As the number of Power Over Ethernet (PoE) powered device (PD) applications grows, market pressures are driving designers to lower the cost and complexity of the DC-DC converters that power them, while improving their performance. This paper provides simple circuit designs that meet those goals. It presents a discrete PD interface circuit that has been shown to work in University of New Hampshire Interoperability Consortium (UNH-IOC) tests. That circuit can be implemented with only a few low-cost components. It gives practical design hints and tips on designing a PD DCDC converter stage. It also presents a galvanically isolated, Flyback DC-DC converter example