Contents
What are the requirements for a SMPS capacitor?
Critical SMPS requirements include a stable output voltage with load current, good temperature stability, low ripple voltage and high overall efficiency. One difference between SMPS and LDO is in the power dissipation.
How are output capacitors used in power supplies?
Output capacitors are a key component in switching power supplies — used to store the charge and for smoothing, so its selection plays a vital role in determining overall performance and its reliability. The designer now can choose between tantalum, ceramic MLCC, NbO niobium oxide and aluminum capacitors.
Where are the C X capacitors located in a power supply?
They are identified as X-capacitors (C X) or Y-capacitors (C Y) depending on the type of noise they help to filter. C X, located between line and neutral, inhibits the SMPS from introducing differential mode interference.
What kind of capacitors are used in switch mode?
The types of capacitors that are commonly used for input and output filtering in switch mode power supply systems include aluminum electrolytic, tantalum, ceramic, and film capacitors.
What should be considered when selecting output capacitors?
Volumetric efficiency, leakage current (for battery operated devices) and cost may also play a key role in the output capacitor selection process. Depending on the application and required transient response, generic SMPS requirements include the output capacitance value, low ESR and physical size.
Why are tantalum capacitors used in power supply applications?
Output capacitor applications may not be an issue as the power supply feedback is controlling the current and thus tantalum capacitors can be used here at up to 80% of the capacitorsí rated voltage (20% derating minimum) [1]. The most frequent field failures reported for tantalum capacitors are caused by applications with excessive current surge.
Can a high value capacitor cause high voltage spikes?
Circuits with an inductance in series with a high value capacitor may cause high voltage spikes when encountering low impedance switching. Mission critical operations should consider adding a diode in parallel with the capacitor for high voltage spike prevention.