Improving Output Ripple

February 2, 2006

The proper way to get good ripple measurment results

Vicor’s DC-DC converter incorporates an output filter that provides ripple/noise levels suitable for most customers. However, in some situations there are much higher requirements for low output noise and quiet supply voltages. These can be achieved by using some additional components such as extra capacitors, LC groups (PI filter) or more complex filters including common mode chokes.

Vicor provides a wide range of passive components and active solutions to help our customers to meet their sophisticated design requirements. A good measurement technique is required to get repeatability and to ensure that other stray elements do not effect your measurement. Therefore, you will also find probe sockets (Johnson Jacks) as part of our list of available accessories, in the Vicor Product catalogue.

The socket ground terminal should be connected closely to the converter output. This minimizes the transformation of common-mode into differential-mode noise by unbalanced probe impedances. Unbalanced impedance results in distorted and misleading scope plots. Module shields are also available to reduce radiated CM noise, which has similar effects on the measurement. Please keep in mind that ripple/noise measurements are taken at a limited bandwidth of 20 MHz.

Comparison of ripple levels of a V48C5C100 DC-DC converter @10A load current with and without µRAM output filter

For convenience, we provide trimming calculators for fixed and for variable output trimming on our web page. Please see both links below.

Vicor’s active output filter solutions provide excellent performance levels down to 3 mVpp. In addition, our µRAM and QPO output filters significantly improve transient response.

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