器件名称: DI-138
功能描述: 1.2 W, Non-isolated Dual Output Supply for White Goods
文件大小: 159.85KB 共2页
简 介:Design Idea DI-138
LinkSwitch-TN
1.2 W, Non-isolated Dual Output Supply for White Goods
Application White Goods Device LNK304DN Power Output 1.2 W Input Voltage 85-265 VAC Output Voltage +7 V, -5 V Topology Buck Derived
Design Highlights
Universal input Excellent regulation – 12 V ±8% and 5 V ±5% (line, load, and tolerance) Temperature compensated Low stand-by input power consumption: <300 mW at 230 VAC with 50 mW output load Meets CISPR-22/EN55022B limits for conducted EMI with >10 dB margin
Resistor RF1 is a fusible ame-proof type that acts as a fuse in the event of a catastrophic failure. Diode D1 provides AC input rectication while C1 and C2 provide smoothing and, together with L1, act as a π lter. This ltering, together with LinkSwitch-TN’s (U1) integrated switching frequency jitter, provides a generous EMI margin (see Figure 3). During each enabled switching cycle, U1’s internal MOSFET is enabled, causing a linear ramp in current through L2 and C5. Once the internal current limit is reached, the MOSFET turns off, and the inductor current can freewheel via D2, C5, and C6. Regulation is maintained by adjusting the ratio of enabled to disabled cycles. A cycle is skipped once the current into the FEEDBACK (FB) pin exceeds 49 μA. As this is specied at a voltage of 1.65 V, it allows this pin to can be used as a reference. With the values of R1 and R2 as shown, this sets the voltage across C5 plus C6 to 12 V. The –5 V output is regulated by Q2 using VR1 as a referenc……
