This paper presents a piezoelectric energy harvesting interface circuit that utilizes a Synchronous Switch Harvesting on Inductor Capacitor (SSHIC) circuit as the buck-boost module, based on one inductor and four capacitors, and replaces the traditional interface circuit's Fixed-Bias Rectifier (FBR) with a preceding switch array. The size of the inductor used is reduced from the traditional circuit’s 100–5 μH, and the total capacitance is reduced to equal the parasitic capacitance of the PEH (CP). This paper analyzes the advantages of the SSHIC buck-boost structure over the SSHI and SSHC in terms of flipping efficiency and proposes an SSHIC buck-boost circuit that divides the flipping phase into the currently highest nine phases, achieving up to 93.5% flipping efficiency and an output power of 35.12 μW. It presents an efficient solution when large inductors cannot be used.