On Semi NCP1308 50W四输出STB电源解决方案
On Semi 公司的NCP1308控制器把电流模式调制器和退磁检测器集成在一起,可以在任何的负载/线路条件下保证有更宽的导通模式,过流保护自动恢复,内部软起动时间1.0s,在AC/DC转换器和离线电池充电器等有广泛用途.本文介绍了NCP1308主要特性, 内部电路架构图, 典型应用电路图以及50W四输出机顶盒(STB)电源电路图和材料清单(BOM).
50 W Four--Output Internal Power Supply for Set Top Box
The NCP1308 combines a true current mode modulator and a demagnetization detector to ensure full borderline/Critical Conduction Mode in any load/line conditions and minimum drain voltage switching (Quasi-Resonant operation). Due to its inherent skip cycle capability, the controller enters burst mode as soon as the power demand falls below a predetermined level. As this happens at low peak current, no audible noise can be heard. An internal 10us timer prevents the free-run frequency to exceed a high frequency (therefore below the 150 kHz CISPR-22 EMI starting limit), while the skip adjustment capability lets the user select the frequency at which the burst foldback takes place.
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