There are three types of feedback control methods for switching regulators: voltage mode, current mode, and hysteresis control. The hysteresis control method has the best transient response characteristics to load current fluctuations. Fixed on-time control is broadly classified as a hysteresis control method, but unlike general hysteresis control methods, only the lower ripple limit of the output voltage is compared by a comparator, and if it is detected to be below the ripple, the switch is turned on for a certain period of time. turn it on. In this way, unlike the voltage mode and current mode, the output voltage is directly monitored by the comparator without going through an error amplifier, so this control method has the advantage of not taking feedback time and obtaining high-speed transient response characteristics.