电解电容寿命纹波电流测试

    ★ The diode D1&D3 work, D2&D4 cut off, the current flows through the load reSIStance RL in a loop and charge the capacitor C up when U2 in the positive half circuit and its value exceeding the voltage Uc which is parallel cONnected in the two terminals of capacitor. When Uc exceeds U2, and causes the diode D1&D3 cut off, the capacitor discharge through the load resiSTance RL and Uc decline slowly according to the principle of index function.

    ★ 当U2为负半周幅值变化到恰好大于Uc时，D2和D4因加正向电压变为导通状态，U2再次对C充电，Uc上升到U2的峰值后又开始下降；下降到一定数值时D2和D4变为截止，C对RL放电，Uc按指数规律下降；放电到一定数值时D1和D3变为导通，重复上述过程。

    ★ As the same reason , when U2 in the negative half cIRcuit and the amplitude is even changed to exceed Uc ,the diode D2&D4 work due to the positive voltage and U2 charge capacitor C up again. Uc start to decline when it's voltage rise to the peak value of U2 and to a certain value , the diode D2&D4 cut off , the capacitor C discharge to RL, Uc decline according to the principle of index function again. When the discharge to a certain value, the diode D1&D3 work again and the cycle repeats.

    2.测试方法/Test Method

    2.1 测试温升计算电容寿命/Life time of capacitor at testing temperature condition

    计算寿命公式/ Formula for calculating lifetime ：

    适用公司/ Corporation suited：Fcon 、KSC、TL、TEAPO、CapXon

    2.2 测试纹波电流计算电容寿命/Life time of capacitor at testing ripple current condition

    计算寿命公式/ Formula for calculating lifetime：

    2.2.1 直接测量电容纹波电流/Direct measure of E-cap ripple current

    开关电路中电容纹波电流分析

    C1为buck电容，其充电时间受到低频交流输入影响，而放电时间则是受到开关管Q1的高频影响。即A点受到低频交流输入影响，频率为交流频率的2倍，100Hz左右，故A点处所测试出电流为电容C1的低频纹波电流（IL）；B点受到高频开关Q1的影响，频率一般为100KHz，故B点所测试出的电流为电容C1的高频纹波电流（IH）。