电容降压有6个常踩的坑，你知道吗？跟随电解电容厂家先来了解一下电容降压的工作原理，就是利用电容在一定的交流信号频率下产生的容抗来限制最大工作电流。

　　There are six holes in capacitor step-down, do you know? Follow the electrolytic capacitor manufacturers to understand the working principle of capacitor step-down, which is to limit the maximum working current by using the capacitance reactance generated under a certain AC signal frequency.

　　例如，在50Hz的工频条件下，一个1uF的电容所产生的容抗约为3180欧姆。当220V的交流电压加在电容器的两端，则流过电容的最大电流约为70mA。虽然流过电容的电流有70mA，但在电容器上并不产生功耗，应为如果电容是一个理想电容，则流过电容的电流为虚部电流，它所作的功为无功功率。

　　For example, at 50 Hz power frequency, the capacitance reactance generated by a 1 UF capacitor is about 3180 ohm. When 220 V AC voltage is applied to both ends of the capacitor, the maximum current flowing through the capacitor is about 70 ma. Although the current flowing through the capacitor is 70ma, there is no power consumption on the capacitor. If the capacitor is an ideal capacitor, the current flowing through the capacitor is imaginary part current, and the work it does is reactive power.

　　根据这个特点，我们如果在一个1uF的电容器上再串联一个阻性元件，则阻性元件两端所得到的电压和它所产生的功耗完全取决于这个阻性元件的特性。

　　According to this characteristic, if we connect a resistive element in series to a 1uF capacitor, the voltage and power consumption at both ends of the resistive element depend entirely on the characteristics of the resistive element.

　　例如，我们将一个110V/8W的灯泡与一个1uF的电容串联，在接到220V/50Hz的交流电压上，灯泡被点亮，发出正常的亮度而不会被烧毁。因为110V/8W的灯泡所需的电流为72mA，它与1uF电容所产生的限流特性相吻合。

　　For example, we connect a 110V / 8W bulb in series with a 1uF capacitor. When connected to a 220 V / 50 Hz AC voltage, the bulb will be on and emit normal brightness without being burned. Because the current required for a 110V / 8W bulb is 72ma, it is consistent with the current limiting characteristic produced by a 1uF capacitor.

　　同理，我们也可以将5W/65V的灯泡与1uF电容串联接到220V/50Hz的交流电上，灯泡同样会被点亮，而不会被烧毁。因为5W/65V的灯泡的工作电流也约为70mA。

　　In the same way, we can connect 5W / 65V bulb and 1uF capacitor in series to 220 V / 50 Hz AC, and the bulb will also be lighted, but not burned. Because the working current of 5W / 65V bulb is about 70ma.

　　因此，电容降压实际上是利用容抗限流。而电容器实际上起到一个限制电流和动态分配电容器和负载两端电压的角色。

　　Therefore, capacitor step-down is actually using capacitive reactance to limit current. In fact, the capacitor acts as a limiting current and dynamically distributing the voltage between the capacitor and the load.

　　下图为阻容降压的典型应用，C1为降压电容，R1为断开电源时C1的泄放电阻，D1为半波整流二极管，D2在市电的负半周为C1提供放电回路，否则电容C1充满电就不工作了，Z1为稳压二极管，C2为滤波电容。输出为稳压二极管Z1的稳定电压值。

　　The figure below shows the typical application of resistance capacitance voltage reduction. C1 is the step-down capacitor, R1 is the discharge resistance of C1 when the power supply is disconnected, D1 is the half wave rectifier diode, D2 is the discharge circuit for C1 in the negative half cycle of the commercial power supply, otherwise the capacitor C1 will not work when it is fully charged, Z1 is the voltage stabilizing diode, C2 is the filtering capacitance. The output is the stable voltage value of the voltage regulator diode Z1.

　　在实际应用中，可以用下图代替上图，这里用了Z1正向特性和反向特性，其反向特性(也就是其稳压特性)来稳定电压，其正向特性用来在市电负半周给C1提供放电回路。

　　In practical application, the figure below can be used to replace the above figure. Here, the forward and reverse characteristics of Z1 are used to stabilize the voltage, and the forward characteristic is used to provide C1 with discharge circuit in the negative half cycle of the mains power.

　　在较大的电流应用中，可以用全波整流，如下图：

　　In larger current applications, full wave rectification can be used, as shown in the following figure:

　　在小电压全波整流输出时，最大输出电流即为：

　　The maximum output current is as follows: 1

　　容抗：Xc=1/(2πfC)

　　Capacitance reactance: XC = 1 / (2 π FC)

　　电流：Ic = U/Xc=2πfCU

　　Current: ic = u / XC = 2 π FCU

　　采用电容降压时应注意以下几点：

　　Attention should be paid to the following points when using capacitor voltage reduction:

　　①根据负载的电流大小和交流电的工作频率选取适当的电容,而不是依据负载的电压和功率。

　　The appropriate capacitance is selected according to the current of the load and the working frequency of the alternating current, rather than the voltage and power of the load.

　　②限流电容必须采用无极性电容,绝对不能采用电解电容。而且电容的耐压须在400V以上。最理想的电容为铁壳油浸电容。

　　The current limiting capacitor must be a non-polar capacitor, not an electrolytic capacitor. And the withstand voltage of capacitor must be above 400V. The most ideal capacitance is the oil immersed capacitor with iron shell.

　　③电容降压不能用于大功率条件,因为不安全。

　　Capacitor step-down cannot be used for high power conditions because it is not safe.

　　④电容降压不适合动态负载条件。

　　The capacitor step-down is not suitable for dynamic load conditions.

　　⑤同样,电容降压不适合容性和感性负载。

　　Similarly, capacitive step-down is not suitable for capacitive and inductive loads.

　　⑥当需要直流工作时,尽量采用半波整流。不建议采用桥式整流。而且要满足恒定负载的条件。

　　When DC is needed, half wave rectifier should be used as far as possible. Bridge rectifier is not recommended. And to meet the conditions of constant load.