A PFWM control method for a combination power supply of the boost converter and the bridge type DC-DC converter which also includes BUCK. A method of using the PFWM to control both boost and DC-DC converters simultaneously. A monitor module senses the bridge type DC-DC converter's output voltage, current or power, to obtain the frequency of PFM for driving switching components; predetermined a duty by design and use a frequency to adjust the boost output so as to adjust the DC-DC output voltage, current or power. Another monitor module senses the input instant voltage and the boost output voltage to obtain a maximum duty which is used to prevent the boost inductor from saturation. Combine above frequency and duty into at least a pair of complement PFWM driving signals, to directly or indirectly drive the combination power supply of boost converter and bridge type DC-DC converter's switching components.