PTC与PFC：家电核心元件解析_pfc的ptc软启动-优快云博客

I have been on a business trip for a really long time. I went to south for a month. And of course I have give the local food many tries. As for me, southern cuisine is too bland; my taste buds are bored.

I have some new concepts to learn. So I will wrute them down to learn them well.

PTC

positive temperature coefficent. It controls the compressor current when it starts. When the compressor is power on, ptc is cold. At this point the resistance is low and it allows huge current come to to the compressor. The huge start current helps the motor generate sufficient starting torque. When the compressor starts for seconds, the ptc goes hot and at the same time, the resistance goes really huge and the current from ptc to compressor is almost shut down. PTC is only used for single-phase motors.

┌───运行绕组───┐
火线 L -----┤ ├──┐
│ │ │
│ │ ├─公共端 C ──压缩机壳体/零线 N
│ │ │
└──PTC继电器─┬─启动绕组───┘
│
└─仅 10–15 mA 维持 PTC 高温

PFC

power factor correction. pfc is kind of stable element, to make full use of electricity.

no pfc:

电网供电波形：～～～～（正弦波）
空调用电：︿︿︿︿（只在峰值吸电）
剩余电能：～～～～（大部分被浪费）

active PFC:

电网供电波形：～～～～～（正弦波）
空调用电：～～～～～（跟随电网波形）
电能利用： ████████（几乎100%利用）

The main aim of pfc is that pfc makes input current flow with input voltage. PFC and her ladies work together to output stable voltage. PFC cannot regulate output current directly. She controls the energy stoarge and release progress of inductance by regulate the 'conduction time of the switch'.

Image that input voltage is kind of waving river, and pfc is kind of reservior and pump. Alternative current is kind of two way river and it flows undulating in a sine wave pattern. The rectifier bridge transforms this bidirectional flow into a unidirectional pulsating current (a “dumpling wave”). The size of dumpling wave still changes with the waving river.

When the wave decreases and the load remains, the pump have to get more water from river. 当输入的电压减小，相当于白白的馒头波减小，这个时候需要更多的闭合时间给电感充电。当开端断开的时候，输入端的电流和电感储存的电能叠加起来输入给电容。在这一小段时间里，输入功率 Pin 是随馒头波起伏的，而 Pout 几乎是恒定的。
于是瞬时并不守恒：
• 当 Pin > Pout，多出来的能量被存进电容；
• 当 Pin < Pout，电容把之前存的多余能量吐出来。
电容就是用来“抹平”这种瞬时盈亏的。这样保证了水库的水位在目标的电压极小的波动。电容不能直接调节电流，只是稳压的功能。恒流 DC-DC负责稳定的开闸放水，给负载提供稳定的直流电流。整流桥先“翻负半周”→ Boost 电路再“抬电压并锁 400 V”→ 电容“抹平纹波”，于是 220 V AC 最终变成稳定的 400 V DC。