How to select switching frequency of buck converter ?

 Selecting the switching frequency of a buck converter requires careful consideration of several factors, including efficiency, component size, cost, and electromagnetic interference (EMI). Here are the steps to follow when selecting the switching frequency of a buck converter:

Determine the required output voltage and current of the buck converter. This will help you calculate the required duty cycle of the converter and the minimum value of the inductor.

Determine the maximum input voltage of the buck converter. This will help you calculate the maximum voltage stress on the power switch and select a suitable switch with a voltage rating higher than the maximum input voltage.

Consider the efficiency of the buck converter. Higher switching frequencies generally result in higher efficiency due to reduced switching losses and smaller passive component sizes. However, this also leads to higher switching noise, which can increase EMI and reduce the converter's reliability.

Consider the size and cost of the passive components. Higher switching frequencies generally require smaller passive components, which can reduce the size and cost of the converter. However, this also leads to higher losses in the passive components and higher EMI.

Consider the EMI performance of the buck converter. Higher switching frequencies generally result in higher EMI due to increased high-frequency noise. This can cause problems with other electronic devices and may require additional filtering components to reduce EMI.

Overall, selecting the switching frequency of a buck converter requires a careful trade-off between efficiency, component size and cost, and EMI performance. A general rule of thumb is to select a switching frequency that is high enough to achieve good efficiency and small component size but not so high that it causes excessive EMI. A typical range of switching frequencies for buck converters is between 100 kHz to 2 MHz, with higher frequencies generally used for smaller form factors and lower power applications.

Here are some additional factors that you may also consider when selecting the switching frequency of a buck converter:

Consider the thermal performance of the buck converter. Higher switching frequencies can increase the temperature of the components due to increased switching losses, which can affect the reliability and lifetime of the converter.

Consider the stability of the control loop. Higher switching frequencies can result in a higher loop bandwidth, which can make the control loop more sensitive to noise and other disturbances.

Consider the impact of the switching frequency on the converter's dynamic performance. For example, higher switching frequencies can result in faster transient response and lower output voltage ripple, which may be important for some applications.

Consider the availability of suitable components. Higher switching frequencies may require specialized components, such as high-speed diodes, capacitors, and inductors, which may be more expensive or harder to source.

Consider the requirements of the application. Some applications may have specific requirements for the switching frequency, such as compatibility with other system components or compliance with industry standards.

By considering these additional factors, you can select a switching frequency that provides optimal performance for your specific application. However, it is important to note that selecting the optimal switching frequency is often a complex trade-off between multiple factors, and may require simulation and testing to verify the performance of the buck converter under different conditions.