The invention discloses a
switching power circuit, which comprises a switching tube, a first resistive divider, a second resistive divider, an inductive component, a
freewheel diode, a
load unit, a load current detection unit, a
comparator, a D latch, an analogue-to-
digital converter, a digital-to-analogue converter, a
pulse width modulation (PWM) operating mode gate driving
voltage generation unit, a first
amplifier, a PWM
comparator, a
pulse frequency modulation (PFM)
control unit, a first either-or selector, a second either-or selector, a digital logic unit and a gate driving unit. When a PFM
control mode is adopted, the
voltage of the switching tube is regulated according to a load to reduce
power consumption in a
light load condition and improve energy transmission efficiency; and in addition, in the
light load condition, the gate driving
voltage and switching
duty cycle of the switching tube are reduced, so that the
power consumption is simultaneously reduced, and the shortcoming that output power is regulated only dependent on the
duty cycle of the switching tube to narrow the variation range of the
duty cycle and further retard the sudden change of the load and cause large output ripples during
mode switching is overcome.