to levels approaching 80 percent,” added Bailey. The chip's no-load power consumption is less than 30 mW (when externally biased; 200 mW when the chip is driven by 265 AC input).

Pricing : The LinkSwitch-II family starts at 60 cents each in 10k pieces. For more information, see the company's Green Room web site (www.powerint.com/greenroom), which includes tips on how to design products that minimize the amount of energy wasted by household and office electronics. The Green Room also provides a comprehensive guide to energy-efficiency standards around the world, as well as a host of reference designs and software to assist in the design of energy-efficient power supplies.

Power Integrations , (408) 414-9200, www.powerint.com

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