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问 请教交流220V电压怎么转换为直流5V电压，最好能有电路图，我在这里先谢谢了~~ 答 1: 电流呢？ 答 2: 转换成直流就行了，电流不用考虑转换成直流就行了，电流不用考虑 答 3: reuse 3842 答 4: 用阻容降压电路 答 5: 给你1个5W（5V/1A）的方案－ACT29可以取代Viper12The 29 belong to the ActiveSwitcherTM family of current-mode PWM power supply controllers that drive an external NPN transistor for high voltage switching. This architecture for high voltage switching. This architecture enables many advanced features to be integrated
into a 3-pin TO-92 package, resulting in lowest total cost solution.The ACT29 allow a low-cost NPN such as ‘13002 or ‘13003 to operate at higher voltage than in a base-drive architecture such as RCC.Operating at 65kHz switching frequency, the ACT29 is capable of delivering up to 5W yet consumes less than 0.25W in standby. The safety features include over-current and under-voltage protection mechanisms. 答 6: 那么复杂用开关电源太复杂了吧
买个充电器就行了 答 7: 不敢相信 答 8: 谢谢各位的建议谢谢各位的建议，不过楼上的那个电路图实在太猛了，小弟看不懂 呵呵~~~ 答 9: 上面电路就是个简单电路啦,看看简单的振荡电路,
再看看些保护电路,看多了,合在一起看就差不多了.