An auxiliary power circuit (14) of a conversion module (1-1 to 1-n) is used to supply power to a control unit (18), and an input end of the conversion module (1-1 to 1-n) includes an even number of energy storage units (122) coupled in series. The auxiliary power circuit (14) includes an even number of primary-side circuits (142) and a secondary-side circuit (144). Each primary-side circuit (142) includes a first switch unit (Q1), a second switch unit (Q2), and a resonance tank (Rt). The first switch unit (Q1) is connected to the second switch unit (Q2) in series, and is correspondingly connected to one of the energy storage units (122) in parallel. The resonance tank (Rt) is connected to the second switch unit (Q2) in parallel. The secondary-side circuit (144) is coupled to the resonance tanks (Rt) of two of the primary-side circuits (142) to acquire power and supply power to the control unit (18).