AC/DC OFF-LINE SWITCHER IC, TOPSWITCH-GX, FLYBACK, 85 VAC -265 VAC, 132 KHZ, 720 MA OUT, 15W, DIP-8

The TOP242PN is a TOPSwitch-GX Integrated Off-line Switcher IC flyback supply provides 4 outputs, delivering 7W from a 230VAC ±15% input. Resistor R7 programs the internal TOP242PN current limit to 78% of nominal, just above the level needed for full load at low line. This feature allows a more continuous transformer design for better efficiency and cross-regulation, without requiring a larger core size. Resistor R12, C10 and L2 filter conducted EMI; R12 is a flameproof fusible type, also functioning as a fuse. For lower cost, if the supply does not have to meet conducted EMI with the output connected to earth ground, the common mode choke can be replaced with a π filter. A Zener clamp (D11 and VR1) was selected over an RCD clamp to minimize zero load consumption.