DC polarity protection

Electronic equipment which is fed from an external DC voltage can easily be damaged if the terminals of the supply are inadvertently transposed. In circuits which have only a small current consumption this danger can be averted by connecting a diode in series with the supply line. The diode will then only conduct if the supply voltage is of the correct polarity. If the diode is replaced by a bridge rectifier, then it no longer matters which way round the terminals are connected. However, particularly in circuits with larger current consumptions, this approach is somewhat unsatisfactory, since it leads to noticeable power losses.