A power supply includes a DC-DC converter, a boost converter, an energy storage element; and a voltage clamping circuit. The DC-DC converter is connected to a power source with an output voltage in a first voltage range. The voltage clamper circuit is configured to discharge at least a portion of energy of the energy storage element and to produce current at a clamped output voltage range that is substantially equal to the first voltage range. The discharged energy provides hold-up time for the power supply.