Isolated DC-DC Power Module What is an isolated DC-DC power supply? What is a non-isolated DC-DC power supply? Being "isolated" means the input power loop and the output power loop don't have their grounds be connected together, thus they can have independent ground level. For the non-isolated DC-DC power supplies, the input power loop and the output power loops share one common ground. The term "DC-DC" means both the input and output voltages are the DC type, as opposed to AC type. The output voltages can be lower or high than the input voltage, the former is sometimes called the buck type and the latter is called boost type. The key parameters of DC-DC power supplies are: nominal output voltage, maximum output current, quiescent input current, input voltage range, efficiency at full load, switching frequency, output ripple voltage, output noise, etc.