# Switching frequency

The switching frequency (with the SI unit : Hz ) indicates the number of switch-on and switch-off processes for an electronic component or circuit per time interval .

${\ displaystyle f _ {\ mathrm {switching}} = {\ frac {1} {T _ {\ mathrm {off}} + T _ {\ mathrm {rise}} + T _ {\ mathrm {on}} + T _ {\ mathrm {waste} }}}}$

It is the period of time in the off state, the rise time , the time when switched on and the fall time . The rise and fall times are normally considerably smaller than the switching state times and can possibly be neglected, so that the equation becomes ${\ displaystyle T _ {\ mathrm {from}}}$${\ displaystyle T _ {\ mathrm {increase}}}$${\ displaystyle T _ {\ mathrm {a}}}$${\ displaystyle T _ {\ mathrm {waste}}}$

${\ displaystyle f _ {\ mathrm {switch}} = {\ frac {1} {T _ {\ mathrm {off}} + T _ {\ mathrm {on}}}}}$

can be simplified.

The higher the switching frequency, the more frequently the switching process can be carried out in a period of time, or the faster the switching process is.

In the case of switched-mode power supplies , the switching frequency is often in the range of 10 kHz to 20 kHz, which is largely within the audible range of the human ear and can be perceived as a monotonous whistling sound.

High switching frequencies of transistors enable z. B. the clock frequencies of modern processors and satellite communication in the GHz range.

The switching frequency should not be confused with the specification of the maximum switching cycles . This indicates the average number of switching operations that can be carried out until the wear and tear of the switching contacts has progressed to such an extent that reliable connection or disconnection can no longer be guaranteed. This information only occurs with mechanical contacts such as relays and reed contacts . The number of switching cycles is unlimited with semiconductors .