Power IC tackles basic, inefficient “droppers”
By Bill Schweber -- EDN, March 4, 2004
In many low-cost, nonisolated applications that can tolerate poor regulation of derived voltage, designers use simple resistors or capacitors to decrease the voltage, but these passive designs are inefficient. The LinkSwitch-TN family from Power Integrations targets these situations with a series of monolithic ICs for load requirements as high as 360 mA (Picture). The buck or buck-boost switching supply you can build around this IC accepts 85 to 265V ac and offers 10% load regulation with typical efficiency better than 75%—far greater than the less elegant, less expensive, brute-force drop technique. The IC-based design maintains this efficiency at light load, which is useful for the standby mode of your application.
The self-powered IC includes a MOSFET power switch, jittered 66-kHz switching frequency to reduce EMI, overload auto-restart, and various fault-protection modes. The 170-mA LNK304P sells for 42 cents, and the 360-mA LNK306P sells for 59 cents (10,000).
Power Integrations,1-408-414-9200, www.powerint.com.
