New family of energy-efficient, off-line switcher ICs introduce primary-side regulation to power supplies up to 90-W

July 25, 2012 // By Paul Buckley
Power Integrations has introduced LinkSwitch-HP, a new family of energy-efficient, off-line switcher ICs that can deliver up to 90 W output power with accurate primary-side regulation (PSR).

LinkSwitch-HP ICs utilize innovative control algorithms and the properties of the main power transformer and output diode – instead of optocouplers and related feedback circuitry – to determine the amount of power to deliver from the primary to the isolated secondary side. The method reduces component count, saving space and cost while enhancing reliability. Popularized more than a decade ago with the advent of Power Integrations’ LinkSwitch line, PSR is now standard in many low-power applications such as mobile-phone chargers but until now has lacked the constant-voltage accuracy required in higher-power products. LinkSwitch-HP devices feature a unique multi-mode control architecture that radically advances the state of the art for PSR, making it a viable approach for power-supply applications from 9 W to 90 W.

The devices automatically select their control mode according to prevailing line and load conditions to optimize conversion efficiency and response to transient load demands, while minimizing output ripple and audible noise. Continuous-conduction-mode (CCM) operation results in reduced RMS currents, leading to higher efficiency and less heat dissipation, while 132 kHz, full-load operating frequency enables the use of smaller magnetics and LC post-filter components. LinkSwitch-HP ICs are capable of no-load power consumption of less than 30 mW at 230 VAC and are more than 50 percent efficient at 0.1 W input power, easily meeting all global energy efficiency regulations such as ErP (EuP), ENERGY STAR EPS V2.0 and EC Ecodesign Directive Tier 2 for external power supplies.

LinkSwitch-HP devices also reduce the cost and complexity of meeting Chinese safety standard GB 4943.1-2011, which mandates the use of warning labels on power supplies that do not meet strict creepage and clearance rules. Similar to UL 60950-2007 and set to become mandatory on December 1st, 2012, the new rule requires designers to increase the primary-to-secondary clearance by a factor of 1.48 for power supplies used in equipment above 2000 m, or else add a warning label to the product.