充电泵电路的原理与实践

充电泵是一种利用电容和高速开关来实现的简单DC-DC变换器，一般用于低电流低成本的场景中。比如在OLED的驱动芯片中，都会集成充电泵电路来为显示屏提供较高的电压。各大芯片厂商都有对应的芯片方案。

下面这个图能够有助于理解充电泵的工作原理：

上图可以实现由正电源（比如+5V）向负电源（-5V）的转换。

Closing S1 and S3 charges the flying capacitor, C1, to V+ in the first half cycle. In the second half, S1 and S3 open and S2 and S4 close. This action connects the positive terminal of C1 to ground and connects the negative terminal to VOUT. C1 is then in parallel with the reservoir capacitor C2. If the voltage across C2 is smaller than that across C1, charge flows from C1 to C2 until the voltage across C2 reaches -(V+).

TI（德州仪器）有一款芯片型号是TPS6040x，就是实现了反向电源转换器的功能，电路非常简单，只需要额外三个电容即可。