New off-line switcher IC family offers line-compensated overload protection and light-load efficiency benefits

October 11, 2012 // By Paul Buckley
Power Integrations has introduced the TinySwitch-4 family, the latest generation of the company’s industry-leading TinySwitch series of off-line switcher ICs.

Featuring line-compensated overload power protection, TinySwitch-4 devices reduce the maximum overload power that can be delivered into the load over the entire AC input voltage range.  The devices incorporate a 725 V MOSFET that easily allows 80 percent de-rating for high reflected voltage and high bus-voltage designs. Efficiency of greater than 70 percent at five percent load enables designers to meet the stringent European standby specifications scheduled to take effect in 2013, while no-load power consumption of less than 30 mW at 230 VAC meets critical energy-saving requirements in the market today.

The line-compensated overload power protection of TinySwitch-4 ICs is helpful in applications such as PC standby and appliances where unusually high current demands from the load may be indicative of a fault. Prompt action by the power supply to limit the current to a designed maximum value may prevent damage to the circuitry and enhance overall system safety and reliability. The BP/M pin permits the MOSFET current limit to be adjusted up or down, allowing designers to optimize power delivery and efficiency in a variety of physical implementations. An on-time extension function extends the low-line regulation range, enabling hold-up time to be met with lower values of input capacitance. TinySwitch-4 devices also feature latching output overvoltage protection (OVP) configurable for fast AC reset by connecting the EN/UV pin resistor to the AC input line. Improved auto-restart ensures that power delivery during an output fault is limited to less than three percent of full load rating.

The TinySwitch-4 family is a scalable family of devices covering an extended power range up to 36.5 W, including such power-supply applications as PC standby and other auxiliary supplies, DVD/PVR and other low-power set-top decoders, appliances, industrial systems, utility meters, and chargers/adapters for mobile and cordless phones, digital cameras, portable audio, etc. Three package options are available: the industry standard PDIP and SOIC packages, and the new SMD eSOP package which enables designers