AC-DC switched-mode power conversion ICs from Power Integrations

LinkSwitch-II, a new generation in Power Integrations’ extremely successful LinkSwitch series of ICs, 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. By integrating all control and protection circuitry plus a 700 V MOSFET in an 8-pin package, LinkSwitch-II significantly reduces component count, space and system cost while increasing reliability. Output CV/CC tolerances of +/-5% and +/-10% respectively are achieved over a 0 – 100 °C temperature range by incorporating precision-enhancing features that compensate for transformer inductance tolerances, input line variations, output cable voltage drop (LNK61x only) and external component temperature variations. LinkSwitch-II also offers frequency jittering to greatly reduce EMI filter costs.

Sophisticated protection and safety features include auto-restart output short circuit protection and hysteretic thermal shutdown. IEC 60950-1 HV creepage requirements between Drain and all other pins are met and all single point failures are handled safely.

In an example cellphone charger design of 5V/1A, 5 W, LinkSwitch-II offers a simple path to ENERGY STAR EPS 2.0 compliance by achieving average efficiency levels of up to 75% at 25%, 50%, 75% and 100% loads across a 115 to 230 VAC input range. The On/Off control scheme employed in LinkSwitch-II, coupled with low IC power consumption and elimination of secondary-side current sense resistor and control circuitry, provides practically constant efficiency across the entire load range and a no-load consumption of under 30 mW.

Comments Doug Bailey, vice president of marketing at Power Integrations: “LinkSwitch-II sets a new standard in the level of integration achievable in a switching power supply design. It uses primary side regulation to accurately control the output current and voltage, eliminating an expensive opto-coupler and all of the secondary feedback and compensation components. A charger designed with LinkSwitch-II has 9 fewer components compared to the previous generation of LinkSwitch and up to 15 fewer components when compared to discrete designs. LinkSwitch-II offers accurate cable drop compensation which significantly reduces the cost of the output cable by minimizing its copper content, without sacrificing output performance. It also requires a smaller transformer using less copper and core material. ”

Bailey continues: “Lack of secondary feedback sensing components increases the efficiency of LinkSwitch-II-powered chargers to levels approaching 80%. Furthermore, LinkSwitch-II dramatically reduces no-load consumption, the power consumed from the wall when disconnected from the appliance, to levels that are difficult to measure, saving consumers money on their electricity bills. Overall, the LinkSwitch-II solution greatly simplifies the design, is less expensive to build, and is easier on the planet's physical resources and energy supply.”

Further underlining LinkSwitch-II’s green credentials, all family members are produced in halogen-free, RoHS-compliant packaging, which is increasingly being demanded by end customers such as Apple, Nokia Samsung and LG.