Common DC/DC Converter Questions and Answers From Torex
Why is the DC/DC converter more effective than the voltage regulator?
In voltage regulators, the Pch MOSFET acts as a variable resistance, and the power loss can be calculated by the multiplication of the flowing current with the input-output differential voltage. In DC/DC converters, the power loss is reduced by the switching operation to gain a high efficiency with the help of inductor energy storage. Since DC/DC converters are composed of several functional elements, it is important to reduce each element resistance for a higher efficiency.
Why is a coil required for DC/DC?
When voltage is applied to the both sides of a coil, the current which flows into the coil increases linearly in proportion to time, and the current in the coil continues to flow even though the switch is turned OFF. The coil plays the role of maintaining the voltage which flows into the CIN and CL to a constant using this characteristic.
What is the ripple voltage of DC/DC?
When the output voltage waveform is observed, the switching noise can be seen and its one of the components is the ripple voltage.
Since this is a change of voltage when the coil current is smoothened by a CL capacitor, the frequency becomes equal to the frequency of the switching operation.
The approximate level of the ripple voltage can be acquired by the product of the ESR of the coil current value and the CL capacitor.
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