A switching controller for power converter comprises a current-sense circuit and a PWM circuit. The current-sense circuit receives high-voltage signal across a first switch to generate a current-sense signal. The PWM circuit generates a switching signal to control the first switch in response to the current-sense signal. The switching controller further comprises a delay circuit. The delay circuit receives the switching signal to generate a delayed switching signal. The current-sense signal and the high-voltage signal ramp up with the same slope during the delayed switching signal is enabled. The current-sense signal will be pulled down to a level of a ground reference during the delayed switching signal is disabled. A delay time provided by the delay circuit avoids the high-voltage signal at the instance which the first switch is being turned off being conducted to a first comparator and a second comparator via a second switch.