ISRs enable High-Efficiency Offline Power Supplies for Consumer Devices

ON Semiconductor Corp. has added three new current-mode, fixed-frequency integrated switching regulators (ISRs) to its power management product portfolio. Targeted at use in compact, high-reliability offline ac-dc switched-mode power supplies, the NCP1129, NCP1126, and NCP1124 incorporate an avalanche-rated 650V MOSFET and frequency foldback along with skip mode that improve the light load and standby efficiency, meeting the ENERGY STAR® EPS 2.0 Standard.

The high degree of integration results in minimal external components and significantly reduces the overall bill of materials, making them suited to power system designs for household appliances, DVD players and set top boxes. The NCP1129, NCP1126, and NCP1124 can deliver up to 25W, 15W and 12W, respectively, and each generate a jittered 65kHz or 100kHz switching frequency, resulting in improvements in electro-magnetic interference (EMI) performance.

“This new NCP112x series of switchers enable power system design engineers to create more energy efficient and more cost effective power supply designs that will fit into confined spaces,” said Shane Chilton, senior director, AC-DC Power Conversion Products at ON Semiconductor. “The design flexibility provided by specifying these devices allows engineers to optimize their design implementations for either heightened power efficiency or reduced board real estate.”

It is possible for the maximum peak current to be adjusted via an external resistor, facilitating ramp compensation, so that stable continuous conduction mode (CCM) operation can be maintained. The frequency foldback mode permits power conversion efficiency levels to be raised under light load conditions, while the skip mode can be activated for reducing standby power consumption at (or close to) a no load scenario - with less than 100mW drawn at high line when in standby mode.

The NCP112x devices all have a wide array of protective features including a 50ms timer-based auto-recovery short-circuit protection function. Furthermore, short-circuit fault conditions can be independently detected from the auxiliary winding voltage, thereby ensuring that comprehensive safeguards against short-circuit occurrences are in place. The devices incorporate built-in thermal shutdown and over-voltage response mechanisms, as well as a 2kV human body model resilience rating to electrostatic discharge. An operational temperature range of -40 to +150 degrees C is supported. The NCP112x integrated switching regulators are offered in Pb-free PDIP-7 packages, with pricing starting at $0.32 per unit in 10,000 unit quantities.