Catalyst Semiconductor has received a patent for a stepdown switching regulator circuit architecture applicable for driving high-brightness LEDs. The patent, titled “LED current bias control using step-down regulator” (patent number 7,323,828), was developed to simplify the design of high-brightness LED lighting in emerging household, commercial and automotive lighting applications.
The patent is embedded in the company’s new line of inductor-based, stepdown LED drivers, which bridge the gap between the two traditional choices for LED driver design: simple-to-use, but power-hungry linear regulators; and switching regulators, which offer lower power dissipation, but are more complex and difficult to implement. The new patent enables a simpler, smaller, more cost-effective and far more power-efficient “green” LED driver alternative to linear regulators.
“When using this new step-down switching scheme, the designer simply selects a control resistor and the patented switching regulation scheme provides an inherently stable and accurate LED bias across a wide range of voltage operating environments without the complicated equations or calculations associated with alternative LED switching regulators,” says Anthony Russell, Catalyst’s power management director and co-inventor of the patent.
Traditional switching regulators operate in both continuous-conduction mode (CCM) and discontinuous-conduction mode (DCM), making them intrinsically complex. Catalyst’s stepdown switching regulator architecture operates at the precise intersection between CCM and DCM, the point Catalyst calls Crossover Conduction Mode (XCM), to offer a simpler and more power-efficient solution.
Catalyst’s XCM architecture enables efficient operation over a wide range of high-voltage system supplies, versus linear regulators, which operate efficiently over a very small supply-voltage range. Additionally, the XCM operation offers unconditional stability and eliminates the need for high-power current sense resistors and associated interface pins, reducing size, complexity and cost.
The first product to incorporate Catalyst’s stepdown switching regulator architecture is its CAT4201, a 7-W buck LED driver optimized for driving high-brightness, 350-mA LEDs at up to 94% efficiency.