A switching mode power supply that supplies power to a load. The circuitry of the power supply of this disclosure may be configured to operate with a constant switching frequency over a range of input voltages and a range of load power demand. The circuitry of this disclosure may modulate a minimum on-time (Ton-min) for a duty cycle for an operating frequency of the circuit based on the magnitude of the input voltage. The circuitry may also operate in continuous conduction mode (CCM) or in discontinuous conduction mode (DCM) based on an operating region. The operating region is based on a combination of the demand from the load (Iout) and the input voltage (Vin). The circuitry of this disclosure may enter an operating region based on a first combination but exit the operating region under a second and different combination of Iout and Vin.