Controllers boost current and voltage accuracy

Available now from Power Integrations, the LinkSwitch-II family of highly integrated AC/DC switched-mode power conversion ICs boast highly accurate primary-side control.

LinkSwitch-II dramatically simplifies constant-voltage, constant-current (CV/CC) convertors, and enables consumer products to meet all worldwide energy-efficiency and no-load regulations, such as Energy Star 2.0 for external power supplies.

The new ICs are ideal for applications such as chargers for cellphones and cordless phones, high brightness LED drivers and other accurate CV or CC applications.

LinkSwitch-II, a new generation in Power Integrations' extremely successful LinkSwitch series of ICs, simplifies the design of accurate output CV/CC convertors 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 700V 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 0-100C 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.

IEC60950-1 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, 5W, 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 230V AC 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 30mW.

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 optocoupler and all of the secondary feedback and compensation components".

"A charger designed with LinkSwitch-II has nine fewer components compared with the previous generation of LinkSwitch and up to 15 fewer components when compared with discrete designs".

"LinkSwitch-II offers accurate cable drop compensation which significantly reduces the cost of the output cable by minimising 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.

Power Integrations' Green Room website contains information on the issue of energy waste from inefficient power supplies, as well as tips on how to design products that minimise 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.