US Patent 11509219 Reservoir capacitor for boost converters

A power supply comprising a first-stage capacitor configured to provide energy to a second stage power converter. An energy transfer element coupled to the first-stage capacitor. A reservoir capacitor coupled to the energy transfer element. The reservoir capacitor is configured to receive charge from the energy transfer element. A power switch configured to control a transfer of energy from an input of the power supply to the first-stage capacitor. A controller coupled to the power switch, the controller configured to generate a hold-up signal in response to the input of the power supply falling below a threshold voltage. A charge circuit comprising a first switch and a second switch configured to be controlled by the hold-up signal. The first switch couples the reservoir capacitor to an input of the energy transfer element. The second switch is configured to uncouple the reservoir capacitor from receiving charge from the energy transfer element.