Source Regulation in a switching power supply refers to the stability of its output voltage when the input supply voltage changes.

When the input supply voltage changes, such as during grid voltage fluctuations, the switching power supply needs to adjust its output voltage to keep it stable. Source regulation measures the extent to which the output voltage changes when the input voltage changes.

Source regulation is usually expressed as a percentage and calculated as follows:

Source regulation = (Vo_max - Vo_min) / Vo_nom * 100%

Where:

• Vo_max is the output voltage at the maximum input voltage;

• Vo_min is the output voltage at the minimum input voltage;

• Vo_nom is the rated output voltage of the switching power supply.

For example, if the rated output voltage is 12V, the output voltage is 11.8V at the maximum input voltage and 12.2V at the minimum input voltage, the source regulation is:

Source regulation = (12.2V - 11.8V) / 12V * 100% = 3.33%

A lower source regulation value indicates better output voltage stability as the input voltage changes. Lower source regulation means that the switching power supply can provide a more stable output voltage under different input voltage conditions, helping protect and stabilize the normal operation of equipment or circuits connected to it.