Power Integrations’ LYTSwitch driver ICs include auto-restart for open control loop and output short-circuit conditions.

These driver chips eliminate the need for many external discrete components.

Integration is the latest global trend in the LED lighting products segment. Integrated driver ICs improve the reliability and quality of solid state lighting solutions, which in turn results in cost effective and long lasting LED lighting systems.

A new generation of LED driver chips is being designed and brought to market that combine many components, dramatically reducing the overall bill-of-material (BOM).

For example, LYTSwitch ICs from Power Integrations combine the controller with a high voltage power MOSFET and eliminate many external discrete components such as resistors, capacitors, diodes and transistors.

According to Doug Bailey, VP Marketing, Power Integrations, this high level of integration and recommended circuit design techniques also ensure that there are fewer parts to fail.

The reference designs also eliminate components that are generally unreliable at the typical operating temperature of a bulb, such as opto-couplers and electrolytic capacitors.

“Driver ICs with controllers and MOSFETS that have been designed to work together allow higher switching speeds, so smaller magnetic components can be used,” Bailey added. “And primary side regulated topologies mean that expensive opto-couplers are redundant.”

In addition, sophisticated protection features can be incorporated on-chip to improve reliability. Line overvoltage protection provides extended line fault, surge withstand, and accurate hysteretic thermal shutdown that ensures safe average PCB temperatures under all conditions.

Fewer components, lower cost

A reduced component count improves reliability and lowers manufacturing cost. In some cases, sophisticated, dimmable LED lighting systems can be configured using fewer than 25 components.

LED driver ICs have already contributed to simplifying and reducing the cost and the number of components in many LED lighting systems. A good example of this is the 60W LED bulb. The 60W replacement LED light bulb is powered by an offline power source and requires a well-regulated constant current source to deliver a constant level of light output.

Even though powering it from an AC input source requires special design techniques with specific design needs, according to Tony Armstrong, director of Product Marketing, Power Products, Linear Technology Corp., it can be done with relatively fewer components and minimal cost.

For a nonisolated version, the cost breakdown is shown in the table below.

As far as the design of LED lighting systems is concerned, not much has changed since 2013 mainly because there have not been any major improvements in LEDs’ light output, also known as efficacy. The latest LED bulbs have a 200 lm/W efficacy, approximately a 20 lm/W improvement over prior versions.

“The efficacy of an LED drives the size of the heat sink required for the necessary cooling of the LED for proper operation and longevity,” said Armstrong of Linear. “It is the LED heat sinks and housing that contribute to the complexity of the lighting system. For the AC/DC LED driver circuits themselves, these are already small and compact with minimal external components.”

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