Phase-cut dimmable driver IC handles power factor correction and constant-current output with a single stage delivering 5% regulation across the LED load.

Power Integrations used the Munich Electronica trade fair as a stage to announce its LYTSwitch LED driver IC family. Targeting solid-state lighting (SSL) retrofit lamps, the driver IC utilizes a single-stage architecture yet delivers power-factor correction and constant-current output with support for Triac or phase-cut dimmers.

In many cases, driver IC companies have adopted two strategies to target the retrofit lamp market – using single-stage designs for low-end lamps, and dual-stage designs for high-end lamps that require power factor correction and dimming. Power Integrations vice president of marketing Doug Bailey said, "We believe we can address the high end with one stage. That`s what LYTSwitch is designed for."

Bailey acknowledged that two-stage designs can remove ripple from the output, but claims that a single stage can be superior in most other ways. He said a single stage eliminates the need for an electrolytic capacitor between stages, is more efficient, and results in a smaller design. Moreover, Bailey said you could still filter the output ripple to the required level with a capacitor on the output.

The company says that the IC can support a power factor greater than 0.95 while delivering total harmonic distortion below 10%. Primary-side regulation delivers constant-current output accurate within +/- 5%.

Retrofit lamp target

The design can be used in a number of retrofit lamp applications. For example, Power Integrations and Cree have developed a reference design for a PAR38 directional retrofit lamp. Apparently that design uses Cree`s new CXA multi-emitter LEDs, announced a few weeks ago. The reference design is surprisingly light – lighter than a legacy lamp – indicating that the efficient design needed little in the way of heat sinking.

There are elements in the design that target other applications, such as LED-based tubes designed for linear T8 fluorescent retrofit applications. Bailey said that the design team ultimately chose a higher switching frequency of 132 kHz based on T8 demands. The higher frequency means a design can use smaller magnetic components, allowing the driver electronics to fit in the constrained space inside a tube behind an LED light engine.

Like virtually every IC vendor announcing a driver IC these days, Power Integrations claims that its new product works with a broad array of dimmers with smooth transitions and no ill-mannered behavior such as popping on belatedly as a dimmer control is raised. Unfortunately, the SSL industry has no way to rate or compare driver IC dimmer performance.

The LYTSwitch is packaged as a through-hole single inline package (SIP) with prices ranging from $0.70 to $1.60 in high volumes. Bailey said that through-hole printed-circuit-board designs are broadly required in retrofit lamps where other components such as magnetics and capacitors aren`t available in surface-mount packages. The IC (pictured nearby) can be mounted vertically or horizontally to the circuit board.

About the Author 

Maury Wright is the Editor of LEDs Magazine.