The use of piezoelectric resonators (PRs) as energy storage elements in dc-dc converters has captured considerable interest, in part due to the ultra-thin planner form factor, excellent frequency/volume scaling properties, and high coupling and quality factors offered by PRs. Traditional PR-based converters, however, exhibit performance diminishment at low voltage conversion ratios (VCRs), rendering them less appealing to applications that require low VCR operation. This article presents a dual-side series/parallel PR (DSPPR)-based hybrid dc-dc converter that integrates two 2:1 switched capacitor (SC) circuits into the operation of the baseline PR-based converter, enabling efficient conversion at low VCRs (VCRs $\leq 0.125$ ), while reducing the active area by up to $23\times$ compared to a baseline discrete converter. Fabricated in 180 nm BCD technology, the converter achieves a peak efficiency of 92.9% at a 20–2.2 V conversion ratio.