The chip of the switching regulator, for example, 24V output, is followed by the load, and the voltage regulator diode is generally selected at 28v and slightly higher than the output voltage value, which has two purposes:

1, when the output voltage is shaken, the voltage regulator diode can clamp the output voltage value is not too high. (Of course, it cannot exceed the dissipation power of the regulator diode).

2, inhibit the output voltage wavering, the voltage regulator diode can also be regarded as an effect of eliminating spikes or output surges, and the disturbance higher than the stable voltage value can play a good inhibitory effect.