An improved switching power converting apparatus (10) includes a power converting circuit (102), a sampling circuit (104), a signal gain adjustment circuit (106), a frequency limiting circuit (108) and a pulse width modulation controller (110). The sampling circuit (104) is configured to detect the power converting circuit (102) to obtain a sampled signal (Vs) and transmit the sampled signal (Vs) to the signal gain adjustment circuit (106). The signal gain adjustment circuit (106) is configured to adjust the sampled signal (Vs) to obtain a control signal (Vcon) and transmit the control signal (Vcon) to the frequency limiting circuit (108). The pulse width modulation controller (110) is configured to control an operating frequency of the pulse width modulation controller (110) based on the control signal (Vcon).