US Patent 11287185 Freeze drying with constant-pressure and constant-temperature phases

Freeze-drying methods and systems include performing a constant-pressure drying phase in a chamber, where a temperature of a heating tray increases. A constant-temperature drying phase is performed in the chamber, where a pressure in the chamber decreases. Additional phases alternate between constant-pressure drying phases and constant-temperature drying phases. The alternating drying phases are halted, responsive to a determination that the temperature of the heating tray has reached a maximum temperature.