Patent ID: 7579820
Filing Date: 2009-08-25
Classification: H02M

Abstract:
1. A PWM/PFM control circuit which, when a load on an object to be controlled is a heavy load of a predetermined value or higher, acts under PWM control for determining a pulse width in accordance with the load, and which, when the load is a light load of less than the predetermined value, acts under PFM control for determining a frequency in accordance with the load, the PWM/PFM control circuit having differential time generating means for forming a differential time signal representing a differential time corresponding to a difference between a pulse width of a PWM control signal and a pulse width of a PFM control signal on condition that the pulse width of the PWM control signal is smaller than the pulse width of the PFM control signal, and wherein an oscillation frequency of a reference signal serving as a reference for forming the PWM control signal is controlled based on the differential time signal to a low value in accordance with the differential time.