Post-silicon validation and debug challenges of system-on-chips (SoCs) are getting increasingly difficult. As we reach the limits of Dennard scaling, efforts to improve system performance and energy efficiency have resulted in the integration of a wide variety of complex hardware accelerators in SoCs. Hence, it is essential to address post-silicon validation and debug of hardware accelerators. High-level synthesis (HLS) is a promising technique to rapidly create customized hardware accelerators. In this paper, we present the Hybrid Quick Error Detection (H-QED) approach that overcomes post-silicon validation and debug challenges for hardware accelerators by leveraging HLS techniques. H-QED improves error detection latencies (time elapsed from when a bug is activated to when it manifests as an observable failure) by 2 orders of magnitude and bug coverage 3-fold compared to traditional post-silicon validation techniques. H-QED also uncovered previously unknown bugs in the CHStone benchmark suite, which is widely used by the HLS community. H-QED incurs less than 2% chip-level area overhead with negligible performance impact, and we also introduce techniques to minimize any possible intrusiveness introduced by H-QED.