用220V直接给单片机供电。

嵌入***

不知道这样危险不危险

cdp***

危不危险看用在哪里, 摸不到的地方就不危险, 如果摸到串电阻一端电不死, 插头一反就看运气.  主要还是看元件选择, 元件耐压散热留比大的余地的话, 也考虑了电网异常的保护情况 , 那也算可靠的.  只不过空间体积, 发热, 安全都要万分注意, 元件选择没问题了, 成本也上去了.  电阻几W的功耗都可以烤灭蚊片了.

cdp***

水泥电阻便宜10W的几毛钱, 具体用几W的可以试验下, 看那种温度可以接受.

晓***

liuzon*** 发表于 2024-9-8 18:32
用100K，才3毫安，单片机启动不了，用20毫安电流的话，电阻必须分开才行要不就要用个大的水泥电阻，一个电 ...

啥单片机需要20mA才能启动嘛

liuzon***

晓*** 发表于 2024-9-8 21:28
啥单片机需要20mA才能启动嘛

既然设计电源就一步到位，直接当供电使了，以后单片机运行不超过20ma就行了。是在不行换2W的电阻。

晓***

liuzon*** 发表于 2024-9-8 21:51
既然设计电源就一步到位，直接当供电使了，以后单片机运行不超过20ma就行了。是在不行换2W的电阻。 ...

那最好用RC降压，20mA可以用334的CBB电容并1M电阻降压，成本5毛钱以内

讲究点呢，再加个1毛钱的高阻值的NTC，缓冲一下上电浪涌电流，那就万无一失了。

cdp***

实际工程中, 小功率大量用的都是阻容降压. 纯电阻的很少, 除非是驱动一个发光管, 或光耦那种很小电流的. 纯电阻的比阻容最大问题就是发热. 放在产品里发热太大感觉不好. 要是不在乎发热, 2种就看成本问题了.

jm***

liuzon*** 发表于 2024-9-8 15:51
My MCU need about 10mA,for the  orther applications that I have not thought about . I think that ,2 ...

10mA is very high for resistive dropper. It will be over 3W on your numbers and 20mA is over 6W !!
That is a lot of heat to remove from any PCB and housing.

You are better to use a R+CAP dropper as above, or even an active on-the-slopes pulse design.

10mA is also very high for a MCU startup, you should work to reduce that.

Does anyone know what a STC MCU part current drain waveform looks like at startup ?


Not many vendors specify reset / starting current, but I've seen Microchip reports say Tiny13A ~ 230uA or AtMega16L ~ 3.6mA and Nuvoton MUG51 say < 200uA when RESET=LOW

liuzon***

jm*** 发表于 2024-9-9 03:36
10mA is very high for resistive dropper. It will be over 3W on your numbers and 20mA is over 6W !!
...

The tick-tap pulse generator you introduced（dropper-regulator part like SS540S ）is too expensive. The stc microcontroller, according to the official data, is within 10 mA / at 35 mhz. Plus I want to drive the circuit I want to drive the MOS tube, the consumption of the protection circuit, about 20 mA is enough, you said the Schottky voltage stabilization tube can work at less than 5 ma, I looked at the curve, it is best to let him consume 5 mA to stabilize. This will provide a minimum of 15 mA.

liuzon***

晓*** 发表于 2024-9-9 00:03
那最好用RC降压，20mA可以用334的CBB电容并1M电阻降压，成本5毛钱以内

讲究点呢，再加个1毛钱的高阻值的N ...

我想从主电路的直流331V直接取电。整流滤波，交给主电路就行。