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 (, 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,

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