電容降壓有6個常踩的坑，你知道嗎？跟隨電解電容廠家先來了解一下電容降壓的工作原理，就是利用電容在一定的交流信號頻率下產生的容抗來限制最大工作電流。
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的工頻條件下，一個1uF的電容所產生的容抗約為3180歐姆。當220V的交流電壓加在電容器的兩端，則流過電容的最大電流約為70mA。雖然流過電容的電流有70mA，但在電容器上并不產生功耗，應為如果電容是一個理想電容，則流過電容的電流為虛部電流，它所作的功為無功功率。
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.
根據這個特點，我們如果在一個1uF的電容器上再串聯一個阻性元件，則阻性元件兩端所得到的電壓和它所產生的功耗完全取決于這個阻性元件的特性。
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，我們將一個110V/8W的燈泡與一個1uF的電容串聯，在接到220V/50Hz的交流電壓上，燈泡被點亮，發出正常的亮度而不會被燒毀。因為110V/8W的燈泡所需的電流為72mA，它與1uF電容所產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，我們也可以將5W/65V的燈泡與1uF電容串聯接到220V/50Hz的交流電上，燈泡同樣會被點亮，而不會被燒毀。因為5W/65V的燈泡的工作電流也約為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，電容降壓實際上是利用容抗限流。而電容器實際上起到一個限制電流和動態分配電容器和負載兩端電壓的角色。
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.
下圖為阻容降壓的典型應用，C1為降壓電容，R1為斷開電源時C1的泄放電阻，D1為半波整流二極管，D2在市電的負半周為C1提供放電回路，否則電容C1充滿電就不工作了，Z1為穩壓二極管，C2為濾波電容。輸出為穩壓二極管Z1的穩定電壓值。
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.
在實際應用中，可以用下圖代替上圖，這里用了Z1正向特性和反向特性，其反向特性(也就是其穩壓特性)來穩定電壓，其正向特性用來在市電負半周給C1提供放電回路。
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.
在較大的電流應用中，可以用全波整流，如下圖：
In larger current applications, full wave rectification can be used, as shown in the following figure:
在小電壓全波整流輸出時，最大輸出電流即為：
The maximum output current is as follows: 1
容抗：Xc=1/(2πfC)
Capacitance reactance: XC = 1 / (2 π FC)
電流：Ic = U/Xc=2πfCU
Current: ic = u / XC = 2 π FCU
采用電容降壓時應注意以下幾點：
Attention should be paid to the following points when using capacitor voltage reduction:
①根據負載的電流大小和交流電的工作頻率選取適當的電容,而不是依據負載的電壓和功率。
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限流電容必須采用無極性電容,絕對不能采用電解電容。而且電容的耐壓須在400V以上。最理想的電容為鐵殼油浸電容。
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電容降壓不能用于大功率條件,因為不安全。
Capacitor step-down cannot be used for high power conditions because it is not safe.
④電容降壓不適合動態負載條件。
The capacitor step-down is not suitable for dynamic load conditions.
⑤同樣,電容降壓不適合容性和感性負載。
Similarly, capacitive step-down is not suitable for capacitive and inductive loads.
⑥當需要直流工作時,盡量采用半波整流。不建議采用橋式整流。而且要滿足恒定負載的條件。
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.