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6.2.6 纹波测量标准JEITA-RC9131
日本电子与信息技术工业协会(JEITA)
Japan Electronics Information Technology Association
同一个被测电源若采用不同的测量装置，其测量的结果是不相同的，若能采用一样的标准测量装置来测，则测量的结果才有可比性。近年来出台了几个测量纹波和噪声的标准，下面介绍一种基于JEITA-RC9131A测量标准的测量装置
该标准规定在被测电源输出正、负端小于150mm处并联两个电容C2及C3，C2为22μF电解电容，C3为0.47μF薄膜电容。在这两个电容的连接端接负载及不超过1.5m长的50Ω同轴电缆，同轴电缆的另一端连接一个50Ω的电阻R和串接一个4700pF的电容C1后接入示波器，示波器的带宽为100MHz。同轴电缆的两端连接线应尽可能地短，以防止捡拾辐射的噪声。另外，连接负载的线若越长，则测出的纹波和噪声电压越大，在这情况下有必要连接C2及C3。若示波器探头的地线太长，则纹波和噪声的测量不可能精确。
The ripple exists because, during aportion of the converter’s operating cycle, energy is transferred to thesecondary from the primary and the output voltage increases slightly. Duringthe time interval when there is no energy transfer to the secondary, the loadcurrent is supplied by stored energy in the output capacitance and inductanceof the converter, and the output voltage decreases slightly as this energy isdepleted. Ripple is a low frequency component and will be occur at the same asthe converter。 纹波是由于开关导通和关断期间电容的充放电引起的电压波动；是一个低频成分，与开关周期或调整周期同步。 Noise is much more variable andharder to predict than ripple. It is caused by ringing in parasitic inductancesdue to the large values of di/dt that occur internally in a switchingconverter. The noise is much higher frequency than the ripple and can be upinto the MHz range. Noise occurs in the form of “bursts” at the time ofswitching activity in the converter, so therefore appears to be superimposedupon the peaks and valleys of the ripple waveform as shown in Fig 1. 噪声是开关管的导通和关断瞬间产生的的高di/dt所引起的，是高频成分。 | 
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