Switching regulator and method of adjusting pulse width

The invention relates to a switching regulator and a method of adjusting pulse width limiting value. In a pulse width limiting circuit (6), a switch (SW11) is arranged between an output end of an inverter (13) and a grounding voltage, or between an output end of a constant current source (12) and the grounding voltage, which is open or close according to testing signals TEST input externally, in testing, through testing the power current flowing over the constant current source (12) when switching off the switch (SW11) and that when switching on the switch (SW11), constant current (i2) is correctly tested, through adjusting a reference current (i1), the constant current (i2) becomes desirable value. Deviation of the pulse width of pulse signals output from the pulse width limiting circuit is reduced, efficiency deviation of light load is reduced, output voltage ripple deviation is reduced.