New LinkSwitch-II Design Ideas from Power Integrations make driving LEDs simple

Power Integrations has announced a series of design ideas to help designers of LED driver circuitry benefit from the company's recently introduced LinkSwitch-II family of AC-DC power conversion ICs. The new design ideas (DI-184, DI-185 and DI-186), demonstrate that LinkSwitch-II ICs are well suited for power supplies and ballasts driving high-brightness LEDs. The devices' highly accurate constant-current performance and low external component count enable LED ballasts that are simpler to design, lower-cost, and more durable than existing converter technology.

LinkSwitch-II features Power Integrations' advanced primary-side regulation (PSR) technology, which utilizes a transformer winding to sense the output current rather than relying on lossy, expensive secondary-side components to provide feedback and regulate the output. This cuts system component count by up to 30 percent, resulting in simpler, more reliable and lower-cost designs with extremely good active and standby energy-efficiency performance.
Power Integrations' PSR technology ensures highly accurate performance, maintaining output current within a +/- 10% range even if load voltage drop, magnetic component tolerance and temperature conditions vary during manufacture or operation. The constant-current drive enabled by LinkSwitch-II ensures that each LED in a series-connected string provides similar light output. This eliminates the current-sharing problem inherent with parallel-connected diodes, and reduces LED binning costs and optical mixing complexity in lighting fixtures.

Unlike many halogen and CFL lights, LED arrays powered by LinkSwitch-II work with traditional AC-based triac dimmers, as well as more modern remote-controlled dimmers. The high standby efficiency of LinkSwitch-II is particularly important with remote dimming; when it is turned off, LinkSwitch-II absorbs only 30 mW of standby power while waiting to re-energize the lights.
The newly released design ideas are suitable for applications of LED lighting less than 5.5W, such as replacement bulbs for halogen installations, refrigerator interior illumination, landscaping and smaller residential lighting fixtures. DI-184 illustrates a circuit for driving 700mA of current through strings of two series-connected high brightness white LEDs. The DC side circuit is electrically isolated from the AC side for safety. DI-185 and DI-186 both drive 350mA of current through strings of three high brightness white LEDs. The former design utilizes an isolated flyback topology, the later features a novel, non-isolated, tapped buck topology which reduces system cost and complexity. Each design includes appropriate EMI suppression components and operates at universal input voltage levels.

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